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首页> 外文期刊>Journal of Materials Processing Technology >Experimental and numerical investigations: Alleviating tensile residual stresses in flash-butt welds by localised rapid post-weld heat treatment
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Experimental and numerical investigations: Alleviating tensile residual stresses in flash-butt welds by localised rapid post-weld heat treatment

机译：实验和数值研究：通过局部快速焊后热处理减轻对接焊缝中的拉伸残余应力

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摘要

Flash-butt welding is commonly used in the manufacture of continuously welded rails (CWR). The finished welds typically exhibit high levels of tensile residual stresses in the rail web. In addition, the surface condition of the web may contain shear drag or other defects resulting from the shearing process. When combined with torsional loading of the web under service loading (particularly at high axle loads), these conditions may contribute to fatigue failure of the weld in a horizontal split web mode. The risk of weld failure may be alleviated by reducing the magnitude of the tensile residual stresses. A sequentially coupled thermo-mechanical finite element (FE) model incorporating the phase transformation characteristics of the rail material has been used to predict the residual stress distribution developed during welding of AS60 and AS68 rails, by approximating the thermal distribution after upset from the heat-affected zone (HAZ) characteristics. The effect of localised, rapid post-weld heat treatment on residual stresses in the web region of the weld was also investigated. An experimental program covering measurement of post-weld cooling rates using infra-red thermography, and residual stresses by the strain-gauge and trepanning, was used to validate the finite element model. The results have shown that the FE model can satisfactorily predict the residual stress distribution. In addition, the (tensile) residual stress levels in both vertical and longitudinal directions of the web can be reduced by rapidly reheating the base of the foot directly after welding. Thereafter, both numerical and experimental approaches will be used to develop modifications to the flash-butt welding procedure that should result in improved weld performance under high axle load conditions.
机译：闪光对焊通常用于连续焊接钢轨（CWR）的制造中。精加工的焊缝通常在钢轨腹板上表现出高水平的拉伸残余应力。另外，纤维网的表面状况可能包含剪切力或剪切过程产生的其他缺陷。当在工作载荷下（尤其是在高轴载荷下）与腹板的扭转载荷结合使用时，这些条件可能会导致水平剖腹板模式下焊缝的疲劳失效。焊接失效的风险可以通过减小拉伸残余应力的大小来减轻。顺序耦合的热机械有限元（FE）模型结合了钢轨材料的相变特性，已被用来预测AS60和AS68钢轨在焊接过程中产生的残余应力分布，方法是根据热影响估算出up锻后的热分布。受影响区域（HAZ）特性。还研究了局部快速焊后热处理对焊缝腹板区域残余应力的影响。一个实验程序涵盖了使用红外热像仪测量焊后冷却速率以及应变计和开裂产生的残余应力的方法，以验证有限元模型。结果表明，有限元模型可以令人满意地预测残余应力分布。另外，可以通过在焊接后直接快速加热脚的根部来降低纤维网的竖直和纵向方向上的（拉伸）残余应力水平。此后，数值和实验方法都将用于改进对接焊接程序的修改，这些修改应导致在高轴负载条件下改善焊接性能。

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