Date of Award


Degree Name

Master of Science


Mechanical Engineering


Calvin M. Stewart


The structural analysis of Industrial Gas Turbine (IGT), Aeroengine, Gen IV nuclear components under in-service conditions at various stress and temperature are susceptible to time-dependent creep deformation and creep induced failure. Such failure phenomena are exacerbated by the randomness in material properties, oscillating loading conditions, and other sources of uncertainty. The demand for physically based probabilistic creep modeling is highly sought by alloy designers. The objective of this study is to develop and validate a probabilistic creep-damage model incorporating multi-sources of uncertainty to replace the traditional deterministic and empirical decision-based modeling. In this study, the deterministic Sine-hyperbolic (Sinh) creep-damage model is carefully tuned into a probabilistic model. The creep test data of alloy 304 stainless steel with replicates over a range of stress and temperature are gathered from the literature. First, the Sinh model is calibrated deterministically to determine the test-specific material constants and their associated statistical variability. A probabilistic framework is developed where the hypothesized sources of uncertainty: test conditions (stress and temperature), pre-existing damage, and material properties are introduced. The sources of uncertainties are carefully tuned based on the ASTM standards, statistical goodness-of-fit test, and the nature of deterministically calibrated constants. The probabilistic distribution function (pdfs) of each sources of uncertainty are determined in sequence to encapsulate the full experimental uncertainty. Single source probabilistic predictions are performed to determine the influence of each source of uncertainty on the creep deformation, damage, and rupture predictions. Full interaction probabilistic predictions are performed to demonstrate the interference effect of all the sources of uncertainty on the prediction of creep deformation, ductility, and rupture. The Sinh model constitutive equations are implemented into a USERCREEP.F, user material subroutine of the ANSYS finite element software. For verification and validation (V&V), a finite element simulation in ANSYS Mechanical APDL (ANSYS Parametric Design Language) is conducted on 1-D and 2-D element model. Furthermore, the probabilistic model is applied to an expanded database of engineering alloys to validate the probabilistic prediction. Future work will focus on developing a multi-stage Sinh, stochasticity, time-dependent pdfs for improved uncertainty quantification.




Received from ProQuest

File Size

83 pages

File Format


Rights Holder

Md Abir Hossain