스크림 프리프레그의 기계적 특성평가

정성균,정성교 서울産業大學校 1999 논문집 Vol.49 No.2

Mechanical characteristics of composite laminates with carbon scrim and glass scrim are evaluated in this paper. Composite laminates in USN125 group are made by inserting carbon scrim and glass scrim between layers. The stiffness properties needed for a plane-stress analysis are modulus(E₁), strength(Xt) in the fiber direction, modulus(E₂), STRENGTH(Yt) transverse to the fiber direction, one of the in-plane Poisson ratios ν12, and desity of composite laminates. These properties are routinely characterized by ASTM standards. Experimental results show that the mechanical properties of UD prepreg the transverse direction were highly improved by inserting scrim.

블라스트와 쇼트피닝이 Al 7075-T6의 피로특성에 미치는 효과에 관한 연구

정성균,조연희,김태형,이재헌 서울産業大學校 2002 논문집 Vol.53 No.1

In this paper, the effects of blasting and shot peening on the fatigue characteristics of Aluminium 7075-T6 alloy are studied. Three types of specimens, such as normal specimen, blasted specimen and shot peened specimen were used to get the experiment results. Rotary bending fatigue test machine was used to obtain the results, The experimental results show that the fatigue life and the fatigue strength were improved by shot peening, However, the fatigue life and the fatigue strength were increase a little bit by blasting.

쇼트피닝 가공한 평기어의 피로특성

정성균,정동건,박충식,김태형,이재헌 서울産業大學校 2002 논문집 Vol.53 No.1

In this paper, the effect of shot peening on the fatigue characteristics have been investigated. Two types of specimens were used to obtain the experimental results. One type of specimen was made by machining and heat-treating SCM415 steel. The other type of specimen was made by machining, heat-treating, and shot peening SCM415 steel. The hydraulic testing machine was used to do the fatigue test (R=0.1, 10Hz). The experimental results show that the fatigue life and strength of shot peened gear were largely improved compared with the unpeened gear.

ESPI를 이용한 복합재료 구조물의 층간분리 검출

정성균,서유원 서울産業大學校 1999 논문집 Vol.49 No.2

In this paper, an artificially delamination in composite structures is detected by the ESPI system. And Chamber is made of acryl for laser to transmit. A specimen and a heat source are put into a chamber, which is sealed up to minimize heat convection. A specimen is heated up to about 5∼7℃ higher than room temperature. Cooling down the specimen, experimentation is accomplished by ESPI system. Experimental results show that the debond in a composite structure can be easily detected by ESPI. Moreover, it was shown that ESPI could be usefully applied to the detection of defects in various kinds of composite structures.

마우스 골수세포 배양시 Prostaglandin E_2가 파골세포-유사세포 생성에 미치는 영향에 관한 연구

고성희,김관식,정동균 대한구강생물학회 1990 International Journal of Oral Biology Vol.14 No.2

Osteoclasts are primary cells responsible for bone resorption. It has been reported that osteoclasts are formed by fusion of mononuclear precursors derived from hematopoietic progenitor cells. Prostaglandin E_2(PGE_2) is known to be a potent bone resorbing agent, but its mechanisms are not known. This experiment was performed to study the effect of PGE_2 and calcitonin on the generation of osteoclasts from their precursor cells. The bone marrow cells were prepared from 7 to 9 week-old male mice. The femur and tibia were dissected aseptically and the marrow cavity was flushed with 1ml α-minimum essential medium by slow injection. The collected marrow cells were cultured at 1.5∼2.0×10^6 cells/well in 24-well plate for 5, 8 and 11 days. In experimental group, PGE_2(10^-5,10^-6,10^-7,10^-8M) and calcitonin(5, 30, 90ng/ml) were added. After cultures, staining for tartrate-resistant acid phosphatase(TRACP)-marker enzyme of osteoclast-was performed according to the modified method of Burstone. The TRACP-positive multinucleated cells, which have 3 or more nuclei were counted, The observed results were as follows. 1. In control group, TRACP-positive mononuclear cells were present, but no TRACP-positive multinucleated cells appeared. 2. In 8 days of culture, PGE_2 increased significantly the number of osteoclast-like cells in a dose-dependent manner in the mouse marrow cell cultures. 3. In 5, 8 and 11 days of culture with PGE_2(10^-6M), the number of osteoclast-like cells was increased up to 8 day and decreased thereafter. 4. In 8 days of culture, calcitonin decreased significantly the number of osteoclast-like cells induced by PGE_2(10^-6M) in a dose-dependent manner.

섬유 강화 복합재료의 인장 특성 평가

서유원,정성균,신용승 서울産業大學校 1997 논문집 Vol.46 No.1

The fundamental way in which fiber reinforced composites differ from conventional engineering materials such as metals is that the material properties are highly directional. This anisotropy affects the way in which the materials are used and the way in which the directions of the individual plies are selected. The stiffness properties needed for a plane-stress analysis are the modulus in the fiber direction E11, the modulus transverse to the fiber direction E22, the in-plane shear modulus G12, and one of the in-plane Poisson ratios ν12 and ν21. These properties are routinely characterized by laboratory experiments. Testing methods are examined to investigate mechanical characteristics of advanced composites, and basic properties are measured. Especially, the testing preparation, test processing, and results are examined in detail.

쇼트피닝 가공에 의한 Al 7075-T6의 피로특성에 관한 연구

김태형,정성균,신용승 한국공작기계학회 2002 한국공작기계학회 추계학술대회논문집 Vol.2002 No.-

The shot peening process is most often used to improve fatigue properties of metal parts. In order to achieve optimum, repeatable and reliable fatigue enhancement from the shot peening process, the important shot peening parameters must be controlled. In this paper, the optimum shot peening condition is investigated. Rotate bending fatigue test was accomplished to investigate the effects of shot peening on the fatigue strength. Experimental results show that the fatigue strength was tremendously increased by optimum peening condition. But the fatigue strength was decreased by under peening or over peening.

쇼트볼의 형상이 피로수명에 미치는 영향

신용승,정성균,강진식,김태형 서울産業大學校 2000 논문집 Vol.51 No.2

To improve fatigue properties, usually the shot peening process is used in the industrial world. In order to achieve optimum, repeatable and reliable shot peening process, the important shot peening parameters must be controlled. The first item needed to achieve high quality shot peening is to keep shot balls in a good quality. This paper discusses of shape of commonly used shot ball. Also, discussed is shot ball Shape's effect of Fatigue Life.

ESPI를 이용한 복합재료 구조물의 결함 검출

김경석,정성균,강진식,장호섭 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.3

본 논문에서는 ESPI 시스템을 이용하여 복합재료 구조물의 인위, 자연 결함을 검출하였다. 복합재료 구조물에서의 ESPI의 적용성을 알아보기 위해 복합재료 적층판 시험편, 하니컴 구조물 시험편, 접착조인트 시험편을 사용하였다. 결함을 검출하기 위해 시편의 표면변형을 쉽게 발생시킬 수 있는 열하중법을 선택하였다. 실험경과는 ESPI를 이용하여 복합재료 구조물의 결함을 쉽게 검출할 수 있고, 다른 여러 복합재료 구조물의 결함의 검출에도 적용할 수 있음을 확인하였다. In this paper, artificial and real defects(delamination and debond) in composite structures were detected by using ESPI system. There types of specimens, that is, composite laminates, honeycomb structures, and adhesive joints, were used to study the applicability of ESPI to composite structures. To detect defects in specimens, we selected thermal loading method that can easily induce the surface deformation of specimen. Experimental results show that defects in composite structures could be easily detected by ESPI. Moreover, it shows that ESPI could be usefully applied to the detection of defects of defects in various composite structures.

기어강의 표면가공에 따른 부식특성

이승호,서유원,정성균 서울산업대학교 산업대학원 2000 大學院論文集 Vol.7 No.-

The surface treatment to increasing corrosion resistance is becoming influence as very important technology. The influence of shot peening on the corrosion resistance of SCM 420 steel is investigated in this work. Then, surface compressive residual stress and hardness considerably increased, which resulted in the increase of corrosion resistance.