High-temperature behaviour and interfacial damage of CGI: 3D numerical modelling

Superior mechanical and thermal properties, high wear resistance and a competitive price of compacted graphite iron (CGI) have made it an integral part of industry worldwide. In its applications in automotive engines, high-temperature environments cause thermal expansion that can result in emergence of interfacial damage in CGI. Although graphite-matrix interfacial damage is considered the main damage mechanism that can lead to total fracture of CGI, extensive research on CGI has not yet fully investigated this phenomenon at the microscale, especially under pure thermal loading. This paper focuses on the high-temperature performance of CGI and the onset of damage in graphite in thermal cycles. Three-dimensional numerical models are developed, with a single graphite inclusion embedded in a unit cell of the metallic matrix. Elastoplastic behaviour is considered for both phases in simulations. The effects of morphology and orientation of graphite inclusions on a response of an entire unit cell to thermal loading are investigated. Also, the influence of periodic and fully-fixed boundary conditions on the damage behaviour of CGI is discussed. The results can give a better understanding of the fracture mechanisms of CGI exposed to elevated temperatures.