Exploring Structural Integrity: A COMSOL Analysis of Truss
Systems.
Michael Rubbo
MNE 252
Prof. Vijay Chalivendra
2/14/2024
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Intro
In the initial COMSOL laboratory session, the focus was on analyzing the maximum
stress and deflection in a support structure, specifically a supporting truss for a helicopter. The
purpose was to analyze the truss problem and see how much forces and stress were in each beam.
This would allow a engineer to know what parts are needed in a truss structure and what parts are
carrying the most load. This was all done by utilizing proficient methods in COMSOL which
would allow us to analyze this problem while comparing it to our handwritten solutions.
Objectives
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Object model sketched accurately.
Material properties defined accurately.
Boundary conditions and loading scenarios applied.
Deflection cannot be over .5 in
Comprehensive analysis conducted.
Better understand how a truss functions
Post-processing activities completed successfully.
[Fig.1] Truss problem
schematic
In the recent lab session, COMSOL was used to analyze a stationary truss problem [Fig.1] step by
step. First, create the shape of the problem by marking points (x,y) into COMSOL , making sure it
matched the distances of the real structure. Then, set material properties (check table 1 ) which are
important for how the structure behaves in the software. Its important to note that these crosssectional areas were determined on the bases that each link does not surpass 25,000 psi. In the prelab
the forces of these links (see APPENDIX) were solved, those calculations were used to determine
what the best cross-sectional area would be on each beam. After that, boundary conditions were
added which involved pinning the points that are attached to the helicopter, allowing the program to
know that the structure is fixed at those points. Next, two 10,000-pound loads were placed on each
side of the helicopter truss in the program, to allow COMSOL to accurately predict the behavior of
the truss. Once everything was set up, COMSOL computed to give us results [Fig.1]. [Fig.1]
accurately depicts the displacement of the helicopter truss under load. Finally, numerical results were
obtained, this is called the post processing section of the lab. In this section displacement in
horizontal and vertical directions, total displacement in the truss points (check table 2), Reaction
forces in the ( x,y) directions (check tables 3), axial forces (check table 4) and axial stress in the links
(check table 5) were found. Lastly, we compared the axial forces of the theoretical hand written
calculations (table 6) to the COMSOL derived solutions. the handwritten calculations on axial force
were achieved through method of joints (refer to the APPENDIX for the pre lab), and they matched
COMSOL solutions. Please note that each beam and node number is represented in [Fig.3]
and [Fig.4] .
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Deflected truss [Fig.1]
Node Numbers [Fig.3]
Beam Numbers [Fig.4]
Non-Deflected truss
[Fig.2]
2
5
3
1
7
4
6
3
8
7
9
5
6
1
2
3
4
Table 1 Material Properties
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Table 2 Deformation Values
Table 3 Reaction Forces
Table 4 Axial Force In Each Beam
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Table 5 Axial Stress In Each Beam.
Table 6 Theoretical Force In Each Beam.
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word
Discussion
The lab experiment results show that the structural elements under review performed properly, as
no recorded deflection was greater than 0.5 inches, even when subjected to a maximum axial
force of 22360 lbs (Table 4). This implies that when significant loads were placed upon them, the
materials remained stable and safe. The exact simulation of structural behavior of [Fig,1] was
made possible by the material settings entered into the analysis software (see Table 1).
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COMSOL was able to produce an in-depth figure that showed the deformation of the structural
model under load conditions. Understanding the response of the structural elements and how
they behave in actual situations was made easier by the useful insights this COMSOL offered.
This allowed engineers to optimize designs while maintaining safety requirements. Through the
identification of load distribution and deformation patterns, the study improves our
comprehension of the theoretical and real-world applications of truss systems. By using this
information, engineers may improve the structural designs' dependability, safety, and efficiency,
thereby improving any structure they want to evaluate using COMSOL
Conclusion
The objective of this lab was to use COMSOL Multiphysics to design and examine a truss
structure that extends off the front of a helicopter. The truss was constructed in COMSOL using
exact coordinates. Boundary conditions held the truss ends in place, and two 10,000-pound loads
were used to simulate the weight of the helicopter basket truss. COMSOL’s study showed
extensive results on how the truss deforms when loads are applied to it. Numerical values for
axial stresses, reaction forces, axial forces in each member, and displacements in the horizontal
and vertical directions along the truss were produced after the data was post-processed. The
method of Joints technique was used to manually compute values, and the results matched the
axial forces from COMSOL. Lastly, it was demonstrated that the truss design remained safe
under load since there was no breach of 25,000 psi and the maximum deflection allowed was less
than 0.5 inches. COMSOL’s simulation and analysis allowed for an in-depth examination of the
truss performance and design optimization. By contrasting the software results with theoretical
manual calculations, the accuracy of the COMSOL model was further validated. All in all, the
lab demonstrated how to use COMSOL Multiphysics to accurately model a truss and further
understand its behavior under load.
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Appendix
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Appendix
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Appendix
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