Abstract
A novel application of the hot disk transient plane source technique is described. The new application yields the thermal conductivity of materials as a function of the thermal penetration depth which opens up opportunities in nondestructive testing of inhomogeneous materials. The system uses the hot disk sensor placed on the material surface to create a time varying temperature field. The thermal conductivity is then deduced from temperature evolution of the sensor, whereas the probing depth (the distance the heat front advanced away from the source) is related to the product of measurement time and thermal diffusivity. The presence of inhomogeneity in the structure is manifested in thermal conductivity versus probing depth plot. Such a plot for homogeneous materials provides fairly constant value. The deviation from the homogeneous curve caused by defects in the structure is used for inhomogeneity detection. The size and location of the defect in the structure determines the sensitivity and possibility of detection. In addition, a complementary finite element numerical simulation through COMSOL Multiphysics is employed to solve the heat transfer equation. Temperature field profile of a model material is obtained from these simulations. The average rise in temperature of the heat source is calculated and used to demonstrate the effect of the presence of inhomogeneity in the system.
Highlights
The conventional nondestructive techniques for material inspection include radiography, ultrasonics, liquid penetrant, eddy current, magnetic and thermal methods
The new application yields the thermal conductivity of materials as a function of the thermal penetration depth which opens up opportunities in nondestructive testing of inhomogeneous materials
The system uses the hot disk sensor placed on the material surface to create a time varying temperature field
Summary
The conventional nondestructive techniques for material inspection include radiography, ultrasonics, liquid penetrant, eddy current, magnetic and thermal methods. Thermal methods work on the principle that two different materials provide distinct thermal response while interacting with thermal signal.[1,2,3] Thermal imaging is a powerful tool for nondestructive characterization of materials It has a wide range of practical applications in industries such as in aerospace. This article shows the possibility of inhomogeneity detection in a material through thermal conductivity variation which is not present in a homogeneous system This method has possible applications in quality control such as testing sample homogeneity and sample reproducibility in characterizing component gradient etc. The printed samples have been prepared with voids of different sizes and positions in the matrix These samples have been studied experimentally using the hot disk method.
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