A review of planar biaxial tensile test systems for sheet metal

The focus of this paper is to present a comprehensive review of the main biaxial test systems that have been developed with primary focus on sheet metal testing. The paper includes a review of biaxial tensile test devices and specimen design for biaxial testing. A description of the scientific significance of the work and the industrial implications arising from results of biaxial testing is also presented. Biaxial testing of metal is becoming prevalent in the sheet metal working industry for establishing the mechanical properties of the sheet material. The primary reason for using the biaxial tensile test, as opposed to the common uniaxial test, is that metal in sheet form is largely anisotropic, i.e. it has varying mechanical strength in different directions due to the forming process used in its manufacture. As the standard tensile test only determines the mechanical properties in one direction the resulting test data may not be applicable to multi-directional forming processes such as deep drawing. Biaxial testing is also becoming increasingly important for testing of metals used in machine and structural components that may be typically loaded in more than one direction during service. Biaxial loading can cause failure of the material at loads much less than that determined by conventional tensile-testing methods. The aforementioned reasons have led to research activity in the area of biaxial testing.