Effects of radial gap and penetration depth on vibration fatigue behaviour of 304L stainless steel piping with socket weld

Abstract

Fatigue related failures of small bore piping caused by vibration of socket welds often occur at nuclear power plants. The purpose of the present study is to evaluate the integrity of the socket weld in nuclear piping under the condition of vibration testing. The specimens were bolted to the shaker table and shaken simultaneously near their resonant frequencies to produce the desired stress. The test results show that the failures at higher stress tend to originate at the toe, while that for the case of lower stress failures tends to occur at the root. The effects of penetration depth and radial gap were also investigated by finite element method. Results show that the higher penetration depth and radial gap can decline the stress distribution in the weld root, which is beneficial to fatigue life. Further, the desired radial gaps can significantly reduce the von Mises stresses, which decrease from 150·4 to 82·7 MPa with the width of radial gap from 0·1 to 0·4 mm.

Keywords:

• Socket weld
• Fatigue
• Failure analysis
• Radical gap
• Penetration depth

The present research work was financially supported by the Project of the National Natural Science Foundation of China (grant nos. 50975196 and 50805103), Key Project in the Science & Technology Pillar Program of Tianjin (Grant no. 11ZCKFGX03000) and Research Fund for the Doctoral Program of Higher Education of China (grant no. 20090032110026).