Rémy Chieragatti

Metal cutting modelling SPH approach

The purpose of this work is to evaluate the use of the smoothed particle hydrodynamics (SPH) method within the framework of high speed cutting modelling. First, a 2D SPH based model is carried out using the LS-DYNA® software. The developed SPH model proves its ability to account for continuous and shear localised chip formation and also correctly estimates the cutting forces, as illustrated in some orthogonal cutting examples. Then, the SPH model is used in order to improve the general understanding of machining with worn tools. At last, a hybrid milling model allowing the calculation of the 3D cutting forces is presented. The interest of the suggested approach is to be freed from classically needed machining tests: Those are replaced by 2D numerical tests using the SPH model. The developed approach proved its ability to model the 3D cutting forces in ball end milling.

Influence of Coating on the Thermal Fatigue Resistance of a Ni-based Superalloy:

In this article, the influence of a M-CrAlY polycrystalline coating on the thermal fatigue behavior of a nickel-base superalloy has been investigated. A special device using a rotating bending machine and two thermal sources has been used to perform thermomechanical tests. The two thermal sources have been set to obtain temperature variations between 750 and 1120 C in the central part of the specimens, with a frequency of 0.1 Hz. The results show a deleterious effect of the coating on the fatigue resistance. Numerical simulations have been carried out on SAMCEF to determine the thermomechanical field of the so-tested specimens. Calculated thermomechanical cycles of critical sites are associated with micro-structure evolution and damage by cracking observed on the specimens. Damage mechanisms related to the presence of the coating are discussed.

Static and Dynamic Behavior of a 3D-Periodic Structure

This paper lies within the context of assessment of damage of an air-to-air compact exchanger subjected to cyclic pressure, temperature and vibrations. The objective is to provide a predictive lifetime model both for accelerated testing and in-service applications. The model should describe the macroscopic behavior and the ageing of the interfaces between the core of the exchanger and all elements attached to the core. These interfaces constitute the critical sites where damage might occur. The modeling reported here is limited to the description of the core behavior in order to evaluate later the efforts that the core generates on the interfaces. The stiffness of the core is calculated in all three directions via an analytical method. In addition, a FE calculation is performed using the FE code Samcef. Also, static tensile tests are carried out on specimens in all three directions.