Development of Optimum Proof Testing Method of Structural Ceramics

本研究的目的是探索结构陶瓷检验的最佳方法。最优法是指这样一种方法，即在S fmin*S d的条件下，获得最高的验证试验存活概率，其中S是验证试验后的最小强度，S d是所需的强度。本研究的主要成果总结如下：1.研究成果。首次研究了均匀应力分布情况下的最优验证试验方法。结果表明，在此卸载速率下，最优试验方法是采用可用最大卸载速率和满足S=S_d的试验载荷。在此基础上，研究了非均匀应力分布情况下的最优验算方法。这种情况很重要，因为实际机械部件通常承受非均匀分布的应力。结果表明，最优的试验方法是采用最大可用卸载速率，试验载荷为…在构件的最大应力点，有较多的ch满足S=S。通过计算机模拟研究了K-V关系对验证试验效果的影响，其中K为应力强度因子，V=da/dt为稳定裂纹扩展速率。研究发现，当卸载速率大于临界卸载速率时，将第一区域的K-V关系外推到第二和第三区域，并不会导致验证试验后的最小强度和通过验证试验的概率的计算有实质性的误差。提出了一种估算临界卸载率的方法，并通过实验验证了该方法的有效性。为了验证试验在陶瓷轴承球上的应用，从实验上阐明了环裂纹萌生强度和压碎载荷下的最终断裂强度的统计特性。此外，还提出了解释实验结果的概率理论。对氮化硅轴承球进行了验证试验，从实验上论证了卸荷率的重要性。较少

The aim of this research is to develop the optimum method of proof testing of structural ceramics. The optimum method implies such a method by which the highest probability of surviving proof testing is attained under the condition that S_<fmin>*S_d, where S_<fmin> is the minimum strength after proof testing and S_d is the required strength. The principal results of the research are summarized as follows.1. The optimum proof testing method was first studied for the case of uniform stress distribution. It was found that the optimum testing method is to use the maximum unloading rate available and the test load which satisfies S_<fmin>=S_d under this unloading rate.2. The optimum proof testing method was then studied for the case of non-uniform stress distribution. This case Is Important as real machine components are generally subjected to non-uniformly distributed stresses. It was found that the optimum testing method is to use the maximum unloading rate available and the test load whi … More ch satisfies S_<fmin>=S_d at the point of the maximum stress in the component.3. The influence of the K-V relation on the effect of proof testing was studied by means of computer simulation, where K is the stress intensity factor and V=da/dt is the stable crack growth rate. It was found that when the unloading rate is larger than the critical unloading rate, exterpolation of the first region's K-V relation to the second and third regions does not result in substantial error in calculation of the minimum strength after proof testing and the probability of surviving the proof test.4. A method for estimating the critical unloading rate was proposed, and the usefulness of this method was demonstrated experimentally.5. For application of proof testing to ceramic bearing balls, the statistical properties of the ring crack initiation strength and the final fracture strength under crushing load were clarified experimentally. Furthermore, a probabilistic theory for interpreting the experimental results was proposed.6. Proof testing of Si_3N_4 bearing balls was conducted and importance of unloading rate was demonstrated experimentally. Less