stefan anders

Division III.2 Storage Systems

Stefan Anders BAM ICHS – San Sebastian – 2007 September 11-13 slide no 1

Stefan Anders

Federal Institute for Materials Research and Testing (BAM)

Thermal Loading Cases of Hydrogen High Pressure Storage Cylinders



Where is the starting point?





Which problems have to be solved?






What has been achieved so far?







Where do we still have to go?





BAM working group ‘Storage SystemsStorage Systems’ conducts within StorHy’sStorHy’s subproject

‘Safety Assessment and RegulationsSafety Assessment and Regulations’

safety assessmentsafety assessment on storage systems for automotive applications.

source: DC




HybridHybrid structuresstructures (composite and metal or plastic liner) are used for compressed storage.

Composite layer is applied on the liner by a winding processwinding process.

RequirementsRequirements:

- up to 70 MPa operating pressure

- temperature range -40°C to +85°C




Test facility at BAM for extreme temperature hydraulic cycling tests

max. pressure: 120 MPa (dynamic) temperature: -60°C to +90°C350 MPa (static)




IdenticalIdentical cylinders from the same batch show differentdifferent safetysafety relevant structural behavior behavior:

Problem:

- burst pressure- number of load cycles to failure

- strain level on the same pressure

Relative strain during Autofrettage 700 bar

0%

20%

40%

60%

80%

100%

120%

140%

160%

0% 20% 40% 60% 80% 100% 120% 140% 160% 180%

rel. eps_x

rel.

eps_

ph

i

averageresidual strainaverage

permanent strain

values on the Autofrettage pressure level plateau

Stefan Anders, BAM

Relative strain during Autofrettage 700 bar

0%

20%

40%

60%

80%

100%

120%

140%

160%

0% 20% 40% 60% 80% 100% 120% 140% 160% 180%

rel. eps_x

rel.

eps_

ph

i

averageresidual strainaverage

permanent strain

values on the Autofrettage pressure level plateau

Stefan Anders, BAM




safefast

production

economic production

Accurate stress analyses for Accurate stress analyses for lifetime predictionlifetime prediction

light weight structure

Structural behavior is strongly depend on the boundary condition temperaturetemperature




Temperature depending modulus out of DMTA

0

1000

2000

3000

4000

5000

-60 -40 -20 0 20 40 60 80 100 120

Temperature [°C]

E',

E''

[MP

a]

E' Young's Modulus

E'' damper Modulus

Tests on resin systemsTests on resin systems showed clearly the strong temperature dependingtemperature depending material behavior.




temperature dependent resin E(T)

metal layer

nonlinear degradation composite stiffness

[C(IFF)]CLT

constitutive equation

fibre prestress

operational load

temperatureambient and filling

pressure

purposely introduced load

autofrettage

total load vector

{ } { } { } { }{ } { }

exp exp( ) ( ) ( )

totalcomposite metal

composite hybrid

pressure temperature ansion temperature ansion

fibre prestress autofrettage

T T Ts s s s

s s

= + +

+ +[ ] [ ] [ ]( ) ( )hybrid composite metal

C T C T C= +

stress analysis

{ } [ ] { }( ) ( ) ( )layer totallayer

T C T Ts eÞ = ×{ } [ ] { }1( ) ( ) ( )

global totalhybridT C T Te s-= ×

Stress analysis model as function of temperature

total load vector

{ } { } { } { }{ } { }

exp exp( ) ( ) ( )

totalcomposite metal

composite hybrid

pressure temperature ansion temperature ansion

fibre prestress autofrettage

T T Ts s s s

s s

= + +

+ +

temperature dependent resin E(T)

metal layer

nonlinear degradation composite stiffness

[C(IFF)]CLT

constitutive equation

[ ] [ ] [ ]( ) ( )hybrid composite metal

C T C T C= +

operational load

temperatureambient and filling

pressure

*

* Stefan Anders, Residual Stresses in Composite-Metal Structures for High H2 Gas Cylinders, CANCOM 07, Winnipeg, Canada



What has been achieved so far?Jokkmokk temperature during a periode of

30 years

DezNovOktSepAugJulJunMaiAprMarFebJan-45-40-35-30-25-20-15-10

-505

1015202530354045

month

tem

pe

ratu

re [

°C]

day average

max. of day average

min.of day average

max. of day

min. of day

temperature distribution

probability density curve (January)distribution cold side

0

0,02

0,04

0,06

0,08

-30 -25 -20 -15 -10 -5 0 5 10 15 20

temperature [°C]

pro

ba

bil

ity

de

ns

ity

[/] probability density function

class frequency

0%

10%

20%

30%

40%

50%

-30 -25 -20 -15 -10 -5 0 5 10 15 20

temperaure classes [°C]

cla

ss

fre

qu

en

cy

[%]

(-27 °C / 0.001 %)

class frequency

-50

to -

45

-40

to -

35

-30

to -

25

-20

to -

15

-10

to -

5

0 to

+5

+10

to

+15

+20

to

+25

+30

to

+35

+40

to

+45

+50

to

+55

0%

5%

10%

15%

20%

25%

fre

qu

en

cy

of

oc

cu

rre

nc

e

temperature classes [°C]

Jokkmokk (cold distribution)

Athens (warm distribution)

overall class frequency

How oftenHow often does each temperature classclass loads the cylinder?



2_ min,

2

( )

21( )

2

T i

i

x

sdi

i

f x esd

--

×= ×× ×


probability density curve (January)distribution cold side

0

0,02

0,04

0,06

0,08

-30 -25 -20 -15 -10 -5 0 5 10 15 20

temperature [°C]

pro

bab

ility

den

sity

[/]

Probability density function(for each calendar months)

Assumption:- temperature distribution

follows a Gaussian (normal) distribution

Input:- mean value of min/max

temperature- abs. min/max temperature

= standard deviationstandard deviation

mean value

mean valueabs. min




Class frequency(for each calendar months)

- setting temperature classes Tk at an increment of T = 5°C

- solving the definite integral for each temperature class

class frequency

0%

10%

20%

30%

40%

50%

-30 -25 -20 -15 -10 -5 0 5 10 15 20

temperaure classes [°C]

cla

ss

fre

qu

en

cy

[%]

(-27 °C / 0.001 %)

1

, 1 1( ( , )) ( ) ( ) ;k kT T

k i k k k kH T T f x dx f x dx with T T+

+ +- -

= -




Overall class frequency

- for all temperature classes Tk of the 12 calendar month the arithmetic mean value is

determined

12

,1

1

12k k ii

H H=

=

-50

to

-4

5

-40

to

-3

5

-30

to -

25

-20

to

-1

5

-10

to

-5

0 t

o +

5

+1

0 to

+1

5

+20

to

+2

5

+3

0 to

+3

5

+4

0 t

o +

45

+5

0 t

o +

55

0%

5%

10%

15%

20%

25%

fre

qu

en

cy

of

oc

cu

rre

nc

e

temperature classes [°C]

Jokkmokk (cold distribution)

Athens (warm distribution)




Thermal stresses Thermal stresses in the liner layer (0°-90°-Al hybrid)

ma

x. fi

llin

g te

mp

era

ture

Jokkmokk – max. stress amplitude – frequency 0.27%

Jokkmokk – max. frequency 19.6%




So far it could be shown:

cold and warm temperatures do loadload or unloadunload the composite and the liner (fatigue)

temperature effect is mainly effective in the resinresin dominateddominated directions

lay-uplay-up influences the degree of temperature temperature effect effect (avoid shear stresses)




Issues which still have to be considered, among others:

influence of dynamic loadingdynamic loading (pressure and temperature load cycles) which leads to fatigue (degradation models)fatigue (degradation models)

long term behavior with visco-elastic visco-elastic effectseffects



Stefan AndersTel.: +49 (0) 30/8104-3981Fax: +49 (0) 30/8104-1327E-Mail: [email protected]

BAM - III.2Unter den Eichen 44-46

D-12205 BerlinGermany

Thank you for your attention

stefan anders

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