基于疲劳性能的热损伤巴氏磁参数表征

Characterizations of Thermal Damage by Magnetic Barkhausen Parameters Based on Fatigue Properties

通过对不同程度激光烧伤的4340M钢试样进行巴克豪森磁信号测试和旋转弯曲疲劳试验,获得了基于疲劳寿命缩减的热损伤程度磁参数评判指标。研究结果表明,烧伤区巴氏磁参量的变化量与疲劳寿命的缩减相对应,且这种变化量与低应力区寿命缩减的对应关系更为显著。同时,巴氏磁参量的变化量与疲劳强度缩减系数线性相关,表明巴氏磁参量的变化量不但能可靠表征热损伤的程度,而且能方便地预测热损伤后的疲劳强度。

To develop an effective and practical evaluation criterion for thermal damage in high strength steel that can correlate the resultant deterioration of the material properties, nondestructive magnetic Barkhausen noise （BN） evaluation and the rotating bending fatigue testing were carried on different laser-burnt specimens of high strength 4340M. The correlations have been established between the Barkhausen Noise Ratio （BNτ, the ratio of the max BN value in the damaged region to the average BN value in the un-damaged region） and the reduction of fatigue properties. Analyses on the results show that the reduction factor of fatigue strength decreases linearly as the BNτ （i. e. thermal damage degree） increases, suggesting that BNτ is a valid and reliable engineering indicator for thermal damage and can be conveniently used to predict the reduction of fatigue strength caused by thermal damage in high strength steel. It is shown that the fatigue life of the thermally damaged specimens decreases sharply initially and then reaches a plateau with increasing BNτ, especially in the region of lower stress amplitude levels. Relative to the fatigue results at high stress amplitude level, the thermal damage is also found to have more effect on the reduction of fatigue life at low stress amplitude level.