Highly localized acoustic emission monitoring of nanoscale indentation contacts

Abstract

This study evaluated a novel approach for acoustic emission (AE) monitoring of nanoindentation. The technique utilizes a miniature AE sensor integrated into a calibrated diamond indenter tip on a commercial nanoindentation system. The evaluation focused on the yield-point phenomenon in W (100); MgO (100); and sapphire C (0001); R (1012); A (1210); and M (1010) single-crystal surfaces. The minimum amount of elastic energy release sufficient to produce AE signal detectable with the indenter tip sensor was nearly two orders of magnitude lower than the minimum energy level required for conventional AE sensors. Wave forms detected with the indenter tip sensor were independent of sample size. A linear relationship between released elastic energies and the corresponding AE energies was observed for all three evaluated materials. The scaling coefficient of the linear relationship was independent of indenter tip size/shape and indentation depth. The differences between the mechanisms of the initial stages of plasticity for the various crystallographic orientations of sapphire were reflected in the following aspects of AE activity: detection of a specific type of AE wave form that correlated to the presence of linear surface features near the indentation sites; AE signal associated with the yield point, consisting either of one or two distinct wave forms; and presence or absence of AE signals after the yield point. The possibility of plasticity onset in sapphire involving both slip and twinning is discussed.

Passive acoustic monitoring of head disc interface interactions

“…An energy approach revealed by Dai et al (2002) and Mate (2007) can be used in quantifying 10 -12 -10 -15 J adhesive energy levels during close proximity between the head and media. This energy range matches well with the detectable equivalent AE energy levels correlated with elastic energy release during nanoindentation as measured by Daugela et al (2001) and Tymiak et al (2003). This fact suggests that a drive level ultra sensitive in situ AE monitoring technique is capable of capturing weak HDI interactions caused by degrading lubricant and particle induced slider and disc interference (e.g.…”

Acoustic Emission Analysis of Nanoindentation-Induced Fracture Events

“…Fortuitously, failure events in brittle materials are accompanied by abrupt changes in stress and strain fields, which lead to the generation of transient elastic waves in the form of acoustic emission. The real-time monitoring of acoustic emission can then be used as a qualitative and quantitative diagnostic tool [6][7][8]. This paper reports on the use of high resolution acoustic emission sensing to monitor nanoindentation induced fracture and characterize the initiation and progression of local failure processes.…”

Ultra sensitive in-situ acoustic characterization system for HDD head disc interface defectoscopy

“…This can be roughly compared to the high speed phenomena (<0.1 ls) such as plasticity yield point, materials phase transformation, and crystalographic orientation induced changes carried out by AE monitored nanoindentation process at the nanometer scale (Daugela et al 2001;Gerberich et al 2002;Tymiak et al 2003). In these experiments AE events were monitored at quasistatic loads of <100 lN.…”

“…Here, the equivalent AE event energy can be obtained through the integration of elastic recovery represented by the loading segment of quasistatic force-displacement curve. Tymiak et al (2003) reported equivalent AE energy levels on the order of 10 -12 -10 -15 J. This fact suggests that a drive level ultra sensitive in-situ AE monitoring technique will be capable of capturing weak HDI interactions caused by degrading lubricant and particle induced slider and disc interference.…”