Papers by Keyword: Inelastic Strain

Abstract: 2D C/SiC ceramic matrix composite (CMC) displays significant damage characteristic coupled with inelastic strain under tension and shear loads, which should be considered in the constitutive model. In this study, a continuum damage mechanics (CDM) model was proposed for this material, in which the process degradation of the material property was described by introducing a set of scalar damage variables, and the damage-coupling effect was also considered. Meanwhile, isotropic hardening theory was applied to form the evolution rule of inelastic strains. The model was then implemented into the UMAT in ABAQUS software and validated by comparison between the simulation and experiment results.

Abstract: Nonlinear finite element analysis is performed to evaluate the reliability of the solder joint of wafer level chip scale package (WLCSP) under accelerated temperature cycling test. The solder joint is subjected to the inelastic strain that is generated during the temperature cycling test due to the thermal expansion mismatch between the various materials of the package and PCB (printed circuit board). The equivalent stress, equivalent inelastic strain, total shear strain, and hysteresis loop of the solder joint are determined in the simulation. The equivalent inelastic strain and total shear strain range of the joint are obtained as damage criterion to predict the solder fatigue. Both Coffin-Manson and Modified Coffin-Manson fatigue life prediction models are used to estimate the thermal fatigue life of WLCSP solder joints under temperature cycling test. Also, the effects of the material properties of the stress buffer layer (SBL) on the fatigue life of the solder joint are discussed.