Materials Science Forum Vols. 580-582

Abstract: In order to investigate the soundness of welds in welding under loads, a series of experiments were carried out under static and cyclic loads. In the case of the experiment under compressive static loads, the defects such as buckling, welding crack, etc. were not observed in all the specimens. On the other hand, in the case of the experiment under compressive cyclic loads, the defects were not observed for the Fillet-type specimen. However, the hot crack was observed for the Butt-type specimen.

Abstract: The influence of laser peening on the fatigue crack growth behavior of friction stir welded (FSW) Aluminum Alloy (AA) 7075-T7351 sheets was investigated. The surface modification resulting from the peening process on the fatigue crack growth of FSW was assessed for two different R ratios. The investigation indicated a significant decrease in fatigue crack growth rates resulting from using laser shock peening compared with unpeened, welded and unwelded specimens. The slower fatigue crack growth rate was attributed to the compressive residual stresses induced by the peening.

Abstract: Because the fastener tension of high strength bolt, nut, and washer set is subject to the environmental factors such as temperature, humidity and storage period, extreme care should be taken during the joining and storage of such products. In case quality change is anticipated, the parts shall certainly be inspected.

Abstract: In order to secure the uniformity and to reduce the scattering of torque coefficient value, which is a decisive factor in the quality of high tension bolt nut and washer sets, effort is required from the manufacturer to standardize manufacturing process and to continuously improve the quality.

Abstract: This paper describes the development of a reconfigurable 3D profile measurement system for welding robot. The system consists of a PC based vision camera and a stripe-type laser diode. The total system is assembled into a compact module which can be attached to the endeffector of welding robots. Especially, the developed system is designed to operate at different working distances. For this purpose, the reconfigurable mechanism which adjusts the focal length and the relative position between the camera and the laser diode is devised. These two configurations are automatically changing, according to the current working distance. Most parts of image processing such as camera calibration, correction of distortion, and line extraction are implemented and running on the PC. After measuring the welding profile, the 3D shape of the parent metal is obtained and some useful features for robot manipulation are calculated.

Abstract: The purpose of this study is to identify the principal factors controlling the formability of TMCP steel for curved hull plate. In order to do it, the initial residual stress in TMCP steel was evaluated using flatness measured in the flat bar cut by flame and analytical approach. Changes of the curved profiles in conventional steel and EH 36 TMCP steel of 50mm thick during cold bending and local heating were investigated using 3 dimensional measuring instruments. It was found that the formability in TMCP steel was mainly determined by the excessive distortion by the relaxation of residual stress during cold bending.