The document describes the adaptation of a tool to replace dampers in the accessory gear box (AGB) of a CFM56-7B aircraft engine. It details modeling the tool and surrounding components in Creo and analyzing the tool's strength under load in ANSYS. The analysis found the maximum stress was below the material yield point with a safety factor of 1.74. The tool and high-load bolt would be made from titanium, while other parts use structural steel. Accuracy was limited by incomplete engine specifications. Reanalysis with more precise weight and mount dimensions is recommended.

1. Internship Supervisor: Amine Rahoui
Intern: Yassine Rayad

2.  The problem at hand involves changing the
dampers of the accessory gear box LH
forward mount.
 The ESM does not have a detailed procedure
for this task that does not involve the removal
and inspection of the AGB.
 The goal of this project was to adapt an
existing tool (used for the damper change on
the CFM 56-3 engine).

3.  CFM56-7B

4.  AGB LH FWD Mount

5. These are the dampers
that are required to be
changed using the
adapted tool.

6.  In order to avoid having to remove and
inspect the entire AGB module, the proposed
solution involves supporting the AGB in the
same position to facilitate the damper
change.
 The tool shall be fixed to the AGB LH FWD
Mount and to the AGB itself.

7.  At this point it is important to note that in order
to perform an accurate analysis of the required
strength for the tool, we must have an accurately
modeled environment.
 This was not completely feasible as the
environment was modeled from the ESM which
does not provide all the necessary dimensions.
 Despite the simplicity of the load case (static
weight loading) the difficulty of modeling the
environment as close to reality as possible made
the project more complicated than it needed to
be as many dimensions and distances had to
measured physically on engines being
maintained or repaired.

8.  The geometry was modeled and assembled
using Creo Parametric 2.0.
 The assembly file was saved in the .igs and
.stp format to allow access with other
software.
 The assembly was then imported into a Static
Structural analysis block in ANSYS Workbench
R14.5.

9.  The modeled environment
◦ The AGB LH FWD Mount
 This is one of the most important parts of the environment and was
modeled mostly from the ESM. Some dimensions such as the distance in
between the two parts were measured physically on a few engines using
a Caliper. This part supports the AGB from the top.

10.  The modeled environment
◦ The AGB Mount Link Assembly
 This part consists of a link with three holes and three fitted bearings. It is
used to link the AGB with the AGB LH FWD Mount. Since inspection of this
part is required in the ESM, key dimensions are given and we were able to
represent this part with better accuracy than the rest of the environment.

11.  The modeled environment
◦ The AGB
 “The Accessory Gearbox (AGB) assembly is mounted on the left-hand side of the fan frame at the 9:00 position. It consists of a
gear train that reduces and increases the rotational speed to meet the specific drive requirements of each accessory.” (ESM
TASK 72-63-00-870-001). For our purposes, the AGB can be considered simply as a static load on the tool being designed.
Considering the difficulty of modeling the entire AGB accurately, we opted for a geometric solution in which we plotted a 2-D
image of the AGB on Creo and traced it. Furthermore, we scaled the part based on some reference dimensions given in the ESM.
This allowed us to get a general visualization of this gearbox and also made it possible to estimate its volume. Since this key
assembly in the engine is made up of multiple parts made from different materials, a general mass was estimated using a forklift
scale device. The mass found was 110 kg.

12.  The modeled tool
◦ As can be seen in the figures below, the tool is attached to the AGB LH FWD Mount via the
points shown. It is important to note that for this solution, the modeled environment was
simplified by omitting the bottom AGB mount. Therefore, the tool designed here is required
to sustain a larger load than it would realistically be required to sustain. Additionally, we
considered a factor of safety of 1.5 in the following static structural analysis. The stress and
deformation results are shown in the following slide. Material selection is also dealt with in
the following slides.
Attachment
points

13.  The mesh shown below is the final refined mesh used in the
latest iteration of the analysis. Element sizes range from
approximately 4-5 mm for the AGB mount and the tool to 10
mm for the AGB. As we can see in the Element Quality Metrics
figure, the element quality is adequate and acceptable.

14.  Stress and Deformation
◦ As can be seen in the figures below, the maximum stress experienced by
the tool under the static load previously described is 533.9 Mpa and
occurs on the bolt that connects the tool to the AGB. The maximum
deformation occurs at the same point with a value of 1.0278 mm. With
these values, we are able to select the appropriate materials.

15.  The tool as modeled should only consist of one part and all the attaching bolts
and screws. In order to address the 1.5 factor of safety, it was decided that the
tool should be manufactured from Titanium as well as the bolt that connects the
tool and AGB. The rest of the parts can be manufactured from Structural Steel. The
following figure displays the overall factor of safety distribution throughout the
tool. The minimum factor of safety which were able to obtain is 1.7419.

16.  In conclusion, a tool for the replacement of dampers in the AGB
LH FWD Mount for the -7B engine was adapted from an existing
tool designed for the -3 engine.
 The attachment points to the engine (flanges B4 and B5) via the
AGB LH FWD Mount were modified to fit the -7B engine
environment.
 It is important to note that the reference dimensions for
modeling the environment accurately were not all available in the
ESM or the EIPC. Hence, certain geometric assumptions were
made. It is safe to say that the model is close to real environment
but there are some unverified dimensions.
 I strongly recommend that the analysis be carried out again with
an accurate weight for the AGB as well as a full model of the AGB
mounts (top and bottom). I also recommend using the original
part dimensions from the manufacturer for the AGB mounts, as
the design/adaptation of the tool depends heavily on these
dimensions.