【作者】 陈亚东；

【导师】 刘纯国；

【作者基本信息】 吉林大学 ， 材料加工工程， 2015， 硕士

【摘要】 近年来，船舶制造技术向数字化、自动化方向发展，但是在加工船体曲面外板时，仍然主要采用水火弯板法成形，生产效率低、劳动强度大，严重制约了造船业的快速发展。多点成形是一种新型的金属板材柔性加工技术，应用在曲面船体外板成形中，不仅能够提高船板的成形精度，还可以缩短生产周期，在船舶制造领域有广阔的应用前景。曲面船板多点成形是在室温下的对压成形，卸载后零件回弹大。而且不同材料、不同厚度、不同几何形状的曲面零件回弹各不相同，回弹对船体曲面外板的成形精度有很大的影响。充分利用多点模具可以快速调整的特点，根据卸载后的回弹量调整多点压机上、下模具包络面的形状，可以有效地控制回弹。本文针对曲面船板多点成形，用有限元方法研究如何计算回弹补偿量，从而减少、甚至消除回弹对曲面船板成形精度的影响。首先在三维造型软件中建立适用于任意船板形状的多点上下基本体群模型，使用有限元方法模拟船板多点对压成形和卸载回弹过程。并对比分析了使用固定曲率冲头和摆动冲头的多点对压成形的成形效果，结果表明摆动冲头能有效的消除船板表面压痕缺陷，使船板表面受力更均匀。对于单曲率曲面件，沿着曲率变化方向将表征曲面件形状的曲线离散，离散点之间的弧为离散微元，根据应力、应变、板厚、弹性模量、目标曲率等参数，推导了回弹前后曲率关系的计算公式，将目标曲面离散微元的曲率作为回弹后曲率，根据此计算公式求出离散微元回弹前曲率。采用曲线插值法求出回弹前离散点的坐标值，使用非均匀有理B样条法把离散点拟合成连续的曲线，利用此曲线生成多点模具成形包络面，使用数值模拟方法验证该方法的有效性。对于三维形状的曲面件，使用点云来表征曲面件的形状，将目标曲面作为成形包络面，进行多点对压、卸载回弹的数值模拟，得到表征成形后曲面的点云数据，结合连线修正法和法向修正法，提出一种多点包络面修正法，利用此方法对目标曲面点云数据和成形后曲面点云数据进行计算，得到多点成形包络面的点云数据，即为多点对压成形的成形包络面，使用数值模拟方法验证该方法的有效性。将多点包络面修正法应用到回弹闭环修正中，根据拉格朗日插值原理，通过n次拉格朗日插值公式求出修正因子，修正因子与多点包络面修正法中的补偿距离相乘，求出多点对压成形的成形包络面，利用此包络面进行多点对压成形，使用数值模拟方法验证了以上方法的有效性，为提高船板多点成形质量提供了理论依据。更多还原

【Abstract】 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.更多还原