Download Lab 2 - Report

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In this experiment, we performed structural static analysis on 2D and 3D truss structures
and also on simple beam elements by considering only steady loading conditions and
ignoring inertia, damping and time varying loads. Static analysis is used to determine
displacements, stresses, strains and forces in structures. In order to perform static analysis
using a finite element analysis software such as ANSYS, the following steps are followed:
1. Build the model
2. Set solution controls
3. Set additional solution options
4. Apply the loads
5. Solve the analysis
6. Review the results
2D Truss Structure
In truss or frame structures, simple elements can be combined together to form larger
structures which are load axially and bending is not considered. First, the model is built by
defining the key points or nodes and then the lines or elements. Following that, the element
type is selected as LINK180 to build the truss structure as there is only axial loading in the
structure and the material properties are defined. On page 27, the lab manual states a
procedure to create the link elements and specify constrains which applies to an obsolete
version of ANSYS. For the current version of ANSYS, to add the link element, we should
use the element type command and add a link element from the sections sub menu. To
define the material properties, the material model command is used from the material
properties sub menu. Then, the element is meshed by defining the meshing size for the
various elements. To specify the geometric constraints, in the solution stage, displacements
and force/moments are applied on key points. At that point, this allows us to solve the
system and review the results in the post processing stage. We can now review and validate
the results by either listing the reactions on certain nodes or elements, define element tables
to see axial stress or member forces and create contour plots and graphs from the element
tables that can be saved.
3D Truss Structure
For 3D truss structures, the finite element analysis procedure is the same as for 2D
structures, except that 3D geometry is defined.
Beam Elements
Beam elements are fundamental structural elements as they are present in most organic
structures such as bones in humans or branches in trees and in most inorganic structures
such as buildings or wings in aircrafts. Beams may be subjected to either distributed
loading or point loading and often involve torsion and transverse loading as well. To create
the beam geometry, similarly to truss structures, key points and lines are defined and then
either BEAM 188, for linear finite strain beams, or BEAM 189, for 3D quadratic finite
strain beams are selected as the element types. In the lab manual on page 43, BEAM3
should read BEAM 188 and BEAM4 should read BEAM 189. Furthermore, the beam’s
cross-section has to be defined from the common sections sub menu located under beam
sections.
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