13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- sandwich plate. To understand the effects caused by the thermal load, several uniform temperature loads, 0 C, 50 C, 90 C TΔ = ° ° ° , are imposed on the plate, whose buckling temperature is verified to be 94 C° . Figure 4. Natural frequency and relative difference The natural frequencies of the sandwich plate subjected to different thermal load are shown in Fig. 4, from which the trend that the natural frequencies reduce with the temperature rising can be seen obviously. The modes for the plate are the same under different temperature. The relative frequency difference of the first natural frequency is much greater than others, which means the effect induced by thermal load is more obvious in fundamental frequency. The incident sound wave which is perpendicular to the plane is applied to the plate. The velocity response at (0.1m, 0.1m) and the sound pressure level responses at (0.1m, 0.1m, 3m) are shown in Fig. 5, from which, one can observe that with the thermal load increasing, the peaks of vibration and acoustic responses float to low-frequency range. a. Velocity b. Sound Pressure Level Figure 5. Dynamic responses 4.2. Different incident angles Plane waves with incident angle of 0 0 °− °, 30 0 °− °,30 30 °− ° are applied on the sandwich plate to discuss the influence caused by the incident angle. Different from the thermal load, the plane sound wave doesn’t change the natural characteristics of the plate. Only the dynamic response is affected. The plate is also subjected to a uniform temperature load of 50 C° .
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