CRACK INITIATION IN CRUCIFORM SPECIMENS WITH HOLES UNDER BIAXIAL RANDOM TENSION-COMPRESSION

摘要

The paper presents the results of fatigue tests for 18G2A structural steel subjected to biaxial random tension-compression. Cruciform specimens with four holes were tested. During the tests, the place and time of crack initiation were observed. A method of indication of the places of fatigue crack initiation was proposed. This method uses FEM and cyclic stress-strain curve for calculating the stress state on the specimens. The multiaxial fatigue failure criterion based on critical plane approach was used for reduction of the random spatial stress state to the equivalent uniaxial one. The critical plane position was established with use of the variance method, and fatigue life was determined with assumption of linear damage accumulation. It was shown, that the proposed method for determination of the places of fatigue crack initiation gave results well correlated with the data obtained from experiments. The proposed method could be applied by engineers in order to identify the places and time of fatigue cracks initiation.