应用Neuber准则分析弹塑性材料缺口件时局部应力应变估计过高,因此预测初始寿命常给出过于保守的结论.由于当量应变能密度(Equivalent strain energy density,ESED)准则在Neuber准则的塑性变形项上增加了系数,局部应力应变估计结果更为...应用Neuber准则分析弹塑性材料缺口件时局部应力应变估计过高,因此预测初始寿命常给出过于保守的结论.由于当量应变能密度(Equivalent strain energy density,ESED)准则在Neuber准则的塑性变形项上增加了系数,局部应力应变估计结果更为准确.基于能量方法讨论了循环加载下材料的塑性应变能密度,发现ESED准则相比Neuber准则多考虑了塑性应变能密度,这是ESED准则局部应变场估计值远低于Neuber准则的估计值的能量理论基础.疲劳试验的结果验证了以上结论.展开更多
讨论了循环加载下材料的塑性应变能、储能和热能耗散,发现当量应变能密度(equivalent strain energy density,ESED)准则相比Neuber准则多考虑了塑性应变能密度,因此当量应变能密度准则局部应变场估计值会远低于Neuber准则的估计值.提出...讨论了循环加载下材料的塑性应变能、储能和热能耗散,发现当量应变能密度(equivalent strain energy density,ESED)准则相比Neuber准则多考虑了塑性应变能密度,因此当量应变能密度准则局部应变场估计值会远低于Neuber准则的估计值.提出改进的当量应变能密度方法,改进方法的估算值比Neuber准则更接近试验值,且寿命估计结果在工程上应用安全.改进的当量应变能密度准则的估计结果与疲劳失效试验结果符合较好.展开更多
The ratcheting response of 316 stainless steel samples at the vicinity of notch roots under single-and multi-step loading conditions is evaluated.Multi-step tests were conducted to examine local ratcheting at differen...The ratcheting response of 316 stainless steel samples at the vicinity of notch roots under single-and multi-step loading conditions is evaluated.Multi-step tests were conducted to examine local ratcheting at different low–high–high and high–low–low loading sequences.The stress levels over loading steps and their sequences highly influenced ratcheting magnitude and rate.The change of stress level from low to high promoted ratcheting over proceeding cycles while ratcheting strains dropped in magnitude for opposing sequence where stress level dropped from high to low.Local ratcheting strain values at the vicinity of notch root were found noticeably larger than nominal ratcheting values measured at farer distances from notch edge through use of strain gauges.Ratcheting values in both mediums of local and nominal were promoted as notch diameter increased.To assess progressive ratcheting response and stress relaxation concurrently,the Ahmadzadeh-Varvani(A-V)kinematic hardening rule was coupled with Neuber’s rule enabling to calculate local stress at notch root of steel samples.Local stress/strain values were progressed at notch root over applied asymmetric stress cycles resulting in ratcheting buildup through A-V model.The relaxation of stress values at a given peak-valley strain event was governed through the Neuber’s rule.Experimental ratcheting data were found agreeable with those predicted through the coupled framework.展开更多
文摘应用Neuber准则分析弹塑性材料缺口件时局部应力应变估计过高,因此预测初始寿命常给出过于保守的结论.由于当量应变能密度(Equivalent strain energy density,ESED)准则在Neuber准则的塑性变形项上增加了系数,局部应力应变估计结果更为准确.基于能量方法讨论了循环加载下材料的塑性应变能密度,发现ESED准则相比Neuber准则多考虑了塑性应变能密度,这是ESED准则局部应变场估计值远低于Neuber准则的估计值的能量理论基础.疲劳试验的结果验证了以上结论.
文摘讨论了循环加载下材料的塑性应变能、储能和热能耗散,发现当量应变能密度(equivalent strain energy density,ESED)准则相比Neuber准则多考虑了塑性应变能密度,因此当量应变能密度准则局部应变场估计值会远低于Neuber准则的估计值.提出改进的当量应变能密度方法,改进方法的估算值比Neuber准则更接近试验值,且寿命估计结果在工程上应用安全.改进的当量应变能密度准则的估计结果与疲劳失效试验结果符合较好.
基金Authors wish to acknowledge the financial support by the Natural Sciences and Engineering Research Council(NSERC)of Canada.
文摘The ratcheting response of 316 stainless steel samples at the vicinity of notch roots under single-and multi-step loading conditions is evaluated.Multi-step tests were conducted to examine local ratcheting at different low–high–high and high–low–low loading sequences.The stress levels over loading steps and their sequences highly influenced ratcheting magnitude and rate.The change of stress level from low to high promoted ratcheting over proceeding cycles while ratcheting strains dropped in magnitude for opposing sequence where stress level dropped from high to low.Local ratcheting strain values at the vicinity of notch root were found noticeably larger than nominal ratcheting values measured at farer distances from notch edge through use of strain gauges.Ratcheting values in both mediums of local and nominal were promoted as notch diameter increased.To assess progressive ratcheting response and stress relaxation concurrently,the Ahmadzadeh-Varvani(A-V)kinematic hardening rule was coupled with Neuber’s rule enabling to calculate local stress at notch root of steel samples.Local stress/strain values were progressed at notch root over applied asymmetric stress cycles resulting in ratcheting buildup through A-V model.The relaxation of stress values at a given peak-valley strain event was governed through the Neuber’s rule.Experimental ratcheting data were found agreeable with those predicted through the coupled framework.
