Influence of Material Property and Geometry on Acoustic Wave Propagation| Chapter 3 | Science and Technology: Recent Updates and Future Prospects Vol. 10

 

The numerical analysis by finite element method offers new and efficient possibilities for different parameter calculus of acoustics phenomena. This paper presents some authors’ results regarding numerical modelling of the acoustic wave propagation, using the Ansys program. The Ansys program has in its finite element library dedicated elements for plane and spatial problems and other specific facilities about which more information is presented in this paper.  The acoustic wave propagation is studied under conditions of the existence of acoustic absorbing panels. Different materials are taken into account (aluminium, foam, oak, polystyrene) for considered acoustic absorbing panels. Also, different dimensions and different cases for fixing the panels were considered. The acoustic wave propagation was studied in stationary conditions and dynamic conditions at different values of sound frequencies. A comparative analysis is performed regarding the influence of different conditions on acoustic wave propagation. Our studies presented in this paper refer to acoustic propagation in an open space, like in airports or around acoustic sources placed in the open space. The aim of this paper is to offer our experience in this field for a numerical analysis of the ways for sound level reduction. Also, the facilities of the Ansys program for the solving of such problems are presented in a practical manner of use.

Author(s) Details

Vasile Nastasescu
“Ferdinand I Military” Technical Academy, Bucharest, Romania.

Ghita Barsan
“Nicolae Balcescu” Land Forces Academy, Sibiu, Romania.

 

Oana-Alexandra Mocian
“Ferdinand I Military” Technical Academy, Bucharest, Romania.

 

Please see the book here:- https://doi.org/10.9734/bpi/strufp/v10/1245

Development of Vibration Annihilation of Sandwiched Beam with MROF DTSMC: A Novel Approach | Chapter 4 | Theory and Applications of Engineering Research Vol. 9

 In the present chapter, an analytical model of a flexible beam fixed at an end with embedded shear sensors and actuators is developed. The smart cantilever beam model is evolved using a piezoelectric sandwich beam element, which accommodates sensor and actuator embedded at distinct locations and a regular sandwiched beam element, having rigid foam at the core. A FE model of a piezoelectric sandwich beam is evolved using laminated beam theory in MATLAB®. Each layer behaves as a Timoshenko beam and the cross-section of the beam remains plane and rotates about the neutral axis of the beam, but it does not remain normal to the deformed longitudinal axis. Keeping the sensor and actuator location fixed in a MIMO system; state space models of the smart cantilever beam is obtained. The proper selection of control strategy is very much crucial in order to obtain the better control. Here a DSM controller is designed to control first three modes of vibration of a flexible cantilever beam modelled based on Timoshenko beam theory. New active vibration control scheme to suppress the vibrations of MIMO model has developed. The actuators are located at 2nd and 5th FE positions while sensors are set at 6th and 10th FE position to form the embedded smart cantilever beam with 10 finite elements. The piezo crystals are located in the central core at prescribed locations, rest core filled with rigid foam, and this central core is sandwiched between two regular steel beams. Modelling a smart structure inclusive of sensor/actuator mass and stiffness and by altering its orientation in the beam from the free end to the fixed end acquaint an ample modification in the system’s structural response attributes. Sensor voltage is lower when the piezo patch is imposed at the free end due to the exiguous strain rate and hence demand more control endeavor. MIMO control is superior over SISO control due to its multifarious interactions of input and output and all-inclusive control endeavor needed by MIMO controller is less than SISO controller and also placing the piezo at two distinct FE locations on the beam establishing the significant modification in the system structural traits than placing it lonely at a location. The multirate output feedback dependent DSMC strategy are more harmonious as compared to the other control approaches viz. periodic output feedback (POF) and fast output sampling (FOS) controllers. The multirate output feedback based DSMC policy are more episodic as compared to the other control techniques. In discrete quasi sliding mode control (DQSMC) with output samples, there is a necessity of switching function for control and hence engendering some chattering phenomenon, while control strategy presented in the present article is the MROF based DSMC technique obtained from Bartoszewicz’s law does not demand any use of switching function and provides control input directly in form of past control data and past samples. The system responds well in closed loop and does not manifest inexpedient chattering phenomenon. MROF based DSMC employ the signum function in the control input and the control is computed from the immediate past control value and the past control output samples. The fractious system takes an extended time to damp out the oscillations in contrast to the system with the designed sliding mode control input means without control the transient response was preeminent and with control, the vibrations are quashed. From simulation results, it can be inferred that sensor output at FE 6 is more than sensor output at FE 10 by approximately 10 times due to its high strain rate at FE 6 as compared at FE 10 and also the control input are approximately 10 times smaller in case of MROF as compared to SISO case. In case of MROF technique, the states of the system are needed neither for switching function assessment nor for the feedback denotation. DSMC algorithm are computationally unpretentious, ensures better enduringness, brisk convergence and exalted steady state authenticity of the system. The technique used is more feasible as the output being used rather than states. Hence, it can be concluded that the multivariable control is best among all the models due to its multilevel interactions on both input and output. A MIMO model furnishes excellent energy distribution and even good administration of actuation forces and minimal requirement of control forces as compared to SISO model for the case of smart cantilever beam with embedded sensors and actuators.

Author(s) Details:

Vivek Rathi,
Mechanical Engineering Department, AMU, Aligarh, India.

Ahmad Ali Khan,
Mechanical Engineering Department, AMU, Aligarh, India.

Please see the link here: https://stm.bookpi.org/TAER-V9/article/view/13827

A Comprehensive Study on Optimizing Mechanical Stress, Contact Temperature, and Electrical Contact Resistance | Chapter 6 | Theory and Applications of Engineering Research Vol. 9

 In recent years, several electrical systems have been installed in modern cars in order to satisfy the needs of comfort, security, and performance and to reduce fuel consumption. Consequently, the demand for electrical power increases. One of the major difficulties of the use of power automotive connectors is the increase of their electrical contact resistance in the running time. This paper attempts to fill this gap and discloses the minimisation of the transient electrical contact resistance and contact temperature by experimental and numerical means. The tested contact samples have the sphere/plane contact shape in order to simulate the real contact in the power automotive connectors and were made with high copper alloys. These contact samples were submitted to high currents (100 A) and different contact forces (50 and 100 N ). Minimisation of electrical contact resistance, contact temperature and maximum stress of contact samples made of recent high-copper alloys under high contact forces and electric current was studied in this work with the help of experimental and numerical means. Experimental results showed that the lower transient values of electrical contact resistance and contact temperature correspond to the contact sample made with copper alloy C19210 which is submitted to the highest contact force (100 N). In order to minimize the electrical contact resistance of the contact sample made of copper alloy C19210, finite element models were developed with one contact point and multipoint contacts using a commercial code. The deformation of contact surfaces, numerical transient values of contact resistance and contact temperature were calculated based on the indirect coupling program which is developed by an APDL language. This program can make the coupling between the mechanical and thermoelectric fields and takes into account the elastoplastic behaviour of the material C19210 which is identified by tensile tests. Results showed that the sample with multipoint contact presents a transient value of contact resistance and contact temperature lower than the ones obtained with one contact point, also the maximum mechanical Von Mises stress obtained for the model with multipoint contacts is not only lower than the yield stress of the material C19210 but also lower than the one obtained for one contact point. Therefore, the gain for the model with multipoint contacts was triple.

Author(s) Details:

Amine Beloufa,
Smart Structure Laboratory, University of Ain Temouchent, Ain Temouchent 46000, Algeria.

Please see the link here: https://stm.bookpi.org/TAER-V9/article/view/13906

Surface Roughness Investigation and Stress Modeling by Finite Element on Orthogonal Cutting of Copper| Chapter 6 | Recent Developments in Engineering Research Vol. 8

 To study the surface roughness of commercially pure copper, a modern non-contacting optical technique was used in this work. The finite element (FE) technique was applied by simulating the machining process to predict the stress during orthogonal cutting. The experimental work focused primarily on the impact of the cutting speed (N) and the feed rate (f) on copper surface roughness. To evaluate surface variations under different machining conditions, the scanning electron microscope (SEM) was used. The mathematical model of Johnson-Cook was adopted and employed to determine the material parameters. In addition, as a function of machining, the maximum Von-Mises stress was projected The circumstances. For the analysis and response surface methodology (RSM) to visualise the outcomes, a software package of code (ABAQUS/CAE) was used. The findings showed an important impact of the interaction of feed rate/cutting speed on surface roughness and copper stress from Von-Mises. By increasing the cutting speed, a 14 percent improvement in surface roughness was observed. A good agreement between the experimental and analytical results was observed. Circumstances. For the study and response surface methodology (RSM) to visualise the findings, a software package of code (ABAQUS/CAE) was used. The results showed a substantial impact on surface roughness and Von-Mises copper stress from the feed rate/cutting speed interaction. By increasing the cutting speed, a 14% increase in surface roughness was perceived. A strong agreement between experimental and analytical findings has been observed. The terms. For the analysis and response surface methodology (RSM) to visualise the effects, a software package of code (ABAQUS/CAE) was used. The results showed a major effect of the interaction between feed rate/cutting speed on surface roughness and copper stress from Von-Mises. By increasing the cutting speed, an increase of 14 percent in surface roughness was perceived. A strong agreement between experimental and analytical findings has been noted.

Author (s) Details

Hussein Zein
Mechanical Engineering Department, College of Engineering, Qassim University, Saudi Arabia and Mechanical Design and Production Department, Faculty of Engineering, Cairo University, Giza 12613, Egypt.

Osama M. Irfan
Mechanical Engineering Department, College of Engineering, Qassim University, Saudi Arabia and Mechanical Engineering Department, Beni Suef University, Beni Suef 62764, Egypt.


View Book :- https://bp.bookpi.org/index.php/bpi/catalog/book/333

Complex Eigenvalue Analysis of Railway Wheel/Rail Squeal: Advanced Study | Chapter 2 | Emerging Trends in Engineering Research and Technology Vol. 3

Wheel/rail squeal noise of trains is one of the challenging problems to be solved. Several models such as self-excited instable vibration due to negative damping, flutter instability, hammering effect due to local defects, etc. were proposed, but a successful model for the squeal problem has not been presented until now. In this study, experimental and numerical methods were applied. Squeal noise and acceleration of the rail were measured in a depot when a subway train was running back and forth at a speed of 20, 25 and 30 km/h. Squeal frequencies above 80 dB(A) were 480, 1220, 2200, 4340, 5420, 8860, 9640, and 9960 Hz, which were consistent with natural vibration frequencies of the rail or wheel.  A new numerical approach was presented to investigate the basic mechanism of the wheel/rail squeal noise, using complex eigenvalue analysis by the finite element method. The positive real parts of the eigenvalues reflect self-exciting instable vibration, which is closely related to the occurrence of squeal noise. The effect of parameters such as friction coefficient, wheel/rail contact position, axle load, etc. on the instable vibration was examined. The instability of the vibration system was sensitive to the stiffness of rail support. In lateral creepage, when the adhesion coefficient was less than 0.1, instable vibration modes did not occur. In longitudinal creepage, when the friction coefficient was high enough, instable vibration modes were generated. The predicted unstable modal shapes were different from those in lateral creepage. The longitudinal creepage caused the natural vibrations of the axle.  Numerical predictions could explain many of the field test results.

Author(s) Details

B. C. Goo
Korea Railroad Research Institute, Uiwang, Korea.

J. C. Kim
Korea Railroad Research Institute, Uiwang, Korea.

View Book :- http://bp.bookpi.org/index.php/bpi/catalog/book/179