Experiment Study On Fatigue Properties Of Ductile Cast Iron Used For Pressure Vessels

As the extensive application of the ductile cast iron, the industry has focused on its standards and regulations. In accordance with EN13445-6published in2004, the ductile cast iron pressure vessels could be designed by analysis, and the calculation method of fatigue life is provided in Annex D which makes the ductile cast iron pressure vessels apply to fatigue conditions. At present, domestic standards and researches about ductile cast iron pressure vessels are relatively backward.Based on the research and comparison of ductile cast iron pressure vessels standards domestic and overseas, the fatigue properties of ductile cast iron is studied by experiment and analysis in this thesis. Main tasks and conclusions are described below:(1)The basic mechanical properties of ductile cast iron used for pressure vessels are obtained by tensile test, including the modulus of elasticity, yield limit, tensile strength and specific elongation. The tensile failure is estimated as ductile fracture by observation of the tensile fracture.(2)Fatigue properties of ductile cast iron used for pressure vessels are studied by fatigue test. According to the observation of fatigue fracture, the tensile failure belongs to the ductile failure and the spheroidal graphite is the root cause of the poor fatigue properties of the material. In addition, the tests showed that the ductile cast iron behaved hardening cyclic and is proved to be one with Masing behavior.(3)The low-cycle design fatigue curve is obtained by the fatigue test results and the curve is proved to be good correlation. The design fatigue curve obtained by fatigue test fits the EN13445-6curve well in the low-cycle part. Thus the test results are reliable.