• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2009년 추계학술발표대회
• /
• pp.79-79
• /
• 2009

Ultrasonic fine welding, cutting, cleaning, inspection and measurement is widely used in various fields over 20kHz. However, for High Frequency of 60kHz or more study areas is still insufficient, and the result is lacking. Therefore, this study used ultrasonic horn to the Bonding of Dissimilar Materials for effective design. Finite element analysis (FEA) is using the equations of motion to establish the model. The optimal design for the basic interpretation of vibration characteristics of the ultrasonic measures horn will examine the design.

• 한국음향학회지
• /
• 제24권7호
• /
• pp.379-386
• /
• 2005

최근까지 개발되었던 청각 보조기 중에서 공기 전도형 보청기의 하울링 (howling) 현상과 수술 후 이소골 등 기존 음향계의 재생이 불가능한 인공 와우 (cochlear implant system)의 단점을 해결하고, 동시에 청음 명료도가 높은 음성 신호를 전달하기 위한 수단으로 연구된 것이 인공중이 (implantable middle ear hearing device) 이다. 본 연구에서는 인공중이의 음성 신호 재현을 위한 진동 장치인 차동전자 트랜스듀서 (differential electromagnetic transducer, DET)에 대한 수학적 모형화와 계의 진동을 기술하는 운동방정식을 유도하고 그 해를 구하였다. 제한된 크기와 인가 전류 $1\;mA_{rms}$ 정현파에서 최대 구동력을 얻기 위해서 전자기력에 대한 유한요소해석을 수행하였고, 결과에 의해서 자석과 코일에 대한 최적 크기를 결정하였다. 사람의 중이 내 등자뼈 (stapes)의 진동 특성과 유사한 진동을 갖는 DET를 설계하기 위해서, 진동막의 강성계수를 변화하면서 진동해석을 시뮬레이션 하였다. 설계된 DET는 마이크로 머시닝 기술에 의해서 제작하였고, 그 진동 특성을 측정 하였다. 최종적으로 측정된 진동 특성에 대한 분석을 통하여 인공중이를 위한 진동 장치로서의 적용 가능함을 확인하였다.

• Computers and Concrete
• /
• 제27권1호
• /
• pp.41-54
• /
• 2021

This paper introduced three new strengthening systems for isolated footings: BFRP wrapping system, CFRP wrapping system, and steel jacketing system. The proposed systems are more practical than the current traditional methods, which involves installing many dowel bars and splicing reinforcing steels to join new and old concrete segments. In the proposed three new systems, BFRP wraps, CFRP wraps, or steel jackets are installed on the exterior surface of the enlarged footing, with construction adhesive or a few steel dowels being applied to the contact surfaces. To investigate the effectiveness of three systems, forty-four models were constructed in ABAQUS, with different parameters being considered. All footings investigated failed in punching shear, including original and retrofitted footings. According to FEA results and parametric studies, the three strengthening systems were capable of improving the punching shear resistance of footings. By introducing a new factor η, the punching shear equation in Eurocode 2 was modified to predict the punching shear resistances of the strengthened footings. A linear formula was developed to present the relationship between the new factor η and the investigated parameters.

• Journal of Magnetics
• /
• 제18권2호
• /
• pp.117-124
• /
• 2013

Single-phase, brushless DC (BLDC) motors have unequal air-gaps to eliminate the dead-point where the developed torque is zero. Unfortunately, these unequal air-gaps can deteriorate the motor characteristics in the cogging torque. This paper proposes a novel design for a single-phase BLDC motor with an asymmetric notch to solve this problem. In the design method, the asymmetric notches were placed on the stator pole face, which affects the change in permanent magnet shape or the residual flux density of the permanent magnet. Parametric analysis was performed to determine the optimal size and position of the asymmetric notch to reduce the cogging torque. Finite element analysis (FEA) was used to calculate the cogging torque. A more than 28% lower cogging torque compared to the initial model with no notch was achieved.

• Journal of Magnetics
• /
• 제22권2호
• /
• pp.266-274
• /
• 2017

In this paper, torques of two motors are compared by Finite Element Analysis (FEA). One has a symmetric rotor structure and the other has an asymmetric rotor structure. The comparison shows that the asymmetric rotor structured motor has reduced torque ripple compared to the symmetric. The torque of the compared motor models was analyzed by separating into magnetic torque and reluctance torque. Through the analysis of torque component separated, it is shown that the magnetic torque and the reluctance torque compensate each other in the motor with the asymmetric structure rotor. Here "compensate" means decrementing the effect of one or more harmonics. It is shown how this compensation appears between the magnetic torque and the reluctance torque by looking into back electro motive force (emf) and the relative permeability distribution of rotor core.

• 한국기계가공학회지
• /
• 제14권6호
• /
• pp.57-62
• /
• 2015

A large variety of pipe flanges are required in the marine and construction industry. Pipe flanges are usually welded or screwed to the pipe end and are connected with bolts. This approach is very simple and has been widely used for a long time; however, it results in high development costs and low productivity, and the products made through this approach usually have safety problems in the welding area. In this research, a new approach for forming pipe flanges based on cold forging and the floating die concept is presented. This innovative approach increases the effectiveness of the material usage and saves time and costs compared with the conventional welding method. To ensure the dimensional accuracy of the final product, finite element analysis (FEA) was carried out to simulate the process of cold forging, and orthogonal experiment methods were used to investigate the influence of four manufacturing factors (stroke of distance, pin die angle, forming of pipe diameter, and speed of the die) and predict the best combination of them. The manufacturing factors were obtained through numerical and experimental studies, which show that the approach is very useful and effective for the forming of pipe flanges and could be widely used in the future.

• 전기학회논문지
• /
• 제58권10호
• /
• pp.1930-1935
• /
• 2009

This paper deals with the torque ripple reduction of permanent magnet synchronous motor using harmonic current injection. Torque ripple of electric motor reduces system stability and performances, therefore efforts to reduce torque ripple are exerted in the design process. Torque ripple can be reduced by appropriate pole/slot combination, skew of rotor or stator, design of magnetic circuit, etc. In addition, torque ripple can be also reduced by input voltage and current, and many researches have been conducted to reduce torque ripple for six-step drive. Torque ripple reduction for current vector controlled permanent magnet synchronous motor also have been conducted and verified by investigating back emf wave form. Torque ripple reduction in this paper started from getting torque profile according to input current and electrical angle calculated by FEA, then instantaneous currents at each electrical angles for constant torque are calculated and applied to experiments. Therefore, 0% of torque ripple can be obtained theoretically with harmonic current injection. In order to maximize the effect of torque ripple reduction, a BLDC motor having high harmonic component of back emf is chosen. With sinusoidal current drive, over 100% of torque ripple is obtained initially, then 0.5 % of torque ripple is obtained by FEA using harmonic current injection. The effect is verified by experiment and the presented method can be effectively applicable to Electric Power Steering(EPS).

• 한국기계가공학회지
• /
• 제18권2호
• /
• pp.102-107
• /
• 2019

The vehicle market has developed environment-friendly vehicles to comply with fuel economy regulations and exhaust regulations that have become stricter and stricter over time. Many studies have been conducted to improve the travel performance and fuel economy of environment-friendly vehicles, and vehicle manufacturers have been studying how to manufacture light-weight vehicles in order to improve the fuel economy of both existing vehicles and the newer environment-friendly vehicles. Exemplary light-weight vehicle technologies optimizes the design of the vehicle body structure, which is a vehicle weight-reducing method that modifies component shapes or layouts to optimize the structure of the vehicle. In addition, the new process technology uses new light-weight and very strong materials, and not typical materials, to manufacture light-weight vehicles. This study aims at the optimal design of vehicle body structures using multi-materials for the Fender-Apron, which is an important frame member for the external front side of a vehicle body, by conducting FEA (Finite Element Analysis) and multi-material bonding.

• 한국지반공학회논문집
• /
• 제35권3호
• /
• pp.17-24
• /
• 2019

본 연구는 지반 위 얕은 기초의 지지력에 대한 특성을 파악하기 위하여 지반 조건, 기초 크기, 기초 형상 등의 다양한 조건에 대하여 3차원 유한요소해석을 수행하여 기존의 지지력 이론과 비교 검토하였다. 유한요소해석 결과 극한지지력은 기초크기에 따라 지지력이 거듭제곱이나 로그 식으로 차츰 수렴하였고, 지반강도가 증가할수록 지지력 증가가 커지지 않는 직선적인 변화를 보였다. 기존 지지력 이론과 비교한 결과 순수모래는 지지력 비($q_{FEA}/q_{theory}$)가 Terzaghi식의 결과와 가장 유사하였다. 순수점토는 약 0.4~0.6, 일반토사는 0.3~1.3 정도로 산정되었고, 지반강도가 증가할수록 지지력 비가 감소하면서 1.0 이하로 나타났다. 기초 크기에 따른 지지력을 1.0m 기초의 지지력으로 정규화시킨 지지력 비($q_u/q_{u(1.0)}$)는 순수모래에서 ${\phi}=25^{\circ}$, $30^{\circ}$, $35^{\circ}$일 때 이론식의 35%, 15%, 5% 정도로 산정되었고, 순수점토는 크기 효과가 없었으며, 일반토사는 지반강도가 작은 경우에 순수모래의 이론식에 대해 약 10% 이하로 나타났다. 지반강도 증가에 따른 지지력 비는 내부마찰각의 영향이 큰 것으로 나타났다. 기초형상별 지지력 비에 따른 형상계수는 기초형상에 따라 다르게 나타났고, 원형기초는 1.5, 정사각형 기초는 1.3, 직사각형 기초와 연속 기초는 1.1~1.0의 형상계수를 나타내었다.

• International Journal of Korean Welding Society
• /
• 제5권1호
• /
• pp.29-34
• /
• 2005

Finite element analysis (FEA) and experimental studies on an elastic bending method have been performed in order to control the angular distortion at the fillet weldment for curved panel. Process parameters for the elastic bending method such as clamping span and release time were analyzed with reference to welding condition and geometric effect of the curved panel, which can minimize or prevent the angular distortion by producing a proper skin stress to the fillet weldment. The amounts of the angular distortion decrease almost in a linear manner with an increase in the skin stress. The skin stress required for non-angular distortion at the fillet weldment is strongly dependent on the plate thickness, not the heat intensity applied. The clamping span for obtaining uniform skin stress was defined as functions of the plate thickness and length of the free edge. Clamp should be removed after the fillet weldment is cooled down to room temperature for non-angular distortion. Effectiveness of the elastic bending method established was verified by its application to an actual curved panel.