Al合金7075-T6の超音波疲労におけるき裂伝ぱ挙動

Translated title of the contribution: Crack Growth Behavior of Al Alloy 7075-T6 under Ultrasonic Fatigue

皮籠石 紀雄, 興 雅博, 後藤 真宏, 陳 強, 王 清遠

Research output: Contribution to journalArticle

Abstract

In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T 6, in ambient air and in N<SUB>2</SUB> gas, and the results were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending one. This was caused by the retardation of a crack initiation and its early propagation. In ultrasonic fatigue, the growth direction of a crack changed macroscopically from a tensile mode to a shear one which the direction was about 35 degrees against to the specimen axis, and fracture mechanism also changed from striations to transgranular facets with voids microscopically. Crack growth rate at the transition of crack growth direction was about 3 × 10<SUP>-9</SUP> m/cycle. The relation between an applied stress σ<I><SUB>a</SUB></I> and a crack depth at the transition of crack growth direction b<I><SUB>T</SUB></I> was expressed by σ<I><SUP>n</SUP><SUB>a</SUB>b<SUB>T</SUB></I>=constant. These results were explained from the time dependent environmental effect and texture of microstructure.
Original languageJapanese
Pages (from-to)1356-1363
Number of pages8
JournalNihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A
Volume72
Issue number721
DOIs
Publication statusPublished - Sep 25 2006

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Crack propagation
Ultrasonics
Fatigue of materials
Cracks
Crack initiation
Environmental impact
Textures
Gases
Microstructure
Direction compound
Air

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Al合金7075-T6の超音波疲労におけるき裂伝ぱ挙動. / 皮籠石紀雄; 興雅博; 後藤真宏; 陳強; 王清遠.

In: Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A, Vol. 72, No. 721, 25.09.2006, p. 1356-1363.

Research output: Contribution to journalArticle

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abstract = "In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T 6, in ambient air and in N<SUB>2 gas, and the results were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending one. This was caused by the retardation of a crack initiation and its early propagation. In ultrasonic fatigue, the growth direction of a crack changed macroscopically from a tensile mode to a shear one which the direction was about 35 degrees against to the specimen axis, and fracture mechanism also changed from striations to transgranular facets with voids microscopically. Crack growth rate at the transition of crack growth direction was about 3 × 10<SUP>-9 m/cycle. The relation between an applied stress σ<I><SUB>a and a crack depth at the transition of crack growth direction b<I><SUB>T was expressed by σ<I><SUP>n<SUB>ab<SUB>T=constant. These results were explained from the time dependent environmental effect and texture of microstructure.",
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AU - 後藤, 真宏

AU - 陳, 強

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AB - In order to investigate the effect of frequency on the crack growth behavior, ultrasonic fatigue tests were carried out for an extruded age-hardened Al alloy, 7075-T 6, in ambient air and in N<SUB>2 gas, and the results were compared with those in rotating bending fatigue. Fatigue strength was higher in ultrasonic fatigue than in rotating bending one. This was caused by the retardation of a crack initiation and its early propagation. In ultrasonic fatigue, the growth direction of a crack changed macroscopically from a tensile mode to a shear one which the direction was about 35 degrees against to the specimen axis, and fracture mechanism also changed from striations to transgranular facets with voids microscopically. Crack growth rate at the transition of crack growth direction was about 3 × 10<SUP>-9 m/cycle. The relation between an applied stress σ<I><SUB>a and a crack depth at the transition of crack growth direction b<I><SUB>T was expressed by σ<I><SUP>n<SUB>ab<SUB>T=constant. These results were explained from the time dependent environmental effect and texture of microstructure.

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