Crack Arrest Fracture Toughness Measurement of a Quenched and Tempered Ship Plate Steel.

摘要

A quenched and tempered HSLA type ship plate steel was used to investigate the influence of dynamic effects on crack propagation and arrest behavior and to measure the static arrest toughness, KIA. The specimen type used was a wedge-loaded modified compact tension specimen which provides fixed grip conditions during crack extension. Under fixed grip conditions no external work is performed on the specimen after crack initiation and only elastic strain energy stored prior to crack initiation is utilized for crack propagation, usually allowing the propagating crack to arrest within the confines of the specimen. The tests conducted on this steel gave results that cast doubt on the geometry and crack velocity independence of the static crack arrest fracture toughness parameter. The test results show crack arrest fracture toughness values appear to decrease with increases in kinetic energy input indicating kinetic energy may be utilized during crack extension. The measured crack arrest fracture toughness values for this steel range from 43 to 60 MPa in the longitudinal orientation and 48 to 62 MPa in the transverse orientation at - 60 deg C. For this series of tests, kinetic energy input was increased by employing side grooves of increasing depth. An increase in side groove depth from a non side grooved specimen to 6% (of specimen thickness) per side decreased the measured Kla by 5% in both longitudinal and transverse orientations, while an increase in the side groove depth to 12% per side decreased the arrest toughness by 12% (measured in the transverse orientation only).... Crack extension, Fracture properties, Steels. Strain energy, Dynamic fracture toughness,