Running Surface Research Articles

Specification of estimation of a passenger car ride smoothness under various exploitation conditions

The stability and smoothness of rolling stock running could be defined accurately by universal Sperling's comfort index. The divergences of variation of Sperling's comfort index of a passenger car under specific operating conditions of running gear are examining in this paper. Numerical simulations of a passenger car running with independently rotating wheels under various conditions have been performing. Gained results showed that divergences of the Sperling's comfort index variation are particularly significant due to running gear component oscillations in the horizontal plane (lateral direction). A field experiment of a passenger car with a solid (traditional) wheelset with a flat running surface proved this hypothesis. The obtained results of this experiment confirmed this assumption. Therefore, the study of the regularities of lateral oscillations of a passenger car is the logical direction of further research.

Running gait biomechanics in females with chronic ankle instability and ankle sprain copers

ABSTRACT Limited evidence exists comparing running biomechanics between individuals with chronic ankle instability (CAI) and those who fully recover (copers). The purpose of this study was to simultaneously analyse running gait kinematics, kinetics, and surface electromyography (sEMG) between ankle sprain copers and individuals with CAI. Twenty-six (13 CAI, 13 Coper) recreationally active females participated and ran shod on an instrumented treadmill at 2.68 m/s. We assessed lower extremity kinematics and kinetics and sEMG amplitude for the fibularis longus, tibialis anterior, medial gastrocnemius, and gluteus medius muscles. Ten consecutive strides from the beginning of the trial were analysed using statistical parametric mapping (SPM) independent t-test. The CAI group had significantly more ankle inversion during 0–6%, 42–53%, and 96–100% of the running stride cycle compared to the coper group. At initial contact (0%), the CAI group was in an inverted ankle position (5.9°±6.8°) and the coper group was in an everted ankle position (−3.2°±5.5°; p = 0.01, d = 1.5). There were no significant differences identified for any other outcome measures. Increased ankle inversion during the swing phase leading into the loading phase is concerning because the ankle is in an open packed position and inversion is a primary mechanism of injury for sustaining a lateral ankle sprain.

Leaning the Trunk Forward Decreases Patellofemoral Joint Loading During Uneven Running.

AminiAghdam, S, Epro, G, James, D, and Karamanidis, K. Leaning the trunk forward decreases patellofemoral joint loading during uneven running. J Strength Cond Res 36(12): 3345-3351, 2022-Although decline surfaces or a more upright trunk posture during running increase the patellofemoral joint (PFJ) contact force and stress, less is known about these kinetic parameters under simultaneous changes to the running posture and surface height. This study aimed to investigate the interaction between Step (10-cm drop-step and level step) and Posture (trunk angle from the vertical: self-selected, ∼15°; backward, ∼0°; forward, ∼25°) on PFJ kinetics (primary outcomes) and knee kinematics and kinetics as well as hip and ankle kinetics (secondary outcomes) in 12 runners at 3.5 ms -1 . Two-way repeated measures analyses of variance ( α = 0.05) revealed no step-related changes in peak PFJ kinetics across running postures; however, a decreased peak knee flexion angle and increased joint stiffness in the drop-step only during backward trunk-leaning. The Step main effect revealed significantly increased peak hip and ankle extension moments in the drop-step, signifying pronounced mechanical demands on these joints. The Posture main effect revealed significantly higher and lower PFJ kinetics during backward and forward trunk-leaning, respectively, when compared with the self-selected condition. Forward trunk-leaning yielded significantly lower peak knee extension moments and higher hip extension moments, whereas the opposite effects occurred with backward trunk-leaning. Overall, changes to the running posture, but not to the running surface height, influenced the PFJ kinetics. In line with the previously reported efficacy of forward trunk-leaning in mitigating PFJ stress while even or decline running, this technique, through a distal-to-proximal joint load redistribution, also seems effective during running on surfaces with height perturbations.

Comparison of Muscle Activity and Ultrasound Response of Lower Extremity Muscles During Treadmill and Track Running

Purpose: The purpose of this study was to compare the changes in lower extremity muscle morphology and electromyography (EMG) signals during treadmill running (TR) and plastic track running (PR). Methods: A total of 10 healthy male runners aged 22.5±1.3 years, height: 175.5±4.5 cm; weight: 71.9±2.7 kg; BMI: 22.1±1.1 volunteered to participate in this study. Muscle morphology data were collected by a portable ultrasound scanner before and after running. Median frequency (MF), mean power frequency (MPF) and root mean square (RMS) were monitored during TR and PR. Results: The results indicated that muscle thickness and pennation angle have increased after running. The muscle thickness after PR showed significantly higher than TR in tested muscle except tibialis anterior (TA) and medial gastrocnemius (MG). In contrast, only the pennation angle of TA and lateral gastrocnemius (LG) after PR was significantly different from that after TR (P <0.001, P = 0.002). The most significant difference in the change rate of muscle thickness was found at TA. In addition, TA and MG showed significantly higher change rate of the pennation angle after TR than that after PR. Both of MF and MPF showed a downward trend after TR and PR. It could discover that the MF and MPF of LG during TR showed a significantly lower than that during PR both in two phases (P =0.001, P <0.001). However, in the last 5 minutes, MF and MPF of MQ during PR were smaller than that during PR (P = 0.001, P = 0.015). Furthermore, MF of RF during TR showed significantly different from that during PR (P = 0.017). From the point of RMS, in the first five minutes, the RMS of medical quadriceps (MQ), lateral quadriceps (LQ), hamstring muscles (HM) and MG during TR was significantly higher than that of PR (P <0.05). In addition, the RMS of all tested muscles after TR was significantly higher than after PR during the last 5 minutes (P <0.05). Conclusions: The current study indicated that TR and PR would cause different effects to lower extremity muscle morphology. In addition, the EMG signals based on running surfaces are also unconformity. Compared with the plastic track, the treadmill will bring more stimulation to the lower extremity muscles. The preliminary findings provide further insights into the rationality of runners’ choice of the running surface.

METHOD FOR HEAT TREATMENT OF THE RUNNING SURFACE OF THE HEAD OF THE PEARLITIC STEEL RAILS

The paper deals with the new approach to the optimization of the pearlitic rail’s head hardening process aimed at balancing the relation between strength and ductility of the head running surface. In the industrial process, efforts have been undertaken so far to maximize the hardness of the rail’s head while maintaining its pearlite structure, resulting in obtaining enhanced wear resistance and resistance to the contact fatigue defects initiation. The new approach, described in this paper, aims at designing the head hardening process enabling achievement of the high hardness of the running surface combined with high ductility expressed in terms of the total elongation. To achieve this aim of the investigation, a computer program was developed capable of predicting the occurrence of the phase transformations during rail head cooling and microstructure features after cooling. The program was linked with dedicated inverse module enabling the adjustment of the cooling conditions to achieve the required state of the pearlitic structure.

Itinerant versus localized plasmons in an assembly of metal-dielectric parallel flat slabs in the presence of a perpendicular magnetic field: Faraday and magneto-optical Kerr effects

The influence of the surface running and surface localized plasmons on the optical properties (including Faraday and magneto-optical Kerr effects) is studied and compared for homogeneous as well as perforated metal-dielectric, sandwichlike structures. Closed-form exact expressions are derived for the macroscopic permittivity tensor of an assembly of metal-dielectric parallel flat slabs in the presence of an externally applied static magnetic field perpendicular to the slab plane. The structure-dependent resonance associated with running surface plasmon appears only in the perpendicular to the surface $zz$ macroscopic permittivity tensor component and does not depend on the perpendicularly applied magnetic field. The other diagonal tensor components vanish at the so-called ``hybrid cyclotron-plasma frequency,'' which depends on the slab thickness and the applied magnetic field. All analytical results are verified by numerical simulations.

Structure, Phase Composition and Properties of Rail Running Surface at Extremely Long Operation Time

Structure, Phase Composition and Properties of Rail Running Surface at Extremely Long Operation Time

Numerical study on the ratcheting performance of rail flash butt welds in heavy haul operations

The ratcheting performance of a new R400HT rail flash butt weld was numerically evaluated under a typical heavy haul in-service condition. Due to varying mechanical properties across the rail weld, the weld region was divided into 23 zones in the numerical study. A dynamic finite element simulation of wheel–rail weld rolling contact was first carried out to obtain the total vertical contact force and its variation along rolling distance. Multiple quasi-static wheel–rail weld contact simulations were then performed by applying the total vertical contact force to determine the non-Hertzian contact pressure distribution when the wheel was located at different positions across the weld in the rolling direction. Based on each normal contact pressure distribution, the Haines and Ollerton's strip theory and Carter's theory were employed to estimate the corresponding longitudinal surface tangential traction distribution. Finally, a cyclic loading simulation was conducted to evaluate the ratcheting performance of the rail weld in terms of RCF initiation life by repeatedly translating these normal contact pressure and longitudinal tangential traction distributions on the running surface. The results reveal that the subzone with the lowest hardness in the softened zone has the shortest RCF initiation life among the weld region, followed by the region around the bond line. The parent rail provides the longest RCF initiation life and therefore has the best resistance to RCF. Additionally, the existence of the softened zone can shorten the RCF initiation life of the parent rail and the bond line section, particularly the regions located adjacent to the softened zone. The possible location of RCF initiation in the softened zone of the rail head can reach deeper than those in the parent rail and the region around the bond line. The results can help us understand the failure of flash butt rail welds in heavy haul operations and the numerical method can be applied to study different rail welds and rail welds under different conditions such as in a curved track.

A preliminary study on enhancing safety of contact features in the terrain park

ObjectivesTerrain park riders use contact features such as fun boxes and rails. Typical fun box and rail features have a design characteristic that can be changed to improve safety. Fun box edge coping and edges of rails are typically constructed of soft steel. Ski/snowboard edges (HRC50) can easily become engaged in the softer metal, causing a chip to develop, suddenly stopping the rider, probably causing a fall and possible injury. The aim of the study is to examine the effect of terrain park running surface hardness on chip development. DesignTesting on steel specimens was performed to research chip development generated by a ski/snowboard edge on steel used in the construction of contact features and on steel that is proposed for such use. An apparatus was constructed to simulate a ski/snowboard edge moving perpendicular to the long axis of coping or rail edge. MethodsThe author performed observation, photographic documentation, metallurgical testing and environmental testing of various contact features at different ski area terrain parks. Several steel specimens of varying hardness were tested at various load levels to study the propensity of chip development by ski/snowboard edges. ResultsTesting of steel samples showed that increasing the hardness of the rail steel or coping steel reduced the propensity for a ski/snowboard edge to engage in the coping or rail. ConclusionsIncreasing steel coping and rail contact surface hardness to HRC 50 and above will likely reduce engagement by steel snowboard/ski edges, which in turn is expected to reduce the chance of a fall and injury.

The effect of uneven terrain conditions during shod vs. barefoot running

Background: The majority of research on barefoot running focuses on acute changes in altering footwear without regard to the runner's experience with barefoot or minimalist footwear running. Objective: The objective of this study was to compare the effect of footwear (standard cushioned running shoes, barefoot) and running surface (flat surface, uneven terrain) on gait in experienced runners using minimalist shoes. Methods: Terrain running was simulated by three custom-made mats with randomly placed firmly attached stones. Seven experienced trail runners participated in this study. All participants were forefoot strikers. Participants underwent three-dimensional kinematic and kinetic analysis consisting of five running trials in each combination of footwear and surface. A trial was successful when the participant maintained a velocity of 3.2 ± 0.16 m/s without targeting a force platform. Results: Uneven terrain conditions along with barefoot conditions led to significantly decreased peak moment of ankle plantarflexion (terrain: p = .041, footwear: p = .026) and decreased second peak of vertical ground reaction force in comparison with other conditions (terrain: p = .026, footwear: p = .004). Uneven terrain conditions also significantly decreased ankle dorsiflexion at initial contact with the ground for both footwear conditions (p = .021). Conclusions: We conjecture that net ankle moments could be decreased by barefoot running in terrain conditions in skilled forefoot runners. Experienced runners using minimalist shoes may incorporate trail running into their barefoot running regime without risk of higher Achilles tendon loading compared to even running.

One Size Doesn't Fit All: Supervised Machine Learning Classification in Athlete-Monitoring

Athlete movement data are integral for optimizing athlete-performance and can lead to reduced fatigue and in turn can mitigate injury risk. There is a substantial amount of scientific literature, which investigates the ability of computer-vision and inertial sensor technologies to classify sport-specific movements. The coupling of automatic sport action labeling and athlete-monitoring data can significantly enhance athlete work-load monitoring. Two recent systematic reviews of the literature, pertinent to sport-specific movement classification, revealed that the majority of journal articles use athlete-dependent classification model training and evaluation methods. These methods can significantly enhance model classification performance, particularly with movements which have high interathlete technique variation. This is because it enables models to learn features distinctive to all athletes during training. This letter details the training and evaluation of supervised machine learning models to automatically classify running surface (athletics track, hard sand, and soft sand) using features extracted from an upper-back inertial measurement unit sensor. Possible classification performance enhancement is demonstrated by comparing athlete independent and athlete dependent supervised machine learning methods. Using athlete dependent methods significantly increased the classification performance in terms of weighted average precision, recall, F1-score, and accuracy (p <; 0.05).

Effects of Running Surface Stiffness on Three-Segment Foot Kinematics Responses with Different Shod Conditions.

Objective The aim of this study was to investigate the effects of surface stiffness on multisegment foot kinematics and temporal parameters during running. Methods Eighteen male subjects ran on three different surfaces (i.e., concrete, artificial grass, and rubber) in both heeled running shoes (HS) and minimal running shoes (MS). Both these shoes had dissimilar sole profiles. The heeled shoes had a higher sole at the heel, a thick base, and arch support, whereas the minimal shoes had a flat base sole. Indeed, the studied biomechanical parameters responded differently in the different footwear during running. Subjects ran in recreational mode speed while 3D foot kinematics (i.e., joint rotation and peak medial longitudinal arch (MLA) angle) were determined using a motion capture system (Qualysis, Gothenburg, Sweden). Information on stance time and plantar fascia strain (PFS) was also collected. Results Running on different surface stiffness was found to significantly affect the peak MLA angles and stance times for both HS and MS conditions. However, the results showed that the joint rotation angles were not sensitive to surface stiffness. Also, PFS showed no relationship with surface stiffness, as the results were varied as the surface stiffness was changed. Conclusion The surface stiffness significantly contributed towards the effects of peak MLA angle and stance time. These findings may enhance the understanding of biomechanical responses on various running surfaces stiffness in different shoe conditions.

On the influence of crossing angle on long-term rail damage evolution in railway crossings

ABSTRACT The rails in railway crossings are subjected to severe load environment leading to degradation of running surface due to wear and accumulated plastic deformation. To compare long-term degradation of three fixed crossings with different crossing angles, nominally designated 1:12, 1:15, and 1:18.5, a multidisciplinary simulation methodology is applied to predict damage of the crossing rail. For a given traffic scenario, including up to 65 MGT of facing move passenger traffic in through route, the results show that damage increases with increasing crossing angle. The ratio between the maximum damage for the crossings with the largest and smallest crossing angles is found to be about three in terms of wear and about two for plastic deformation. Initially high rate of plastic deformation reduces significantly after the first 2–5 MGT, and after 10–30 MGT it approaches a nearly constant value that is significantly lower than the wear rate.

Residual strain–stress in manganese steel railway crossing determined by synchrotron and laboratory X-rays

The residual stress within the nose of a worn manganese steel railway crossing was investigated. The macroscopic residual stress at the running surface was determined in areas with and without visual faults by laboratory X-rays. To get information about the penetration depth of the residual stress, synchrotron X-ray diffraction was used to map the distribution of local (within grain) residual strains below the running surface. The laboratory X-ray measurements revealed significant compressive stress on the rail running surface. The synchrotron measurements documented that local strains exist through the entire depth investigated. Relations between residual stress, plastic deformation, and crack formation are analysed, leading to a discussion on potentials/limitations of the two experimental methods for investigations of residual stress in large engineering components.

Dynamic characteristics and growth curve of rail corrugation at saturation stage

Rail corrugation, which causes the vibration and the noise, is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and that there are three stages in the evolution process of the corrugation: formation, growth and saturation. In this paper, we analyze the dynamic characteristics of the track and vehicle in the saturation stage, propose a growth curve of corrugation, and verify them based on measured data obtained on commercial lines. As a result, it is confirmed that when the roughness amplitude grows and exceeds the critical roughness amplitude, there are two characteristics: the significant increase of the contact force fluctuation and the acceleration of the rail and wheel, formation of higher-order roughness components of the corrugation. The growth curve of the corrugation can be approximated by a logistic function.

Influence of change in frictional condition of track rail surfaces on interaction forces in the “wheel/rail” contact

Determination of frictional condition of the running surface and side surface of the top of rail (lubrication) that ensures the best interaction of the rolling stock wheels and the rail, reduces the force action and thus ensures the track stability and reduced side wear of rails in the curved tracks is relevant for all the rail net.The objective of research is to determine the influence of frictional condition of the track rail surfaces on the interaction forces in the “wheel/rail” contact with various motion parameters (speed, radius).The theoretical and experimental methods were used in the research. The theoretical methods include multioptional computer modelling of axial and lateral forces that appear in the curved tracks during the freight train movement in the software package “Universal Mechanism”. The modelling results were processed with the use of correlation and regression analysis. The experimental methods include full-scale measurements in the existing track and results processing.According to the research results, the theoretical algorithms for assessment of influence of the running surface lubrication on the forces. The option of frictional condition of the wheel and rail interaction surfaces has been established to ensure reduction in the operating expenses for surfacing and rail replacement, energy costs for haulage of freight train.

Pouch conveyor drive system dynamics

Pouch conveyors commonly employ point-contact drive systems, indenting a rigid drive wheel into the viscoelastic running surface of the conveyor. Rigid indentation of a viscoelastic surface exhibits regions of stick and slip, reducing the tractive limits of the contact. By modelling the conveyor cover as both an elastic material, and using a 3-parameter Maxwell approximation, a comparison can be made to predict the attainable traction of both indentation and load dependent contacts, highlighting the influence of viscoelasticity in the drive contact. Accurate prediction of the slip within the contact region allows appropriate drive placement and spacing along a conveyor, maximising transmission of drive power and efficiency, while minimising capital/operating cost and surface wear. Experimental results are presented to validate the model, using both polished steel and wheels with polyurethane, ceramic and rubber lagging.

Пожежостійкість і постпірогенний відпад соснових лісів лівобережної частини Харківської області за різних рівнів пожежної небезпеки за умовами погоди

Пожежі є одними з найнебезпечніших чинників дестабілізації лісів. Визначення особливостей постпірогенного розвитку сосняків дає змогу пом’якшити негативні наслідки, спричинені лісовими пожежами, та допомогти в прийнятті рішень стосовно ведення господарства в таких лісах. Виявлено, що санітарний стан насаджень залежав від значення комплексного показника пожежної небезпеки (КППН) на момент пожежі та погіршувався у міру його збільшення (r = 0,71; p = 0,05). За вищих значень КППН підвищуються інтенсивність тепловиділення під час пожежі та ступінь вигорання лісової підстилки. Встановлено, що за КППН від 1 500 до 3 000 балів індекс санітарного стану насаджень варіює від II,0 до III,9; частка відпаду сягає 20 %. За подальшого збільшення значень КППН понад 5 000 балів індекс стану насадження через рік після пожежі становить III,5–V,0. З’ясовано, що висота полум’я та висота нагару на стовбурах достовірно не залежать від рівня пожежної небезпеки за умовами погоди. Вдосконалено підходи до прогнозування постпірогенного відпаду на рівні насадження з урахуванням характеристик пожежонебезпечного сезону, ступеня пошкодження дерев у насадженні та його таксаційних характеристик.

The life cycle assessment of the used rails according to the results of cyclic high-frequency tests

The article presents the results of the strength tests and the metallographic studies of used rails with the significant running surface wear. On the basis of the accelerated modeling of the continuously welded rail life cycle, an assessment system is proposed to evaluate the life cycle of the used continuously welded rails that are sent to the rail repairing depots.

Prediction of contact-fatigue damage to rails using computational-experimental methods

Analysis of the operational data related to rails failure showed that contact-fatigue defects consistently hold a prominent place. The goal of the study is to show the possibilities of using modern numerical methods in calculation assessment of the service life of rails before the onset of contact fatigue crack formation on a running surface depending on the values of axial load. To calculate a stress-strain state in the area of contact interaction between the wheel and rail a detailed finite-element model implemented in the MSC. Marc software package is used. The analysis revealed complex multiaxial and non-proportional nature of the stress-strain state. The Brown – Miller multiaxial fatigue model implemented in the MSC. Fatigue software package was taken to determine accumulation of the contact fatigue damages on a rail running surface. The model is based on the assumption that maximum fatigue damages in the metal occur in the area with the maximum shear stress. The impact of normal stresses in this area is also taken into account. The results of a comparative computational analysis of the rail life time confirm that the service life decreases with increasing axial loads, all other conditions being the same. With a share of 20% of freight trains with axle loads of 25 tonf in a daily pattern one should expect a decrease in the contact fatigue life of rails by 3 – 4 %. It is possible to improve the method for prediction of the contact fatigue life of rails in terms of experimental definition of the fatigue and strength characteristics of the rail steel depending on the degree of hardening of the running surface, their probabilistic properties and the use of a cumulative distribution of vertical forces taking into account the structure of the freight traffic passing through the section.