Effect of the volume of a functionally graded material layer on frictionally excited thermoelastic instability

► A finite element model is used to identify the effect of volume of FGM during the process of TEI. ► We found that the optimal volume of FGM layer has the highest critical speed. ► The critical speed of some FGM volumes is much lower than that of homogeneous steel layer. ► The critical speed is always high at the same nonhomogeneous parameter, for all volumes of FGM layer.