Wear Index Research Articles

Research on the wheel wear and rolling contact fatigue of metro vehicle induced by the rail corrugation

The rail corrugation is a common disease on the track, which exacerbates the wheel-rail interaction and accelerates wheel wear and crack propagation. This study focuses on the wheel wear and rolling contact fatigue of metro vehicle under the rail corrugation. Firstly, the characteristics of the rail corrugation under service conditions are determined by the statistical analysis of the field data, and the rail corrugation is applied to the established vehicle-track coupled dynamics model. Then, the wear index and the work of friction force as indicators of wheel wear are studied. Finally, based on the Shakedown Map and the criterion of maximum amplitude of shear stress, the simulation analysis of wheel-rolling contact fatigue under the rail corrugation is carried out. The results show that the increases in superficial fatigue index and accumulated fatigue are 1.52 and 6.16 times in the wavelength range of 30-90 mm larger than those in the range of 90-210 mm, respectively. Furthermore, the cracks more easily occur 2-4 mm from the outer surface of wheel, and expand along the wheel tread.

Durability Investigation of Ultra-Thin Polyurethane Wearing Course for Asphalt Pavement

In this study, a wear-resistant ultra-thin wear layer was fabricated with polyurethane as an adhesive to investigate its durability for pavement applications. Its road performance was investigated based on indoor tests. First, the abrasion test was performed using a tire–pavement dynamic friction analyzer (TDFA), and the surface elevation information of the wear layer was obtained by laser profile scanning. The relationship between the anti-skid properties of the wear layer and the macro-texture was analyzed. Second, a Fourier infrared spectrometer and scanning electron microscope were employed to analyze the evolution of polyurethane aging properties in the pull-out test and accelerated ultraviolet (UV) aging test. The results showed that the mean profile depth (MPD), arithmetic mean wavelength of contour (λa), surface wear index (SBI), stage mass loss rate (σ), and total stage mass loss rate (ω) of the abrasive layer aggregate had significant multivariate quadratic polynomial relationships with the skidding performance of the abrasive layer. The tensile strength of the polyurethane ultra-thin abrasive layer decreased by only 2.59% after 16 days of UV aging, indicating a minimal effect of UV action on the aggregate and structural spalling of the polyurethane abrasive layer.

The influence of physical vapor deposition (PVD) coating on the microgeometry of high-speed steel (HSS) cutting tools during the machining of wood-based composites

ABSTRACT The aim of this work was to analyze the impact of a multilayer TiN/AlTiN nano coating deposited using the physical vapor deposition (PVD) method on the microgeometry and durability of replaceable knives made of high-speed steel (HSS). The blunting process took place while milling standard medium density fireboard with a thickness of 16 mm. Seven reference knives and seven coated ones were used. During durability tests, the wear index value, i.e. the maximum wear on the clearance face VBmax = 0.3 mm was adopted as the blunting criterion. After the blunting stage, the tools were subjected to a precise geometric analysis based on a contact profilometer. In this way, a number of geometric parameters and rounding factors K were obtained for coated and uncoated blades at various points along the cutting edge on a distance 10 mm with 0.5 mm increments. Then, these data were subjected to statistical analysis using the Bonfferoni method. The results showed statistically significant changes in the values of some asymmetry coefficients K at the stage of tool lapping.

Evolution of bamboo derivative fiber-mollusk shell based calcite particulate hybrid reinforced epoxy bio-composites for sustainable applications

This study focused on the development of environmentally friendly epoxy-based biocomposites by incorporating bamboo fiber (BF) and calcite particles (CP) as reinforcements. A total of 125 specimens were fabricated with different weight percentages of BF and CP ranging from 0% to 15% to the epoxy. The biobased reinforcements were processed before incorporation, and the hand layup technique was used to fabricate the composites, which were then cured at ambient temperature. Evaluations of selected properties were carried out to ascertain the most probable areas of application, while the fracture surfaces were examined using SEM. The results indicated that the inclusion of these hybrid bio-reinforcements significantly enhanced the properties of the biocomposites compared to unreinforced samples. The optimal composition was identified as 12 wt% BF/CP, which demonstrated the highest ultimate tensile strength (32.84 MPa) and tensile modulus (1.9 GPa), attributed to the strong interfacial bonding between the epoxy matrix and the BF/CP reinforcements. Additionally, the flexural strength (55.38 MPa) and modulus (2.72 GPa) were improved due to the effective load transfer and stiffening effect of the calcite particles. The hardness (67 HS) and wear index (0.015 mg) were enhanced by the toughening mechanism provided by the bamboo fibers, while the density (1.195 g/cm³) remained within a desirable range for lightweight applications. Composites with 9 wt% BF/CP exhibited the highest impact strength (22.66 J/m2), likely due to the optimal balance of fiber-matrix interaction and energy absorption capacity. These findings indicate that the developed hybrid-reinforced biocomposite compositions hold great promise with the improved physical and mechanical properties as seen and can be utilized for various applications, including automotive, aerospace, and other engineering applications.

INFLUENCE OF GRAPHITED DUST ON THE ABRASION PROCESSES OF COMPOSITE MATERIAL BASED ON POLYTETRAFLUOROETHYLENE

Purpose. Study of the influence of graphitized dust on abrasive wear of polytetrafluoroethylene-based composites. Research methods. Experimental studies were performed using modern methods of physical and mechanical tests, which ensures the reliability of the results. A laboratory mixer with a rotating electromagnetic field and a hydraulic table press TU 10003 TORIN were used for the production of samples. Weighing of samples for experiments was carried out on a VLR-200 scale, abrasion assessment was carried out on a HECKERT machine. The friction surfaces were studied using a BIOLAM-M microscope. Results. The conducted studies showed that the index of abrasive wear of the composite with a polytetrafluoroethylene matrix decreases from 2.974 mm3/m to 2.539 mm3/m with a content of 10 % of graphitized dust. This helps to increase the service life of parts, which will reduce the frequency of their replacement, as well as reduce production costs. Given that graphitized dust is a waste of metallurgical production, its secondary use as a filler for composite materials allows to partially solve the environmental problem of disposal of production waste. Scientific novelty. Today, the production of products from composite materials is one of the promising directions of production, because the combination of a polymer matrix with various fillers makes it possible to obtain more economically profitable materials, forming the necessary physical properties. The possibility of using production waste as a filler allows solving the current problem of recycling and disposal of environmentally harmful substances. Therefore, the conducted research opens up new ways to solve a complex of environmental and economic problems. Practical value. The obtained results are important in the further process of manufacturing composite materials. The ability to increase the resistance of the material to abrasive abrasion allows the production of parts that work in friction conditions.

Effect of SiO2 concentration on the mechanical and anticorrosive properties of the hybrid PMMA/SiO2 coating synthesized in situ by sol-gel process.

Abstract Anti-corrosive evaluation of a hybrid polymethylmethacrylate (PMMA) with silica particles (SiO2) is presented, the hybrid (PMMA-SiO2) was synthetized in situ by sol-gel process. The SiO2 particles were embedded into to matrix PMMA at different concentrations. The hybrid structure of the coatings was characterized and observed with Fourier Transform Infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The deposition of the hybrid in aluminum 7075-T6 (Al7075) substrates was made with the blade coating technique, measuring wet and dry film thickness. For the preparation of the hybrid, PMMA was used without any type of curing, which allowed us to save resources. All tests were performed according to American Society for Testing and Materials (ASTM international) standards. The incorporation of SiO2 to concentrations significantly improved the mechanical and anti-corrosive results. PMMA-SiO2 coating, once deposited on the surface of Al7075 plates, has been tested inside a salt fog chamber (CNS) operated under accelerated conditions. They were improved up to 920 h its corrosion resistance. The abrasion tests had an increase of 50%, its hardness up to 4H and the wear index improved by 50% compared with the hybrids with minor SiO2 concentration, which shows that a higher concentration of SiO2 particles has a higher performance of the coating.

Sensitivity of different part-mouth recording methods using a modified tooth wear index.

High prevalence of tooth wear (TW) worldwide makes it important to assess its level in different populations. In developing countries, a shift towards geriatric population makes the evaluation of this condition even more relevant. Most indices for tooth wear are full mouth indices, which make mass population screening challenging. The objective of this study was to establish whether part-mouth recordings using selective teeth can provide similar sensitivity of the modified tooth wear index. This cross-sectional study was carried out over 40 working days on 400 dentate individuals aged 14-70 years, having at least 16 scorable teeth. Firstly, full mouth tooth wear of study population was recorded and categorized into four groups based on severity and extent of tooth wear. Following this, group wise data extraction was done using the full mouth scores and six different types of part-mouth analyses was done to arrive at the system which provides the best sensitivity. These part-mouth recordings should be specific such that it can differentiate to the same groups of tooth wear in the reduced data as well. Data were analyzed by means of SPSS version 21.0 (P<0.05). In 83%, at least one tooth had the exposed dentine. Part-mouth recording using "12 anterior teeth" as index teeth showed a high level of sensitivity (87.8%) than others for measuring tooth wear data. The prevalence of tooth wear is high and "the part-mouth recording applied to the 12 anterior teeth" is a faster and reliable method in large population surveys for measuring tooth wear.

Influence of dispersed filler on the abrasive wear index of ultra-high molecular polyethylene

Influence of dispersed filler on the abrasive wear index of ultra-high molecular polyethylene

The Severity of Tooth Surface Loss in Adult Patients Presenting to a Private Dental Hospital

This study aimed to assess the severity of tooth surface loss (TSL) in adult patients at a private dental hospital for 6 months. This research explored the severity of TSL using the Smith and Knight Tooth wear index (TWI). Study participants underwent intraoral examination in dental chairs with adequate lighting using a mouth mirror. Prior to examination, sterile cotton swab was used to clean and dry the teeth and to eliminate any plaque residue. Each tooth surface (buccal, lingual, cervical and occlusal/incisal) were evaluated using the TWI and documented on the research proforma. Only the most affected teeth and teeth surfaces were noted in a patient. A total of 320 patients were observed between ages (18-40 years), out of which 140 had tooth wear according to TWI. The male patient had a ratio of 40.91% while female were 50.08%. The mandibular anterior teeth had score 2 in 97.1% of the patients and maxillary premolars had score 1 and 2 which were 96.4% and 92.9% respectively. The occlusal surface was involved in 58% of maxillary teeth and 100% in mandibular teeth. Our study indicates that the mandibular anterior occlusal surfaces are particularly susceptible to the impacts of tooth wear. This may lead to aesthetic concerns, exposure of pulp with advanced wear and occlusal imbalance, which will require extensive treatment. Hence, it is imperative to raise awareness among individuals regarding the early indicators and symptoms of tooth wear.

The Prevalence of Tooth Wear and Their Associated Etiologies Among Adult Subjects Visiting Umm Al-Qura University Dental Clinic in Makkah City, Saudi Arabia.

In the past two decades, changing trends in socioeconomic status, dietary habits, and individual lifestyles of individuals have led to the emergence of tooth wear as an oral health problem. The present study aimed to investigate the prevalence and the associated etiologies of tooth wear in a convenience sample of adult patients visiting outpatient clinics of the Faculty of Dentistry at Umm Al-Qura University. This cross-sectional study was conducted on adult patients (18-40 years old) visiting outpatient clinics of the Faculty of Dentistry, Umm Al-Qura University. Two trained examiners visually assessed patients' tooth wear using Smith and Knight's Tooth Wear Index (TWI). Following the clinical examination, patients completed a self-administered questionnaire detailing risk factors such as the frequency of intake of acidic food and medicines, general health, chewing habits, dietary factors, and oral health-associated preventive behaviors. The resulting collected data were tabulated and statistically analyzed using Statistical Product and Service Solutions (SPSS, version 21; IBM SPSS Statistics for Windows, Armonk, NY). The total prevalence of tooth wear was 74%, and the recorded mean wear score (TWI) was 0.380 ± 0.386; anterior teeth exhibited greater wear than posterior teeth. Numerous associations were recorded between tooth wear and the tested variables in demographics, habits, diet, and medications, but most of them were not statistically significant. When toothbrushing habits were explored, the only factors to played a significant role in abrading the tooth structure were the type of brush bristles used (P-value = 0.026) and the frequency of brush renewal (P = 0.043). Patients who frequently ate citrus fruits and other acidic foods recorded high wear scores (0.509 ± 0.311 and 0.508 ± 0.402, respectively), although the difference was not statistically significant. When chewing occurred on both sides of the mouth, less tooth wear was recorded than if chewing was on the right or left side only (0.371 ± 0.260, 0.422 ± 0.273, and 0.520 ± 0.419, respectively). The study data support an association between tooth wear and patient occupation, use of hard-bristled and new toothbrushes, eating of citrus and other acidic food, and chewing on one side, as all of these factors increased the risk of tooth wear.

Suspension parameter optimization for high-speed train with severe tread wear

ABSTRACT The suspension parameters are optimized to improve the dynamic performance of high-speed train with severe tread wear and suppress the formation of severe tread wear. Except for the common indicator of high-conicity stability (A high ) for the vehicle dynamic performance with severe tread wear, a hollow wear index (HWI) is proposed to reduce the development rate of wheel hollow wear. Moreover, the low-conicity ride comfort (W low ) is considered for the dynamics performance with new tread. Yaw stiffness (YS) and the ratio of yaw damping to lateral damping (RYL) are proposed to characterize the suspension parameters matching. Results show that HWI is strongly positively correlated with W low , and is negatively correlated with A high . Increasing the RYL can enhance W low , and the YS should be reduced to improve HWI under the condition of sufficient hunting stability margin. Hunting bifurcation analysis elucidates that the model with better HWI is easy to form supercritical bifurcation.

Factors associated with prevalence and severity of erosive tooth wear in patients with reflux oesophagitis.

Extrinsic factors for erosive tooth wear (ETW) have been widely reported, but the intrinsic factors for wear remain unclear. The aim of this study was to evaluate the factors associated with the prevalence of ETW in patients with reflux oesophagitis (RO). To prevent severe ETW with RO, factors associated with severity of ETW were also evaluated. A total of 270 patients with RO were recruited. A modified tooth wear index was used to evaluate the prevalence and severity of ETW. Salivary secretion and buffering capacity were assessed prior to endoscopy. Subjects were asked to complete a medical condition and oral self-care questionnaire. Univariate and multivariate analyses were employed to identify factors collectively associated with the prevalence and severity of ETW. A total of 212 cases were categorized as patients with ETW (148 with mild ETW and 64 with severe ETW). Multivariate analyses indicated that saliva secretion, severity of RO and proton pump inhibitor (PPI) resistance were associated with the prevalence of ETW, whereas age, BMI and severity of RO were associated with the severity of ETW. The odds ratio of saliva secretion and BMI were less than 1, meaning that higher saliva secretion resulted in a lower prevalence of ETW and lower BMI was associated with severe ETW. Saliva secretion, severity of RO and PPI resistance were associated with the prevalence of ETW, whereas age, BMI and severity of RO were associated with the severity of ETW. Lower saliva secretion and BMI were significant factors for ETW.

Experimental Comparison of the Effect of Using Synthetic, Semi-Synthetic, and Mineral Engine Oil on Gasoline Engine Parts Wear

This paper includes the laboratory and experimental methodology used to compare the effect of using mineral, semi-synthetic, and synthetic engine oil on the parts wear of a four-stroke gasoline internal composition engine (ICE). Three test platforms included three engines with identical, technical, and design specifications. They were operated under the same investment, ambient, and climatic conditions. The first engine was equipped with synthetic oil, the second with semi-synthetic oil, and the third with mineral engine oil. All of them had (SAE10W40 API: SL/CF). All test platforms were operated through three stages with variable loads for up to 1,500 operating hours (hr). Oil drain intervals (ODI) were every 100 operating hours. Used oil samples were taken to analyze the physical and chemical characteristics of viscosity, total base number TBN, flash point, metals wear Irion (Fe), copper (Cu), chromium (Cr), and wear index (WI) to investigate the effect of all oils on the wear of engine parts and by comparing the changes in wear. The used oil analysis (UOA) results were drawn that showed the superiority of the use of synthetic oil over semi-synthetic and mineral. It prolonged the technical engine’s lifetime.

The effectiveness of different wear indicators in quantifying wear on railway wheels of freight wagons

Railway infrastructure relies on the dynamic interaction between wheels and rails; thus, assessing wheel wear is a critical aspect of maintenance and safety. This paper focuses on the wheel–rail wear indicator T-gamma (Tγ). Amidst its use, it becomes apparent that Tγ, while valuable, fails to provide a comprehensive reflection of the actual material removal and actual contact format, which means that using only Tγ as a target for optimization of profiles is not ideal. In this work, three different freight wagons are evaluated: a meter-gauge and a broad-gauge heavy haul vehicles from South American railways, and a standard-gauge freight vehicle operated in Europe, with different axle loads and dissimilar new wheel/rail profiles. These vehicles are subjected to comprehensive multibody simulations on various tracks. The simulations aimed to elucidate the intricate relationship between different wear indicators: Tγ, wear index, material removal, and maximum wear depth, under diverse curves, non-compensated lateral accelerations (Anc), and speeds. Some findings showed a correlation of 0.96 between Tγ and wear depth and 0.82 between wear index and material removed for the outer wheel. From the results, the Tγ is better than the wear index to be used when analyzing wear depth while the wear index is more suited to foresee the material lost. The results also show the low influence of Anc on wear index and Tγ. By considering these factors together, the study aims to improve the understanding of wheel–rail wear by selecting the best wear analysis approaches based on the effectiveness of each parameter.

Numerical determination of pavement mean texture depths at different degrees of traffic polishing-induced wear

All existing digital image-based numerical mean texture depth (MTD) calculation methods are unable to achieve a consistent level of acceptable accuracy for MTD values calculated at different degrees of pavement polishing. To solve this problem, a novel procedure is proposed to determine MTD as a function of degree of polishing represented by a texture statistic ‘directional wear index’ DWI. First, a relationship is established between DWI and the elevation H eq that defines the equivalent top surface of MTD. H eq is derived from 3-D digital image based on the concept of planation surface. Through studying laboratory specimens and field pavements polished to different degrees, a well-defined relationship between DWI and H eq was established. Knowing H eq from the H eq–DWI relationship, MTD is calculated as the mean depth of the voids between H eq and the test surface. The digital image-based procedure is able to concurrently determine MTD and the surface's degree of polishing.

Sixty-month comperative evaluation of a glass hybrid restorative and a composite resin in non-carious cervical lesions of bruxist individuals

ObjectiveTo compare the clinical performance of a glass hybrid (GH) restorative and a nano-ceramic composite resin (CR) in the restoration of non-carious cervical lesions (NCCLs) of bruxist individuals in a 60-month randomized clinical trial.Materials and methodsTwenty-five bruxist candidates having NCCLs were recruited in this clinical study. The depth, height (cervico–incisal), width (mesio-distal), internal angles of the NCCLs, degree of tooth wear (TWI) and gingival index (GI) were measured. One hundred-and-forty-eight NCCLs were restored either with a GH restorative (Equia Forte Fil) or a CR (Ceram.X One Universal). Modified USPHS criteria was used to evaluate restorations after 1 week and 12, 24, 36 and 60 months. Pearson’s Chi-Square, Fisher’s Exact and Cochran Q tests were run for analysis. Survival rates of the restorations were compared with Kaplan–Meier analysis (p < 0.05).ResultsAfter 60 months, 97 restorations in 15 patients were examined. The recall rate was 60.0%. Retention rates were 73.5% for CR and 66.7% for GH. A total of 29 restorations were lost (13CR (26.5%), 16GH (33.3%)). There was not a significant difference between tested restoratives in retention (p = 0.464), marginal adaptation (p = 0.856) and marginal discoloration (p = 0.273). There was no relationship between internal angle, depth, height or width and retention of the GH or CR restorations (p > 0.05). The increase in retention loss and marginal discoloration of both restorations over time were significant (p < 0.001). Sensitivity or secondary caries were not detected after 60 months.ConclusionGH and nano-ceramic CR showed similar clinical performances in NCCLs after 60 months in patients with bruxism.Clinical significanceAfter 60 months, CR and GH materials showed clinically acceptable performances in restoration of NCCLs in patients with bruxism.

An Investigation Into the Grinding Characteristics and Wear Evolution of Micro-Elastic Composite Grinding Pads

Abstract This paper introduces a novel micro-elastic composite grinding pad for material removal. The study also developed a new grinding wear formula grounded in microcontact mechanics, which is crucial in examining the evolution of interface characteristics under optimal parameter combinations. The results showed that the material removal rate (MRR), reduction of roughness height (σ), and peak curvature radius (ρ) increase were the highest in the initial stage, followed by a slight increase in the real-contact area in the second stage. This research suggests that abrasive particles primarily detach from the elastic pad in the second stage. The plasticity index (ψ) decreases during grinding, which suggests a transition from an elastic–plastic mixed contact interface to a predominantly elastic contact interface. This shift in the interface mechanics explains the gradual reduction in wear at the grinding interface. Both the plasticity index and the MRR are consistent throughout the grinding process. However, the plasticity index is a more effective index of interface wear than the conventional H/E ratio because it considers the surface roughness’s shape and size, which is essential in mild grinding operations. The findings of this study can be used to improve the design and performance of micro-elastic composite grinding pads and to optimize the grinding process for improved efficiency and sustainability.

Dental Erosion-An Occupational Hazard among Battery Manufacturing Industry Workers in Hyderabad, India.

Dental erosion is a condition that results from exposure of the enamel and dentin to non-bacterial acids of extrinsic and intrinsic origin, causing mineral loss on the surface of the tooth. Occupational exposure to sulfuric acid fumes has been described in association with dental erosion in battery manufacturing industry workers. Hence, this study aimed to assess the dental erosion among battery factory workers in HBL Power Systems Ltd, Hyderabad. The sample consisted of 90 battery factory workers (62 males and 28 females). Demographic data with regard to age, gender, and length of exposure were recorded. Clinical examination was done to assess dental erosion using the tooth wear index given by Smith and Knight. Data were statistically analyzed by using Fisher exact test. P <0.05 was considered statistically significant. Among 90 workers examined, 43.3% showed prevalence of erosion with higher occurrence rate in females (54%) than males (38.7%). 66.6% of affected workers had erosion score of 1, and 33.4% showed erosion score of 2 and 3. We also observed statistically significant highest prevalence and increased severity of dental erosion in workers with prolonged duration of employment (>11 years). The present study revealed increased prevalence of dental erosion among battery factory workers. Hence, it highlights the importance of protective measures with efficient surveillance and monitoring in the workplace environment.

Prediction of abrasive wear and surface hardness of printed parts by SLA technology

In the present study, a prediction of hardness deterioration and abrasive wear was performed through a neural network using artificial intelligence on a material printed in SLA. This article aims to predict the mechanical properties, wear resistance and surface hardness of parts manufactured by SLA stereolithography printing. A full factorial DOE was used to associate the peculiar parameters (print orientation, cure time, layer height) to perform experiments. The mechanical properties were evaluated according to ASTM regulations, with the objective of obtaining feeding data and validation of the predictions of the Taber Wear Index and hardness using an artificial neural network. The experimental results are in good agreement with the measured data with satisfactory prediction errors with a mean square error (MSE) of 0.01 corresponding to abrasive wear using the clear resin and a mean absolute error (MSE) of 0.09 with an R2 of 0.756, the prediction with the neural network with a mean square error (MSE) of 2.47 corresponding to abrasive wear using the tough resin and a mean absolute error (MSE) of 14.3 with an R2 of 0.97. It was shown that the accuracy of the prediction is reasonable, and the network has the potential to be improved if the experimental database for training the network could be expanded. Therefore, wear and hardness mechanical properties can be predicted appropriately with an ANN.

Research on wheel-rail dynamic interaction of high-speed railway under low adhesion condition

Due to the inherent openness of the wheel-rail system, the wheel-rail interface is subject to the influence of a third medium, resulting in a low adhesion state. This study investigates the dynamic interaction between the wheel and rail under low adhesion conditions through the development of a numerical model employing anti-skid control strategies and infinite long track simulation technology. The model's validity is established by comparing its calculations with data from both the multi-body dynamics software UM and field tests. The numerical simulations uncover that the implementation of rail side lubrication significantly reduces longitudinal creep forces, thereby diminishing the wheelset's steering capabilities. Furthermore, it induces a notable increase in lateral wheel-rail interaction, consequently lowering safety indicators in vehicle operations. Rail side lubrication is found to substantially reduce rail side wear, resulting in an approximate 60% decrease in the maximum wear depth. Comprehensive friction control on the rail surface concurrently mitigates rail side and top surface wear. In instances of local low adhesion on both sides, the wheelset experiences pronounced stick-slip vibrations, leading to a deterioration in the longitudinal dynamic performance between the wheel and rail. Unilateral low adhesion situations prompt noticeable yawing and shaking motions within the low adhesion zone, resulting in evident lateral impact phenomena. Upon re-entering the normal adhesion zone from the low adhesion zone, the rail wear index experiences a significant peak, which means that the rails in this area are prone to severe local wear or fatigue.