Evaluation of Reliability in Harmonic Material System

近年来，人们对材料的性能提出了更高的要求，将材料与结构相结合的智能材料系统也应运而生。人们期待着一种不同于传统材料设计的新方法。在这些材料中，一种新的方法来确保材料的可靠性或设计材料和结构以便于筛选成为重要的问题。本研究基于材料谐和设计的新方法，研究了一种新的非接触无损评价方法，并开发了由金属和金属间化合物组成的层状材料，因为这些材料具有良好的抗裂纹扩展性能。利用激光声发射系统对氧化铝/SUS304钢涂层进行了热循环试验，成功地探测到了试验过程中由于微断裂而产生的声发射波形。高灵敏度激光干涉仪的研制对微小裂纹的检测分析提出了更高的要求。为了提高激光声发射系统的灵敏度，利用最新研制的解调器降低噪声分量，研制了激光声发射系统。通过对检测点的聚焦和信号的平均，改善了系统的噪声。该系统最终实现了高信噪比的声发射测量。研究了制备Ti/Ti-Al层状材料的工艺条件，分析了材料的力学性能和裂纹扩展过程。研究了具有较薄金属层的Ni/Ni-Al层状材料。对镍层进行热处理，以提高材料的延性和抗裂纹扩展能力。研究了金属间化合物相的形成机理和残余应力对断裂韧性的影响，为材料设计提供了指导。

High performance is recently requested for materials, and also smart materials system which combine materials and structure has been developed. Novel approach for materials design which is different from the conventional one is expected. In these materials a new method to ensure a reliability of materials or a design of materials and structure for easy screening becomes important problems. In this research a novel non-contact nondestructive evaluation method was investigated based on the new approach of materials harmonic design, and also layered materials consist of metal and intermetallic component was developed because these materials demonstrates excellent crack prorogation resistance. Thermal cycle tests of alumina/SUS304 steel coatings was employed and acoustic emission waveforms due to microfracture during tests was successfully detected by laser AE system. The development of laser interferometer with high sensitivity is requested for the detection and analysis of small microfracture. We developed the laser AE system for improvement of the sensitivity and reduced the noise components by newly developed demodulator. The noise of the system was also improve by the focused detection points and averaging signals. The system finally enabled the measurement of AE with high signal/noise ratio. Processing conditions for Ti/Ti-Al layered materials were investigated, and mechanical properties and crack propagation process were analyzed. Also Ni/Ni-Al layered materials with thin metal layer was investigated. Heat treatment of Ni layer was tried to improve the ductility of materials and crack propagation resistance. The mechanisms of fabrication of intermetallic phase and the effect of residual stress on fracture toughness were also studied and finally a guide for materials design was obtained.