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ASME Conference Presenter Attendance Policy and Archival Proceedings

2013;():V005T00A001. doi:10.1115/DETC2013-NS5.
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This online compilation of papers from the ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE2013) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Affordances

2013;():V005T06A001. doi:10.1115/DETC2013-12349.

Function-based design is the traditional approach in engineering design theory, proving useful and practical in many cases but showing limitations in others. Affordance-based design is an alternative approach that attempts to address some of function theory’s limitations by focusing attention on the interactions between systems. This paper compares function-based design with affordance-based design by examining their philosophies, tools, abilities, and suitability along a number of dimensions. We conclude that the approaches are compatible and suggest future work to realize their integration.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A002. doi:10.1115/DETC2013-13130.

In design classes, functional analysis is a process that is typically used to assist students with identifying essential functions to aid in the development of their concepts. However, it has been observed that students sometimes struggle with this part of the design process. In this study, a group of 26 students were studied in a 3-level within-subject study (n = 78) to determine which of three common functional analysis approaches (i.e. top-down, energy-flow, and unstructured) was most effective. Participants were asked to dissect a hair dryer, power drill, and NERF pistol and generate function trees describing how these work. Measures of effectiveness include the number of functions generated, the number of errors, the number of levels of abstraction represented in the tree, and the number of unique subsystems and functions identified. No statistical difference between the approaches was found, and there was also no practical difference between the approaches. These results suggest that for novice engineers, there is no difference between methods used. This possibly indicates that for novice engineers, formal methods may not be any more effective than an unstructured approach.

Commentary by Dr. Valentin Fuster
2013;():V005T06A003. doi:10.1115/DETC2013-13170.

When developing an artifact, designers must first capture and represent consumer needs. These needs can then be transformed into system requirements or objectives. This paper proposes a formalized affordance-based method for capturing consumer needs which leverages previous work in the area of Affordance-based design. The creation of an affordance basis and a relational structure (the Desired Affordance Model) facilitates the use of affordances to represent consumer needs. This formalization has the potential to improve model quality and consistency, while managing model creation time. Further, this formalization imposes a level of abstraction which forces solution independence but is capable of capturing the large range of consumer needs.

Topics: Design , Modeling
Commentary by Dr. Valentin Fuster
2013;():V005T06A004. doi:10.1115/DETC2013-13191.

Patents contain valuable information for engineering design. However, the increasing number of annual patent publications makes it difficult for any individual designer to assimilate all up-to-date knowledge hidden in patent documents. In this paper, we proposed a computational approach to interpret design structure embedded in patent claims using pre-developed ontology libraries. The study combined natural language processing (NLP) techniques, text data-mining, ontological engineering, and our rule-based tree generation method. Data sources and adopted tools included online patent documents, knowledge gathered from engineering textbooks, WordNet, a part-of-speech tagger developed by the Stanford NLP group, and Graphviz. We showed that the framework proposed in the paper not only could help minimize manual work required for obtaining design structures but also enable automatic dissimilarity comparison between patents.

Topics: Design , Ontologies , Patents
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Biologically Inspired Design

2013;():V005T06A005. doi:10.1115/DETC2013-12549.

Traditionally, consumer preference is modeled in terms of preference for the aesthetic and functional features of a product. This paper introduces a new means to model consumer preference that allows for the experience of and interaction with a product to account for not only for how a product looks and functions, but also how it feels to use it. Traditional conjoint-based approaches to preference modeling require a user to judge preference for a product based upon a 2D product representation or a feature list. While the aesthetic forms and functional features of a product are certainty important, the decision to buy or not to buy a product often depends on more, namely the experience or feel of use. We introduce the concept of experiential conjoint analysis, a method to mathematically capture preference for a product through experience-based preference judgments. Experience-based preference judgments are made based upon the use, or simulated use, of a product. For many products, creating enough physical prototypes to generate a preference model is cost prohibitive. In this work, virtual reality technologies are used to allow the subjects an interactive, immersive, and realistic product experience, provided at little investment. The results of this work show not only that preference judgments of the interaction of a 3D virtual product representation can be used to generate accurate preference models, but that non-experiential judgments of the same product’s 2D forms lead to the generation of different preference models. Further, the virtual reality experience is found to provide an advantage in the form of confidence, information, and/or realism. Such experiential-based preference models provide previously unavailable design insight with which to inform the design generation process.

Commentary by Dr. Valentin Fuster
2013;():V005T06A006. doi:10.1115/DETC2013-13147.

In what ways and to what extent are bioinspired designs (BIDs) and the biological systems that inspire them ‘efficient’? The answer to this question provides insight into the potential role BID could have in the generation of energy- and materials-efficient designs. By qualifying and clarifying efficiency-related claims in the context of biological evidence, this paper contributes to the theoretical foundation for BID for efficiency and provides guidance to those developing design tools and methodologies aimed at using BID to enhance the efficiency of engineered products and systems.

This paper is organized into three main sections. First, a study is presented examining the reasons authors in the BID community cite when motivating their work. Of the 127 sources analyzed, 40 referenced ‘efficiency’, establishing empirically that efficiency of BIDs and the biological organisms that inspire them is a central motivation for work in BID.

Second, efficiency-related claims most commonly made by authors in BID are explained and analyzed using authoritative biological and BID literature. Ultimately, some of the claims prove problematic. However, when qualified appropriately, these claims provide significant insight into how the oft-cited examples of efficiency in biology and BID have arisen.

Finally, a study uncovering trends in sustainable BIDs is presented, and the efficiency-related trends are discussed. This study provides examples of some efficiency-related characteristics of biological systems that are successfully being transferred to engineered products and systems through BID. Specifically, the sustainable BIDs analyzed are shown to frequently meet four efficiency-related green design guidelines (GDGs) better than functionally-equivalent non-bioinspired alternatives. Additionally, passive mechanisms, multifunctional designs, and optimized geometries are discussed and shown to be prevalent in the sample of sustainable BIDs studied.

Topics: Design , Biomimetics
Commentary by Dr. Valentin Fuster
2013;():V005T06A007. doi:10.1115/DETC2013-13160.

Identifying applicable biological systems for engineering design remains a persistent challenge for bioinspired design. Previous researchers have proposed an Engineering-to-Biology thesaurus that allows designers to identify biological keywords that are functionally similar to terms in the Functional Basis. This work presents an experimental examination of the effectiveness of the Engineering-to-Biology thesaurus. A group of 100 mechanical engineering students are presented with a simple design problem: to create a device to remove the husk and silk from ears of corn. The participants read passages drawn from a large biology corpus with keywords from the Engineering-to-Biology thesaurus and indicate which passages prompt some idea for solving the design problem. The analysis of student responses indicates that students’ level of design training is not a significant factor in the number of analogies they found in the passages and that some non-random criteria is used to identify passages as useful for idea generation. Passages that rarely offer participants ideas can be reasonably well classified as either being too technical for a lay-reader to understand or lacking information on a biological system. Passages that typically offer ideas cannot be so easily classified. Finally, keywords from the Engineering-to-Biology thesaurus are examined to find that keywords very specific to biology and those that are very common words with multiple meanings are rarely contained in sentences that offer strong design inspiration.

Commentary by Dr. Valentin Fuster
2013;():V005T06A008. doi:10.1115/DETC2013-13274.

Understanding and tailoring the visual elements of a developing product to evoke a desired emotional response and aesthetic perception is a key challenge in industrial design. To date, computational approaches to assist this process have either relied on stiff geometric representations, or focused on superficial features that exclude often elusive shape characteristics. In this work, we aim to study the relationship between product form and consumer emotions through a visual deconstruction and abstraction of existing final products. In particular, we attempt to answer three questions: (1) Do observers’ aesthetic judgments rely on the product as a whole, including fine geometric details, superficial surface features, and brand-revealing icons, or are large, prominent shape characteristics sufficient to make this determination? (2) Is it possible to isolate shape features that give rise to specific emotional responses? (3) Is there a relationship between consumers’ ability to recognize a brand and the emotional attributes they associate with that brand. At the heart of our investigation is a shape analysis method that produces a spectrum of abstractions for a given 3D computer model. This produces a hierarchical simplification of an end product, whereby consumer response to geometric elements can be statistically studied across different products, as well as across the different abstractions of one particular product. The results of our study show that emotional responses evoked by coarse product “impressions” are strongly correlated with those evoked by final production models. This, in turn, highlights the importance of early aesthetic assessment and exploration before committing to detail design efforts.

Topics: Shapes
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Creativity and Ideation

2013;():V005T06A009. doi:10.1115/DETC2013-12289.

Many times when working together, designers feel they are inspired by each other. This effect can be explained by collaborative stimulation, occurring when the design entities or questions stimulate generative cognitive processes. To this point, four types of collaborative stimulation have been identified: prompting, seeding, clarifying and correcting, through observations in collaborative design settings by retrospective protocol analysis. Consistent relationships between collaborative stimulation and the cognitive processes they stimulate have also been identified. However, impact of collaborative stimulation on the “quality” of design entities, or the ideas produced, remains unknown. This paper identifies the novelty of design entities in the collaborative setting, and compares those which resulted directly from collaborative stimulation to those which were created by individuals working alone. It was found the collaborative stimulation types of seeding and correcting resulted in the greatest increases in novelty of design entities. This finding indicates that these types of collaborative stimulation tend to stimulate novelty. Interventions are suggested to encourage seeding and correcting in the design process.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A010. doi:10.1115/DETC2013-12620.

Measuring design creativity is crucial to evaluating the effectiveness of idea generation methods. Historically, there has been a divide between easily-computable metrics, which are often based on arbitrary scoring systems, and human judgement metrics, which accurately reflect human opinion but rely on the expensive collection of expert ratings. This research bridges this gap by introducing a probabilistic model that computes a family of repeatable creativity metrics trained on expert data. Focusing on metrics for variety, a combination of submodular functions and logistic regression generalizes existing metrics, accurately recovering several published metrics as special cases and illuminating a space of new metrics for design creativity. When tasked with predicting which of two sets of concepts has greater variety, our model matches two commonly used metrics to 96% accuracy on average. In addition, using submodular functions allows this model to efficiently select the highest variety set of concepts when used in a design synthesis system.

Topics: Creativity , Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A011. doi:10.1115/DETC2013-13087.

Designers commonly interact with products in the early phases of design in order to understand the solution space and gain inspiration for new designs. Although designer-product interaction methods such as visual inspection and product dissection are recognized as a pivotal component of the engineering design process, little data is available on how these practices affect idea generation or when these activities are most useful for inspiring creative thought. Therefore, the current study was developed to understand the impact of these activities on creative idea generation. During our controlled study, fifty-nine undergraduate engineering students were instructed to either visually inspect or physically dissect an example milk frother and then generate ideas for a new, innovative design. These concepts were then evaluated for their novelty, variety, quality and quantity. Our analysis (ANOVA) revealed that participants who physically dissected the example frother produced ideas that were more novel but of lower quality than those that simply inspected the frother. Our results provide insights on the impact of designer-product interactions on creativity and we use these findings to develop recommendations for the use and alterations of these practices for improving creativity in engineering design.

Commentary by Dr. Valentin Fuster
2013;():V005T06A012. doi:10.1115/DETC2013-13164.

Inclusive design aims to provide equitable use of a product irrespective of the user’s ability. Currently, sufficient tools are not available for practicing inclusive design. Recent research efforts have developed a method for inclusive design during the conceptual phase; the method consists of applying an empirically derived set of inclusive design rules to the actionfunction diagram of a product. This exploratory study investigates the effectiveness of this inclusive design representation scheme in generating ideas for conceptual design. An experiment is conducted in which participants generate ideas for an inclusive product design with and without the inclusive design representation scheme. The participants are also trained to use the representation scheme before implementing it in the experimental condition. Presently, there is no pre-defined metric to measure the inclusiveness of a conceptual design. Consequently, this paper introduces a metric to evaluate the inclusiveness of an idea; inter-rater reliability is also established for the metric. The ideas generated in the control and experimental conditions are compared based on quality and inclusivity. The results indicate that the inclusive design representation scheme helps the designer perform inclusive product design to a limited extent. This representation scheme is a promising method and needs detailed exploration of its individual elements. Moreover, the inclusivity metric serves as a foundational block for benchmarking various methods for inclusive design.

Commentary by Dr. Valentin Fuster
2013;():V005T06A013. doi:10.1115/DETC2013-13262.

The Alternative Uses Test is a measure of divergent thinking in which participants are asked to list non-obvious uses for a common object in a fixed amount of time. In this study, participants were asked to list alternative uses for a paperclip in three minutes. From a pool of over 2000 participants including engineering professionals and students, 293 were chosen and evaluated. Using infrequency of responses as a measure of novelty, it was found that participants that produced more responses had more novel responses and a higher average novelty score. Later responses were significantly more novel than early responses and unoriginality of responses decreased with quantity. On average, a participant would list 9 responses before arriving at highly novel responses. Participants that did not reach 9 responses in the study were likely to have few if any highly novel responses.

If this test maps to real world problem solving, it suggests that the first ideas we think of are likely to have been suggested already by others and thus not original. The results of this study can help restructure the format of the Alternative Uses Test.

Topics: Students
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Design Computing

2013;():V005T06A014. doi:10.1115/DETC2013-12040.

The morphological matrix is an important element of the engineering design methodology and is present in many textbooks. This method originally aimed at generating an exhaustive set of solutions for a given problem, by decomposing it into subproblems, finding solutions to each subproblem, and combining them. One issue associated with the morphological matrix has been the necessity to deal with the combinatorial explosions of solutions, especially at the conceptual design phase, when the still fuzzy nature of the design problem precludes the use of automated search for an optimal solution by means of specific algorithms (the “manual engineering design” context), apart from a few exceptions. Several heuristics based on the reduction of the number of combinations are investigated, and their efficiency is assessed. It is showed that the often-recommended compatibility matrix heuristic is the least efficient and can result in overlooking potentially interesting combinations. In fact all heuristics, even combined, generally fail to decrease the number of combinations to a level that can be handled by the designers, unless the original number of combinations is low. However, if one abandons the principle of an exhaustive investigation of the combinations in order to find the “best” solution, it can be showed statistically that the probability of ending up with a “good” concept among a very large number of combinations can be attained. Moreover, it is showed that the number of combinations one is willing to investigate also can contribute to increase this probability. Moreover the experience gained from the first round of investigation can serve as a guide to choose and assess other combinations. Based on those results, some recommendations for using the morphological matrix with all the different heuristics are given. Moreover, this paper discusses and relativizes the importance of the combinatorial explosion issue of morphological matrix compared with some other advantages and shortcomings of the method.

Commentary by Dr. Valentin Fuster
2013;():V005T06A015. doi:10.1115/DETC2013-12041.

Module formation is the step in which a product’s architecture is established in such a way that complex interactions are intra-modular and inter-modular interactions are more simple. If a matrix representation exists, such as a Design Structure Matrix, this involves clustering system entities into groups with strong intra-dependencies. For simple products, clustering may be done manually, but for complex products, computer tools are required. Existing clustering algorithms are either slow, or unable to guarantee a globally optimal solution. To enable iterative work and to make cluster analysis useful also in the detailing steps, efficient and effective computer algorithms are required. This paper presents an efficient and effective Genetic clustering algorithm, with the Minimum Description Length measure. To significantly reduce the time required for the algorithm to find a good clustering result, a knowledge aware heuristic element is included in the GA process. The efficiency and effectiveness of the algorithm is verified with four case studies.

Topics: Algorithms , Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A016. doi:10.1115/DETC2013-12537.

Ever since computers have been used to support human designers, a variety of representations have been used to encapsulate engineering knowledge. Computational design synthesis approaches utilize this knowledge to generate design candidates for a specified task. However, new approaches are required to enable systematic solution space exploration. This paper presents an approach that combines a graph-based, object-oriented knowledge representation with first-order logic and Boolean satisfiability. This combination is used as the foundation for a generic, automated approach for requirement-driven computational design synthesis. Available design building blocks and a design task defined through a set of requirements are modeled in a graph-based environment and then automatically transferred into a Boolean satisfiability problem and solved, considering a given solution size. The solution is then automatically transferred back to the graph-based domain. The method is validated through the synthesis of automotive powertrains. The contribution of the paper is a new method that is both able to determine that an engineering task is solvable or not given a set of design building blocks and able to systematically explore the solution space.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A017. doi:10.1115/DETC2013-12557.

Architecture generation and evaluation are critical points in complex systems design. System architecting starts with the exploration of a set of potential solutions that is progressively focused towards the most promising ones. In theory, these solutions are identified through their potential ability to reach system requirements. However, in early design stages, data supporting design choices are fuzzy and uncertain, making difficult the evaluation a priori of the future system architecture performance. In this paper, we propose a method using Bayesian Networks (BN) and Constraint Satisfaction Problem (CSP) to first generate potential system architectures, and then select the best ones regarding system requirements. The association of these two approaches allows to enhance architecture evaluation through integration of component placement optimization. This approach is demonstrated and implemented in radar antenna architecture generation. In the end, we also discuss some of the limits of the proposed approach as well as future research directions.

Topics: Optimization
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: DTM Retrospectives

2013;():V005T06A018. doi:10.1115/DETC2013-12280.

This paper describes the development and evolution of research themes in the Design Theory and Methodology (DTM) conference. Essays containing reflections on the history of DTM, supported by an analysis of session titles and papers winning the “best paper award”, describe the development of the research themes. A second set of essays describes the evolution of several key research themes. Two broad trends in research themes are evident, with a third one emerging. The topics of the papers in the first decade or so reflect an underlying aim to apply artificial intelligence toward developing systems that could ‘design’. To do so required understanding how human designers behave, formalizing design processes so that they could be computed, and formalizing representations of design knowledge. The themes in the first DTM conference and the recollections of the DTM founders reflect this underlying aim. The second decade of DTM saw the emergence of product development as an underlying concern and included a growth in a systems view of design. More recently, there appears to be a trend toward design-led innovation, which entails both executing the design process more efficiently and understanding the characteristics of market-leading designs so as to produce engineered products and systems of exceptional levels of quality and customer satisfaction.

Commentary by Dr. Valentin Fuster
2013;():V005T06A019. doi:10.1115/DETC2013-13035.

The problem this paper addresses is the tension between descriptive and normative approaches to design theory and methodology. Descriptive approaches typically seek to document, formalize and/or automate existing ad hoc design methods, towards the goal of making current best practices available to all. In contrast, normative approaches attempt to improve upon existing design practices, towards a new method for how design should be done. Both approaches have strengths and weaknesses. This paper seeks to resolve some of the tension between the two approaches. It presents a new method for designing a design system that synergistically exploits the strengths while remedying the weaknesses of both normative and descriptive methods. An illustration that employs immersive computing technology (ICT) to remedy some of the cognitive biases that might occur in a normative mathematical model for disassembly planning is presented.

Topics: Design theory
Commentary by Dr. Valentin Fuster
2013;():V005T06A020. doi:10.1115/DETC2013-13302.

Empirical methods used for studying design thinking have included verbal protocols, case studies, and controlled experiments. Studies have looked at the role of design methods, strategies, tools, environment, experience, and group dynamics. Early empirical studies were casual and exploratory with loosely defined objectives and informal analysis methods. Current studies have become more formal, factor controlled, aiming at hypothesis testing, using statistical DOE and analysis methods such as ANOVA. Popular pursuits include comparison of experts and novices, identifying and overcoming fixation, role of analogies, effectiveness of ideation methods, and other various tools. A variety of data may be collected, related to both the process and the outcome (designs).There are still no standards for designing, collecting and analyzing data, partly due to the lack of cognitive models and theories of design thinking. Data analysis is tedious and the rate of discoveries has been slow. Future studies may need to develop computer based data collection and automated analyses, which may facilitate collection of massive amounts of data with the potential of rapid advancement of the rate of discoveries and development of cognitive models of design thinking.

Topics: Design
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Engineering Innovations

2013;():V005T06A021. doi:10.1115/DETC2013-12252.

There is an increasing need for products that are able to react to changing operating conditions and user demands to achieve a high level of performance. Adaptronic solutions allow for property adjustments without major effects on system weight and size when they are applied in early phases of the design process. Since a framework for the design of adaptronic solutions is not yet established, this paper introduces an initial procedure and principles to provide design knowledge. The paper first gives an overview on adaptronics and adaptability as well as principles and guidelines for designing adaptable products. Fifteen adaptronic solution principles are derived from adaptronic solutions to provide the information needed for the design of adaptable products. A framework is proposed to apply the introduced principles within the conceptual design phase to avoid design conflicts and undesired effects. Finally, the framework is used for the design of adaptive joints for robotic applications.

Commentary by Dr. Valentin Fuster
2013;():V005T06A022. doi:10.1115/DETC2013-12635.

While rapid prototyping has proved to be an invaluable resource for expediting particular phases of the design process, its decreasing cost of operation and increasing accessibility reveal greater potential for these tools to substantially impact the design process itself. While many studies have investigated the advantages of creating and interacting with physical models in engineering design, this study explores the value of delaying decisions and pursuing many prototypes as it applies to individual designers in the earliest phases of the design process. Inspired by The Second Toyota Paradox, we propose the use of Kolb’s theory of experiential learning to reconcile the implications of set-based rather than point-to-point engineering with the value of an individual designer’s learning through interactions with concrete objects. We compared the performance of engineering students in a design challenge. The independent variable was the number of prototypes the participant was required to produce in the first iteration. Participants who were instructed to produce more prototypes in the same amount of time in which their control counterparts were only required to produce one expressed much higher levels of time constraint and dissatisfaction in their primary prototypes. However, multiple-design participants’ prototypes performed better, showed significantly greater improvement between iterations; in addition, satisfaction increased significantly after completion of the final prototype. We look to Kolb’s theory of experiential learning and an individualized application of corporate concurrent engineering to suggest a new design process heavy in low-fidelity, low-quality physical models in early design stages.

Commentary by Dr. Valentin Fuster
2013;():V005T06A023. doi:10.1115/DETC2013-12700.

The importance of prototyping in the design process has been widely recognized, but less research emphasis has been placed on the appropriate timing and detail of so-called “throwaway” prototyping during the preliminary design phase. Based on a study of mid-career professional graduate students, statistically significant correlations were found between the time such prototypes were created and design outcome. Building prototypes early on in the design process, or performing additional rounds of benchmarking and user interaction later on during the project (in addition to the typical early stage efforts), correlated with better design outcome, although the total time spent on these activities did not. The correlation between project presentations and reviewer scores are also touched upon. These findings suggest that the timing of design activities is more important than the time spent on them.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A024. doi:10.1115/DETC2013-12737.

Features, or visible product attributes, are indispensable product components that influence customer evaluations of functionality, usability, symbolic impressions and other qualities. Two basic components of features are visual appearance and size. This work tests whether or not eye-tracking data can (1) predict the relative importances between features, with respect to their visual design, in overall customer preference; and (2) identify how much a feature must change in size in order to be noticeable by the viewer. The results demonstrate that feature importance is significantly correlated with a variety of gaze data. Results also show that there are significant differences in fixation time and count for noticeable vs. unnoticeable size changes. Logistic models of gaze data can predict both feature importance and saliency of size change.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A025. doi:10.1115/DETC2013-13116.

Although simulation has become a very important aspect in product development today, a study of current design methodologies by Dohr and Vielhaber has shown that there is currently no methodology fully incorporating simulation within the context of mechatronic product development. The results of this study are used to derive specific needs of a simulation-based design process. Based on these requirements a process model for simulation-based mechatronic design is developed which is based on process steps of established design methodologies. In order to integrate simulation, the process model consists of two activity streams: analysis activities are linked to the specific design activities of mechatronic systems. Based on these two streams guidance is provided on which simulation technique should be used for specific activities and how the results from the simulation have to be handled in order to improve design without macro-iterations. With regard to mechatronic interdisciplinarity as well as data and model management, the use of a system model as a platform for the exchange of information and knowledge is integrated into the process model. Finally an outlook on future work regarding the detailing of the process model as well as on the application of the process model is provided.

Topics: Simulation , Design
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Human Behavior in Design

2013;():V005T06A026. doi:10.1115/DETC2013-12128.

Our prior work presented a method for computationally structuring patent databases as a basis for an automated design-by-analogy tool. In order to examine the validity and sensibility of the prior work as the basis for a design tool, its output is compared in detail to expert designers’ mental models of the domain being structured, i.e., a set of 45 patents and their inter-relationships. The comparison sought first to gauge the intuitiveness and sensibility of the computational method of structuring to human minds, and further to ascertain whether any differences between the method’s and the experts’ structures indicate potentially novel or surprising ways of approaching the space of patents, or indicate that the output was nonsensical, invalid or needing modification in order to be useable. The results indicate that, when compared to expert thinking, the computationally generated structure is sensible in its clustering of patents and in its organization of these clusters into a structure or space. The results also suggest that the computationally-generated structure represents a version of the patent space upon which experts can find common ground and consensus — making it likely to be intuitive and accessible to a broad cohort of designers. Thus, the prior work which presented a computational method for structuring design databases has been found to offer a resource-efficient way of usefully representing the space that is sensible to expert designers, while still preserving an element of surprise and unexpectedness, making it promising as the basis for a computational design-by-analogy inspiration tool.

Topics: Design , Testing
Commentary by Dr. Valentin Fuster
2013;():V005T06A027. doi:10.1115/DETC2013-12403.

A battery of tests assessing the cognitive skills needed for the conceptual design is being developed. Tests on Divergent thinking and visual thinking are fully developed and validated. The first version of the qualitative reasoning test has also been developed; this paper focuses on the lessons learned from testing of the first version of the test (alpha version) and the improvements made to it since then.

A number of problems were developed for each indicator of the qualitative reasoning skill (deductive reasoning, inductive reasoning, analogical reasoning, and abductive reasoning). Later, a protocol study was done with the problems to make sure that the problems assess the desired skills. The problems were also given to a randomly chosen population of undergraduate senior-level or graduate-level engineering students. Data was collected from the test results on the possible correlations between the problems (e.g. technical and non-technical problems); feedback on clarity, time allocation, and difficulty for each problem was also collected. Based on all of the observed correlations, the average performance of the test takers, and test parameters such as validity, reliability, etc. the beta version of the test is constructed.

Commentary by Dr. Valentin Fuster
2013;():V005T06A028. doi:10.1115/DETC2013-12535.

As electric vehicles are moving in on the automobile market, safety relating to acoustic perception is an important issue. It is a growing concern, particularly with respect to pedestrians, cyclists or visually impaired people. This can be addressed by adding sounds to the vehicle whilst at low speed. However, adding artificial sounds to an electric vehicle begs the question as to what kind of sound is appropriate. Appropriateness concerns technical specifications and is also linked to affective reactions of recipients of such a sound. Emotional reactions to 17 artificial exterior sounds for electric vehicles were investigated in an experimental setting with a total of 40 participants, 34 novice users and six sound experts.

Word association was used to elicit emotional reactions to the different sounds. Novice users employ more character-related terms to describe the sounds, while experts use more composition-based words. Analysis of variance and conjoint analysis was used to analyze participants’ assessments of sounds according to two semantic scales (pleasantness and appropriateness). Considerable inter-individual differences in the ratings of pleasantness and appropriateness indicate a great diversity of opinion about the sounds. Novice users indicate their preference for the sound of the traditional combustion engine as a possible proposition. Whilst participants saw the necessity, there was generally little enthusiasm for adding sounds to electric vehicles. The contribution of the paper concerns the methodology to analyze the results of the experiment and implications for the design of sounds for electric vehicles.

Commentary by Dr. Valentin Fuster
2013;():V005T06A029. doi:10.1115/DETC2013-13628.

Cognitive efficiency describes how individuals optimize limited mental resources to achieve improvements in learning and problem-solving. Research on expert performance and expertise has shown that expert designers structure the organization of cognitive actions more efficiently than novices. However, cognitive efficiency in engineering design processes has not been well studied because of technical limitations at the neurological level and lack of quantitative methods for analyzing information contained in designers’ cognitive processes at the performance level. The purpose of this study is to introduce Kolmogorov complexity to measure information contained in the changes of sketches generated by designers. The Kolmogorov complexity of each design move is calculated by the number of cognitive actions and transitions between different levels of information processing. In this study, sketches and verbal protocols generated by 15 participants were analyzed. Cognitive efficiency was determined by the quality of design outcomes and the expenditure of mental effort. The results indicate that Kolmogorov complexity is negatively related to cognitive efficiency; the higher the Kolmogorov complexity, the lower the cognitive efficiency.

Commentary by Dr. Valentin Fuster
2013;():V005T06A030. doi:10.1115/DETC2013-13691.

User experience (UX) design involves combination of different design attributes with their corresponding attribute levels to form different product profiles. This raises the issue of how to integrate corresponding UX of individual design attribute levels (i.e., partworth UX measures) into a holistic measure of UX of the entire product profile. Traditional methods often use a weighted sum of single partworth UX strategy without considering their dependence. This paper proposes to use utility copulas to accommodate the dependence of individual partworth UX measures. Single utility functions are constructed based on cumulative prospect theory, based on which multivariate Archimedean utility copulas are constructed using a nested structure based on the modularized attributes. A case study of aircraft cabin interior design is demonstrated to show the potential and feasibility of the proposed methodology.

Topics: Design , Aircraft
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Managing Design and Fostering Innovation

2013;():V005T06A031. doi:10.1115/DETC2013-12154.

Integrated product design and development in today’s highly competitive, demanding and economically challenging world is a complex process depending upon input of many individuals, groups, organizations and even communities, which collaborate to realize the product. Due to the multi-technology nature of modern products, the design process requires multi-disciplinary resources.

Engineering design literature provides an extensive knowledge base of product design processes, most of which are specific in an explicit or an implicit way to a specific discipline. This is because some time ago, the products were perceived to be rather mono-disciplinary.

Recently, design processes have been described for integrated products from inter-disciplinary and multi-disciplinary team perspective (e.g. [1]), however, they too take product specific and discipline specific point of view.

This paper takes a transdisciplinary perspective towards product design and presents results from an empirical study carried out to analyze the design process of different integrated products belonging to different disciplines/industrial segments; all of which involve multi-disciplinary or transdisciplinary involvement.

A framework based on key findings from the transdisciplinary consolidation of academic design process models presented by Gericke and Blessing and Eisenbart et al. is developed and used to provide answers to the following research questions:

• How well does the literature based trans-disciplinary design process apply to the trans-disciplinary industrial context?

• Are there similarities between design processes across organizations regarding presence of process stages and design states?

• Are there any elements that deviate from the literature-based framework?

Commentary by Dr. Valentin Fuster
2013;():V005T06A032. doi:10.1115/DETC2013-12581.

In this paper, we introduced an activity-based adaptive process model that views innovative design as a complex adaptive system. Instead of predefining the process architecture, we constructed the model framework by adaptively selecting the design activity by the activity value. We defined the activity value as the complexity reduction associated with the possibility of satisfying the design targets and design stages. Moreover, this paper contributes an expert evaluation methodology to evaluate the activity value in order to balance innovation and control. Finally, we applied the model to an industrial case and analyzed the simulation results.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A033. doi:10.1115/DETC2013-13072.

Prototyping may be simultaneously one of the most important and least formally explored areas of design. Over the last few decades, designers and researchers have developed many methodologies for ideation, product architecture, design selection, and many other aspects of the design process. However, there have been relatively few methodologies published regarding the efficient and effective development of prototypes for new products. This research explores a methodology for enhancing the prototyping process. It is founded on extensive literature review of the best practices of engineering prototype development. These findings have been aggregated and form the foundation of a methodology for formulating prototyping strategies. This methodology has then been experimentally evaluated in a controlled design environment, and its effect on the performance of prototypes has been demonstrated. The method consists of a set of guiding questions with corresponding flowcharts and foundational equations that assist the designer to make choices about how to approach the prototyping process in an efficient and effective manner.

Topics: Design
Commentary by Dr. Valentin Fuster
2013;():V005T06A034. doi:10.1115/DETC2013-13096.

Product dissection is a tool widely used in industry and academia as a means to understand components of existing products and identify opportunities for design. Dissection activities have the potential to impact design creativity because dissection is performed in the early phases of design, which is arguably the most influential phase of the design process. However, researchers have only just begun to explore the relationship between dissection and creativity, and thus little research to date has identified how variations in dissection activities impact creativity. Therefore, in this paper we respond to this research gap by presenting the results of a controlled experiment developed to understand how the type and number of products dissected and the structure and medium of the dissection task (electronic versus physical) impacts creativity. Our quantitative findings (from ANOVAs) are paired with qualitative analysis (interview results) to provide rationale for our results and insights into their cognitive underpinnings. The results from this study indicate that the structure of the dissection activity, the medium of dissection, and the number of products dissected impacts the variety of the generated concepts while the analogical distance and number of products impacts design novelty. These findings are used to develop recommendations for the alteration of dissection methods for inspiring creative thought in engineering design.

Commentary by Dr. Valentin Fuster
2013;():V005T06A035. doi:10.1115/DETC2013-13232.

Companies that develop new products increasingly outsource design, a trend that has prompted much concern but little prescription on how best to manage such projects. One challenge is the lack of understanding of what constitutes success in outsourced design. To provide clarity, this paper identifies academic and practical perspectives on success from the literature as well as our own interviews with design consultants and consulting clients, organizes the perspectives into a typology featuring seven distinct dimensions of success, and then prioritizes the key success measures using a survey of 194 additional practitioners. The results suggest that past research has generally focused on the wrong success measures, overstating the impact of problems during development and the relative importance of return on investment, and omitting key measures such as working relationship quality, project value, and client satisfaction. Not all success measures are well correlated; a project may do very well on some but poorly on others. While each measure has it merits, client satisfaction appears to be a promising summary measure.

Topics: Design
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Risk, Uncertainty and Robustness

2013;():V005T06A036. doi:10.1115/DETC2013-12188.

This paper describes a complex networks approach to study the failure tolerance of mechatronic software systems under various types of hardware and/or software failures. We produce synthetic system architectures based on evidence of modular and hierarchical modular product architectures and known motifs for the interconnection of physical components to software. The system architectures are then subject to various forms of attack. The attacks simulate failure of critical hardware or software. Four types of attack are investigated: degree centrality, betweenness centrality, closeness centrality and random attack. Failure tolerance of the system is measured by a ‘robustness coefficient’, a topological ‘size’ metric of the connectedness of the attacked network. We find that the betweenness centrality attack results in the most significant reduction in the robustness coefficient, confirming betweenness centrality, rather than the number of connections (i.e. degree), as the most conservative metric of component importance. A counter-intuitive finding is that “designed” system architectures, including a bus, ring, and star architecture, are not significantly more failure-tolerant than interconnections with no prescribed architecture, that is, a random architecture. Our research provides a data-driven approach to engineer the architecture of mechatronic software systems for failure tolerance.

Commentary by Dr. Valentin Fuster
2013;():V005T06A037. doi:10.1115/DETC2013-12626.

In this paper, we develop a method that produces recommendations, usable by a designer, that reduce the likelihood of a failure occurring. Prior work introduced the Function Failure Rate Design Method (FFRDM) which uses historical data as evidence to generate new design requirements. This paper presents improvements to FFRDM by including an iterative loop within the method that begins with specific recommendations. This allows evidence from the analysis to support the addition of new requirements and functionality into the design. Once the iterative loop has converged with no new requirements left to generate, all recommendations are used for concept generation. In addition, metrics are developed that can be used later to analyze the design. These metrics are important to ensure that the design has considered the full set of recommendations. Specifically, the updated FFRDM improves the original FFRDM with 1) a systematic and repeatable heuristic to group failure modes and determine which failure modes are predominate, 2) a categorization of the recommendations, 3) metrics built for the recommendations used in concept generation to make them measurable, and 4) using recommendations to develop new requirements and functionality. To show the usefulness of each improvement to FFRDM, a case study using an electrical power system (EPS) is provided.

Commentary by Dr. Valentin Fuster
2013;():V005T06A038. doi:10.1115/DETC2013-12913.

Testing components, prototypes and products comprise essential, but time consuming activities throughout the product development process particularly for complex iteratively designed products. To reduce product development time, testing and design processes are often overlapped. A key research question is how this overlapping can be planned and managed to minimise risks and costs. The first part of this research study investigates how a case study company plans testing and design processes and how they manage these overlaps. The second part of the study proposes a significant modification to the existing process configuration for design and testing, which explicitly identifies virtual testing, that is an extension to Computer Aided Engineering which mirrors the testing process through product modelling and simulation, as a distinct and significant activity used to (a) enhance and (b) replace some physical tests. The analysis shows how virtual testing can mediate information flows between overlapping (re)design and physical tests. The effects of virtual testing to support overlap of test and (re)design is analysed for the development phases of diesel engine design at a case study company. We assess the costs and risks of overlaps and their amelioration through targeted virtual testing. Finally, using the analysis of the complex interactions between (re)design, physical and virtual testing, and the scope for replacing physical with virtual testing is examined.

Commentary by Dr. Valentin Fuster
2013;():V005T06A039. doi:10.1115/DETC2013-13536.

This paper proposes a diagnostic approach to quantify the maintainability of a Commercial Off-the-Shelf (COTS)-based system (CBS) by analyzing the complexity of the deployment of the system. The approach integrates architectural dependencies and the system’s concept of operations to derive a network-based representation of the software system. A greater understanding of the deployment complexity is gained by comparing the in-degree distribution of the derived network to the power-law distribution. The resultant measure is useful in evaluating the maintainability of the operational system while the system is being designed and throughout the lifetime of the system. The measure is applied to deployed production systems with known maintainability histories to validate the approach.

Topics: Maintainability
Commentary by Dr. Valentin Fuster

25th International Conference on Design Theory and Methodology: Sustainability in Design

2013;():V005T06A040. doi:10.1115/DETC2013-12495.

We use nonlinear behavior of thin-walled structures — an approach inspired by biological systems (the human airway, for example) — to address one of the most important problems facing subsistence farmers in developing countries: lack of access to inexpensive, water-efficient irrigation systems. An effective way of delivering water to crops is through a network of emitters, with up to 85% of the water delivered being absorbed by plants. However, of the 140 million hectares of cropped land in India alone, only 61 million are irrigated and just 5 million through drip irrigation. This is, in part, due to the relatively high cost of drip irrigation. The main cost comes from the requirement to pump the water at relatively high pressure (>1bar), to minimize the effect of uneven terrain and viscous losses in the network, and to ensure that each plant receives the same amount of water. Using a prototype, we demonstrate that the pressure required to drive the system can be reduced significantly by using thin-walled structures to design emitters with completely passive self-regulation that activates at approximately 0.1bar. This reduction in driving pressure could help bring the price of drip irrigation systems from several thousand dollars to approximately $300, which is within reach of small-scale farmers. Using order-of-magnitude calculations, we show that due to increased sensitivity of the proposed design to the applied pressure differential, a pressure compensating valve for drip irrigation could be built without using costly silicone membranes.

Commentary by Dr. Valentin Fuster
2013;():V005T06A041. doi:10.1115/DETC2013-12588.

The Leveraged Freedom Chair (LFC) is a low-cost, all-terrain, lever-propelled wheelchair designed primarily for use in developing countries. LFC technology was conceived because 70 percent of wheelchair users in these markets live in rural areas and no currently available mobility aid enables them to travel long distances on rough terrain and maneuver in tight, indoor confines. Because developing world markets impose constraints on cost, durability, and performance, a novel solution was required to satisfy stakeholder requirements. The key innovation behind the LFC is its single speed, variable mechanical advantage lever drivetrain. The user effectively changes gear by shifting his hands along the levers; grasping near the ends increases torque, while grasping near the pivots enables a larger angular displacement with every stroke, which increases speed. The drivetrain is made from low-cost bicycle parts found throughout the developing world, which enables the LFC to be sold for $200 and be repairable anywhere.

During three user trials in East Africa, Guatemala, and India, stakeholder feedback was used to refine the chair between trials, resulting in a device 9.1 kg (20 lbs) lighter, 8.9 cm (3.5 in) narrower, and with a center of gravity 12.7 cm (5 in) lower than the first iteration. Survey data substantiated increases in performance after successive iterations. Quantitative biomechanical performance data were also measured during the Guatemala and India trials, which showed the LFC to be 76 percent faster and 41 percent more efficient during a common daily commute, and able to produce 53 percent higher peak propulsion force compared to conventional, pushrim-propelled wheelchairs. The LFC offers comparable performance at less than one-twentieth the cost of off road wheelchairs available in the rich world. Stakeholder feedback and the highly-constrained environment for which the LFC was created drove the technology towards a novel, innovative solution that offers a competitive advantage in both developing and developed markets. The paper concludes with a description of how the LFC is a “constraint-driven innovation.” This idea ties together the theories of “disruptive innovation” and “reverse innovation,” and may be used as a design tool for engineers striving to create technologies that have global impact.

Commentary by Dr. Valentin Fuster
2013;():V005T06A042. doi:10.1115/DETC2013-12677.

Product design for emerging markets in the developing world is a rapidly growing field due to a steadily increasing market and an interest in profitably transforming consumer quality of life for this population. Economic and cultural barriers as well as other constraints present a daunting challenge for designers working in this area. This study documents current best practices and proposes a framework for future designers with a focus on creating products that foster micro-enterprise. These guidelines are drawn from existing literature and interviews with practicing designers of products for emerging markets. Four case studies are presented ranging across several product categories.

Commentary by Dr. Valentin Fuster
2013;():V005T06A043. doi:10.1115/DETC2013-12973.

The gap between customers preferring sustainable products in surveys and actually buying sustainable products in the market can be addressed through design. Our previous research proposed a method for creating design features that trigger thoughts of sustainability, termed ST (sustainability triggering) features. In the research presented here, a selection of ST features generated from the previous experiment was designed into realistic toaster prototypes. Subjects participated in a test vs. control purchase experiment, in which some “customers” saw a subset of toasters with ST features during purchasing tasks and some did not. First, subjects selected a subset of toasters for purchase. Then, they chose one from that set for a final purchase. Next, they wrote an email with instructions on how to select a toaster to a hypothetical purchasing agent. Finally, they answered interview questions and rated/ranked toasters. The coded email and interview results demonstrate that exposure to ST features significantly triggered the possible use of sustainability as a purchase criterion.

Commentary by Dr. Valentin Fuster
2013;():V005T06A044. doi:10.1115/DETC2013-13459.

Much progress has been made in sustainable design over the past 20 years since the first publications on design for the environment started to appear in the mechanical engineering literature. Engineering design methods now attempt to include environmental considerations and Life-Cycle Analysis is a commonly used approach nowadays. Nevertheless, some fundamental problems seem to be recurring and remain unresolved. More so, some of these problems can have significant effects on the efficacy of design methods. Without consideration or even acknowledgement of these problems, proposed sustainable design methods may not bring us closer to sustainability at all. In this paper, we highlight a few of these recurring problems. Although true sustainable design should also include social and financial considerations, we will focus primarily on the environmental issues in this paper.

Topics: Green design
Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Bevel Gears

2013;():V005T11A001. doi:10.1115/DETC2013-12058.

In this study, an optimization methodology is proposed to systematically define optimal head-cutter geometry and machine tool settings to simultaneously minimize tooth contact pressures and angular displacement error of the driven gear and to reduce the sensitivity of face-hobbed spiral bevel gears to misalignments, while concurrently confining the loaded contact pattern within the tooth boundaries and avoiding any edge- or corner-contact conditions. The proposed optimization procedure relies heavily on a loaded tooth contact analysis for the prediction of tooth contact pressure distribution and transmission errors influenced by the misalignments inherent in the gear pair. The targeted optimization problem is a nonlinear constrained optimization problem. The core algorithm of the proposed nonlinear programming procedure is based on a direct search method. Effectiveness of this optimization was demonstrated on a face-hobbed spiral bevel gear example. Drastic reductions in the maximum tooth contact pressure (62%) and in the transmission errors (70%) were obtained.

Commentary by Dr. Valentin Fuster
2013;():V005T11A002. doi:10.1115/DETC2013-12233.

Face hobbing has been successfully applying in manufacturing straight bevel gears using a virtual hypocycloidal straight-line mechanism. This method is a continuous indexing and double-flank cutting process, and is recognized its high productivity and precision. In order to improve gear contact condition, three types of flank modifications are frequently used in gear industry: profile crowning, lengthwise crowning, and longitudinal twist. In the design of the spiral bevel and hypoid gear, under satisfying a specified accuracy requirement, three types of modifications are blended properly during gear design to absorb assembly and manufacture errors. Circular cutter blades are normally adopted to accomplish the first type modification. The second can be achieved by a cutter radius change or a cutter tilt with adjusted pressure angles. The last can be achieved by a cutter tilt or modified tool path (for example, helical motion and modified roll). This paper proposes a lengthwise crowning method for face-hobbed straight bevel gear (SBG) using a hypocycloidal mechanism. This modification is applied to the pinion only. A numerical example drive with point-contact tooth surfaces is adopted to validate the proposed mathematical model. Finally, two evaluations, ease-off topography and tooth contact analysis (TCA), are made to investigate the contact condition of this numerical case.

Topics: Bevel gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A003. doi:10.1115/DETC2013-12351.

Spiral bevel gears are widely used in the tail rotor drive trains of most rotorcraft. The loads associated with the tail rotor drive train are generally much more variable than those in the main rotor drive train primarily resulting from maneuvers. Over the life of any particular military rotorcraft it is not uncommon for the aircraft’s operating gross weight to steadily increase, causing the aircraft to fly at higher mean power levels and thus increasing the operating load spectrum associated with the tail rotor drive train. Special missions and equipment such as pulling a mine sweeping sled or very high altitude high gross weight assaults can put severe load demands on the tail drive train. This paper details an effort conducted to evaluate the effects of short to moderate duration overloads on the spiral bevel gears of the UH-60 helicopter tail rotor drive train. The focus of the effort was on the Tail Take-off gear mesh (TTO). An initial analytical assessment of the effect of loads above the endurance limit was conducted using an American Gear Manufacturers Association (AGMA) based approach. To confirm the validity of this approach, overload testing of the TTO gear mesh was conducted by the U.S. Army’s Aviation Applied Technology Directorate at the Navy’s test facility in Paxtuent River MD. Following the testing, the gear tooth bending and surface fatigue lives were analyzed using a microstructure based probabilistic tool developed by Sentient Corporation. The tool, known as Digital Clone was able to run hundreds of virtual tests that closely simulated the actual testing thus providing a low cost method for increasing the confidence associated with the effects of short to moderate high transient loads.

Commentary by Dr. Valentin Fuster
2013;():V005T11A004. doi:10.1115/DETC2013-12899.

The paper presents a hyperboloidal hob cutter similar to a cylindrical hob cutter used to fabricate spur and helical gear elements today. This hyperboloidal cutter can be used to manufacture bevel and hypoid gear elements using an existing CNC hobbing machine. These bevel and hypoid gear elements can be either spur or spiral. This hyperboloidal hob cutter is entirely different from the circular face cutters today as part of face hobbing. A brief overview of the existing circular face cutting technology is presented along with some of its geometric limitations. Subsequently, concepts of the hyperboloidal hob cutter are presented. These concepts include crossed hyperboloidal gears, cutter spiral angle, invariant speed relations, and cutter coordinates. Two illustrative examples are presented to demonstrate the concept of the hyperboloidal hob cutter. The first example is a spur bevel gear pair and the second example is a spiral hypoid gear pair. Virtual models of the cutter in mesh with the gear elements are presented.

Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Gear Analysis, Materials, Fatigue

2013;():V005T11A005. doi:10.1115/DETC2013-12037.

The gear trains are conventionally designed following AGMA standards developed by using basic Lewis formula with several modifications; these standards are very conservative. The finite element methods provide an accurate assessment of bending and contact stresses and a comparison is made in this paper with AGMA values to understand the over design and safe characteristic of the standards versus FE values.

Commentary by Dr. Valentin Fuster
2013;():V005T11A006. doi:10.1115/DETC2013-12183.

Pitting and tooth root breakage are typical fatigue failure modes of case hardened gears. Both failure types are usually initiated at the surface or close to the surface. General trends in modern gear industry, such as improved gear design with adequate flank modifications, high-quality gear materials and high-performance lubricants, modern manufacturing processes with additional post-processes as shot peening and superfinishing as well as advanced calculation methods, have allowed an optimized utilization of the allowable pitting and bending stress numbers in recent years. As a result of the increased power density, however, the stresses below the surface rise with the consequence of an increased risk of fatigue failure initiation in the material below the surface.

This paper describes main characteristics of a failure mode characterized by tooth breakages which start in the area of the active flank from cracks that are typically initiated at a considerable depth beneath the loaded flank surface. Based on theoretical and experimental investigations, relevant influence parameters related to gear design, operating conditions and material strength on the failure mode “Tooth Flank Breakage” will be discussed and basic principles of a developed calculation model to evaluate the risk of such failures presented. Finally, exemplarily experimental results from gear running tests, which failed due to flank breakage, are compared to the results of the new calculation model.

Commentary by Dr. Valentin Fuster
2013;():V005T11A007. doi:10.1115/DETC2013-12511.

In this study, a crack initiation life prediction methodology for the tooth bending fatigue of hypoid gears is proposed. This methodology employs a previously developed finite-element based hypoid gear root stress model [1] of face-milled and face-hobbed hypoid gears to establish the multiaxial stress time histories within the root fillet regions. These stress time histories are combined with a multiaxial crack initiation fatigue criterion to predict life distributions along roots of the pinion and the gear. The predictions of the multiaxial fatigue model are compared to those from a conventional uniaxial fatigue model to establish the necessity for a multiaxial approach. The model is exercised with an example face-milled hypoid gear set from an automotive application to demonstrate the impact of various misalignments as well as the key cutting tool parameters on the resultant tooth bending lives.

Commentary by Dr. Valentin Fuster
2013;():V005T11A008. doi:10.1115/DETC2013-12852.

Root stresses of thin-rimmed helical gears with symmetric and asymmetric web arrangement of helix angle β0 = 10° and 20°, which were meshed with solid helical gear, were measured from the beginning of engagement to the end of the engagement by using the strain gauge method. The changes of root stresses from the beginning of engagement to the end of engagement were examined. The effects of helix angle, rim thickness, web thickness and web structure on the root stresses, the maximum root stress and the meshing position, where the maximum root stress (worst loading position) occurs, were clarified. Furthermore, the obtained results were compared with the results of the solid helical gear. On the basis of these results, the maximum root stress of thin-rimmed helical gears with helix angle β0 = 10° occurs at the outer point of single tooth contact, and at the position of a transverse base pitch distant from the tip toward the root along the line of action for β0 = 20°. For thin-rimmed helical gears with the same rim thickness, web thickness and web structure, maximum root stress increment ratio (maximum root stress of thin-rimmed helical gear divided by maximum root stress of solid helical gear) of thin-rimmed helical gears with helix angle β0 = 10° are larger compared to the case of β0 = 20°.

Topics: Stress , Helical gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A009. doi:10.1115/DETC2013-13363.

QuesTek Innovations LLC will present an overview of its Ferrium® C61™ and Ferrium C64™ high-performance gear steels. QuesTek designed, developed and implemented these two new steels using its Materials by Design® technology, an “Integrated Computational Materials Engineering” (ICME)-type approach. Both steels are commercially available (Ferrium C61 falls under Aerospace Materials Specification [AMS] number 6517 and Ferrium C64 falls under AMS 6509) and both can significantly reduce rotorcraft weight and manufacturing costs while increasing operational robustness (including gear steel oil-out/high temperature survivability). Ferrium C61 and C64 are new high strength, secondary hardening gear steels that offer different levels of case hardness. These highly-processable steels exhibit excellent hardenability, and were explicitly designed to leverage the advantages of high-temperature vacuum carburization. Ferrium C61 (AMS 6517) exhibits both excellent surface fatigue and core properties (225 ksi yield strength, 240 ksi ultimate tensile strength, 130 ksi•?in fracture toughness), and is a good candidate for integral gear/shaft applications where maximum torque transfer with minimum weight is tantamount. Ferrium C64 (AMS 6509) exhibits excellent surface hardness (62+ HRC after vacuum carburization), with the potential for significantly better surface fatigue performance as compared to incumbent gear steels such as AISI 9310 (AMS 6265) and Pyrowear® Alloy 53 (AMS 6308). The final tempering temperatures of both C61 and C64 (482–510°C) are 200–300°C higher than most incumbent gear steels, providing excellent scoring resistance and superior thermal stability in high-temperature environments and “oil-out” emergency conditions. Rotorcraft applications underway include an evaluation of C64 by Bell Helicopter under the U.S. Army Future Advanced Rotorcraft Drive Systems (FARDS) program, and of C61 for the forward rotorshaft of Boeing’s CH-47 Chinook under a U.S. Army Small Business Innovation Research (SBIR) Phase II project.

Topics: Steel , Gears
Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Gear Dynamics and Noise

2013;():V005T11A010. doi:10.1115/DETC2013-12130.

The purpose of this study was to develop a numerical calculation method for gear system vibration, which changes depending on nonlinear structural components such as bearing clearance and spline contact. The numerical calculation method uses multibody dynamics simulation with the following features: a) the use of theoretical tooth shapes and stiffness to represent the tooth contact of gear pairs, b) the use of finite element models to express the gear system, including the nonlinear structural components causing the variation, c) consideration of the coupled vibration between the tooth contact and gear system. The numerical calculation method allowed the prediction of the variation tendency due to changes in some clearances and spline contacts.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2013;():V005T11A011. doi:10.1115/DETC2013-12284.

Mesh forces of helical gears produce forces and moments in bearings, which generate the housing vibration, and noise radiates. It is difficult to know the noise contribution of a gear box, because the gear box usually has very complex geometry. This work used a cylindrical shell-type gear box with end circular plates to understand the noise and vibration characteristics of a simple gear box and investigated the noise and the vibration of the helical gear box due to the force excitation. The helical gear box of this study consisted of a pairs of helical gears, shafts, bearings, and a gear box. Finite element analysis for the helical gear box calculated mode shapes and natural frequencies and the forced harmonic response by the commercial software. The models were validated by the impact test. Using the forced harmonic response, acoustic analysis was conducted by the commercial software and relations on vibration and noise were discussed.

Topics: Acoustics , Gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A012. doi:10.1115/DETC2013-12438.

This paper concerns the experimental validation of an elastodynamic model of an external gear pump for steering systems in vehicles. The elastodynamic model takes into account the most important phenomena involved in the operation of this kind of machines. Two main sources of noise and vibration can be considered: pressure and gear meshing. An experimental apparatus has been set up for the measurements of the case accelerations and force components in operational conditions. The model was validated by comparison between simulations and experimental results concerning forces and moments: it deals with the external and inertia components acting on the gears, estimated by the model, and the reactions and inertia components on the pump case and the test plate, obtained by measurements. The validation is carried out comparing the level of the time synchronous average in the time domain and the waterfall maps in the frequency domain, with particular attention to identify system resonances. The validation results are globally satisfactory.

Commentary by Dr. Valentin Fuster
2013;():V005T11A013. doi:10.1115/DETC2013-12439.

In this work a combined model for the vibro-acoustic analysis of an external gear pump for automotive applications is presented and experimentally assessed. The model includes a lumped-parameter model, a finite-element model and a boundary-element model. The lumped-parameter (LP) model regards the interior parts of the pump (bearing blocks and gears), the finite element (FE) model regards the external parts of the pump (casing and end plates), while the boundary element (BE) model estimates the noise generation in operational conditions. Attention has been devoted to the inclusion of the oil effect inside the pump casing: the fluid-structure interaction between oil and pump casing was taken into account. The model has been assessed using experiments: the experimental accelerations and acoustic pressure measured in operational conditions have been compared with the simulated data coming from the combined LP/FE/BE model. Eventually, model results and limitations are presented.

Topics: Acoustics , Gear pumps
Commentary by Dr. Valentin Fuster
2013;():V005T11A014. doi:10.1115/DETC2013-12750.

Parameter excited oscillations induced by the varying tooth mesh stiffnesses of the gear pairs cause severe vibration in gear systems. The oscillations become more complex and serious in multi-mesh gear system because more mesh stiffnesses variation occur, which are necessary to be investigated in deeply. To illustrate the complex oscillation phenomena, a 8 degrees of freedom (DOF) non-linear dynamic model of a multi-mesh gear system is developed to study the responses of the system with considering time-varying mesh stiffnesses. Interactions between the mesh stiffness variations at the two meshes are examined. Seven different mesh phases are defined according to the alternating engagement of single and double gear teeth. The effects of different phases of the mesh stiffnesses between the two meshes on the typical multi-mesh gear system are identified by using numerical simulation. The results show that the oscillations of the multi-mesh gear system could be reduced by changing the phase of the mesh stiffnesses.

Commentary by Dr. Valentin Fuster
2013;():V005T11A015. doi:10.1115/DETC2013-12864.

The present paper describes a digitizing method for the measured gear noise and a construction of a neural network system for gear noise diagnosis.

Gear noise emitted from automobile transmissions should be evaluated by gear noise experts. Although quietness performance estimates from measured noise levels of the transmissions on some production lines, the estimation must be very difficult. There is not a certain relationship between the measured noise levels and the evaluations by the gear noise experts. Therefore, the estimation should be severe. As a result, such an automatic gear noise diagnosis system must yield transmissions with over-quality.

The present study deals with a new gear noise diagnosis system to which an artificial intelligence, that is, a neural network system is applied. The previous evaluations by the new gear noise diagnosis system were good when the statistical property of the teacher signals from which the neural network system learned was similar to that of population. This fact means that many teacher signals are necessary on the practical use.

Proposed digitizing method of gear noise levels provided good evaluations of neural network system even when the statistical properties of the teacher signals were not similar to that of the population. In addition, a new method, “Moment method” for determining the construction of the neural network system was introduced instead of “Back Propagation Method”. The Moment Method contributed to the improvement of the system judgments.

The neural network system constructed using the Moment Method brought good performance. And the number of intermediate layers in the neural network system could be small enough to obtain good performance. It was found that the Moment method provided good learning because of connecting weights update function. When the Moment method was used for determining the connection weights between neurons in the neural network system, the developed gear noise diagnosis system achieved high and stable correct answer ratio. And the number of intermediate layers in the neural network system was only one enough for obtaining good performance of the system. Four intermediate layers, which was the maximum in this paper, did not provide much good performance.

Commentary by Dr. Valentin Fuster
2013;():V005T11A016. doi:10.1115/DETC2013-12890.

Differential hypoid gears play an important role on the Noise, Vibration and Harshness (NVH) signature of vehicles. Additionally, friction developed between their teeth flanks under extreme loading conditions adds another source of power loss in the drivetrain which can mitigate vibrational energy. The paper considers the coupling between dynamics and analytical tribology to study dynamic response of hypoid gear pairs with lateral motion of support shafts also included in the analysis framework. Friction of teeth flank pairs is assumed to follow elastohydrodynamic lubrication under elliptical point contact geometry with lubricant film behavior conforming to Non-Newtonian thermal shear, also with surface asperity interactions. Tooth Contact Analysis (TCA) has been used to obtain the input data required for the investigation. The dynamic behavior and efficiency of a differential hypoid gear pair under realistic operating conditions is determined. The proposed tribo-dynamic framework provides a useful platform to conduct an extensive series of parametric studies.

Commentary by Dr. Valentin Fuster
2013;():V005T11A017. doi:10.1115/DETC2013-13275.

This paper is based on Honda product development and maturation related to noise and vibration. During the development, it was discovered that the vibration level of the vehicle did not meet the desired level.

These studies are aimed to reduce the noise and vibration felt in vehicle by improving the powertrain as the main source of the vibration. During the investigation, it was discovered that manufacturing process change from tooth shaving to tooth honing could have significant impact on the final tooth profile that essentially impact the noise and vibration level of the vehicle.

The studies focus on bias control to improve the vibration level. This paper will show complete relationship between actual gear profile, vibration level of unit as powertrain, and finally airborne noise level of the complete vehicle as the final product. The studies resulted in shifting bias control target for the gear tooth profile, which translates to improved noise and vibration level in vehicle.

Topics: Gears , Vehicles
Commentary by Dr. Valentin Fuster
2013;():V005T11A018. doi:10.1115/DETC2013-13594.

From the existing experimental results and previous studies, the torque load has great influence on the mesh and dynamic characteristics of hypoid gear drive. To have more insights on the load dependent mesh parameters and dynamic response of hypoid and spiral bevel gear, a load dependent mesh model is developed by using 3-dimensional loaded tooth contact analysis (LTCA). The contact ratio and time-varying mesh parameters including the mesh stiffness, transmission error, mesh point and line-of-action of the mesh force are examined within a wide torque range. Then a nonlinear multi-body dynamic analysis is performed considering the effect of backlash nonlinearity. Simulation results show that the contact ratio and mesh stiffness generally increases as the toque load increases. The effect of torque load on dynamic mesh force is found to be frequency dependent due to the resonance frequency shifts and peak magnitude changes. This study provides an in-depth understanding of hypoid gear tooth load sharing and dynamic behaviors in terms of change in operating load. Therefore, the proposed model can be employed to assist in gear design optimization.

Topics: Torque , Stress
Commentary by Dr. Valentin Fuster
2013;():V005T11A019. doi:10.1115/DETC2013-13650.

Being compact and efficient power transmissions, planetary gears are widely used in helicopters, wind turbines and spacecraft. Due to the nonlinearity introduced by the combination of backlash and different teeth damage at different locations, however, the complicated dynamic behaviors of the planetary gears are less understood and investigated. Unfortunately, since the dynamic behavior of the system is highly dependent on the changing point-to-point contact forces between gear pairs, it is nearly impossible to simulate a damaged planetary gear with theoretical models. Therefore, very few research results are published. In this paper, a practical two-stage planetary gear with various types of teeth damage is designed using CAD and analyzed with the multi-body dynamics software ADAMS. The region of point-to-point contact along the involute profile is modeled elastically and accounts for teeth flexibility. Several important parameters such as the stiffness, force exponent, penetration depth, and damping coefficients are carefully chosen based on practical modeling experience. Constraints, bearing resistant torques, and some key parameters are applied to emulate realistic operation conditions. Comprehensive frequency-domain analysis of dynamic contact forces will reveal unique vibration spectra called modulated sidebands, at distinct frequencies around the stage mesh frequencies, and sub- and super-synchronous frequencies. These spectral lines comprise a substantial portion of the vibration and are closely related to the complicated nonlinear dynamics induced by the interaction between backlash and damaged teeth at different locations on different components of the transmission system. The results may serve as the useful fault indicators of the planetary gears. In addition, joint time-frequency analysis (JTFA) is performed on the two-stage damaged planetary gear analysis based on transient start-up conditions, and demonstrates how the frequency content of the contact force evolves over time. As an effective detection tool utilized by industry, JTFA health monitoring is simulated for the first time using a damaged two-stage planetary gear in this paper.

Commentary by Dr. Valentin Fuster
2013;():V005T11A020. doi:10.1115/DETC2013-13676.

The main purpose of the supercharger timing gears is to keep the rotors from contacting each other. They are often lightly loaded and designed for low noise. As timing gears, they have by definition a ratio of 1.0. Furthermore, the timing gears are presently spur gears due to the cost of assembling helical gears onto the rotor shafts without allowing timing errors between the rotors. The original timing gear designs were spur gears with contact ratios slightly above 2.0. A major NVH issue has been gear whine noise, because most applications are in luxury vehicles and are evaluated with the hood open and the engine at idle. In this operating condition, the background noise is very low and any tonal gear whine noise is audible. The first effort was to push the gear manufacturing quality to the limits of modern grinding capability. In order to further reduce gear whine noise, the designs have evolved to finer pitch gearing with a contact ratio over 3.0 to reduce transmission error. Micro-geometries were optimized for low transmission error (TE) at low load. OSU Gear Lab’s RMC and LDP became primary tools in optimizing the gear designs for minimum TE. An important factor when increasing the contact ratio is to not increase the sliding friction significantly to keep the fixed oil sump temperature from increasing too much and cause wear issues in operation. Typically, the new high contact ratio spur gear designs in production have reduced the gear whine levels by more than 6 dB and have had very few noise complaints.

Commentary by Dr. Valentin Fuster
2013;():V005T11A021. doi:10.1115/DETC2013-13678.

The effect of preload torque on planetary gear behavior is investigated with experiments and mathematical models. Natural frequencies, mode shapes, and damping are influenced by mean torque levels. Natural frequencies increase with greater torque. Damping increases in some modes and decreases in others. The mode shapes undergo various changes as torque increases as demonstrated in the trajectory of a planet gear in a high frequency mode. A finite element bearing model is used to obtain the load dependent stiffness of the planet bearings, and these values greatly increase the accuracy of a lumped parameter model in predicting the natural frequencies measured in experiments.

Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Gear Geometry

2013;():V005T11A022. doi:10.1115/DETC2013-12222.

Tooth surface modifications are small, micron-level intentional deviations from perfect involute geometries of spur and helical gears. Such modifications are aimed at improving contact pressure distribution, while minimizing the motion transmission error to reduce noise excitations. In actual practice, optimal modification requirements vary with the operating torque level, misalignments, and manufacturing variance. However, most gear literature has been concerned with determining optimal flank form modifications at a single design point, represented by fixed, single load and misalignment values. A new approach to the design of tooth surface modifications is proposed to handle such conditions. The problem is formulated as a robust design optimization problem, and it is solved, in conjunction with an efficient gear contact solver (LDP), by a direct search, global optimization algorithm aimed at guaranteeing global optimality of the obtained micro-geometry solutions. Several tooth surface modifications can be used as micro-geometry design variables, including profile, lead, and bias modifications. Depending on the contact solver capabilities, multiple performance metrics can be considered. The proposed method includes the capability of simultaneously and robustly handling several conflicting design objectives. In the present paper, peak contact stress and loaded transmission error amplitude are used as objective functions (to be minimized). At the end, two example optimizations are presented to demonstrate the effectiveness of the proposed method.

Commentary by Dr. Valentin Fuster
2013;():V005T11A023. doi:10.1115/DETC2013-12231.

Beveloid gears are widely applied in fields like ships, automobiles and industrial precision transmissions. In this paper, the formulas of the beveloid gear tooth surface used in marine transmissions were derived and a mesh model for the intersected beveloid gear pair was setup. Then loaded tooth contact analysis was performed using the finite element method considering the coupling of the assembly errors and the elastic deformation of tooth surface. Through the analysis, the influences of assembly errors on contact patterns, mesh force and tooth surface deformations were investigated. In a further step, the tooth profile modifications were performed to alleviate the edge contact and a subsequent major improvement of the mesh condition was obtained. Finally, loaded tooth contact experiments for marine gearboxes with small shaft angle were conducted. The tested results showed good correlation with the computed results. This work may provide some value for the practical design aiming at improved contact characteristics of the beveloid gears with intersected axes.

Topics: Gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A024. doi:10.1115/DETC2013-12234.

Hyperboloid drives (spatial skew-axes gears) are used to transform rotation between shafts with non-parallel and non-intersecting axes. In this paper the principles of mathematical modelling of a tooth contact synthesis for this common gearing case are discussed. The presented research shows that synthesis of hyperboloid gear drives can be achieved by application of mathematical model upon a pitch contact point. This approach is applied to the synthesis of spatial gear sets of Spiroid and Helicon types.

Commentary by Dr. Valentin Fuster
2013;():V005T11A025. doi:10.1115/DETC2013-12566.

A mathmatical model of generating face-gear by grinding disk is developed. The influence of all kinds of errors of alignment and profile on face-gear flank deviation is considered and investigated in this model, such as offset error and pressure angle error of grinding disk, location error of virtual pinion axis. A optimization method for decreasing flank deviation is proposed. The corresponding correction parameters of machine which can be used for manufacturing face gear can be computed by this optimization method. In this method, the square sum of tooth surface deviation is taken to be the objective function. A grinding experiment of face-gear is performed on a CNC grinding machine with five degrees of freedom, and the tooth flank deviation is measured on gear measuring center. The flank deviation is very large due to some alignment errors in the beginning. When the grinding machine is adjusted by optimization computation results mentioned above, the measurement results show that the deviation of grinded face-gear flank is reduced substantially. The benefit is to improve the grinding quality of face-gear by this method.

Topics: Simulation , Grinding , Gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A026. doi:10.1115/DETC2013-12637.

This paper describes the research and development of asymmetric tooth spur gears for modernization of the light multipurpose helicopter gearbox amplifying its load capacity to utilize more powerful turboshaft engines.

The paper also presents numerical design data related to development this gearbox.

Commentary by Dr. Valentin Fuster
2013;():V005T11A027. doi:10.1115/DETC2013-12837.

This paper investigates the contact ellipse and contact stress of a modified curvilinear gear set with localized bearing contact. The proposed modified curvilinear gear set with profile modifications was generated by male fly cutters with a circular-arc normal section. This gear drive exhibits point contact and parabolic transmission error under an ideal meshing condition according to the results of tooth contact analysis. The principal directions and curvatures of the mating pinion and gear surfaces were derived from those of the generating surfaces on the basis of differential geometry and theory of gearing. The Hertzian contact stress and contact ellipses of the mating tooth surfaces were determined with our developed computer program based on formulae of curvature analysis and Hertzian contact theory. Numerical examples were also provided to demonstrate the computational results.

Topics: Stress , Bearings , Gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A028. doi:10.1115/DETC2013-13401.

This paper presents a new conjugation theory and a new design methodology for the advanced conjugation design based on CAD (computer aided design) and CAE (computer aided engineering). A general conjugation theory called manifold conjugation is established based on the classic conjugation theory and manifold theory. It leads to both smooth conjugation modeling and discrete conjugation modeling. The former one has been studied in the previous work for design optimization of analytical conjugation properties. The latter one is a desirable methodology for the conjugation design based on CAE simulation. The paper brings up a new perspective towards conjugation representation theory, leading to a new design process. Contrary to the traditional idea that CAD has to be known before and separated from CAE, the new theory suggests using discrete manifold to bridge CAD and CAE. Furthermore, discrete modeling techniques from CG (computer graphics) such as subdivision can be employed for conjugation modeling and design. Two planar examples that minimize gear PPTE (peak to peak transmission error) show that the methodology is capable of and effective in conjugation optimization.

Topics: Design , Gears , Manifolds
Commentary by Dr. Valentin Fuster
2013;():V005T11A029. doi:10.1115/DETC2013-13409.

This paper rigorously presents a new theory called compensated conjugation for gear transmission error balance. The proposed theory is a systematic study based on conjugation equation and transmission function. The basic idea is that conjugation is essentially impaired by loading condition but can be compensated by modifying transmission function. In contrast to the traditional method which is mainly applicable for planar involute gears, the new idea generally applies for all conjugation types based on the same concept of transmission. Multiple Concepts of conjugation and transmission are rigorously modeled and defined by screw theory. A theorem about the continuity of motion and conjugate geometries is presented and proved in order for desirable modification. The proposed theory is consistent with the standard manufacturing process for tooth modification. Tooth geometries and cutter geometries can be obtained after the theoretical transmission error function is designed. For the most important application — planar involute gear design, a practically convenient method with a direct rack-cutter modification is proposed and rigorously analyzed by kinematics and differential geometry. Examples show the effectiveness of the methodology.

Commentary by Dr. Valentin Fuster
2013;():V005T11A030. doi:10.1115/DETC2013-13687.

In the last few decades in Hungary, the Budapest University of Technology and Economics and the University of Miskolc have been intensively focusing on the research field of worm gear drives [2, 5].

Our results at the University of Miskolc have also been published in a book published in the USA as well [2].

A new geometric worm gear drive has been developed, that is the conical worm gear drive having arched profiled in axial section [3].

The aim of our publication is to present the advantages, the geometric questions and the possible application fields of this new type worm gear drive.

Topics: Worm gears
Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Gear Wear

2013;():V005T11A031. doi:10.1115/DETC2013-12335.

Gear pair dynamic loads can increase significantly with involute profile changes caused by wear resulting in vibration and noise issues. Tooth stresses such as root stress and contact stress can also increase reducing gear life. Wear prediction is important during the design phase to minimize the effects of worn tooth surfaces on product performance. Some analytical models have been proposed to predict gear tooth wear; however published correlations of predictions with experimental results are still limited, especially from the gear industry. But they are vital to build confidence in analytical tools. This paper presents a correlation of wear predictions with experimental results of spur and helical gear pairs that are used in commercial vehicle transmissions. Four different gear lubricants were considered, and also three tooth finishes, grinding, honing, and shaving. A modified Archard’s wear model was used for wear predictions. The model combines a gear contact model and an iterative numerical procedure to account for tooth surface changes. Wear coefficients were determined from experiments. The correlation between predictions and dynamometer testing data was established.

Commentary by Dr. Valentin Fuster
2013;():V005T11A032. doi:10.1115/DETC2013-12748.

Gear drives are widely used in various mechanical systems. Therefore, the understanding for the failure mode of gear tooth provides the improvement of various machines. The wear on the tooth surface is one of the important failure modes for the gear drives. The tooth wear changes its profile, and frequently increases gear vibration and noise. However, there are many unclear phenomena about the wear on the tooth surface for the gear drive. In this study, we investigated wear of spur gear using a power circulating-type gear testing machine, and measured the change in tooth profile of the test gears. Furthermore, we developed a computer program to predict the amount of the wear on the tooth surface for the spur gears. The method employs two equations. One is based on the wear theory under lubricated condition that was deduced by Soda. The other is derived from the ploughing wear model. Using these equations, the wear depth on the tooth surface is calculated with the contact stress, the sliding velocity, the oil film thickness, etc. The calculated value of the wear agreed with the experimental data.

Topics: Wear , Spur gears
Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Gearbox Design, Reliability, and Diagnostics

2013;():V005T11A033. doi:10.1115/DETC2013-12361.

Seeded fault experiments were conducted on the planetary stage of an OH-58C helicopter transmission. Two vibration based methods are discussed that isolate the dynamics of the sun gear from that of the planet gears, bearings, input spiral bevel stage, and other components in and around the gearbox. Three damaged sun gears: two spalled and one cracked, serve as the focus of this current work. A non-sequential vibration separation algorithm was developed and the resulting signals analyzed. The second method uses only the time synchronously averaged data but takes advantage of the signal/source mapping required for vibration separation. Both algorithms were successful in identifying the spall damage. Sun gear damage was confirmed by the presence of sun mesh groups. The sun tooth crack condition was inconclusive.

Topics: Vibration , Sun gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A034. doi:10.1115/DETC2013-12708.

Most research work has been performed within laboratory environments with seeded defects or accelerated testing and there is little published in the public domain on in-service defects with operational helicopter HUMS data. This study focuses on the actual service experience gathered from HUMS equipped AH64D helicopter belonging to the Republic of Singapore Air Force. Operational HUMS data from three helicopters with similar in-service defects found on their Tail Rotor Gearbox are analyzed and correlated with tear-down inspection findings. From analysis of the HUMS vibration spectrum, fault patterns which show the progression from localised to generalised damage in the bearing can be observed consistently across the defective gearboxes. The observed fault patterns are extracted as Condition Indicators (CI) to diagnose the different stages of bearing degradation within the gearbox. As the defects between the gearboxes are similar, the historical trends of the extracted CIs are used to developed prognostic model using parameter estimation approach.

Commentary by Dr. Valentin Fuster
2013;():V005T11A035. doi:10.1115/DETC2013-12761.

Innumerable solutions can be obtained when the pitch surface of a hypoid gear is solved from the requirements of two cones. The pitch angle is determined by the Gleason method based on the idea that the tooth lengthwise curvature corresponds to the cutter radius. This study proposes a new design method that can optimize the contact ratio using the pitch angle, using the new tooth geometry advocated by Honda. The balance of the contact ratios of the convex and concave sides of a gear can be optimized by designing the pitch angle. By optimizing the contact ratio, noise and vibration performance can be improved. In addition, highly efficient gear design can be achieved by decreasing the spiral angle.

The effectiveness of this optimized design method is confirmed by measuring transmission errors under load. Design examples of a highly efficient gear by reducing the spiral angle and a gear which ensures high noise and vibration performance are shown. Using this proposed method expands the design freedom of hypoid gears.

Commentary by Dr. Valentin Fuster
2013;():V005T11A036. doi:10.1115/DETC2013-12993.

We developed a new diagnostic method by using a laser beam. This method is as follows: A tooth surface is irradiated by the zonal laser beam from an oblique direction, and then the irradiated laser beam line is shifted along the surface of the tooth according to gear rotation. If the damage on the irradiated tooth surface exists, the voltage proportional to laser reflection increases. We developed the method to predict and make the reflection benchmark on the normal condition according to the gear surface. To make the benchmark of the diagnosis, the three dimensional basic-data map (x: irradiated angle, y: irradiated distance, z: reflection intensity) was created by measuring the gear only whose material, heat treatment, and roughness were same as the targeted gear. By using the equations of tooth profile and fillet curves calculated from the specifications of the targeted gear, the distance and angle relations between the laser sensor and the tooth surface can be derived. By using the three dimensional basic-data map, the benchmark can be created. The measured reflection data of the non-damage gear agreed well with the benchmark, therefore we can diagnose the various specification gears, if the targeted gear’s material, heat treatment, and roughness are same. Finally, by using the benchmark which was made by our developed method, we proposed a novel diagnosis method. The procedure of the method is as follows:

1) The benchmark is made from the targeted gear’s specifications.

2) To take into account the fluctuation of the benchmark line influenced by the roughness on the gear surface, normal condition area of the reflected data is defined in the range between −0.05 V and +0.05 V of the benchmark line.

3) The normal condition area and measured data is compared, if the measured data is deviated from the normal condition area, there is defined as the abnormal area possible to be damaged.

To confirm the validity of this diagnosis method, the measured value of the damage area with caliper directly and calculated value from the method as mentioned above. The errors of the area and the location were within 20 %. Therefore, the effectiveness of the method using the benchmark data can be confirmed.

Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Lubrication and Efficiency

2013;():V005T11A037. doi:10.1115/DETC2013-12080.

In this study, an optimization methodology is proposed to systematically define optimal tooth modifications introduced by head-cutter geometry and machine tool settings to minimize the influence of misalignments on EHD lubrication characteristics in face-hobbed spiral bevel gears. The goal is to simultaneously maximize the EHD load carrying capacity of the oil film and to minimize power losses in the oil film when different misalignments are inherent in the gear pair. The proposed optimization procedure relies heavily on the EHD lubrication analysis developed by the author of this paper. The core algorithm of the proposed nonlinear programming procedure is based on a direct search method. Effectiveness of this optimization was demonstrated on a face-hobbed spiral bevel gear example. Drastic increase in the EHD load carrying capacity of the oil film and reduction in the power losses in the oil film were obtained.

Commentary by Dr. Valentin Fuster
2013;():V005T11A038. doi:10.1115/DETC2013-12182.

The emissions of CO2 worldwide are actually an often discussed topic. To reduce these emissions, gear boxes offer several starting points. There are possibilities for loss reduction in gears, bearings and oil supply. Load dependent gear losses provide a big potential to improve efficiency at operating points with high load. At no-load, bearings, oil viscosity and oil supply can be optimized.

Aim of this study was the reduction of losses in power trains by about 30%. Main target of this project was the experimental investigation and verification of measures for loss reduction within one optimized gear box. Several approaches were combined for that.

Load-dependent gear losses can be reduced by about 60% by using lowloss gears. In this case, basic idea is to concentrate the gear contact around the pitch point for lower sliding speeds. Different surface topologies were investigated. These were manufactured by deterministic laser structuring, grinding or superfinishing. Especially for running conditions at low speed power loss reduction could be achieved by very smooth superfinished tooth flank surfaces. Reduction of power losses could also be reached by applying diamond like carbon (DLC) coatings. Loss savings by DLC coatings were measured especially at higher speeds with thick surface separating lubricant films. This is caused by a thermal isolation effect of coatings.

Topics: Gears
Commentary by Dr. Valentin Fuster
2013;():V005T11A039. doi:10.1115/DETC2013-12329.

New regulations make it imperative that the European and US automotive industries meet strict, lower greenhouse gas emission standards. It is well documented that isotropic superfinishing automotive rear axle gears can play a significant role in reducing these emissions. Rear axle gears have been commercially isotropic superfinished using conventional vibratory finishing for many years, but this process has often been viewed as being too expensive and cumbersome for large-scale automotive production. After five years of development and testing, the drag finishing process has been perfected to a point that rear axle gears can be isotropic superfinished economically in a matter of minutes. The gears are rapidly mounted and dismounted to the machine via magnetic fixturing making this equipment amenable to full robotic operation.

This paper will give details on the reduction of greenhouse gas emissions by isotropic superfinishing, the drag finishing machine, the magnetic fixture of the rear axle gears, the achievable surface finish, and the superfinishing cycle time.

Topics: Gears , Emissions
Commentary by Dr. Valentin Fuster
2013;():V005T11A040. doi:10.1115/DETC2013-12872.

The present work is focused on the theoretical study of the performance of journal bearing operating under steady state condition, with particular emphasis on the influence of lubricant supply arrangements. In this paper the influence of the location of the grooves with respect to the load line and influence of groove dimensions on the performance parameter were investigated. The optimum location of the groove axis lies between 60° to 90° to the load line. It is also concluded that smaller groove length yielded lower load carrying capacity.

Commentary by Dr. Valentin Fuster
2013;():V005T11A041. doi:10.1115/DETC2013-13192.

A new fluid dynamics model is proposed to predict the power losses due to pocketing of air, oil, or an air-oil mixture in the helical gear meshes. The proposed computational procedure treats a helical gear pair as combination of a number of narrow face width spur gear segments staggered according to the helix angle and forms a discrete, fluid dynamics model of the medium being pocketed in the gear mesh. Continuity and conservation of momentum equations are applied to each coupled control volume filled with a compressible fluid mixture to predict fluid pressure and velocity distributions from, which the instantaneous pocketing power loss is calculated. The proposed model is exercised in order to investigate fluid pressure and velocity distributions in time, as well as pocketing power loss as a function of speed, helix angle and oil-to-air ratio.

Topics: Helical gears
Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Special Power Transmission Topics With Panel Discussion

2013;():V005T11A042. doi:10.1115/DETC2013-13039.

Windage losses in gearboxes account for a large portion of the total power loss in high-speed drive trains. Very little actual data has been collected specifically quantifying these losses. Traditional techniques to measure the effects of baffles in high speed gearing applications have been done by trial and error on very complex systems. This trial and error technique is used throughout the gearing industry to solve problems without isolating each individual gear windage effect. These solutions are usually sub-optimum. They cause time-consuming delays and cost overruns in many programs. This paper describes two gear baffle test rigs that were built to quantify and minimize the gear windage losses in high-speed drive trains. The intent of the first gearbox baffle test rig was to isolate and measure the windage effects on a single high-speed bevel gear with various baffle configurations. The results of these tests were used to define a basic set of ground rules for designing baffles. This set of ground rules was then applied to another rig replicating the F-35 Liftfan gear box configuration. Immediate benefits were seen. Without this work Lockheed Martin’s X-35 STOVL aircraft would not have been able to operate.

Topics: Hardware , Gears
Commentary by Dr. Valentin Fuster

ASME 2013 Power Transmission and Gearing Conference: Transmission Systems Including Novel Concepts

2013;():V005T11A043. doi:10.1115/DETC2013-12089.

The open rotor engine is a next generation aero-engine that satisfies the demand for high fuel efficiency and low CO2 emission. A differential planetary gear system is incorporated in the open rotor engine to connect the turbine output shaft and fan rotors in order to counter-rotate the fan rotors as well as allow the turbine and fan rotors to operate at more efficient speeds. The open rotor gear system is required to have not only 20,000 hp high power transmission, but also an increasingly high efficiency, high reliability and light weight. To achieve these requirements, the following design works were conducted; (1) a low misalignment and lightweight carrier, (2) a flexible structure to absorb the displacement caused by the flight load, (3) an optimum gear tooth modification and (4) reduction of oil churning and windage losses. Also, extensive analyses and simulations such as lube oil flow CFD, FEA and tooth contact analysis were conducted. A full scale prototype gear system was manufactured and validation tests were conducted using a newly constructed test rig to validate the design concept. A slow roll test, rated performance test and efficiency test were conducted. And the design concept was found to be valid. This paper describes details of the prototype design and the results of the validation tests.

Commentary by Dr. Valentin Fuster
2013;():V005T11A044. doi:10.1115/DETC2013-12220.

Increasing power density is an on-going objective for engineers of fixed wing and rotary wing aircraft. The powertrain system is one of the largest contributors to the total mass of the aircraft and the geartrain is the largest contributor to the mass of the powertrain system. As such, the geartrain becomes the primary focus of many power density studies and is the focus of this paper.

Epicyclic geartrains are known to provide high power density and have become the geartrain of choice for the main power flow in virtually all aircraft designs. This paper presents a unique compound planetary design targeting a helicopter main gearbox transmission application. The design significantly improves power density through its innovative planet gear load-sharing configuration along with the utilization of high-performance materials for gears and bearings. Design studies were conducted comparing the power density of this new design to a baseline gearbox design. The results of these studies demonstrate an estimated 38% power density improvement over the baseline configuration. Of the total improvement, 86% is attributed to the novel load-sharing configuration while 14% is attributed to utilization of advanced materials and processes.

Commentary by Dr. Valentin Fuster
2013;():V005T11A045. doi:10.1115/DETC2013-12458.

High turbine reliability is of utmost importance to keep the cost of wind energy to a minimum. A considerable problem in this regard is that of premature drivetrain failures, which have plagued the wind turbine industry since its inception. Accurate prediction of the loads encountered by the drivetrain components during their lifetime is essential for reliable wind turbine design. Of particular interest are transient load events, which are expected to have a detrimental effect on the lifetime of drivetrain components, especially when they give rise to torque reversals. At the electrical side of the wind turbine, transient events worth investigating include grid faults, emergency stops and grid loss. Unlike previous research on the impact of these events, which typically uses simplified gearbox representations, this paper investigates the dynamic behavior of wind turbine drivetrains during grid faults using a coupled simulation of a flexible multibody model of a commercial multimegawatt wind turbine drivetrain and a Simulink model of a doubly fed induction generator (DFIG) and its controller. The mathematical modeling of the DFIG as well as the flexible multibody modeling of the drivetrain are described. Both gear and bearing forces on several components of the gearbox are examined during a symmetrical and asymmetrical voltage dip, and the influence of gearbox flexibility on these loads is assessed.

Commentary by Dr. Valentin Fuster
2013;():V005T11A046. doi:10.1115/DETC2013-12538.

Load balancing mechanism is an important design for planetary gear drives. Among the well-known designs the flexible pin mechanism has advantage for even load sharing among more than three planet gears. However, there is no sufficient information about how to design such mechanisms. The goal of the paper is to propose an analysis approach of flexible pin mechanisms for planetary gear drives numerically and experimentally. Two types of flexible pin mechanisms are analyzed in the study, a conventional design and a novel design. Numerical analysis is carried out by software KISSsoft and FEM to evaluate the influence of the design parameters of flexible pin mechanism on the deformation performance. An experiment was finally conducted to verify the analysis results.

Commentary by Dr. Valentin Fuster
2013;():V005T11A047. doi:10.1115/DETC2013-13638.

The Wind Turbine Gearboxes (WTGs) are highly subjected to variable torsional and non-torsional loads. In addition, the manufacturing and assembly process of these devices results in uncertainty in the system. These gearboxes are reported to fail in their early life of operation, within three to seven years as opposed to the expected twenty years of operation. Their downtime and maintenance process is the most costly of any failure of subassembly of wind turbines. The objective of this work is to perform a probabilistic multibody dynamic analysis (PMBDA) of the high-speed-parallel-helical stage of the gearbox of wind turbine that considers uncertainty of generator side torque loading and the input shaft speed, assembly errors and design parameter uncertainty. System reliability, probability of failure, and probabilistic sensitivities of all the input variables towards several performance functions have been measured and conclusions have been drawn. PMBDA has demonstrated a new dimension of design and installation of wind turbine gearboxes than traditional deterministic approach. In addition to revealing system reliability or under-performance through probability of failure, the method will also help designers to consider certain variables critically through the sensitivity results.

Commentary by Dr. Valentin Fuster

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