ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V012T00A001. doi:10.1115/IMECE2018-NS12.

This online compilation of papers from the ASME 2018 International Mechanical Engineering Congress and Exposition (IMECE2018) 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presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Materials: Genetics to Structures: Bioinspired Materials, Structures, and Applications

2018;():V012T11A001. doi:10.1115/IMECE2018-86309.

Additive manufacturing technology has significantly matured over the last two decades. Recent progress in 3D printing has made it an attractive choice for fabricating complex shapes out of select materials possessing desirable properties at small and large scales. The application of biomimetics to the fabrication of structural composites has been shown to enhance their toughness and dynamic shear resistance. Building homes from bioinspired composites is possible if the process is automated. This can be achieved through additive manufacturing where layers of hard and soft materials can be deposited by 3D printing. This study examines mechanical properties of reinforced concrete fabricated by 3D printing. Preliminary results of 4-point bend tests are presented and the implications of 3D-printed home building on current conventional construction practices are discussed.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Fracture and Damage: Nano- to Macro-Scale

2018;():V012T11A002. doi:10.1115/IMECE2018-86417.

Corrosion fatigue growth behavior of structural steels at low cyclic frequency is characterized by an increase in crack growth rate in the threshold and Paris regions, due to the simultaneous action of cyclic mechanical load (fatigue) and corrosive environment. Knowledge on the effect of load sequence on corrosion fatigue crack growth is important to set out the realistic design and prognosis criteria for components operating under corrosive environments.

In this study, the corrosion fatigue crack growth rate under the effect of hold-time (1000s), at a maximum stress intensity factor (Kmax), interspersed during cyclic load on was studied experimentally on a Mn-Ni-Cr steel under 3.5% NaCl solution at a constant stress intensity factor range (ΔK) of 15 MPa √m; the corrosion crack growth rate was evaluated for three different frequencies of: 0.01, 0.1 and 1 Hz. As a result of hold time at the peak load, the exposure time for the crack-tip to interact with the environment increased, which could enhance the corrosion crack growth rates. To verify if this corrosion effect can be contained, electrode potential of (−) 850 mV and (−) 950 mV SCE was applied to the specimen to reduce the extent of corrosion contribution to crack growth rate.

The fatigue crack growth rate (da/dN) increased when the frequency was decreased from 1 to 0.01 Hz at all electrode potentials. However, the crack growth rate at 0.01 Hz increased by an order of magnitude with a tensile hold at Kmax for 1000 s compared with the crack growth rate during continuous cyclic load for a given electrode potential. The crack growth rate reduced when the electrode potential was decreased to −950 mV SCE. The enhancement of corrosion fatigue crack growth rate with the introduction of a hold-time is explained using crack-tip strain rate assisted anodic dissolution.

Commentary by Dr. Valentin Fuster
2018;():V012T11A003. doi:10.1115/IMECE2018-86650.

Healing technology for metallic materials is an important subject in terms of long-term reliability and durability of structural members, a healing technology to heal fatigue crack by applying heat treatment at annealing temperature level has been discovered. In this study, the influences of plasticity-induced crack closure on healing were evaluated by obtaining the crack opening load during the pre-crack introduction and evaluating the fatigue crack propagation characteristics before and after the healing heat treatment, using compact tension specimens made of carbon steel with different test conditions. As a result, the specimen with high crack opening load showed high healing effect and were able to heal up to 95% of the pre-crack length. This suggested that the residual compressive stress due to the plasticity-induced crack closure accelerates the solid-state diffusion bonding during the crack healing process and this leads to the improvement of the healing effect.

Commentary by Dr. Valentin Fuster
2018;():V012T11A004. doi:10.1115/IMECE2018-87264.

Various brittle fractures have been found to occur at grain boundaries in polycrystalline materials. In thin film interconnections used for semiconductor devices, open failures caused by electro- and strain-induced migrations have been found to be dominated by porous random grain boundaries that consist of a lot of defects. Therefore, it is very important to explicate the dominant factors of the strength of a grain boundary in polycrystalline materials for assuring the safe and reliable operation of various products.

In this study, both electron back-scatter diffraction (EBSD) analysis and a micro tensile test in a scanning electron microscope was applied to copper thin film which is used for interconnection of semiconductor devices in order to clarify the relationship between the strength and the crystallinity of a grain and a grain boundary quantitatively. Image quality (IQ) value obtained from the EBSD analysis, which indicates the average sharpness of the diffraction pattern (Kikuchi pattern) was applied to the crystallinity analysis. This IQ value indicates the total density of defects such as vacancies, dislocations, impurities, and local strain, in other words, the order of atom arrangement in the observed area in nano-scale. In the micro tensile test system, stress-strain curves of a single crystal specimen and a bicrystal specimen was measured quantitatively. Both transgranular and intergranular fracture modes were observed in the tested specimens with different IQ values.

Based to the results of these experiments, it was found that there is the critical IQ value at which the fracture mode of the bicrystal specimen changes from brittle intergranular fracture at a grain boundary to ductile transgranular fracture in a grain. The strength of a grain boundary increases monotonically with IQ value because of the increase in the total number of rigid atomic bonding. On the other hand, the strength of a grain decreases monotonically with the increase of IQ value because the increase in the order of atom arrangement accelerates the movement of dislocations. Finally, it was clarified that the strength of a grain boundary and a grain changes drastically as a strong function of their crystallinity.

Commentary by Dr. Valentin Fuster
2018;():V012T11A005. doi:10.1115/IMECE2018-87278.

Electroplated gold thin films have been used for micro bumps in flip chip packing structures. However, it has been reported that physical properties and micro texture of the electroplated thin films vary drastically comparing with those of conventional bulk material, depending on their electroplating process. In addition, since one bump is going to consist of a few grains or a single grain due to the miniaturization of the 3D structures, it shows strong anisotropic mechanical properties because a face-centered cubic crystal essentially has strong anisotropy of physical properties. Therefore, there should be the wide distribution of characteristics of the micro bumps depending on their micro structure and the variation of the crystallinity of grains and grain boundaries enlarges the width of the distributions of various properties. Particularly, it was found that the long-term reliability of micro bumps and interconnections is degraded drastically by porous grain boundaries with a lot of defects because of the acceleration of atomic diffusion along the porous grain boundaries under the application of high current density (electromigration) and high mechanical stress (stress-induced migration).

In this study, the effect of crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films on the EM resistance was investigated experimentally. The crystallinity of the gold thin films was varied drastically by changing the under-layer material used for electroplating; such as Cr (30 nm) / Pt (50 nm)/ Au (200 nm) and Ti (50 nm) / Au (100 nm). The mechanical properties of the electroplated gold thin films were measured by using a nano-indentation test. Also, the micro textures such as crystallinity and crystallographic orientation of gold thin films were investigated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and heat treatment conditions after electroplating. This variation of the crystallinity should have caused the wide variation of mechanical properties of the electroplated gold films. Therefore, it is very important to control the crystallinity of the under layer used for electroplating in order to control the mechanical properties and reliability of the electroplated gold thin films.

Topics: Thin films
Commentary by Dr. Valentin Fuster
2018;():V012T11A006. doi:10.1115/IMECE2018-88403.

Self-piercing riveting (SPR) is a key joining technique for lightweight materials, and it has been widely used in the automobile manufacturing. However, complex process parameters and huge configurations of substrate materials can cause potential button cracks, which bring significant challenges for quality inspection. This paper presents a failure crack detection and evaluation method based on image processing. Firstly, the SPR rivet cracks image is preprocessed through gray-scale transformation and interested area selection; next, the binary crack image is utilized to identify the crack parameters; finally, a crack evaluation method is developed to evaluate the rivet crack quality with quantized scores. In addition, subject matter experts (SME)’ knowledge is incorporated to verify the crack detection and quality evaluation, and case study is conducted to demonstrate feasibility of the proposed method.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Material Processing of Flexible Electronics, Sensors, and Devices

2018;():V012T11A007. doi:10.1115/IMECE2018-86263.

This paper presents the additive manufacturing of electrically conductive polydimethylsiloxane (PDMS) nanocomposites for in-situ strain sensing applications. A straight line of pristine PDMS was first 3D printed on a thin PDMS substrate using an in-house modified 3D printer. Carbon nanotubes (CNTs) were uniformly sprayed on top of uncured PDMS lines. An additional layer of PDMS was then applied on top of CNTs to form a thin protective coating. The 3D printed PDMS/CNT nanocomposites were characterized using a scanning electron microscope (SEM) to validate the thickness, CNT distribution, and microstructural features of the sensor cross-section. The strain sensing capability of the nanocomposites was investigated under tensile cyclic loading at different strain rates and maximum strains. Sensing experiments indicate that under cyclic loading, the changes in piezo resistivity mimic, both, the changes in the applied load and the measured material strain with high fidelity. Due to the high flexibility of PDMS, the 3D printed sensors have potential applications in real-time load sensing and structural health monitoring of complex flexible structures.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Materials and 3D Printing for Biology and Medicine

2018;():V012T11A008. doi:10.1115/IMECE2018-86998.

Whispering gallery mode (WGM) resonators exhibit high quality factor Q and a small mode volume; they usually exhibit high resolution when used as sensors. The light trapped inside a polymeric micro-cavity travels through total internal reflection generating the whispering gallery modes (WGMs). A laser or a lamp is used to power the microlaser by using a laser dye embedded within the resonator. The excited fluorescence of the dye couples with the optical modes. The optical modes (laser modes) are seen as sharp peaks in the emission spectrum with the aid of an optical interferometer. The position of these optical modes is sensitive to any change in the morphology of the resonator. However, the laser threshold of these microlasers is of few hundreds of microjoules per square centimeter (fluence) usually. In addition, the excitation wavelength’s light powering the device must be smaller than the microlasers size. When metallic nanoparticles are added to the microlaser, the excited surface plasmon couples with the emission spectrum of the laser dye. Therefore, the fluorescence of the dye can be enhanced by this coupling; this in turn, lowers the power threshold of the microlaser. Also, due to a plasmonic effect, it is possible to use smaller microlasers. In addition, a new sensing modality is enabled based on the variation of the optical modes’ amplitude with the change in the morphology’s microlaser. This opens a new avenue of low power consumption microlasers and photonics multiplexed biosensors.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Materials Processing and Characterization

2018;():V012T11A009. doi:10.1115/IMECE2018-86043.

The objective of this research is to describe the consequence of thermal ratcheting on the long-term creep property of HDPE material. The thermal ratcheting phenomenon amplifies significantly the creep strain of HDPE in comparison to the steady creep strain under constant temperature. The magnitude of creep strain of HDPE increases by 8% after just 20 thermal cycles between 28 and 50°C. The creep modulus which is inversely proportional to the creep strain depletes further under thermal ratcheting. Both properties change significantly with the number of thermal cycles. The coefficient of thermal expansion (CTE) of HDPE varies with the applied compressive load, with successive thermal cycles and with the thermal ratcheting temperature. The impact of thermal ratcheting diminishes with increase in initial steady creep exposure time-period but still the magnitude cumulative damage induced is noteworthy. The magnitude of growth in creep strain drops from 8 to 2.4% when thermal ratcheting is performed after 1 and 45 days of steady creep, respectively. There is a notable change in thickness of the material with each heating and cooling cycle even after 45 days of creep however, the thermal ratcheting strain value drops by 80% in comparison to thermal ratcheting strain after 1 day of creep and under similar test conditions.

Commentary by Dr. Valentin Fuster
2018;():V012T11A010. doi:10.1115/IMECE2018-86248.

In recent years, conventional materials are rapidly replaced by advanced aluminium composites due to its lighter in weight and high-performance characteristics. These materials find vast applications in automotive components because of its excellent combination of properties such as high specific strength, high specific stiffness, better dimensional stability and enhanced wear characteristics. The present work is focused on hybrid composites manufactured by stir casting route where the A356 alloy is the matrix and SiC + Moringa Oleifera Ash (MOA) particles as reinforcements. The influence of Moringa Oleifera Ash (MOA) particles (self-lubricant) on the wear behaviour of the composites is studied. Fabricated composites are tested on a pin-on-disc test rig at dry sliding wear conditions to study the influencing input parameters such as load, sliding distance and composites. A356 Aluminium alloy is reinforced with 5% SiC as primary reinforcement, varying MOA particles with 1% and 3% as secondary reinforcement. The design of experiments (DOE) approach using Taguchi method was adopted to perform the experiments according to L9 orthogonal array and analyse the results. From Taguchi analysis, combination of best suited values is identified and reported. Inquest of influential wear test parameters and its effect on wear and friction is determined using the signal-to-noise ratio and analysis of variance (ANOVA).

Commentary by Dr. Valentin Fuster
2018;():V012T11A011. doi:10.1115/IMECE2018-86268.

Basalt Fibre Reinforced Polymers (BFRP) was feasibly utilized as a preferable replacement to the Glass Fibre Reinforced Polymers (GFRP) due to their superior property and behaviour. Besides, reinforcing nano and micro fillers with basalt fiber will result in even better mechanical properties. In this research study, epoxy resin was blended with Cashew Nut Shell Liquid (CNSL) hardener, it beneficial to minimize the healing period. For 50% of epoxy resin, the ratio of CNSL hardener was taken as 50%. Standard Hand lay-up technique was utilized to produce the composite structures. In addition, 20g of nano and micro fillers were mixed with each epoxy-CNSL proportion. Accordingly, both (SiC & Banana) filler reinforced composites were fabricated and cut to the ASTM standard. Finally, the result of mechanical properties such as flexural and the impact (Charpy) of silicon carbide (SiC) and banana filler reinforced samples were compared.

Commentary by Dr. Valentin Fuster
2018;():V012T11A012. doi:10.1115/IMECE2018-86420.

An experimental investigation of the fatigue response of commonly used structural stainless steel — SS 304 L(N) and SS 316 L(N) — and its weld was carried out through automated cyclic ball indentation (ABI). A Tungsten Carbide (WC) spherical ball indenter of 1.57 mm diameter was used for compression-compression fatigue testing of the specimen under load control at a low frequency of loading (typically 0.1 Hz to 1 Hz). The force-displacement response during fatigue loading was logged continuously during fatigue test and the data was analyzed to extract details such as variations in: total depth of penetration, loading and unloading slopes, loading/unloading intercept, displacement range as a function of number of cycles. From the results, one could identify an unsteady response of material during cyclic loading after some cycles of fatigue loading — typical of failure; this input was used to compare the fatigue response of different zones of the weld.

Even though the applied frequency of loading is relatively less (∼ 1 Hz), due to the high levels of plastic deformation that is developed during the indentation process, one could expect an effect of strain rate on the fatigue response during cyclic ball indentation. To verify this, experiments were carried out at three distinct frequencies of 0.1 Hz, 0.5 Hz and 1 Hz for a given loading condition. Further, it was observed that the material response in weld region is the best, followed by the base metal. This can be corroborated with the weld microstructure that is obtained as a consequence of processing. Frequency of loading did not have significant influence on the fatigue failure life.

Numerical simulation of cyclic ball indentation was carried out to extract some relevant parameters for failure life such as mean stress and local stress ratio. This will serve as input to correlation of failure life data obtained from conventional specimens.

Topics: Fatigue
Commentary by Dr. Valentin Fuster
2018;():V012T11A013. doi:10.1115/IMECE2018-86448.

Microstructural adaptation of cast iron alloys by inoculation is a well-known practice to swell their mechanical properties. In foundries, several inoculants have been used to refine grain structure, and to obtain uniform distribution of graphite flakes. Inoculation is one of the most critical steps in cast iron production. The effectiveness of inoculants depends on melt temperature, method of addition, type of inoculants, and holding time. In this paper, the effect of Ca-based, Ba-based, Ca-Ba based and Sr-based inoculants on microstructure and tensile properties of grey cast iron IS-210 and spheroidal graphite iron IS-1862 is reported. Results showed both Ca and Ba based inoculants were effective in obtaining uniform distribution of flaky and nodular graphite in IS-210, and IS-1862 cast irons, respectively. But in a case of Sr-based inoculant were highly effective for increase the nodularity of SG cast iron as well as succeed supreme yield strength for both grey and ductile cast iron. The amounts of ferrite in the as-cast matrix are excess with controlled granulometry for elimination of primary carbide in Sr-based inoculant.

Commentary by Dr. Valentin Fuster
2018;():V012T11A014. doi:10.1115/IMECE2018-86465.

Despite the many advances made in material science, stainless steel and aluminum remain the structural materials best-suited for the naval fleet. While these metallic materials offer many benefits, such as high strength and good toughness, their persistent exposure to the maritime environment inevitably leads to issues with corrosion. Among the various manifestations of corrosion, pitting corrosion is of particular concern because the transition of corrosion pits to stress-corrosion cracks can lead to catastrophic failures. Traditional pitting corrosion analyses treat the pit shape as a semi-circle or ellipse and typically assume a growth pattern that maintains the original geometrical shape. However, when the underlying microstructure is incorporated into the model, pit growth is related to the grains surrounding the pit perimeter and the growth rate is proportional to crystallographic orientation. Since each grain has a potentially different orientation, pit growth happens at non-uniform rates leading to irregular geometries, i.e., non-circular and non-elliptical. These irregular pit geometries can further lead to higher stresses.

This work presents a detailed look at corrosion pit growth coupled with mechanical load through a numerical model of a two-dimensional stable corrosion pit. Real microstructural information from a sample of 316 stainless steel is incorporated into the model to analyze microstructural effects on pit growth. Through this work, stress distributions and stress concentration factors are examined for a variety of pit geometries, including comparisons of their range of values to a typical, semi-circular pit. The consequences of these stress distributions and concentration factors are discussed.

Topics: Stress , Corrosion , Modeling
Commentary by Dr. Valentin Fuster
2018;():V012T11A015. doi:10.1115/IMECE2018-86498.

Both high corrosion costs and an over-abundance of plastic waste have significant global impacts. This research seeks to help in both areas by utilizing recycled plastic as an anticorrosive coating. Many plastic-based coatings, especially those developed in more recent years, already contain recycled content. This research, which utilizes 100% recycled high density polyethylene (HDPE) as a powder coat, will add to the increasingly sustainable catalog of anti-corrosive coatings. The HDPE was applied to mild steel samples with traditional electrostatic powder coating equipment. The coating thickness was measured using scanning electron microscope (SEM) characterized and was found to be roughly 116 μm. The SEM analysis did not reveal any porosity in the coating. The immersion corrosion test in 5% H2SO4 for 2–3 days showed corrosion products at the bottom of the beaker. The maximum corrosion obtained was 424.4 mills/year (mpy) after 70.45 hours of immersion and the minimum corrosion obtained was 0.0 mpy after 5.58 hours of immersion. The acid immersion tests indicated that the corrosion started from the edges and advanced towards the inner surfaces. The coating on the edges was not uniform and may be porous. The salt immersion test in 5% NaCl solution by mass showed the sign of corrosion products after 5.5 hours and increased with time. A few samples showed corrosion over 25% of the surface after 70.5 hours of immersion. This is again attributed to the fact that the edges were not coated completely. The corrosion resistance can be improved by avoiding the sharp edges on the part.

Topics: Density , Coatings
Commentary by Dr. Valentin Fuster
2018;():V012T11A016. doi:10.1115/IMECE2018-86662.

Aluminium based metal matrix composites (MMCs) have received considerable attention in the last decade for its potential industrial applications. One of the challenges encountered using Aluminium based MMCs is understanding the influence of the reinforcement particles on the corrosion resistance and mechanical properties. In this study the corrosion behaviour and mechanical properties of Al6063 reinforced with egg shell ash and rice husk ash were investigated. Waste Egg Shell Ash (ESA) and Rice Husk Ash (RHA) 212 μm in size were used to produce the composites with 10 wt% of reinforcements via stir casting technique. The RHA and ESA were added in the ratios of 10:0, 7.5:2.5, 5:5, 2.5:7.5, 0:10. Unreinforced Al6063 was used as baseline material. Immersion tests, potentiodynamic polarization techniques, tensile tests, optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the composites. The results showed that reinforcing with 7.5 wt% RHA + 2.5 wt% ESA provided the highest resistance to corrosion. Generally, a reduction in the corrosion rates were observed for the reinforced composites as the wt% of RHA increased. Porosity levels of the composites reduced with an increase in the percentage of ESA in the matrix. Microstructural characterization using SEM and OM revealed a distribution of pits on the composite surfaces which was more severe with increasing RHA percentage. The UTS (ultimate tensile stress) results revealed that the composite containing 10 wt% RHA had the maximum value of 161 MPa. The results demonstrate that rice husk ash and eggshell ash can be useful in producing low cost Aluminium composites with improved corrosion resistance and tensile properties.

Commentary by Dr. Valentin Fuster
2018;():V012T11A017. doi:10.1115/IMECE2018-86854.

This study presents an experimental laboratory investigation done on the Polyethylene terephthalate – PET that is used for food grade (water bottle) by mixing with ionic liquid. Both thermal and mechanical properties with a varying weight percentage of ionic liquid are investigated. Mainly, at different mixing ratios of PET-Ionic liquid of (2, 3, 5, 7 and 10%), impact of the ionic liquid on the characteristics of the PET are examined through MFI (melt flow index), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), nanoindentation methods as well as Fourier Transform Infrared (FTIR) spectroscopy. In general, the estimated results indicated that the stiffness as well as the hardness acquired from nanoindentation test for the PET blends, decrease as long as the concentration increases.

Commentary by Dr. Valentin Fuster
2018;():V012T11A018. doi:10.1115/IMECE2018-86915.

The low carbon, nitrogen enhanced SS 304 L(N) stainless steels are one of the most potential candidates for the structural members in chemical industries and powerplants operating at hostile environments of temperature and corrosion. In service, the structural members fabricated using welding process, when subjected to a combination of mechanical load and elevated temperature can fail by fatigue. The Welding of Austenitic stainless steels using Tungsten Inert gas (TIG) is often limited by the depth of weld penetration, which can be achieved during a single pass. This necessitates for the use of multiple passes resulting in weld distortion and generation of residual stress. The Use of an electronegative flux (Activating flux) during the TIG welding (A-TIG) is known to enhance the weld penetration, thereby reducing the number of passes.

The present study evaluates the fatigue crack growth in stainless steel weldment (304L(N) welds) joined using conventional Multipass TIG welding and Activated flux TIG welding at 673K. Compact Tension (C(T)) specimens having a width of 50.8 mm and a thickness of 4 mm were extracted from the location of heat-affected zone (HAZ) and weld metal (WM) for A-TIG and MP-TIG configurations. From the micro-structural evaluation of A-TIG welds, it is noted that high heat input in a single pass has favored the formation of coarse equiaxed grains along the weld center. The use of multiple passes at reduced heat input has resulted in the formation of finer grains, with the orientation of grains changing along each weld pass interface. This finer randomly oriented grains has resulted in increasing crack path resistance through the MP-TIG welds compared to A-TIG welds. Thus from a view point of fatigue crack growth, due to the presence of fine grains, conventional Multi-pass weld is superior compared to A-TIG, but in cases where there is a creep or creep-fatigue combination, the A-TIG weld may prove to be useful.

Commentary by Dr. Valentin Fuster
2018;():V012T11A019. doi:10.1115/IMECE2018-86978.

The use of natural fiber reinforced composites has emerged as an advantageous option in many industrial applications. Generally, composites are manufactured in net or near-net shape, but under specific design specifications, secondary manufacturing processes such as drilling, milling and turning become a requirement. In this context, current paper presents an experimental study that investigates the machinability of newly developed natural fiber composites under conventional end-milling. Two types of bio-composites; date palm fronds reinforced polypropylene (DPF/PP) and pine needles reinforced polypropylene composite (PN/PP) were developed and physically tested in order to optimize their mechanical strength. Then, machinability of such class of bio-composites is statistically analyzed using Design of Experiment method. Statistical modeling including response surface plots are utilized to analyze the combined effect of input processing parameters (feed rate, axial depth, spindle speed) on the induced delamination during end-milling. It is shown that feed rate is the most dominant factors in DPF/PP milling, and axial depth of cut is the most significant factor on PN/PP milling. Results are also compared with those of milled neat polypropylene, which confirm that delamination of machined bio-composites can be improved over the neat polypropylene matrix. This qualifies the developed bio-composites to be used in industrial applications in which machining is required.

Commentary by Dr. Valentin Fuster
2018;():V012T11A020. doi:10.1115/IMECE2018-87237.

Aluminium based metal matrix composites with nano particle reinforcement are currently finding wide spread applications in automobile, aerospace and space structures because of their high strength, fatigue life, excellent wear resistance, low thermal coefficient value. However, in order to use these materials for critical automotive applications, extensive study in terms of manufacturing feasibility of the composites have to be carried out. Based on the objectives, the present investigation focuses on the development of Aluminium-SiC nano composite for structural applications. The aim of this research work is to arrive at an optimum weight faction of nano particle which gives the highest properties of the nano composite. The composites were produced by stir casting route. The base alloy and the composites were extruded and subsequently subjected to age hardening treatment. Microstructural evaluation, hardness studies were carried out on both the base alloy and the composites in the as-cast and extruded conditions. The effect of extrusion on the microstructure and properties of the AA2014-0.8 wt.%SiC composites have been discussed in detail.

Commentary by Dr. Valentin Fuster
2018;():V012T11A021. doi:10.1115/IMECE2018-87295.

Nitinol shape memory alloy is well known for its shape memory effect and super elastic effect. In the present work, the improvement of mechanical properties of nitinol alloy like yield strength, ultimate tensile strength and micro-hardness is discussed along with the study of evolution of micro-structure after every pass to extend the applications of shape memory alloys into high strength application areas. Severe plastic deformation processes are usually adopted for producing fine grain structures which improve the mechanical properties of a material. One such severe deformation process is constrained groove pressing, which is considered as one of the best severe plastic deformation techniques for sheet metals. The results of constrained groove pressing process on nitinol alloy show that the yield strength and the ultimate tensile strength have increased by about 3.6 times 2.5 times respectively, with an increment of 50% and 74% in micro-hardness after 1st pass of constrained groove pressing and 2nd pass of constrained groove pressing respectively. Microstructure shows increase in martensitic phase after constrained groove pressing processing. Increasing in twinning and grain boundary density can be observed in constrained groove pressing processed nitinol, which are the reasons for the tremendous increase in the strength of the alloy. Thus, the constrained groove pressing process on nitinol alloy can increase its range of application for high strength requirements.

Commentary by Dr. Valentin Fuster
2018;():V012T11A022. doi:10.1115/IMECE2018-87625.

Mordenite-rich tuff is one of most available zeolitic rocks all over the world. Because of this, the research of natural mordenite as a raw material of geopolymeric materials can provide an almost unlimited source of solid precursor for manufacturing such building materials. Despite efforts to shed light on the behaviour of mordenite-rich tuff during geopolymeric reaction, the performance of these novel materials is barely understood. The aim of this study is to explore the effect of the content of calcium hydroxide, CH, and water-to-solid ratio, W/S, as mixing parameters on compressive strength of mordenite-based geopolymers, MBG, and its thermal conductivity.

As solid precursor was used mordenite-rich tuff and mixed with sodium hydroxide (NaOH) at 10M that kept constant during the experiment. Two experimental parameters were selected as independent variables i.e, the content of CH and water-to-solid ratio, and their levels, according to a central composite experimental design. All these designed mixes were characterized by using quantitative X-ray diffraction (QXRD), Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetry and differential scanning calorimetry (TGA-DSC), scanning electron microscopy coupled with energy dispersed spectroscopy (SEM-EDS), in addition thermal conductivity tests were also run according to standard method ASTM C177 at 9, 24, 39°C. The overall results suggested that MBG can be used as building material, however its thermal conductivity was higher than that of commercial isolate building material. The experimental design analysis indicated that the optimum water-to-solid ratio was 0.35, but in the case of the content of CH, the optimum value was not observed on this experimental range because the compressive strength increased as the content of CH increased as well. The compressive strength of MBG was observed in the range between 8.7 and 11.3 MPa. On the other hand, QXRD and FTIR showed that mordenite reacted during the geopolymeric reaction, but instead quartz, also found in zeolitic tuff, acted as inert filler.

Commentary by Dr. Valentin Fuster
2018;():V012T11A023. doi:10.1115/IMECE2018-87789.

A common failure mode of electronic printed circuit boards (PCB’s) is the appearance of cold solder joints between the component and PCB, during product life. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. As fatigue life decreases with increasing plastic strain, creep occurrence should have significant impact, especially during thermal cycles and, thus, should be studied. Through the cooling phase, on the production of PCB assembly’s by the reflow technology, the hoven atmosphere temperature is adjusted in order to control the cooling rate. Narrow criteria is used so as to control the inter-metallic compounds (IMC) thickness, PCB assembly distortion and defects due to thermal shock. The cooling rate also affects solder microstructure, which has direct impact on creep behaviour and, thus, on the soldered joint reliability.

In this paper, a dynamic mechanical analyser (DMA) is used to study the influence of the solder cooling rate on its creep behaviour. SAC405 samples with two distinct cooling rates were produced: inside a hoven cooling and by water quenching. Creep tests were made on three-point-bending clamp configuration, isothermally at 25 °C, 50 °C and 75 °C and under three separate levels of stress, 3, 5 and 9 MPa. The results show that creep behaviour has a noticeable cooling rate dependence. It was also noticed that creep propensity is exacerbated by the temperature at which stresses are applied, especially for the slower cooling rates. Creep mechanisms were related to the solder microstructural constituents, namely by the amount of phases ant their morphology.

Topics: Creep , Copper , Silver , Solders
Commentary by Dr. Valentin Fuster
2018;():V012T11A024. doi:10.1115/IMECE2018-88471.

The advent of additive manufacturing allows for the design of complex 3D geometries that would otherwise be difficult to manufacture using traditional processes. Stereolithographic printing of geometrically reinforced structures gives promise for tunable energy-absorbing composite materials for impact applications. These materials may be suitable for applications in personal sport protection equipment such as knee-pads or helmets. The flexible nature of additive manufacturing can be easily scaled and modified to serve a variety of impact loading applications. In the present study, a three-dimensional nested array of ridged polymeric mesh with tiered high-temperature UV-cured polymer were embedded in a polyurethane matrix to form a new class of functional composite materials designed for multi-use low velocity impact events, and a single-use high velocity or high force impact event. The reinforcements were designed to absorb impact energy by the sequential bending, bucking, and failure of the layers of nested reinforcing members. The energy absorption capacity is further enhanced by the connective elastomer matrix which serves to retain the fractured mesh structure after initial breakage. The peak load is maintained at a relatively modest level while maximizing absorbed energy. Quasi-static loading tests were conducted to measure the peak load, total energy absorbing capability of the material. The energy absorption capability is measured using force-displacement plots and multiple interactions of material combination of reinforcement ring arrays. Tests with and without elastomer matrix, were conducted to understand peak load minimization and energy absorption character of the material.

Commentary by Dr. Valentin Fuster
2018;():V012T11A025. doi:10.1115/IMECE2018-88640.

Fire protective clothing is crucial in many applications, in military/government (Navy, Marine Corps, Army, Air Force, Coast Guard, and Law Enforcement) and industry (working with furnaces, casting, machining and welding). Fire resistant clothes provide protection to those who are at risk for exposure to fire hazards (intense heat and flames) and provide inert barrier between the skin and fire and shields the user from direct exposure to fire and irradiation. Flame retardant and chemical protective apparel consumption was 997 million m2 in 2015. This market size expected to grow more due to substantial increase in military and industrial demand. Advanced materials have long history in these areas to protect human life against the hazards. There are two main application techniques for producing fire resistant clothing: 1) Using fire retardant materials directly in the textile, and 2) Spray coating on the garments. Over the time these physically and chemically treated cloths begin to degrade and become less protective due to UV and moisture exposure, abrasion, wear, and laundry effects which will shorten the useful wear life of those cloths. The study compared the improved fire resistance of fabrics when treated with recycled graphene solution.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Modeling, Simulation, and Design of Multifunctional Materials

2018;():V012T11A026. doi:10.1115/IMECE2018-86598.

A multiphysics Internal State Variable (ISV) theory that couples the thermoelastoviscoplastic damage model of Bammann-Horstemeyer with electricity-related electromagnetic phenomena is presented in which the kinematics, thermodynamics, and kinetics are internally consistent. An extended multiplicative decomposition of the deformation gradient that accounts for elasticity, plasticity, damage, thermal expansion, electricity, and magnetism is introduced. The different geometrically-affected rate equations are given for each phenomenon after the ISV formalism and have a thermodynamic force pair that acts as an internal stress-like quantity. Guidelines for practical implementation, recommendations for simplifying assumptions, and suggestions for future work supplement the theoretical model. The abstraction of the model can capture the full multi-physics described above; however, the robustness of the model is realized when any of the listed phenomena are not included in the boundary value problem, the model reduces to the previous form — the model will revert to the Bammann-Horstemeyer plasticity-damage ISV model.

Topics: Metals , Damage
Commentary by Dr. Valentin Fuster
2018;():V012T11A027. doi:10.1115/IMECE2018-86794.

It is reported that carbon nanotube (CNT)-based conductive polymer composites have potential application prospect in structural health monitoring and flexible sensors. However, the current price of CNTs is relatively high compared with other fillers. To reduce the materials cost and ensure the sensing characteristics of this type of materials, the most economic and least amount of CNTs needed should be found, this balance value is called as electrical percolation threshold (EPT) in this study. First, a large number of numerical models containing CNTs with three-dimensional random distribution and epoxy resin matrix are established by Monte Carlo method. Then, the construct of conductive network is observed using these models, and the influence of electron tunneling between two adjacent CNTs on the EPT is investigated. Furthermore, the influence of length-diameter ratio (L/D) of CNTs, length variation and angle distribution of CNTs on EPT is investigated. This research provides useful information on how to produce conductive composites more economically.

Commentary by Dr. Valentin Fuster
2018;():V012T11A028. doi:10.1115/IMECE2018-86856.

Robotic grippers are useful in designing prosthetics and manufacturing. “Robotic hands often fall into two categories: simple and highly specialized grippers often used in manufacturing, and general and highly complicated grippers designed for a variety of tasks.” Ramond et al. [1] Within these two categories there are two main categories of research. These are hard structure and soft structure robotics. Hard structure robotics rely on a mechanical design with a motor or actuator to move a hard-linked part. Soft structure uses a mechanical design, soft material and a pneumatic pump to create the desired movement. The soft material is designed in a way that when it is pumped full of a fluid (i.e. air) it has a specific deformation. Hard robotics have an advantage in their ability to output a large force, but soft robotics have increased degrees of freedom. Dexterity (readiness and grace in physical movement) is another advantage over hard robotics. This project focuses on the process of designing actuators that can feasibly be used for devices falling into either of the two main categories of robotics. Such an actuator could be effectively implemented toward simple applications such as manufacturing-style gripping devices to advanced applications found in modern human prosthetics or areas where high dexterity combined with a delicate touch are required. The simulations show that the designs created work within a pressure range of 0.5 PSI to 1 PSI. This low pressure does not output a lot of force. The high dexterity and small air compressors needed make it a good design for use in areas like manufacturing or medical. If a stronger material was applied to these designs allowing the designs to handle higher pressures these designs could output much higher forces. This increase would make the designs more usable in areas like prosthetics and advanced robotics.

Topics: Robotics
Commentary by Dr. Valentin Fuster
2018;():V012T11A029. doi:10.1115/IMECE2018-87255.

A successful approach to the development of reinforced materials for enhanced cutting tool inserts requires the formulation and application of innovative concepts at each step of material design development. In this paper, reinforced ceramic-based cutting tools with enhanced thermal and structural properties are developed for high-speed machining applications using a computational approach. A mean-field homogenization, effective medium approximation and J-integral based fracture toughness evaluation using an in-house code are used for predicting the effective structural and thermal properties for tool inserts as a function of reinforcement type, volume fraction, particle size and interface between matrix and reinforcement. Initially, several potential reinforcements are selected at the material design phase. SiC, TiB2, cBN and TiC were all found to be suitable candidates when reinforced into an alumina matrix as both single and hybrid inclusions for the enhancement of thermal and structural properties. For validation purposes, alumina-cubic boron nitride-silicon carbide composites are developed using Spark Plasma Sintering as hybrid systems, which are in line with the designed range of volume fraction and reinforcement particle size. Structural and thermal properties such as elastic modulus, fracture toughness and thermal conductivity are measured to complement the computational material design model.

Commentary by Dr. Valentin Fuster
2018;():V012T11A030. doi:10.1115/IMECE2018-88071.

Atomistic simulations play an important role in the material analysis and design by being rooted in the accurate first principles methods that free from empirical parameters and phenomenological models. However, successful applications of MD simulations largely depend on the availability of efficient and accurate force field potentials used for describing the interatomic interactions. As a powerful tool revolutionizing many areas in science and technology, machine learning techniques have gained growing attentions in the field of material science and engineering due to their potentials to accelerate the material discovery through their applications in surrogate model assisted material design. Despite tremendous advantages of employing machine learning techniques for the development of force field potentials as compared to conventional approaches, the uncertainty involved in the machine learning interpolated atomic potential energy surface has not drew much attention although it is an important issue. In this paper, the uncertainty quantification study is performed for the machine learning interpolated atomic potentials, and applied to the titanium dioxide (TiO2), an industrially relevant and well-studies material. The study results indicated that quantifying uncertainties is an indispensable task that must be performed along with the atomistic simulation process for a successful application of the machine learning based force field potentials.

Commentary by Dr. Valentin Fuster
2018;():V012T11A031. doi:10.1115/IMECE2018-88095.

Coiled structures made from polymer and Carbon Nanotube (CNT) yarns are used as artificial muscles, stretchable conductors, and energy harvesters. The purpose of this work is to present our latest understanding of the mechanical behavior of these CNT-based structures. CNT yarns are fabricated by inserting twists in sheets spun from CNT forests. Over twisting the CNT yarns results in coiled CNT yarns, similar to a spring where the spring radius is comparable to the diameter of the CNT yarn. In this study, we explain the development and validation of a viscoelastic model, to capture damping and hysteresis in CNT yarns under quasi-static and dynamic loads. Confirmation of linear viscoelastic behavior of CNT yarns can lead us to the development of a model for coiled CNT yarns. Coiled CNT yarns, on the other hand, show a complex non-linear viscoelastic behavior. Possible mechanisms responsible for this non-linear behavior are discussed.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Multifunctional Composite Materials and Structures

2018;():V012T11A032. doi:10.1115/IMECE2018-86484.

This work will demonstrate the development and experimental validation of the stochastic models to predict the composite material’s mechanical and electromagnetic response as a function of the constituent reinforcing materials. First, stochastic micromechanics models will be developed for the case of multiple disparate supporting materials. These micromechanics models will then be validated against traditional finite element models and experimental results over the feasible parameter space. The developed models will then be utilized to define the optimal geometry of the composite flywheel including constraints such as displacement, stress, flux, magnetic field density, and manufacturability.

Commentary by Dr. Valentin Fuster
2018;():V012T11A033. doi:10.1115/IMECE2018-86847.

Dispersing micro and nanoparticles into polymeric materials has proven to induce multifunctional properties in polymer composites, including their magnetic, electrical, thermal and mechanical characteristics. Adding carbon-based nanoparticle inclusions such as Graphene Nano-Platelets (GNP) to polymeric materials typically leads to thermal, electrical and mechanical property enhancements. Raising thermal conductivity by adding highly thermally conductive fillers particularly harbors great potential given diverse possible applications, such as in the electronics industry. In this study, the focus is on increasing the thermal conductivity of an epoxy by dispersing GNP in the pre-polymer. The influence of various process parameters such as filler loading, influence of swelling, use of solvent and additives, sonication time and amplitude, as well as curing cycle were determined. By means of a Design of Experiments approach the parameters which have the greatest effect on thermal conductivity enhancement were identified. Through this study a better understanding of the influence of process parameters was achieved in a qualitative and quantitative manner. The study further aids in selecting ideal process parameters for maximum thermal conductivity enhancements.

Commentary by Dr. Valentin Fuster
2018;():V012T11A034. doi:10.1115/IMECE2018-87211.

An Arrhenius relationship is employed to develop a model for prediction of gas permeation in the polymeric materials. A permeation cell was designed to measure the gas permeation. The permeation of Helium was examined over a range of low to high temperature and pressure conditions. The results of the experiments were used to verify the accuracy of the prediction model.

The obtained model was successful in predicting gas permeation rate at two different pressures. The results showed that pressure’s effect is insignificant on models. The predicted results for different pressure were close, and both models can be used to obtain an approximation for gas permeation rate for the examined material where no experimental data exists.

Commentary by Dr. Valentin Fuster
2018;():V012T11A035. doi:10.1115/IMECE2018-88661.

This paper details the experimentally-measured thermal conductivity, k, of concrete composite samples consisting of various mixtures of extruded polystyrene waste chips and concrete for the purpose of better insulative value and lighter weight. A “hot box” apparatus was designed based on the parameters of ASTM C1363, and was constructed primarily out of 4” rigid polystyrene insulation and designed to force the majority of the heat generated in the enclosure through the test samples. The design allowed for the indirect measurement of thermal conductivity, k, by directly measuring the internal and external surface temperatures of the samples and heat input required to maintain a steady state internal temperature. Several samples with well documented k values were first tested to calibrate the hot box apparatus. Prototype samples were made in sheets and also in cylindrical format to test for thermal conductivity and also compression testing, respectively. Results showed that although the insulative values of the concrete composite increased with additional polystyrene aggregate, as would be expected, at some point there is a rapid fall-off in compressive strength.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Multifunctional Nanomaterials

2018;():V012T11A036. doi:10.1115/IMECE2018-86286.

By using the internal state variable (ISV) theory (Horstemeyer and Bammann, 2010), we developed a finite deformation anisotropic and temperature dependent constitutive model to predict elastoviscoplasticity and progressive damage behavior of short fiber reinforced polymer (SFRP) composites. In this model, the SFRP is considered as a simple anisotropic equivalent medium (lamina), and the rate dependent plastic behavior of the SFRP is captured with the help of three physically-based ISVs. A second-order damage tensor is introduced to describe the anisotropic damage state of the SFRP and the tensorial damage evolution equations are used based on the damage mechanism of micro voids/cracks nucleation, growth and coalescence. The constitutive model developed herein arises employing standard postulates of continuum mechanics with the kinematics, thermodynamics, and kinetics being internally consistent. The developed model is then calibrated to a 35 wt% glass fiber reinforced polyamide 66 (PA66GF-35) for future numerical analyses.

Commentary by Dr. Valentin Fuster
2018;():V012T11A037. doi:10.1115/IMECE2018-87691.

Biopolymers are emerging materials with numerous capabilities of minimizing the environmental hazards caused by synthetic materials. The competitive mechanical properties of bio-based poly(lactic acid) (PLA) reinforced with cellulose nanocrystals (CNCs) have attracted a huge interest in improving the mechanical properties of the corresponding nanocomposites. To obtain optimal properties of PLA-CNC nanocomposites, the compatibility between PLA and CNCs needs to be improved through uniform dispersion of CNCs into PLA. The application of chemical surface functionalization technique is an essential step to improve the interaction between hydrophobic PLA and hydrophilic CNCs. In this study, a combination of a time-efficient esterification technique and masterbatch approach was used to improve the CNCs dispersibility in PLA. Nanocomposites reinforced by 1, 3, and 5 wt% functionalized CNCs were prepared using twin screw extrusion followed by injection molding process. The mechanical and dynamic mechanical properties of pure PLA and nanocomposites were studied through tensile, impact and dynamic mechanical analysis. The impact fractured surfaces were characterized using scanning electron microscopy. The mechanical test results exhibited that tensile strength and modulus of elasticity of nanocomposites improved by 70% and 11% upon addition of functionalized CNCs into pure PLA. The elongation at break and impact strength of nanocomposites exhibited 43% and 35% increase as compared to pure PLA. The rough and irregular fracture surface in nanocomposites confirmed the higher ductility in PLA nanocomposites as compared to pure PLA. The incorporation of functionalized CNCs into PLA resulted in an increase in storage modulus and a decrease in tan δ intensity which was more profound in nanocomposites reinforced with 3 wt% functionalized CNCs.

Commentary by Dr. Valentin Fuster
2018;():V012T11A038. doi:10.1115/IMECE2018-88637.

The development of sustainable, cost-effective, reliable, efficient and stable materials and methods for continuous fresh water production is crucial for many regions of the world. Among the many other options, graphene nanoflakes seem to be good option to solve the global water problem due to their low energy cost and simple operational process to purify waste water. The produced water can be used for drinking, agriculture, gardening, medical, industrial and other purposes. Most of the nanofilter-based multifunctional fresh water systems do not require large infrastructures or centralized systems, and can be portable to remote regions for efficient water treatment. Graphene was discovered as a single-layer of isolated graphite atoms arranged in 2D hexagonal shape, making it the thinnest and strongest material known to date. Despite its intriguing mechanical, thermal and electrical properties, usage of graphene for different industries has not been investigated in detail. The present study investigated the availability and practical use of graphene inclusions for desalination of salt water to produce fresh water. In the present study, graphene was added to 3.5wt% salt water (similar to sea water) at different percentages. Graphene has a high absorption capability to convert solar energy into heat to enhance the evaporation rate of salt water. The graphene inclusions can also be used to remove bacteria, viruses, fungi, heavy metals and ions, complex organic and inorganic compounds, and other pathogens and pollutants present in various water sources (e.g., surface, ground water, and industrial water).

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Nanoengineered, Hierarchical, Multiscale Materials and Structures

2018;():V012T11A039. doi:10.1115/IMECE2018-86227.

This work addresses the integration of an analytical uncertainty quantification approach to multi-scale modeling of single-walled carbon nanotube (SWNT)-epoxy nanocomposites consisting of pristine systems. The computational modeling starts with the dendrimer growth approach, which is used to build an epoxy-SWNT network. Next, the molecular dynamics simulations are performed to obtain thermal and mechanical properties. The SWNT orientations are assumed to have natural stochasticity which is modeled by an analytical uncertainty algorithm. Next, the propagation of the uncertainties to the volume-averaged properties of the SWNT and nanocomposite is obtained. The uncertainties are shown to affect the macro-scale properties such as stiffness, thermal expansion, thermal conductivity and natural frequencies.

Commentary by Dr. Valentin Fuster
2018;():V012T11A040. doi:10.1115/IMECE2018-86855.

Liquid crystal polymers (LCP’s) comprise a class of melt-processable materials that derive specialized mechanical, chemical, and electrical properties from long-range molecular ordering. This unique microstructure gives rise to anisotropic bulk behavior that can be problematic for industrial applications, and thus the ability to model the orientation state in the polymer is necessary for the design of isotropic material manufacturing processes. Previous efforts to model LCP directionality have been primarily restricted to structured grids and simple geometries that demonstrate the underlying theory, but fall short of simulating realistic manufacturing geometries. In this investigation, a practical methodology is proposed to simulate the director field in full-scale melt-processing set-ups, specifically cast film extrusion, to predict the bulk material orientation state. The hybrid approach utilizes separate simulations for the polymer flow with commercial computational fluid dynamics (CFD) software, and the material directionality through a user-defined post-processing script. Wide-angle x-ray scattering (WAXS) is used to experimentally validate the simulated directionality during extrusion processing. It is shown that the model is capable of predicting both the direction and degree of orientation in the polymer resulting from processing, and the model produces strong agreement with experimental measurement of the polymer orientation state.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Nanomaterials for Energy

2018;():V012T11A041. doi:10.1115/IMECE2018-87830.

The outstanding properties of single-layer graphene sheets for energy storage are hindered as agglomeration or restacking leads to the formation of graphite. The implications of the aforementioned arise on the difficulties associated with the aqueous processing of graphene sheets: from large-scale production to its utilization in solvent-assisted techniques like spin coating or layer-by-layer deposition. To overcome this, aqueous dispersions of graphene were stabilized by cellulose nanocrystals colloids. Aqueous cellulose nanocrystals dispersion highlights as a low-cost and environmentally friendly stabilizer towards graphene large-scale processing. Colloids of cellulose nanocrystals are formed by electrostatic repulsion of fibrils due to de-protonated carboxyl or sulfate half-ester functional groups. Graphene dispersions are obtained by hydrothermal reduction of electrochemically exfoliated graphene oxide in the presence of cellulose nanocrystals. This approach allows the preservation of the intrinsic properties of the nano-sheets by promoting non-covalent interactions between cellulose and graphene. The dispersions could be cast to form free-standing flexible conducting films or freeze-dried to form foams and aerogels for capacitive energy storage.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Phase Transformations in Materials Processing

2018;():V012T11A042. doi:10.1115/IMECE2018-86911.

Two phases of the Nb-Pt system namely Nb3Pt and NbPt3 have been studied using first principles approach in CASTEP. Structural, elastic and electronic properties of the concerned binary alloys were determined and examined against each other. Although both alloys have the same structure, it was observed that the percentage difference in the change of lattice parameters varied. Nb3Pt exhibited a 0.073% change while NbPt3 had a 14.809% change making Nb3Pt more stable structurally than NbPt3. The elastic properties showed that both binaries are ductile materials but NbPt3 proved to be more ductile than Nb3Pt based on Born, Pugh’s and Frantsevich’s criteria. Through the electronic properties, both binaries were proven to be conducting and their bonding nature seen as a combination of ionic metallic and covalent bond.

Topics: Elasticity , Alloys , Bonding
Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Posters

2018;():V012T11A043. doi:10.1115/IMECE2018-87099.

Systematic first-principles calculations based on density functional theory were performed on Dy2HfxO3+2x (x = 0, 1, and 2) compositions. A complete set of elastic parameters including elastic constants, Hill’s bulk moduli, Young’s moduli, shear moduli and Poisson’s ratio were calculated. Analyses of densities of states and charge densities and electron localization functions suggest that the oxide bonds are highly ionic with some degree of covalency in the Hf-O bonds. Thermal properties including the mean sound velocity, Debye temperature, and minimum thermal conductivity were obtained from the elastic constants.

Commentary by Dr. Valentin Fuster
2018;():V012T11A044. doi:10.1115/IMECE2018-87799.

In the present work, the use of nano silica fume in developing a compressive strength of concrete that can lead to improvement in concrete construction is carried out in the present work. One of the parameters considered is a number of curing days for measuring the compressive strength. The measured results demonstrate the increase in compressive. To achieve our goals, concrete cubes were cast and tested for compressive strength, all concrete sample has the same mixing ratio and sub-classified to standard, and Silica fume added by weight of cement (5%, 10%, 15%, 20% and 30%). The results show that the recommended addition was 15% of Silica fumes for optimum compressive strength that reaches 74.8 MPa.

Commentary by Dr. Valentin Fuster

Materials: Genetics to Structures: Recent Developments in Tribology

2018;():V012T11A045. doi:10.1115/IMECE2018-86703.

A significant amount of energy dissipates from frictional losses of moving components in machinery and devices in industry. This contact friction leads to the wear and eventual failure of industrial mechanical components over extended time through adhesion, abrasion, fatigue, or corrosion. Frictional losses could be mitigated by utilizing more effective lubricants, which would allow the translating surfaces to slide over one another more fluently. There is reason to study eco-friendly alternatives over traditional lubricants to reduce negative impact to the environment. The implementation of Ionic Liquids (ILs) as additives to oil-based lubricants is a development in tribology with the potential to lower the friction coefficient and reduce wear. When carbon nanotubes are dispersed into these ionic liquids, the reduction of losses due to friction and wear can be even greater. In this experiment, single-walled carbon nanotubes (SWCNTs) of four concentrations, 0 wt.%, 0.01 wt.%, 0.02 wt.%, and 0.03 wt.% were dispersed in a room temperature ionic liquid, Trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl) phosphinate, or [THTDP][Phos] for short, to form four homogeneous mixtures. Then, each mixture was added in 1 wt.% to a base vegetable oil. Friction tests were also conducted with pure vegetable oil for comparative purposes. The experiments consist of a pin-on-disk rotational tribometer and a ball-on-flat reciprocating tribometer both applying a steel-steel (AISI 52100) contact to evaluate the lubricating ability of combining SWCNTs and ILs as lubricant additives. The load, speed, wear radius, sliding distance, and duration of the experiment were held constant to isolate lubrication as the experimental parameter. Optical microscopy (OM), thermogravimetric analysis (TGA), and viscometer analysis were utilized after experimentation to analyze and discuss the wear mechanisms of the worn surfaces. Results differed between rotational and translational experiments, with the rotational results yielding a decrease of 14.21% in wear loss with the VO+1%[THTDP][Phos] lubricant. The translational results yielded a continuous decrease in wear loss with the increase in SWCNT wt.%.

Commentary by Dr. Valentin Fuster
2018;():V012T11A046. doi:10.1115/IMECE2018-86810.

In manufacturing processes, the cost of tooling contributes to a significant portion of operating costs. Several papers have been dedicated to various improvements on tool life, including monitoring the effect of temperature conditions and flood cooling. Flood cooling is not economical, so research has also been done to investigate minimum quantity lubrication and the effects of different additives, such as nanofluids. Another additive, ionic liquids, have become popular in tribological studies because they have unique properties that allow them to form ordered molecular structures, which is ideal in lubrication. Research has proven ionic liquids to be effective in reducing wear and friction coefficients. Currently, utilizing ionic liquids specifically to reduce tool wear has been almost exclusively limited to titanium and steel applications. The goal of this study is to improve tribological performance of the subtractive manufacturing process using ionic liquid add-ins to widely available machine shop coolants and oils. A series of reciprocating ball-on-flat experiments will be conducted using a 1.5mm diameter 250 Chrome Steel G25 ball and 6061-T6 aluminum disk to simulate cutting conditions often seen in manufacturing processes. 6061 Aluminum is an alloy commonly seen in machine shops and large-scale manufacturing scenarios because of its versatile material properties and wide availability. The tests were run at constant sliding distance, velocity and load. The lubricating mixtures were prepared by adding 5 wt % of a phosphonium based ionic liquid, Trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ([THTDP][NTf2]), to the base fluids Trim Sol™ emulsion fluid and Mobilmet™ 766 high performance neat cutting oil. The addition of the ionic liquid to both base lubricants (oil and coolant) increased the friction coefficient (18.60% and 4.89%, respectively) while the wear volume was reduced (28.75% and 7.84%, respectively). The results for the oil provided evidence that the ionic liquid did have an effect to reduce wear, however, the same conclusion could not be drawn for the coolant.

Commentary by Dr. Valentin Fuster
2018;():V012T11A047. doi:10.1115/IMECE2018-86875.

In this study, the tribological behavior of the Trihexyl tetradecylphosphonium-bis(2,4,4-trimethylpentyl)phosphinate [THTDP][Phos] ionic liquid with and without single-wall carbon nanotubes (SWCNT) dispersion as a thin boundary layer was intended for investigation. However, the surface heat treatment process was not sufficient to form a thin film on the sample surfaces. Thus, in each test condition, the lubricating agents were used as external (liquid) lubricants. Specifically, [THTDP][Phos] and ([THTDP][Phos]+0.1 wt.% SWCNT) boundary film layers were applied on 6061-T6 aluminum alloy disk samples and tested under sliding contact with 1.5 mm diameter 420C stainless steel balls using a ball-on-flat linearly reciprocating tribometer. A commercially available Mobil Super 10W-40 engine oil (MS10W40) was also tested and used as this investigation’s datum. The tribological behavior of [THTDP][Phos] and ([THTDP][Phos]+SWCNT) boundary film layers was analyzed via wear volume calculations from optical microscopy measurements, as well as by observation of the transient coefficient of friction (COF) obtained through strain gauge measurements made directly from the reciprocating member of the tribometer. Results indicate the potential for reduction of wear volume and coefficient of friction in the IL lubricated steel-on-aluminum sliding contact through (SWCNT) dispersion in the ionic liquid. Wear results are based on measurements obtained using optical microscopy (OM). Results discussed display improved tribological performance for both [THTDP][Phos] and ([THTDP][Phos]+SWCNT) over baseline MS10W40 oil lubricant for both roughness values tested for the steel-on-aluminum contact. No measurable improvements were observed between [THTDP][Phos] and ([THTDP][Phos]+SWCNT) tests.

Commentary by Dr. Valentin Fuster
2018;():V012T11A048. doi:10.1115/IMECE2018-87002.

Lubricants play a vital role in improving energy efficiency and reducing friction in any type of frictional contact. The automotive industry is facing strict regulations in terms of emissions from the petroleum fuel. Strict government norms are compelling automotive manufacturers to push their technological limits to improve the fuel economy and emissions from their vehicles. Improving the efficiency of the engine will ultimately result in saving fuel thus improving the fuel economy of the engine. Concerning energy consumption; 33% of the fuel energy developed by combustion of fuel is dissipated to overcome the friction losses in the vehicle [1]. Out of this, 11.56% of the total fuel energy is lost in engine system. The distribution of this 11.56% fuel energy lost in engine system includes 3.5% consumed in bearings, 1.16% in pumping and hydraulic viscous losses, 5.2% and 1.73% consumed in piston assembly and valve train respectively [1]. If we consider losses only in bearings, piston assembly and valve train it results in 10.4% energy loss as compared to the total energy generated by the fuel. In the last decade, ionic liquids have shown potential as lubricants and lubricant additives. This study focusses on the use ionic liquids as additives for friction and wear reduction resulting in energy conservation in an internal combustion engine. In this work, the contact between piston ring and cylinder wall was simulated using a ball-on-flat tribometer. Most of the engine oils are based on mineral oils and results showed that adding 1% of the ionic liquid to mineral oil reduced friction loses by 27% [2], which corresponds to conserving 2.8% of fuel energy if just the frictional loss in piston assembly, valve train and bearing are considered. In the United States, there are 253 million vehicles on average consuming 678 gallons of fuel per year [3], the use of ionic liquid can save an estimated 4.8 billion gallons of fuel per year, which results in estimated saving of 11.56 billion dollars.

Commentary by Dr. Valentin Fuster

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