钛合金薄板带热沉GTAW焊的应力场

STRESS FIELD OF GTAW WITH A SPOT HEAT SINK ON TITANIUM ALLOY THIN PLATE

采用数值模拟和试验相结合的方法 ,比较钛合金常规钨极氩弧焊 (GTAW )及带热沉的钨极氩弧焊 ,即动态控制低应力无变形 (DC LSND ,dynamicallycontrolledlowstressno distortion)GTAW焊接过程中应力场的形态与发展历史。DC LSND焊接过程中 ,热沉的急冷收缩对热沉作用部位与熔池之间已凝固但仍处于高温状态的金属产生很强的拉伸作用 ,使焊缝中拉伸塑性变形增大 ,近缝区压缩塑性变形相应减小 ,从而导致焊缝与近缝区不协调应变减小 ,残余应力降低。与常规焊最大残余拉应力位于焊缝中心不同 ,在所选用的焊接条件下 ,DC LSND焊最大残余拉应力位于近缝区 。

The stress field pattern and the stress developing history were studied numerically and experimentally for both the conventional gas tungsten arc welding (GTAW) and dynamically controlled low stress no-distortion (DC-LSND) GTAW of a Titanium alloy Ti-6Al-4V. Results showed that high tensile effect generated by heat sink with sharp cooling and contraction of weld metals is acting in the zone between the arc and the trailing heat sink during DC-LSND GTAW, which increased tensile plastic strain of weld and decreased compress plastic strain in the zone near the weld. All of these phenomena mitigate the incompatible strain in the weld and the zone nearby, hence, the residual stress is reduced. The maximum residual tensile stress is located in the zone close to the weld in DC-LSND GTAW, while in conventional GTAW the maximum residual tensile stress is located in the weld. The distribution patterns of residual stress are different from each other.