Elastic Analysis of a Skull

1973 ◽  
Vol 40 (4) ◽  
pp. 838-842 ◽  
Author(s):  
C. H. Hardy ◽  
P. V. Marcal
Keyword(s):  
Finite Element ◽  
Composite Material ◽  
Elastic Stress ◽  
Shell Element ◽  
Elastic Analysis ◽  
Triangular Shell Element ◽  
Skull Measurements ◽  
Doubly Curved

A finite-element elastic analysis is made of a skull. Measurements were made of the geometry and thickness of a skull. The skull was then idealized with a doubly curved and arbitrary triangular shell element. Results suggest that the skull is well built for resistance to front loads. The importance of using a composite material through the thickness of the shell was established. On the basis of tensile cracking at maximum elastic stress, loads of 3500 lb and 1400 lb were predicted for the first cracking of the skull due to front and side loading, respectively.

Control Effectiveness of Segmented Actuators Laminated on Ring-Shells

1997 ◽  
Author(s):  
R. Ye ◽  
H. Bahrami ◽  
H. S. Tzou
Keyword(s):  
Finite Element ◽  
Distributed Control ◽  
Piezoelectric Actuators ◽  
Shell Element ◽  
Circular Ring ◽  
Control Effectiveness ◽  
Triangular Shell Element ◽  
Circular Ring Shell ◽  
System Equations ◽  
Ring Shell

Abstract Distributed control effectiveness of ring-shells laminated with segmented actuators is investigated in this paper. A new laminated quadratic piezoelastic triangular shell FE is developed using the layerwise constant shear angle theory. Element and system equations are also derived. The developed piezoelastic triangular shell element is used to model a semi-circular ring shell with various segments of distributed piezoelectric actuators. Finite element (triangular shell FE) solutions are compared with the theoretical, experimental, and finite element first. Natural frequencies and distributed control effects of the ring shell with different length of piezoelectric actuators are also studied. Control effectiveness is evaluated and optimal length of the actuator is recommended.

scholarly journals Optimum Design of a Gearbox for Low Vibration

1993 ◽  
Vol 115 (4) ◽  
pp. 1002-1007 ◽  
Author(s):  
K. Inoue ◽  
D. P. Townsend ◽  
J. J. Coy
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Shell Element ◽  
Optimization Method ◽  
Vibration Energy ◽  
Nasa Lewis Research ◽  
Element Analysis ◽  
Constant Weight ◽  
Triangular Shell Element ◽  
Exciting Frequency

A computer program was developed for designing a low vibration gearbox. The code is based on a finite element shell analysis, a modal analysis, and a structural optimization method. In the finite element analysis, a triangular shell element with 18 degrees-of-freedom is used. In the optimization method, the overall vibration energy of the gearbox is used as the objective function and is minimized at the exciting frequency by varying the finite element thickness. Modal analysis is used to derive the sensitivity of the vibration energy with respect to the design variable. The sensitivity is representative of both eigenvalues and eigenvectors. The optimum value is computed by the gradient projection method and a unidimensional search procedure under the constraint condition of constant weight. The computer code is applied to a design problem derived from an experimental gearbox in use at the NASA Lewis Research Center. The top plate and two side plates of the gearbox are redesigned and the contribution of each surface to the total vibration is determined. Results show that even the optimization of the top plate alone is effective in reducing total gearbox vibration.

Analysis of Tank Car Deformations Using Multibody Systems and Finite Element Algorithms

2015 ◽  
Author(s):  
Liang Wang ◽  
Huailong Shi ◽  
Ahmed A. Shabana
Keyword(s):  
Finite Element ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Railroad Vehicles ◽  
Contact Formulation ◽  
Triangular Shell Element ◽  
Railroad Vehicle ◽  
Strong Dynamic

This investigation demonstrates the effect of the tank flexibility and plate thickness on the wheel/rail contact and the nonlinear dynamic behavior of railroad vehicles. To this end, a flexible tank is modeled using the finite element (FE) floating frame of reference formulation (FFR). The tank car finite element model is integrated with a three-dimensional railroad vehicle using computational non-linear multibody system (MBS) framework in which the wheel/rail interaction is formulated using a three-dimensional elastic contact formulation that allows for the wheel/rail separation. A triangular shell element is used to build the tank car and describe its deformation, The effect of the coupling between different modes of displacements is demonstrated by comparing the results of the simulations of the flexible and rigid tank car models. It is shown that there is a strong dynamic coupling between different modes of displacements of the tank car, the plate thickness, and the wheel/rail contact parameters. The effect of the flexibility and plate thickness of the tank car on the vehicle critical speed and dynamic characteristics are also examined.

Nonlinear Analysis of Twisted Wind Turbine Blade

2016 ◽  
Vol 34 (3) ◽  
pp. 269-278 ◽  
Author(s):  
M. Yangui ◽  
S. Bouaziz ◽  
M. Taktak ◽  
M. Haddar ◽  
A. El-Sabbagh
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Degrees Of Freedom ◽  
Rotation Speed ◽  
Three Dimensional ◽  
Nonlinear Problems ◽  
Shell Element ◽  
Element Model ◽  
Angular Rotation ◽  
Triangular Shell Element

AbstractModal analysis is developed in this paper in order to study the dynamic characteristics of rotating segmented blades assembled with spar. Accordingly, a three dimensional finite element model was built using the three node triangular shell element DKT18, which has six degrees of freedom, to model the blade and the spar structures. This study covers the effect of rotation speed and geometrically nonlinear problems on the vibration characteristics of rotating blade with various pretwist angles. Likewise, the effect of the spar in the blade is taken into consideration. The equation of motion for the finite element model is derived by using Hamilton's principle, while the resulting nonlinear equilibrium equation is solved by applying the Newmark method combined with the Newton Raphson schema. Results show that the natural frequencies increase by taking account of the spar, they are also proportional to the angular rotation speed and influenced by geometric nonlinearity and pretwist angle.

Vibration Analysis of Rotating Cambered Helicoidal Turbomachine Blades

1997 ◽  
Author(s):  
J. S. Rao ◽  
C. V. Ramakrishnan ◽  
K. Gupta ◽  
K. K. Rao
Keyword(s):  
Finite Element ◽  
Plane Stress ◽  
Vibration Analysis ◽  
Shell Element ◽  
Stress Effect ◽  
Shell Finite Element ◽  
Doubly Curved

A procedure for the vibration analysis of rotating cambered helicoidal blades using curved shell finite element based on Mindlin theory is given. The strain displacement relations of Gol den’veizer are used in the development of a thick doubly curved helicoidal shell element including initial in-plane stress effect. The method is applied to rotating cambered pretwisted blades.

Hybrid Strain Based Finite Element Modeling of Laminated Plates With Distributed Piezoelectric Components

2001 ◽  
Author(s):  
C. W. S. To ◽  
Wei Liu
Keyword(s):  
Finite Element ◽  
Lower Order ◽  
Degrees Of Freedom ◽  
Shear Deformation Theory ◽  
Shell Element ◽  
Laminated Plates ◽  
Computational Time ◽  
Hybrid Strain ◽  
Triangular Shell Element ◽  
Piezoelectric Effects

Abstract A layerwise hybrid strain based lower order flat triangular laminated composite shell finite element with piezoelectric effects has been developed and reported in this paper. This layerwise three-node triangular shell element is formed by stacking a lower-order flat triangular shell element with piezoelectric effects. In every node there are seven degrees of freedom (dof). These include three translational dof, three rotational dof, and one electric potential dof. The important drilling dof (ddof) is included in every node. The degenerated three dimensional solid assumption and the first order shear deformation theory (FSDT) were adopted. Consequently, shear and membrane lockings are eliminated. This feature is superior to those elements based on the displacement formulation. Explicit expressions for the consistent element mass and stiffness matrices were obtained by using the symbolic algebraic package, MAPLE V. Thus, it reduces considerably the computational time as opposed to those applying numerical matrix inversion and numerical integration for the derivation of element matrices.

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