Numerical Evaluation Method of CED in Piezoelectric Materials and Influence of Loading History on Their Values

概要

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The CED (Crack Energy Density) was proposed first with ordinary materials in mind as the parameter that is defined regardless of constitutive equation and enables a unified description of behavior of a crack throughout its life. Subsequently the concept was extended, on the basis of facts that its applicability had been shown successfully for ordinary materials, so as to be applied to piezoelectric materials and some fundamental relations related to CED and its derivatives such as mechanical and electrical parts of CED and electrical enthalpy density were given. Aiming at exploring the applicability of these quantities to crack problems for piezoelectric materials, in this paper, a method for evaluating CED and its derivatives numerically with practically sufficient accuracy through finite element analyses of a piezoelectric material is studied concretely by using the relations above. As a result, it is shown that the values of mechanical and electrical parts of CED depend on the loading history, that is, how to apply mechanical and electrical loads, even for a linear problem and its influence should be taken into consideration, while CED and electrical enthalpy density are independent of the loading process.