Crack Propagation in Plate under Bending Load

Abstract

To investigate crack propagation behavior in plate under bending load, the following experiments were carried out using carbon-manganese steel (NK's KL24B) for LPG tank material and alminium alloy (A5083-O) for LNG tank material. (l) Surface crack propagation test under dynamic pure bending load. (2) Through crack brittle fracture test under pure bending load. Main findings from the above tests are as follows: From experiment (l): a) A surface crack penetrates the plate when the crack length becomes about 15 times the plate thickness under pure bending load. b) The propagation rate of surface crack can be well expressed by the following formula. da/dN=C(αΔσ_b√<πa>)^m α=0.2&sim;0.4 From experiment (2): a) The equivalent tensile stress σ_<eff> for brittle fracture initiation under pure bending load can be expressed as follows: σ_<eff>=βσ_b β:<0.52 for carbon-manganese steel=0.47 for alminium alloy The above effective coefficient obtained by the experiments well correspond with theoretical ones. b) Brittle crack propagation length in alminium alloy is small under pure bending load.