Wear Problems Research Articles

A new predictive model for normal and compound impact wear

This work presents a new model that predicts the wear that results from impacts occurring between two solid bodies under both normal and compound impact, a capability lacking from existing approaches. This frequently occurs in many engineering and industrial situations and depending on the relative sizes of the bodies, bulk material properties, and the number and frequency of impacts, damage can result. Although this eventually causes severe wear problems that limit service life, it is one of the least investigated types of primary wear mechanism. Due to this, robust data, and validated models derived from that data, are rare.The new model considers the contact with respect to shear force. It can predict wear volume loss and be used to improve understanding of the role of different impact angles during impact, and thus inform the design of machines, however it is currently valid for ductile materials only since hardness is a parameter. Empirical inputs to the model were developed using data produced specifically for this work. Predictions made by the model were then validated, with good correlation, for three common metal alloys by means of comparison with experimental data available in the literature.

A Review on Mechanisms and Testing of Wear in Slurry Pumps, Pipeline Circuits, and Hydraulic Turbines

AbstractThis paper presents an overview about particulate wear that occurs in various components of slurry pumps, pipeline systems, and hydraulic turbines due to the mechanical action caused by the flow of solid–liquid mixtures. Three most common wear problems, namely, erosion, erosion–corrosion, and abrasion occur in different industries like thermal and hydro power plants, mining, chemical, and marine industries. Therefore, the efficiency of these industries and power plants highly depends on the wear damages. So, it becomes necessary to govern the wear phenomenon. In this paper, the various properties of particles and target are discussed on which the particulate wear depends. Present overview explains the experimental methods of measuring the particulate wear at in situ and ex situ conditions by using the different types of testers, rigs, and pilot plant test loops. Moreover, the empirical and analytical correlations or models for the prediction of particulate wear in pumps, piping circuits, and hydraulic turbines are also discussed in present literature review. By studying the all possible advantages and disadvantages, the gaps in knowledge of wear prediction methods and models are highlighted. At the end, a “think-model” for the prediction as well as reduction of wear in the various components is presented on the basis of different experimental and computational fluid dynamics (CFD) based simulation work. Further investigations can be carried out to develop the more accurate and flexible models that can be used to predict the particulate wear in a wide range of applications.

Novel highly-efficient and dress-free polishing technique with plasma-assisted surface modification and dressing

Slurry is widely used in polishing difficult-to-machine materials. However, it is accompanied with some issues, such as the agglomeration of abrasives and high disposal cost. Although using fixed abrasive grains instead of slurry can solve these issues, the problems of wear and of loading fixed abrasive grinding stones, which result in decrease of material removal rate (MRR), also need to be solved. Many researches have been conducted on the self-sharpening of fixed abrasive grinding stones. However, the self-sharpening of grinding stones is not efficient with ultra-low polishing pressure, which is not large enough to break bonds so as to expose new abrasives. In this study, a novel dress-free dry polishing process was proposed, where it combines plasma-assisted polishing and plasma-assisted dressing using Ar-based CF4 plasma and a vitrified-bonded grinding stone. Polishing experiments were conducted on sintered AlN wafer. Also, as the main component of vitrified bond materials, silica was etched using CF4 plasma, which is equivalent to the continuous dressing of grinding stone surfaces. Since new abrasives could be constantly exposed, a high MRR was maintained. Thus, a dress-free high integrity polishing process was realized. Moreover, the CF4 plasma irradiation increased the MRR twice, as CF4 plasma can not only dress a grinding stone in real time but can also modify AlN to AlF3, which can easily be removed.

The influence of temperature on the engagement process of the wet clutches

The wet clutch is an important component in the vehicle transmission system, which has an important influence on the smoothness and rapidity of the vehicle starting and shifting processes. As a friction element, wet clutches are usually troubled by the wear and breakage problems, caused by high temperature. To solve this problem and reveal the operating mechanism, a dynamic model, along the circumferential and axial direction is proposed to describe the engagement process. In addition, a lumped thermal resistance model is established to predict the changing trend of the temperature during the engagement process. Then, with these two models, an integrated model is proposed. From the simulation results, the initial temperature has little effect on the temperature rise of the wet clutch. While, it has an obvious influence on the viscous torque, the higher the temperature is, the smaller the viscous torque is. While, for the asperity torque, it is opposite.

Reconstruction of the tail heating surfaces of CHP boilers in order to improve the efficiency

Recently, the share of non-design fuel use of coal at thermal power plants has increased, which negatively affects the operation of existing equipment. On the territory of the Irkutsk Region, there are 9 combined heat and power plants operating mainly on brown coals of the Irkutsk and Kansk-Achinsk basins. The main fuel at many CHPs is brown coal from the Mugunskoye deposit, the quality of which is deteriorating year by year. At the Novo-Irkutsk CHP, there is a prospect of continuing the supply of the Mugunsky coal with a sulfur content of up to 2.5%, which significantly exceeds the sulfur content of the design coals, which is 0.5%. This leads to the condensation of sulfuric acid vapors in the flue gases and, as a result, the heating surfaces are subject to sulfuric acid corrosion. In addition, there is a problem of erosive wear of air heaters at CHPs, caused by high flow rates and ash concentrations, which is also caused by a deterioration in the composition of the burnt coal. To solve the problem associated with low-temperature sulfuric acid corrosion of the boiler air heater tanks, it is proposed to place additional heating surfaces in the bypass gas ducts, which will reduce the temperature of the gases by cooling the flue gases with network water, and allow the obtained heat to be used in the added sections of the calorifier for heating the inlet (cold) air. While bypassing 25% of gases using the heat of gases in the calorifiers, erosion wear is reduced due to a decrease in the gas velocity in the air heater from 13 m/s to 9 m/s. The proposed technical measures will make it possible not only to increase the efficiency of the boiler and the plant as a whole, but also to increase the degree of fuel heat use.

Modeling of wear factor of locomotive wheel flange taking into account the traction conditions

Since the advent of railways for nowadays the problem of wear of wheel flange isn’t completely solved. It is especially relevant on the main railways. In this paper the mathematical model is proposed for impact assessment of traction conditions on the wear of the flanges of locomotive wheels during the movement of the rail track. It was obtained on the basis of the kinematic scheme of interaction of the wheel with the rail. As a factor of wear was taken the work of friction forces per unit distance traveled. It is well known, the wear factor of the flange is directly proportional to the relative sliding, which depends on the traction conditions and can be determined by the value of the relative sliding surface of the guide wheel and the geometric parameters of the curve. Thus the model that relates the wear factor to the parameters of the kinematic scheme of interaction of the wheel with the rail and allows to take into account a traction conditions was obtained. The proposed model allows to improve the modeling of the interaction of track and rolling stock as well as the design process of devices that reduce the intensity of wear of the flanges and rails. LOCOMOTIVE, FLANGE, WEAR-OUT FACTOR, TRACTION CONDITIONS, RELATIVE SLIDING, SLIPPAGE, MATHEMATICAL MODEL

Рекомендации по снижению абразивного износа гидротранспортных трубопроводов систем золошлакоудаления ТЭС

In the vast majority of cases, hydraulic ash and slag removal systems are used for conveying ash and slag at the coal-fired thermal power plants (TPPs) in Russia. Such technical solutions related to the evacuation of slag from boilers and transportation of fly ash after electrostatic precipitators have been replicated since the Soviet times. Hydraulic ash and slag removal systems cause significant damage to the natural environment in the area of coal-fired TPPs location. It should be noted, that the average age of TPPs is about 45-50 years. The inter-repair period and reliable operation of pipelines of TPP ash and slag removal systems significantly depend on abrasive wear, which is one of the main problems when transporting fine bulk materials like ash and slag. Abrasive wear or erosion in pipelines leads to a decrease in the reliability of the entire wet ash removal system; there is a need for the unplanned downtime caused by fistulas in pipelines, resulting in the release of ash and slag slurry into the environment. In addition, the thinning of the c'u'u pipeline wall thickness leads to the increase in the diameter of pipes, which, in turn, leads to deterioration in the eco- au'a nomic efficiency of transporting the ash and slag slurry. The article deals with the problem of abrasive wear of slurry pipelines of TPP ash and slag removal systems. Based on the research results, the main measures for extending the service life of straight and shaped sections of pipelines of TPP wet ash and slag removal systems are described. In order to reduce the intensity of abrasive wear, it is possible to apply regime measures that do not require investment in the reconstruction of existing hydrotransport installations. These measures include: turning the straight horizontal and inclined sections of pipelines around their axis; transporting the slurry with optimal parameters. In addition to the mentioned group of measures, constructive measures are considered that require investment in the reconstruction of hydrotransport installations to varying degrees, such as: optimizing the shape of curvilinear sections of pipelines; performing sections of hydrodynamic flow stabilization at the entrance and exit of the curvilinear (shaped) sections of pipelines, taking into account the zone of maximum wear; anti-abrasive inserts in the shaped sections of pipelines; stone-cast products; pipes with an aluminum-thermal coating. The maximum effectiveness of implementing anti-abrasive recommendations is achieved by combining regime and constructive measures.

Movement Control Method of Magnetic Levitation System Using Eccentricity of Non-Contact Position Sensor

This paper presents a method of utilizing a non-contact position sensor for the tilting and movement control of a rotor in a rotary magnetic levitation motor system. This system has been studied with the aim of having a relatively simple and highly clean alternative application compared to the spin coater used in the photoresist coating process in the semiconductor wafer process. To eliminate system wear and dust problems, a shaft-and-bearing-free magnetic levitation motor system was designed and a minimal non-contact position sensor was placed. An algorithm capable of preventing derailment and precise movement control by applying only control without additional mechanical devices to this magnetic levitation system was proposed. The proposed algorithm was verified through simulations and experiments, and the validity of the algorithm was verified by deriving a precision control result suitable for the movement control command in units of 0.1 mm at 50 rpm rotation drive.

Study on the Leakage and Inter-Stage Pressure Drop Characteristics of Two-Stage Finger Seal

To solve the high leakage and high wear problems faced by sealing devices in aeroengines under the condition of high axial pressure difference, the two-stage finger seal is proposed in this paper. The finite element method and computational fluid dynamics (FEM/CFD) coupling iterative algorithm of the two-stage finger seal is developed and validated. Then the performance advantages of two-stage finger seal compared to the one-stage finger seal are studied, as well as the leakage and the inter-stage pressure drop characteristics of two-stage finger seal are investigated. Finally, the measure to improve the inter-stage imbalance of pressure drop of two-stage finger seal is proposed. The results show that the two-stage finger seal has lower leakage and lower contact pressure than the one-stage finger seal at high axial pressure difference, but there exists an inter-stage imbalance of pressure drop. Increasing the axial pressure difference and the root mean square (RMS) roughness of finger element can aggravate the imbalance of pressure drop, while the radial displacement excitation of rotor has little influence on it. The results also indicate that the inter-stage imbalance of pressure drop of the two-stage finger seal can be improved by increasing the number of finger elements of the 1st finger seal and decreasing the number of finger elements of the 2nd finger seal.

A New Look at the Problem of Wear on Wheel Rolling

A New Look at the Problem of Wear on Wheel Rolling

Study of the socio-economic living conditions of the rural population of the Krasnoyarsk Territory

This article examines the socio-economic sphere of life of the rural population at the level of the region and individual municipal districts. The aim of the work was to obtain objective assessments of the level of social and economic well-being of the rural population and determine the list of infrastructure facilities, the introduction of which will lead to an improvement in living conditions in rural areas. The object of the study was the rural areas of the Krasnoyarsk Territory and the quality of life of rural households. The research methodology was based on the use of the index method for aggregating data characterizing various aspects of the social well-being of a rural resident. As a result of the study, it was found that most of the rural population of the region under consideration lives in conditions that are significantly different from living in an urban environment. The disproportions in the level of income, housing improvement, the availability of social engineering infrastructure, and the availability of basic social services are highlighted. About 63% of rural residents do not have access to centralized water supply, heat supply and sewerage systems. The problem of wear and tear of fixed assets in healthcare, education, and transport infrastructure is critical. The highest degree of compliance of rural living conditions with urban standards of social comfort is observed in the regions of the Far North, which have a special legal status and industrial specialization of the territorial economy. Rural territories with a predominantly agrarian type of economy cannot provide the necessary volume of investment in fixed assets, mass employment and an acceptable level of income for rural households.

TBM cutter wear prediction in inclined shaft project based on tunnelling parameters

Cutter wear is one of the important factors affecting the safety and efficiency of shield or TBM tunnelling. Based on the inclined shaft tunnelling project with long distance, large slope and constant excavation in Bulianta coal mine, regression analysis is applied to investigate the relationship between cutter wear and tunnelling parameters such as cutterhead rotation velocity, cutterhead torque, advance velocity, total thrust and penetration, and thus the prediction model of cutter wear is established. The results indicate that cutter wear is significantly correlated with each tunnelling parameter, and that the regression model expressed by cutterhead torque, total thrust and penetration can account for 97.8 percent of the cutter wear issue induced by potential influencing factors. The model has good effect on the prediction and could provide certain guidance and reference for the cutter wear problem in similar geological condition.

Load-reduction mechanism of microstructure broach inspired by dung beetle surface

Broaching is extensively used in aerospace industry due to the good dimensional quality and surface integrity condition obtained. However, the coupled workload of heat and cutting forces make broaching tool having the problem of serious wear. Many studies have shown that the use of biomimetic microstructure can reduce the cutting load, but the load reduction mechanism is unclear. In this regard, a novel dry broaching experiment, inspired by the dung beetle surface, was designed to investigate the load reduction mechanism of microstructure broach. To reveal the mechanism, the broaching load, chip reduction coefficient and tool-chip adhesion length were compared with four kinds of rake face microstructures, which is conventional broach (without microstructures), biomimetic one (BM), micro-pit (PM) and micro-groove (GM). And all of above microstructures were fabricated by single point diamond tool (SPDT). It can be found that the biomimetic microstructure (BM) can reduce more tool-chip contact area, meanwhile enhance the ability of capturing debris. Otherwise, the obtained results revealed that biomimetic microstructures (BM) broach could reduce broaching load, chip reduction coefficient and tool-chip adhesion length by amount of 12.31 %, 8.23 % and 18.38 % compared to conventional one, respectively.

A Miniature Flapping Mechanism Using an Origami-Based Spherical Six-Bar Pattern

In this paper, we suggest a novel transmission for the DC motor-based flapping-wing micro aerial vehicles (FWMAVs). Most DC motor-based FWMAVs employ linkage structures, such as a crank-rocker or a crank-slider, which are designed to transmit the motor’s rotating motion to the wing’s flapping motion. These transmitting linkages have shown successful performance; however, they entail the possibility of mechanical wear originating from the friction between relative moving components and require an onerous assembly process owing to several tiny components. To reduce the assembly process and wear problems, we present a geometrically constrained and origami-based spherical six-bar linkage. The origami-based fabrication method reduces the number of the relative moving components by replacing rigid links and pin joints with facets and folding joints, which shortens the assembly process and reduces friction between components. The constrained spherical six-bar linkage enables us to change the motor’s rotating motion to the linear reciprocating motion. Due to the property that every axis passes through a single central point, the motor’s rotating motion is filtered at the spherical linkage and does not transfer to the flapping wing. Only linear motion, therefore, is passed to the flapping wing. To show the feasibility of the idea, a prototype is fabricated and analyzed by measuring the flapping angle, the wing rotation angle and the thrust.

Numerical Analysis of Wear Characteristics of Zirconia Coated Aluminum 6061 Alloy

Any mechanical systems with moving parts encounter the problem of wear and industriesacross the world are trying to reduce its detrimental effects. In this paper, Finite Element Method (FEM) is used for analysis of wear characteristics of Yttrium stabilized Zirconia coating on Al6061 Aluminum alloy. Aluminum alloy 6061, having high strength to weight ratio, is used as the substrate material upon which Thermal Barrier Coating (TBC) is applied. Friction and wear coefficient obtained from Continuous Sliding Motion (CSM) of Yttrium stabilized Zirconia coating over Aluminum oxide disc material is used for the numerical analysis inputs. Tribological characteristics such as contact pressure, frictional stress and wear thickness are evaluated numerically using ANSYS Mechanical based on Archard wear model.

Research of micro EDM/ECM method in same electrolyte with running wire tool electrode

A micro rod machining method which can switch between electrical discharge machining (EDM) and electrochemical machining (ECM) by attaching/detaching a diode to/from a bipolar pulse generator in parallel to the working gap was newly developed using a wire electrode made of tungsten. The problem of the wire electrode wear was eliminated by the use of the wire electrochemical turning (WECT) method in which the tungsten wire electrode is continuously running. The ultra-short bipolar pulse current was generated by the electrostatic induction feeding method where a pulse voltage is coupled to the working gap through a feeding capacitance. The machining characteristics of three types of wire guide; disk-shaped WC guide, laminated wire guide and cylindrical acrylic guide, were studied. The experimental results showed that the cylindrical acrylic guide has the best machining characteristics without the influence of guide wear and with less stray current flowing through the working gap. Using the cylindrical acrylic guide, the influences of the feeding capacitance C1, and the total amplitude of the pulse voltage on the machining characteristics were studied. Finally, a stainless steel SUS 304 micro-rod with a high aspect ratio of 14 was fabricated efficiently by using the EDM and ECM modes for rough and finish machining in sequence with the same setup, pulse generator, and neutral electrolyte.

Технологическое обеспечение фреттингостойкости плоских затянутых соединений

The problem of wear in contacting flat surfaces with the periodic micro-movement in the joint – the so-called fret-ting process is considered. There are defined peculiarities in the formation of operation roughness in the joint depend-ing on loading and a possibility for obtaining equilibrium roughness through the method of diamond abrasion-planetary honing.

Coupling Fractal Model for Fretting Wear on Rough Contact Surfaces

Abstract In this paper, a fretting damage model based on fractal theory is proposed. The Weierstrass–Mandelbrot function of fractal theory is used to represent the rough contact surface, and a corresponding contact parameter analysis method is also established. Based on neural network algorithm, the values of fractal parameters are fitted, and the fitting accuracy has been greatly improved compared with traditional methods. According to the fractal parameters of the actual surface, the fretting wear process of the rough contact surface is analyzed based on theory of adhesive and three-body abrasive wear. A generic program for the analysis of three-dimensional fretting wear problems is also proposed. Compared with material tests, the prediction error of the fretting wear simulation model is 13.4% for wear depth and 16.7% and 3.9% for width and length of wear scar in stable wear stage. The prediction results show that the model can be applied to the prediction of the actual three-dimensional fretting wear model.

Clothing of righteousness: exploring tensions of halal maternity wear on online apparel websites

PurposeThis paper aims to explore marketing practices related to online halal maternity wear by examining the characteristics of halal maternity wear promoted to Muslim women (Muslimah) and how these differ between sponsoring websites.Design/methodology/approachA qualitative content analysis of 24 websites promoting halal maternity wear to pregnant customers was undertaken.FindingsSeveral issues related to the availability and promotion of halal maternity wear online, particularly when addressing the needs of Western Muslim women, were found. Successful marketing solutions to the problems of halal maternity wear require solving a number of tensions arising at the intersections of the following distinctions: mahram versus non-mahram settings, crude versus stylish fashion and the normative perceptions of immodesty versus modesty.Practical implicationsCareful research and attention need to be taken before promoting and targeting products as appropriate for Muslimah maternity wear. Those brands that display the requisite skills and knowledge necessary to determine whether a product meets the needs of modesty, fashionability and local climate/weather conditions in their maternity lines have much to gain from the Muslimah maternity market.Social implicationsThe availability of maternity wear that makes Muslimah feel comfortable and satisfied with their appearance will contribute to a positive pregnancy body image. Positive pregnancy body image is associated with positive pre and postnatal infant attachment by the mother, which in turn leads to beneficial outcomes for mother and baby.Originality/valueResearch to date has focused on Islamic fashion in general, with a dearth of research on Islamic maternity wear. This paper addresses the gap by focusing on maternity wear and associated marketing practices, from the Islamic point of view.

Problems of modelling the bond reinforcement in concrete

Traditional design research typically focuses on the design and construction of new structures, buildings and structures. A large proportion of existing concrete structures have wear problems. The longitudinal shear stress created by a load in reinforced concrete at the boundaries of concrete and reinforcement is considered. The parameters of numerous variables affecting this relationship are given, including the strength and cover of concrete, the type of reinforcement, the use of transverse reinforcement, the state of the reinforcement surface, the length of the anchorage, the stress state in the reinforcement, loading, and environmental influences. An empirical model obtained by the best comparison with test results is presented. The results of the mutual influence between loading and corrosion of reinforcing steel are presented. Research results show that loss of bond caused by structural failure becomes more critical compared to other types of failure as the life of the structure increases.