A method for simulating the filling and solidification processes was developed using the numerical particle method of smoothed particle hydrodynamics (SPH). First, a specific algorism based on SPH was designed to simulate the filling and solidification of casting alloy. Then it was employed to simulate JIS-ADC12 conical molds, focusing on the formation of defects such as shrinkage cavity and porosity. The results showed that : 1) the SPH method based on the algorism can clearly simulate the formation of shrinkage cavities formed in the JIS-ADC12 conical mold, and 2) the method using the simulated gas particles is able to predict the location of porosities in casting materials.
Tensile properties, fatigue strength and machinability of spheroidal graphite cast irons with different microstructures were studied. Work-hardening and tensile strength increased with increasing pearlite volume fraction. In situ neutron diffraction during tensile deformation revealed that phase stresses and intergranular stresses are generated with deformation resulting in high work-hardening and high tensile strength with increasing pearlite volume fraction. It was found that graphite grains bear almost no stress, and strongly influence fatigue crack initiation as well as propagation. Therefore graphite refinement is very effective to realize high fatigue strength. The tool life for cutting becomes shorter with increasing pearlite volume fraction. The balance of mechanical properties and machinability was considered.
Aluminum alloy die-cast specimens (ADC12) containing cold flakes were subjected to fatigue test and broken at about 330 × 103 cycles. During the fatigue test, ultrasonic measurement was carried out in synchronization with the loading cycle to obtain the intensity of reflection from the oxide layer of the cold flake without stopping the fatigue tester. With increasing number of fatigue cycles, the reflection intensity monotonically decreased with the number of cycles at 80 × 103 cycles or larger, and then the phase of the reflection wave changed at about 220 × 103 cycles. After the change in the phase of the reflection wave, the reflection intensity gradually increased with the number of cycles. From these results, it was found that the oxide layer of the cold flake detached from the matrix at 80 × 103 cycles or less, namely less than 30 % of the fatigue life.