Degradation Analysis Techniques Degradation Analysis Techniques Dr Pavan Addepalli, Research Fellow...

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Degradation Analysis Techniques

Dr Pavan Addepalli, Research Fellow

03 June 2019

2 © Cranfield University 2019

• Overview

• Degradation Drivers & Failure Modes

• The ‘Big Five’ NDT

• The maintenance perspective

• USE Case: Active Thermography

• Summary

Outline


Loss of relevant properties that determine the performance of the material and or a part

belonging to the asset

Natural or induced

Results in the form of a physical, mechanical, material or chemical phenomena

Intrinsic or specific to operational activity of the asset

Overview

Deterioration

A continuous process pertaining to the deterioration of the structure of the part / asset

Driven by a combination of deterioration mechanism / physics and the operation of the asset –

loading conditions & service environment

Degradation


Why is this important?

http://www.youtube.com/watch?v=9m7zRLJEIvw



http://news.bbc.co.uk/1/hi/world/europe/986737.stm

http://www.deltatest.de/en/dienstleistungen/turbinenschaufelpruefung.php

http://news.aviation-safety.net/2012/04/17/atsb-releases-report-on-qantas-

boeing-747-uncontained-engine-failure



http://www.cnde.iastate.edu/ultrasonics-and-composites/modeling-cracks-and-delaminations-carbon-fiber-composites-frank-margetan

http://news.bbc.co.uk/sport1/hi/other_sports/sailing/1364392.stm

Crack



http://www.telegraph.co.uk/news/newstopics/howaboutthat/4206116/UFO-turbine-mystery-the-theories-in-full.html

https://www.nde-ed.org/GeneralResources/IntroToNDT/GenIntroNDT.htm


Degradation Drivers

Use Case: Precision Ball Bearings


Failure Modes

Source: ISO 15243:2017


Cause-Effect Model

Use Case: Precision Ball Bearings


The ‘Big Five’ NDT techniques in industry

Radiography

Ultrasound

Eddy current

MPI

LPI

Magnetic

particle

Magnetic field

Crack

N SS

N


The maintenance perspective

Inspired by: Non-destructive inspection techniques to determine structural distress indicators in water mains Rajani, B.; Kleiner, Y.

Evaluation and Control of Water Loss in Urban Water Networks, Valencia, Spain, June 21-25, 2004, pp. 1-20

Asset with low cost of failure Asset with high cost of failure


The maintenance perspective

Inspection effectiveness is assigned a value of 1 (low), 2 or 3 (high) according to the reduction of probability

of failure that it produces in a particular case. To reduce the probability of a component failure from high to

low would require a high level of inspection effectiveness, whereas to reduce the probability from medium to

low would require a medium level inspection effectiveness.


Aim:

Better visualise the damage of composites in a relatively easy-to-use way and automatically and

quantitatively measure the properties of the degradation.

Use Case: Active Thermography

Degradation Assessment of Composites

Specimen

Preparation

Thermography Inspection

Feature Extraction

ClassificationDamage

VisualisationValidation


Active Thermography: Principle

asource: G.C.Holst,”Common sense approach to thermal imaging”, p.320, SPIE Press, Bellingham,WA(2000)bsource: Thermal Wave Imaging Inc,”ThermoScope II®user manual”,Ch.5Thermal Equations & Calculations, TWI Inc,Frendale,MI(2011)

ThermoScope

Pulsed

Flash

Pulsed

Flash

Temperature decay of a point from a

temporal sequence of thermal imagesa, b


Visualisation 1: RAW Thermal Image

RAW TSR

1st Derivative 2nd Derivative


Visualisation 2: Temperature decay curve

TSR 1D 2D

TSR

contrast

1D

contrast

2D

contrast


Comparison of thermography, X ray and Ultrasonic imaging

Detection of Foreign Object Debris in a graphite-epoxy sandwich panel

TWI Thermography X-Ray UT (transmission)

Thermal Wave ImagingTHE ART OF INSPECTIONSource: Thermal Wave Imaging Inc.


Clustering results using the CCA method

The classification results based on the scatter of the first order coefficient and the second order

coefficient for all specimens, where the green colour denotes the detected sound pixels and the red

colour denotes the detected damaged pixel.


Case study of CCA – Impact Damage

Snapshot of 6 studied specimens. Left: Impact damage is visible from the impacted side of the specimens;

right: the rear surface of the samples present invisible or subtle evidence of damage.

Visualisation of the detected defect area

for all specimens in the binary form

Reconstructed data visualisation of

damage across a range of samples,

where the colour indicates the complexity

of damaged structure.


Measurement

Colour Binary Connected

component analysis

Damage

enhancement

Sizing


Fingerprint – Area visualisation

The patterns were produced using Shepard’s method.

S. Shepard, Y. Hou and J. Lhota, "Quantitative characterization of thermographic sequence data," in 16th WCNDT 2004 - World Conference on NDT, 2004.


Thermal material property measurement

Thermal diffusivity measurement for a defect-free composite sample using a novel nonlinear system identification

(NSI) method. Left: the map of measured thermal diffusivity; right: the histogram of measured thermal diffusivity.


A Confidence Map based Damage Assessment Approach

1. Defect detection

2. Confidence map

3. Depth map with high confidence


Summary

• Degradation in high-value products (gas turbine and aero-engines) is a demanding and

challenging area and understanding & establishing a cause-effect model will help maintain the

asset

• Such damage reduces performance and shortens the life of the product

• Potential to cause ‘in-service’ product failure and the need for multiple maintenance strategies is

essential

• Response strategies in design and service conditions based on degradation and mitigating their

propagation mechanisms is the current trend

• Non-destructive inspection is a mandatory requirement during service to evaluate the remaining

component life

www.through-life-engineering-services.org

Thank you for your attention

Dr Pavan Addepalli

Research Fellow in Mechanical Component Degradation Analysis, SATM

TES Centre, Building 30, Cranfield University, Cranfield MK43 0AL. UK

T: +44 (0)1234 758346

E: [email protected]

Degradation Analysis Techniques Degradation Analysis Techniques Dr Pavan Addepalli, Research Fellow...

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