Tech Briefs Magazine - October 2021 - MD-13

Staying on Track: Performing
Analyses with COMSOL
Multiphysics
Using COMSOL Multiphysics and its
add-on modules, the Raychem team
structurally optimized the individual
components of the ATD, while also
performing a multibody analysis to
study the coupled motion of these
components for a system-level analysis.
The team first imported a typical
assembly (Figure 2) and then applied
the appropriate boundary conditions
to account for the effects of dynamic
loading. They performed a study to
find the tension in the outer cable
along with the variation in spring
force. The results of the analysis
(Figure 3) represent the cable displacement
and tension. It can be clearly
seen that the tension remains
unchanged, which accomplishes one
of the objectives of the project.
For the modular cantilever, an initial
model was imported into COMSOL
Multiphysics. While analyzing the
cantilever model, the team quickly
realized that the MC was rather bulky
and the stresses were distributed un -
evenly. They then performed a structural
optimization of the design and
carried out a multivariable optimization,
where the minimization of total
strain energy is set as an objective
function along with the minimization
of total mass criteria.
Using topology optimization, the
system's mass was reduced by 75%
compared to the initial geometry
(Figure 4, left) without violating the
design specifications. A 3D model was
then created using the optimization
study and later subjected to both static
and dynamic structural loading (Fig -
Fixing
Figure 2. Geometry of the ATD.
Pulley
ure 4, right) to emulate the impact of
a train moving at 250 km/h.
Riding Forward: How Structural
Analyses Helped the Team
Using the observations from the simulation
analyses, the entire ATD assembly
was completely redesigned to incorporate
a foldable design with a 50% reduction
in the assembly size. Moreover, the
team also replaced the metallic spring
with a polymer spring, which was de -
signed using the Nonlinear Structural
Materials Module, an add-on to the
Structural Mechanics Module and COMSOL
Multiphysics. All of these design
changes led to an 80% decrease in the
weight of the entire assembly. " With the
help of the structural and multibody
analyses we performed on the ATD, we
were able to reduce the number of components
from 20 in the earlier design to
just eight, " said Jain.
25000
24000
23000
22000
21000
20000
19000
18000
17000
16000
15000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Cable Displacement (m)
Figure 3. Cable displacement on the applying load (left) and tension in the cable (right).
Motion Design, October 2021
Cov
ToC
13
CAM
Further, a simulation model was es -
tablished to optimize the conventional
overhead modular cantilever with the
help of topology optimization in COMSOL
Multiphysics. The resulting mod -
el was used to create a simplified de -
sign concept and was later subjected to
a detailed structural analysis in terms
of strength and vibration modes to verify
the optimized results. Simulation
was instrumental in reducing the de -
sign complexity, with the number of
components reduced from 12 to 5 and
the weight reduced by approximately
33%.
Out of the two designs proposed, the
Indian Railways Board has already
accepted one design while the other is
in the approval stage. According to
Jain, " Structural optimization of the
modular cantilever assembly with COMSOL
has enabled Raychem to secure
four patents for our different designs. "
Tension in the Cable vs. Displacement of Cable
Fixing
Spring Casing
Cable
Cable Tension (N)

http://info.hotims.com/79418-936

Tech Briefs Magazine - October 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - October 2021