预应变下高强结构钢低温断裂性能

Research on fracture toughness of high-strength structural steel with prestrain at low temperature

为了测试高强结构钢Q420力学性能和断裂韧度,对其原材料和塑性变形材料分别进行了不同温度下的拉伸试验和断裂韧性试验.结果表明,结构钢的断裂韧性随着温度的降低显著减小,使其倾向于脆性断裂;而预应变虽然提高了钢材的屈服强度与抗拉强度,但显著降低了钢材的塑性及断裂韧性,进一步增加了脆性断裂发生的可能性.同时利用有限元分析得出,预应变对延性断裂向脆性断裂转变的促进作用源于预应变引起裂纹尖端应力场的增大.在重要工程设计、选材、安全分析及评定时,应充分考虑温度和预应变对结构断裂行为的影响.

The mechanical properties and fracture toughness of high-strength structural steel Q420 were studied by tension tests and three-point bending tests.The results indicated that the temperature had significant influence on fracture toughness of structural steel and the fracture toughness reduced significantly with the decrease of temperature resulting in brittle fracture.The prestrain increased the yield strength and tensile strength of structural steel,but significantly reduced its plasticity and fracture toughness,and further increased the possibility of brittle fracture.The prestrain facilitated the brittle fracture due to the activation of the near crack tip stress fields because of the prestrain based on the FEA.Thus the effects of the temperature and the prestrain should be considered in the important engineering design,material selection,safety analysis and evaluation.