低温环境下十字形非传力角焊缝接头的疲劳性能

为了研究低温环境下钢桥焊接细节的疲劳行为和性能，以典型的十字形非传力角焊缝接头为对象，开展室温和?60 °C下的高周常幅疲劳试验；基于三维裂纹扩展数值模拟，分析低温对该焊接细节疲劳裂纹扩展寿命的影响机理. 结果表明，该焊接细节的室温和?60 °C条件下试验S-N疲劳寿命未表现出显著区别，初始焊接缺陷裂纹会在细节焊趾处的多个位置同时扩展；由低温环境导致的钢材断裂韧性的降低不会对该焊接细节的疲劳寿命产生明显影响. 虽然低温会增强钢材抵抗疲劳裂纹扩展的能力，但是该焊接细节的疲劳寿命主要受焊接过程产生的多样化初始裂纹缺陷因素控制；建议采用考虑多裂纹耦合扩展的三维裂纹扩展数值模拟来更加精确地预测疲劳裂纹扩展寿命.

Fatigue performance of non-load-carrying cruciform fillet-welded joints at low ambient temperature

A series of the high-cycle constant-amplitude fatigue tests on the non-load-carrying cruciform fillet-welded joints were conducted at room temperature and ?60 °C in order to analyze the fatigue behavior and performance of the welded joints in the steel bridges. The effect mechanism of the low temperature on the fatigue crack propagation life of those joints was analyzed through three-dimensional crack propagation simulation. The experimental results show the marginal effect due to the low temperatures on the S-N fatigue of the cruciform fillet-welded joints. The initial crack-like defects always propagate simultaneously at several sites along the weld toes. The fatigue crack propagation life is affected negligibly by the deteriorated fracture toughness in steel materials induced by the decreasing temperature. Although the resistance to fatigue crack propagation in steel materials is enhanced by the decreasing temperature, the fatigue life of those fillet-welded joints is still dominated by the diverse initial defects produced during the welding processes. Adopting the three-dimensional multi-crack coupled propagation analysis was recommended to predict more accurately the fatigue life of welded joints in the further research.