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Study on the High Temperature Strength of Ceramics and Ceramics Coating Materials Using Laser Speckle Strain/Displacement Gage

利用激光散斑应变/位移计研究陶瓷和陶瓷涂层材料的高温强度

基本信息

批准号：
06452151
负责人：
OGURA Keiji
金额：
$ 4.54万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

In this study, fatigue crack growth tests for alumina ceramics and silicon nitride ceramics were performed at both room and elevated temperature. The crack opening displacement was also measured during the tests. Then the crack growth characteristics of ceramics were discussed using these experimental data. The results concerned with the crack growth tests are as follows.1.The crack growth rate was found to decrease gradually with a further crack growth, and after some crack extension a crack stopped growing temporary for both ceramics materials.2.It was found from the relationship between COD and stress intensity factor, K,that a crack opening level, Kop, increased with increasing the number of cycles. A little bit wide hysteresis was also observed in these curves. These hysteresis were thought to correspond with the effect of particle bridging on the crack opening behavior. Furthermore, the compliance of sample varied discontinuously with increasing the number of cycles.3.Both the cr … More ack arrest mentioned the above and the variation on the compliance related to the existence of the particle bridging effect near the crack tip. The stress intensity factor at crack tip was reduced by subtracting the friction stress due to this bridging effect.Next, fatigue tests for ceramics coating materials were conducted at both room and elevated temperature. The results for coating materials are as follows.1.While the blasted sample at room temperature has a higher fatigue limit than the annealed sample at the same temperature, the alumina coated sample has a lower fatigue limit that the blasted sample.2.Though the ceramics coated sample shows the elastic deformation at an early stage of fatigue life under a higher applied stress level, the plastic deformation increased with increasing the number of cycles at a middle stage of fatigue life. This behavior corresponded with the cyclic softening behavior of substrate. At a final stage of fatigue life the surface strain of the sample varied discontinuously. This means that the region with no strain due to the delamination among a coat material and a substrate appeared.3.Under a lower applied stress level, the sample was under an elastic state at an early stage, and gradually showed the plastic deformation behavior. At a final stage of fatigue life, however, the plastic strain range of sample decreased with increasing the number of cycles. This means that a single main crack can only propagate under this condition. Less

在这项研究中，在室温和高温下对氧化铝陶瓷和氮化硅陶瓷进行了疲劳裂纹扩展试验。试验期间还测量了裂纹张开位移。然后利用这些实验数据讨论了陶瓷的裂纹扩展特性。裂纹扩展试验的结果如下：1.两种陶瓷材料的裂纹扩展速率随着裂纹的进一步扩展而逐渐降低，并且在裂纹扩展一段时间后，裂纹暂时停止扩展。2.从COD与应力强度因子K之间的关系发现，裂纹张开水平Kop随着循环次数的增加而增加。在这些曲线中还观察到了一点点宽的滞后。这些滞后被认为与颗粒桥接对裂纹张开行为的影响相对应。此外，随着循环次数的增加，样品的柔顺性变化不连续。3.上述的裂纹抑制和柔顺性的变化都与裂纹尖端附近颗粒桥接效应的存在有关。通过减去桥接效应产生的摩擦应力，可以降低裂纹尖端的应力强度因子。接下来，在室温和高温下对陶瓷涂层材料进行了疲劳测试。涂层材料的结果如下：1.虽然室温喷砂样品比相同温度下的退火样品具有更高的疲劳极限，但氧化铝涂层样品的疲劳极限低于喷砂样品。2.虽然陶瓷涂层样品在较高的外加应力水平下在疲劳寿命早期表现出弹性变形，但在疲劳寿命中期，塑性变形随着循环次数的增加而增加。这种行为与基材的循环软化行为相对应。在疲劳寿命的最后阶段，样品的表面应变不连续变化。这意味着出现了由于涂层材料和基底之间的分层而没有应变的区域。3.在较低的施加应力水平下，样品早期处于弹性状态，并逐渐表现出塑性变形行为。然而，在疲劳寿命的最后阶段，样品的塑性应变范围随着循环次数的增加而减小。这意味着单个主裂纹只能在这种条件下扩展。较少的