DEFORMATION PROCESS OF A STRAIGHT FILLET WELDED JOINT

Single-curvature polyhedron hydrobulging technology for manufacturing spherical vessels can be adopted to build spherical pressure vessels w ithout using heavy presses and large-size dies. It has been proved tha t the cost and production time is greatly reduced. When using the tech nology, one of the difficulties to be overcome is buckling of a straig ht fillet welded joint that can increase the pressure under which the polyhedron is bulged into a spherical vessel and makes the straight fi llet welded joint split along the tangential direction of the fillet w elded joint. This paper studies the buckling mechanism of a latitudina l straight fillet welded joint of an orange polyhedron. The result sho ws that the buckling process of a straight fillet welded joint can be divided into three stages: (a) single-buckle stage; (b) multiple-buckl e stage; (c) circularizing stage. A direct reason for buckling of a st raight fillet welded joint is the action of unevenly distributed tensi le stress perpendicular to the fillet welded joint. Avoiding serious g eometry discontinuity on a polyhedron wall, adopting a polyhedron stru cture with greater dihedral angles or increasing loading capability of the polyhedron can decrease the height of buckles although using thes e measures can not prevent buckles from emerging. (C) 1997 Elsevier Sc ience Ltd.