Exploration in the preliminary mechanical design of tradeoffs between automative architecture constraints and aggregate noise performances.

Summary In this thesis, we propose a methodological framework for the preliminary design phase in the automotive industry, in order to manage the trade-off between, on the one hand, the architectural constraints to which a mechanical subsystem is subjected, and on the other hand, a satisfactory contribution of the subsystem to the minimization of noise in the vehicle interior. The proposed methodology allows us to engage in negotiations between automotive architects and mechanical engineers on the compliance or non-compliance of architectural constraints of a subsystem or a component, as well as on the achievement of the targets of the specifications regarding the vibro-acoustic performances. The proposed methodological framework consists of five steps: 1, modeling of the design problem, including (a) modeling of the vibro-acoustic performances and (b) modeling of the architecture constraints. 2, the metamodeling (mathematical approximation) of the resulting design problem using kriging metamodels. 3, the formulation of the design problem as a multi-objective optimization problem. 4, the generation of this multi-objective optimization problem using the Pareto boundary metamodel and the normalized constraints method. 5, a negotiation step between the architecture constraints and the performance of the mechanical subsystem. To handle the problem of archtecture constraints, in the preliminary design phase, we introduce a method to express, by a so-called architecture criterion, the compliance or non-compliance with ge��ometric constraints. The originality of this method consists in the fact of migrating the step of allocating envelope volumes under a CAD system to a CAE system that is more accessible to engineers since it is in this system that they manage their finite element models. We also introduce a method for aggregating the vibro-acoustic performance of a mechanical subsystem into a single real-valued criterion (indicator). This technique allows an efficient reduction of the important dimension of a design problem related to the study of a mechanical subsystem with multiple vibro-acoustic performances. The application of the methodology to a case study, in the automotive domain, allowed to demonstrate its efficiency to significantly improve the vibro-acoustic performances of a body-in-white (bare body of an automobile) while respecting tight architectural constraints due to an envelope volume allocated to the vehicle powertrain. Finally, with this methodological framework, negotiations between architects and engineers are no longer based on qualitative judgments, but are now based on quantitative criteria for both architectural constraints and mechanical performance.