ABSTRACT A design process to reduce mass and sound pressure for automatic transmissions of vehicles is presented. The proposed process uses a newly developed topography optimization technique. Additionally, useful and necessary techniques including sound pressure optimization and the beta method are described. As a demonstrative problem, the design process is successfully applied to reduce mass and sound pressure of a 6 speed AISIN AW FWD automatic transmission. INTRODUCTION Reducing the mass of vehicles is becoming more significant for improving environmental quality and energy consumption [1]. In addition, noise performance is also one of the most important quality measures for vehicle comfort. However, reduction of both mass and sound pressure for automatic transmissions can produce a design problem with conflicting objectives. To overcome this difficulty, we propose new structural optimization techniques. To reduce radiated noise, we proposed direct reduction of sound pressure for the field point using large scale modal frequency response analysis, sound pressure optimization and topometry optimization [ 2]. This method enables us to find effective locations to reduce radiated noise for entire range oftargeted loading frequencies. Topometry optimization is a special form of large scale sizing optimization [ 3]. We need to create shell elements on the surface boundary of solid components. This method shows the most effective locations to add material, but this method cannot identify where material needs to be removed. Therefore topometry optimization results in adding additional mass to reduce sound pressure. Dai and Ramnath proposed reducing radiation noise using topography optimization [ 4]. Their method is to minimize overall surface velocities for shell elements. Kosaka et al. proposed to reduce radiated noise using topography and freeform optimization techniques [ 5]. The finite element model is made of solid elements. In the case of topography optimization, thin shell elements are applied on the designable surface region. Because both topography and freeform are types of shape optimization, they can result in the removal of material, as well as the addition of material. Therefore we employ this method to reduce mass and sound pressure. The rest of the paper is organized as follows. First, the analysis and optimization that we used in this design process (including large scale modal frequency response analysis [6,7], acoustic analysis, topography optimization and beta method) are discussed. Then design considerations of automatic transmissions, the detailed model description of an Reduction of Mass and Sound Pressure for Automatic Transmission Using Topography Optimization2012-01-0774 Published 04/16/2012 Takanori Ide Aisin AW Co., Ltd. Hiroyuki Kitajima Aw Engineering Co. Ltd Juan Leiva and Brian Watson Vanderplaats R & D Copyright © 2012 SAE International doi:10.4271/2012-01-0774Downloaded from SAE International by Imperial College London, Sunday, September 09, 2018example problem and the goal of optimization are described. Next, the optimization results using the proposed design process are presented. Finally, the proposed process and benefits are summarized in the conclusion. ANALYSIS AND OPTIMIZATION In order to perform analysis for the optimization process, two separates discretized models must be created. The first one is the structural finite element model, used to compute surface velocity from modal frequency response analysis. The finite element model is constructed to precisely represent geometry since structural optimization will be performed. The other model is the fluid boundary element model, used to compute acoustic transfer vector. The boundary element model is constructed using a coarsened mesh since computational time is dramatically increase if the model size increased [ 8,9]. In the proposed process, two important optimization techniques, topography optimization to design shape of the struct