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The objective of this paper is to determine fretting parameters of hoisting rope according to the hoisting parameters in coalmine and to explore the effect of contact load on fretting-fatigue behavior of steel wires.

Based on the mechanical model of hoisting rope in coalmine, the dynamic tension simulation of hoisting rope was performed. Static equations of hoisting rope under tension and torsion and theories of contact mechanics were applied to obtain fretting parameters. Fretting-fatigue tests of steel wires at different contact loads were conducted using a fretting-fatigue test rig. The fretting regime, normalized tangential force and fretting-fatigue life were studied. The morphologies of fretting contact scars and fracture surfaces were observed by scanning electron microscopy and optical microscopy to examine wear and failure mechanisms.

Dynamic tension changes from 0 to 30,900 N. In outer strand layer, contact loads between steel wires in certain wire layers are 60.5 and 38.3 N compared with 378 and 102.7 N between wire layers; relative displacements between wires are 62.5 and 113.2 μm, respectively. Mixed fretting regimes develop in all cases. Increasing contact load decreases the stabilized relative slip and normalized tangential force, reduces the fretting fatigue life, induces accelerated adhesive wear and fatigue wear and results in rougher fracture surface topographies. In all cases, fretting zone induces crack initiation; crack propagation and rupture zones present brittle cleavage and longitudinal splitting, respectively.

This paper presents the systemic study on determination of fretting parameters of hoisting rope according to the hoisting parameters in coalmine and the fretting-fatigue behavior of its internal steel wires. The results of fretting-fatigue tests show that the increase of contact load decreases the stabilized relative slip in mixed fretting regime and normalized tangential force, reduces the fretting fatigue life, induces accelerated adhesive wear and fatigue wear and results in rougher fracture surface topographies.

The authors warrant that the paper is original submission and is not being submitted to any other journal. And the research does not involve confidentiality, copyright infringement, leaks and other issues, all the responsibilities that the authors will take.

The purpose of this study is to investigate the microstructure of fretting wear behavior in 6061-T6 aluminum alloy. The fretting wear of blind riveted lap joints of 6061-T6 aluminum alloy plates, which are widely used in aircraft construction, was investigated. Fretting damages were investigated between the contact surface of the plates and between the plate and the rivet contact surface.

Experiments were carried out using a computer controlled Instron testing machine with 200 kN static and 100 kN dynamic load capacity. Max package computer program was used for the control of the experiments. Fretting scars, width of wear scars, microstructure was investigated by metallographic techniques and scanning electron microscopy.

It was found that fretting damages were occurred between the plates contacting surface and between the plate and rivet contact surface. As load and cycles increased, fretting scars increased. Fretting wear initially begins with metal-to-metal contact. Then, the formed metallic wear particles are hardened by oxidation. These hard particles spread between surfaces, causing three-body fretting wear. Fretting wear surface width increases with increasing load and number of cycles.

The useful life of many tribological joints is limited by wear or deterioration of the fretting components due to fretting by oscillating relative displacements of the friction surfaces. Such displacements are caused by vibrations, reciprocating motion, periodic bending or twisting of the mating component, etc. Fretting also tangibly reduces the surface layer quality and produces increased surface roughness, micropits, subsurface microphone.

In our August issue we published summaries of two papers given at the Symposium on Fretting Corrosion organised by the American Society for Testing Materials. Three more papers are summarised below. They are concerned with testing equipment for evaluating fretting corrosion, the influence of fretting corrosion on the fatigue strength of fitted members, and the fretting corrosion tendencies of combinations of materials.

To review the most commonly used mechanical surface enhancement (MSE) techniques and their applications available in aerospace industry.

A brief description of each technique, as well as advantages and disadvantages over other techniques are given. The effects of those techniques on the surface characteristics and service properties of treated components are summarised. Finally, the applications of such techniques in the aerospace industry are presented with descriptive illustrations.

Provides a know‐how information and also comparison of techniques. Guides researchers and engineers to proper and appropriate use of each technique for relevant case or application.

The list of techniques can be extended to a wider range which may perhaps include specific and special purpose surface enhancement methods. The applications given in the paper are mainly industrial examples of such techniques which may reduce its usefulness in academia.

A very useful source of information and reference for companies and engineers working in repair and production technologies of aerospace components, and also a valuable guidance for researchers and academia or for those who are intending to make a research on surface enhancement technologies.

This paper introduces the most commonly used MSE techniques and their effects on the service properties of aerospace components, and provides a practical help and information for people in the industry and academia.

The misaligned condition in splines coupling brings more relative motion between the engaging tooth surface and subsequently a rise of wear phenomenon. The sliding friction between the spline surfaces and initial gap between the teeth are the key roles in wear behaviour in both crowned and straight splines. The paper aims to discuss these issues.

There is a design constraint to include fretting and wear damage of spline surface in design criteria. It becomes very essential to use a finite element tool to evaluate the wear behaviour of spline surface in order to design for severe environmental conditions. The fretting fatigue and fretting wear damage mechanisms on the spline surfaces are mainly dependent on the forces between the spline surfaces and relative movement between the teeth. This study focusses on the effect of sliding friction coefficients on the wear damage of the spline surfaces based on mating condition.

Analysis shows that the contact pressure and root stress increase with increasing friction coefficient and misalignment. This is irrelevant to the crowned type of splines. This case becomes worst when the spline has more misaligned condition.

The fretting wear damage of straight spline is essential criterial for the application in aero engines and the crowned spline under controlled misaligned condition provides better wear life compared to straight spline surfaces.

The aim of this paper is to research grease and additives' influence on fretting wear of mild steel.

Experiments were performed on a laboratory stand with contact conditions cylinder on flat. The mild steel couples were tested under dry conditions and lubricated with mineral and synthetic greases containing as additives: graphite, molybdenum disulphide, ZDDP and molybdenum dithiocarbamate in different concentrations.

The results revealed a significant influence of grease consistency and its welding load on the fretting wear of steel couples. Graphite and molybdenum disulphide were effective in a 10 percent concentration. ZDDP additive in a more than 1 percent concentration increased fretting wear. Molybdenum dithiocarbamate was not more effective than molybdenum disulphide powder. Grease lubrication of the fretted couple changed significantly the wear mechanism observed on SEM photographs of fretting scars.

The paper presents some indications of proper selection of grease for fretting prevention.

The influence of the main features of grease on fretting wear was confirmed on the basis of extensive investigation.

Pre‐stressing. SURFACE EFFECTS Controlled Pre‐Stressing is the impingement on a surface of relatively small spherical particles of steel, glass or ceramic. These particles on impact, yield the skin and deform the surface plastically, leaving a residual compressive stress. The magnitude of that stress varies with the material being treated and the kinetic energy on impact.

The purpose of this paper is to develop an approach to optimize the cycles‐to‐failure of a peened component with respect to laser peening (LP) variables: pressure magnitude, mid‐span, and spot size when the component is subject to a variable amplitude loading.

To optimally design an LP process, an experimentally validated 3D finite element simulation of the LP process, a cycles‐to‐failure estimation capability incorporating residual stress, and a particle swarm optimization strategy were developed and employed to maximize the cycles‐to‐failure of a component of a titanium turbine disk.

The most critical finding of this research is that a minor difference in the residual stress profile can lead to a large difference in the cycles‐to‐failure. This finding implies that selecting the optimization objective to be the cycles‐to‐failure is a better option as compared to the residual stress profile.

The LP‐induced residual stresses are assumed static and do not change as number of load cycles increase.

The paper develops a framework that relates the LP variables and the cycles‐to‐failure of a peened component. A modified particle swarm optimization approach is developed to optimize the fatigue life of a turbine disk.

PETER O'Hara, vice president of the U.K. Division of Metal Improvement Co Inc, is an active member of a steering committee based in the School of Mechanical Engineering at Cranfield Institute of Technology who are working to define and introduce international standards which will effect the manufacture, maintenance and repair of aircraft. To date, the aerospace manufacturers have defined and enforced their own widely varying specifications and standards. The committee have lobbied prime aircraft manufacturers, several of whom are members of the committee, together with influencial authorities such as the C.A.A. and M.O.D. The committee firmly believes it is in the interests of the manufacturers, support organisations and consumers to standardise and improve specifications internationally. Indeed, there is evidence to suggest that many manufacturers are currently upgrading their specifications to benefit from improved technology.