NATURAL FREQUENCY CONSTRAINED OPTIMAL STRUCTURAL MODIFICATION USING A SENSITIVITY DERIVATIVE OF DYNAMICALLY CONSTRAINED MASS AND STIFFNESS MATRICES

1998 ◽  
Vol 211 (3) ◽  
pp. 527-536 ◽  
Author(s):  
R.K. Srivastava ◽  
T.K. Kundra
Keyword(s):  
Natural Frequency ◽  
Structural Modification ◽  
Stiffness Matrices ◽  
Sensitivity Derivative

Vibration Analysis of Radial Drilling Machine Structure Using Finite Element Method

2012 ◽  
Vol 472-475 ◽  
pp. 2717-2721 ◽  
Author(s):  
Rajiv Kumar ◽  
Mohinder Pal Garg ◽  
Rakesh C. Sharma
Keyword(s):  
Machine Tool ◽  
Natural Frequency ◽  
Mode Shapes ◽  
Drilling Machine ◽  
Element Analysis ◽  
Stiffness Matrices ◽  
Machine Tool Structure ◽  
Radial Drilling ◽  
Machine Structure

Manufacturing industries now a days have stringent expectation from the machine tools in terms of productivity as well as quality of products.Vibration plays an important role in determining the quality of product.If the pattern of vibration prevailing in the machine tool during cutting is known,then machine tool structure can be designed in such a way so that natural frequency of machine tool structure can be isolated from the forced frequency.So, this study is focused on finding the natural frequency and mode shapes of radial drilling machine structure.Finite element analysis has been done to find out the natural frequencies and mode shapes of radial drilling machine structure.Assembled mass and stiffness matrices are obtained for each element and solved by using inverse iteration technique.

Vibration control of a two-link flexible manipulator

2015 ◽  
Vol 23 (12) ◽  
pp. 2023-2034 ◽  
Author(s):  
H Karagülle ◽  
L Malgaca ◽  
M Dirilmiş ◽  
M Akdağ ◽  
Ş Yavuz
Keyword(s):  
Natural Frequency ◽  
Rigid Body Dynamics ◽  
Experimental Results ◽  
Time Dependent ◽  
Flexible Manipulator ◽  
Vibration Signals ◽  
End Point ◽  
Stiffness Matrices ◽  
Inertia Forces ◽  
Deceleration Time

In this study, a two-link manipulator with flexible members is considered. The end point vibration signals are simulated by developing a MatLAB code based on the finite element theory and Newmark solution. Experimental results are also presented and compared with simulation results. The mass and stiffness matrices are time dependent because the angular positions of the links change during the motion. Trapezoidal velocity profiles for the actuating motors are used. The time dependent inertia forces are calculated by using the rigid body dynamics. The inertia forces are due to the motors, end point payload mass and distributed masses of the links. The acceleration, constant velocity and deceleration time intervals of the trapezoidal velocity profile are selected by considering the lowest natural frequency of the manipulator structure at the stopping position. Various starting and stopping positions are considered. The root mean square (RMS) acceleration values of the vibration signals after stopping are calculated. It is observed that the residual vibration is sensitive to the deceleration time. The RMS values are lowest if the inverse of the deceleration time equals to the first natural frequency. It is highest if the inverse of the deceleration time equals to the half of the first natural frequency. It is observed that simulation and experimental results are in good agreement.

A Computationally Efficient Objective Function for the Evaluation of the Natural Frequency in Structural Modification and Optimization Problems

1997 ◽  
Vol 119 (4) ◽  
pp. 618-623
Author(s):  
Tien-Sheng Chang ◽  
E. B. Magrab
Keyword(s):  
Objective Function ◽  
Natural Frequency ◽  
Structural Modification ◽  
Optimization Problems ◽  
Computationally Efficient ◽  
Original Design ◽  
Additional Advantage ◽  
Cpu Time ◽  
Design Changes ◽  
Modification Technique

A highly computationally efficient objective function for measuring the change in the natural frequency when a structure is modified is introduced. When the optimization of an orthotropic plate is studied, a decrease in CPU time by at least a factor of 40 is obtained when the new objective function is compared to that derived from the minor structural modification technique. The greater the number of finite elements affected by the design changes the higher the factor of improvement will be. This new objective function has the additional advantage that it can be used for substantial modifications to the original design.

Cristal-growth dynamics of n-doped gaAs

1992 ◽  
Vol 50 (2) ◽  
pp. 1544-1545
Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay
Keyword(s):  
Crystal Growth ◽  
Spatial Resolution ◽  
Epitaxial Layer ◽  
Outer Surface ◽  
Gaas Substrate ◽  
Structural Modification ◽  
Growth Dynamics ◽  
Argon Laser ◽  
High Anisotropy ◽  
Crystal Gaas

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.

Influence of the distribution of the shear walls on the seismic response of the buildings

2020 ◽  
Vol 15 (1) ◽  
pp. 37-44
Author(s):  
El Mehdi Echebba ◽  
Hasnae Boubel ◽  
Oumnia Elmrabet ◽  
Mohamed Rougui
Keyword(s):  
Structural Analysis ◽  
Seismic Response ◽  
Natural Frequency ◽  
Structural Design ◽  
Structural Response ◽  
Shear Walls ◽  
Structural Elements ◽  
Analysis Software ◽  
Ansys Apdl ◽  
The Impact

Abstract In this paper, an evaluation was tried for the impact of structural design on structural response. Several situations are foreseen as the possibilities of changing the distribution of the structural elements (sails, columns, etc.), the width of the structure and the number of floors indicates the adapted type of bracing for a given structure by referring only to its Geometric dimensions. This was done by studying the effect of the technical design of the building on the natural frequency of the structure with the study of the influence of the distribution of the structural elements on the seismic response of the building, taking into account of the requirements of the Moroccan earthquake regulations 2000/2011 and using the ANSYS APDL and Robot Structural Analysis software.

Effect of Curved Thin-film Device on Natural Frequency of Rectangle Membrane under Uniaxial Tension

2019 ◽  
Vol 18 (0) ◽  
pp. 73-80 ◽  
Author(s):  
Masanori MATSUSHITA ◽  
Nobukatsu OKUIZUMI ◽  
Yasutaka SATOU ◽  
Osamu MORI ◽  
Takashi IWASA ◽  
...  
Keyword(s):  
Thin Film ◽  
Uniaxial Tension ◽  
Natural Frequency ◽  
Thin Film Device
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