THROUGH THICKNESS FATIGUE PROPERTIES OF STEEL PLATE; PROPERTIES OF HEAVY SECTION NUCLEAR PLATES (To Purchase Call 1-800-854-7179 USA/Canada or 303-397-7956 Worldwide)
Axial load-controlled fatigue tests on steel specimens machined from welded assemblies of 11/2 in. thick plates were conducted to evaluate the through thickness (ST@ Z-direction or short transverse) fatigue characteristics of a normalized steel used for the construction of offshore drilling rigs. Short transverse properties of steel are important because many welded joints require loads to be transferred through the thickness of a plate. When designing and fabricating such joints@ the possibility of lamellar tearing during welding should be considered. In the series of experiments undertaken@ no lamellar tearing was detected in the welded assemblies prior to final machining. Cylindrical specimens were cut from the welded assemblies and threaded at both ends so that loads could be applied parallel to the through thickness direction (normal to the rolling surface) of the test plate which was located in the center. The steel@ Grade EH 32 which conforms to American Bureau of Shipping standards@ exhibited good static through thickness ductility (greater than 20% ROA). In comparison with the properties of the weld metal and the longitudinal direction of the plate@ the through thickness section did not perform as well under complete load reversal (R = -1) in both high and low cycle loading. Inspection of fracture surfaces with a scanning electron microscope clearly shows that non-metallic inclusions affect both the static and fatigue failure mechanisms in the short transverse direction. Fatigue crack initiations at the surface of flat inclusions running parallel to the rolling direction were observed in etched cross sections viewed through an optical microscope.