• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10b
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• pp.138-142
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• 2003

In this study, to show well favorable characteristics of warm forged material, we compared and analyzed microstructure and mechanical properties of general hot-forged material which finished heat treatment with warm-forged material which was produced by control cooling condition. Along with this, we suggested better direction of control cooling condition to be able to remove heat treatment process while satisfying mechanical properties.

• Transactions of Materials Processing
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• v.3 no.3
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• pp.282-290
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• 1994

The outer race of BJ type C.V.Joint has a complicated shape and ball grooves. It is produced by cold or warm precision forging. Especially, the precision level of the ball grooves determines the quality of the part. The objective of the present study is to develop process conditions of the cold forging using the plasticine. Because the cold forging consists of forward extrusion, upsetting, backward extrusion and cold sizing, the study was focused on finding the best perform for each process. The data obtained from the study will be used in the design of the cold forging process for the outer race.

• The Journal of Korea Robotics Society
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• v.9 no.4
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• pp.264-271
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• 2014

In this study, we have developed the humanoid joint modules which provide a variety of service while living with people in the future home life. The most important requirement is ensuring the safety for humans of the robot system for collaboration with people and providing physical service in dynamic changing environment. Therefore we should construct the mechanism and control system that each joint of the robot should response sensitively and rapidly to fulfill that. In this study, we have analyzed the characteristic of the joint which based on the target constituting the humanoid motion, developed the optimal actuator system which can be controlled based on each joint characteristic, and developed the control system which can control an multi-joint system at a high speed. In particular, in the design of the joint, we have defined back-drivability at the safety perspective and developed an actuator unit to maximize. Therefore we establish a foundation element technology for future commercialization of intelligent service robots.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.120-127
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• 2008

The constant velocity joint(CVJ) used for transmitting torque to the front wheels is an important part in automotive drive system. There are several types of constant velocity joints. Typically, they are classified by fixed and plunging constant velocity joints. The axial force generated in plunging constant velocity joints influences significantly the noise, vibration and harshness. For heaps of time, many constant velocity joint markers have been studying and developing a valid method to reduce the axial force and extensive tests have been carried out on rigs. This paper presents the analysis method to predict the axial force of a double offset constant velocity joint(DOJ), a kind of plunging constant velocity joint, and the influence of ball-cage dimension tolerance on the axial force.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1160-1165
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• 2004

The purpose of this study was to calculate three dimensional angular displacements, moments and joint reaction forces of the ankle joint during the waist pulling, and to assess the ankle joint reaction forces according to different perturbation modes and different levels of perturbation magnitude. Ankle joint model was assumed 3-D ball and socket joint which is capable of three rotational movements. We used 6 cameras, force plate and waist pulling system. Two different waist pulling systems were adopted for forward sway with three magnitudes each. From motion data and ground reaction forces, we could calculate 3-D angular displacements, moments and joint reaction forces during the recovery of postural balance control. From the experiment using falling mass perturbation, joint moments were larger than those from the experiment using air cylinder pulling system with milder perturbation. However, JRF were similar nevertheless the difference in joint moment. From this finding, we could conjecture that the human body employs different strategies to protect joints by decreasing joint reaction forces, like using the joint movement of flexion or extension or compensating joint reaction force with surrounding soft tissues. Therefore, biomechanical analysis of human ankle joint presented in this study is considered useful for understanding balance control and ankle injury mechanism.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.81-88
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• 2006

Present study is to know the relation with throwing speed according to the uniform torque by the shoulder joint, over 20 persons of professional baseball, and were measured the uniform torque by the shoulder joint accordance with throwing speed between (A-low speed) and (B-high speed) of each group. In the present study, three components were measured, and analyzed with having an approximated output value appearing by changing angular velocity, and in $30^{\circ}/sec$, the maximum strength of muscles was measured, and in$210^{\circ}/sec$, the points of endurance strength of muscles were measured and analyzed, and the following result could be obtained. 1. In muscles strength (peak torque)of inner rotation, and outer rotation for respect to each speed of shoulder joint, though there did not appear outstanding difference between A group and B group in the $30^{\circ}/sec$, it showed that group B has priority in a little. Also in outer rotation by shoulder joint, though there appeared the same difference between A group and B group, B group is tended to be prior to A group in a little. 2 In the view of muscles strength (peak torque)of inner rotation, and outer rotation for respect to each speed of shoulder joint, though there did not appear outstanding difference between A group and B group in the $30^{\circ}/sec$, it showed that group B has priority in a little. Also in outer rotation by shoulder joint, though there appeared the same difference between A group and B group, B group is tended to be prior to A group in a little. 3. In the view of muscles strength(peak torque)of inner rotation, and outer rotation for respect to each speed of shoulder joint, though there did not appear outstanding difference between A group and B group in the $30^{\circ}/sec$, it showed that B group has priority in a little. Also in outer rotation by shoulder joint, though there appeared the same difference between A group and B group, B group is tended to be prior to A group in a little. 4. In the view of peak torque for respect to the weight accordance with each velocity of shoulder joint, there did not appear outstanding difference between A group and B group. In outer rotation by the shoulder joint, there was not appeared clear difference between A group and B group. 5. In the concern of the peak torque for respect to the weight accordance with each velocity of shoulder joint, there did not appear outstanding difference between A group and B group in $30^{\circ}/sec$. In outer rotation by the shoulder joint, there was not appeared clear difference between A group and B group. 6. In the concern of the peak torque for respect to the weight accordance with each velocity of shoulder joint, there did not appear outstanding difference between A group and B group in $210^{\circ}/sec$. In outer rotation by the shoulder joint, there was not appeared clear difference between A group and B group. As conclusion, there did not appear a correlation of uniform torque by shoulder joint versus the speed throwing by a pitcher of professional base ball.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.209-214
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• 2003

We developed a new type of human-sized BWR (biped walking robot), named KUBIR1 which is driven by the closed-chain type of actuator. A new type of the closed-chain actuator for the robot is developed, which is composed of the four-bar-link mechanism driven by the ball screw which has high strength and high gear ratio. Each leg of the robot is composed of 6 D.O.F joints. For front walking, three pitch joints and one roll joint at the ankle. In addition to this, one yaw joint for direction change, and another roll joint for balancing the body are attached. Also, the robot has two D.O.F joints of each hand and three D.O.F. for eye motion. There are three actuating motors for stereo cameras for eyes. In all, a 18 degree-of-freedom robot was developed. KUBIR1 was designed to walk autonomously by adapting small 90W DC motors as the robot actuators and batteries and controllers are on-boarded. The whole weight for Kubir1 is over 90Kg, and height is 167Cm. In the paper, the performance test of KUBIR1 will be shown.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.221-230
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• 2014

This study deals with a series of experimental investigations on multi-stage cold forging of an outer race used for a constant velocity (CV) joint with six inner ball grooves. The multi-stage cold forging, which consists of forward extrusion, upsetting, backward extrusion, and combined sizing-necking including ironing, was used to produce a prototype of the outer race. The cold forging tools such as forging punches and dies required in this multi-stage cold forging were also designed and fabricated. For the combined sizing-necking, especially, the longitudinally six-segmentallized punches were developed to easily eject from the necked inner groove of the outer race with consideration of the operating mechanism. Spheroidized SCr420H billet was used in the experimental study. To verify the suitability of the proposed process, the obtained parts were obtained from each forging operation, and the geometries were compared with the target dimensions. It was confirmed that the outer race with six inner ball grooves was well forged by adopting the proposed multi-stage cold forging, and the dimensional accuracy of the forged outer race matched well with the requirements.

• Transactions of Materials Processing
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• v.23 no.4
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• pp.211-220
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• 2014

The outer race of a constant velocity (CV) joint having six inner ball grooves has traditionally been manufactured by multi-stage warm forging, which includes forward extrusion, upsetting, backward extrusions, necking, ironing and sizing, and machining. In the current study, a multi-stage cold forging process is examined and an assessment for replacing and modifying the conventional multi-stage warm forging is made. The proposed procedure is simplified to the backward extrusion of the conventional process, and the sizing and necking are combined into a single sizing-necking step. Thus, the forging surface of the six ball grooves can be obtained without additional machining. To verify the suitability of the proposed process, a 3-dimensional numerical simulation on each operation was performed. The forging loads were also predicted. In addition, a structural integrity evaluation for the tools was carried out. Based on the results, it is shown that the dimensional requirements of the outer race can be well met.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.919-926
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• 2002

In this study, the numerical prediction of the thermal fatigue lie? of a $\mu$BGA (Micro Ball Grid Array) solder joint was focused. Numerical method was performed using the three-dimensional finite element analysis for various solder alloys such as Sn-37%Pb, Sn-3.5%Ag, Sn-3.5%Ag-0.7%Cu and Sn-3.5%Ag-3%In-0.5%Bi during a given thermal cycling. Strain values obtained by the result of mechanical fatigue tests for solder alloys, were used to predict the solder joint fatigue life using the Coffin-Manson equation. The numerical results showed that Sn-3.5%Ag with the 50-degree ball shape geometry had the longest thermal fatigue life in low cycle fatigue. A practical correlation for the prediction of the thermal fatigue life was also suggested by using the dimensionless variable γ. Additionally Sn-3.5Ag-0.75Cu and Sn-2.0Ag-0.5Cu-2.0Bi were applied to 6$\times$8$\mu$BGA obtained from the 63Sn-37Pb Solder. This 6$\times$8$\mu$BGA were tested at different aging conditions at 130$\^{C}$, 150$\^{C}$, 170$\^{C}$ for 300, 600 and 900 hours. Thickness of the intermetallic compound layer was measured thor each condition and the activation energy thor their growth was computed. The fracture surfaces were analyzed using SEM (Scanning Electron Microscope) with EDS ( Energy Dispersive Spectroscopy).