DevTMF – Code of Practice for Thermo- Mechanical Fatigue Crack Growth

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DevTMF – Code of Practice for

Thermo-Mechanical Fatigue Crack Growth

S. Stekovic

a

_{, M. Whittaker}

b

_{, C. Hyde}

c

_{, S. Pattison}

d

_{, V. Norman}

a

_{, J. Jones}

b

_{, B. Engel}

c

_{, B. Grant}

d

_,

D. Leidermark

a

_{, R. Lancaster}

b

_{, J. Rouse}

c

_{, and S. Williams}

d

a

_{Department of Management and Engineering, Linköping University, Sweden}

b

_{College of Engineering, Swansea University, Swansea, United Kingdom}

c

_{Faculty of Engineering, Nottingham University, Nottingham, United Kingdom}

d

_{Rolls-Royce plc., Derby, United Kingdom}

TMF Workshop 2019

13-15 November 2019, Berlin, Germany

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• Introduction to DevTMF

• Experimental methods

• Results

• Conclusions

• Questions

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Background and motivation

This project has received funding from the European

Union’s Horizon 2020 research and innovation programme

and Joint Undertaking Clean Sky 2 under grant agreement No 686600.

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Strain controlled TMF:

EU CoP

ASTM E2368 – 10

ISO 12111:2012

Force controlled TMF:

A CoP developed by Rolls-Royce MTOC

TMF crack growth:

Not covered by CoP or standard

Investigated in isolation and with

limited conditions

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This project has received funding from the European Union’s Horizon 2020

research and innovation programme and Joint Undertaking Clean Sky 2

under grant agreement No 686600.

Background and motivation

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• P. Häfner, E. Affeldt, T. Beck, H. Klingelhöffer, M. Loveday, C. Rinaldi,

Code of

Practice for strain controlled TMF testing

, EU FP5 project TMF STANDARD

• S. Brookes, A. Scholz, H. Klingelhöffer, M. Whittaker, M. Loveday, A.Scholz, A.

Wisby, N. Ryder, R. Lohr, S. Stekovic, J. Moverare, S. Holdsworth, D. Dudzinski,

Code of Practice for force-controlled TMF testing

, Rolls-Royce MTOC

Development and

evaluation of

TMF crack growth

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Introduction to DevTMF

Clean Sky 2: Drivers and technical challenges

• Reduce perceived external noise by

50%

by 2020

and

65% by 2050

• Reduce fuel consumption and CO

₂

emissions by

50% by 2020

and

75% by

2050

• Reduce No

_x

emissions by

80% by 2020

and

90% by 2050

Vision 2020

and

Flight 2050

targets are

for new aircraft technology relative to

2000 performance

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Increase of operation and service life

Lower fuel consumption/environmental

impact

Optimised performance and efficiency

Reduced overhaul and replacement costs

Cost effective product

Enhance competitiveness

Market advantage

Higher turbine

temperature

McMillan (1956). ISBN 0-471-85546-4. LCCN 56002849.

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Introduction to DevTMF

Objectives:

Development of Experimental Techniques and Predictive

Tools to Characterise Thermo-Mechanical Fatigue Behaviour

and Damage Mechanisms

Funded:

Horizon 2020 and Clean Sky 2

Start date:

1 st

_{of Feb 2016}

Duration:

48 months + 6 months (extension)

Consortium

: 3 partners (Linköping University, Swansea University and the

University of Nottingham) and 1 topic manager (Rolls-Royce plc)

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Introduction to DevTMF

Objectives

• Validate TMF test methods

(both strain TMF and TMF CG)

• Generate accurate and high

quality TMF test data

• Develop material models

• Validate with component

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• To harmonise TMF CG experimental method between partners with

respect to appropriate heating/cooling methods, crack monitoring

techniques and specimen design

• To establish guidelines and procedures for local Code of Practice for the

tests at the consortium level

• To draft a Code of Practice with support from the HTMTC organisation

• To promote further collaboration towards standardisation of TMF CG

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Experimental methods

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o 3 laboratories

o 2 different specimen designs

o 3 different crack growth measurement methods

o 2 different heating methods

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TMF CG back-to-back testing:

• Validation of coil designs

• Validation of heating methods

• Validation of temperature measurement and control

• Pre-cracking procedures

• Effect of heating zone at crack tip

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SEN specimen

used at

Nottingham

SEN specimen

used at

Linköping

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TMF CG back-to-back testing

: heating methods

o Induction with different coil set-ups

o Infra-red lamp furnace

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• 400-750°C

• Stress controlled

• R=0

• In-phase (IP) and out-of-phase (OP)

• Variations in the pre-crack procedure

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TMF CG back-to-back testing:

TMF cycles

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Experimental methods

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• Pyrometer and thermography

offer non-invasive measurements

• Accurate temperature control with

thermography

• TCs unfavourable to weld

• TCs are complex set up

• Temperature at shoulder not

stable

• Surface emissivity and

pre-exposure can cause shorter fatigue

life with pyrometer but not with

thermography

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TMF CG back-to-back testing

: crack growth measurement methods

o Direct Current Potential Drop (DCPD)

o Compliance method

o Alternating Current Potential Drop

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Experimental methods

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TMF CG back-to-back testing:

effect of lamp furnace vs induction coil, Swansea

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Results

Ti-6246 CC tested at the same isothermal conditions,

using three different heating methods

CG rates are consistent across heating methods

For OP no evidence seen of variability in CG rate

Similar results in IP tests but more variability in CG

rates overall

J. Palmer et al., Development of test facilities for thermo-mechanical fatigue testing.

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OP CG rates are consistent

between the laboratories

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IP CG rates are mostly consistent

between the laboratories

Faster crack growth rates in one

specimen from LiU (dominated

by microstructure effect)

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Results

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Recommendations:

• Heating methods – effect of induction on DCPD negligible

• Coil design – non-uniform multi-turn longitudinal field helical coil

• Pre-cracking procedure – different stages

• Temperature measurements – use of thermocouples, pyrometry and

thermography

• Crack tip heating – no significant effect

• Specimen design – similar results obtained

• Accurate readings from both DCPD, compliance method and ACPD

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Disseminate the project results

Share experience on TMF CG testing

Answer your questions

Discuss next steps:

• Support CoP (who, how)

• Back to back testing (include more laboratories)

• Funding sources

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Transferring the results of DevTMF into Code of Practice:

• Share with the HTMTC members for comments and feedback

• To be published under the HTMTC umbrella and forwarded to the ISO

TC164 SC4 WG6 convenor

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Conclusions

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• Reproducibility and repeatability of the TMF CG results

• Robustness of the TMF CG testing and dependency on test laboratory

• Towards standardisation of TMF CG test method

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