Design and Fabrication of an Aluminum Engine Cradle for a General Motors Vehicle 1999-01-0659
Automotive manufacturers have intensified their efforts to increase vehicle fuel economy by reducing weight without sacrificing vehicle size and comfort. Vehicle areas that offer the potential to reduce weight include chassis structural components. A cradle or a subframe is a chassis structural component that is utilized to support the engine/powertrain in front wheel drive vehicles. Traditionally, engine cradles have been manufactured by using stamped steel weldments. Recently, automotive designers are considering alternative processes, i.e., hydro-forming, as well as fabricating engine cradles using lightweight materials.
The objective of this paper is to describe the development of an aluminum engine cradle for a General Motors's midsize vehicle. The design criteria and structural performance requirements for this cradle are presented along with an overview of the manufacturing processes used to produce this lightweight structural part. The aluminum cradle design is packaged for the current midsize vehicle architecture and the imposed requirement is to attain a structural performance that is comparable to the previous generation stamped steel cradle. Structural performance is evaluated in terms of stiffness, noise and vibration, strength, fatigue, crashworthiness, and corrosion resistance.
The cradle assembly is made using high precision aluminum extrusions and stamped components. These components are machined, heat-treated, and welded to an assembly. The innovative design of these components achieved the objectives of this project. Specifically,
Weight reduction of the cradle assembly by 30%.
Satisfied structural performance requirements.
Improved corrosion performance.
Development of a manufacturing process suitable for high volume production.