Gizo BokuchavaGizo Bokuchava

  Frank Laboratory of Neutron Frank Laboratory of Neutron PhysicsPhysics

Joint Institute for Nuclear Joint Institute for Nuclear ResearchResearch

STI 2011, JUNE 6-9, DUBNA

Q 1

Q

2

Det

ect

or 1

Det

ect

or 2

n0

Diffraction experiment for Diffraction experiment for measuring of internal stresses measuring of internal stresses inside material or componentinside material or component

incident neutron beam

diaphragm

sample

By two detectors at 90 one can measure stresses in both Q1 and Q2 directions simultaneously

gauge volume

-F e(1 1 0 ) (a -a 0)/a 0= 0 .0 01

(a -a 0)/a 0= -0 .0 0 0 1(20 M P a)

(2 0 0 M P a )

2 .0 2 0 2 .0 2 5 2 .0 3 0 2 .0 3 5d , Å

fe-str

Peak shift for steel sample (E=200 Gpa)at stress value of 20 MPa and 200 MPa

Peak shift under applied loadPeak shift under applied load

a/a0 = (d – d0)/d0 - peak shift (macro-stress)

Bragg law: 2dexpsin =

d = tμs/(505.556 Lmsin) (TOF-method)

a/a0 = (d – d0)/d0 - peak shift (macro-stress)

Bragg law: 2dexpsin =

d = tμs/(505.556 Lmsin) (TOF-method)

Diffraction peak broadening effectsDiffraction peak broadening effects

Resolution function (standard Al2O3 sample) and peak broadening effect due to crystallite size (dispersive Ni).

0 .0 1 .0 2 .0 3 .0 4 .0 5 .0d 2 , Å

0

0 .0 0 0 1

0 .0 0 0 2

0 .0 0 0 3

0 .0 0 0 4

0 .0 0 0 5

0 .0 0 0 6

W2 , Å

Sam ple1Sam ple 2d 0sam ple

Peak broadening due to microstrain. Estimated microstrain value:e=0.012±0.004 (Sample 1)e=0.0100.004 (Sample 2)

W2 = W02 + C1d2 + C2d4 – diffraction peak width

C1 = <ε>2 – variance of d (microstrain)

C2 ~ 1/<D>2 – crystallite size

W0 – instrument resolution function

W2 = W02 + C1d2 + C2d4 – diffraction peak width

C1 = <ε>2 – variance of d (microstrain)

C2 ~ 1/<D>2 – crystallite size

W0 – instrument resolution function

IBR-2 SpectrometersIBR-2 Spectrometers

IBR-2 pulsed reactorIBR-2 pulsed reactor

Courtesy of J.Emelina

-3 0 0 -2 0 0 -1 0 0 0 1 0 0 2 0 0 3 0 0t , s

IB R -2 , T O FW = 3 0 0 sR = 0 .0 1

IB R -2 , R T O FW = 2 0 sR = 0 .0 0 0 7

to f-rto f

High-resolution Fourier diffractometry for long pulse neutron sourceHigh-resolution Fourier diffractometry for long pulse neutron source

IBR-2 is a long-pulse neutron source.Δt≈300 μs, R ≈ 0.01 (L=25 m, d=2 Å)IBR-2 is a long-pulse neutron source.Δt≈300 μs, R ≈ 0.01 (L=25 m, d=2 Å)

Objective: R ≤ 0.001 (L=25 m, d=2 Å) Objective: R ≤ 0.001 (L=25 m, d=2 Å)

F-chopper parameters

(FSD):

N=1024

Vmax=6000 rpm

Ωmax=100 KHz

Δt0≈10 μs

F-chopper parameters

(FSD):

N=1024

Vmax=6000 rpm

Ωmax=100 KHz

Δt0≈10 μs

Fast Fourier chopper

Fourier chopperFourier chopperSlit width 0.7 mm

RotorStator

Transmission function

Binary signals

1. P.Hiismaki1. P.Hiismaki,, Introduction of RTOF-method Introduction of RTOF-methodNeutron Inelastic Scattering, IAEA, Vienna, 1972, 803

2. The first realization of RTOF Fourier-method2. The first realization of RTOF Fourier-methodR.Heinonen, P.Hiismaki, A.Piirto et al, New Methods and Techniques in Neutron Diffraction, Report RCN-234, Petten, 1975, 347

Schematic diagram of the Fourier Schematic diagram of the Fourier diffractometerdiffractometer

Resolution of a TOF - diffractometerResolution of a TOF - diffractometer

R(t, θ) = Δd/d = [(Δt0/t)2 + (Δθ/tgθ)2+2+d2/<D>2]1/2, t

~L·d·sinθ, R→0 if Δt0→0 or L→∞

and Δθ→0 or θ→π/2

FSD diffractometer, IBR-2 (RUSSIA)FSD diffractometer, IBR-2 (RUSSIA)

R(t) ≈∫g(ω)cos(ωt)dω, ΔR=Δt0≈ 1/Ωm=(Nωm)-1=(1024·100 kHz)-1≈10 μs

For Δt0≈10 μs and L≈6.5 m:time component Δt0/t ≈ 2.5·10-3 for d=1 Å and 2=90

R(t) ≈∫g(ω)cos(ωt)dω is Fourier transformation of g(ω).

Resolution function (peak shape)Resolution function (peak shape)

0

Ωm

g(ω) is frequency distribution(frequency window)

Frequency windowFrequency window

FSD: Blackman window

g(u)=1 + p·cosπu + q·cos2πu

where p=1.03, q=0.08, u=ω/ωmax

Simulation: Simulation: RTOF data RTOF data acquisitionacquisition

FSD – FSD – FFourier ourier SStress tress DDiffractometeriffractometer

at the IBR-2 pulsed reactor (JINR, Dubna)at the IBR-2 pulsed reactor (JINR, Dubna)

3,400 19,000

0,184

5,500

M od era to r

N i G u id e Tub e

"IS O M E R " Ins trum ent

F ourier C hop p er F ull C irc leG o niom eter

D etec to rs

V M E

VM E c o n tro l a nd o p e ra tive

vis ua liz a tio n /a na lys is

VM E S ta tio n (O S /9 )D a ta A c q u is itio n

E the rN etD a ta Tra ns fe r

I B R - 2

F L N P

F S D

F o urie r S tres s D iffra c to m e ter

90º-detectorNeutron guide

Sample position

FSD diffractometerFSD diffractometer

Backscattering detector

Current status of the detector system :

Three modules of ZnS(Ag) +90° (left) detector are installed on FSD. The similar three modules are installed on -90° (right)

detector.

FSD detector system:FSD detector system:combined geometrical and electronic focusingcombined geometrical and electronic focusing

Right bank of 90º-detector consists of 7 ZnS(Ag) based modules.

Flexible the scintillation screen allows each element of the detector to approximate the time focusing surface of the scattered neutrons with a necessary accuracy.At the same time, the electronics provides the adding up of signals from separate detector elements on a single TOF-scale. This combination leads to a sharp increase of the solid angle of the detector system and as a results, to an increase of its luminosity preserving high resolution d/d410-3.

Courtesy of Valery Kudryashov

Interior arrangement of the single detector module

FSD detector system:FSD detector system:combined geometrical and combined geometrical and

electronic focusingelectronic focusing

0 500 1000 1500 20000

1x105

2x105

Inte

nsi

ty

TOF Channels

0 500 1000 1500

0

1x105

2x105

3x105

4x105

5x105

6x105

Inte

nsi

ty

TOF channels

1540 1560 1580 1600 1620 1640

TOF channelsRTOF spectra focusing

Scale coefficients for each detector element:ki = Lisin(i) / L0sin(0),

where L is flight path, is scattering angle for i-th and base detectors, correspondingly.

E.S. Kuzmin, A.M. Balagurov, G.D. Bokuchava et al., J. of Neutron Research, Vol. 10, Number 1 (2002) 31-41

Radial collimatorRadial collimatorMultisectional radialcollimator

Multisectional radial collimator system: 7° and 10° modules are installed

Single modules of the collimator

Gauge volume = 2 mm, Number of slits = 160,Length = 600 mm, Focus distance = 350 mm

Measured spatial resolution function for radial collimator (FHWM2 mm)

Gauge volume definition: neutron intensity distribution map for radial collimator. Incident beam width ~10 mm

46

48

50

52

54

15000

20000

25000

30000

35000

46

48

50

52

54

46 48 50 52

Y, m

m

X, mm

Y, m

m

-6 -4 -2 0 2 4 6 8 10 12 14

3500

4000

4500

5000

5500

6000

6500

7000

7500Sample surface

Region 3Region 2

Measured Calculated

Inte

nsi

ty

X, mm

Region 1

Sample surface scan with radial collimator

Residual stress study by neutron diffraction within bulk sample using radial collimators

FSD resolution function measured on -Fe powder at maximal Fourier chopper speed Vmax=6000 rpm

Part of neutron diffraction pattern from the -Fe standard sample measured on FSD in high-resolution mode by BS- (top) and 90 (bottom) detectors. Experimental points, profile calculated by the Rietveld method and difference curve are shown.

Measured spectra and resolution functionMeasured spectra and resolution functionFSDBackscattering detector

0 .5 1 .0 1 .5 2 .0d ,

-100

10

FSD90°-detector

0 .5 1 .0 1 .5 2 .0d ,

-100

10

0.5 1.0 1.5 2.0 2.5 3.00.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

d

/d

d, Å

FSD Backscattering detector +90° detector -90° detector

0,0000 0,0002 0,0004 0,0006 0,0008 0,00100

10

20

30

40

50

60 Experimental points Linear Fit: Y = 58279.625 * X

t0,

s

1 / Vmax

, rpm-1

Effective neutron pulse width dependence versus maximal Fourier chopper speed

1 .1 4 1 .1 6 1 .1 8 1 .2d , Å

0

2 0 0 0 0

4 0 0 0 0

6 0 0 0 0

Inte

nsit

y

FSD , BS - detectorfe189-194

1 0 0 0 rp m2 0 0 0 rp m3 0 0 0 rp m4 0 0 0 rp m5 0 0 0 rp m6 0 0 0 rp m

V m ax

Diffraction peak shape dependence versus maximal Fourier chopper speed

Diffraction peak shape and pulse widthDiffraction peak shape and pulse width

FSD operation parametersFSD operation parameters

Neutron guide mirror, Ni-covered Beam cross-section at exit 1075 mm2

Moderator – sample distance 28.14 mChopper – sample distance 5.55 mFourier - chopper (disk) high-strength Al based alloy outer diameter 540 mm slit width 0.7 mm number of slits 1024 max. rotation speed 6000 rpm max. modulation frequency 100 kHzThermal neutron pulse width: low-resolution mode 320 s high-resolution mode 9.8 sNeutron detectors: Backscattering (2 = 141, 6Li) 2.310-3 ASTRA (2 = ±90, ZnS) 4.010-3 Wavelength interval 0.9 ÷ 8 ÅFlux at sample position: without Fourier chopper 1.8106 n/cm2/sec with Fourier chopper 3.7105 n/cm2/sec

5 – axis HUBER goniometer

,-axis, x,y,z-table

Sample Sample environmentenvironment

Investigated sample installed on “Huber” goniometer.

Sample Sample environmentenvironment

Mirror furnace

Two standard halogen lamps (output power of 1 kW) with a common focus at sample position provide a working temperature range up to 1000 C (can be upgraded up to 2000 C) and temperature stability of 0.2 C. The design of the furnace allows one to use wide range of neutron scattering angles: in the scattering plane - 360, in the vertical plane - 22.

Stress rig ”TIRAtest” (Fmax=60 kN)

Sample Sample environmentenvironment

New stress rig LMNew stress rig LM-20-20 for FSD diffractometer for FSD diffractometer(produced in NPI, Řež, Czech Republic)

Force range - ±20 kN, temperature range - up to 800 ºС

Mechanical testing machine LM-20 during test experiments in FLNP JINR.

Steel sample with mechanical extensiometer

Typical samplesSample heating by direct current

New SONIX+ instrument control systemdeveloped by Kirilov A.S., Murashkevich S.M., Petukhova Т.B., Yudin V.E.

(SONIX - SOftware for Neutron Instruments on X11 base)

New SONIX+ instrument control systemdeveloped by Kirilov A.S., Murashkevich S.M., Petukhova Т.B., Yudin V.E.

(SONIX - SOftware for Neutron Instruments on X11 base)

Sonix+ advantages:

-GUI user friendly interface-flexible Python-based script language-simple data visualization-low cost

Sonix+ advantages:

-GUI user friendly interface-flexible Python-based script language-simple data visualization-low cost

Four point bending device with test sample. Scan points are shown in blue

Lattice strain vs X coordinate

Four point bend experimentFour point bend experiment

xSample

-50 0 50 100 150 200 250 300 350 400 450-0.001

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

S

trai

n

Applied stress, MPa

1 2 3 4

0.000 0.001 0.002 0.003 0.004

0.000

0.001

0.002

0.003

0.004

Ela

stic

str

ain

Sample elongation

1 2 3 4

E, GPa 67.21 69.95 68.79 68.512 1.97 1.78 0.03 0.01

Experimental values of Young‘s modulus for D16 Al alloy (russ. grading)

Mean value <Е> = 68.62 0.82 GPa for D16 alloy

Elastic lattice strain versus applied load. Sample Nr.4 undergoes plastic deformation

Elastic lattice strain versus sample deformation in elastic region (up to ~0.004)

Further development

-Additional elements for detector system;

- 2nd radial collimator;

- Sample environment improvement.

Conclusions

- the obtained results show that the RTOF neutron diffraction method can be used for residual stress studies in various industrial components and new advanced materials;

- the achieved parameters of the FSD (high resolution, wide dhkl-range, high contrast of Fourier chopper, appropriate neutron intensity spectral distribution) allows one to study residual stresses with required accuracy.

- further expansion of the solid angle of the detector system (preserving a high resolution level d/d2.3÷410-3) will lead to a sharp increase of experiment effectiveness.

Thank you for attention!Thank you for attention!