Abstract
This work presents an advanced crystal plasticity model for the simulation of the mechanical behavior of multiphase advanced high-strength steels. The model is based on the Visco-Plastic Self-Consistent (VPSC) model and uses information about the material’s crystallographic texture and grain morphology together with a grain constitutive law. The law used here, based on the work of Pantleon, considers how dislocations are created and annihilated, as well as how they interact with obstacles such as grain boundaries and inclusions (carbides). Additionally, strain rate sensitivity is implemented using a phenomenological expression derived from literature data that does not require any fitting parameter. The model is applied to the study of two bainitic steels obtained by applying different heat treatments. After fitting the required parameters using tensile experiments in different directions at quasi-static and high strain rates, formability properties are determined using the model for the performance of virtual experiments: uniaxial tests are used to determine r-values and stress levels and biaxial tests are used for the calculation of yield surfaces and forming limit curves.
Highlights
The viscoplastic self-consistent model (VPSC) [1] allows simulating the plastic behavior of polycrystalline materials, taking into account their crystal structure, grain shape and crystallographic texture
The main novelty of VPSC90 is the usage of a different algorithm, capable of finding a direct solution to grain stresses based on the Newton method
Y is the annihilation distance; C2 and σimb are two constant related with the incidental necessary boundaries (INBs) and geometrically necessary boundaries (GNBs), respectively; and λis the mean free path, which is calculated according to the equation: cpvp
Summary
The viscoplastic self-consistent model (VPSC) [1] allows simulating the plastic behavior of polycrystalline materials, taking into account their crystal structure, grain shape and crystallographic texture. A novel approach is used to model strain rate sensitivity, while work hardening is described combining several physical and phenomenological laws. The model is applied to the study of bainitic steels Due to their good combination of properties, which include competitive production costs with enhanced mechanical properties that can range from very high levels of strength and toughness to improved ductility, hardenability or weldability, depending on specific composition and treatments [11,12], bainitic steels are some of the most promising materials as third-generation advanced high-strength steels (AHSS), with increasing importance in the automotive industry [13,14]. In the rest of this Introduction, it is discussed how the work hardening, strain rate sensitivity and formability of steels have been previously studied.
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