am part integrity: the ndt in-process and post-build...
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AM part integrity: the NDT in-process
and post-build perspectives
Ben Dutton
EIS Seminar - AM
18-06-2019
MTC, Coventry
Contents
In-process NDT
Post built NDT
Post built Metrology
NDT standard
AFRCAdvanced Forming Research Centre
CPICentre for Process Innovation
NAMRCNuclear Advanced ManufacturingResearch Centre
AMRCAdvanced Manufacturing Research Centre
MTCManufacturing Technology Centre
WMGWarwick Manufacturing Group
NCCThe National Composites Centre
MTC also hosts the European Space Agency (ESA) AM Benchmarking Centre since May 2017
HIGH VALUE MANUFACTURING CATAPULT
MTC has become the first ASTM AM Center of Excellence (CoE) in Europe since July 2018
MANUFACTRUING INNOVATION
Dimensional & surface Metrology and NDT
M&NDT: TECHNOLOGY COVERAGE HIGHLIGHTS
High-precision tactile instruments High-precision optical instruments Portable tactile instruments Portable optical Instruments
Tactile surface measurement Optical surface measurement Portable surface measurement Microscopes
3D Computed Tomography Computed Radiography
Portable NDT (phased array ultrasound, eddy current flexible array, x-ray backscatter and GPR)
Non-contact laser ultrasound inspection
Dimensional Metrology
Surface Metrology
Non-destructive Testing
In-process NDT
Potential advantages
• As other manufacturing processes, additive manufacturing (AM) inspection has typically relied on post-process/post build NDE, but due to AM’s geometrical complexity, surface finish, material density and in particularly large parts, ideally NDE would be better placed at an earlier stage.
• AM process has a unique advantage due to its build process: layer-by-layer or bead-by-bead, hence both process monitoring and inspection may be exploited.
• Current AM in-process monitoring relies mainly on surface measurements, potentially missing subsurface defects. Additionally AM processes are at high temperatures. NDE methods such as Laser Ultrasound Testing (LUT) have the potential to detect both surface and sub-surface defects making it ideal for AM.
In-process NDT
LUT on calibration and real Powder Bed AM samples
Courtesy AMAZE EU project
Calibration and real samples tested
• Calibration samples consisted of Ti64 cuboids with dimensions (10 x 10 x 30 mm) with Electric Discharge Machining (EDM) through holes (400 µm diameter) representing subsurface defects.
• AM part with process subsurface isolated 200 µm and 300 µm gas pores.
Why LUT
• LUT, being a non-contact ultrasound testing method, is capable to work at elevated temperatures of at around 1000 C, and the system at the MTC is capable to work on rough samples which are expected to be in AM process.
• Research based unit with capability for integration to industrial applications
• MTC has been working on projects showing LUT capability for some AM industrial applications.
In-process NDT
LUT on a DED AM Titanium sample with LOF defects
Capable to detect fusion irregularities between side by side and top and bottom beads.
Sample and scan details A-Scans B-ScansCourtesy AMAZE EU project
In-process NDT
LUT integrated demonstration
Courtesy AURORA IUK project
In-process NDT
LUT integrated demonstration
Courtesy AURORA IUK project
Video
In-process NDT
LUT detection of isolated bulk pores in laser powder DED
Courtesy OpenHybrid EU project
Scan
dir
ecti
on
15
mm
Rayleigh wave
Diameter: 0.270 mmDepth: 0.330 mm
Diameter: 0.300 mmDepth: 2.700 mm
Diameter: 0.200 mmDepth: 2.700 mm
XCT vertical slice
LUT B-scan
Sample picture
• LUT showing capability to detect isolated pores in a TiDED as built sample
Post built NDT Potential
Methods capability: selector tool output for a simple block with machined surface finish
Courtesy AMAZE EU project
Class Type Sub-type Including… Surf
ace
brea
king
crac
ks /
lack
-of-
fusi
on
Surf
ace
brea
king
void
s
Inte
rnal
cra
cks
/
lack
-of-
fusi
on /
laye
r def
ects
Isol
ated
/
clus
tere
d
poro
sity
Inte
rnal
voi
ds,
incl
. cro
ss-l
ayer
defe
cts
Incl
usio
ns
Trap
ped
pow
der
(Pow
der B
ed
Fusi
on o
nly)
Nea
r sur
face
mic
rost
ruct
ure
vari
atio
n
Sub-
surf
ace
mic
rost
ruct
ure
vari
atio
n
Nea
r sur
face
resi
dual
str
ess
Sub-
surf
ace
resi
dual
str
ess
Contact or near-contact (a i r-
coupled)
Single / twin / array probe,
Time of Fl ight Di ffraction
Immers ion
Vibration analysis Resonance testing
Acoustic pattern
recognition
SimpleAids such as l ighting /
boroscope etc.
Dye-penetrant Fluorescent / vis ible
Conventional , 2D
Fi lm / Computed / Real -
time / Digi ta l
Computed Tomography
2D (fan beam) / 3D (cone
beam) CT / Laminography
Diffraction
Flash
Laser
Electrically excited Induction-heated
Vibrationally excited Thermosonics
Eddy current Single / array probe
Magnetic particle
Barkhausen
Alternating Current Field
Measurement
Eletromagnetic-MechanicalElectromagnetic Acoustic
Transducer Ultrasound
Laser Ultrasound
Spatia l ly Resolved Acoustic
Spectroscopy
Shearography
Electronic speckle pattern
interferometry
Laser Speckle Photometry
Grazing Incidence
Ultrasound MicroscopyOptical-MechanicalMixed
Electromagnetic Magnetic field
Thermal
Optically excited
Radiographic X-ray
Optical / visible
light
Mechnical
Ultrasonic
Courtesy AMAZE EU project
The tool shows that commonly used NDE methods such as Contact/immersion UT and die penetrant for bulk and surface breaking defects respectively, would be capable.
Post built NDT PotentialMethods capability: selector tool output for a complex lattice structure and as built surface condition
Courtesy AMAZE EU project
The tool shows that the most appropriate NDT method for the majority of defects is X-ray computed tomography and resonance testing.
Class Type Sub-type Including… Surf
ace
brea
king
crac
ks /
lack
-of-
fusi
on
Surf
ace
brea
king
void
s
Inte
rnal
cra
cks
/
lack
-of-
fusi
on /
laye
r def
ects
Isol
ated
/
clus
tere
d
poro
sity
Inte
rnal
voi
ds,
incl
. cro
ss-l
ayer
defe
cts
Incl
usio
ns
Trap
ped
pow
der
(Pow
der B
ed
Fusi
on o
nly)
Nea
r sur
face
mic
rost
ruct
ure
vari
atio
n
Sub-
surf
ace
mic
rost
ruct
ure
vari
atio
n
Nea
r sur
face
resi
dual
str
ess
Sub-
surf
ace
resi
dual
str
ess
Contact or near-contact (a i r-
coupled)
Single / twin / array probe,
Time of Fl ight Di ffraction
Immers ion
Vibration analysis Resonance testing
Acoustic pattern
recognition
SimpleAids such as l ighting /
boroscope etc.
Dye-penetrant Fluorescent / vis ible
Conventional , 2D
Fi lm / Computed / Real -
time / Digi ta l
Computed Tomography
2D (fan beam) / 3D (cone
beam) CT / Laminography
Diffraction
Flash
Laser
Electrically excited Induction-heated
Vibrationally excited Thermosonics
Eddy current Single / array probe
Magnetic particle
Barkhausen
Alternating Current Field
Measurement
Eletromagnetic-MechanicalElectromagnetic Acoustic
Transducer Ultrasound
Laser Ultrasound
Spatia l ly Resolved Acoustic
Spectroscopy
Shearography
Electronic speckle pattern
interferometry
Laser Speckle Photometry
Grazing Incidence
Ultrasound MicroscopyOptical-MechanicalMixed
Electromagnetic Magnetic field
Thermal
Optically excited
Radiographic X-ray
Optical / visible
light
Mechnical
Ultrasonic
Courtesy AMAZE EU project
Post build NDT
Current method (XCT) limits of detection assessment
Microscope image of cut-up and polish sectionL-PBF of a calibration sample X-ray CT image (slice) using 225 kV XCT
system
• X-ray Computed Tomography
(XCT) and cut-ups comparison
where defects that are present in
both are circled in green and
defects that are present only on
cut-up are circled in red.
• The limits of detection, for this
particular sample and XCT
settings, which provided a voxel
resolution of 41 µm, is expected
to be at least twice the voxel
resolution (82 µm). No defects
were found at 82 µm, the closest
was 132 µm.
Courtesy AMAZE EU project
65.4 mm
Post build NDT
Emerging method non-linear resonance method assessment
Non-Linear
Resonance (NLR)
testing showing
identifiably different
responses for a
‘good’ and a ‘bad’
part (tests performed
by Theta Tech)
Corresponding non-linear responsesaPod 2 ‘good’ (top) and ‘bad’ (bottom) builds
Courtesy AMAZE EU project
Post build NDT
Emerging method, Process Compensated Resonance Testing (PCRT)
Courtesy of Vibrant for ISO TC 261 JG59, Additive manufacturing – General principles – Nondestructive evaluation of additive manufactured products, under development.
• PCRT has demonstrated capability to differentiate better between seeded (S1 & S2) and the non-seeded defects parts (S0).
Post build NDT
Automated hybrid NDT methods assessment
Courtesy RASCAL IUK project
• The robotic cell demonstrator was successful identifying the following defects in hinge brackets from the aerospace sector (validation was performed with X-ray CT):
Internal tight cracks via NLRExternal open cracks and notches via Thermography
• Capable to run and automatically indicate PASS/FAIL, generate a report and data can be accessed through the network.• The system will be used to demo at the MTC and/or other events.
Post built Metrology
Post-Processing: Geometrical effect from HIP on L-PBF
Build 1287 workflow: HIP only
Build plate bent inwards Build plate bent outwards
Courtesy AMAZE EU project
Post built Metrology
Post-Processing: Geometrical effect from Heat Treatment (HT) and part separation
Build 1289 workflow: HT and part separation
Build plate bent inwards Build plate bent outwards No part distortion
Courtesy AMAZE EU project
Post built Metrology
Post-Processing: Geometrical effect of Heat Treatment and HIP
Build 1377 workflow: Heat treatment and HIP
Build plate bent inwards Build plate bent outwards No part distortion No part distortion
Courtesy AMAZE EU project
Post built Metrology
Post-Processing: Geometrical effect of HIP
Defect before HIP Defect after HIP
Source: Brown, A., Jones, Z. Tilson, W., Classification, Effects, and Prevention of Build Defects in Powder-bed Fusion Printed Inconel 718, NASA Marshall Space Flight Center, 2016.
Defect morphology effect of HIPing: after HIP a defect becomes a crack like shape which may be more detrimental to the part integrity.
NDT Standard
ISO TC 261/ASTM F42 JG59 NP 52905
ISO/ASTM joint group activity led by MTC through British Standards Institute (BSI).
Ben Dutton, Technical Specialist at MTC is the convener.
This standard is to provide a best practice guide presenting NDT methods potential to detect defects which are not covered by current standards.
Post-built NDT
In-process NDT
Draft is under review.
Aim for final submission Sep. 2019.
MTC
Courtesy of ISO TC 261 JG59, ‘Additive Manufacturing — Non-Destructive Testing and Evaluation — Standard Guideline for Defect Detection in Metallic Parts’
Summary
In-process NDT
It is important to consider in-process inspection for AM since it has the potential to reduce or eliminate the need for inspection at the end of the build, reducing both cost for final part inspection and scrap of parts;
In some cases where NDT methods will not be capable to inspect the build parts due to their large or complex nature, in-process inspection may be the only option;
MTC’s work on LUT has showed good capability to detect surface and subsurface defects as small as 200 µm in diameter on as built L-PBF rough surface.
Post build NDT
The NDT selector tool showed an indication of how effective NDT methods will be on AM parts considering the level of geometrical complexity and surface finish;
XCT limits of detection highlights that the size of the part will influence the detection capability of even the ‘best’ NDT method currently available;
It is important to keep up-to-date of emerging and less used NDT methods, such as Non-linear Acoustics and PCRT which have shown promising results for AM part inspection.
Post built metrology and heating processes
Metrology showed good capability detecting geometrical deviations from the original CAD and actual build in addition to post processes such as HT and HIP have on AM part;
HT and HIP may be useful to reduce residual stresses and increase part density, respectively, but care must be taken that part quality is not reduced due to defects becoming more crack like.
NDT standard
MTC have been leading the development of NDT standards for AM, through ISO/ASTM JG59 and other ASTM participations, but more work is necessary to expedite the quality assurance of such parts.
Thank YouBen.Dutton@the-mtc.org
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