Prediction and Verification of Ductile Crack Growth From Simulated Defects in Strength Overmatched Butt Welds

<p>Defects that develop in welds during the fabrication process are frequently manifested as embedded flaws from lack of fusion or lack of penetration. Fracture analyses of welded structures must be able to assess the effect of such defects on the structural integrity of weldments; however the transferability of R-curves measured in laboratory specimens to defective structural welds has not been fully examined. In the current study the fracture behavior of an overmatched butt weld containing a simulated buried lack-of-penetration defect is studied. A specimen designed to simulate pressure vessel butt welds is considered; namely a center crack panel specimen of 1.25 inch by 1.25 inch cross section loaded in tension. The stress-relieved double-V weld has a yield strength 50% higher than that of the plate material and displays upper shelf fracture behavior at room temperature. Specimens are precracked loaded monotonically while load-CMOD measurements are made then stopped and heat tinted to mark the extent of ductile crack growth. These measurements are compared to predictions made using finite element analysis of the specimens using the fracture mechanics code Warp3D which models void growth using the Gurson-Tvergaard dilitant plasticity formulation within fixed sized computational cells ahead of the crack front. Calibrating data for the finite element analyses namely cell size and initial material porosities are obtained by matching computational predictions to experimental results from tests of welded compact tension specimens. The R-curves measured in compact tension specimens are compared to those obtained from multi-specimen weld tests and conclusions as to the transferability of R-curves is discussed.</p><p>This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact and remains as true to the original work as possible. Therefore you will see the original copyright references library stamps (as most of these works have been housed in our most important libraries around the world) and other notations in the work.</p><p>This work is in the public domain in the United States of America and possibly other nations. Within the United States you may freely copy and distribute this work as no entity (individual or corporate) has a copyright on the body of the work.</p><p>As a reproduction of a historical artifact this work may contain missing or blurred pages poor pictures errant marks etc. Scholars believe and we concur that this work is important enough to be preserved reproduced and made generally available to the public. We appreciate your support of the preservation process and thank you for being an important part of keeping this knowledge alive and relevant.</p>