노즐-플래퍼 방식 전기유압 서보밸브의 히스테리시스 특성 향상에 관한 연구

박진현 부경대학교 2014 국내석사

A Study on the Hysteresis Characteristics for on an Electro-hydraulic Servo Valve Equipped with Nozzle and Flapper Components Park, Jin-Hyun Department of Mechanical Engineering, Graduate School of Pukyong National University ABSTRACT Recently, a hydraulic system for controlling of position, velocity and force is using in a variety of industry because of higher power and accuracy performance. An electro-hydraulic servo valve is one of structure elements for a servo control system. The knowledge of working mechanism of the servo valve, in the industry, is not clear yet. Thus, studies in detail for the electro-hydraulic servo valve are more needed. This study focuses on evaluation of a hysteresis characteristic of the electro-hydraulic servo valve equipped with a nozzle and flapper components. In simulation of the nozzle and flapper type servo valve, a hysteresis curve for a rated flow and supplied current were obtained by MATLAB Simulink software. A prototype of the electro-hydraulic servo valve was fabricated to evaluate the hysteresis according to materials applied and geometric dimension of a flexure tube. The SUS630 material for the flexure tube showed less hysteresis than the SUS304. A higher stiffness was obtained at a large slenderness of the flexure tube.

CAE를 이용한 소형박육제품의 변형 패턴에 관한 연구

배현선 부경대학교 2018 국내석사

An FPC(Flexible Printed Circuit) connector is a part that connects a flexible circuit board and transmits a signal. A housing product made by injection mold is main part of FPC connector and it’s warpage is generated by the difference of shrinkage ratio at each part of the molded product. This warpage causes poor contact of assembling the FPC connector and the flexible circuit board and poor soldering of SMT(Surface Mounter Technology) in PCB(Printed Circuit Board) board. Modification of a mold needs a lot of cost and time to reduce warpage. Therefore, it is necessary to make effort to optimize the product design and mold design by predicting the problems expected in the injection molding process through the molding analysis. In this study, analysis results of warpage according to shape of FPC were confirmed and difference of results between CAE and actual products was compared. As a result, the minimum warpage of 0.041mm was occurred in the analysis and the mold sample had 0.036 ~ 0.048mm. So, it indicates that warpage results of analysis and products are similar. Thus, the warpage can be effectively reduced through the analysis of injection molding process in advance.

알루미늄 소재의 전자연마 공정에서 가공 특성 평가 및 최적화에 관한 연구

손출배 부경대학교 대학원 2020 국내박사

The final status of workpiece surface decides product quality, manufacturing cost and improvement of functionality. Thus, numerous traditional finishing methods such as super-finishing, honing, grinding are widely employed for fine surface. However, these conventional techniques with rigid tools have limitation of complex shape of surface and productive efficiency. Since demands for better surface characteristics for free-form shape with less time and cost, it is necessary to develop advanced finishing ones which are required to achieve better surface integrity. Among the novel processes, magnetic finishing processes in the presence of the magnetic field have been especially attracted in the last decades. This is because it could acquire high geometric precision by adjusting magnetic force acting on free-form surface with the flexible tool. Although these processes have a number of benefits, it has also limitation of time consuming and process efficiency for non-ferrous materials due to lack of magnetic permeability. Some of research has attempted to increase magnetic intensity by applying permanent magnets for non-ferrous materials but distribution of magnetic flux density directly related to magnetic force is not symmetrical unlike ferrous materials. Consequently, this phenomenon leads to getting non-uniform surface and removing edge of the workpiece excessively. In order to overcome drawbacks of magnetic abrasive finishing, this study suggests a electro-magnetic finishing(EMF) process which combined magnetic energy derived form rotating disc with permanent magnets and kinetic energy acting on magnetic pins as polishing medium in the alternating magnetic field. To optimize magnitude and distribution of magnetic flux density in EMF process, finite element analysis is carried out by using Ansys workbench. In addition, experiments is carried out applying a Taguchi’s L9(34) orthogonal method based on computational simulation to verify effects of EMF process on improving surface roughness and burr removal rate. According to the results, grey relational analysis(GRA) is conducted to find out an optimal condition satisfying both requirements simultaneously. Moreover, it is proved that suggested EMF method in this study is valuable for manufacturing industries based on experimental results applied to the holder of solenoid valve.

열경화성 복합재를 이용한 헬기용 블레이드 성형에 관한 연구

이희철 부경대학교 대학원 2014 국내석사

The purpose of this study was to identify the characteristics of thermosetting composite materials and the optimum conditions of the helicopter blades molding process. The characteristics of thermosetting composite were investigated through the simulation and experiment. As a results, The carbon-epoxy prepreg TSN125 used for helicopter blades had optimal molding temperature, 126℃. And this temperature was approaching required specifications that showed proper temperature at a fast curing point and efficiency. The structural stability of the blade mold of SS400 material was confirmed by structure analysis. In the results of structure analysis, the deformation of mold was occurred as 0.03~0.2㎛. But the mold without structure deforms to over 60㎛. The maximum compressive stress of mold with structure was distributed as 0.402~1.18MPa. The tensile strength, as 0.191~0.367MPa, was higher than conventional material properties. The dimension of mold and blade was evaluated by the 3-axis coordinate measurement machine of Hexagon lambda 706030. The dimensional errors was distributed within the range of tolerance. The mold measurement results to Y-axis length direction from the reference point has maximum (+) error 0.05mm at 1619.70mm and maximum (-) error 0.057 mm at 6619.70mm. The blade measurement results has maximum (-) error 0.1425mm at 1619.70mm and minimum (-) error 0.009mm at 6619.7mm point. At maximum (+) error part of mold, the blade showed the maximum (-) error. The change of thickness of blade was caused by shrinkage and pull of resin. Thus, the amount of Epoxy filled in cavity between mold and thermosetting composite materials affected the dimensional accuracy of blade.

자기연마가공을 이용한 마이크로 복합패턴의 형상정밀도 향상

진동현 부경대학교 2016 국내석사

본 논문에서는 turning machine을 이용하여 미세 복합패턴을 제작하고, 보다 효율적인 디버링 방법으로 자기연마 디버링을 제시하였다. 자기연마 디버링을 활용하여 미세 복합패턴의 형상정밀도를 향상시키고자 하였다. 또한, 반응표면기법을 이용하여 패턴의 높이에 대한 예측식을 도출하고, 공정변수의 최적화를 하고자한다.

신경회로망과 CSM을 이용한 Ni-Ti 합금의 회전연마특성 예측모델 개발

정여경 부경대학교 2022 국내석사

For decades demands for small components requiring high precision have been steadily increasing. Among them, the use of Ni-Ti alloy materials increases, and the need to improve surface roughness that affects the performance and quality of products is emphasized. However, the conventional finishing processing methods were limited in the size and shape of the workpiece. Hence, this study presents a magnetic transporter rotational finishing(MTRF) process using a magnetic field that was not restricted by the shape of the workpiece. This study aims to explore the optimal condition of the process parameter in the MTRF to improve the surface roughness of Ni-Ti alloy. The MTRF process simultaneously processes a plurality of complex-shaped components using a flexible tool. However, it is not economical in terms of cost and time to find the optimal surface finishing processing conditions by performing numerous experiments with an expensive Ni-Ti alloy material to reduce surface roughness. Hence, finite element analysis was employed to predict and score the surface integrity by considering the movement of the magnetic transporter in proportion to the abrasive motion. Since the magnetic transporter flow was affected by magnetic force, the magnetic flux density distribution was simulated using the magnetostatic simulation. Surface integrity was scored based on impulse, contact time, and contact distribution from the transient structural simulation results. Also, image classification was conducted by using a convolutional neural network(CNN) and the EfficientNet with compound scaling method(CSM). This study is significant for applying a predictive model that does not undergo trial and error to the simulation result image. The prediction results of these networks were compared to evaluate the surface integrity of Ni-Ti alloy in the MTRF process. As a result, the CSM model achieved excellent performance for classification accuracy with 98.4% and 93.8% of train datasets and validation datasets compared to the CNN model, respectively.

CNT-Co를 응용한 전해-자기 복합가공의 특성평가 및 최적화에 관한 연구

김태희 부경대학교 일반대학원 2012 국내석사

산업이 발전함에 따라 초정밀 가공기술로 제작된 부품을 기반으로 하는 우주항공, 반도체, 디스플레이 및 광학 등 다양한 분야의 발전으로 인해 정밀도가 우수한 공정 기술 개발에 대한 요구가 증가되고 있다. 그에 따라 초정밀/초미세 가공 기술에 대한 연구가 활발히 진행되고 있다. 하지만 마이크로-나노 부품의 표면 정밀도 향상에 관한 연구는 CMP (chemical mechanical polishing) 등과 같이 광범위 평탄화 공정으로 편중 되어 다양한 부품 형상에 유연하게 적용할 수 있는 표면 정밀도 향상 기술이 필요하다. 이러한 목적을 달성하고자 제시된 방법 중 하나가 전자석 및 영구자석을 이용한 자기연마법이다. 자기연마법은 자기장에 의해 형성된 자기력선 방향으로 미세한 연마입자와 자성입자가 정렬하여 브러쉬 역할을 수행하며 금속표면을 연마하는 방법으로 공구의 형상이 유연성을 갖기 때문에 공작물 또는 가공부위의 형상에 구애를 받지 않는 장점을 지니고 있다.(1) 그러나, 기존의 자기연마법의 경우 특수합금강, 스테인리스 강 등과 같이 뛰어난 물리적 성질을 가진 난삭재의 가공에서는 효율이 현저히 저하된다. 이러한 자기연마의 기계적 한계를 극복하기 위해서 자기연마와 전해연마를 복합함으로써 기존의 전해연마 및 CMP 가공에서 불가능한 난삭재의 3차원 형상 가공이 가능하고 기계적 가공과 전기화학적 제거가공을 동시에 적용하여 높은 가공효율을 기대할 수 있는 최적화된 전해-자기 복합가공기술을 제시하고자 한다. Industrial growth has led continuously a demand for an achievement of high efficient, new surface finishing that has become an important goal for developing of precision polishing process or system. Obtaining high quality in surface, traditional machining technologies involving a single process cannot satisfy the present demand for both high quality and efficiency simultaneously. Hence, an application of a hybrid machining process that integrates several processes is a new trend in the field of surface finishing. Magnetic abrasive polishing is one of the most promising finishing methods applicable to complex surfaces. In this process, the working gap between workpiece and inductor is filled with mixture of small ferro-magnetic particles and abrasive powder, which are well known as magnetic abrasive particles. These particles form a flexible magnetic abrasive brush. That can remove a very small amount of materials from a workpiece and then a better surface can be produced after polishing of the workpiece without any damages on thesurface. Nevertheless this process has a low efficiency when applied to very hardened materials. Therefore, it is necessary to improve the efficiency of this process. In this study, an EP-MAP hybrid process using CNT-Co composite which consisted of carbon nanotube and cobalt particle was developed. CNT-Co composite is suitable abrasive in the EP-MAP hybrid process, since CNT-Co composite has high strength, good electrical and magnetic property. To evaluate the synergy effect in the EP-MAP hybrid process, an experiment was performed according to each experimental condition. The experimental parameters are selection of electrolyte, magnetic flux density, spindle speed, electric potential, electrolyte concentration and working gap. As a result, CNT-Co composite in NaNO3 was chemically stable. NaNO3 was suitable for an electrolyte of the EP-MAP hybrid process. when magnetic flux density was 30, 50mT, it was confirmed that surface roughness was improved than magnetic flux density of 70mT. Surface roughness after the EP-MAP hybrid process showed a tendency to be improved with the increasing of spindle speed, increasing of Electric potential and deceasing of electrolyte concentration. And, when a working gap was 1mm, the superior surface roughness was acquired. And it seems that the level 2 parameter A(magnetic flux density) and level 3 parameter B(electric potential), C(spindle speed) and level 2 parameter D(feed rate) may provide optimum result of EP-MAP hybrid process using CNT-Co composite.

MC Nylon의 선삭가공에서 절삭조건과 노즈각도가 표면거칠기에 미치는 영향

엄성진 부경대학교 2020 국내석사

This paper investigates the effect of cutting conditions and nose angle on surface roughness when turning MC nylon. Taguchi technology in experimental design was used to reduce the number of experiments. Investigate the effect of five factors on surface roughness. Investigate the effects of cutting speed, feed rate, depth of cut, nose angle and nose radius. The results of variance analysis of the experimental results are as follows. Sensitivity affecting surface roughness when turning MC nylon was in the order of feed speed, nose angle, cutting speed, and depth of cut. Nose radius affects surface roughness. Under the same cutting conditions (cutting speed, feed rate, depth of cut, nose angle), 0.8mm nose radius showed better surface roughness value than 0.4mm nose radius. The feed rate shows very high sensitivity compared to other factors. Feed rate is the most important factor affecting surface roughness in MC nylon turning. The change in nose angle was found to be a significant condition for turning MC nylon. The smaller the nose angle, the better the surface roughness. Cutting speed and depth of cut are not critical for the formation of surface roughness in MC nylon turning.

음향방출신호 기반 마찰접합재의 인프로세스 강도 예측기술 개발

김명겸 부경대학교 산업대학원 2012 국내석사

In this study, the friction welding of aluminum alloy experiments were performed by using the design of experiment to evaluate parameters of friction welding. As a results, the heating pressure had most effect on improving strength of welding part. Therefore, the optimal welding condition was selected as 25MPa of heating pressure, 50MPa of upsetting pressure, 0.5sec of heating time and 5sec of upsetting time. And the signal data acquired by acoustic emission sensor were analyzed to predict the tensile strength of friction welding part at friction welding process for Al6061 aluminum alloy. A dimensionless coefficient(∅AE), which consisted in the square of AE rms and variance, was defined as the characteristic of friction welding and the prediction equation was obtained by using linear regression. As a result of analysis, it was seen that the correlation between predicted and measured values became very close and on-line prediction of the ensile strength was possible in friction welding part.

Surface Roughness Prediction Using Hierarchical Neural Network in Rotational Electro-magnetic Finishing

서윤수 부경대학교 대학원 2020 국내석사

자기에너지를 이용한 연마는 고정된 공구를 가지는 기존의 연마 방법으로 가공할 수 없는 표면을 처리할 수 있어 많은 연구가 진행되고 있다. 또한, 공정 성능을 높이기 위해 초음파, 진동 등을 추가로 적용하는 복합 공정이 제시되고 있다. 이러한 복합 공정은 표면 품위 향상에 작용하는 변수들이 많아 공정의 특성 및 예측 모델을 이론적으로 제시하기가 어려운 실정이다. 이러한 어려움을 극복하기 위해 최근 딥 러닝이 큰 주목을 받고 있다. 본 연구는 복합 자기연마의 일종인 회전 전자기연마를 이용하여 STS316의 표면거칠기 예측 모델을 개발하였다. 예측 모델 개발에 앞서 공정 변수의 유의성과 특성을 분석하기 위해 다구찌 방법과 분산분석을 실시하였다. 신호 대 잡음비를 이용하여 도출한 최적 조건은 핀의 길이가 3 mm, 핀의 직경이 0.7 mm, 핀의 양이 1.4 kg, 희석 액의 양이 1.0 l, 회전 속도가 1,400 rpm, 그리고 공정 시간이 30 min 일 때로 나타났다. 최적 수준의 조합으로 도출된 최적 조건을 이용하여 공정 성능을 평가한 결과 실험을 통해 나온 표면거칠기 계수의 값이 0.318에서 0.397로 24.8% 향상 되었다. 분산 분석을 통해 핀의 직경이 공정 성능의 변동에 가장 큰 영향을 미치는 것으로 나타났으며 변동에 미치는 기여율은 43.52% 로 나타났다. 회전 전자기연마의 예측 모델 개발을 위해 회귀 분석과 딥 러닝을 활용하였다. 회귀 모델의 형태는 다중 선형 모델, 2차 다항 회귀 모델, 그리고 레벨-로그 회귀 모델의 성능을 비교하여 결정하였으며 2차 다항 회귀 모델이 결정 계수와 제곱오차평균이 각각 0.920과 0.443×10-3으로 가장 좋은 성능을 보였다. 딥 러닝 모델로 심층신경망과 심층신뢰망을 사용하였으며 구조에 따른 성능 비교를 통해 구조를 결정하였다. 심층신경망과 심층신뢰망의 구조는 각각 [7, 21, 14, 1]과 [7, 14, 14, 1]로 결정되었다. 제시된 세 모델에 대한 예측 성능을 비교한 결과 심층신뢰망이 학습 데이터에 대한 결정 계수 0.990, 검증 데이터에 대한 결정 계수 0.934, 그리고 학습에 참여하지 않은 새로운 수준의 데이터에 대한 제곱오차평균 2.909×10-3로 가장 좋은 성능을 보였다. 또한 제시된 심층신뢰망에 유전자 알고리즘을 적용하여 최적 조건과 결과를 도출하였다. 심층신뢰망을 활용하여 도출된 최적 조건은 핀의 길이가 3 mm, 핀의 직경이 0.7 mm, 핀의 양이 1.258 kg, 희석 액의 양이 1.0 l, 회전 속도가 1,322 rpm, 그리고 공정 시간이 35.5 min 일 때로 나타났고 이때의 표면거칠기는 초기 표면거칠기 대비 53% 향상되었다. 이러한 결과를 바탕으로 심층신뢰망을 이용한 모델이 회전 전자기연마의 예측 모델로 적합함을 확인하였고 이를 활용하여 최적화를 수행하여 공정 성능을 높일 수 있음을 입증하였다. 이를 제조 분야에 적용할 경우 공정 효율을 높일 수 있을 것으로 기대된다.