Buckling of Shape Memory Alloy Columns. 2nd Report. Anti-Buckling Effect of Straight Columns.

Abstract

The buckling characteristics of straight SMA (shape memory alloy) columns were investigated in this study. A parameter called anti-buckling capability was introduced and used to judge the stability of SMA columns under axial compression. The anti-buckling capability of SMA columns with different lengths and axial loads were calculated using a simple method. It was found for all considered lengths of columns that with the increase of axial load the anti-buckling capability decreases to a minimum value first, increases again to a maximum value and at last decreases monotonically to negative. This special anti-buckling capability versus axial load curve of SMA columns is due to the special non-linearity of stress-strain curve of the SMA. The anti-buckling capability at the minimum point can be either positive or negative depending on the length of a column. Since a SMA column buckles at the smallest value of the axial load, at which the antibuckling capability becomes negative, the sign of the anti-buckling capability at the minimum point of the anti-buckling capability versus axial load curve is critical to the buckling load of column. If the anti-buckling capability at the minimum point is negative, the column buckles at a significantly low axial load. However, the absolute value of the negative anti-buckling capability is relatively small and it can easily be changed to positive by very simple strengthening so that tthe buckling load of the column can be significantly increased.