A Non-Schmid Crystal Plasticity Finite Element Approach To Multi-Scale Modeling Of Nickel-Based Superalloys

Published

August 1, 2016

Author(s)

Shahriyar Keshavarzhadad, S K. Ghosh, Andrew C. Reid, Stephen A. Langer

Abstract

This paper develops non-Schmid crystal-plastic constitutive models at two length scales, & bridges these length scales in a multi-scale framework. The constitutive models address thermo-mechanical behavior of Nickel-based superalloys for a large temperature range, 300K to 1300K, & include orientation dependencies & asymmetry in tension and compression. The orientation dependencies of the constitutive modes result in asymmetry in tension & compression for almost all orientations on the standard unit triangle. However simulations show different trends for the stronger direction (tension or compression) in terms of yield stress & hardening. For orientations close to [001] tension is the stronger direction while the behavior is reversed by approaching to orientations close to [011] & the asymmetry disappears by approaching to [111] orientations. For the first length scale examined, the sub-grain scale, a size-dependent, dislocation density-based FEM model of the representative volume element (RVE) with explicit depiction of the y-y' morphology is developed as a building block for homogenization. For the next scale, an activation energy based crystal plasticity (AE-CP) model is developed for single crystal Ni-based superalloys that can be implemented in simulations of polycrystalline aggregates. The homogenized AE-CP model develops functional forms of constitutive parameters in terms of characteristics of the sub-grain y-y' microstructural morphology. The homogenized parameters are expressed as functions of y' shape, volume fraction & y channel-width in the sub-grain microstructure. This homogenized model has the advantage of significantly expediting crystal plasticity FE simulations due to parameterized representation of the morphology, while retaining accuracy with respect to the explicit representation. The model is validated with results of single crystal tension & compression tests for different temperatures & orientations, which were available in the literature.

Citation

ACTA Materialia

Pub Type

Journals

Keywords

Ni-based superalloys, homogenization, crystal plasticity, morphology, Non-Schmid

Citation

Keshavarzhadad, S. , Ghosh, S. , Reid, A. and Langer, S. (2016), A Non-Schmid Crystal Plasticity Finite Element Approach To Multi-Scale Modeling Of Nickel-Based Superalloys, ACTA Materialia (Accessed December 26, 2024)