Linearized Frequencies and Damping in Composite Laminated Beams Subject to Buckling

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Dimitris I. Chortis ◽  
Dimitris S. Varelis ◽  
Dimitris A. Saravanos
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Composite Laminates ◽  
Small Amplitude ◽  
Nonlinear Damping ◽  
Nonlinear Stiffness ◽  
Viscoelastic Solid ◽  
Modal Damping ◽  
Strip Shape ◽  
Stiffness And Damping

This paper considers the damped small-amplitude free-vibration of composite laminated strips subject to large in-plane forces and rotations. A theoretical framework is formulated for the prediction of the nonlinear damping of composite laminates subject to large Green–Lagrange axial strains and assuming a Kelvin viscoelastic solid. An extended beam finite element is developed capable of providing the nonlinear stiffness and damping matrices of the system. The linearized damped free-vibration equations associated with the deflected strip shape in the pre- and postbuckling region are presented. Numerical results quantify the strong geometric nonlinear effect of compressive in-plane loads on the modal damping and frequencies of composite strips. Measurements of the modal damping of a cross-ply glass/epoxy beam subject to buckling were also conducted and correlate well with the finite element predictions.

Study on Nonlinear Damping Properties of Hydro-Pneumatic Suspension System for XP302-Pneumatic Tyred Roller

2014 ◽  
Vol 945-949 ◽  
pp. 987-991
Author(s):  
Bang Sheng Xing ◽  
Ning Ning Wang ◽  
Le Xu
Keyword(s):  
Dynamic Performance ◽  
Nonlinear Damping ◽  
Suspension System ◽  
Nonlinear Stiffness ◽  
Damping Properties ◽  
Vehicle Dynamic ◽  
Nonlinear Mathematical Model ◽  
Computer Simulation Program ◽  
Pneumatic Suspension ◽  
Stiffness And Damping

The nonlinear stiffness and damping properties of the hydro-pneumatic suspension system are introduced, and the nonlinear mathematical model of it is established. Using MATLAB 2009b to establish the computer simulation program and draw out the nonlinear stiffness curve and damping properties curve of the hydro-pneumatic suspension system. Then, researching the influences of related parameters' changes on the nonlinear stiffness and damping properties of the hydro-pneumatic suspension system. The simulation of vehicle dynamic performance research's foundation is provided.

scholarly journals Experimental and Finite Element Studies on Free Vibration of Skew Plates

2014 ◽  
Vol 19 (2) ◽  
pp. 365-377 ◽  
Author(s):  
C.V. Srinivasa ◽  
Y.J. Suresh ◽  
W.P. Prema Kumar
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
Free Vibration ◽  
Composite Laminates ◽  
Natural Frequencies ◽  
Experimental Studies ◽  
Orientation Angle ◽  
Laminated Composite ◽  
Skew Angle ◽  
Experimental Values

Abstract The present paper deals with the experimental studies carried out on free vibration of isotropic and laminated composite skew plates. The natural frequencies were also determined using QUAD8 finite element of MSC/NASTRAN and a comparison was made between the experimental values and the finite element solution. The effects of the skew angle and aspect ratio on the natural frequencies of isotropic skew plates were studied. The effects of the skew angle, aspect ratio, fiber orientation angle and laminate sequence (keeping the number of layers constant) on the natural frequencies of antisymmetric composite laminates were also studied. The experimental values of natural frequencies are in good agreement with the FE solutions. The natural frequencies are found to increase with an increase in the skew angle. The variation of natural frequencies with the aspect ratio is small and negligible both for isotropic and laminated composite skew plates.

scholarly journals Finite Element Studies on Free Vibration of Laminated Composite Cylindrical Skew Panels

2014 ◽  
Vol 6 ◽  
pp. 174085
Author(s):  
Srinivasa Chikkol Venkateshappa ◽  
Suresh Yalaburgi Jayadevappa ◽  
Premakumar Wooday Puttiah
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Fundamental Frequency ◽  
Composite Laminates ◽  
Orientation Angle ◽  
Laminated Composite ◽  
Skew Angle ◽  
Element Analysis ◽  
Number Of Layers ◽  
Fiber Orientation Angle

This paper presents the finite element studies made on free vibration of isotropic and laminated composite cylindrical skew panels. A finite element analysis is performed using CQUAD4 and CQUAD8 elements of MSC/NASTRAN software. The effects of the panel angle, skew angle, aspect ratio, and length-to-thickness-ratio on fundamental natural frequency of vibration of isotropic cylindrical skew panels are studied. The effects of additional parameters such as fiber orientation angle, numbers of layers (keeping total thickness constant), and laminate stacking sequence on the fundamental frequency of vibration of antisymmetric composite laminates have also been studied. During validation and convergence study, it is found that the CQUAD8 element yields more accurate results than the CQUAD4 element. Hence the CQUAD8 element has been employed for the remaining part of the investigation. The fundamental frequency is found to increase with the panel angle and skew angle. The variation of the fundamental frequency with the number of layers is not appreciable when the number of layers is greater than about 6. It is also seen that the boundary conditions have significant influence on the fundamental frequency.

scholarly journals Finite element studies on free vibration of laminated composite cylindrical skew panels

2014 ◽  
Vol 19 (1) ◽  
pp. 165-180
Author(s):  
C.V. Srinivasa ◽  
Y.J. Suresh ◽  
W.P. Prema Kumar
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Fundamental Frequency ◽  
Composite Laminates ◽  
Orientation Angle ◽  
Laminated Composite ◽  
Skew Angle ◽  
Fundamental Frequencies ◽  
Number Of Layers ◽  
Fiber Orientation Angle

Abstract This paper presents the finite element studies on free vibration of isotropic and laminated composite cylindrical skew panels. The analysis is performed using CQUAD4 and CQUAD8 elements of MSC/NASTRAN. The effects of the panel angle, skew angle, aspect ratio and length-to-thickness-ratio on fundamental frequency of isotropic cylindrical skew panels are studied. The effects of additional parameters such as the fiber orientation angle, numbers of layers and stacking sequence on the fundamental frequency of antisymmetric composite laminates are also studied. It is found that the CQUAD8 element yields better results than the CQUAD4 element in the validation and convergence studies. The CQUAD8 element is employed for the remaining part of the studies. The fundamental frequencies are found to increase with the panel angle and skew angle. When the number of layers in the laminate is large, the variation of the fundamental frequency with the number of layers is not appreciable. The boundary conditions are found to have a significant influence on the fundamental frequency

Application of Viscous and Iwan Modal Damping Models to Experimental Measurements From Bolted Structures

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Brandon J. Deaner ◽  
Matthew S. Allen ◽  
Michael J. Starr ◽  
Daniel J. Segalman ◽  
Hartono Sumali
Keyword(s):  
Nonlinear Damping ◽  
Beam Structure ◽  
Single Degree Of Freedom ◽  
Mechanical Joints ◽  
Single Degree ◽  
Mechanical Joint ◽  
Damped System ◽  
Modal Damping ◽  
Nonlinear Mechanical ◽  
Stiffness And Damping

Measurements are presented from a two-beam structure with several bolted interfaces in order to characterize the nonlinear damping introduced by the joints. The measurements (all at force levels below macroslip) reveal that each underlying mode of the structure is well approximated by a single degree-of-freedom (SDOF) system with a nonlinear mechanical joint. At low enough force levels, the measurements show dissipation that scales as the second power of the applied force, agreeing with theory for a linear viscously damped system. This is attributed to linear viscous behavior of the material and/or damping provided by the support structure. At larger force levels, the damping is observed to behave nonlinearly, suggesting that damping from the mechanical joints is dominant. A model is presented that captures these effects, consisting of a spring and viscous damping element in parallel with a four-parameter Iwan model. The parameters of this model are identified for each mode of the structure and comparisons suggest that the model captures the stiffness and damping accurately over a range of forcing levels.

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