中碳钢摩擦焊接头的切口强度及切口敏感性

NOTCH STRENGTH AND NOTCH SENSITIVITY OF FRICTION WELDED JOINT OF MILD CARBON STEEL

盘 +轴等异型部件的摩擦焊接结构和带飞边直接使用的摩擦焊接构件 ,其外形均具有几何不连续性 ,可视为广义的“切口” ,因此 ,对于组织和性能不均匀的摩擦焊接接头的切口强度及切口敏感性的研究对于摩擦焊接结构设计和安全使用具有重要意义。本文研究了中碳钢摩擦焊缝处的切口强度 ,结果表明 45钢摩擦焊接头焊缝处切口件的断裂具有脆性断裂特征 ,焊缝处的切口强度服从对数正态分布 ,其对数均值对应的切口强度在所研究的应力集中系数范围内几乎不随应力集中系数Kt 的增大而变化 ,且均大于母材的抗拉强度 ,即 45钢摩擦焊接头的焊合区对切口不敏感。最后估算了 45钢摩擦焊接头的切口敏感度系数KbN,只要接头的应力集中系数Kt<KbN,则接头对切口不敏感 ,这对于摩擦焊接头的设计和广泛应用具有重要的意义。

Friction welded (FW) elements of dissimilar outer dimensions and those used in aswelded condition are of geometry discontinuity, which can be regarded as notch in broad sense. Therefore, the notch strength and the notch sensitivity of FW joints are of great importance in the design and the failure assessment of FW structures. In the present paper,the notch strength and the notch sensitivity of notched FW joints of 45 steel, similar to AISI 1045 steel, are investigated. Test results show that the fracture of 45 steel FW joints with notch in the welding area seems to be of brittle characteristics. The notch strength of 45 steel FW joints follows the log normal distribution. In the range of the stress concentration factors investigated, the mean notch strength of FW joints is approximately constant and greater than the ultimate strength of base metal. It means that 45 steel FW joints are not sensitive to notch. In addition, the notch sensitivity factor, K bN of 45 steel FW joints is estimated. If the stress concentration factor, K t of 45 steel FW joints is lower than K bN , the fracture strength of 45 steel FW joints will be higher than the ultimate strength, i.e., non sensitive to notch, which is important to the design and engineering applications of FW joints.