• Title/Summary/Keyword: 굽힘 효과

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Mechanical Properties and Stress-Strain Model of Re-Bars Coldly Bent and Straightened (굽힌 후 편 철근의 기계적 성질과 응력-변형률 모델)

  • Chun, Sung-Chul;Tak, So-Young;Ha, Tae-Hun
    • Journal of the Korea Concrete Institute
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    • v.24 no.2
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    • pp.195-204
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    • 2012
  • In the construction of high-rise buildings, bent re-bars are manually straightened to connect slabs to core-walls, which are usually cast before floor structures. During cold bending and straightening of re-bars, plastic deformation causing work hardening, Bauschinger effect and aging hardening is unavoidable. Tensile tests of coldly bent and straightened re-bars were conducted with test parameters of grade, diameter, and bend radius of re-bars as well as age between bending and straightening. Test results showed that proportional limits were lower and strain hardening occurred without yield plateaus. Inside and outside of re-bars with compression and tension deformations, respectively, during bending showed lower yield points due to Bauschinger effect and no yield plateaus due to work hardening, respectively. When re-bar grade was higher, yield point became significantly lower where Grade 400 re-bars had yield strengths lower than specified yield strength of 400 MPa. Because the surface of re-bar has higher strength than the core of re-bar, Bauschinger effect was more obvious for higher-grade re-bars. When age between bending and straightening was greater, yield strength increased and elongation decreased (i.e. embrittlement occurs). Using measured data, stress-strain relationship for straightened re-bars was developed based on Ramberg-Osgood model, which can be used to evaluate stiffness of joints when straightened re-bars are applied.

The Effect of Reinforcing Materials on the Transverse Strength of Denture Base Resin (의치상 레진 강화재가 의치상 굽힘강도에 미치는 영향)

  • Lee, Jun-Sik;Song, Young-Gyun;Cho, In-Ho
    • Journal of Dental Rehabilitation and Applied Science
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    • v.28 no.4
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    • pp.327-337
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    • 2012
  • The object of this study was to find out the effect of various reinforcing materials including Quarts Splint$^{TM}$ Mesh on the transverse strength of the denture resin. QC-20 and Lucitone199$^{(R)}$ were used as the denture resin, and polyethylene fiber Ribbond$^{(R)}$, light curing quarts fiber Quarts Splint$^{TM}$ Mesh, metal mesh were used as the reinforcing materials. Ten specimens were fabricated for each group and the size of specimens was $2.0{\times}10.0{\times}65.0mm$. To compare the effect of resin thickness, additional specimens of $2.5{\times}10.0{\times}65.0mm$, $3.0{\times}10.0{\times}65.0mm$ were fabricated. In the control group, the transverse strength of Lucitone199$^{(R)}$ was significantly higher than that of QC-20(p<0.05). Among the specimens of 2.0 mm thickness fabricated with $Lucitone199^{(R)}$ and QC-20, they showed high transverse strength in the order of metal mesh, Quarts Splint$^{TM}$ Mesh, Ribbond$^{(R)}$, and control group. In the specimens of 2.0 mm, 2.5 mm thickness, the transverse strength of Quarts Splint$^{TM}$ Mesh were significantly higher than that of QC-20(p<0.05). But in the specimens of 3.0 mm thickness, there was no significant difference.

An Analysis of Axisymmetric Deep Drawing by the Energy Method (에너지법에 의한 축대칭 디프드로잉의 해석)

  • 양동열;이항수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.1
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    • pp.51-61
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    • 1993
  • A systematic approach of the energy method is proposed for analysis of axisymmetric deep drawing in which the total deforming region is divided into five sections by the geometric characteristic. The corresponding solution is found through optimization of the total energy dissipation with respect to some parameters assumed in the kinematically admissible velocity field defined over each region. The sheet blank is divided into three-or five-layers to consider the bending effect. For the evaluation of frictional energy, it is assumed that the blank holding force acts on the outer rim of the flange and that the contact pressure acting on punch shoulder or die shoulder has uniform distributions, respectively. The computed results by the present method are compared with the experiment and the computed results by the elastic-plastic finite element method for the distribution of thickness strain and the relation between the punch stroke and punch load. The results for the case of multi-layers show better agreements than for the case of a single layer in load vs. stroke relation and strain distribution. It is thus shown that the multi-layer technique can be effectively employed in analyzing axisymmetric deep drawing in connection with the energy method.

Effect of kinesio taping on ankle strength, movement and function in patients with common peroneal nerve paralysis (키네지오 테이핑이 온종아리신경 마비를 가진 환자의 발목관절의 근력, 움직임 및 기능에 미치는 영향)

  • Park, Si Eun;Cho, Kyun-Hee;Park, Shin Jun
    • Journal of Industrial Convergence
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    • v.18 no.1
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    • pp.59-64
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    • 2020
  • The effect of kinesio taping in patients with common peroneal nerve paralysis (PNP) have not been investigated. This purpose of this study was to evaluate the effects of kinesio taping on patients with common PNP. Ten subjects who had common PNP were included in this study. Kinesio taping was applied to the ankle joint (direction of dorsiflexion and eversion). The measurements were by manual muscle test (MMT; tibialis anterior, peroneus longus), active ROM (ankle dorsiflexion, eversion), pain (visual analogue scale (VAS), pressure pain threshold (PPT)), and balance (one leg standing). Subjects were assessed at baseline and 8 weeks of intervention. In the results, all subjects showed improvements in MMT, active ROM, Pain and balance at the 8-week. These findings are considered to be effective in applying kinesio taping on ankle joint in common PNP patients.

The Comparison of the Effects of Joint Mobilization, Incline Board and PNF stretching to Increase the Dorsiflexion of the Ankle Joint on Ankle Dosiflexion and the Muscle Tone of the Plantar Flexor the Ankle in Subjects with Stroke (발등 굽힘 관절가동범위를 증가시키기 위한 관절가동술과 경사대, PNF 스트레칭이 뇌졸중 환자의 발등 굽힘 및 발바닥 굽힘근의 근 긴장도에 미치는 효과 비교)

  • Ryu, Bueong-ho;Hong, Hyun-pyo
    • The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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    • v.26 no.1
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    • pp.55-63
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    • 2020
  • Background: This study was conducted to compare the effects of an incline board, proprioceptive neuromuscular facilitation (PNF) stretching, and joint mobilization on the dorsiflexion of the ankle joint and muscle tone of the plantar flexor and ankle in stroke patients. Methods: Forty-five stroke subjects were randomly divided into three groups: each JMG (Joint Mobilization Group), IBG (Inclined Board Group) and PSG (PNF Stretching Group). The experiment was performed for eight weeks between August 1 and October 31, 2018. Results: The dorsiflexion of the ankle joint was significant between the groups and by period (p<.05). JMG had a significant change by period (p<.05). Differences between groups by period increased after 8 weeks in the PSG and the JMG (p>.05). The gastrocnemius lateral muscle tone was significant between the groups (p<.05), and medial muscle tone was interacted between groups and time (p<.05). Conclusion: An effective intervention method to increase the dorsiflexion of the ankle joint and decrease the muscle tone when performing PNF stretching, and joint mobilization in stroke patients was confirmed. Future studies are recommended to variety research of PNF stretching and joint mobilization.

Bending Fatigue Reliability Improvements of Cu Interconnects on Flexible Substrates through Mo-Ti Alloy Adhesion Layer (Mo-Ti 합금 접착층을 통한 유연 기판 위 구리 배선의 기계적 신뢰성 향상 연구)

  • Lee, Young-Joo;Shin, Hae-A-Seul;Nam, Dae-Hyun;Yeon, Han-Wool;Nam, Boae;Woo, Kyoohee;Joo, Young-Chang
    • Journal of the Microelectronics and Packaging Society
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    • v.22 no.1
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    • pp.21-25
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    • 2015
  • Bending fatigue characteristics of Cu films and $8{\mu}m$ width Cu interconnects on flexible substrates were investigated, and fatigue reliability improvement was achieved through Mo-Ti alloy adhesion layer. Tensile bending fatigue reliability of Cu interconnects is 3 times lower than that of Cu films, and even compressive bending fatigue reliability of Cu interconnects is 6 times lower than that of Cu films. From these results, mechanical crack formation could be fatal in Cu interconnects. With Mo-Ti adhesion layer, fatigue reliability of Cu films and interconnects were enhanced due to the increase of adhesion strength and the suppression of slip induced crack initiation.

Bend-Twist Coupling Behavior of 10 MW Composite Wind Blade (10 MW급 복합재 풍력 블레이드의 굽힘-비틀림 커플링 거동 연구)

  • Kim, Soo-Hyun;Shin, Hyungki;Bang, Hyung-Joon
    • Composites Research
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    • v.29 no.6
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    • pp.369-374
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    • 2016
  • In this study, a structural optimal design of 10 MW composite blade was performed using bend-twist coupled(BTC) design concept. Bend-twist coupling of blade means the coupling behavior between the bending and torsional deflections due to the composite lamina with fiber angle biased from the blade longitudinal axis. This can potentially improve the overall performance of composite blade and reduce the dynamic loading. Parametric studies on layup angle, thickness and area of off-axis carbon UD were conducted to find the optimum coupling effect with weight reduction. Comparing the results of fatigue load analysis between conventional model and BTC applied model, the damage equivalent load(DEL) of blade root area were decreased about 3% in BTC model. To verify the BTC effect experimentally, a 1:29 scaled model was fabricated and the torsion at the tip under deflection behavior of blade stiffener model was measured by static load test.

Effect of UV-Absorber Treatment on the Mechanical Properties of Cotton Fabrics (자외선 차단 가공에 의한 면직물의 역학적 특성 변화)

  • Kwon, Young-Ah;Kang, Mi-Jung;Cho, Hyun-Hok
    • Journal of the Korean Society of Clothing and Textiles
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    • v.26 no.12
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    • pp.1701-1708
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    • 2002
  • 본 연구의 목적은 자외선 차단 가공 처리 및 자외선 조사처리에 의해 면직물의 역학적 특성 변화를 조사하고 가공제 처리조건에 따른 차이점을 분석하는 것이다. 시료로는 100% 면직물을, 자외선 흡수제로 2,2'-dihydroxy-4,4'-dimethoxy benzophenone을, 첨가제로 Triton X-100, polyethylene glycol 400, MgCl$_2$.6$H_2O$를 사용하였다. 자외선 흡수제 처리는 Atlas Launder-O-meter로 75$^{\circ}C$에서 60분간 흡진법으로 하였다. 미처리 시료 및 처리시료는 모두 xenon 램프에 80시간 동안 노출되었으며, 자외선 조사 전후 시료의 역학적 특성은 KES-F시스템을 사용하여 측정하였다. 본 연구의 결과는 다음과 같이 요약할 수 있다. 자외선 흡수제 처리는 처리 농도에 상관없이 면직물의 선형인장성(LT), 인장레질리언스(RT), 굽힘강성(B), 굽힘이력(2HB), 전단강성(G), 전단이력(2HG5), 표면마찰계수(MIU)등을 증가시켰으며 표면거칠기(SMD)는 감소시켰다. 압축특성은 처리농도의 영향을 받아서 고농도의 자외선 흡수제 처리는 압축특성을 감소시켰으며, 저농도의 처리는 압축특성을 증가시켰다. 자외 선 흡수제 처리는 처리농도에 상관없이 면직물의 fullness/softness를 유의하게 증가시키는 반면 stiffness, crispness및 anti-drape stiffness를 감소시켜서 가공포의 종합태(THV)는 가공 전에 비하여 저하하였다. 자외선 조사는 가공 전 면직물의 경우 B, 2HB, G, 2HG, 2HG5, LC를 감소시켰다. 자외선 조사는 처리농도와 상관없이 가공포의 WT, 굽힘특성 , 전단특성을 감소시켰으며, 저농도의 흡수제 처리포의 경우 SMD를 증가시켰으며, 고농도의 흡수제 처리포의 경우 SMD를 감소시켰다. 자외선 조사는 처리농도와 상관없이 가공포의fullness/softness, stiffness, anti-drape stiffness를 유의하게 감소시켜서 자외선 조사 전 보다 THV가 37% 저하하였고 미 가공포의 THV를 저하율보다는 저하가 낮았다. 자외선 흡수제 처리에 의해 면직물의 태는 가공 전보다 감소하지만, 자외선 흡수제 처리는 자외선 조사에 의한 태 감소율을 낮추는 데 유의 한 효과가 있다.

A Novel Procedure for Mooring Chain Fatigue Prediction based on Maximum Principal Stress Considering Out-of-Plane and In-Plane Bending Effects (면내외 굽힘 효과를 고려한 최대 주응력 기반 계류 체인 피로 평가 기법 개발)

  • Choung, Joonmo;Han, SeungOh
    • Journal of the Society of Naval Architects of Korea
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    • v.53 no.3
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    • pp.237-248
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    • 2016
  • As OPB and IPB moment-induced fatigue damage on mooring chain links were reported for a offloading buoy, verification of OPB and IPB fatigue has been a key engineering item in offshore structure mooring design. Mathematical and physical features of the conventional approach which was mainly explained in BV guideline are reviewed and disadvantages of the conventional approach are addressed in terms of stress proportionality and nonlinearity of OPB and IPB moments. In order to eradicate these disadvantages, a novel approach is newly proposed which is able to dispel apprehension on stress proportionality and is not dependent of nonlinearities of OPB and IPB moments. Significant differences between two approaches are suggested by comparing relations of OPB moment versus OPB interlink angle and IPB moment versus IPB interlink angle. For periodic OPB tension angle processes having three different OPB angle ranges with a simple irregular tension process, fatigue damage calculation reveals that OPB moment-induced fatigue damage has dominant portion to total fatigue damage. Comparative studies between two approaches also show that the conventional approach based on BV guideline predicts fatigue damage far conservatively since it assume unrealistic high stress concentration factor for tension load. Meanwhile IPB moment-induced fatigue damage is negligible compared to tension-induced fatigue damage.

Limit Loads for Circular Wall-Thinned Feeder Pipes Subjected to Bending and Internal Pressure. (원형 감육이 발생한 중수로 피더관의 한계하중 평가)

  • Je, Jin-Ho;Lee, Kuk-Hee;Chung, Ha-Joo;Kim, Jong-Sung;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.11
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    • pp.1675-1680
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    • 2010
  • Flow Accelerated Corrosion (FAC) occurring during in-service conditions results in localized wall-thinning in the feeder pipes of CANDU. The wall-thinning of the feeder pipes is the main degradation mechanisms affecting the integrity of piping systems. In this paper, we assess the integrity of wall-thinned feeder pipes by limit load analysis. The limit loads for wall-thinning feeder pipes subjected to in-plane bending and internal pressure were determined on the basis of finte element limit analyses. The limit loads are determined from the results of limit analyses of elasticperfectly-plastic materials using the large geometry change. Closed-form approximations of limit load solutions for wall-thinning feeder pipes subjected to in-plane bending and pressure are proposed.