LC4CS铝合金的超高周疲劳寿命分布

GIGACYCLE FATIGUE LIFE DISTRIBUTION OF ALUMINUM ALLOY LC4CS

采用超声高频疲劳试验机进行了LC4CS铝合金实验样本容量为66的超高周疲劳寿命实验．结果表明,超高周疲劳寿命具有双峰分布特征,这一特征与疲劳裂纹的萌生点有关:较短疲劳寿命的样品的裂纹萌生于夹杂等缺陷处,而较长疲劳寿命的样品的裂纹萌生于表面．寿命分布的双峰特征使得传统的升降法不能用于确定材料的超高周疲劳的条件疲劳极限,超高周疲劳寿命的分散性远大于低周和高周疲劳寿命的分散性．

Very high cycle fatigue （VHCF） test of 66 specimens of aluminum alloy LC4CS was done by piezo-electric fatigue testing machine, and the fatigue life data showed that the fatigue life distribution of the alloy under VHCF has a characteristic of duplex peak, which is related to the locations of fatigue crack initiation. For the specimens with shorter fatigue life the fatigue cracks initiate at the defects, such as inclusions and caves, and for the longer ones the cracks initiate near the surfaces of the specimens. This characteristic makes the staircase method measuring the fatigue limit inconsequential, and the fatigue life scatter of the VHCF is far larger than those of low cycle fatigue （LCF） and high cycle fatigue （HCF）.