Influence of Stress State on the Yield Strength of Aluminium Alloy

Abstract

The basic mechanical properties of structural materials (e.g. yield strength, ultimate tensile strength, uniform and total ductility, anisotropy coefficient, etc.) represent fundamental material characteristics. These parameters are mostly detected by a static tensile test. From the stress state point of view, it is therefore a uniaxial tension stress state. However, the service load usually means acting of wide range of stress states. For this reason, the department of engineering technology at TUL developed a device enabling loading the sample by planar bi-axial loading with the possibility to change ratio of their loading. It is therefore possible to load the material from uniaxial tension to equi-biaxial stretching. The aim of this paper is to determine the change of one basic material mechanical properties (yield strength) based on the adjustment of various stress states - from the conventional uniaxial tensile stress state (static tensile test) to equi-biaxial stretching. The own evaluation is performed on the measured stress-strain curves for the tested aluminium alloy AA6111. The results can then be used not only to describe the effect of stress state on the deformation behaviour of tested material, but can also serve as input data in numerical simulations of forming technologies.