Use Of Acoustic Emission Signals Research Articles

Determination of elastic characteristics of cement stone to predict the fatigue life of concrete

Introduction. The problem of fatigue failure of concrete is one of the least studied in computational practice. The lack of reliable data on the actual processes of accumulation of fatigue damage occurring in the structure of this material during cyclic exposure does not allow us to form a methodology for calculating concrete structures that perceive such loads. To develop the above methodology, it is proposed to use structural simulation modeling. For this purpose, mathematical models of concrete damage under the influence of cyclic loading are considered. The purpose of the study is to determine the elastic and strength characteristics of cement stone for further development of a methodology for predicting the fatigue life of concrete, taking into account the nonlinear kinetics of damage accumulation.
 
 Materials and methods. The strength limits of cement stone during bending and compression were determined by conducting a full-scale experiment on a testing machine and a hydraulic press. Elastic characteristics of cement stone were obtained as a result of static tests of cement stone samples of various shapes on the universal electromechanical system with the joint use of the digital optical system for analysis of deformation and displacement fields and the acoustic emission signal recording system.
 
 Results. During the tests of cement samples for bending and compression, the values of the corresponding bending and compression strength limits were obtained, which made it possible to confirm the design strength class of cement 32.5 N. Inhomogeneous fields of longitudinal and transverse deformations were obtained using a digital optical system to further determine the basic elastic characteristics of the material. Obtaining acoustic emission signals during the experiment made it possible to reflect the dependences of various acoustic emission parameters on time.
 
 Conclusions. The first stage of the proposed methodology for predicting the fatigue life of concrete is performed, taking into account the nonlinear kinetics of damage accumulation, as a result of which the modulus of elasticity and the Poisson’s ratio for cement stone are determined. The obtained data can be used to create a numerical model of the concrete structure, and the use of acoustic emission signals allows us to estimate the kinetics of damage accumulation in the material.

Flank wear prediction in tungsten carbide tool using acoustic signal amplitude in conventional turning operation

A tool wear prediction system that senses the cutting tool wear and allows for the optimum utilization of the tool is a deciding factor in achieving good surface quality of machined products. In recent years, the use of acoustic emission signals that emerged during machining operations has gained great significance in accurately predicting the tool condition. The objective of this work is to determine the variation in acoustic signal characteristics with tool flank wear in conventional turning process using Fast Fourier Transformation (FFT). Unlike the previous works, the experiments in this work were performed after optimizing the distance of the sensor position from the tip of the tool, since the optimum position of the sensor determines the transmission of the acoustic signals with minimum attenuation. The obtained raw signal output of the acoustic sensor is processed using FFT and the spectral analysis of the signal is carried out to determine the frequencies and also the magnitude of signal content at each frequency. This study establishes a correlation between the flank wear and the amplitude of acoustic signals. The model is validated using three sets of experiments at various cutting conditions. The average percentage deviation of the predicted tool wear from the experimental results is found to be 9.97%. This study indicates that the AE signals can be used to model the flank wear progression and can be useful for the accurate flank wear prediction in machining processes.

The use of acoustic emission signal (AE) in mechanical tests

The use of acoustic emission signal (AE) in mechanical tests

Determining kinetic energy distribution of the working medium in a centrifugal disc finishing process\u2014part 1: theoretical and numerical analysis with DEM method

The centrifugal disc finishing process is an abrasive technique of mass machining, and it is very effective but very frequently time consuming. In this paper, a simulation of the centrifugal disc finishing process was presented in order to estimate the kinetic energy distribution of the working medium and to find its regions that make the process more efficient. Numerical results were obtained using an explicit method in the Ansys/Ls-Dyna program. Due to the fact that the physical properties of numerous objects in free motion need to be calculated in a simulation process, the discrete element method (DEM) was used. Results from the numerical simulations indicate that the velocity and energy of particles is variable in an axial cross-section of working medium. The article presents particle velocity distributions in the working chamber for various rotational speeds of the rotor. The typical changes in velocity in the function of time are also discussed. Statistical important functions of the average kinetic energy of the working medium and accumulated energy by machining surface have been estimated in respect to the rotational speed and machining time with a high value of adjustment coefficients. This article constitutes the first stage of research, which is continued in order to experimentally verify the results in the real process, as presented in the companion paper (Part 2: Experimental analysis with the use of acoustic emission signal).

Determining kinetic energy distribution of the working medium in a centrifugal disc finishing process\u2014part 2: experimental analysis with the use of acoustic emission signal

This paper addresses the problem of estimating the kinetic energy distribution of the working medium in a centrifugal disc finishing process. Centrifugal disc finishing is a highly effective way of finishing surfaces, especially in the case of complex shapes, made from a variety of materials. The process is, however, frequently very time-consuming. The identification method of a region with a high kinetic energy potential by measurement of acoustic emission signal is described and verified by surface roughness tests. Signal analysis was carried out in both time and frequency domain. The results presented in experimental tests and analyses indicate that various parameters of the AE signal, including its energy, are variable and determined by abrasive particles’ velocity and location in an axial cross section of the working medium. On the basis of the root mean square value of the signal, the maps of the distribution of the energy potential of the working medium are presented. Experimental results demonstrate process improvement and a significant reduction (approx 60%) of the arithmetic mean deviation of surface roughness, obtained at the same time of machining. The article also presents the functional relations between the selected AE signal descriptors and the rotational speed of the working chamber rotor. Since the article is a continuation of the previous studies, the results obtained were briefly referred to the simulation results.

Acoustic emission technology can warn of impending iatrogenic femur fracture during femoral canal preparation for uncemented hip replacement. A cadaveric animal bone study

During uncemented hip arthroplasty the femoral prosthesis can be fitted too tightly into the femoral canal, causing a hoop-stress fracture of the proximal femur. The research undertaken evaluated Acoustic Emission (AE) technology as a potential method of detecting a fracture forming in this manner, in an attempt to assess whether this technology may be used as a means of early warning of impending fracture during surgery. Deer femora were prepared in a manner similar to surgery and uncemented hip arthroplasty broaches were inserted until fracture occurred. AE sensors were mounted on the femoral cortex and also on the broach. Five femora were fractured manually by hammering the broaches in a manner similar to surgery. Four femora were fractured using a hydraulic loading machine to insert the broach. Stepwise increases in the AE signals coincided with stepwise increases in surface strain of the femoral cortex, crack mouth growth and fracture. Both sensors recorded similar signal profiles. The sensor on the femur registered greater magnitude signals than the sensor on the broach, suggesting that there is signal impedance across the bone-broach interface. AE signals from sensors mounted on the femur and on the broach can detect damage processes happening within the femur during insertion of the broach in the time period of approximately 100 s prior to fracture. These damage processes may represent micro cracking, and ultimately fracture. This supports the possibility of the use of AE signals as a means to monitor internal damage within the femur and possibly predict impending fracture. It is clear that AE signals change significantly prior to fracture however in order to attempt to develop a warning system, further understanding of the significance of the signals and limitations of these methods must be gained.

Differentiation of journal bearing friction states and friction intensities based on feature extraction methods applied on acoustic emission signals

Abstract For diagnosis and predictive maintenance of mechatronic systems, monitoring of bearings is essential. An important building block for this is the determination of the bearing friction condition. This paper deals with the possibility of monitoring different journal bearing friction states, such as mixed and fluid friction, and examines a new approach to distinguish between different friction intensities under several speed and load combinations based on feature extraction and feature selection methods applied on acoustic emission (AE) signals. The aim of this work is to identify separation effective features of AE signals to subsequently classify the journal bearing friction states. Furthermore, the acquired features give information about the mixed friction intensity, which is significant for remaining useful lifetime (RUL) prediction. Time domain features as well as features in the frequency domain have been investigated in this work. The combination of several features generates feature spaces. The position of the objects within these spaces has proved that it is possible to differentiate between journal bearing friction states with the use of AE signals and suitable feature extraction methods. In addition, features that indicate different mixed friction intensities have been found.

Erratum to: Control with micro precision in abrasive machining through the use of acoustic emission signals

Erratum to: Control with micro precision in abrasive machining through the use of acoustic emission signals

Control with micro precision in abrasive machining through the use of acoustic emission signals

By using acoustic emission (AE) it is possible to control minuscule grit and workpiece interaction during micro and macro grinding processes. The single grit (SG) tests used in this work display that the intensities from approaching grit in air display an increasing intensity. As the grit interacts with the workpiece by forming a scratch, different intensities are recorded with respect to a changing measured depth of cut (DOC). It is these different recorded intensities of approaching touch (as the grit get closer the AE intensities increase), touch (rubbing) and mechanisms with greater plastic deformation (ploughing and cutting) that change needs to need to be identified for greater precision (especially approaching grit as this allows verification of CNC position). By extracting AE signals, correlated to both elastic and plastic material removal mechanisms, this affords a robust and reactive setup for controlling micro machining processes. Such control methods can be useful for grinding dressing ratios as well as against deviation errors. Two different aerospace materials (CMSX4 and Titanium64) were used for the same SG tests to verify the control regime is robust and not just material dependent. In addition, both Neural Networks (NN) and Classification and Regression Trees (CART) based rules were used to implement a real-time simulation displaying how such a control system could be implemented.

Investigation of twinning dynamics in VT1-0 titanium using acoustic emission

Use of acoustic emission signals makes it possible to analyze deformation processes in the bulk of a crystalline titanium structure formed under the effect of a concentrated strain created by loading of a diamond pyramid. The obtained results of the process of development of deformation twins make it possible to assert that their formation, output, and storage on the specimen’s surface are possible under certain external stresses exceeding the value of internal stresses in the crystal bulk.

Influence of microstructure on fracture toughness of cold work tool steels : W. Liebfahrt et al. (Böhler Edelstahl GmbH, Kapfenberg, Austria)

The work concerns the possibilities of applying various methods with the purpose to increase the life of forging tools, which, based on the experience and research of the author, realized in cooperation with the forging industry, exhibit the highest effectiveness in improving the life of forging tools. Durability of forging device is determined by the presence of destructive mechanisms under the extreme work conditions of forging tools - a high cyclic mechanical loads (up to 1000 MPa) and thermal (from 800 °C to 800 °C on the surface). The tool life is also an element which affects the quality of the forgings, as too high and intensive wear/damage of the dies and stamps causes a change in the geometry of the manufactured product, and any surface faults (cracks, defects) are represented on the forged product. The presented investigation results refer to: selection of the tool material for a particular process, its adequate thermal and thermo-chemical treatment, use of surface engineering techniques: hybrid with the use of coatings applied physically from the gaseous phase, use preventive pad welding, as well as optimization of the die shape and construction of the instrumentation set. The work also presents the use of control and measurement systems, allowing for full monitoring of the forging process, and the application of innovative solutions (use of acoustic emission signal) allowing for an effective improvement of the life of the forging tools and instrumentation. At present, by way of applying a range of methods, which the most popular shows in this article, as well as many other computer-aided tools, it is possible to solve many problems related to a short tool life.

Use of acoustic emission signals for determining the coordinates of developing defects in anisotropic shells and plates

Use of acoustic emission signals for determining the coordinates of developing defects in anisotropic shells and plates