필로티는 현대건축에서 주차공간의 활용, 보행자의 통로 등 여러 가지 이점을 가지고 있기 때문에 아파트와 오피스텔과 같은 고층건축물에 많이 사용되고 있다. 이러한 고층건축물의 필로티 형태 특성상 강풍이 불 때 바람이 집중되기 때문에 필로티 천장과 벽 면에 위치하고 있는 외장재 및 주골조가 파손되기 쉽다. 그리고 이러한 외장재 및 주골조의 탈락으로 인해 2차 피해가 발생할 우려가 있다. 하지만 건축구조기준(KBC-2016)에서는 고층건축물에 대한 천장 및 벽면의 풍압계수만을 제시할 뿐 필로티에 대한 기준이 명시 되어 있지 않다. 본 논문은 고층건축물에서 사용되는 필로티의 종류로서 관통형, 개방형 필로티를 선정하였고, 필로티의 폭과 깊이를 변수로 하여 풍동실험을 진행하였다. 그리고 변수에 따른 풍압계수의 특성을 파악하였고 비교 및 분석하였고 본 논문의 실험결과를 통 하여 필로티 설계 시 활용할 수 있는 주골조 및 외장재 설계용 풍압계수를 제시하였다.

Aluminum alloys are the light weight materials, they are commonly used in many industrial applications such as electronic, aerospace, automotive, and medical industry. Because they are used in these such applications. Therefore, their light weight and high surface quality are required. In this paper, the surface improvement round flat aluminum alloy using lapping finishing method was explored. In order to find the optimal condition, lapping parameters such as, rotational speeds, abrasive grain sizes of pad, processing times, and lapping oils were investigated in this study. The improvement in surface roughness was found to be highest with optimal condition at 200 rpm of rotational speed, 1 ㎛ abrasive grain size of pad, 0.5ml of light oil for 720 sec. By using the optimal condition, the initial surface roughness Ra of round flat aluminum alloy can be enhanced from 2.59㎛ to 0.02 ㎛. This can be concluded that the small CNC machine with lapping finishing method can be used to enhance the surface roughness of round flat aluminum alloy effectively.

본 연구는 거친 표면에서의 유동장 특성에 대해 실험 및 수치해석적 연구를 수행하였다. 완전 발달한 두꺼운 난류경계층은 풍동 내 바닥에 깔린 거친 표면을 이용하여 생성하였다. 평균유동과 난류강도 및 왜도와 같은 난류경계층의 특성을 열선유속계를 이용해 측정하였다. 풍동실험결과와의 비교를 위해 난류경계층은 수치해석을 이용하여 모사하였다. 거친 벽표면은 기본적으로 난류경계층 생성에 사용되었으며 입출구면에는 주기경계조건이 적용되었다. 본 연구결과로서 난류경계층이 거친 표면 위에서 성공적으로 생성 되었으며 평균유동과 난류강도 및 왜도와 같은 난류경계층의 특성은 지표면조도에 따라 달라진다는 것을 확인하였다.

As product diversity increases and product life cycle gets shorter, lead time reduction and manufacturing cost saving of die & mold are getting important in machinery, automotive, and electronics industries. To develop a novel free-machining die & mold steel, we try to modify the chemical compositions of AISI P20 mold steel by adding boron, nitride, and sulfur. After making three types of mold steels which are base metal of AISI P20 mod., boron and nitrogen added, and boron, nitrogen, and sulfur added to the base metal. Milling tests are carried out using TiN, TiCN, and TiAlN coated WC end-mills under various cutting conditions. Boron and nitrogen added steel machined by TiN coated tool shows the most excellent tool wear and surface roughness characteristics. The results might come from BN inclusions in base metal acting as a stress concentration source and lowering strain resistance during cutting process. The relationship between tool wear and surface roughness are also discussed including feed rate effects.

Recently, as road users have become increasingly important, the importance of functional performance as much as structural one has been important to provide comfortable and safe road services. As a result of the survey on the customer satisfaction of the highway, the road surface condition is selected as the most important area of the road service, and the functional performance such as driving comfort and noise is pointed out as an important problem. Therefore, many studies have been conducted to improve this problem. In most cases, there is a fundamental limitation in providing a comfortable road to the user through the roughness management of the final layer. In this paper, a study was carried out to improve the roughness of the final layer by controlling the roughness of each layer. In construction field of Busan-ChangWon expressway, roughness was measured by three methods according to construction phases of subbase, 1st and 2nd base layer, intermedia layer and surface layer. As a result of the analysis, it was found that the roughness of the lower layer affects the roughness of the upper layer. Especially, the roughness of 1st base layer was relatively clear correlation with the intermedia and the surface layer IRI. In the future, after getting more field data and establishing the management standards, it is possible to provide a comfortable road to users.

최근 강풍으로 인한 시설물 피해가 증가함에 따라 구조물 설계 시 설계풍속을 반영하고 있으며, 설계풍속 산정 시 기상청에서 제공하고 있는 연최대풍속 년도별 풍속 자료를 활용한다. 하지만 기상청에서 제공하고 있는 연최대풍속은 지형이나 지표면조도에 의해 할증되거나 감소된 관측풍속 중 최댓값을 제공하고 있어 실제 기본풍속 조건에서의 연최대풍속과는 상이하기 때문에 기상청에서 제공하는 연최대풍속을 활용하여 통계적 빈도분석을 수행할 경우 풍속이 과소 또는 과대평가 될 수 있다. 따라서 본 연구에서는 40 년치 이상의 관측자료가 있는 전국 60개 지점의 기상관측소의 일최대풍속을 지형 및 지표면 조도에 따라 기본풍속 조건으로 보정하고 보정된 일최대풍속 중 연최대풍속을 선별하여 빈도분석을 통해 재현기간 풍속을 산정하였으며, 보정하기 전의 일최대풍속을 이용하여 연최대풍속을 선별한뒤 선별된 연최대풍속을 보정하여 산정된 재현기간풍속과 비교·분석하였다. 분석 결과 100년 재현기간 풍속 기준으로 최대 4.2m/s 차이를 보였으며, 평균적으로 약 0.33m/s의 차이를 보였다.

Because of the economy and construction simplicity, Jacketing method has been widely used in strengthening RC columns in Korea. Although some studies on the compressive performance of jacketed elements have been conducted by experimental or analytical methods, the correlation between the axial performance and the surface roughness of the jacketed element has not been performed. In this study, the surface roughness of chipped surface of old element was measured and the compressive strength test was performed to evaluate the surface roughness and jacketed effects. The test results are as follows; (1) Compressive strength was improved by 1.8%∼3.1% by chipping, (2) Compressive performance of the jacketed elements reduced to 85%∼93% of theoretical values, (3) As a result of analysis of correlation between surface roughness index and axial strength, surface roughness index based on the wave length was more effective than existing methodology for evaluation surface roughness.

Fecralloy coating layer with large surface area is suitable for use as a filter media for efficient removal of hot gaseous pollutants exhausted from combustion processes. For uniform preparation of a Fecralloy coating layer with large surface area and strong adhesion to substrate, electrospray coating and thermal treatment processes are experimentally optimized in this study. A nano-colloidal solution with 0.05 wt% Fecralloy nanoparticles is successfully prepared. Optimized electrospraying conditions are experimentally discovered to prepare a uniform coating layer of Fecralloy nanocolloidal solution on a substrate. Drying the electrospray coated Fecralloy nano-colloidal solution layer at 120oC and subsequent heating at 600oC are the best post-treatment for enhancing the adhesion force and surface roughness of the Fecralloy coating layer on a substrate. An electrospray coating system, consisting of several multi-groove nozzles, is also experimentally confirmed as a reasonable device for uniform coating of Fecralloy nano-colloid on a large area substrate

구조물의 풍하중을 산정할 때의 설계풍속은 10분 평균풍속 또는 가스트풍속(3초평균풍속)을 적용한다. 건축물의 경우 10분 평균풍속 사용하고 있으나, 외장재 등과 같이 고진동수를 가지는 구조물의 경우에는 가스트풍속을 사용한다. 가스트풍속은 기상대 주변의 영향을 크게 받기 때문에, 일반적으로 10분 평균풍속에 돌풍율을 곱하여 산정하는 것이 편리하다. 본 연구는 최근 우리나라의 기상변화와 경제 발전에 따른 기상대 주변의 지표면상태의 변화를 반영하여 지표면조도에 알맞은 돌풍률을 평가한 것이다. 해석자료는 최근 40년간(1973년~2012년)의 전국 68개 기상관측소의 기상자료와 선행연구에서 제시한 지표면조도구분을 활용하였다. 돌풍률을 추 정할 때 평균풍속의 월최대값 범위는 16m/s~36m/s로 하였고, 16m/s 이하와 36m/s 이상에서는 돌풍률을 일정하게 하였다. 연구결과 지표면조도구분 B지역과 C지역의 돌풍률은 거의 유사하게 나타났고, 지표면조도구분 D지역은 다른 지역의 돌풍률과 차이를 보였다. 따라서 지표면조도구분 B, C지역의 돌풍률은 통합하여 평가하였고, 지표면조도구분 D지역만 따로 분류하여 돌풍률을 평가하여 제시하였다.

In this study, we carried out interrupted cutting of carbon steel for machine structure(SM20C) with uncoated carbide tool and analyzed anova test and confidence interval to find influential factor to surface roughness, and obtained regression equation. Rhe results are follows: First, we found that affected factor to surface roughness in interrupted cutting was feed rate. Secondly, the cutting speed and depth of cut was small affected to surface roughness. Finally, from multi-regression analysis of interrupted cutting experimental result, obtained regression equation and it’s coefficient determination was 0.814 and it means that regression equation was predictable. Compared with other continuous cutting, if feed rate increase, surface roughness will grow in interrupted cutting.

The relationship the between electrical properties and surface roughness (Ra) of a wet-etched silicon wafer were studied. Ra was measured by an alpha-step process and atomic force microscopy (AFM) while varying the measuring range 10×10, 40×40, and 1000×1000μm. The resistivity was measured by assessing the surface resistance using a four-point probe method. The relationship between the resistivity and Ra was explained in terms of the surface roughness. The minimum error value between the experimental and theoretical resistivities was 4.23% when the Ra was in a range of 10×10μm according to AFM measurement. The maximum error value was 14.09% when the Ra was in a range of 40×40μm according to AFM measurement. Thus, the resistivity could be estimated when the Ra was in a narrow range.

Measurement of surface roughness is an important metrology procedure widely used in the industry during the final phases of the manufacturing process for quality control. This paper presents a measurement system that uses an optical microscope equipped with a vision sensor to measure the surface roughness of bearings. Shape from Focus / Defocus method is applied to measure the 3D surface coordinates of the object surface from which roughness calculations can be undertaken.

본 연구에서는 국내외의 구조물 설계 기준에서 제시하는 지표조도에 따른 풍속의 보정 계수 산정 절차와 기준을 국내 지역에 적용하여 차이와 원인을 분석하였다. 이를 위하여 우리나라 건축구조설계기준(KBC2009), 호주/뉴질랜드설계기준(AS/NZS 1170.2:2002), 유럽기준 (EUROCODE), 일본도로교기준을 비교하였으며, 분석 대상지역은 효과적인 비교를 위해 복합적인 조도가 존재하는 도시지역, 해안가에 위치한 대도시지역, 부드러운 조도가 주로 분포하는 섬지역으로서 수원, 부산, 울릉도로 선정하였다. 본 연구에서 각국의 설계기준에 따라 산정한 고도분포계수는 대체적으로 EUROCODE에 Procedure2에 해당하는 값들이 높게 나타났으며, KBC 2009의 경우 타 설계기준에 비해 수원 동쪽, 북쪽을 제외하고 작은 값이 나타났다. 이러한 고도분포계수값의 차이는 복합적인 지표조도에 대한 보정 방법과 분석대상풍상영역의 범위에 기인한 것으로 사료된다.

In General, the surface roughness of turning is depends on cutting condition which are cutting speed, depth of cut, and feed, etc. This study was carried out to presume for mutual relation of turning condition to get optimum surface roughness and experimental equation by variance and multi regression analysis As the result, multiple correlation coefficient was calculated 97%, the coefficient of determination (R2) was calculated 95% and the adjusted coefficient was calculated 97% by multiple regression analysis So, the formula was made by this multiple regression analysis is reliable.

Green strength is an important property of powders since high green strength guarantees easy and safe handling before sintering. The green strength of a powder compact is related to mainly mechanical and surface characters, governed by interlocking of the particles. In this study, the effect of powder surface roughness on the green strength of iron powders was investigated using a transverse rupture test. Three-dimensional laser profiler was employed for quantitative analyses of the surface roughness. Two different surface conditions, i.e. surface roughness, of powders were compared. The powders having rough surfaces show higher green strength than the round surface powders since higher roughness leads increasing interlocked area between the contacting powders.

표면조도에 의해 발생하는 난류유동은 공학적, 물리적 분야에서 매우 중요하게 다루어지고 있다. 표면조도는 선박에서도 설계, 용접, 도장 등 각각의 단계에서 다양한 측면으로 고려되어야 할 중요한 요소이다. 본 연구는 표면조도 형상을 일반화하여 PIV기법을 적용하여 수조실험을 수행하였다. 표면조도 조건은 거칠기 형상의 간격에 대해 변화를 주었으며, 실험유속은 Re = 1.1×104, Re = 2.0×104, Re = 2.9×104 에서 시간평균에 대한 난류강도를 알아보았다. 거칠기 계수 증가에 따라 표면 거칠기 형상 근처에서 발생한 난류성분에 의해 난류강도는 강하게 나타났으며, 자유흐름 영역으로 갈수록 유동 방향의 변동이 전혀 없는 흐름이 나타났다. 실험유속 조건 변화에 대한 난류강도의 편차는 크게 영향을 받지 않았다.