Fracture Mechanics Interaction of MicroーFlaws with Ceramic Grain Boundaries.

微缺陷与陶瓷晶界的断裂力学相互作用。

• 批准号: 01550598
• 负责人: SAKAI Mototsugu
• 金额: $ 1.34万
• 依托单位: Toyohashi University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1989
• 资助国家: 日本
• 起止时间: 1989 至 1990
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01550598/
• 关键词: Polycrystalline ceramics; Grain boundary; Fracture toughness; Flaw-defect; Fracture Mechanics interaction; R-curve; 粒界; 破壊靱性値

The main objective of the present study is to elucidate the role of ceramic grain boundaries in toughening polycrystalline ceramic materials by examining the micromechanics interaction between the strengthーcontrolling small flaws and the grain boundaries of ceramics.1. Experimental detailsConducted were the measurements of the mechanical strength and the fracture toughness of oxide ceramics including MgO and Al2MgO4 with different grain sizes, as well as polycrystalline graphite materials, where we focused mainly on the influence of the ratio of (sintered grain size) / (strength-controlling flaw size) on these fracture parameters.2. Brief outline of the results and discussion(1) There exists a finite difference in the experimentally determined fracture toughness values obtained from test specimens with a macro-notch or a macro-crack and with a micro-flaw. The decrease in the grain boundary bonding forces of polycrystalline ceramics enhances this difference.(2) The macroscopic fracture … More toughness decreases, while the microscopic fracture toughness in the IM-method increases, with decreasing grain boundary bonding forces. This toughness increment in the IM-method for weak grain boundaries may result from the microscopic local relaxation of the crackーtip stress field through stress-induced microcracking along the grain boundaries.In addition, it has been disclosed in the present study that this fracture toughness difference between macro- and micro-cracked specimens is closely related to the R-curve behavior of the polycrystalline ceramic.(3) Critically reviewed was the conventional concept of the "microstructural R-curve effect" which has been introduced to explain the apparent decrease of fracture toughnss with the progressive decrease of the strength-controlling flaw size. It has been emphasized and concluded that the transition (switching) of the strength-controlling fracture origin from the artificially induced flaws to the intrinsic flaws and vice versa is most essential to dictate the fracture strength and fractue toughness of polycrystalline ceramics with defects/cracks/flaws whose dimensions are in the same order of the magnitude of sintered grains. Less

本研究的主要目的是阐明陶瓷晶界在增韧多晶陶瓷材料中的作用，通过研究控制小缺陷的强度因子和陶瓷晶界之间的微观力学相互作用.实验内容：1.对不同晶粒尺寸的MgO、Al 2 MgO 4氧化物陶瓷以及多晶石墨材料的力学强度和断裂韧性进行了测试，重点研究了烧结晶粒尺寸/强度控制缺陷尺寸之比对这些断裂参数的影响.结果和讨论的简要概述（1）从具有宏观缺口或宏观裂纹的试样和具有微观缺陷的试样获得的实验确定的断裂韧性值存在有限的差异。多晶陶瓷的晶界结合力的降低增强了这种差异。(2)宏观断裂 ...更多信息 韧性下降，而在IM方法的微观断裂韧性增加，降低晶界结合力。这种韧性增量的IM-方法中的弱晶界可能是由于裂纹尖端应力场的微观局部松弛，通过应力诱导的微裂纹沿沿着.此外，它已被披露在本研究中，这种断裂韧性之间的差异宏观和微观裂纹试样是密切相关的R-曲线行为的多晶陶瓷。(3)对传统的“微观结构R曲线效应”概念进行了批判性的评述，该概念被用来解释断裂韧性随强度控制缺陷尺寸的逐渐减小而明显降低的现象。本文强调并得出结论：强度控制断裂起源从人工缺陷到本征缺陷的转变（转换），以及从本征缺陷到人工缺陷的转变，是决定多晶陶瓷断裂强度和断裂韧性的关键。少

项目成果

T. Miyajima, M. Inagaki and M. Sakai: "An Application of Indentation Method to the Fracture Mechanics Study of a Polycrystalline Graphite" J. Mather. Sci.

T. Miyajima、M. Inagaki 和 M. Sakai：“压痕法在多晶石墨断裂力学研究中的应用” J. Mather。

M.Sakai and K.Takahashi: "Interaction of Surface flaws with Grain Boundaries of Polycrystalline Mg Al_2O_4ーCeramics." J.Am.Ceram.Soc.

M.Sakai 和 K.Takahashi：“表面缺陷与多晶 Mg Al_2O_4ー陶瓷晶界的相互作用”。

T.Miyajima,M.Inagaki and M.Sakai: "An Application of Indentation Method to the Fracture Mechanics Study of a Polycrystalline Graphite" Journal of Materials Science.

T.Miyajima、M.Inagaki 和 M.Sakai：“压痕法在多晶石墨断裂力学研究中的应用”材料科学杂志。

M. Sakai and T. Miyajima: "Effect of Flaw-Flaw Interaction on the Strength of a Soda-Lime Glass" J. Europ. Ceram. Soc.

M. Sakai 和 T. Miyajima：“缺陷与缺陷相互作用对钠钙玻璃强度的影响”J. Europ。

M.Sakai and T.Miyajima: "Effect of FlawーFlaw Interaction on the Strength of a SodaーLime Glass" Journal of European Ceramic Society.

M.Sakai 和 T.Miyajima：“缺陷相互作用对软石灰玻璃强度的影响”欧洲陶瓷学会杂志。