An automotive engine cradle supports many crucial components and systems, such as an engine, transmission, and suspension. Important performance measures for the design of an engine cradle include stiffness, natural frequency, and durability, while minimizing weight is of primary concern. This paper presents an effective and efficient methodology for engine cradle design from conceptual design to detailed design using design optimization. First, topology optimization was applied on a solid model which only contains the possible engine cradle design space, and an optimum conceptual design was determined which minimizes weight while satisfying all stiffness constraints. Based on topology optimization results, a design review was conducted, and a revised model was created which addresses all structural and manufacturability concerns. Shape and size optimization was then performed in the detailed design stage to further minimize the mass while meeting the stiffness and natural frequency targets. Lastly, the final design was validated for durability. The initial design domain had the mass of 82.6 kg; topology optimization in conceptual design reduced the mass to 26.7 kg; and the detailed design task involving shape and size optimization further reduced the mass to 21.4 kg.

Conceptual and detailed design of an automotive engine cradle by using topology, shape, and size optimization

This paper reviews the recent developments of hydroforming technology in China. Limited corner radius, ring hoop tension test and tube bulging test were introduced on fundamentals of hydroforming. New hydroforming and hydro-bending process of ultra-thin tubes were investigated. Ultra-thin Y-shaped parts and complex section components were manufactured and applied in aerospace and aviation industry. Applications of tube hydroforming in automotive industry in China are also presented, including the hydroforming machines and production lines, typical automotive parts and potential market. New sheet hydroforming process with controllable radial pressure was proposed to increase the formability of sheets metals. Warm tube and sheet hydroforming were analyzed and discussed. [doi:10.2320/matertrans.MF201122]

New Developments of Hydroforming in China

Single point incremental forming is a cost-effective alternative of conventional stamping process. However, due to inadequate knowledge, the process has not yet been employed on industrial scale. In this study, the role of tool radius in causing and controlling development of defects in single point incremental forming is investigated. Throughout the course of investigations, AA1060 aluminum is used as the experimental material. Initially, a range of tests with tool radius (r) ranging from 1to to 2.35to (where to is sheet thickness) are conducted. It is found that defects, namely, pillow, wall and material-fold, develop in a part if forming is performed with an unduly small tool (i.e. r<2to). Furthermore, as a result of these defects, the part accuracy and sheet formability reduce. In the second stage, the effect of selected process parameters (i.e. feed rate, yield strength, wall angle, sheet thickness and step size) on the growth (or size) of aforesaid defects is examined. The test results reveal that t...

Experimental investigations on the role of tool size in causing and controlling defects in single point incremental forming process

In general, hydroforming optimization aims to make a desired shape of a plastically deformed structure under dynamic forces. The automotive industry has shown great interest in tube hydroforming, which is a metal-forming process. The forces from the hydraulic fluid are utilized to deform a tube. The internal pressures and the axial feedings (of the axial forces) determine the quality of the deformed product. In this research, an optimization process is employed to evaluate the appropriate external forces but defects are prevented. The equivalent static loads method for non-linear static response structural optimization is used for the optimization process because the tube-hydroforming process is analysed by non-linear dynamic response analysis. The equivalent static loads are the static loads that generate the same response field as that of non-linear dynamic analysis and are utilized as the loading conditions in linear static response optimization. A novel process is added to the original equivalent stat...

Optimization of the loading path for the tube-hydroforming process

Strength and Formability Designs of Tube-hydroformed Automotive front Sub-frame☆

The hydroforming technology may bring many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower springback, improved strength and durability and design flexibility. In this study, the whole process of front sub-frame parts development by tube hydroforming using steel material having tensile strength of 440 MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydroformability in details. Effects of parameters such as internal pressure, axial feeding and geometry shape in automotive engine cradle by the hydroforming process were carefully investigated. Overall possibility of hydroformable engine cradle parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydroforming. At the die design stage, all the components of prototyping tool are designed and interference with the press is examined from the point of deformed geometry and local thinning.

B. I. Choi

Papers

Development of automotive engine cradle by hydroforming process