寿命系数定寿的原理和方法

通过对疲劳载荷谱损伤值的研究,发现金属材料的疲劳寿命与疲劳试验载荷谱损伤值成线性关系,即金属材料的疲劳寿命随疲劳试验载荷谱的轻重成线性关系。由此规律推导出寿命系数,通过寿命系数可以降低全尺构件的疲劳试验时间。根据已有的疲劳试验数据研究的寿命系数值显示,在平均谱(疲劳损伤值为50%)基础上加重至58.33%损伤谱可降低全尺寸疲劳试验时间11%,75%损伤谱可降低36%,91.5%损伤谱可降低51%。由此得出:为了减少全尺疲劳试验时间,可以用加重载荷谱进行全尺寸疲劳试验,获得重谱下的寿命,再利用样件的寿命系数将其还原到平均谱下的平均寿命,然后用规范规定的疲劳分散系数除以平均寿命,给出使用寿命。这样既实现了减少疲劳试验时间的目的,又不违背规范规定的疲劳分散数值,使飞机定寿既经济又可靠。

Theory and method of determination life by life factor

This paper, through research on damage value of fatigue load spectrum, finds out that the fatigue life of metallic material is linear with the damage value of fatigue test load spectrum, namely, the fatigue life of metallic material is linear with the weight of fatigue test load spectrum. Life factor can be deduced from the regularities, and the fatigue test time of full-scale component can be reduced from life factor. From what is displayed in the life factor of existing fatigue test data research, when adding damage value on the basis of average spectrum(fatigue damage value is 50%), 58.3% damage spectrum can reduce 11% of the full-scale component fatigue test time, 75% damage spectrum can reduce 36% and 91.5% damage spectrum can reduce 50%. It comes to the conclusion in this paper as follows:for the purpose of reducing full-scale fatigue test time, load spectrum enhancement is to be employed in full-scale fatigue test, which renders the life in load spectrum enhancement. Then the life factor of sample is used to revert it to the average life under average load spectrum. This average life is then divided by the standard fatigue dispersion coefficient, which renders service life. This method reduces the fatigue test time without violating the standard fatigue dispersion values, making the determination of aircraft life economical and reliable.