A novel approach to modelling and simulating the contact behaviour between a human hand model and a deformable object

A deeper understanding of biomechanical behaviour of human hands becomes fundamental for any human hand-operated Q2 activities. The integration of biomechanical knowledge of human hands into product design process starts to play an increasingly important role in developing an ergonomic product-to-user interface for products and systems requiring high level of comfortable and responsive interactions. Generation of such precise and dynamic models can provide scientific evaluation tools to support product and system development through simulation. This type of support is urgently required in many applications such as hand skill training for surgical operations, ergonomic study of a product or system developed and so forth. The aim of this work is to study the contact behaviour between the operators’ hand and a hand-held tool or other similar contacts, by developing a novel and precise nonlinear 3D finite element model of the hand and by investigating the contact behaviour through simulation. The contact behaviour is externalised by solving the problem using the bi-potential method. The human body’s biomechanical characteristics, such as hand deformity and structural behaviour, have been fully modelled by implementing anisotropic hyperelastic laws. A case study is given to illustrate the effectiveness of the approac

Fabrication, 3d finite element analysis and characterization of an optical passive microsensor

In this work we present the 3D Finite Element Analysis (FEA) of an optical passive microsensor for measuring pressure in biofluids and the simulation of the required characterization setup. Previously, we reported the design and analysis of a prototype where simulations were performed by using the Finite Element Method (FEM) in order to analyze the mechanical behavior of the grating;the results were exported to an optical software for diffraction analysis. The microsensor is based on a deformable diffraction grating made of an elastomeric polymer (PDMS); as the PDMS membrane containing the diffraction grating is subjected to a pressure, its optical properties are varied and an indirect measurement of the pressure is attainable. Now, we report the fabrication and characterization of the optical passive microsensor. The simulation of the setup required for characterization brings many advantages as it enables a rapid understanding of the optical properties of the microsensor without implementing it. Therefore, a correct model of both the optical and the mechanical model accelerates the development-time of the prototype so as to carry out possible re-designs in the future.Fil: Braggio, Luciano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico. Centro de Investigación de Métodos Computacionales; ArgentinaFil: Guarnieri, Fabio Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico. Centro de Investigación de Métodos Computacionales; Argentina. Universidad Nacional de Entre Rios; Argentin

Thermomechanical Stabilities in Automotive Brakes & Clutches Systems

This thesis involves three related topics in the area of thermal stress resulting from sliding contact of frictional materials. These three contributions collectively and the discussion of them herein form a collective basis furthering the research and understanding within this field. Firstly, the effect of convective cooling on thermoelastic instability is evaluated using finite element analysis involving insertion of a thermal convection term in the formula for frictional heat generation. It has been found that convection or radiation heat dissipation can stabilize the thermal-mechanical feedback process, leading to a raised critical sliding velocity. Two representative models for brake and clutch systems are studied. The computational results reveal that the effect of thermal convection on critical sliding speed is significant for liquid cooling, but negligible for air convection. With a practical range of convection coefficients estimated from fundamental heat transfer theories, critical speed in the presence of convection can be doubled or tripled. However, the wave number for the lowest critical speed remains nearly unchanged regardless of convective dissipation. Comparisons between linear and quadratic finite element interpolations are also made via a set of convergence studies. The results show that implementing quadratic elements in the friction layer has an obvious advantage over implementing linear elements due to rapidly-oscillating temperature-variations across the thermal skin layer. This is particularly important for future studies when higher-dimension problems are of interest. Secondly, a finite element model is developed for the fractionally excited thermoelastic instability problem in intermittent sliding contact with finite geometries and realistic friction materials. Existing analytical solutions are used to validate the method in several limiting cases. It is concluded that some caution must be taken for the commonly-used strategy of assuming time-averaged, frictional heat generation for intermittent contact. Predictions made by half-plane analytical solutions that assume thermally-nonconductive, rigid frictional surfaces considerably overestimate dimensionless critical speeds of realistic brake and clutch systems. Long wavelength perturbations become unstable at a dimensionless sliding speed approaching zero, which opposes the convergence of two unity in half-plane solutions. Averaging the heat input over the entire circumference is appropriate only when the period of frictional contact is longer than that of separation. These results merit the use of finite element analysis in more general applications involving intermittent contact. Thirdly, in the automotive world, the usage of sliding-disk mechanical systems that produce friction has ever led engineers to address problems regarding friction, heat, and distortion of materials, particularly friction discs themselves, with many examples found when disassembling working systems. Engineers have witnessed the phenomenon of thermal buckling, the conditions of which are analyzed herein from the perspective of moments that lead to buckling. Various parameters of system configuration, geometry, and graphical analyses based on theoretical calculations of buckling potential are considered. Distribution of temperature as a system parameter is given particular importance. It is our belief that these three contributions each provide further understanding of their respective domains while their results and their implications provide bases from which future research can be based to further a more unified understanding

A Non-Equilibrium, Pressure-Pressure Formulation for Air-Water Two-Phase Flow and Heat Transport in Porous Media

The detection of trace explosives in the subsurface is an active area of research for landmine detection. Understanding the air-water flow and heat transport phenomena in the subsurface plays an important role in improving chemical vapor detection. Implementing a finite element method that accurately captures water vapor transport in the vadose zone is still an open question. A non-equilibrium, pressure-pressure formulation has been implemented based on Smits, et al [22]. This implementation consists of four equations: a wetting phase (water) mass balance equation, a non-wetting phase (air) mass balance equation, a water vapor transport equation, and a heat transport equation. This work will compare two implementations, a fully coupled approach and an operator splitting approach for the water vapor and heat transport equations. The formulation of the methods will be presented and the methods will be tested using collected data from physical experiments

Spectral/hp element methods: recent developments, applications, and perspectives

The spectral/hp element method combines the geometric flexibility of the classical h-type finite element technique with the desirable numerical properties of spectral methods, employing high-degree piecewise polynomial basis functions on coarse finite element-type meshes. The spatial approximation is based upon orthogonal polynomials, such as Legendre or Chebychev polynomials, modified to accommodate C0-continuous expansions. Computationally and theoretically, by increasing the polynomial order p, high-precision solutions and fast convergence can be obtained and, in particular, under certain regularity assumptions an exponential reduction in approximation error between numerical and exact solutions can be achieved. This method has now been applied in many simulation studies of both fundamental and practical engineering flows. This paper briefly describes the formulation of the spectral/hp element method and provides an overview of its application to computational fluid dynamics. In particular, it focuses on the use the spectral/hp element method in transitional flows and ocean engineering. Finally, some of the major challenges to be overcome in order to use the spectral/hp element method in more complex science and engineering applications are discussed

Hazards and incident investigation at palm oil mill industry

Occupational Safety and Health Act (OSHA) is a discipline with broad scope involving many specialized fields. This research was conducted to determine the relationship between the hazards occurring and the control measures to overcome the hazards occur in the Palm Oil Mill located at Ulu Keratong, Segamat, Johor. Nowadays, the workers are lack of safety and health practice from their companies based on the statistics that have shown the number of fatality and permanent disablement cases due to the accident in the palm oil mill. Which causes the accidents and injuries happened due to management control that does not emphasized on the safe practise of workers. Information and data collection were carried out by using HIRARC Form and Preliminary Hazard Analysis (PHA) in the Palm Oil Mill RISDA which will be further discuss in the methodology part. The main objective of this study is to promote adaptable occupational environment and suggest some countermeasures to solve the potential hazard and the consequent responsibilities relevant to professional engineering practice. There were seven hazards have been identified such as crash by rotating machine, struck by heavy palm fruit and slippery floor, excessive heat, excessive pressure of tractor tire, chemical spillage and noise hazard. From the result and findings, the hazards and control measures identified are able to determine improvements in knowledge and risk perceptions among the workers and visitors towards health policies and essential interventions for hazard prevention. Effective job safety and health programs help reduce worker injuries and illness in the long term

A hysteretic multiscale formulation for nonlinear dynamic analysis of composite materials

This article has been made available through the Brunel Open Access Publishing Fund.A new multiscale finite element formulation is presented for nonlinear dynamic analysis of heterogeneous structures. The proposed multiscale approach utilizes the hysteretic finite element method to model the microstructure. Using the proposed computational scheme, the micro-basis functions, that are used to map the microdisplacement components to the coarse mesh, are only evaluated once and remain constant throughout the analysis procedure. This is accomplished by treating inelasticity at the micro-elemental level through properly defined hysteretic evolution equations. Two types of imposed boundary conditions are considered for the derivation of the multiscale basis functions, namely the linear and periodic boundary conditions. The validity of the proposed formulation as well as its computational efficiency are verified through illustrative numerical experiments