平板で座屈を防止する引張－圧縮試験の実験精度の検証

抄録

Measurement of stress-strain curves under tension-compression reverse loadings is crucially important for the understanding of the Bauschinger effect of aluminum alloy sheets. Uniaxial compression of sheet metals is carried out with supporting flat plates, which clamp a specimen to prevent it from buckling. The clamp forces generate the thickness stress and the friction forces. In the present study, influence of the thickness stress and the friction force on the stress-strain curve and the validity of corrections of these effects were investigated by using the finite element analysis. It is revealed that the correction of thickness stress effect by using the equivalent stress did not work appropriately. While, subtraction of the friction force from the measured load corrected the friction effect. Furthermore, the uniaxial tension/compression experiments demonstrated the effectiveness of correction of friction effect. A rectangular window was machined on the supporting plate so as to measure the deformation of a specimen by the digital image correlation method. Analysis of the measured displacements in the window was able to detect the occurrence of wrinkling and buckling during uniaxial compression. Eventually, using the present plate-type antibuckling fixture, the stress-strain curves for several reverse loadings were successfully measured.