Measurement and characterization of Thermo-Mechanical Fatigue in Compacted Graphite Iron

In diesel engine cylinder heads of Compacted Graphite Iron (CGI), heating and cooling cycles can lead to localized cracking due to Thermo-Mechanical Fatigue (TMF). Test results together with numerical calculations showed that TMF in CGI is governed by crack growth according to the Paris equation for both smooth and notched specimens. For a typical ΔK value, using a new crack length measurement procedure, the crack growth rate was confirmed to be in reasonable agreement with the calculated one. Finally, it was found that TMF crack growth in CGI is not influenced noticeably by the accumulation of cyclic plasticity of bulk material.

► Thermo-Mechanical Fatigue tests were performed on Compacted Graphite Iron.
► Smooth and notched specimens were used with five notch depth values.
► TMF test results were matched with calculated lifetimes using the Paris’ equation.
► The TMF lifetime of CGI is consumed by crack growth and not by crack initiation.
► The accumulation of cyclic plasticity does not affect TMF lifetimes noticeably.