Near-field beamforming performance analysis for acoustic emission source localization

This paper attempts to study the localization performance of a near-field acoustic emission (AE) beamforming by varying parameters such as array types, localization velocity, the maximum diameter of the array and the sensor spacing. To investigate how those parameters affect localization performance, an improved finite element method is established to obtain AE signals which take real propagation characteristics and have high signal to noise ratio. And AE signals of the finite element simulation under different parameters are obtained based on the presented method. Then AE beamforming is used to localize AE sources, and the influences of these parameters on the AE beamforming localization performing are analyzed. The results indicate that the parameters have impact on the localization accuracy clearly. This work can provide a reference for the selection of parameters when the beamforming is used to localize AE sources

Design and analysis of a novel eddy current damper based on three-dimensional transient analysis

With advantages of no mechanical contact, vacuum compatibility, oil-free, and high reliability, an eddy current damper has a great potential use in space. In this paper, a passive magnetic damper system is developed by using the eddy current damping effect. The proposed eddy current damper utilizes a stationary permanent magnet and two conductive plates, and has significant performance than the model with only one plate. An accurate analytical model based on the electromagnetic theory for this novel eddy current damper is proposed, and the three-dimensional transient analysis based on finite element method is carried out to predict the magnetic field and current density. To optimize the design, simulations are conducted and the design parameters are evaluated from the thickness of magnet and two plates. Simulations for the optimized eddy current damper finite element model are conducted and the damping coefficient as high as 124.079 Ns/m is achieved. The results demonstrate that this novel eddy current damper has high damping performance but simple structure, which is applicable in some vibration isolation systems of spacecraft

Numerical prediction of temperature effect on propagation of rubbing acoustic emission waves in a thin-walled cylinder structure

Temperature field has serious effects on the accuracy of rubbing acoustic emission (AE) source localization in a thin-walled cylinder structure, but it is difficult to explore the functioning mechanism through experiments. This paper aims to propose a thermos-elastic coupling simulation procedure to reveal the effect of the uniform temperature and non-uniform temperature field on the propagation characteristics of AE waves. To obtain the behaviors of guiding wave in the thin-walled cylinder, an efficient numerical simulation tool for AE wave propagation modeling is explored. The numerical results of AE propagation in a plate are compared with the experimental data. Then the semi-analytical finite element method is introduced to calculate the characteristics of multi-modal and dispersion. To remove the unwanted reflections from boundaries generated by the numerical simulation, a methodology combined with the infinite element and Rayleigh damping is presented. Consequently, several AE wave propagation simulations are carried out respectively, including the model with the uniform temperature in a range of 20-700 °C, and the non-uniform temperature field with the temperature of the central region, 649 °C. On the basis of the modeling and evaluation results, both the peak-to-peak amplitude and arrival time versus temperatures are summarized and analyzed. The validation results demonstrate that the proposed approach could be used efficiently to research rubbing AE source localization applications with a high degree of accuracy

Impulsive noise cancellation of acoustic emission signal based on iterative mathematical morphology filter

This paper aims to propose an iterative mathematical morphology (IMM) filter methodology to de-noise the acoustic emission (AE) signal with impulsive noise. To develop the principle of IMM filter, a simulation signal is used to be de-noised by the conventional MM filter. Moreover, a novel approach is introduced to eliminate the end effect of MM filter by connecting the initial point with the end point of the time series. Therefore, the IMM filter can be realized based on the operations of MM filter and the elimination method of end effect. The noise elimination of a simulation signal indicates that the IMM filter can remove the impulsive noise more effectively than the MM filter and maintain useful information as much as possible. Two AE signals acquired from rock compression experiment, which are polluted by electromagnetic impulsive noise, are de-noised by the IMM filter, the conventional digital filter and the wavelet filter respectively. Compared with the other two methods, the IMM filter can preserve the essential information contained in AE signal better, especially the arrival time. These two experiments manifest the effectiveness of the IMM filter in de-noising issues of AE signals polluted by impulsive noise

Simulation and feature analysis of modal acoustic emission wave in planar C/SiC composite

A catastrophic accident may be caused for nearby spacecraft due to the damage occurred in C/SiC thermal protection structure. Therefore, it is significant to analyze the damage feature of the ceramic composite structure. Acoustic emission (AE) is an effective non-destructive testing method which is widely used in aerospace industry. However, some key problems should be solved when the AE technology applied to the engineering field. In this paper some propagation characteristics of AE waves in C/SiC plate were investigated based on the finite element method. Firstly, two kinds of AE sources were established by combining plate wave theory and finite element method. Secondly, a novel simulation model was established which included the mechanical characters of C/SiC composite. Then to simulate the AE source, a stepped load and a dipole force is applied to generate the release of power loss. Additionally, the results of simulation are validated through the AE experiment with the analysis method of Choi-Williams transformation. Finally, the attenuation of AE signals propagation in C/SiC plate is discussed. The results of this research work demonstrated that the simulation method of AE waves in C/SiC structure proposed in this paper can be effectively used to study the wave propagation phenomeno

Design and analysis of a novel eddy current damper based on three-dimensional transient analysis

With advantages of no mechanical contact, vacuum compatibility, oil-free, and high reliability, an eddy current damper has a great potential use in space. In this paper, a passive magnetic damper system is developed by using the eddy current damping effect. The proposed eddy current damper utilizes a stationary permanent magnet and two conductive plates, and has significant performance than the model with only one plate. An accurate analytical model based on the electromagnetic theory for this novel eddy current damper is proposed, and the three-dimensional transient analysis based on finite element method is carried out to predict the magnetic field and current density. To optimize the design, simulations are conducted and the design parameters are evaluated from the thickness of magnet and two plates. Simulations for the optimized eddy current damper finite element model are conducted and the damping coefficient as high as 124.079 Ns/m is achieved. The results demonstrate that this novel eddy current damper has high damping performance but simple structure, which is applicable in some vibration isolation systems of spacecraft

Design and analysis of a novel eddy current damper based on three-dimensional transient analysis

With advantages of no mechanical contact, vacuum compatibility, oil-free, and high reliability, an eddy current damper has a great potential use in space. In this paper, a passive magnetic damper system is developed by using the eddy current damping effect. The proposed eddy current damper utilizes a stationary permanent magnet and two conductive plates, and has significant performance than the model with only one plate. An accurate analytical model based on the electromagnetic theory for this novel eddy current damper is proposed, and the three-dimensional transient analysis based on finite element method is carried out to predict the magnetic field and current density. To optimize the design, simulations are conducted and the design parameters are evaluated from the thickness of magnet and two plates. Simulations for the optimized eddy current damper finite element model are conducted and the damping coefficient as high as 124.079 Ns/m is achieved. The results demonstrate that this novel eddy current damper has high damping performance but simple structure, which is applicable in some vibration isolation systems of spacecraft

Design and Damping Analysis of a New Eddy Current Damper for Aerospace Applications

Abstract In order to reduce the structural vibrations of a mechanical system used in aerospace, a new sketch of eddy current damper (ECD), consisting of one cylindrical permanent magnet, two ring-shape copper plates, one axial transmission shaft and electromagnetic shield, is proposed. Three dimensional (3D) electromagnetic transient analysis on damping performance of the proposed damper is conducted by ANSYS to determine the dimensions of the designed damper. And a series of damping tests for the damper subjected to sinusoid excitations with amplitudes of around 0.1 and 1 mm are respectively carried out under frequencies ranging from 1 to 50 Hz. The experimental results validate that the 3D transient analysis method with ANSYS is effective to guide the design of ECDs. Moreover, it is found that the proposed ECD has high damping, which is significantly superior to the one-plate ECD with the same structure and dimensions

Inactivation of Venom PLA2 Alleviates Myonecrosis and Facilitates Muscle Regeneration in Envenomed Mice: A Time Course Observation

Snake venom is a complex cocktail of toxins which induces a series of clinical and pathophysiological manifestations in victims, including severe local tissue damage and systemic alterations. Deinagkistrodon acutus (D. acutus) ranks among the “big four” life-threatening venomous species in China, whose venom possesses strong myotoxicity and hematotoxicity that often lead to permanent disability or muscle atrophy. Varespladib, an inhibitor of mammalian phospholipase A2 (PLA2), has been recently reproposed as an effective antidote against snakebite envenomation. The present study aimed at evaluating the protective role of varespladib on muscle regeneration in envenomed mice. Mice were grouped and subjected to inoculation with D. acutus venom or a mixture of venom and varespladib or control vehicle in the gastrocnemius muscle. Local injuries including hemorrhage, myonecrosis, ulceration, and systemic damages including general dysfunction, visceral failure, and inflammatory responses were observed at 1, 3, 7, 14, and 21 days. The results indicated that most of the muscle myonecrosis and hemorrhage were alleviated by varespladib. Besides, the pretreated mice recovered rapidly with lesser atrophy and muscle fibrosis. In conclusion, the findings of the present study suggested that varespladib is an effective antidote that could neutralize D. acutus venom and allow for earlier and improved rehabilitation outcome