Research On Technical Parameters Prediction For Line Heating Based On The Deflection Deformation Of Hull Plates

The automation of lofting,marking-off,pretreatment of steel plate,cutting and welding has been realized in shipbuilding production line.The forming of curved hull plates has become a bottleneck restricting ship construction.There are a large number of complex hull plates need to be formed.The efficiency and precision of forming process are difficult problems for double curved hull plates.In the context of "Made in China 2025" and "Intelligent Manufacturing",it is urgent to realize automatic forming of hull plates as soon as possible.Line heating is a main forming method for complex double curved hull plates.At present in shipyards,this process is done manually by experienced workers,which causes low efficiency and instability of forming quality.The technical parameters prediction is the key to realize automatic processing of line heating.Therefore,a large number of research has been carried out by scholars at home and abroad.In traditional research,the design surface was developed to obtain local deformation.Then the relationship between technical parameters and local deformation was studied based on the numerical simulation and physical experiment,and the related models were established.The prediction method of technical parameters for line heating was studied based on the development results of design surface and relationship models.Only local shrinkage of hull plates was taken into account and the whole deformation was ignored in traditional method,which causes large errors in the calculation of thick plate and big curvature plate.To improve the defects of thick plate and large curvature plate only based on local deformation,the whole deformation was considered in the form of deflection on the basis of local deformation.The development calculation of complex undevelopable plate was avoided.The research done in this paper can be divided into the follow parts.(1)Research on numerical simulation of line heating based on deflection deformation of hull platesTo improve the shortcomings of prediction method for the technical parameters of thick plate and big curvature plate based on curved surface development,a numerical method for line heating considering the deflection deformation of hull plate was studied.The finite element model considering the deflection deformation of hull plate was established according to the actual characteristics of hull plate forming process.Different from the previous simple supported constraints,the unidirectional elastic support of the short side of the hull plate was adopted.The improved numerical model is more practical to calculate the deflection deformation.The verification experiment was designed.The temperature fields,local deformation and deflection deformation were measured by thermal infrared imager,digital caliper and displacement sensor respectively.The real-time monitoring of temperature fields and deformation fields data in line heating process was realized.The reliability of the numerical simulation model was verified by comparing with experiment.The prediction of deflection deformation calculation in the numerical model of line heating was improved.It lays the foundation for the research of the relationship between the deflection deformation and the local deformation of hull plates.(2)Mathematical models research on the relationship between deflection defornation and local deformation of hull platesThe influence factors of deflection deformation for line heating were analyzed,and then the influence regularities of the deflection deformation were researched.On the basis of the influence factors for local deformation,the important factors affecting defection deformation such as plate length,plate breadth,radius of curvature,position of heating line were added.The forming efficiency of line heating was studied,and the optimum heating velocities under different plate thickness were obtained.To establish the connection between deflection deformation and local deformation of hull plate,the concept of influence factor of deflection(IFD)was proposed,which is the ratio of deflection to shrinkage.The grid database of IFD was constructed.IFD can be obtained according to the basic parameters of hull plates and technical parameters.The reliability of the mathematical models for IFD was verified by the examples of hull plates.For the management of measured data of experiment plates and real hull plates,an expert knowledge database was developed to express the mapping relationships between design surface data and technical parameters.This expert knowledge database can provide the data support for the technical parameters prediction of line heating.(3)Research on prediction method of technical parameters for line heating based on deflection of hull platesAccording to the actual characteristics of line heating for complex curved hull plates,the optimization objective and the constraints condition of the optimization algorithms for line heating were analyzed.Prediction algorithms for line heating based on deflection deformation were proposed.The prediction software of technical parameters for line heating was developed based on the VB.NET platform.The interface with common auxiliary ship design and construction software Tribon was set up in this prediction software.The technical parameters of real hull plate were calculated by this prediction software.The reliability of the prediction algorithms was verified by comparing with the technical parameters according to experience.To avoid large errors of design surface calculation due to the lack of the offset data,the interpolation calculation method of offset data for curved surface was studied.To apply the detection data of curved plates directly to the prediction of reforming technical parameters,the principles of detection for hull plates forming were analyzed.The measurement and expression method for the detected curved surface was discussed.Then an optimization method to predict reforming technical parameters was proposed,which can apply the detection results of curved plates directly.