Mechanical Properties Involved in the Micro-forming of Ultra-thin Stainless Steel Sheets

Abstract

The objective of this paper is to characterize the mechanical behavior of an ultra-thin stainless steel, of 0.15-mm thickness, that is commonly used in the manufacturing of miniature connectors. The main focus is the relationship between some microstructural features, like grain size and surface roughness, and the macroscopic mechanical behavior investigated in uniaxial tension and simple shear. In tension, adaptations to the very small sheet thickness, in order to hold the specimen under the grips, are presented. Yield stress, initial elastic modulus, and evolution of the loading-unloading slope with plastic deformation were evaluated. Moreover, the kinematic contribution to the hardening was characterized by monotonic and cyclic simple shear test and reproduced by a mixed hardening law implemented in Abaqus finite element code. Then, the evolution of surface roughness with plastic strain, both in tension and simple shear, was analyzed. It was shown that in the case of an ultra-thin sheet, the stress levels, calculated either from an average thickness or when considering the effect of the surface roughness, exhibit a significant difference. Finally, the influence of surface roughness on the fracture of a tensile specimen was also investigated.

Numerical Study on the Formability of Metallic Bipolar Plates for Proton Exchange Membrane (PEM) Fuel Cells

“…Typically, the forming tools are assumed rigid in the numerical simulation, while the deformation of the metallic sheet is described by an elastoplastic material model (strain rate-insensitive), as described in the previous section. Hence, in the present study, the tools surface The plastic anisotropy coefficients of the stainless steel SS304 were experimentally calculated by Pham et al [43] in the rolling and transverse directions. They obtained similar values for both directions, close to 0.9, which are in agreement with the values presented by Raj [44] for the SS304 with a thickness of 0.5 mm.…”

“…The comparison between the experimental and numerical stress-strain curves is presented in Figure 3, highlighting the accurate description of the work hardening behaviour by the Swift law. The plastic anisotropy coefficients of the stainless steel SS304 were experimentally calculated by Pham et al [43] in the rolling and transverse directions. They obtained similar values for both directions, close to 0.9, which are in agreement with the values presented by Raj [44] for the SS304 with a thickness of 0.5 mm.…”

Crystal plasticity and phenomenological approaches for the simulation of deformation behavior in thin copper alloy sheets

“…A sample geometry was prepared according to ISO 6892-1 standard, similarly to Pham et al (2015). In order to evaluate material anisotropy, room temperature monotonous tensile tests were performed at 0 • , 45 • and 90 • from the RD.…”

Understanding Size Effects and Forming Limits in the Micro-Stamping of Industrial Stainless Steel Foils

“…Often common 2 of 20 methods to analyse material properties and tune material models cannot be directly applied. Previous studies have developed special tests [17] and sample dimensions [18] to enable calibration of kinematic hardening and fracture model parameters. These models do not account for size effects.…”