Theoretical and experimental investigations of fatigue crack growth in ferroelectrics under cyclic electromechanical loading

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Fatigue crack behaviour is of most importance for the assessment of reliability and durability of smart structures in engineering practice. The aim of the present research proposal is the qualitative explanation and the quantitative description of fatigue crack growth mechanisms in ferroelectric and piezoelectric ceramic materials. For this purpose an approach is planned, combining experimental investigations, theoretical modelling and numerical simulations. The main emphasis is on the fracture process zone, where domain switching phenomena induce nonlinear effects and control the failure mechanisms. Therefore, micromechanical and phenomenological constitutive models will be developed, implemented into FEM-codes and applied to simulate the fatigue crack behaviour under mechanical, electrical and combined loading. Experiments will be undertaken to investigate the nonlinear effect of domain switching and to measure fracture toughening and fatigue crack growth rates. Suitable fracture criteria and fatigue crack growth laws will be proposed and verified by experiments. The results will provide guidelines for component design and reliability evaluation of smart ferroelectric structures under cyclic electromechanical loading.