基于3D-ILC超声场致脆性固体单内裂纹扩展规律研究

为揭示超声场(UF)作用下脆性固体裂纹扩展贯通等特性演变,首次引入3D-ILC技术,开展含有内裂纹脆性固体的UF试验,揭示不同激励时长及不同超声功率下的裂纹扩展及试样破坏过程规律。通过分析断口特征揭示超声致裂物理机制,基于Paris疲劳理论开展数值模拟,得到不同超声参数下的内裂纹扩展路径,并与试验结果对比验证。结果表明:(1)3D-ILC有效性得到了证明,为UF的研究提供了一个有力工具。(2)UF下裂纹沿尖端方向扩展,断口存在贝纹线特征,局部存在粉末,判断UF物理机制包含超高周/高周疲劳断裂、裂纹面摩擦、温度荷载。(3)超声波对固体作用集中在原预制裂纹面,完整区域未出现损伤,可认为超声作用具备高度的"裂纹敏感性"。(4)裂纹扩展程度与超声作用时间、超声功率成正相关。(5)利用Paris疲劳模型开展UF数值模拟,裂纹扩展程度与荷载幅值和循环周次成正比,裂纹扩展路径与试验一致。3D-ILC的引入为UF的试验规律、物理机制研究提供了全新的手段,数值模拟方法得到了UF下裂纹扩展路径,与传统上以应力–应变、塑性区等目标的分析方法相比,是一个很好的补充。

Ultrasonic fracturing of brittle solids with an internal crack based on 3D-ILC method

In order to reveal the evolution of crack propagation and penetration in brittle solids under the action of ultrasonic field,the 3 D-ILC method is introduced to ultrasonic fracturing tests for the first time,with different excitation durations and ultrasonic powers. The ultrasonic fracturing mechanism was revealed by analyzing the characteristics of fracture surfaces. The crack propagation path under different ultrasonic parameters was obtained through numerical simulation based on the Paris fatigue model and compared with the experimental results. The results show that 3 D-ILC method is a powerful tool for ultrasonic fracturing research. Under the action of ultrasonic filed,cracks propagate along the tip,and the fracture surface shows the characteristics of shellfish veins and has powder locally. It can be judged that the ultrasonic fracturing mechanism includes ultra-high cycle/high cycle fatigue fracture,friction and temperature load. Ultrasonic action on solids is concentrated on original pre-cracked surfaces and no damage occurs in the intact region,which indicates that the ultrasonic action has "crack priority". The area of crack propagation is positively correlated with the ultrasonic action time and ultrasonic power. Numerical simulation using the Paris fatigue model reveals that crack propagation is proportional to load amplitude and cycle number and that the crack propagation path is consistent with the test results. 3 D-ILC provides a new means for the experimental and theoretical research of ultrasonic fracturing. Compared to traditional numerical methods based on the analysis of stress-strain and plastic zone,adopting numerical simulation to obtain the crack path under ultrasonic fracturing provides a good complement.