Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 1 1

HYCOMAT: test rig under high

pressure of gaseous hydrogen at

Pprime Institute, France

Gilbert Hénaff, Sylvie Castagnet,

Denis Bertheau, Guillaume Benoit

Institut P’ • UPR CNRS 3346

Département Physique et Mécanique des Matériaux ENSMA • Téléport 2 1, avenue Clément Ader • BP 40109

F86961 FUTUROSCOPE CHASSENEUIL Cedex

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 2

Outline • Presentation of Pprime Institute – Damage & Durability

• Design approach

• Safety

• Capabilities

• Gas management

• Test specimens

• Problems (solved or not)

• Test procedures: – tensile and compressive test, explosive decompression failure,

dilatation (polymers)

– Fatigue crack growth (metals)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 3

Damage & Durability Group – Pprime

Institute • Pprime Institute: > 500 persons – 3 scientific departments (Fluid

mechanics, Combustion, Energetics, Mechanical Engineering, Materials Science)

• Department of Physics & Mechanics of Materials, Damage & Durability Group

– Academic staff: 30 persons (11 CNRS + 19 ENSMA/UP)

– Staff: 18

– PhD students: 45

• FUNDINGS: ~1 M€ per year without salaries of permanent staff – 50 % industrial contracts

– 25 % european and national programs

– 25 % institutional grants

• Relations between microstucture, mechanical behavior and durabilty

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 4

HYCOMAT design approach

• Flexibility: Suitable for

mechanical testing on metals

as well as on polymers, in H2

as well as in CO2

• Servo-hydraulic load frame

• Dedicated metrology

• Maximum pressure: 40 MPa

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 5

HYCOMAT design approach (Cont’d)

• Pressure vessel and gas supply : design by TOP INDUSTRIE®

• Specific cells for : – Instron Servo hydraulic test

frame

– Power unit

– Outdoor Chiller

– Remote control for gas and test

– Outdoor gas storage and gas surpressors

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 6

Schematic overview

Surpressor H2

Surpressor CO2 Bouteille CO2

Bottle

H2 Bottle

N2 Bottle

flush

Pressure and

temperature

monitoring

Servo-

hydraulic

Machine

Cell

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 7

HYCOMAT : Safety

• Metallic structure for the test cell

• Separated command room /

Concrete wall

• H2 and CO2 detectors with 2 levels

of detection linked to :

– A double speed exhaust fan

– Interlocks (Vessel purge)

• Bursting discs

• Limited H2 volumes

• Water cooling flow and

temperature detectors

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 8

HYCOMAT capabilities

• Pressure : up to 400 Bars (40 MPa)

• Gas nature : H2, CO2, N2

• Temperature : up to 150°C

• Load cells:

– 25 kN (tension) pressure compensated internal cell Sixaxes®,

– Lower rod pressure compensated, no

piston effect due to internal pressure

– 25 kN external cell Instron®

• Actuator displacement (LVDT) : 20

mm (7,9 in)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 9

HYCOMAT capabilities (Cont’d) • 2 front doors :

– 40 mm (15,7in) diameter window up

to 40 Bar

– 26 mm (10,2 in) diameter window up to 400 Bar

– 1 rear window 26mm up to 400 Bar

(10,2 in)

• Electrical connections for strain

gages and DCP

• Gas temperature measurement

(K-type TC)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 10

HYCOMAT : capabilities (continued)

• Self alignment of the rods with ball joint

• Frequency : up to 20 Hz

• Test monitoring : Instron softwares :

– Wavematrix ® (Multi purpose software)

– Advanced Crack Growth ®

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 11

HYCOMAT : Gas Management • Automatic regulation for temperature and

pressure (PID control)

– Max H2 compression rate : 30 bar/minute

– Max H2 decompression rate : 50 bar/minute

• Manual purge of the vessel with inert gas (N2)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 12

HYCOMAT: Test Specimens

• CT specimen (W= 40 mm,

B=8mm)

• Optical for observations

and measurements -

Questar®

• DCP crack measurement

• Strain gage for Crack

closure measurement

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 13

HYCOMAT: Test Specimens

• Cylindrical specimens

• Standard tension specimens (polymers)

• Strain measurement by patterning

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 14

HYCOMAT: Problems (solved or not)

Hardware Problems Responses

Gas compressor Valves & diaphragm

failures

Frequent changes

Water jacket Seals Explosive

decompression of seals

due to CO2

experiments

Anti extrusion ring

Rods Rod galling Anti extrusion ring

Internal load cell Residual deformation

of the compensation

socket

New design

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 15

Test procedures: tension &

compression test (polymers) • Specimen design : flat dumbbell

specimens (tension, cylindrical samples (compression)

• Metrology : crosshead displacement / optical extensometer

• Example of results : hydrogen influence on some key mechanical properties for gas high-density polyethylene for current gas networking (=> 3 MPa)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 16

Test procedures: tension &

compression test (polymers) (Cont’d)

0

1

2

3

4

5

6

7

1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1,E+06 1,E+07 1,E+08

time (s)

log

ari

thm

ic s

train

(%

)

H2

air

fluage long-termelong-term creep

y = 17,072 x + 38,363

y = 20,227x + 28,214

0

50

100

150

200

250

300

0 2 4 6 8 10 12 14

ligament (mm)

sp

ecif

ic w

ork

of

fractu

re (

KJ.m

-²)

0

50

100

150

200

250

300

350

400

0 2 4 6 8 10 12 14

displacement (mm)

forc

e (

N) l

t

W

L

F

rupture ductile (EWF)ductile fracture (Essential Work of Fracture)

0

5

10

15

20

25

30

35

0 0,05 0,1

logarithmic strain

Ca

uch

y s

tre

ss (

MP

a)

air

N2 (3 MPa)

H2 (3 MPa)

H2 (10 MPa)

tension

Limitations and

challenges: length /

extension ratio to be

compromised

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 17

Depressurization of a silicon rubber at 15 MPa/min after 1h-saturation at Psat = 24 MPa

Specimen design : flat and cylindrical samples (especially for

superimposed tension or compression)

Metrology : CCD camera => optical detection of cavitation onset (magnification of

pictures)

current hydrostatic pressure value

Depressurization of a polyethyl acrylate rubber at 10 MPa/min after 1h-saturation at Psat = 12 MPa

primary / satellite

bubbles

star-shape

morphology

Test procedures: Explosive

Decompression Failure

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 18

Test procedures: Explosive

Decompression Failure • Example of Results

• Limitations and challenges: experimental protocol limited to transparent rubbers, detection of early stages of cavitation (acoustic emission?)

Decompression rate (MPa/min)

variable hydrostatic pressure

at cavitation onset

Current pressure at cavitation(MPa)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 19

Test procedures: dilatation test

(rubber)

V/V

0

Pre

ssu

re (

MP

a)

Time (min)

Specimen design : cylindrical and spherical samples

weak volume changes during saturation vs. large ones upon decompression

Metrology :

Example of results : silica filled NBR rubber

Limitations and challenges : large

temperature transients => calculation needed to extract the

volume change linked with gas

diffusion

two devices :

(a) (b)

holder

sample

reference

observation zone

0,2 mm

low resolution (lens 12.5–75 mm f1.8)

high resolution (Questar)

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 20

Test procedures: fatigue crack growth

in metals • Specimen design: Compact Tension

W=40mm B=8mm

• Advanced Crack Growth Instron®

software

• Crack length monitoring: potential drop

(DC) technique (Current intensity 1A)

• Crack growth calculation: ASTM E647

• Possibility to monitor the crack growth by

means of a long-distance microscope

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 21

Fatigue crack propagation: Results

10-9

10-8

10-7

10-6

10-5

10-4

4 5 6 7 8 9 10 20 30 40

15-5 PH

R=0.7

20Hz, room temperature

air LT

air TL

H2 0.09 MPa

H2 9MPa

da

/dN

(m

/cy

cle

)

K (MPa x m1/2

)

Influence of pressure

in a precipitation-

hardened martensitic

stainless steeel

→Sharp increase in

da/dN at 9 MPa H2

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 22

Fatigue crack propagation: Results

10-10

10-9

10-8

10-7

10-6

10-5

10-4

4 5 6 7 8 9 10 20 30 40

0.9 MPa / 20Hz

0.9 MPa / 0.2Hz

da

/dN

(m

/cy

cle

)

K (MPa x m1/2

)

mean curve 9MPa/20Hz

mean curve 0.09MPa/20Hz

Influence of frequency at low pressure → da/dN enhancement associated with a change in fracture mode

Meeting on Advancing Materials Testing in Hydrogen, Gas,Sandia National Laboraties, Livermore CA 23

Acknowledgements

• Fundings: ANR, FEDER…

• Co-workers: J. Jaravel, J.-C. Grandidier,

M. Morisset, Z. Sun…