Wear of paper slitting blades: the effect of slitter machine settings

Results are presented by wear tests on slitter blades, using a laboratory apparatus designed to simulate an industrial paper slitting machine. Experiments on blades worn with and without paper dust confirmed that three-body abrasion is the principal wear mechanism. A critical open cut distance of 350 μm for 70 g m^?2 paper was found to limit the life of blades under each setting condition and critical open cut distances were determined for various grades of paper. A mill trial confirmed that open cut distance is a valid measure of the life of blades. The results were analysed using a simple modification of abrasive wear theory and a linear relationship between volumetric wear and running distance was obtained. A mathematical model to determine the wear angle of blades was shown only to be valid during the ‘running-in’ period     

An apparatus for measuring wear of paper slitting blades

A laboratory apparatus for measuring wear of rotary paper slitting blades of the Koegel type is described. There is provision for adjusting blade setting parameters and for running the blades in contact with paper dust. Wear at blade tips is measured in situ using a mechanical profilometer. It is shown that the initial rates of wear are very high and the extent of wear at the tips of top and bottom blades differ. The wear of a pair of slitter blades is measured using the concept of open cut distance and, for 70 g m⁻² paper, loss of cut quality occurs when open cut distance increases to 350 μm     

A statistical model describing wear traces in three-body abrasion

Cutting wear is a mechanism by which material is removed through three-body abrasion. In the present paper, a statistical model describing the wear traces on a worn surface is proposed for three-body abrasion, to estimate cutting wear as a proportion of the total wear of the test materials. Using this model, a statistical analysis of the traces on the worn surface was made after short-travel, three-body abrasion tests. The results showed that cutting was not a great proportion of the total wear of the test materials under the conditions of three-body abrasion.     

Dicing of hard and brittle materials with on-machine laser-dressed metal-bonded diamond blades

The ultra-precision dicing of hard and brittle materials causes high wear on the abrasive tool which results in the deterioration of blade cross section as well as the decrease of diamond grain exposure. Resin-bonded diamond blades are used due to their in-process self-sharpening capability. Nevertheless, the shape of the blade cross section generated by self-sharpening is random which leads to poor accuracy when precise grooves need to be produced. Metal-bonded diamond blades feature higher tool lifetime and shape accuracy compared to resin-bonded blades, but are not capable of performing self-sharpening. In this study, the laser dressing of metal-bonded diamond blades is investigated to enable their use in the ultra-precision dicing of hard and brittle materials by continuous laser dressing. We investigated laser dressing with and without the presence of cooling water. The sharpness (grain exposure) after dressing is measured by the cutting face surface roughness. The dicing performance is evaluated by observing the dicing results in terms of cutting depth consistency and by monitoring the spindle power during dicing. Dicing blades which have been laser dressed in an environment with coolant feature less grain exposure than dicing blades which have been laser dressed in dry condition. The dicing results show an improvement in the sharpness and durability of laser-dressed dicing blades in comparison with new or conventionally dressed blades. The ability to apply and perform laser dressing on a dicing machine in an environment with coolant shows the feasibility of laser technology for continuous dressing.     

Abrasive wear response of cryotreated EN45 steel in simulated wear test rig fixture

Wear by sand abrasion occurs in cutter blades of sugarcane cutting machine. The wear life of components used under sand abrasion conditions is governed by process parameters, properties of abrasive particles in the soil and material properties. In this article, the wear performance of conventionally and cryotreated specimens was tested in the soil containing 20% silica at different blade speeds such as 300, 400, 600 and 750?rev?min^??1 at the varied cutting times of 8, 16, 24 and 32?h respectively using simulated test rig fixture of sugarcane cutting machine. In addition, treated specimens were characterised for the microstructural features, hardness and surface roughness. Microstructural study indicated fine structure of tempered martensite with addition of segregation of silicon and carbon spots in the cryotreated specimen. The surface roughness of cryotreated material was decreased by 50% with respect to conventionally treated one. The mass loss of cryotreated cutting blades was reduced by 28% over conventional treatment at 750?rev?min^??1. The wornout surface and subsurface of conventionally treated specimens showed predominant dislodgment of wear particles.     

硬质颗粒复合合金的组织和耐磨性

本文强调基体合金组织对硬质颗粒复合合金耐磨性的决定作用,设计并通过“真空吸附铸件表面合金化工艺”,在灰铁铸件表层稳定地制得了以不同粒度的铸造碳化钨颗粒均匀分布于高合金铬钨白口铸铁中的复合合金。磨料磨损试验表明：基体合金组织对复合合金二体尤其是三体高应力磨损耐磨性有决定性的作用;以马氏体合金白口铁为基体合金的复合合金,在二体及三体磨损条件下均具有极高的耐磨性,铸造碳化钨颗粒愈粗,复合合金耐磨性愈高,当颗粒尺寸由140～200目增大到18～28目时,其在二体和三体磨损条件下的耐磨性分别是马氏体白口铁15Cr2Mo1Cu的9～31倍和2.8～6.7倍。     

The wear of ultrafine WC–Co hard metals

The wear performance of ultrafine-grained tungsten carbide–cobalt (WC–Co) hard metals during three-body abrasion and particle erosion has been evaluated and compared to that of similar conventional coarser grained hard metals. The tungsten carbide grain size varied between 0.5 and 3 μm with cobalt contents ranging from 6 to 15%. Silica particles were used in both forms of testing. Erosion was carried out at 60 ms⁻¹ at an impact angle of 75° and abrasion at a velocity of 0.5 ms⁻¹ and a load of 50 N.

The wear resistance of the ultrafine grades was found to be at least double that of the closest conventional fine grained hard metals. These increases in wear performance are considerably higher than any corresponding increase in hardness which is, at most, 25% and is not achieved at the expense of fracture toughness which is maintained at a similar level to that of conventional fine grained hard metals. The increase in wear resistance coincides with a change in the mechanism of material removal. Sub-micron materials experience ductile deformation and bulk removal of material whilst coarser grades display more localised response with extensive fragmentation of the WC grains.     

Kinematics and Wear of Tool Blades for Scrap Tire Shredding

The wear of tool blades for cost-effective scrap tire shredding is investigated. Rotary disk cutters are widely used for cutting scrap tires into small pieces. The hard, wear-resistant tool blades mounted on the periphery of disk cutters maintain a narrow gap between blades and generate the cutting action. The kinematics of the relative motion of two adjacent disk cutters is derived to model the overlap region on blades during cutting. The model predictions match well with the actual shapes of the worn regions on used tool blades. The wear of tool blades made of AISI D2 and CRU-WEAR (CW) tool steels for scrap tire shredding is evaluated. A coordinate measurement machine was used to measure the tool wear. The wear on the blade surface is not uniform. Regions with high wear rate are explained using the kinematics analysis. The CW blades show a lower wear rate, about half of that of D2 blades, and a potential choice for cost savings.     

Kinematics and Wear of Tool Blades for Scrap Tire Shredding

Abstract

The wear of tool blades for cost-effective scrap tire shredding is investigated. Rotary disk cutters are widely used for cutting scrap tires into small pieces. The hard, wear-resistant tool blades mounted on the periphery of disk cutters maintain a narrow gap between blades and generate the cutting action. The kinematics of the relative motion of two adjacent disk cutters is derived to model the overlap region on blades during cutting. The model predictions match well with the actual shapes of the worn regions on used tool blades. The wear of tool blades made of AISI D2 and CRU-WEAR (CW) tool steels for scrap tire shredding is evaluated. A coordinate measurement machine was used to measure the tool wear. The wear on the blade surface is not uniform. Regions with high wear rate are explained using the kinematics analysis. The CW blades show a lower wear rate, about half of that of D2 blades, and a potential choice for cost savings.     

Micro/nano-scale differential wear of multiphase materials: pole tip recession in magnetic-tape heads

Wear of multiphase materials at the micro/nano-scale is important in devices such as magnetic tape and disk drives, where the read-write heads are multiphase. Differential wear, which is caused by differences in wear resistance among the heads’ phases, causes the thin-film poles to recede from the bearing surface; this is called pole tip recession (PTR). It is a problem because it increases spacing between the poles and medium, resulting in lower readback amplitude. Here, PTR in tape heads is studied to understand micro/nano-scale differential wear. Test results suggest that three-body abrasion, which leads to primarily plastic wear, is the operative wear mode. Most of the three-body abrasive particles originate from the tape surface; the alumina head-cleaning agents (HCAs) in the tape, which function as load bearing particles at the interface, are believed to be the primary abrasives. Some of the particles originate from the head. These are important if the substrate material is relatively soft. Differential wear can be reduced by choosing a substrate that is harder than the tape’s HCAs, choosing a pole material that is as close as possible to the hardness of the substrate, and lowering the thickness of the head’s thin-film region. Material hardness matching will not reduce differential wear if a substrate is chosen that is less hard than the HCAs. An analytical model that accounts for the observed wear is presented. The model shows that each of the following leads to higher differential wear: increasing the thickness of three-body particles, increasing tension, decreasing thin-film hardness, and increasing the thin-film wear coefficient. An increase in thin-film wear coefficient can be caused by an increase in thin-film thickness or an increase in the number of particles at the interface.     

An Experimental Study of the Wear Caused by Loose Abrasive Particles in Oil

Abrasive powders were added to a highly-refined petroleum oil and run in a vane pump. With no antiwear additive, wear was successive and volumetric efficiency dropped rapidly. With 0.1% oleic acid or stearyl amine added to the oil the abrasive wear of the particles was essentially eliminated. Also, precoating the particles with the antiwear additive before adding to the base oil greatly retarded wear. Oleic acid performed best on iron oxide (basic), stearyl amine best on silica (acidic). No reduction in abrasive wear by oleic acid was observed when a steel ball was loaded against a grinding wheel. It is concluded that the antiwear additives prevent three-body abrasion (abrasion by loose Articles) by preventing the particles from adhering to one of the wing surfaces where they can act like small cutting tools.     

Influence of hardness of the counterbody in three-body abrasive wear — an overlooked hardness effect

The resistance to three-body abrasion of some common metals, mainly a tool steel and an aluminum alloy, both heat treated to different hardnesses, has been evaluated in two different tribosystems. The different materials have been tested against each other in different combinations to study the influence of the relative hardness of the two bodies on the wear rate in three-body abrasion. In all tests the abrasives have been much harder than the metals. It was observed that the wear rate of asolid body in three-body abrasion strongly depends on the hardness of the counterbody. In three-body abrasion a material may, under some circumstances, be most strongly worn if the counterbody is softer than the metal to be worn. This is because the abrasive particles can be embedded in the softer surface and groove the harder one. However, many parameters of the tribosystem influence the embedding of particles and the wear rate in three-body abrasion. It is shown that the size of the area in which the abrasives are embedded compared to the size of the wear scar in the counterbody as well as the smoothness of the surfaces are of importance.     

雕塑曲面体混流式叶片的多轴联动数控加工编程技术

转轮叶片是水轮机能量转换的关键部件,也是最难加工的零件,目前多轴联动数控加工是解决该类大型雕塑曲面零件最有效的加工方法。多轴联动数控加工编程则是实现其高精度和高效率加工的最重要环节。本文介绍混流式水轮机叶片五轴联动数控加工大型雕塑曲面编程中涉及到转轮叶片三维造型、刀位轨迹计算、切削仿真、机床运动碰撞仿真、后置变换等关键技术。通过对这些技术的链接和研究,开发实现了大型叶片的多轴联动加工。     

砂粒粒径对航空涡轴发动机压气机叶片冲蚀磨损的影响研究

高原、沙漠和沿海等服役环境中不同粒径的砂粒不可避免地对涡轴发动机压气机叶片造成冲蚀磨损,破坏叶片叶型和动力学特性,严重危及涡轴发动机使用寿命和直升机飞行安全。基于Finnie冲蚀磨损理论推导了颗粒对金属表面的磨损率表达式,分析颗粒粒径对材料冲蚀磨损率的影响,以某型涡轴发动机压气机动叶和静叶为研究对象,设计搭建砂粒冲击速度测试装置和钛合金冲蚀磨损实验装置,通过典型砂粒粒径下冲蚀磨损实验获取磨损率表达式中与靶材材料和冲击速度相关的关键参数,结合气固两相流动力学分析开展砂粒粒径对压气机动叶和静叶冲蚀磨损的影响研究。结果表明：砂粒粒径与冲击速度存在内在关联,材料冲蚀磨损率与砂粒冲击速度呈幂函数关系。实验条件下,砂粒粒径由177 μm增至423 μm时,其冲击速度平均降低约17%。压气机动叶和静叶的磨损集中区域不随砂粒粒径的改变而变化,但磨损程度差异明显,其中177 μm砂粒对动叶和静叶造成的最大冲蚀磨损率浓度值相比423μm砂粒分别增加91%和131%。研究结果为涡轴发动机压气机叶片抗磨损设计提供了理论参考。     

Prolonging the service life of shot-blaster blades made from high chromium cast iron

By using chill technology in the sand mold and improved heat treatment technology, superior shot-blaster blades were made from high chromium cast iron near eutectic composition. When steel pellets are shot, the service life of this kind of blade was 670 h, about twice the 328 h of the GF blades (made in Switzerland). Under the condition of shooting white iron pellets, the service life of this kind of blade was 380 h, about 1.5 times the 245 h of the domestic high quality blades.It was shown by performing a worn surface analysis of discarded blades and by a trial run of pilot blades that the wear of blades when shooting steel pellets was mainly caused by spalling, and there was little microcutting. Decreasing the amount of retained austenite and improving the toughness of martensitic matrix increased the wear resistance of these blades effectively. The wear of blades was mainly caused by microcutting when shooting white iron pellets, but spalling also contributed to wear. Increasing the hardness and decreasing the amount of retained austenite were beneficial to wear resistance of these blades. Unidirectional carbide arrangement perpendicular to the wearing surface also improved wear resistance of both types of blades.     

Toolpath dependent chatter suppression in multi-axis milling of hollow fan blades with ball-end cutter

Aiming at the issue of toolpath dependent machining vibration in multi-axis milling of hollow fan blades, this paper presents an optimal selection method of cutting parameters based on single-line toolpath to suppress cutting chatter. Firstly, the impact of hollow structure on the blade structural modal was analyzed by using the modal analysis method. And the unstable regions of hollow blade surface have been predicted, which were prone to induce machining deformation and vibration. Secondly, the relationship between the hollow structure and the dynamic characteristics was revealed by analyzing the dynamic responses to the different cutting positions of blade surface. Thirdly, the optimization of cutting parameters based on single-line toolpath was proposed by establishing the 3D stability lobe diagram. Finally, the feasibility and effectiveness about the analysis of dynamic characteristics and the suppression method of cutting chatter were verified by a milling experiment of hollow blade.     

硬质合金涂层刀片磨损寿命的评估计算

使用CP425牌号硬质合金涂层刀具进行切削速度、进给速度和切削深度三因素三水平正交磨损试验。通过对磨损试验结果的分析,得出影响CP425牌号硬质合金涂层刀片磨损性能的重要次序。并利用泰勒公式和MATLAB软件,得出刀片磨损寿命的评估计算公式,有利于指导选择最优的切削参数。     

The tribology of advanced digital recording (ADR) systems

The advanced digital recording system, a linear tape recording system is examined with respect to the tribology involved at the head/tape interface. Using atomic force microscopy (AFM), Auger elcetron spectrocopy (AES) and scanning Auger microscopy (SAM) surface characterisation techniques, several wear mechanisms are isolated: scratching, attributed to the polishing action of the tape asperities; microfracture then pullout of the Al₂O₃–TiC ceramic used as tape bearing surface; and ploughing due to three-body action of ceramic pullouts entrapped on the recessed poles. A ceramic differential wear is found to occur at the expense of the Al₂O₃ component, which therefore forms the ceramic recessed regions. The ceramic pullouts involved in the poles' three-body abrasion, however, appear to consist of TiC particles. A model for the ceramic wear mechanism is proposed. A transferred mixture of possibly magnetic pigments, binder and lubricant from the tape to the head is observed in the form of adhesive deposits. The iron component of this transfer is found in higher concentrations on the pole tips and the prominent part of the ceramic.     

Wear of metal stirring rods in molten aluminium and suspensions of alumina particles in molten aluminium

The wear of stainless steel and titanium stirring rods in molten aluminium and a suspension of alumina particles in molten aluminium was studied. The known characteristic of more rapid wear by stainless steel than titanium was confirmed and the suspension of alumina particles was found to accelerate wear of both metals. Examination of worn specimens revealed that the stainless steel rods were separated from the liquid aluminium by a layer of iron, chromium and aluminium. Wear proceeded by the shedding of projections that formed on the layer into the liquid aluminium. Alumina particles accelerated wear by abrasion of the projections. The titanium was surrounded by a much thinner layer of titanium and aluminium mixture with no projections into the molten aluminium. The distribution of wear around the blades was controlled by the flow of liquid metal and of the alumina particles around each blade.     

Comparison of wear properties of tool steels AISI D2 and O1 with the same hardness

Two commercial cold work tool steels, AISI D2 and O1, were heat treated in order to obtain the same hardness 700 HV (60 HRc) and were subsequently tested in three different modes of wear, namely in adhesion, three-body and two-body abrasion, by using pin-on-disk, dry sand/rubber wheel apparatus and pin abrasion on SiC, respectively. Even though AISI O1 and D2 steel are heat treated to the same hardness, they perform differently under the three modes of wear examined. The results show that the steel microstructures play the most important role in determining the wear properties. For relatively low sliding speeds AISI O1 steel performs up to 12 times better than AISI D2 steel in adhesive wear. For higher sliding speeds, however, this order is reversed due to oxidation taking place on the surface of the AISI D2 steel. The wear rate of both tool steels in three-body and two-body abrasion wear is proportional to the applied load. In three-body abrasive wear, AISI D2 exhibits a normalised wear rate about two times lower than the AISI O1 tool steel, and this is due to the presence of the plate-like hard carbides in its microstructure. Both tool steels perform 3–8 times better in three-body abrasive wear conditions than in two-body abrasive wear.