msc. thesis presentation by kevin morales mc lernon · msc. thesis presentation by kevin morales mc...

The information in this presentation is proprietary and confidential and shall not be disclosed to or

used by a third party unless specif ically authorised by the relevant GKN plc group company.

Bi-Metallic design of mount lugs for a jet engine

components using additive manufacturing technology

1

MSc. Thesis presentation by Kevin Morales Mc Lernon

Proprietary and confidential restrictions on title slide apply throughout this presentation

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Presentation Overview

This presentation covers the most fundamental aspects of the thesis work, and proceeds as following:

1. Background and Problem description

2. Objectives Realization/Execution

3. Results Showcase

4. Discussion

5. Conclusions / Further work


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Problem description

A current performance trend indicates increased exit temperatures in future jet engine designs

which in turn requires the use of incremental ”thermally robust” superalloys.

The problem in question concerns the TRS ( Turbine Rear Structure) – A structural and

aerodynamic element located at the rear of the engine. Its primary functions are :

• Serve as structural support for connecting

the engine to the aircraft pylon.

• House the rear LP (Low pressure) rotor rear

bearing and provide tubes for oil.

• Correct the aerodynamic swirl.

• Connect the plug and many other jet engine

components.


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Problem description (continuation)

• This increase in temperature means that the super alloy Haynes 282 is more suitable when compared

to the previously used Inconel 718:

This material can withstand higher temperatures (maintain its mechanical an creep/oxidation resistance) than

IN718, yet its mechanical properties ( UTS, YTS ) are significantly lower (especially for certain manufactured

conditions) and therefore a re-dimensioning for many elements would be required, which is particularly

disadvantageous for some elements, such as mount lugs:

– Increased dimensions could give clearance problems in the engine-mount connection, which requires

coordination with the aircraft manufacturer and must be avoided.

– Increased weight if lugs where to be made thicker


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Why is IN718 desirable over H282 in the lugs?

• If one wishes to maintain the lug width (and pin and bushing size) – and comply with a

certain Margin of Safety (MoS):

Equal geometry and loading but a different allowable (Yield stress) – Gives a different MoS for each

material (At a specified temperature):

It is important to notice that the lug region operate in a temperature ranges that is perfectly suitable for

IN718, and H282 is only needed in the hotter regions.


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Thesis Objectives

To study the feasibility of additive manufacturing the lugs in IN718 over a Haynes

282 TRF :

1. Identifying appropriate AM methods – Through literature and interviews with various engineers through

the company.

2. Identifying what design considerations one has to take when implementing this technology. – Automated

process (Largest part/current focus of the thesis)

3. Interpreting the results and addressing the unknowns/further work to enable a more thorough study.

Haynes 282

Inconel 718


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Objectives Realization/Execution

1. Identifying suitable AM methods

• Implemented as a descriptive study:

1. Look at what AM methods are practical: Build resolution, tolerances, speed, part

complexity, obtained mechanical properties, etc…

2. Find papers on the considerations one has to have when implementing AM

3. Interview engineers at the company and consider the existing knowledge / technology

level and available machines at GKN


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Sector (Without Lugs) Lugs

Casted

PBF

EBM

LBM/SLM

SLM

PBF

EBM

LBM/SLM

Selective Laser Melting (SLM)

Electron Beam Melting (EBM)

Electron Beam Forming

(Usually wire)

Cast

Laser Metal Deposition

Summary – Method permutations


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2. Identifying design considerations

One of the most critical design choices is the interface positioning – One must avoid the stress “Hotspots”

in such interface. – If there is any plasticity in the bimetallic interphase numerous problems would arise.

As an automated process:

1. Use a parametric TRF model – The geometries can be changed by associated expressions linked to certain

dimensions:

2. Set up a mesh and analysis process “connected” to the geometry → when the geometry is updated so is the

mesh/analysis.

3. Run this process for numerous designs and analyze sensitivities.


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The interface position and shape greatly affects the applicable manufacturing method:

Flat interface and fixture: PBF methods ?

Non planar geometry:DED methods?


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Automated process description

1. Parametric model: Initially only lug geometric parameters

2. “Baseline Model” All .prt ,.fem and .sim files linked within the SIEMENS NX Simcenter PLM

(Product Lifecycle Management) software. An update from the geometry is transferred down the tree

3. “Design of experiments” (DOEs) A file that lists all design parameters to be evaluated


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Resulting automated process overview


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How?

• By Setting a baseline linked process and

using a script to execute it automatically +

loop it for all the designs:

With Visual Basic (Vb) code that

Simcenter executes.

+

ANSYS APDL script for Postprocessing


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Model setup considerations

Node selections for

Postprocessing (updated for each

design)

Loading and mechanical constraints

Mesh mating (Ensuring correct

mesh between bodies)


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3. Analysis and interpretation of the results

Once the data is extracted and processed one can correlate certain design parameters (or

showcase a method to do this) with the AM process:

• Position of the interphase

• Morphology (shape)

• Applicable AM method to obtain desired geometric quality/ mechanical properties / manufacturing

“practicality” – With current or possibly future AM machines.


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Results examples

Contours for lugs with different

interface positions

Stress distributions for different lug morphologies

Interface stress distributions


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Result examples

Multiple lug geometries with associated interface positions (4 variations in the

“showcase study”)

Fillet variation effect on “duck

feet” stress hotspots


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Design of an interface for a known stress distribution

No “optimum” interface has been obtained in

this study yet, due to:

- Method simplifications

- Dependent on the loading conditions

- Actual trustworthy results require including

more aspects such as crack propagation

If the stress distribution is known – For a particular

geometry and loadset – then one can design the

interface shape to minimize the stress levels present

in it (Avoid “hotspots”).


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Endless design possibilities !


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Conclusions

• The existing Product Lifecycle Management Softwares (Such as Simcenter 3D) enable the

rapid generation and analysis of models for design exploration, which coupled with versatile

manufacturing methods (such as AM) give the engineer a design freedom that is

unprecedented.

• Implementing such automation processes is accessible thanks to an extensive documentation

and online support / coupled with the developer options that the software facilitates.

• If one looks at the potential/limitations characteristics of each method (Obtained mechanical

properties, resolution, build size, porosity, etc…) – Selective Laser melting (SLM) sets a

promising option if the following conditions are met:

• Planar interface

• Fixture specific to enable a flat surface

• Machine with enough space to include the fixture and H sector.

• Possibility of changing powders during build


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Conclusions (continuation)

• If these conditions are not an option (a machine would have to be specifically tailored for this purpose)

then directed energy deposition processes, specifically LMD-p is a proven and viable option to print

on existing parts (the interface would have to comply with the muti-axis head that holds the DED

nozzle).

• There are numerous questions regarding the manufacturing method that transcend the AM application:

• Bimetallic Heat Treatment – How to implement a treatment suitable for both materials.

• Hot Isostatic Pressing – Necessary to reduce porosity and better mechanical properties

• Non Destructive Testing - Ensure reproducibility and reliable quality methods

• Further Machining of surfaces to comply with tolerances and related to mechanical life aspects -

As interface to the pylon the lugs must comply with tight dimensional tolerances.


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Further Work

Here are some recommended proposals on how further development of this method

could take place:

• Constraint the DOE space to avoid evidently flawed lug designs and implement a sensitivity study to

restrict the number of parameters to use.

• Introduce the process in an MDO framework.

• Understand material/microstructural properties of the interface and how different manufacturing

parameters affect its characteristics.

• Include more complexity into the simulation with a pin/bushing connection, suitable load set, thermal

conditions and non-linear material data.

• Create a crack propagation study for bimetallic AM methods / or design practice to address this.


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Thank you for your attention!

Any Questions ?

msc. thesis presentation by kevin morales mc lernon · msc. thesis presentation by kevin morales mc...

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