Fernando M.,Tun Abdul Razak Research Center |
Fei W.H.,Rubber Technology Center |
Hull C.,Tun Abdul Razak Research Center
Rubber Chemistry and Technology | Year: 2012
Curing rubber is a complex process that involves the insertion of cross-links to convert the rubber into a useful functional material. The estimation of the cure time needed for product manufacture of small or thin walled products is often arrived at by means of a rheometer trace. Although this has been recognized as adequate for thin walled products, the production of large rubber articles requires a more rigorous analysis of cure kinetics for an essentially non-isothermal process. Often finite element analysis is used to generate non-isothermal temperature histories in a thick component, and then an appropriate cure kinetic equation is solved to predict the state of cure. In addition to generating the capability for cure time prediction, there is a need in the industry to minimize cycle time, improving productivity and therefore costs involved in product manufacture. For large products, the viability of the use of extrusion molding, where the rubber is extruded into a heated mold at the same temperature as the mold, has been demonstrated in previous reported work in this laboratory. The present work explores, via simulation, the feasibility of using extrusion molding as a manufacturing method for large components. The cure simulation module of Autodesk Moldflow has been used to compare the state of cure of a laminated bearing manufactured by conventional compression molding and extrusion molding. Previous experimental data on the temperature histories of a large laminated bearing manufactured using compression molding are compared with simulation data. Simulation data are then presented on manufacturing the bearing using extrusion molding. The aim is to demonstrate the usefulness of extrusion molding for very large components and to illustrate the advantages of using simulation codes to assist in shortening the cycle time in product manufacture.
Dona M.,University of Padua |
Muhr A.H.,Tun Abdul Razak Research Center
Constitutive Models for Rubber IX - Proceedings of the 9th European Conference on Constitutive Models for Rubbers, ECCMR | Year: 2015
The Rolling Ball Rubber Layer (RBRL) earthquake isolation system, described by Dona et al. (2015a), is intended to have isotropic force-displacement behaviour in the horizontal plane. As with all earthquake isolation systems, time-history analyses are required for assessment of performance during strong ground motion excitation, for which a time-domain model is essential. A simplified preliminary analytical biaxial model is proposed, motivated by experimental results together with observed physical effects and the viscoelastic nature of rubber. © 2015 Taylor and Francis Group.
Roberts A.D.,Tun Abdul Razak Research Center
Materials Science Forum | Year: 2011
This review describes early work on rubber wiper blades and subsequent investigations. Observations on model wipers pressed against glass showed that the dry contact width was greater than that predicted by the classical Hertz equation, due to adhesion. That led to the establishment of the JKR equation to account for the adhesion. Although originally intended for 'soft' contacts, the equation now finds wide use. Surprisingly, the boundary lubrication aspects of the work revealed the action of repulsive forces that could be directly measured between rubber and glass in the presence of water. The quality of lubrication is subject to the acidity/alkalinity of the water. © (2011) Trans Tech Publications.
Roberts A.D.,Tun Abdul Razak Research Center
Rubber Chemistry and Technology | Year: 2014
Research on rubber wiper blades led to the establishment of the now widely used Johnson, Kendall, Roberts (JKR) equilibrium equation that determines the strength of adhesion between surfaces. The equation was adapted to allow for the viscoelasticity of rubber, leading to explanations of how adhesion can impact on tack; rebound resilience; and rolling, static, and sliding friction. The adhesion of rubber to ice was found to depend on salt concentration in the ice, thus providing insight into winter tire performance. The development of optical techniques has greatly aided studies, particularly for measuring the thickness of thin liquid films sandwiched between rubber surfaces. Measurements on water films squeezed between rubber and glass revealed the action of repulsive surface forces that can reduce adhesion and friction. The efficacy of water lubrication depends upon whether surfactants are present and upon the acidity or alkalinity of the water. Improved understanding of adhesion and friction mechanisms offers design guidance for a range of rubber articles. © 2014, Rubber Division of the American Chemical Society. All rights reserved.
Ahmadi H.R.,Tun Abdul Razak Research Center |
Muhr A.H.,Tun Abdul Razak Research Center
Rubber Chemistry and Technology | Year: 2011
A relatively simple time-domain model is proposed with the scope to capture those aspects of the uniaxial stress- strain behavior of filled rubber that are most significant in engineering applications, and is discussed in the context of a literature review. Its performance is investigated in simple shear using analytical expressions. Attention has been given to assembling the model from separate physical contributions, each already established in the literature, so that not only is the number of parameters small but also they may be at least semi-quantitatively related to the formulation of the elastomer. The small number of parameters helps to keep tests for fitting them simple, while their connection to mechanisms also enables a degree of utility of the model even when extrapolated to situations beyond those covered by tests.
Karbakhsh Ravari A.,University of Malaya |
Bin Othman I.,University of Malaya |
Binti Ibrahim Z.,University of Malaya |
Ab-Malek K.,Tun Abdul Razak Research Center
Journal of Structural Engineering (United States) | Year: 2012
Seismic isolation systems constitute an accepted and simple technique for earthquake protection of structural systems and sensitive components. This approach has considerable potential in preventing the structures and their equipment from earthquake destruction. For predicting the behavior of an isolation bearing, Haringx's theory is usually employed. According to this theory, the mechanical properties of an elastomeric isolation bearing can be predicted and described. Many investigators have proposed a nonlinear, mechanical model for multilayer elastomeric bearings. However, in previous theoretical and experimental studies, the effects of initial rotation at the ends of the bearings have been neglected. In this study, Haringx's theory is extended and an analytical method is presented by considering the initial rotations of the upper and lower ends of multilayer rubber bearings as new boundary conditions. Three boundary conditions have been considered for modeling the elastomeric isolation bearing: (1)equal rotation at the bottom and top end of a bearing, (2)rotation only at the bottom end, and (3)rotation only at the top end of a bearing. According to these boundary conditions, variations of the lateral displacement and interior rotation of the laminated rubber bearings are obtained. The variations of horizontal stiffness, internal bending moment, and interior shear force of the bearing have also been presented. Examples are presented to demonstrate the validity of the development method in predicting the mechanical properties of elastomeric bearings with specified geometric parameters. The results of this study have shown that initial rotation as a boundary condition will change the mechanical properties of the laminated rubber bearings. © 2012 American Society of Civil Engineers.
Agency: GTR | Branch: Innovate UK | Program: | Phase: Innovation Voucher | Award Amount: 5.00K | Year: 2014
Tun Abdul Razak Research Center | Date: 2014-11-11
Rubber compounds comprising one or more rubber with polar functionality and one or more polar filler are prepared by a method comprising the steps: (i) adding a polar volatile liquid to the polar filler; (ii) mixing the one or more rubber with polar functionality with the polar volatile liquid and polar filler to produce a dispersion of the polar filler in the one or more rubber, and (iii) removing the polar volatile liquid from the dispersion. The invention Improves the consistency and uniformity of mixing of rubber compounds based on elastomers having polar functionality, such as epoxidized natural rubber, containing polar reinforcing fillers, such as precipitated silica, The compounds, when vulcanized, have improved mechanical properties. The method is particularly useful in the manufacture of vehicle tyres.
Tun Abdul Razak Research Center | Date: 2012-07-20
A bearing preset system for inhibiting movement of bearings in a construction comprises a first plate (1) having an upper and a lower surface wherein the upper surface (3) of the first plate is adapted for mounting onto and being secured to a lower surface of a first bearing member and a second plate (2) having an upper and a lower surface wherein the lower surface (5) of the second plate is adapted for mounting onto and being secured to an upper surface of a second bearing member and wherein the conformation of the lower surface (7) of the first plate and the conformation of the upper surface (9) of the second plate are such as to prevent movement in at least one shear direction between the first and second plates.
Tun Abdul Razak Research Center | Date: 2014-09-05
A rubber part for use as a structural component for incorporation into a brick or masonry wall structure in a reinforced concrete frame, to be located within the plane of the wall, has a length x and a stiffness along its length of S_(x), a width y and a stiffness across its width of S_(y), and a thickness z and a stiffness across its thickness of S_(z), the stiffness of the part being anisotropic with S_(y)>S_(x). The part is adapted such that, when in use, it is capable of controlling vibrations of the wall caused by seismic activity and also of having a damping effect thereby increasing the energy dissipation capacity of the structure. The rubber part is preferably in the form of a sheet and can be laminated on one or both major surfaces. The two major surfaces of the sheet may be contoured, for instance being corrugated across its width.