| Popis: |
A comprehensive fracture toughness testing program focused principally at providing statistical assurance of the American Society of Mechanical Engineers (ASME) K I R fracture toughness design curve is presently underway.While the overall program represents testing of 50 heats of typical production materials,including A533-B, Class 1 plate; A508, Class 2 forging; A540-B-23 and B-24, Class 3 bolting material; submerged arc, manual metal arc, and shielded metal arc weldments; and associated heat-affected zone material, the data presented herein represent the initial results of an interlaboratory round robin program and the first seven heats of A533-B Class 1 plate tested in the program. Mechanical tests performed include tension, drop weight-nil ductility transition (NDT) temperature, Charpy V-notch, instrumented precracked Charpy, static and dynamic compact fracture, and dynamic three-point bend. Of these tests, instrumented precracked Charpy, dynamic three-point bend, and dynamic compact fracture are nonstandard procedures. Methodology for performance of these nonstandard tests is outlined. The fracture mechanics tests were performed on specimens up to 1-in. thick (4-in.-thick specimens will be tested later). Loading rates ranging from quasistatic to stress intensity rates (K) of 5×10 5 ksi √in.s were applied. Testing and data analysis procedures for dynamic fracture toughness testing were developed. Special emphasis was placed on the assurance of adequate electronic response in conjunction with control of the time to fracture for ensuring reliable test results. Elastic-plastic data analysis techniques were applied to test results and included both the J-integral and the equivalent energy approaches. Maximum load was used in the J-integral and equivalent energy analysis for lack of an experimental technique for determining crack initiation over a range of loading rates. It is recognized that this approach can lead to nonconservative toughness values when crack growth occurs prior to maximum load. However, for completeness elastic-plastic data analyzed using this criteria are included. |
