K. Malekipour, M. Mashayekhi, M. Badrossamay, " Meso-scale damage mechanics modeling for high cycle fatigue behavior of additively manufactured components", Mechanics of Materials 160, PP. 103951, 2021.

Abstract:

Despite significant improvements in the mechanical and metallurgical properties of additively manufactured metallic components, the fabricated parts may suffer from low fatigue properties due to the microstructure internal defects such as porosity. This study attempts to evaluate the high cycle fatigue (HCF) behavior of the additively manufactured specimens using damage mechanics approach in Meso-scale. In order to gain a realistic perception, Representative Volume Elements (RVEs) are selected from the microstructural images of fabricated parts captured by optical microscopy. While, The Chaboche-Lemaitre damage model is used to simulate the evolution of stress-induced damage, the damage growth caused by plastic flow at the stress concentration domain around the internal defects is modelled using the Lemaitre damage model. The HCF and uniaxial tensile tests of AISI 316 L parts, utilizing the technology of selective laser melting (SLM), are carried out to identify the models’ material constants. Agreement between experimental fatigue life and numerical fatigue life prediction demonstrate the capability of the numerical model. Numerical modeling indicates that the damage initially grows around the pores from all areas of stress concentration. Still in the end, the concentration of damage in critical region causes the damage to stop in other areas. In addition, the modeling results suggest the coalescence of porosities after reaching the critical size of the pores. Finally it is found that the presence of small-scale porosities with lower than 5 μm length reveal no detrimental effect on accelerating the damage growth unless are located in the path of damage growth. Accordingly they also may redirect the path of the damage growth.