Application of Proton Radiography Method

for Investigations of Dynamic Fracture

of Condensed Matter

Sergey V. RazorenovInstitute of Problems of Chemical Physics RAS, Chernogolovka, Russia

2st Workshop on High Energy Proton Microscopy HEPM-2010Chernogolovka, 2010

MAIN DIRECTIONS OF THE SHOCK WAVE PHYSICS

Mechanical

properties

Computer

simulations

Techniques

of experimentsTechnological

applications

Detonation

phenomena

Electrical and

optical properties

Phase

transitions

Equations of state

MOTIVATIONS

It is known the strength behavior of materials

depends on their structure.

However, the structural effects have not been yet

systematized and characterized quantitatively.

Meanwhile, it is natural to expect that

establishing of unambiguous relations between the

material structure parameters and the resistance

to spall fracture would promote the use of spall

methods in the material science applications.

SPALL PHENOMENON

First discription: Griffits (1914)

SPALL PHENOMENA UNDER SHOCK LOADING

x

x

Free

surface

x

Free

surface

x

Spalling is the process of internal rupture of a body due to tensile stresses

generated as a result of a compression pulse reflected from the free surface.

The investigation of spall fracture –

single way to measure of material strength

under dynamic loading

Spall fracture by nucleation and growth of pores or cracks

1145 aluminum Armco iron

During the dynamic fracture process, many microvoids or microcracks undergo nucleation,

growth, and coalescence in a volume of material to form a failed or spalled region.

Curran et al., [1987]

THE WAVE DYNAMICS AT REFLECTION OF A

SHOCK PULSE FROM THE FREE SURFACE

Acoustic approach: fsoosp uc 2

1

The peak tensile stress just before the

fracture corresponds to the intersection

point K of the Riemann’s isentropes

K

um

u0

(tail)Spall

Strength

0

C-

C+

C+

Riemann's

Isentropes

Hugoniot

u

pt

x

K

C_

C+

Spall

Free

surfaceShock fro

nt

0

ufs

uf

um

u0

ufs

t0

Intragranular and intergranular

fracture of copper

Influence of the loading history

Koller D.D., Hixson R.S., Gray III G.T., et al., J. Appl. Phys. 98, 103518 (2005)

Influence of shock-wave profile shape on dynamically induced damage

in high-purity copper.

Influence of rolling direction onstrength properties of aluminum alloy D16T

0 100 200 300 400 5000

200

400

600

AS

HEL

II

T

Fre

e s

urf

ac

e v

elo

cit

y,

m/s

Time, ns

Rolling direction

Transversal direction

Measured resistance to spall fracture in rolling direction is varied from one

experiment to another due to higher structure heterogeneity of as-received

samples;

Loading of samples in transversal direction leads to decreasing of fracture stresses

under spall conditions;

Samples of 2 mm in thickness; Impactor – Al, 0.4 mm (630±30 м/с );

σHEL σsp

II 0.7 GPa 1.7 GPa

┴ 0.8 GPa 1.3 GPa

The main goal of SPD methods:

The creation of polycrystal materials with grain sizes d0<1 µm

The forging (pressing)

in three directions

Equal-channel angular pressing (ECAP) The example of inner structure

of Armco-iron after SPD

Advantages:

High homogeneity of inner structure of metals

Methods of Severe Plastic Deformation (SPD)

for Forming of Ultra Fine Grained Materials

Average grain size ~28 м

Hardness H = 1560 MPa

The forging

in three directions

Gross deformation: ~1500%;

Hardnes H = (3000100) MPa

As-resieved

Submicrosecond strength

of ultra-fine grained titanium VT1-0

0,0 0,1 0,2 0,3 0,40,0

0,2

0,4

0,6

0,8

1,0

10-15 м ,

0.3 м

Fre

e s

urf

ace

ve

locity, km

/s

Time, s

0 2 4 6 8 100,0

0,5

1,0

1,5

2,0

, simple tensionx

uniaxial shock

compression

10-3 с

-1

~106 с

-1

VT1-0 0.3 м

VT1-0 10-15 м

Flo

w s

tre

ss, G

Pa

Strain, %

There is practically No difference in character of dynamic deformation

and fracture of titanium under dramatically reducing of average grain size;

104

105

106

107

2

3

4

5

6

7

8

9

10

Armco-iron

3D-forging

As-received

Single crystals

.

Cri

tica

l fr

actu

re s

tre

ss, G

Pa

V/V0, с

-1

0 400 800 1200 16000

200

400

600

800

1000

1200

1400

Рфаз

~13,4 GPa

Рфаз

~13 GPa

HEL

~ 2.86 GPa

HEL

~ 1.66 GPaArmco-iron

146 м/s

as-received

3D-forging

Fre

e s

urf

ace v

elo

city,

m/s

Time,ns

172 м/s

Phase transition

SPD leads to increasing of HEL

and phase transition pressure

SPD leads to increasing

of spall strength

Influence of SPD on dynamic deformation

and fracture of Armco-iron

Submicrosecond strength

of ultra-fine grained Tantalum

The reducing of grain sizes with a factor ~100 due to SPD processing

leads to decreasing of HEL value, changing the character of elastic-

plastic transition, and increases spall strength for 15-20%;

-0,15 0,00 0,15 0,30 0,45 0,60 0,750

100

200

300

400

500

ufs 3D-pressing

As-received

Tantalum

Fre

e s

urf

ace v

elo

city, m

/s

Time, s

HELas-rec.

HELSPD

ufs >

0

1

2

3

4

-80 -40 0 40 80 120 1601

2

3

4

As-received -

After SPD -

Мк

Мн

Ак

Ан

Ti51.1

Ni48.9

HEL

spall

Lo

w-t

em

pe

ratu

re p

ha

se

Mixture

Hig

h-t

em

pe

ratu

re p

ha

se

Fra

ctu

re s

tre

ss

, G

Pa

Temperature, 0С

Hu

go

nio

t e

las

tic

lim

it,

GP

a

T, ºC σHEL, GPa σspall ,

GPa

Coarse-grained

Martensite 0.2 3.4

Mixture 0.5 3.3

Austenite 1.7 4.1

Ultra-fine grained

Martensite 0.2 2.5

Mixture 1.2 2.9

Austenite 2.4 4.0

Strength properties of Ti51.1 Ni48.9 alloyover the whole temperature range

The highest strength characteristics are realized in austenite phase;

The SPD processing leads to decreasing spall strength over the whole temperature range;

Preconclusion (on UFG-materials)

The forming of ultra-fine grained inner structure in polycrystalline

metals and alloys with SPD methods often influences not so

significantly on the character of dynamic deformation and fracture in

comparison with static and quasistatic loading conditions.

This influence is ambiguous.

The changes of inner structure of metals and alloys due to

preliminary thermo-treatment, phase transitions or variation of initial

material temperature frequently overbalance the influence of

mechanical reducing of grain sizes on their strength properties under

dynamic loading.

Previous USING of Proton Radiography method

for spall phenomenon investigations

Aluminum 6061-T6

23.2 s after detonation ignition

32.8 s after detonation ignition

Holtkamp, D.B. et al., “A Survey of High Explosive-Induced Damage and Spall in Selected

Metals using Proton Radiography,” in Shock Compression of Condensed Matter, 2003 (M.D.

Furnish, Y.M.Gupta, J.W. Forbes, eds.), part I, pp. 477-482.

CONCLUSION

• Spall fracture is studied near one hundred years, and undoubtedly a lot of information humanity has got about this phenomenon already.

• But:

Spall fracture is stage kinetic process, no experimental information about fist stages of spall, usually samples recovered after shock are studied, no dynamic data of fracture development

No data of fracture development on different structural levels (-macro, -meso, -micro)

• The study of this phenomenon will be useful both for numerical simulation of dynamic behavior of constructive materials under pulse loading and using of new experimental data for material science (development new technologies for improvement a material properties, understanding a basic mechanisms of process of dynamic fractures over a wide range of any kind of condensed matter.

FAILURE WAVE PHENOMENON

Razorenov S.V., Kanel G.I., Fortov V.E., Abasehov M.M.

The fracture of glass under high-pressure impulsive loading. –

High Pressure Research, 1991, v.6, p.225-232.

IMPACT CRACKING OF A GLASS

PLATE

H. Schardin. Velocity effects in fracture.

In: Fracture, ed. B.L. Averbach et el., MIT Press, Cambridge, 297-330 (1959)

• Increasing of velocity impact leads to crack branching

• The growing cracks form a failure front

FAILURE WAVE IN SHOCK-COMPRESSED GLASS

• The failure wave is a network of cracks that are nucleated on the surface and

propagate with subsonic speed into the stressed body;

• Investigation of failure wave in shock-compressed glasses may provide

information about the mechanisms and general rules of nucleation, growth and

interactions of multiple cracks and lead to a better understanding of experiments

on brittle ceramics and rocks.

Dis

tance

Time

Re-r

efle

ctio

n

Unloading

Ela

stic

sho

ck

tr

Glass

Plate

Glass

Surface

Failure wave

Base plate

Incipient microcracks always exist on

the glass surface.

HIGH SPEED RECORDING OF FAILURE WAVE

IN “PYREX” GLASS

Bourne, N. K., Rosenberg, Z., Field, J. E.

High-speed photography of compressive failure waves in glasses. J. Appl. Phys. 78, 3736-3739 (1995).

CONCLUSION

• During more then last fifteen years after discovering of this phenomenon the fact of forming of failure wave was repeatedly confirmed and broad data about kinetic mechanisms of their propagation in shock-compressed brittle materials were collected.

• But it is ambiguous:

what is mechanism of failure wave propagation in brittle materials under compressive stresses in detail,

what defines a failure wave propagation velocity and its stability,

what material properties and loading conditions are needed for failure wave triggering.

• The study of this phenomenon will be useful both for numerical simulation of dynamic fracture of brittle materials under compression by explosive or high velocity impact and for understanding a basic mechanisms of catastrophic fractures under long time action (f.e. earthquarke).

Previous USING of Proton Radiography method

for failure wave phenomenon investigations

No data…………………….

Chernogolovka, 2010