To improve the efficiency of ultrasonic testing for plastic bonded explosive( PBX) materials, and ensure the reliability and safety of the final product, a non-contact and nondestructive testing method of internal defects in PBX based on laser ultrasonic technique was studied. Based on thermo-elastic mechanism, a finite element numerical calculation method and model for the laser ultrasound of PBX material were established. The distribution of internal transient temperature and ultrasound fields of PBX material under the pulsed laser irradiation was obtained. The interaction between the laser ultrasound with the internal hole and crack defects of PBX was simulated. The numerical results show that using 5 laser beam to stimulate simultaneously, it can greatly improve the detection ability of laser ultrasound on internal defect within the safety temperature range of PBX. The detection of the cracks with length of more than 0. 5 mm and the holes with diameter of more than 0. 2 mm can be realized. The feasibility of laser ultrasound for the internal defect detection of PBX materials is preliminarily validated%为提高高聚物粘结炸药(PBX)材料超声检测效率,保证最终产品的可靠性与安全性,研究了一种基于激光超声技术的PBX内部缺陷非接触无损检测方法.基于热弹机制,建立了PBX材料激光超声的有限元数值计算方法和模型.得到了脉冲激光照射下PBX材料内部瞬态温度场和声场分布.模拟了激光超声与PBX内部气孔和裂纹缺陷之间的相互作用.数值结果表明,采用5激光束同时激励,可在保证PBX安全温度范围内大幅度提高激光超声对内部缺陷的检测能力,可实现长度大于0.5 mm裂纹,直径大于0.2 mm孔洞的检测.初步验证了激光超声对于PBX材料内部缺陷检测的可行性.
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