Hee-Yong Kang

Fracture Energy in Friction Stir Welding Al6061-T6 by Micro Shear Punch Test

Fracture energy was analyzed for FSW (Friction Stir Welding) joint in accordance with the tool rotation speed and feed rate in the thermo-mechanically affected zone. Al6061-T6 sheet with thickness 5mm was welded with 9 conditions (tool rotation speed: 900, 1000, 1100rpm, feed rate: 270, 300, 330mm/min). Tool with shoulder diameter of 18mm and probe diameter of 5mm was used. Specimen size was 10×10×0.5mm. The MSP (Micro Shear Punch) test was carried out to evaluate the load-displacement properties of FSW sheet along the center line of cross section of weldment. The maximum fracture energy was 0.771 J at the tool rotation speed of 1000 RPM and the feed rate of 300 mm/min, which was about 35.9 % of the minimum value. The reason is considered to be that the shape and distribution of precipitates in the weld zone were different and affected the weld strength and ductility.

Evaluation on Displacement Property of Ceramic Belt by Using FEM

Ceramics are becoming one of the most important materials due to its good mechanical properties such as high strength, hardness, chemical safety, and high modulus of elasticity. Ceramics have been used widely as a material not only for construction, but also for vehicles, planes, and bones for the human body. Despite these advantages, ceramics have some limitations in actual use due to its brittle fracture characteristic. In order to develop ceramic belt in this study, the data regarding stiffness and strain is necessary. For this purpose, the sensitivities of maximum stress value and displacement are analyzed by applying the load change on ceramic belt with finite element method program.

Creep life Prediction for W.M. of High Cr-Mo Steel using Modified Power-law

Abstract The high temperature creep properties of the generating plants high temperature tube, pipe and header and such are very significant in accordance with long-time exposure to the high temperature and pressure environment. Not only this, but as the welding procedure is compulsory for the cohesion of components, the creep properties regarding the local microstructures of steel weldment are very important. In order to understand the creep properties regarding the local microstructures of steel weldment, the SP-Creep test which is easy to get sample from the field component was conducted. The local microstructure of steel weldment, that is, W.M. and B.M.s microstructures were observed using the SEM. The rupture time of W.M. was longer as 110 % averagely in a same condition, which is the consequence of the difference of the microstructure. Each lethargy coefficient of B.M. and W.M. is evaluated by the relation among the temperature, load and the rupture time from SP-Creep Test. The life estimation equation can be induced by the transformation of Power-law. B.M. and W.M. for each 550 ℃ and 575 ℃, the very similar to normal temperature of the domestic thermal power generation in working, are estimated.