• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.10a
• /
• pp.133-137
• /
• 2003

The shock absorber for vehicles is the important component to absorb the shock in driving. These essential components, piton and piston rod, must be made of S25C, S45C and SCM440 generally depending on kind of vehicles, precisely machined and assembled by the bolt. And it has been difficult to weld this sort of dissimilar materials. They could be unstable in the quality by the conventional arc welding. And also they have a lot of technical problems in manufacturing. But by the friction welding technique, it will be able to be made without such problems. These factors above necessitate nowadays the domestic development of the shock absorber by friction welding and a new approach of study on real-time quality evaluation by AE techniques.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.4
• /
• pp.64-69
• /
• 2011

Magnesium alloy has been known as lightweight material in automobile and electronic industry with aluminum alloy, titanium alloy and plastic material. Friction welding is useful to join different kinds of metals and nonferrous metals they are difficult to be joined by such as gas welding, resistance welding and electronic beam welding. In this study, friction welding was performed to investigate optimization process of Mg alloy with a 20mm diameter solid bar. For that, the orthogonal array $(L_{9}(3^{4}))$ was used that contained four factors and each factor had three levels. Control factors were heating pressure, heating time, upsetting pressure and upsetting time. Also tensile tests were carried out to measure mechanical properties for welded conditions. The levels of heating pressure and upsetting pressure used were 15, 25, 35MPa, and 30, 50, 70MPa, respectively. In addition those of heating time and upsetting time were 0.5, 1, 1.5 sec and 3, 4, 5 sec., respectively, rotating speed of 2000rpm. From the experimental results, optimization condition was estimated as follows; heating pressure=35MPa, upsetting pressure=70MPa, heating time=1.5sec, upsetting time=3sec.

• Journal of Ocean Engineering and Technology
• /
• v.7 no.2
• /
• pp.121-130
• /
• 1993

A study off riction welding of high speed steel(SKH 51) bar for blade side to carbon steel(STC 3)bar for shank side was carried out experimentally through tensile test, hardness test, microstructure, and acoustic emission (AE) test. So, this paper deals with optimizing the welding conditions and the real-time quality (strength) evaluation of friction weleded joints by acoustic emission technique. The results obtained are summarized as follows: (1) For friction welded joints of SKH 51to STC 3 steel bars, the total upset (U) increases linearly with an increase of heating time (t sub(1)). (2) The determined optimum welding conditions are heating time (t sub(1)) 7-9 sec, upsetting time (t sub(2)) 5 sec, heating pressure(P sub(1)) 12 kg sub(f)mm supper(2), upsetting pressure (P sub(2)) 15 kg sub(f) mm supper(2) and rotating speed (n) 2, 000 rpm, resulting in a computed relationship between the tensile strength of the joint .sigma. (kg sub(f) mm supper(2)) and the heating time t sub(1) (sec) as the following. sigma.=2.39t sub(1)

• Journal of Welding and Joining
• /
• v.32 no.5
• /
• pp.50-57
• /
• 2014

Friction Stir Welding (FSW) is a complex process with several mutually interdependent parameters. A slight difference from known settings may lead to imperfections in the stirred zone. These inhomogeneities affect on the mechanical properties of the FSWed joints. In order to prevent the failure of the welded joint it is necessary to detect the most critical defects non-destructive. Especially critical defects are wormhole and lack of penetration (LOP), because of the difficulty of detection. Online thermography is used process-accompanying for defect detecting. A thermographic camera with a fixed position relating to the welding tool measures the heating-up and the cool down of the welding process. Lap joints with sound weld seam surfaces are manufactured and monitored. Different methods of evaluation of heat distribution and intensity profiles are introduced. It can be demonstrated, that it is possible to detect wormhole and lack of penetration as well as surface defects by analyzing the welding and the cooling process of friction stir welding by passive online thermography measurement. Effects of these defects on mechanical properties are shown by tensile testing.

• Journal of Welding and Joining
• /
• v.31 no.4
• /
• pp.73-79
• /
• 2013

Burr grinding, Tungsten Inert Gas (TIG) dressing, ultrasonic impact treatment, and peening are used to improve fatigue life in steel structures. These methods improve the fatigue life of weld joints by hardening the weld toe, by improving the bead shape, and by creating the compressive residual stress. In this study, a new post-weld treatment method improving the weld bead shape and metal structure at the welding zone using Friction Stir Processing (FSP), a welding process, is proposed to enhance fatigue life. For that, a pin-shaped tool and processing condition employing Friction Stir Processing (FSP) is established through experiments. Experimental results revealed that fatigue life is improved by around 50% compared to as-welded fatigue specimens by reducing the stress concentration at the weld toe and by generating a metal structure finer than that of flux-cored arc welding (FCAW).

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.11
• /
• pp.1060-1066
• /
• 2007

When a high-energy ultrasound propagates through a solid body that contains a crack or a delamination, the two faces of the defect do not ordinarily vibrate in unison, and dissipative phenomena such as friction, rubbing and clapping between the faces will convert some of the vibrational energy to heat. By combining this heating effect with infrared imaging, one can detect a subsurface defect in material efficiently. In this paper a detection of the welding defect of thin SUS 304 plates using the UIR (ultrasonic infrared imaging) technology is described. A low frequency (20kHz) ultrasonic transducer was used to infuse the welded thin SUS 304 plates with a short pulse of sound for 280ms. The ultrasonic source has a maximum power of 2kW. The surface temperature of the area under inspection is imaged by a thermal infrared camera that is coupled to a fast frame grabber in a computer. The hot spots, which are a small area around the defect tip and heated up highly, are observed. From the sequence of the thermosonic images, the location of defective or inhomogeneous regions in the welded thin SUS 304 plates can be detected easily.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.26 no.4
• /
• pp.425-429
• /
• 2017

During ultrasonic welding, plastic deformation, elastic hysteresis, and friction generate heat at the contact portions of the two materials to be welded, theoretically analyzing and experimentally measuring the temperature at the welded part are very important for identifying the heat affected zone. However, the welding temperature during ultrasonic welding wherein welding is performed in less than a second is a challenge. We investigated the effects of welding conditions such as welding time, welding pressure, and the ultrasonic vibration amplitude of horns on the temperature of welded surface of a Ni sheet of thickness 0.1 mm. We used a horn with a resonance frequency of 40 kHz and an ultrasonic welder. The temperature was measured using a intrared sensor, and its characteristics were investigated. Experimental results showed that increase in welding time and pressure and ultrasonic vibration amplitude of horns generally caused the increase in surface temperature of the weld.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.434-441
• /
• 2016

Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.41-41
• /
• 2009

To evaluate the applicability of dissimilar joining between Mg and Al alloys in automobile manufacturing process, solid state joining processes such as magnetic pulse welding(MPW), friction stir welding(FSW) and friction spot joining(FSJ) were attempted successfully. MPW process has been concentrated mainly on round section tube to tube and tube to bar welds. AZ31 Mg alloy has been successfully welded to pure Al A1070 as well as to Al alloy A3003. While, for friction stir welding of dissimilar sheet joints, AZ31B/A6061 with the thickness of 2mm were used and a square butt joint with a good quality was obtained at the conditions of 0.8mm/sec of travel speed and tool rotation speed of 850rpm. The maximum tensile strength of 179 MPa, which was about 80 % of the Mg base metal tensile strength, has been obtained. Finally, friction spot joining was attempted to make a dissimilar lap joint between AZ31(0.8mm) and A6061(1mm), while the joint exhibited the same level of tensile shear strength as that of similar Mg joint.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.5
• /
• pp.99-104
• /
• 2017

Friction stir welding is a solid-state joining process and is useful for joining dissimilar metal sheets. In this study, the experimental conditions of the friction stir welding were determined by the two-way factorial design to evaluate the characteristics of the dissimilar friction stir welding of AZ31 and AZ61 magnesium alloys. The levels of rotation speed and welding speed, which are welding variables, were 1000, 2000, 3000 rpm and 100, 200, 300 mm/min, respectively. From the results, the greater the rotation speed and the lower the welding speed of the tool were, the greater the tensile strength of the welded part was. The contribution of the welding speed of the tool is larger than that of the rotation speed of the tool. In addition, the optimal conditions for tensile strength in the dissimilar friction stir joint were predicted to be the rotation speed of 3000 rpm and welding speed of 100 mm/min, and the tensile strength under the optimal conditions was estimated to be $214{\pm}6.57Mpa$ with 99% reliability.