Papers by Keyword: Signal Analysis

Abstract: The numerical model is developed to study the vibration response due to the localized defect of ball bearing in rotating machinery. In order to simulate the dynamic response, the equations of motions are developed based on the rotor-bearing system where two identical rotors mounted on symmetric flexible shaft and supported by ball bearings are considered in this model. The presence of defect is introduced on a bearing outer raceway and lubrication effect between bearing components is also included. The numerical results are obtained by applying Runge–Kutta method to solve governing equations of motions. It has been observed that the vibration spectrum of the ball pass frequency outer race and its harmonics for the defect bearing is relatively higher than the good one. Moreover, this dynamic model can effectively enhance the understanding of vibration responses for good and defective bearing.

Abstract: This paper presents the initial developments of a prototype device intended to perform measurements of the fastening torque in the range bellow 1 N.m – hereby denominated microtorque. The device is intended to yield data for analysis of in vitro torquing and detorquing experiments, for fixation and removing of abutments in dental implants and implants in artificial bones. The analysis of the data acquired allowed the authors to observe characteristic fingerprints or signal signatures associated to the type of abutment or implant under experimentation as well as of the mechanical prototype characteristics. In this paper, two different systems of abutment and implant were analyzed. The correlation between the phenomena associated to the signal fingerprints indicate that the developed measurement protocol may be extended to other implant / abutment systems. The authors suggest that the insertion and removal torque curves evaluated in this study would facilitated the correlation between the abutments stability in actual patients and the dynamical behavior under masticatory function.

Abstract: Background: While treatment monitoring of healthcare interventions is mainly conducted at the hospital, most information on a patient’s health status could be obtained from his everyday life activities. Therefore, there is a great interest in methods for long term (home) monitoring applications. However, there is still a lack of quantitative methods allowing everyday life activities monitoring such as gait analysis at home. While video-based systems have been employed given their high accuracy, they remain expensive and obtrusive with the range of motion of a patient limited to the set up measurement volume. Body worn sensors on the other hand present as an excellent opportunity to remotely and unobtrusively monitor gait characteristics not only at home, but during activities of everyday life. Technical limitations as well as changes in the patient’s gait patterns challenge the extraction of specific gait parameters. Methods: We propose a hybrid system comprising of a markerless video-based motion capturing system and a wearable sensor system with foot worn sensors. A study protocol is presented that will be used to validate the systems against each other. Discussion: This study will evaluate whether a markerless motion capturing system is feasible as a complementary tool for everyday gait analysis. Further, we will validate the accuracy of the sensor system using the video-based system as a gold standard. In the future, the combination might allow a recalibration of algorithmic sensor parameters based on deviations from the reference video-based system, and the combination of both modalities may enhance gait analysis in home monitoring.

Abstract: The method using Born-Jordan transformation has been developed for the evaluation of response signals obtained by rail fastening analysis. In the paper the laboratory measurements and dynamic parameters analyses of flexible fastening of Vossloh SKL14 type have been descripted. This method can also be used for designing new fastening systems and their parts, for comparison of various rail fastening types and so on.

Abstract: Coating is an application of a surface finish to another material and it provides the surfaces of manufactured parts with a number of desirable physical, chemical, and appearance qualities. Nearly all manufactured or fabricated products made of metal or having metal components have some types of surface coating. The coating increases sturdiness, prevents corrosion, provides hardness, or gives an attractive finish to an object. The amount of coating applied to a material, that is, the coating thickness, is crucial to the product’s final use and cost. On the other hand, in the case of surfaces subjected to wear, the same thickness is very important in the life of the product. There are several non-destructive methods of measuring coating thickness. The aim of this paper is the development and validation of an impulse excitation technique and laser measurements to determine coating thickness of metallic or nonmetallic surface.

Abstract: Metallic materials are subjected to degradation mechanisms when working in corrosive environments, such as those created by mineral oils and residues of a motor fuel. The camshaft is subjected to multiaxial stresses, creep, fatigue, corrosion and abrasion. As a result of the operation in special conditions of high temperature and high pressure can lead to forming cracks, damages or failure. In such cases it is necessary for these components to be repaired by welding, followed by a rectification process. This paper presents a method for determining the quality of welding repairs and rectification results from the analysis of vibration signals. A Fast Fourier Transform algorithm and an algorithm based on Prony's series method are used for processing the sampled signals.

Abstract: The paper presents a vibroacoustic method to determining the stiffness of coated steel with various materials such as metal oxides, metallic paints, polymers etc and Young's modulus for coating materials. The method consists in measuring the dynamic response of the steel in the form of a rectangular bar subjected to external impulse. One of the latest non-destructive experimental techniques in this field is based on the analysis of vibrating signal response recorded with a condenser microphone. A Fast Fourier Transform algorithm is used for processing the sampled signals. Knowing the mechanical properties of steel plates prior to coating with metal oxides, and determining the same properties after coating, can be obtained the mechanical properties of metal oxides and their influence on the properties of the ensemble.

Abstract: The development of modern technologies requires new materials and technologies prepared for specific technical applications. Aluminum is one of these materials, it can be welded and anodized, which gives them anticorrosive characteristics. The determination of mechanical properties (Young’s modulus and shear modulus) is of great importance from both scientific and practical points of view. Most of the known methods for determination of the Young’s modulus and shear modulus are sample destructive and base on measuring a force (energy) necessary for break the sample. This paper presents a nondestructive method for the determination of the elastic properties of welded aluminum plates by vibration tests and laser measurements using Doppler velocimeter. A Fast Fourier Transform algorithm is used for processing the sampled signals.

Abstract: The present work aimed to identify the defluidization region of a gas-solid fluidized bed system composed by Geldart group D particles using the Gaussian spectral pressure distribution technique, which is based on pressure fluctuation measurements in the plenum. In experiments, the defluidization condition of glass beads with apparent density of 2,450 kg/m³ was induced in a plexiglas column of 0.11 m in inner diameter and 1.0 m in height. The gas-solid behavior close to the incipient fluidization condition was assessed for two fixed bed heights (0.10 and 0.20 m) and two mean sizes of particles (1.55 and 2.18 mm in diameter). The bed was fluidized with air at environment temperature. The experimental equipment was instrumented with a pressure transmitter connected to a data acquisition system in order to record the pressure fluctuations of the gas-solid flow. The results showed that the defluidization region can be detected efficiently by using the Gaussian spectral pressure distribution technique, which contributes for a better control of fluidized bed processes.

Abstract: For the non-stationary vibration signals of wind tower, using a new method based on KPCA to eliminate the interference of the vibration signal. After cancellation noise according to the method based on EMD, the vibration signals are decomposed and the vibration characteristics of the signals are finally extracted. The experimental analysis indicates that this method can provide an effective reference for the health detection of wind tower.