Study on Reduction of Residual Stress of Welding Joint Using Vibration

焊接广泛用于许多结构的建造。由于局部受热，焊缝附近存在残余应力。表面上的拉伸残余应力降低了累积损伤的强度。提出了降低残余应力的方法。本文提出了一种新的方法，其中使用振动载荷在焊接操作过程中，并提出了一种分析方法，所提出的方法。这种方法的优点是振动载荷是由一个小的振动器产生的。该方法可望成为一种实用的方法。首先，对残余应力的降低进行了实验研究。使用两个100 mm宽的板。两块一般用途的轧制钢板（JIS SS 400）通过螺栓支撑在支撑装置上，并在焊接过程中通过小型振动器进行振动。采用CO_2气体保护自动焊机对试件进行对接焊。凹槽为V形。焊接通过一个通道完成。激励频率选择为60Hz， ...更多信息 焊接前试件的基频。为了考察非共振频率下残余应力的降低效果，激励频率也选择为100Hz。采用化学去除淬火氧化皮的方法，用带闪烁计数器的平行光束X射线衍射仪测量了焊缝的残余应力，发现焊接过程中施加振动载荷时，焊缝上的残余拉应力明显降低。在焊道附近的点处，残余应力也减小。在远离焊道的点处，压缩残余应力倾向于拉伸。残余应力随激振振幅的增大而减小。其次，对用该方法减小残余应力的解析方法进行了检验。由于初始残余应力很大，且接近屈服应力，因此残余应力的降低是由局部塑性变形引起的。因此，分析模型，其中包括质量和预载弹簧的弹塑性特性。分析表明，残余应力的降低率随激振振幅的增大而增大。实验和分析表明了该方法的有效性。少

Welding is widely used for construction of many structures. There exists residual stress near the bead because of locally given heat. Tensile residual stress on the surface degrades strength for cumulative damage. Some reduction methods of residual stress were presented. In this paper, a new method is proposed in which vibrational load is used during welding operation and an analytical method for the proposed method is presented. Advantage of this method is that vibrational load is generated by a small shaker. This method is expected to be a practical one.First, reduction of residual stress is examined experimentally. Two plates of 100mm width are used. Two plates of rolled steel for general use (JIS SS400) are supported on the supporting devices by bolts and shaken by a small shaker during welding. Specimens are butt welded using automatic CO_2 gas shielded arc welding machine. Groove is V-shaped. Welding is completed through one pass. Excitation frequency is chosen as 60Hz which is t … More he fundamantal natural frequency of specimens before welding. In order to examine reduction effect of residual stress at non-resonane frequency, excitation frequency is also chosen as 100Hz. Residual stress is measured by removing the quenched scale chemically and using a parelelled beam X-ray diffractometer with a scintillation counter.From the experiment, it is found that on the bead, tensile residual stress is significantly reduced when vibrational load is acting during welding. At points near the bead, residual stress is also reduced. At points far from the bead, compressive residual stress tends to be tensile. Residual stress decreases as the amplitude of excitation increases.Next, an analytical method for reduction of residual stress by the proposed method is examined. It is obvious that reduction of residual stress is caused by local plastic deformation because initial residual stress is great and nearly equal to yielding stress. Thus, an analytical model which consists of mass and preloaded spring with elasto-plastic characteristic is used. From the analysis, it is found that reduction rate of residual stress increases as the amplitude of excitation increases. Thus, effectiveness of the proposed method can be demonstraited by experimnet and analysis. Less