Drucker’s postulate

Fig. 4. Left Elasto-plastic (un-)loading including a non-imiqueness regime. Right Illustration of the ID-stress-strain-curve interpolation, the yield stress calculation and Drucker s postulate.

By knowledge of the total strain the only remaining unknown variable is eP. In other words, the decomposition of g into an elastic and plastic part must be determined, see Figure 4. For this reason Drucker s postulate can be used, which yields, inter alia, an associated flow rule as follows ... 

Fig. 3.27. Illustration of Drucker s postulate. For a specified plastic strain rate...

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