Experimental Wear Data Research Articles

Special use of the ball on disc standard test

A possible procedure is proposed, which basically refers to tribological variables commonly used in engineering screen tests and in principle allows extended use of experimental wear data from the ball on disc standard system when the reference configuration has different geometry (e.g. flat pin on disc pairs) or nominal sliding conditions. The method is approximated and has been conceived to simplify comparative analysis of wear behaviour, in particular at equal nominal pressure. Expressing the ratio of wear constants on the basis of geometrical experimental variables for sphere and disc, it also aims to reduce time consumption in profilometry sessions and to split real-time linear wear curves for mating members from the overall approach pattern. An experimental example illustrates the proposed procedure, although full validation needs additional testing.

An Integrated Transient and Steady-State Adhesive Wear Model

The integrated adhesive wear model tokes into account both the transient wear and the steady-state wear in wear testing. The transient wear volume is described by an exponential equation while the steady-state wear by a revised Archard's equation. In this study, the integrated wear model was used to analyze experimental wear data obtained previously for an A6061-T6 alloy and MMC-D, an aluminium alloy matrix composite containing 20% spherical alumina particles. Two loads of 7.5 kgf and 10.0 kgf, and a speed of 4.58ms−1 were used in conducting the experiments. Both the standard wear coefficient and the net steady-state wear coefficient values for both types of materials were determined. On the average, the average standard steady-state wear coefficient, as compared with the net steady-state wear coefficient, was about 52% higher for MMC-D and 246% higher for A6061-T6. A higher load was found to have the effect of increasing the wear coefficient values. Scheduled for Presentation at the 58th Annual Meeting in New York City April 28–May 1, 2003

Low stress abrasion of laser irradiated GFRP composites: an experimental and microstructural study

The present paper reports, the mechanism of material removal during low stress abrasive wear of high weight percent glass fibre reinforced polymer (GFRP) composites. Two different geometries of glass fibre reinforcement namely woven roving (WR) and chopped strand mat (CSM) were used. Unsaturated isophthalic polyester and bisphenol based epoxy resins were used as matrix for the reinforcement. Rubber Wheel Abrasion Tester (RWAT) was used for evaluating the abrasive wear behaviour of the composites. The composite samples were irradiated using a low power He-Ne laser for different time periods, having intensity of 5 mW. The abrasive wear performance of the composites has been determined as a function of applied load, sliding distance and laser irradiation time. The microstructural features of the abraded surfaces of both the laser irradiated and unirradiated composites have been observed by using a scanning electron microscope. Unsaturated polyester based glass fibre woven roving (WR) composite had a higher wear volume as compared to the epoxy based composite. The trend reversed in the case of chopped strand mat (CSM) composites, in which epoxy-based composite showed higher wear volume. The abrasive wear volume of all the composites decreased on irradiating it with laser. These results have been discussed, based on experimental wear data and observed microstructural features of the abraded surfaces.

Prediction of flank wear by using back propagation neural network modeling when cutting hardened H-13 steel with chamfered and honed CBN tools

Productivity and quality in the finish turning of hardened steels can be improved by utilizing predicted performance of the cutting tools. This paper combines predictive machining approach with neural network modeling of tool flank wear in order to estimate performance of chamfered and honed Cubic Boron Nitride (CBN) tools for a variety of cutting conditions. Experimental work has been performed in orthogonal cutting of hardened H-13 type tool steel using CBN tools. At the selected cutting conditions the forces have been measured using a piezoelectric dynamometer and data acquisition system. Simultaneously flank wear at the cutting edge has been monitored by using a tool makers microscope. The experimental force and wear data were utilized to train the developed simulation environment based on back propagation neural network modeling. A trained neural network system was used in predicting flank wear for various different cutting conditions. The developed prediction system was found to be capable of accurate tool wear classification for the range it had been trained.

Stress-overstress-surface fatigue: new approach in the understanding of the tribology of plasma coated sintered steels

This paper deals with the tribological evaluation of plasma nitrocarburizing of commercially sintered low alloy steels. The samples were tested in dry sliding conditions against a cast iron pin. A model for particle detachment in the coatings is proposed, which takes into account the volume expansion in the coating process as a source of internal stresses in the compound layer. Two different routes were used for plasma nitrocarburizing—a ferritic (560°C) and an austenitic (600°C) treatment—and the tribological behaviour of the coatings was found to reflect the stress condition in the compound layer as a function of its thermal history. The experimental wear data fit well with the model, and the ferritic treatment was found to induce more stress in the coating, as predicted. Comparative results of tribological tests (wear and friction data) for as-received, coated and polished samples reinforce the ‘stress-overstress-fatigue’ sequence.

A map for wear mechanisms in aluminium alloys

A quantitative wear map for aluminium and its alloys has been constructed using normalized test variables and the physical modelling approach proposed by Lim and Ashby for steels. New model equations based on a different state-of-stress criterion suitable for aluminium alloys have been developed and found to match well with reported experimental wear data on aluminium alloys. The field boundaries between various interfacing wear mechanisms were constructed by using critical values of experimental wear data which manifest themselves in discontinuities in the slope of wear curves. However, within a given wear regime, the model equations developed here agreed fairly well with the reported wear data. The wear mechanisms successfully modelled here include oxidation dominated wear, delamination wear, severe plastic deformation wear, and melt wear.

Simulation of Tube-to-Support Dynamic Interaction in Heat Exchange Equipment

Abstract Tubes within tube and shell heat exchange components are supported at intermediate points by support plates. Flow-induced vibration of a tube can cause it to impact or rub against a support plate or against adjacent tubes and can result in tube fretting-wear. The tube-to-support dynamic interaction is used to relate experimental wear data from test rigs to real multi-span heat exchanger configurations. Analytical techniques are required to estimate this interaction in real heat exchangers. Simulation results from the VIBIC code are in good agreement with three examples from the open literature and are in reasonable agreement with measurements from the CRNL single-span room temperature fretting-wear rigs. Therefore, the VIBIC code is a good analytical tool for estimating tube-to-support dynamic interaction in real heat exchangers.

Analysis of wear statistics for polymer composites

The wear rate of polymeric short-fibre composites has been analysed by means of a wear lifetime model using a statistical methodology. The wear lifetime model of a power law relationship has been derived from fracture mechanics concepts and the observed wear-induced microstructures. Experimental wear data have been correlated with the model.

Oxidational wear

The paper examines the problem of deducing the rate at which a given volume is lost between surfaces in unlubricated sliding contact, given that the type of wear is “mild”. It deals with methods of obtaining estimates of the temperature ( T 0) at which wearing contacts oxidize. An hypothesis of oxidational wear is then reviewed and its predictions compared with experimental wear data. It is shown that this hypothesis leads to a valid expression for the wear rate, provided one assumes that the real areas of contact oxidize at temperatures of the order of those to be expected from dynamic thermocouple experiments, and that the activation energy for such oxidation is less than for oxidation of the materials under normal static oxidational conditions.

A Study of Oxidation Phenomena in Corrosive Wear

A mathematical model based on the existing theories of corrosion and wear is proposed for analyzing the controlling phenomena in corrosive wear caused by atmospheric oxygen. The model is applied to experimental wear data, making the assumption that all of the wear proceeded by a corrosion mechanism, i.e., the growth of an oxide layer and its subsequent removal by rubbing. The analytical results show that the rate of metal oxidation is the more important factor in determining the wear rate. The proposed model, assuming oxidation to follow a parabolic rate law, predicts a much higher rate constant and a lower activation energy for oxidation in corrosive wear than in static corrosion at the same “hot spot” temperature. It is postulated that this is due to a mechanical activation phenomena caused by rubbing action. The increase of wear at higher loads can be accounted for by a simple increase in oxidation rate at a higher surface temperature. Presented as an American Society of Lubrication Engineers paper at ...

Measuring Abrasiveness of Solid Fuels and Other Materials by a Radiochemical Method

A new method for predicting pulverizer grinding element wear has been developed. This paper describes a laboratory model, ball-and-race, grinding machine, and a radioactive tracer technique used to determine the relative abrasiveness of solid fuels. A procedure for determination of the quartz content of coals was developed, and its relationship to abrasiveness is discussed. Results of testing the abrasiveness of numerous coals and some materials other than coal are presented. A comparison of laboratory abrasion results with actual field wear data is given. Included is a method of application of the experimental wear data to design considerations for new units and also in anticipating wear rates of milling equipment in use.

A Relation between Adhesive Wear and Heat of Adsorption for the Vapor Lubrication of Graphite

A recently developed model of adhesive wear for liquid lubricants has been modified to include the effect of vapor pressure on the wear rate for vapor lubricants at low pressures or high vacuum. Two distinctly different tests of the model were made with published data on the wear of graphite in varying atmospheres. In addition to correlating the experimental wear data as a function of pressure and heat of adsorption, the calculated value of the wear coefficient km for graphite-graphite contact from both correlations is internally consistent. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Minneapolis, Minnesota, October 18–20, 1966.