【作者】 胡自化；

【导师】 张平；

【作者基本信息】 湘潭大学 ， 一般力学与力学基础， 2008， 博士

【摘要】 薄壁件在航空航天、机械、土木等领域应用非常广泛,许多重要零部件(如航空发动机叶片等)的先进制造技术涉及军事和重要民用领域的关键技术,被各国视为机密而对外严格封锁,我国在这方面远落后于西方制造强国。由于薄壁件低刚度特性和一些零部件复杂不可展曲面形状使得制造难度极大。围绕薄壁件高精度加工需求和提高加工效率进行数控加工基础理论与应用研究具有重大的理论意义和工程应用价值。本文综述了国内外研究现状,采用理论分析、有限元和切削实验相结合的方法,以矩形薄板、航空叶轮叶片的数控侧铣为对象,开展了薄壁件数控侧铣的力学和数控基础理论、有限元模拟和切削实验综合分析研究,取得了以下研究成果:1.通过将移动载荷作用问题转化为固定载荷作用问题,建立起移动集中载荷作用下悬臂矩形板对称弯曲和非对称弯曲的力学模型,移动集中载荷作用下悬臂矩形板的对称和非对称弯曲挠度试验函数,进而获得矩形薄板侧铣加工变形的近似理论解。有关结果与有限元预测结果以及切削实验测量结果吻合较好。2.提出螺旋立铣刀侧铣加工的切削力模型,通过建立铣削力系数与切削用量的多项式模型,利用四因素回归正交实验法确定了模型常量。建立了进行精确变形预测和误差控制分析的基础。3.提出冗余误差控制三次NURBS曲线直接插补算法,通过引入进给倍率因子,适度提高插补速度可改善小曲率情形误差过度冗余,提高了加工效率。实验表明该算法对加工精度和加工效率具有综合协调控制能力。提出了三轴空间刀具半径补偿算法,实验表明算法正确有效。4.提出了倾斜摆头型和带角度铣头五轴机床等含特殊铣头的五轴后置处理算法,实验表明算法正确可靠。提出了锥形球头铣刀侧铣加工不可展直纹面的刀位优化算法,实验表明建立的算法可极大提高不可展曲面侧铣加工精度。5.分别建立了矩形薄板的单轴侧铣加工变形的有限元数值预测模型和航空叶轮叶片的五轴侧铣加工变形的有限元数值预测模型,并提出了控制变形的刀轨优化误差补偿方法。实验表明所建立的加工变形预测模型正确,误差补偿方法有效。有关研究理论成果为薄壁件加工变形预测与刀轨优化的分析和应用提供了理论指导,部分研究成果已经实现实际应用。更多还原

【Abstract】 Thin-walled components are widely used in the field of aeronautic and aerospace industry, mechanical engineering industry and civil engineering industry, etc. Advanced manufacturing technologies of various important components involve key technologies for military use and important civil use, which are locked as national privacy in every country. For this case our country has fallen behind those west manufacturing power countries. Due to the characteristic of poor rigidity and some due to complex non-developed surface shape, it is tremendous difficult to ensure thin-walled components machining accuracy using the traditional machining craft techniques. So, surrounding the demand of high machining quality and high machining efficiency of thin-walled components, it has great academic and engineering values for developing the numerical control fundamental research and application.Based on a survey of domestic and foreign research status, by combining theoretical analysis, FEM and machining experiment study methods, and taking peripheral milling process with a thin-walled rectangular plate and an impeller blade as the subject studied, the integrated research on mechanics and NC basic theory, FEM simulations and cutting experiments for thin-walled components peripheral milling are developed in this dissertation. The research achievements are summarized as the following:1. By means of transformation from a moveable loading problem to a fixed loading problem, the thin-walled cantilever rectangular plate symmetrical and nonsymmetrical bending models, flexibility testing functions have been proposed. Thus proximative theoretical solutions are obtained. The corresponding results are good in agreement with FEM simulation results and experimental results.2. The mechanistic model of spiral end milling has been built. A multinomial model between milling force coefficients and quantities in cutting is set up. The milling experiment by means of regression-orthogonal method with four factors is designed to confirm constants of cutting force model. The work is the perfect basis for deflection prediction and error control and analysis.3. An interpolation algorithm for Non Uniform Rational B-Spline(NURBS) curves to control redundancy errors is proposed. A feedrate factor is introduced to improve errors redundancy by properly raising feedrate when the instantaneous curvature was too small, and the machining efficiency is increased. Experimental results demonstrate the combinative capability of the proposed algorithm for compatibility controling machining quality and efficiency. Testing results show that the proposed algorithm is highly effective and correct.4. Post processing algorithms are deduced for five-axis CNC machines with the titling milling head and with the angle milling head. The correctness and effectiveness of the proposed post processing algorithms is verified by means of a cutting experiment. Tool path optimization algorithms are developed for flank milling undevelopable ruled surfaces. Experimental results show that the proposed algorithms can improve machining accuracy greatly in peripherial milling undevelopable surfaces.5. FEM models for predicting machining deflections are established for single axis side milling a thin-walled rectangle plate and five-axis peripheral milling an impeller blade, respectively. The errors compensation strategies of optimizing tool paths are also proposed to control machining deflections. Testing results show that the models for predicting machining deflections are reliable and the strategies for compensating deflection errors are effective.The related theoretical achievements of this paper provide the theoretical guidance for prediction of machining deflections and optimization of tool paths for thin walled components. And some have been realized practical application.更多还原