The research team discovered surprising findings about the cyclic fatigue of amorphous materials

Researchers at the University of Tokyo have shown that for amorphous materials, the cyclic fatigue of the material can begin to fail at the same stress level as fractures due to constant loading. Using computer simulations, the team was able to distinguish between four different failure modes. This work can increase the life of industrial equipment.

Damage to industrial parts is expensive, causes delays and can be dangerous for factory workers. But now scientists from Japan have simulated the destruction of materials that have a special physical characteristic and are widely used in domestic, industrial and scientific purposes. Their works, published in Communication materialshas shown surprising results that can help prevent damage to industrial parts.

If you’ve ever been bored in a meeting and tried playing with a paper clip to pass the time, you may have noticed something strange. Although a paper clip begins to bend and return to its original shape several times, it can suddenly snap after enough cycles. This is an example of “fatigue” in which cracks and defects accumulate when an object is subjected to cyclic loading and unloading of stress. Material fatigue is a serious problem in many industrial applications, and especially for machine and aircraft parts that are subjected to many cycles of loading and for which a sudden failure can be catastrophic As a result, gaining a better understanding of the underlying process material fatigue can offer significant benefits, especially for non-crystalline materials.

A group of researchers from Tokyo University’s Institute of Industrial Science studied the physical mechanisms of small-cycle fatigue failure in the case of amorphous solids such as glass or plastics using computer simulation. For crystalline materials it has been shown that pre-existing defects and grain boundaries can cause a fatigue fracture.

However, the relevant mechanism of Art amorphous materials not clear enough. Although it seems intuitive that the stress required to cause fracture is much lower for cyclic stresses compared to constant stress, scientists have found that is not the case. “Contrary to popular belief, we have shown that the critical stress in degraded materials that corresponds to the onset of irreversible deformation is the same for both fatigue and monotonic fractures” says co-author Yuji Kurotani.

This is because for conventional amorphous systems, higher density leads to higher elasticity and slower dynamics. This density dependence of mechanical properties couples shear strain with density fluctuations. Cyclic shear can then amplify the density fluctuations until the sample ruptures via cavitation, resulting in the formation of voids.

“This situation is like an overcrowded train,” says co-author Hajime Tanaka. “Dynamic and elastic asymmetry with respect to density changes can lead to a relationship between shear strain and density These authors mention that these results should be confirmed by experiments, which will also help materials scientists better understand fracture initiation.