International Journal of Research in Engineering and Innovation Vol-1, Issue-1 (May-2017), 6-11 ____________________________________________________________________________________________________________________________ International Journal of Research in Engineering and Innovation (IJREI) journal home page: http://www.ijrei.com ISSN (Online): 2456-6934 ___________________________________________________________________________________ Corresponding author: Arshad Mehmood 6 Email address: Arshad10.07@gmail.com Vibration analysis and response characteristics of a half car model subjected to different sinusoidal road excitation Arshad Mehmood Department of Mechanical Engineering, College of Engineering/ University of Buraimi, OMAN ______________________________________________________________________________________________________________ Abstract The displacement response of different masses of half car model. The analysis has been done for different car models also to see the dynamic response of the driver body coupled with the seat of a vehicle. It has been assumed the driver body is rigidly coupled with seat of the vehicle. The vehicle has been modeled for two D.O.F, in two D.O.F Half car model two motion (Pitch and Bounce) have been considered. The response of the vehicle has been obtained for different velocities and different amplitudes sinusoidal bump excitation. © 2016 ijrei.com. All rights reserved Key words: Half car Model, Degree of Freedom, Model development, Lagrange equation ___________________________________________________________________________________________________ 1. Introduction This paper deals with the dynamic characterization of an automotive shock absorber, a continuation of an earlier work Vibration is undesirable, not only because of the unpleasant motion, the noise and the dynamic stresses, which may lead to fatigue and failure of the structure, but also because of the energy losses and the reduction in performance which accompany the vibrations [1-2]. Vibration analysis should be carried out as an inherent part of the design because of the devastating effects, which unwanted vibrations could have on machines and structures. The shock absorber is one of the most important elements in a vehicle suspension system. It is also one the most non-linear and complex elements to model. The current method of characterizing the dynamic properties of shock absorbers for CAE models involves testing at discrete frequencies, displacements, and preloads using an MTS test machine. The dynamic stiffness (K) and damping (C) are extracted by fitting a linear model of the form F(w)=K*x(w)+C*v(w) to the measured input displacement (x), velocity (v), and output force (F). The excitation technique is a pure sine excitation at the desired frequency and amplitude. These harmonic excitations are then swept through all desired frequency and amplitudes. First, it is commonly understood and accepted that human response to dynamic excitation depends on many mechanical, physical, physiological and psychological parameters [3]. The biodynamic response characteristics of seated occupants influenced by several factors, among which body posture, body weight and vibration excitation type and amplitude probably represent the most influential parameters [4]. Half car has been modelled as two DOF systems, in which bounce and pitch motion has been considered, the driver body and vehicle body has considered as one mass. The mathematical analysis of the suspension system has been performed to develop the model. Dynamic analysis has been performed, for solving the half car model. The goal of this study was to determine if the current excitation technique holds true when more than one frequency is present. In recent years, commercial demand for comfortable and quiet vehicles has encouraged the industrial development of methods to accommodate a balance of performance, efficiency, and comfort levels in new automobiles. Particularly, the noise, vibration, and harshness (NVH) characteristics of cars and trucks are becoming increasingly important [5]. 2. Mathematical Modeling 2.1 Half Car Model: Two Degree of Freedom The vehicle mass is set at 750kg, and the mass of human body is assumed to be 55.2kg coupled with the vehicle body. It has a moment of inertia about the center of mass of