By referring to the national standard GB / t6398-2000 test method for fatigue crack growth rate of metallic materials, the sample is cut into standard parts. The normal stress was applied and the crack propagation experiment was carried out. The growth of mode I crack, the change of stress intensity factor at the crack tip and the crack growth rate of 42CrMo steel were studied. The research can provide some reference for the safe life of 42CrMo steel members with crack defects.
Before the test, samples were taken from 42CrMo plate according to the national standard GB / t6398-2000. Before the test, the sample shall be prefabricated to prevent the propagation of interference crack causing notch. The geometry and dimensions of the sample are given in Figure 1. It is processed by milling and wire cutting. The compact tensile test shall be made according to the standard astme647-05 to seek the unification of the crack generation direction and the rolling direction of the sample steel plate.
The dimension diagram of compact tensile specimen of 42CrMo steel is shown in Figure 1. The width is w = 40mm and the thickness is b = 6mm. The original cut length of the sample is 14 mm and the width is 2.5 mm.
The fatigue crack propagation experiment was carried out on the MTS810 electro-hydraulic servo material experimental system (Fig. 2). The data were collected by the displacement extensometer of mts632.02f-20 to record the crack length α And crack tip stress intensity factor Δ K experimental data.
The main technical parameters of MTS810 electro-hydraulic servo material experimental system are: the maximum load and maximum static load are 100kN; Maximum static load: 100kN; Maximum dynamic load: 80KN; Frequency range: 0-30Hz.