细晶化和余热处理抗震钢筋的高应变低周疲劳行为分析*

摘要

基于钢筋混凝土中钢筋在地震交变载荷下的失效模型，采用恒应变控制方式，室温下对细晶化和余热处理两种生产工艺得到的400 MPa 级抗震钢筋的高应变低周疲劳性能进行了研究。疲劳寿命数据用双参数威布尔统计方程处理后采用 Coffin-Manson 和Hollomon 公式拟合。为了计算地震载荷下钢筋的能量吸收率，建立一个新的预测模型并命名为循环韧度。结果表明，相对于余热处理钢筋，细晶钢筋具有更高的循环韧度、低周疲劳寿命，以及疲劳过渡寿命。余热处理钢筋在±1％应变幅以上加速循环软化，这是由于其表层回火马氏体中二次裂纹在循环载荷下萌生并快速扩展造成的。细晶钢筋循环塑性应变均匀，裂纹开裂几率小，具有较好的高应变低周疲劳性能。%Based on the failure model of rebars in reinforced concrete structures under earthquake loading,under total strain controlled,high strain and low cycle fatigue(HSLCF)behaviors of 400 MPa grade rebars produced by the technology of grain refinement and tempcore were tested at room temperature.After double-parameter weibull equation processed,the fatigue data were fitting by Coffin-Manson and Hollomon relationship.In order to calculate the rate of energy absorption under seismic loading,a new model named “cyclic toughness”were proposed.It was concluded that as compared with grain refinement rebar,tempcore rebar have higher cyclic toughness,low cycle fatigue life and fatigue transition life.Tempcore rebar accelerate its cyclic softening under strain amplitude of 1%,the reason was that the second crack propagated quickly in the surface of self-temper martensite.For grain refine rebars,cyclic plastic strain was uniform,and crack initiated probability was small, so that it have better high strain and low cycle fatigue performance.