基于附加力矩和刚度演变的航空结构件加工全过程变形研究

Machining deformation of aerospace monolithic component is the results of the interaction of stresses equilibrium, evolution under new rigidity condition during the machining process. Based on the structure stiffness identification, the influence of different aircraft structure forms was studied. And the influence of different aircraft structure forms on the sensitivity of structure stiffness was analyzed; aerospace monolithic component stiffness evolution law for material removal process was obtained. Based on the stress balance and self-consistent relationship of aerospace monolithic component after some piece of material removal, using multiple layered sheet metal model and equal strain boundary conditions between the laminates, building aircraft structure parts retained material stress balance and self-consistent model. Through initial stress and additional stress superposition of removed blank material, building aircraft structure parts additional equivalent external torque load after the material was removed. Sress state-the workpiece stiffness evolution-machining deformation was analyzed as a system, the aircraft structure machining deformation mechanics model was build. It would reveal the mechanism of stiffness evolution, the stress and deformation mechanism. This can provide strong support for the precision manufacturing of the monolithic components usually used in big aircraft and advanced fighter.

航空整体结构件的数控加工变形是材料去除过程中在新刚度条件下应力调整平衡的作用结果。通过航空整体结构件加工过程不断变化新刚度的识别，研究不同局部结构组合形式对其抗变形能力的影响，获得材料去除过程航空整体结构件刚度演变规律。基于材料去除后的应力平衡关系，以航空整体结构件毛坯初始应力场加工过程平衡自洽为基础，利用多金属片分层模型和层间应变相等边界条件，分析航空整体结构件加工材料去除后保留部件应力场分布。通过毛坯材料初始应力和去除材料产生的二次应力的迭加，研究材料去除产生的附加等效外力矩载荷，建立基于航空整体结构件成形特性的附加外力矩计算方法。将工件刚度演变-应力状态-工件变形作为一个系统进行分析，构建航空整体结构件加工变形预测模型，揭示工件刚度演变-应力变化与变形之间的内在机理，为解决民用大飞机和国防工业新机型制造中有关航空整体结构件加工变形预测与控制提供理论支撑。

针对航空整体结构件加工变形问题，本项目通过结构件刚度演变，结合通过毛坯材料初始应力和去除材料产生的二次应力的迭加来研究航空整体结构件的加工变形。（1）选择了三类典型航空件作为研究对象，包括航空板结构件、航空长梁结构件和航空框类结构件。解释加强筋、隔框等工件刚度变化的影响规律。综合考虑局部增强结构提高整体构件刚度的基本原理，研究材料去除顺序与自位支撑刚度之间的关系，揭示航空整体结构件数控加工过程中刚度变化规律。对于板件，计算出不同位置隔框单位体积材料对刚度的影响为0.748%、2.180%、0.387%、2.281%、1.520%；对于U型截面梁的抗弯刚度值为2.76Nm。相对于加工结束后的隔框梁的刚度4.33Nm，加强肋板能够提高结构刚度157.8%。（2）结合裂纹柔度法所测量的60mm厚度的7050-T7451航空铝合金毛坯初始应力，进行材料去除应力场再平衡自洽计算，完成材料去除后工件产生的附加力矩分析，进行了基于均衡应力释放和工件几何结构特征的航空结构件加工工艺分析。结果表明：当去除压应力区域材料时，变形挠度转变为正值，并且在该区域变形量一直呈增大趋势，当加工去除拉应力区域材料时，变形逐渐减小。当去除12mm至27mm厚度拉应力区域材料时，由于该部分材料产生的附加力矩与压应力区域材料附加力矩相反，变形减小。（3）将工件刚度演变-应力状态-工件变形作为一个系统进行分析，揭示工件刚度演变-应力变化与变形之间的内在关系，以此为基础进行了基于变形最小化的航空框类整体结构件加工策略分析。对于整体框类零件，去除中间圆孔材料对工件变形的影响大于周边材料，而去除隔框材料对工件变形的影响又大于中间圆孔材料。先去除对变形影响最大的隔框材料时，其周边材料和中间圆孔材料都会提供一个刚度支撑，可以最大程度减小工件的变形。