両端自由衝撃曲げによる構造用セラミックスの高温衝撃破壊じん性の計測

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A new instrumentation system was developed for the measurement of dynamic fracture toughness of ceramic materials at elevated temperatures up to 1200 deg C by impact test with a free end bend specimen (one-point-bend specimen). The specimen was of Charpy type (6 mm width, 8 mm height and 50 mm length) made of silicon carbide (SiC) and a notch of 0.2 mm width was cut by a diamond wheel. The specimen was hanged in an infrared image furnace by a couple of thin ceramic threads cemented onto the end surfaces of the specimen. Thus the heat conduction that usually takes place through support structure could be avoided or kept to a minimum. The impact force was provided by a falling steel cylinder of 6 mm dial and 1500 mm length with a pair of semiconductor strain gauges cemented onto a cylindrical surface to measure the stress wave history and hence to determine the impact force. Since the thin threads are thought to be broken at the moment of impact, the specimen is supposed to fracture without any constraint at both ends. A simple formula was employed for determining the dynamic stress intensity factor from the measured impact force with a microcomputer used for processing the experimental data. A series of impact tests were performed with drop-height increased gradually and the dynamic fracture toughness was determined from the test data of the minimum drop-height that caused specimen fracture. The dynamic fracture toughness values obtained by the impact test were compared with the results of quasi-static tests. It was shown that the developed system is satisfactory for measuring the dynamic fracture toughness of ceramic materials at elevated temperatures.
社団法人日本材料学会の論文
1988-08-15

両端自由衝撃曲げによる構造用セラミックスの高温衝撃破壊じん性の計測

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