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A method extensively used in the production of optically flat and finely finished surfaces is that of lapping the surface upon a plate using a loose abrasive mixed into a slurry…
Abstract
A method extensively used in the production of optically flat and finely finished surfaces is that of lapping the surface upon a plate using a loose abrasive mixed into a slurry form with a carrying fluid. If the surfaces finished in this way are in continuous or intermittent sliding contact, it is the author's opinion that any abrasives retained in their surfaces will affect surface wear. This paper reported on some exploratory work to indicate the degree of embedment of abrasive in certain materials lapped by hand.
The effects of a number of metals and alloys on the thermal stability of Avtur 50 have been evaluated from ASTM‐CRC and high temperature coker tests. The materials tested are used…
Abstract
The effects of a number of metals and alloys on the thermal stability of Avtur 50 have been evaluated from ASTM‐CRC and high temperature coker tests. The materials tested are used in current aircraft fuel systems or are possible alternatives for fuel systems of supersonic aircraft where they will be in contact with hot fuel. The alloys currently used in aircraft fuel systems have been classified and their probable effects on the stability of hot fuel listed. A number of the materials affected stability adversely, particularly alloys containing significant amounts of copper, and the use of these should be avoided. The pick‐up of copper by Avtur 50 at ambient temperature from alloys such as brass and gun‐metal has also been investigated. The results indicated that sufficient copper to affect thermal stability adversely is readily picked up from these alloys.
This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder…
Abstract
This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.
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Srinivasula Reddy I. and Vadivuchezhian Kaliveeran
This paper aims to focus on the effect of normal load, sliding speed and temperature on the coefficient of friction of Al 6061-T6 alloy under dry sliding conditions.
Abstract
Purpose
This paper aims to focus on the effect of normal load, sliding speed and temperature on the coefficient of friction of Al 6061-T6 alloy under dry sliding conditions.
Design/methodology/approach
Dry sliding experiments were conducted using rotary type pin on disk tribometer. Pins with 3 mm radius of contact and circular disks of 165 mm diameter were fabricated to simulate Hertzian contact configuration. Experiments were conducted by applying three different normal loads (1, 1.5 and 2 kg) and three different sliding speeds (1.25, 2 and 3 m/s) at different temperatures [room temperature (31 ± 1 °C), 60 °C, 100 °C and 150 °C].
Findings
Coefficient of friction at end of the first cycle of sliding, stabilized stage, unsteady state and steady state are reported elaborately in this study. Adhesive and abrasive wear mechanisms were observed in the dry sliding of Al 6061- T6 alloy contacts from the microscopic analysis of worn contact surfaces. The coefficient of friction was more influenced by the increase in normal load than the increase in sliding speed and temperature.
Practical implications
The results obtained from this study are significant for the design of aluminium-to-aluminium contacts in aerospace engineering and automobile engineering.
Originality/value
This study reveals the coefficient of friction of aluminium-to-aluminium (Al 6061-T6 alloy) contacts under cylinder on flat contact configuration.
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The increasing demand for fine pitch interconnections has led to a growth of interest in anisotropically conductive adhesives (ACAs) as an alternative to solder joints in high…
Abstract
The increasing demand for fine pitch interconnections has led to a growth of interest in anisotropically conductive adhesives (ACAs) as an alternative to solder joints in high density applications. The understanding of the conduction mechanisms for ACAs is of vital importance when choosing the right adhesive for a specific application. In the conductivity model, a formula has been created that can be used to estimate how the degree of deformation of the particles effects the resistance, especially in the case of soft metal‐coated polymer particles. Using this model, it is possible to estimate the total contact resistance. Some comparisons are made with real measurements for gold and indium‐tin‐oxide (ITO) surfaces, using gold‐coated polymer particles and gold bumped chips. For gold surfaces, the measurements have shown reasonably good correlation with the model. In the case of the ITO surface, the interface resistances seem to be the major part of the total resistance.
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Adrian Cubillo, Jeroen Vermeulen, Marcos Rodriguez de la Peña, Ignacio Collantes Casanova and Suresh Perinpanayagam
Integrated vehicle health management has been developed for several years in different industries, to be able to provide the required inputs to determine the optimal maintenance…
Abstract
Purpose
Integrated vehicle health management has been developed for several years in different industries, to be able to provide the required inputs to determine the optimal maintenance operations depending on the actual health status of the system. The purpose of this paper is to demonstrate the potential of a physics-based model (PbM) for prognostics with a real case study, based on the detection of incipient faults and estimate the remaining useful life of a planetary transmission of an aircraft system.
Design/methodology/approach
Most of the research in the area of health assessment algorithms has been focused on data-driven approaches that are not based on the knowledge of the physics of the system, while PbM approaches rely on the understanding of the system and the degradation mechanisms. A physics-based modelling approach to represent metal-metal contact and fatigue in the gears of the planetary transmission of an aircraft system is applied.
Findings
Both the failure mode caused by metal-metal contact as caused by fatigue in the gears is described. Furthermore, the real-time application that retrieves the results from the simulations to assess the health of the system is described. Finally the decision making that can be executed during flight in the aircraft is incorporated.
Originality/value
The paper proposes an innovative prognostics health management system that assesses two important failure modes of the planetary transmission that regulates the speed of the generators of an aircraft. The results from the models have been integrated in an application that emulates a real system in the aircraft and computes the remaining useful life in real time.
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Yanzhe Yang, G.D. Janaki Ram and Brent E. Stucker
Recently, a number of research projects have been focused on an emerging additive manufacturing process, termed ultrasonic consolidation (UC). The purpose of this paper is to…
Abstract
Purpose
Recently, a number of research projects have been focused on an emerging additive manufacturing process, termed ultrasonic consolidation (UC). The purpose of this paper is to present an analytical energy model aimed at investigating the effects of process parameters on bond formation in UC.
Design/methodology/approach
In the model, two factors are defined, energy input to the workpiece within a single cycle of ultrasonic vibration (E0) and total energy input to the workpiece (Et), to evaluate to the magnitude of transmitted energy into the workpiece during UC.
Findings
It is found that linear weld density, E0 and Et are affected by process parameters in similar manners.
Research limitations/implications
The current model is developed based on several simplifying assumptions, and energy dissipation and bond degradation during UC are not considered in the model.
Originality/value
The current model gives a useful understanding of the effects of process parameter on the bond formation in UC from an energy point of view.
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Panayota Vassiliou and Constantine T. Dervos
In this work, commercial silver metal contacts welded on top of silver plated brass or brass substrates have been exposed to air rich in NaCl. Scanning electron microscopy and…
Abstract
In this work, commercial silver metal contacts welded on top of silver plated brass or brass substrates have been exposed to air rich in NaCl. Scanning electron microscopy and energy dispersive analysis of the exposed contact surfaces were performed to identify the corrosion by‐products on top of the silver contacts, suspending wafers, and welding materials. Surface corrosion products were mainly found to consist of small spherules of Cu‐Zn or Ag‐Cu compounds which cover the surface of the contact proper with low adhesion properties. They mainly originate from the underplating wafer or welding materials. Electrical characterization of the contacting materials was based on dc temperature overheat tests, current switching cycle tests, and energy storage during ac current excitation. The experimental results display that the operating environment is indeed a very significant parameter determining the overall performance of the electrical contacts. New design rules as well as material selection properties may have to be systematically considered to allow for electrochemical induced degradation in saline operating environments.
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To form and develop a new mode of mixed elastohydrodynamic lubrication (mixed EHL) which is more realistic and of more application values to a practical elastohydrodynamic contact…
Abstract
Purpose
To form and develop a new mode of mixed elastohydrodynamic lubrication (mixed EHL) which is more realistic and of more application values to a practical elastohydrodynamic contact on gears, cams and roller bearings than the previous and current existing mixed EHL models.
Design/methodology/approach
The representative theoretical and experimental studies on elastohydrodynamic lubrication (EHL) and mixed EHL carried out in the previous and recent time, including those of the author, are reviewed. The obtained results on EHL and mixed EHL in those studies and the viewpoints on the mode of mixed EHL based on those results developed in those studies are compared and evaluated. Strong proves are formed on the new mode of mixed EHL proposed in the present paper based on these comparisons and evaluations.
Findings
Strong viewpoints are formed on the mode of the occurrence of dry contact in EHL in a practical concentrated contact. A new mode of mixed EHL is proposed by incorporating this mode of the occurrence of dry contact in EHL. Also, comments and evaluations on the previous researches on mixed EHL are made.
Practical implications
A very useful material for the engineers who are engaged in the design of EHL on gears, cams and roller bearings, and for the tribology scientists who thrust efforts in studying EHL and mixed EHL both by theoretical modeling and by experiments.
Originality/value
A new mode of mixed EHL is originally proposed by incorporating the finding of a more realistic mode of the occurrence of dry contact in EHL. This new mode of mixed EHL should become the direction of the theoretical research of mixed EHL in the future time. It provides a clearer way to this research.
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A review of corrosion problems in domestic building is presented with emphasis on the behaviour of non‐ferrous metals in various environments. The durability of metals in contact…
Abstract
A review of corrosion problems in domestic building is presented with emphasis on the behaviour of non‐ferrous metals in various environments. The durability of metals in contact with building mortars and with soils is discussed with particular reference to aluminium and zinc. The author is optimistic for the wider deployment of non‐ferrous metals in building in the future and points out that the quoted examples of failure, although alarming in prospect, represent a truly minor proportion of building applications.