• Journal of Ocean Engineering and Technology
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• v.21 no.5
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• pp.33-38
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• 2007

The welding methods have been applied in the most structural products from multi-field of automobile, ship construction and construction, and so on. The structure steel must have enough strength of structure. In this study, SS400 steel and STS304 steel were used to estimate the corrosion characteristics of the weld thermal cycle simulated HAZ. To evaluate the corrosion characteristics, also, the materials with two conditions were used in 3.5% NaCl. The one is to the drawing with diameter of ${\Phi}10$ and the other is to the residual stress removal treatment. The electrochemical polarization test and immersion test were carried out. From test results, corrosion potential, corrosion current density, weight loss ratio and corrosion rate were measured. In the kinds of SS400 steels, corrosion potential of weld thermal cycle simulated specimens after the heat treatment showed somewhat the direction of noble potential. And in the base metal to be drawing weight loss ratio and corrosion rate occurred higher than the other kinds. In the kinds of STS304 steels, the result of base metal to be drawing was similar to results of SS400 steels, too. Two kinds of $750^{\circ}C$ and $1300^{\circ}C$ of weld thermal cycle simulation after the heat treatment were rather higher than the other kinds in weight loss ratio and corrosion rate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.6
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• pp.565-571
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• 2016

This paper investigates macro- and microscopic fractography performed on fracture specimens from low cycle fatigue (LCF) testings through an Alloy 617 base metal and weldments. The weldment specimens were taken from gas tungsten arc welding (GTAW) pad of Alloy 617. The aim of the present study is to investigate the macro- and microscopic aspects of the low cycle fatigue fracture mode and mechanism of Alloy 617 base metal and GTAWed weldment specimens. Fully axial total strain controlled fatigue tests were conducted at room temperature with total strain ranges of 0.6, 0.9, 1.2 and 1.5%. Macroscopic fracture surfaces of Alloy 617 base metal specimens showed a flat type normal to the fatigue loading direction, whereas the GTAWed weldment specimens were of a shear/star type. The fracture surfaces of both the base metal and weldment specimens revealed obvious fatigue striations at the crack propagation regime. In addition, the fatigue crack mechanism of the base metal showed a transgranular normal to fatigue loading direction; however, the GTAWed weldment specimens showed a transgranular at approximately $45^{\circ}$ to the fatigue loading direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.569-575
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• 1984

The characteristics of the stress corrosion cracking of SUS 304 stainless steel weldments were studied with the speciments of the constant displacement type under the environment of 42% MgC $l_{2}$ boiled solution (143.+.-.2.deg.C). The susceptibility of initiation and propagation of the stress corrosion crack was quantitatively inspected in the weld metal, heat affected zone and heat affected zone with including the reinforcement shape, respectively. Also, those susceptibility were discussed in connection with the change of mechanical and microstructural characteristics caused by heating cycle of welding. Main results obtained are as follows: (1)Stress corrosion cracking is easiest to initiate and propagate in the heat affected zone of weldment. (2)The susceptibility of stress corrosion cracking of the weldment is largely improved by eliminating the reinforcement part of the weld bead. (3)The dominant factor of the cracking susceptibility of the heat affected zone appeared to be the phenomenon of softening and sensitizing caused by welding heat cycle. (4)Under the low loading conditions, the behavior of stress corrosion cracking of the SUS 304 steel weldment is largely influenced by the pitting phenomenon in the front region of the main crack.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.109-115
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• 2019

In arc-welding applying to the present automobile part manufacturing process, a wrist-hollow type arc welding robot can shorten the welding cycle time, because feedability of a welding wire is not affected by a robot posture and thus facilitates high-quality arc welding, based on stable feeding with no entanglement. In this paper, we will propose the optimization of wrist design for a wrist-hollow type 6-Axis articulated robot. Specifically, we will perform the investigation on the optimized design of inner diameter of hollow arms (Axis 4 and Axis 6) and width of the upper arm by using the simulation of robot motion characteristics, using a Genetic Algorithm (i.e., GA). Our simulations are based on $SolidWorks^{(R)}$ for robot modeling, $MATLAB^{(R)}$ for GA optimization, and $RecurDyn^{(R)}$ for analyzing dynamic characteristics of a robot. Especially $RecurDyn^{(R)}$ is incorporated in the GA module of $MATLAB^{(R)}$ for the optimization process. The results of the simulations will be verified by using $RecurDyn^{(R)}$ to show that the driving torque of each axis of the writs-hollow 6-axis robot with the optimized wrist design should be smaller than the rated output torque of each joint servomotor. Our paper will be a guide for improving the wrist-hollow design by optimizing the wrist shape at a detail design stage when the driving torque of each joint for the wrist-hollow 6-axis robot (to being developed) is not matched with the servomotor specifications.

• Journal of Welding and Joining
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• v.25 no.2
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• pp.62-69
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• 2007

A kinetic model fur the particle coarsening behavior was developed. The proposed model considered the critical particle size which can be derived from Gibbs-Thomson equation unlike the conventional approach. In this study, the proposed particle coarsening model was applied to study the coarsening behavior of titanium nitride (TiN particle) in microalloyed steel weld HAZ. Particle size distributions and mean particle size by the proposed model were in agreement with the experimental results. Meanwhile, using additivity rule, the isothermal model was extended to predict particle coarsening behavior during continuous thermal cycle.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1493_1494
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• 2009

초고압 전력 케이블용 도체 접속을 위한 접속방법으로 압축형(compressing type), 용접형(welding type), 압축-용접형(CW type; compressing-welding type)의 슬리브는 물론 동과 알루미늄의 이종(nonidentical materials) 접속을 위한 슬리브를 개발 하였으며, 전기적, 기계적으로 검증된 제품 개발을 위하여, 슬리브의 구조 변경과 접속 방법의 차이뿐 아니라 접속 전후의 응력 평가를 위해 슬리브 시편의 인장시험(tensile strength) 결과에 따른 슬리브 제작 및 시험을 진행하였다. 신뢰성 있는 제품 개발과 데이터를 얻기 위하여 초고압용 지중 고압 케이블을 시험 시료로 적용하여 시험 선로(test loop)를 구성하였으며, 이를 통하여 구조와 재질에 따른 접속 방법, 이상 온도 상승 또는 국부적인 고온 부위 발생 여부 등의 전기 시험 및 열싸이클 전압 시험(heating cycle voltage test) 조건을 설정하여 시험 전후의 열신축 등 전기적, 기계적 특성을 평가하였다. 접속 슬리브의 구조 및 재질에 따른 위치별 발열 양상을 체크하였으며, X-ray 장비를 이용하여 슬리브 내부의 압축 및 충진 정도를 점검함으로써 기존 접속 슬리브 보완은 물론 개발된 접속 슬리브의 설계 기준 및 안전율을 설정 할 수 있었다.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.92-98
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• 2003

This paper describes the numerical prediction of the thermal fatigue life of a $\mu$BGA(Micro Ball Grid Array) solder joint. Finite element analysis(FEA) was employed to simulate thermal cycling loading for solder joint reliability. Strain values, along with the result of mechanical fatigue tests for solder alloys were then used to predict the solder joint fatigue life using the Coffin-Manson equation. The results show that Sn-3.5mass%Ag solder had the longest thermal fatigue life in low cycle fatigue. Also a practical correlation for the prediction of the thermal fatigue life was suggested by using the dimensionless variable ${\gamma}$, which was possible to use several lead free solder alloys for prediction of thermal fatigue life. Furthermore, when the contact angle of the ball and chip has 50 degrees, solder joint has longest fatigue life.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.117-126
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• 1994

APAL (Aramid Patched ALuminum alloy) was manufactured, which was a material that was consisting of a A12024-T3 aluminum alloy plate bonded to single-side of it with aramid/epoxy laminates. The aramid/epoxy laminates were bonded to it in condition of 1, 2 ply and fiber orientation of .+-.45, 0.deg./90.deg. Fatigue crack propagation tests were performed at stress ratio R-0.2, 0.5 with Al 2024-T3, APAL 45-1P, APAL 0/90-1P, APAL 45-2P, APAL 0/90-2P specimens to examine behavior of retardation in fatigue crack propagation. All the APAL specimens showed superior fatigue crack resistance. Number of cycle spended for crack to propagate from $a_{M}$=37 to $a_{M}$=65 mm in case of APAL 0/90-2P specimen was half that of Al 2024-T3 specimen. Fatigue crack propagation rate of APAL 0/90 specimens were retarded more compared to APAL 45 specimens and the amounts of retardation at R=0.5 were larger than that at R=0.2. It was found that the retardation in fatigue crack propagation was caused by intact fibers in the wake of crack.ack.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.74-80
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• 2014

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from their devices and system. Especially, reliability issue of lead-free solder joint is increasing in car electronics due to ELV (End-of-Life Vehicle) banning from 2016. We have prepared engine control unit (ECU) modules soldered with Sn-40Pb and Sn-3.0Ag-0.5Cu (SAC305) solders, respectively. Degradation characteristics of solder joint strength were compared with various conditions of automobile environment such as cabin and engine room. Thermal cycle test (TC, $-40^{\circ}C$ ~ ($85^{\circ}C$ and $125^{\circ}C$), 1500 cycles) were conducted with automotive company standard. To compare shear strength degradation rate with eutectic and Pb-free solder alloy, we measured shear strength of chip components and its size from cabin and engine ECU modules. Based on the TC test results, finally, we have known the difference of degradation level with solder alloys and use environmental conditions. Solder joints degradation rate of engine room ECU is superior to cabin ECU due to large CTE (coefficient of thermal expansion) mismatch in field condition. Degradation rate of engine room ECU is 50~60% larger than cabin room electronics.

• Journal of Advanced Marine Engineering and Technology
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• v.9 no.4
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• pp.328-338
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• 1985

When the low temperature service steels are used as materials for welded structure, some problems-brittleness and weld cracking, etc.-occur in welded part due to the change of mechanical and metallurgical characteristics resulted from the thermal cycle during the welding procedure. In this study, the experiments were conducted to investigate the change of mechanical and metallurgical characteristics of the welded part for the low temperature and high pressure service steels. Moreover, the Static and Dynamic Implant Test Method was introduced to this study in order to find out the mechnism of weld cracking. In addition, the fracture toughnesses of welded bond were inspected under the various low temperature environments. Main results obtained are as follows; 1) The effect of the hydrogen on the fatigue characteristics of the weld bond can be estimated by the new self-contrived Dynamic Implant Test equipment. 2) The fine micro-structure and low hardness in the heat affected zone can be obtained by the small heat input multi-pass welding. 3) The susceptibility of the delayed cracking is largely affected by the condition of used electrode. 4) The transition temperature of the fracture surface in weld bond appears to be higher 20 .deg. C than that in base metal.