A Sheet Metal Bi-Axial Testing Rig

摘要

This paper describes a new rig design for investigating the influence of moderate temperatures to 300℃ upon biaxial tensile deformation and fracture strain in forming grades of sheet steel and aluminium (yield stress # 200 MPa). The rig further allows creep tests to be conducted under steady loads and temperatures for other low strength metallic and non-metallic materials. The features discussed include extension and thinning measurements of a cruciform testpiece, gripping and alignment under deadweight biaxial loadings and the heating method. Calibrations are made on the influence of temperature upon the displacement transducers during a cycle of heating and cooling. This allows for the true displacements of a the testpiece under load. Formulae for the conversion of applied load and measured displacement to respective testpiece stress and strain are given. A preliminary equi-biaxial loading test shows the suitability of the chosen gripping method and the extent to which load alignment is achieved. Refinements to the existing rig design and the test procedure are discussed in the light of these results.