• Title/Summary/Keyword: defense structures

Search Result 280, Processing Time 0.033 seconds

A Numerical Study on the Dynamic Characteristics of Power Metal using Split Hopkinson Pressure Bar (홉킨스바 장치를 이용한 분말금속의 동적 특성에 관한 수치해석적 연구)

  • Hwang, Du-Sun;Lee, Seung-U;Hong, Seong-In
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.24 no.12
    • /
    • pp.2972-2979
    • /
    • 2000
  • Dynamic characteristics of powder metal is very important to mechanical structures requiring high strength or endurance for impact loading. But owing to distinctive property of powder metal, that is relative, it has been investigated restrictively compared to static characteristics. The objectives of this study is to investigate dynamic characteristics of powder metal and compare it to a fully density material. To find the characteristics, an explicit finite element method is used for simulation of Split Hopkinson Pressure Bar experiment based on the stress wave propagation theory. We obtained a dynamic stress-strain relationship and dynamic behavior of powder metal, as well as the variation of material properties during dynamic deformation.

QSPR Studies on Impact Sensitivities of High Energy Density Molecules

  • Kim, Chan-Kyung;Cho, Soo-Gyeong;Li, Jun;Kim, Chang-Kon;Lee, Hai-Whang
    • Bulletin of the Korean Chemical Society
    • /
    • v.32 no.12
    • /
    • pp.4341-4346
    • /
    • 2011
  • Impact sensitivity, one of the most important screening factors for novel high energy density materials (HEDMs), was predicted by use of quantitative structure-property relationship (QSPR) based on the electrostatic potential (ESP) values calculated on the van der Waals molecular surface (MSEP). Among various 3D descriptors derived from MSEP, we utilized total and positive variance of MSEP, and devised a new QSPR equation by combining three other parameters. We employed 37 HEDMs bearing a benzene scaffold and nitro substituents, which were also utilized by Rice and Hare. All the molecular structures were optimized at the B3LYP/6-31G(d) level of theory and confirmed as minima by the frequency calculations. Our new QSPR equation provided a good result to predict the impact sensitivities of the molecules in the training set including zwitterionic molecules.

An Experimental Study on the Mechanical Properties of T-Joints Structure using CFRP/Al Honeycomb Sandwich Composite (CFRP/Al하니콤 샌드위치 복합재 T-Joint 구조물의 기계적 물성에 대한 실험적 연구)

  • Cho, Ki-Dae;Ha, Sung-Rok;Kang, Kwang-Hee;Kim, Jie-Eok;Yang, Sung-Chul
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.29 no.3
    • /
    • pp.313-318
    • /
    • 2012
  • Application of composite structures on naval ships strongly depends on the mechanical strength and collapse behavior of the T-joints of the whole structure. Because of the weight advantages over single skin composite and bolt fastening joining, three types of T-joints using both honeycomb sandwich composite and adhesive bonding were suggested to determine the effect of T-joint configuration. It was found that joining with a urethane foam block and overlaminates using the secondary co-bonding technique improves T-joint strength.

Finite element analysis of RC walls with different geometries under impact loading

  • Husem, Metin;Cosgun, Suleyman I.;Sesli, Hasan
    • Computers and Concrete
    • /
    • v.21 no.5
    • /
    • pp.583-592
    • /
    • 2018
  • Today, buildings are exposed to the effects such as explosion and impact loads. Usually, explosion and impact loads that act on the buildings such as nuclear power plants, airports, defense industry and military facilities, can occur occasionally on the normal buildings because of some reasons like drop weight impacts, natural gas system explosions, and terrorist attacks. Therefore, it has become important to examine the behavior of reinforced concrete (RC) structures under impact loading. Development of computational mechanics has facilitated the modeling of such load conditions. In this study, three kinds of RC walls that have different geometric forms (square, ellipse, and circle) and used in guardhouses with same usage area were modeled with Abaqus finite element software. The three configurations were subjected to the same impact energy to determine the geometric form that gives the best behavior under the impact loading. As a result of the analyses, the transverse impact forces and failure modes of RC walls under impact loading were obtained. Circular formed (CF) reinforced concrete wall which has same impact resistance in each direction had more advantages. Nonetheless, in the case of the impact loading occurring in the major axis direction of the ellipse (EF-1), the elliptical formed reinforced concrete wall has higher impact resistance.

A Study on Impact of an Adjacent Structure by a Rocket Plume (유도탄 화염이 인접 구조물에 미치는 영향 연구)

  • Yang, Young-Rok
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.42 no.6
    • /
    • pp.488-494
    • /
    • 2014
  • Rocket Plumes can cause serious damage to launch vehicles and adjacent structures. This paper describes the impact of an adjacent structure by a rocket plume. Each parameter related with dynamic behavior of a missile is modeled with probabilistic distributions of variables. Flyout analyses of initial behavior of a vertically launched missile are performed using Monte-Carlo simulation and flow-motion analyses were conducted by using CFD. In this way, when a missile is fired by a ship, the impact of an adjacent structure by a rocket plume was analyzed.

Quality Management Study of Weapon System using Ontology (Ontology를 활용한 무기체계 품질경영 연구)

  • An, Youngjun;Seo, Yoonho
    • Journal of Korean Society for Quality Management
    • /
    • v.44 no.4
    • /
    • pp.735-749
    • /
    • 2016
  • Purpose: This study is addressing the establishment of the knowledge information system supplying the quality management of weapon system. It is going to support the continuous quality management through the linkages and integration between the product structure and the quality information. Methods: The interrelated relationship of the product structure information and quality information of weapon system would be expressed explicitly by taking advantage of the ontology concept. The quality information of distributed systems would be integrated through the SOA(Service Oriented Architecture)-based Web services. After defining the inference rules, which could be utilized in the quality management, in the constructed knowledge information system, the quality information would be inferred through the queries. Results: By building the integrated quality information knowledge system through the ontology and SOA, the connectivity between the product structures and dispersed quality information was enhanced. The utility and applicability of this study were checked up through the inferences on the products and quality information by using the information built by the semantic relationship of facts. Conclusion: We established the knowledge and information system as a systematic approach to support the quality management of weapon system. This is not affected by the organizations and systems, and it seems that it could be utilized across the quality management as the efficient knowledge sharing architecture supporting the quality management of weapon systems in the aspect of the product integration.

Numerical Analysis for Shotcrete Lining at SCL Tunnel in NS2 Transmission Cable Tunnel Project in Singapore (싱가포르 케이블터널 프로젝트 NS2현장 SCL 터널에서의 숏크리트 라이닝의 변형거동 특성)

  • Kwang, Han Fook;Kim, Young Geun
    • Tunnel and Underground Space
    • /
    • v.27 no.4
    • /
    • pp.185-194
    • /
    • 2017
  • This technical paper is a study on the unique displacements of Shotcrete Lining at the mined tunnel during excavation period through deep consideration with real time data from monitoring instrumentations correlation with the numerical analysis to identify the rock stresses and the rock spring points at the working face of the Conventional tunnelling by the Drill and Blast, based on the geological face mapping results of the project NS2, Transmission cable tunnel project in Singapore. The created geometry of numerical model was prepared to the real mined tunnel construction site including, vertical shaft, construction adit, tunnel junction area, and 2 enlargement caverns. The convergence measurements by the monitoring instrumentation were performed during the tunnel excavation and shaft sinking construction stages to guarantee the safety of complicated underground structures.

A Parametric Study of Ridge-cut Explosive Bolts using Hydrocodes

  • Lee, Juho;Han, Jae-Hung;Lee, YeungJo;Lee, Hyoungjin
    • International Journal of Aeronautical and Space Sciences
    • /
    • v.16 no.1
    • /
    • pp.50-63
    • /
    • 2015
  • Explosive bolts are one of pyrotechnic release devices, which are highly reliable and efficient for a built-in release. Among them, ridge-cut explosive bolts which utilize shock wave generated by detonation to separate bolt body produce minimal fragments, little swelling and clean breaks. In this study, separation phenomena of ridge-cut explosive bolts or ridge-cut mechanism are computationally analyzed using Hydrocodes. To analyze separation mechanism of ridge-cut explosive bolts, fluid-structure interactions with complex material modeling are essential. For modeling of high explosives (RDX and PETN), Euler elements with Jones-Wilkins-Lee E.O.S. are utilized. For Lagrange elements of bolt body structures, shock E.O.S., Johnson-Cook strength model, and principal stress failure criteria are used. From the computational analysis of the author's explosive bolt model, computational analysis framework is verified and perfected with tuned failure criteria. Practical design improvements are also suggested based on a parametric study. Some design parameters, such as explosive weights, ridge angle, and ridge position, are chosen that might affect the separation reliability; and analysis is carried out for several designs. The results of this study provide useful information to avoid unnecessary separation experiments related with design parameters.

Noise Reduction by Using Eigenfilter in Cyclic Prefix System Based on SNR (SNR에 기초한 순환적 전치 부호를 가지는 시스템에서 고유필터를 사용한 잡음 제거)

  • Kim, Jin-Goog
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.39B no.10
    • /
    • pp.700-707
    • /
    • 2014
  • In this paper, we propose the noise reduction method by using the eigenfilter in cyclic prefix system based on SNR. To obtain the signal eigenvectors for the eigenfiltering, we propose a method of obtaining the autocorrelation matrix by exploiting the circulant property of the received block which results from the cyclic extension of the OFDM symbol. Since the structures of the transmitter and the receiver are not changed, the proposed method is easy to apply to the conventional OFDM system. To verify the proposed method, we evaluate the persistency of excitation (POE) criterion for the input and demonstrate the effectiveness of the proposed method in the simulation results.

Purification and Characterization of the Functional Catalytic Domain of PKR-Like Endoplasmic Reticulum Kinase Expressed in Escherichia coli

  • Yun Jin-A;Chung Ho-Young;Kim Seong-Jun;Cho Hyun-Soo;Oh Jong-Won
    • Journal of Microbiology and Biotechnology
    • /
    • v.16 no.9
    • /
    • pp.1453-1458
    • /
    • 2006
  • PKR-like endoplasmic reticulum (ER) kinase (PERK) is a type I transmembrane ER-resident protein containing a cytoplasmic catalytic domain with a Ser/Thr kinase activity, which is most closely related to the eukaryotic translation initiation factor-$2{\alpha}$ ($eIF2{\alpha}$) kinase PKR involved in the antiviral defense pathway by interferon. We cloned and expressed the PERK C-terminal kinase domain (cPERK) in Escherichia coli. Like PERK activation in cells under ER stress, wild-type cPERK underwent autophosphorylation when overexpressed in E. coli, whereas the cPERK(K621M) with a methionine substitution for the lysine at amino acid 621 lost the autophosphorylation activity. The activated form cPERK which was purified to near homogeneity, formed an oligomer and was able to trans-phosphorylate specifically its cellular substrate $eIF2{\alpha}$. Two-dimensional phosphoamino acids analysis revealed that phosphorylation of cPERK occurs at the Ser and Thr residues. The functionally active recombinant cPERK, and its inactive mutant should be useful for the analysis of biochemical functions of PERK and for the determination of their three-dimensional structures.