Modeling for fracture in materials under long-term static creep loading and neutron irradiation. Part 2. Prediction of creep rupture strength for austenitic materials

Abstract

We present some results of prediction of creep rupture strength and plasticity for austenitic materials prior to and after irradiation with variable neutron flux rates, based on physicomechanical model as outlined in Part 1. The calculated results are compared with the available experimental data.Keywords: creep rupture strength, plasticity, void, neutron flux rate. Creep Rupture Strength and Plasticity of 1Kh18N10T Steel in Its Initial State.Based on the physico-mechanical model for intercrystalline fracture [1], calculations were performed to predict creep rupture strength and plasticity in 1Kh18N10T austenitic steel under uniaxial loading. For calculating the creep rupture strength and plasticity curves we simulated steady-load tests and therefore creep rupture strength is expressed in terms of stresses active at the initial time of testing, i.e., conventional stresses. It is known that under the creep tension conditions the cross section of a specimen is reduced [2]. The true stress F true (i.e., the stress corrected for the cross-section reduction) was calculated bywhere F c is the conventional stress in the specimen. The calculation involves temperature-dependent and temperature-independent parameters. The last-mentioned ones include Ω, R 0 , k η , ρ max , and d g .* According to [3], the initial radius of a void arisen R 0 is taken 5 10 4 ⋅ − mm, Ω = ⋅ − 1 21 10 29 . m 3 [4]. As per [5] the grain size d g was set equal to 0.1 mm. The k d g η ratio was determined from the data on stress rupture plasticity in a unirradiated material at T =°650 C. We used ρ max and c α as adjustable parameters and found them by the criterion of the best agreement between the experimental and calculated data on creep rupture strength at various temperatures in the life time range up to 10 3 h. Also, it was established that c α parameter can be constant, i.e., independent of temperature. Hence, we obtained c α = 9 and ρ max =1000 m −2 .The temperature-dependent parameters are as follows: D b b δ governs the grain-boundary diffusion, a c , n c , and m c determine creep {Eq. (32) in [1]}, a p controls the strain hardening, and σ Y is the yield stress. To describe the temperature dependence of D b b δ we used (25) [1], where δ b b D 0 13 2 10 = ⋅ − mm 3 /s and Q b =167 kJ/mole [4].* Hereinafter we will use the notation as in Part 1 [1] unless otherwise defined.

In-situ Creep Testing Capability Development for Advanced Test Reactor

“…The effects of irradiation on creep properties of various materials has been investigated by in-pile or/and post-irradiated creep test conducted using several methods; including MTRs, fission reactors, cyclotron or other setups. [42][43][44][45][46][47][48] Irradiation creep has been extensively investigated to provide data that can be used for component analysis.…”

A method for predicting fracture resistance of material in cyclic loading under viscoelastoplastic deformation and neutron irradiation conditions

“…The structure operation time is, for example, 2 10 5 ⋅ h. The inelastic strain range in cycles is the same. Based on [14][15][16], we have ε ε…”

“…This relation can be derived using stress rupture ductility data for a material irradiated with a neutron flux Φ and pre-irradiated with neutron fluence F [14][15][16]. Figure 2 shows schematically the dependence of creep rupture strength σ and stress rupture ductility ε f on time to failure t f together with the transgranular and intergranular fracture regions.…”

“…can be determined from the functions ε f f t ( ) derived by means of a physical-mechanical model of intergranular fracture [14][15][16]. Consider prediction of fatigue curves by the Coffin-Manson equation [12,13]:…”

“…h −1 ) [21]. Let us assess ξ * by using the proposed method and data provided in [14][15][16]. Figure 8 shows the calculated ε ξ f ( ) function at T =°600 C for steels of Kh18N9 and Kh18N10T grades in the initial state (Φ = 0).…”