Full Content is available to subscribers

Subscribe/Learn More  >

Further Development of Modified Theta Project Creep Models With Life Fraction Hardening

[+] Author Affiliations
W. David Day

PSM, Ansaldo Energia Group, Jupiter, FL

Ali P. Gordon

University of Central Florida, Orlando, FL

Paper No. GT2017-63675, pp. V006T24A007; 11 pages
  • ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
  • Volume 6: Ceramics; Controls, Diagnostics and Instrumentation; Education; Manufacturing Materials and Metallurgy
  • Charlotte, North Carolina, USA, June 26–30, 2017
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-5091-6
  • Copyright © 2017 by ASME


In order to optimally design a hot section component for creep, the designer and turbine durability specialist must have confidence in their predictive tools and be able to gain design insight from these analytical tools. The modified theta projection (MTP) creep model was previously presented as an accurate means of describing creep behavior as a function of stress, temperature and time. The MTP was then implemented in an analytical model using a life fraction hardening (LFH) rule to calculate creep in the presence of time-varying stresses, and the results presented in a second paper. This paper presents improvements to the technique through the use of state variables in addition to the previously shown strain life fraction (ELF) and temperature margin (TMar). The need for performing multiple creep analyses is avoided by adding state variables to that track estimates of the effect of temperature changes on stress relaxation and life fraction, as well as an allowance for material variability and an inexact fit of material behavior.

The results of creep tests, on a nickel blade alloy, with incrementally increasing or decreasing loads are presented to provide validation of the accuracy of the life fraction hardening rule. The use of MTP and LFH has now been expanded to steels. Incremental testing results are examined for a NiCrMoV rotor steel to further validate the technique. The effect of true stress on model accuracy is also presented. Now that an accurate creep model and hardening rule have been implemented, expansion of the techniques to provides more useable design information and allows us to improve the structural integrity of turbine blades, vanes and rotors.

Copyright © 2017 by ASME
Topics: Creep , Hardening



Interactive Graphics


Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In