STRESS-INDUCED MICROCRACKS AND FRACTURE ENERGY IN CERAMICS

Research Project

Project/Area Number	60550551
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	無機工業化学
Research Institution	TOYOHASHI UNIVERSITY OF TECHNOLOGY
Principal Investigator	SAKAI MOTOTSUGU TOYOHASHI UNIVERSITY OF TECHNOLOGY, 工学部, 助教授 (50124730)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥2,100,000 (Direct Cost: ¥2,100,000) Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000) Fiscal Year 1985: ¥1,400,000 (Direct Cost: ¥1,400,000)
Keywords	CERAMICS / GRAPHITE MATERIALS / FRACTURE MECHANICS / STRESS-INDUCED MICROCRACKS / NONLINEAR FRACTURE / FRACTURE ENERGY / GRAIN BRIDGING EFFECT / ウェイク
Research Abstract	A POLYGRANULAR GRAPHITE WAS USED TO ELUCIDATE THE RELATIONSHIP OF FRACTURE ENERGY WITH STRESS-INDUCED MICROCRACKS. "DIMENSIONLESS LOAD-DISPLACEMENT UNIVERSAL CURVE" METHOD WAS PROPOSED IN THE PRESENT PROJECT TO MAKE QUANTITATIVE ANALYSES OF NONLINEAR FRACTURE, WHICH ENABLE TO DISCUSS THE NONLINEAR FRACTURE BY SEPARATING FRACTURE ENERGY INTO LINEAR AND NONLINEAR TERMS. THE R-CURVE BEHAVIOR WAS INTENSIVELY STUDIED TAKING INTO ACCOUNT THE ROLES OF GRAIN BRIDGING AND RESIDUAL STRAIN EFFECTS DUE TO MICROCRACKING AND GRAIN PULLOUT. IN WAS CONCLUDED THAT THE GRAIN BRIDGING DOMINATES THE RISING R-CURVE BEHAVIOR OBSERVED AT THE INITIAL STAGE OF CRACK EXTENSION. IN ADDITION TO THIS CONCLUSION, THE GRAIN BRIDGING WAS RECOGNIZED TO HAVE A SUBSTANTIAL EFFECT ON THE HIGHER FRACTURE ENERGY PARAMETERS OF THE POLYGRANULAR GRAPHITE. ACOUSTIC EMISSION (AE)TECHNIQUE WAS APPLIED TO DETECT THE STRESS-INDUCED MICROCRACKS IN FRONTAL PROCESS ZONE. ALTHOUGH THE AE-SIGNAL ASSOCIATED WITH THE MAIN CRACK EXTENSION WAS SO STRONG, THE AE OF MICROCRACK FORMATION WAS NOT DETECTABLE BECAUSE OF THE VERY LOW FRACTURE ENERGY RELEASE PATE OF MICROCRACKS. INSTEAD OF USING AE-TECHNIQUE, IN-SITU SEM OBSERVATION OF A FRACTURE SPECIMEN UNDER THE EXTERNAL LOAD WAS SUCCESSUFULLY CONDUCTED TO EVALUATE THE CRITICAL STRESS FOR MICROCRACK FORMATION WHICH ALLOWS US TO DISCUSS THE INFLUENCE OF THE MICROCRACKING PROCESS ZONE ON THE CRACK GROWTH RESISTANCE.