Contact Patch Research Articles

Mechanism of Tire / Road Noise Emission and Reduction Technology

The significant noise reduction has been brought by recent electrification of power train of vehicles. More concern about impact on the health due to the environmental noise, especially road traffic noise, requires further reduction of tire / road noise emission caused by the contact between the tire and road surface. The tire / road noise emission mechanism can be described by three different systems such as the excitation, the response, and the propagation. The excitation is composed of the road excitation, the tread excitation, the air-pumping and the friction. The tire structural response and the acoustic response in the void formed inside contact patch are respectively excited by those sources. The recent technology development in numerical analysis and test methods allow us to investigate the detailed behavior of tire in various rolling condition. The present article gives progresses on the mechanism understanding of tire / road noise emission and some reduction technologies.

Impact of the contact-patch gap on sound radiation from a tyre

Depending on location, vibrations on a rolling tyre may vary significantly in the noise they produce. Calculation of their amplification is thus central to tyre-noise prediction. However, the appropriate representation of sound propagation through the contact-patch region remains uncertain. More fundamentally, it is not even known whether this aspect is important. Here, this question is investigated via Boundary Element Method calculations for an idealised geometry, in which the irregular gap in the contact patch is represented by a constant-height channel between the road and the flattened-off portion of a cylinder. Compared to calculations with no gap, the results show attenuation of the high amplification levels in the horn-like region where the tyre nears the road, and introduction of source amplification within the gap. These features are evident for a gap as small as 1% of the cylinder radius (approximately 3 mm for a representative tyre). On this basis, it appears that the contact-patch region must indeed be modelled, and that parts of the tyre other than the horn may be significant contributors to the radiated noise.

Results of Patch Testing to Botanicals: Review of the Mayo Clinic Experience Over 2 Decades (1997-2017).

Background: Botanicals are increasingly incorporated into skincare products. Although allergic contact dermatitis due to botanicals is recognized, data describing the prevalence of positive patch tests to botanicals are sparse. Objective: To report the Mayo Clinic experience of patch testing to selected botanical products in the standard, extended standard, fragrance, and plant series. Methods: IRB-approved retrospective study of the Mayo Clinic experience with patch testing to botanicals from 1997 to 2017. Results: In total, 12,169 people were patch tested to botanicals in the standard, extended standard, fragrance, and plant series; 4032 were men and 8137 were women. The mean age of the population tested was 54 (standard deviation 17.7) years. Almost 11% (1320/12,169) of the patch-tested population exhibited positive reactions to at least 1 botanical agent. Myroxylon pereirae resin 25% was the most common positive allergen in the series. Patients who had positive reactions to at least 1 botanical agent were more (19.8%) likely to have a positive reaction to at least 1 additional botanical than those patients who did not have any positive tests. Most patients presented with generalized involvement (334) or involvement of the hands (284) or face (232). Conclusion: Physicians should be aware of the high prevalence of allergic contact dermatitis and patch test positivity associated with botanical products.

Research into the Peculiarities of the Individual Traction Drive Nonlinear System Oscillatory Processes

Auto-oscillations may occur in moving vehicles in the area where the tire interacts with the support base. The parameters of such oscillations depend on the sliding velocity in the contact patch. As they negatively affect the processes occurring in the electric drive and the mechanical transmission, reducing their energy efficiency, such processes can cause failures in various elements. This paper aims to conduct a theoretical study into the peculiarities of oscillatory processes in the nonlinear system and an experimental study of the auto-oscillation modes of an individual traction drive. It presents the theoretical basis used to analyze the peculiarities of oscillation processes, including their onset and course, the results of simulation mathematical modeling and the experimental studies into the oscillation phenomena in the movement of the vehicle towards the supporting base. The practical value of this study lies in the possibility to use the results in the development of algorithms for the exclusion of auto-oscillation phenomena in the development of vehicle control systems, as well as to use the auto-oscillation processes onset and course analysis methodology to design the electric drive of the driving wheels.

Tyre–Road Heat Transfer Coefficient Equation Proposal

Tyres are one of the most important elements of a vehicle because they are the link to the road and have a huge impact on traffic-related pollution. Knowing their behaviour, thus being able to use them at their best and reducing their wear rate, is one of the means of improving their lifetime, which means decreasing traffic environmental impact. In order to understand how tyres behave and to predict the real-time tyre–road coefficient of friction, which is strongly influenced by the temperature, in the last few years several complex thermo-mechanical models of heat transfer inside the tyre have been developed. However, in the current state of the art of the literature and practice, there is still an important parameter regarding such models that is not deeply studied. This parameter is the heat transfer coefficient between the tyre and the road at the contact patch, which usually is considered as a constant. The current research paper allows understanding that such an approximation is not always valid for all of the speeds and tyre loads of city and race cars; instead, it is developed an equation that, for the first time, calculates the real-time, dynamic tyre–road heat transfer coefficient, taking into account the tyre’s travelling speed and the footprint length. The equation results are in good agreement with the empirical values coming from the literature and permit understanding how much such a parameter can vary, depending on the tyre use range. The formulation is simple enough to be easily implemented in existing thermodynamic tyre models without requiring meaningful computational time.

A vehicle-bridge interaction model considering contact patch size and vehicle self-generated excitation – A theoretical study

This paper presents an improved theoretical damped single-axle vehicle-bridge dynamic interaction model to consider the effect of the contact patch size and motor-induced vehicle excitation. The contact patch issue is critical as it determines the minimum time step for simulation and maximum identifiable frequency, while the inclusion of the motor-induced vehicle excitation benefits the design of autonomous self-driven rather than towed vehicles. Estimations of the contact patch size for both the pneumatic tire and solid wheel scenarios are discussed. The contact patch responses, which degenerate into contact point responses when the contact patch size is assumed to be infinitely small, were derived for the first time both from the vehicle and bridge responses to confirm their equivalence. The minimum time step, which determines maximum identifiable frequency but is arbitrarily chosen in literature, is proposed to be determined by the vehicle speed and contact patch length. The procedures to extract multiple bridge triad information including natural frequencies, mode shapes, and damping ratios from the vehicle responses are also presented. Based on extensive parametric analyses, the sinusoidal vehicle excitation becomes more prominent as its amplitude and/or frequency increase and may overshadow the analysis of bridge frequencies of interest. The vehicle acceleration leads to a more accurate extraction of bridge mode shapes and damping ratios than the vehicle displacement since the displacement is dominated by the fundamental mode of bridge vibration. The damping ratio extraction shows an average error of 0.28% from the instantaneous amplitude of the vehicle acceleration signal.

Omicron variants of SARS CoV-2 indicate how small molecules can interfere with spike glycoprotein trimerization

In our search for a possible achilles’ heel of SARS-CoV-2, we explored the variability of 1,382,462 complete sequences of the viral spike glycoprotein, all the ones that we could retrieve from the NCBI SARS-CoV-2 databank as of 6 March 2023. Then, by using the Shannon entropy algorithm, we quantified the sequence variability of SARS-CoV-2 spike glycoprotein. With PDBePISA, we have performed a detailed analysis of protomer-protomer interfaces of the spike glycoprotein for two representative structures of different viral variants. The largest protomer-protomer contact patch that is present in the stem region of both structures is highly conserved. It is remarkable that the Asp796Tyr mutation, centered in this patch, is always present in all the Omicron variants. The structure of the SARS-CoV-2 Omicron spike glycoprotein trimer indicates that Tyr796 and Phe898 of the same protomer form a network of aromatic sidechains with Tyr707 of another protomer, yielding a strong constraint that stabilizes the spike glycoprotein quaternary assembly. We believe that the resulting structural stability of the viral trimer is among the key features for the successful proliferation of Omicron variants. This finding also supports the fact that disrupting this network of aromatic moieties with suitable small molecules would represent a powerful antiviral strategy.

Measurement of Contact Patch Pressure Behaviors in High-Speed Dynamic Conditions

ABSTRACT Many of the challenging problems in tire dynamics are related to what happens inside the contact patch. Important tire performance attributes such as grip/friction, wear, and noise are all directly related to the contact patch. Calspan and its technology partner Tekscan have developed a novel sensor system that measures the contact patch pressure of the tire as it is rolling at high speed on a flat-belt tire test machine. The measurement results provide detailed insights into the dynamic contact patch pressure (DCPP) in a wide range of realistic and relevant operating conditions on a flat roadway surface. The contact patch behaviors of three tires of similar size and type, but from different manufacturers, were compared. The results highlight how differences in tire design decisions influence the contact patch behavior and in turn the overall tire performance. Additional applications of the DCPP data are presented and discussed.

Identification of Characteristic Tire Parameters for the Virtual Steering System Design

ABSTRACT The virtual design of steering systems requires suitable premises for predicting realistic steering rack forces. This includes the proper tire used for the parking maneuver. It is important to select the tire from a portfolio that generates the highest rack forces at the vehicle, so that the electro-mechanical dimensioning of the steering system can be safeguarded for all tires of a vehicle. To avoid time-consuming and expensive full vehicle measurements, drilling torques of tires are measured on a Flat-Trac to determine the so-called worst-case tire. However, the determined drilling torques do not correlate with the measured rack forces. This work therefore investigates the suitability of a Kinematics & Compliance test rig converted to a tire test rig. First, it is investigated whether the wheel movements from the parking maneuver can be decomposed into their individual elements on the test bench. In addition, reproducibility studies are carried out and three different methods for determining the aligning torque under camber are presented. Furthermore, measurements for static and dynamic friction values, as well as stiffnesses and the contact patch, are integrated into the new measurement procedure. It becomes apparent that temperature and wear level of the tire play a major role in the reproducibility of the measurements. If the measurement procedure described in this paper is followed exactly, the scatter of the drilling torque can be reduced by up to 24% compared to the old procedure. For the dynamic and the static friction values, the scatter is reduced by about 17% and 22%, respectively. Stiffness scatter can be reduced by up to 16%. With the new measurement procedure, the worst-case tire can be reliably determined. The drilling torques correlate with the rack forces and the additional tire characteristics permit finer resolution. After evaluation and interpretation, recommendations for future developments are discussed.

A Soft Sensor for Estimating Tire Cornering Properties for Intelligent Tires

Intelligent tire systems are promising solutions for achieving precise vehicle state estimations, localization, and motion control in the context of autonomous driving. Tire cornering properties, namely, lateral force, aligning moment, and pneumatic trail, are crucial factors that should be accurately estimated for vehicle dynamics control purposes. In this work, a soft sensor for estimating tire cornering properties based on intelligent tire and machine learning is developed. The intelligent tire system is based on a triaxial accelerometer mounted on the inner liner of the tire tread, which provides acceleration measurements from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$</tex-math> </inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$</tex-math> </inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z$</tex-math> </inline-formula> directions. Partial least squares and variable importance in the projection scores (PLS-VIP) are used in the feature extraction of the acceleration signals over the contact patch. A Gaussian process regression (GPR) model is trained to predict the cornering properties with confidence intervals under different input conditions. Based on the variances in the GPR predictions and minimum mean-square error criterion, a data fusion method for pneumatic trail estimation is proposed. It is demonstrated that the developed GPR models for cornering properties and the data fusion method for pneumatic trail estimation have satisfactory accuracy and reliability. The experimental results show that the soft sensor proposed in this work is a strong candidate for further applications in the development of vehicle state estimation and control algorithms.

Comprehensive Grounding Performance Evaluation of Tires Based on the Analytic Hierarchy Process

ABSTRACT The contact patch between tire and road surface has a direct impact on tire grounding performance. Acquiring tire grounding performance either by testing or simulation is not only time intensive but comes at a high cost. This paper proposes an effective means of evaluating tire grounding performance based on the tire-ground contact pressure distribution. This paper adopts fifteen characteristics to describe the tire-ground contact patch in which twelve structural schemes were designed for a certain type of tire. By using the simulation test method, the grounding performance characteristics such as grip performance, rolling resistance, wear performance, and the tire footprint characteristics were obtained. Correlation analysis was used to explore the relationship between tire grounding performance and footprint characteristics. Based on the correlation analysis and expert judgement, the analytic hierarchy process (AHP) model for comprehensive grounding performance evaluation of a tire was constructed. Then judgment matrix of the AHP model was established, and the consistency or otherwise of the judgment matrix was verified. The model was then used to evaluate and predict the four design schemes of tires. The evaluation results were in good agreement with the simulation test results, which shows that the construction method of the tire comprehensive grounding performance evaluation system proposed in this paper is practical. It is also evident that grounding performance evaluation of a tire based on the tire footprint is feasible.

Friction Law for Rubber from Laboratory Abrasion Tester

ABSTRACT This paper aims to devise a method to obtain an empirical friction law for rubber using the Laboratory Abrasion Tester (LAT 100). The LAT 100 experiments, which aim to measure the side force at various slip angles, loads, and speeds, are carried out, followed by finite element simulation using ABAQUS. A friction law is implemented using a subroutine (UFRIC), which calculates the friction coefficient at each node on the contact patch based on contact pressure and slip velocity at the corresponding node. Coefficients of the frictional law, μ = a + b × e−1/(αp) + c × e−1/(βv), have been estimated by using a series of simulations along with minimizing the error between experiment and simulation side forces. The procedure followed in this paper can be used to fit friction models for rubber using LAT 100 side force experiments.

Simulation model of contact interaction during surface strengthening of steel parts

In the processes of surface strengthening of steel parts, the stress-strain state is decisive for explaining the physical processes of strengthening, forming the dimensions of the contact area. Analytical dependences of contact parameters are quite approximate. In this work, based on the Ansys software complex, a simulated model of the contact of a truncated torus with a cylinder is proposed, which demonstrates the kinetics of the process of pressing a hard alloy tool into a steel workpiece - a cylinder. The experiment was conducted for 4 seconds in order to determine the maximum level of stresses, the distribution of stresses and the amount of residual stresses after removing the load. The clamping force was applied mainly in the zone of elastic deformations. The results showed an uneven stress distribution with a maximum in the center of the contact spot of 1082 MPa. After changing the load direction, small residual deformations at the level of 0.00311 μm were observed in the center of the contact patch. This indicates a violation of the elastic region on a small contact area, which does not affect the general nature of the stress distribution and can be removed during the finishing process. The results of simulation of the stressed state are used for the correlation with the observed structural changes of the material during the action of thermal and power stresses. The stress peak was formed at a distance of 200 μm, which contributes to the formation of maximum values of microhardness at this depth.

A new scaled testing methodology for the analysis of rolling contact fatigue in railway steels.

Twin disc testing is a relatively cost effective and practical method of investigating the damage resistive properties of rail steels in a scaled environment. The loading conditions and dimensions used in testing are scaled in such a way that the Rolling Contact Fatigue (RCF) generated on a twin disc rig are representative of the conditions experienced at the full-scale. Typical methodologies to generate RCF on a twin disc rig involve the application of water to the contact patch throughout the test, with perhaps a few thousand dry cycles being run beforehand. This research explores the use of weather data to reflect the real-world contact conditions more accurately between a wheel and rail. Met Office weather data collected from 1981 to 2010 shows the average annual precipitation in the UK is around 133 days of rain or snow, which is nearly 36 % of the year. In this study, weather data was used to determine the ratio of wet to dry cycles in the testing methodology.&amp;nbsp; 50k dry cycles are run in intervals of 5k and then transitioned to 25k of wet cycles, which is 30% of the total cycles. Intervals were kept at 5k so attaining 36%. If RCF is not initiated after the first 75k cycles, which ends with 25k wet cycles, then the same dry and wet cycles are repeated. RCF data generated using this methodology demonstrated expected differences in the RCF resistive properties of two rail steel grades, R260 and R350HT. In test 1 the point of initiation for each grade was not captured, though cracks were visible around the expected cycles to initiation, which was verified using optical microscopy. The cracks viewed on the softer R260 steel samples, ‘’260’’ referring to the Brinell hardness value of the steel, were more developed at 85k cycles and showed signs of spalling, whilst the cracks on the harder R350HT sample were much smaller. In test 2 the point of initiation was found for each grade. Optical microscopy was also used to show the depth and direction of head check cracks to ensure the damage viewed from the head was RCF and not plastic flow or cyclic wear. This paper shows the necessity for considering the number of wet cycles applied during twin disc testing and demonstrates it is possible to run a high number of wet cycles which are more representative of real-world conditions when generating RCF on twin disc rigs.&amp;nbsp;&amp;nbsp;

Numerical Investigation of Elastic Layer Effects in Wheel–Rail Rolling Contact

In railway systems, layered structures could be induced in wheel–rail contact interfaces due to several causes, such as head hardening, work hardening, plastic deformation, and mechanical or thermal excursion-induced phase transformation. This study proposes an explicit finite element (FE) method for investigating elastic layer effects in wheel–rail rolling contact. The proposed method is first validated by comparing its solution with that of Kalker’s boundary element method (BEM) when the layer is not present, with a focus on the tractive rolling contact. To investigate general layer effects, the rail is assumed to consist of two layers, i.e., the top layer and the matrix material. The top layer is assumed to have different elastic moduli from the matrix material and then the top elastic layer effects on contact characteristics such as contact stress, contact patch, and subsurface stress are investigated. Different layer thicknesses are also considered. It is observed that a harder layer tends to introduce larger contact pressure and surface shear stress, but a smaller contact patch. A harder layer also produces larger subsurface stresses. A thicker layer may intensify these effects. The results suggest that in engineering applications, the analysis of wheel–rail rolling contact consequences such as wear and rolling contact fatigue (RCF) may need to consider the layered structures using appropriate methods.

The tyre blow-out vehicle lateral pulling control using an active suspension system with comfort-lateral trajectory based control scheme.

When a tyre blows out, the vehicle’s trajectory deviates from the intended path, resulting in an accident and death. Because of its larger contact patch, applying more steering force to the flat tyre will cause the tyre to separate from the wheel. Also, improper braking effort causes rollover related issues due to the sudden vehicle’s centre of gravity (C.G.) displacement and weight transfer towards the blow-out tyre. Therefore, this research attempts to return the C.G. to its initial position through the suspension control. The force supplied between the sprung and unsprung masses of the flat tyre through suspension actuator is estimated and controlled by the model predictive control (MPC) scheme with respect to its input signals. For the non-linear simulation, the four-wheel passenger car vehicle dynamic model and the combined empirical model for the tyre inflation pressure effect are used. And the equivalent plant model is identified through a simple system identification method for the MPC design. The passive and active based suspension of standalone, roll-resistant interconnected and pitch-resistant interconnected systems, including the proposed comfort-lateral trajectory controlled standalone active suspension, were examined. To assess the effectiveness of each suspension and its control strategy in a tyre blow-out scenario, a vehicle was analysed with various longitudinal velocities along with and without steer input.

The investigation of the contact and wear of railway axle bearings under various race conformities

The bearing race conformity is a design parameter that determines the degree of contact between rollers and races. This paper investigates the effect of race conformity on wear distribution in a railway spherical roller bearing under boundary lubricated condition in which contact behaves like a dry contact. The results showed that the traction/micro-slip distributions were substantially dependent on the level of conformity. The wear is found to be highly sensitive to the race conformity, with lower conformity resulting in lower wear. For example, 5.2% increase of conformity factor, a parameter that represents race conformity mathematically, reduces worn area by 52% in inner contact that is 60% in outer contact where conformity factor increase is 5.8%. This is mainly due to high value micro-slip being truncated at the edges as the traction distribution is compressed into the smaller contact patch. The bearings with ceramic rolling elements show lower wear than for steel rolling elements due to lower wear coefficient. The higher elastic modulus of ceramic causes the traction magnitude to be higher in the ceramic-steel case over the steel-steel case. Therefore, race conformity can be taken into consideration to optimize roller bearing wear life.

Investigation on the transient rolling contact behaviour of corrugated rail considering material work hardening

The process of work hardening in the corrugation zone of the steel rail results in an uneven distribution of hardness, with higher hardness in the corrugation troughs and lower hardness in the corrugation crests. To study the influence of hardness on the rolling contact behavior of the wheel-rail at corrugation zone, a three-dimensional wheel-rail transient rolling contact finite element model is established based on the measured corrugation and hardness distribution of the rail to reveal the influence of the non-uniform distribution of hardness at corrugation zone on the wheel-rail contact state and the wear and fatigue of the rail surface. The results indicate that: (1) work hardening in the corrugation zone leads to an increase in equivalent stress and strain within the contact patch between the wheel and rail. However, due to the increase in yield strength, plastic deformation and residual strain are somewhat reduced; (2) The uneven distribution of hardness in the corrugation zone results in an elevation of longitudinal shear strain between the wheel and rail, which may initiate tangential fatigue cracks and spalling of the steel rail surface; (3) the wear on the rail surface is large near the wave crest and small near the wave trough, work hardening will change the wear difference between the wave crest and wave trough while reducing the wear, resulting in the “peak shaving and valley filling” phenomenon developing faster in the early wave wear period and slower in the later period.

SUBSTANTIATION OF INDUCTION HEATING DURING FLANGING OF TUBULAR WORKPIECES BY ROLLING FORMING

Rolling forming (RF) processes are among the most efficient methods of metal forming. The required profile of the workpiece in rolling processes is formed by local deformation with conical or cylindrical rolls using sound technological schemes. When roll forming pipe billets with a ratio of the height of the initial deformed part to the wall thickness of more than 2.5, the flange seating process is made impossible by the loss of billet stability with subsequent fold formation. This phenomenon makes it impossible to produce wide flanges by drawing. To form workpieces with particularly wide flanges, we have developed a flanging method by rolling stamping. The essence of the flanging method is that at the initial stages of rolling, the top of the conical roll is shifted in the direction of the contact patch. At intermediate stages, to prevent the workpiece wall from turning inside out, the top of the roll is shifted in the opposite direction (along the workpiece axis). The main technological constraints are imposed by the insufficient ductility of the billet material, which can cause fracture. To develop the flanging processes in a reasonable manner, we studied the mechanics of outer flange deformation and methods of controlling material flow. The stress-strain state (SSS) of the material was analyzed using the hardness measurement method and the mesh method. The nature of the change in the stress-strain state in the most dangerous zones of the workpiece was determined, depending on the ratio of the flange diameter to the initial workpiece. Based on the experimental results, a mathematical model of the deformation trajectory of material particles of the outer surface of the flange in the coordinates of deformation intensity - an indicator of the stress state - was constructed. To assess the deformability of the material, a damage summation model with a power law approximation of the damage function was used. The model allows us to determine the ultimate fracture dimensions of the flange, as well as the plasticity resource used at intermediate stages. The condition for the suitability of metals for flanging by rolling stamping for engineering calculations is obtained. The necessity of applying induction heating in the processes of culling by rolling stamping is substantiated. This makes it possible to expand the technological capabilities of flanging processes by developing and using induction heating of workpieces, due to an increase in the plasticity characteristics and a decrease in the strength characteristics of metals in the process of deformation.

Twisting torque – A simplified theoretical model for bicycle tyres

In this paper, the twisting torque of bicycle tyres is studied. The twisting torque is just the self-aligning torque for null lateral slip and non-null camber. The relationship between twisting torque and contact patch area has been analyzed. As the latter increases, twisting torque increases as well. A theoretical model to evaluate twisting torque has been implemented. Since twisting torque is mainly due to longitudinal slip in cambered wheel, increasing the contact patch area the stresses are located at a larger distance from the median plane of the contact patch. The resulting torque will be higher in magnitude.Finally, the model has been validated comparing the outcomes with the experimental data, with a mean error less than 3% for camber angles less than 10°.