Acoustic emission monitoring of abrasive particle impacts on carbon steel

Abstract

The estimation of energy dissipation during particle impact is a key aspect in evaluating the abrasive potential of impact process. Whereas numerous numerical and analytical approaches exist, aimed at explaining observed wear phenomena, few researchers have attempted to measure the energy dissipation during impact. This article reports the results of systematic acoustic emission (AE) energy measurements aimed at detecting the amount of energy dissipated in a carbon steel target during airborne particle impact. Three experimental arrangements were used to investigate three impact regimes; low velocitylow mass (impact speeds of 12.5 m/s and masses of 4.9 Â 10 À6 to 2.3 Â 10 À4 g), low velocityhigh mass (sphere masses of 0.0012 g), and high velocitylow mass (impact speeds of 416 m/s). Within each of these regimes, both single-particle and multiple-particle impacts were studied in order to investigate the effect of overlapping events. Two parameters, particle diameter and particle impact speed, both of which affect the energy dissipated into the material were investigated and correlated with AE energy. The results show that AE increases with the third power of particle diameter, i.e. the mass, and with the second power of the velocity, as would be expected. The diameter exponent was only valid up to particle sizes of around 1.5 mm, an observation which was attributed to different energy dissipation mechanisms with the higher associated momentum. The velocity exponent, and the general level of the energy were lower for multiple impacts than for single impacts, and this was attributed to particle interactions in the guide tube and/or near the surface leading to an underestimate of the actual impact velocity in magnitude and direction.

Monitoring acoustic emission (AE) energy of abrasive particle impacts in a slurry flow loop using a statistical distribution model

“…The experimental set-up (Figure 1) used an AE system with a carbon steel target assembly identical to those used for earlier tests using an air jet [7] and a slurry impingement jet [9]. The flow loop consisted of a positive displacement pump (model C22BC10RMB, Mono pump driven by a 1.1 kW geared motor to give an output speed of 587 rpm), standard 23 mm PVC piping, a 50 litre conical tank and choke valves.…”

“…The pipe wall opposite to the stream was milled flat in order to have a plane area to mount the AE sensor and the bend was machined to give an internal bore of 5 mm with a conical transition, giving 7 mm wall thickness at the site where the sensor was mounted. The length of the target section was 75 mm giving an overall impingement area similar to the other studies [7,9,21]. A broad band piezoelectric AE sensor (Micro-80D, Physical Acoustics Corp.) was coupled by means of high vacuum grease onto the outside surface of the bend directly above the impingement area then clamped onto the bend using a magnetic clamp.…”

“…A number of studies [2][3][4] have shown a correlation between the rate of dissipated incident kinetic energy due to particle impact and the rate of material removal. Also, amongst researchers in applications of Acoustic Emission (AE) monitoring, there is a general agreement that the AE energy associated with particle impingement is proportional to the incident kinetic energy [1,[5][6][7][8], where the relevant mass, m, and velocity, vi, may be for an individual particle or, more often, an assemblage of particles. Therefore, the measurement of AE energy associated with particle-laden liquid impingement seems likely to offer a quantitative means of monitoring sand particle impacts and hence slurry erosion.…”

“…Studies of the effect of particle impingement parameters on erosion and the effects peculiar to erosion where the carrier fluid is liquid (reviewed in detail elsewhere [7,9]), have lent impetus to the application of AE as a tool to monitor erosion damage caused by solid particle impacts. Monitoring particle impact using AE is based upon a fraction of the incident kinetic energy of each impacting particle dissipating as elastic waves through the target medium (whose shape and elastic properties affect the propagation characteristics of the signal) before being detected by a suitable AE sensor.…”

“…The approach in the present work has been to carry out a graded set of experiments where particle impact is initially highly controlled (dropping particles under gravity and with air assist) [7], followed by slurry impingement tests with light and heavy particle loading and various impingement rates [9], to a final series of experiments where the control of particles is limited to controlling the particle density in a flow loop.…”