skmm 3033 finite element method
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SKMM 3033Finite Element Method
Topic 1: Introduction to Finite Element Method
DR WILLIAM CHONG WOEI FONGDepartment of Aeronautics, Automotive and Ocean
Engineering Faculty of Mechanical Engineering
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The students are expected:
• To explain the advantages and disadvantages of using FEM• To understand the types of elements used in FEM
Bytheend ofthenotes:
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Concept design &
2D drawingPrototyping Field test and tuning
Production
YesModify design
No
!! EXPENSIVE !! Satisfaction?
Traditional methodofproductdevelopment
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Concept design &
2D drawingPrototyping
Adjustment
Production
Field Test
Advanced methodofproductdevelopment
COMPUTER AIDED ENGINEERING
(CAE) e.g. Finite Element Method
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Example:
NissanShatai Co.Ltd.
Takes19monthstogofromstylingfreezetomassproduction
Through CAE via FEA,
• Reduced cycle to 12 months
• Reduced development cost by 50%
• Improved product quality
Advanced methodofproductdevelopment
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To analyse engineering designs, can we use simple analytical approaches ??
Quite Impossible
Advanced methodofproductdevelopment
We break a complex structure into simple structures we can analyse, and connect them with continuity
However, using Finite Element Method
!!It is possible !!Using Finite Element Method
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Break a complex structure into simple structures we can analyse, and connect them with continuity
Complexity makes computation essential
Finite Element Method (FEM)
FiniteElementMethod
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• Structural design – Static Stress Analysis, Dynamics, Crashworthiness• Heat transfer – Steady-state, Transient• Fluid Flow• Soil Mechanics• Acoustics
Some application areas of finite element method includes:
A numerical method commonly used to solve complex engineering problems,involving complex geometries, combined loadings and advanced materials,where analytical solutions might too complex or not yet available
FiniteElementMethod
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• Handles bodies with complex geometries• Accepts simple to complex loading conditions• Application of advanced material properties• Considers various types of support conditions• Variable element type and size• Ease of model modification for design optimisation• Nonlinear problems (geometric & material)
Advantages of finite element method include:
FiniteElementMethod
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Just a model – “garbage in, garbage out”
Necessary steps before reliable predictions can be made:
Verification
• Confirms that the model is numerically correct
• But not that it represents reality
Validation
• Confirms that the model represents reality
• By comparison with laboratory/test data
Disadvantages of finite element method include:
FiniteElementMethod
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Is this method accurate?
Among the sources of error involved in this method include:• Geometrical simplification• Interpolation function• Material properties• Round-off
Yes, for simple problems and if material properties and loading condition aremodeled very close to the actual conditions.
No, especially when the problems to be solved are too complex.
FiniteElementMethod
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1-D elements
2-D elements
3-D elements
TypesofElements
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• Beam model of a bicycle frame• Elements cross-sections are scaled according to cross-sectional properties• Links between elements are crucial:
1. Trusses: pin/revolute joints tension/compression only2. Beams: welded joints can transmit moments tension/compression OR bending
1-D elements :
TypesofElements
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Plate-like geometry: sheet metal, composite structures, shells, pressure vessels
TypesofElements
• A structural member that is small in one direction and large in the twoother directions
• 2D elements also may be defined in 3D• Dimensions of the structure should be ~10 or more times the thickness• Plate elements are flat and Shell elements are curved• Membrane elements are like shells, but stiff only in-plane (flexible in
bending)• Shell elements can be used for most problems
2-D elements :
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Complex geometry, solid structures, no dominant dimensions
• Bulk structures, irregular shapes, highly varying section thicknesses etc.
• Direct solution for deformations, stresses and strains in three dimensions
TypesofElements3-D elements :
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You are expected to be able:
• To explain the advantages and disadvantages of using FEM• To understand the types of elements used in FEM
Bytheend ofthenotes: