Unified physics theory explains how materials transform from solid to liquid

The mucus layer on the soles of snails is an example of soft materials. It yields to a certain degree of pressure, and then it flows. Researchers at the University of Illinois at Urbana-Champaign have simplified this behavior in a new study, which is what helps snails move without inconvenient sliding, similar to many other natural and synthetic materials, from mud To the additive that makes toothpaste flow when squeezed.

By University of Illinois Urbana`Champaign The research led by Simon Rogers, professor of chemical and biomolecular engineering at the branch campus, published a unified mathematical expression that defines how soft and hard materials transition from solid to liquid flow when they exceed a specific stress threshold. The research results were published in the journal Physical Review Letters.

“Traditionally, the behavior of a yield stress fluid is defined as an attempt to combine the physics of two different types of materials: solid and liquid,” lead author Kutas Kaman Nee said he is a graduate student in chemical and biomolecular engineering at the University of Illinois. “But now, we have shown that these physical states-solid and liquid-can coexist in the same material, and we can use a mathematical expression to explain it.”

Toothpaste flows when it is squeezed, which makes it known as a yield-stress fluid by researchers.

In order to develop this model, the team conducted a lot of research to put various soft materials under pressure, and at the same time use a device called a rheometer to measure the similarities. Strain response of solids and liquids.

Rogers said: “We can observe the behavior of a material, and see the continuous transition between solid and liquid,” he is also the University of Illinois, Beckman Advanced Science and Technology Research A member of the institute. “Traditional models all describe a sudden change in behavior from solid to liquid, but we can solve two different behaviors, reflecting the energy dissipation through solid and liquid mechanisms.”

The research report states that this development provides researchers with a simple model that makes it easier to perform large-scale calculations, such as those required to simulate and predict catastrophic events such as mudslides and avalanches.

“Existing models are computationally expensive, and researchers need to struggle with numbers to make the calculations as accurate as possible,” Rogers said. “Our model is simple and more accurate. We have proved this through many proof-of-concept experiments.” As well as those involved in industrial processes such as new material development, 3D printing, and waste transportation cost minimization, the complex yield-stress study of fluids is a hot topic. “Our model defines a basic example of solid-to-liquid behavior, but I think it will serve as a springboard for researchers to make significant progress in defining more complex yield stress fluid phenomena.”