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AlON透明陶瓷动态压痕加载响应研究

STUDY ON THE DYNAMIC INDENTATION LOADING RESPONSE OF ALON TRANSPARENT CERAMICS

  • 摘要: 透明陶瓷兼具有优秀的透光性能和抗冲击破坏性能, 冲击载荷下材料的加载响应特性对掌握材料破坏机制至关重要. 为阐明透明陶瓷在复杂应力状态下的破坏响应, 利用分离式霍普金森压杆(SHPB)系统, 开展了AlON透明陶瓷材料的动态压痕加载实验, 并通过捕获压杆表面入射, 透射以及反射的应变信号, 获得了材料在球形压头动态加载下的P-h响应曲线. 利用光学显微镜对比分析了透明陶瓷在静、动态载荷下破坏特征的异同. 将压头加载过程等效为球型孔洞在内压pi的加载力下向外膨胀的变形过程, 并对卸载过程中的有效压头形状进行修正, 建立了改进后的球形压头加载下的嵌入式扩展中心(ECD)模型, 计算了动态压痕过程中的加载响应过程以及陶瓷内部的应力场分布状态. 结果表明, AlON透明陶瓷在动态压痕过程中将出现明显的塑性变形响应, 相较于静态加载, 材料表面破坏程度加剧并出现一定程度的崩落现象; 材料的布氏硬度HB存在明显的应变率效应以及压痕尺寸效应(ISE); 压头半径R, 材料的应变硬化指数n以及无量纲参数εb对压痕加载过程影响显著; 在压头卸载过程中, 塑性应力场的存在导致了动态压痕过程中径向裂纹的萌生.

     

    Abstract: Transparent ceramics exhibit outstanding light transmission and impact resistance, the loading response characteristics under impact loads are crucial for understanding the material's failure mechanisms. To elucidate the failure response of transparent ceramics under complex stress conditions, dynamic indentation loading experiments on AlON transparent ceramic materials were conducted using a split Hopkinson pressure bar (SHPB) system. By capturing strain signals of incident, transmitted, and reflected waves on the surface of the bars, the P-h response curves of the material under dynamic loading with a spherical indenter were obtained. The damage characteristics of transparent ceramics under static and dynamic loads were comparatively analyzed using an optical microscope. The indenter loading process was equivalent to the deformation process of a spherical cavity expanding outward under internal pressure pi, with corrections made to the effective indenter shape during unloading. An improved embedded center of dilatation (ECD) model under spherical indenter loading was established to calculate the loading response process and the stress field distribution inside the ceramic during dynamic indentation. The results indicate that the dynamic indentation tests based on the Split Hopkinson Pressure Bar (SHPB) system can characterize the dynamic deformation response of ceramics. AlON transparent ceramics exhibit significant plastic deformation response during dynamic indentation. Compared to static loading, the surface damage of the material is aggravated and shows a certain degree of spalling. The Brinell hardness (HB) of the material shows significant strain rate sensitivity and indentation size effect (ISE), that is, the hardness gradually decreases with the increase of loading force. The indenter radius R, the strain hardening index n of the material, and the dimensionless parameter εb have significant effects on the indentation loading process. During the unloading process of the indenter, the presence of the plastic stress field leads to the initiation of radial cracks in the dynamic indentation process.

     

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