Effect of residual stresses on design assessment of partial penetration laser welds in a pressure valve component
- Ohio State Univ., Columbus, OH (United States)
Three autogenous laser welds joining the cap fitting, the outlet fitting and the inlet fitting to the valve body were analyzed using the ANSYS code. This stress analysis evaluated various weld penetration conditions from 0.020 inches to 0.040 inches. The evaluation criteria included fracture, fatigue and general yielding of welds at three load conditions: the maximum operating pressure (500 psi), proof pressure (750 psi) and burst pressure (1,250 psi). It is concluded that, without considering welding-induced residual stresses, weld penetration of 0.020 inches is adequate for normal use of the three valve components investigated. The factor of safety for 0.020 inches weld penetration is greater than 4 for all three valve fitting. Because the material is thin and ductile, residual stresses affect only the plastic zone size and shape. Weld shrinkage causes compressive radial stress at the joint surface and the weld root. The mid-section of the weld penetration is in tension in both radial and longitudinal directions. The Von Mises equivalent stress in the weld is increased due to residual stresses, which reduces the safety factor by a range of 30 to 50%. However, the factors of safety for all cases are still greater than 2.7 at burst pressure. The root gaps of all three weld fittings with penetration greater than 0.02 inches are nonpropagating and fracture stable due to the compressive residual stress surrounding the root gap. For a conservative design to relax the postweld inspection requirement or to prevent failure from unexpected overloading situation, a minimum of 0.030 inches weld penetration is recommended for the cap and outlet fittings. The minimum weld penetration required for the inlet fitting is 0.020 inches.
- OSTI ID:
- 403194
- Report Number(s):
- CONF-960706-; ISBN 0-7918-1774-1; TRN: IM9651%%229
- Resource Relation:
- Conference: American Society of Mechanical Engineers (ASME) pressure vessels and piping conference, Montreal (Canada), 21-26 Jul 1996; Other Information: PBD: 1996; Related Information: Is Part Of Residual stresses in design, fabrication, assessment and repair. PVP-Volume 327; Warke, R.W. [ed.] [Edison Welding Inst., Columbus, OH (United States)]; Dong, P. [ed.] [Battelle Memorial Inst., Columbus, OH (United States)]; Dermenjian, A. [ed.] [Sargent and Lundy, Chicago, IL (United States)]; PB: 207 p.
- Country of Publication:
- United States
- Language:
- English
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