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A Study on High Temperature Fatigue Strength of Plasma-Sprayed Notched Members by Using Laser Speckle Measurement

激光散斑测量等离子喷涂缺口构件高温疲劳强度研究

基本信息

批准号：
10650089
负责人：
NISHIKAWA Izuru
金额：
$ 1.34万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

There are so many discontinuous parts in service machines that fatigue problems of notched member are to be solved. Metallic materials used at high temperature were applicable up to 1000degC. The special materials are needed for further high temperature usage. The ceramic-sprayed material was one of the useful materials for high temperature. The purpose of this study is to clarify the characteristics of high temperature fatigue in ceramic-sprayed materials. Specially, an emphasis was put on the fatigue properties of notched members. It was found that the notched sample with 1mm in notch root radius was manufactured for the fatigue test.The bi-axial strain at notch root was monitored using a laser speckle strain/displacement measurement system, consequently. While the lateral strain at notch root was too small to measure, the longitudinal strain was large enough to examine the cyclic strain properties. It was found that the notch root was put on the plane strain condition and the fatigue life of notched specimen was nearly equal to the life in smooth specimen. The reason for the similarity in fatigue life was considered that notch constraint was limited to develop the strain hardening/softening behavior. From the observation of sample sections, a crack initiated at top coatings is not the same to a crack in the substrate. It was concluded that the coating material was not affected to the fatigue life of ceramic-sprayed specimen.

在役机械中存在大量的不连续零件，缺口件的疲劳问题亟待解决。在高温下使用的金属材料适用于高达1000摄氏度。进一步高温使用需要特殊材料。陶瓷喷涂材料是一种实用的高温防护材料。本研究的目的是阐明陶瓷喷涂材料的高温疲劳特性。重点研究了缺口构件的疲劳性能。实验中制作了缺口根部半径为1 mm的缺口试样，利用激光散斑应变/位移测量系统对缺口根部的双轴应变进行了监测。而缺口根部的横向应变太小，无法测量，纵向应变足够大，以检查循环应变特性。结果表明，缺口根部处于平面应变状态，缺口试件的疲劳寿命与光滑试件的疲劳寿命相当。疲劳寿命相似的原因被认为是缺口约束限制了应变硬化/软化行为的发展。从样品截面的观察来看，在顶部涂层处产生的裂纹与在基底中产生的裂纹不同。结果表明，涂层材料对陶瓷喷涂试样的疲劳寿命没有影响。