Numerical and experimental estimation of thermomechanical fields heterogeneity at the grain scale of 316L stainless steel

Abstract

International audiencePolycrystalline metallic materials are made of an aggregate of grains more or less well oriented with respect to the loading axis. During mechanical loading, the diversity of grain orientations leads to heterogeneous deformation and it is well known that most of the plastic work generated during the deformation process reappears in the form of heat whereas a certain proportion remains latent in the material and is associated with microstructure changes. To access the local stored energy, experimental and numerical energy balances are needed at a suitable scale. In this way experiments have already been done in-house on 316L stainless steel to monitor the evolution of temperature and deformation fields at the microstructural scale. The aim of the present study is now to develop a simplified numerical model, based on experimental observations and able to simulate the thermomechanical behavior, in order to provide a first assessment of the stored energy level and heterogeneity. Our model renders well the average thermomechanical behavior of the specimen and reveals a high heterogeneity of the stored energy at the microstructure scale. Better knowledge of the stored energy at this scale should improve our understanding of strain localization mechanisms

Experimental and numerical study of the evolution of stored and dissipated energies in a medium carbon steel under cyclic loading

“…In this perspective, the recent experimental progress in the determination of the thermomechanical fields at a local (i.e. grain) scale should help in improving the parameter identification procedure (Seghir et al, 2012).…”

Regularized InfraRed Image Correlation Applied to Laser-Induced Thermal Shocks

“…The use of IR cameras in the field of experimental mechanics is more and more common [1][2][3][4][5][6][7][8][9][10][11][12][13] in order to quantify the thermomechanical response of materials under load. Most of the time the sought information consists of the kinematic and temperature fields.…”

“…Most of the time the sought information consists of the kinematic and temperature fields. Both are induced by either the mechanical loading [1][2][3][4][5][6][7][8][9][11][12] or the applied thermal history [10,[13][14]. In the first case, temperature elevations are of few degrees Celsius, and accessing the thermomechanical response may provide a better understanding of localization and dissipative phenomena [1][2][3][4][5][6][7][8][9][11][12].…”

“…One of them requires the use of two cameras, namely, one working in the IR and the second in the visible light wavelength range [1][2][3][4][5][6][7][8][9]10,[13][14]. The visible light camera is not sensitive to temperature variations and the DL conservation assumption is satisfied.…”

On the influence of microstructural gradients in the fatigue lifetime estimation of a railway axle

“…A proposition for approximating grain orientation inspired by [5] is then made. Comparison with computations made with crystalline constitutive laws is under way.…”