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Smart Sensing and its Impact on Future Product Quality

Christian Boller�

Chair in NDT & QA (LZfPQ), Saarland University, Saarbrücken, Germany

6th CEOC - EUROLAB - IFIA International Safety Conference Brussels/Belgium, November 10, 2015

�

www.strassen.nrw.de

Ageing Infrastructure & Enhanced Maintenance Effort

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Lack of Quality in Civil Engineering

Source: www.matcoinc.com, www.engineeringcivil.com

Operational Quality of Pipeline Systems

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Source: FAZ

Source: Monitor

Source: WDR

Source: Spiegel

Quality in High Performance Structures

•  Load (assumed) –  Static Load: Ultimate Load –  Fatigue Load:

•  Constant Amplitude Load •  Random Load (Service Load)

•  Geometry (given) –  Notches –  Stress States/Multiaxial Loading

•  Material (to be selected) –  Strength –  Ductility

Load

Applied Stress

Allowable Stress

Allowable Stress >

Applied Stress ?

Structural Design

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Critical Crack Length

Detectable Crack Length

Cra

ck L

engt

h

Number of Loading Cycles or Time

ΔN

Δa

Damage/Crack Propagation and Inspection

Inspection Interval 1

Crack Length

Life (Flight)

detectable

critical

Inspection Interval 2

Inspection Interval 3

Inspection Interval ...

No Crack Found

Crack!!! ΔN/2

Defined by design

Defined by inspection

From Safe Life to Fail Safe

Damage Tolerance (the tolerance to live with cracks) Inservice Inspection is part of the design (Inspectability) NDT-based inspection/maintenance plan is configured along structural and fatigue design and defines the ‚hot spots‘ (concurrent or simultaneous engineering);

Safe Life A component is replaced after a defined number of load cycles with no critical damage; No inservice inspection required (NDT)

Fail Safe A derivative of damage tolerance; components can fail while others take over the loads. Only relevant in the case of accidental damage.

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The use of noninvasive techniques to determine the integrity of a material, component or structure

or quantitatively measure some characteristic of an object.

i.e. Inspect or measure without doing harm.

Definition of Non-Destructive Testing (NDT)

Source: NSF, www.ndt-ed-org

What is mainly associated with NDT today?

•  Standard –  Visual –  Vibrations –  Ultrasonics –  Eddy Current –  X-Ray –  Thermography –  Microscopy

•  Non-Standard –  Acoustic Emission –  Magnetics –  Nuclear Magnetic

Resonance –  Microwave/Radar –  Optical Coatings –  Nanoagents/-coatings

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Ultrasonics & Image Reconstruction

1x1 2x2 3x3 4x4 5x5 6x6 7x7 8x8 9x9 10x10 11x11 12x12 13x13 14x14 15x15 16x16

1

Phased Array Transducer

2 3

4

5 6

Phased Array Transducer

1

2 3

4

5 6

Off-line evaluation of clamp load by offline ultrasonic technique is state-of-art: The time-of-flight (TOF) of a longitudinal wave is measured before and after the fastening, clamp load and/or torque and/or elongation is calculated using appropriate calibrations.

L 0L ε

ΔL

U ltrason ic-p robeAmp litu d e

t-=2Lv

0

Δt#≈ ΔLΔt#≈ F, #σLo ng

Ultra

sonic-time8of

8flig

htUltra

sonic-pa

th-le

ngth

t -=2 (L + L )

v0 Δ

ε

Measuring Tensile Force by Ultrasonics

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N S

Hf-coil

Magnet yoke

Ultrasonic wave

Hall probe Cladding

EMAT-transducer for dynamic magnetostriction measurements

Electromagnetic Transduction

EC receiver coil

EMAT transmitter coil

EMAT receiver coil

Top view on coil

B

H

Saturation

Rotation

Irreversible motion Blochwall Pinning point

Reversible motion

Ferromagnetischer Werkstoff

Magnetic domains

Bloch walls

Externes Magnetfeld, H

Bloch wall movement

H H

Rotation

H

Ferromagnetic material External magnetic field, H

Microstructural Phenomena in Ferromagnetic Materials

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Barkhausen Effect

Heinrich Barkhausen (1881 – 1956)

Source: www.bbaw.de

Amplifier

Specimen

~ Actuator n.Elektromag

Simulated service time at 400°C [h]

Analogy between mechanical and magnetic hardness

EM measurement of hardness change due to copper precipitations in Cu-rich pressure steel 15 NiCuMoNb 5

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EM Measurement of Cyclic Fatigue

conventional measurand

ndt measurand

changes in micro- and macrostructure

e.g.

dis

loca

tion

reac

tion

form

atio

n an

d pr

opag

atio

n of

mic

rocr

acks

prop

agat

ion

of

mac

rocr

acks

incr

easi

ng

fatig

ue

dam

age

0.20

0.15

0.10

0.05

0.00 103 104 105

number of cycles

200

150

100

50

0

SAE 4140 σa = 620 MPa

Active Thermal Inspection Methods – Excitation by Ultrasound

Setup Sono-Thermography

IR Camera

Sonotrode

Specimen

Control unit

Time lapse Data acquisition Image processing Data analysis

Flaw IR Radiation

Ultrasonic transducer (50 W – 2.5 kW)

Sound (20 kHz)

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The Need for Automation in Inspection

•  More than 99% of inspection results are ‘nor failures found’

Photo: Airbus Photo: Sandia Labs.

Structural Health Monitoring (SHM)

•  … is the integration of sensing and possibly also actuation devices to allow the loading and damaging conditions of a structure to be recorded, analysed, localised and predicted in a way that non-destructive testing becomes an integral part of the structure. SHM is not an additional NDT application, nor QNDT, a fatigue analysis, vibration analysis, signal processing, material science or any other single technological area but rather lateral integration of all those in terms of a structure’s life cycle management.

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NDT Technologies Mainly Associated with SHM

•  Acoustics –  Guided Waves –  Acoustic Emission –  Piezoelectric Transducers

•  Eddy Current –  EM Foils

•  Modal/Vibration Analysis •  Miscellaneous

–  Thermal –  Comparative Vacuum

Monitoring

•  NDT with SHM potential –  Visual –  Ultrasonics –  Acoustic Emission –  Vibrations –  Magnetics/Eddy Current –  Thermography –  Optics –  Nanoagents/-coatings

Fibre-Optic Bragg Grating Sensors for Loads Monitoring

Intensity

Spectrum

Intensity

Spectrum

Filter

Photodetector

Intensity

Spectrum

FBG 1 FBG 2 FBG 3

Input Output

Fibre Optic Bragg Grating

Bragg Grating

Bragg-Wavelength Core

refractive Index

refractive Index-Modulation

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Piezoelectric fibre actuators

Electrodes

Piezofibres

Polymer matrix

Active strain

Source: www.tau.ac.il & Airbus

Piezoelectric Sensing & Actuation

Electromagnetic Smart Skins

Source: UCLA, USA

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•  Multi-layered (often 3) composite made of ferromagnetic layers (Fe- or Ni-alloys, Permalloy, 4-6nm) separated by paramagnetic, electric conductive layer (Cu, 3-5nm) of nm-thickness.

•  Spin-coupling exists because of small thickness, resulting in closed domains along interfaces.

•  Electric resistance of the device mainly influenced by scattering of the conductive electrons in the Cu-layer along the interfaces.

•  For the antiparallel configuration Rel is high.

Giant Magneto Resistors (GMR)

No field:

domain moment vector directions

With field:

Current direction

Giant Magneto-Resistance- (GMR-) Sensor

Sensitive Direction

Detectable Crackdirection

Hallsensor GMR

Giant Magneto Resistors (GMR)

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crack indications

sensor array

Crack Detection with GMR Sensing

Source: Fraunhofer IZFP

3D Printed PCB Using Additive Manufacturing

Source: www.additivemanufacturing.com

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Switch Box

Amplifier Data Acquisition

Processor

Amplifier Waveform Generator

Smart Suitcase™ Smart Layer®

with 12 transducers

Smart Sensing System with 1 input and output

What is a Sensor in SHM?

Sensor = Sensor System

Non-Destructive Testing has a Mission

Quality &

Life Materials Characterisation Damage Detection

Manufacturing Processes

Life Cycle Management

NDT for: NDT for:

conventional future

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Example: Bridge over Highway 202 in Wayne/NJ, USA

Established: 1983 Cost to rebuild: 11,9 Mio. € Year of analysis: 2010 Condition: Acceptable with minor damage in the primary structure

Source: VCE, ViennaAustria

Analysis Result: Bridge Highway 202 in Wayne/NJ, USA

Corrosion in Support Bearings

Enhanced dynamic loading due to settlement and increased traffic

Source: VCE, Vienna/Austria

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Residual Life: Bridge Highway 202 in Wayne/NJ, USA

No additional measures take Residual life 17 years Maintenance cost: 506 k€

Additional maintenance on support and deck structure, sealant and bearings Residual life 25 years Maintenance cost: 1.155 k€

Additional maintenance on support & deck structure, sealnat and bearings; modified structural dynamics Residual life 32 years Maintenance cost: 1.363 k€

1983 2103

Source: VCE, Vienna/Austria

Conclusion: Bridge Highway 202 in Wayne/NJ, USA

857 k€ invested today will allow a new investment of 11.900 k€ to be delayed by 15 years and will save the public 3.100 k€. This

is just one out of countless examples. 1983 2103

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Conclusion Monitoring Infrastructure has a Value

The Impacts

•  Longer operational life (or lighter weight design) •  Higher resource efficiency •  Higher operational reliability •  Lower operational cost •  Enhanced sensor integration •  More data management •  ‚Smarter‘ structures