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THE MODELING EFFECT OF COMBINED WPS ON BRITTLE DURABILITY OF HEAT-RESISTANCE STEEL

THE MODELING EFFECT OF COMBINED WPS ON BRITTLE DURABILITY OF HEAT-RESISTANCE STEEL. P. Yasniy, Yu. Pyndus, V. Hlado, I. Okipny, I. Shulhan. Ternopil State Ivan Pul’uj Technical University, Ternopil, Ukraine. SCHEMES LOADING. f=15…25 Hz; Δ K= 20 MPa √m. T 1 = Т 2 = 350 ° C T 3 =20°C.

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THE MODELING EFFECT OF COMBINED WPS ON BRITTLE DURABILITY OF HEAT-RESISTANCE STEEL

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  1. THE MODELING EFFECT OF COMBINED WPS ON BRITTLE DURABILITY OF HEAT-RESISTANCE STEEL P. Yasniy, Yu. Pyndus, V. Hlado, I. Okipny, I. Shulhan Ternopil State Ivan Pul’uj Technical University, Ternopil, Ukraine

  2. SCHEMES LOADING f=15…25 Hz; ΔK= 20 MPa√m T1=Т2=350°C T3=20°C

  3. Local fracture criterions [Hahn G.T., Hoagland R.G., Rosenfild A.R, 1971] [KarzovG.P. at all 1993] [PokhodnyaI. K. at all 1998] [YasniyP.V., HutcaylyukV.B., 2001] [TroshchenkoV.Т., PokrovskyV.V., atall 1997]

  4. Compact specimen from 15Cr2MFA steel with t=19 mm (25 mm) and scheme of WPS K, К 1с К 1c К = K 3 f Н К 1 t l b Т Т Т 3 1

  5. The measure of CTOD at room temperature CT-specimen Transducer Transducer

  6. CTOD - calculation b 1 r 1 r 2 l -[1] Schwalbe K.N. -[2]Panasyuk V.V. r1 = 2...3 mm, r2  5...6 mm

  7. Chemical composition and mechanical properties 15Cr2MFA steel

  8. Residual CTOD (res) versus distance to crack tip (r) after WPS on T=350 0C in 15Cr2MFA steel. Front face (1); back face (2); averaged values (3).

  9. Residual CTOD (res) versus SIF range К at WPS (t = 25mm (1) and 19 mm (2) ) in 15Cr2MFA steel. CTOD calculated equation [Schwalbe K.N.]

  10. Ö K , М P а m f Critical SIF Кf non- hydrogenated (1) and hydrogenated (2, 3) 15Cr2MFA steel at 20°C versus f (a) and f + res (b), equation [Schwalbe K.N.], [Panasyuk V.V.], t = 19 mm (1, 2) and 25 mm (3). Dark symbols –WPS, light – combined WPS 1 140 2 3 130 120 110 100 70 90 110 130 d m , m f a b

  11. The critical SIF Кf of the non-hydrogenated (1) and hydrogenated (2, 3) 15Cr2MFA steel at T= 20 0C versus SIF range. t= 19 mm (1, 2) and 25 mm (3)

  12. The measurement of the cleavage initiation distance (CID) in the fracture surface

  13. Finite element model (based on PLANE82 mesh) of CT -specimen with crack (ANSYS ver.9.0)

  14. PLANE82 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.

  15. S- diagrams of 15Cr2MFA steel under of tensile deformation (1, 2) and combined tensile deformation (3) at 20 0С (1) and 350 0С (2, 3)

  16. Normal stress y - a, and stressintensityi - bdistributionat the crack tip at Kmax = 80 МPа√m after combinedWPS: 1 – K1 = 0; 2 – K1 = 70 МPа√m; 3 – K1 = 80 МPа√m; 4 – K1 = 90 МPа√m; 5 – K1 = 100 МPа√m; 6 – K1 = 110 МPа√m а b

  17. Dependences of the 15Cr2MFA steel cleavage stress on distance X for virgin material (1) and after combined WPS at K1=100 МPа√m, ΔK=20 MPa√m(2) s , МPа сl 2050 CID = 300 µm 2000 2 1950 1 1900 X , mm 1 0 0,2 0,4 0,6 0,8 1,0

  18. The normal stress distribution (1 – 5) and cleavage stress cl (6) at the crack tip after combined WPS with K1 = 94MPam and  K = 20MPam under Kmax = 70 MPam (1); 80 MPam (2); 90 MPam (3); 103 MPam (4); 110 MPam (5) Kf = 103 MPa m - calculated Kf = 108 MPa m - experiment

  19. The dependence of Kf/K1С20on K1/ KQ5%350under the combined WPS of the 15Cr2MFA steel with K = 20 MPam at 350 0C. 1 – FEM calculation, 2– experiment, 3 –Hahn G.T., at all Hahn G.T., at all

  20. Conclusion 1. Detailed fractography showed that the initiation of cleavage fracture 15Cr2MFA steel in initial state and after WPS takes place approximately at the distance CID  of 300 μm from fatigue crack tip. 2. The approach of influencing of combined WPS on ductitility of fracture of heat resistance steel of 15Cr2MFA. A method is based on the FE calculation of the stress-strain state (in the elasto-plastic mode) and local fracture criteria – cleavage stress. Fracture occur, when at the certain distance of CID normal stress achieve cleavage stress cl of material. The temperature change of mechanical properties of 15Cr2MFA steel, Bauschinger’s effect and kinematics hardening of material taken into account. 3. The dependences of critical SIF Кf of 15Cr2MFA steel on maximal SIF К1 at combined WPS were calculated.

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

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