Fracture Mode Study of AH36 Steel Cloverleaf Deck Sockets

摘要

This report describes mechanical testing performed on AH36 steel deck socketsfollowed by a fracture mode study. For all specimens, 'untreated' designates deck sockets, which possess a hardened martensite surface layer, a cold worked layer, and surface microcrack. The 'treat' specimens have a newly ground cloverleaf lobe surfaces and were heat-treated at 1150 deg F for 10 min. The 'welded' specimens designate specimens in which a brittle weld bead was desposited on the untreated surface of the cloverleaf lobe and notched to initiate a brittle crack. The 'milled' socket was manufactured by a modified process, in which milling, instead of coining, was used to round the corners of the cloverleaf lobe after flame cutting and no heat treatment was performed after the milling process. Small coupons were removed from untreated, treated, welded, and mill deck sockets and monotonically loaded until failure to exmaine the effect of cloverleaf lobe surface treatments. These results showed that under an overload condition, the untreated and welded deck sockets could initiate brittle cleavage fracture at room temperature. The treated deck sockets and the milled socket failed in an ductile manner with a large amount of plastic deformation prior to failure.