SSRG International Journal of Mechanical Engineering (SSRG-IJME) – Volume 7 Issue 2 – Feb 2020 ISSN: 2348 – 8360 www.internationaljournalssrg.org Page 26 Modelling the Car Seated Human Body using Composite Ellipsoidal Bodies and Evaluation of Size and Shape Specific Stiffness Data for Various Human Segments Purnendu Mondal #1 , Subramaniam Arunachalam *2 # Doctoral Researcher, School of Architecture, Computing and Engineering, University of East London, (Docklands Campus), London, E16 2RD, UK * Senior Lecturer, School of Architecture, Computing and Engineering, University of East London, (Docklands Campus), London, E16 2RD, UK Abstract Automobile is one of the primary modes of worldwide transport system, which must offer highest level of health, safety and comfort levels for the occupants inside. Health, safety and comfort of any moving vehicle and its human occupants are mainly characterized by the level of the vibration generated inside the human body. With the development of modern computer based technologies, over last few decades computerized simulations have been gaining huge importance to anticipate the level of vibration generated inside the automotive seated human body. Many simulation based research works had been conducted in past to predict the effect of vibration inside automotive-human assembly, though one of the key parameters to define the simulation set up, namely stiffness values of different human segments; had been collected from past relevant research studies or available testing data resources, which overlooked the real shapes and sizes of the human portions, hence, lacking the practical feasibility. In this research paper, a simplified car seated human made of ellipsoidal segments has been proposed. The segmental dimensions and masses have been extracted from anthropometric database and later, the formulations for composite fibre-matrix configuration have been implemented. A systematic approach has been outlined to evaluate the three- dimensional stiffness values for all the human portions. The obtained stiffness values have been validated by comparing to the data obtained from similar kind of investigations and test results. Keywords — Ellipsoidal human segment, car seated human driver, three dimensional stiffness, computerized Simulation, human size specific stiffness. I. INTRODUCTION As the modern technologies evolved, computer based simulation methods for monitoring, assessing and measuring the effects of vibration inside automotive seated human portions became popular in last few decades. Depending on the nature of study, either lumped mass parameter, multi-body or finite element method is used to judge the level of vibration in terms of frequency, acceleration or displacement. Each of the methods got its own pros and cons and numerous combinations of input factors, portions of interest and output results can be taken into account while carrying out an effective simulation methodology, however, one of the inevitable and common input parameters for the past explorations have been identified as stiffness values of human segments. Automotive rear impact was analyzed using a bio-dynamic human model in MSC Visual Nastran 4D-2001 environment [1], where the seating postures were assigned based on a real life photograph of a car seated human body. The same study further explored the structure by assigning the contact mechanism between the automotive seat and human body by splitting the mating areas into rectangular or trapezoidal shapes, though was restricted to allow only a single frictional co-efficient value for all the portions. To, model the entire simulation with more reasonable frictional coefficients, the structure was taken to MATLAB environment, which was able to simulate the torso, back and buttocks of human body. The investigation recorded the simulation outputs at 50th ms, 89th ms, 100th ms, 150th ms, 200th ms, 250th ms and 300th ms. The entire course of analysis work used the stiffness values of human torso joints from BMH model and Bourdet-Willinger model. Bio- dynamic numerical algorithms were generated for the seated human body [2] under the effect of vertical vibration by considering four and seven degrees of freedom models and assuming hypothetical stiffness parameters from standard database. Research work on the vertical vibration [3] used the spring-dashpot system for vibration transmission and stated that the damping and stiffness values of the automotive seat cushion would be the major defining parameters for