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.

Quantitative elastography of renal transplants using supersonic shear imaging: a pilot study

Abstract: Purpose To evaluate the reliability of quantitative ultrasonic measurement of renal allograft elasticity using supersonic shear imaging (SSI) and its relationship with parenchymal pathological changes.

Ensemble averaging stress–strain fields in polycrystalline aggregates with a constrained surface microstructure – Part 2: crystal plasticity

Abstract: The effect of three-dimensional (3D) grain morphology on the deformation at a free surface in polycrystalline aggregates is investigated by means of a large-scale finite element and statistical approach. For a given two-dimensional surface at z = 0 containing 39 grains with given crystal orientations, eight 3D random polycrystalline aggregates are constructed having different 3D grain shapes and orientations except at z = 0, based on an original 3D image analysis procedure. They are subjected to overall tensile loading conditions. The continuum crystal plasticity framework is adopted and the resulting plastic strain fields at the free surface z = 0 are analyzed. Ensemble average and variance maps of the plastic strain field at the observed free surface are computed. In the case of elastoplastic copper grains, fluctuations ranging between 2% and 80% are found in the equivalent plastic slip level at a given material point of the observed surface from one realization of the microstructure to another. The obt...

Fatigue crack initiation detection by an infrared thermography method

Abstract: In this paper, the study of the temperature variation during fatigue tests was carried out on different materials (steels and aluminium alloys). Tests were performed at ambient temperature using a piezoelectric fatigue system (20 kHz). The temperature field was measured on the surface of the specimen, by means of an infrared camera. Just at the beginning of the test, it was observed that the temperature increased, followed by a stabilization which corresponds to the balance between dissipated energy associated with microplasticity and the energy lost by convection and radiation at the specimen surface and by conduction inside the specimen. At the crack initiation, the surface temperature suddenly increases (whatever the localization of the initiation), which allows the determination of the number of cycles at the crack initiation and the number of cycles devoted to the fatigue crack propagation. In the gigacycle fatigue domain, more than 92% of the total life is devoted to the initiation of the crack. So, the study of the thermal dissipation during the test appears a promising method to improve the understanding of the damage and failure mechanism in fatigue and to determine the number of cycles at initiation.

Lipolysis and metabolism of fatty acids in cheese

Abstract: Enzymatic hydrolysis (lipolysis) of milk glycerides to free fatty acids is essential for flavor development in cheese. The principal lipolytic agents in cheese include lipoprotein lipase from raw milk, pregastric esterase in cheeses made using rennet paste, and enzymes from the starter and nonstarter microbiota. Lactic acid bacteria are weakly lipolytic and mainly possess nonlipolytic esterases located intracellularly. Lipolysis level is, thus, low in many internal bacterially ripened cheeses. It is higher in certain varieties, such as Swiss cheese, smear-ripened, and particularly mold-ripened cheeses, in which specific lipolytic secondary microbiota develops. Exogenous lipases are occasionally used to develop flavor. Short-chain fatty acids directly contribute to flavor, but fatty acids can also act as precursors for the production of a wide range of other flavor compounds, such as esters, lactones, and methylketones that are associated with diverse flavors. Methods for determining levels of fatty acids are also discussed.