• Computers and Concrete
• /
• 제19권2호
• /
• pp.133-142
• /
• 2017

Two-stage concrete (TSC), also known as pre-placed aggregate concrete, is characterized by its unique placement technique, whereby the coarse aggregate is first placed in the formwork, then injected with a special grout. Despite its superior sustainability and technical features, TSC has remained a basic concrete technology without much use of modern chemical admixtures, new binders, fiber reinforcement or other emerging additions. In the present study, an experimental database for TSC was built. Different types of cementitious binders (single, binary, and ternary) comprising ordinary portland cement, fly ash, silica fume, and metakaolin were used to produce the various TSC mixtures. Different dosages of steel fibres having different lengths were also incorporated to enhance the mechanical properties of TSC. The database thus created was used to develop fuzzy logic models as predictive tools for the grout flowability and mechanical properties of TSC mixtures. The performance of the developed models was evaluated using statistical parameters and error analyses. The results indicate that the fuzzy logic models thus developed can be powerful tools for predicting the TSC grout flowability and mechanical properties and a useful aid for the design of TSC mixtures.

• Nuclear Engineering and Technology
• /
• 제54권12호
• /
• pp.4393-4411
• /
• 2022

In recent years, beryllium oxide has been widely utilized in multiple compact nuclear reactors as the neutron moderator, the neutron reflector or the matrix material with dispersed nuclear fuels due to its prominent properties. In the past 70 years, beryllium oxide has been studied extensively, but rarely been systematically organized. This article provides a systematic review of the application history, thermal properties, mechanical properties, corrosion behavior and fabrication methods of beryllium oxide. Data from previous literature are extracted and sorted out, and all of these original data are attached as the supplementary material, so that subsequent researchers can utilize this paper as a database for beryllium oxide research in reactor design or simulation analysis, etc. In addition, this review article also attempts to point out the insufficiency of research on beryllium oxide, and the possible key research areas about beryllium oxide in the future.

• 연구논문집
• /
• 통권32호
• /
• pp.77-84
• /
• 2002

A martensitic precipitation hardening stainless steel, 17-4PH has been widely used in the aircraft, chemical and nuclear industries for long time, owing to the excellent mechanical properties with corrosion resistance that can be achieved by simple heat treatment. The microstructure and mechanical properties of the 17-4PH stainless steel cast parts for aircraft, such as impeller, are largely affected by heat treatment condition. But the database of heat treatment has not been clearly established in the domestic investment casting industries because the domestic aerospace, industry lags behind the advanced countries. In this study, the microstructural evolution and mechanical properties of cast 17-4PH stainless steel depending on the heat treatment conditions and aging at $400^{\circ}C$ were investigated.

• 항공우주기술
• /
• 제3권2호
• /
• pp.1-6
• /
• 2004

위성을 설계함에 있어 질량제어 계획을 작성하고 질량자료를 유지하며 시스템의 질량특성을 계산하고 제어하는 것은 기계 시스템 담당자가 수행하는 임무 중에 하나이다. 위성의 질량특성은 자료수집, 특성예측 그리고 실제 측정의 순서로 설계 및 제작이 진행됨에 따라 수행된다. 질량특성 데이터베이스는 설계과정을 통하여 작성하게 되며 질량특성 측정 시험을 수행하여 데이터베이스의 신뢰성을 확인할 수 있어야 한다. 본 논문에서는 위성에서의 질량 제어계획의 일반적인 내용과 시스템 수준의 질량중심 및 관성 모멘트 계산과 관련된 여러 가지 구체적인 사항을 고려한 이론적 질량 특성 데이터베이스를 개발하고, 다목적 실용위성 2호 개발을 수행하면서 얻게 된 실제적인 자료/경험을 토대로 본 연구에서 개발된 데이터베이스의 신뢰성을 확인하였다.

• 열처리공학회지
• /
• 제34권1호
• /
• pp.10-16
• /
• 2021

Exhaust manifold is a very important component that is directly connected to air environment pollution and that requires strict mechanical properties such as high temperature fatigue and oxidation. Among stainless steels, the ferritic stainless steel with body-centered cubic structure shows excellent resistance of stress-corrosion cracking, ferromagnetic at room temperature, very excellent cold workability and may not be enhanced by heat treatment. The microstructural characteristics of four cast ferritic stainless steels which are high heat-resistant materials, were analyzed. By comparing and evaluating the mechanical properties at room temperature and high temperature in a range of 400℃~800℃, a database was established to control and predict the required properties and the mechanical properties of the final product. The precipitates of cast ferritic stainless steels were analyzed and the high-temperature deformation characteristics were evaluated by comparative analysis of hardness and tensile characteristics of four steels at room temperature and from 400℃ to 800℃.

• 대한기계학회논문집A
• /
• 제25권6호
• /
• pp.1015-1022
• /
• 2001

The objective of this paper is to develop an expert system called NPIES for nuclear piping integrity. This paper describes the structure and the development strategy of the NPIES system. The NPIES system consists of 3 part; the data input part, the analysis part and the output part. The data input part consists of the material properties database module and the suer interface module. The analysis part consists of the LEFM, CDFD, J/T, limit load modules and the 12 analysis routines for different cracks and loading conditions are provided respectively. Analysis results are presented to screen, printer and text file in the output part. Several case studies on circumferentially cracked piping were performed to evaluate the accuracy and the usefulness of the code. Maximum piping loads predicted by the NPIES system agreed well with those by the 3-dimensional finite element analysis. In addition, even if the material properties were not fully given, the NPIES system provided reasonable evaluation results with the predicted material properties inferred from the material properties database module.

• Steel and Composite Structures
• /
• 제31권5호
• /
• pp.517-527
• /
• 2019

To move forward in large steps rather than in small increments, the community would benefit from a systematic and comprehensive database of multi-scale composites and measured properties, driven by comprehensive studies with a full range of types of fiber-reinforced polymers. The multi-scale hierarchy is a promising chemical approach that provides superior performance in synergistically integrated microstructured fibers and nanostructured materials in composite applications. Achieving high-efficiency thermal conductivity and mechanical properties with a simple surface treatment on single-walled carbon nanotubes (SWCNTs) is important for multi-scale composites. The main purpose of the project is to introduce ozone-treated SWCNTs between an epoxy matrix and basalt fibers to improve mechanical properties and thermal conductivity by enhancing dispersion and interfacial adhesion. The obvious advantage of this approach is that it is much more effective than the conventional approach at improving the thermal conductivity and mechanical properties of materials under an equivalent load, and shows particularly significant improvement for high loads. Such an effort could accelerate the conversion of multi-scale composites into high performance materials and provide more rational guidance and fundamental understanding towards realizing the theoretical limits of thermal and mechanical properties.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.84-89
• /
• 2007

In order to guarantee the safety of the facility systems, one of the essential components is information on mechanical properties of materials used for the construction. However, acquisition or accumulation of the mechanical property data in industrial fields is limited because this operation does not yield profit, excepting few materials production companies. Corresponding to the urgent needs and poor economical features, the MOCIE has founded the National Center for Standard Reference Data in the KRISS and also designated the Data Center of Mechanical Properties for Metallic Materials (DCMP) as a principal operating section. The DCMP plays roles of collection, edition and evaluation of the mechanical data and development of reference standards. In this study, several functions of the DCMP and standardization procedures of mechanical properties data will be introduced the prospective of standard reference researches will be discussed based on active feedbacks from industrial fields.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.61-66
• /
• 2004

Fracture toughness database system was developed with Visual Foxpro 6.0 and operates in MS Windows environment. The database system contains 10,278 sets of $K_{IC}$ data, 7,046 sets of $K_{C}$ data, 784 sets of $J_{IC}$ data, 571 sets of CTOD data, 62 sets of $K_{a}$ data and 26 sets of $K_{Id}$ data. The data were collected from JSMS(Society of Material Science, Japan) fracture toughness data book and USAF(United States Air Force) crack growth database. In addition, the database was applied to predicting $K_{IC}$ from tensile material properties using artificial neural networks.

• 로봇학회논문지
• /
• 제11권3호
• /
• pp.133-139
• /
• 2016

Increasing interest of human health, building bio-database (Bio DB) has been become a hot issue in life science. Consequently, Single Cell Analysis (SCA) which can explain biodiversity of lives has been a significant factor for building Bio DB. In numerous studies from these analyses, they have been showed that mechanical properties of cells can serve explanation of biological heterogeneity and criterion of disease states. Therefore, measuring mechanical properties of cells have great potential to be used in bio-medical applications. However, traditionally, many researchers have undergone difficult and time consuming work because handling small sized cells usually requires high-skilled technique. Thus, this paper shows robotized stiffness measurement technique using fixed ended beam sensor, precision motorized stage and substrate which have wall structure.