Certification of new welding systems for naval ship construction involves demonstrating that the system will provide adequate structural performance under severe loading conditions. The standard test used by the Navy to demonstrate that a weld can withstand extensive plastic deformation in the presence of a flaw is the Explosion Bulge/Explosion Crack Starter test. This test uses a rather large specimen fabricated from 1 in. or 2 in. (25.4 or 50.8 mm) thick plate that is explosively loaded. Consequently, conducting an explosion bulge test series can be very expensive. The test is also rather extreme in the level of plastic deformation developed in the plate. The loading condition simulates the strain rate that might be caused by direct shock in an underwater explosion, but is not necessarily representative of typical surface ship loading rates.
For certification purposes it would be desirable to develop relevant structural performance requirements and then use a simple, inexpensive test to determine if the welding system will meet the requirement. The objective of this study was to determine what combination of material properties the weld system must have to obtain the required performance. Structural performance was assessed by conducting tests on a structural performance element that was representative of plate thickness and loading conditions. Scaling models are presented that compare the structural performance element with the traditional Explosion Crack Starter specimen. Failure probabilities were calculated using the Weibull stress concept, the transition temperature and the Master Curve. The transition temperature and probability of failure are incorporated into criteria that the weld system must meet to ensure that the structure will have the desired performance.
The proposed approach for determining structural performance-based material selection criteria was used to interpret the results from a series of tests on HSLA-65 welds. Fracture toughness, structural elements and the Explosion Crack Starter tests were conducted to characterize the fracture performance of the various welds. The results from these tests are presented and the relationship between the material properties and the resulting structural performance is discussed.