Impulse Function Properties

2015 ◽  
Author(s):  
J. Scott Tyo ◽  
Andrey Alenin
Keyword(s):  
Impulse Function

scholarly journals Lamb Wave Scattering Analysis for Interface Damage Detection between a Surface-Mounted Block and Elastic Plate

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 860
Author(s):  
Mikhail V. Golub ◽  
Alisa N. Shpak ◽  
Inka Mueller ◽  
Sergey I. Fomenko ◽  
Claus-Peter Fritzen
Keyword(s):  
Damage Detection ◽  
Elastic Plate ◽  
Lamb Wave ◽  
Wave Scattering ◽  
Hybrid Approach ◽  
Guided Wave ◽  
Open Crack ◽  
Damage Indices ◽  
Impulse Function ◽  
Thin Walled

Since stringers are often applied in engineering constructions to improve thin-walled structures’ strength, methods for damage detection at the joints between the stringer and the thin-walled structure are necessary. A 2D mathematical model was employed to simulate Lamb wave excitation and sensing via rectangular piezoelectric-wafer active transducers mounted on the surface of an elastic plate with rectangular surface-bonded obstacles (stiffeners) with interface defects. The results of a 2D simulation using the finite element method and the semi-analytical hybrid approach were validated experimentally using laser Doppler vibrometry for fully bonded and semi-debonded rectangular obstacles. A numerical analysis of fundamental Lamb wave scattering via rectangular stiffeners in different bonding states is presented. Two kinds of interfacial defects between the stiffener and the plate are considered: the partial degradation of the adhesive at the interface and an open crack. Damage indices calculated using the data obtained from a sensor are analyzed numerically. The choice of an input impulse function applied at the piezoelectric actuator is discussed from the perspective of the development of guided-wave-based structural health monitoring techniques for damage detection.

scholarly journals On the convergence rate for the estimation of impulse response function in the space Lp(T)

2018 ◽  
pp. 36-41
Author(s):  
I. Rozora
Keyword(s):  
Linear System ◽  
Convergence Rate ◽  
Impulse Response ◽  
Response Function ◽  
Estimation Error ◽  
Impulse Response Function ◽  
The Space Lp ◽  
Stochastic Linear System ◽  
Impulse Function ◽  
Active Research

The problem of estimation of a stochastic linear system has been a matter of active research for the last years. One of the simplest models considers a ‘black box’ with some input and a certain output. The input may be single or multiple and there is the same choice for the output. This generates a great amount of models that can be considered. The sphere of applications of these models is very extensive, ranging from signal processing and automatic control to econometrics (errors-in-variables models). In this paper a time-invariant continuous linear system is considered with a real-valued impulse response function. We assume that impulse function is square-integrable. Input signal is supposed to be Gaussian stationary stochastic process with known spectral density. A sample input–output cross-correlogram is taken as an estimator of the response function. An upper bound for the tail of the distribution of the estimation error is found that gives a convergence rate of estimator to impulse response function in the space Lp(T).

On "Theztransform of an impulse function"

1967 ◽  
Vol 12 (5) ◽  
pp. 621-622 ◽  
Author(s):  
W. Rugh ◽  
T. Johnson ◽  
R. Calvin ◽  
D. Chenoweth ◽  
C. Phillips
Keyword(s):  
Impulse Function

The Effect of Humidity on the Thermodynamic Behaviour of Atmospheric Air

1999 ◽  
Author(s):  
D. A. Kouremenos ◽  
X. K. Kakatsios ◽  
R. N. Krikkis
Keyword(s):  
Practical Interest ◽  
Ideal Gas ◽  
The State ◽  
State Variables ◽  
Moist Air ◽  
Humidity Ratio ◽  
Atmospheric Air ◽  
Thermodynamic Behaviour ◽  
Impulse Function ◽  
Wide Range

Abstract The present work considers the thermodynamic behaviour of moist air as a function of the state variables temperature, density and humidity ratio. Moist air is treated as an ideal mixture which is composed of two real gases, air and steam. The state functions of the mixture are expressed using the corresponding explicit relations of the two species from which the three isentropic exponents describing the real gas isentropic change are calculated. Saturated conditions are determined by solving the Vapour Liquid Equilibrium problem for real water. Numerical results show the effect of humidity as well as the effect of pressure on the thermodynamic behaviour of atmospheric air (such as the three isentropic exponents kpρ, kTp, kTρ, the classical isentropic exponent k and the velocity of sound) for a wide range of temperatures and pressures. Furthermore the isentropic change is approximated by explicit relations having mathematical forms similar to those of the ideal gas but with different constants and exponents. The obtained accuracy is remarkable, being better than 0.32%. In this way the isentropic change, of moist air can be computed by simple explicit relations having as independent variable the Mach number and the humidity ratio. The effects of humidity are examined on certain cases of practical interest such as the critical state (M = 1), the impulse function and the mass flow rate.

Modeling of Human Reactions to Whole-Body Vibration

1987 ◽  
Vol 109 (3) ◽  
pp. 210-217 ◽  
Author(s):  
Farid M. L. Amirouche
Keyword(s):  
Human Body ◽  
Equations Of Motion ◽  
Vertical Direction ◽  
The Body ◽  
Whole Body ◽  
Connective Tissues ◽  
Finite Segment ◽  
Body Vibration ◽  
Forcing Function ◽  
Impulse Function

A computer-automated approach for studying the human body vibration is presented. This includes vertical, horizontal, and torsional vibration. The procedure used is based on Finite Segment Modeling (FSM) of the human body, thus treating it as a mechanical structure. Kane’s equations as developed by Huston et al. are used to formulate the governing equations of motion. The connective tissues are modeled by springs and dampers. In addition, the paper presents the transient response of different parts of the body due to a sinusoidal forcing function as well as an impulse function applied to the lower torso in the vertical direction.

Vibration Analysis of Deep Groove Ball Bearings With Local Defect Using a New Displacement Excitation Function

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Chengcheng Li ◽  
Yi Qin ◽  
Yi Wang ◽  
Haizhou Chen
Keyword(s):  
Excitation Function ◽  
Mechanical Equipment ◽  
Local Defect ◽  
Ball Bearings ◽  
Defect Zone ◽  
Proposed Model ◽  
Deep Groove ◽  
Impulse Function ◽  
Rolling Elements ◽  
Vibration Signal Analysis

Abstract Bearings are vital parts of many mechanical equipment, the vibration signal analysis of bearings with local defects is important in guiding the fault diagnosis. In this paper, a dynamic analysis method is proposed to investigate the vibration response of the deep groove ball bearings (DGBBs) with local defect using a new displacement excitation function based on the Hertz contact theory and Newton's second law. The DGBB is modeled as a two degrees-of-freedom system, and an additional friction force in the defect zone, the influence of centrifugal force, the gravity of rolling elements, and lubrication traction/slip force between rolling elements and raceway are considered. And this model is used to study the dynamic signals of DGBB under different fault sizes and rotation speeds. Results indicate that the simulation signal has many continuous impacts and change over the time which is closer to the actual situation compared with the one-shot impulse function such as rectangular or half-sine or piecewise function when the rolling elements passed through the defect zone. Finally, the validity of the proposed model is verified by experiments. The simulated and experimental results indicate that the proposed model would achieve a more appropriate and accurate dynamic simulation.

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