アルミニウム鋳造合金の介在物群まわり弾塑性応力に対する不確定応力振幅の影響

抄録

The fatigue crack initiation mechanism of cast aluminum alloy has been addressed by using the synchrotron radiation which gives a high resolution CT images to visualize the microstructure. By the 4D imaging, we have observed the crack initiation and propagation by low-cycle fatigue where the source of crack was the fracture of Si particle or debonding of Al-Si interface. The micromechanical finite element analysis can be performed with the precise microstructure based on the CT images. To investigate the effect of a small uncertainty in the applied cyclic loading on the stress and strain around the silicon particles which were fractured and initiated a crack in the fatigue test, the elastic-plastic finite element analyses was carried out with ten cycles of loading. The fractured silicon particles were identified from chronological CT observation. A method to make a reasonable waveform with precise mean and standard deviation was proposed. The small uncertainty coming from the experimental error was considered, and two types of cyclic loading waveform was made and used in the simulation. From those results, we found that the small uncertainty of applied stress had an significant effect on the maximum stress in silicon particles and increased it gradually by the cyclic loading.