conducting plates are used to generate an electric field around the first piezoelectric member which induces a shape change in the first piezoelectric member this shape change exerts a force on the specimen since the specimen is constrained against the second piezoelectric member the applied force will cause the specimen to deform and induce a force on the second piezoelectric member this force will be translated to deformation in the second piezoelectric member thus producing an output electric signal that is picked up by the output conducting plates knowing the fundamental material constants of the piezoelectric material stresses and strains are calculated from the input and output electrical signals the magnitude of the applied electric field determines the applied load or force exerted on the specimen the electric field can be applied such that the specimen is in tension or compression or it can be cycled from one to the other thus tension or compression or tension compression cyclic testing can be performed both the first piezoelectric member and the second piezoelectric member are governed by the following equation where s is the strain of the material e is the electric field applied t is the stress in the material the meaning of each material constant is given in the table below the equations are expanded for one.