外文翻译--动力减振镗杆结构参数优化

附录 A 动力减振镗杆结构参数优化 摘要：深孔镗削过程中，镗杆不可避免产生振动，影响孔的加工质量，为了提高加工质量，本文针对动力减振镗杆建立力学模型，通过对模型的研究得出减振器的最优参数，应用 ADAMS 动力学仿真软件和试验验证了理论优化的正确性。通过和普通镗杆对比分析，结果表明动力减振镗杆有效地达到了减振效果。 关键词：减振器结构；动态性能；参数优化 1引言 在深孔镗削过程中，受到孔的尺寸限制，镗杆长径比较大，刚度小，固有频率低，在受到机床自身激励和外部激励时，很容易发生振动，影响工件的加工精度和表面质 量。三菱公司通过减轻镗杆头部的的重量来提高镗杆的刚度，美国Kenametal公司生产的减振镗杆 (最大长径比 L /D = 8 ) 主要采用特殊材料来提高镗杆静刚度 ,这些方法受到长径比的限制。 动力减振镗杆可以进一步提高长径比，在深孔加工方面具有很大的优势。Warburton 通过对附加在镗杆上的减振器的参数进行优化来实现对主系统的减振，减振器包括弹簧，阻尼和减振块。在载荷作用下， J iaJang W u 研究了减振器螺旋弹簧的惯性效应对镗杆动态特性的影响。 Felipe Antonio Chegury Viana 等人基于蚁群算法设计出可调动态减振器。这些方法所设计出的动力减振镗杆成本较高，结构复杂，维护麻烦，当前应用不广泛。 针对上述问题，下面将采用虚拟样机技术，在 ADAMS 环境下进行减振器结构优化，最后进行实验验证，通过对比分析，表明理论优化的结果、仿真结果和实验结果基本一致，降低了设计成本。 2动力减振镗杆理论及建模 动力减振是将主系统的能量转移到减振器系统上，减小主系统的振动。减振镗杆结构如图 1 所示，建立的力学模型如图 2 所示。动力学方程可表示为 主系统的振动幅值为 对不同的值所作出的主系统的 幅频响应曲线如图 3 所示，当 =时，镗杆和减振器之间没有相对运动，成为单自由度系统，时其幅频曲线只有一个峰值，等效于普通镗杆。当 介于 0 和之间时，系统为两自由度，产生两个共振点。阻尼的存在使主系统的共振幅值减少，但并不能完全消除主系统的振动。图 3中所有的曲线都相交于 P、 Q 两点 , 表明 P、 Q 两点的频率和幅值与 的变化无关，得出方程式为 求出 P、 Q 两点的频率 ,带入 ( 2 )式得到 P、 Q两点的幅值。从 ( 2 ) 、 ( 3 ) 式可以看出，对确定的主系统而言，幅值和频率取决于减振器的质量和 弹簧。减振器最理想的结构参数应该是在 P、 Q 两点达到峰值，并且数值相等。根据这种思路，可按下述步骤选择减振器的最优参数。 对于确定的主系统和选定的减振块质量，结构最优参数解为： 进而确定减振器的刚度 在 P、 Q 两点取驻点的条件下，求得减振器的阻尼率 3动力学仿真 为了验证所建模型的有效性，在 ADAM S 环境下进行仿真。应用 ADAMS中有限元模块将镗杆杆体模型转变成柔体，在刀头端部创建输入和输出通道，然后进行系统的振动分析，通过仿真计算，在后处理模块中得出系统的模态和频响函数 。 减振器初始参数 kgm 02144.02 ， mkNk /102 ， mNsc /10 。镗杆杆体的结构尺寸：直径 D = 0. 016 m ,长度 L =0. 192 m ,长径比为 12: 1；材料属性：密度 = 7 801 kg/m，弹性模量 E = 2. 07E + 011 N /m2，泊松比 = 0. 29。根据结构图建立振动模型。 减振块质量的变化对幅频曲线的影响。当 m 2 = 0. 02 kg 时，得到前两阶自然频率为 253 Hz 和 452 Hz,共振时的最大幅值为 - 95. 16 dB 和 - 103. 3 dB；当 m 2 = 0. 10 kg 时，前两阶的自然频率为 128 Hz 和 406 Hz，共振时的最大幅值为 - 95. 2 dB - 95. 3 dB。对不同的质量值绘制主系统的幅频响应曲线如图 4 所示。可以看出自然频率随着减振块质量的增加而降低，当外部激励的频率与主系统的自然频率接近时，可以通过修改减振块质量的方法来避免发生共振，而减振块质量对幅值的影响不敏感。 图 4 频响函数随质量变化曲线 阻尼的变化对幅频特性曲线的影响。当 c2 = 10 N s/m时，前两阶自然频率为 253 Hz 和 452 Hz,共振时最大幅值为 - 94. 75 dB 和 - 103. 24 dB； c2 = 2 N s/m ,前两阶的自然频率为 253 Hz 和 452 Hz, 共振时最大幅值为 - 90. 11 dB , 和 - 95. 49 dB。图 5 为振动分析后绘制的频响曲线图，表明阻尼的变化对幅值的影响比较大，幅值随阻尼的增大而减小，当共振不可避免时，通过修改阻尼来减小振幅，而阻尼对自然频率的影响不太明显。 图 5 频响函数随阻尼变化曲线 刚度的变 化对幅频特性的影响。当刚度 k2 = 10 kN /m时，前两阶的自然频率为 253 Hz和 452 Hz，共振时的最大幅值为 - 94. 71 dB 和 - 108. 20 dB； 当 k2 = 200 kN /m 时，前两阶的自然频率为 284 Hz 和 898 Hz, 共振时的最大幅值为 - 90. 27 dB 和 - 110. 06 dB。图 6 为绘制的频响函数图，表明自然频率随刚度的增加而增大，刚度的变化对幅值的影响比较大，通过修改刚度可避免共振和调整幅值。 图 6 频响函数随刚度变化曲线 4减振 优化 根据动力减振镗杆振动分析模型，以减振器的刚度和阻尼作为设计变量，使用 ADAMS 中 View 变量和振动宏作为目标函数，使目标函数最小。约束条件为振动幅值小于减振器和镗杆内腔之间的距离，优化采用 OPTDES-GRG 广义递减梯度算法。参数优化的目的就是在给定的镗杆结构和减振块质量一定的条件下，优化出减振器的刚度和阻尼参数，当采用最优参数时主系统的振动幅值最小。当减振块质量 m 2 =0. 021 44 kg，优化后的曲线和普通镗杆曲线如图 7 所示。 图 7 普通镗杆和优化后减振镗杆 优化后减振器的参数是 k2 = 58 662 N /m， c2 = 22. 34N s/m，前三阶的自然频率为 228 Hz、 309 Hz 和 392 Hz,前两阶的自然频率的比值 0. 7378，根据公式 ( 4)计算出前两阶自然频率的比值为 0. 7376,相对误差为 0. 04%。仿真优化的阻尼率为 0. 221,公式 ( 6)得出的阻尼率为 0. 216,相对误差为 2. 2%。根据上述定量分析，得出仿真优化和理论优化结果基本一致，表明仿真优化有效可行。 从图 7 中可以看出，在激励条件不变的情况下，与普通镗杆相比，减振镗杆的 振型得到明显的改善，振型变得更加光滑，幅值也明显减小。共振时最大幅值为 - 102. 33 dB，根据信号处理理论，实际幅值和曲线幅值的对应关系 M agnitude 为仿真曲线幅值，根据上式得到实际振幅为 0. 007 6 mm。普通镗杆与优化减振镗杆对比见下表，表明在长径比较大的情况下，动力减振镗杆振动幅值仅是普通镗杆幅值的 23%，具有很好的减振效果。 5. 结论 在动力学仿真技术的基础上，较为系统的探讨了动力减振镗杆的动态特性，以及减振器参数的变化对主系统的影响，并对参数进行优化，参数优化结果和 理论优化结果吻合良好，最后通过和加工范围。该方法对于进一步提高深孔加工领域的水平和相关技术的研究具有十分重要的理论意义和实际应用价值。 参考文献 1 D G Lee, H Y Hwang and J K Kim. Design and manufacture of acarbon fiber epoxy rotating boring bar J . Composite Structures,2003, 60 ( 1) : 115 124. 2 SANJ I G TEWAN I, KE ITH E ROUCH and BRUCE L WALCOTT A study of cutting p rocess stability of a boring bar with ac2tive dynam ic absorber J . I Mach. Tools Manufact 1995, 35 ( 1) : 91 108. 3 G B W arburton. Op tim um absorber parameters for m inim izing vibration response J . Journal of Earthquake Engineering and Structural Dynam ics , 1981, 9: 251 262. 4 J ia - Jang W u . Study on the inertia effect of helical sp ring of the absorber on suppressing the dynam ic responses of a beam subjected to a moving load J . Journal of Sound and V ibration. 2006, 297 ( 3- 5) : 981 999. 5 Felipe Antonio Chegury V iana, Giovanni Iam in Kotinda, Tuningdynam ic vibration absorbers by using ant colony op tim ization J .Computers and Structures, 2008, 86 ( 1314) : 1539 1549. 6 邵俊鹏 ,秦柏 .基于 ADAMS 的动力减振镗杆仿真分析 J .机械设计与研究 , 2008, 24 ( 1) : 84 88. 7 师汉民 . 机械振动系统 、分析 测试 建模 对策 M . 武汉 :华中科技大学出版社 , 2004. 附录 B A Study of Optimum Parameters of A Boring Bar with Passive Dynamic Absorber Abstract: The vibration of the boring bar directly affects the processing quality in the deep hole machining In order to improve the processing quality, theoretical model of a boring bar with passive dynamic absorber has been developed and derived the optimum parameters of the absorber Both the dynamic simulation based on ADAM S and the experim ents were conducted to verify the theory Comparing w ith boring bar, numerical results reveal that boring bar with dynamic absorber has the effect of vibration decrease. Keywords: passive dynamic absorber structure； dynamic character； optimum parameter 1. Introduction In the process of deep-hole boring, restricted by the size of holes, boring bar larger aspect ratio, stiffness of small, low natural frequencies. Inspired by the machine itself and external incentives, it is prone to vibration, impact on the machining accuracy and workpiece surface quality. Mitsubishi boring bar by reducing the weight of the head of the boring bar to increase the stiffness, the United States produced Kenametal vibration boring bar (maximum aspect ratio L / D = 8) the main use of special materials to increase the static stiffness boring bar, which aspect ratio method by the restrictions. Driving force for boring bar vibration can be further enhanced aspect ratio, and has great advantage in the deep processing of. Through the pole attached to the parameters of the shock absorber,Warburton achieve the main system of the vibration, shock absorber, including springs, dampers and damping block. In the load, J iaJang W u studied coil spring shock absorber of the inertial effect on the dynamic properties of boring bar impact. Felipe Antonio Chegury Viana, who designed the Ant Colony Algorithm Based on Dynamic adjustable shock absorber. These methods have the power to design high cost of boring bar vibration, structural complexity, the maintenance of trouble, the current application is not widespread. The following will be used virtual prototyping technology in response to these problems. In the ADAMS environment damper structural optimization, and finally to carry out experiments. By comparing the analysis results show that the theory of optimization, simulation results and experimental results are basically the same, lower design cost. 2. Driving force for boring bar vibration theory and modeling Damping is the main driving force for the energy transfer system to the shock absorber system to reduce the vibration of the main system. Boring bar vibration structure as shown in Figure 1, the establishment of the mechanical model shown in Figure 2. Kinetic equation can be expressed as 1.the body of Boring Bar 2. rubber ring 3.gasket 4.damping block 5. damping 6.blocking 7.segment Fig.1 Boring bar vibration structure Fig.2the establishment of the mechanical mode The main system for the vibration amplitude For different values of the main system by the amplitude-frequency response curve as shown in Figure 3. Fig.3 different damping ratio of vibration amplitude-frequency characteristic curve When = , the boring bar and there is no relative motion between the shock absorber, a single degree of freedom system, when amplitude-frequency curve is only one peak, equivalent to an ordinary boring bar. When the range of between 0 and , the system of two degrees of freedom, resulting in the two resonance points. The existence of the damping of the resonance amplitude of the main system to reduce, but it does not completely eliminate the vibration of the main system. Figure 3 are all of the curves intersect at P, Q two points, indicating that P, Q two points and the frequency and amplitude changes in has nothing to do, come to the equation for Calculated P, Q two points in the frequency Into (2) to be P, Q two points of the amplitude. From (2), (3) style can be seen that the main system for determining, the amplitude and frequency depend on the quality shock absorber and spring. Structural parameters of the best shock absorber should be in the P, Q two points to reach the peak, and the same values. According to this line of thought, according to the following steps to select the optimal parameters of shock absorber. For the determination of the main system and the selected block damping quality, the structure of the optimal solution for the parameters: To determine the stiffness of shock absorber In P, Q two points from stagnation conditions, the shock absorber damping rate obtained 3. Dynamics Simulation In order to verify the validity of the model, ADAM S in the simulation environment. ADAMS application modules in the finite element model boring into flexible, in the head end of the creation of input and output channel, and then the vibration system analysis, through simulation, in the post-processing module to draw modal system and frequency response function. The initial parameters of shock absorber m2=0.02144， k2=10kN/m， c=10Ns/m。The size of boring structure: diameter D = 0. 016 m , length L =0. 192 m , aspect ratio of 12: 1. Material properties: density = 7 801 kg / m, youngs modulus E = 2. 07E + 011 N / m2, poissons ratio = 0. 29. Damping block changes in the quality of the effects of amplitude-frequency curves.When m 2 = 0. 02 kg, the first two-order natural frequency of 253 Hz and 452 Hz, the maximum amplitude at resonance for the - 95. 16 dB and - 103. 3 dB；when m 2 = 0. 10 kg, order the first two natural frequency of 128 Hz and 406 Hz, the maximum amplitude at resonance for the - 95. 2 dB - 95. 3 dB. The quality of the different values of the main system mapping amplitude-frequency response curve shown in Figure 4. As can be seen as the natural frequency of vibration pieces to reduce the increase in quality, when the external excitation frequency and the main system close to the natural frequency, they can block the quality of vibration by modifying the way to avoid the occurrence of resonance, while the damping quality of the block not sensitive to the effects of amplitude. Frequency/Hz Fig.4 With the quality of frequency response function curve Changes in damping characteristics of the amplitude-frequency curves. When c2 = 10 N s / m, the first two-order natural frequency of 253 Hz and 452 Hz, maximum amplitude of the resonance for the - 94. 75 dB and - 103. 24 dB； c2 = 2 N s / m, the first two bands of 253 Hz natural frequency and 452 Hz, maximum amplitude of the resonance for the - 90. 11 dB, and - 95. 49 dB. Figure 5 after the draw for the vibration analysis of the frequency response curve, indicating that changes in damping the impact of relatively large amplitude, the amplitude increases with decreasing damping, when the resonance unavoidable, by modifying the damping to reduce the amplitude, natural frequency and damping of the impact of less marked. Frequency/Hz Fig.5 Frequency response function with the damping curve Changes in stiffness of the effects of amplitude-frequency characteristics. When Amplitude/dBB Amplitude/dBB the stiffness k2 = 10 kN / m, the first two natural frequency band 253 Hz and 452 Hz, the maximum amplitude at resonance for the - 94. 71 dB and - 108. 20 dB； When k2 = 200 kN / m, the first two natural frequency band 284 Hz and 898 Hz, the maximum amplitude at resonance for the - 90. 27 dB and - 110. 06 dB. Figure 6 The frequency response function for drawing maps showing the natural frequency with the increase of stiffness, rigidity of the impact of change on the relatively large amplitude, can be avoided by modifying the rigidity and adjusting the amplitude of resonance. Frequency/Hz Fig.6 Frequency response function curve with the stiffness 4. Damping optimization Damping according to driving force for boring bar vibration analysis model of shock absorber stiffness and damping as a design variable, the use of ADAMS and vibration in the View macro variables as the objective function, so that the smallest objective function. Constraints for the amplitude of vibration damper and the boring bar is less than the distance between the cavity and optimize the use of generalized OPTDES-GRG reduced gradient algorithm. The purpose of optimization is in a given structure and the boring bar vibration quality block under certain conditions, to optimize the stiffness of the damper and damping parameters, when using the optimal parameters of the main system when the minimum amplitude of vibration. When the quality of damping block m 2 = 0. 021 44 kg, the optimized curve and the general curve of boring bar shown in figure 7. Amplitude/dBB Ordinary boring bar Frequency/Hz Fig.7 Ordinary boring bar and boring bar vibration optimized Optimized the parameters of shock absorber is k2 = 58 662 N / m, c2 = 22. 34N s / m.Before the third-order natural frequency of 228 Hz, 309 Hz and 392 Hz, the first two bands of the ratio of the natural frequency of 0.7378. According to the formula (4) to calculate the natural frequency of the first two bands for the ratio of 0.7376, the relative error is 0.04%. Simulation and optimization of the damping rate of 0.221, the formula (6) derived from the damping rate of 0.216, the relative error is 2.2 percent. According to the quantitative analysis and theoretical simulation and optimization to optimize the results are basically the same, indicating that simulation optimization is effective and feasible. From Figure 7 can be seen in the excitation conditions remain unchanged, compared with the ordinary boring bar, boring bar vibration of the vibration mode has been marked improvement in vibration mode becomes more smooth, the amplitude is also significantly reduced. Maximum amplitude for the resonance - 102. 33 dB, based on signal processing theory, the actual amplitude and the amplitude of the correlation curve actual amplitude=10Magnitude/20 (7) M agnitude amplitude curve for the simulation, according to the real amplitude of type 0. 007 6 mm. General Boring Bar Boring Bar Vibration and Optimization of contrast in the table below that in the case of larger aspect ratio, power vibration amplitude vibration boring bar is just an ordinary boring bar of 23% amplitude, with very good damping effect . Amplitude/dBB Optimization of boring bar the results of comparative table ordinary boring bar and boring bar to optim