Q690高强钢疲劳损伤后力学性能试验研究

服役结构材料疲劳损伤后的残余力学性能对结构可靠性的评估有着至关重要的作用.为此,对Q690高强钢经不同疲劳损伤后的残余力学性能进行了试验研究.根据Q690高强钢在不同疲劳荷载作用下的疲劳寿命,设定了3级疲劳荷载和9组损伤振动次数,并将Q690高强钢试件在各疲劳荷载下进行不同次数的预损伤疲劳振动.然后,对这些具有不同疲劳...

Experimental study on mechanical properties of Q690 high strength steel after fatigue damage

The residual mechanical performance of in-service structure after fatigue damage is regarded as a crucial indicator for structural reliability assessment. The residual strength of Q690 high strength steel subjected to different levels of fatigue damage was investigated. According to the fatigue life of Q690 high strength steel, three fatigue loads and nine life fractions were first determined. Fatigue damage was induced by subjecting the specimens to these nine different life fractions under three fatigue loads.And then subsequent tensile tests were conducted on these damaged specimens to obtain their stress-strain curves and associated mechanical properties (yield strength, ultimate strength, Young’s modulus and ultimate elongation). Significant differences are observed in the position and the morphological features of Q690 high strength steel after different fatigue damages. In addition, there is no yield plateau in the stress-strain curves of Q690 high strength steel under static tension after fatigue damages. Meanwhile, the stress-strain curves exhibit many wrinkles which are attributed to the phenomenon of strain invariance and stress reduction. Furthermore, significant reductions in the yield strength, ultimate strength and ultimate elongation are observed due to the effect of fatigue damage. In contrast, the influence of fatigue damage on Young’s modulus is negligible. Based on the test data, a new set of predictive equations are proposed to determine the mechanical properties of Q690 steel with different fatigue damages, which can effectively evaluate the mechanical properties of Q690 high strength steel after fatigue damage.