Mikrorisses

Mikrorisses are small cracks or fissures in solids with dimensions on the micrometer to submillimeter scale. They occur across a wide range of materials, including metals, ceramics, polymers, composites, concrete, and natural rocks. Mikrorisses often precede larger crack growth and failure, but in some materials a network of microcracks can contribute to toughness or stress redistribution.

Formation and causes

Mikrorisses initiate where local stress concentrates at flaws such as inclusions, porosity, grain boundaries, or surface defects. They can form under cyclic loading (fatigue), sustained overload, thermal cycling, chemical attack, moisture ingress, or irradiation. Microstructural features such as grain size, phase distribution, and residual stresses influence initiation sites and propagation paths.

Detection and measurement

Detection relies on non-destructive and destructive methods. Optical microscopy of polished surfaces and scanning electron microscopy provide high-resolution imaging of crack geometry. X-ray computed tomography maps three-dimensional crack networks. Acoustic emission monitoring tracks crack activity during loading, while digital image correlation studies surface strain fields associated with microcracking.

Impact and applications

Mikrorisses reduce stiffness and strength and can increase permeability and diffusion of fluids. Their growth under service conditions influences the long-term durability of concrete and metals and affects porosity and mechanical properties in rocks. In some engineered materials, controlled microcracking is used to improve toughness through mechanisms such as crack deflection or energy absorption.

See also

Microcrack, fracture mechanics, fatigue, porosity.