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Abstract

ABSTRACT

Measurement for temperature changes and surface roughness of fracture according to welding conditions by using infrared thermography

Kim Dong Lyul Advisor : Prof. Kim Kyeong-Suk, Ph.D. Dept. Advanced Parts & Materials Engineering. Graduate School of Chosun University

The objective of this paper is to investigate volume and temperature evolutions of fracture crack surfaces of welded specimen. In the test, Welded specimens were loaded by a fatigue machine with loads until they were broken. On the basis of fracture experiments, the variation of outside condition is appeared to the temperature and volume, surface roughness of specimen. Fracture experiments were performed to with development of Computer technology and CCD’s(Charged Coupled Devices). In the accordance with, the evolution is detected to Infrared camera and charged coupler device(CCD). This condition is associated with each other. The thesis found it the association. That research isn't attempt to other technician so it has important things. The analysis of experiment will explain the next contents. Firstly, the tendency of volume variation according to temperature was measure liner. So the variation of temperature increase fracture moment. Also the surface roughness of fractured surround district increase abruptly because of fracture influence. The infrared thermography(IRT) measures the radiated energy of object and translate to thermal image of surface of object. IRT has merits such as non-contact, non-destructive, real time measurement technique. Mechanical deformation by temperature evolutions is very important to industries. In this paper, relationship between volume and temperature evolutions is investigated under different tensile speed. The result shows that temperature evolution of specimen depends on volume evolution and tensile speed. As a result, Temperature evolution of specimen could be predicted by known volume evolution. The roughness of the fracture crack surfaces thereafter were measured by 3D Surface Profiling System. From the results, it was confirmed that Surface profiling System could measure the roughness of the various types of the crack surface. In this paper, finally a possibility to predict the magnitude of loads by roughness measurement of the fracture crack surface was proposed. As a result of this study, It was identified that the average roughness are similar at the position that has a same loads by comparing the results with the loads on the specimen according to the position. Secondly, the fractured surface roughness isn't has variation in the changed tensile speed. This result explained which that roughness according to changed tensile speed influence the surround district. Third, the analysis explain the specimen surface appear to necking situation. Also using the above analysis data measured necking position. Lastly, the temperature and surface roughness are detectable in the required distance of fractured surface. That result is very useful in the nondestructive testing method in industry. It can the surface displacement on large area with real-time, high resolution and non-contactㆍnon- destructive method, so these are utilized in various industry field for vibration analysis, deformation analysis and non-destructive testing. With advanced computer science and image processing technology, Because of these technology development, Metal fracture experiments will change to digitalized CCD camera and IR has evolved to digital technology that is united with image process technique. In the Future, Metal Fracture experimental research is needed on the Poisson’s ratio of the welded specimens.