In this study, residual stresses of cold-forged ball studs were investigated by the contour method with using widely available wire-Electro-Discharging Machine (wire-EDM) and Coordinate Measuring Machine (CMM). After the wire-EDM cutting, one of the steps of the contour method, it was revealed that the surface contour data was affected from the cutting step. Therefore, to increase the accuracy of the measured residual stresses, one of the ball studs were heat-treated to normalize residual stresses due to cold forging. The contour data of the heat-treated sample was subtracted from the as-forged surface contour to eliminate any cutting-induced artefacts. The final residual stress profiles suggested that the subtracting procedure minimized the cutting errors. In addition, a new classification approach for the cutting-induced errors for the contour method was introduced. According to final stress maps obtained by the contour method, it was revealed that high compressive residual stresses were obtained at the socket regions of the ball studs, as expected. Balancing tensile residual stresses were observed at the inner regions.

在这项研究中，冷锻球头螺栓的残余应力通过轮廓法使用广泛使用的线材放电加工机 (wire-EDM) 和坐标测量机 (CMM) 进行了研究。电火花线切割后，轮廓方法的步骤之一，表明表面轮廓数据受到切割步骤的影响。因此，为了提高测量残余应力的准确性，对其中一个球头螺栓进行了热处理，使冷锻产生的残余应力正常化。从锻造表面轮廓中减去热处理样品的轮廓数据，以消除任何切割引起的伪影。最终的残余应力分布表明减法程序将切削误差降至最低。此外，引入了一种新的轮廓方法的切割引起的误差分类方法。根据通过等高线法获得的最终应力图，正如预期的那样，在球头螺栓的球窝区域获得了高压缩残余应力。在内部区域观察到平衡的拉伸残余应力。