Free vibration of high-speed rotating Timoshenko shaft with various boundary conditions: effect of centrifugally induced axial force

2014 ◽  
Vol 84 (12) ◽  
pp. 1691-1700 ◽  
Author(s):  
Benyamin Gholami Bazehhour ◽  
Seyed Mahmoud Mousavi ◽  
Anoushiravan Farshidianfar
Keyword(s):  
Free Vibration ◽  
Boundary Conditions ◽  
Axial Force ◽  
High Speed ◽  
Various Boundary Conditions

Film breakup of tilted impinging spray under various pressure conditions

2019 ◽  
Vol 21 (2) ◽  
pp. 330-339 ◽  
Author(s):  
Di Xiao ◽  
Ichikawa Yukihiko ◽  
Xuesong Li ◽  
David Hung ◽  
Keiya Nishida ◽  
...  
Keyword(s):  
Film Thickness ◽  
Boundary Conditions ◽  
Liquid Film ◽  
High Speed ◽  
Injection Pressure ◽  
Laser Induced Fluorescence ◽  
Parameter Study ◽  
Fluorescence Signal ◽  
Fuel Film ◽  
Various Boundary Conditions

Fuel film on engine walls caused by spray impingement would dramatically cause engine friction deterioration, incomplete combustion, and significant cycle-to-cycle variations. In a previous work, it has been demonstrated that fuel film would break up via wave entrainment induced by the high-speed coflow. Meanwhile, the film breakup dynamics depend on various boundary conditions, such as injection pressure, ambient pressure, and so on. However, such impact on the wall film formation was not investigated thoroughly in existing literature. This work aims to perform a parameter study to investigate possible means to enhance wave entrainment effect as to reduce the amount of impingement fuel mass. In this study, simultaneous measurements of macroscopic structure and its corresponding footprint of impinging spray are conducted using a single-hole, prototype injector in a constant volume chamber. The macroscopic spray structure was captured by high-speed backlit imaging, and the film was obtained using laser-induced fluorescence under different conditions. The laser-induced fluorescence signal is converted to film thickness following a calibration procedure where laser-induced fluorescence signals from a series of known-thickness film are captured. A mathematical processing method is used to analyze both the dynamic behavior of film thickness and amount of droplet detachment caused by high-speed coflow. It is found that at the leading edge of film waves, a remarkable amount of liquid droplets detaches from the liquid film and the quantity of film mass on the wall decreases during this process. Quantitative analysis is conducted and the mass ratio of detached droplets over residual liquid film is estimated. We hold that the film breakup percentage increases with both ambient and injection pressure due to the enhanced high-speed coflow. Then, variation laws for various boundary conditions are obtained based on the observations.

FREE VIBRATION ANALYSIS OF DISCRETELY STIFFENED SKEW PLATES

2001 ◽  
Vol 01 (01) ◽  
pp. 125-144 ◽  
Author(s):  
HUAN ZENG ◽  
CHARLES W. BERT
Keyword(s):  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Ritz Method ◽  
Free Vibration Analysis ◽  
Vibration Characteristics ◽  
Skew Angle ◽  
Various Boundary Conditions ◽  
Skew Plate ◽  
Convergence Study

Stiffened skew plates find application in various engineering fields. The free vibration characteristics of such plates have been studied by various methods. An orthogonally stiffened skew plate is a skew plate with stiffeners running orthogonal to two opposite edges. To the best knowledge of the present investigators, no previous work has been done for free vibration characteristics of skew plates of such stiffening geometry. The present work studies the free vibration of such plates. The pb-2 Rayleigh–Ritz method was employed due to its accuracy and computational efficiency. The conventional finite element method was also used as a comparative check. A convergence study was first performed for various boundary conditions. Then the vibration of orthogonally stiffened skew plates with different boundary conditions was studied. Close agreement was found between these two methods. The variations of natural frequencies with different parameters, including skew angle ϕ, edge ratio b/a, and height-thickness ratio f/h, were investigated for three types of boundary conditions.

Free vibration and buckling analysis of laminated composites and sandwich microbeams using a transverse shear-normal deformable beam theory

2019 ◽  
Vol 26 (3-4) ◽  
pp. 214-228 ◽  
Author(s):  
Armagan Karamanli ◽  
Metin Aydogdu
Keyword(s):  
Free Vibration ◽  
Boundary Conditions ◽  
Transverse Shear ◽  
Couple Stress Theory ◽  
Laminated Composite ◽  
Beam Theory ◽  
Modified Couple Stress Theory ◽  
Arbitrary Boundary ◽  
Various Boundary Conditions ◽  
Aspect Ratios

In this paper, the free vibration and buckling responses of laminated composite and sandwich microbeams with arbitrary boundary conditions are investigated. The governing equations based on the modified couple stress theory are derived by using the total potential energy of a microbeam and employing a transverse shear-normal deformable beam theory. Extensive analysis results in terms of dimensionless fundamental frequencies and dimensionless critical buckling loads are introduced for various boundary conditions, aspect ratios, orthotropy ratios, fiber orientation angles, thickness to material length scale parameter ratios, and core thickness to face layer thickness ratios.

scholarly journals On the Flexural-Torsional Vibration and Stability of Beams Subjected to Axial Load and End Moment

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
M. Tahmaseb Towliat Kashani ◽  
Supun Jayasinghe ◽  
Seyed M. Hashemi
Keyword(s):  
Boundary Conditions ◽  
Axial Force ◽  
Axial Load ◽  
Natural Frequencies ◽  
Compressive Force ◽  
Elastic Beam ◽  
Axial Compressive Force ◽  
Various Boundary Conditions ◽  
Linear Eigenvalue Problem ◽  
The Moment

The free vibration of beams, subjected to a constant axial load and end moment and various boundary conditions, is examined. Based on the Euler-Bernoulli bending and St. Venant torsion beam theories, the differential equations governing coupled flexural-torsional vibrations and stability of a uniform, slender, isotropic, homogeneous, and linearly elastic beam, undergoing linear harmonic vibration, are first reviewed. The existing formulations are then briefly discussed and a conventional finite element method (FEM) is developed. Exploiting the MATLAB-based code, the resulting linear Eigenvalue problem is then solved to determine the Eigensolutions (i.e., natural frequencies and modes) of illustrative examples, exhibiting geometric bending-torsion coupling. Various classical boundary conditions are considered and the FEM frequency results are validated against those obtained from a commercial software (ANSYS) and the data available in the literature. Tensile axial force is found to increase natural frequencies, indicating beam stiffening. However, when a force and an end moment are acting in combination, the moment reduces the stiffness of the beam and the stiffness of the beam is found to be more sensitive to the changes in the magnitude of the axial force compared to the moment. A buckling analysis of the beam is also carried out to determine the critical buckling end moment and axial compressive force.

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