Abstract
Advanced high strength galvanized steel sheet has been one of the dominant materials of modern automotive panels because of its outstanding mechanical properties and corrosion resistance. The zinc coating thickness of hot dip galvanized steel sheet is only about 10–20 μm, which is a discarded object on the macro level. However, it is obvious to damage and impact on stamping performance. Therefore, this paper takes zinc coating as the research object and builds its mechanical constitutive model based on a nano-indentation test and dimensional analysis theory. We separated the zinc coating from the galvanized steel substrate and constructed a sandwich material model by introducing a cohesive layer to connect the zinc coating and the steel substrate. We obtained the interface binding energy between the zinc coating and the steel substrate through the nano-scratch test. The accuracy of the model is verified by the finite element analysis of hemispherical parts. We used the five-layers element model with 0 thickness cohesive layer to simulate the zinc coating damage of galvanized steel sheet. The hemispherical part drawing experiment is used to verify the feasibility of the finite element analysis results. The results demonstrate that it is more accurate to consider the finite element numerical simulation of the zinc coating, introducing the cohesive element to simulate damage between the coating and the substrate. Drawing depth, stamping force, and the strain of the numerical simulation are closer to the experimental results.
Highlights
Galvanized advanced high strength steel (AHSS) has become the dominant material of automotive lightweight because of its superior strength, elongation, and outstanding corrosion resistance, which can follow the requirements of collision safety, energy saving, emission reduction, and environmental protection [1]
The hot dip galvanized high strength steel DP600 is chosen as the research object
We studied mechanical behavior and its damage with the steel substrate
Summary
Galvanized advanced high strength steel (AHSS) has become the dominant material of automotive lightweight because of its superior strength, elongation, and outstanding corrosion resistance, which can follow the requirements of collision safety, energy saving, emission reduction, and environmental protection [1]. The upper and lower surface of the galvanized steel sheet is zinc coating, and the intermediate substrate is a steel sheet We can understand it as three-layers of composite material, like a sandwich equivalent to the stamping of multiple layers of material. Kim et al [29] studied the fracture of the coating layer of galvanized steel using V-bending test and numerical simulation of the solid element. The coating is taken into consideration in the above studies, the element model of numerical simulation still cannot describe the deformation model of the coating and substrate of galvanized AHSS. In this paper, a coupled element model based on solid shell element and shell element is introduced to simulate the deformation of galvanized AHSS sheet, which recognized the scale effect of the coating.
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