Traction Boundary Conditions in Hybrid-Stress Finite-Element Model

The fatigue resistance of metallic structures is inherently random due to environmental and boundary conditions, and microstructural geometry, including discontinuities, and material properties. A new methodology for fatigue life prediction is under development to account for these sources of randomness. One essential aspect of the methodology is the ability to perform truly multiscale simulations: simulations that directly link the boundary conditions on the structural length scale to the damage mechanisms of the microstructural length scale. This presentation compares and contrasts two multiscale methods suitable for fatigue life prediction. The first is a brute force method employing the widely-used multipoint constraint technique which couples a finite element model of the microstructure within the finite element model of the structural component. The second is a more subtle, modified multi-grid method which alternates analyses between the two finite element models while representing the evolving microstructural damage. Examples and comparisons are made for several geometries and preliminary validation is achieved with comparison to experimental tests conducted by the Northrop Grumman Corporation on a wing-panel structural geometry.

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A Method to Determine the Boundary Conditions of the Finite Element Model of a Slender Beam Using Measured Modal Parameters

Journal of Vibration and Acoustics ◽

10.1115/1.2888208 ◽

1996 ◽

Vol 118 (3) ◽

pp. 474-478 ◽

Cited By ~ 8

Author(s):

Wang Fengquan ◽

Chen Shiyu

Keyword(s):

Finite Element ◽

Boundary Conditions ◽

Finite Element Model ◽

Interpolation Method ◽

Element Model ◽

Accurate Method ◽

Modal Parameters ◽

Computation Method ◽

Modal Parameter ◽

The Finite Element Model

In this paper, a method used to determine the boundary conditions of the Finite Element Model of a slender beam with measured structure modal parameters is presented. On deriving the method, the finite element model theory for dynamic calculating is used. Combined with the modal parameters from experiment, an FEM-modal parameter equation to determine the boundary conditions is put forward. For solving the equation, three methods are given. The first is the accurate method. The second is the full mode computation method by means of generalized inverse matrix. The third is the interpolation method of frequency. A numerical simulation with computer is given and the results of calculation fully verify the effectiveness of the method offered and also verify that the accuracy of the method is satisfying. Finally, an applied example is given and the results of calculation fully verify the effectiveness of the method offered.

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Investigation of Residual Thermal Stresses in Fiber-Reinforced Composites Incorporating Inhomogeneous Interphase Region

Volume 9: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2010-40337 ◽

2010 ◽

Author(s):

M. M. Shokrieh ◽

A. R. Ghanei Mohammadi

Keyword(s):

Finite Element ◽

Boundary Conditions ◽

Finite Element Model ◽

Thermal Stresses ◽

Element Model ◽

Fiber Reinforced Composites ◽

Radial Coordinate ◽

Reinforced Composites ◽

Fiber Reinforced ◽

Fe Method

In this paper, a new finite element model has been introduced with the aim of efficient investigation of residual thermal stresses in fiber-reinforced composites, in which the inhomogeneous interphase is considered. For the inhomogeneous interphase modeling, four different kinds of material properties variation of the interphase (power, reciprocal, cubic and exponential variations) with the radial coordinate have been used. A mono fiber circular unit cell is considered using a finite element (FE) method. Extending the mono fiber model, FE models with different arrays of fibers have been created to investigate the effects of neighboring fibers on the results. In order to assure the convergence of results, a convergence analysis has been carried out for each of the models. To verify the finite element model, the FE results are compared with theoretical results available in the literature. In this paper, three different types of RVE configurations, circular, square and hexagonal are modeled and the effects of each type of fiber packing are studied. Performing an extensive study, the appropriate boundary conditions for RVEs are presented. The boundary conditions presented in this research are proved to be able to model the overall behavior efficiently.

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Dynamic Behavior of Electronic Module Spring Clips, Retention Bar, and Backplane Connector: Modeling and Testing

Volume 5: Electronics and Photonics ◽

10.1115/imece2009-11403 ◽

2009 ◽

Author(s):

Kenneth P. Vandevoordt ◽

Michael Feng

Keyword(s):

Finite Element ◽

Boundary Conditions ◽

Finite Element Model ◽

Element Model ◽

Guidance System ◽

Printed Wiring Board ◽

Wiring Board ◽

Electrical Components ◽

Hardware Test ◽

The Finite Element Model

Electronic modules for a guidance system are mounted in a rack with spring clips resisting motion normal to the printed wiring board (PWB) and an aluminum bar with an elastomer pad keeping the module connected to a backplane. The elastomer pad also resists motion normal to the board. The proper boundary conditions for the spring clips, retention bar, and connector are needed in a finite element model in order to evaluate the shock and vibration transmitted to the module’s electrical components. The finite element model of the module was assembled, and an actual module was tested under random vibration and a 1g sine sweep. The printed wiring board elastic modulus was artificially set higher in the FEM than a measured value to account for the stiffening effect of board components which were omitted from the model. By also choosing the proper boundary conditions to represent the spring clips, retention bars, and backplane connection, the finite element model was able to match the first and second mode frequencies from the hardware test results.

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Identification of Free-Free Modes From Constrained Vibration Data for Flexible Multibody Models

Volume 7A: 17th Biennial Conference on Mechanical Vibration and Noise ◽

10.1115/detc99/vib-8231 ◽

1999 ◽

Author(s):

Tong Y. Yi ◽

Parviz E. Nikravesh

Keyword(s):

Finite Element ◽

Boundary Conditions ◽

Finite Element Model ◽

Degrees Of Freedom ◽

Multibody System ◽

Element Model ◽

Flexible Body ◽

Fe Model ◽

Modal Data ◽

Vibration Data

Abstract This paper presents a method for identifying the free-free modes of a structure by utilizing the vibration data of the same structure with boundary conditions. In modal formulations for flexible body dynamics, modal data are primary known quantities that are obtained either experimentally or analytically. The vibration measurements may be obtained for a flexible body that is constrained differently than its boundary conditions in a multibody system. For a flexible body model in a multibody system, depending upon the formulation used, we may need a set of free-free modal data or a set of constrained modal data. If a finite element model of the flexible body is available, its vibration data can be obtained analytically under any desired boundary conditions. However, if a finite element model is not available, the vibration data may be determined experimentally. Since experimentally measured vibration data are obtained for a flexible body supported by some form of boundary conditions, we may need to determine its free-free vibration data. The aim of this study is to extract, based on experimentally obtained vibration data, the necessary free-free frequencies and the associated modes for flexible bodies to be used in multibody formulations. The available vibration data may be obtained for a structure supported either by springs or by fixed boundary conditions. Furthermore, the available modes may be either a complete set; i.e., as many modes as the number of degrees of freedom of the associated FE model is available, or it can be an incomplete set.

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BOUNDARY CONDITIONS IN FINITE ELEMENT MODELING OF STRATIFIED COASTAL CIRCULATION

Coastal Engineering Proceedings ◽

10.9753/icce.v21.190 ◽

1988 ◽

Vol 1 (21) ◽

pp. 190

Author(s):

George C. Christodoulou ◽

George D. Economou

Keyword(s):

Finite Element ◽

Boundary Conditions ◽

Finite Element Model ◽

Finite Element Modeling ◽

Coastal Waters ◽

Stratified Flow ◽

Element Model ◽

Numerical Computations ◽

Element Modeling ◽

Sponge Layer

The effect of boundary conditions on numerical computations of stratified flow in coastal waters is examined. Clamped, free radiation and sponge layer conditions are implemented in a two-layer finite element model and the results of simple tests in a two-layer stratified basin are presented.

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