INITIATION LIFE OF WELD UNDERCUTS FATIGUE

 CRACK IN PRESSURE VESSEL

WEI An’an  YOU Yikuang  LU Yi  GAO Guangfan  Wang Lei

( Jiangsu key Laberatory of Oil and Gas Storage and Transportation, Jiangsu Polytechnic University, Changzhou 213016 )

Abstract: Aiming at the pressure condition of the weld undercuts of the air spherical tank under the fluctuant pressure in an enterprise, the mechanics model of the structure with undercuts is built, the graphology and finite element method are respectively used to calculate the elasticity stress concentration factor, then the nominal stress about the undercut tip is calculated. Then the initiation life of fatigue crack is estimated according to the experimental estimate expression. Using the samples with equal thickness to the tank and with the same size as the real undercuts, a simulation fatigue testes are performed under the stress range of an actual structure. As a result, the estimating life according to the experimental estimate expression approaches to the experimental life. Sequentially, theoretical basis and the experimental data for study on fatigue crack initiation life of the undercut is provided. Considering some safety factor, the remain life of the tank is 9 years, the remain initiation life of fatigue crack is 6 years.

Key words: Undercut  Fatigue crack  Initiation life

CLC No: TQ051.3

中石化科研资助项目(X503018). Received 20051026,  received in revised form 20060328