Determination of Biaxial Anisotropy Coefficient for LDX2205 Duplex Stainless Steel

Abstract

In sheet metal forming processes such as deep drawing, planar anisotropy plays a crucial role in determining the final geometry. The formability of sheet metals depends on their anisotropic behavior; therefore, anisotropy can be a limitation of forming. Accurate finite element modeling of sheet metal forming processes requires a robust description of anisotropic behavior. The standardized approach for determining anisotropy is tensile testing at different angles relative to the sheet metal's rolling direction. Biaxial behavior is also important for the yield function of the materials. Although several methods are available for determining biaxial properties, the disk compression test is relatively simple and easy to perform and, therefore, a favorable method in an industrial environment. The goal of the present study is to determine the biaxial anisotropy coefficient of LDX2205 duplex stainless steel (DSS). Although the proper lubrication and the appropriate test methodology are unknown, a comparison is needed to define the methods and lubricants for further investigations. The tests were conducted with three lubricants to identify the most reliable one: a high-contact-pressure grease, a graphite-containing grease, and PTFE sheets. Based on measurements, the greatest deformation occurred when PTFE sheets were applied; therefore, further tests were performed using these sheets. Three series of compression tests were performed: a fully compressed series, a gradually compressed series, and a load-driven series. The investigations were carried out to examine the influence of the different methods on the parameter. Microhardness tests were conducted on the as-delivery-conditioned material and on the compressed material.