Lecture-chap10-11-lee

# Lecture-chap10-11-lee - Objectives • Formulations of...

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Unformatted text preview: Objectives: • Formulations of Finite-Element Methods (FEM). • Finite-Element Modelling and mesh generation (several approaches). • Case Study. Finite-Element Modelling and Analysis – Ch. 8 • CAE software used to analyze kinematic and dynamic responses of assemblies being designed. • Recall examples – DADS and ADAMS. • Examples of Finite-Element tools – NASTRAN and ANSYS. • Early applications of Finite Element methods (FEM) in structural mechanics – plane stress analysis. • Current applications include heat transfer, electrostatic potential, fluid mechanics, vibration analysis , etc. Introduction to Finite-Element Analysis (FEA) Introduction to Finite-Element Analysis (FEA) Figure 8.1 Application of the finite-element method to analyze temperature distribution. Application is for door handle of refrigerator to calculate temperature distribution after injection mold filled with molten resin. Examples of software – C-MOLD and MOLDFLOW. Introduction to Finite-Element Analysis (FEA) Figure 8.2 Problems that cannot be solved analytically. (a) Cantilever beam – difficulty increases if composed of many materials. (a) Temperature distribution in an object. Introduction to Finite-Element Analysis (FEA) Figure 8.3 Approximation of each object by an assemblage of finite elements. (a) Cantilever beam problem – approximation using triangular elements. (a) Object approximated by quadrilateral elements for solving temperature distribution. • Several finite elements may be chosen to approximate object. • Depending on problem, choice of proper element(s) important. • Size of elements also matter of engineering judgement. • In general, larger the number of elements ( h version) or higher the degree of shape function ( p version) = greater the accuracy, but greater the computational expense. • Other problems – mesh generation for 3D objects of complex geometry – labour intensive. • Software available to automate mesh generation (ex., Altair Hypermesh) Introduction to Finite-Element Analysis (FEA) • Once object approximated by finite elements, nodes associated with unknowns to be solved (ex., x and y displacements for cantilever beam). • Displacement of element derived from displacement at nodes by presumed shape function of element – thus only displacements at nodes are unknowns. • Strains derived from partial derivative of displacement function, and stresses computed from strains. Introduction to Finite-Element Analysis (FEA) • Material properties specified for each element, and boundary conditions imposed. • Different material properties for different elements allow analysis of object comprising of different regions of various materials....
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Lecture-chap10-11-lee - Objectives • Formulations of...

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