Abrasive Wear Mechanisms of Sand Particles Intruding into ATM Roller-scraper Tribosystem

The roller-scraper tribosystem of automatic teller machine(ATM) plays an important role in reliable cash requests.However,the abrasive wear of the polymer tribosystem becomes a prominent problem when operating in sandy environment.The wear behavior of the tribosystem in a simulated sandy environment has been experimentally studied previously.However the abrasive wear mechanism of roller-scraper tribosystems is still unknown to new design.The wear rates of polymer rollers were examined comprehensively and several jumping variations were found in the full data extent.Three wear stages were classified by the magnitude of wear rates,and different dominant wear mechanisms corresponding with different particle diameter were found by examining the worn surfaces.Accordingly a presumption was proposed that wear mechanisms in different stages were correlated with sand particles of different diameter.In a verification experiment,three typical wear mechanisms including cutting,ploughing,and wedging were found corresponding with different wear stages by scanning electron microscope(SEM) examination.A theoretical analysis was carried out with a simplified sphere particle intrusion model and the transfer conditions for different wear mechanisms were studied referring to the slip-field theory.As a main result,three typical wear models versus friction coefficient of particle/roller,and particle radius were mapped with variant hardness of the polymer roller and ratio of contact shear stress to bulk shear stress.The result illuminated the abrasive wear mechanism during particle intrusion.Particularly,the critical transition conditions gave the basis for improving the wear performance of roller-scraper tribosystems in a sandy environment.     

铁硼共晶犁铧的试验研究

本文从铁硼共晶组织具有耐磨粒磨损特性的角度出发,应用简单易行的工艺,研制了铁硼共晶犁铧,使犁铧的寿命比等温淬火的犁铧提高1.5倍左右,并具有良好的自磨刃效果。此种犁铧具有明显的经济效益和广阔的使用前景。     

磨料射流中磨料粒子的加速机理和运动规律

根据二相流理论讨论了磨料射流中磨料粒子的加速机理和运动规律，按喷咀收缩段为准二维流场，对磨料粒子运动方程进行了求解，并对磨料粒子速度和流场速度进行了比较，从而为磨料射流在实际应用中充分发挥效益提供了理论依据。     

水力喷射和水力磨粒喷射加工原理及工业应用

水力喷射和水力磨粒喷射加工(WJM和AJWM)作为一种新技术在现代工业上己崭露头角。本文系统地阐述了喷射加工原理及其先进工艺系统,介绍了喷射加工试验研究结果及加工数据,并对该加工技术在工业上的应用做了概述。文章指出,喷射加工由于具有其它加工方法不可及的优点,其工业应用将日益广泛。     

High stress abrasive wear behavior of sillimanite-reinforced Al-alloy matrix composite: A factorial design approach

An attempt has been made to explore the possibility of using a natural mineral, namely sillimanite, as dispersoid for synthesizing aluminum alloy composite by solidification technique. The abrasive wear behavior of this composite has been studied through factorial design of experiments. The wear behavior of the composite (Y _composite) and the alloy (Y _alloy) is expressed in terms of the coded values of different experimental parameters like applied load (x ₁), abrasive size (x ₂), and sliding distance (x ₃) by the following linear regression equations:

Low-Stress Abrasive Wear Behaviour of a 0.2% C Steel: Influence of Microstructure and Test Parameters

A low (0.2%) carbon steel has been subjected to heat treatment to form varying quantities of ferrite plus martensite in its microstructure. This was achieved by holding the samples in the two-phase (ferrite plus austenite) region at three different temperatures (750, 780, and 810°C) for a specific duration followed by quenching in ice water. In another exercise, the steel was also subjected to annealing treatment by austenitizing at 890°C followed by furnace cooling for comparison purposes. The samples were subjected to low-stress (three-body) abrasion tests using an ASTM rubber wheel abrasion test apparatus at different wheel speeds (150, 273 and 400rpm corresponding to linear speeds of 1.79, 3.26 and 4.78m/s respectively) for different sliding distances at a fixed load of 49N. Crushed silica sand particles of size ranging from 212 to 300 m were used as the abrasive medium. The wear rate of samples decreased progressively with sliding distance until a (nearly) steady-state condition was attained. This was considered to be due to abrasion-induced work hardening of subsurface regions as well as the greater tendency of protrusion of the harder martensite/pearlite phase at longer sliding distances, thereby providing greater resistance to wear. Decreasing wear rate with increasing treatment temperature 750–810°C could be attributed to the greater volume fraction of the hard martensite phase in the samples containing ferrite plus martensite. The lower wear rate observed in the case of the samples containing ferrite plus martensite over the annealed ones comprising ferrite and pearlite was attributed to the higher bulk hardness of the former. Increasing linear speed from 1.79 to 3.26m/s led to an increase in wear rate. This could be attributed to greater tendency of the abrasive particles to create deeper scratches and scouping (digging). A reduction in wear rate with a further increase in the linear speed from 3.26 to 4.78m/s could be due to a change in the mechanism of wear from predominantly sliding to rolling of the abrasive particles in view of the increased plastic deformability characteristics of the specimens due to higher frictional heating. The present investigation clearly suggests that it is possible to attain a desired combination of bulk hardness and microstructure (consisting of ferrite plus martensite) leading to optimum abrasion resistance in low-carbon steels. The quantity of the two phases in turn could be varied by suitably controlling the heat-treatment temperature.     

壳体镶套修复研究

介绍了镶套工艺在壳体修复中的应用     

Three-body abrasive wear behaviour of particulate-filled glass–vinyl ester composites

The incorporation of silicon carbide (SiC) and graphite fillers on three-body abrasive wear behaviour of glass–vinyl ester (G–V) composites has been investigated. Dry sand/rubber wheel abrasion tests (RWAT) were carried out at 200 rpm test speed. The tests were carried out at 22 and 32 N loads by varying the abrading distance from 270 to 1080 m in steps of 270 m. The worn surfaces were examined using scanning electron microscopy (SEM). The wear volume and specific wear rate of G–V composite reduces significantly on the addition of SiC filler. Graphite filler, however, performed poorly resulting deterioration in wear performance of SiC-filled G–V composite. The SEM studies indicate the reasons for failure of composites and influencing parameters.     

Analysis of microstructure and wear strength of hard facing used by the sugar and alcohol industry

The sugar and alcohol sector has seen huge growth in recent years in Brazil; however, maintenance in this industry comes at a high cost due to loss of metal from the equipment via wear mechanisms. The objective of this work is to evaluate the abrasive wear resistance and the microstructure of hard claddings deposited in a single layer. Four types of consumables are used in the sugar and alcohol industry: a clad electrode of FeCrC alloy, 4.0 mm of diameter and three self-shielded tubular wires, all 1.6 mm in diameter, of FeCrC, FeCrCNb and FeCrCTiMo alloys. The base metal used was SAE1020 steel. The welds with the tubular wires were produced in short circuit transfer mode, with the same welding current and voltage values. For the wear test a rubber wheel was used, in accordance with ASTM standard G65-91. The wear test pieces were removed from the central region of the test plates, and from the same region two groups of samples were removed for microstructural analysis (under an optical microscope). The results of the tests with the rubber wheel showed that the FeCrCNb alloy had the highest wear resistance, followed by the clad electrode, and the FeCrCMoTi alloy and FeCrC alloy had the worst performance. The FeCrC alloy (for both the clad electrode and for the tubular wire) showed a microstructure formed by M7C3 primary carbonates distributed in a matrix of lower hardness; the alloy containing Nb showed a similar microstructure as well as the presence of NbC carbonates; in turn, the alloy with Ti and Mo added revealed the presence of large primary titanium carbonates.     

Investigation of tribotechnical and service characteristics of diamond-containing materials based on SHMWPE and PTFE

Investigation results of service characteristics (specific consumption of diamonds, machining capacity, glazing of tools) of diamond abrasive materials based on high-molecular polyethylene and polytetrafluoroethylene are discussed. Optimum graininess and concentration of microgrit as well as conditions of steel and mineral material machining have been evaluated for both binders. It is shown that the tools based on PTFE are advantageous for a short-time grinding of steels, while the ones based on SHMWPE are better for a long-run grinding of minerals and steels.