Effect Of Casting Residual Stress On Pressure-bearing Performance Of Ductile Casr Iron Pressure Vessel

As the extensive application of the ductile cast iron pressure vessel, the industry has focused on its standards and regulations. The author of this paper discovered the difference between ASME and EN standard on the requirement of relief annealing to the ductile cast iron pressure vessels. The research object of this paper is helpful to interpret this difference while accumulating useful data for the release of our national standard on ductile cast iron pressure vessel. Moreover, this paper established a systematic research method which can be applied to similarities.A certain type of Air/Oil Separator was investigated to reveal the effect of casting residual stress on pressure-bearing performance of ductile cast iron pressure vessels, adopting approaches of numerical simulation and experiment. Main tasks and conclusions are described below:(1) The geometry model and mesh was set up in Unigraphics and HyperMesh. Then the mesh of the model was imported into ProCAST. Based on the correct settings of process and software-run parameters, the solidification process of the castings was simulated and the temperature and stress fields of the vessel during the process were obtained.(2) The casting residual stress field was imported into Abaqus as an initial stress boundary condition. Based on the settings of material, loads and boundary conditions, an FEA elastic-plastic analysis of the prelum-process was carried out, and the distribution of the stress-strain was obtained.(3) Two identical type Air/Oil Separators by different heat treatment were selected for the experiment. The vessels were separately pressurized by the testing system and the strain data was acquired by the gages on the body of vessels during the experiment.(4) The simulation result fits the experiment data well. Thus, the numerical simulation method adopted in this paper is reliable.(5) According to the simulation result and experiment data, the effect of casting residual stress on pressure-bearing performance is not notable when the pressure load is relatively low. But the casting residual stress can undermine the pressure-bearing performance of the vessel under a relatively high pressure load.(6) Comparing the plastic collapse load of the vessels obtained from the numerical simulation, the casting residual stress can reduce the collapse load of the vessel, but this effect is quite limited confined to the Air/Oil Separators in the experiment.