교류가 흐를 때 주위에 생기는 유도 자기장과 유도 전기장

연규황,임은지 한국물리학회 2014 새물리 Vol.64 No.5

The magnetic field induced by a direct current is inversely proportional to the distance from the current flow. However, when a time-dependent current flows, it is not inversely proportional to the distance from the current flow, and an electric field is induced, along with the magnetic field. When a capacitor is connected to a circuit in which a direct current flows, the current decays in an extremely short time. We point out an inconsistency in the postulate often used to explain Maxwell’s displacement current in many physics textbooks. When an alternating current is carried in two long, straight wire and a capacitor is inserted between the wires, an electric field and a magnetic field are induced around the inside and the outside of both the wires and the capacitor. The result is the same as that of the well-known induced electric and magnetic fields when a direct current is carried in a long, straight wire. 일정한 전류가 흐를 때 유도되는 자기장은 거리에 반비례한다. 그러나 일정하지 않은 전류가 흐를 때는 자기장뿐만 아니라 전기장도 유도 되고 유도자기장이 거리에 반비례하지도 않는다. 직류가 흐를 때 축전기를 연결하면 전류 흐름이 짧은 시간 내에 급격히 줄어들어 더 이상 흐르지 않는다. Maxwell 변위 전류를 설명할 때 물리적으로 모순된 교과서의 가정을 지적하고, 무한히 긴 도선에 교류 전류가 흐를 때 도선 내부와 외부에서 유도 전기장과 유도 자기장을 구한다. 축전기 내에서 유도 전기장과 자기장도 구한다. 직류가 흐를 경우인 잘 알려진 결과로 각각 전기장과 자기장이 유도 되는가도 점검한다.

Plastic Property Identification Using Surface Displacement Field from Vickers Indentation Testing

D. Park(박동휘),N. Kim(김낙수) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

An indentation testing is one of the methods to identify material properties. In this research, a method to identify plastic property of a material using surface displacement field generated from a Vickers indentation testing is proposed. The plastic property is defined using Swift type flow stress curve. Digital image correlation technique is adopted to measure the surface displacement field. Finite element simulations have been conducted to generate a database for the surface displacement field with Swift type flow stress coefficients and the Coulomb friction coefficient. Normalization of the displacement field using indentation load is developed which helps to reduce the size of the database and select the indentation load in the experiment. Al 6061 specimen is adopted to verify the plastic property identification method. Plastic property of Al 6061 is identified using tensile tests. Vickers indentation tests have been done on the same material and its plastic property is extracted from the measured surface displacement fields. The identified Swift flow stress coefficients are compared and the maximum difference is 5.4%.

야전운용제원 RAM 분석 결과를 활용한 함정 배수량과 신뢰도의 상관관계에 관한 연구

조은별(Eun-Byeol Jo),정영인(Young-In Jung),하성철(Sung-Chul Ha) 한국신뢰성학회 2023 신뢰성응용연구 Vol.23 No.1

Purpose: To examine the correlation between warship displacement–associated with total life cycle cost and warship capability–and reliability using field data Reliability, Availability, and Maintainability (RAM) analysis results. Methods: The Defense Agency for Technology and Quality recorded data on existing warships beginning in 2014. A field data RAM analysis was conducted on the data using Microsoft Excel correlation analysis and trend line. The results were analyzed to determine the correlation between warship displacement and reliability. Results: The correlation between warship light displacement and basic reliability was greater than mission reliability; the correlation between the warship displacement and basic reliability was declining. The basic reliability decreased by -0.0017 as the light displacement increased. Conclusion: The effective target reliability setting method can be discovered by; (1) utilizing the correlation between warship light displacement and basic reliability, (2) conducting additional research to discover other factors affecting reliability and (3) applying various statistical techniques on the data.

현장인발시험을 통한 가압 그라우팅 쏘일네일의 변형특성

천병식(Chun Byungsik),박주석(Park Joosuck),박시삼(Park Sisam),정종주(Jung Jongju),공진영(Kong Jinyoung) 한국지반환경공학회 2008 한국지반환경공학회논문집 Vol.9 No.2

본 연구에서는 PGSN(Pressurized Grouting Soil Nailing) 시스템이라는 가압 그라우팅 쏘일네일링 공법을 고안하였으며, 본 공법의 보강제의 길이변화 및 보강재의 변화 등의 설계인자에 따른 거동변화를 파악해 보기 위해 변위제어방식의 현장인발시험을 수행하였다.본 연구에서 수행한9차례의 현장인발시험에서 그라우트 주입비의 변화를 살펴 보기위해 계측을 수행하였으며, 단기거동특성을 평가하기 위해 일반 쏘일네일링 시스템과 비교해 보았다. 가압 그라우트 쏘일네일링 공법의 인발거동 특성을 통해, 중요한 설계인자인 주입압 및 그라우트 주입비 등의 영향을 살펴보았다.시험 결과 가압효과에 따른 인발변형 특성은 중력식 그라우팅 쏘일네일에 비해 가압 그라우팅 쏘일네일의 경우 유발되는 변위량이 30~36% 정도 감소하였고, 보강재 변화에 따른 인발 특성을 살펴보면 이형철근에 비해 강관의 경우 유발되는 변위량이 31~32% 정도 감소하는 것으로 나타났다. In this study, a newly modified soil nailing technology named as the PGSN (Pressurized Grouting Soil Nailing) system is proposed. Effects of various factors related to the design of the pressurized grouting soil nailing system, such as the length of re-bars and type of reinforcement materials, were examined throughout a series of the displacement-controlled field pull-out tests. 9 displacement-controlled field pull-out tests were performed and the ratio of injected grout volume to grout hole volume were also evaluated based on the measurements. In addition, short-term characteristics of pull-out deformations of the newly proposed PGSN system were analyzed and compared with those of the ordinary soil nailing system by carrying out field pull-out tests. The test results were shown that the displacements of pressurized grouting soil nailing system were decreased 30~36% in comparison with using gravity grouting soil nailing system by the pressurized effect. The displacements of steel tube were diminished 31~32% comparison with using deformed bar by the reinforcement type change from the field pull-out tests.

Evaluation of responses of semi-rigid frames at target displacements predicted by the nonlinear static analysis

Vijay Sharma,Mahendra K. Shrimali,Shiv D. Bharti,Tushar K. Datta 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.4

Responses of semi-rigid frames having different degrees of semi-rigidity obtained by the nonlinear static analysis (NSA) are evaluated at specific target displacements by comparing them with those obtained by the nonlinear time-history analysis (NTHA) for scaled earthquakes. The peak ground accelerations (PGA) of the earthquakes are scaled such that the obtained peak top story displacements match with the target displacements. Three different types of earthquakes are considered, namely, far-field and near-field earthquakes with directivity and fling-step effects. In order to make the study a comprehensive one, three degrees of semi-rigidity (one fully rigid and the other two semi-rigid), and two frames having different heights are considered. An ensemble of five-time histories of ground motion is included in each type of earthquake. A large number of responses are considered in the study. They include the peak top-story displacement, maximum inter-story drift ratio, peak base shear, total number of plastic hinges, and square root of sum of the squares (SRSS) of the maximum plastic hinge rotations. Results of the study indicate that the nonlinear static analysis provides a fairly good estimate of the peak values of top-story displacements, inter-story drift ratio (for shorter frame), peak base shear and number of plastic hinges; however, the SRSS of maximum plastic hinge rotations in semi-rigid frames are considerably more in the nonlinear static analysis as compared to the nonlinear time history analysis.

사면의 지표변위 측정을 위한 레이저 거리측정기의 활용

조용찬(Yong-Chan Cho),송영석(Young-Suk Song) 한국지반신소재학회 2014 한국지반신소재학회 논문집 Vol.13 No.1

본 연구에서는 레이저 거리측정기를 이용하여 사면의 지표변위를 효과적으로 측정하는 방법을 제안하였다. 기존 사면의 지표변위 혹은 지중변위를 측정하기 위한 복잡하고 고가의 장비 대신에 제안된 방법을 적용할 경우 보다 간편하고 쉽게 지표변위를 측정할 수 있다. 레이저 거리측정기는 적색 레이저를 측정을 원하는 피사체에 시준하면 반사되는 레이저를 이용해 거리를 측정하는 기기로 작동방법이 용이하고 측정정밀도도 아주 높으며, 가격이 저렴한 장점이 있다. 제안된 방법의 활용가능성을 검토하기 위하여 실제 지표변위가 지속적으로 발생되는 현장에 적용하였다. 대상지역은 석탄폐석 적치장의 영향으로 하부에 위치하는 절취사면 및 자연사면의 여러 위치에서 지표변위가 발생된 현장이다. 대상지역에 지표변위를 직접적으로 측정하기 위하여 6개의 측정구간과 26개의 측정지점을 선정하였다. 일정한 기간 동안 제안된 방법을 이용하여 측정한 결과 누적 지표변 위량 뿐만 아니라 지표변위속도까지 측정이 가능하였다. 그리고 이들 결과를 종합적으로 분석하여 지표변위 발생방향을 확인 및 예측할 수 있다. In this study, the method to measure effectively the ground surface displacement of slope was proposed using the Laser Distance Measurer (LDM). Applying the proposed technique is more simple and easier than the complicated and high-priced instrument to measure the ground surface displacement. LDM is an instrument that the red laser aimed at the target and then the reflected laser used for calculating the distance. The advantages of LDM are easy operating method, high measurement precision and lower in price. To check the feasibility, the proposed method applied to the real site that the ground surface displacement of slope was occurred continuously. The ground surface displacements were occurred in various points of the natural and cut slopes located at the lower part of coal mine waste heap due to the load of waste heap. To measure directly the ground surface displacement in this site, 6 measurement sections and 26 measurement points were selected. As the result of the displacement measured by the proposed technique within a certain period time, the accumulative ground surface displacement could be measured as well as the velocity of displacement could be estimated. Also, the progress direction of ground surface displacement can be confirmed and predicted through the analysis of all measured result.

New twelve node serendipity quadrilateral plate bending element based on Mindlin-Reissner theory using Integrated Force Method

Dhananjaya, H.R.,Nagabhushanam, J.,Pandey, P.C.,Jumaat, Mohd. Zamin Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.5

The Integrated Force Method (IFM) is a novel matrix formulation developed for analyzing the civil, mechanical and aerospace engineering structures. In this method all independent/internal forces are treated as unknown variables which are calculated by simultaneously imposing equations of equilibrium and compatibility conditions. This paper presents a new 12-node serendipity quadrilateral plate bending element MQP12 for the analysis of thin and thick plate problems using IFM. The Mindlin-Reissner plate theory has been employed in the formulation which accounts the effect of shear deformation. The performance of this new element with respect to accuracy and convergence is studied by analyzing many standard benchmark plate bending problems. The results of the new element MQP12 are compared with those of displacement-based 12-node plate bending elements available in the literature. The results are also compared with exact solutions. The new element MQP12 is free from shear locking and performs excellent for both thin and moderately thick plate bending situations.

Performance of sandwich structure strengthened by pyramid cover under blast effect

Mazek, Sherif A. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4

The number of explosive attacks on civilian structures has recently increased. Protection of structure subjected to blast load remains quite sophisticated to predict. The use of the pyramid cover system (PCS) to strengthen sandwich structures against a blast terror has great interests from engineering experts in structural retrofitting. The sandwich steel structure performance under the impact of blast wave effect is highlighted. A 3-D numerical model is proposed to study the PCS layer to strengthen sandwich steel structures using finite element analysis (FEA). Hexagonal core sandwich (XCS) steel panels are used to study structural retrofitting using the PCS layer. Field blast test is conducted. The study presents a comparison between the results obtained by both the field blast test and the FEA to validate the accuracy of the 3-D finite element model. The effects are expressed in terms of displacement-time history of the sandwich steel panels and pressure-time history effect on the sandwich steel panels as the explosive wave propagates. The results obtained by the field blast test have a good agreement with those obtained by the numerical model. The PCS layer improves the sandwich steel panel performance under impact of detonating different TNT explosive charges.

New twelve node serendipity quadrilateral plate bending element based on Mindlin-Reissner theory using Integrated Force Method

H.R. Dhananjaya,J. Nagabhushanam,P.C. Pandey,Mohd. Zamin Jumaat 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.5

The Integrated Force Method (IFM) is a novel matrix formulation developed for analyzing the civil, mechanical and aerospace engineering structures. In this method all independent/internal forces are treated as unknown variables which are calculated by simultaneously imposing equations of equilibrium and compatibility conditions. This paper presents a new 12-node serendipity quadrilateral plate bending element MQP12 for the analysis of thin and thick plate problems using IFM. The Mindlin-Reissner plate theory has been employed in the formulation which accounts the effect of shear deformation. The performance of this new element with respect to accuracy and convergence is studied by analyzing many standard benchmark plate bending problems. The results of the new element MQP12 are compared with those of displacement-based 12-node plate bending elements available in the literature. The results are also compared with exact solutions. The new element MQP12 is free from shear locking and performs excellent for both thin and moderately thick plate bending situations.

Performance of sandwich structure strengthened by pyramid cover under blast effect

Sherif A. Mazek 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.4

The number of explosive attacks on civilian structures has recently increased. Protection of structure subjected to blast load remains quite sophisticated to predict. The use of the pyramid cover system (PCS) to strengthen sandwich structures against a blast terror has great interests from engineering experts instructural retrofitting. The sandwich steel structure performance under the impact of blast wave effect is highlighted. A 3-D numerical model is proposed to study the PCS layer to strengthen sandwich steel structures using finite element analysis (FEA). Hexagonal core sandwich (XCS) steel panels are used to study structural retrofitting using the PCS layer. Field blast test is conducted. The study presents a comparison between the results obtained by both the field blast test and the FEA to validate the accuracy of the 3-D finite element model. The effects are expressed in terms of displacement-time history of thesandwich steel panels and pressure-time history effect on the sandwich steel panels as the explosive wave propagates. The results obtained by the field blast test have a good agreement with those obtained by the numerical model. The PCS layer improves the sandwich steel panel performance under impact of detonating different TNT explosive charges.