Tread Region Research Articles

Shoe tread wear occurs primarily during early stance and precedes the peak required coefficient of friction

Worn shoes contribute to injuries caused by slip-and-fall accidents. The peak required coefficient of friction (RCOF) has been associated with tread wear rate. However, the temporal relationship between RCOF and shoe wear is unknown. The purpose of this study was to determine whether the contact region at the time of peak RCOF is consistent with the region of shoe wear. The shoe contact region at peak RCOF was imaged by frustrated total internal reflection. Images of worn tread after months of use were captured. The worn tread region was more posterior than the contact region at RCOF and did not correlate with the contact region at the time of RCOF. The contact regions observed during earlier stance (within 83 ms of heel contact) were more consistent with the worn region, suggesting that RCOF may not directly cause tread wear. These results serve to motivate future studies to identify early stance gait parameters associated with tread wear development.

Simulation based Sensitivity Study of Tread Pattern and Materials on Cooling Efficiency of M1 Vehicle Tyres

Tread wear of tyres is one of the serious issues in automobiles. Higher amount of heat is generated due to lesser availability of air in the tread region when the vehicle is travelling at high speeds. The existing M1 vehicle tyre has some specific standards of tread angle. In this paper, flow simulation and drop tests of M1 vehicle tyre are carried out using Solidworks. The objective of the work is to improve the cooling efficiency of tyre for vehicle speeds as 40 kmph, 80 kmph and 120 kmph. Various tread patterns for tyres made with hard rubber, Nylon66 and Nylon6 materials were simulated to predict the temperature distribution. Based on the temperature distribution and drop test results from the simulation, improved designs of M1 vehicle tyre are presented.

Locomotive wheel failure from gauge widening/condemning: Finite element modeling and identification of underlying mechanism

Gauge change in straight plate, locomotive, railway wheels is studied using finite element analysis. The study accounts for residual stresses generated during wheel manufacturing and fitment of the wheel on locomotive axle. A validated thermal model accounting for heat loss to rail, brake blocks and ambient air is considered for accurate prediction of wheel temperatures for a given train running and braking history. Results are obtained for low- and high-friction, composite brake blocks used by Indian Railways for two limiting braking scenarios: (i) synchronized braking where braking effort is uniformly distributed on all brake blocks and (ii) independent braking where braking effort to decelerate a train is provided solely by locomotive brake blocks. Results show that bending at hub–disc interface predominantly governs the gauge change. While compressive hoop stresses in the tread region, occurring from rim heating during braking, cause gauge reduction, tensile hoop stresses in the tread region, occurring during wheel cool down cause an increase in wheel gauge. Importantly, while gauge condemning is a transient phenomenon occurring only during braking, gauge widening is “permanent” as it exists even after the wheels cool to room temperature. Allowable reduction of wheel gauge of 0.5mm, currently used by Indian Railways, is found to be highly restrictive. In fact, in service wheel failure based on this criterion is observed in all braking scenarios considered.

Estimation of railway wheel running temperatures using a hybrid approach

Accurate prediction of railway wheel temperatures, for a given running and braking history, is crucial for estimation of service induced thermal stresses which can affect wheel gauge and fatigue crack growth, particularly in tread region. In this work, a three step approach is adopted for estimating wheel temperatures. Firstly, a train running model employing brake block friction, wheel–rail traction-slip, and train running resistance characteristics are used to estimate heat generation rates at brake block–wheel and wheel–rail interfaces. Next, a two dimensional boundary element method, proposed in this work, is used to estimate heat partitioning at the said interfaces as a function of brake block type, geometry, and thermal properties. Lastly, finite element method is used to estimate wheel temperatures taking inputs from the train running model and the boundary element method. The adopted methodology is validated using wheel temperatures, on rim and rim–disc interface, from field trials of a locomotive fitted with cast-iron brake blocks. A good match between simulation and field trial results was obtained despite highly complex speed and braking patterns encountered in the field trial. For periodic braking with no stopovers, heat lost to the rail, cast-iron brake blocks, via radiation, and convection are seen to be comparable to one another. Enhanced convective cooling of railway wheels and use of higher diffusivity brake blocks are seen to be effective ways of reducing the wheel temperatures and resulting thermal stresses.

Cardiomyocyte growth and sarcomerogenesis at the intercalated disc

Cardiomyocytes grow during heart maturation or disease-related cardiac remodeling. We present evidence that the intercalated disc (ID) is integral to both longitudinal and lateral growth: increases in width are accommodated by lateral extension of the plicate tread regions and increases in length by sarcomere insertion within the ID. At the margin between myofibril and the folded membrane of the ID lies a transitional junction through which the thin filaments from the last sarcomere run to the ID membrane and it has been suggested that this junction acts as a proto Z-disc for sarcomere addition. In support of this hypothesis, we have investigated the ultrastructure of the ID in mouse hearts from control and dilated cardiomyopathy (DCM) models, the MLP-null and a cardiac-specific β-catenin mutant, cΔex3, as well as in human left ventricle from normal and DCM samples. We find that the ID amplitude can vary tenfold from 0.2 μm up to a maximum of ~2 μm allowing gradual expansion during heart growth. At the greatest amplitude, equivalent to a sarcomere length, A-bands and thick filaments are found within the ID membrane loops together with a Z-disc, which develops at the transitional junction position. Here, also, the tops of the membrane folds, which are rich in αII spectrin, become enlarged and associated with junctional sarcoplasmic reticulum. Systematically larger ID amplitudes are found in DCM samples. Other morphological differences between mouse DCM and normal hearts suggest that sarcomere inclusion is compromised in the diseased hearts.

Prediction of residual stresses in low carbon bainitic–martensitic railway wheels using heat transfer coefficients derived from quenching experiments

Low carbon bainitic–martensitic (LCBM) steels have been recently developed for railway wheels and have been shown to provide superior properties compared to conventional pearlitic railway wheel steel grades. Pearlitic railway wheels are generally quenched at the tread region to promote the formation of compressive residual stresses in the rim to mitigate the initiation and propagation of cracks due to fatigue. However, this conventional quenching method has been shown to be unsuitable for LCBM railway wheels. Alternative quenching methods were evaluated using a FE model to develop a successful quenching process to produce LCBM railway wheels. Heat transfer coefficients were determined by employing a full scale experimental rig and were used in the FE model to model various coolant spray intensities and configurations. The FE model was used to determine optimal quenching conditions that impart compressive residual stresses to the rim of the LCBM railway wheel and the prediction of residual stresses were verified experimentally.

Enhancing rail vehicle stability using bogie direction reversal

Steel wheels are facing the problem of plastic deformation and wear during their operation. Wheel wear within the flange and tread regions can affect the dynamics of rail vehicles. A number of methods are commonly employed to decrease the wear rate within both the flange and the tread regions of wheels. This paper focuses on the running-in period, and on a procedure for Bogie Direction Reversal 1 (BDR) to indicate the importance of operational aspect on the dynamics improvement of wheelset behaviour, and hence, vehicle safety and stability. Test results of eight wheels in a case study have been presented and analysed.

1112 低燃費性能向上を目指した分割トレッドタイヤのキャンバ制御(OS2-3 路面とタイヤ,OS2 交通・物流システムのダイナミクス,オーガナイズド・セッション(OS))

This paper proposes variable camber angle control by optimize tread use on the tire with two layer compound for tread part to improve automobile fuel efficiency. Based on this concept, the tire with two tread regions was developed: one with low rolling resistance (low loss) and the other with high grip. Initially the tire characteristics were analyzed using a tire testing machine. For comparison, the characteristics of a low loss tire and a high grip tire were also measured. The effect of proper use of the low loss and high grip regions was confirmed. In vehicle experiments, the tire with two layer compound for tread part was evaluated for both rolling resistance and full braking characteristics. The proper combination of camber control and the tire with two layer compound for tread part was shown to result in both reduced fuel consumption and improved braking performance.

Rail vehicle wheel wear prediction: a comparison between analytical and experimental approaches

There are a number of theoretical and practical techniques to compute rail vehicle wheel wear. For instance, the Archard equation is a well-known tool to determine the worn volume in sliding contact, as a function of normal load, sliding distance and the surface hardness. Of course, the wear coefficient (called K) used in this equation to differentiate the wear models implicitly comprises the conditions that govern the contact surface. Two situations can be taken into account when considering a sliding contact in a rail vehicle wheels, particularly along a curved track: (i) when the radial force prevails the lateral tangential force, which is mainly the frictional force but before flanging and (ii) during flange contact. Also, the Archard equation is employed within the tread and flange regions separately, both the regions being of interest in this paper. A number of approaches are then used to find the distance slid. The authors compare the field test results and the outcome of the analytical approaches. When the wheel wear results acquired from the two test bogies on Iranian Railways, all technical (rigid frame bogies with new assemblies and components) and operational items were identical, except for changing the bogie orientation in the second test trial for a short period. Good agreement was found between the analytical and practical investigations.

Stress Analysis of Tire Sections

Abstract An experimental stress-strain analysis by means of the Moiré method was conducted in the area of the tread and belt regions of tire sections. A special loading fixture was designed to support the tire section and load it in a manner simulating service loading and allowing for Moiré measurements. The specimen was loaded by imposing a uniform fixed deflection on the tread surface and increasing the internal pressure in steps. Moiré fringe patterns were recorded and analyzed to obtain strain components at various locations of interest. Maximum strains in the range of 1–7% were determined for an effective inflation pressure of 690 kPa (100 psi). These results were in substantial agreement with results obtained by a finite element stress analysis.

Low noise pneumatic tire tread with voids balanced over each half tread region

A low noise pneumatic tire tread and method for producing same characterized by the minimization of the total amount of acoustic energy produced by a tire's tread as it rolls over a road surface by the strategic placement of grooves in a tread design such that the amount of groove void across at least one of the trailing and leading edges of the tread's footprint is substantially uniform about the circumference of the tire.

Load, Speed, and Pressure Effects on Passenger Car Tire Rolling-Loss Distribution

Abstract The procedure explained in this paper permits calculation of individual tire region contributions to rolling loss without altering the tire. Many different tire-build configurations can be considered using this technique. Different belt, bead, and subtread materials' contributions to rolling-loss distribution can be studied; different tire shapes and thicknesses can be considered. Only a single tire of each configuration need be built, and it can be retested if necessary. Results obtained here show that the tread region of the tire tested behaves differently than the other regions. Changes in tire pressure, load, and speed lead to changes in the remaining individual tire regions' contributions that are in the same direction as the overall tire loss. A tire design that is altered to accommodate new specifications may lead to an increase in rolling loss that is greater than some designated value. An analysis of the type presented here may show which region of the new tire design should be changed to bring the loss within desired limits. The heat-transfer coefficient of the tire in this model is a linear function of velocity, independent of tire load and pressure. We have confidence in this relation as the model results are derived from both loss measurements and tire surface temperature measurements made in the laboratory. The model output is based on fundamental heat-transfer precepts and treated mathematically by established analysis techniques.

Load, Speed and Inflation Pressure Effects on Rolling Loss Distribution in Automobile Tires

Abstract The effect of tire load, speed, and cold inflation pressure on the rolling loss contribution of any tire region is determined by numerical calculations involving both laboratory measurements and thermal modeling techniques. Laboratory measurements include tire surface temperature distributions obtained from an infrared camera system; thermal modeling is based on finite-difference procedures. Results are presented in two formats: (1) plots of rolling loss distributions from bead to bead and (2) contributions of tread, shoulder, sidewall, and bead regions. The first format is a direct result of the thermal model; the second is derived from multiple-regression operations. Both formats are given as functions of load, cold inflation pressure, and speed. Beahvior in the tread region is shown to be unique.

Simulation Model of Tire Vibration

Abstract A mass-spring tire model having five degrees of freedom is used to analyze the tangential and radial axial forces that result from a tire hitting a cleat. The belt and tread region is modeled by a rigid ring. Deflections from the cleat are absorbed by a line spring and those from the smooth portion of the test wheel (the ground) are absorbed by a plane spring; both are attached to the rigid ring. Calculated results agreed well with experimental results.

Ultrasonic Method of Tire Inspection

The principles of a method are discussed for detecting internal defects in pneumatic tires, such as ply separations, by the attenuation of transmitted ultrasonic waves. Equipment for carrying out tire inspections by this method is described. It includes provisions for inspecting a large range of tire sizes, scanning the tread region from shoulder to shoulder and is suitable for operation by inspection personnel. A useful form for recording the results of a tire inspection is described. One of the principal applications for this method of inspection is the examination of tires to determine their suitability for recapping.