Dynamic Behavior of Three-wheeled Vehicle Under Random Road Characteristics Using FEM
In general three wheelers are one of the most popular city transport vehicles in the world and particularly in developing countries especially for short hauls. In the present work finite element model of three wheeled motor vehicle chassis has been developed using ANSYS software by taking into account the chassis longitudinal/cross members, the suspensions, the axles and the tires. Modal analysis is carried on the three wheeled motor vehicle chassis using Block Lanczo's technique to obtain the natural frequencies and mode shapes. Vertical dynamic response of the three wheeled motor vehicle chassis has been carried in the frequency domain by performing the spectrum analysis using ANSYS software. When the vehicle moving at 45 kmph on different Indian and International roads, and the response is obtained at four significant points i.e. at node 2 (rear part of the chassis sprung mass), at node 8 (passenger seat position), at node 657 (rear axle) and at node 34 (steering position). The response i.e. power spectral density of acceleration is compared between the Indian and International roads and different modes which affect the passenger comfort are also discussed using spectrum analysis. Parametric study has also been carried out using the finite element model to study the effect of various parameters and to find the optimum values both quantitatively and qualitatively, in the ride response of the vehicle. Finally based on the above analysis certain recommendations are made about manufacturer point of view.
Power Spectral Density Analysis of Vehicle Vibration Using the NASTRAN Computer Program
Frequency response and power spectral density analyses are implemented on the NASTRAN computer program for the purpose of assessing the vibratory response of automotive vehicles. A review of theoretical concepts related to the frequency domain techniques is presented, followed by a derivation of the equations of vertical motion for a linearly elastic automotive vehicle. Special emphasis is given to the discussion of random loading, and the cross-spectral density matrix for the terrain input to a four-wheel vehicle is derived. Example calculations are performed for a compact-size vehicle exposed to moderately severe road roughness.
The NASTRAN computer program for structural analysis
Abstract NASTRAN is a large digital computer program for static and dynamic structural analysis by the finite element approach. It is nearing completion after three years of development under NASA sponsorship. It will be made available to all interested users and it will be maintained by NASA. It is currently programmed for the IBM 360, the UNIVAC 1108, and the CDC 6600 computers. The major functional capabilities of NASTRAN are static analysis of structures with either linear or nonlinear material properties; buckling analysis; vibration modes analysis of either conservative or damped systems; frequency response analysis; and transient response analysis. Many convenience features are provided to the user including an extensive list of structural elements; the automatic generation of several types of loads including gravity loads and loads induced by thermal strains; plots of deformed and undeformed structures; and the choice of alternate methods of analysis, including, for example, either direct or modal formulations of dynamic problems. NASTRAN is intended primarily for large problems with hundreds or thousands of degrees of freedom. All mathematical subroutines have been designed to provide for the efficient solution of large problems by taking maximum advantage of matrix sparsity and bandedness. A flexible Executive System is provided that facilitates the addition of new functional capabilities to NASTRAN.