• 제목/요약/키워드: Mechanical field analysis

검색결과 1,932건 처리시간 0.034초

Cable anomaly detection driven by spatiotemporal correlation dissimilarity measurements of bridge grouped cable forces

  • Dong-Hui, Yang;Hai-Lun, Gu;Ting-Hua, Yi;Zhan-Jun, Wu
    • Smart Structures and Systems
    • /
    • 제30권6호
    • /
    • pp.661-671
    • /
    • 2022
  • Stayed cables are the key components for transmitting loads in cable-stayed bridges. Therefore, it is very important to evaluate the cable force condition to ensure bridge safety. An online condition assessment and anomaly localization method is proposed for cables based on the spatiotemporal correlation of grouped cable forces. First, an anomaly sensitive feature index is obtained based on the distribution characteristics of grouped cable forces. Second, an adaptive anomaly detection method based on the k-nearest neighbor rule is used to perform dissimilarity measurements on the extracted feature index, and such a method can effectively remove the interference of environment factors and vehicle loads on online condition assessment of the grouped cable forces. Furthermore, an online anomaly isolation and localization method for stay cables is established, and the complete decomposition contributions method is used to decompose the feature matrix of the grouped cable forces and build an anomaly isolation index. Finally, case studies were carried out to validate the proposed method using an in-service cable-stayed bridge equipped with a structural health monitoring system. The results show that the proposed approach is sensitive to the abnormal distribution of grouped cable forces and is robust to the influence of interference factors. In addition, the proposed approach can also localize the cables with abnormal cable forces online, which can be successfully applied to the field monitoring of cables for cable-stayed bridges.

Engineering characteristics of dune sand-fine marble waste mixtures

  • Qureshi, Mohsin U.;Mahmood, Zafar;Farooq, Qazi U.;Qureshi, Qadir B.I.L.;Al-Handasi, Hajar;Chang, Ilhan
    • Geomechanics and Engineering
    • /
    • 제28권6호
    • /
    • pp.547-557
    • /
    • 2022
  • Dune sands are poorly graded collapsible soils lacking fines. This experimental study explored the technical feasibility of sustainable invigoration of fine waste materials to improve the geotechnical properties of dune sand. The fine waste considered in this study is fine marble waste. The fine waste powder was mixed with dune sand at different contents (5, 10,15, 20, 25, 50%), where the gradation, void ratio, compaction, and shear strength characteristics were assessed for each fine marble waste -dune sand blend. The geotechnical properties of the dune sand-fine marble waste mix delineated in this study reveal the enhancement in compaction and gradation characteristics of dune sand. According to the results, the binary mixture of dune sand with 20% of fine marble waste gives the highest maximum dry density and results in shear strength improvement. In addition, a numerical study is conducted for the practical application of the binary mix in the field and tested for an isolated shallow foundation. The elemental analysis of the fine marble waste confirms that the material is non-contaminated and can be employed for engineering applications. Furthermore, the numerical study elucidated that the shallow surface replacement of the site with the dune sand mixed with 20% fine marble waste gives optimal performance in terms of stress generation and settlement behavior of an isolated footing. For a sustainable mechanical performance of the fine marble waste mixed sand, an optimum dose of 20% fine marble waste is recommended, and some correlations are proposed. Thus, for improving dune sand's geotechnical characteristics, the addition of fine marble waste to the dune sand is an environment-friendly solution.

Industrial application of WC-TiAlN nanocomposite films synthesized by cathodic arc ion plating system on PCB drill

  • Lee, Ho. Y.;Kyung. H. Nam;Joo. S. Yoon;Jeon. G. Han;Young. H. Jun
    • 한국표면공학회:학술대회논문집
    • /
    • 한국표면공학회 2001년도 춘계학술발표회 초록집
    • /
    • pp.3-3
    • /
    • 2001
  • Recently TiN, TiAlN, CrN hardcoatings have adapted many industrial application such as die, mold and cutting tools because of good wear resistant and thermal stability. However, in terms of high speed process, general hard coatings have been limited by oxidation and thermal hardness drop. Especially in the case of PCB drill, high speed cutting and without lubricant process condition have not adapted these coatings until now. Therefore more recently, superhard nanocomposite coating which have superhard and good thermal stability have developed. In previous works, WC-TiAlN new nanocomposite film was investigated by cathodic arc ion plating system. Control of AI concentration, WC-TiAlN multi layer composite coating with controlled microstructure was carried out and provides additional enhancement of mechanical properties as well as oxidation resistance at elevated temperature. It is noted that microhardness ofWC-TiA1N multi layer composite coating increased up to 50 Gpa and got thermal stability about $900^{\circ}C$. In this study WC-TiAlN nanocomposite coating was deposited on PCB drill for enhancement of life time. The parameter was A1 concentration and plasma cleaning time for edge sharpness maintaining. The characteristic of WC-TiAlN film formation and wear behaviors are discussed with data from AlES, XRD, EDS and SEM analysis. Through field test, enhancement of life time for PCB drill was measured.

  • PDF

피압 작용에 따른 DCM 개량체의 지반공학적 특성 (Geotechnical Characteristics of DCM-Improved Specimen Under Artesian Pressure)

  • 윤대호;김윤태
    • 대한토목학회논문집
    • /
    • 제42권2호
    • /
    • pp.187-195
    • /
    • 2022
  • 본 연구에서는 피압이 DCM 개량체의 역학적 특성에 미치는 영향을 알아보기 위해 피압의 크기를 조절할 수 있는 공시체용 수조를 제작하여 실내실험을 수행하였다. 피압의 크기는 실험실 규모 및 동수경사를 고려하여 결정하였다. 실험 결과, 피압의 크기가 증가함에 따라 일축압축강도, 할선탄성계수, 단위중량은 선형적으로 감소하고, 함수비는 증가하였다. 또한, 개량체의 응력-변형 거동은 피압이 증가함에 따라 취성에서 연성 형태의 거동을 보었다. 피압 작용으로 발생한 유출수는 개량체의 용탈현상으로 인해 페놀프탈레인 용액에 반응하는 결과를 보였다. 또한, SEM 촬영 결과 입자 사이에 작은 양의 에트린자이트가 형성되어 있는 것을 확인하였다.

Develop a sustainable wet shotcrete for tunnel lining using industrial waste: a field experiment and simulation approach

  • Jinkun Sun;Rita Yi Man Li;Lindong Li;Chenxi Deng;Shuangshi Ma;Liyun Zeng
    • Advances in concrete construction
    • /
    • 제15권5호
    • /
    • pp.333-348
    • /
    • 2023
  • Fast infrastructure development boosts the demand for shotcrete. Despite sand and stone being the most common coarse and fine aggregates for shotcrete, excessive exploration of these materials challenges the ecological environment. This study utilized an industrial solid waste, high-titanium heavy slag, blended with steel fibers to form Wet Shotcrete of Steel Fiber-reinforced High-Titanium Heavy Slag (WSSFHTHS). It investigated its workability, shotcrete performance and mechanical properties under different water-to-cement ratios, fly ash content, superplasticizer dosage, and steel fiber content. The tunnel excavation and support were investigated by conducting finite element numerical simulation analysis and was used in 3 tunnel lining pipes in Zhonggouwan tailing pond. The major findings are as follows: (1) The water-to-cement ratio (w/c ratio) significantly impacted the compressive strength of WSSFHTHS. The highest 28-day compressive strength of 60 MPa was achieved when the w/c ratio was 0.38; (2) Adding fly ash improved the workability and shotcrete performance and strength development of WSSFHTHS. The best anti-permeability performance was achieved when the fly ash constituted 15%, with the lowest permeability coefficient of 4.596 × 10-11 cm/s; (3) The optimum superplasticizer dosage for WSSFHTHS is 0.8%. It provided the best workability and shotcrete performance. Excessive dosage resulted in water bleeding and poor aggregate encapsulation, while insufficient dosage decreased flowability and adversely affected shotcrete performance; (4) The dosage of steel fibers significantly impacted the flexural and tensile strength of WSSFHTHS. When the steel fiber dosage was 45 kg/m3, the 28-day flexural and tensile strengths were 8.95 MPa and 6.15 MPa, respectively; (5) By integrating existing shotcrete techniques, the optimal lining thickness was 80 mm for WSSFHTHS per simulation. The results revealed that after using WSSFHTHS, the displacement of the tunnel surrounding the rock significantly improved, with no cracks or hollows, similar to the simulation results.

DEVELOPMENT OF LIGHTWEIGHT OPTICAL TELESCOPE KIT USING ALUMINUM PROFILE AND ISOGRID STRUCTURE

  • Park, Woojin;Lee, Sunwoo;Han, Jimin;Ahn, Hojae;Ji, Tae-Geun;Kim, Changgon;Kim, Dohoon;Lee, Sumin;Kim, Young-Jae;Kim, Geon-Hee;Kim, Junghyun;Kim, Ilhoon;Pak, Soojong
    • 천문학회지
    • /
    • 제55권1호
    • /
    • pp.11-22
    • /
    • 2022
  • We introduce the Transformable Reflective Telescope (TRT) kit that applies an aluminum profile as a base plate for precise, stable, and lightweight optical system. It has been utilized for optical surface measurements, developing alignment and baffle systems, observing celestial objects, and various educational purposes through Research & Education projects. We upgraded the TRT kit using the aluminum profile and truss and isogrid structures for a high-end optical test device that can be used for prototyping of precision telescopes or satellite optical systems. Thanks to the substantial aluminum profile and lightweight design, mechanical deformation by self-weight is reduced to maximum 67.5 ㎛, which is an acceptable misalignment error compared to its tolerance limits. From the analysis results of non-linear vibration simulations, we have verified that the kit survives in harsh vibration environments. The primary mirror and secondary mirror modules are precisely aligned within 50 ㎛ positioning error using the high accuracy surface finished aluminum profile and optomechanical parts. The cross laser module helps to align the secondary mirror to fine-tune the optical system. The TRT kit with the precision aluminum mirror guarantees high quality optical performance of 5.53 ㎛ Full Width at Half Maximum (FWHM) at the field center.

볼트의 크기 및 판두께의 차이에 따른 고장력볼트 이음부의 역학적 거동에 관한 연구 (Mechanical Behavior of High-tension Bolted Joints with Varying Bolt Size and Plate Thickness)

  • 이승용;최준혁;김성훈;박철우
    • 대한토목학회논문집
    • /
    • 제26권1A호
    • /
    • pp.67-74
    • /
    • 2006
  • 장대교량 건설의 증가와 강교량의 합리화 추세에 따라 최근 후판 강재의 사용이 늘어가고 있다. 후판 부재의 현장이음에서는 M30 고장력볼트와 같은 대형볼트의 사용이 불가피하나 현재 국내 시방기준에는 대형볼트의 사용에 대한 규정이 없는 실정이다. 따라서 본 연구에서는 대형볼트인 M30 고장력볼트의 사용성을 검토할 목적으로 볼트의 크기와 부재의 판두께를 변수로 하여 릴렉세이션과 미끄러짐 거동을 시험적으로 분석하였다. 또한, 유한요소해석을 통하여 판두께의 차이에 따른 내부압축응력을 분석하였으며, 이를 볼트축과 볼트구멍 내벽에 부착한 변형률게이지로부터 얻어진 응력분포와 비교하였다. 그 결과 M30 고장력볼트를 사용한 경우에도 릴렉세이션은 10%를 초과하지 않았으며, 미끄러짐 계수도 시방기준을 초과하는 충분한 내력을 확보하는 것으로 나타나 사용상에 문제가 없는 것으로 판단된다.

Development and application analysis of high-energy neutron radiation shielding materials from tungsten boron polyethylene

  • Qiankun Shao;Qingjun Zhu;Yuling Wang;Shaobao Kuang;Jie Bao;Songlin Liu
    • Nuclear Engineering and Technology
    • /
    • 제56권6호
    • /
    • pp.2153-2162
    • /
    • 2024
  • The purpose of this study is to develop a high-energy neutron shielding material applied in proton therapy environment. Composite shielding material consisting of 10.00 wt% boron carbide particles (B4C), 13.64 wt% surface-modified cross-linked polyethylene (PE), and 76.36 wt% tungsten particles were fabricated by hot-pressure sintering method, where the optimal ratio of the composite is determined by the shielding effect under the neutron field generated in typical proton therapy environment. The results of Differential Scanning Calorimetry measurements (DSC) and tensile experiment show that the composite has good thermal and mechanical properties. In addition, the high energy-neutron shielding performance of the developed material was evaluated using cyclotron proton accelerator with 100 MeV proton. The simulation shows a 99.99% decrease in fast neutron injection after 44 cm shielding, and the experiment result show a 99.70% decrease. Finally, the shielding effect of replacing part of the shielding material of the proton therapy hall with the developed material was simulated, and the results showed that the total neutron injection decreased to 0.99‰ and the neutron dose reduced to 1.10‰ before the enhanced shielding. In summary, the developed material is expected to serve as a shielding enhancement material in the proton therapy environment.

미세먼지 필터 성능향상을 위한 primitive 구조의 유동 제어 연구 (Study on Flow Control of Primitive Structures for Enhancing Particulate Matter Filter Performance)

  • 이종배;황승현;김지연;김현;안동규;정성용
    • 소성∙가공
    • /
    • 제33권4호
    • /
    • pp.270-276
    • /
    • 2024
  • In order to improve the performance of the PM (Particulate Matter) filter, the TPMS structure was used as a flow controller to control the flow entering the filter. Among various TPMS structures, a primitive structure that is easy to utilize 3D printing technique was selected and the effect of unit cell size was analyzed. In addition, numerical analysis was performed and swirl ratio was analyzed to confirm changes in filter inlet flow characteristics that affect changes in filter performance. Unit cell size is closely related to filter performance, and both PM collection efficiency and pressure drop increase as unit cell size decreases. Through quality factor (QF) comparison, which comprehensively evaluate collection efficiency and pressure drop, it was confirmed that when the unit cell size is 5 mm, PM collection efficiency increases, but the flow controller actually reduces filter performance. QF values are similar for unit cell sizes of 10 and 20 mm, and it is advantageous to select the unit cell size among these two considering collection efficiency and operating costs. The filter's collection performance increases due to the increase in swirl flow caused by the primitive structure, and the filter's collection efficiency increases due to the swirl flow that increases throughout the flow field as the unit cell size becomes smaller.

설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
    • /
    • 제29권6호
    • /
    • pp.327-340
    • /
    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.