DETROIT – Rocker Bob Seger once described the songwriting process as “what to leave in, what to leave out.” Great engineering requires the same process, but a lot more math is involved.

In the never-ending quest to chop weight, engineers constantly are trying to take mass out of vehicle structures by scalloping edges and cutting holes, but removing material from the wrong areas can severely reduce strength. That compels them to do many time-consuming computer simulations to find the best places to cut.

At the SAE World Congress Experience here, FCA engineers Barry Lin, Ramachandra Bhat, Shawn Zhang, Taylor Sykes-Green, Nitin Sharma and Kevin Thomson reveal a faster process to determine the optimal size and dimension of weight-saving “lightening holes” without impacting strength or durability.

Strategically cutting holes can reduce the weight of frame components up to 5%. That is especially significant when dealing with big, heavy parts. In one example, the FCA engineers say the process resulted in a 15-lb. (6.8-kg) weight reduction on a pickup truck frame.

The engineers, part of an FCA group called Product Validation, Vehicle Sciences and Virtual Analysis, developed multiple algorithms to quickly and precisely determine the optimal size and shape of lightening holes.

During vehicle development, complex computer models of vehicle structures called finite frame element models are run through countless simulations that stretch and bend them in a thousand different ways to test their strength and long-term durability. But these FEA models contain 300,000 to 500,000 data points and eat up huge amounts of computing time even for simple simulations.

When optimizing weight in structures, engineers typically have had to resort to using the complex computer models for stress tests to find areas where they can safely remove material.

However, the Product Validation, Vehicle Sciences and Virtual Analysis team found a simpler method that zeroes in on simulation of fatigue performance as the design target and provides all the information needed to find spots they can cut out without harming structural integrity.

In their jointly-authored SAE paper, the engineers say this new approach saves time and effort by eliminating the need to create intermediate design targets and simplifying the whole procedure, enabling it to easily be integrated into daily design and analysis duties.

In medical terms, it could mean the difference between getting a simple X-ray rather than an MRI to find an easily identified problem. And that is no small feat.

dwinter@wardsauto.com