基于金属磁记忆技术的18CrNi4A钢缺口试件疲劳损伤模型

Fatigue Damage Model of Notched 18CrNi4A Steel Specimens by Metal Magnetic Memory Method

对18CrNi4A钢缺口试件进行了疲劳试验和磁记忆检测,研究了磁信号在疲劳过程中的变化规律,基于连续损伤力学理论,采用磁信号特征参量作为损伤参量,提出了一种新的18CrNi4A钢缺口试件疲劳损伤模型。结果表明,在稳定循环阶段,磁信号随疲劳循环周次增加无显著改变,疲劳裂纹萌生后,磁信号逐渐增加,并在断裂后发生激变。磁信号特征参量绝对值在疲劳过程中表现为三阶段变化特征,随疲劳损伤程度的加剧而逐渐增加。磁信号特征参量绝对值与应力水平存在强烈的相关性,应力水平越大,其值越大。疲劳损伤试验结果与基于磁信号特征参量的疲劳损伤模型显示的疲劳损伤演变规律符合较好。

Fatigue tests of notched 18CrNi4A steel specimens are carried out and metal magnetic memory （MMM） signals are detected. The variation of the MMM signals in the process of fatigue testing is investigated. Based on continuum damage mechanics theory, two fatigue damage variables are established on the basis of the MMM signal feature parameters, and two new fatigue damage models are founded accordingly. The re- suits show that the variation of the MMM signals is unobvious before the cracks initiate, but that the MMM signals increase obviously with the propagation of the cracks and vary abruptly after rupture. The MMM signal feature parameters demonstrate three stages, and their absolute values rise with the increase of the fatigue damage. In addition, there is an inherent relationship between fatigue stress and the feature parameters; the larger is the fatigue stress, the larger are the absolute values of the feature parameters. The MMM signal feature parameters demonstrate three stages, and their absolute values rise damage. In addition, there is an inherent relationship between fatigue stress larger is the fatigue stress, the larger are the absolute values of the feature damage variable based on the MMM signal feature parameters is measured with the increase of the fatigue and the feature parameters; the parameters. The MMM signal during the stress-controlled fatigue experiments to verify the new MMM signal fatigue damage model, which is in good agreement with the results.