Nouvelle methode d'evaluation des scenarios de fin de vie pour des produits en phase de conception preliminaire

Following the growth of the consumer society, the environmental impact provoked by the increasing number of manufactured products is becoming a problem we can no longer ignore. In this context, all products' life cycle stages must be given special attention. However, the stage which is becoming more and more crucial is the end-of-life stage. Landfills are saturated which leads to the rejection of harmful substances in the soil and water. Uncontrolled incinerated wastes release dangerous gases into the atmosphere. In addition, disposing used products which may contain valuable materials produces a significant waste of raw materials. In response to this phenomenon, regulations have been created. They impose strict rules regarding the recovery and processing of used products. In order to respect these regulations all the while remaining competitive in the market, companies must adopt a preventive behavior and modify their products by acting at the commencement of the process cycle, that is to say, during the design phase. By optimizing the design parameters for the end-of-life, it's possible to choose environmental-friendly end-of-life scenarios which respect the laws as well as allow for making a substantial profit. To achieve this goal, the most suitable end-of-life scenario must be chosen during the preliminary design stage: before setting final design parameters but having enough information to make an appropriate choice.;In order to develop the method, we tried to achieve each of these goals. The methodology begins with a literature review on Design for the Environment and Design for end of life. It helps to identify all parameters which influence the products' end-of-life and which are available during preliminary design stage. The literature review also highlights the key aspects of recovery processes and end-of-life treatments. These aspects are classified under the four main criteria (Income generated from sales, Treatment costs, Compliance with regulations, Environmental impact) used to evaluate each end-of-life option (Reuse, Remanufacturing, Recycling With Disassembly, Recycling Without Disassembly, Incineration With Energy Recovery, Disposal). From this classification, a three-level hierarchy is built and forms the basis of the multicriteria decision problem. In order to solve it, the TOPSIS multicriteria decision method is applied and is used with the fuzzy logic set theory, which enables the processing of imprecise and unquantifiable information and is therefore highly appropriated to our problem. The performance of each end-of-life option according to the various criteria is calculated using the influence parameters previously chosen from the literature review. Furthermore, a weight of importance is assigned to each criterion and may be modified if needed by the designer. From these elements, ELSEM provides an assessment of each end-of-life option for each sub-assembly of the product. This assessment helps the designer in constructing arguments used to negotiate the technical characteristics of the product with the members of the design team and performing the end-of-life decision-making process.;ELSEM can be used under certain conditions: (i) there is an existing collection system adapted to the product end of life; (ii) this system allows for the consideration of several end-of-life options and (iii) the organization or company responsible for recovering the discarded product is concerned with all criteria taken into account in the TOPSIS method.;An Excel tool is created in order to provide the designer with a way to implement the method and to obtain clear results. Using this tool, ELSEM is tested on various modules of a car and a computer. The method gives results in accordance with current industry practices in 9 cases out of 11. Its complete validation remains to be done on other modules. Indeed, it could have not been achieved given the limited information available in the literature. However, ELSEM meets the initial objectives of speed, simplicity, flexibility and precision, and can be used in preliminary design phase.;End-of-life selection during early design stage is a complex issue that requires taking into account many aspects such as: laws, costs, income, environment, etc. Therefore, designers may need a tool to help them evaluate alternatives. However, most existing tools are not applicable during early design stage or require an expertise that the designer may not have. Other tools give a unique end-of-life option for the entire product whereas most of the time, various subassemblies are given different end-of-life options. The ELSEM method (End-of-Life Scenario Assessment Method) was created in order to overcome the weaknesses belonging to other end-of-life assessment methods. ELSEM can be used during the early design phase in a quick, flexible and simple way. It gives relevant and precise results and leads to the creation of manufactured products which the design is adapted for their end-of-life. As a consequence, it allows for the selection of end-of-life scenarios with lower environmental impacts.;After the determination of an appropriated end-of-life scenario, the corresponding design parameters must be chosen. For this, the use of ELSEM must be combined with effective attachment and material selection methods as well as modularization methods. The final design will therefore achieve the overall goal of reducing environmental impact of products end-of-life stage.