Photoacoustic Method For Testing The Material Thermal Diffusivity And Thermal Overflow Rate

The measurement of thermal diffusivity and thermal effusivity by photoacoustic(PA) technique was developed in 1960s, when the laser was brought in the research of it.The analysis of the thermal diffusivities and thermal effusivities of metal materials by a photoacoustic cell system was described in this paper, which was based on the Rosencwaig and Gersho's photoacoustic theory of solid sample, and the White's theory of thermoelastic:1. The research of theory model. A one-dimensional theory model has been build, based on samplifying the theory before and the boundary conditions in the system. The relation of the photoacoustic signal and the thermal diffusivity or thermal effusivity of materials have been obtained.2. The research of photoacoustic cell. The study of the structure of PA cells in some published articles has been carried out, some important problems of designing a photoacoustic cell have been confirmed. Finally, several kinds of photoacoustic cells have been completed, which of them was uesd in the photoacoustic system has been introduced in details.3. The research of photoacoustic system. The equipments used in the system have been introduced, especially of the pre-amplifier and the microphone. The measurement of aluminum and copper have been carried out in order to verify the experiment system, then the measurement of some metal materials and liquid materials have been accomplished.4. The research of accuracy. Based on the theory above, accuracy analysis of several different kinds of materials has been done, and the relations between the accuracy and thermal diffusivity or thermal effusivity have been obtained, the reasons have been find out.The research has shown that: the thermal diffusivities and thermal effusivities of materials can be measured by the PA cell system in this paper, the relative error between the experiment data and the reference data are all less than 3%, and the variance are all below the magnitude of 10-3, which indicates that the method of measuring thermal properties is stable and reliable. And by the accuracy analysis indicates that, to the different materials, the accuracy becomes higher as the thermal diffusivity and the thermal effusivity increased; to the same sample, the accuracy of thermal effusivity is higher than thermal diffusivity.In conclusion, the photoacoustic cell system provides a method of studying the thermal properties of the metal materials efficiently.