The distance between arc and heat sink is one of the most important parameters in DC-LSND welding technique. The influence of distance between heat sink and arc on strain in welded joint is studied. The results show that the temperature between arc and heat sink sharply reduced and the temperature of the point under the heat sink center in the weld is the lowest among those of all the points in the weldment because of the cooling effect of coolant. The temperature histories are different for the points in the weld with different distances between arc and heat sink, so as to plastic strain histories and residual plastic strain histories. The nearest of the distance between arc and heat sink, the strongest of the stretching effect. When the distance between arc and heat sink is near enough, the tensile plastic strain can be bigger than the compressive plastic strain caused in the heating process, which not only compensates the compressive plastic strain, but also causes the tensile plastic strain in the weld.%热源与热沉的距离D是动态控制低应力无变形焊接技术的关键参数之一.采用有限元技术开展了热源与热沉中心的距离对焊接接头应变影响的研究.研究发现:冷却介质的急冷作用使得热源与热沉之间的温度陡降,温度梯度变大,热沉作用处成为焊缝中心线上温度最低的位置;不同的D值引起的焊缝中心点的温度历史不同,塑性应变的历史不同,残余态结果也不同.热源与热沉之间距离越近,拉伸作用越强.热源与热沉中心的距离较近时,可以产生大于加热阶段形成的压缩塑性应变的拉伸塑性应变,从而不仅补偿加热时产生的缩短应变,而且还使焊缝中存在拉伸塑性应变.
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