Contact Patch Research Articles

Tire tread optimization method to improve to push aside the water from the road contact patch

The paper is devoted to the development of a method for optimizing the tread pattern to push aside the water from the road contact patch. This technique works with ready-made tread patterns of any type. Today, the methodology under consideration is relevant, since it prevents the occurrence of one of the most common causes of road accidents - aquaplaning. Currently, it is impossible to eliminate the risk of such an effect. It can only be reduced by slowing down or ensuring a uniform load on all wheels, trying to drive through the puddle with all four wheels.

Atlas motion platform split-axle mecanum wheel design

The Atlas motion platform was conceptually introduced in 2005 as a 2.90 m diameter thin-walled composite sphere housing a cockpit. Three active mecanum wheels provide three linearly independent torque inputs enabling the sphere to enjoy a 100% dexterous reachable workspace with unbounded rotations about any axis. Three linearly independent translations of the sphere centre, decoupled from the orientation workspace, are provided by a translational three degree-of-freedom platform. Small-scale and half-scale demonstrators introduced in 2005 and 2009, respectively, gave us the confidence needed to begin the full-scale design. Actuation and control of the Atlas full-scale design is nearing completion; however, resolution of several details have proven extremely elusive. The focus of this paper is on the design path of the 24 passive mecanum wheels. The 12 passive wheels below the equator of the sphere help distribute the static and dynamic loads, while 12 passive wheels above the equator, attached to a pneumatically actuated halo, provide sufficient downward force so that the normal force between the three active wheel contact patches and sphere surface enable effective torque transfer. This paper details the issues associated with the original twin-hub passive wheels and the resolution of those issues with the current split-axle design. Results of static and dynamic load tests are discussed.

Detailed wheel/rail geometry processing using the planar contact approach

The use of detailed wheel/rail contact models has long been frustrated by the complicated preparations needed, to analyse the profiles for the local geometry and creep situation for the planar contact approach. A new software module is presented for this that automates the calculations in a generic way. Building on many components developed by others, this greatly simplifies the running of CONTACT for generic wheel/rail contact situations. Fully 3-d contact search algorithms are implemented. This uses the contact locus approach, that's simplified for wheel-on-rail situations and extended to wheel-on-roller contacts. A main characteristic of the new module is its extensive use of the multibody formalism, using markers to represent coordinate systems, using a newly designed, generic, object oriented-like software foundation. The contact geometry is analysed twice; first for the location of contact patches, and then for the local geometry of the contact patches. The contact search starts from profiles in their actual, overlapping positions. This yields the extent of interpenetration areas as needed for the potential contact definition. Different strategies may be employed for the tangent plane needed in the planar contact method. Creepages are formed automatically using rigid body kinematics, including wheel and track flexible bending. Numerical results illustrate the viability, generality, and robustness of the approach. The extension to conformal contacts is presented in an accompanying paper.

Influence of Full-Life Cycle Wheel Profile on the Contact Performance of Wheel and Standard Fixed Frog in Heavy Haul Railway

Wheel wear is unavoidable, which affects the contact performance of the wheel and rail. This article explores the effects of wheel profile wear on the static contact and dynamic interaction between wheel and standard fixed frog in heavy haul railway. The coupling dynamic models of the vehicle-fixed frog system are established to calculate the change regulation of displacement, contact force, and acceleration when a vehicle passes through the standard fixed frog at a speed of 50 km/h in the facing move in the diverging line. Besides, the finite element models of wheel and standard fixed frog at key positions are developed to simulate the contact patch and distribution of von Mises stress in the regions of the wheel-fixed frog. Compared with the standard profile, the maximum lateral displacement of the worn profile can be reduced by up to 9 mm. The vertical contact force can be reduced from 750 kN to 320 kN, and the decrease is 57.3%. The von Mises stress could decrease up to 34% compared with the standard. And the results show that the wheel profile wear changes the positions of the wheel-rail contact points along the longitudinal direction and affects the dynamic interaction of vehicle and standard fixed frog. For the measured worn wheel profiles in this article, profile wear relieves the dynamic responses and it is good for the nose rail.

Experimental study on wheel-soil interaction mechanics using in-wheel sensor and particle image velocimetry Part I: Analysis and modeling of normal stress of lightweight wheeled vehicles

This study aims to develop a wheel-soil interaction model for a lightweight wheeled vehicle by measuring the normal stress distribution beneath the wheel. The main contribution of this work is to clarify the wheel-soil interaction using a wheel testbed that equips multiple sensory systems. An in-wheel sensor accurately measures the normal stress distribution as well as the contact angles of the wheel. Particle image velocimetry with a standard off-the-shelf camera analyzes soil flow beneath the wheel. The proposed model for the normal stress distribution is formulated based on these experimental data and takes into account the following phenomena for the lightweight vehicles that have not been considered in the classical model: (1) the normal stress distribution takes the form of a Gaussian curve; (2) the normal stress distribution concentrates in the front region of the wheel contact patch; (3) the distribution is divided into two areas with the boundary determined by the maximum normal stress angle; and (4) the maximum normal stress exponentially decreases as the slip ratio increases. Then, the proposed model is experimentally validated. Furthermore, a simulation study for the wheel driving characteristics using the proposed model confirms the accuracy of the proposed model.

False profile view is independently associated with serum metal levels in patients with metal-on-metal hip arthroplasty.

Elevated levels of serum metal ions can be found in some patients with metal-on-metal (MoM) hip replacements. This study seeks to identify whether there is a significant association between the contact patch to rim distance (CPRD) and the anterior center edge angle (ACEA), respectively, and serum cobalt (Co) and chromium (Cr) levels in patients treated with unilateral MoM hip replacements by using standing anteroposterior and false profile view radiographs. This is a retrospective analysis on 53 patients with either unilateral ReCap or M2a-Magnum MoM hip replacements operated in 2006 or 2007. Univariate linear regression and multivariable linear regression (MLR) analyses were performed using the CPRD and ACEA along with risk factors for elevated serum levels of Co and Cr previously suggested in the literature as explanatory variables. Serum Co and Cr were measured using inductively coupled plasma mass spectrometry. The MLR model showed that the same three variables (gender, CPRD and ACEA) were significantly associated with serum levels of both Co and Cr explaining approximately half of the variation. A univariate analysis showed a polynomial association between both anteversion angle and the ACEA with serum levels of Co and Cr. The vertex of the polynomial function was located at approximately 20° and 40°, respectively. Gender, CPRD and ACEA are independently associated with serum levels of Co and Cr. Both ACEA and anteversion angles have optimae associated with low serum metal levels which may be useful for post-surgery evaluation of cup positioning.

Design of Two-Wheeled Motorcycle Tire Crown Contour Bioinspired by Cat Paw Pads

The grip force of tires is crucial for vehicle security and drivability under different driving conditions. A small contact area and stress concentration in the contact patch of two-wheeled motorcycle (TWM) tires result in a reduction in grip performance and wear resistance. Even worse, improving the grip and wear resistance together is difficult to achieve. The purpose of the current study is to analyze the dynamic grounding characteristics and geometry of a cat paw pad and then apply its structure to the TWM tire to improve the contact area and wear resistance under different operating conditions. A nonlinear finite element tire model that could accurately reconstruct the tire structure and realistically reflect the mechanical response to different loads was employed. Then, the accuracy of the tire model was validated by a static test with a control tire. For cats, the dynamic grounding characteristics and topology of paw pads were determined using a pressure-sensitive walkway and a three-dimensional (3D) laser scanner. The results indicated that the cat forepaw third pad (CFTP) exhibited excellent grip capacity. According to similarity transformation, a bionic tire crown was designed according to the lateral fitting curve of the CFTP. Comparative results showed the enlargement of the contact area and decreases in peak pressure and frictional energy rate for the bionic tire under different conditions. With these improvements, the grip performance was improved, and the service life was extended synchronously. These research results can be applied for the design of TWM tires, especially cross-country motorcycle tires.

Modeling of braking thermal effect for wheel-rail contact parameters

The Hertzian contact parameters are evaluated by taking into account the increase in temperature of the wheel due to braking under a steady mechanical loading. An equivalent mechanical load is evolved by Finite Element Analysis (FEA) to produce the same effect of the mechanical and thermal loading. The values obtained by FEA and Hertz theory for steady mechanical loading as well as for equivalent mechanical loading are matching. The contact parameters are found to vary linearly with temperature and equations are developed to obtain these parameters under thermal and mechanical loading. For 146.3 °C temperature of wheel due to braking, the contact pressure is 941.3 MPa, shear stress is 378 MPa and for solo mechanical loading, they are 519.8 MPa and 191 MPa correspondingly. The area of contact patch has increased from 0.0652 m2 to 0.142 m2 by 2.2 times due to thermal effect.

Reduction of freight car wheel wear of 1520 mm gauge railways

A brief description is given of the comprehensive modernization of standard freight car trucks through the use of devices of American companies adapted for railways with a 1520 mm gauge and wheels with ITM-73 specially developed wear-resistant profile, which allows several times to increase the resource of problematic running gears. An approximate method is proposed for solving the wheel–rail interaction problem with determining the position and size of non-elliptic contact patches, including with conformal contact. Using this method, new profiles have been developed for turning worn wheels (ITM-73-01), as well as new wheels for cars with an axial load on rails of 23.5 tf (ITM-73-02) and 25 tf (ITM-73-03). The data of experimental studies showed that the average wear rate of the wheel flanges of freight cars with complex modernized trucks equipped with wheels with ITM-73-01 profile is 3.5-5 times lower than that of a standard car with a standard wheel profile. According to forecast estimates, the use of wheels with profiles ITM-73-02, ITM-73-03 will allow to achieve even greater increase in the resource indicators of wheelsets for wear of the flanges.

Detailed wheel/rail geometry processing with the conformal contact approach

This paper proposes a new way of considering wheel–rail contact in multibody systems simulation that goes beyond the traditional planar constraint and elastic approaches. In this approach, wheel–rail interaction is modelled as a force element with pressures and shear stresses distributed over a contact area that may be curved, supporting conformal contact situations. This by-passes the selection of the contact reference location and reference angle, which are delicate aspects of planar contact approaches.The idea is worked out introducing the curved reference surface as the new backbone for the computations, instead of the tangent plane used previously in planar contact approaches. The steps are described by which the curved reference is constructed in CONTACT, using generic facilities for markers, grids, and coordinate transformations, by which generic wheel/rail configurations can be analyzed in a fully automated way.Numerical results show the capabilities of the new method for measured, worn profiles, suppressing discontinuities in the forces when multiple contact patches split or merge. A further application concerns the evaluation of strategies used in planar contact approaches. There we find that the tangent plane’s inclination is of the biggest importance. This should be defined in an averaged way to achieve maximum correspondence to the more detailed curved contact approach.

Rail/wheel rolling noise generation due to parametric excitation

When a wheel rolls over a railway rail, it ‘sees’ a varying stiffness downwards because the rail is periodically supported by sleepers, leading to parametric excitation of the rail/wheel system. This study investigates the importance of parametric excitation on railway noise generation. Because the problem is non-stationary, it is modelled in the time domain. Rail and wheel impulse response functions, together with an iteration scheme to match boundary conditions in the rail/wheel contact patch, yield rail and wheel response plus contact force at each wheel position on the rail. Forward velocity and rotation of the elastic wheel are accounted for. Feedback coupling between response and force takes part in the excitation. Numerical simulations show that, for a rail on stiff pads, parametric excitation is a major excitation mechanism, above all leading to increased excitation and noise levels in a broad frequency region around the pinned–pinned frequency.

Optimization and Design of a Railway Wheel Profile Based on Interval Uncertainty to Reduce Circular Wear

Wheel tread wear is a form of wheel damage that can seriously affect the performance of freight vehicles. A new numerical approach to optimizing wheel profiles can reduce circular wear on the LM wheel in the design cycle. This approach considers the influence of different line conditions and speed fluctuation on wheel wear, along with the performance of the wheel and the rail as the materials wear. In this approach, a nonlinear numerical optimization model for the wheel tread profile is built through a backpropagation (BP) neural network method. The multipoint Kik–Piotrowski (KP) contact mechanics model is applied to calculate the wheel/rail normal force, tangential creep force, the stick-slip area, and the size and shape of the contact patch. The optimal profile is obtained through the genetic algorithm (GA) method. In order to better reflect the random characteristics of wheel/rail matching and interval uncertainty, a random sampling technique is used to generate a random data sample at typical operating speeds.

A detailed study of allergic contact dermatitis, clinical patterns, allergens and patch testing

Allergic contact dermatitis (ACD) is a common skin condition that causes significant disruption of a country's economy as a result of rising school and work-related absenteeism besides the persistent medical expenses. 1. To determine the demographic profile of ACD patients 2. To determine the source of allergens and its preferred sites of involvement 3.To evaluate the patch test and its relationship with various allergens. This study enrolled 60 patients diagnosed with ACD attending the Department of Dermatology, Venereology and Leprosy Vinayaka Mission Medical College & Hospital, Salem and relevant history, clinical examination and patch test were done using standard protocols. Data were entered in Microsoft Excel [2007] and analyzed using Statistical Package for Social Sciences [SPSS] version 21.0 Chicago, USA. The mean age of the subjects were 40.4±13.7 years. The males and females were affected in the ratio of 3:2. Housewives (28.3%) hugely contracted ACD followed by agriculturists (20.0%), masons (15.0%), students (11.7%), professionals (10.0%) cement factory workers (8.3%), and others (6.7%). Nickel sulphate and potassium dichromate were the most common allergens found. The patch test was positive for 51.7% of the subjects while it was negative and doubtful for 35.0% and 13.3% respectively. India being a developing nation, has seen rising rates of occupational dermatosis in the venture of its rapidly expanding urbanization. Hence vibrant protection measures at all occupational levels in addition to the stricter implementation of regulatory control and warranting public education about the safety protocols has to be exercised in all set ups.

Tire Force Estimation in Intelligent Tires Using Machine Learning

The concept of intelligent tires has drawn attention of researchers in the areas of autonomous driving, advanced vehicle control, and artificial intelligence. The focus of this paper is on intelligent tires and the application of machine learning techniques to tire force estimation. We present an intelligent tire system with a tri-axial acceleration sensor, which is installed onto the inner liner of the tire, and Neural Network techniques for real-time processing of the sensor data. The accelerometer is capable of measuring the acceleration in x,y, and z directions. When the accelerometer enters the tire contact patch, it starts generating signals until it fully leaves it. Simultaneously, by using MTS Flat-Trac test platform, tire actual forces are measured. Signals generated by the accelerometer and MTS Flat-Trac testing system are used for training three different machine learning techniques with the purpose of online prediction of tire forces. It is shown that the developed intelligent tire in conjunction with machine learning is effective in accurate prediction of tire forces under different driving conditions. The results presented in this work will open a new avenue of research in the area of intelligent tires, vehicle systems, and tire force estimation.

The Influence of Non-Pneumatic Tyre Structure on its Operational Properties

A non-pneumatic tyre (NPT) is a novel type of safety tyre that is designed to provide similar elastic properties to those offered by conventional pneumatic tyres. The main advantage of NPT is the lack of compressed air (like in a pneumatic tire) to ensure adequate traction forces and directional control. Suitable materials and the appropriate geometry of the supporting structure allows to achieve properties provides by pneumatic tires. Flexible spokes and closed structure like honeycomb are the most common solutions of supporting structure. Appropriate geometry, thickness and materials of this part affect the NPT properties; radial stiffness, unit pressure in the contact patch and the parameters of an area in contact with a non-deformable surface. The paper presents the FEM NPT model (NPT_0), which was validated with the results of experimental research of NPT. The NPT_0 model is subject to further modifications (layout and shape of the radial spokes) was used in the study. Seven new geometries of NPT supporting structure were selected for simulation tests. During the numerical tests the radial stiffness, unit pressure in the contact patch and the parameters of an area in contact with a non-deformable surface were determined. It has been observed that an increase in the curvature of the spokes reduced radial stiffness and increased the length of the contact path.

An Experimental Setup for Investigations on the Boundary Layer Dynamics

<div class="section abstract"><div class="htmlview paragraph">The frictional behavior of a tribological contact is influenced by the dynamics in the forming boundary layer. Recurring structures, built up through self-organizing effects, were found in various frictional systems. To investigate those phenomena on a macroscopic scale and to better understand dynamical processes such as the formation and decay of contact patches, the first revision of the Wear Debris Investigator (WDI) was introduced in 2017. A friction gap is formed between two coaxial horizontally arranged discs. To mimic the presence of particles, artificial wear dust is fed into the gap. With a camera the formation of the boundary layer is recorded in situ. An implemented normal force and torque sensor enables to recognize correlations between the formed boundary layer and the occurring frictional forces. Numerous measurements revealed an insufficient precision of the previous WDI. Consequently, an innovative measurement and load unit was developed and implemented on the WDI allowing much more accurate statements to be made on the interactions between the contact surfaces and the particles in the friction gap. With the new load unit, much more accurate measurements can be carried out. In combination with an intelligent image data evaluation, it is now possible to show quantitative relationships between the external variables and the patch formation for the first time. We want to show first metrological results on patch dynamics and reservoir dynamics.</div></div>

Sensitivity analysis of tire-ice friction coefficient as affected by tire rubber compound properties

Previous studies show that the material properties of the rubber are among the most important factors when designing a tire. In this study, we investigated the effects of different rubber properties on tire performance on ice. A theoretical model that incorporates these tire material properties was developed. The model was used to estimate the height of the water film generated due to friction and the friction coefficient for both, dry and wet regions at the tire-ice contact patch. After validating the results using experimentally collected data, the model was used to perform a sensitivity analysis on the tire performance with respect to six material properties of the tread rubber: thermal conductivity, rubber density, Young’s modulus, specific heat, roughness parameter of the rubber, and radii of spherical asperities of the rubber. To study the effect of each parameter, the desired material property was varied within a specific range while the other parameters were kept constant. The results from this study show the sensitivity of the magnitude of the friction coefficient to the rubber material properties. The friction coefficient has a direct relationship with the density of the rubber and has an inverse relationship with Young’s modulus, specific heat, and roughness parameter.

Whole virus detection using aptamers and paper-based sensor potentiometry.

Paper‐based sensors, microfluidic platforms and electronics have attracted attention in the past couple of decades because they are flexible, can be recycled easily, environmentally friendly and inexpensive. Here, we report a paper‐based potentiometric sensor to detect the whole Zika virus with a minimum sensitivity of 0.26 nV/Zika and a minimum detectable signal (MDS) of 2.4x107 Zika. Our paper sensor works very similar to a P‐N junction where a junction is formed between two different regions with different electrochemical potentials on the paper. These two regions with slightly different ionic contents, ionic species and concentrations, produce a potential difference given by the Nernst equation. Our paper sensor consists of 2‐3 × 10 mm segments of paper with conducting silver paint contact patches on two ends. The paper is dipped in a buffer solution containing aptamers designed to bind to the capsid proteins on Zika. We then added the Zika (in its own buffer) to the region close to one of the silver paint contacts. The Zika virus (40 nm diameter with 43 kDa or 7.1 × 10−20 gm weight) became immobilized in the paper's pores and bonded with the resident aptamers creating a concentration gradient. Atomic force microscopy and Raman spectroscopy were carried out to verify that both the aptamer and Zika become immobilized in the paper. The potential measured between the two silver paint contacts reproducibly became more negative upon adding the Zika. We also showed that a liquid crystalline display (LCD) powered by the sensor can be used to read the sensor output.

Misalignment effect on gearbox failure: An experimental study

Overhang-meshing gears, deflection of pinion/gear shaft, bearing wear, assembly error, poor adjustment of bearings and foundation are the reasons of misalignment in gear drives.In the present work, the misalignment effect on gearbox failure is investigated experimentally using vibration analysis. Misalignment between motor and gearbox is measured using laser alignment system (LAS). The effect of input shaft speed and load on the gearbox failure is also discussed.The misalignment effect primarily observes on the gearbox drive end taper roller bearing and distresses gear transmission. Physical and microscopic examinations of the dismantle gearbox confirm similar findings as observe from vibration spectrum. Severe damages in taper roller bearing (32206) and multiple pits on all the rollers and cone. The bearing cage is deformed badly due to overload and misalignment. The effect of bearing failure on gear’s damage is also investigated. Non-uniform contact patch is observed on the meshing gears in the plane of action. Misalignment results in scuffing failure on the pinion addendum and gear dedendum regions due to limited lubricant in the overstress region. At the end of the test, all the four seals appears safe, while the coupling spiders damage seriously.

Application of tire sensors for an integrated approach to evaluate longitudinal tire characteristics for braking performance

Braking performance is a key requirement for tires, significantly affecting the braking distance of vehicles. Considering longitudinal tire dynamics, tire characteristics and parameters, as well as influences from vehicle and ambient conditions have to be identified for an integrated evaluation of tire performance. Various testing methods for identification of tire characteristics are available, yet most of them lack the ability to measure directly at the tire/road contact. Tire sensors have been a popular research topic, which may allow for identification of tire properties during test maneuvers in the contact region. This article features the analysis of longitudinal tire dynamics at full (ABS) braking by means of three 3-axis accelerometers fixed to the inner liner of four different sets of front and rear summer tires. Considering both steady-state and dynamic tire braking properties, skid trailer measurements of force–slip characteristics as well as brake tests with the tire accelerometers are presented for the different tires and compared with each other. Characteristics, affecting the overall braking performance, measured by the tire accelerometers at the contact patch indicate a meaningful correlation to the measured steady-state force–slip characteristics. A basic model-based analysis, utilizing the tire brush model, completes the evaluation of longitudinal tire characteristics with respect to braking performance.