bluuebunny/crossref_metadata_2025 huggingface dataset:
Razvijeni oblik trgovine na robnim berzama - trziste robnih fjucersa -
Authors: Eremic Milan
Published: June 2006

At the very beginning of this paper, we stress the fact that capitalism, during a very long period of its emergence and development, was based on simple forms of commodity trading. It is true that capital left its mark on these simple forms. However, it did not change its simple character. Several centuries were to pass in for capital to build its own autochthonous forms of commodity exchange, the forms inherent in capitalism. The early forms of commodity futures, as the basic instrument of this developed commodity exchange, are thought to have been introduced on the Chicago Board of Trade - CBOT in 1985. The introduction of commodity futures contracts into commodity exchange enabled commodity markets to be divided into physical commodity markets and contract markets. This was the beginning of a complex system of commodity trade, the emergence of new economic entities in commodity markets and the development of a very complex system of trading, settlement and trade clearing through commodity futures contracts. The construction of this new system of commodity trade has lasted more than a century and during its gradual development a tremendous construct has been created, a market structure of extraordinary internal complexity and a solid logical design. The process of creating commodity futures market in the USA was outlined only in the early 1970s. We can say that it is an almost perfectly developed system, being today a dominant system in the world. Almost 100 percent of all commodity futures markets in the world are based on the commodity futures markets in the USA. The only exception is the London Metal Exchange, which is, although not being any less perfect, essentially different from the American exchanges.
Brokers and brokerage in the process of trading in commodity futures markets
Authors: Eremic Milan
Published: June 2006

This paper mainly deals with the analysis of a very complex process of brokerage in commodity futures markets. Unlike a classical commodity market in which brokers are not a necessity, sales and purchases in commodity futures markets cannot be carried out without brokers. Brokers who act as agents of buyers and sellers of futures are a necessary condition for trading in organized markets, such as commodity futures markets. The structure of brokers in futures trading is multilayer and involves participants in futures trading from floor brokers, immediate futures traders and the members of clearing and the clearing house itself, on the one hand, to numerous other necessary actors whose activities out of the stock exchange and the clearing house contribute to the efficient functioning of futures market. The fact that transactions between buyers and sellers in futures markets are not carried out directly but through brokers means that the obligations of buyers and sellers are formally conveyed to brokers, providing at the same time the guarantee by the broker that the actual buyer and the actual seller will fulfill their contractual obligations. At the very beginning of futures trading, the relationship between the seller and the buyer is transformed into a relationship between two brokers. Since that moment on, the original relationship is conveyed to higher levels of brokerage reaching the level of the clearing house. In the process of transformation of the buyer-seller relationship and transmitting obligations and guaranteeing their fulfillment, the clearing house itself becomes the buyer relative to all sellers and the seller relative to all buyers. In this way, it guarantees that obligations regarding all transactions in futures market will be fulfilled. The whole process is carried out in accordance with the prescribed procedures conducted on the floor of commodity exchange, in its administrative departments and in the clearing house itself.
Value added tax-theoretical and practical aspects
Authors: Raicevic Bozidar
Published: June 2006

Value added tax has been applied for four decades now and as a novelty it has already worn off both in theory and practice. It has indisputable advantages and relatively minor shortcomings compared to other forms of consumption taxation. Today it is one of the most widely used form of consumption tax in the world, being levied in about 120 countries accounting for around 70 per cent of the world population, including all European countries except Serbia and Bosnia and Herzegovina (the Federation and the Republic of Srpska). The burden of value added tax is visible at each stage in the production and distribution chain, thus eliminating taxation accumulation and is borne ultimately by the final consumer of final goods and services in the consuming country. The consumption type is a dominant type of value added tax. It ensures that the fixed and current assets purchases are exempt from VAT, and as such, it encourages technological progress and investment. By applying the country of destination principle (VAT is chargeable in the country where the goods or services are consumed - exports are exempt from tax while imports are taxed), value added tax eliminates double taxation and retains tax sovereignty of the importing country. In the last ten years there have been attempts to introduce value added tax in Serbia. The introduction of value added tax is the condition for the accession to the EU and we should expect that the latest attempt to introduce this tax in the Serbia taxation system will be successful. Namely, VAT Act is expected to be passed during 2004 and enforced as of January 1, 2005.
Corporate strategy and the organizational structure of companies in international business
Authors: Aleksic Ana
Published: June 2006

The aim of this paper is to illuminate the importance of corporate strategy and organizational structure as crucial variables for successful international business. We wanted to point out that companies, in order to exploit opportunities in international environment, must develop a high level of consent between the applied strategy and the model of organizational structure. Today all organizations, no matter how big they are, are affected by the international environment and its management must consider very carefully the benefits and costs of alternative strategies and the corresponding models of organizational structure.
The characteristics of successful entrepreneurs
Authors: Pokrajcic Dragana
Published: June 2006

This paper examines the economic, psychological and social-behavioral theories of the entrepreneur in order to determine the characteristics of a successful entrepreneur. The major contribution of economic theories of the entrepreneur is better understanding of the entrepreneur and his/her role in economic development. The psychological characteristic theory of entrepreneur argues that successful entrepreneurs possess certain personality traits that mark them out as special, and tries to determine and to evaluate these special traits. The social-behavioral theories stress the influence of experience, knowledge, social environment and ability to learn on the entrepreneur?s success as well as his/her personality traits. Neither of the examined theories of entrepreneur gives a satisfactory explanation of the entrepreneur?s success, but taken as a whole, they can explain key factors of entrepreneur?s success. The entrepreneur?s success comes about as a result of his/her personality traits, ability to learn from experience and ability to adjust to his/her environment.
Structural adjustment of Serbian commodity exports to the EU demand for imports
Authors: Nikolic Goran
Published: June 2006

In this paper we have calculated indexes of export-import similarity (Serbian exports and EU imports) by using certain statistical methods. A considerable increase in indexes of export-import similarity, after the approval of the EU preferential, shows that Serbian exports used to be adjusted to the EU market. After suddenly increasing, indexes of export-import similarity then decreased followed by a fall in the share of manufactured products in total exports, although the total exports and exports to the EU recorded a further increase. This fact clearly shows that a growth in exports was achieved mainly by primary products, which widened a gap between the Serbian export structure and that of the EU import structure. Therefore, a growth in Serbian exports can not be sustained without radical restructuring of the Serbian export sector.
Uticaj prosirenje Evropske unije (EU) na stare clanice
Authors: Kovacevic Radovan
Published: June 2006

According to available empirical assessments, any direct boost to economic growth in the western European economic region brought about by the enlargement of the EU on 1 May 2004 is only minor and temporary. However, it will intensify distribution conflicts among the existing member states and in particular, place considerable adjustment pressure on wages and jobs among low-qualified workers. Furthermore, it will necessitate adjustments in those member countries with extensive social services and welfare benefits. The adjustment process will be particularly perceptible in countries close to Eastern Europe. It is up to the politicians in the member states to initiate the necessary steps. There are considerable differences between the member states in their willingness to make adjustments. The three large continental European countries of Germany, France and Italy have substantial problems in implementing the necessary reforms. Failure to achieve far-reaching reforms in these countries would call the expected positive effects, which are already modest, into question. A similar effect would be achieved by any steps taken towards a pan-European harmonization of social policy. As far as the new member states are concerned, enlargement will afford an additional boost to their already dynamic catching up process. However, the economic momentum of the accession countries will not be enough to generate a perceptible increase in the growth rate of the EU as a whole. The new member states are economically still too insignificant for their in some cases very good - growth performance to make a significant impact on the EU's economic growth.
Spoljnotrgovinski rezim Republike Srbije i zona slobodne trgovine
Authors: Kovacevic Mirjana , Vasic Jelena
Published: June 2006

Key to economic recovery and regional stability in Southeastern Europe (especially Western Balkans) economies is establishing institutions supporting competitive markets and integration into European markets. This should meet institutional, legal and economic objectives. From the institutional perspective, the new trade policy should be simpler in order to reduce the administrative burden and to minimize incentives for corruption. From the legal viewpoint the WTO will be the anchor of the trade policy of the countries in the region. From the economic perspective countries should seize the opportunity to sign Free Trade Agreements which boost their current and future growth, and contribute to solving their pending economic and institutional problems. Serbia and Montenegro has started to harmonize their tariff systems. This harmonized tariff should serve as the base for the negotiations with the other members of WTO before Serbia and Montenegro becomes the member of this organization.
Postkomunisticki sudski sistemi - dubokoukorenjene teskoce prevazilazenja socijalistickog nasledja - sa posebnim osvrtom na Hrvatsku
Authors: Schoenfelder Bruno
Published: June 2006

Postcommunist lawlessness has caused considerable concern and resulted in much misguided theorizing. The paper criticizes some of the more common misconceptions. Among them are the disregard for private law enforcement, the failure to realize the interdependence between the range of rights to be enforced and the costs of enforcement, the mistaken view that the rule of law is basically a matter of public choice, and the preference for administrative remedies over judicial remedies. After discarding such attempts at explanation, the paper proposes that the analysis should instead focus on other issues. All of them happen to be related to communist legacies. These are the downgrading of civil and constitutional law, the instability of legal rules, the underdeveloped separation of powers, and the very peculiar causes of court congestion.
Postmodern organization and new forms of organizational control
Authors: Loncar Dragan
Published: June 2006

This article displays post bureaucratic organisational concept as an adequate representative of all emerging organizational forms which are natural result of persistent initiatives to flexibly and intensify working process. Under this term we assume all budding ?sub-representatives' such as Total Quality Management (TQM), Just-in-time concept (JIT), network systems and joint ventures, virtual organizations, teamwork and other related structures. The author concludes that main virtues of new organizational paradigm are flexibility, decentralization, higher employee empowerment, knowledge and information sharing, responsibility for the system as a whole and permanent learning. On the other hand, some downsides become obvious. Those are danger from anarchy, responsibility and stress, greater employees' insecurity and resistance to new practices. Furthermore, the paper shed light on power and identity dynamics through the lens of improved and still intentional methods of organizational control. The main argument is that compulsive desire to control never fades away, only the methods of control takes different, more advanced forms through organizational culture, vocabulary and discourses monitoring at a distance, peer evaluation inside teams, employee selection and many others.
Value-based management: Theoretical base, shareholders' request and the concept
Authors: Kalicanin Djordje
Published: June 2006

The pressure of financial markets, which is a consequence of shareholder revolution, directly affects the solution to the following dilemma: is the mission of corporations to maximize shareholders' wealth or to satisfy interests of other stakeholders? The domination of shareholder theory has caused the appearance of the valuebased management concept. Value-based management is a relevant concept and a process of management in modern environment. The importance of shareholder value requires transformation of traditional enterprise into value driven enterprise. This paper addresses theoretical base, shareholder revolution and the main characteristics of value-based management.
A general strong Nyman-Beurling criterion for the Riemann hypothesis
Authors: Baez-Duarte Luis
Published: June 2006

For each [FORMULA] formally consider its Miintz transform [FORMULA]. For certain ?'s with both [FORMULA] it is true that the Riemann hypothesis holds if and only if ? is in the L2 closure of the vector space generated by the dilations [FORMULA]. Such is the case for example when ? = X(0,1) where the above statement reduces to the strong Nyman criterion already established by the author. In this note we show that the necessity implication holds for any continuously differentiable function ? vanishing at infinity and satisfying [FORMULA]. If in addition ? is of compact support, then the sufficiency implication also holds true. It would be convenient to remove this compactness condition .
Frenkel's theory of sintering
Authors: Ristic Momcilo , Milosevic S.Dj.
Published: June 2006

Principles of Frenkel's Theory of Sintering are presented in this paper. This theory represents the first physical theory of sintering, in which sintering takes place in two stages as a consequence of "viscous" flow. .
Dynamics of Tire, Wheel, and Suspension Assembly
Authors: Yu H. J. , Aboutorabi H.
Published: June 2006

A combined tire, wheel, and suspension FE model is described. The system simulates the tire mounted on the vehicle. The natural frequencies are calculated successfully for this highly non-linear system where the tire is in the inflated and loaded condition. The random vibration response of the model to the road roughness is calculated.
Application of the Lateral Stress Theory for Groove Wander Prediction Using Finite Element Analysis
Authors: Peters J. M.
Published: June 2006

Ride is a critical component for driver and passenger satisfaction. Groove wander is a ride disturbance experienced on grooved highways. Screening new tire designs for groove wander requires accurate measurement or accurate prediction tools. This paper presents a review of published theories for groove wander. A new theory for groove wander is presented and validated using an indoor test developed at Smithers. In addition, the development and validation of a finite element analysis (FEA)-based groove wander model by application of the lateral stress theory will be reviewed.
Deformation and Fracture of Rubber under Tensile Impact Loading
Authors: Bekar I. , Fatt M. S. H. , Padovan J.
Published: June 2006

An impact experiment is designed to obtain the deformation and fracture characteristics of SBR specimens under tensile impact loading. The experimental apparatus is capable of achieving very large strains (about 300%) and high strain rates (between 10 and 1000 s−1) in the specimen. Dynamic stress-strain curves reveal that SBR goes through several phases of deformation and fracture as the strain rate increases in the specimen. In the first phase, the initial modulus, yield stress, tensile strength, and fracture strain increase, while the final modulus remains fairly constant with increasing strain rate. Increases in the initial modulus, tensile strength, and strain at fracture with increasing strain rate are due to a lack of stress relaxation in constituents that have longer relaxation times than the load duration. Local scale relaxation times are shorter than the load duration in this phase so that the final modulus is almost insensitive to strain rate. In the second phase, the initial modulus and the yield stress remain roughly constant while the final modulus increases with increasing strain rate. The tensile strength also increases, but the fracture strain decreases as the strain rate increases. Increases in the final modulus and tensile strength are due to a lack of relaxation on a local scale. The tensile fracture strain decreases because convolutions do not have sufficient time to slip completely. In the third phase, all stress-strain curves follow a master curve, but both the tensile strength and fracture strain decrease with increasing strain rate. The decrease in tensile strength as the strain rate increases could be due to stress concentration at the tip of microcracks within the SBR.
Analysis of Tire Models for Rolling on a Deformable Substrate
Authors: Shoop S. , Darnell I. , Kestler K.
Published: June 2006

The objective of this research is to produce a finite element model of tire-terrain interaction that can be used to explore the effects of tire and terrain variables on vehicle mobility and terrain deformation. Such a model would need to account for the deformable nature of both the tire and the terrain and be fully three-dimensional. Thus, it is important that the tire model be very efficient at rolling yet retain realistic surface contact and deformation related to contact. A promising methodology was developed by Darnell for efficiently modeling a tire for vehicle dynamics simulations. The performance of the Darnell model was examined with respect to measured tire deformation as well as to conventional models of the same tire. The Darnell tire model was then rolled across a soil simulating the sand used in off-road vehicle experiments. The combined tire-terrain model presented is fully operational, but optimization and validation are in progress.
The Compression Properties of Tire Reinforcements
Authors: Orjela G. , Riva G. , Fiorentini F.
Published: June 2006

The need for precise measurement of tire cord compression properties is essential for FEA models of tires. In this paper, the details of the Pirelli Pure Moment Dynamometer (PPMD) used for these measurements are given as well as a study on the impact of process variables on the compression properties of various reinforcement materials used in tires.
Thermal Engineering Analysis of Rubber Vulcanization and Tread Temperatures During Severe Sliding of a Tire
Authors: Sakai H. , Araki K.
Published: June 2006

Tire skid marks at the scene of an accident are often used as evidence and are a very important phenomenon. However, the mechanism of this complex phenomenon has not yet been fully examined.

Tires are manufactured by a chemical reaction in which rubber molecules are combined into a network structure during a process called vulcanization, in which the tire is heated in a mold. The transient temperature distribution is important in determining the state of vulcanization, but the analysis is very difficult.

We treat the tire tread as a rubber slab to estimate the temperature history during heating and cooling. Then we calculate the vulcanization index using Arrhenius's equation, assuming that the rate of chemical reaction approximately doubles as the temperature increases by 10° C.

Finally, we calculate the transient temperature distribution of the tread due to the heat generated by internal friction (rolling resistance of the tire), and the heat generated by sliding friction under conditions of severe cornering and braking. We investigate a criterion for modeling the occurrence of tire skid marks, assuming that skid marks are caused by exceeding the softening temperatures of the rubber and asphalt.
Tire Model To Predict Treadwear
Authors: Fujikawa T. , Uchiyama Y. , Yamaguchi I.
Published: June 2006

This study examines treadwear on tires caused by low severity cornering during free roll. The authors previously proposed a method to predict treadwear using rubber pad wear tests. This method required measurements from actual tires to obtain the tread frictional parameters, i.e., the sliding distance, sliding velocity, and contact pressure. The present study proposes an analytical tire model for predicting treadwear that does not require measurements from actual tires. This enables treadwear prediction during the tire design stage, prior to test tire construction. A continuous tread model for lateral tread deformation is described to evaluate the frictional parameters. The treadwear is then predicted from the parameters and the rubber pad wear rate. The predicted treadwear rates are compared with actual treadwear rates and are found to be valid in the tread center area.
Effect of Fatigue Step Loading Sequence on Residual Strength
Authors: Sun C. , Gent A. , Marteny P.
Published: June 2006

Miner's rule is often assumed to hold in accelerated fatigue tests. This rule implies that the order in which loads are applied is not significant. Whether particular loads are applied early in the test or later is unimportant; they are expected to cause the same amount of damage if they are imposed for the same number of cycles. In order to test this hypothesis, we have investigated the effect of loading sequence on residual strength using two levels of tensile strain and several representative rubber compounds. In all cases, a series of increasing strains was found to reduce the strength to a greater degree than the same strains applied in decreasing order. Thus, Miner's rule does not hold for the fatigue failure of these compounds. However, the relative rankings of the compounds remained the same in both step-up and step-down strain sequences.
Influence of Tire Characteristic Properties on the Vehicle Lateral Transient Response
Authors: Schröder C. , Chung S.
Published: June 2006

This paper summarizes results from a recent program of tire-vehicle system research, using simulation techniques to identify the influence of tire characteristics on the vehicle response functions of yaw rate and lateral acceleration. Tire characteristics such as cornering stiffness, cornering stiffness-wheel load dependency, self-aligning torque, and dynamic tire behavior were varied with respect to a control tire. Computer simulations of vehicles undergoing a steering wheel pulse input were carried out using ADAMS full vehicle models and the Magic Formula tire model. Frequency responses were obtained from these vehicle handling simulations. The Four Parameter Evaluation Method of Lateral Transient Response was used to judge the vehicle handling performance. The influences of tire characteristic properties on the vehicle lateral transient response are explained by this method.
Tire Contribution in the Context of Automobile Noise Reduction
Authors: Rimondi G.
Published: June 2006

Requirements to reduce the external noise emitted by automobiles are continuously evolving because of the increasing number of vehicles circulating in urban areas and the growing demand for a better quality of life.

In this paper, an updated review will be presented of different approaches to noise reduction in the two main world car markets, Europe and the United States, showing today's legal requirements and future trends. In this context, the role of the tire will be analyzed by describing the mechanisms through which it generates external noise, its importance with respect to other vehicle noise sources, and the possibilities that exist to reduce its contribution.
Theory of Optimum Tire Contour and Its Application
Authors: Nakajima Y. , Kamegawa T. , Abe A.
Published: June 2006

A new approach to determine an optimum tire contour was developed and was applied to improve various tire performances following the corresponding objective function and constraints. Although several tire contour theories have been proposed in the past, some of them were based on a simple model and could not be used to improve tire performances effectively. On the other hand, others were not described by an equation and their application was limited. In the new approach, the optimization technology was applied to efficiently obtain the optimum contour by minimizing an objective function, while satisfying the constraints. The new approach was verified to be able to improve various tire performances.
The Three-Dimensional Contact Patch Stress Field of Solid and Pneumatic Tires
Authors: Pottinger M. G.
Published: June 2006

Contact patch (footprint) physics is fundamental to the generation of vehicle control forces, tire and road wear, and tire structural mechanics. Footprint physics depends strongly on tire design, pavement topography, and operating conditions. This paper discusses the three-dimensional contact patch stress field of two generic tire types: solid and pneumatic. The discussion is limited to the comparison of the static and free rolling states of both tire types, examination of the effect of the bead-rim boundary condition in the pneumatic tire, and a brief look at the effect of the friction coefficient and viscoelasticity on the solid tire. The discussion is based on experimental results for a smooth-treaded urethane solid tire and a low-pull-force smooth-treaded radial which are assumed to generally represent solid and pneumatic tires. The results obtained offer significant guidance to those who are attempting to mathematically model tires, understand wear, and comprehend the physics of the tire contact patch.
Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads
Authors: Jeusette J. P. , Theves M.
Published: June 2006

During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.
Analysis of the Contact Deformation of Tread Blocks
Authors: Akasaka T. , Kabe K. , Koishi M. , Kuwashima M.
Published: June 2006

The deformation behavior of a tire in contact with the roadway is complicated, in particular, under the traction and braking conditions. A tread rubber block in contact with the road undergoes compression and shearing forces. These forces may cause the loss of contact at the edges of the block.

Theoretical analysis based on the energy method is presented on the contact deformation of a tread rubber block subjected to compressive and shearing forces. Experimental work and numerical calculation by means of the finite element method are conducted to verify the predicted results. Good agreement is obtained among these analytical, numerical, and experimental results.
Reinforcing Function of Polymer Cords Embedded in Rubber under Compression
Authors: Du X. W. , Qu W. , Wan Z. M. , Ma H. , Yao M. , Jiang J. Y.
Published: June 2006

Whether polymer cords embedded in rubber under compression have a reinforcing function is still an important question in the analysis of tire structures. In this paper, on the basis of experimental results, it is confirmed that polymer cords embedded in rubber present some stiffness, thus playing a reinforcing role to a certain extent. When the cord volume fraction in the cord-rubber composite is sufficiently large, the reinforcing function of the polymer cords is so significant that the properties of the cord-rubber composite are mainly influenced by those of the cord.

When the compressive stress reaches a certain value, the cord-rubber composite specimen yields by buckling if the cord volume fraction is large enough and the cord angle is within a certain small range. The buckling stress, which may be considered to be a failure stress, decreases with an increase in temperature. On the other hand, the effect of the cord angle on the buckling stress is found to be insignificant.
Uneven Wear of Vehicle Tires
Authors: Walters M. H.
Published: June 2006

Advances in tire construction have led to major increases in tire life over the past twenty years, mainly by increasing the lateral stiffness and thus reducing slip during cornering. However, this general increase in tire life has tended to highlight the problem of uneven wear.

In the present paper, three new experimental techniques are described which have been developed to study treadwear distributions. These techniques are evaluated and their results compared with a finite element analysis. Taken together, they indicate some of the causes of uneven wear and may be used to identify tire design and service features which contribute to uneven wear.
Reduced Basis Technique for Evaluating Sensitivity Derivatives of the Nonlinear Response of the Space Shuttle Orbiter Nose-Gear Tire
Authors: Noor A. K. , Tanner J. A. , Peters J. M.
Published: June 2006

A study is made of the sensitivity of the nonlinear tire response to variations in the design variables. The tire is discretized by using three-field mixed finite element models. An efficient reduced basis technique is used for calculating the nonlinear tire response as well as the first-order and second-order sensitivity coefficients (derivatives with respect to design variables). In this technique the vector of structural response and its first-order and second-order sensitivity coefficients are each expressed as a linear combination of a small number of basis (or global approximation) vectors. The Bubnov-Galerkin technique is then used to approximate each of the finite element equations governing the response and the sensitivity coefficients by a small number of algebraic equations in the amplitudes of the vectors. Extensive numerical results are presented for the sensitivity coefficients of the Space Shuttle orbiter nose-gear tire, when subjected to uniform inflation pressure.
Critical Speed Estimation for Aircraft Tires
Authors: Brockman R. A. , Braisted W. R.
Published: June 2006

This paper introduces a semi-analytic finite element technique for predicting standing wave motions (critical speed phenomena) in pneumatic tires. A general formulation is presented which encompasses inflation and rotation of the tire as well as vibratory motions superimposed upon the inflated and rotating state. The use of sinusoidal basis functions for the circumferential variation of each displacement component reduces the finite element model to two dimensions and improves solution accuracy for higher-frequency modes. Under suitable assumptions, the harmonic components uncouple, and the three-dimensional problem may be solved as a sequence of smaller two-dimensional analyses. The proposed technique provides improved accuracy over three-dimensional analysis at a small fraction of the cost and modeling effort.
FEM Simulation of the Tire/Rim Seating Process
Authors: Pelle R. G.
Published: June 2006

Finite element studies have been conducted in the past, which involved the simulation of the tire/rim seating process under a variety of sophisticated loading conditions up to and including full 3-D loading with braking and cornering considered. However, the seating of the tire against the rim due to inflation pressure alone is an important and interesting phenomenon in its own right and time spent examining this 2-D seating case in more detail is well spent. This study will limit itself to this simpler 2-D case as three modeling strategies are compared for their applicability. Parametric results and frictional effects will be examined using the most accurate of these modeling techniques.
Static Frictional Contact of the Space Shuttle Nose-Gear Tire
Authors: Tanner J. A. , Martinson V. J. , Robinson M. P.
Published: June 2006

A computational procedure has been presented for the solution of frictional contact problems for aircraft tires. The Space Shuttle nose-gear tire was modeled using a two-dimensional laminated anisotropic shell theory with the effects of variation in material and geometric parameters, transverse shear deformation, and geometric non-linearities included. Contact conditions were incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with the contact and friction conditions. The contact friction algorithm was based on a modified Coulomb friction law. Elemental arrays were obtained by using a modified two-field, mixed variational principle that was obtained by augmenting the functional of the variational principle by two terms: the Lagrange multiplier vector associated with nodal normal and tangential contact load intensities and a regularization term which is quadratic in the Lagrange multiplier vector.

Experimental measurements were made to define the response of the Space Shuttle nose-gear tire to combined inflation pressure loads and static normal loads against a rigid flat plate. These experimental results describe the static load-deflection characteristics of the tire and the normal and tangential load intensity distributions in the tire footprint for the various static vertical loading conditions. Numerical results were obtained for the Space Shuttle nose-gear tire subjected to combined inflation pressure and contact loads against a rigid flat plate. Comparisons were made between the experimental measurements and the numerical results.
Indoor Test Procedures for Evaluation of Tire Treadwear and Influence of Suspension Alignment
Authors: Yamazaki S. , Fujikawa T. , Hasegawa A. , Ogasawara S.
Published: June 2006

Laboratory wear test procedures for automobile tires are described, as are the influences of alignments such as camber angle and toe angle. Ply-steer and conicity were considered in determining slip angles in straight-ahead rolling on a drum. Wear patterns produced by different alignment configurations simulated the range of patterns observed in road tests. This, together with good wear rate comparisons, supports our belief that road-test conditions are sufficiently reproducible in the laboratory to yield valid wear test results.
Refined Methods for Tire Computation
Authors: Domscheit A. , Rothert H. , Winkelmann T.
Published: June 2006

Realistic computation of automobile tires is best achieved by modeling the whole tire with finite element methods. A numerical solution of the quasi-static contact problem for the whole tire requires a refined mesh of elements with redundant degrees of freedom when nonlinear material assumptions are considered. Both laminated shell elements and incompressible continuum elements are used here. The stiffness matrix of a shell element is determined by numerically integrating all layers within the thickness of each element. Numerical studies have been made by a finite element technique that includes shell elements and Swanson's material model, which covers large deformations. The major contribution of this paper is implementation of a composite theory that includes effects of large displacements on the stiffness into an existing element. Swanson's material law was also simplified and implemented.
Effect of Material Properties on Tire Performance Characteristics — Part II, Tread Material
Authors: Futamura S.
Published: June 2006

This report, on the effect of tread materials on tire performance, continues the study in Part I [1] on the analogous effects of cords. A new “deformation index” concept for the characterizing energy loss is proposed. Principles are developed for maximum correlation of this index to rolling resistance, wet and dry traction, ice traction, and cornering force. The deformation index is used to determine the dynamic property most relevant to each of these tire functions.
Tire/Vehicle Pull: An Introduction Emphasizing Plysteer Effects
Authors: Pottinger M.
Published: June 2006

Automobiles operate at a sideslip angle even when traveling in a straight line, the trim state. If the driver must work to maintain trim on a smooth level road, a pull problem exists. Pull problems often arise from tire properties. Tire-induced pull problems are discussed in this paper with special emphasis placed on plysteer-associated problems.
A Laboratory Facility for the Study of Rubber Traction and Wear Resistance
Authors: Bandel P. , Di Bernardo C.
Published: June 2006

Phenomena occurring at the interface between the tread compound and the road surface are responsible for at least two main tire characteristics: traction capability and wear resistance. Both depend on the road surface geometry, the presence of thin films of water, local contact pressure, tread element stiffness, temperature, tangential slip, etc. To discount the effect of tire construction, a laboratory test using a small solid rubber wheel has been considered. A rig is designed to easily change the “road” surface, and convert it from wet to dry conditions, run the rubber wheel on such surfaces under high braking or driving torque, and measure torque against longitudinal slip. The rig features a flat disk on which different surfaces can be simulated and two separate electric motors driving the disk and the test wheel in order to control slip instead of torque and to avoid instability at high driving or braking torques. Results show longitudinal characteristics versus slip in different test conditions and simulation of severe abrasion conditions leading to typical abrasion patterns.
Study of the Quasi-Yield Phenomenon in Cord-Reinforced Rubber Under Off-Axis Tension
Authors: Du X. , Qu W. , Gu Z.
Published: June 2006

From experimental results, it is found that the stress-strain relationship of cord-reinforced rubber (CRR) under off-axis tension consists of several stages. In one of them, the stress either remains constant or increases slightly with an increase in strain. Since this phenomenon is similar to the yielding of mild steel, it is called the quasi-yield phenomenon. Further observations with enhanced radiography indicate that the quasi-yield phenomenon in CRR stems from the loosening of twisted filament bundles in the cords.
Laboratory Tire Wear Simulation Derived from Computer Modeling of Suspension Dynamics
Authors: Wright C. , Pritchett G. L. , Kuster R. J. , Avouris J. D.
Published: June 2006

A method for determining the effect of suspension dynamics on tire wear has been developed. Typical city cycle maneuvers are defined by instrumented vehicle testing and data in the form of forward velocities and steer angles are used as an input to an ADAMS computer model of the vehicle. A simulation of the maneuvers generates a tire's operating environment in the form of normal load, slip, and camber variations, which contain all the subtle effects of the vehicle's suspension, steering, and handling characteristics.

A cyclic repetition of the tire's operating environment is constructed and used to control an MTS Flat-Trac machine. In this way, accelerated tire wear can be generated in the laboratory which is directly related to the design features of the vehicle's suspension and steering systems.
Adhesion of Polyester Tire Cord to Rubber and Cord Strength of Polyester Improved by Using Carboxylated VP-Latex
Authors: Hisaki H. , Nakano Y. , Suzuki S.
Published: June 2006

The adhesion of polyester tire cord to rubber decreases during service when it is used in large tires. This phenomenon is recognized as the result of hydrolysis of the polyester by the amine compounds contained in rubber. The carboxylated latex based on the conventional vinylpyridine-butadiene-styrene latex was found to have the function of improving both the adhesion and the cord strength. For further improvement, a latex having more functional groups possessing a function of penetration prevention of amines was found to be effective when it is used in a double layer adhesive system.
Finite Element Evaluation of the State of Cure in a Tire
Authors: Toth W. J. , Chang J. P. , Zanichelli C.
Published: June 2006

Curing is one of the most important steps in the tire manufacturing process. During this process, a green tire is formed to the desired shape and the compound is converted to a strong, elastic material to meet tire performance needs. The process of curing, commonly called vulcanization, is usually accomplished under pressure and an elevated temperature provided by the mold. The curing process is energy-consuming and has a strong effect on material properties. To attain an optimal state of cure for different compounds of various dimensions at minimal capital and energy costs requires proper evaluation of the state of cure in a tire.

Various numerical models have been proposed to determine the state of cure of rubber compounds in molds. Their applications are limited to simple geometry and boundary conditions. For a tire, which has complex shape and variable boundary conditions, the finite element method appears to be an ideal candidate because of its versatility. In this paper, a commercial finite element code, ABAQUS, is used to determine the temperature history of a tire in the curing press. In order to evaluate the state of cure throughout a tire, a user subroutine, HETVAL, is implemented. In the subroutine, the state of cure is determined based on the temperature history using a selected kinetic model, whose cure rate parameters are obtained from moving die rheometer (MDR) measurements. The heat generation due to chemical reaction is also included.

The evaluation of the state of cure using the finite element method is benchmarked using a number of rubber compounds with simple geometries and boundary conditions. Both isothermal and nonisothermal conditions are tested. The predicted temperature history of a tire is then verified by the temperature history obtained from the thermocouples embedded in the tire. Parametric studies are carried out to evaluate the effect of various temperature histories on the state of cure in a tire. The results are used to shorten the curing cycle.
Numerical Simulation of Tire Sliding Events Involving Impacts with Holes and Bumps
Authors: Nakajima Y. , Padovan J.
Published: June 2006

This paper extends the finite element simulation scheme to handle the problem of tires undergoing sliding (skidding) impact into obstructions. Since the inertial characteristics are handled by the algorithm developed, the full range of operating environments can be accommodated. This includes the treatment of impacts with holes and bumps of arbitrary geometry.
Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part III: Results of Supplementary and UTQG Treadwear Test Series
Authors: Veith A. G.
Published: June 2006

The effect of tread compound variation on tire treadwear was studied using bias and radial tires of two aspect ratios. Compound variations included types of rubber and carbon black as well as the levels of carbon black, process oil, and curatives. At low to moderate test severity, SBR and an SBR/BR blend performed better than NR while at high test severity NR and SBR were better than the SBR/BR blend. The SBR/BR blend was the best at low severity testing. Higher structure and higher surface area carbon black gave improved treadwear at all severity levels. The concept of a “frictional work intensity” as the primary determinant of treadwear index variation with test severity is proposed. Some factors which influence frictional work intensity are discussed.
Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear
Authors: Oblizajek K. L. , Veith A. G.
Published: June 2006

Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.