negative eigenvalues are not possible
left/right Cauchy-Green Deformation Tensors are positive definit https://de.wikipedia.org/wiki/Deformationsgradient
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@ -575,10 +575,6 @@ class DADF5():
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R_inv = np.transpose(np.matmul(U,Vh),(0,2,1)) # transposed rotation of polar decomposition
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U = np.matmul(R_inv,defgrad['data']) # F = RU
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(D,V) = np.linalg.eigh((U+np.transpose(U,(0,2,1)))*.5) # eigen decomposition (of symmetric(ed) matrix)
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neg = np.where(D < 0.0) # find negative eigenvalues ...
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D[neg[0],neg[1]] = D[neg[0],neg[1]]* -1 # ... flip value ...
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V[neg[0],:,neg[1]] = V[neg[0],:,neg[1]]* -1 # ... and vector
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d = operator['V#ln'](D)
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a = np.matmul(V,np.einsum('ij,ikj->ijk',d,V))
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@ -589,7 +585,7 @@ class DADF5():
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'meta' : {
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'Unit' : defgrad['meta']['Unit'],
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'Description' : 'Strain tensor ln(V){} ({})'.format(defgrad['label'],defgrad['meta']['Description']),
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'Creator' : 'dadf5.py:add_deviator v{}'.format(version)
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'Creator' : 'dadf5.py:add_strain_tensor v{}'.format(version)
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}
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}
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