Genetic system for project support with the sequencing problem

One of the main problems faced by manufacturing companies in the production sequencing, also called scheduling, which consists of identifying the best way to order the production program on the machines for improving efficiency. This paper presents the integration of a simulation model with an optimization method to solve the problem of dynamic programming with stochastic demand

Image-based stress field reconstruction in complex media

International audienceIn many instances in life, materials around or within us suffer deformation at high rates. This is the case when engineering structures undergo e.g. impact, crash, forming or pulsed welding. Another important area concerns biological tissues injuries. In those contexts, the transience and inhomogeneous aspect of such loadings as well as the strong multi-physic couplings induced by quasi-adiabatic conditions make both: the experimental capture of the mechanical response very challenging and all the potential assumptions regarding the constitutive relation of the deforming material extremely hazardous. To overcome both issues, we demonstrate in the following that experimental full-field measurements of accelerations can be directly used to inverse the local equilibrium equation and reconstruct fields of stress tensor with no assumption at all on the constitutive relation and its potential spatial and temporal variations. It is also demonstrated that both experimental stress and strain fields can be recombined to eventually identify the local tangent stiffness tensor of the material. The latest constitutes a first step in the field of "model identification", as opposed to parameters' model identification

Image-based stress field reconstruction in complex media

In many instances in life, materials are subject to deformation at high rates, for example: impact, crash, metal forming or pulsed welding. In this context, the transient and inhomogeneous nature of such loading as well as the strong multi-physic couplings induced by quasi-adiabatic conditions make: the experimental capture of the mechanical response very challenging. Additionally, assumptions regarding the constitutive relation of the deforming material are generally required. To overcome both issues, we demonstrate that experimental full-field measurements of acceleration fields can be directly used to invert the local equilibrium equation and reconstruct fields of the stress tensor with no assumption on the constitutive relation and its spatial and temporal variations. We also demonstrate that both experimental stress and strain fields can be recombined to eventually identify the local tangent stiffness tensor of the material. This study constitutes a first step in the field of “direct model identification”, as opposed to standard parametric model identification.</p

Experimental and numerical study of the evolution of stored and dissipated energies in a medium carbon steel under cyclic loading

Lien vers la version éditeur: http://www.sciencedirect.com/science/article/pii/S0167663613000288To obtain robust estimations of the fatigue limit from energy-based fatigue criteria, constitutive laws must include a correct description of the energy balance when modeling the cyclic behavior. The present paper aims at providing a better understanding of the evolution of the energy balance at both microscopic and macroscopic scales in a medium carbon steel. First, an experimental procedure is used to estimate the amount of energy which is either stored in the material or dissipated into heat at a macroscopic scale. The energy balance is observed to be very dependent on the stress amplitude and the number of loading cycles. A model is then developed to investigate the energy balance at a microscopic scale. From the simulation results, both the stored energy and dissipated energy fields are found to be strongly scattered. The dispersion is mostly explained by the crystallographic orientation distribution and the two-phased microstructure

IBII test for high strain rate tensile testing of adhesives

This paper presents the application of the new Image-Based Inertial Impact (IBII) test methodology to study the high strain rate response of adhesives. It relies on an inertial impact (spalling-like) test configuration and the use of ultra-high speed imaging to record the deformation of the test specimen in the MHz range. The underlying novelty is to use the acceleration obtained from the time-resolved displacement maps to derive stress information leading to the identification of the material constitutive parameters. Here, an epoxy adhesive is tested at strain rates up to 1000 s −1 and its modulus and tensile strength are successfully derived from just the deformed images. </p

Clustering and Discernment of Bee Pollen Using an Image Analysis System

In this paper, we suggest a framework for multi-focal image classification and identification, the methodology being demonstrated on microscope pollen images (image processing and classification techniques). The framework is intended to be generic and based on a brute force-like approach aimed to be efficient not only on any kind, and any number, of pollen images (regardless of the pollen type), but also on any kind of multi-focal images. Both stages of the framework's pipeline are planned to be used in an automated Fashion. First, the optimum focus is chosen using the absolute gradient method. Then, pollen grains are collected using a coarse-to-fine method involving both clustering and morphological techniques. Finally, features are extracted and selected using a generalized method, and their classification is checked using hierarchical cluster analysis (HCA). Our findings indicate that HCA meets the demands for automatic pollen detection making it an alternative method for research concerning pollen