CAUSES OF CLEAVAGE FRACTURE IN SHIP PLATE, HIGH YIELD STRENGTH STRUCTURAL STEEL.

The primary objective of the investigation was to study the effect of variations in steel composition on the temperatures at which the mode of failure changed from ductile shear to brittle cleavage type. These transition temperatures were determined by means of tension tests on notched plates and welded structural assemblies. Three types of specimens were used, two simple notched specimens and one that provided restraint to plastic flow at a corner produced by welding together steel plates set along three mutually perpendicular planes. The specimens were tested in tension at various temperatures and at a low rate of strain in order to determine the transition temperatures of four different heats of high yield strength structural steels. Auxiliary tests were conducted by using a simple bend test to determine the effect of welding on the behavior of the steels. Results of the tests show that the four high yield strength structural steels used in this investigation, when tested in the form of restrained welded specimens, have transition temperatures that vary from -65F for one of the steels, to as high as -75F for one of the others. The tests of notched specimens showed transition temperatures for a particular steel that were approximately 50F lower than those indicated by tests of the large specimens. However, it was found that the steels are rated in the same order of transition temperatures by all three of the tests.