Actuator and Sensor Conditions

It can be verified by substitution into Eq. (3.64) which should result in the constitutive relation. Thus it becomes apparent that the utilized matrix of constitutive properties has to be sjnmnetric. While this is given for the formulation with the matrix C introduced on the right-hand side of Eq. (4.33), the conventional variant C to the left-hand side proves to be of no avail. 

Remark 4-6. For the actual application of piezoelectric materials, free charges in the volume are excluded. 

Since no volume charges qA will be specified, the corresponding term in the virtual work of external charges vanishes, see Eqs. (3.53) and (3.62) respectively. 

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