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The load separation method was employed to determine the mixed modeplastic pl η and CODpl η factors for the tension plate with an inclined centre crack in thecase of power law hardening materials. The crack orientation angle was varied frompure mode I (θ = 0 ) to mixed (modes I+II) mode. The separation parameters ij S havebeen calculated from the FE computed load – plastic displacement (or COD) curves foreach case. The slope of the log(S ) log(b /W) ij i − lines gives the η -factors. It was shownthat the mixed mode plastic pl η factor is a function of both the crack angle orientationθand the strain hardening exponent. At the same time, the normalized mixed modeplasticη (θ )/η (θ = 0) pl pl factor does not depend on specimen configuration.The mixed plastic CODpl η factor exceeds the value of pl η over the whole domain of thecrack orientation angle.