bluuebunny/crossref_metadata_2025 huggingface dataset:
Rural development limitations at the transitional terms
Authors: Nikolic Marija , Maksin-Micic Marija
Published: June 2006

European countries have been reaffirtmating the role and the significance of agricultural multifunctionality for rural areas development. The transition countries have to make the assessment of their weaknesses and opportunities before facing the necessary significant investments in agriculture, rural settlements and deprived rural areas. Overall economic development should provide for further agriculture employment reduction, along with taking measures for the agriculture farms modernization and changes in the structure of agriculture production, within the process of integrated rural development. Declining population at mountain areas might be a prerequisite for intensified farm restructuring, namely through development reorientation, achieving more balanced agriculture economy, along with rediscovering comparative advantages in the development of new activities linked to social changes and changes in lifestyle - green tourism, leisure activities, health care, as well as to forestry, traditional crafts etc. Subsequent to European experience in maintenance of the necessary level of spatial development in sparsely populated and neglected rural areas, the development of priority mountain areas in Serbia should be defined at national level, and the new system of support should facilitate the preparation and the implementation of different projects for integrated rural development of this priority areas.
Central bank and the monetary commitment
Authors: Jaksic Miomir
Published: June 2006

The central bank as the key monetary institution has to assure monetary policy credibility, which is of vital importance in the process of macroeconomic stabilization. The author analyses the concepts of central bank independence and accountability as a basis for successful macroeconomic policy, and the concept of monetary commitment which is of essential importance for monetary regime and formulation of monetary rules.
Logika preferencija na grubim i rasplinutim skupovima
Authors: Boricic Branislav , Konjikusic Snezana
Published: June 2006

Theories of fuzzy sets and rough sets, as alternatives to the usual set theory founded on the two valued classical logic, present an appropriate context for developing the basic notions of the logic of preference and consequently, of the social choice theory. In this paper we present an introductory survey of two non-classical concepts of set: fuzzy set and rough set, as originally introduced by L. A. Zadeh and Z. Pawlak respectively, and then we prove that a preference relation defined by means of rough sets has the same basic properties as the classical or the fuzzy one. Moreover, we prove that The Liberal Paradox, as originally formulated by A. Sen, holds in the framework of theory of rough sets as well.
Integrated corporate performance measurement systems
Authors: Gajic Biljana
Published: June 2006

Corporate performance measurement is a key prerequisite for successful management, a process of guiding the enterprise from the existing to the particular, desired performance. Traditional performance measurement systems, based on the use of financial indicators, do not satisfy the needs of modern enterprises. They provide the measurement of the past results, but they do not provide enough quality information for improvement of performance in the future. Nowadays, a great number of different performance measurement systems have been developed. They have a more complex approach to performance analysis, using both financial and non financial indicators grouped in a certain number of performance perspectives. The disadvantages of this modern performance measurement systems can be diminished through their integration, which leads to creating new, integrated performance measurement systems.
The position of developing countries in international trade
Authors: Kovacevic Radovan
Published: June 2006

Recent years have seen a substantial reduction in trade policy and other barriers inhibiting developing country participation in the world trade. Lower barriers have contributed to a dramatic shift in the pattern of developing country trade -away from dependence on commodity exports to much greater reliance on manufactures and services. In addition, exports to other developing countries have become much more important. These changes have profound implications for the role played by developing countries in the world economy and the trade system. Developing countries have become major players in the global economy. The outward-oriented strategies of many economies in emerging Asia have been reflected in high trade growth and a steady increase in their share in the world trade.
Why monetary board: Monetary board and endogenic price flexibility
Authors: Basic Tamara
Published: June 2006

The paper presents a model which proves that a unilateral exchange rate fixing, i.e. monetary board, as opposed to certain opinions, is an optimal policy since it increases flexibility of nominal prices, which is the ultimate goal of a flexible exchange rate policy. A suitable calibration of the model shows that the higher the initial price flexibility, the lower the difference needed for "utility increase" in getting the producers to switch from fixed to flexible prices. The results obtained in all cases indicate that exchange rate fixing increases price flexibility, which proves that a unilateral exchange rate fixing, i.e. monetary board, could be an optimal monetary policy.
Ecological taxes in some European countries
Authors: Filipovic Sanja
Published: June 2006

Production and consumption of fossil fuels is one of the major causes of the green house effect, which is in economics known as a form of ecological externality. Fiscal solution, as one way of internalization of externalities, is based on polluters-pay principle and the imposition of tax on emission. Although the implementation of ecological tax was intensified during the previous decade, fiscal revenues are modest and account for only 5% of the total fiscal revenues of the European Union. Taxes on energetic products, accounting for 76%, are dominant among ecological taxes. Since the EU Directive 82/92 imposes minimum excise rates on oil products, during the last decade Central Eastern European countries have increased excise rates on fossil fuels and fully engaged in the field of ecological policy.
Ten years of transition Stiglitz's criticism and counterarguments
Authors: Djurdjevic Ljiljana
Published: June 2006

IMF supports the transition process in most ex-socialist countries through concessionary financing, recommendations for economic policy and technical assistance. Results vary across countries and have been analyzed by a number of authors. In this context, some authors have dealt with the IMF's "guilt" Stiglitz's criticism having struck the most responsive chord in public triggering violent reactions. The paper deals with the key hypotheses of this criticism as well as the main counter arguments.
Foreign direct investment and the investment climate in South-East Europe
Authors: Penev Slavica , Rojec Matija
Published: June 2006

Foreign direct investment (FDI) has played an important role in the restructuring of economies of the new member countries of the European Union. FDI levels in South East Europe (SEE) are much lower than in the CEE countries in transition, what reduces the potential restructuring impact of FDI in SEE. The issue here is, how to strengthen FDI inflows in SEE. Along these lines, the aim of the paper is to analyze the countries of SEE as a location for FDI. In the first section we present the economic situation and trends in SEE countries, which are of specific relevance for investors from abroad. Second section deals with FDI trends and situation in SEE countries while the third section analyses individual elements of investment climate in SEE countries. In section four we argue that EU and regional integration processes in SEE are important for making the region a more attractive location for FDI.
The public debt of the Republic of Serbia: The current situation and perspectives
Authors: Bosnjak Marinko
Published: June 2006

The paper deals with the internal and external debt situation of the Republic of Serbia based on the data relating to 2000 and 2004, issued by the Ministry of Finance, as well as the basic macroeconomic assumptions for the regular servicing of debts. The general results of this research indicate that the key institutional assumptions for the strengthening of annuity payment ability are consistent reforms and economic policies, and the key economic assumptions for debt repayment are economics growth, stability and reduction in the volume and changing the structure of government consumption. Investment and export growth which provides for growth in gross domestic product and income in foreign currency, which should be sufficient for debts repayment in the next five years, expressed in time periods as well as annuity payments per year, are the key significance for servicing of debts. Increase in economy efficiency, as well as the efficient use of resources obtained by credit facilities, are guaranties of maintaining the balance between volume and repayment capabilities of debts.
Some results of analytic functions in the unit disc
Authors: Polatoglu Y.
Published: June 2006

We investigate the generalization of the starlikeness of complex order and the generalization of convexity of complex order for the analytic functions in the unit disc D = {z: \z\ < 1}.
Probabilities on first order models
Authors: Ferenczi Miklos
Published: June 2006

It is known that set algebras corresponding to first order models (i.e cylindric set algebras associated with first order interpretations) are not ?-closed, but closed w.r.t. certain infima and suprema i.e. [FORMULA] and [FORMULA] for any infinite subsequence y1, y2,... yi,... of the individuum variables in the language. We investigate probabilities denned on these set algebras and being continuous w.r.t. the suprema and infima in (*). We can not use the usual technics, because these suprema and infima are not the usual unions and intersections of sets. These probabilities are interesting in computer science among others, because the probabilities of the quantifier-free formulas determine that of any formula and the probabilities of the former ones can be measured by statistical methods. .
Contribution of Frenkel's theory to the development of materials science
Authors: Pavlovic V.B.
Published: June 2006

The original and comprehensive research of Yakov Ilich Frenkel in physics and physical chemistry of condensed states, nuclear physics, electrodynamics, science of sintering has significantly contributed to the development of modern scientific knowledge and his scientific ideas are still an inspiration to many scientists. Having in mind the wealth of scientific ideas he had in the research of electroconductivity in metals, crystal structure imperfections and phase transitions and in founding the science of sintering, the contribution of individual theories of Frenkel of significance to materials science are presented in this paper.
Rheological model for viscous flow densification during supersolidus liquid phase sintering
Authors: German R.M.
Published: June 2006

A model is derived for the viscous flow densification of prealloyed powders heated to just over the solidus temperature, a process termed supersolidus liquid phase sintering. The model builds from the viscous flow concepts first introduced by Frenkel with a new porosity effect. Viscous flow densification starts with the formation liquid on the grain boundaries inside the particles, with subsequent spreading of liquid to form a capillary bond between contacting particles. Pores lower the initial semisolid viscosity, but as densification progresses the viscosity increases. On the other hand, viscosity decreases higher temperatures increase. Densification is induced by the capillary force acting against the semisolid system, but densification is delayed until the particles sufficiently softened from liquid spreading on the grain boundaries. Thus, both viscosity and strength vary with the liquid content and particle microstructure. Distortion in sintering traces to an excess of liquid that lowers the skeletal rigidity, mainly due to grain growth with a concomitant release of grain boundary liquid. This often occurs after full densification is achieved. This modification to the model includes the correction for porosity effects on viscosity. The model is compared with data on a 316L stainless steel doped with boron, subjected to in situ densification and slumping observations. .
Peculiarities of structure state and mechanical characteristics in ion-plasma condensates of quasibinary system borides W2B5-TiB2
Authors: Sobol O.V. , Grigoryev O.N. , Kunitsky YU.A. , Dub S.N. , Podtelezhnikov A.A. , Stetsenko A.N.
Published: June 2006

In order to create high-durable, wear-resistant materials for a wide range of functional applications, comparative investigations of the structure and mechanical characteristics of ion-plasma Ti-W-B nano-crystalline condensates were carried out. The range of condensation rates 0.11?0.25nm/s was found to be critical for the coatings obtained from the target with 80 vol% W2B5-20 vol% TiB2. Below this, a phase with a cubic lattice (W,Ti)B0.7?1.2(O,N,C)0.3?0.2 formed, while over this range, a solid solution (W,Ti)B2 with a hexagonal lattice and element composition close to the sputtered target was observed. The structure state of the material changed from cluster-crystalline (under low sputter potentials U=0.6?1.0 kV) to textured- crystalline (under U>2.2 kV). Structure perfection improvement with U increase results in higher hardness and elastic modulus of condensates. The conditions of cluster component formation and its effect on hardness and elastic modulus of condensates are discussed. .
A Test to Evaluate Fatigue Crack Growth in Rubber Compounds under Mixed Mode Loading
Authors: Giuliani G. P. , Medri G. , Pirondi A.
Published: June 2006

An experimental method to evaluate the crack growth rate in rubber compounds under mixed mode loading is presented. This method for measuring fatigue crack growth resistance of compounds for truck tire applications yields results that are comparable in ranking to field tests.
Effects of Variations in Geometry and Material on the Non-uniformity of Tires
Authors: Meijuan Y. , Yuankan D. , Gall R. , Rodriguez N. D.
Published: June 2006

Finite element analysis is used to predict radial force variations caused by geometry and material imperfections in the tire. Imperfections, such as a change in tread compound modulus or an increase in product thickness, are applied in a 180° section of the tire model. The radial load variation for a given deflection is then computed. Experimental studies are carried out to confirm the numerical results.

Further studies investigate the influence of the inflation pressure and address the application of results to other tire designs.
Prediction of Mixed-mode Fracture in Participate Composite Using a Damage Criterion
Authors: Chow C. L. , Tai W. H. , Liu C. T.
Published: June 2006

In this paper, a damage-coupled Mooney-Rivlin hyperelastic material model and a damage failure criterion are developed based on the theory of damage mechanics. The model is applied to predict the crack initiation angle and fracture load of particulate composite plate under mixed load. The prediction is achieved by implementing the damage model in a finite element package ABAQUS through its user-specified material subroutine. The inclined angles of the pre-crack are θ = 0, 15, 30, 45, 60, and 75°. The predictions are compared with the test results and found to be in satisfactory agreement.
Finite Element Modelling of Rotating Tires in the Time Domain
Authors: Olatunbosun O. A. , Burke A. M.
Published: June 2006

Finite element analysis presents an opportunity for a detailed study of the dynamic behavior of a rotating tire under real operating conditions providing a better understanding of the influence of tire construction and material detail on tire dynamic behavior in such areas as ride, handling and noise and vibration transmission. Modelling issues that need to be considered include non-linear effects due to tire inflation and hub loading, tire/road contact and time domain solution of the equations of motion. In this paper techniques and strategies for tire rotation modelling are presented and discussed as a guide to the creation of a successful model.
Non-linear Hysteretic Characterization of Elastomers under Multi-axial Loading Conditions
Authors: Gurvich M. R. , Andonian A. T. , Shaw C.
Published: June 2006

An approach to describe hysteretic energy loss under three-dimensional (3D) cyclic loading is proposed for visco-elastic materials. The approach is simple, highly accurate, and takes into account the non-linearity of deformations along with the 3D nature of cyclic loading. It is shown that a two-parameter variant of the approach is, in general, a very good approximation of hysteretic loss even for highly non-linear deformations. Simple relationships between proposed material parameters and classical characteristics of visco-elasticity (storage modulus, loss modulus, and loss factor) are considered as well. Experimental confirmation was provided for a typical elastomeric compound, and the statistical reliability of the prediction was found to be very high. The proposed approach may also be used to characterize hysteretic material properties using test results under 2D or 3D loading.
The Finite Element Approach to Predict the Plysteer Residual Cornering Force of Tires
Authors: Ohishi K. , Suita H. , Ishihara K.
Published: June 2006

It is well known that the plysteer residual cornering force (PRCF) of tires plays an important role in assessing vehicle pull problems, and efforts have been made in the tire industry to clarify the underlying mechanisms and to control the phenomenon from the engineering point of view. The magnitude of PRCF of radial tires is affected not only by the belt construction but also by the design of tread pattern for which the experimental evaluations are time- and cost-consuming tasks in the tire development process. This paper proposes the finite element approach to predict PRCF of tires that is supposed to overcome those difficulties. Results of the finite element predictions are compared with experiments, and discussions are also presented.
Analysis of Tire Force and Moment Response During Side Slip Using an Efficient Finite Element Model
Authors: Darnell I. , Mousseau R. , Hulbert G.
Published: June 2006

This paper describes the application of a new type of non-linear 3D finite element tire model for simulating tire spindle force and moment response during side slip. The simulation model, briefly described in the paper, is composed of shell elements, which model the tread deformation, coupled to special purpose finite elements that model the deformation of the sidewall and contact between the tread and the ground. The sidewall special purpose element uses a pre-computed look-up table to efficiently calculate the sidewall shape and the forces acting on the tread. The model is designed to predict the forces at the spindle and ground and the overall tire shape, as opposed to the internal stress fields. This paper considers the following deformation scenarios: 1) a vertically loaded tire deforming laterally on a flat surface and 2) a tire rolling straight ahead under a prescribed sideslip angle. Experimental data is also presented to verify the force predictions.
Tire Vibration Modes and Tire Stiffness
Authors: Kao B. G.
Published: June 2006

Tire radial stiffness is traditionally calculated from the wheel load deflection measurement. Statically, this stiffness serves to provide the support for the vehicle. However, this stiffness does not provide sufficient understanding of how the tire behaves dynamically: the tire first radial modes, no matter how they were measured, cannot be correlated with this statically measured stiffness. A comprehensive explanation for this phenomenon is needed for better understanding of tire dynamics and hence building the dynamic tire models. In this paper, the relationship between the tire static stiffness and the tire radial vibration modes is investigated using the bushing analogy tire (BAT) modeling concept. It is found that the tire first radial mode, though it can be of different values through different measuring methods, can be explained consistently with this model. A procedure to obtain consistent tire stiffness for the tire model is also proposed as a result of this investigation.
Estimation of Tire Wear and Traumatic Event Intensities
Authors: Bagdonavičius V. , Bikelis A. , Kazakevicius V.
Published: June 2006

A tire wear model including dependence of the distribution of the traumatic failures of various modes on the wear is proposed. Non-parametric, semi-parametric and parametric methods of estimation for the main reliability characteristics of tires are given. The model makes it possible not only to estimate unconditional functions such as the survival function and the mean failure time of tires and the probabilities of failures of the particular modes, but also to predict residual characteristics such as the probability of survival given the run and the wear of a tire, to estimate the ideal reliability characteristics and to predict reliability of tires when causes of the particular traumatic failure modes are eliminated. Analysis of the real failure time and degradation data of tires is given.
Stress Analysis of the Multi-Layered System of a Truck Tire
Authors: Zhang X. , Rakheja S. , Ganesan R.
Published: June 2006

In this paper, a nonlinear finite element tire model is developed as an effective fast modeling approach to analyze the stress fields within a loaded tire structure, with the contact patch geometry and contact pressure distribution in the tire-road interface as functions of the normal load and the inflation pressure. The model considers the geometry and orientations of the cords in individual layers and the stacking sequence of different layers in the multi-layered system to predict the interply interactions in the belts and carcass layers. The study incorporates nearly incompressible property of the tread rubber block and anisotropic material properties of the layers. The analysis is performed using ANSYS software, and the results are presented to describe the influence of the normal load on the various stress fields and contact pressure distributions. The computed footprint geometry is qualitatively compared with the measured data to examine the validity of the model. It is concluded that the proposed model can provide reliable predictions about the three-dimensional stress and deformation fields in the multi-layered system and the contact pressure distribution in the tire-road interface.
Road Load Analysis
Authors: Sobhanie M.
Published: June 2006

Severe loading in a tire/suspension system arises when a rolling tire impacts an obstacle, such as a curb or pothole. Forces and moments at suspension hard points are needed during an impact for component specification, component durability, and endurance analysis. Today, automotive manufacturers and suppliers are promoting virtual prototyping by use of a computer-aided engineering (CAE) tool. CAE consists of a tire model, a suspension model, and a solver for equilibrium equations. The tire models can be classified either by a parametric tire model (PTM) or by a finite element tire model. In the former tire model, tire stiffness is represented by a set of springs; tire forces and moments are estimated by Pajeka equations. This class of tire models is limited to modeling a vehicle's performance, such as ride and handling.

In recent years, explicit dynamic modeling of a rolling tire impacting a road imperfection has been used to calculate forces transmitted to a suspension system. The tire model consisted of a single layer of shell elements; solid elements were considered for the tread cap. The beads were not considered in this tire model.

In this analysis, ABAQUS Explicit was used to model the rolling and transient impact of a tire. ABAQUS Explicit's modeling results were compared to ABAQUS Standard's results. The comparison included the tire forces, footprint pressure distribution at a free rolling condition, and resonant frequencies. In addition, modeling results of a tire/suspension system traversing an obstacle were presented. The suspension components, except spring and shock, were modeled by rigid elements connected together.
Surface Shape Optimization of Tire Pattern by Optimality Criteria
Authors: Nakajima Y. , Takahashi F. , Abe A.
Published: June 2006

A new optimization procedure to design the surface shape of tire patterns is proposed in which the optimality criteria is combined with finite element method. The effectiveness of this new procedure to control tread-element contact pressure distribution was verified by building and testing the rubber block samples. The objective function was the pressure uniformity on the block and the constraint was to keep the contact area in the optimization process. The shape of the optimized surface was round at the edges and concave at the center where the pressure was large in the flat surface block. The pressure of the block with the optimized surface became uniform and the friction coefficient increased 10% on dry compared with the flat surface block. Furthermore, this procedure was applied to complicated block shapes such as tire patterns and it was verified that the optimized surface effectively improved vehicle handling, riding comfort and irregular wear.
Lateral-Acceleration Experience of Six Commercial Vehicles
Authors: Winkler C. , Sullivan J. , Bogard S. , Hagan M. , Goodsell R.
Published: June 2006

This communication provides a detailed review of the lateral-acceleration experience of six tractor-semitrailer combinations in real commercial service for approximately one year. Lateral-acceleration experience is described in histograms of travel time. Influences of speed, load, road geometry, driving style, and longitudinal position on the vehicle are examined. Distributions of both path curvature and lateral acceleration are presented. The six vehicles studied were all five-axle, tractor-semitrailer combinations. The semitrailers were cryogenic tankers for transporting liquid nitrogen. The fleet operated from La Porte, Indiana and serviced much of Illinois, Indiana, Michigan, and Wisconsin. Data from nearly 10,000 hours and more than 770,000 km of travel were collected and analyzed.
Evaluation of Tire Tread and Body Interactions in the Contact Patch
Authors: Koehne S. H. , Matute B. , Mundl R.
Published: June 2006

Today's tread pattern design development is done independently from the tire body construction in order to achieve the best traction and uniform local wear performance. Nevertheless, a better understanding of the interaction between tread and body is necessary to improve the above mentioned properties. An identical tire has been investigated in four pattern steps, starting from a smooth tire, carving a block structure with longitudinal and lateral grooves, and finishing with additional sipes in the blocks. A new developed test stand, which is capable of measuring the stresses in the contact patch of the rolling tire in all directions with a resolution of 1 mm, is described. The local contact stresses of the investigated tread blocks are simulated by FEA using the measured loading conditions of the smooth tire. The results of this simulation are compared with measurements and mechanically interpreted.
Prediction of Tire Tread Wear with FEM Steady State Rolling Contact Simulation
Authors: Zheng D.
Published: June 2006

A procedure based on steady state rolling contact Finite Element Analysis (FEM) has been developed to predict tire cross section tread wear profile under specified vehicle driving conditions. This procedure not only considers the tire construction effects, it also includes the effects of materials, vehicle setup, test course, and driver's driving style. In this algorithm, the vehicle driving conditions are represented by the vehicle acceleration histogram. Vehicle dynamic simulations are done to transform the acceleration histogram into tire loading condition distributions for each tire position. Tire weight loss rates for different vehicle accelerations are generated based on a steady state rolling contact simulation algorithm. Combining the weight loss rate and the vehicle acceleration histogram, nine typical tire loading conditions are chosen with different weight factors to represent tire usage conditions. It is discovered that the tire tread wear rate profile is changing continuously as the tire is worn. Simulation of a new tire alone cannot be used to predict the tire cross-section tread wear profile. For this reason, an incremental tread wear simulation procedure is performed to predict the tire cross section tread wear profile. Compared with actual tire cross-section tread wear profiles, good results are obtained from the simulations.
BAT Model Lateral Parameters Characterization Using Finite Element Model
Authors: Kao B. G. , Warholic T.
Published: June 2006

The bushing analogy tire (BAT) model has been shown to be capable of modeling tire dynamics in vehicle dynamic simulations. In a recent paper, the tire and vehicle data have been used to demonstrate that the BAT model yields reasonable predictions of the vehicle vertical suspension dynamic responses up to the tire 2nd vertical mode (∼90 Hz). This paper studies the modeling of the tire dynamics in the lateral direction as the next step toward completion of the BAT model as a consistent 3-dimensional tire dynamics model.

Finite element (FE) analysis is an advanced analytical method for engineering analysis and has been accepted as the standard analytical tool for tires in the automotive industry. The tire data generated with FE models are also repeatable, without the data noise contained in physically measured laboratory tire data. FE models are also ideal for tire modeling studies because they enable the analysts to precisely control the modeling parameters. A tire FE model is, therefore, used here to generate the needed tire data, including mass, static forces and dynamic vibration modes for BAT model characterization.

The BAT model parameters, including the tire lateral stiffnesses and the tire/wheel mass and inertia, are extracted from the FE analysis results. The analytically predicted lateral vibration modal frequencies of the BAT model are then compared with the corresponding lateral vibration modes of the same FE model. It is shown that the resulting BAT model is a good approximation for the FE model in the lateral direction up to the third lateral (including rotational) vibration mode (∼70 Hz).
A New Paint Test for the Quantitative Evaluation of Irregular Wear
Authors: Chung S. R. , Lee K. S. , Yu H. J.
Published: June 2006

An improved method for a paint test is presented. The test consists of applying a single layer of paint to the tread surface by spraying, measuring the intensity of reflecting light to check the evenness of the paint thickness, running the tire on a vehicle for a short distance, and assessing the wear rate by measuring the intensities of reflecting light at various locations, and comparing them with the fresh paint values. The wear rate is the change in gray level at each point on the tread block. Under well-controlled test conditions, the wear rate can be measured with a very high resolution. An example is provided to show the wear distribution from shoulder to shoulder of a truck tire. Using the presented technique, the effect of wheel alignment and tire type on uneven wear is studied.
Electric Vehicle Traction and Rolling Resistance in Winter
Authors: Shoop S.
Published: June 2006

Low rolling resistance tires help optimize the economy of electric vehicle (EV) operation. Five types of EV tires were evaluated under cold weather conditions and compared with traditional winter tires in terms of traction and rolling resistance. Other contributions to vehicle resistance (brake drag, wheel bearing resistance, driveline resistance, and air drag) were also measured and used to estimate changes in total vehicle resistance and associated changes in range with temperature. At low speeds, tire rolling resistance is the primary contribution to increased vehicle resistance at cold temperatures, with snow tires having both higher resistance and a stronger dependence on temperature than low rolling resistance tires. Lowering tire pressure increases both resistance and temperature dependence for most tires but also improves traction and therefore may serve as a temporary safety measure in winter conditions.
A Finite Element System for the Hierarchical Design of Agricultural Tires
Authors: Fodor E. , Kriston S. , Nándori F. , Sárközi L. , Szabó T.
Published: June 2006

Due to the many requirements with respect to the processing and operational activities of agricultural tires, their design is not an easy task. To provide support, a special purpose nonlinear FE package called Agrotyre/2D/3D has been worked out, by which 2D asymmetric and 3D boundary problems can be solved for the case of inflation and for the case of vertical loading. In the latter situation, the whole tire is meshed into 16-noded elements including all of the lugs. By assuming the circumferential strain to be equal to zero, the asymmetric model can be analyzed for given prescribed radial displacements, and the results of the cord force distributions can be compared with that of the results of the 3D analysis. The preprocessing of the 2D and 3D meshes are on a common basis for which the data are transferred from a CAD system. In the package there is a further module by which the strength behavior of a unique lug can also be investigated. The paper presents some characteristic pictures that illustrate the usage of this new software.
Effect of Cohesion Loss Factor on Wet Skid Resistance of Tread Rubber
Authors: Takino H. , Isobe N. , Tobori H. , Kohjiya S.
Published: June 2006

The effect of cohesion loss factor on wet skid resistance has not been studied systematically using three major factors, i.e., adhesion, hysteresis, and cohesion. Two different abrasions, PICO and BPST, as the cohesion loss factor were investigated for different polymers, carbon black grades, and carbon black/oil loadings. These two abrasion mechanisms are quite different, and BPST abrasion was concluded to be more suitable as a cohesion loss factor for the BPST (wsn) and tire wet μa. From the difference between PICO and BPST abrasions, superior material factors were analyzed from the viewpoint of the compatibility of both abrasion life and wet skid resistance of tire.
Tire Temperature and Rolling Resistance Prediction with Finite Element Analysis
Authors: Ebbott T. G. , Hohman R. L. , Jeusette J.-P. , Kerchman V.
Published: June 2006

A finite element-based method is demonstrated to predict tire rolling resistance and temperature distributions. Particular attention is given to the material properties and constitutive modeling as these have a significant effect on the predictions. A coupled thermomechanical method is described where both the stiffness and the loss properties are updated as a function of strain, temperature, and frequency. Results for rolling resistance and steady state temperature distribution are compared with experiments for passenger and radial medium truck tires. An extension of the method for transient temperature predictions is also demonstrated.
A Rolling Resistance Simulation of Tires Using Static Finite Element Analysis
Authors: Shida Z. , Koishi M. , Kogure T. , Kabe K.
Published: June 2006

A practical rolling resistance simulation method for tires using a static finite element method is presented that fulfills three requirements: (1) easy input data preparation, (2) shorter computation time, and (3) adequate accuracy. The method implements a static deflection analysis first and the stress and strain thus obtained, together with the loss factors of the materials determined separately, are used to estimate the energy dissipation of a rolling tire.

First, the stress and strain profiles of all element groups that have the same cross-sectional coordinates and are located along the circumferential direction are obtained. Second, hysteresis loops are computed by introducing a viscoelastic phase lag between the stress and strain profiles. The sum of the areas of the hysteresis loops is regarded as the dissipation energy density of the element group. The loss factors of the rubber materials are experimentally obtained and the effective loss tangents of the fiber-reinforced rubber are determined by the homogenization theory of dynamic viscoelasticity. The rolling resistance simulation of a passenger radial tire using this approach accurately captures the trends of an actual tire.
The Effects of Tire Properties and Their Interaction with the Ground and Suspension on Vehicle Dynamic Behavior — A Finite Element Approach
Authors: Zhang Y. , Hazard C.
Published: June 2006

The effects of tire properties and their interaction with the ground and the suspension system on vehicle dynamic behavior was studied using a newly developed finite element analysis method. This analysis method used the explicit nonlinear dynamic code LS-DYNA as a solver and contained finite element models for both the vehicle body structure and subsystems like chassis/suspension. The case presented in this paper is curb impact. Different tire properties such as tire/wheel assembly mass, tire stiffness, tire inflation pressure, tire size, etc., as well as different curb heights, were used with the same vehicle body and suspension system. Simulation results of the impact forces, wheel center jumps, and vehicle body roll/pitch angles at impact are compared for different parameters of the tires and the curb. The analyses presented in this paper provided an accurate and practical method for tire and vehicle dynamics analysis.
Effects of Carcass Cords' Properties on Sidewall Indentation in a Monoply Tire
Authors: Lim W.-W. , Yoon K.-Y. , Cho C.-T.
Published: June 2006

Sidewall indentation is a cosmetic problem in monoply tires. To improve the indentation, we modeled two simple indentation phenomena. We also evaluated an actual indentation depth in inflated tires using several textile cords of different moduli.

We used two models of sidewall indentation. One was that the indentation occurs in tires having the same cords applied to the carcass. In this case the indentation depth had a strong relationship with cord modulus. Another is the case where a higher elongation cord than that of a nonsplice region was used at a localized splice region. In this case the depth was expressed by an equation including the moduli and a number of cords.

The indentation depth could vanish theoretically at the modulus ratio of 0.5 between splice and nonsplice regions (Es/Ens = 0.5).

The above prediction is verified by experiments on the actual sidewall indentation for given tires having a specific construction. The indentation depth minimized at the ratio of elongation at specified load (EASL) of splice and nonsplice region of 2.0 or the modulus ratio of 0.5 (EASLs/EASLns = 2.0 or Es/Ens = 0.5).
Tire Cord Shape Influence on Stresses Using a Micromechanics Model
Authors: Kocak S. , Pidaparti R. M.
Published: June 2006

This paper investigates the influence of cord shape in cord-rubber composites using a three-dimensional micromechanical model. The micromechanical model integrates a solid rubber finite element with a twisted cord finite element that takes into account various coupling effects. The developed micromechanical model is used to investigate the effect of cord shape on deformations and interface stresses. Numerical results of deformations and stress distributions are presented to illustrate the influence of cord shape, cord properties, loading, and rubber thickness.
A Three-Dimensional Dynamic Tire Model for Vehicle Dynamic Simulations
Authors: Kao B. G.
Published: June 2006

Traditional multibody dynamic (MBD) tire models concentrate on the tire patch force development and the tire in-plane characteristics. The tire lateral dynamics and nonlinear effects caused by the tire compliances during rough terrain driving and severe maneuvers are mostly neglected in vehicle analytical simulations. The tire finite element models, though capable of dealing with these phenomena, are basically not designed for quick vehicle dynamic evaluations. A simple three-dimensional (3-D) MBD tire model for full vehicle performance and maneuvering simulations over various road surfaces is therefore desirable for the ever expanding analysis capabilities and the improved accuracy of the computer-aided vehicle design analysis.

In this paper a tire modeling concept to extend the in-plane dynamic tire model to full 3-D tire dynamics is proposed. Essentially, this tire model divides the traditional tire/wheel system model into three elements: two rigid bodies representing the wheel mass/inertia and the tire tread mass/inertia, and a spring/damper representing the sidewall visco-elasticity. Thus, 6 degrees-of-freedom (DOFs) are added for each tire over traditional tire models. Using any existing tire patch force calculation model, this proposed model can be used to simulate full 3-D dynamic responses of a vehicle.

To implement this model, techniques to extract the nonlinear spring rates of the sidewalls and to enhance the tire patch force calculations over uneven terrains are explained in this paper. Results of the vehicle simulation using this tire model were compared with measured field data. They showed that this tire modeling concept yields a practical representation for tire 3-D nonlinear dynamic characteristics.
The Strain Generated on a Rubber Surface in the Course of Pattern Abrasion
Authors: Iwai T. , Uchiyama Y.
Published: June 2006

The surface strain on a rubbing rubber surface was examined in the course of pattern abrasion. Rubbing experiments between the outermost surface of a rotating isoprene rubber wheel and a cylindrical lens were conducted. Observations of the contact area were made through the lens. Markers were put on the rubbing rubber surface to measure strain. The maximum strains at the inclined rubber surface between the ridges were from around 40% to 100%. In order to measure the strain at the crack-propagating area, a marker was put on the lower front part of the ridge. It was found that the strain necessary for crack propagation underneath the ridge was 750%, which was almost equivalent to its breaking strain, irrespective of the applied load. At that moment, newly generated crack surface was confirmed. However, no visible crack was observed through an optical microscope when the strain was measure at 200% to 400%.
Tire/Suspension Aligning Moment and Vehicle Pull
Authors: Yu H. J.
Published: June 2006

Vehicle drifts are affected by the forces and moments of the tire and the suspension. A steering moment equation that calculates the residual aligning torque (RAT) of a tire matched to a vehicle is derived. Using this equation, tire makers can save on development cycle time by delivering matching tires as soon as the suspension configuration is defined.
Influence of Friction on the Cyclic Response of Simple Straight Wire Rope Strands under Axial Loads
Authors: Labrosse M. , Nawrocki A. , Conway T.
Published: June 2006

The frictional damping properties of axially loaded simple straight wire rope strands are studied using an analytical model for cables of current design. Since the cable axial response is driven by the interwire local pivoting, a first linear model is built in which pivoting occurs without friction. A hysteretic model is then built after a specific law of friction is established. Using comparisons with experimental results described in the literature, the frictional energy dissipated over a load cycle is shown to be very small compared to the elastic strain energy and other dissipations. This result is in agreement with the experimental fact that axially loaded simple straight strands do not experience fretting-induced failures, except when they are close to the terminations.
Internal Temperature Distribution in a Rolling Tire
Authors: Oh B. S. , Kim Y. N. , Kim N. J. , Moon H. Y. , Park H. W.
Published: June 2006

A computer program is developed to calculate the internal temperature distribution in a rolling tire. The geometry of the tire cross section is transformed to simple computational domains by using a boundary-fitted coordinate transformation method. A heat transfer equation in the tire is also transformed to be calculated in the computational domain. Heat generation rates are estimated from load, speed, contained air pressure, and a static stress and strain analysis. An unsteady two-dimensional heat conduction equation is solved with heat convection and radiation boundary conditions. External surface temperature distributions are measured by an infrared camera system and the temperature of the contained air is measured by a thermocouple. The conductivities of various materials in the tire and various heat transfer coefficients along the tire boundary are given in an input file. Some internal temperatures measured by buried thermocouples in the actual tire are compared with the calculated temperatures.
Investigation into the Influence of Tire Construction on Coast-by Noise
Authors: Doan V. Q. , Brackin D. , Nishihata S. , Sauerzapf J.
Published: June 2006

It is generally known that a high peak value exits at around 1 kHz in the coast-by noise spectrum and dominates the coast-by noise level. This phenomenon occurs in tires having tread patterns and for blank tires. Therefore this noise at around 1 kHz is not only generated by tread patterns (pattern blocks, pipe resonance etc.) but also by the vibrations of the tire components, especially the tread portion. Experimental and FE analyses were carried out to clarify the relation between coast-by noise and tread vibration, and the influence of changes in tire construction on tread vibration.
Optimum Young's Modulus Distribution in Tire Design
Authors: Abe A. , Kamegawa T. , Nakajima Y.
Published: June 2006

A new approach to determine the optimum compound characteristics in each tire material is developed and applied to improve various tire performances following the corresponding objective functions and constraints. In the new approach, optimization technology is combined with a finite element method so that the optimum compound characteristics in each tire material are obtained by minimizing an objective function, while satisfying the constraints. Hence, the targets of rubber characteristics in each material of a tire can be determined by the proposed approach to improve tire performance. When we optimize the compound characteristics in each element of a tire model, the number of design variables becomes more than a few hundred. Therefore, the sensitivity of the stiffness matrix in the optimization is obtained by a semi-analytical (or implicit differentiation) method and computational time is greatly reduced compared to the finite difference method. The new approach is applied and verified to improve the rolling resistance of a tire. Furthermore, we can obtain guidelines for a new topological tire structure by the Young's modulus optimization, considering that the rubber material should be removed from the initial tire design, if the optimum Young's modulus is almost zero at the element.