Daniel Froelich

New Representation of the True Stress for Uniaxial Extension of Crosslinked Rubbers

The elasticity of different natural rubbers and SBR rubbers has been studied in simple extension at constant strain rate. The true stress has been plotted as a function of λ2−λ−1 as suggested by the molecular theory. A series of straight lines which do not pass through the origin have been obtained, and consequently two parameters σ0 and G have been introduced. These results allow one to hypothesize that the tensile stress is the sum of two terms: a Gaussian entropic contribution and a further contribution reaching rapidly a steady state value σ0. The σ0 term is found to depend only on the chemical nature of the rubber and may be ascribed to local interaction of the segments of the network, whereas the value of G depends on the degree of crosslinking and seems to represent the rubbery modulus of the kinetic theory. A number of experimental data for various natural rubbers and PDMS networks from the literature have been replotted in the same way in order to check the validity of our representation, and a s...

Disassembly for valorization in conceptual design

The valorization rate improvement depends on the product disassembly characteristics. So, researchers develop and implement the Design for Disassembly (DfD) methodology to increase the valorization. The design process of technical products is critical to define the End of Life (EoL) disassembly characteristics of a product. It is the reason why several tools have been developed to evaluate the product disassembly at the end of the design process, when all product characterizations are defined. Nevertheless, it appears that the product disassembly improvement cannot be possible without a real redesigning of the product. In fact, all the existing tools don’t take into account the influence of design parameters on the disassembly results; they focus on the future disassembly process. In previous studies, we have shown that the conceptual design is the most important phase to integrate disassembly constraints in design process. But, this design phase is not addressed by current approach of DfD. We also note that a systematic methodology, which incorporates disassembly evaluation earlier in a design process, is absent. In this paper, we present our proposition concerning a methodological approach to design product easy to disassemble. In our approach, we use a Conceptual Disassembly Model (CDM) to help designers to consider disassembly. A case study is presented to understand the approach and to illustrate our purpose.

Ecoselection of Materials and Process for Medium Voltage Products

This article addresses the ecodesign of medium voltage electrical switchgear. These products are electrical units possessing particular specificities, associated with the conditions of use. They operate at elevated voltage and current, and are guaranteed for a minimum service life of twenty years. This demands a very high level of quality and implies the use of specific materials and manufacturing processes. This requirement makes it difficult to predict the end-of-life management. It is therefore important to examine the various alternatives for incorporating ecodesign in these units. This entails the assessment of the environment of existing products and the study of the design procedure employed. The approach described here is valid for other products in different sectors. It is based on the simplification of life cycle assessments to focus only on the most important life cycle phases and environmental indicators which offer a wider margin for improvement. For the case of medium voltage switchgear, stress is placed on the manufacturing and end-of-life phases.

Evolution of the fresh water distribution in Nouakchott after the commissioning of the Aftout Es Saheli project (water from the Senegal River)

AbstractMauritania is characterized by an arid climate with limited water resources. Nouakchott has experienced tremendous growth, from a population of several hundred people in 1960 to over 700,000 in 2005 according to the National Statistics Office, this growth has generated abnormal pressure on core infrastructure, particularly for drinking water and wastewater management. The water needs of the population of Nouakchott were exclusively met by the excessive exploitation of Idini aquifer’s well field. In late 2010, Mauritania began operating the Aftout Es Saheli project supplying the city with water pumped from the Senegal River. The aim of this paper is to present the evolution of the water situation in the city before and after the Aftout Es Saheli project, and to recommend ways to improve the management of this situation, especially in the peripheral neighborhoods. Our study focused on the water’s availability and physico-chemical and bacteriological qualities in both poor neighborhoods supplied by a...