Acoustic Emission Power Research Articles

Spectral analysis of acoustic emission during cyclic deformation of copper single crystals

Abstract Acoustic emission (AE) is investigated during fatigue at constant-plasticstrain control of copper single crystals oriented for easy glide, aiming at AE monitoring of structural transformation and dislocation self-organization during cyclic deformation. The results of AE analysis are compared with the cyclic response and hysteresis loop shape on different stages of fatigue. It is shown that the modern AE technique employing spectral analysis is sensitive to all essential structural changes in dislocation ensembles during fatigue such as matrix hardening, formation of veins and channels, persistent slip band (PSB) nucleation and development until crack initiation. The evidence is given for early identification of strain localization by means of AE. It is shown that the maximum of median frequency of the AE power spectral density at the intermediate stage of rapid hardening can be considered as an indicator of local softening followed by strain localization in PSBs. The moment of crack nucleation is...

Effect of Crystallographic Orientation and Grain Boundary on Acoustic Emission in Aluminium Single- and Bi-crystals

Acoustic emission (AE) in aluminium single crystals of different tensile orientations and bicrystals with different types of grain boundaries (GB) is studied with the aim to clarify the role of boundaries in AE. It is shown that AE in single crystals depends on the tensile orientation so that the maximum AE power appears to be roughly proportional to the work hardening coefficient during Stage II of plastic deformation. The strong effect of GB on AE is established. The GB does not only laterally restrict dislocation motion inside the grain but it also provides specific AE sources which are related to the additional slip in the GB affected zone. An increase in plastic strain incompatibility at the GB increases AE.

Classification of chip form based on AE analysis

Application of an adaptive information processing system to chip form classification on the basis of acoustic emission (AE) signals is described. The system is composed of an AE sensor, a spectrum analyzer and an adaptive empirical modeler which automatically determines the relations between features of AE power spectrum and the chip form.

Behavior of Crack Propagation and AE in CFRP Laminates under In Situ SEM.

The fracture behavior and crack propagation process of carbon-fiber-reinforced laminate composites are examined by in situ SEM, and acoustic emission (AE) signals are measured simultaneously. As a result, the fractures of matrix, fiber-matrix interface and bridge fiber give rise to AE signals, and the patterns of AE event count rate are found to depend strongly on the fiber orientation in a laminate. The direction of crack propagation is along the fiber orientation even for cross laminates and crack propagation is terminated by the reinforced fibers. The amplitude of the AE signal is low at the period of initial crack occurrence, but becomes high and the number of AE events increases rapidly as the crack propagates. This means that microfractures in the material increase during crack propagation. This result can also be confirmed by the results of an AE power spectrum analysis. Furthermore, by matching AE signals to the fractographs, it is found that AE activity is weak and has a low amplitude in the region of a flat fracture surface, while it is strong and has a high amplitude in the rough surface region, especially for a unidirectional material A.

ＡＥ等を用いた土質判別装置の実験的研究 シールド工事への適用性について

The purpose of this study is to develop new methods for soil type classification, mainly grain size distribution, using AE (Acoustic Emission) sensor and accelerometor under the invisible condition. These methods utilize the sound and the vibration phenomena which is generated while penetrating a cone into a soil or while shaving a bit on a ground surface.The penetration cone is provided with an AE sensor and an accelerometor for measuring sound and vibration of cone and with a load cell for measuring penetration resistance. Laboratory experiments have been performed on several kinds of soil which have different grain size distributions. The results of the laboratory experiments indicate that both the mean value of the AE signal and the acceleration increase with the increase in the penetration resistance and in the 30% grain diameter D30.The sliding contact type soil classification device, which is equipped with AE sensor, is also experimented. The results of the primary experiments show that the different AE power spectrum appear with variation of soil grain sizes and the AE power spectrum is not depended upon a sliding speed or a load.The penetration cone method is applied to a subway tunnelling works by a earth pressure balance type shield machine to investigate its usefulness for soil classification in the invisible chamber. The results of the field tests are agree with the data of laboratory experiment.