Session: 18-03 Failure Prediction and Life Assessment I

Paper Number: 129453

129453 - An Advanced Sine-Hyperbolic Creep-Damage Model Incorporating Threshold Strength 

This study aims at improving the classic Sine-Hyperbolic (Sinh) creep-damage model to predict minimum-creep-strain-rate (MCSR), rupture, damage, and creep deformation. The Sinh model employs a continuum-damage-mechanics-based framework to model secondary and tertiary creep regimes. In Sinh, the creep strain and damage rate equations exhibit an implicit threshold stress that arises during numerical optimization. Herein, the Sinh model is modified to include an explicit threshold strength as a material property and the tensile strength. Threshold strength is defined as the lower limit for creep activation at a given temperature. Stresses are applied below the threshold, resulting in infinite life. The advanced Sinh offers several advantages including; a physical significance of stress ratios where the onset of creep is defined by threshold strength, a closed-form solution where the rate equations remain finite at any combination of stress and temperature, and adaptability in finite element analysis where the solution space remains numerically stable.

 

Experimental creep data of 304SS and 316SS at multiple isotherms are gathered from NIMS. The advanced Sinh is calibrated to the MCSR and SR data of 304SS. The calibration of threshold strength follows a standard procedure from literature and is observed to be realistic for stainless steel at elevated temperatures. The MCSR and SR predictions illustrate the Sigmoidal bend and demonstrate zero creep rate and infinite life at or below threshold strength. The creep deformation and damage predictions exhibit agreement with experimental data. The advanced Sinh is validated via MCSR, SR, damage, and creep deformation predictions of 316SS to ensure the applicability of the model across a range of materials. The advanced Sinh improved creep response prediction and added physical realism to the model’s framework.

Presenting Author: Calvin M. Stewart The Ohio State University

Presenting Author Biography: Calvin M. Stewart is the College of Engineering Innovation Scholar and Associate Professor in the Department of Aerospace and Mechanical Engineering and the Department of Materials Science and Engineering at the Ohio State University. Dr. Stewart directs Materials at Extremes which focuses on the advanced manufacturing, mechanical testing, and theoretical mechanics of materials subject to thermal, mechanical, and chemical extremes. Within the gamut of extremes: creep, fatigue, thermomechanical fatigue, and fracture are key focus areas.

Authors:

Md Abir Hossain The Ohio State University
Mohammad Shafinul Haque Angelo State University
Jacob Pellicotte The Ohio State University
Calvin M. Stewart The Ohio State University