Dynamic Characteristics Analysis and Structure Design of Improvement for Exhaust Manifold Cover

The exhaust manifold cover is the main source of surface radiate noise of a 6 360 vehicle's engine.By using the finite element analysis technology,a finite element model of the cover is established,and then the modal analysis is done theoretically with this model,the result is consistent with the experiment.On this basis,the transient response of the cover under the excitation of engine block's vibration is analyzed.The result show that the free edge is the main source of radiate noise,because its normal velocity is maximal.The improved measures are adopted which is based on the practical structure of the cover.The analysis of the improved structure shows that the measures are effective,the radiate noise of the cover is decreased distinctly.     

Testing and modal analysis on multi stage planetarygearbox housing of shield tunnelling machine

The finite element model is developed for the multi stage planetary gearbox housing in shield tunnelling machine (STM), and the the eigenvalue problem is solved by using block Lanczos method, and then the low order natural frequencies and corresponding modes are extracted. Based on the theory of experimental modal analysis, the modal testing is made for the gearbox housing by pulse excitation method. The least squares complex frequency domain (LSCF) estimation method is used to analyze the modal data, and the natural characteristics of housing is obtained. According to the modal assurance criterion (MAC), the experimental modal parameters are validated. Modal analysis shows that the experimental data is coincided with analytical results, which indicates the accuracy of the theoretical model and testing method. The coupling sympathetic vibration is disappearing between the gears train and housing, the local vibration is large at the high speed side of gearbox housing, and the torsional mode is outstanding under operating condition. The research results provide theoretical basis and experimental support for the structural optimization of the gearbox of STM.     

Dynamic FEM Analysis of Automobile and Software Development

In this article, modal analysis technology about dynamic analysis was studied. Free interface model comprehensive method was used to dynamic analysis and design of automobile structure based on theory background of model analysis, test technology conditions, data reliability and precision. In order to test the efficient and possibility of the method, main vibration features about space double layer has been calculated based on this method, comparing this with the precise solution of finite element method, the result shows that this method is suitable not only for simple interfaces between components but also for high reductive interfaces. In addition, the method also has high comprehensive precision. Furthermore it creates conditions to dynamic analysis in automobile structures.     

simulation and improvement of an all terrain vehicle muffler

Aiming at a muffler of a 400 all terrain vehicle(ATV), a vibration model and an acoustics model of the muffler were built by finite element method(FEM). The vibration and acoustics characteristic analysis of the muffler are carried out according these models, it shows the 3D model is exact and it is possible to generate regeneration noise. Acoustics model can help to know further about the characteristic of each chamber and intention of the designer. According the demand of factory, some projects of improvement are offered. The final result of road test proves that he improved muffler is feasible.     

Finite element model of coupled systems for vibration reduction plates with smart constrained layer damping

Considering the relationships of coupling movement and compatible displacement among bonding layer, piezoelectric layer, damping layer, and base structure, a finite element dynamic model of coupled systems for vibration reduction plates is established. The model combined with piezoelectric theory, finite element theory and ADF model of viscoelastic damping material can be suitable for vibration model of complex SCLD structure. The dynamics parameters for clamped-clamped steel plate with partially treated smart constrained layer damping are obtained by theoretical calculation, ANSYS modal analysis and modal experiment. The results show that theoretical values are closer to the test results and ANSYS analysis, and the methods proposed is more accurate and effective.     

Junction stiffness analysis and vibration noise prediction of wind power speed-increase gearbox

In order to study the vibration characteristics and radiation noise of wind power speed-increase gearbox, a torsional vibration model of wind power speed-increase gearbox is established based on the analysis of supporting stiffness of bearing and contact stiffness of gear pairs. By solving the vibration differential equation with the help of Matlab, the frequency and corresponding vibration mode are obtained. With taking stiffness excitation, error exaction and meshing impact exaction into account, the dynamic finite element model of speed-increase gearbox is set up, and the dynamic response simulation is carried out. Regarding vibration displacement of the nodes on gearbox surface as boundary condition, an acoustic boundary element model of speed-increase gearbox is built. The surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The results show that there is a great difference between torsion frequency and excitation frequency of wind power speed-increase gearbox, and so the resonance doesn't occur. The maximum structural noise and radiation noise mainly appear near the double octave of the gears meshing frequency of high-speed grade.     

Analysis and test on vibration and acousticnoise of GWC6066 marine gearbox

The mesh stiffness of gear tooth is simulated by spring elements, the connected bolt between various housings are simplified as bar elements, and the sliding bearing and rolling bearing are simplified as spring dumping elements. Based on them, the gear-shaft-bearing-housing coupled finite element model and boundary element model of GWC6066 marine gearbox are established. Finally, the dynamic response under internal dynamic excitation is analyzed and the vibration severity, structural-borne noise and air-borne noise of the gear system are forecasted. Through the experimental modal analysis of gear system, and the test of vibration response and air pressure, the natural frequencies, vibration severity, structural-borne noise and air-borne noise are obtained. Compared with numerical results, two results show good agreement.     

Comparative study on the identification of structural modal parameter using different methods

Chongqing Chaotianmen Yangtze River Bridge is the world's longest-span arch bridge. The node connections on its main truss’s lower chords are to bear millions of large-amplitude stress cycles caused by automobile and light-rail train loads. However, there exists no referential designing and testing experience in such detailing on long-span steel bridges at home and abroad as yet. High-cycle fatigue behavior testing on a detailing model has been conducted to study the fatigue reliability of the bridge’s critical node connections. The testing cycling load on the model is determined according to conventional specifications and the expected traffic flow on the Bridge. The 1/2-scale detailing model is carefully fabricated to simulate the node prototype and undergo the 2 million-cycle testing with the design load. Through testing, fatigue reliability of Chaotianmen Yangtze River Bridge’s main-truss lower-chord node connections during the design service life is verified. In addition, static test data are compared with those calculated by finite element analysis to prove the validity of the node model. In the end, fatigue destruction test of the model was carried out to get the fatigue failure law of the node connection and provide necessary parameters and reference for designing and monitoring of this bridge in the future.     

体育馆大跨度预应力次梁楼盖竖向振动模态分析

以重庆市铜梁县新城核心区小学建设项目3^#楼（体育馆）工程为背景，对其大跨度预应力次梁楼盖竖向振动模态进行模拟分析，并与实测结果相比较，评价其控制竖向振动舒适度的效果。根据建模思路精确建立的该大跨楼盖有限元模型，其模态分析结果与模态实测结果接近，相对误差约为5%；模拟分析及工程实测结果表明，该大跨楼盖前三阶振型均以竖向振动为主，结构自振基频满足我国现行相关规范的要求，竖向振动舒适度符合标准；与无底板的大跨次梁楼盖相比，增加底板后，其增幅最小的一阶频率增长了19.9%，表明增加底板可有效地控制大跨度预应力次梁楼盖的竖向振动。     

Dynamic characteristic analysis of an all terrain vehicle body

The body is a key part of all terrain vehicles (ATV). Its dynamic characteristics greatly effect the vibration of the ATV assembly. Simulation and experimental methods are combined to analyze ATV body vibration characteristics. A computer aided design(CAD) model is built using UG4.0. A finite element method(FEM) model of an ATV body and a body with an engine are created using Hypermesh. The FEM model is imported to Msc.Nastran to calculate the free mode. The simulation model is verified by the experimental modal result. The results indicate that after the frame with engine, the first bending mode increases due to the engine increasing the body stiffness, while the first torsion mode decreases due to the engine mass. The effects on the dynamic response of the road and engine excitation are analyzed respectively. Vibration characteristic improvement methods and suggestions regarding the body are provided.     

A valve camshaft load torque calculation and camshaft vibration control analysis

Aiming at the overhead camshaft valve mechanism,the theoretical and numerical solutions of camshaft load torque are calculated respectively by a derived formula and transient finite element analysis. The two solutions show good agreement,thus the correctness of the transient finite element model is verified. By combining with camshaft instantaneous constraint modal analysis and vibration response with consideration of gas pressure,it is found the position of camshaft which easily excites resonance and the main influence factors of camshaft vibration. Then the effect of the width of bearing seat on the camshaft vibration is investigated and the results show that the vibration of camshaft is mainly bending vibration,appropriate width of bearing seat can effectively control the camshaft vibration.     

Existing Frame Structure in Reconstruction and ExtensionProject in Security Analysis

Structure security is the most main structural reliability, at the request of active service in time to make a frame structure security assessment, in safe premise to prolong the service life, and has a certain social significance and economic benefits. Combining with the actual situation reconstruction projects, using the theory analysis frame structure of the active safety, the finite element SAP2000 on the original structure and rebuilt structure modal analysis, the effect of the structure security index that contrast reconstruction of the frame structure than the frame structure of the security it can improve.     

Dynamic analysis of high speed motorized spindles with eccentrics

In order to study dynamic behaviors of high speed motorized spindles under different eccentric conditions,the dynamics of high speed motorized spindles is analyzed by using finite element method on the basis of its structure,and an analytical dynamic model of high speed motorized spindles is established. Based on electromagnetism and mechanical system dynamics,expressions of general unbalanced force of high speed motorized spindles are established. Thus,dynamic characteristics of spindles,such as natural frequencies and unbalance response,can be obtained from the proposed model while spindles have different preloads and bearing configurations. The parameters of a 120MD60Y6 motorized spindle are substituted into the model and a simulation is carried out by Matlab/Simulink. The result shows good agreement with the data obtained from experimental modal analysis,which proves that the proposed model is correct.     

Modal Analysis and Vibration Control of Benfield Frame

There is a low frequency and great amplitude on Benfield frame of Jianfeng chemical plant. With finite element modal, the reasons and mechanism of the vibration on Benfield frame are analyzed and confirmed. And a method of vibration control about the main vibration resource (100V10) is proposed to reduce the amplitude of Benfield frame vibration.     

Experiment Modal Analysis System Based On GraphicCell Object

A structure input and output method of graphic cells object oriented is proposed, and input and output model based on OpenGL graphic industry standard is founded. Using the technologies of MFC and OpenGL, the input, display and dynamic output of 3D graphics are realized, which are based on graphic cells such as node, beam, triangle, quadrangle element. Graphic cells keep consistency well with the elements of finite element in the aspects of geometry, reading and writing of structure files and so on. Using the model, the functions of structure input, data gathering and analyzing, and modal vibrating shapes output etc are finished. A visual experiment modal analysis system is daeloped.     

structural optimization of high power marine gearbox

Taking the influences of joggle forces and gravity into account, a static model of a high power marine gearbox was established using the finite element method. The gearbox workload capacity was calculated in four working states. Gearbox strength and structural rigidity were analyzed. Combining theories of optimization and reliability design, the gearbox optimization model was obtained based on the intensity principle. To insure a safe structure, optimization designs were put in practice to improve the gearbox structure. As a result, the gearbox weight was reduced 1 060 t by structural optimization. The strength of the improved gearbox is more symmetrical and the structure of the improved gearbox is more reasonable than previoius designs, indicating the method has certain theoretical and practical engineering values.     

切割片减振降噪的优化设计

为了研究切割片在工作过程中的振动及噪声问题,基于有限元方法,借助于ANSYS APDL有限元软件建立了切割片有限元模型;采用反转法施加载荷,简化模型及分析过程,在振动特性分析中,得出调整切割片结构参数可以降低切割片振动幅度的结论;基于振动能量与速度的平方关系,以测试点的速度平方和为目标函数,设计了优化程序对切割片模型进行调整优化,获得了一组最优调整数据,为实际生产提供了参考依据。     

Topology optimization for constrained layerdamping material in structures using ESO method

Topology optimization for constrained damping material in structures is investigated in order to suppress structural vibration through the optimal placement of constrained damping material in structure. A mathematical model to describe the topology optimization problem is established. In the topology optimization approach, structural modal damping ratio is designed as objection function, while constrained damping material consumption is considered as constraint condition. The sensitivity of modal damping ratio to the place is analyzed. An evolutionary criterion for placement of constrained damping material in a structure is presented. The formula of sensitivity is derived and used to determine the optimized placement of constrained damping material in structure. The topology optimization problem is further solved by evolutionary structural optimization (ESO) method. The numerical examples are given. The results show that a stable and dramatic increase of the modal damping ratio during the course of iterations can be observed. Therefore, an optimal layout of constrained damping material in structure is obtained. The comparison of amplitude frequency characteristics with the optimal and fully covered layout validates the effectiveness of proposed topology optimized approach.     

卧式青核桃脱皮机链板输送机构的设计与有限元分析

为了分析卧式青核桃脱皮机中刀片及刀片安装板等核心关键部件的结构强度和力学性能,通过设计和计算确定了刀片及刀片安装板的结构参数,采用UG三维模型软件,创建了刀片及刀片安装板的分析模型,并通过ANSYS有限元分析软件对刀片及刀片安装板进行了静力学分析和模态分析。结果表明：刀片及刀片安装板既可以实现对青核桃的输送功能,又可以实现刀片对青皮的切割作用;刀刃边缘位置的变形最大,最大值为0.509 mm;刀片折弯位置的应力和应变值最大,最大值出现在0°刀片的折弯位置,最大值为114.7 MPa;在工作过程中最大等效应力远小于材料的屈服强度,刀片及刀片安装板的模态分析前三阶固有频率分别为466.99、1 206.8、2 199.7 Hz,而机构的工作频率远小于所分析零部件的固有频率,刀片及刀片安装板的结构能够满足强度和刚度要求,且工作过程中不会出现共振问题,这为研制卧式青核桃脱皮机链板输送机构提供了理论依据。     

风电增速齿轮箱动力学性能优化方法

建立增速齿轮箱动力学分析有限元模型,利用Lanczos法求得齿轮系统的振动模态;以齿轮副时变啮合刚度激励、齿面综合误差激励和轮齿啮合冲击激励为内部作用激励,采用直接积分法求得箱体表面节点的动态响应。选取箱体上12个主要结构参数作为动力学性能优化的设计变量,齿轮箱体积为状态变量,以齿轮箱表面振动加速度的均方根值最小为动力学性能优化的目标函数,利用零阶与一阶优化算法求得最优设计变量。结果表明：优化前后箱体均不产生共振,且满足静力学条件;优化后目标函数减小37.5%,箱体各计算点的振动响应均有较大幅度的减小,最大减小量为54%。