Fracto-emission: The role of charge separation

Dickinson, J. T.; Jensen, L. C.; Jahan-Latibari, Ahmad

doi:10.1116/1.572682

Cited by 75 publications

(30 citation statements)

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“…The following high intensity emission event indicates the moment at which the coating fails resulting in a wear trace characterised by both surface cracks and partial delamination (Figure 4b). This is in accordance with previous studies that suggest that emission is due to the high energy generated during the damage of the surface, in particular crack formation [17,19,31,32]. The third region shows relatively few high emission events, occurring due to wearing of the remaining coating.…”

Section: Triboemission Measurementssupporting

confidence: 79%

The Use of Triboemission Imaging and Charge Measurements to Study DLC Coating Failure

2017

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We present a study on the simultaneous evolution of the electron emission and surface charge accumulation that occurs during scratching tests in order to monitor coating failure. Steel discs coated with a diamond-like-carbon (DLC) film were scratched in both vacuum (~10 −5 Torr) and atmospheric conditions, with electron emission and surface charge being measured by a system of microchannel plates and an electrometer, respectively. The results highlight a positive correlation between emission intensity values, surface charge measurements and surface damage topography, suggesting the effective use of these techniques to monitor coating wear in real time.

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Section: Triboemission Measurementssupporting

confidence: 79%

The Use of Triboemission Imaging and Charge Measurements to Study DLC Coating Failure

2017

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“…The average angle with the wear track has been found around 60° with a standard deviation of 12. This experimental evidence supports the hypothesis that triboemission occurs due to charge separation resulting from crack formation [18]. This technique of triboemission visualisation by an MCP could provide a powerful tool to visualize crack growth, in real time, giving information on their size and direction.…”

Section: Spatially Resolved Measurementssupporting

confidence: 69%

“…This model however, does not explain why the energy of the tribo-emitted electrons can be lower than the work function of the sample [14]. To account for these low energy electrons, Dickinson et al suggested that the work function of the surface could be locally decreased by small defects in the highly strained areas [18].…”

Section: Introductionmentioning

confidence: 99%

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Spatially Resolved Triboemission Measurements

Rouzic

Reddyhoff

2014

Tribol Lett

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Electron emission that occurs when surfaces undergo wear has been studied since the 1950s, and is the subject of continued speculation due to its possibly crucial role in the formation of boundary lubricating films and the degradation of hard drive lubricants. Despite this, the mechanisms by which this type of emission occurs are poorly understood. In order to shed light on this phenomenon, we report for the first time how friction stimulated electron emission can be visualised, by scratching an aluminium oxide surface, positioned 10 mm from a microchannel plate in a high vacuum. The microchannel plate is coupled to a phosphor-screen displaying the spatial distribution of electrons that are emitted in individual bursts as wear is accruing. The probability density of this emission has been calculated and a Shannon spectral entropy of 0.11 for a 10 ms time window, suggesting partially deterministic mechanisms are responsible. These emission maps help to elucidate the obscure mechanisms that cause emission, in a way that has not been possible with previous spatially averaged measurements. For example, linear distributions support the theory that electron emission arises due to the formation of surface cracks. In addition to this, as the contact moves over the specimen surface, certain locations show an increased propensity to emit, which further suggests the presence of localised defects. Furthermore, in certain cases sustained after-emission is observed from localised defects exiting the contact. These results highlight the possibility of using the technique to monitor very low levels of wear and even image crack formation in real time.

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“…The term electromagnetic emission (EME) comprises a wide range of emission effects. This can be electromagnetic radiation directly emitted during and after local mechanical processes, such as fracture [1,2], plastic deformation [3,4] or friction [5,6] as well as the emission of charged particles (sometimes referred to as fracto-emission [7,8]). As sources for the electromagnetic fields, the separation, displacement or movement of bound or free charges are considered.…”

Section: Introductionmentioning

confidence: 99%

Measurement and Study of Electromagnetic Emission Generated by Tensile Fracture of Polymers and Carbon Fibres

Gade

Sause

2016

J Nondestruct Eval

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Electromagnetic emission (EME) signals generated by tensile fracture of four different types of polymers and three different carbon fibre types are presented and discussed. A suitable set-up for the detection of the electric field component of EME generated by fracture of solids is proposed. Basic theoretical considerations are made about the coupling between these field components and the capacitive sensors used to directly measure the short ranged and low frequency (kHz-MHz) electric fields emitted by the generation of free surface charges and their spatial movement as dictated by the vibrational motion of the crack walls. Special focus is put on solids with low conductivity, where the influences of the material on the emitted fields is small and the detected electric signals almost solely depend on the source dynamics and the sensor characteristics. Analysis of the influence of the acquisition circuit is presented. The discussion of the electric signals emitted by tensile fracture of carbon fibres and polymer specimens comprises the influences of the material properties on the signals as well as correlations between the signals and the crack dynamics, including the crack propagation velocities.

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Fracto-emission: The role of charge separation

Cited by 75 publications

References 0 publications

The Use of Triboemission Imaging and Charge Measurements to Study DLC Coating Failure

The Use of Triboemission Imaging and Charge Measurements to Study DLC Coating Failure

Spatially Resolved Triboemission Measurements

Measurement and Study of Electromagnetic Emission Generated by Tensile Fracture of Polymers and Carbon Fibres

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