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Computer simulation technique gains exposure

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Computer simulation technique gains exposure

Zhen Chen, C.W. La Pierre Professor of civil and environmental engineering, and doctoral student Shan Jiang.

Zhen Chen, C.W. La Pierre Professor of civil and environmental engineering, and doctoral student Shan Jiang are developing and using computer simulation techniques to model impact and deformation.

Zhen Chen never expected to see an application of the work initiated by him and his colleagues in an Academy Award-winning film. Yet 20 years after the team began investigations into what has been termed the “Material Point Method” (MPM), there it was on the silver screen.

The film was the Disney animated feature “Frozen,” which earned the 2014 Oscar for Best Animated Feature. Animators adapted MPM, a computer-based tool developed to simulate impact and penetration scenarios to the films’ special effects. Such simulations can demonstrate the effects of explosions on blast- and impact-resistant materials, as well as being used to create snow “effects,” such as those seen in the interactions between characters in the film’s snowy environment, making some of the most realistic snow effects used in an animated motion picture.

Chen, C.W. LaPierre Professor in the University of Missouri’s Civil and Environmental Engineering Department, was one of the three researchers who started working on development of MPM in the early 1990s, publishing their first paper on the topic, “A Particle Method for History-Dependent Materials,” in Computer Methods in Applied Mechanics and Engineering in 1994. Chen has continued to work on MPM applications since joining MU in 1995.

“Motivated by the need for better simulations that demonstrate impact and penetration phenomena, we developed the MPM more than 20 years ago,” Chen said. “Since then, the MPM has been further developed and applied by many global research teams to real-world problems, including fire, explosions and impacts in buildings and structures. Our first study on the MPM has been cited more than 400 times, and Disney is now using physics-based simulation methods as they create sequences for their popular animated movies including ‘Frozen.’”

The use of the method in the film attracted plenty of attention, including that of the National Science Foundation, and websites such as Science Daily, Science Codex, Animated Film Reviews and Eurekalert.

A three-dimensional configuration of the solid particle/rod assembly.

A three-dimensional configuration of the solid particle/rod assembly confined by gaseous fluid. The computation model includes both Dissipative Particle Dynamics (DPD) particles at the nanoscale/mesoscale, and Material Point Method (MPM) particles at the continuum — macroscopic — level. A particle-based multiscale numerical scheme within the MPM framework has been proposed to realize this simulation.​

Chen has spent years working to reduce the damage to buildings from blasts and impacts, including work trying to reduce the damage to public buildings from car or truck bombs, which earned him a National Science Foundation CAREER Award in 1999. The funding allowed for the development of a computer test-bed that can create scenarios to determine how different structural designs can improve resistance to blasts and impacts.

He also has worked on projects funded by the National Research Council, the Air Force Office of Scientific Research, the Army Research Office, General Motors and others.

Blast-resistant technology is one of several important areas in which simulation-based engineering science (SBES) is making an impact in a variety of research topics. In 2006, an NSF blue-ribbon panel identified a multitude of areas in which SBES “can play a remarkable role in promoting developments vital to the health, security and technological competitiveness of the nation.”

SBES has become integral as computer simulation has developed to the point where it can produce tangible data through a virtual test.

“If you run experiments, it’s time-consuming, expensive and has an impact on the environment,” Chen said. “So it’s better to use simulation-based engineering science to run simulations first — get an idea, then run small-scale, in-lab experiments.”

Computer simulation in engineering also has practical applications in not just national security and safety, but also in medicine, energy and industry, among others.

Shan Jiang, a doctoral candidate in the Civil Engineering Department who is working with Chen, is testing one such application, alongside Professors Thomas Sewell and Donald Thompson from MU’s Chemistry Department. Team members have been exploring the mechanical properties and deformation patterns of metallic nanostructures and energetic materials for use in alternative energy under extreme loading conditions. The work uses simulations that focus more narrowly than the conventional MPM while also using the MPM framework for a broader look. They were invited to the 12th U.S. National Congress on Computational Mechanics to present their findings on this multiscale version of the technology as it is used to help create alternative energy sources.

“If you want to get the details, you need to zoom in,” Jiang said. “This is looking at why defects happen when you stretch the nanorods. If you zoom in, you can see the defects and details of why the deformations happen. In the broader area, we may just use the conventional MPM.”

While the success of “Frozen” may foster a greater mainstream appreciation of the broad world of SBES and the more focused world of MPM, Chen said he’s hoping for an increased level of interest in members of the younger generations. There currently is a big push toward improving education and development in the areas of science, technology, engineering and math — STEM for short.

A  Material Point Method (MPM) simulation of a soft target penetrated by a hard projectile.

A Material Point Method (MPM) simulation of a soft target penetrated by a hard projectile. The stress contour is shown with different colors.

Computers and smaller, handheld devices increasingly are becoming a part of everyday life and are ubiquitous in younger demographics. From Chen’s point of view, with their increasingly innate interest in technology and computers, perhaps young people can be reached on an educational level through their use of those devices. He is hoping the appeal of computers to young students and the growing applications of computer simulation could pique interest in STEM education. Films using technologies such as MPM can only help to increase the appeal.

“Young people now like to use computers to simulate many things,” Chen said.

“I think the best way to motivate our younger generation to study STEM is to let them know what you learn today will be very useful for your daily life. I think SBES can promote STEM to younger generations.”

The most recent paper from Chen’s research team, “A Particle-Based Multiscale Simulation Procedure within the MPM Framework” was accepted for publication in Computational Particle Mechanics.

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