비틀림 荷重에 따른 破壞擧動

趙熙燦 忠州大學校 1986 한국교통대학교 논문집 Vol.19 No.2

When we design the members of machine subjected to torsion, we must consider the torsion that is the main factor of machine design. There are many papers studied on the torsion. I intend to explain structurally the knowledge on the torsion based on many papers concerned with the study on the torsion. Therefore, in this paper, I made an experiment on the torsion of mild steel(SM 15C) at normal temperature. And I considered the behavior of fracture due to torsion : mechanical properties, stress distribution in elastic and plastic zone, analysis of fracto graphy and crack propagation in macro and micro level, and fracture due to torsional velocity.

압전 외팔보의 폭 변화에 따른 정적 특성

조희찬 忠州大學校 2010 한국교통대학교 논문집 Vol.45 No.-

Recently, studies of intimate environmental energy harvesting have drawn attention with developments of sensor, MEMS, small electric devices and so on. There are a lot of energy harvesting equipments using solar, wind, piezoelectric energy and so on as power generator. In this paper, unimorph piezoelectric cantilever beams due to width variation have been studied in static state. The smaller the ratio of widths get, the larger deflections of free ends, bending stresses in each section and stiffness of each beam grow. The analyzed results show that the triangular cantilever beam as mechanical structure of piezoelectric energy harvester using low frequency vibrations to occur in circumference is effective shape

정전용량형 압력센서에서 센터 보스를 갖는 원형 다이어프램의 특성해석

조희찬 忠州大學校 2012 한국교통대학교 논문집 Vol.47 No.-

It is an effective to improve a structure and shape of a diaphragm as a sensing part for enhancing sensitivity and performance of a capacitive pressure sensor. Therefore, the characteristics of the circular diaphragm with a center boss in a capacitive pressure sensor have been studied for getting high performance in a low pressure in this paper. When the boss has a large radius in circular diaphragm, the capacitive pressure sensor has the higher sensitivity than that of the circular diaphragm which doesn’t have a boss structure in this research. But It is thought that the endurance of the diaphragm reduce for the reason of an excess shearing force to act on the diaphragm in the case of that the center boss radius is a more than about 36% of diaphragm radius.

경계요소법을 이용한 방음벽의 형상에 따른 음향방사특성해석

趙熙燦 忠州大學校 1997 한국교통대학교 논문집 Vol.32 No.1

The boundary element method is widely used for acoustic problems. This paper also is concerned with an application of the B.E.M. for the analysis of sound radiation characteristics of different shapes of soundproofing wall. The relations between various shapes of soundproofing wall and sound fields have been studied. And soundproof effect at geometrical viewpoint on the assumption of no diffraction have been considered. Generally, this study presents that the soundproof area of end-slanted walls becomes wide in the case of near field and that soundproof area of end-straight walls becomes wide in the case of far field. Based on these results, I suggest a more decisive design data of shape of soundproofing wall for effective soundproofing due to various sound fields.

자유단에 표준 질량을 갖는 압전 외팔보의 동적 특성

조희찬 忠州大學校 2011 한국교통대학교 논문집 Vol.46 No.-

Recently, studies of intimate environmental energy harvesting have drawn attention with developments of sensor, MEMS, small electric devices and so on. There are lots of energy harvesting equipments using solar, wind, piezoelectric energy and so on as power generator. In this paper, a bimorph piezoelectric cantilever beam with a proof mass added on the free end has been studied in dynamic characteristics due to base excitation to occur from a circumference vibration with low frequency. The frequency equation of the beam be closely related to the ratio of beam and proof mass. Therefore, it is possible to estimate a proof mass due to the frequency of base excitation and a beam mass. The output voltages can be induced from theoretical calculation and it is dependent upon the beam length and thickness. The shorter beam length, the larger thickness, the output voltages increase

퍼지 추론을 이용한 피로균열성장단계의 특성화

趙熙燦 충주대 2001 한국교통대학교 논문집 Vol.36 No.1

The estimation of fatigue crack growth and fatigue life prediction of machinery and structures is important in design.There are three stages of fatigue crack growth.Characterization of each stage cannot be performed manually because of the massive amount and fuzziness of data.This paper proposes a new algorithm for characterization of the stage of fatigue crack growth using fuzzy inference.This method enables us to mechanically characterization without manual computation.

衝擊荷重에 따른 破壞擧動

趙熙燦 忠州大學校 1984 한국교통대학교 논문집 Vol.17 No.1

When We design pressure Vessels and structural components, We consider ultimate tensil stress, safty factor, toughness (absorbed energy), stress intensity factor, temperature, state of corrosion and so on particularly, We must consider toughness at that time. There are many measure method of toughness, but, generally, use the impact test. In this paper, 1 used charpy v - notch impact specimen of ductile material at normal temperature, and considered behavior of fracture due to impact on macro and microscopic level.

Production of Submicron Particles by Centrifugal Mill

조희찬,이훈 한국자원공학회 2007 Geosystem engineering Vol.10 No.4

A centrifugal mill can be advanced by changing the gyration diameter ratio (G/D). The submicron grinding characteristics of four different minerals (limestone, talc, illite and silica) were investigated at various operating conditions by using a centrifugal mill. The result was that the optimum G/D ratio to produce submicron particles was different for each mineral. The size distribution was modified by interpolation and the final median size of the product was 110 nm.

자원활용분야 게재논문을 통해 살펴본 시대적 연구경향 고찰

조희찬 한국자원공학회 2012 한국자원공학회지 Vol.49 No.5

This paper presents an analysis of historical patterns and R&D trends in mineral processing in Korea for the last 50 years. The analysis is based on the papers published in the Journal of the Korean Society for Geosystem Engineering for the time period 1960 through 2012. It shows that the number of papers related to mineral processing has steadily increased at an annual rate of 46% for the last 40 years. Separation/concentration was the most frequent topics in 1960’s, but in recent years, the topics has since diversified into other area and are fairly evenly divided between five different areas: separation/concentration, metallurgical processing, material processing, and recycling. 본고에서는 학회지에 수록된 자원 활용 분야의 논문에 대하여 시대별로 주요 관심 분야를 분석함으로써 학회의 시대적 변천사를 간접적으로 살펴보았다. 자원활용분야 논문 수는 1960년 이후 연 평균 46%의 증가율을 보였다. 1960년대는 분리/선별에 관한 논문이 가장 많았으나 후 점차 다양화 하여 최근에는 분리/선별, 제련, 소재, 리싸이클링 분야에 골고루 분포하고 있다.

크랙先端과 노치先端에서의 應力分布에 對한 考察

趙熙燦 忠州大學校 1982 한국교통대학교 논문집 Vol.15 No.1

As tensile loading (Mode I Defermation) acts on the notched or cracked thin plate (2-Demension), there occurs a local plastic zone in the notch tip or crack tip due to the stress concentration. In this paper, I considered the stress distribution of the tip plane in the plastic zone and the elastic zone. Particularly, I considered the stress distribution how to be effective by the local plasticity in the elastic zone.