In this study, the design of the lower arm, a type of suspension for a 4 wheel drive vehicle, was dealt with through structural analysis. In the case of the existing lower arm, cracks occurred in the neck, so it is necessary to reduce the maximum stress in order to extend the life of the analysis model. Based on this, various design changes were made, and the maximum stress generated was compared through structural analysis of each design change model. For structural analysis, a unit load (1N) was applied in the vertical direction to the lower arm model, and the results were analyzed relative to each other. As a result of analysis through various design changes, case 3, a model in which the stress concentration applied to the lower arm was relieved, showed an increase in strength of about 51% compared to the existing model.

In order to develop a 1 ton truck rear wheel air suspension module, this study designed and manufactured a Z-type spring and air suspension module test jig to optimize the design and reliability of the Z-type spring and vibration-free air suspension module, which are core parts, and to secure the reliability of the developed parts. We were able to achieve the technology development goal of this thesis by making a prototype and conducting a test evaluation at an external test and research institute to perform the vibration endurance test aimed in this study.

In this study, the models with types A, B and C of the commercial electric kickboard suspensions were modeled and the structural analyses were carried out. Types A and C have the deformations less than type B. The coil spring can reduce the deformation by installing the suspension. In types A and C, the forces applied to the bolt became same, but more deformation occurred in type C. This is the difference due to whether or not there is a fixed part. Type A was fixed and type C not. This fixation indicates that the bolt has been fully tightened to the end. Therefore, the use of products thatarefully contacted to the end by tightening with bolts can reduce the deformation greatly. Based on the data obtained from this study, it is assumed that the more efficient and stable product will be designed if the suspension absorber of the suspension is designed. Without the test on the durability of electric kickboard suspension, the durability can be seen as the deformation and stress are investigated through the structural analysis.

We synthesized YOF(yttirum oxyfluoride) powders through solid state reactions using Y2O3 and YF3 as raw materials. The synthesis of crystalline YOF was started at 300 oC and completed at 500 oC. The atmosphere during synthesis had a negligible effect on the synthesis of the YOF powder under the investigated temperature range. The particle size distribution of the YOF was nearly identical to that of the mixed Y2O3 and YF3 powders. When the synthesized YOF powders were used as a raw material for the suspension plasma spray(SPS) coating, the crystalline phases of the coated layer consisted of YOF and Y2O3, indicating that oxidation or evaporation of YOF powders occurred during the coating process. Based on thermogravimetric analysis, the crystalline formation appeared to be affected by the evaporation of fluoride because of the high vapor pressure of the YOF material.

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of 1300℃ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. Yb2O3 and SiO2 are used as the raw starting materials to form ytterbium disilicate (Yb2Si2O7). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., SiO2, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

고압균질화 기반 nanosuspension화은 난용 혹은 불용인 기능성 물질의 가용성을 높이는 기술로서 식품산업체로부터 관심을 받고 있다. 그러나 nanosuspension은 나노 크기로 분산된 난용성 입자들은 응집 또는 Ostwald ripening 현상에 쉽게 노출되기 때문에, 저장안정성이 낮다. 그러므로 이러한 nanosuspension에 유화제 및 고분자 물질 등의 분산안정제를 도입함으로써 위의 현상을 지연시키거나 방지하기 위해 반드시 필요하다. 이 연구는 분산안정제의 특성이 nanosuspension화된 분지쇄아미노산의 용해도 및 저장안정성에 미치는 영향을 평가했다. Tween 80, Span 80 또는 lysolecithin을 10 mM 인산 완충 용액(pH 7)에 녹이고, pH를 3 또는 6으로 보정하여 안정제 용액을 제조하였다. 분지쇄아미노산 혼합물(L-leucine:L-isoleucine:L-valine=2:1:1)을 최종 농도가 5%(w/v)가 되도록 안정제 용액에 첨가 하였다. 모든 분지쇄아미노산 현탁액을 25°C에서 2 시간 동안 교반하였다. 분지쇄아미노산를 함유한 나노서스펜션을 제조하기 위해서 70°C로 예열된 분지쇄아미노산 현탁액을 고압균질화기를 사용하여 100 MPa에서 5 회 균질화를 진행하였다. pH에 관계없이 고압균질화를 통해 분지쇄아미노산의 가용성을 증가되었지만, 가용성이 장기간 동안 유지 되지 않았다. 분산안정제에 의해 분지쇄아미노산의 포화 농도는 증가하였고, 분지쇄아미노산의 포화 농도 증가에 대한 안정제의 영향은 pH 6에서 더 확연했다. pH 6에서 Tween 80은 분지쇄아미노산와의 혼합 비율과는 무관하게 분지쇄아미노산 nanosuspension의 저장안정성을 크게 증가 시켰지만, pH 3에서는 그렇지 않았다. 그러나 lysolecithin과 Span 80을 적용한 분지쇄아미노산 nanosuspension의 저장안정성은 pH와 안정제의 혼합 비율에 따라 영향을 받았다.

Lanthanum/gadolinium zirconate coatings are deposited via suspension plasma spray with suspensions fabricated by a planetary mill and compared with hot-pressed samples via solid-state reaction. With increase in processing time of the planetary mill, the mean size and BET surface area change rapidly in the case of lanthanum oxide powder. By using suspensions of planetary-milled mixture between lanthanum or gadolinium oxide and nano zirconia, dense thick coatings with fully-developed pyrochlore phases are obtained. The possibilities of these SPS-prepared coatings for TBC application are also discussed.

Yttria-stabilized zirconia (YSZ) coatings are fabricated via suspension plasma spray (SPS) for thermal barrier applications. Three different suspension sets are prepared by using a planetary mill as well as ball mill in order to examine the effect of starting suspension on the phase evolution and the microstructure of SPS prepared coatings. In the case of planetary-milled commercial YSZ powder, a deposited thick coating turns out to have a dense, vertically-cracked microstructure. In addition, a dense YSZ coating with fully developed phase can be obtained via suspension plasma spray with suspension from planetary-milled mixture of Y2O3 and ZrO2.

The flat type automotive cross members with high strength steel have advantages in light weight and fewer parts compared to the hump type cross members. But the complex part shape of the flat type cross member and the poor formability of high strength steel make it difficult to form the parts without forming defects, such as splits and wrinkles. The purpose of this study is to develop the flat type automotive cross member with high strength steel. For that purpose, drawing processes are evaluated using PAM-STAMPTM and proper draw die and blank designs are proposed. Using the proposed die and blank design, the flat type upper and lower cross member could be formed successfully without forming defects.

본 논문에서는 한국기계연구원에서 개발된 자동차 서스펜션을 대상으로 한 협업설계 지원 엔지니어링 프레임워크 개발에 관하여 기술한다. 개발된 엔지니어링 프레임워크는 각 분야별 전문가 지식에 기초한 엔지니어링 task agent를 포함한 다양한 복수 계층의 소프트웨어 에이전트로 구성된다. 본 프레임워크는 폭 넓은 국내 중소제조기업 적용 확산을 목적으로 JADE(Java Agent Development Framework)와 같은 공개 소스 프로그램 기반으로 개발하였으며, 프레임워크의 확장성을 유지하기 위하여 관련 H/W 및 응용 S/W의 독립성을 가능한 한 유지하도록 노력하였다. 개발된 프레임워크는 제품개발과 정에 있어 지역적으로 분산된 사용자 및 엔지니어링 자원 등을 효과적으로 활용할 수 있는 통합된 협업 설계환경을 제공한다. RR/FR lower arm 및 RR cross member와 같은 몇 개의 실제 자동차 서스펜션 모듈의 설계엔지니어링 문제에의 적용을 통하여 본 시스템의 적용성과 효율성을 확인하였다.

멤브레인 여과 실험에서 얻어진 데이터 처리에 간단한 수치해석을 적용하여 삼투압(osmotic pressure) 과 구배확산계수(gradient diffusion coefficient)를 도출하는 새로운 방법론을 제시하였다. 삼투압과 구배확산계수는 이론 및 실험적으로 쉽게 구할 수 없는 물리적 특성치로서 멤브레인 여과의 특성 규명에 중요하다. 모델 라텍스 콜로이드의 여과시간에 따른 투과플럭스(permeate flux) 값과 이에 대한 수치적분과 수치미분 데이터로부터 분산된 입자농도의 함수인 삼투압 관계식을 구했다. 이로부터 계산된 열역학적 계수(thermodynamic coefficient)는 입자농도가 증가할수록 감소하는 거동을 보였고, 여기에 기존에 제시되어 있는 수력학적 계수(hydrodynamic coefficient)를 도입하여 구배확산계수를 산출하였다. 아울러, 본 연구에서 계산된 입자농도에 따른 구배확산계수의 결과와 동일한 멤브레인과 라텍스 콜로이드의 여과에 대해서 기존에 통계역학적 시뮬레이션으로 예측한 결과를 비교하였다.

비구형 입자들의 크기와 형태에 따른 침강 특성의 영향을 검토하였다. 비구형입자를 포함하는 서스펜션의 침강에서 log μC대 log ε로부터 얻은 기울기 지표n값은 형태와 크기가 다른 입자는 같은 부피 농도에서 흡착되는유체량이 달라져 입자크기가 감소하거나 불균일한 경우 증가하는 경향을 나타내었다. 실험결고 비구형입자를 포함하는 서스펜션의 침강에서 기울기 지표 ni값에 대하여 ni=n(a+b/dv)와 같은 식을 얻었으며 이때 a, b는 입자형태에 따른 상수이다.

Most of outdoor mobile robots have a suspension on each wheel in order to relieve the shock by ground obstacles and to improve the driving stability. Typically, in the actual operations, the suspensions have been used under a given set of conditions as all the damping and spring coefficients of the suspensions are fixed. However, it is necessary to readjust the coefficients of the suspensions according to surface conditions that may cause the unstable shaking of a robot body at high speed driving. Therefore, this paper is focused on the mobility analysis of an outdoor robot when the coefficients of suspensions (in particular, damping coefficients) are changed while driving on an uneven road surface. In this paper, a semi-active suspension with twelve damping coefficient levels was used and a small sized vehicle with the suspensions was employed to analyze the mobility dependent on a change of the damping coefficient. And the mobility was evaluated through driving experiments on a bumped slope.