12th CIRP Conference on Computer Aided Tolerancing

The purpose of this paper is to decipher the process of modelling driving to the product behaviour simulation. A simple example of simulation, tolerance stackup, allows illustrating this process. The tolerance stackup is used daily in industry, however, designers do they know exactly what they do? Are they aware of the assumptions they are introducing? To answer to these questions, concepts of GeoSpelling and of GPS ISO standards such as skin model, operations, operators and other concept are introduced such as finite and infinite models

Comparison of different Multiple-criteria decision analysis methods in the context of conceptual design: application to the development of a solar collector structure

At each stage of the product development process, the designers are facing an important task which consists of decision making. Two cases are observed: the problem of concept selection in conceptual design phases and, the problem of pre-dimensioning once concept choices are made. Making decisions in conceptual design phases on a sound basis is one of the most difficult challenges in engineering design, especially when innovative concepts are introduced. On the one hand, designers deal with imprecise data about design alternatives. On the other hand, design objectives and requirements are usually not clear in these phases. The greatest opportunities to reduce product life cycle costs usually occur during the first conceptual design phases. The need for reliable multi-criteria decision aid (MCDA) methods is thus greatest at early conceptual design phases. Various MCDA methods are proposed in the literature. The main criticism of these methods is that they usually yield different results for the same problem. In this work, an analysis of six MCDA methods (weighed sum, weighted product, Kim & Lin, compromise programming, TOPSIS, and ELECTRE I) was conducted. Our analysis was performed via an industrial case of solar collector structure development. The objective is to define the most appropriate MCDA methods in term of three criteria: (i) the consistency of the results, (ii) the ease of understanding and, (iii) the adaptation of the decision type. The results show that TOPSIS is the most consistent MCDA method in our case

Critical review of multi-criteria decision aid methods in conceptual design phases: application to the development of a solar collector structure

At each stage of the product development process, the designers are facing an important task which consists of decision making. Two cases are observed: the problem of concept selection in conceptual design phases and, the problem of pre-dimensioning once concept choices are made. Making decisions in conceptual design phases on a sound basis is one of the most difficult challenges in engineering design, especially when innovative concepts are introduced. On the one hand, designers deal with imprecise data about design alternatives. On the other hand, design objectives and requirements are usually not clear in these phases. The greatest opportunities to reduce product life cycle costs usually occur during the first conceptual design phases. The need for reliable multi-criteria decision aid (MCDA) methods is thus greatest at early conceptual design phases. Various MCDA methods are proposed in the literature. The main criticism of these methods is that they usually yield different results for the same problem [22,23,25]. In this work, an analysis of six MCDA methods (weighed sum, weighted product, Kim & Lin, compromise programming, TOPSIS, and ELECTRE I) was conducted. Our analysis was performed via an industrial case of solar collector structure development. The objective is to define the most appropriate MCDA methods in term of three criteria: (i) the consistency of the results, (ii) the ease of understanding and, (iii) the adaptation of the decision type. The results show that TOPSIS is the most consistent MCDA method in our case

Linking objective and subjective modeling in engineering design through arc-elastic dominance

Engineering design in mechanics is a complex activity taking into account both objective modeling processes derived from physical analysis and designers’ subjective reasoning. This paper introduces arc-elastic dominance as a suitable concept for ranking design solutions according to a combination of objective and subjective models. Objective models lead to the aggregation of information derived from physics, economics or eco-environmental analysis into a performance indicator. Subjective models result in a confidence indicator for the solutions’ feasibility. Arc-elastic dominant design solutions achieve an optimal compromise between gain in performance and degradation in confidence. Due to the definition of arc-elasticity, this compromise value is expressive and easy for designers to interpret despite the difference in the nature of the objective and subjective models. From the investigation of arc-elasticity mathematical properties, a filtering algorithm of Pareto-efficient solutions is proposed and illustrated through a design knowledge modeling framework. This framework notably takes into account Harrington’s desirability functions and Derringer’s aggregation method. It is carried out through the re-design of a geothermal air conditioning system

L’analyse des phénomènes physiques, éléments essentiels vers la résolution de problèmes industriels

In this paper, we present the different elements of connection between users requirements and physical phenomena created during the use of products. We propose a structured methodology which goes from the analysis of the significant moments until the identification of the appreciation criteria of the user and design variables necessary to the product definition. The time decomposition of the product use in significant moments makes it possible to identify all actions realized by the user, to extract the physical effects and to qualify them in term of relevance. The methodological tools ensure the exhaustiveness of the analysis, to define the physical sizes associated with the criteria and the design variables as well as the relations between the criteria and design variables. Then we can take into account users requirements during preliminary design phase. This methodology is applied to the integration of the user requirements at the time of the opening for a telephone foldable

Taxonomie des connaissances en conception préliminaire

The design activity is the transformation of functional requirements into design parameters. This article presents a structuring method for the design problem exploiting existent and mastered knowledge. The proposed energy analysis leads to the structural definition of the product and the definition of a basis of functions and components. This approach allows efficient implementation of optimization models in preliminary design

Carbon epoxy composites thermal conductivity at 80 K and 300 K

The in-plane and in-depth thermal conductivities of epoxy-carbon fiber composites have been measured at 77 K and 300 K. The experimental technique rests on the hot disk method. The two thermal conductivities as well as the thermal contact resistance between the probe and the composite materials are estimated from measurement data and an analytical heat transfer model within the experimental configuration. The results obtained at 77 K explained well the ignition test results performed on the composites at 77 K with regards to liquid oxygen storage

L'analyse des phénomènes physiques, éléments essentiels vers la résolution de problèmes industriels

Nous présentons ici les éléments de la prise en compte de la liaison entre les besoins utilisateurs et les phénomènes physiques mis en jeu lors de l'utilisation du produit. Nous proposons une démarche structurée qui va de l'analyse des moments significatifs jusqu'à l'identification des critères d'appréciation de l'utilisateur et des variables de conception indispensables à la définition du produit. La décomposition de la phase d'utilisation du produit en moments significatifs permet de recenser les actions exécutées par l'utilisateur, d'extraire les effets physiques présents et de les qualifier en terme de pertinence. L'exhaustivité de l'analyse s'appuie sur des outils méthodologiques et permet de définir les grandeurs physiques impliquées associées aux critères et aux variables de conception ainsi que les relations les liant. On peut ainsi impliquer les attentes utilisateur dès la conception préliminaire. Cette démarche est appliquée à l'intégration des besoins « utilisateur » lors de l'ouverture d'un téléphone « foldable »

Energy Based Functional Decomposition in Preliminary Design

The authors wish to thank Dr. Jonathan Maier, Dr. Gregory Mocko and Mr. Benjamin Caldwell for their valuable comments on the draft of the paper.This paper presents an energy based approach to functional decomposition that is applicable to the top down design (system to subsystems to components) of mechanical systems. The paper shows that the main functions of convert and transmit are sufficient to focus on the “functional flow” or main energy flow resulting in the specific action sought as a result of the artifact being designed, and can be expanded upon at the lowest level when looking for specific solutions based upon the energy and mass balances and the knowledge within the design team. This approach considers function as a transformation and also fits the approach presented in TRIZ. The standard energy, material, and signal flows are seen as forms of energy flows, and it is only their transformation and transmission that is sought. This simplified approach, coupled with an aspect of control and interaction between a reference state and the artifact or between various components is sufficient to comprehensively describe the system that matches very nicely the value function approach of Miles. Furthermore, as these interactions can be considered as artifactartifact affordances when considering the artifact for either artifact interaction or within an environment, its relation to the user and to the reference state can be addressed during the design phase, in addition to the functions

A 2D topology optimisation algorithm in NURBS framework with geometric constraints

In this paper, the Solid Isotropic Material with Penalisation (SIMP) method for Topology Optimisation (TO) of 2D problems is reformulated in the Non-Uniform Rational BSpline (NURBS) framework. This choice implies several advantages, such as the definition of an implicit filter zone and the possibility for the designer to get a geometric entity at the end of the optimisation process. Therefore, important facilities are provided in CAD postprocessing phases in order to retrieve a consistent and well connected final topology. The effect of the main NURBS parameters (degrees, control points, weights and knot-vector components) on the final optimum topology is investigated. Classic geometric constraints, as the minimum and the maximum member size have been integrated and reformulated according to the NURBS formalism. Furthermore, a new constraint on the local curvature radius has been developed thanks to the NURBS formalism and properties. The effectiveness and the robustness of the proposed method are tested and proven through some benchmarks taken from literature and the results are compared with those provided by the classical SIMP approach