The Theoretical And Experimental Research On Thick Steel Plate Under External Load With Thermal Stress Coupling

Ship plate surface forming is one of the most important processes of ship manufacturing. At present, the traditional line heating process also has low heating efficiency and the forming accuracy relies mainly on the workers experience. High frequency induction heating heat source, with high heating efficiency and easy to be heated and can be controlled accurately, will gradually replace line heating process in the future. So that it can improve the quality of ship plate forming and reduce the operation difficulty and labor intensity. In order to achieve large plate deformation more easily, with the aid of external load and thermal stress coupled forming is possible. The process is a complex work in theoretical and experimental study.The mainly work is theoretical and experimental study in this article. In the theory study, the sheet forming mechanism of thermal- mechanical coupling problem is discussed in the first place. With the inherent strain theory in the process of sheet metal welding, the forming mechanism of Marine medium plate and strain is studied in the process of bending deformation and the stress or strain and bending moment are obatained. Secondly, the external load and thermal stress coupled mechanical problems is researched using Duhamel match, and the action of external load and thermal stress coupled constitutive relation with temperature is established. Thirdly, the mathematic expression of the equivalent force is established, combined with the principle of conservation of energy. Finally, the plate deformation under the external load and thermal stress coupling is analysised with ANSYS, and bending Angle and radius of curvature is obtained.In the experimental research, the deformation of 12 mm thick Q345 steel under temperature and external force coupling is researched on the high frequency induction heating equipment. Under the coupled action of thermal stress and external force, the deformation law of bending Angle and curvature radius curve is obatained using the experimental data and MATLAB surface modeling method. The mathematical model between the external force and deformation is got, compared with theoretical calculation; the precision of the model is higher.Finally, the sheet metal material mechanics performance after forming in different cooling conditions is studied. Experiment results show that the the hardness and tensile strength on the back of metal after forming are improved obviously, appearing "reverse strengthening" phenomenon. The internal organization is observed by metallographic microscope, which explains the above phenomenon. This "reverse strengthening" phenomenon of ship plate is extremely beneficial for ship manufacture and use.In this paper, the inherent strain is used to analysis the temperature load of stress, strain and thermal stress bending moment. External load and thermal stress coupled forming mechanism is studied through Duhamel, and the thermal –force coupling nonlinear constitutive relation is deduced under the coupled situation. The experimental data are used to establish the mathematical model among the temperature, bending moment and deformation. Finally, with the help of material test method, the plate mechanical performance after cooling is researched. Above work may provide a method to solve the problem of sheet metal forming mechanism and coupling large deformation. And it is also laid the foundation of high-precision large deformation processing and the automation of Marine board manufacturing.