ParisTech

About: ParisTech is a education organization based out in Paris, France. It is known for research contribution in the topics: Finite element method & Residual stress. The organization has 1888 authors who have published 1965 publications receiving 55532 citations. The organization is also known as: Paris Institute of Technology & ParisTech Développement.

A study on the frictional response of reptilian shed skin

Abstract: Deterministic surfaces are constructs of which profile, topography and textures are integral to the function of the system they enclose. They are designed to yield a predetermined tribological response. Developing such entities relies on controlling the structure of the rubbing interface so that, not only the surface is of optimized topography, but also is able to self-adjust its tribological behaviour according to the evolution of sliding conditions. In seeking inspirations for such designs, many engineers are turning toward the biological world to study the construction and behaviour of bio-analogues, and to probe the role surface topography assumes in conditioning of frictional response. That is how a bio-analogue can self-adjust its tribological response to adapt to habitat constraints. From a tribological point of view, Squamate Reptiles, offer diverse examples where surface texturing, submicron and nano-scale features, achieves frictional regulation. In this paper, we study the frictional response of shed skin obtained from a snake (Python regius). The study employed a specially designed tribo-acoustic probe capable of measuring the coefficient of friction and detecting the acoustical behavior of the skin in vivo. The results confirm the anisotropy of the frictional response of snakes. The coefficient of friction depends on the direction of sliding: the value in forward motion is lower than that in the backward direction. Diagonal and side winding motion induces a different value of the friction coefficient. We discuss the origin of such a phenomenon in relation to surface texturing and study the energy constraints, implied by anisotropic friction, on the motion of the reptile.

Reynolds number influence on preferential concentration of heavy particles in turbulent flows

Abstract: We present a study of the preferential concentration and clustering in homogeneous and isotropic turbulence. Using Voronoi diagrams, we have formerly quantified preferential concentration as a function of the Stokes number in moderate turbulence conditions up to Reynolds number based on Taylor microscale of the order of Rλ ~ 120. Using an active grid recently implemented in our windtunnel, we investigate in the present study, the effect of Reynolds number on particles clustering, in the range Rλ ~ 200 – 400.

A study on the influence of bond material on honing engine cylinder bores with coated diamond stones

Abstract: A consistent increase in demand for special tools designed to enhance an efficient honing of engine cylinder bores is observed. Metallic Bonded Diamond Stones (Dia-M) are more and more used for their wear resistance and their high tool life. However, the hardness of this Metallic Bond leads to the degradation of the honed surface aspect by the formation of smudgy grooves edges (blechmantel). This torn and folded metal affects the required functional performances of the cylinder bore. In this study, two new diamond coated abrasive stones with Vitrified and Resinoid Bonds (respectively Dia-V and Dia-R) are tested and compared to the Dia-M sticks. The influences of bond material on the honing reliability are studied in terms of honed surface aspect, material removal rate and wear properties. Results reveal that the stiffness and the openness structure of the Resinoid Bond leads to a better trade off between surface aspect and tool life.