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Reliability Evaluation of small Specimen by Laser AE System

激光AE系统对小试件可靠性评估

基本信息

批准号：
15360364
负责人：
ENOKI Manabu
金额：
$ 9.66万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

The objective of this research project is to improve the laser based AE (acoustic emission) technique by theoretical consideration and its application and demonstrate the effectiveness of this method for reliability evaluation. Research target was clearly focused by analyzing the advantages and weak points of conventional nondestructive evaluation (NDE) method and AE technique. Although here are some problems in the conventional AE method using PZT elements concerning adhesion of sensor, AE measuring technique using laser interferometer has some advantages such as absolute measurement of surface velocity, NDE in severe environment and so on. This technique was applied to the evaluation of dielectric breakdown process of thin dielectric film, and it was demonstrated that fracture morphology was classified by generation electric field value and frequency and precursor current was not due to phase transition and microfracture. Small partial discharge was successfully detected as AE signal … More by this method directly in liquid. Thermal deformation process in active composite materials was investigated and it was clearly shown that the cause of non-linearity of operating characteristics was due to microfracture induced by thermal stress. Also temperature range where damage was introduced was evaluated. Wavelet analysis of AE was used to understand the fracture process these composites. This method was also applied to thin metallic films with thickness of several tens micron and AE signals of these samples due to deformation and damage were successfully detected. This laser AE technique was applied to materials processing and reliability of materials was evaluated by in-process monitoring. Sintering of ceramics was monitored by laser AE technique and microcracks generated over 1500℃ were measured. These results were obtained by this unique laser AE technique and it was demonstrated that this technique was very useful for understanding of the fracture behavior and design of materials processing. Less

本课题旨在从理论和应用两方面对基于激光的声发射技术进行改进，并验证该方法在可靠性评估中的有效性。通过分析传统无损检测方法和声发射技术的优缺点，明确了研究目标。虽然传统的压电元件声发射测量方法存在传感器粘附性等问题，但激光干涉仪声发射测量技术具有表面速度绝对测量、恶劣环境无损检测等优点。将该技术应用于介质薄膜的介电击穿过程评价，结果表明，介质薄膜的断裂形态可根据产生电场值和频率进行分类，且前驱体电流不受相变和微断裂的影响。用该方法直接在液体中成功地检测到小的局部放电作为声发射信号。研究了活性复合材料的热变形过程，明确了热应力引起的微断裂是导致活性复合材料工作特性非线性的主要原因。同时，对引入损伤的温度范围进行了评估。利用声发射小波分析分析了复合材料的断裂过程。将该方法应用于厚度为几十微米的金属薄膜，成功地检测出了这些金属薄膜由于变形和损伤而产生的声发射信号。将激光声发射技术应用于材料加工，并通过过程监测对材料的可靠性进行评价。采用激光声发射技术对陶瓷烧结过程进行了监测，并对1500℃高温下产生的微裂纹进行了测量。这些结果是通过这种独特的激光声发射技术获得的，证明了这种技术对理解材料的断裂行为和设计材料的加工非常有用。少