unigraphics

HYPERMESH

INRODUCTION TO FINITE ELEMENT MODELING

04/08/23 1M.S.RAMAIAH SCHOOL OF ADVANCED STUDIES

PRADEEP KUMAR

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Definition of FEM

• It is the procedure of converting continuous model to discrete model(Finite degrees of freedom).

04/08/23 M.S.RAMAIAH SCHOOL OF ADVANCED STUDIES 2

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Finite element procedure


• Step1:- Modeling the physical object This is usually done by CAD software's like UG,CATIA,PRO-E etc.

• Step2:-Discretization of the structure(Meshing) This is the process of converting physical model to FEM model, generally this is done by HYPERMESH,ANSA etc.

• Step3:-Formation of element stiffness matrix.

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Step4:-Assembly of element stiffness matrix to form a global stiffness matrix in the form KU=F where ,K=Global stiffness matrix

U=Model displacement matrix

F=Nodal force matrix

• Step5:-Application of boundary conditions and usage of elimination technique

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• Step6:- Calculating the primary data(Nodal displacement)

• Step7:-Calculating the secondary data(stress and strain)

• Step8:-Presentation of results by applying different theories of failure.

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Advantages


• Can readily handle complex geometry

• Can handle complex loading

• Special geometric effects can be modeled

• Can handle complex restraints

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Disadvantages


• The FEM is applied to an approximation of the mathematical model of a system

• Experience and Judgment are needed in order to construct a good FEM

• Susceptible to user introduced modeling errors

Poor choice of element types Distorted elements Geometry not adequately modeled

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Limitations


• Larger unwanted data

• Selection of proper mesh size is very difficult

• Incapable of handling incompressible fluids

• Obtaining material properties other than isotropic is very difficult

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General analysis in FEM


• Structural analysis

• Fluid analysis

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Stages of Ansys


Pre- processing

Processing(Solution)

Post -processing

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Pre-processing


• In this stage the following tasks are carried out

Building the solid model Selecting the proper element type Selection of suitable analysis type

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Post -processing


• In this stage results can be viewed or listed

• Data can be queried

• Multiple plots are possible

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Basic Definitions


• Geometry:-The area mathematics which deals with lines, shapes, points, angles etc

• Point:-It is the exact position on plane surface

• Line:-A set of points constitutes a line or

The distance between two points

• Plane:-Three non collinear points defines a plane or A flat geometry with zero thickness

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• Surface:-Boundary of a figure OR a finite area bounded by at least 3 or more lines, they may be curved

• Solid:-It is three dimensional geometric body free from cavities.

• Element:- The division of physical structure is called an element

• Node:-Is the most basic finite element entity

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Element Types


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• HYPER Beyond or Above normal

• MESH A material made up of a network of Wire or thread

Is a high performance finite element pre-processor that provides a highly interactive and visual environment to analyze product design performance

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Meshing


• Creation of grid on the surface.

• Discretization of a physical geometry is known as meshing

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Hyper Mesh Command Keys


• F1=Hidden line

• F2=Delete

• F3=Replace

• F4=Distance

• F5=Mask

• F6=Edit element

• F7=Node edit

• F8=Create node

• F9=Line edit

• F10=Check elements

• F11=Quick edit

• F12=Auto mesh

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Basic Element Types - Shapes


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Hyper Mesh Geometry Terminology


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There are four types of surface edges:

• 1. Free edges

• 2. Shared edges

• 3. Suppressed edges

• 4. Non-manifold edges


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• Free Edges

A free edge is an edge that is owned by only one surface. Free edges are colored red by default.

• Shared Edges

A shared edge is an edge that is owned, or shared, by two adjacent surfaces. Shared edges are colored green by default.

• Suppressed Edges A suppressed edge is shared by two surfaces but it is

ignored by the auto mesher. Suppressed edges are colored blue by default.


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• Non-manifold Edges

A non-manifold edge is owned by three or more surfaces. Non-manifold edges are colored yellow by default.


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How to Decide the Element Type


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Rules for modeling holes and fillets


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Basics of Finite Element Analysis


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3-D Element types


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Preliminary steps to be followed Import the geometry Geometry cleanup Check for symmetry Split the geometry Identify the critical features Assign collector Mesh Check for equivalence Check elements


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Symmetry


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unigraphics

Documents

element stiffness

element types

manifold edges

suppressed

free edges

ramaiah school

advanced studies

shared edges