• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.517-518
• /
• 2011

본 논문에서는 국내 원자력 발전소용 고압케이블의 열화평가를 위해 열적, 화학적 시험을 진행하였다. 최근 설계수명이 종료되는 원자력 발전소와 케이블들에 대한 열화평가 연구가 시작되고 있다. 그러나 현재까지 기초연구 수준에 머물러 있기 때문에 체계적인 열화평가 이루어지고 있지 않다. 따라서 본 논문에서는 국내 원전 고압케이블의 열적, 화학적 시험을 통해 기초 물성자료를 구축하고 열화평가에 이용하기 위해 본 시험을 수행하였다.

• Journal of the KSME
• /
• v.32 no.4
• /
• pp.358-370
• /
• 1992

균열이 형성되어 있는 설비가 고온에서 정하중을 받으면, 크립 조건에서 균열이 성장하여 파손이 발생한다. 이 때 잔여수명 평가법을 설명하기 위해 발전소 헤더의 경우를 예로하여 잔여수명 평가절차, 이에 필요한 기초이론 및 Cr-Mo강의 관련 재료 물성 데이터 등을 설명하였다. 현재 국내발전소들이 노후화되어 잔여수명평가의 필요성이 증대되고 있으므로, 이 분야의 연구 및 기 술개발은 시급하고 중요한 과제라고 생각된다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.33 no.9
• /
• pp.859-869
• /
• 2009

The sharp indenters such as Berkovich and conical indenters have a geometrical self-similarity in theory, but different materials have the same load-depth curve in case of single indentation. In this study, we analyze the load-depth curves of conical indenter with angles of indenter via finite element method. From FE analyses of dual-conical indentation test, we investigate the relationships between indentation parameters and load-deflection curves. With numerical regressions of obtained data, we finally propose indentation formulae for material properties evaluation. The proposed approach provides stress-strain curve and the values of elastic modulus, yield strength and strain-hardening exponent with an average error of less than 2%. It is also discussed that the method is valid for any elastically deforming indenters made of tungsten carbide and diamond for instance. The proposed indentation approach provides a substantial enhancement in accuracy compared with the prior methods.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.729-732
• /
• 2008

Naphthalenic admixture(PNS) has been widely used as main component of AE reducing agent among superplasticizers for concrete for a long time. However its noxiousness has been appointed because of formaldehyde compound applied during in synthetic process. In this study, AE reducing agent prepared using PNS and substituted-PNS agent(ECO-AEM) without formaldehyde compound added to concrete. For these agent, the basic performance of concrete and ecological affinity properties were evaluated and compared.

• 한국도로학회:학술대회논문집
• /
• 2009.11a
• /
• pp.167-170
• /
• 2009

• Magazine of RCR
• /
• v.14 no.2
• /
• pp.28-34
• /
• 2019

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.4 no.2
• /
• pp.74-84
• /
• 2009

The study aims that high quality recycled sand by wet manufacturing system can be used in practical way through basic material property. The basic material property test was done by 4 categories, dry manufacturing system (1) tandem and (2) parallel, wet manufacturing system (3) large capacity and (4) small capacity. RS-IV is the final production of (1) to (4) method, it is tested via KS F 2573 (recycled fine aggregate). RS-IV is satisfied with 4 items, those are absolute dry density, 0.08mm sieve throughput, clay lump amount, and organic impurity substance content. However, absorptivity item has problem in (1) and (2) method, (3) and (4) method are confirmed with norms 5% low. Also, the production quality of wet manufacturing system is better than dry manufacturing system in absolute dry density, absorptivity, 0.08mm sieve throughput, and clay lump amount.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.10
• /
• pp.1229-1237
• /
• 2013

In this study, the theory of spherical indentation based on incremental plasticity is extended to an indentation method for evaluating creep properties. Through finite element analysis (FEA), the point where the elastic strain effect is negligible and the creep strain gradient constant is taken as the optimum point for obtaining the equivalent strain rate and stress. Based on FE results for spherical indentation with various values of creep exponent and creep coefficient, we derive by regression an equation to calculate creep properties using two normalized variables. Finally a program is generated to calculate creep exponent and creep coefficient. With this method, we obtain from the load-depth curve creep exponents with an average error of less than 1.5 % and creep coefficients with an average error of less than 1.0 %.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.1
• /
• pp.17-28
• /
• 2012

In this study, we suggest a method for material property evaluation by dual-triangular pyramidal indenters using the reverse analysis. First, we demonstrated that load-displacement curves of conical and triangular pyramidal indenters are different for the same material. For this reason, an independent research on the triangular pyramidal indenter is needed. From FE indentation analyses on various materials, we then investigated the relationships among material properties, indentation parameters and load-displacement curves. From this, we established property evaluation formula using dual-triangular pyramidal indenters having two different half-included-angles. The approach provides the values of elastic modulus, yield strength and strain-hardening exponent within an average error of 3% for various materials.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.2 no.1
• /
• pp.10-18
• /
• 2014

This study carried out to evaluate the hydration heat analysis and fundamental characteristics such as air content, slump, compressive strength and dry shrinkage according to concrete with premixed cement, ternary concrete and OPC concrete for using concrete with premixed cement. The results of experiment are founded that concrete with premixed cement have sufficient performances such as workability, compressive strength and dry shrinkage. Also, the results of hydration heat analysis are founded that concrete with premixed cement have more performance than ternary concrete and OPC concrete at a point of view for the quality control such as thermal crack reducing and economic benefit. Therefore, it is desirable that concrete with premixed cement should be used to rise durability performance and convenience of maintenance.