Experimental and Numerical Simulation Study of Plasticity-Induced and Roughness-Induced Fatigue Crack Closure

Abstract

In this study, fatigue crack closure behavior was investigated in the aluminum alloy 6061-T6 and the carbon steel JIS. S25C. It was found that crack closure in the aluminum alloy 6061-T6 showed the characteristics of plasticity-induced fatigue crack closure (PIFCC), whereas the carbon steel JIS. S25C showed the characteristics of roughness-induced fatigue crack closure (RIFCC). The experiments included the determination of the crack-opening levelsKopas a function of stress intensity factor range ΔKand the effect of surface removal on the crack-opening level. In order to simulate the behaviors of the plasticity-and the roughness-induced fatigue crack closure, the finite element method was adopted. The results of FEM were in good agreement with the experimental results. It was cconcluded that at a given yield strength level , a low Youngs modulus and a low work-hardening coefficient will favor PIFCC, whereas a high Youngs modulus and a high work-hardening coefficient will favor RIFCC.

A Novel Methodology for Calculating Crack Opening Stress under Tension‐Compression Cyclic Load

“…An elastic-perfectly plastic model is given to the material of steel, where the modulus of elasticity is 200 GPa, the yield stress is 300 MPa, and Poisson's ratio is 0.3. e eight-node quadrilateral element (PLANE 183) is used to establish the two-dimensional finite element model. Moreover, nodes to rigid line contact pair are established on the crack surface and notch boundary to prevent the crack from penetrating, namely, the negative displacement of nodes on crack surface [34]. e parameters of contact pairs are obtained from trial calculation with the command of CNCHECK, so as to improve the contact parameters in the final model.…”

Novel Characterizations of Effective SIFs and Fatigue Crack Propagation Rate of Welded Rail Steel Using DIC

“…The classical Paris model does not consider the effect of the crack-tip plasticity-induced crack closure effect, and it is still an international academic issue to accurately characterize the effective stress-intensity factor ∆K eff under consideration for the crack-tip plasticity-induced crack closure effect. At present, research on the effect of plasticity-induced crack closure locally and abroad mainly includes both numerical simulation [3][4][5] and experimental methods [6][7][8]. Among the experimental methods, DIC technology is a noncontact, high-precision method for full-field displacement, deformation, and stress measurement, which is increasingly used in various fields because of its extremely relaxed test environment requirements and its advantages of full-field measurement, strong anti-interference ability, and high measurement accuracy.…”