Fatigue Damage Accumulation Modeling of Metals Alloys under High Amplitude Loading at Elevated Temperatures

Jarosław Szusta,Andrzej Seweryn

doi:10.3390/met8121030

Abstract

This article presents an approach related to the modeling of the fatigue life of constructional metal alloys working under elevated temperature conditions and in the high-amplitude load range. The article reviews the fatigue damage accumulation criteria that makes it possible to determine the number of loading cycles until damage occurs. Results of experimental tests conducted on various technical metal alloys made it possible to develop a fatigue damage accumulation model for the LCF (Low Cycle Fatigue) range. In modeling, the material’s damage state variable was defined, and the damage accumulation law was formulated incrementally so as to enable the analysis of the influence of loading history on the material’s fatigue life. In the proposed model, the increment of the damage state variable was made dependent on the increment of plastic strain, on the tensile stress value in the sample, and also on the actual value of the damage state variable. The model was verified on the basis of data obtained from experiments in the field of uniaxial and multiaxial loads. Samples made of EN AW 2024T3 aluminum alloy were used for this purpose.

Highlights

During operation, machine parts are frequently subjected to fatigue loading at elevated temperatures
The fatigue damage accumulation models of materials working under low-cycle loading conditions at elevated temperatures presented in the literature are modified functions formulated to estimate the material’s fatigue life at room temperature
An additional cracking condition should be introduced, in which it is accepted that crack reaches critical value, that is: initiation will occur when the damage state variable induced by plastic strains on any physical plane maxωn = 1

Summary

Introduction

Machine parts are frequently subjected to fatigue loading at elevated temperatures. The authors tested the material within the entire safe temperature range, and determined that, in the case of this alloy, the Manson–Coffin fatigue life model does not allow for the prediction of the material’s fatigue life at elevated temperatures due to the length of the phase between fatigue crack initiation and its propagation. The fatigue damage accumulation models of materials working under low-cycle loading conditions at elevated temperatures presented in the literature are modified functions formulated to estimate the material’s fatigue life at room temperature. The process of calculating these parameters is not complicated in Metals 2018, 8, x FOR PEER REVIEW working under low-cycle loading conditions at elevated temperatures presented in the literature are modified functions formulated to estimate the material’s fatigue life at room temperature.

Fatigue

Modeling

Results

11. Evolution

Conclusions