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在焊接时,焊缝及其附近的金属由于在高温下的变形受到阻碍,产生了压缩塑性变形,这个区域称为塑性变形区。该区内的塑性变形分布如图1所示,它的存在使构件相当于受到一个外加压力P_f的作用而产生纵向缩短和纵向残余应力（图2）。对低碳钢和低合金钢而言,其附近塑性区的拉应力数值可达屈服极限σ_s。焊接内应力与工作压应力共同作用可能降低压杆的临界应力,为了弄清焊缝塑性区对压杆稳定性的影响,这里首先讨论焊缝塑性区是否能承受外力的问题。以图1表示的应力变形模型为研究对象。
During welding, the weld and the metal near it are hindered by the deformation at high temperatures, resulting in a compressive plastic deformation. This area is called a plastic deformation zone. The plastic deformation distribution in this area is shown in Fig.1. Its existence makes the component equivalent to longitudinal shortening and longitudinal residual stress (Figure 2) due to an applied pressure P_f. For mild steel and low alloy steels, the value of the tensile stress in the plastic zone near it reaches the yield limit σ_s. In order to find out the influence of the plastic zone of the weld on the stability of the press bar, the plastic zone of the weld is able to withstand the problem of the external force first. The stress-strain model shown in Fig.1 is the research object.