EI、Scopus 收录
中文核心期刊

试样疲劳性能尺度效应的概率控制体积方法

PROBABILISTIC CONTROL VOLUME METHOD FOR THE SIZE EFFECT OF SPECIMEN FATIGUE PERFORMANCE

  • 摘要: 试样尺度、缺口和加载方式通常对材料的疲劳性能具有重要影响. 因此,发展关联试样尺度、缺口和加载方式对疲劳强度影响的方法对于从材料疲劳性能到结构件疲劳性能的预测具有重要意义.首先,采用旋转弯曲加载和轴向加载方式对不同几何形状EA4T车轴钢试样进行了疲劳实验.实验结果表明, 由于试样尺度的增加,轴向加载下狗骨形试样的疲劳强度明显低于沙漏形试样; 相同寿命下,缺口显著降低试样的疲劳强度. 疲劳断口扫描电镜观测结果表明,疲劳裂纹均起源于试样表面.沙漏形试样和狗骨形试样疲劳断口大多只有一个裂纹源,而缺口试样疲劳断口均具有多裂纹源特征. 然后,采用概率控制体积方法研究了试样尺度、缺口和加载方式对疲劳强度的影响,并与临界距离和应变能密度方法进行了比较. 结果表明,概率控制体积方法能够更好地关联试样尺度、缺口和加载方式对EA4T车轴钢疲劳强度的影响.最后, 提出一种基于控制体积的结构件疲劳强度预测方法,并用于具有不连续高应力区域车轴钢试样的疲劳强度预测,预测结果与实验结果 吻合.

     

    Abstract: The effects of specimen size, notch and loading type usually have important influence on the fatigue properties of metallic materials. Therefore, it is vital to modelling the effects of specimen size,notch and loading type on the fatigue strength, which is of great importance for predicting the fatigue property of the structural parts from that of the materials. In this work, rotating bending and axial loading fatigue tests are first performed on the specimens of an EA4T axle steel with different shapes. Experimental results indicate that the fatigue strength of the dogbone specimen is lower than that of the hourglass specimen due to the increase of the specimen size, and the notch reduces the fatigue strength of the specimen in terms of the nominal stress due to the large stress gradient at the notch root. The fracture surface observation by the scanning electron microscope indicates that all the tested specimens fail from the surface of the specimen. For hourglass and dogbone specimens, most of the fracture surfaces only have single crack initiation site, while for the notched specimen all the fracture surfaces have the characteristic of multiple crack initiation sites. Then, the probabilistic control volume method is used for correlating the effects of specimen size, notch and loading type on the fatigue strength of the EA4T steel, which is also compared with the critical distance method and the strain energy density method. It is indicated that the probabilistic control volume method gives better predictions for correlating the effects of specimen size,notch and loading type on the fatigue strength of the EA4T steel. Finally, a method based on the control volume is proposed for predicting the fatigue strength of structural parts, and is used for the specimens of axle steel with discontinuous highly stressed regions. The predicted results are in agreement with the experimental data.

     

/

返回文章
返回