FACTORS INFLUENCING THE YIELDING CONSTRAINT
BY CRACKED WELDED COMPONENTS*
Dražan Kozak, University of Osijek, Mechanical Engineering Faculty in Slavonski Brod, Trg Ivane Brlić-Mažuranić 18, HR-35000 Slavonski Brod, Croatia
Jelena Tuma, Inštitut za kovinske materiale in tehnologije, Lepi pot 11, SI-1001 Ljubljana, Slovenia
NenadGubeljak, University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, SI-2000 Maribor, Slovenia
Damir Semenski, University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Ivana Lučića 5, HR-10000 Zagreb, Croatia
Abstract
It is well known that yielding of crack front surrounding material in the middle of the component is more constrained with the thickness increasing. In-plane and out-of-plane constraint effects on crack tip stress fields are studied by means of three-dimensional finite element analyses. The crack tip constraint by standard fracture toughness specimens has been quantified through the stress triaxility factor calculation. The variation of local stress triaxility factor according to the thickness of specimen is presented.
The effect of component geometry on the yielding zones spreading may be associated with present materials dissimilarity in the welded joint. In that sense the influence of the butt welded joint shape (I-, K- or X-shape) and the a/W ratio as well as slenderness of the welded joint (W-a)/H on the stress distribution around the crack has been investigated. This depends also on the crack location (middle of the specimen or heat affected zone) and on type of loading (tensile, bending etc.). These investigations have been performed for the different levels of mismatch factors M in the joint.
At the end, plastic yield load solution has been derived using limit finite element analyses in the case of single edged fracture toughness specimen subjected to bending consisting X-shaped heterogeneous weld joint. The corresponding fully plastic yield loads were obtained directly from the finite element solutions for the same portion of the overmatched and undermatched metal in the weld joint.All range of influencing parameters has been analysed to be able to derive an analytical expression for the yield loadFY. It was founded that several key parameters most affecting the fracture behaviour of the specimen: degree of strength mis-match M, (W-a)/H and a/W ratios.
* KM – kovinski materiali