Bažant-Le-Kirane Paradox of fatigue failure in engineering materials

Author: Mahendra Gattu, Department of Civil Engineering, NIT-Rourkela-769008.

Abstract

The problem of fracture in quasi-brittle materials is strongly linked with a zone of micro-cracking known as the fracture process zone (FPZ). For monotonic loading, the material length scale parameter D0 is used in strength scaling law to describe the transition from strength criteria to linear elastic fracture mechanics criteria.

The Paris Law approach to quasi-brittle materials for cyclic loading introduces another length scale parameter, D0c. Experimental testing of concrete, rock, and sandstone showed two contradictory results. A few experiments showed that the parameter D0c is higher than D0, and the cyclic FPZ is larger than monotonic FPZ. Another set of experiments showed that D0c is smaller than D0, and the cyclic FPZ is smaller than monotonic FPZ. This interesting contradiction is named the Bažant-Le-Kirane Paradox (B-L-K Paradox) after the scientists involved in the experimentation. The B-L-K paradox is the holy grail of fatigue fracture mechanics, and solving this problem will allow for the rational design of concrete structures.

Keywords: Cyclic fracture process zone; Monotonic fracture process zone; Fatigue; Fracture; Sandstone; Concrete;

Link to paper: https://doi.org/10.1515/ijmr-2024-0038

Link to video: https://youtu.be/s1hD_NnTgk8