• Journal of the Korean institute of surface engineering
• /
• v.45 no.5
• /
• pp.181-187
• /
• 2012

The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, microstructures and mechanical properties of FSLW in A5052 alloy were investigated under varying rotating speed and probe length. Investigating the characteristics as FSLWed conditions were as below ; Failure Maximum load by shear fracture was increased proportional to the width of joint area, which was increased by input heat, stirring intensity in the case of 2.3 mm probe length. Tensile fracture occurred, and maximum load was determined due to side worm hole of joint area and softening of microstructure in the case of 3.0 mm probe length. In the case of 3.7 mm probe length, material hook and bottom worm hole were appeared at the end interface of joint area. The most sound FSLW condition with no defects was 3.0 mm probe length and 1500 rpm-100 mm/min. No defects were showed in 1500 rpm-100 mm/min and 1800 rpm-100 mm/min, but Vickers microhardness distribution in TMAZ/HAZ which was fracture zone was lower in 1800 rpm-100 mm/min than in 1500 rpm-100 mm/min. In this condition highest tensile strength, 215 MPa (allowable rate 78% of joint efficient) was obtained.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.293-296
• /
• 2008

Most of the guided weapons have been kept and transferred at the launching tube and fired in case of necessity in these day. Launching tube is a kind of case to protect the guided weapons from external environments and conducted as a guide when they are fired. When we attached the guided weapons to launching tube we usually has used explosive bolt. Explosive bolts have been used explosives when they had to be separated. But when they are separated there are some bad effects; a flame, fragments and pyro-shock. Because of these bad effects there are many restriction to use bolt as joining devices to precision guided weapons. To solve these problems, it has been invented ball type bolt. The present work was represented quantitively the margin of separation safty and separation mechanism in ball type bolt to analyse the dynamic separation test. Unlike explosive bolt, ball type bolt is separated without a flame, fragments and pyro-shock. And it also has a good mechanical properties as much as those of explosive bolt.

• Steel and Composite Structures
• /
• v.43 no.1
• /
• pp.19-30
• /
• 2022

The static strength and fatigue crack resistance of the aircraft skin structures depend on the materials used and joint type. Most of the commercial aircraft's skin panel structures are made from aluminium alloy and carbon fibre reinforced epoxy. In this study, the fatigue resistance of four joint configurations (metal/metal, metal/composite, composite/composite and composite/metal) with riveted, adhesive bonded, and hybrid joining techniques are investigated with experiments and finite element analysis. The fatigue tests were tension-tension because of the typical nature of the loads on aircraft skin panels susceptible of experimenting fatigue. Experiment results suggest that the fatigue life of hybrid joints is superior to adhesive bonded joints, and these in turn much better than conventional riveted joints. Thanks to the fact that, for hybrid joints, the adhesive bond provides better load distribution and ensures load-carrying capacity in the event of premature adhesive failure while rivets induce compressive residual stresses in the joint. Results from FE tool ABAQUS analysis for adhesive bonded and hybrid joints agrees with the experiments. From the analysis, the energy release rate for adhesive bonded joints is higher than that of hybrid joints in both opening (mode I) and shear direction (mode II). Most joints show higher energy release rate in mode II. This indicates that the joints experience fatigue crack in the shear direction, which is responsible for crack opening.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.1
• /
• pp.22-27
• /
• 2022

In accordance with the growing trend of decommissioning nuclear facilities, research on the cutting process is actively proceeding worldwide. In general, a thermal cutting process, such as plasma cutting is applied to decommissioning a nuclear reactor pressure vessel (RPV). Plasma cutting has the advantage of removing the radioactive materials and being able to cut thick materials. However, when operating under water, the molten metal remains in the cut plane and re-solidifies. Hence, cutting is not entirely accomplished. For these environmental reasons, it is difficult to cut thick metal. The contact arc metal cutting (CAMC) process can be used to cut thick metal under water. CAMC is a process that cuts metal using a plate-shaped electrode based on a high-current arc plasma heat source. During the cutting process, high-pressure water is sprayed from the electrode to remove the molten metal, known as rinsing. As the CAMC is conducted without using a shielding gas, such as Argon, the electrode is consumed during the process. In this study, CAMC is introduced as a method for dismantling nuclear vessels and the relationship between the metal removal and electrode consumption is investigated according to the cutting conditions.

• Journal of the Microelectronics and Packaging Society
• /
• v.31 no.1
• /
• pp.35-42
• /
• 2024

Recently, with the miniaturization and high integration of semiconductor chips, the bump bridge phenomenon caused by fine pitches is drawing attention as a problem. Accordingly, Cu pillar bump, which can minimize the bump bridge phenomenon, is widely applied in the semiconductor package industry for fine pitch applications. When exposed to a high-temperature environment, the thickness of the intermetallic compound (IMC) formed at the joint interface increases, and at the same time, Kirkendall void is formed and grown inside some IMC/Cu and IMC interfaces. Therefore, it is important to control the excessive growth of IMC and the formation and growth of Kirkendall voids because they weaken the mechanical reliability of the joints. Therefore, in this study, isothermal aging evaluation of Cu pillar bump joints with a CS (Cu+ Sn-1.8Ag Solder) structure was performed and the corresponding results was reported.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.19 no.4
• /
• pp.269-279
• /
• 2003

This study investigated the mechanical properties of precious metal-ceramic alloy joined by the laser-welding and the soldering compared with the parent metal. Twenty-four tensile specimens were cast in precious metal-ceramic alloy and divided into three groups of eight. All specimens in the control group(group 1) were left in the as-cast condition. Group 2 and 3 were the test specimens, which were sectioned at the center. Eight of sectioned specimens were joined by soldering with a propane-oxygen torch, and the remaining specimens were joined by laser-welding. After joining, each joint diameter was measured, and then tested to tensile failure on an Instron machine. Failure loads were recorded, and then fracture stress(ultimate tensile strength), 0.2% yield strength and % elongation calculated. These data for three groups were subjected to a one-way analysis of variance(ANOVA). Neuman-Keuls post hoc test was then used to determine any significant differences between groups. The fracture locations, fracture surfaces were examined by SEM(scanning electron microscope). The results were as follows: 1) The tensile strength and 0.2% yield strength of the soldered group($280.28{\pm}49.35MPa$, $160.24{\pm}26.67MPa$) were significantly less than both the as-cast group($410.99{\pm}13.07MPa$, $217.82{\pm}17.99MPa$) and the laser-welded group($383.56{\pm}59.08MPa$, $217.18{\pm}12.96MPa$). 2) The tensile strength and 0.2% yield strength of the laser-welded group were about each 98%, 99.7% of the as-cast group. There were no statistically significant differences in these two groups(p<0.05). 3) The percentage elongations of the soldered group($3.94{\pm}2.32%$) and the laser-welded group($5.06{\pm}1.08%$) were significantly less than the as-cast group($14.25{\pm}4.05%$) (p<0.05). 4) The fracture of the soldered specimens occurred in the solder material and many porosities were showed at the fracture site. 5) The fracture of the laser-welded specimens occurred also in the welding area, and lack of fusion and a large void was observed at the center of the fracture surface. However, the laser-welded specimens showed a ductile failure mode like the as- cast specimens. The results of this study indicated that the tensile strengths of the laser-welded joints were comparable to those of the as-cast joints and superior to those of the soldered joints.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.19 no.2
• /
• pp.75-86
• /
• 2003

The purpose of this study was to evaluate their mechanical properties after laser-welding or soldering of precious and non-precious dental alloys. For this study, 30 Co-Cr alloy specimens, 15 gold alloy specimens, 15 palladium alloy specimens were casted and seperated on the middle area. 15 sperated Co-Cr specimens and 15 seperated gold alloy specimens were laser welded (GW Group). 15 sperated Co-Cr specimens and 15 sperated gold alloy specimens were soldered by coventional soldering method (GS Group). 15 sperated Co-Cr specimens and 15 seperated palladium alloy specimens were laser welded (PW Group). 15 sperated Co-Cr specimens and 15 sperated palladium alloy specimens were soldered by coventional soldering method (PS Group). Tensile strength, 0.2% yield strength, % elongation were recorded in nine specimens of each group. Bending strength were record in six specimens of each group. These data for four groups were subjected to a two-way analysis of variance(ANOVA). The fracture locations, fractured surfaces were examined by SEM(scanning electron microscope). The results were as following: 1) In the same alloy combination, the tensile strength and 0.2% yield strength and of the laser welded group with same metal combination were significantly less than soldered groups(p<0.05). 2) In the combination of Co-Cr/Palladium, the bending strength of laser welded group were significantly less than that of soldered groups(p<0.05). In the combination of Co-Cr/Gold, the bending strength of laser welded group were significantly higher than that of soldered groups(p<0.05). 3) In the same method of joint, the tensile strength and 0.2% yield strength and bending strength of the Co-Cr/gold were significantly higher than Co-Cr/palladium(p<0.05). 4) There was no significantly statistical difference between each group in the % elongation(p>0.05). 5) The fracture of the laser welded specimens occured in the welding area and a large void was observed at the center of the fracture surface. 6) The fracture of the soldered specimens occured also inthe soldered area and many porpsities were showed at the fracture sites.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.51-51
• /
• 2010

Recently just as in the automobile industry, shipbuilders also try to reduce material consumption and weight in order to keep operating costs as low as possible and improve the speed of production. Naturally industry is ever searching for welding techniques offering higher power, higher productivity and a better quality. Therefore it is important to have a details research based on the various welding process applied to steel and other materials, and to have the ability both to counsel interested companies and to evaluate the feasibility of implementation of this process. Submerged-arc welding (SAW) process is usually used about 20% of shipbuilding. Similar to gas metal arc welding(GMAW), SAW involves formation of an arc between a continuously-fed bare wire electrode and the work-piece. The process uses a flux to generate protective gases and slag, and to add alloying elements to the weld pool and a shielding gas is not required. Prior to welding, a thin layer of flux powder is placed on the work-piece surface. The arc moves along the joint line and as it does so, excess flux is recycled via a hopper. Remaining fused slag layers can be easily removed after welding. As the arc is completely covered by the flux layer, heat loss is extremely low. This produces a thermal efficiency as high as 60% (compared with 25% for manual metal arc). SAW process offers many advantages compared to conventional CO2 welding process. The main advantages of SAW are higher welding speed, facility of workers, less deformation and better than bead shape & strength of welded joint because there is no visible arc light, welding is spatter-free, fully-mechanized or automatic process, high travel speed, and depth of penetration and chemical composition of the deposited weld metal. However it is difficult to application of thin plate according to high heat input. So this paper has been focused on application of the field according to SAW process for thin plate in ship-structures. For this purpose, It has been decided to optimized welding condition by experiments, relationship between welding parameters and bead shapes, mechanical test such as tensile and bending. Also finite element(FE) based numerical comparison of thermal history and welding residual stress in A-grade 3.2 thickness steel of SAW been made in this study. From the result of this study, It makes substantial saving of time and manufacturing cost and raises the quality of product.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.12
• /
• pp.1421-1426
• /
• 2014

To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical $CO_2$ ($S-CO_2$) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the $S-CO_2$ system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to $650^{\circ}C$. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to $550^{\circ}C$. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.12
• /
• pp.1367-1372
• /
• 2014

As the awareness of the environmental crisis has recently increased around the world, numerous studies in the transport industry have been conducted to solve this problem through lightweight car bodies. The hot-stamping process has been presented as solution to achieve a light weight. Hot-stamping is a method that is used to obtain ultra-high strength steel (1,500 MPa or greater) by simultaneously forming and cooling boron steel in a press die after heating it to a temperature of $900^{\circ}C$ or above. This study involved a, fundamental examination of laser parameters to investigate the laser weldability of boron steel. As a result, the following optimum parameters for the shielding gas were found: Q = 20 l/min, ${\alpha}=40^{\circ}$, d = 20mm, and l = 0 mm. The hardness of butt weldment increasesed sharply as a result of martensite formation at the fusion zone.