Research On Line Heating Forming Mechanism Of High Strength Steel For Curved Hull Plate

In order to ensure the safety of the hull,withstand external water pressure and resist the impact of waves,there are high strength requirements for the hull plates in the process of shipbuilding.There are high strength and tensile strength on high strength steel.Under the premise of safety,the thickness of steel plate can be reduced,so as to reduce weight and energy consumption.Its application in ship construction is becoming more popular.Shipbuilding generally includes production design,plates cutting,bending,assembly welding,outfitting and painting process.The forming of the curved hull plate is important.Line heating,as the main processing method for complex double curvature hull plates forming,is still mainly realized manually from forming inspection,its automation is low.This kind of forming processing method,which is highly dependent on the operation experience of workers,resulting in low forming efficiency and difficult to guarantee the forming quality.The existing researches on the line heating for hull plate forming mostly focuses on the situation that the plate material is low carbon steel,and the attention to high strength steel is insufficient.There are fewer researches on the line heating for high strength steel forming.In order to achieve the prediction of heating parameters of high strength steel,it is necessary to research the mechanism of high strength steel line heating forming by comparing the research of low carbon steel.The research work done in this thesis can be divided into the following aspects:(1)Numerical calculation of high strength steel line heating forming for curved hull plate considering deflectionBased on the thermal-elastic-plastic theory,a numerical calculation model of high strength steel line heating forming for curved hull plate considering deflection and shrinkage was constructed.Thermal boundary conditions suitable for numerical calculation of high strength steel were obtained by combining the performance parameters of high strength steel and the characteristics of line heating forming process.The numerical calculation model for high strength steel line heating forming was established.The time course and distribution law of the temperature field and deformation field were obtained.The rationality of the numerical calculation model of high strength steel forming was verified by comparing with the numerical simulation results of low carbon steel.In order to solve the problem of low forming efficiency of high-strength steel,numerical calculation method of line heating for high strength steel forming with multi-heating lines was researched based on the single heating line numerical calculation model.Numerical calculation model of line heating for high strength steel forming with multi-heating lines was established.(2)Analysis and regularity research of influencing factors of heating deflection deformation of high strength steel line heating forming.In order to solve the problem of high strength steel forming and guide the selection of process parameters,the influencing factors of high strength steel line heating forming were analyzed.The influence regularities of the deflection deformation were researched.The regularities of heating speed,heating line length,heating line position,heating line spacing,plate length,plate width,curvature radius and plate thickness on high strength steel line heating forming were obtained.A multivariate regression model of the relationship between deflection and influencing factors was established.The regularities of deflection superposition error under multi-heating lines interaction was revealed.In order to predict the deflection caused by combined action of multi-heating lines,the superimposed deflection of single heating lines was modified based on the area centroid method.(3)Design and analysis of an automated forming equipment considering multi-heating lines for efficient formingIn order to solve the problems of tedious processing procedures and low forming efficiency of high strength steel for curved hull plate,the line heating forming equipment considering multi-heating lines was designed.According to the actual processing characteristics of line heating forming and the property parameters of high strength steel,the design requirements of the line heating forming equipment considering multi-heating lines were proposed.The main property parameters and structural parameters of the equipment were determined,and a three-dimensional model was established.The structural design of the forming equipment was completed.Through the static analysis and modal analysis of equipment structure,the equipment structure was optimized,and the strength and stiffness of equipment structure meet the requirements.