Mir Hamid Reza Ghoreishy

Three-dimensional Finite Element Modeling of Rubber Curing Process

This paper describes the development of a finite element model for the simulation of the rubber curing process in a mold. Thermal conductivity and heat capacity of the rubber are assumed to be dependent on temperature. The cure kinetic behavior of the rubber is also assumed to be described by an empirical model proposed by Kamal and Sourour. The governing equation is solved using the finite element method in a three-dimensional Cartesian coordinate system. The applicability of the model is verified by a comparison between the results of the simulation of the vulcanization of a rubber part in the mold with experimentally measured temperature profile. It has been shown that there is very good agreement between the model predictions and the actual data.

Modeling the transient flow of rubber compounds in the dispersive section of an internal mixer with slip-stick boundary conditions

The aim of this article is to describe the development of a mathematical model for the simulation of the flow of polymer melts inside internal mixers. The rheological behavior of the polymeric fluid is assumed to be described by the Carreau equation. The flow regime is considered to be non-isothermal. The set of the governing equations are solved using the finite element method for both steady-state and transient conditions. In the steady-state case, the flow equations are solved by the penalty method using the standard Galerkin technique. Petrov-Galerkin schemes based on both consistent and inconsistent streamline upwinding methods are employed to solve the energy equation and the obtained results are compared. Transient velocity, pressure, and stress fields are modeled using implicit θ method. In addition to implicit θ method, two versions of the Taylor-Galerkin approach are used to solve the transient energy equation. Slip-stick on the solid walls, encountered in the flow of viscous fluids, is incorporated in the model by the use of Naviers slip conditions. We describe two new methods for the inclusion of this condition in the working equation. Our simulations yield the velocity field, distribution of pressure, stress and temperature in the steady state and the variations of these parameters with respect to time under transient conditions. As an example of the applicability of the developed model, a typical mixing problem which involves convection of carbon black with flowing rubber in a domain representative of the section under the blade of a tangential rotor mixer is simulated. Concentration profiles of carbon black in the rubber matrix in this case is obtained by the solution of carbon mass continuity equation in conjunction with the flow model. This solution gives the distribution of filler volume fraction at different mixing times in the mixer. Comparison of the obtained results with the available experimental data gives some indication of the validity of the model.

Oxidative coupling of methane in a fixed bed reactor over perovskite catalyst： A simulation study using experimental kinetic model

Abstract The oxidative coupling of methane (OCM) to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separate energy equations for the gas and solid phases coupled with an experimental kinetic model. A lumped kinetic model containing four main species CH4, O2, COx (CO2, CO),and C2 (C2H4 and C2H6) was used with a plug flow reactor model as well. The results from the model agreed with the experimental data. The model was used to analyze the influence of temperature and feed gas composition on the conversion and selectivity of the reactor performance. The analytical results indicate that the conversion decreases, whereas, C2 selectivity increases by increasing gas hourly space velocity (GHSV) and the methane conversion also decreases by increasing the methane to oxygen ratio.

Morphology and dynamic-mechanical properties of PVC/NBR blends reinforced with two types of nanoparticles

This article relies on the effect of two types of nanoparticle on morphology and dynamic-mechanical properties of polyvinyl chloride (PVC)/acrylonitrile butadiene rubber (NBR) blends. The results of mechanical investigation revealed that tensile strength and modulus of PVC/NBR nanocomposites reinforced with 1 phr of single-walled nanotube (SWNT) are very close to the case of reinforced with 5 phr of nanoclay. The outcomes of dynamic-mechanical properties revealed that the storage modulus increases with the addition of nanoparticles and the intensity of tan δ get reduced, in two cases. Morphological investigation of nanocomposites was determined by scanning and transmission electron microscopy. In the case of PVC/NBR/nanoclay, fracture surface of specimens were much rough while the fracture surface of virgin PVC/NBR was very smooth. In PVC/NBR/SWNT nanocomposites, with introducing of carbon nanotubes to polymer matrix, dispersion and distribution of NBR as minor phase in PVC as matrix got improved.

PP/EPDM Blends and their Developments up to Nanocomposites

In this article a review is presented of studies on polypropylene and ethylenepropylene-diene terpolymer nanocomposites, reported in the period from 1970 to 2007. The article has two major parts; first it discusses TPVs made up of a thermoplastic and a volcanizable elastomer, and second it explains about nanocomposite technology and its remarkable effects on the properties, morphology, and applications of TPVs.

Finite element analysis of steady rolling tyre with slip angle: effect of belt angle

Abstract The purpose of the present research was to study the effect of different belt angles on the steady state rolling behaviour of a steel belted radial tyre with slip angle. To achieve this goal, a finite element model has been developed using ABAQUS computer software. The simulation started with an axisymmetric model to analyse the tyre under inflation pressure. Then a full 3D model was generated to model the tyre under static vertical load. Having obtained the tyre configuration under contact load, a steady state rolling analysis was conducted using a mixed Lagrangian/Eulerian technique. The final stage of the modelling was the inclusion of the slip angle in the model. Each set of simulations was repeated for three belt angles and the effect of the belt angle variation on the tyre structural variables, including contact pressure and area, lateral force, interlayer shear stress and total strain energy was examined. In addition, the computed value of the number of revolutions per kilometre was compared with experimentally reported data which confirms the accuracy of the present model.

The Effects of Silica/Carbon Black Ratio on the Dynamic Properties of the Tread compounds in Truck Tires

NR is the major constituent in the rubber compound used for the tread on the truck tires. A general compound formulation of the tire tread includes NR and BR as polymer base and carbon black as the reinforcing filler, and curative components. In this paper the effects of dual filler system (carbon black and precipitated silica) on the dynamic properties of tire treat has been studied. The results show by increasing of precipitated silica, significant improvement was observed in fatigue resistance, rolling resistance and heat buildup of the tire. Tensile strength and modulus and wet grip of tire tread decrease with increasing of silica in rubber compound formulation.

Steady State Rolling Analysis of a Radial Tyre: Comparison with Experimental Results

Abstract This research paper is devoted to the description of a finite element model for the numerical study of a radial tyre under steady state rolling condition. The finite element model was developed using the commercial computer software ABAQUS. The simulation started with an axisymmetric model to analyse the tyre under inflation pressure load. Then a full three-dimensional model was generated for the modelling of the tyre under static vertical load. Having obtained the tyre configuration under contact load, a steady state rolling analysis was conducted using a mixed Lagrangian/Eulerian technique. In this stage, a constant ground velocity was assumed and the spinning velocity was changed to find the free rolling speed of the tyre. The computed loaded dimensions of the tyre in both static and dynamic situations were also compared with experimentally measured data for three commercial tyres available on the market. The comparison verified the validity and applicability of the proposed model. In addition, the distributions of pressure and frictional shear stress fields at the contact zone are presented and discussed.

Chemical and physical properties of self-crosslinked poly(vinyl chloride)/nitrile rubber nanocomposites prepared by melt-mixing process

Abstract In this article, poly(vinyl chloride) (PVC)/acrylonitrile butadiene rubber (NBR)/clay nanocomposites were melt-mixed using the computerized Brabender plasticorder. During preparation of the nanocomposites self-crosslinking (crosslinking without aid of any crosslinking agent) occurs and affects all properties of a sample. The extent of crosslinking reaction depends on the processing temperature, rotor speed and mixing temperature and it increased with increasing each of mixing parameters. The mechanism of the self-crosslinking reaction was examined by the Fourier transform infrared spectroscopy test. The morphology of the materials was characterized using X-ray diffraction and scanning electron microscope. The swelling test and tensile test were applied to distinguish the effects of self-crosslinking phenomena on physical properties of NBR/PVC nanocomposites. Dynamic mechanical thermal analysis tests of nanocomposites were also performed to study the physical properties, such as glass transition temperature (T g). The results showed that the crosslinking reaction made a material more strong with high modulus and tensile strength. Thus, it can be deduced that crosslinks convert the NBR/PVC nanocomposites to stiffer materials that are less penetrable by the solvent. The results drawn from the loss tangent (tan δ) curves of nanocomposite samples can be used as further evidence for the above conclusions.

Finite element analysis of flow of thermoplastic elastomer melt through axisymmetric die with slip boundary condition

Abstract A finite element model for the flow of thermoplastic elastomers in extrusion dies has been developed. The rheological behaviour of the polymer melt is assumed to be described by the generalised Newtonian models and as a special case, the well known, power law equation was selected. Owing to the very low variation of the temperature field, the flow regime was considered to be isothermal. The set of governing equations are solved using the finite element method in a cylindrical (r, z) coordinate system. Slip–stick of the polymer melt on the solid wall, encountered in the flow of highly viscous fluids, is incorporated into the model by the use of Naviers slip condition. A new method based on a technique developed previously is described for the inclusion of this condition in the working equations. The applicability of the model was verified by a comparison between the results of the simulation of a polypropylene–nitrile/butadiene rubber thermoplastic elastomer with experimentally measured data. These comparisons show that there are very good agreements between the model predictions and actual data, provided that the slip of the polymer melt during the flow in extrusion die has been taken into consideration.