Fracture Behavior Analysis Of Q390D Steel Under Impact Load

Pressure vessel is an important industrial equipment widely used in various fields,its safety is very important.The working environment of the pressure vessel on the ship is complex.In addition to the highly pressure load,it may also be subjected to dynamic loads such as wave,explosion impact.Because of the welding,forging and other manufacturing processes used in the manufacturing process of pressure vessels,cracks,holes and other technological defects are inevitable,if the defect extends under pressure in normal service,or the crack extends under accidental impact load,the pressure vessel will burst,it will cause serious damage to the ship equipment.Therefore,it is of great significance to analyze the impact fracture behavior of typical pressure vessel materials and study its impact fracture law for the safe operation of pressure vessel equipment.In this paper,the impact fracture of Q390D steel is studied.The main contents are as follows:The Charpy impact test of Q390D steel was carried out by Zwick / roll pendulum impact testing machine,and the impact absorption energy curve and load displacement curve were obtained.The test curve and the fracture morphology of the specimen were qualitatively analyzed,and the fracture law was studied.The crack initiation point and crack initiation time of Q390D steel Charpy impact specimens were determined by flexibility change rate method,and the applicability of quasi-static J-integral formula under dynamic conditions was determined.The dynamic J-integral is obtained by using quasi-static formula.The dynamic crack growth resistance curves of specimens are solved by J-integral increment method and Schindler method,and the advantages and disadvantages of the two methods are compared.The results show that Schindler method is more simple and fast,but the results are relatively conservative;the results of J-integral increment method are more accurate.Finally,the Charpy impact test process of Q390D specimen is simulated by finite element software,and the load displacement curve and impact absorption energy curve obtained by simulation and test are compared.The results show that the dynamic fracture process can be accurately simulated by using J-C constitutive model,and the simulated fracture morphology is in good agreement with the experimental results.A typical Q390D steel pressure vessel model is established,and the weak position of the structure is obtained by using ABAQUS static analysis module.The finite element model of the pressure vessel with cracks is established.The dynamic implicit algorithm is used to simulate the different explosion impact loads that may be suffered by the pressure vessel for ships.The crack propagation process of the structure under two different explosion impact loads is obtained,and the crack propagation law is analyzed.