Most of the norms used in the field of digital image (and volume) correlation to register two images (or volumes) lead to ill-posed problems. One of the frequent solutions is to enforce a restricted kinematics requiring a compromise between the richness of the solution (i.e., the spatial resolution) and the measurement uncertainty. An alternative route is to use a displacement norm that permits to alleviate this compromise by the means of a mechanical regularization used when the gray levels do not give enough information. It is then possible to compute a displacement vector for each pixel or voxel, inducing lower residuals (in terms of experimental data) while decreasing the noise sensitivity. The resolution performance of these different approaches is discussed, and compared for the analysis of a tensile test on a cast iron specimen based on a pair of tomographic images. As representative reconstructed volumes lead to a large number of degrees of freedom, a dedicated GPU computational strategy has been developed and implemented.

Osteoporosis is a disease characterized by a loss of bone density and an altered bone architecture. These modifications lead to an increased risk factor for bone fracture, particularly of the femoral neck. This disease can be explained by a disorder in the bone remodeling process which is triggered by the apparition of micro-cracks within the bone. According to Frost’s theory [1], these micro-cracks appear for a specific local strain threshold. Thus, the knowledge of the microarchitecture and quality of trabecular bone is essential to determine this local strain threshold. This paper studied the mechanical trabecular bone behavior of 43 patients diagnosed as osteoporotic whose femoral heads were replaced by hip prosthesis. From each patient, a cylinder-shaped of trabecular bone samples was cored. Each sample was scanned by X-ray micro-tomography before a compression test in order to reconstruct a reliable Finite-Element (FE) model of the bone architecture in Abaqus. The force-displacement curves were recorded for all the samples and calibrated by the experimental responses. The force-displacement numerical curves were adjusted to the experimental ones, by modifying the tissue microscopic mechanical behavior. This process leads to the determination of the local strain threshold responsible for triggering the bone remodeling process.

Evaluation of the dynamic properties of quasi-brittle materials is of the utmost importance for assessing the vulnerability of structural components under dynamic loadings such as collision or explosion. To investigate the dynamic strength of (quasi)-brittle material, three-point bending tests are performed on a modified Split Hopkinson Pressure Bar. Such an apparatus is often used with pre-cracked specimen to determine the dynamic stress intensity factor of metallic materials. With quasi-brittle materials special care has to be paid to the processing of the test since fracture can occur at very low strains. The specimen remains in an out-of equilibrium state and fracture occurs before the support reactions appear as if it was a support-free impact test. A special non-equilibrium analytical approach has been developed to process the tests. Finite-element simulations are used to assess relevance of the proposed analysis for normalized short beams. Experimental results on brick and concrete samples showing a significant dynamic strength increase are presented.

This paper is based on additional treatments of the experimental results obtained by L. Bodelot, L. Sabatier, E. Charkaluk, P. Dufrénoy [Experimental setup for fully coupled kinematic and thermal measurements at the microstructure scale of an AISI 316l steel, Mater. Sci. Eng. A 501 (2009) 52–60]. In order to perform inter- and intragranular thermomechanical analyses in a metallic polycrystal at the grain scale, a crystallography-based projection technique of the thermal and displacement fields on a polynomial basis is proposed. It enables intragranular coupled analysis of strain and temperature full-field data consistent with the plastic slip activation observed on specimen surface after the test.

In this paper, an analytical approach is proposed to model chip formation in the case of turning process. Numerical simulations of chip genesis are performed in order to fit efficiently the proposed analy- tical model. In particular, cutting edge radius influence, temperature and internal stresses distribution are studied using finite element modelling. Numerical model setting is made with experimental and literature data using forces and chip thickness.

Stirred bead mills used in industry allow to split up particules in suspension by agitating a milling medium. The multiple impacts may damage beads and thus reduce the stirred milling process efficiency. A discrete numerical approach including simple fluid effects is proposed and carried out in this paper to model and study finely the damage phenomenon. The simulation data allow to identify internal variables of the milling medium and to localize high energy zones. The order of magnitude of contact forces including fluid contribution will enhance the bead wear law.

Since 1994, HDS is a major player in the design of complex composite parts, especially for racing sailing yachts [1]. In this paper, we suggest to present our approach in the design and finite-element modelling of the rigid wing-sail of the trimaran that won the 33rd America’s Cup, held in February 2010. From the decision to design the wing-sail to the assembly on the maxi trimaran, we will present the different steps of design and computation: principles and assessment of the aerodynamic loads, structural design and modelling with tools adapted to each problem, mass optimization. Then, we will detail some of the numerical problems that we faced in this project.