Actual Wear Research Articles

Wear Resistance of Rails

The operational wear of rails is analyzed and the actual wear is determined in measurements within the OAO RZhD network and in the laboratory. The wear resistance of rail steel is investigated as a function of the chemical composition and the microstructure (specifically, the dispersity). The microstructure of rail steel with different wear resistance is investigated by means of an electron microscope. Metallurgical approaches to improving the wear resistance of steel are described. Operational measures are also noted.

Impact of structural features on dynamic breathing resistance of healthcare face mask

In order to provide an overall evaluation and characterization of the comfort sensation and performance of face mask related to breathing resistance for healthcare in fog and haze weather, and address the influence of structural features on breathing resistance properties, an experimental set-up was developed, which was able to continuously change the direction and rate of air flow and the breathing frequency to simulate the dynamic breathing process during the actual wearing of face mask. The dynamic changes of airflow rate and the breathing resistance were acquired by a virtual instrument (VI) system and a microelectronics system. Six evaluation indices were defined for the dynamic performance and comfort sensation of face mask, derived from the source data of dynamic breathing resistance. Twelve types of face masks from different department stores with different features such as shape, respiratory valve, brand, main materials and protection level were tested using the experimental set-up. The one-way ANOVA analysis was carried out to identify the significance of the differences of the indices among the test masks. The results showed that each evaluation index was significantly different (P < 0.05) among different test masks. The change rate of breathing resistance could be obtained using the dynamic measurement of breathing resistance and could be applied for the dynamic performance evaluation of face mask compared with the static measurement of breathing resistance under constant airflow rate. The influences of structural features such as respiratory valve, shape and main materials on breathing resistance were evaluated and analyzed. The face masks with respiratory valve had lower change rate of breathing resistance. Moreover, the cup type mask had lower change rate of breathing resistance than the folding mask. Furthermore, the cotton mask had lower change rate of breathing resistance than the nonwoven fabric mask.

Sediment-wear morphology prediction method of hydraulic machine based on differential-quadrature method

Damage caused by abrasive wear is a significant problem for hydraulic machinery in rivers with sediments. Traditional prediction methods of abrasive wear morphology with the fixed geometrical boundary are difficult to reflect the physical reality of wear because of the interaction of sediment wear, flow pattern and flow boundary. In this study, a gradual wear method based on the idea of differential-quadrature is established to investigate the asymptotic wear behavior of hydraulic machinery. The average wear rate and depth of voxels on the geometrical boundary can be obtained by the unsteady numerical simulation with RNG [Formula: see text]-[Formula: see text] turbulent model and DPM multiphase flow model. Segmented voxels of geometrical boundary of flow are reconstructed after a calculation period until the end of the total running time. So, the progressive wear morphologies of flow-passage walls can be revealed step by step. The prediction method is used to predict the wear of the clearance flow in the guide vane. The numerical results are in good agreement with the actual wear depth on the wear surfaces at the actual running time, which indicates that the specified prediction method in this paper is applicable and effective.

Self-adjustable Spectacle Wearing Compliance and Associated Factors among Rural School Children in Ghana.

Self-adjustable spectacles are increasingly being used in refractive service delivery programs in developing countries. Despite the success of self-refraction as a refraction technique, compliance with actual wear of adjustable spectacles has not been evaluated. Findings in this study have significant programmatic implications for the effectiveness and sustainability of this mode of correction in developing countries. The purpose of this study was to assess compliance with wearing of adjustable spectacles and factors associated with compliance in pre-teen schoolchildren at 6 months after spectacles were dispensed. A cohort of 86 children aged 6 to 12 years with presenting vision worse than or equal to 6/12 in the better eye that could be improved to better than or equal to 6/7.5 by subjective refraction and who were identified from a randomized sample of 18 primary schools in the coastal areas of Cape Coast in Ghana received free FocusSpecs adjustable spectacles after successfully completing self-refraction and cycloplegic subjective refraction. Follow-up examination to assess compliance and to determine reasons for noncompliance was conducted at 6 months after spectacle provision. Logistic regression models assessed factors associated with spectacle wear compliance (95% confidence intervals [CIs]). Spectacle wear compliance was 33.7% (95% CI, 31.3 to 36.1%); an additional 29% had their spectacles with them but were not wearing them. The major reasons given by the children for noncompliance were "loss" (32%; 18/57) and "breakage" (23%; 13/57). Modest compliance (49%) was observed among the poorer children who attend public schools. Attending public school was the only predictor of compliance to spectacle wear (odds ratio, 3.096; 95% CI, 1.228 to 7.805; P = .02). Despite accurate self-refraction by most children, only a small proportion was compliant with actual wear of the spectacles. Loss and breakage were the major reasons for noncompliance. The poorer children who attend public schools, who stand to benefit most from the technology, were the ones more likely to be compliant with wear.

Modeling Solid Contact between Smooth and Rough Surfaces with Non-Gaussian Distributions

In this study, we constructed a solid contact asperity distribution model based on height and curvature that is capable of considering surface properties, such as skewness and kurtosis, corresponding to actual wear surfaces. Our model is in good agreement with actual measurements of asperity height distribution on wear surfaces with various skewness and kurtosis values. We applied our distribution model to the Greenwood-Williamson model to develop a formula for real contact area and contact force between a rough surface and a smooth surface. Although the tendencies of the change in contact area with respect to the film thickness ratio differ depending on skewness and kurtosis, the contact area predicted by the model agrees well with theoretical solutions when pure plastic deformation is assumed. Additionally, we calculated the mean real contact pressure (the ratio of contact force to real contact area) with skewness and kurtosis and confirmed that the tendencies of change with respect to the film thickness ratio change significantly. This appears to suggest that the tendencies of friction and wear characteristics differ according to the skewness and kurtosis.

Three body type abrasive wear characteristics of multi-component white cast irons

Abrasive wear can occur on tooth and suspension parts such as construction machinery power shovels and bulldozers. In order to reach high safety and low cost, it is important to develop wear resistant material and estimate of life service during abrasion.The amount of alloy element dissolved in the matrix is changed by the type of carbide and microstructure due to the addition content of alloy. However, it is important to consider the relationship the actual wear situation with environment reproducible testing machine.In the present study, nickel (Ni) which will encourage the carbides formation by suppressed the solid solution of the carbide-forming elements into the matrix was added into the traditional Fe-2C-5Cr-5Mo-5W-5 Nb-5Co system multi-component white cast iron. The effect of Ni on the three type of abrasive wear characteristics of this new material was investigated. A rubber wheel type abrasion tester was used for the abrasion tester. Test piece was pressed against the circumferential portion of the rubber wheel rotating at 100 ± 1 rpm with a load of 196 N. Silica sand of 170–220 µm was supplied at a rate of about 4.2 g/s from the popper between them, an abrasion test was conducted for 5 min.As a results, in both 0Co and 5Co type specimens, the specimens added with 3% Ni showed good three body type abrasive wear characteristics. In particular, the hardness of 3Ni-5Co showed a high value of 790 HV, showing the most excellent three type abrasive wear characteristics. With or without addition of Co, there was no difference in wear loss for 0Ni and 5Ni specimens. This is because there was no significant difference in hardness between 620 and 690 HV. Thereby, it can be concluded, the wear loss tended to decrease with increasing hardness of specimens.

Investigation of characteristic rippling topology produced during UHMWPE sliding

Ultra-high molecular weight polyethylene (UHMWPE) remains the sole polymer bearing material for use in orthopedic implants and its behavior has been studied extensively. Various techniques, such as crosslinking, have been employed to reduce the total wear volume. However, little is known about the actual wear mechanisms that contribute to the removal of debris from the bulk. A nearly universal observation of the wear surfaces after multidirectional sliding of UHMWPE is the presence of regularly-spaced parallel ripples whose wavelength closely matches debris size. In spite of the fact that this phenomenon has been observed for decades in both retrieved implants as well as wear simulation studies, the specific causes of the rippled topology have not yet been identified. Proposed mechanisms have included abrasion, crystallinity effects, fatigue, stick-slip behavior, thermal softening, and Schallamach waves. This investigation involved an experimental and computational factorial test design to determine the role of various parameters involved in the rippling phenomenon. The authors employed a film buckling theoretical model and applied it to UHMWPE using a finite element modeling approach. Wear testing was performed on a two-axis tribometer to expose the polymer to multi-directional sliding. Characteristic ripples developed on all wear surfaces, but with varying periodicity. Two regimes of the ripple phenomenon were observed: localized long wavelength (2.2–3.2 µm) ripples which appeared to dominate before steady state wear was established, and long-range shorter-wavelength (approximately 1 µm) ripples which indicated a steady-state condition. Surprisingly, feature wavelength showed little dependence on roughness or temperature but were slightly affected by contact pressure. The wear surfaces were cleaved and examined by SEM to gauge the thickness of the plastically deformed quasi-film layer. These layers were on the order of 10–20 nm thick. Further examination of the surfaces confirms the development of a deformed layer which acts similarly to a buckled thin film.

Methods for determination of low-cycle properties from monotonic tensile tests of 1.2344 steel applied for hot forging dies

Selected methods for determining fatigue life in the strain-life approach, described by the Manson-Coffin-Basquin (MCB) equation based on results of static tensile tests are presented in this paper. These methods served for determining low-cycle characteristics for 1.2344 steel applied for dies used in forging at high temperatures. The authors presented the results of tensile tests performed at room temperature and at elevated temperatures (300 °C, 500 °C, 600 °C, and 700 °C). Data obtained from these tests enabled to theoretically determine fatigue life characteristics according to the methods: universal slope, 4-point correlation, Mitchell’s, modified universal slope method, Baumel’s and Seeger’s method, modified 4-point-correlation method, Roessle’s and Fatemi’s method, as well as median method. Curves obtained on this basis were then compared to charts obtained from periodic deformation tests. Results obtained in this manner were compared to actual wear of tools (made of 1.2344 steel) used in the hot forging process of a cover-type forging. Fatigue tests covered deformation of specimens with uniaxial, periodically variable load until their cracking, and were performed at temperatures 20 °C, 300 °C, and 600 °C and at four levels of total strain eac: 0.5%, 0.8%, 1.0%, and 2.0%. Clear differences between the values of coefficients and exponents of the MCB equation were observed depending on the applied theoretical method and depending on test temperature. The research goal is description of different methods for determining fatigue life in strain-life approach based on results of static tensile tests and comparison them with the results from experiment. This will allow choosing the best method to predict the fatigue life of tools made of steel 1.2344 and usage of this method in the future, saving time, and costs related to the performance of experimental tests.

Materials for Hip Prostheses: A Review of Wear and Loading Considerations.

Replacement surgery of hip joint consists of the substitution of the joint with an implant able to recreate the articulation functionality. This article aims to review the current state of the art of the biomaterials used for hip implants. Hip implants can be realized with different combination of materials, such as metals, ceramics and polymers. In this review, we analyze, from international literature, the specific characteristics required for biomaterials used in hip joint arthroplasty, i.e., being biocompatible, resisting heavy stress, opposing low frictional forces to sliding and having a low wear rate. A commentary on the evolution and actual existing hip prostheses is proposed. We analyzed the scientific literature, collecting information on the material behavior and the human-body response to it. Particular attention has been given to the tribological behavior of the biomaterials, as friction and wear have been key aspects to improve as hip implants evolve. After more than 50 years of evolution, in term of designs and materials, the actual wear rate of the most common implants is low, allowing us to sensibly reduce the risk related to the widespread debris distribution in the human body.

Segmentation of the Wear Area of Planar Shoeprint Using Mean Shift

In the field of forensic science, the wear area of planar shoeprint is a useful information for analysis of criminal suspects. However, the identification of shoeprint wear areas is often subjective to the expert’s personal experience. In this paper, considering the characteristics of planar shoeprint images, a segmentation algorithm based on mean-shift is proposed to process planar shoeprint image to get the wear area. Firstly, the multiplicative intrinsic component optimization method(MICO) is employed to pre-segment the image. This method combines the level set with the offset field correction method to segment the outline of the unevenly printed shoeprint image. Secondly, we use mean shift to segment the image. Finally, we compare the actual wear area with the segmented wear area. It is found that the segmentation effect is good. By pattern recognition method, the wear area of the shoeprint is segmented to provide more objective technical support for detecting cases.

Phantom-Mobility-Based Prosthesis Control in Transhumeral Amputees Without Surgical Reinnervation: A Preliminary Study.

Transhumeral amputees face substantial difficulties in efficiently controlling their prosthetic limb, leading to a high rate of rejection of these devices. Actual myoelectric control approaches make their use slow, sequential and unnatural, especially for these patients with a high level of amputation who need a prosthesis with numerous active degrees of freedom (powered elbow, wrist, and hand). While surgical muscle-reinnervation is becoming a generic solution for amputees to increase their control capabilities over a prosthesis, research is still being conducted on the possibility of using the surface myoelectric patterns specifically associated to voluntary Phantom Limb Mobilization (PLM), appearing naturally in most upper-limb amputees without requiring specific surgery. The objective of this study was to evaluate the possibility for transhumeral amputees to use a PLM-based control approach to perform more realistic functional grasping tasks. Two transhumeral amputated participants were asked to repetitively grasp one out of three different objects with an unworn eight-active-DoF prosthetic arm and release it in a dedicated drawer. The prosthesis control was based on phantom limb mobilization and myoelectric pattern recognition techniques, using only two repetitions of each PLM to train the classification architecture. The results show that the task could be successfully achieved with rather optimal strategies and joint trajectories, even if the completion time was increased in comparison with the performances obtained by a control group using a simple GUI control, and the control strategies required numerous corrections. While numerous limitations related to robustness of pattern recognition techniques and to the perturbations generated by actual wearing of the prosthesis remain to be solved, these preliminary results encourage further exploration and deeper understanding of the phenomenon of natural residual myoelectric activity related to PLM, since it could possibly be a viable option in some transhumeral amputees to extend their control abilities of functional upper limb prosthetics with multiple active joints without undergoing muscular reinnervation surgery.

FTIR and Raman study of the structural properties and tribological characteristics of collagen

A collagen solution was added as a joint-lubricating fluid to extend the service life of UHMWPE liners. Adding this solution could effectively increase the adsorption of collagen onto zirconia surfaces, thereby reducing grinding parts (UHMWPE) wear. In this experiment, the thermal denaturation properties of collagen were used to manipulate the structural state of collagen molecules. The resulting structural alterations were observed using Fourier transform infrared spectroscopy, which indicated that the molecular structure of collagen changed from a triple-helix structure to a disordered molecular structure due to thermal effects. Collagen adsorption experiments also demonstrated that helical collagen molecules displayed higher rates of adsorption than disordered collagen molecules. Actual wear tests showed that larger quantities of adsorbed collagen led to lower friction coefficients and wear.

Analytical force model for orthogonal machining of unidirectional carbon fibre reinforced polymers (CFRP) as a function of the fibre orientation

Machining of carbon fibre reinforced polymer (CFRP) still represents a significant challenge due to its anisotropic material structure and brittle fracture behaviour. The material causes distinctive tool wear, which results in a significant increase of process forces. Analytical force models are crucial to optimise tool geometries and process parameters for efficient machining of CFRP with various fibre orientations. This research aims to develop an analytical force model for orthogonal machining which considers the influence of fibre orientation, tool geometry and increasing tool wear.The fibre orientation interval from 0° to 180° is sub-divided into four independent sub-models: (1) θ=0°=180°, (2) 15°≤θ≤75°, (3) θ=90° and (4) 105°+γ≤θ≤165°. For machining fibres with orientation (1) θ=0°=180°, the considered chip formation mechanisms are micro-buckling for axial loading and exceeding shear strength for transverse loading. Furthermore, spring back effects due to elastic deformation are taken into account. For fibre orientations in the range of (2) 15°≤θ≤75°, a bending beam surrounded by matrix material is modelled on elastic foundation, using minimum potential energy principle (MPEP) and WINKLER’s elastic foundation approach. After a first crack initiation at initial tool-fibre contact, further potential cracks due to bending of the now unilaterally supported fibres are taken into account. In the third sub-model (3) with the fibre orientation θ=90°, the modelled fibre fracture criterion is the local exceed of the compressive strength due to bending deformation. After the first crack initiation, further potential cracks are considered in the modelling approach, being affected by the varying tool-fibre contact point with progressing cutting motion. Using the same bending beam approach with MPEP for the sub-model (4) 105°+γ≤θ≤165°, the fibres are both axially compressed (buckling) and transversely bent during the cutting process. This superimposed combination results in a “peeling”-removal of the CFRP material.In order to consider tool wear effects, a characteristic description of the cutting edge is proposed using five micro-geometry parameters. The focus of this paper is on the force model, however simulation of tool wear is part of future research. The comparison of the simulated and experimental process forces, depending on the actual wear state and current tool micro-geometry shows a good correlation.

시니어 남성용 드레스폼 개발을 위한 정장착의 실태조사

시니어 남성용 드레스폼 개발을 위한 정장착의 실태조사

Research on Wear Evolution Laws of the Work Rolls during Hot Temper Rolling Process

Due to the special working conditions, work rolls are severely worn during hot temper rolling process, which adversely affects the shape accuracy of the strip. However, most of the existing literature about roll wear concern more about hot rolling than hot temper rolling. In this study, the wear mechanism of the work rolls is analyzed based on numerous measured wear contours and wear characteristic of the work rolls. To reveal the wear evolution laws, a high-precision elastic–plastic finite element method (FEM) analysis of tempering rolling is built using the FEM software ABAQUS. Simulation results show the distribution laws of contact pressure are very consistent with the wear evolution laws. Field application proves that the actual wear of the work rolls shows good agreement with the obtained wear evolution laws, indicating that the wear evolution laws are accurate and reliable. This research has the important theory and application value for the analysis of the influencing factors of roll wear and the improvement in non-uniform wear.

Tool Condition Monitoring in Micro-End Milling using wavelets

In this work, Tool Condition Monitoring (TCM) strategy is developed for micro-end milling of titanium alloy and mild steel work-pieces. Full immersion slot milling experiments are conducted using a solid tungsten carbide end mill for more than 1900 s to have reasonable amount of tool wear. During the micro-end milling process, cutting force and vibration signals are acquired using Kistler piezo-electric 3-component force dynamometer (9256C2) and accelerometer (NI cDAQ-9188) respectively. The force components and the vibration signals are processed using Discrete Wavelet Transformation (DWT) in both time and frequency window. 5-level wavelet packet decomposition using Db-8 wavelet is carried out and the detailed coefficients D1 to D5 for each of the signals are obtained. The results of the wavelet transformation are correlated with the tool wear. In case of vibration signals, de-noising is done for higher frequency components (D1) and force signals were de-noised for lower frequency components (D5). Increasing value of MAD (Mean Absolute Deviation) of the detail coefficients for successive channels depicted tool wear. The predictions of the tool wear are confirmed from the actual wear observed in the SEM of the worn tool.

Wear Prediction of Earth-Moving Machinery Joint Bearing via Correlation between Wear Coefficient and Film Parameter: Experimental Study

ABSTRACTA wear life prediction of a grease-lubricated bearing in earth moving machinery has to be made based on actual wear data for its accuracy, but much effort should be devoted to obtain the wear data from the actual bearing. Currently, manufacturers provide a very conservative maintenance guide to schedule the replacement of the bearings to prevent the mechanical failure due to wear, causing economic losses, and the market requires finding optimal maintenance cycles to reduce maintenance costs. In this study, an economical wear prediction methodology for the grease-lubricated bearing based on typical pin-on-disk (POD) tests is proposed. POD tests were performed under boundary and mixed lubrication regimes considering the actual operating conditions of the bearings. It was found that there is a linear relation between the lubrication film parameter and the wear coefficient in log-log scale. The amount of wear of actual bearings was estimated by the wear coefficient from the linear regression analysis based on the POD test. The wear tests were further performed with the actual bearing under two loading cases and then the lubrication film parameter and wear coefficient were calculated, respectively. The estimated amount of wear shows good agreement with the measurement of wear depth. This leads us to conclude that it is possible to economically predict the wear amount in an actual bearing from POD wear test results by analysis of the correlation between the wear coefficient and the lubrication film parameter.

Predicting the Technical State of a Turning Tool on the Basis of Phase-Chronometric Measurement Information

We describe a predictive method for monitoring the state of a turning tool during processing. The results of the prediction, based on phase-chronometric measurement information, are considered. The possibility of practical application of the described prediction technique in combination with phase-chronometric data is shown. We present an algorithm for predicting the actual wear of the tool using an example of simplest turning.

An Accurate and Fast Method to Inspect Rail Wear Based on Revised Global Registration

Rail wear inspection is vitally important in the railway industry. Conventional methods mainly use manual or static measurements to detect rail wear, which are inefficient, imprecise, and unreliable. To improve the accuracy and efficiency of rail wear inspection, a dynamic detection system based on a revised fast global registration (RFGR) algorithm was employed. First, the framework for online detection of rail wear with multi-profile was put forward to reduce the influence of vibrations of individual sections. Second, the RFGR method was proposed by using a robust weight function to convert the non-convex registration model to a convex problem, and the Levenberg–Marquardt method was used to solve nonlinear least-squares systems robustly. Finally, the Hausdorff distance was introduced to visualize the distance between the wear profile and the reference profile after alignment. The experimental results demonstrated that the RFGR algorithm was more accurate, robust, and effective than iterative closest point (ICP), sparse ICP, Yi’s sparse ICP, and the fast global registration algorithm. For actual wear detection, the proposed method was more efficient and robust for the online dynamic detection of rail wear when compared with the single-profile-section-based inspection method.

Определение фактического износа дорожных покрытий шипованными шинами

Определение фактического износа дорожных покрытий шипованными шинами