| A temperature model of NDT by PT is studied by using the basic theory of heat transfer. The traditional model treats the laser pulse as transient pulse heat source and designs the model using the theory of Fourier heat conduction, but in fact, the effect of non-Fourier will appear when the heat source is a very short time heat disturbance. This paper uses the surface absorbing model of interaction between laser pulse and materials to link the laser pulse length and the depth of defects and a new way how to determine the depth of defects is advised. The impact of the heat convection and the heat radiation is studied by the body absorption model. The relation between the surface absorb model and the body absorb model is studied; this offers a theory to choose the model about interaction between laser pulse and materials. The model of the interaction between the nanosecond laser pulse whose time and space are Gaussian distribution and the materials is established by the numerical simulation, these build the theoretical foundation to study thermal properties of materials and the NDT of sub-surface. |
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