螺旋弹簧快速疲劳试验加载优化方法

新设计以及投产加工制造的高应力圆柱螺旋弹簧都需进行快速疲劳试验,试验时间短。要求圆柱螺旋弹簧加载频率高,使用寿命长,实际疲劳断裂主要为正断型疲劳断裂模式。金属材料扭转疲劳断裂机制图诠释了材料的疲劳断裂寿命、屈服强度、外施交变切应力振幅和疲劳断裂模式之间的关系。利用原理图表述不同试验条件下引发疲劳断裂模式发生的替代变化。缩短快速试验时间的主要方法:提高加载应力水平;最大正应力不变条件下,降低应力比值;对圆柱螺旋弹簧进行优化的二次喷丸处理等。给出快速疲劳试验的一般试验程序。

An optimized method of loading for the helical spring fast fatigue test

High stress helical springs of new designed and put into production all need proceed with fast fatigue under the shorter test time.It is required that helical spring loading frequency is high,service life is long,actual fatigue fracture is mainly normal tensile fracture mode.Torsional fatigue fracture mechanism diagram of metallic materials reveal relationship among materials fatigue fracture life,yield strength,applied alternative shear amplitude and fatigue fracture mode.It is illustrated that causing fatigue fracture mode change in different test condition by using principle diagram.The methods of shortening fast test time are as follows: to increase loading stress level;in condition of maximum normal stress constant,stress ratio is decreased;helical spring is produced by the optimized treatment of secondary shot peening etc.The general test procedure of fast test method is given.