Numerical Simulation Study On The Springback Control Of Multi-point Forming For Curved Hull Plate

In recent years, the development of manufacturing technology of shipping is towards thedirection gitization and automation,but traditional line-heat forming is still the general way forcurved hull plate forming in shipyards. Because of heavy labor intensity and low productionefficiency, line-heat forming has seriously impeded the rapid development of shipbuildingindustry. As a new flexible forming technology, multi-point forming(MPF) will improveforming precision and reduce production cycle, which has a broad prospect of application inthe field of shipbuilding.MPF of curved hull plate is at room temperature, springback of the part is large afterunloading. For different materials, thicknesses and geometrical shapes, the springback varies,which has a great influence on forming precision. Take full advantage of that multi-point diecan be quickly adjusted, and adjust multi-point die’s shape according to the springback afterunloading, thus, the springback could be controlled effectively. In the paper, springbackcompensation in MPF of curved hull plate has been studied through FE method, thereby, toreduce or eliminate the influence of springback on forming precision.Firstly, the multi-point element model modified for any plate shape is established in the3D modeling software and then the process of forming and unloading is calculated withnumerical simulation method. The MPF effect with traditional punch and swinging punch iscompared, the latter can effectively eliminate the dimple defect on the plate surface, which ismore uniformly forced.For single curve surface parts, the curve of surface parts is discrete along the curvaturechanged direction, the micro arc is between the discrete points. According to stress, strain,plate thickness, elastic modulus and target rate curvature calculation formula is deduced tocalculate the curvature before springback, then the curvature of target surface is taken as thecurvature after springback, consequently, the curvature before springback is calculated. Coordinate values of distracte dpoints before springback are obtained using the curveinterpolation method. Distracted points are fitted to continuous curves through NURBS.The effectiveness of the above progress is verified by numerical simulation method. For3Dcurve parts, a kind of geometric compensation method of multi-point envelop is proposed,which is based on the results of numerical simulation and is combined with stampingcompensation method, connection compensation method and normal compensation method.The effectiveness is discussed by numerical simulation. The method is applied in theclosed-loop correction of springback. According to the principle of Lagrange interpolation, thecorrection factors are calculated by Lagrange n interpolation formula, which are applied in thecompensation distance in the multi-point envelope method. At last, the multi-point formingenveloping surface is obtained. Numerical simulation is used to verify the validity of theabove methods.