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| Investigation on toughness index of high grade steel drill pipe |
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LI Fang po1,2, HAN Li hong2, LIU Yong gang2, WANG Yong1
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(1.College of Electromechanical Engineering in China University of Petroleum, Qingdao 266555, China;2.CNPC Tubular Goods Research Institute, Xi 'an 710065, China)
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| Abstract: |
| Due to the development and application of ultra deep well and directional well drilling technologies, high grade steel drill pipes, such as G105 and S135, are used widely. The drill pipe failure incidents occur frequently. The fatigue crack length of high grade steel drill pipe is about 60 80 mm at steady developing stage. The impact energy formula of "leak before break" failure mode was proposed, and stress strength coefficient was introduced for the first time. The results show that the impact energy value increases with the increase of critical crack length, stress strength coefficient square, and steel grade. The impact energy values of high grade steel drill pipe and anti sulfur drill pipe are not less than 80 J and 110 J respectively to ensure drill pipe under "leak before break" failure mode. |
| Key words: high grade steel drill pipe failure mode fatigue impact energy toughness index |
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