In butt welded joints, a gap remains between two joined plates due to incomplete penetration (weld penetration problem). This gap may initiate a crack when the joint is subjected to loading. Often the butt welded joints with the above mentioned defect is used in a wide variety of engineering constructions such as bridge, boilers, pressure vessels, piping systems, ships, automobile industries, off-shore structures etc. The greatest advantage of using butt welds for joining metals is simplicity in use and higher joint strength.
The incomplete penetration defect can be compared as a rectangular notch and stress concentration will be more at its tip, Which may cause initiation of the crack that leads to failure of the welded joints, when it is subjected to low temperature, dynamic or cyclic loading. Hence, it is necessary to reduce the length of the defect to reduce stress concentration. This defect may be eliminated by suitable edge preparation. However the cost of making joints increase with edge preparation, it is necessary to find out optimization of weld-penetration defect length, from economical point of view.
So far, extensive research has been conducted to identify a permissible defect length by studying the stress concentration factor (S.C.F) for double V Butt welded joint, using photo elasticity technique. In the present analysis, stresses are analyzed using Finite Element Analysis and then stress concentration factors have been determined for single-V, single-J, double-V, and double –J butt welded joints and then weld penetration problem is optimized.