인장속도에 따른 마찰교반용접된 Al6061 합금의 파단부 상태변화에 대한 연구

Abstract

In general, welding is a technique for bonding for two metallic materials by heating. By various welding methods developed with the development of modern industry it has been recognized as an important technique essential for iron and non-ferrous metal bonding. however, the welding has a significant effect on the destruction of welding structure due to bounding through an heat or external effect in a short time. So, welding make the change of material property, residual stress, deformation of the material or welded defects. Research on fracture prediction of steel material has been reported in many different ways. The fracture portion is deformed due to the heat caused by breaking materials and this heat causes decreasing the strength of materials due to changes the mechanical and fracture properties. In this paper, aluminum specimen was welded according to welding speed using Friction stir welding process. Aluminum alloys are lightweight, high-performance characteristics in recent years due to energy savings and environmental dimension has widened its application range. In addition, ships, railways, automobiles, aircraft, etc. is becoming an aluminum alloy used in the manufacture of car body parts and aircraft equipment are increasingly expanding. Due to this effect, the study of the weld is made of an aluminum alloy continuously. Also useful as a welding method for bonding the aluminum alloy is laser-welded, as well as the conventional arc welding (MIG, TIG), friction stir welding (FSW), the study of the friction stir spot joining (FSSW) are being actively investigated. In this paper, aluminum specimen was welded according to welding speed using Friction stir welding process. To produce a tensile test, the friction stir welding specimen was added tension according to tension speed rate using MTS tensile test machine. When friction stir welding specimen are tension rate, breaking section shape, yield strength and strength change are shown in the specimen. The hot cracking occurs in the welded part by a reduced cross section of the welded part. In addition this heat frequently make problem such as the discontinuity of the base metal cold cracking, stress corrosion cracking. This problem can be analyzed using a infrared thermography camera. If the load receiving object radiation infrared heat energy by the deformation, the stress can be reduced by using the infrared radiation. Base on this principle, the temperature represents the highest stress value for the part during welding, and movement of temperature that can non-destructively predict the evolution of fatigue cracks. So, infrared thermography were able to shown about relationship between the heat-affected specimen when the local contraction at fracture part and it showed the relation between the temperature change in the fracture rate and tensile speed of the friction stir welding. In addition, as compared to the temperature change shown in the graph of the volume of the specimen according to the relationship between a tensile rate has been described. In conclusion, notch, crack, was observed for tensile, infrared thermography camera, the volume change to the welding conditions and this study will be safety, health, promotes a conservative and expected to contribute to basic research.