A computational lifetime prediction of a thermal shock experiment. Part I: thermomechanical modelling and lifetime prediction

Abstract

A B S T R A C TThe SPLASH experiment has been designed in 1985 by the CEA to simulate thermal fatigue due to short cooling shocks on steel specimens and is similar to the device reported by Marsh in Ref.[1]. The purpose of this paper is to discuss the mechanical and the fatigue analysis of the experiment using results from FEM computations. The lifetime predictions are obtained using a modified dissipated energy with a maximal pressure term and agree with the experimental observations. The numerical analysis of the mechanical state shows an important evolution of the triaxiality ratio during the loading cycle. Further comparisons and discussions of the fatigue criteria are provided in the second part of the paper (Part II) 2 .A = elastic 4th order tensor c, k = thermal capacity and conductivity E, ν = young's modulus and Poisson's coefficient J 2 = second invariant of the deviatoric stress tensor P = hydrostatic pressure p = cumulated plastic strain q = thermal flux r = heat source T = temperature field TF = triaxiality factor u = displacement field W p = dissipated energy density per cycle σ , = equivalent stress and strain ranges , e = strain tensor and its deviatoric part e , p = elastic and plastic strain tensors ρ = volumic mass σ Y = elastic limit σ, s = stress tensor and its deviatoric part I N T R O D U C T I O NA series of industrial structures like turbines, engines, nuclear or classical thermal plants are subject to thermomechanical cycling leading to fatigue. The actual design and

Hybrid Stereocorrelation Using Infrared and Visible Light Cameras

“…In order to assess thermal fatigue occurring in nuclear power plants [1][2][3], a new experimental setup is developed for which thermal shocks are applied to stainless steel plates with a pulsed laser [4]. IR and visible light cameras are used to measure 2D kinematic and thermal fields, respectively [5].…”

A computational lifetime prediction of a thermal shock experiment. Part II: discussion on difference fatigue criteria

“…In this section, we present results obtained with four different fatigue criteria. For the SPLASH experiment, we have obtained the stabilized mechanical cycle by complete elastoplastic finite element computations described in the first part of the paper (Part I) 2 . The uniaxial isothermal LCF tests in Ref.…”

“…The mechanical analysis presented in Part I 2 considered the cyclic temperature field as the loading of the test. It further assumed that the elastoplastic constitutive law is uncoupled from the damage evolution in the material.…”

“…The purpose of this paper is to discuss the application of different fatigue criteria in this case. The fatigue criteria: dissipated energy, Manson Coffin, Park and Nelson, dissipated energy with a pressure term, are determined for the experiment using results from FEM computations presented in the first part of the paper (Part I) 2 and compared with results from uniaxial and multiaxial experiments from literature. The work emphasizes the evolution of the triaxiality ratio during the loading cycle.…”

Thermo-mechanical fatigue behaviour of welded tubular parts made of ferritic stainless steel

“…26). Both strain distribution and stress triaxiality have a strong impact on the low cycle fatigue lifetime and in particular on thermal fatigue ( [31] [32], [33], [34]). From the analysis of fatigue lifetime of these types of specimens, it should then be possible to decide on the most relevant model.…”