变幅载荷作用下点焊焊接接头的疲劳损伤

对拉剪点焊试样进行了多级变幅疲劳加载,载荷块分别为低-高、高-低和低-高-低形式,测量了疲劳破坏过程中的固有频率.基于疲劳寿命试验结果和固有频率随疲劳寿命的变化,分析了点焊结构疲劳损伤累积的特点和加载次序对疲劳寿命的影响.结果表明,载荷块形状,即加载次序对疲劳寿命的影响并不明显,使用线性疲劳累积损伤理论预测的疲劳寿命接近实际疲劳寿命.依据固有频率的变化,可以监测疲劳寿命过程中出现的损伤,并确定损伤的程度.按照损伤力学中损伤随寿命的演化规律,可进行疲劳寿命预测,寿命预测结果与试验疲劳寿命吻合较好.

Fatigue damage of spot welding under variable amplitude load

Multi-stage variable amplitude load with low-high, high-low and low-high-low were applied to tension-shear spot welding specimen, and natural frequency were obtained during fatigue process. Damage accumulation and effects of loading sequence on fatigue life were analy sed according to experimental lives and change of natural frequency.Experiment results shows loading block shape, namely loading sequence, has few effect on fatigue life, and life predicted with linear damage accumulation rule agrees well with experimental lives.Changes of natural frequency can be used to detect damage during fatigue process, and define damage extent.Fatigue lives predicted according to the damage evolution principle of damage mechanics were identical to experimental results.