Papers by Keyword: Acoustic Emission (AE)

Abstract: Neutron diffraction method has been applied in the ex-situ investigation of the residual stresses in Mg-5wt.%Al-1 wt.%Sr (AJ51) magnesium alloy reinforced with short Saffil® fibers deformed in compression at room temperature. The residual stresses were measured in the axial and radial directions with respect to the load direction. It is shown that in the initial state the tensile stress is present in the matrix phase. The in-situ acoustic emission measurements were performed with the aim to reveal the main deformation mechanisms operating in the particular stages of the plastic deformation. Ex-situ neutron diffractions experiments showed that the tensile axial residual stress in the matrix increases with increasing plastic deformation while the radial residual stress decreases. In situ acoustic emission measurements indicate that the main deformation mechanisms are twinning and glide of bigger dislocation ensembles in the early stages of the compressive deformation while the fibers breakage was observed in the vicinity of the maximum stress.

Abstract: This is accomplished by a variety of indoor rock mechanics experiments and experimental sound emission, taking Chengde area of Hebei Province the tunnel rock made of rock as research object to simulate various loading rock failure process. To analysis the data obtained of acoustic emission and Dynamics in the process obtaining the characteristic parameters of rock failure process in order to Monitor and Forecast. Through the three axial compression test and the process of acoustic emission signal acquisition discussed the relation between the mechanical parameters of rock acoustic emission parameters of stress. The characteristic parameters of acoustic emission signals with stress and time change through analyzing the acoustic Emission characteristics of each stage in the process of rock failure provide the basis for the prediction of rock burst.

Abstract: In this paper, we produced the 0-3 PZT/P(VDF-TFE) piezoelectric composite film with 80μm thickness using PZT piezoelectric ceramics and fluorine resin P(VDF-TFE) by weight 85/15 ingredients through the hot rolling machine and corona-discharge method. A sensor with 4cm×1.3cm area is designed and produced by using this film. We have carried out the breaking of a pencil lead pressed against an aluminum plate acoustic emission testing. The result shown that the sensor is with fast response and high sensitivity advantage, the sensor can be used as acoustic emission sensor. Meanwhile the sensor is very easy to use due to it is a soft film sensor.

Abstract: 304 stainless steel and 316L stainless steel are conventional materials of primary pipeline in nuclear power plants. The present work is to summarize the acoustic emission (AE) characteristics in the process of pitting corrosion of 304 stainless steel, intergranular corrosion of 316L stainless steel and weldments of 316L stainless steel. The work also discussed the current shortcomings and problems of research. At last we proposed the coming possible research topics and directions.

Abstract: Change the deformation mechanism in metallic materials may be detectable using infrared thermography and acoustic emission. For samples of mild steel is the creation of Lüder’s bands presented in the infrared spectrum. Follow-number increase of these bands is also presented. In the system of acoustic emission is for this deformation mechanism described signal, which allows detection of the deformation process of these technologies.

Abstract: This paper seeks to outline the concept and application of health monitoring system in aircraft structure. The focus is placed on the principles and methods of the structural health monitoring system, including SMART layers, electric potential method, Acoustic Emission, etc. The difference between the above monitoring methods is justified and clarified. Finally a perspective view on structural health monitor techniques is discussed.

Abstract: In order to get a deep understanding of composite failure mechanisms, the new advanced signal processing methodologies are established for the analysis of acoustic emission (AE) data obtained from the quasi-static tension test of composite materials. Tensile test were carried out on twill-weave composite specimens, and acoustic emissions were recorded from these tests. AE signals were decomposed into a set of Intrinsic Mode Functions (IMF) components by means of Empirical Mode Decomposition (EMD) , the Hilbert-Huang Transform (HHT) of each IMF component was performed, it was shown that the frequency distribution of IMF component in time-scale could be directly related to composite materials failure mechanisms.

Abstract: Propagation rule of acoustic emission (AE) signal in coal and rock is an important basis when AE technique forecasts coal and rock dynamical disasters. Based on correlative theory of quality factor Q, Acoustic emission signal propagation attenuation formula in non-perfect elastic coal and rock are analyzed, Based on the theoretic formula, Effects of different quality factor and propagation distance on AE propagation attenuation are theoretically analyzed ;Based on theoretic analysis results, AE signal propagation numerical simulation and field test programs are designed, AE signal propagation rules in elastoplastic coal and rock are obtained. Field test and numerical simulation experimentation results validate rationality of theoretic forumla. Study production can guide AE technique that forecasts mine and rock dynamical disasters.

Abstract: Polypropylene fiber reinforced concrete (PPFRC) is such a composite material that can enhance and improve the mechanical property of the concrete with small mixing amount of polypropylene fiber. By taking into consideration the heterogeneous characteristics of materials at meso-scopic level, the initiation of micro cracks, the propagation and the coalescence between cracks have been simulated in PPFRC specimens with different amount of addition under three point bending load. The numerical analysis shows that there is only little difference on failure pattern and path between PPFRC and plain concrete. However, polypropylene fiber can reduce or even eliminate plastic cracking and can help to control crack expansion and it could be identified that most fibers in PPFRC are broken under tensile stress. Furthermore, polypropylene fiber plays different roles during the substrate plastic shrinkage and hardening stages. The toughness and deformability have been significantly improved with mixing of polypropylene fibers but the rupture strength is almost the same. Meanwhile, it also could be found that, with the increasing amount of polypropylene fiber, the deformation ability and the toughness have been increased, but the strength is kept almost the same, while the elastic modulus is actually decreased.

Abstract: As concrete is one of the most popular building materials, it is important to know its basic properties and behaviour especially at loading. When cracks occur in concrete, released fracture energy will be proportionally transformed into the energy contained in acoustic emission. According to this physical phenomenon, acoustic emission technique provides an effective monitoring method for fracture process of concrete through generated acoustic emission. However, such monitoring is limited in qualitative evaluation of fracture process in most occasions. Quantitative interpretation of fracture process is difficult to accomplish by simply acquiring the amount of acoustic emission generated or by conducting parameter-based acoustic emission analysis. This paper investigates the use of the double-K fracture model and acoustic emission for prediction of load at the beginning of stable crack propagation in three-point bending tests of concrete specimens. Double-K model combines the concept of cohesive forces acting on the effective crack increment with a criterion based on the stress intensity factor.