• 디지털융복합연구
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• 제20권2호
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• pp.317-323
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• 2022

본 연구는 3차원 가상모형을 이용하여 하악 제2소구치 교두 변이 양상을 정성적으로 분석하고, 교두 변이에 따른 치아 표면적의 정량적 분석과 함께 좌·우측 대칭성을 분석하고자 하였다. 127개의 하악 제2소구치 가상치아를 준비한 후, RapidForm2004(INUS technology INC, Seoul, Korea)을 이용하여 각 교두의 절대적/상대적 단면적, 전체 치관 단면적, 교합면의 중심구 형태 등을 분석하였다. 통계방법은 Independent t-test, Kruskal-Wallis test 및 교차분석을 시행하였다. 연구 결과, 중심구의 형태는 양측간 높은 대칭성을 보였다. 좌측에서 U 형태이면 우측도 100.0% U 형태를 나타냈으며, 나머지 H 형태와 Y 형태는 각각 73.7%, 78.9% 비율로 양측간 동일한 중심구 형태를 나타냈다(p<.001). 본 연구에서 얻은 결과는 CAM/CAM을 이용한 보철물 제작 시 참고자료로 활용이 가능할 것이며, 향후 맹출 직후의 하악 제2소구치를 포함한 더 많은 샘플을 대상으로 한 후속연구가 이루어지기를 기대한다.

• 비파괴검사학회지
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• 제21권6호
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• pp.658-662
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• 2001

후방산란된 초음파의 입사각 의존성을 이용한 표면 결함유형의 평가가 시도되었다. 평탄한 유리위에 순수한 홈, 구리로 채워진 홈, 표면위 붙여진 구리선등의 표면결함 시편에 대한 후방산란 프로파일은 제 1 임계각에서 종파의 산란과 관련된 새로운 프로파일을 보여주었다. 결함에 의한 산란효과가 클수록 후방프로파일들의 정점 위치는 작게 나타났으며 후방복사 프로파일과 정점 위치에서의 파열의 모양은 결함의 유형과 위치에 따라 누수파와 산란파의 복합적 요인에 의해 다른 형태를 보여주었다.

• 대한기계학회논문집A
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• 제26권2호
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• pp.300-307
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• 2002

Partial penetration welding joint is defined as groove welds welded from one side, without steel backing or groove welds welded from both sides but without back gouging. So it has an unwelded portion at the root of the weld. Study of partial penetration weldment fracture behavior includes residual stress analysis and fracture analysis. The J-integral loses its path independency in residual stress field. Therefore, it is necessary to introduce a new J-integral, J, which is defined including the effect of plastic deformation and thermal strain. In this study, theoretical formulation and program were developed for the evaluation of J-integral for the crack tip located in the weldment. Evaluations of fracture behavior were performed for partial penetration multi-pass weldment of 25.4mm thick plate by J-integral. From a point of fracture in partial penetration multi-pass welding, it seemed to be better to control root face smaller than 6.35mm.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.68-74
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• 1999

One of the recent changes in machining technology is rapid application of micro- and high precision grinding processes. A fine groove generation is necessary for the fabrication of optic, electronic and semiconductor parts, and achieved by chemical or mechanical processes. Slot grinding is very efficient for the generation of micro ordered groove with hard and brittle materials. As slot grinding is continuous, the ground depth become gradually shallow because of wheel wear. The form accuracy become worse from the increase of ground slot width by the loading phenomena at wheel side, results on chipping damage of the workpiece. The experiments achieve to the enhancement of the form accuracy and chipping free of the brittle materials using V shaped cast iron bonded diamond wheels. In this study we focused on the investigation of the effect of the high pressure air jet on the grinding characteristics. As a results, we found that the high pressure air jet is very effective on the reductions of the wheel wear, enhancement of the form accuracy.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1813-1819
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• 2001

Partial penetration welding Joint defines that groove welds without steel backing, welded from on side, and groove weeds welded from both sides but without back gouging, that is. it has an unwelded portion at the root of the weld. In this study we analysed fur residual stress and displacement distribution on partial penetration welding condition of thick plate metal. For 25.4mm thick plate, theoretical residual stress and displacement analysis by finite element method using ABAQUS was carried out and compared with the experimental result using hole-drilling method. In results of the condition of partial penetration, it appeared that longitudinal stress at welding area was a little difference and transverse stress did not have any effect by partial penetration multi-pass welding. From a point of welding distortion in partial penetration multi-pass welding, it seemed to be better to control root face smaller than 6.35mm.

• 센서학회지
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• 제14권6호
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• pp.374-380
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• 2005

Vibration sensors have a wide scope of applications in the field of monitoring systems that needs to perceive an undesirable physical vibration before a critical failure occurs in a system, and then costly unplanned repairs can be avoided. The conventional vibration sensors developed so far have many disadvantages, such as complex manufacturing process, bulkiness, high cost, less reliability and so on. This paper reports a simple-structured vibration sensor, which has been developed using a commercialized conductive ball and silicon bulk-micromachining technology. The sensor consists of a conductive ball placed in $600{\mu}m$-deep micromachined silicon groove, in which Au thin film has been patterned using a shadow mask technique. Prior to the formation of the Au thin film, the sharp convex corner was rounded for smooth meatl deposition on the non-planar surface at the edge of the groove. The measurement results of the fabricated vibration sensor demonstrate a stable response characteristic to low-frequency vibration range ($1{\sim}30{\;}Hz$).

• 한국안전학회지
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• 제22권6호
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• pp.27-34
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• 2007

Static or dynamic elastomeric O-ring seals are installed between joining parts, and play key roles of high pressure-tightening. Sealing performance and structural safety of the O-ring are dependent on groove design, plain diameter, squeeze and applications such as pressure and temperature. In this study, to solve O-ring problem squeezed and highly pressurized under laterally one-sided constrained condition, hyperelastic FE analyses are performed, and FE results are compared with measured ones by computer-aided tomography, deformed shape and extrusion depth of the O-ring. Through the comparisons, FE analysis technique was verified. In order to evaluate design sensitivity, Taguchi method was used to select FE analysis cases. Adjustment parameters are clearance gap, groove comer radius, plain diameter and squeeze. By means of verified FE analysis technique, it has been analysed how the parameters have effects on contact stress fields, internal stress fields, and extrusion depths. Sealing performance has been evaluated based on contact stress fields and contact widths, and structural safety on internal stress and strain, extrusion lengths.

• Journal of Welding and Joining
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• 제5권2호
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• pp.44-52
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• 1987

The fracture toughness, $J_{IC}$ of high frequency electric resistance welded steel pipe for smooth and side-grooved CT specimen was evaluated by unloading compliance method. The crack growth, .${\delta}a$ was obtained from the equation of Donald and Saxena & Hudak, and $J_{IC}$ was determined from the curve of J-${\delta}a$ relations. The crack growth on the experiment using unloading compliance method is underestimated as compared with ${\delta}a$ measured directly by the SEM, so the reliability of $J_{IC}$ from saxena & Hudak equation is large than that from Donald. The $J_{IC}$ value of side-grooved CT Specimen is estimated less than that of smooth, and this is the effect of the side-groove, the shear-lip of crack tip and the reduction of crack tunnelling phenomena.

• 한국안전학회지
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• 제13권4호
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• pp.79-86
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• 1998

The effect of specimen thickness on fatigue crack growth behavior has been carried out by compact tension specimens of thickness of 3mm, 10mm and 25mm for maraging steel and Al 7075-T6. The closure points were determined during the test by means of a clip-gage situated at the notch mouth. Specimen thickness have no apparent influence on the fatigue crack growth rate of maraging steel, but the crack growth rate of 25mm thickness specimen for Al 7075-T6 is faster than that of 3 and 10mm specimens. The difference of crack growth rates can be successfully explained by considering the different stress state of plane strain and plain stress due to the variation of specimen thickness. Also the crack opening ratio of 25mm specimen is greater than those of 3 and 10mm specimens. When a side groove is introduced in a 10mm specimen, the crack growth rate is approximately similar to that of 25mm specimen. The effective thickness expression of $B_e=B_o-(B_o-B_N)^2B_o$ is the most appropriate to evaluate the crack growth rate of side-grooved specimen. Fatigue crack growth rates can be well described by $\Delta K_{eff}$ of the crack closure points in regardless of all thickness and side-grooved specimens.

• Structural Engineering and Mechanics
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• 제54권1호
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• pp.35-54
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• 2015

The performance of a newly generated steel connection known as SidePlateTM moment connection for seismic loading and progressive collapse phenomenon has been investigated in this paper. The seismic evaluation portion of the study included a thorough study on of interstory drift angles and flexural strengths based on 2010 AISC Seismic Provisions while the acceptance criteria provided in UFC 4-023-03 guideline to resist progressive collapse must be satisfied by the rotational capacity of the connections. The results showed that the SidePlate moment connection was capable of attaining adequate rotational capacity and developing full inelastic capacity of the connecting beam. Moreover, the proposed connection demonstrated an exceptional performance for keeping away the plastic hinges from the connection and exceeding interstory drift angle of 0.06 rad with no fracture developments in beam flange groove-welded joints. The test results indicated that this type of connection had strength, stiffness and ductility to be categorized as a rigid, full-strength and ductile connection.