930 A GENERAL SOLUTION FOR A LOADED BOLT-HOLE IN PIEZO-COMPOSITE PLATES

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Thermally loaded functionally graded materials with embedded defects

The material properties of a functionally graded material (FGM) may be very complicated functions of spatial position. Therefore, the development of a fracture mechanics analysis model for FGMs with arbitrarily distributed properties is essential. This article investigates the penny-shaped crack problem in FGMs with properties that are arbitrary functions of the axial coordinate. In the analysis, the graded region is modelled by a large number of layers stacked along the axial direction with each layer having different material properties. By utilizing the Hankel transform technique, dual integral equations for the entire elastic region are obtained. Thermal stresses and thermally induced crack deformations are computed by solving the dual integral equations numerically. As a numerical illustration, crack-tip fields for a metal substrate coated with an FGM subjected to an axial thermal flux are presented for different material nonhomogeneity parameters and coating thickness. It is found that the fracture strength of an FGM coating is much higher than that of a pure ceramic coating

Thermally induced fracture of a smart functionally graded composite structure

Discussed is the fracture behavior of a cracked smart actuator on a substrate under thermal load. The actuator is made of piezoelectric material with functionally graded material (FGM) properties. Integral transform method is used to reduce the problem to the solution of a set of singular integral equations and is solved numerically. This paper is completed by including graphical plots of the thermal flow, stress and electric displacement intensity factors around the crack for different crack positions and material gradients. Directions of crack initiation are also predicted by using the energy density criterion

Fracture of a piezoelectric material strip under steady state thermal load

Thermal effects become important when the piezoelectric material has to be operated in either extremely hot or cold temperature environments. It is essential to know the interaction of mechanical defects with thermal changes. In this article, we examine the piezothermoelastic problem for a Griffith crack that is located in a piezoelectric material strip. The strip is infinite along the x-direction and has finite thickness in the y-direction. The crack plane is parallel to the boundary of the strip. The polarized axis of the piezoelectric material is either normal or parallel to the y-direction. The basic entities are the Fourier transform and singular integral equation techniques. The crack-tip fields are obtained. The variation in crack-tip field intensity factors due to changes of the crack size and location is studied for different poling directions