文献翻译-驱动桥振动与噪声的研究

THE VIBRATION AND NOISE RESEARCH OF DRIVE AXLELai Fei Deng Zhaoxiang Zhang Jian(State Key Laboratory of Mechanical Transmission, Chongqing University, China)Abstract: By building the whole assembled model of the rear axle, which is one of the main vibration and noise sourceson the power driveline of the vehicle, and then take transient、h armonic and noise analysis. In this paper, Make use of CAD/CAE technology, and analyze the noise of a mini-vehicles rear axle, and then lodge the structure-improved idea. On the condition that not to interfere with the old structure and make big modifications, introducing the method of shank to modify the structure of the main noise radiation source. The simulation of the modified structure indicates the modified rear axle can reduce the noise of radiation source effectively.Key words: Drive axle Vibration Noise Boundary element Finite element0. INTRODUCTIONThe rear axle is the one of mainly vibration and noise resources on the power train of the vehicle. It can produce the noise of gears and axletrees, and excite the vibration of shell to eradiate noise. In addition, as the rear axle is sustained by suspension, the rear axles flexural and torsion vibrations and the bumpy road can also make big noise.With the development of software、har dware、m odern design and analysis technology, it is a trend way to solve the problems in experiment and test using the method of modern analysis technology. In this paper, it will use the simulation software ANSYS and ADAMS to analyze the dynamic characteristic and vibration force. Then use SYSNOISE to calculate the radiation noise due to the vibration of the exterior of rear axle. Base on it, forecast the noise of rear axle accurately and do some corresponding modified measures. Finally it will use the technology of numeric analysis to predict the effect of the improved structure. Using the method of numeric analysis to study the problem of noise about rear axle can save time、labor and money, at the same time, it also can obtain more relative data information.1.MODELING THE REAR AXLE AND MAKING SURE THE BOUNDARY CONDITIONSThe rear axle is made up of main reducing gear, differential mechanism, half shaft and rear axle housing. It delivers the engine torque passed by universal drive shaft to drive wheel that can slow the speed and increase the torque. It also sustains and protects the rear axle differential and half shaft etc, at the same time; it can fix the axial relative position of drive wheel and sustain the frame and other assemblies with slave axle. When moving, it can sustain the force and torque of road reaction from the wheel, and pass it to the frame by suspension.The main reducing gear of vehicle widely uses hypoid gears, which are bevel gear wheels operate between cross shafts. As the axis lines of the small and big gears are not intersect, but offset some distance. When they are mating, they can roll in the circle direction and slide in the tine direction quite and smoothly. In order to reduce the vibration and noise, some other requirements must satisfied: 1) using large overlap coefficient to assure the number of mating gears is between 2 to 3 or more; 2) using the small number of teeth of the small gear to obtain large drive ratio and save space; 3) assembling exactly to make the mating surface exceed 50 percent.1.1 Partition of finite element meshThe material of rear axle housing is forged iron and its density 7850 kg/m3, Youngs modulus of elasticity 2.07e5Mpa, Poisson ratio 0.28, shear modulus 8.02e4,usingshell163element.Thematerial of drive gear is 20GrMnTi steel and its density 7800 kg/m3, Youngs modulus of elasticity 2.1e5Mpa, Poisson ratio 0.3, shear modulus 8.02e4, using solid164 element.Fig 2 FEM but gears and drive axle housingFig 3 The set assembling of rear axle1.2 The determination of boundary conditionsThe boundary conditions of vibration analysis of rear axle include: the drive gears speed, the follower gears initial speed load, the constraint condition of the rear axle housing.1.2.1 The deduction of drive gears speed1) The type of drive wheel is 155R13 and the diameter of air-filled 576 mm.2) Assuming the wheelline speed is 90km/h, be equal to 25 m/s, so the angular velocity is 86.8rad/s.As the drive ratio of follower gear and drive gear is 41:8, so the angular velocity of drive gear is:86.8*41/8=444.88rad/s. And the relational expression of input shaft and output shaft is:w2 output angular velocity, w1 input constant angular velocity, a1 angle between input shaft and connection shaft, a2 angle between output shaft and connection shaft, 1 is the rotate speed of input shaft. a1=a2=a=7.5 , =444.88rad/s.1w1.2.2 The follower gears initial speed loadThe vehicles speed cant be 90km/h at the start point actually, but gradually increase into steady state. If the initial speed is not applied or applied inaccurately, the gears may generate great impact. Only when applying accurate initial speed load, the gears deform can be appropriate.1.2.3 The constraint condition of rear axle housingThe load that the housing bears comes from the impact when the gears mate. The impact is passed to the housing by the axle and bearing, and result in the housings vibration.Fig 4 The constraint of rear axle housing2.EXTRACTING THE DATE OF REAR AXLE TRANSIENT ANALYSISThe main purpose of transient analysis is to extract the load data of rear axle housing. The method to deal with the bearing and housing is node-pasted. So the nodes of exterior of surface (fig2 C, D, E) are the points needed to analyze. All of the nodes amount to 552. According to the analysis of bearing axial and circumferential different nodes, we can find that the nodes response are almost the same. So when dealing with the load data, we can regard the time-domain curve of the nodes of the same bearing equally. This simplified representation is proper and also reduces the amount of work. After obtaining the time-domain vibration signals, it is needed to transform them to frequency-domain signals: 1) to find which frequency can cause wide vibration, and then do some major research on it to reduce the vibration in the frequency finally, 2) to use them as load data in SYSNOISE software.From the diagram below, we can find there is great vibration at frequencies followed as 71.43Hz, 128.57Hz, 200Hz and 271.43Hz. So the load data of the three different frequencies should be imported to SYSNOISE software for harmonic response analysis.(As the response of D and E are very much alike, so only the response of D is listed below)Fig 5 The frequency-domain response in 2000Hz at CFig 6 The frequency-domain response in 2000Hz at D3.ANALYSIS OF REAR AXLES NOISEFirstly, we import the displacement result of the harmonic response and corresponding frequency. And then we can use Boundary Element Method (BEM) to solve the noise problem. The purpose is to find the main noise source and to provide some proof for later improvement. Some documents have pointed out that the rear axle noise is resulted from the structural surfaces vibration, such as rear axle housing. Referred to the research result of FEM, we know the housings vibration focus on housing rear cover and main reducing gear shell, both of which are located in the middle of the housing. So when set the field points, we should consider emphatically the noise radiation condition in the middle placeFig 7 Field collocationAt frequency 128.57Hz, the result of sound pressure level (SPL) is below:Fig 8 The SPL of back housingFig 9 The SPL of up housingFrom the figure, we can find the main noise source locate at main reducing gear shell and back housing. A great amount of faint yellow appears at these places and the SPL of these places is between 94.19db and 98.7db.For the sake of comparison, we list the calculation result of all frequencies as follows:By comparison, we can conclude: housing main radiation area nclude: back housing shell, main reducing gear shell and housing shell abdominal area. And back housing shell is the main area. So any measure to reduce the housing noise must aim at back housing shell.4. MODIFIED STRUCTURE OF REAR AXLEAs the back housing shell is always the main source of radiation noise, this paper controls the housing shells vibration by cross shank and rice character shank. And it aims at two frequencies 128.57Hz and 592 Hz at which the noise is maximizing.Fig10 The cross shank on rear axle housings capFig11 The rice shank on rear axle housings capTaking cross shank for example, we compare the noise result with that before (at 128.57Hz). And we set the indication range as before. To our surprise, the SPL maximum of the rear axle housing turns to 91.95 dB by 96.45dB, reducing about 4 dB. And the SPL maximum of the rear axle housing turns to 77.93 dB by 86.13 dB, the same result as the method of rice character shank.5.CONCLUSIONSBased on the research of the rear axle housings vibration and noise analysis, this paper identifies the main radiation noise resource and improves the structure that reduces the response of the housing to exciting force, diminishing the sound radiation coefficient of the radiation surface of noise. And the fewer radiation noise energy will be produced when at the same exciting condition. Finally some conclusions can be deduced:(1) The back area of the rear axle housing shell is the main radiation noise resource place;(2) The SPL will increase when the speed of vehicle arises. And when the speed is at the low range, the vibration of low frequency of housing will sharp. If the speed increases, the frequency of the maximum noise will slow down and the noise will be more acute.(3) By the method of shank, the noise can be reduced effectively. But the density of the shank plays a little role in slowing down the vibration and reducing the noise.Reference1 S.P.Healy, T.Heppenstall, and D,Hodgetts, “An experimental study of vehicle driveline vibrations” Noise and Vibration of Engines and Transmissions, I Mech E Conferences,1979-102 Sheng-Jiaw Hwang, Joseph L.Stout,Ching-Chung Ling “Modeling and Analysis of Powertrain Torsional Response” SAE 9802763 Frank Fahy, Sound and Structural Vibration Radiation, Transmission and Response, London: Academic Press, 19854 Akira Ishihara. Measurement of Rotational Movement of Gear by Hibert Transform Method, JSAE, Proof Sheet 952 for Spring Scientific Lecture Meeting, 1995驱动桥振动与噪声的研究赖菲 邓兆祥 张建（中国重庆大学机械传动国家重点实验室）摘要：因为后桥是振动和噪声的主要来源，所以通过构建整个后桥的装配模型，然后采取瞬态、谐波和噪声分析。本文利用 CAD / CAE 技术分析了一种小型汽车后桥的噪声,然后提出结构改良意见。在不改变其原有结构和做大的修改的情况下，介绍了通过利用采用柄的方法改进主要噪音源的结构。仿真结果表明对后桥结构的改进可有效减少噪音。关键词： 驱动桥，振动，噪音，边界元，有限元 引言 后桥是汽车动力传输机构的一个主要噪音源。它的齿轮传动装置和轴类装置都能产生噪音，外壳的振动也能产生噪音。此外，由于后桥是由悬架支撑的，后桥的弯曲和扭转振动和道路的崎岖不平,都能产生很大的噪音。随着软件开发、硬件、现代设计与分析技术的发展, 使用现代分析技术实验和检测来解决问题已经成为了一种趋势。在这篇文章中,将用仿真软件 ANSYS和 ADAMS 来分析动态特性和激振力。然后用 SYSNOISE 计算辐射由后桥表面振动产生的噪声。在此基础上,准确预测出后桥的噪音并采取相应的改进措施。采用数值分析的方法来研究后桥的噪音问题可以节省时间、劳动和金钱,同时,它也可以获得更多相关信息利用 UG、ANSYS 建立后桥的几何和有限元模型边界条件利用 LS-DYNA 进行顺态分析并提取时域信号FFT 频 域 信 号不满足 满足1. 后桥的建模及边界条件的确定后桥主要是由主减速器、差速器、半轴和后桥壳组成。它的功能是传递发动机扭矩，通过驱动轴驱动车轮，并减速增扭。它也支撑和保护后桥差速器、半轴等,同时也对车轮轴向定位并支撑车身和从动轴的其它组件。在行驶时,它还承受着力和路面通过车轮传递的力矩,并通过悬架传递到车身。车辆主减速器广泛运用双曲面斜齿轮，这种锥齿轮运转在十字轴中。由于使用 SYSNOISE 进行谐波和噪音分析合计分析与评价、做一些改进措施完 成小、大齿轮得轴线不相交,所以偏离一些距离。当它们进行啮合时,它们可以在圆周方向 很顺畅的运转,在齿顶方向接触的撞击很轻。为了降低了振动动和噪音,一些条件必须要满足:1)使用大的重叠系数,保证交配齿轮 2 3 个或更多之间;(2)使用齿数少的小齿轮以获得大传动比、节省空间;3)装配精确至少达到50%的表面接触表 1 的数据的齿轮 主动齿轮 从动齿轮 螺旋角 a 20 20 齿顶高系数 h*a 0.82 0.82 顶隙系数 C * 0.188 0.188 变位系数 x 0.375 -0.375 分锥角 11.041 78.959 分度圆直径 d 32.336 164.984 锥距 R 84.048 84.048 齿宽系数 R 0.365 0.297 宽度 b 30.706 25 齿顶高 ha 4.809 1.791 齿高 h 7.356 7.356 齿根高 hf 2.547 5.565 齿顶圆直径直径 da 41.776 165.67 齿根角 1.736 3.788 顶锥角 a 14.829 80.695 齿顶角 a 3.788 1.736 圆齿厚 7.971 4.671 曲率半径 73.27 73.27 1.1 有限元区域的划分 汽车后桥壳材料是其密度 7850 kg/m3 的锻铁，杨氏弹性模量2.07e5Mpa，泊松比 0.28，剪切模量为 8.02e4，使用 163 系元素。驱动装置的材料,其密度个 20GrMnTi 钢公斤/方,年轻的弹性模量的 2.1e5Mpa、泊松比 0.3,8.02e4 剪切模量,利用 solid164 元素。图 2 齿轮和驱动轴的有限元建模 图 3 后桥的固定装配 1.2 确定边界条件 边界条件下的振动分析,包括:驱动后桥从动齿轮的速度,齿轮的初始速度负荷、桥壳的约束条件。1.2.1 传动齿轮的速度的影响 1）这种驱动轮的型号是 155R13，当充满气时车轮直径为 576mm。2)假定车轮的线速度是 90km/h,相当于 25m/s,因此车轮的角速度是 86.8 rad/s。由于主动轮和从动轮的传动比是 41：8，所以主动轮的角速度为：86.8*41/8=444.88rad/s。输入轴和输出轴的关系表达式是： w2 为输出角速度，w1 为输入恒定角速度，A1 角输入轴与连接轴之间的角度，A2 输出轴与连接轴之间的角度，1 是输入轴的旋转速度。a1=a2=a=7.5, w1=444.88rad/s.1.2.2 从动齿轮的初始速度负荷 事实上车辆在刚起步时速度不可能达到 90 km/h,但逐渐增加到平稳的状态。如果起步速度不合适或者不太合适,可能对齿轮产生剧烈的冲击。只有应用精确地起步速度，齿轮的变形才会有所改善。 1.2.3 后桥壳约束条件 壳体承受的来自齿轮紧密配合时表面冲击产生的载荷。这种冲击通过轴和轴承传到壳体并引起壳体的震动。图 4 后桥壳约束 2.提取后桥瞬态分析的时间瞬态分析主要是为了提取后桥的负载数据。这种处理轴承和外壳的方法叫做交点法。所以表面的节点(图 C、D、E)需要分析。总共有 552 个节点。通过分析轴承轴向和圆周不同的节点,我们可以发现节点的反应是几乎相同的。所以当处理负荷数据时,我们可以把时域曲线节点与轴承上的点等同。这个简化图是合适的,也减少了工作量。在得到时域信号后，我们需要把它转换成频域信号:1)以发现什么频率能够引起大的振动，然后着重研究这些频率并最终减少振动,2)在 SYSNOISE 软件里用他们作为负荷数据。 从图中,我们可以发现当频率为 128.57Hz,200Hz ，71.43Hz，271.43Hz 时，引起比较大的振动。所以在 SYSNOISE 软件的谐响应分析里三种不同的频率的负荷数据是非常重要的。(由于 D、E 的响