Related Experiment Video
Updated: May 31, 2026
07:37
Full-field Strain Measurements for Microstructurally Small Fatigue Crack Propagation Using Digital Image Correlation Method
Published on: January 16, 2019
Falling through the Cracks: Energy Storage along Segmented Brittle Crack Fronts
1École Polytechnique Fédérale de Lausanne (EPFL), Institute of Mechanical Engineering, School of Engineering, 1015 Lausanne, Switzerland.
Physical Review Letters
|May 29, 2026
Summary
Stepped cracks form material ligaments that concentrate strain energy. This ligament acts as a cohesive zone, linearly increasing fracture energy with its rupture area, advancing brittle fracture mechanics.
Area of Science:
- Fracture Mechanics
- Materials Science
- Solid Mechanics
Background:
- Brittle crack propagation often results in stepped crack fronts.
- These stepped cracks create material ligaments, altering crack stability and mechanics.
- Quantitative analysis of stepped crack mechanics and ligament behavior is lacking.
Purpose of the Study:
- To quantitatively analyze the mechanics of stepped cracks and the role of the material ligament.
- To resolve the 3D deformation field around and within the ligament feature.
- To establish a relationship between ligament properties and macroscopic fracture energy.
Main Methods:
- In situ 3D measurements using laser sheet scanning of hydrogel samples.
- Tracking scattered light intensity from embedded tracer particles to capture deformation.
- Extraction of local stress fields to define an effective traction-separation law.
Main Results:
- The material ligament concentrates strain energy density.
- A new metric, "Ligament Equivalent Energy," is introduced.
- Macroscopic fracture energy scales linearly with Ligament Equivalent Energy normalized by ligament rupture area.
Conclusions:
- The ligament acts as an effective cohesive zone in brittle fracture.
- The Ligament Equivalent Energy provides a quantitative link between local ligament behavior and global fracture energy.
- Findings advance the understanding of brittle crack propagation mechanics.
Related Concept Videos
01:20Microcracking in Concrete
Microcracking in concrete refers to the tiny cracks that can form within the material even before any external load is applied. These microcracks typically occur at the interface between the coarse aggregate and the hydrated cement paste, often as a result of differential volume changes prompted by variations in stress-strain behavior, as well as thermal and moisture movement. Initially, these microcracks remain stable and do not grow substantially until the concrete is stressed to about 30...
01:21Fatigue
Fatigue occurs when materials rupture under repeated or fluctuating loads, even at stress levels far below their static breaking strength. It typically results in brittle failure, even for ductile materials. It is a critical consideration in designing machines and structural components subjected to repetitive or varying loads. The nature of these loadings can range from fluctuating loads like unbalanced pump impellers causing vibrations to repeatedly bending a thin steel rod wire back and forth...
01:28Types of Non-structural Cracks in Concrete
Non-structural cracks are primarily of three types: plastic, early-age thermal, and drying shrinkage cracks. Plastic cracks are further classified into plastic shrinkage cracks and plastic settlement cracks.
Plastic shrinkage cracks typically form within hours after the concrete is poured. The concrete's surface dries faster than the bottom, creating tensile stress that the still-plastic concrete cannot withstand, leading to diagonal or randomly patterned cracks on the concrete surface.
Plastic...
Plastic shrinkage cracks typically form within hours after the concrete is poured. The concrete's surface dries faster than the bottom, creating tensile stress that the still-plastic concrete cannot withstand, leading to diagonal or randomly patterned cracks on the concrete surface.
Plastic...
01:24Stress-Strain Diagram - Brittle Materials
Brittle materials, including glass, cast iron, and stone, exhibit unique characteristics. They fracture without considerable change in their elongation rate, indicating that their breaking and ultimate strength are equivalent. Such materials also show lower strain levels at the point of rupture. The failure in brittle materials predominantly results from normal stresses, as evidenced by the rupture created along a surface perpendicular to the applied load. These materials do not display...
01:20Elastic Strain Energy for Shearing Stresses
As discussed in previous lessons, strain energy in a material is the energy stored when it is elastically deformed, a concept crucial in materials science and mechanical engineering. This energy results from the internal work done against the cohesive forces within the material. When a material undergoes shearing stress and corresponding shearing strain, the strain energy density, which is the energy stored per unit volume, is calculated. Within the elastic limit, where the stress is...
01:23Behavior of Concrete Under Compressive Load
Concrete exhibits specific behaviors under different compressive loads. Understanding this is crucial for understanding its structural integrity. When concrete undergoes uniaxial compression, it tends to develop cracks that run parallel to the direction of the force. These parallel cracks stem from localized tensile stresses that occur perpendicular to the compression direction. Additionally, angled cracks may appear due to the formation of shear planes.
As the concrete specimen fractures under...
As the concrete specimen fractures under...