New discovery shows tensile cracks can shatter classical speed limits, approach near-supersonic velocities

Researchers at the Racah Institute of Physics, Hebrew University of Jerusalem, have made a groundbreaking discovery that challenges the conventional understanding of fracture mechanics. Led by Dr. Meng Wang, Dr. Songlin Shi, and Prof. Jay Fineberg, the team has experimentally proven the existence of “supershear” tensile cracks that defy classical speed limits and reach near-supersonic velocities. Their groundbreaking study has been published in the prestigious journal Science.

In the field of fracture mechanics, it has long been observed that brittle materials fail due to the rapid propagation of cracks. Classical fracture mechanics states that tensile cracks release elastic energy in a localized zone at their tips, limiting their speed to the Rayleigh wave speed (CR). However, the recent findings by the Hebrew University researchers have unveiled a paradigm shift in this understanding.

By conducting experiments using brittle neo-Hookean materials, the team discovered the occurrence of “supershear” tensile cracks that smoothly accelerate beyond the classical speed limit of CR. Surprisingly, these cracks even surpass the shear wave speed (cS). In some cases, the velocities of these supershear cracks approach dilatation wave speeds, revealing phenomena that were previously unobserved in classical fracture mechanics.

Perhaps the most remarkable aspect of this discovery is that supershear dynamics follow different principles than those governing classical cracks. This non-classical mode of tensile fracture occurs at critical strain levels dependent on the material properties, and it is not a random occurrence.

Commenting on the research, Prof. Jay Fineberg, the corresponding author, stated, “This finding represents a fundamental shift in our understanding of the fracture process in brittle materials. By demonstrating the existence of supershear tensile cracks and their ability to surpass classical speed limits, we have opened up new avenues for studying fracture mechanics and its practical applications.”

The significance of this research extends beyond the field of physics. The revelation that tensile cracks can exceed their classical speed limits has laid the foundation for a fresh perspective on fracture mechanics.