ISSN: 2277-3754                                              ISO 9001:2008 Certified                      International Jo...
ISSN: 2277-3754                                              ISO 9001:2008 Certified                      International Jo...
ISSN: 2277-3754                                             ISO 9001:2008 Certified                     International Jour...
ISSN: 2277-3754                                              ISO 9001:2008 Certified                      International Jo...
ISSN: 2277-3754                                            ISO 9001:2008 Certified                    International Journa...
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Psd analysis ijeit

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PSD Analysis of automobile dash panel- Dr N V srinivasulu

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Psd analysis ijeit

  1. 1. ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 1, July 2012 PSD Analysis of an Automobile Dash Panel Dr. N.V.Srinivasulu, S.Jaikrishna, A.Navatha Abstract:-In this paper, PSD analysis of an automobile used dash panel are the steering wheel and the instrumentdash panel is performed in order to reduce the vibrations that cluster. An instrument cluster includes instrument gaugesoccur when force is given as input by keeping a damping such as a speedometer, tachometer, and oil indicator, etc.material between the panel and a doubler sheet. Modal The top of a dash panel usually contains speakers for theanalysis and Spectrum Analysis of the finite element modal is audio system, and vents for the heating and A/C system.performed. By doing this we are comparing the resultsobtained with the images and data given .In the initial study A glove box is often found on the passenger side. Wewe are trying to compare with the bare dash panel and further look at the dash panel more than any other area of ourstudy the effect of the Permacel double damp material. Mode cars interior. It makes sense, therefore, that we shouldshapes from the modal analysis of this FE model were give it some special attention. The dash panel and thecompared with the transfer function obtained from the Laser deck under the rear window also take the brunt of damageVibrometer Test. Tried to identify peaks in the transfer from sun exposure. In order to keep your used dash panelfunction graph to the natural frequencies and velocity from from cracking and fading, regular treatment is necessary.the spectrum analysis of the panel. II. PROBLEM DESCRIPTION I. INTRODUCTION PSD analysis is a probabilistic approach used in Here in this project we consider two cases .In case 1,random vibration analysis. PSD i.e. the power spectral PSD analysis of the bare dash panel is performed and indensity is the magnitude of the random input. Random case 2, a damper is kept between the dash panel andVibration Analysis uses Power spectral density to doubler sheet. In PSD analysis of the bare dash panel, thequantify the loading. PSD is a statistical measure defined vibrations that occur are high, so in order to reduce theas the limiting mean-square value of a random variable. It noise or the vibrations we use a damping material. Tois used in random vibration analyses in which the measure the vibrations, a setup is made i.e. the car bodyinstantaneous magnitudes of the response can be specified or in other words the front part i.e. the dash panel part isonly by probability distribution functions that show the kept on a rod where the excitations are created. Theseprobability of the magnitude taking a particular value. It excitations are measured practically by placing a laseris a graph of the PSD value versus frequency, where the vibrometer on that rod. Mode shapes from the modalPSD may be a displacement PSD, velocity PSD, analysis of this finite element (FE) model are comparedacceleration PSD, or force PSD. Mathematically, the area with the transfer function obtained from the Laserunder a PSD-versus-frequency curve is equal to the Vibrometer Test (practically) and also the vibrationsvariance (square of the standard deviation of the produced in case of bare dash panel analysis and the dashresponse).The term Power in Power Spectral Density panel with a damper (permacel) is compared.seems to come from the fact that when random vibrationmeasurements were taken, they were actually recordedelectronically and so the power levels were used in thecalculations. This type of analysis is basically used forvibration and noise reduction and control, acousticanalysis and it is a type of spectrum analysis. Dash panels are panels under the windshield of avehicle, containing indicator dials, compartments, andsometimes control instruments. It is necessary that acareful examination should be made of the complete dashpanel and dash areas . It is of vital importance as it keepsengine fumes, dust and water out of the passengercompartment. Used dash panel should be checked for atight fit around all wires, conduits, and controls.Particular attention should be paid to the possibleomission of the radio antenna wire grommet in the rightside of the used dash panel. This area is not readilyvisible and is commonly overlooked as a possible dustand water leak source.Many different things are mountedon dash panels. The most important items located on the 1
  2. 2. ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 1, July 2012 III. THE DASH PANEL The model as generated from the IGES data. Fig.1. PSD Analysis of the Bare Dash Panel Fig.2.Actual Model. The model of the dash panel is imported to ANSYS.For the dash panel shell99 element type is used as it is FE Modelgenerally used for layered applications of a structural Bareshell model. While SHELL99 is an eight nodded element FE Model for the bare dash panel is as shown below.and does not have some of the nonlinear capabilities ofSHELL 91, it usually has a smaller element formulationtime. SHELL99 allows up to 250 layers. If more than 250layers are required, a user-input constitutive matrix isavailable. The element has six degrees of freedom at eachnode: translations in the nodal x, y, and z directions androtations about the nodal x, y, and z-axes. The pointwhere the excitations are created is taken as the mass21element which is a point element having six degrees offreedom i.e. the translations in nodal X,Y,Z directions Fig.3 .Bareand rotations about the nodal X,Y,Z axes. Dash panel In this case (bare dash panel) there is only one material After obtaining the mode shapes, spectrum analysisused i.e. steel, which has the following material option is chosen and also the type of spectrum analysisproperties... i.e. the PSD analysis option is chosen. The number of Table 1 modes from the modal analysis to include in the PSD Young’s modulus (Pa) 2.07 e11 analysis is specified. The type of response spectrum (force spectrum) is chosen. Then the PSD vs frequency Poisson’s ratio 0.29 graph values are entered in a table and the graph is plot. Density (kg/m3) 7850 The base PSD excitation node i.e. the mass element is chosen and the excitation direction (Uy) is given. NowOne set of real constants are defined with thickness of the the participation factor (PF) for the specified PSD table islayer as 0.8mm. The model is then meshed freely and calculated and the calculation controls are set. Then it isthen the boundary conditions are applied to the dash panel solved for the random vibration solution. After thisand the mass model. Then the modal analysis is solution is obtained the mode combination is set and thenperformed and the mode shapes are obtained. In modal the mode combinations and the 1 sigma response areanalysis modal extraction method i.e. the Block element. calculated. Finally the results are read and the responseThe mass element is constrained in all degrees of freedom PSD graph is plotted.and, master and slaves constraints are given to the mass PSD analysis of the dash panel with damperelement and the dash panel Lanczos method is chosen and The model of a 3 layered dash panel i.e. the panel, thenumber of modes to extract and number of modes to damping material (permacel) and the doubler sheet isexpand are given. imported and shell99 element type is used for the panel and the point on the rod is taken as a mass21 element 2
  3. 3. ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 1, July 2012which is a point element having six degrees of freedom.In this case two materials are used and the materialproperties are defined for both the materials. Steel forpanel and doubler sheet Permacel as a damping material Table 2. Material Properties: Material Young’s Poisson’s Density Modulus Ratio (Kg/m3) (Pa)Dash panel 2.07 E11 0.29 7850 Dash Doubler Permacel& Doubler Sheet material Sheet panel Permacel 1.836 E8 0.35 560 Fig.5.FE Model for the model with Doubler and PermacelThe Poisson’s ratio for Permacel is an approximate After obtaining the mode shapes, spectrum analysisvalue. option is chosen and also the type of spectrum analysis Three sets of real constants are defined with thickness i.e. the PSD analysis option is chosen. The number ofof the first layer (panel) as 0.8mm, second layer modes from the modal analysis to include in the PSD(permacel) as 0.7mm and third layer (doubler sheet) as analysis is specified. The type of response spectrum0.8mm. The model is then meshed freely and then the (force spectrum) is chosen. Then the PSD vs frequencyboundary conditions are applied to the dash panel and the graph values are entered in a table and the graph is plot.mass model. Then the modal analysis is performed and The base PSD excitation node i.e. the mass element isthe mode shapes are obtained. In modal analysis modal chosen and the excitation direction (Uy) is given. Nowextraction method i.e. the Block element. The mass the participation factor (PF) for the specified PSD table iselement is constrained in all degrees of freedom and, calculated and the calculation controls are set. Then it ismaster and slaves constraints are given to the mass solved for the random vibration solution. After thiselement and the dash panel Lanczos method is chosen and solution is obtained the mode combination is set and thennumber of modes to extract and number of modes to the mode combinations and the 1 sigma response areexpand are given. calculated. Finally the results are read and the response PSD graph is plotted. IV. RESULTS Modal Analysis Results Given below are the natural frequencies of the bare dash panel model, which coincide with the peaks as shown in the transfer function, obtained from the vibrometer test.Fig.4. Doubler sheet with damping treatment sandwiched between the steel sheetsPermacelThe FE Model for the model with Doubler and Permacelis as shown below. Fig.6. Bare dash panel 3
  4. 4. ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 1, July 2012 Natural Natural VI. CONCLUSION Peaks from Peaks fromFrequencies Frequencies Tested Tested from from Form the analysis it is concluded that… Transfer Transfer Analytical Analytical Functions Functions Study Study  In case of the single layered dash panel the first 73.33 75.00 432.91 435.00 92.80 96.25 440.80 438.75 natural frequency obtained is 73.33 Hz. 136.83 137.50 445.63 451.25  In case of the three layered sandwiched dash 144.00 141.25 457.08 468.75 panel, the first natural frequency is 77.5 Hz. 153.37 156.25 492.65 475.00 Here the natural frequency is increased and 178.66 167.50 499.13 493.75 hence the vibrations are reduced by 5.38% 183.34 177.50 507.89 508.75 which is safe and noise controlling. The 194.49 198.75 526.18 527.50 damping material (permacel) used absorbs 209.25 212.50 541.49 546.25 vibrations and prevent them from reaching the 220.58 223.75 551.78 552.50 passenger’s end. 251.02 238.75 573.60 567.50  So, such type of dash panels which are 262.44 256.25 595.36 595.00 sandwiched with a damping material are noise 267.25 270.00 626.44 621.25 controlling and safe to use. 276.94 278.75 654.70 652.50 300.81 297.50 672.66 672.50 305.55 308.75 679.05 682.50 339.85 342.50 685.52 688.75 373.19 345.00 700.49 700.00 377.42 362.50 729.12 726.25 387.37 388.75 763.81 762.50 401.27 403.75 776.82 771.25 418.64 416.25 782.41 780.00 425.78 425.00 798.25 796.25 Fig.8. 1 sigma displacementFig.7. Modal results at first natural frequency in Ux and Uy Fig.9.1 sigma velocity at first natural frequency V. SPECTRUM ANALYSIS RESULTS In spectrum analysis the 1 sigma displacement, 1sigmavelocity, 1 sigma acceleration and 1 sigma unit staticsolutions are obtained. 1σ results are typically used forFatigue calculations. Based on the premise that the stresslevel is at or below 1σ 68.2% of the time, between1σ=and 2σ 27.2% of the time (95.4-68.2), and between2σ=and 3σ 4.3% of the time (99.7-95.4), and above Fig.10. 1 sigma acceleration with and without3σ=less than .3% of the time. 4
  5. 5. ISSN: 2277-3754 ISO 9001:2008 Certified International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 1, July 2012 Fig.11. 1 sigma displacement AND 1 sigma velocityGiven below are the natural frequencies of the dash panelwith damper model, which coincide with the peaks asshown in the transfer function, obtained from thevibrometer test.Dash panel with damper (permacel) Natural Natural Peaks from Peaks from Frequencies Frequencies Tested Tested from from Transfer Transfer Analytical Analytical Functions Functions Study Study 77.75 75.00 456.86 435.00 106.74 96.25 465.14 438.75 123.82 137.50 484.19 451.25 146.32 141.25 492.13 468.75 158.62 156.25 492.95 475.00 177.59 167.50 499.67 493.75 205.84 177.50 508.13 508.75 220.05 198.75 523.09 527.50 232.23 212.50 542.03 546.25 252.73 223.75 549.28 552.50 263.37 238.75 567.69 567.50 266.88 256.25 582.57 595.00 270.65 270.00 620.55 621.25 281.13 278.75 649.97 652.50 297.34 297.50 673.89 672.50 314.35 308.75 680.40 682.50 338.76 342.50 685.15 688.75 353.87 3450 700.23 700.00 369.65 362.5 720.44 726.25 381.21 388.75 757.70 762.5 400.72 403.75 772.15 771.25 418.57 416.25 781.56 780.00 425.69 425.00 795.67 796.25 5

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