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--- doc:user:elements:volumes:yield_stress [2020/07/08 09:43] – papeleux
+++ doc:user:elements:volumes:yield_stress [2020/07/08 10:27] (current) – [SellarsTeggartYieldStress] papeleux
@@ Line 300: / Line 300: @@
-===== SellarsTeggartYieldStress=====
+===== SellarsTeggartYieldStress =====
 Yield Stress used for hot rolling defined by  :
   * a Static term :
 $$
-S0 = \sqrt(3)  \; KK (\sqrt(3)  \;\bar{\varepsilon}^{vp})^{M0}
+S0 = \sqrt{3}  \; KK (\sqrt{3}  \;\bar{\varepsilon}^{vp})^{M0}
 $$
   * a Dynamic Term :
 $$
-Ss = As  \; asinh(\frac{\dot{\bar{\varepsilon}}^{vp}}{Zs})^{Ms}
+Ss = As  \; asinh((\frac{\dot{\bar{\varepsilon}}^{vp}}{Zs})^{Ms})
 $$
   * for the Yield Stress computed by :
@@ Line 328: / Line 328: @@
+===== PythonYieldStress =====
+User defined Yield Stress by a pythonDirector :
+Python Director allows user to define their own Yield Stress law. Four functions has to be defined in the Python Class : a constructor (__init__), a destructor (__del__) that must never be called, and the computation functions : getYieldStress (returning YieldStress) and getYieldHardening (returning h).
+See the example below of a Perzyna law :
+<code>
+class MyYieldStress(PythonYieldStress):
+    def __init__(self, _no, _svm0, _h, _K, _m):
+        print("MyYieldStress: __init__")
+        PythonYieldStress.__init__(self,_no)
+        self.svm0 = _svm0
+        self.h    = _h
+        self.K    = _K
+        self.m    = _m
+    def __del__(self):
+        print("MyIsoH : __del__")
+        print("callToDestructor of MyYieldStress not allowed. Add MyIsoH.__disown__()")
+        input('')
+        exit(1)
+    def getYieldStress(self, evpl, deltaEvpl, dTime, yieldGPState, pLaw):
+        #print "MyYieldStress compute Yield Stress"
+        if dTime > 0.0:
+            dEvpl = deltaEvpl/dTime
+        else:
+            dEvpl = 0.0
+        sigH = self.svm0+evpl*self.h
+        sigV = self.K*pow(dEvpl, self.m)
+        #yieldGPState.setVpStress(sigV)
+        return sigH+sigV
+    def getYieldHardening(self, epl, deltaEvpl, dTime, yieldGPState, pLaw) :
+        if dTime > 0.0:
+            dEvpl = deltaEvpl/dTime
+            h = self.h + (self.K*pow(dEvpl, self.m-1))/dTime
+        else:
+            dEvpl = 0.0
+            h = self.h
+        return h
+</code>