Unidirectional multiple cracking of coatings described through random sequential placement of rods on a line

• Published in: Thin solid films 2000-01, Vol.358 (1), p.46-55
• Main Authors: Mézin, A., Sajid, B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Brittleness; Coatings; Condensed matter: structure, mechanical and thermal properties; Cracks; Exact sciences and technology; Mechanical and acoustical properties; Metals. Metallurgy; Physical properties of thin films, nonelectronic; Physics; Statistics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(99)00714-2

The phenomenon of unidirectional multiple cracking of coatings is described through a statistical analysis by Widom for random sequential placement of impenetrable rods on a line. Each rod represents the zone of the coating around the crack which is relieved of stress by the crack formation. The rupture probability density is assumed zero in the ‘exclusion zones’, and unchanged elsewhere. Eventual overlapping of the ‘exclusion zones’ is taken into account. Applicability of the model is examined and exemplified by an experimental case of a Cr coating deposited on high speed steel. The rupture probability and exclusion zone size can be determined at low and intermediate crack densities (intercrack distance higher than approximately ten times the film thickness). The model constitutes a simple and efficient tool for interpreting the multiple cracking test of coatings.