车体结构铝合金焊接接头疲劳性能研究

Research on fatigue property of aluminum alloy welding joints for car body structure

铝合金因其质量轻、力学性能好成为列车车体制造的首要选择。而焊接是铝合金车体制造的主要方式,但铝合金焊接接头的疲劳性能与钢相比较差,疲劳断裂是铝合金焊接结构的主要失效方式之一。采用疲劳试验与数值分析相结合的方式,研究铝合金焊接接头的疲劳性能。研究结果表明:铝合金焊接接头是在比较低的交变应力条件下发生断裂的。瞬断区上有明显的舌状花样,断裂方式为典型的解理断裂,在断口上有较低的脊岭。材料中产生的空穴往往是裂纹源萌生的源头。焊接缺陷气孔和未焊透造成试件在几何形状上的不连续和截面面积的减小,导致应力集中现象产生,降低试件疲劳性能。

Aluminum alloy is the good choice of train car body manufacture for small density and good mechanics. Welding is the main mode to car body manufacture of aluminum alloy but welding joints of aluminum alloy is not as good as joints of steel. Fatigue and fracture is one of the primary disabled modes. This paper presents a study of the fatigue properties of aluminum alloy based on fatigue test and numeric analysis. The results showed that the fracture was taken placed at lower stress and the instantaneous fracture zone show ray florets, the fracture mechanism was cleavage fracture,there existed lower ridge. The caves were the origin of the cracks. The air-hole and lack of fusion both made the geometric discontinuities and cross-sectional area decreases, then caused the stress concentration and cut down the fatigue properties.