Abstract

Because of its characteristics of good rigidity and strong ant-vibration, heavy-duty welding turning tools are widely applied in the rough machining of water chamber heads. However, welding residual stress is induced around the welding seam of the tool. During the heavy-duty machining, cracks easily occur due to an influence of impacts, high-temperature and thermal-mechanical loading, which causes tools failure. In this paper, ANSYS finite element model of heavy-duty cutting tools is established based on thermal elastic-plastic theory in order to analyze thermal stress field distribution in welding process. Secondly, actual welding residual stress distribution is obtained by the nano indentation experiment, verifying that the model can effectively analyze the stress and strain distribution. The welding tool failure mechanism is explored further. Finally, vibration aging and ultrasonic impact treatment methods are adopted to reduce welding residual stress of heavy-duty cutting tools. Two methods are compared for the influence of welding residual stress. Through the above research, finite element model can exactly reflect the welding residual stress distribution. The ultrasonic impact treatment is better than vibration aging treatment to reduce the welding residual stress and then extend their service life.

摘要

重型焊接车刀因其刚性好、抗振性强等特点，广泛应用于水室封头的粗加工。然而，在工具的焊缝周围会产生焊接残余应力。在重载加工过程中，由于冲击、高温和热机械载荷的影响，容易产生裂纹，从而导致刀具失效。本文基于热弹塑性理论建立重型切削刀具ANSYS有限元模型，分析焊接过程中的热应力场分布。其次，通过纳米压痕实验得到了实际的焊接残余应力分布，验证了该模型能有效分析应力应变分布。进一步探讨了焊接工具的失效机理。最后，采用振动时效和超声冲击处理方法降低重型切削刀具的焊接残余应力。比较了两种方法对焊接残余应力的影响。通过以上研究，有限元模型可以准确反映焊接残余应力分布。超声波冲击处理比振动时效处理更能降低焊接残余应力，从而延长其使用寿命。