厚壁矩形中空截面冷弯型钢纵向残余应力试验研究

对壁厚超过6mm的厚壁矩形中空截面冷弯型钢进行试验研究。矩形中空截面采用两种成型方法:直接法(直接形成矩形)和间接法(先形成圆形,再转换成矩形)。采用两种方法(钻孔法和X射线衍射法)计算纵向残余应力的大小和分布。研究了沿截面周长方向和厚度方向的纵向残余应力的大小和分布。结果显示,沿厚度方向的纵向残余应力在外表面为拉力,内表面为压力,表现出类似于正弦曲线的非线性特性。此外,讨论了厚壁矩形中空截面冷弯型钢的成型过程和截面几何尺寸对残余应力的大小和分布的影响。最后,针对厚壁矩形中空截面冷弯型钢两种不同成型过程,分别给出相应的残余应力分布情况。

Experimental Investigation on Longitudinal Residual Stresses for Cold-Formed Thick-Walled Square Hollow Sections

This paper presents the experimental study on cold-formed thick-walled square hollow sections with thickness greater than 6 mm. Square hollow sections are formed using two different forming processes of a "direct square" way and an "indirect way from circular to square". Two test methods of the hole-drilling method and the X-ray diffraction method are used to measure the magnitudes and distributions of longitudinal residual stresses. The magnitudes and distributions of longitudinal residual stresses along the section perimeter as well as along the section thickness are obtained in this study. It is shown that the longitudinal residual stresses are in tension at outer surface and in compression at inner surface, and present nonlinear distributions, which seems like "sine" curve along the section thickness. Furthermore, the effects of forming process and cross-section geometry on the magnitudes and distributions of longitudinal residual stresses for cold-formed thick-walled square hollow sections are discussed. At last, two distribution patterns have been proposed for the square hollow sections formed using two different forming processes, respectively.