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論文 |
論文
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神宮, 利夫 ; 永倉, 和郎 ; 根津, 紀久雄 ; 坂本, 賢治
概要:
application/pdf<br />Journal Article<br />The crack propagation velocity in tensile fracture is determined by comparison of the unloading wave observed by the strain gage method with the theoretical analysis based on postulating the
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crack growth models which are backed by the fractographic analysis using the photograph taken by the scanning electron microscope (SEM). The effect of elongation, contraction of notch bottom and load rate just before rupture on the crack propagation velocity is investigated using the notched round bar specimens of annealed JIS-SS41, S45C and quenched SKS93 steel. The fracture surface of SS41 and S45C is a dimple and SKS93 a cleavage. The deformation of SS41 is largest and in turn S45C, SKS93. It is shown that the crack speed slightly decreases as elongation or contraction of notch bottom increases. Particuraly, the decrease of crack speed of quenched SKS93 is a very little. The reduction of crack speed attributes to softening of notch bottom.
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| 2.
論文 |
論文
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神宮, 利夫 ; 永倉, 和郎 ; 根津, 紀久雄 ; 坂本, 賢治
概要:
application/pdf<br />Journal Article<br />Since the tensile fracture is governed by the load rate, the unstable crack fracture must be observed under the condition in which the load rate is smaller than crack speed. In this paper, the
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time-dependent stress caused by the compression wave emanated from the rupture section of a notched round bar is observed by the strain gauge method, while the problem of the same condition is theoretically analysed by postulating the crack growth models. The crack speed is determined from a comparison of the experimental result with theoretical result. Furthermore, the present paper experimentally distinguishes the effect of various factors, load rate and stress intensity factor, strain hardening, and area contraction of the material on the crack speed in tensile fracture, and suggests the experimental condition in observing the unstable crack fracture by the tensile test.
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