SUMMARYThis paper presents new achievements in the extended finite element modeling of large elasto-plastic deformation in solid problems. The computational technique is presented based on the extended finite element method (X-FEM) coupled with the Lagrangian formulation in order to model arbitrary interfaces in large deformations. In X-FEM, the material interfaces are represented independently of element boundaries, and the process is accomplished by partitioning the domain with some triangular sub-elements whose Gauss points are used for integration of the domain of elements. The large elasto-plastic deformation formulation is employed within the X-FEM framework to simulate the non-linear behavior of materials. The interface between two bodies is modeled by using the X-FEM technique and applying the Heavisideand level-set-based enrichment functions. Finally, several numerical examples are analyzed, including arbitrary material interfaces, to demonstrate the efficiency of the X-FEM technique in large plasticity deformations.
A microstructure sensitive criterion for dwell fatigue crack initiation in polycrystalline alloys is proposed in this paper. Local stress peaks due to load shedding from time dependent plastic deformation fields in neighboring grains are responsible for crack initiation in dwell fatigue. A calibrated and experimentally validated crystal plasticity finite element model (CFEM) is employed for predicting slip system level stresses and strains. Vital microstructural features related to the grain morphology and crystallographic orientations are accounted for in the FEM by construction of microstructures that are statistically equivalent to those observed in OIM scans. The output of the FEM is used to evaluate the crack initiation condition in the post processing stage. The functional form of the criterion is motivated from the similarities in the stress fields and crack evolution criteria ahead of a crack tip and dislocation pileup. A specific model is developed for estimating the pileup length necessary for the nucleation criterion using the notion of geometrically necessary dislocations. The crack nucleation criterion is calibrated and validated by using experimental data obtained from ultrasonic crack monitoring techniques. In order to be able to model a large number of cycles to failure initiation, a dual-time scaling algorithm is proposed using wavelet induced decomposition. The algorithm decouples the governing equations into two sets of problems corresponding to two different time scales. One is a long time scale (low frequency) problem characterizing a cycle-averaged solution, while the other is a short time scale (high frequency) problem for a remaining oscillatory portion. The method significantly reduces the computational time till crack initiation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.