We perform a detailed analysis of the contact force network in a dense confined packing of pentagonal particles simulated by means of the contact dynamics method. The effect of particle shape is evidenced by comparing the data from pentagon packing and from a packing with identical characteristics except for the circular shape of the particles. A counterintuitive finding of this work is that, under steady shearing, the pentagon packing develops a lower structural anisotropy than the disk packing. We show that this weakness is compensated by a higher force anisotropy, leading to enhanced shear strength of the pentagon packing. We revisit "strong" and "weak" force networks in the pentagon packing, but our simulation data provide also evidence for a large class of "very weak" forces carried mainly by vertex-to-edge contacts. The strong force chains are mostly composed of edge-to-edge contacts with a marked zig-zag aspect and a decreasing exponential probability distribution as in a disk packing.
The paper aims to highlight the advantages of using data supplied by digital image correlation (DIC) and infrared thermography (IRT) to study the thermomechanical behaviour of materials. It describes an experimental procedure for the determination of mechanical energy and heat sources involved locally during a heterogeneous tensile test. This procedure involves two complementary imaging techniques: DIC provides in‐plane displacement fields, while IRT enables the temperature distribution at the specimen surface to be monitored. Numerous different application examples are successively proposed to underline the promising potential of this experimental approach. Kinematical assessments can reveal the extent of homogeneity of the deformation state for a given gauge length. They can also help to determine the relevance of the variables and/or material parameters introduced in the behavioural description at the length scale imposed by the spatial resolution of optical systems (typically 0.1 mm). Moreover, infrared and kinematical data can be used to derive heat source fields induced by the specimen loading and then to generate information on the dissipative or coupled nature of the deformation mechanisms.
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