Design of heterogeneous interior notched specimens for material mechanical characterization

Abstract

Nowadays, virtual predictions are essential in the design and development of new engineering parts. A critical aspect for virtual predictions is the accuracy of the constitutive model to simulate the material behavior. A state-of-the-art constitutive model generally involves a large number of parameters, and according to classical procedures, this requires many mechanical experiments for its accurate identification. Fortunately, this large number of mechanical experiments can be reduced using heterogeneous mechanical tests, which provide richer mechanical information than classical homogeneous tests. However, the test’s richness is much dependent on the specimen's geometry and can be improved with the development of new specimens. Therefore, this work aims to design a uniaxial tensile load test that presents heterogeneous strain fields using a shape optimization methodology, by controlling the specimen's interior notch shape. The optimization problem is driven by a cost function composed by several indicators of the heterogeneity present in the specimen. Results show that the specimen's heterogeneity is increased with a non-circular interior notch. The achieved virtual mechanical test originates both uniaxial tension and shear strain states in the plastic region, being the uniaxial tension strain state predominant.

A relative approach for uncertainty quantification of inversely identified material behavior using a heterogeneous test for sheet metal

“…An innovative heterogeneous mechanical test proposed in [20,19] was the base to generate synthetically deformed images that were used as reference virtual material data in the approach, as well as used for the iterative analysis. The geometry of the heterogeneous specimen is depicted in Figure 2.…”

“…This FEMU technique compares both the experimental and numerical strain fields using the DIC subset-based method for the strain measurements, minimizing the error between the two. The mechanical test that feeds the FEMU is a heterogeneous test proposed in [19], which was originated by a shape optimization design approach based on a heterogeneity indicator. The constitutive model under consideration is the Swift hardening law and, for the anisotropy behavior, the Yld2000-2d yield function.…”

Spline-based specimen shape optimization for robust material model calibration

“…The first family does not consider any specific constitutive model: it relies on a measure of the heterogeneity of material states. The idea is usually to quantify the ability of a specimen to well sample the behaviour in the principal stresses/strains plane [15][16][17][18] or to target a specific triaxiality [19]. These methods are designed to ensure that the specimen correctly samples the behaviour, which is useful for discriminating between different constitutive models.…”

“…Given the highly ill-posed nature of the problem, the spirit is not to determine the ideal specimen (if it exists) but to further improve an existing manually designed or parametrically optimized specimen. Here, the use of a spline-based geometric shape optimization as in [18] is proposed because it allows free-form geometry modifications with unchanged topology. It is possible to keep a low number of design variables and a design sub-space made of regular shapes thanks to spline functions.…”

Parameter Identification of Swift Law Using a FEMU-Based Approach and an Innovative Heterogeneous Mechanical Test

“…It is very important to have adequate input data for the FEMU. Therefore, an innovative heterogeneous mechanical test for uniaxial loading conditions developed in [16] using an optimization approach based on a heterogeneity indicator is going to be used for the parameter identification of the Swift law. Although it seems unnecessary to use a heterogeneous test for the calibration of the Swift law, it was concluded otherwise with the methodology present in [17].…”