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Friday, March 31, 2017

Vehicle Lightweighting – A Triumph of Up-Front Engineering Optimization

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light weighting

In Thursday's Detroit Free Press there is a review of the new Chevy Equinox SUV: read review here

“Chevrolet has been performing magic lately, making hundreds of pounds of vehicles’ weight disappear without reducing their comfort or features. The ★★★★ 2018 Equinox compact SUV may be its best trick yet. The new Equinox shed 400 pounds and 4.7 inches versus its predecessor, but it remains one of the most accommodating and best-equipped vehicles in the red-hot compact SUV class.”

This story is being repeated over and over: The Cadillac ATS, already a couple of years old, is hundreds of pounds lighter than its BMW 3-series competitors.

In the early 2000s, a small group of talented CAE structural engineers in GM became frustrated that their design recommendations were not being adopted. They were always “too late to change that.” So, they went in search of where the design decisions were actually being made.

That search took them into the “Advanced Vehicle Engineering” (AVE) group, a relatively small organization of “vehicle architects” who work on the left hand side of the systems engineering “Vee”, long before any commitment to execute a vehicle program is made, or any complete CAD is available for 3D structural analysis.

The first reports were not promising. AVE was in chaos, they changed their minds every day, and there was never enough time to analyze the current state before it was obsolete. But, the CAE engineers persisted. They adopted tools like SFE Concept (since acquired by Dassault Systemes) and Genesis from Vanderplaats Research (VR&D) to be more quickly able to respond with recommendations on vehicle architecture decisions.

Most importantly, perhaps, they also analyzed the engineering process and the “decision progression”. Which decisions were made when? Which decisions were dependent on previous decisions? And, most insightful, which decisions were coupled, and needed to be made together?

This analysis was critical. There is nothing that disrupts an engineering program more than having to revisit and change previous decisions.

So, GM adopted tools and changed their process to use tools like topology optimization to make vehicle architecture (chassis and structure layout) decisions, and shape optimization to do gauge (thickness) and material selection for the body-in-white sheet metal structure.

GM is now also taking advantage of the “knock-on” effects, a real systems view of the vehicle. A lighter body means a smaller powertrain, means a downsized suspension …

Anyone familiar with automobile engineering will understand that taking 400 lbs. out of a mass-market vehicle like the Equinox is an incredible achievement. Even more so, since the performance metrics of the previous vehicle (crash safety, acceleration, fuel economy) are being equaled or exceeded.

This conversation will continue at the CIMdata workshop on Product and Manufacturing Innovation in Chicago on June 6-7: http://www.cimdata.com/en/education/knowledge-council-workshops/joint-kc-workshop-2017

Plan now to join us in Chicago!

Keith

Keith Meintjes

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