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Effects of Alloying Elements and Nitrocarburizing on Rolling Contact Fatigue Life (회전접촉피로수명에 미치는 합금원소 및 침질탄화처리의 영향)

  • Jin, Jai Koan;Kim, Dong Keon
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.4
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    • pp.262-269
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    • 1994
  • This study has been carried out to evaluate effects of alloying elements and nitrocarburizing on rolling contact fatigue life. Manganese has a significant influence on the distribution of retained carbides and microstructural changes after rolling contact fatigue test. The effect of the manganese addition stabilized fine retained carbide particles during rolling contact fatigue life test, and so increased fatigue life markedly. High carbon chromium bearing steel with different matrixes were nitrocarbunzed by austenitic nitrocarburizing process at $850^{\circ}C$ for 4hrs. Rolling contact fatigue life of the nitrocarburized specimen was increased 2 times than full hardening treated.

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Cracking of Precast Bridge Decks with Loop Joints (루프 이음 프리캐스트 교량 바닥판의 균열)

  • Ryu Hyung Keun;Chang Sung Pil;Kim Young Jin;Kim Byung Suk
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.05a
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    • pp.750-753
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    • 2004
  • In this paper, experimental test on the full scale model of steel and concrete composite plate girder with prefabricated slabs under hogging moments was conducted cautiously and observed in order to study cracking in precast decks. Details of prefabricated slab transverse joints were determined from previous research. A test specimen was overhanging simple support beam, totally 28 meter length. Through the 4-point flexural test, the behaviour of the composite girder under hogging moments was observed. From the test results, crack development and crack widths were observed.

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Fatigue Characteristic Evaluation in Water Pipe Welds Considering of Welding Residual Stress (용접잔류응력을 고려한 상수도 강관의 피로특성 평가)

  • Choi, Jung-Hun;Song, Weon-Keyu;Koo, Jae-Mean;Seok, Chang-Sung
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.7-10
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    • 2007
  • In case of large steel water pipe, it have been observed that its fracture mostly occurs due to the complicated outside fatigue load on the pipe in the underground. It is also well known that its damage and leakage happen mainly in a weld zone. In this study we evaluated the fatigue characteristics based on size effect and residual stress by comparing the test results on the standard specimen collected from real pipe with those on full scale pipe.

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Study on the behavior of beam-column connection in precast concrete structure

  • Kataoka, Marcela N.;Ferreira, Marcelo A.;El Debs, Ana Lucia H.C.
    • Computers and Concrete
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    • v.16 no.1
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    • pp.163-178
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    • 2015
  • Due to the increase of the use of precast concrete structures in multistory buildings, this paper deals with the behavior of an specific type of beam-column connection used in this structural system. The connection is composed by concrete corbels, dowels and continuity bars passing through the column. The study was developed based on the experimental and numerical results. In the experimental analysis a full scale specimen was tested and for numerical study, a 3D computational model was created using a finite element analyze (FEA) software, called DIANA. The comparison of the results showed a satisfactory correlation between loading versus displacement curves.

Experimental study on seismic performances of steel framebent structures

  • Liang, Jiongfeng;Gu, Lian S.;Hu, Ming H.
    • Earthquakes and Structures
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    • v.10 no.5
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    • pp.1111-1123
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    • 2016
  • To study seismic performance of steel frame-bent structure, one specimen with one-tenth scale, three-bay, and five-story was tested under reversed cyclic lateral load. The entire loading process and failure mode were observed, and the seismic performance indexes including hysteretic loops, skeleton curve, ductility, load bearing capacity, drift ratio, energy dissipation capacity and stiffness degradation were analyzed. The results show that the steel frame-bent structure has good seismic performance. And the ductility and the energy dissipation capacity were good, the hysteresis loops were in spindle shape, which shape were full and had larger area. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. It can be helpful to design this kind of structure in high-risk seismic zone.

Prediction of Effective Material Properties for Triaxially Braided Textile Composite

  • Geleta, Tsinuel N.;Woo, Kyeongsik;Lee, Bongho
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.2
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    • pp.222-235
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    • 2017
  • In this study, finite element modeling was used to predict the material properties of tri-axially braided textile composite. The model was made based on an experimental test specimen which was also used to compare the final results. The full interlacing of tows was geometrically modelled, from which repeating parts that make up the whole braid called unit cells were identified based on the geometric and mechanical property periodicity. In order to simulate the repeating nature of the unit cell, periodic boundary conditions were applied. For validation of the method, a reference model was analyzed for which a very good agreement was obtained. Material property calculation was done by simulating uniaxial and pure shear tests on the unit cell. The comparison of these results with that of experimental test results showed an excellent agreement. Finally, parametric study on the effect of number of plies, stacking type (symmetric/anti-symmetric) and stacking phase shift was conducted.

First Report of Gymnosporangium globosum Causing American Hawthorn Rust in Korea

  • Yun, Hye-Young;Lee, Kyung-Joon;Kim, Young-Ho;Lee, Seung-Kyu
    • The Plant Pathology Journal
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    • v.24 no.1
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    • pp.84-86
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    • 2008
  • Field surveys and specimen collections of the rust fungal pathogen Gymnosporangium were carried out for 15 years from 1985 through 1999 in various locations of Korea. Macroscopic and microscopic examinations of morphological characteristics of aecia from the collected specimens revealed that Gymnosporangium globosum is the causal agent of American hawthorn rust disease on Crataegus pinnatifida and C. pinnatifida varmajor. The host plants are new for this rust fungus. G. globosum was found only in Gyeonggi and Chungbuk provinces, indicating that its distribution in Korea is limited. This is a first full description on morphological characters of aecia of G. globosum in Korea.

Cyclic behaviour of beam-to-column welded connections

  • Mele, Elena;Calado, Luis;De Luca, Antonello
    • Steel and Composite Structures
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    • v.1 no.3
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    • pp.269-282
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    • 2001
  • In this paper the results of an experimental program devoted to the assessment of the cyclic behaviour of full scale, European type, beam-column subassemblages with welded connections are presented. Six tests (five cyclic and one monotonic) have been carried out on three different series of specimens, encompassing a total of eighteen tests. The three specimen series have been designed with the aim of defining the effect of the column size on the connection behaviour, under different applied loading histories. The tests have evidenced the effect of the column size and panel zone design and of the applied loading history on the cyclic behaviour and failure modes of the connections.

Experimental study on flexural strength of modular composite profile beams

  • Ahn, Hyung-Joon;Ryu, Soo-Hyun
    • Steel and Composite Structures
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    • v.7 no.1
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    • pp.71-85
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    • 2007
  • This study suggests modular composite profile beams, where the prefab concept is applied to existing composite profile beams. The prefab concept produces a beam of desired size having two types of profile: side module and bottom module. Module section will improve construction efforts because it offers several benefits : reduction of deflections due to creep and shrinkage, which might be found in existing composite profile beams; increase in span/depth ratio; and free prefabrication of any required beams. Based on the established analysis theory of composite profile beams, an analysis theory of modular composite profile beams was suggested, and analysis values were compared with experimental ones. The behavior of individual modules with increase of load was measured with a strain gauge, and the shear connection ratio between modules was analyzed by using the measured values. As a result of experiment, it was found that theoretical flexural strength on condition of full connection was 57%-80% by connection of modules for each specimen, and it is expected that flexural strength will approximate the theoretical levels through further module improvement.

A Study on the Fatigue Strength of a Welded Joint with Misalignment of a U-type Trough Rib in a Steel Deck Plate (강상판(鋼床版) U형(形) 트라프리브 단차용접(段差熔接)이음부(部)의 피로강도(疲勞强度)에 관(關)한 연구(硏究))

  • Lee, Dong Uk;Seo, Won Chan
    • Journal of Korean Society of Steel Construction
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    • v.8 no.3 s.28
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    • pp.13-20
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    • 1996
  • With the adoption of welded joints rather than bolted joints, we investigate the fatigue strength and the fatigue crack initiation of U-type trough rib and welded specimen with misalignment in a steel deck plate. The stress concentration factor of welded specimens with a misalignment is also verified by a finite element method. The main conclusions obtained from this study are as follows Experimental results of full-scaled U-type trough rib models have indicated that fatigue life depends on misalignments of welded joints in steel deck plate ; The more misalignments are, the less the fatigue life is. It has also shown that fatigue crack propagates from the welded root to the bead surface. We have also obtained the same results from both the fatigue test of welded specimens with a misalignment and the stress analysis of a finite element method.

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