Fatigue Crack Propagation Characteristic and Fatigue Fracture Toughness in 780 MPa Grade High Strength Steel Weldments at Low Temperature

Abstract

Fatigue test and fracture toughness test in 780 MPa grade high strength steel weldments in the temperature range from 98 K to room temperature were experimentally carried out. Both the tests were performed with a compact tension specimen by using a program-load-controlled 0.98 MN fatigue testing machine.
Main results obtained are summarized as follows:
(1) The fatigue crack propagation rate in the base metal shows a similar value in both the weld metal and HAZ.
(2) The trend of fatigue crack propagation characteristic in weldments in the temperature range from 223 K to room temperature is in good agreement with the dislocation dynamics theory of fatigue crack propagation.
(3) Fatigue fracture toughness, K_fc and fracture toughness, K_c in the base metal are larger than in both the weld metal and HAZ.