Pulsed infrared thermography is applied to the study of a mold casting Chinese bronze lei 罍 dated to the late Shang dynasty (c.a.1250–1050 BC), currently housed in the Capital Normal University Museum. Many spacers and a defective area of this ancient bronze are partly covered with repair material. By analyzing thermographic images using a one-layer thermal diffusion model, it is found that the spacers were specifically made for this bronze. The thickness of the repairing material in the defective area is measured using thermal quadrupole modelling in multilayer materials. This is the first application of this method to the field of cultural heritage conservation. These results provide a deeper understanding of the manufacturing process of ancient Chinese bronzes from the viewpoint of archaeological research. They also help assess the repair status from the conservation viewpoint.
This paper mainly explores the application of thermal signals generated by sequential laser pulses in the detection of metal material defects. Here we use flat bottom holes with different sizes on stainless steel as our sample. Sequential laser pulses are used as thermal excitation source and the surface temperature field is recorded by infrared thermal imager.By analyzing the relationship between the surface temperature of the defect area under sequential pulse excitation, the defect aspect ratio can be obtained due to different 3D thermal diffusion process. The experimental scheme and data processing method described in this paper provide a new method and theoretical basis for the measurement of metal defects size by sequential laser pulses, and have certain reference value for the detection and research of other metal material defects
Emissivity is one of the important parameters to reflect the thermal characteristics of the surface of an object. It plays a great role in the research of infrared coatings with high or low emissivity. In this paper, a novel non-contact experimental method is proposed to measure the coating’s emissivity using the dual-temperature method, and the error of the measured infrared emissivity with different base board materials is analyzed.
With the continuous progress of modern industry, the traditional nondestructive testing methods cannot meet the growing demand. At present, as a novel approach, the thermography non-destructive testing (TNDT) technology has been widely used in various industrial fields. In this paper, we present the study of a three-layer "metal-air-metal" structure, firstly through the modeling by finite element analysis software COMSOL Multiphysics, and then under the laboratory conditions using flash lamp as excitation methods for TNDT. Based on the preliminary simulation and experimental results , it is proved that it is possible to detect the bottom layer defects with a certain aspect ratio in the multilayer structure. It has practical significance in many scenarios, such as the locating the rivet holes under aircraft skin, the detection of defects below insulation layer and tomographic inspection of post-impact multilayer composites.
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