Experimental Mechanics (2015) 55:761–769 DOI 10.1007/s11340-014-9975-y Stress Network Analysis of 2D Non-Cohesive Polydisperse Granular Materials using Infrared Thermography C. Chaiamarit · X. Balandraud · I. Preechawuttipong · M. Gr´ ediac Received: 18 March 2013 / Accepted: 3 December 2014 / Published online: 8 January 2015 © Society for Experimental Mechanics 2015 Abstract The objective of the study is to analyze the hydrostatic stress network in two-dimensional cohesionless polydisperse granular materials under confined compres- sion. Infrared (IR) thermography and thermoelastic stress analysis were used for this purpose. As model materi- als, the granular media under study were composed of cylinders made in POM polymer. Three cylinder diame- ters were used to prepare different samples differing in terms of the ratio between the numbers of cylinders of each diameter. These samples comprised between 200 and 324 cylinders. The temperature variations due to thermoelastic coupling under loading were measured on a cross-section of the cylinder network using an IR camera. The process- ing enabled us to identify the hydrostatic stress network in the samples. Molecular dynamics (MD) simulations were then performed to obtain a numerical network of hydro- static stresses for each sample. The fields obtained from IR experiments and MD simulations are rarely in agree- ment, except in some zones of the sample. This was expected as it is not possible to have exactly the same geometrical configurations with both approaches. How- ever, a good agreement is obtained in terms of statistical distributions. C. Chaiamarit · I. Preechawuttipong Department of Mechanical Engineering, Faculty of Engineering, Chiang Mai University, 239 Huay Kaew Rd., Muang District, Chiang Mai 50200, Thailand X. Balandraud () · M. Gr´ ediac Clermont Universit´ e, Universit´ e Blaise Pascal, Institut Franc ¸ais de M´ ecanique Avanc´ ee, Institut Pascal, CNRS UMR 6602, BP 10448 63000 Clermont-Ferrand, France e-mail: Xavier.Balandraud@ifma.fr Keywords Granular material · Infrared thermography · Thermoelastic stress analysis · Hydrostatic stress network · Molecular dynamics simulation Introduction Granular materials are employed in many engineer- ing domains, for instance in geotechnical, agronomical, pharmaceutical and chemical industries. Many subtances in these industries are prepared from grains or powders. The macroscopic mechanical behavior of a granular medium is generally complex. Indeed, continuum mechanics is not directly applicable and must be replaced by a grain- scale (microscopic) description [1]. Many studies have been undertaken over the last thirty years with the aim of understanding the macroscopic behavior from simula- tions at the scale of the particle network. Various param- eters have been numerically investigated: the stiffness of the contact between the particles, the particle shape, the friction between particles, the cohesive or non-cohesive character of the contacts, etc. In terms of experimental approaches, some full-field measurement techniques have been employed. Most of them are based on kinematic data, either at the surface or in the volume of granu- lar samples. For instance, the particle image velocimetry technique is based on optical photography to analyze the particle flows [2]. X-ray tomography has been used to study the internal structure of deformation inside three- dimensional (3D) granular media [3]. For the direct mea- surement of contact forces, the carbon paper method can be used in a two-dimensional (2D) section of a 3D granular material [4]. Concerning stress measurement, photoelas- ticimetry has been employed using particles which had the property to become birefringent under mechanical load.