内撑约束大型薄壁回转体零件加工变形与振动机理研究

In some national major engineering fields, e.g. aerospace, there is a class of large complex thin-walled rotary workpiece in high-level equipments. They usually have high performance, long manufacturing cycle and poor manufacturability. The bulging-tire type fixture is often untilized to support the inner surface of thin-walled rotary workpiece during machining outer surface.The inner surface is forced to abutt the supporting surface of fixture as much as possible. However, a complicated interaction is generally formed at the contact interface between workpiece and fixture. As a result, machining deformation and cutting vibration of thin-walled workpiece are inevitably induced because of uneven clamping stress distribution and inconsistent abutting condition respectively. To address gemetric retaining ability and machining vibration is urgent for the large complex thin-walled rotary workpiece under inner supporting constraint. Firstly, the constraint mechanism of inner supporting force and the effect of multi-factors with strong coupling on machining deformation and cutting vibration are revealled. Then, a machining accuracy evolution model is established for the large complex thin-walled rotary workpiece with inner supporting constraint. Further, some innovative technologies are carried out, which include inner clamping force optimizing, workpiece stress distribution and abutting condition measuring, deformation expressing and compensating based on mid-surface deformation geometry and cutting vibration iduced by time-varying mode analyzing. Finaly, comprehensive experiments and engineering application verifications are implemented utilizing rocket nozzle as typical workpiece. The proposed research work would have positive significance to enhance capacity of machining accuracy control for large complex thin-walled workpiece.

航空航天等重大工程领域的高端装备中存在一类大型复杂薄壁回转体零件，其性能要求高、制造周期长、加工难度大。对该类零件外廓面进行切削加工，常利用胀胎式夹具在其内部支撑，并尽量使得工件与夹具紧密贴合。在该内撑约束状态下，工件-夹具界面形成了极其复杂的接触关系，致使装夹后工件应力分布不均匀、工件与夹具贴合状态不一致，进而诱发加工中的零件变形和切削振动。本项目针对内撑约束下大型复杂薄壁回转体零件加工过程中的几何保持性和加工稳定性控制难题，通过揭示内撑力约束作用机理、强耦合多因素对加工变形与振动的作用机制，建立内撑约束下大型复杂薄壁回转体零件加工精度演变规律模型，研究装夹内撑力优化、工件应力分布和贴合状态测量、基于中面变形几何学的加工形变表示、时变模态诱导的加工振动分析等新方法、新技术，并以火箭喷管等为典型件进行综合实验和应用验证。研究工作对于提升大型复杂薄壁零件精度控制技术水平具有积极意义。

航空航天等重大工程领域的高端装备中存在一类大型复杂薄壁回转体零件，其性能要求高、制造周期长、加工难度大。对该类零件外廓面进行切削加工，常常利用胀胎式夹具支撑其内部，并使得工件与夹具紧密贴合。在该强内撑约束状态下，工件-夹具界面形成了极其复杂的接触关系，致使装夹后工件应力分布不均匀、工件与夹具贴合状态不一致，进而诱发加工中零件变形和切削振动。.项目针对大型薄壁回转体类复杂薄壁件高质高效加工难题，开展了强内撑约束下薄壁零件加工变形与振动机理研究，主要研究工作包括：在内撑定位与多点夹持约束分析基础上，提出了预应力约束控制的大型回转体薄壁件安装方法，设计了内胎曲面支撑的工装夹具构形，提高了系统刚性；建立了平面应力超声检测的应力-声时解耦通用模型，提出了傅里叶插值和高斯函数局部细化的亚纳秒声时高精度计算方法，对比“滤波-相关分析-包络”的常规方法，声时计算精度提高了31%；发明了薄壁件靠模装夹贴合状态超声检测与评估方法，发明了一种对称径向注液、双层多孔筛整流与反圆弧导流的新型超声喷流器；建立了基于中面形变几何学的复杂薄壁件加工变形表示模型，提出了面向多工步测量-加工的整体几何面形误差匀化方法、基于关联柔度系数预估的局部回弹变形补偿方法；建立了“刀具-工件”系统多自由度时域离散动力学模型以及薄壁件时变模态的敏度分析模型，提出了基于结构动力修改的薄壁件频响函数反演方法；提出了基于品质因子的薄壁件加工状态信号特征辨识与智能诊断方法，实现了对颤振敏感分量的准确辨识。.以液体火箭发动机喷管、大型发射筒段等为典型件，提出了大型薄壁零件剩余壁厚可控数字化加工方法，开发出喷管加工专用软件系统；提出了基于多过程参量在线反馈的大型筒体-端框精确对装方法，设计了多点内撑装夹系统；均获得工程应用，得到了航天制造企业的一致认可。.本项目研究工作对于提升大型复杂薄壁零件精度控制技术水平具有积极意义。