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Research on Plate Beam Minimum Vibration Power Flow under the Action of Determine Excitation

Author: YangYi
Tutor: LiZhiYuan
School: Hefei University of Technology
Course: Mechanical Manufacturing and Automation
Keywords: Forklift vibration NVH Structural dynamics Continum elastic vibration Power flow Optimization
CLC: TH242
Type: PhD thesis
Year: 2012
Downloads: 34
Quote: 0
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Abstract


This Paper is based on the background of the projects undertaken by the laboratory. By theoretical analysis and numerical calculation method, the paper took the vibration power flow as an objective function, studied the plate with different boundary conditions, and simply supported elastic beam vibration characteristics. The results have the important theory significance and the practical value.A large number of plate beam structure used in mechanical engineering, its vibration response characteristics need to be researched. In order to identify the Minimum vibration response under the Action of Determine Excitation, a more in-depth research of theory is needed. This paper investigated the vibration characteristics of the plate beam structure, and those researched results have clear application object.By theoretical analysis and numerical calculation, the paper studied the plate structure vibration characteristics.That different structure parameters how to affect the plate structure vibration characteristics was analysed.The conclusions of designing plate structure with good vibration characteristics were drawed. It provides reference for designing the structure. A numerical optimization program was programmed with minimization peak power optimization strategy.For three different boundary conditions plate structure was optimized.After the comparison of three kinds of different boundary plate structure model of the optimized results, draw a coclution that the three fixed edges plate vibration power flow peak is minimum and the two fixed edges plate vibration power flow peak is maximum. It provides a theoretical reference guide for engineering design.The paper contents are as follows:Firstly the basic concepts, basic principles and calculation method of power flow was studied. Then, based on vibration theory, the paper studied plate vibration analysis methods under the action of determine excitation. Regards plate structure as the research object, using structural dynamics, mechanical admittance theory and processing method, From the power flow of the basic concept and the basic principle, the paper deduced the different power flow equations and numerical calculation result of the plates, such as two edges fixed and the other two edges free plate, quadrilateral fix plate, three edges fixed plate,under the action of determine excitation, with different conditions, such as the excitation point position, length, width, thickness and other parameters. The study on the plate structure dynamic response analysis provides a method for designing these dynamic characteristics and provides a theoretical basis for the design improvement. Some general conclusions of engineering significance were drawed. Some general conclusions of engineering significance as follows:For the three kind of boundary conditions of the plate,(1) As the thickness of the plate is increased, power flow peak is reduced.So,when a Mechanism structure is designed, as long as under the condition of the engineering design allows,the thicker the plate is,the less the power flow peak is.(2) As the Plate loss factor is increased, power flow peak is reduced. So, when a Mechanism structure is designed, we should choose the big loss factor.(3) The Plate longth increased and power flow peak reduced.So, when a Mechanism structure is designed, we should choose the longer Plate.(4) As the Plate width is increased, power flow peak is reduced, when a Mechanism structure is designed, we should choose the narrower Plate.Some modal in narrower plate was not excited, so the vibration energy was very small. The vibration is very small when the some modal are not excited. Plate structure is widly used in Practical engineering, so we should design to avoid the excited modal.(5) As Quadrilateral fixed plate and two sides fixed two sides free plate were conserned, they are Symmetric boundary; the vibration power flow peak caused by excitation point in the center of the plate is greater than those caused by the excitation point in the corner of the plate.Although the number of modal excited by in the center were a few, those mode once are excited, peak energy is larger than those that excited by incentive point not in the center, although many modal was incentived, the peak is smaller. When a Mechanism structure is designed, we should pay attention to whether those modal were excited by the incentive point in the center of the board. As three sides fixed plate and two sides fixed two sides free plate are conserned, the position of exciting point is not only to avoid the plate center, but also to avoid the free edge of it.(6) When a Mechanism structure is designed, we should pay attention not to putting the incentive point in the center of the plate. With the different incentive point position the peak changed from big to small alternately, we must calculate carefully to find the minimum peak.(7) When the excitation point position is same, each of the three kinds of boundary conditions plate has advantages and disadvantages, depending on the incentive location. When a Mechanism structure is designed, we should choose the boundary conditions by calculation.As the beam structure is corncerned, by analyzing in theory, we obtained a series of practical engineering significance results.(1)The longer of the beam structure is, the less of the power flow is.(2) Wall thickness needs to appropriate select.(3) As the Beam loss factor is increased, power flow peak is reduced. So, when a Mechanism structure is designed, we should choose the big loss factor.(4) The hight increased with the power peak decreased under the condition of constant beam cross section. So, when a Mechanism structure is designed, we should choose the big hight and small width. When incentive point position is shifting from the middle of the beam to two ends of it, power flow peak is varying with from bigger to smaller. The incentive point postion should be putted the two ends or its vicinity. The order of design pivot-elastic supported beam is designing its basic parameters, and then according to the sturucture to support the stability and vibration needs, design elastic supporting rigidity range. After using the frequency equation numerical method to determine the natural frequency, based on the summary of the law, we compute its stiffness, longth, width, hight, wall thickness.Finally applying the commercial software ANSYS to board model, to beam model is simulated and analyzed. Obtained consistent with the theoretical analysis conclusion, this has also verified the correctness of theoretical analysis.The main structure of present forklift is welded steel frame; power device is supported on the frame.Forklift vibration has plagued enterprises, restricting the performance improvement of forklift NVH. On the results of this study can be well applied to the structural design of the forklifts, and quickly promote forklift ideal NVH performance and the enterprise efficiency growth.

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CLC: > Industrial Technology > Machinery and Instrument Industry > Lifting machinery and transport machinery > Loading and unloading machinery > Automatic loading and unloading of vehicles
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