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Study on Strength Evaluation of Ceramic/Metal Joints

陶瓷/金属接头强度评价研究

基本信息

批准号：
01460095
负责人：
KOBAYASHI Hideo
金额：
$ 4.35万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
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

项目摘要

Four-point bend tests were conducted for Si_3N_4/S45C and Si_3N_4 joint smooth and precracked specimens. Analytical studies on joining residual stresses were also performed by the FEM method. The results obtained are as follows :(1) There is a reason for the decrease of the fracture strength in the Si_3N_4/S45C joint additional to the existence of the interface and interlayer.(2) Cracks are easily initiated from the inherent defect during mechanical cutting after joining.(3) In the case that there is a crack and tensile residual stresses at the ceramic near the interface, the strength decreases drastically. The strength of the joint can be evaluated by the stress intensity factor using the plane strain fracture toughness of Si_3N_4.(4) In the case that an indentation precrack is introduced at the ceramic side near the interface, the precrack is kinked toward the interface, so, the indentation method is not suitable to introduce a precrack near the interface.(5) The result of the axi-sy … More mmetric analysis on the joining residual stresses shows a good agreement with the results of the three dimensional analysis and the pack stress can be approximately estimated by superposing results of the two plane stress analysis.(6) The residual stresses redistribute after cutting of the ceramic/metal joint and the peak tensile stress occurs on the new free surface at the ceramic near the interface. It is emphasized that the residual stress at a same point decreases after cutting, but the maximum value does not change. The effects is almost the same as that of the changing the size and aspect ratio of the joint specimen.(7) Residual stresses at the ceramic near the interface were measured nondestructively by the X-ray method for the Si_3N_4/S45C joints before and after cuttings. The local residual stress distribution near the interface can be measured nondestructively by the PSPC/RSF system used in this study. The residual stresses redistribute by the cutting. The distribution characteristics do not change, although the absolute value of the residual stresses at the same position decreases. The comparison between the results of the X-ray measurement and the result of the FEM analysis shows a good agreement qualitatively.(8) The singularity of residual stresses at the ceramic near the interface is characterized by elastic-plastic properties of ceramic and insert materials. The exponent of the elastic-plastic singularity is larger than that of elastic singularity.(9) The decrease in the fracture strength for the Si_3N_4/S45C joints compared with those for the Si_3N_4 /Si_3N_4 joints is explained by considering the singular stress field of residual and applied stresses at the ceramic near the interface of the joint. Less

对Si_3N_4/S45C和Si_3N_4节理光滑和预裂试样进行了四点弯曲试验。采用有限元法对接头残余应力进行了分析研究。结果表明：(1)Si_3N_4/S45C接头断裂强度下降的原因除了界面和中间层的存在外；(2)连接后机械切割时，由于固有缺陷容易产生裂纹。(3)在界面附近存在裂纹和拉伸残余应力的情况下，陶瓷强度急剧下降。用Si_3N_4的平面应变断裂韧性作为应力强度因子来评价接头的强度。(4)在靠近界面的陶瓷侧引入压痕预裂缝时，预裂缝向界面方向弯曲，因此，压痕法不适合在靠近界面处引入预裂缝。(5)连接残余应力的轴向对称分析结果与三维分析结果吻合较好，并可通过两平面应力分析结果的叠加来近似估计堆垛应力。(6)陶瓷/金属接头切割后残余应力重新分布，峰值拉应力出现在靠近界面的陶瓷新自由表面。强调切削后同一点的残余应力减小，但最大值不变。这种影响与改变接头试件的尺寸和纵横比几乎相同。(7)采用x射线法对Si_3N_4/S45C接头切割前后陶瓷界面附近的残余应力进行了无损测量。本研究使用的PSPC/RSF系统可以无损地测量界面附近的局部残余应力分布。残余应力通过切削重新分布。同一位置的残余应力绝对值减小，但分布特征不变。x射线测量结果与有限元分析结果的定性比较表明，两者吻合较好。(8)陶瓷界面附近残余应力的奇异性由陶瓷和插入材料的弹塑性特性来表征。弹塑性奇异指数大于弹性奇异指数。(9) Si_3N_4/S45C接头的断裂强度比Si_3N_4/ Si_3N_4接头的断裂强度降低的原因是考虑了接头界面附近陶瓷残余应力和外加应力的奇异应力场。少