某商用车怠速油底壳异响问题分析研究*

针对产品开发过程中某柴油车型发动机油底壳怠速时“呜呜”异响问题,通过噪声与振动的测试及仿真分析,对油底壳异响原因进行分析。结果表明,怠速时机油泵的工作激励频率与油底壳模态频率耦合,形成“呜呜”声,并通过油底壳表面辐射出来。进一步实验研究表明,随着机油温度的升高,机油泵功率、工作激励幅值会逐步减小,异响逐步减小。同时实验研究表明,机油量对油底壳模态频率有影响,油底壳内机油加注量越多,油底壳模态频率越低,油底壳表面振动幅值及异响均逐步减小。针对该异响问题,明确该发动机机油加注上限及下限时油底壳对应频率范围后,通过优化怠速转速,提高油底壳模态频率等使机油泵激励频率与油底壳模态频率避频,解决了该异响问题。     

基于整车控制参数同步采集的车辆异响识别分析

针对整车控制参数引发的车辆异响问题,介绍了一种基于整车控制参数与NVH数据同步采集的分析方法,通过采用数据协议和格式的双转换,实现了整车/发动机控制参数和整车NVH测试数据的同步采集,并通过控制参数和NVH信号的时域相关性分析,快速准确地定位异响原因。通过底盘冲击异响、涡轮气流异响、整车换挡抖动异响三个案例,介绍了整车控制参数同步采集在工程中的实际应用,快速准确的识别异响原因,并完成优化验证,为异响排查和控制提供了新的方法和思路。 关键词：整车异响;车辆控制参数;数据同步采集;相关性分析     

复杂封闭声场面板声学贡献度识别的等效源法

针对由复杂结构振动形成的封闭空间声场,提出了一种基于等效源法的面板声学贡献度分析方法。该方法首先利用基于等效源法的内部声全息技术,重构出振动结构表面的法向振速并实现对整个内部封闭声场的预测。再将振动结构的每个面板在腔体内部场点产生的声压分别用位于空腔表面附近的等效源在该点产生的辐射声压代替,将复杂的封闭非自由声场问题转化为简单的内部自由场问题,结合重建出的结构表面法向振速进而识别出封闭振动结构各面板对腔体内任意位置的声学贡献度。通过对复杂结构内声场的数值仿真和验证实验,分析了等效源的数量及与重建面距离等参数对重建精度的影响,结果表明所提方法不仅能够达到传统数值分析方法的计算精度,而且具有更简单的求解过程。      

基于太阳能驱动转轮除湿的蒸发冷却冷水系统

针对现有的蒸发冷却系统冷量不足的问题,提出了基于太阳能驱动转轮除湿的蒸发冷却冷水系统。系统由太阳能热水、低温驱动双转轮除湿及露点式蒸发冷却冷水三个子系统组成。太阳能热水系统为低温驱动双转轮除湿系统提供再生驱动热源。低温驱动双转轮除湿系统为露点式蒸发冷却冷水系统提供低露点的处理空气。研究了系统的工作原理、热力学过程,并建立系统的热力计算模型,研究结果表明:在典型夏季实例下,当系统再生温度取80℃时,系统出水温度低至12℃,相比传统直接蒸发冷却系统的理想出水温度25. 8℃,降低了53. 5%,湿球效率可达248. 4%。结果表明基于太阳能驱动转轮除湿的蒸发冷却冷水系统能很好解决传统蒸发冷却系统冷量不足的问题,使该系统替代传统压缩式冷水机组成为可能。     

神光Ⅲ原型装置直接驱动均匀辐照设计及在快点火中的潜在应用

研究了基于间接驱动设计的神光Ⅲ原型装置在直接驱动方式下提供的辐照均匀程度,在考虑激光瞄准偏差以及激光束间能量偏差的情况下,通过优化激光光斑内部光强分布实现了球靶表面较高程度的均匀辐照。研究表明光强均方根随激光偏差的减小而降低。在优化结果基础上,分析了优化光强与实际光强的联系,指出可通过同步放缩具有长度量纲的量调整靶球表面平均光强,为后续靶设计提供了依据。最后,研究了优化结果在直接驱动快点火技术途径下的应用,分析了导引锥对激光传输的影响,表明当导引锥位于靶球两极方向,并且半锥角小于30°时,导引锥对锥外部靶球表面的光强分布影响较小,优化结果亦可应用于直接驱动快点火。     

基于扰动源分类控制的二维陀螺平台过顶稳定方法

针对二维陀螺平台方位瞄准线控制在过顶位置时因驱动轴和敏感轴存在非线性约束导致的不稳定问题,分析了不同类型扰动源对方位瞄准线稳定的影响及其随俯仰角变化的规律,提出了基于扰动源分类控制的过顶稳定方法。该方法采用反馈和前馈双通道复合控制结构,在过顶位置时基于控制结构自身消除陀螺测量噪声放大导致的内生力矩扰动,通过增加前馈通道的滤波环节,抑制横滚扰动高频分量引起的力矩扰动,解决了过顶位置时方位驱动轴震荡的问题,同时通过反馈通道和前馈通道分别实现对方位扰动和横滚扰动低频分量的有效隔离。仿真结果表明,该方法能够大幅衰减陀螺测量噪声和横滚扰动高频分量引起的方位电机力矩扰动幅值,增强系统稳定性。最后通过某二维陀螺平台进行了实验,过顶位置时瞄准线方位经受振动条件下的稳定精度由82.4 μrad 减小为44.6 μrad,经受摇摆条件下的隔离度由?14.54 dB提升至?27.85 dB。实验结果验证了该方法能够有效提升过顶位置方位瞄准线的扰动隔离性能。     

轴类超声检测的波束扩散成像*

大型轴类工件安装完成后通常只能从其端面进行检测,危害性的裂纹类缺陷不易检出,针对上述问题,本文提出了轴类对象基于波束扩散的端面网格化超声检测层析成像方法,搭建了轴类超声检测试验平台,在端面对其内部的平底孔缺陷进行检测,基于波束扩散设计叠加算法进行数据处理,然后根据结果重构出代表每个深度内部信息的伪彩色横截面图像,以方便快速识别内部缺陷位置和范围。与常规方法对比得出,基于波束扩散的叠加算法处理数据成像质量更佳,提高缺陷检测灵敏度达到12dB以上。     

典型结构的单轴和三轴随机振动响应对比

发展多轴振动试验技术、推动多轴振动试验在曲线结构上的应用是非常必要的。单、多轴振动试验究竟会对产品响应带来哪些不同的影响？是在研究多轴振动试验技术中首先应该了解的问题。以某典型结构（见图1）为例，通过理论分析和试验研究，对比了该结构（包括线性和非线性部分）在单轴和三轴随机振动载荷下响应的差别。     

离子束驱动压力型内爆靶

离子束的贯穿能力强，能使绝大部分能量透过靶球外壳，进入到驱动并沉积在驱动层中，从而产生强大的压力。讨论了离子束直接驱动压力型ＩＣＦ靶球内爆的可能性。结合压力型内爆靶驱动效率的近似分析公式，讨论了靶球的设计原则，给出了一个典型的靶球结构以及相应的数值模拟结果。     

普适的基于能量的分块方法计算甲烷水合物簇的精确结合能和拉曼光谱

甲烷水合物在化学、能源和环境科学等领域中都具有重要作用. 本文采用普适的基于能量的分块(GEBF)方法计算了多种甲烷水合簇的结合能和拉曼光谱. 首先使用这些甲烷水合簇的在显相关耦合簇[CCSD(T)(F12^*)]水平下得到的GEBF结合能,评估了一系列密度泛函计算的结果. 计算结果表明B3PW91-D3和B97D泛函表现最佳,与GEBF-CCSD(T)(F12^*)基准相比的平均绝对误差分别仅为0.27和0.47 kcal/mol. 然后用GEBF-B3PW91-D3方法计算得到了单、双笼甲烷水合簇的结构和拉曼光谱,得到的甲烷C-H键伸缩拉曼振动峰与实验值的偏差小于3 cm^-1,说明B3PW91-D3泛函可以很好地重现实验结果. 随着水笼尺寸的增加. 甲烷C-H键伸缩拉曼峰发生红移,该现象与实验中提出的“松笼-紧笼”模型吻合. 此外,甲烷分子邻近环境(水笼)的改变对拉曼光谱的影响很小,环境从单笼变为双笼导致C-H键伸缩拉曼振动峰的蓝移不超过3 cm^-1. 甲烷水合簇的理论拉曼光谱与实验拉曼光谱结合可以用来研究海底或星际冰体内部的甲烷水合物的结构. 结合B3PW91-D3或B97D泛函和机器学习模型,可以进一步应用分子动力学模拟研究甲烷水合物的成核/生长机制和相变过程.     

某汽车传动系扭振测试、诊断与数据处理分析

本文针对某轻型卡车由于传动系扭振导致加速过程中驾驶室内出现异常振动与轰鸣噪声现象进行研究。首先,为弄清车内振动噪声产生机理,对整车的扭振和车内振动噪声进行了实车道路试验;其次,对整车试验异常数据进行后处理,通过低通滤波和设置电压波动缓冲区的方法对其进行去噪和再生成,消除了加速工况下转速曲线失速和异常峰值的现象;最后,通过分析转速、振动和噪声数据得出：样车加速过程中发动机2阶激励频率达到整车传动系的固有频率时,引起了传动系扭转共振,连同传动轴的不平衡转动自振,通过悬置、中间支撑和后桥板簧传入到车内,引起驾驶室异常振动和轰鸣噪声。     

FREE VIBRATION ANALYSIS OF A SPINNING FLEXIBLE DISK-SPINDLE SYSTEM SUPPORTED BY BALL BEARING AND FLEXIBLE SHAFT USING THE FINITE ELEMENT METHOD AND SUBSTRUCTURE SYNTHESIS

Free vibration of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft is analyzed by using Hamilton's principle, FEM and substructure synthesis. The spinning disk is described by using the Kirchhoff plate theory and von Karman non-linear strain. The rotating spindle and stationary shaft are modelled by Rayleigh beam and Euler beam respectively. Using Hamilton's principle and including the rigid body translation and tilting motion, partial differential equations of motion of the spinning flexible disk and spindle are derived consistently to satisfy the geometric compatibility in the internal boundary between substructures. FEM is used to discretize the derived governing equations, and substructure synthesis is introduced to assemble each component of the disk-spindle-bearing-shaft system. The developed method is applied to the spindle system of a computer hard disk drive with three disks, and modal testing is performed to verify the simulation results. The simulation result agrees very well with the experimental one. This research investigates critical design parameters in an HDD spindle system, i.e., the non-linearity of a spinning disk and the flexibility and boundary condition of a stationary shaft, to predict the free vibration characteristics accurately. The proposed method may be effectively applied to predict the vibration characteristics of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft in the various forms of computer storage device, i.e., FDD, CD, HDD and DVD.     

Hybrid acoustic synthesis – Assessment of rear final drives in an early stage of development,on the basis of transfer path analyses and test bench measurements

In order to be able to assess the acoustic characteristics of new rear axles respectively rear final drives at an early stage of development, a hybrid evaluation procedure was developed: this makes it possible to compare various construction stages on the basis of vehicle and test bench measurements. Transfer path analyses are used to calculate what contribution of the sound pressure on the driver’s ear is made up of structure-borne sound from the rear final drive (based on operational acceleration measured on the test bench and the bodywork’s transmission characteristics measured on the vehicle), which is used to classify the various construction stages. To use the test bench measurements for forecasting, the test object must have vibration characteristics that are as close as possible to those of the vehicle. In view of the above, comprehensive comparative measurements were taken with the help of artificial excitation and operational excitation. The measurement positions identified in the process were used to validate the calculation method by operating the very same rear final drive on the test bench and in a vehicle. In both cases, the rear final drive’s contribution of the total vehicle interior noise level was calculated, in one case on the basis of excitation from the vehicle measurement and in the other case on the basis of excitation from the test bench measurement. The good correlation between the vehicle-based and test bench-based calculations confirmed the applicability of the method. The “virtual” installation of the rear final drive enables faster construction stage comparisons because there is no need for alteration work on the vehicle and the rear final drive that is to be compared can simply be integrated into the existing test bench environment.     

Vibration of a rolling wheel— preliminary results

Preliminary results are presented of the axial vibration of a railway wheel on a vehicle travelling at speeds of up to 100 miles/h. Frequency analysis shows that the wheel response is resonant, at modes of vibration which have been identified from static tests. Further developments of measurement and analysis techniques will be necessary before a more complete picture of the importance of wheel vibration on wheel/rail noise radiation can be determined.     

Effect of grease type on abnormal vibration of ball bearing

The abnormal vibration of ball bearings lubricated with grease was studied. The test bearings were lubricated with three types of grease: Li soap/silicone oil grease, Na soap/mineral oil grease and Li soap/mineral oil grease. In the experiments, the axial-loaded ball bearings were operated at a constant rotational speed, and the vibration and the outer ring temperatures of the test bearings were measured. In addition, the shear stress and shear rate of the greases were measured by a rheometer. The experimental results showed that the abnormal vibration occurs on the test bearings lubricated with all three types of grease. Based on the experimental results, the generating mechanisms of the abnormal vibrations were discussed. From the discussions, it seems reasonable to conclude: (1) Li soap/silicone oil grease and Na soap/mineral oil grease both have a negative damping moment characteristic. The abnormal vibrations of the ball bearings lubricated with these greases are generated by the negative damping moment. (2) The abnormal vibration of the ball bearings lubricated with Li soap/mineral oil grease is generated by the decreasing positive damping moment of the grease due to the rising temperature.     

Reduction of vibration and noise radiation of an underwater vehicle due to propeller forces using periodically layered isolators

Using periodic structure theory, the suppression of vibration and noise radiation from an underwater vehicle due to excitation from propeller forces is investigated. The underwater vehicle is modelled in two parts (the hull and the propeller/shafting system). A model of the propeller/shafting system is constructed using a modular approach and considers the propeller, shaft, thrust bearing, isolation structure and foundation. Different forms of isolator are considered – a simple spring-damper system, a continuous rod and a periodically layered structure. The dynamic properties of the underwater vehicle and the isolation performances of various isolators are compared and analysed. The stop band properties of the periodic isolator are used to enhance the passive control performance. Furthermore, an integrated isolation device is proposed that consists of the periodic isolator and a dynamic absorber, and its isolation performance is investigated. The effects of the absorber parameters on the performance of the integrated device are also analysed. Finally, the radiated sound pressure is calculated to verify the attenuation. The numerical results show that the vibration and noise radiation are greatly attenuated in the stop bands. By optimising the design of the periodic isolators and its integrated structures, the suppression of the vibration and noise radiation can be improved effectively.     

怠速工况下燃油系统的噪声评价和改善*

在实车怠速工况下的噪声振动性能评价过程中,燃油系统是发动机诸多子系统当中一个重要的声源。针对这一子系统产生的车内脉动噪声偏大的问题,总结出了对燃油类液体的脉动噪声振动控制机理、原因及诊断方法。首先,采用在燃油轨内追加阻尼器的方案很好地抑制了谐频噪声;然后,从燃油泵这一主要激振源出发,提出了设定燃油泵单品噪声振动、声品质等目标值的策略,即从源头上控制关键产品的噪声性能。在此基础之上,与之相应的解决方案实施之后,怠速工况下的车内噪声提升到了较好的水平,而且,燃油系统噪声的主观评价结论也认为得到了明显改善。     

Passive and active interior noise control of box structures using the structural intensity method

This paper presents passive and active vibro-acoustic noise control methods for attenuating the interior noise level in box structures which can be an analogy of cabins of vehicle and aircraft. The structural intensity (SI) approach is adopted to identify the predominant vibration panels and interior noise sources for box structures. In the study, the finite element method is used to determine the structural vibration and structural intensity in the box surfaces. According to structural intensity vectors plot and structural intensity stream lines presentation, the possible effective control positions where the dampers may be attached and the active control forces may act to reduce vibration and interior noise, are identified. From the study, it can be demonstrated that the structural intensity approach and stream line presentation are possible methods for identifying the vibro-acoustic interior noise source and predominant panels which may be modified to reduce the interior noise level. The structural intensity methodology, passive and active noise control results can be extended to the further study of the vibration and interior noise control of actual cabins of vehicles and aircraft.     

Theoretical model of ball joint squeak

The theoretical model for the ball joint squeak problem is proposed. The ball joint is modeled as a sphere attached to a rotating flexible beam and it is in contact with a semi-spherical rigid socket. The relative rotation and vibration between the ball and socket produces friction stresses causing the dynamic instability of the system. The squeak propensity of the ball joint system is numerically investigated through the eigenvalue sensitivity analysis at the sliding equilibrium. Stability analysis shows that the bending modes of the beam can produce the dynamic instability under the negative friction-velocity slope. It is also highlighted that the squeak propensity under the poor friction characteristics can be controlled by the system parameters such as the sliding speed, the contact stiffness, the radius of the ball, the axial load and the tilting angle.     

Transverse vibration of a rotor system driven by a Cardan joint

The transverse vibration of a rotor system driven by a Cardan joint is analyzed and the effect of the transmitted torque on the dynamic stability of the system evaluated. As a result of the analysis, the following facts are proved: when the driving shaft and driven shaft (rotor shaft) are included, both parametric and self-excited vibrations arise due to transmitted torque; asymmetrical stiffness of the rotor supports has the effect of stabilizing this self-excited vibration.