The Quantification of Internal Noise Levels and Wall Pressure Spectra in Industrial Gas Pipelines

This paper addresses the issue of quantifying the internal noise levels/wall pressure fluctuations in industrial gas pipelines. This quantification of internal noise levels/wall pressure fluctuations allows for external noise radiation from pipelines to be specified in absolute levels via appropriate noise prediction models. Semi-empirical prediction models based upon (i) estimated vibration levels and radiation ratios, (ii) semi-empirical transmission loss models, and (iii) statistical energy analysis models have already been reported on by Norton and Pruiti 1,3 and are not reported on here.

Analysis of Dynamic Systems With Periodically Varying Parameters via Chebyshev Polynomials

In this paper a general method for the analysis of multidimensional second-order dynamic systems with periodically varying parameters is presented. The state vector and the periodic matrices appearing in the equations are expanded in Chebyshev polynomials over the principal period and the original differential problem is reduced to a set of linear algebraic equations. The technique is suitable for constructing either numerical or approximate analytical solutions. As an illustrative example, approximate analytical expressions for the Floquet characteristic exponents of Mathieu’s equation are obtained. Stability charts are drawn to compare the results the proposed method with those obtained by Runge-Kutta and perturbation methods. Numerical solutions for the flap-lag motion of a three blade helicopter rotor are constructed in the next example. The numerical accuracy and efficiency of the proposed technique is compared with standard numerical codes based on Runge-Kutta, Adams-Moulton and Gear algorithms. The results obtained in the both examples indicate that the suggested approach extremely accurate and is by far the most efficient one.

Shock and Sine Response of Rigid Structures on Nonlinear Mounts

The dynamic environment of embarqued structures such as radars or more generally electronic equipments consists of impacts, sine and large power spectrum excitations. Under these real conditions and amongst different kinds of isolation, the passive damper with nonlinear parameters can provide good performances. This paper is concerned with the dynamic behavior of rigid bodies on highly nonlinear mounts. The numerical simulation and the experiment carried out, show that the load-deflection behavior of the dampers have to be slightly ajusted with respect to impact vibrations to obtain a well designed behavior.

The Use of Noise and Vibration Analysis on the Hydraulic Networks

This paper is concerned with Analysis of Vibration and Noise in a hydraulic networks. In the analysis it is tried to find the discrete frequencies. So, we are able to recognize the damages or to redesign the system. The most important effectiveness on the system ought to the flow in the phase of vorticity.

On the Inherent Characteristics of the Dynamics of Robot Manipulators

The inherent characteristics of the (nonlinear) dynamics of robot manipulators are studied. The study is based on a new method, referred to as the trajectory pattern method. The inverse dynamics models of the manipulator are divided into classes of inverse dynamics models, each corresponding to a different trajectory pattern. For each trajectory pattern, the structure of the resulting inverse dynamics model is fixed and is used to study the characteristics of the dynamics of the manipulator by examining the harmonic content of the required actuation torques (forces) and the relative significance of each harmonic. The harmonic content of the actuating torques is shown to be a function of the path length in the joint coordinate space and the harmonic content of the selected trajectory pattern, but is independent of the number of degrees-of-freedom of the manipulator. The relative contribution of each harmonic is a function of the path length, direction of motion, the position of the path of motion within the workspace of the manipulator, and the magnitude of the fundamental frequency. The study provides a systematic approach to path and trajectory planning from the vibration control point of view. As an example, the characteristics of the dynamics of a spatial 3R manipulator is studied for motions with two different path lengths, starting from a specified point and extending in different directions.

An Experimental Study of Tendon Vibration Control System for Flexible Space Structures

The idea of a tendon vibration control system for a beam-like flexible space structure has been proposed. To verify the feasibility of the concept, an experimental tendon control system has been constructed for the vibration control of a flexible beam simulating Large Space Structures (LSS). This paper discusses modeling, identification, actuator disposition, and controller design for the experimental system. First, a mathematical model of the whole system of the beam and tendon actuator is developed through a finite element method (FEM). Second, to obtain an accurate mathematical model for designing a controller, unknown characteristic parameters are estimated by using an output error method. The validity of the proposed identification scheme is demonstrated by good agreement between the transfer functions of the experimental system and an identified model. Then, disposition of actuators is discussed by using the modal cost analysis. Finally, controllers are designed for SISO and MIMO systems. The feasibility of the proposed controller is verified through numerical simulation and hardware experiments.

Vibration Analysis Methods Applied to Forensic Engineering Problems

Forensic engineering problems are reviewed to demonstrate how vibration analysis methods can be utilized in certain instances to determine cause of system failures and injury mechanics associated with certain vehicular accidents. A brief overview of injury criteria and biomechanical analysis methods for evaluation of motor vehicle occupant kinematics induced by shock impact loadings is also included.

A Preprocessor for the Treatment of Elastic Bodies in Multibody Systems

A preprocessor providing the inertia data of elastic bodies for multibody algorithms is considered. The desired capability of including stress stiffening terms leads to a high computational effort. The method presented allows a straight forward implementation of the basic formulas by starting with the development of a special purpose symbolic calculator. A rotating elastic ring serves as an example.

H ∞ Control of Smart Structure Helicopter Rotor Blade

Active vibration control of helicopter rotor blade is studied. For the purpose of illustration, we have considered only flap wise vibration of a hingeless rotor blade, and modelled it, using finite element method, by 20 beam elements. The first 12 bending modes of the system are considered in the model. A H∞ controller is designed for the plant formulated as above. The result of the numerical simulation of the closed-loop system shows that the control introduces an appreciable amount of damping in the frequency region of interest. The consideration of the modelling uncertainty in the synthesis of the controller resulted in a design which is robust stable in presence of formulated model uncertainty.

The Importance of Transient Analysis on Internal Combustion Engines Structures

Because of difficulties of applying Transient Analysis in complex structure we use a set up of instruments by exploiting the experimental results of known structures of engines. Considering the combustion process as a dynamic excitation, we measure the noise and teh vibration on chosen points on a Spark Ingnition (S.I) engine and a Compression Ingnition engine (C.I). By doing that we come no conclusions concerning the combustion flow. In this experimetnal work appear the spectra of the noise and vibration measurements in connection with the R.P.M. fo the engine. From the comparison between the spectra, we extract important results concerning the chanage of the combustion flow in every different type of engine in several stages. The mesurements have been taken on a S.I. and C.I. engine in Special Engineering Laboratory.