Bending Spaghetti to Better Understand Crack Formations and Control FracturesPeter Brown | August 15, 2018
You’d think the researchers at MIT would have better things to do than to test the strength of spaghetti and why when you hold a noodle at each end it won’t break into just two pieces instead of shattering into numerous pieces.
However, that’s what they have done and it turns out the research may have farther ranging impacts than just discovering the mystery of spaghetti. The discovery of how to break a noodle into two equal parts may enhance the understanding of crack formation and how to control fractures in other rod-like materials such as multifiber structures, engineered nanotubes or even microtubules in cells.
Research into spaghetti noodles has been going on for years with the discovery that the noodles when bent evenly from both ends never break near the center where it is most curved, and instead the initial break triggers an effect and vibration that fractures the stick into many parts.
MIT found a way to break spaghetti sticks by bending and twisting them in an apparatus built specifically for the task. If the stick was twisted past a certain critical degree, then slowly bent in half, it will break in two.
“It will be interesting to see whether and how twist could similarly be used to control the fracture dynamics of two-dimensional and three-dimensional materials,” said Jörn Dunkel, associate professor of physical applied mathematics at MIT. “In any case, this has been a fun interdisciplinary project started and carried out by two brilliant and persistent students — who probably don’t want to see, break or eat spaghetti for a while.”
How They Did It
MIT researchers built a mechanical fracture device to control the twisting and bending of spaghetti sticks where two clamps on either end of the device hold a stick of spaghetti in place. One clamp then is rotated to twist the noodle at various degrees while the other clamp slides toward the twisting clamp to bring the two spaghetti ends together, bending the stick.
The team bent and twisted hundreds of spaghetti sticks, recording the fragmentation process, and found that by twisting the noodle at almost 360 degrees then slowly bending the stick it snapped exactly in two. The finding was consistent across two types of spaghetti.
Researchers developed a mathematical model to explain how twisting can snap a stick in two and found if a 10-inch long spaghetti stick is first twisted by about 270 degrees then bent, it will snap in two because of two effects. First, the snap-back — where the stick will spring back in the opposite direction from which it was bent — is weakened in the presence of the twist. Second, the twist-back effect where the stick will essentially unwind to its original configuration releases energy from the rod, preventing additional fractures.
“Taken together, our experiments and theoretical results advance the general understanding of how twist affects fracture cascades,” Dunkel said.
The full research can be found in the journal Proceedings of the National Academy of Sciences.