Originally published by Michigan Technological University
When working on telescopes that will be launched into orbit, accuracy is king because it is nearly impossible to implement a fix in a million mile orbit. The stresses and degrees of freedom are inspected, verified, and validated far beyond the decimal, and any changes in the numbers between simulations are carefully evaluated. Through the use of simulation, software engineers are able to examine the inputs and determine why a solution changed, rather than wondering what changed between physical test runs in the internal or external environment of the prototype model. Dr. David Wallerstein has been pushing the limits of innovation in the world of simulation since graduation, and his early models had 30,000 degrees of freedom, maxing out the computers of the day.
Fast forward to today, and his automobile models have 30 to 40 million degrees of freedom. Initially beginning his simulation career working with ADAMS code for rigid body mechanics, he soon transitioned to NASTRAN’s nonlinear flexible body code. Wallerstein’s initial forte with NASTRAN was with the famed Skunkworks SR71 project at Lockheed Martin for NASA. In 1982 he joined MSC Software to further develop the NASTRAN code base that included, under Ford Motor Company contract, the first commercially viable design sensitivity and design optimization methods. To keep pace with newer simulation tools, Wallerstein rewrote the NASTRAN operating system in the 1990s and has also worked to improve design optimization features and model sensitivity.
“Accuracy is important. NASA has that game with telescopes, looking at stresses down to the ninth decimal place, and they get worried if the results change between releases. Simulation can be used to explain why a solution changed.”
Simulation with NASTRAN has played an increasing role in automotive design, with automotive engineers exploring the vehicle interior and tires, seeking to suppress road noise and keep vehicles quiet. Crash analysis is also involved in the simulation process to quantify energy absorption and acceleration rates on vehicle impact. NASTRAN’s recent releases have coupled non-linear analysis for noise and vibration with a focus on automobiles to enable engineers to examine how the body-frame structure responds to inputs from the road through the vehicle’s suspension system. “In today’s simulation environment, everything becomes a coupled analysis. The aerospace engine designers are happy to rev their engines up and ensure the blades won’t come off; however, the customer wants to know what is happening as they perceive the noise entering the passenger compartment,” says Wallerstein. “Passenger perception and passenger safety both need to be considered before a design is validated and market-ready.”
Having led development at MSC Software for many years, Wallerstein’s impact on the simulation industry is, ironically, incalculable. With countless models running daily at client locations worldwide, each producing better, safer designs, untold failures are avoided and product value is realized. Never accepting the status quo, he continues to move NASTRAN forward, assuring his engineering peers that the software will remain at the vanguard of simulation well into the future.