On the determination of cyclic plastic strain energy with the provision for microplasticity

Microstructure-sensitive estimation of fatigue life using cyclic thermodynamic entropy as an index for metals

“…To obtain microplastic strain energy accumulation in the microstructure, the contribution of each element needs to be identified and summed to obtain the total value. The following two-parameter Weibull probability function can be used to obtain the distribution of micro-plastic strains under any cyclic load amplitude from the monotonic stressstrain curve of a metal [16] .…”

“…Specifically, Wilson et al [12] examined BCC, FCC, and HCP crystals of Ferritic Steel, Nickel Ti-6Al-4V, and Zircaloy4, respectively, and presented microstructurally-sensitive fatigue crack growth. Jirandehi and Khonsari presented a statistical method of estimating the microplastic strain energy per cycle based on monotonic tensile test and on the basis of the yielding heterogeneity of poly-crystalline metal grains [16]. A twoparameter Weibull function was implemented to account for the distribution of cyclic microplastic deformations.…”

“…These studies consider the heterogenic nature of grain-level mechanical properties in a poly-crystalline metal and properly estimate the energy associated with cyclic deformations. However, the method offered in [16] provides a relatively simple engineering approach that yields realistic results at any scale.…”

“…The present work proposes a fatigue life estimation method by linking the microstructurebased cyclic strain energy with the thermodynamically-based fatigue criterion. The model for the Statistical Estimation of Plastic Strain Energy (SEPSE) introduced by the authors in a recent study [16] is utilized to obtain the plastic strain energy (PSE) per cycle of low carbon steel (LCS 1018) and aluminum 7075-T6 (Al 7075-T6) specimens. The FFE for each case is estimated following the finite element (FE) simulations to obtain the steady-state temperature.…”

Application of thermoelectricity in fatigue of metals

“…In recent years, the energy‐based method has become widespread due to the technological advances associated with infrared (IR) thermography and its application in entropic characterization of fatigue 13 . Indeed, the introduction of irreversible thermodynamics in the analytical prediction of fatigue life 14,15 has paved the way in this regard and has proved its efficiency and reliability in experimental studies 16–20 . Thermography has also shown its potentials in high‐cycle fatigue 21,22 .…”