Therefore, the three-dimensional unsteady heat conduction differential equation is:
where T (x, t) is the temperature of the spot x at the time t and is also the coefficient of thermal diffusivity used to measure the heat transfer and storage ability of the material, which varies with temperature and position. Equation (5) gives the form of three-dimensional heat transfer function. It is generally difficult to find the analytical solution because of the complexity of the actual solution conditions. Therefore, this equation is often simplified to the form of one-dimensional heat conduction in the engineering practice. While the one-dimensional heat conduction theory cannot explain all the thermal phenomena, the one-dimensional heat conduction …show more content…
The pulsed excitation source was placed on the same side of the defect, and the thermal infrared imager is located on the same side of the detector. The pulse excitation generates heat that propagates through the material. As the heat transmission rate in the defect part differs from that in the non-defect part, more heat is concentrated in the defect part, forming an island of high temperature. The infrared thermogram monitors and records the temperature changes on the surface of the test object, thermogram, and stores the change process in the form of an infrared image sequence. Quantitative detection of defects can be achieved by analyzing thermogram sequence.
3.1 Brief description of test object
As shown in Figure 2, two wedge-shaped grooves of the same shape were made on a PVC slab sized 152.00×110.00×3.00 mm3, and numbered as defects #1 and #2. The maximum width is 9.00 mm, the width at the narrowest point is 3.00 mm, and the tip of the groove is a semicircle with a diameter of 3.00 mm. The lengths of #1 and #2 grooves are 101 and 100 mm , respectively. The depths of #1 and #2 defects are 1.50 and 1.00 mm, respectively. The test object is depicted in Figure
where T (x, t) is the temperature of the spot x at the time t and is also the coefficient of thermal diffusivity used to measure the heat transfer and storage ability of the material, which varies with temperature and position. Equation (5) gives the form of three-dimensional heat transfer function. It is generally difficult to find the analytical solution because of the complexity of the actual solution conditions. Therefore, this equation is often simplified to the form of one-dimensional heat conduction in the engineering practice. While the one-dimensional heat conduction theory cannot explain all the thermal phenomena, the one-dimensional heat conduction …show more content…
The pulsed excitation source was placed on the same side of the defect, and the thermal infrared imager is located on the same side of the detector. The pulse excitation generates heat that propagates through the material. As the heat transmission rate in the defect part differs from that in the non-defect part, more heat is concentrated in the defect part, forming an island of high temperature. The infrared thermogram monitors and records the temperature changes on the surface of the test object, thermogram, and stores the change process in the form of an infrared image sequence. Quantitative detection of defects can be achieved by analyzing thermogram sequence.
3.1 Brief description of test object
As shown in Figure 2, two wedge-shaped grooves of the same shape were made on a PVC slab sized 152.00×110.00×3.00 mm3, and numbered as defects #1 and #2. The maximum width is 9.00 mm, the width at the narrowest point is 3.00 mm, and the tip of the groove is a semicircle with a diameter of 3.00 mm. The lengths of #1 and #2 grooves are 101 and 100 mm , respectively. The depths of #1 and #2 defects are 1.50 and 1.00 mm, respectively. The test object is depicted in Figure