Numerical modeling of transient heat transfer in a multilayer bimetallic plate

When using the method of active thermal non-destructive testing to detect latent defects in multilayer bimetallic products, the adequate choice of technological modes of testing is of great importance. One of the important parameters is the optimum observation time, at which a sufficient amplitude of the temperature signal over the defect is provided. This value depends on the controlled object geometry, its thermophysical characteristics, and also selected testing modes and procedures. Various experimental studies are used to determine the optimum observation time. Preparing bimetallic plates samples for full-scale experiments is a technologically complex and expensive task. Therefore, a large amount of preparatory research is carried out in the form of a numerical experiment, during which, with certain assumptions, changing the thermal state of the control object is simulated. Aim. Determination of optimal parameters of the thermal NDT process for a three-layer steel-aluminum plate with a planar delamination defect between the metal layers. For different variants of mutual location of the temperature registration device and source of heat flux of different power it is necessary to determine the heating time at which the sufficient amplitude of temperature signal is observed. Materials and methods. The methods of mathematical and computer modeling were used. Solving the task by the finite element method with the Agros2D code is given. Results. The calculation data have been obtained, which are used as the basis for constructing the temperature signal distribution over the bimetallic plate surface above the defect under different heating modes, heat flux rate, relative position of the heat stimulation source and temperature registration device, as well as determining the temperature signal dependence over the defect on the heating time. Conclusion. On the basis of modeling the temperature dependences necessary for interpretation of the results of thermal NDT of multilayered bimetallic plates have been determined, as well as the relations between the parameters of the heating process, which contribute to obtaining a temperature signal of sufficient amplitude. The results can be used for further experimental studies of the active thermal NDT processes of multilayer bimetallic materials.