Fatigue characterization and modeling of AZ31B magnesium alloy spot-welds

Abstract

Cyclic behavior of AZ31B spot-welds was studied using different specimen configurations, and compared with steel and aluminum spot-welds. Fatigue strength of magnesium spot-welds was similar to aluminum and less than steel. Three failure modes were observed in tensile-shear specimens and one mode of failure in cross-tension specimens. Fatigue crack initiation life was 50% and 30% of the total life for tensile-shear and cross-tension specimens, respectively. A number of available fatigue models were assessed by predicting fatigue life of magnesium spot-welds. Although these models do not account for the asymmetric cyclic hardening behavior, some of them performed successfully for magnesium spotwelds.

A phenomenological stress–strain model for wrought magnesium alloys under elastoplastic strain-controlled variable amplitude loading

“…The stress-strain hysteresis loops, calculated with the constitutive model developed in [42], were compared with experimentally determined stress-strain hysteresis loops and reach good agreements even at lower strain ranges. A numerical fatigue analysis of an automotive substructure was carried out in [43] with constant amplitude loading, using the model described in [42].…”

“…[40][41][42][43][44][45][46]). Some of the models aim on deep drawing simulations for sheet metal forming (e.g.…”

“…Wang et al [44][45][46] developed crystal plasticity based constitutive models for hexagonal close packed crystals using AZ31 wrought semi-finished products for the verifications. The models described in [44,45] calculate stress-strain paths similar as in [40][41][42][43] with the advantage that they are more physics-based and are able to capture the texture evolution during cyclic loading. Furthermore, the models in [44,45] are able to calculate a smooth transition between elastic and plastic deformation instead of a sharp bend as shown in [40,41].…”

“…Behravesh [42] developed a constitutive model with the focus on the fatigue analysis of spot welded magnesium sheets. The stress-strain hysteresis loops, calculated with the constitutive model developed in [42], were compared with experimentally determined stress-strain hysteresis loops and reach good agreements even at lower strain ranges.…”

“…The constitutive models [40][41][42][43] were developed for 2D and 3D finite element analyses and thus, the simulation time for one cycle is comparatively large. A large computational effort per cycle is also necessary using crystal plasticity models for polycrystals, which contain large number of orientations at each integration point [40].…”