Earticle

알루미늄합금 6061-T6 판재에 대하여 마찰교반용접과 텅스텐 이너트 가스 용접의 교차 용접부의 미세조직과 기계적 특성에 있어서 용접 순서의 영향을 분석하기 위한 시험편을 성공적으로 제작하였다. FSW-ED 시험편이 다른 조합들보다 가장 좋은 기계적 특성을 나타내었다. 흥미롭게도, TIG-FSW ED 시험편이 FSW-TIG ED 시험편보다 높은 인장강도를 나타내었다. 용접부 경도의 경우, FSW 시편이 TIG-FSW 및 FSW-TIG 시험편보다 높은 값을 나타내었고, TIG-FSW 시험편이 FSW-TIG 시험편보다 높은 값을 나타내었다. FE-SEM을 이용한 인장 파면에 대한 관찰을 통하여, 모든 시험편에서 연성파괴를 나타내는 다양한 크기의 딤플들이 관찰되었다. FSW-TIG 시험편의 파면에서는 용융지(熔融池) 표면 영역에서 기공들이 관찰되는 반면, TIG-FSW 시험편에서는 기공의 형성은 관찰되지 않았다. 경도와 미세조직의 결과를 통해 TIG-FSW 공정이 FSW-TIG 공정보다 높은 인장강도를 확보할 수 있는 공정임을 확인하였다.

The cross-welded joints for 6061-T6 aluminum alloy sheets were successfully manufactured through friction stir welding(FSW) and tungsten inert gas(TIG) welding methods to reveal the effect of welding sequence on microstructure and mechanical properties of the joints. Results revealed that FSW-ED joint shows maximum joint strength compare to other combinations. Interestingly, TIG-FSW joint shows much higher tensile strength than FSW-TIG joint. It is seen that the average hardness in SZ of friction-stir-welded specimen is comparatively higher than that of TIG-FSW and FSW-TIG joints. TIG-FSW specimen also shows higher hardness compare to FSW-TIG. Through FE-SEM observation for tensile fracture surface, various size of dimples clearly observed indicating ductile type of failure mode in all specimens. In case of FSW-TIG process, several voids were observed at the surface region of weld pool. On the contrary, no as such void formation has been observed in TIG-FSW process. The micro hardness and microstructural results clearly justify the higher tensile strength in TIG-FSW process.

The human body has many degrees of freedom (1-3 degrees of freedom) per joint, enabling smooth and stable walking. However, unlike humans, robots require many more joints, and their design necessitates the control of numerous motors. However, controlling more motors leads to lower walking stability. Therefore, this paper studies a real-time control method for stable walking of a bipedal robot. To enable stable walking of a bipedal robot with 12 degrees of freedom, we study a method for generating and supplementing walking patterns between each joint using numerical analysis of the multi-joint robot's kinematics and learning-based AI. This research is to apply the adaptive control of neuron networks for the real-time attitude control of Multi-articulated robot. Multi-articulated robot is expressed with a complicated mathematical model on account of the mechanic, electric non-linearity which each articulation of mechanism has, and includes an unstable factor in time of attitude control. If such a complex expression is included in control operation, it leads to the disadvantage that operation time is lengthened. Thus, if the rapid change of the load or the disturbance is given, it is difficult to fulfill the control of desired performance. In this research we used the response property curve of the robot instead of the activation function of neural network algorithms, so the adaptive control system of neural networks constructed without the information of modeling can perform a real-time control. The proposed adaptive control algorithm generated control signs corresponding to the non-linearity of Multi-articulated robot, which could generate desired motion in real time.

In this study, SM45C-STKM13B hollow shaft of different thickness was joined by friction welding. After friction welding, we treated to specimen of annealing(post-weld heat treatment). The specimens were tested as-welded and post-weld heat treatment(PWHT). The mechanical properties including tensile test and vickers micro-hardness were examined. And then, the mechanical properties were compared for as-welded and PWHT in SM45C to STKM13B. Microstructure of joining part were examined in the weld interface and weld region and heat affected zone and base metal of weld parts.

In order to reduce environmental pollution, it is necessary to increase the recycling rate of waste. For this, the separation of recyclables is of utmost importance. The paper conducted a study to automatically discriminate containers by material for beverage containers among recyclables. We developed an algorithm that automatically recognizes containers by four materials: metal, glass, plastic, and paper by measuring the vibration signal generated when the beverage container collides with the bottom plate of the collection box. The amplitude distribution, time series information, and frequency information of the vibration signal were used to extract the characteristics indicating the characteristic difference of the vibration signal for each material, and a classifier was developed through machine learning using these characteristics.

In this study, the design of parking brake mounting bracket for SUVs (sports utility vehicles) was handled through structural analysis. For safety evaluation, we conducted a shape analysis of parking brake mounting bracket, discovered improvement measures for weak areas, and reflected them in the design. In addition, a strength analysis was performed and the analysis results were reflected in the design. As a result of analysis through various design changes, it was possible to suggest an appropriate parking brake mounting bracket shape. In addition, the effect of changes in the shape of the reinforcement and mounting bracket on the stiffness and strength of the parking brake mounting bracket was investigated.

This study analyzed the methods and characteristics of hydrogen production, storage, transportation, charging, and use of hydrogen presented as an energy supply and demand system for hydrogen. Hydrogen produced by reforming hydrogen, which exists in the form of compounds, is essential to use metal materials exposed to the hydrogen atmosphere in storage and transportation. The mechanism of hydrogen embrittlement and damage cases, which are phenomena in which hydrogen atoms penetrate into the crystal lattice of metal and cause crack failure, were investigated. In addition, it is intended to present a research direction related to the evaluation of physical properties such as thermal conductivity, thermal expansion coefficient, and heat capacity, which are the criteria for selecting materials for hydrogen in a cryogenic environment.

In this study, we intend to develop a control valve with oxidation resistance for hydrogen fluoride that can be applied to the semiconductor production process. Operated Valves currently in use is a form of assembling an air cylinder to the valve body. These valves generally have a cylinder body made of aluminum (Al), so they may corrode depending on the external environment, and the solution leaks along the rod inside the cylinder, causing damage to parts due to corrosion. To solve this problem, the valve plug shape was developed by devising and applying a plug using a valve different from the existing method, and it is possible to block the inflow of hydrogen fluoride into the valve control unit, thereby preventing damage to parts as well as maintaining stable valve operation.

This study is based on the screen printing method with heat resistant thin film as base material and development for expansion is proceeding. Therefore, it is convenient to be applicable to the installation and it will be possible to reduce the cost compared with the existing construction such as heat trace by 50% or more. As a result, it is possible to develop and commercialize the market for Polar ship, shipbuilding and offshore plants as it is possible to secure CNT(Carbon Nano Tube) based surface heating element and heating paste composition technology as a heating element material at a cryogenic temperature. It is expected that the efficiency will be great when this method is applied to other industries.

The purpose of this study was to improve the noise measurement method of noise sources and the corresponding noise reduction measures during each manufacturing process closest to the workers in the large and hige power machine. To this end, the noise generated in the large and high power machine was measured and analyzed, and the frequency characteristics of noise sources and the causes of noise were identified. The noise map was used to predict the noise reduction effect. Moreover, it is expected that this will ultimately contribute to the reduction of human risks caused by the noise of the large and high power machine.