FREE VIBRATION ANALYSIS AND OPTIMIZATION OF STREEING KNUCKLE

Transcription

1 FREE VIBRATION ANALYSIS AND OPTIMIZATION OF STREEING KNUCKLE R.Premraj M.Chandrasekar K.Arul kumar Mechanical,Engineering, Sasurie College of Engineering,Tiruppur ,India Abstract The main objective of this project is to reduce the weight of a steering knuckle by applying the topology optimization technique and minimized the mass of steering knuckle. Steering knuckle is an important component of the vehicle which is connected to the suspension system. CAD Model of steering knuckle has been done in Catia V5 and meshed in HYPERWORKS. Static analysis was done in HYPERWORKS 12 with the help of RADIOSS. Then different conditions of load are applied to the steering arm. Free vibration modal analysis is done to find natural frequencies and mode shapes of component. From the analysed results, design parameters were compared for SG Iron and MDI knuckle the results shows that MDI (Mar tempered Ductile Iron) is better one. Keywords: Hyperworks,natural frequencies and mode shapes of component 1 INTRODUCTION Vibration is time dependent displacement of a particle or a system of particles with respect to an equilibrium position. If these displacements are repetitive and their repetitions are executed at equal interval of time with respect to equilibrium position the resulting motion is said to be periodic. One of the most important parameters associated with engineering vibration is the natural frequency. Each structure has its own natural frequency for a series of different nodes which control its dynamic behaviour. Whenever the natural frequency of a mode of vibration of a structure coincides with the frequency of the external dynamic loading, this leads to excessive deflections and potential catastrophic failures. This is the phenomenon of resonance. An example of a structure failure under dynamic loading was the well-known Tacoma Narrows Bridge during wind induced vibration. In practical application the vibration analysis assumes great importance. For example, vehicle-induced vibration of bridge and other structures that can be stimulate as beams and the effect of various parameters, such as suspensions design, vehicle weight and velocity, damping, matching between bridge and vehicle natural frequencies, deck roughness etc., on the dynamic behaviour of such structure have been extensively investigated by a great number of researchers. Every structure which is having some mass and elasticity is said to vibrate, when the amplitude of these vibrations exceeds the permissible limit, failure of the structure occurs. *Correspondingauthor.Tel.: ;. address:premrajmechanical@gmail.com 2. MODAL ANALYSIS 157

2 A promising approach for developing a solution for structural vibration problems is provided by an advanced numerical discretisation scheme, such as, finite element method (FEM). The finite element method (FEM) is the dominant discretization technique in structural mechanics. The basic concept in the physical FEM is the subdivision of the mathematical modal in to disjoint (non-over lapping) components of simple geometry called finite elements or elements for short. The term Finite Element Method actually identifies abroad spectrum of techniques that share common features outlined in above sections. Two sub classifications that fit well applications to structural mechanics are FEM Formulation Displacement Equilibrium Mixed FEM Solutions Stiffness Flexibility The variants listed above, emphasis is placed on the displacement formulation and stiffness solution. This combination is called the Direct Stiffness Method or DSM. In finite element method frequency of free vibration of knuckle is obtained by using analysis software(altair HYPERWORKS). 3 EXPERIMENTAL ANALYSIS OF VIBRATION 3.1 Experimental Set Up The PULSE software analysis was used to measure the frequency ranges to which the foundations of various machines are subjected to when the machine is running with no load and full load. Experimental set up shown in figure 1.1 Figure 1.1 Experimental Setup of FFT. 158

3 3.2 Equipment Required Model hammer Accelerometer Portable pulse Connectors Model no :: AO 0087D Specimen Display Unit and the Figures 1.2 indicate the signal flow of FFT analyser. Vibrating machine or structure Vibration transducer or pick up Signal conversion instrument Display unit, recorder of computer Data analysis Figure 1.2 Flow Chart of FFT Free Vibration Measurement Scheme Model Hammer The model hammer exists the structure with a constant force over a frequency range of interest. Three interchange tips are provided to determine the width of the input pulse and thus the band width of the hammer structure is acceleration compensated to avoid glitches in the spectrum due to hammer structure resonance. Hammer position was indicated in figure

4 Figure 1.3 Hammer Position Accelerometer Accelerometer combines high sensitivity, low and small physical dimensions making them ideally suited for model analysis. Wax was used to mount the accelerometer on knuckle component brake calliper portion. Generally accelerometer has mass of 4g and 10g, 4g accelerometer was used for better sensitivity Display Unit This is mainly in the form of PC when the excitation occurs to the structure the signals transferred to the portable PULSE and after conversion comes in graphical form through the software. Mainly the data includes graphs of force vs time; frequency vs time resonance frequency data, etc. 3.2 Setup Procedure Steering knuckle Component were placed on damper to avoid other vibrations from ground which is placed on table the connection of the FFT analyser, PC,transducer and model hammer along with the requisite power connection were made as shown in figure The accelerometer (4g) was fixed by wax to strut portion at one of the nodal point The modal hammer was kept ready to strike the knuckle strut portion at the singular points then at each point the modal hammer was struck once and the amplitude Vs frequency graph was obtained from graphical user interface 160

5 Using this method, either one row or one column of the frequency response function matrix is measured. There are three principally identical modifications of the single point excitation method. SISMO (Single Input Single Output) SIMO (Single Input Multiple Output) as shown in Figure 1.4 the connection were made for FFT test Figure 1.4 Connection of FFT Analyser 4 Fast Fourier Transform (FFT) Analyser 4.1 Dual Channel Analysis The basic scheme of dual channel FFT (Fast Fourier Transform) analyser. During a simultaneous analysis of signals in at least two channels, the signals themselves are not in the forefront any more, but rather properties of the physical system responsible for the differences between those signals. The methods can be theoretically expanded to any number of channels, but basically two of them are processed simultaneously each time. 4.2 Auto spectrum Auto spectrum is a function commonly explored both in signal and system analysis. It is computed from the instantaneous (Fourier) spectrum. There is a new fundamental function cross spectrum in the dual channel processing. It is computed from instantaneous spectra of both channels. All other function in the scheme are computed post processing from the cross spectrum and the two auto spectra of course, all function are the function frequency. 161

6 4.3 Cross spectrum Based on complex instantaneous spectra A(f) and B(f), the cross spectrum Sab (from A to B) is defined as. It can be seen that the measured auto spectrum is a sum of the true auto spectrum and auto spectrum of noise, whilst the measured cross spectrum is equal to the true cross spectrum. 4.4 System descriptors when the signals A and B represent input and output of the physical system, frequency response function H(f) in the frequency domain and impulse response function h(t) in the time domain are used to describe the relationship between these two signals. frequency response function are so called system descriptors. They are independent of the signals involved. 4.5 Specification of FFT equipment Software used: RT Pro Photon 6.34 Accelerometer: Model: 3055b4 Ref Sensitivity:49.9 mv/g Controller: Photon + Rating: 5v, 0.5A max Hammer: Model: 5800B4 Ref sensitivity: 9.8/Lb.F 4.6 FFT Analysis Result The First five modes that were top five peak amplitude modes of natural frequency were taken into an account in experimental FFT analysis test. These five modes values when compared with the virtual modal analysis give nearly same result. 162

7 Figure 1.5 Amplitude Vs Frequency Graph SG Iron knuckle 163

8 Figure 1.6 Amplitude Vs Frequency Graph MDI knuckle Due to real time constraints like damping base which hold the knuckle and errors like machine, Manual and homogeneous properties of real component, etc. were the reason for the result variations in experimental test when compared to the virtual values. 5 VIRTUAL ANALYSIS OF STEERING KNUCKLE The general process for a modal analysis consists of Build the model Obtain the solution Review the result 5.1 Build the model The CAD model was created in CATIA V5 and has been imported into HYPERWORKS. The second order element has been chosen because tetra element is more appropriate than the beam element in the modal analysis. The materials properties such as young s modulus, Poisson Ratio and Density were given as input in the software. Table 1.1 SG Iron knuckle Material Properties for Modal Analysis PROPERTIES Young s modulus VALUE 1.6*10^5 N/mm2 Poisson ratio 0.28 Poisson ratio 7200 kg/m3 Table 1.2 MDI knuckle Material Properties for Modal Analysis PROPERTIES Young s modulus VALUE 1.82*10^5 N/mm2 Poisson ratio 0.26 Poisson ratio 7100 kg/m3 5.1 Loading and obtain the solutions Free free vibration analysis steering knuckle model was taken for modal analysis to find out natural frequency. The number of mode twenty has selected and the block Lanczos method was choose for analysis. This method is 164

9 especially powerful when searching for Eigen frequencies is a given part of the Eigen values spectrum of a given systems. The frequency is used to extract n modes beyond the starting values of FREQB, the algorithm extract the n modes at the same speed as it extracts the lowest n modes, 5.2 Review the Virtual Analysis Results After solving the model, the result was viewed from HYPERWOKS. The Figure 5.7 shows the result summary of modal analysis. Totally 20 modes result were obtained from the solution. The range of frequency was 0 HZ to 5000 HZ. Figure 1.7 Results Procedure of Modal Analysis 165

10 Figure 1.8 SG Iron and MDI Knuckle Results of Mode Shape 1 166

11 Figure 5.9 SG Iron and MDI Knuckle Results of Mode Shape 2 Figure 5.10 SG Iron and MDI Knuckle Results of Mode Shape 3 167

12 Figure 5.11 SG Iron and MDI Knuckle Results of Mode Shape 4 Figure 5.12 SG Iron and MDI Knuckle Results of Mode Shape 5 168

13 6 Result and discussion From the twenty mode values, the mode 7 to 11 of five modes were considered and taken into an account. The values of natural frequencies for twenty modes are in the table 5.2 Table1.2 Modal Analysis Natural Frequency Values Modal Analysis Results Frequency (Hz) MODES SG Iron Knuckle MDI Knuckle

14 Table 1.3 Result Comparison of Natural Frequencies Mode Number Natural Frequency (Hz) Value SG iron knuckle Natural Frequency (Hz) Value MDI knuckle FEA Experimental FEA Experimental

15 The virtual analysis result and experimental test results from the free vibration analysis are shown in table 5.4 and the natural frequencies of MDI knuckle is higher when compared to SG Iron knuckle. 7 Conclusions From the free vibration analysis, the virtual and experimental test of SG Iron and MDI knuckle has been analysed. The mode shapes and the natural frequencies values were compared and tabulated for these steering knuckles. From the comparison, the natural frequency of MDI steering knuckle is less than SG Iron knuckle. Topology optimization of the steering knuckle generates an optimized material distribution pattern set of constraints and loads within a given limited design space. 6. References 1.Babu.B, Prabhu.M, Dharmaraj.P, Sampath.R (2014), Stress Analysis On Steering Knuckle Of The Automobile Steering System, International Journal of Research in Engineering and Technology, Vol.3, No.3, PP Chang Yong Songa, Jongsoo Lee.b, (2011), Reliability-based design optimization of knuckle component using conservative method of moving least squares meta-models, Probabilistic Engineering Mechanics Vol. 26, PP Jungang Wu, SiqinZhang,Qinglong Yang (2012), Deformation Effect Simulation and Optimization for Double Front Axle Steering Mechanism,International Conference on Computer Modeling and Simulation Vol.22, PP Khairnar H. P, Mahendra Shelar. L (2014), Design Analysis and Optimization of Steering Knuckle Using Numerical Methods and Design of Experiments,International Journal of Engineering Development and Research Vol.2, No.3, PP Mahesh Sharma.P, DenishMevawala.S, Harsh Joshi, DevendraPatel.A (2014), Static Analysis of Steering Knuckle and Its Shape Optimization,Journal of Mechanical and Civil Engineering Vol. 3, PP

16 6.Nassir S. Al-Arifi, Abu S. Zamani, and Jalaluddin Khan (2011), Billet Optimization for Steering Knuckle Using Taguchi Methodology,International Journal of Computer Theory and Engineering, Vol. 3, No. 4, PP PurushottamDumbre A. K., Mishra V. S (2014), Structural Analysis of Steering Knuckle for Weight Reduction, International Journal of Emerging Technology and Advanced Engineering Vol. 4, No. 6, PP Sharad Kumar Chandrakar, DheerajLalSoni and ShohelGardia (2013) FEA of A Steering Knuckle for Life Prediction, International Journal of Engineering Research and Technology, ISSN Vol. 6, No. 5, PP