Biomedical Engineering (MEng)
Finite Element Analysis and Applications
The aim of the course is to teach the students to be able to use Finite Element programs in a practical way to solve problems in linear elastic stress analysis. A student who has studied the course should be able, in a later industrial setting, to undertake the analysis of real problems with a fair understanding of sensible modelling procedures. In support of this, the course is split into two stages:
- Theoretical study of the Finite Element method, with emphasis on understanding what goes on inside a typical, modern, commercial program
- Practical experience in analysis using an industry-standard, interactive, Finite Element program.
ECTS units: 7
Contributing to Course Elements: 7 to ME4-mLCTVS Electives
On successfully completing this module, students will be able to:
- Explain the basic theoretical principles of the Finite Element method
- Combine skills from the core course and other sources for FE modelling of industry relevant problems
- Employ industry-standard software for interactive FE model generation, analysis and the post-processing of results
- Interpret the output from the software critically and intelligently in order to yield the required information
- Formulate the boundary conditions of a problem in a suitable form for correct analysis
- Assess alternative strategies (of element type, mesh design, boundary condition definition etc.) for economical and accurate FE modelling of specific 2D, 3D and axisymmetric structural problems
- Introduction: with application to statis stress analysis. Context and history.
- Truss frame example: division into elements, selection of variables and shape functions, stiffness derivation, assembly of stiffness equations, application of boundary conditions, solution for displacements, computation of element stresses and strains.
- The constant strain triangle: Continuum model and role of continuum elements; Geometry of constant strain triangle (CST), nodal variables and shape functions, stiffness derivation (plane stress and plane strain), element stress and strain computation.
- Element forumulation: the need for more advanced and generalised procedures; element stiffness by virtual work; general procedure applied to CST; detailed derivation of linear rectangular element (Gauss quadrature, location of element integration points etc.); quadratic rectangular element, axisymmetric elements, 3-dimensional solid elements, truss and beam elements, membrane, plate and shell elements. Isoparametric elements, Jacobian mapping for arbitrarily shaped elements. Element performance: Stiffness and accuracy considerations. Nonconforming elements, reduced integration.
- Element libraries: elements offered by commercial programs (shapes, nodes, degrees of freedom, allowable load types, etc.). Materials, loads, supports and solution: analysis procedure for modern commercial programs (definition of structure and loads, supports and other constraints, solution, post-processing); material property definitions and matrices; geometric properties (thicknesses, cross-sectional areas etc.); load types (point forces and moments, pressure, body forces, thermal) and internal conversion to nodal loads; supports, prescribed displacements, rigid links; symmetric and antisymmetric boundary conditions and their application to reduce model size; stiffness transformations to model supports or loads at arbitrary angels; stiffness matrix assembly and solution, bandwidth and its minimisation; Other types of solution (structural dynamics, material plasticity, large deflections, contact problems, fracture mechanics).
- Guide to good modelling: Identification of appropriate domain of solution (2-/3-dimensional, axisymmetry, beams/shells etc.). Selection of elements, degrees of freedom, stress assumptions etc. Creation of mesh (refinement, shape, aspect ratios, curvature); Definition of material and geometric properties; application of loads and supports; pre-analysis checks; post-processing results - typical options; importance of verification, development of checking strategies; sources of inaccuracies and errors.