Optimum Design of Spot Weld Joints and Nondestructive Measurement of Weld Quality for Light Weight Structures

电阻点焊已被广泛应用于薄板结构的施工。在这些结构中，点焊缝的分布方向不同，间距不同，这是由经验数据确定的。然而，点接头的数量和位置在设计和制造过程中具有重要的技术和经济影响。尤其是强度评估是点焊结构优化设计的重要工具。然而，即使在静载荷作用下，多点焊接结构的强度评估也并不总是成立的。为了发展点焊结构的强度评估和优化设计方法，本研究对点焊结构的三种构件进行了应力-应变分析和拉伸-剪切试验。此外，还尝试了一种非破坏性的测量方法，以发展他们对应力…的过程中保证根据应力-应变分析，点节点的位置影响应力分布，而应力分布与拉剪试验中产生的轴力和弯矩有关。横向点焊试件的应力分布没有明显的相互影响，说明强度是由本构焊点焊强度之和决定的。在与施力方向平行的点焊试件中，外表面和内表面的应力分布有较大差异。这种差异与弯矩有关，并影响试件的强度。与单点焊的强度对比表明，这种影响是由材料特有的、与板厚和宽度无关的广义曲线所给出的。试验结果表明，利用该广义曲线可以对试件的强度进行估算。在点焊斜向试件中，强度是由上述两个试件的联合作用提供的。基于三种试件的强度评估可用于点焊数量和位置的优化设计。研究表明，电极位移是一种有用的在线测量方法，可用于焊缝尺寸的无损评估和喷溅的检测。较少

Resistance spot welding has been widely used for the construction of thin sheet metal structures. In these structures, the spot welds are distributed in various direction and with different intervals, which are determined by the empirical data. However, the number and location of spot joints have significant technical and economical effects in the design and manufacturing processes. Especially, the assessment of strength is an important tool for the optimum design of spot welded structures. Nevertheless, the assessment of strength for multi-spot welded structures is not always established even in the static loading.In order to develop the assessment of strength and the method for optimum design of spot welded structures, in this study, the stress-strain analysis and the tensile-shear test were performed on three types of specimens, which are constitutive elements of spot welded structures. In addition, a nondestructive measurement was tried to develop their in-process assurance of stre … More ngth.According to the stress-strain analyses, the location of spot joints affects the stress distribution which is related to the axial force and bending moment induced in the tensile-shear test. In the specimens with spot welds in the transverse direction to the applied force, no mutual effect appeared in the stress distribution, from which it was shown that the strength was given by the summation of strength of constitutive spot welds. In the specimens with spot welds in the parallel direction to applied force, on the other hand, large difference appeared in the stress distribution between outer and inner surfaces. This difference is related to the bending moment and affects the strength of specimen. It was shown from the comparison of strength with single spot welds that this effect was given by the generalized curve, which was peculiar to the materials and was independent of the plate thickness and width. The experimental results showed that the strength of specimens was estimated by this generalized curve. In the specimen with spot welds in the oblique direction, the strength was shown to be given by the combined effect of two specimens above mentioned. The assessment of strength based on three types of specimens was available to the optimum design for the determination of number and location of spot welds. The displacement of electrode was clarified to be a useful in-process measurement for the nondestructive evaluation of weld size and for the detection of expulsion. Less