Acoustic emission

About: Acoustic emission is a research topic. Over the lifetime, 16293 publications have been published within this topic receiving 211456 citations.

Acoustic Emission Behavior and Monitoring of Soils

Abstract: As far as nondestructive testing methods are concerned, acoustic emission techniques are relatively recent additions to the rock monitoring area (dating from the late 1930's) and to the metal testing area (dating from the 1950's). Its application to soils is an even more recent event with little activity prior to the 1970's. However, over the past five to ten years, interest has been generated in the soils area to the point where at least five equipment manufacturers are currently marketing acoustic emission systems specifically for geotechnical engineering applications. This activity is seemingly well founded, for acoustic emissions are indeed generated by deforming soil masses and technical feasibility is now firmly established. This state-of-the-art paper on acoustic emission activity in soils presents these findings on the basis of fundamentals, small-scale laboratory tests, and large-scale laboratory tests. Furthermore, the technique has been applied to field situations in a number of cases. These include slope stability monitoring of dams and embankments, soil movements arising from horizontal and vertical deformations, seepage monitoring, and grout/hydrofracture monitoring. Specific case histories in each group are presented. Collectively taken, the information available seems encouraging enough for many investigators to use the technique for a wide variety of applications. With a multifaceted attack, the current qualitative status of the technique (that is, no acoustic emission indicates stability; low acoustic emission indicates small movement; moderate acoustic emission indicates larger movement; high acoustic emission indicates instability) should move into a better defined quantitative status. In this latter case, acoustic emission signatures of different soils could lead to instant assessment of actual stress levels in any given situation. (Authors)

Identification of Cracking Mechanisms in Scaled FRP Reinforced Concrete Beams using Acoustic Emission

Abstract: Acoustic emission was used to monitor the cracking mechanisms leading to the failure of scaled concrete beams having Glass Fiber Reinforced Polymer (GFRP) longitudinal reinforcement and no shear reinforcement. Dimensional scaling included that of the effective depth of the cross section, which is a key parameter associated with the scaling of shear strength; and maximum aggregate size, which affects the shear-resisting mechanism of aggregate interlock along shear (inclined) cracks. Five GFRP reinforced concrete (RC) beams with effective depth up to 290 mm and constant shear span-to-effective depth ratio of 3.1 were load tested under four-point bending. Two types of failures were observed: flexural, due to rupture of the GFRP reinforcement in the constant moment region; and shear, due to inclined cracking in either constant shear region through the entire section depth. Acoustic emission (AE) analyses were performed to classify crack types occurring at different points in the load history. The results of this study indicate that appropriate AE parameters can be used to discriminate between developing flexural and shear cracks irrespective of scale, and provide warning of impending failure irrespective of the failure mode (flexural and shear). In addition, AE source location enabled to accurately map crack growth and identify areas of significant damage activity. These outcomes attest to the potential of AE as a viable technique for structural health monitoring and prognosis systems and techniques.

Precursory deformation and fracture before brittle rock failure and potential application to volcanic unrest

Abstract: [1] Small-magnitude earthquakes and ground deformation are the precursors most frequently recorded before volcanic eruptions. Analogous signals (using acoustic emissions) have also been reported before the bulk brittle failure of crustal rock in the laboratory. Models based on laboratory and field data have focused on precursory behavior during deformation under a constant stress. A new model is proposed for extending analyses to deformation under an increasing stress. It describes how precursory time series can be determined from a parent relation between fracturing and stress, together with time-dependent changes in applied stress and rock resistance. The model applies to rock in which these stresses do not interact with each other and occupy volumes much smaller than the total volume being deformed. It identifies how the amounts of fracturing observed during deformation are controlled not only by stress concentrations at macroscopic heterogeneities, such as crack tips but also by rock composition, temperature, confining pressure, and the distribution of energy among atoms. The results appear to be scale independent, and so may be used to investigate whether the approach to bulk failure is limited by changes in applied stress or in rock weakening. When applied to pre-eruptive data from Hawaii, the analysis suggests that precursory signals are controlled by an increase in applied stress, rather than by creep deformation under a constant stress.