arXiv subjects

Chuang-Shi Shen

Publications and source records attributed to Chuang-Shi Shen.

3 recordsLinked to original sources

arXiv2020

Cutting and tearing thin elastic sheets: two novel single-period cracks and the first period-doubling crack

Two novel single-period cracks were observed in experiments of cutting a folded sheet with a blunt object and tearing a thin brittle sheet under the guidance of a meterstick. Additionally, we observed a period-doubling crack in the tearing experiment. We cut and tore the sheet in different directions. The experimental results suggested that the anisotropy of the thin sheet played an important role in the formation of these two types of saw-tooth cracks. We demonstrated that the formation of the period-doubling crack was closely correlated with the changing of the contact region between the sheet and the meterstick. We also showed that the growth process of crack made by cutting was a logistic growth process (S-curve), while the cracks made by tearing propagated in the form of approximate power-law function.

cond-mat.soft↗

arXiv2019

Origin of instability in dynamic fracture

Unstable growth of cracks (rough crack surface and crack branching) in dynamic fracture has long been observed in various materials. Until now, there was no universally agreed upon explanation for these instabilities. Here, we demonstrate that: 1) Due to the non-uniform stress distribution in the cracked body and the expansion of high stress region as the crack velocity increases, a force-bearing cracked body can be treated as a temporary layer-like material (TLLM) with a "brittle layer" that the area of its automatically increases. 2) For this TLLM, it takes only one crack for the stress in its "brittle layer" to fall below a certain value at small velocities. Coupled with the asymmetry of the whole system, this results in a rough crack surface. 3) The "brittle layer" is large enough when the crack velocity reaches a certain value. Two cracks must be formed, or else the stress cannot be reduced below the certain value, resulting in crack branching. Crack propagation can be compared to cars traveling on a road: the high stress region in the cracked body provides a "road" to let cracks "pass ."

cond-mat.soft↗

arXiv2019

Fragmentation of shells: An analogy with the crack formation in tree bark

How does a shell explode into a series of fragments upon impact? The well accepted explanation is Mott's theory, which considers the fragmentation of shells as a random process controlled by defects. However, Mott's theory is inadequate due to its assumption of energy conversion, and it is incapable of explaining the lack of change in saturation fragment length with the increase in expansion velocity. In this paper, we present a theory to explain the physical mechanism for fragmentation of shells and propose a highly efficient model for predicting the number of necks after fragmentation. We recognize that the fragmentation problem in shells is analogous to the cracking behavior of tree bark, and closed form solutions is obtained to describe the relationship between the expansion velocity and the number of necks with consideration of the strain rate dependent strength of the shell material. The theoretical results show excellent correlation with the experimental results.

cond-mat.soft↗