THE THE MODELING MODELING EFFECTEFFECT OF OF COMBINED WPS ON BRITTLE COMBINED WPS ON BRITTLE

DURABILITY OF HEAT-DURABILITY OF HEAT-RESISTANCE STEELRESISTANCE STEEL

P. Yasniy, Yu. Pyndus, P. Yasniy, Yu. Pyndus,

V. Hlado, I. Okipny, I. V. Hlado, I. Okipny, I. ShulhanShulhan

Ternopil State Ivan Pul’uj Technical Ternopil State Ivan Pul’uj Technical University, Ternopil, UkraineUniversity, Ternopil, Ukraine

SCHEMES LOADINGSCHEMES LOADINGSCHEMES LOADINGSCHEMES LOADING

K

T

K =Kf 3

K IC

K 1

K 2

T 1T3 T2

K

T

K =Kf 3

K IC

K 1

K 2

T 1T3 T2

TT11==ТТ22==350350°°C TC T33=20°C=20°CTT11==ТТ22==350350°°C TC T33=20°C=20°Cf=15…25 f=15…25 Hz; Hz; ΔΔK= 20 K= 20

MPaMPa√m√m f=15…25 f=15…25 Hz; Hz; ΔΔK= 20 K= 20

MPaMPa√m√m

Local fracture criterionsLocal fracture criterions32

2.01

cl

CK [Hahn G.T., Hoagland R.G., Rosenfild A.R, 1971]

),(

)0

(

CSI

diTemI

[Karzov G.P. at all 1993]

)2/1ln()2/1()2/1ln(1

kSIcMC

R

1

1ln);1,0(92,0 eе [Pokhodnya I. K. at all 1998]

)(22.0

)(3

1

сl

cK

[Yasniy P.V., Hutcaylyuk V.B., 2001]

cXdpid

HcocK

2)(

dpid

Hcoс

)(

[Troshchenko V.Т., Pokrovsky V.V., at all 1997]

Compact specimen from 15Cr2MFA steel with t=19 mm (25 mm) Compact specimen from 15Cr2MFA steel with t=19 mm (25 mm) and scheme of WPSand scheme of WPS

l

b Н

t

К3 = Kf

K, К1с

Т

К1

Т3 Т1

К1c

The measure of CTOD at room temperatureThe measure of CTOD at room temperature

Transducer CT-specimen

Transducer

CTOD - calculationCTOD - calculation

b1

l

r1 r2

126,04,0

)(4,0

rlb

lbres

1/

//

11

12111

rl

rlf

r1 = 2...3 mm, r2 5...6 mm

-[1] Schwalbe K.N.

-[2] Panasyuk V.V.

Chemical composition and mechanical properties 15Cr2MFA Chemical composition and mechanical properties 15Cr2MFA steelsteel

Chemical composition ( wt.

%)

Т, 0C 0,2 u

MPa %

Steel 15Cr2MFA 0,18С; 0,62Мо; 0,27Si; 0,29V; 0,48Mn; 2,58Cr; 0,019S; 0,16Ni; 0,013P; 0,011Ti

20 900 1000 15,8 39,2

177 750 826 8,5 23,0

300 653 694 11,7 36,0

Residual CTOD (Residual CTOD (resres) versus distance to crack tip (r) after WPS ) versus distance to crack tip (r) after WPS

on T=350 on T=350 00C in 15Cr2MFA steel. Front face (1); back face (2); C in 15Cr2MFA steel. Front face (1); back face (2); averaged values (3).averaged values (3).

0 0,5 1,0 1,5 2,0 2,5

0

2

4

6

8

10

12

14

16 res(r), m

r, mm

1 2 3

Residual CTOD (Residual CTOD (res) versus SIF range res) versus SIF range К К at WPS (t = 25mm at WPS (t = 25mm (1) and 19 mm (2) ) in 15Cr2MFA steel. CTOD calculated (1) and 19 mm (2) ) in 15Cr2MFA steel. CTOD calculated

equation equation [[Schwalbe K.N.Schwalbe K.N.]]

0 5 10 15 20 2

4

6

8

10

12

14

16

res, m

К, МPаm

1 2

Critical SIF КCritical SIF Кff non- hydrogenated (1) and hydrogenated (2, 3) non- hydrogenated (1) and hydrogenated (2, 3)

15Cr2MFA steel at 2015Cr2MFA steel at 20°°C versus C versus f f (a) and (a) and f f + + resres (b), equation (b), equation

[[Schwalbe K.NSchwalbe K.N.], [.], [Panasyuk V.V.],Panasyuk V.V.], t = 19 mm (1, 2) and 25 mm t = 19 mm (1, 2) and 25 mm (3). Dark symbols –WPS, light – combined WPS(3). Dark symbols –WPS, light – combined WPS

b

70 90 110 130

100

110

120

130

140

Kf, МPаm

f+res, µm

a

70 90 110 130

100

110

120

130

140

Kf, МPаm

f, m

1 2 3

The critical SIF КThe critical SIF Кff of the non-hydrogenated (1) and hydrogenated of the non-hydrogenated (1) and hydrogenated

(2, 3) 15Cr2MFA steel at T= 20 (2, 3) 15Cr2MFA steel at T= 20 00C versus SIF range. t= 19 mm C versus SIF range. t= 19 mm (1, 2) and 25 mm (3)(1, 2) and 25 mm (3)

0 5 10 15 20

100

110

120

130

140

Kf, МPаm

К, МPаm

1 2 3

The measurement of the cleavage initiation distance (CID) in the The measurement of the cleavage initiation distance (CID) in the

fracture surfacefracture surface

CID

fatigue crack

Finite element model (based on PLANE82 mesh) of CT -Finite element model (based on PLANE82 mesh) of CT -specimen with crack specimen with crack

(ANSYS ver.9.0)(ANSYS ver.9.0)

PLANE82 geometryPLANE82 geometry

This 8-node element is defined by eight nodes having two degrees of freedom at each node: translations in the nodal x and y directions. The element has plasticity, creep, swelling, stress stiffening, large deflection, and large strain capabilities.

S-S- diagrams of 15Cr2MFA steel under of tensile deformation (1, diagrams of 15Cr2MFA steel under of tensile deformation (1, 2) and combined tensile deformation (3) at 20 2) and combined tensile deformation (3) at 20 00С (1) and 350 С (1) and 350 00С С

(2, 3)(2, 3)

Normal stress Normal stress yy - - aa, , and stressand stress intensityintensity ii - - bb distributiondistribution at the at the

crack tip atcrack tip at K Kmaxmax = 80 М = 80 МPPа√а√m after combinedm after combined WPSWPS: 1 – K: 1 – K11 = 0; = 0;

2 – K2 – K11 = 70 М = 70 МPPа√а√mm; 3 – K; 3 – K11 = 80 М = 80 МPPа√а√mm; 4 – K; 4 – K11 = 90 М = 90 МPPа√а√mm; 5 ; 5

– K– K11 = 100 М = 100 МPPа√а√mm; 6 – K; 6 – K11 = 110 М = 110 МPPа√а√mm

0 0,5 1,0 1000

1500

2000

2500

3000

y, МPа

CID

- 1 - 2 - 3 - 4 - 5 - 6

X, mm

0,5 1,0 0

500

1000

CID

X, mm

i, МPа

а b

Dependences of the 15Cr2MFA steel cleavage stress on distance Dependences of the 15Cr2MFA steel cleavage stress on distance X for virgin material (1) and after combined WPS at X for virgin material (1) and after combined WPS at KK11=100 =100

МPа√mМPа√m, , ΔΔK=20 MPaK=20 MPa√m√m ((22))

CID = 300 µm

1 2

0 0,2 0,4 0,6 0,8 1,0

1900

1950

2000

2050

X1, mm

сl , МPа

The normal stress distribution The normal stress distribution (1 – 5) (1 – 5) and cleavage stress and cleavage stress clcl (6) at the (6) at the

crack tip after combined WPS with Kcrack tip after combined WPS with K11 = = 9494 MPaMPam and m and K K = = 2020

MPaMPam under Km under Kmaxmax = 70 = 70 MPaMPam m (1); 80 (1); 80 MPaMPam m (2); 90 (2); 90 MPaMPam m (3); (3);

103 103 MPaMPam m (4); 110 (4); 110 MPaMPam m (5)(5)

0 0,5 1,0 1000

1500

2000

2500

3000

3500

X, mm

y,cl, МPа

1 2 3 4 5 6

CID

cl

Kf = 103 MPam Kf = 103 MPa m - m - calculatedcalculated

Kf = 108 MPa m - m - experimentexperiment

The dependence of KThe dependence of Kff //KK1С1С2020 on on KK11 / K/ KQ5%Q5%

350350 under the combined WPS of the under the combined WPS of the 15Cr2MFA steel with 15Cr2MFA steel with K = 20 MPaK = 20 MPam at 350 m at 350 00CC. 1 – . 1 – FEM calculation, 2FEM calculation, 2– –

experiment, 3 –experiment, 3 –Hahn G.T.Hahn G.T., at all, at all

0,0 0,2 0,4 0,6 0,8 1,0 0,95

1,00

1,05

1,10

1,15

1,20

1,25

1,30

1,35

1,40

- 1

Kf/ K1C20

K1 / KQ5%350

- 2

- 3

m

Qc

f

K

KC

K

K

350%5

120

1

1

3)(

22.01

pl

ecl

CK

Hahn G.T.Hahn G.T., at all, at all

ConclusionConclusion1. Detailed fractography showed that the initiation of cleavage 1. Detailed fractography showed that the initiation of cleavage

fracture 15Cr2MFA steel in initial state and after WPS takes fracture 15Cr2MFA steel in initial state and after WPS takes place approximately at the distance CID place approximately at the distance CID of 300 μm from of 300 μm from fatigue crack tip. fatigue crack tip.

2. The approach of influencing of combined WPS on 2. The approach of influencing of combined WPS on ductitility of fracture of heat resistance steel of 15Cr2MFA. A ductitility of fracture of heat resistance steel of 15Cr2MFA. A method is based on the FE calculation of the stress-strain method is based on the FE calculation of the stress-strain state (in the elasto-plastic mode) and local fracture criteria – state (in the elasto-plastic mode) and local fracture criteria – cleavage stress. Fracture occur, when at the certain distance cleavage stress. Fracture occur, when at the certain distance of CID normal stress achieve cleavage stress of CID normal stress achieve cleavage stress clcl of material. of material. The temperature change of mechanical properties of The temperature change of mechanical properties of 15Cr2MFA steel, Bauschinger’s effect and kinematics 15Cr2MFA steel, Bauschinger’s effect and kinematics hardening of material hardening of material takentaken into account. into account.

3. The dependences of critical SIF К3. The dependences of critical SIF Кff of 15Cr2MFA steel on of 15Cr2MFA steel on maximal SIF Кmaximal SIF К11 at combined WPS were calculated. at combined WPS were calculated.

AknowledgementsAknowledgements

The work has been carried out as The work has been carried out as part of Project which is financially part of Project which is financially supported by the Ukrainian Ministry supported by the Ukrainian Ministry of education & Science. of education & Science.