航空发动机近净成形叶片自适应加工工艺模型构建

Adaptive machining is an efficient solution to machine aero-engine’s near-net-shape formed blades with high efficiency and precision. Adaptive construction of missed area’s model on complex surfaces with geometric uncertainty is a core problem in adaptive machining of this kind of parts. Firstly, a hierarchical model is established by correcting compensation errors of probe radius to measure the complex surfaces with geometric uncertainty. This part converts the geometric shape of complex surfaces from uncertainty to certainty. Secondly, an appropriate balance between shapes’ matching degree and tolerance margin is sought according to the influence mechanism of tolerance constraints on the matching degree. This part converts the location and position of complex surfaces from uncertainty to certainty. In the last part, a similarity model and an error-mapping model are built between actually formed and theoretically designed curves. The final completed processing model of complex surfaces with geometric uncertainty is then constructed for adaptive machining. This research is helpful to establish the basic theory and processing method for adaptive machining of complex surfaces with geometric uncertainty. It provides technically supports to improve overall manufacturing level of our country for high-performance parts such as aero-engine’s near-net-shape formed blades.

自适应加工技术是实现航空发动机近净成形叶片高效精密数控加工的一种有效方案，几何不确定曲面缺失区域模型的适应性构建问题是该类零件自适应加工中的核心问题。本项目通过建立几何不确定曲面测球半径补偿误差修正的层级模型，高效精准地获得几何不确定曲面的测量数据，将“几何形状不确定”问题转化为“几何形状确定”问题；通过研究公差约束对曲面形状匹配度的影响机制，寻找曲面定位过程中形状匹配度与公差安全裕度间的平衡关系，将“空间位置不确定”问题转化为“空间位置确定”问题；通过建立曲面特征曲线的形状相似度模型和误差映射模型，构建适用于几何不确定曲面自适应加工的整体工艺模型。研究成果有助于建立几何不确定曲面自适应加工的基础理论和工艺方法，可提高我国航空发动机近净成形叶片等高性能复杂曲面零件的整体制造水平。

航空发动机近净成形叶片叶身型面直接成形，后续数控加工仅需去除榫齿、缘头等区域的少量材料，既提高了叶片的型面质量和加工效率，又减少了原材料的使用量。然而，航空发动机近净成形叶片数控加工时存在叶片几何形状不确定、叶片空间位置不确定、缘头区域的加工形状难以适应叶身区域形状变化等问题，严重制约了该类零件的工程应用。针对以上问题，本项目开展航空发动机近净成形叶片自适应加工工艺模型构建方法研究，完成的主要工作如下：（1）建立了基于测球半径补偿的复杂曲面测量规划方法。针对近净成形叶片自适应加工中的几何形状不确定问题，开展测量点非均匀分布及测量路径最优化模型研究，建立测球半径误差补偿的层级修正模型，并对测量数据进行分类、排序及异常值处理，获得了近净成形叶片几何不确定曲面的实际形状。（2）建立了耦合公差约束下的曲面最优化匹配模型。针对近净成形叶片无精确基准导致的空间位姿不确定问题，建立无约束条件下的叶片曲面形状匹配度模型，分析形位公差和加工余量对叶片形状匹配度的影响机制，建立了复杂公差约束的曲面配准评价模型及求解算法，实现了测量数据与理论曲面之间的最优匹配定位。（3）提出了叶片曲面缺失区域模型的适应性构建方法。针对近净成形叶片毛坯缘头区域测量数据缺失问题，开展叶片特征曲线的形状相似度建模，建立了基于中弧线和厚度的叶片变形误差映射模型，提出了缘头缺失区域的叶型轮廓相似预测方法，实现了近净成形叶片缘头缺失区域模型的适应性构建。本项目所研究的基础理论和关键技术得到了实验验证，并应用于国产大涵道比航空发动机复材风扇叶片的预研试制，相关零件实现了装机试车。