中文摘要：

以40Cr试样的两级疲劳试验为基础,系统分析低幅载荷作用后试样疲劳强度变化规律,发现存在一个载荷最佳锻炼次数,低幅载荷的强化和损伤作用以这个最佳锻炼次数为分界点。在分界点之前,低幅载荷作用后试样疲劳强度逐级提高,低幅载荷表现为强化作用;在分界点之后,低幅载荷作用后虽然试样疲劳强度仍然得到强化和提高,但疲劳强度提高的程度逐级降低,即低幅载荷的强化作用逐级减弱,表明损伤的逐级增加。这种特性为产品轻量化设计时合理确定载荷谱中低幅载荷的等级及其作用次数提供重要参考。

英文摘要：

Based on fatigue tests of 40Cr specimen, analysis of the fatigue strength change law under low amplitude load, it was founded that a best training time exist, the training time is the demarcation point of strengthening and damaging under low amplitude load. Before the demarcation point, the specimen＇ s fatigue strength gradually increase under low amplitude load, low amphtude load show strengthening-effect; after the demarcation point, the specimen＇ s fatigue strength still improve, but gradually reduce under low amplitude load, low amplitude load＇s strengthening-effect gradually weakened, damaging-effect gradually increased. This feature can provide an important reference to determine a reasonable low amplitude load level and its training time in the load spectrum for lightweight product designing.