L. V. V. Gopala Rao

Under low-frequency excitation, the human subject is highly sensitive to Whole Body Vibrations (WBV). In the present paper, a biodynamic human model is seated posture without backrest support and also with backrest support at different angles (i.e., 0°, 15° and 30°) is formulated to analyse the influences of the frequency and the magnitude of the vibration, backseat support and the angles of inclination of the backseat support on Seat To Head Transmissibility (STHT) of the biodynamic human subject in seating position exposed to WBV. The model parameters such as damping, mass and stiffness of the mathematical model considered in this paper are derived from an alternate methodology which is based on anthropometric data. The STHT is computed analytically with the help of MATLAB software for all the considered cases. The effect of vibration and excitation frequencies on STHT is analysed. The results of STHT evaluated from this work are justified by comparing the same with the mean STHT characteristics reported in past studies and the results of the present analysis come out to be in good agreement with past published research.

The work presents the Finite element study of the effect of elliptical chords on the static and dynamic strength of tubular T-joints using ANSYS. Two different geometry configurations of the T-joints have been used, namely Type-1 and Type-2. An elastic analysis has been considered. The Static loading conditions used are: axial load, compressive load, In-plane bending (IPB) and Out-plane bending (OPB). The natural frequencies analysis (dynamic loading condition) has also been carried out. The geometry configurations of the T-joints have been used, vertical tubes are called brace and horizontal tubes are called chords. The joint consists of brace joined perpendicular to the circular chord. In this case the ends of the chord are held fixed. The material used is mild steel. Using ANSYS, finite element modeling and analysis of T-joint has been done under the aforementioned loading cases. It is one of the most powerful methods in use but in many cases it is an expensive analysis especially due to elastic–plastic and creep problems. Usually, three dimensional solid elements or shell elements or the combination of two types of elements are used for generating the tubular joints mesh. In tubular joints, usually the fluid induced vibrations cause the joint to fail under resonance. Therefore the natural frequencies analysis is also an important issue here. Generally the empirical results are required as guide or comparison tool for finite element investigation. It is an effective way to obtain confidence in the results derived. Shell elements have been used to model the assembled geometry. Finite element ANSYS results have been validated with the LUSAS FEA and experimental results, that is within the experimentation error limit of ten percentage.

In this paper, the control of the stationary random response of a two degree of freedom (DOF) quarter car vehicle model traversing a homogenous rough road with skyhook damper control strategy is considered. The parameters of the skyhook damper, namely the damping coefficient and the constant which determines the extent of the skyhook damper participation are optimally determined. The skyhook damper control strategy is realised through a feedback control scheme. The optimal parameters of the skyhook damper are determined by equating the control force of the feedback system to that obtained by linear quadratic regulator (LQR) stochastic optimal control in a mean square equivalence sense. The random road profile is modelled as the output of a second-order linear spatial filter to white noise, which takes into account the effect of the rolling contact of the tyre with the road. The average behaviour of the system is described by the zero-lag covariance matrix of the response state vector. In the LQR control the vehicle suspension is optimised to improve the vehicle performance given by a performance index which is a weighted integral of the mean square acceleration, suspension stroke, road holding and control force.