飞机弱刚性肋缘条加工变形分析与控制技术基础研究

The aircraft rib is the key structure for assembling wing and airframe with high precision, but the analysis and control for machining distortion are difficult because of its unusual characters of structural mechanics, high level and complex distribution residual stresses of blank, which has seriously restricted the research and produce of many types of great aircrafts in China. Aim at the status of modeling for predicting distortion lacks theory support, this project will study and submit the rule and mathematics model of residual stresses mixing and repeating in thin-walls, the structural mechanics characteristic of pool rigidity and slightness rib, build a mechanics model of rib according with its impersonality distortion rules, and enhance the accuracy of analyzing the machining distortion. Focus on the problem of control machining distortion induced by complex residual stresses, this project will study the relationship among residual stress field, distortion potential energy and distortion shape, submit an index for estimating the change of residual stress field; study new methods for adjusting the distribution and release of residual stresses in the blank by optimizing blank structure and machining allowance, explore the technics means for modulating the shear components of machining induced residual stresses, and finally put forward new technologies for control the machining distortion by adjusting residual stresses. The study of this project has very important academic significance and engineering value to clarifying the special mechanics mechanism of machining distortion of pool rigidity rib, analysis and control distortion with high level precision and promoting the research and produce of great aircrafts in China.

飞机对接肋缘条是保证机翼与机身精确对接的关键结构件，但是其结构力学性质特殊、毛坯残余应力幅值高且分布复杂带来了加工变形分析精度低和控制困难的问题，严重制约了我国大型飞机的研制和生产。针对高精度变形分析建模缺乏理论支撑的现状，项目拟研究并揭示薄壁内残余应力混合叠加规律和数学模型、弱刚性细长缘条的结构力学特性，建立符合缘条变形客观规律的力学模型，提高加工变形分析精度；针对复杂残余应力导致的加工变形控制难题，项目拟研究残余应力场与变形势能、变形形态的内在关系，提出残余应力场演变的量化指标，研究通过优化毛坯结构和加工余量调节毛坯残余应力分布和释放过程的方法，探索调节切削剪切残余应力的工艺手段，最终形成基于残余应力量化调节的加工变形控制技术。项目研究对阐明弱刚性缘条加工变形的独特力学机理，高精度地分析和控制缘条加工变形，促进我国大飞机的研制和生产，具有重要理论意义和工程价值。

针对壁厚变化、截面开敞、结构细长的飞机对接肋缘条的加工变形分析和控制难题，本研究从缘条的结构特点、加工变形的力学特性，以能量理论为全新视角阐述了加工变形的本质原因，以弱刚性结构件为研究对象，进行了变形控制的深入研究。.（1）以薄板拉伸为基础进行了拉伸铣削实验，对薄壁件表层耦合应力分布进行测量，通过有限元切削仿真进行验证。对表层耦合应力分布进行分析和建模，为零件变形仿真提供更加准确的应力条件。.（2）以实验力学为基础，开展了毛坯材料的残余应力测试与建模基础研究。根据剪力滞后等原理，提出了试样尺寸设计准则。针对结构的几何特征，研究了薄板残余应力测试、建模与修正问题。.（3）采用能量理论分析加工变形问题，阐述了变形问题的影响因素。建立典型缘条零件的数值模型，通过仿真研究加工变形的动态过程，量化分析了初始应变能、变形过程动能和附加变形的应变能的相互转化关系，探明了应变能初始状态和动态释放速度对加工后应力分布和零件变形的影响规律。.（4）加工变形在不同的阶段由不同的因素主导，粗加工阶段变形主要由初始残余应力释放导致。精加工阶段变形由结构弱刚性与加工残余应力共同作用导致。 通过缩比试验件的数值仿真和试验研究，通过加工余量优化调节加工过程的残余应力释放对加工变形进行了有效改善。