• Title/Summary/Keyword: T-응력

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Experimental Investigation of Fatigue Crack Growth Behavior in Friction Stir Welded 7075-T651 Aluminum Alloy Joints under Constant Stress Intensity Factor Range Control Testing (For LT Orientation Specimen) (일정 응력확대계수범위 제어 시험하의 마찰교반용접된 7075-T651 알루미늄 합금 용접부의 피로균열전파 거동의 실험적 고찰 (LT 방향의 시험편에 대하여))

  • Jeong, Yeui Han;Kim, Seon Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.6
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    • pp.775-782
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    • 2013
  • In this study, as a series of studies aimed at investigating the spatial randomness of fatigue crack growth for friction stir welded (FSWed) 7075-T651 aluminum alloy joints, the fatigue crack growth behavior of FSWed 7075-T651 aluminum alloy joints was investigated for LT orientation specimens. Fatigue crack growth tests were conducted under constant stress intensity factor range (SIFR) control for 5 specimens of the FSWed 7075-T651 aluminum alloy, including base metal (BM), heat affected zone (HAZ), and weld metal (WM) specimens. The mean fatigue crack growth rate of WM specimens was found to be the highest, whereas that of HAZ and WM specimens was the lowest. Furthermore, the variability of fatigue crack growth rate was found to be the highest in WM specimens and lowest in BM specimens.

Analysis of residual drying stress in Larix Kaempferi wood used as glulam laminar (집성재 라미나용 낙엽송 재내 잔류 건조응력 변화 분석)

  • Han, Yeonjung;Chang, Yoon-Seong;Park, Yonggun;Jeong, Gi-Young;Hong, Jung-Pyo;Lee, Jun-Jae;Yeo, Hwanmyeong
    • Journal of the Korean Wood Science and Technology
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    • v.41 no.6
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    • pp.535-543
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    • 2013
  • The objective of this study was to analyse the residual stress in Larix kaempferi board during and after kiln-drying. The boards were primarily intended for using as laminar of cross laminated timber (CLT). In this study, the equivalence of moisture content by equalizing treatment was proved and reduction of residual stress by conditioning treatment was quantified. Prong test and slice test were carried out to analyse the residual stress in wood during drying. Transverse casehardening was measured immediately after making prong sample. Residual stress of four parts in wood from surface to center was analyzed quantitatively based on elastic deformation after just cutting slices from board. Tensile stress and compressive stress on the surface of board during drying did not exceed 2.2 MPa when boards were dried by kiln-drying schedule of T10-C4 and T12-D5. Because the tensile strength and compressive strength of transverse direction of Larix kaempferi lumber are 2.65 MPa and 4.60 MPa, application of more severe drying schedule can be recommended. Cup and twist were reduced by about 40% by equalizing and conditioning treatments after drying.

Estimation of C(t) -Integral Under Transient Creep Conditions for a Cracked Pipe Subjected to Combined Mechanical and Thermal Loads Depending on Loading Conditions (열응력 및 기계응력이 작용하는 균열배관의 하중조건에 따른 천이 크리프 조건 C(t)-적분 평가)

  • Oh, Chang-Young;Song, Tae-Kwang;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.6
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    • pp.609-617
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    • 2011
  • There is a trend towards the progressive use of higher operating temperatures and stresses to achieve improved efficiencies in power-generation equipment. It is important to perform the crack assessment under hightemperature and high-pressure conditions. The C(t)-integral is a key parameter in crack assessment for transient creep states. The estimation of the C(t)-integral is complex when considering the mechanical and thermal loads simultaneously. In this paper, we study estimation of C(t)-integral under combined mechanical and thermal load depending on loading conditions.

Axial Behavior of Reinforced Concrete Columns Externally Strengthened with Unbonded Wire Rope and T-Shaped Steel Plate (와이어로프와 T 강판으로 비부착 보강된 철근콘크리트 기둥의 중심 축하중 거동)

  • Yang, Keun-Hyeok;Sim, Jae-Il;Byun, Hang-Yong
    • Journal of the Korea Concrete Institute
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    • v.20 no.2
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    • pp.221-229
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    • 2008
  • An improved unbonded-type column strengthening procedure using wire rope and T-shaped steel plate units was proposed. Eight strengthened columns and an unstrengthened control column were tested under concentric axial load. The main variables considered were the volume ratio of wire rope and the flange width and configuration of T-shaped steel plates. Axial load capacity and ductility ratio of columns tested were compared with predictions obtained from the equation specified in ACI 318-05 and those of conventionally tied columns tested by Chung et al., respectively. In addition, a mathematical model was proposed to evaluate the complete stress-strain relationship of concrete confined by the wire rope and T-plate units. Test results showed that the axial load capacity and ductility of columns increased with the increase of the volume ratio of wire rope and the flange width of T-plates. In particular, at the same lateral reinforcement index, a much higher ductility ratio was observed in the strengthened columns having the volume ratio of wire rope above 0.0039 than in the tied columns. A mathematical model for the stress-strain relationship of confined concrete using the proposed strengthening procedure is developed. The predicted stress-strain curves were in good agreement with test results.

Synthesis of the material releasing thermal stress by designing FGM (경사기능층의 디자인에 의한 열응력분산재료 합성에 관한 연구)

  • 김유택;박진호
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.2
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    • pp.240-244
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    • 1999
  • Monolithic SiC and SiC/C functionally gradient material (FGM) layers were deposited on graphite substrates by CVD method. Temperature a profiles and thermal stress distributions in the deposited layers under the thermal shock were calculated by a commercially available software package. The designed FGM specimens were found to show an efficient relaxation of thermal stresses at the interfaces, and the specimens were intact even under a thermal shock of $\Delta$T=1600 K.

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The application of forman equation for fatigue crack propagation in welding residual stress region (溶接殘留應力領域에서의 疲勞균열傳播에 대한 Forman式의 適用)

  • 김상철;이용복
    • Journal of Welding and Joining
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    • v.5 no.1
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    • pp.42-56
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    • 1987
  • Fatigue Fracture behaviors of the TIG-welded aluminum alloys, such as Al 2024-T4, A1 5050-0 and Al 7075-T7 were investigated when a crack propagated from tensile residual stress region and compressive residual stress region. The experimental values were compared with the values expected by the Forman equation. The experimental results are summarized as the following: (1) In case of fatigue crack propagation from residual stress region, the values predicted by Forman equation were Found to exactly corresponded to the experimental values. (2) When the stress intensityfactors affected by compressive residual stress, Kres, were greater than the stress intensity factors by minimum applied stresses. Kmin, the Forman equation was found to be improper to be applied directly, but the equation appeared to be proper, if the stress ratio was modified to zero. (3) The experimental results confirmed that residual stress was relaxed by repeated tensile loading and the relaxing trend was greater in case of compressive residual stress than that of tensile residual stress.

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A Study on Stree Analysis and Bending Fatigue Strength of One Side Fillet Welded T-joint (T형 평면용접이음재의 응력해석과 굽힘피로강도에 관한 연구)

  • Gang, Seong-Won;Lee, Tae-Hun;Jeon, Jae-Mok;Kim, Chung-Hui
    • Journal of Ocean Engineering and Technology
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    • v.13 no.2 s.32
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    • pp.51-57
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    • 1999
  • In this study, one side fillet welded T-joint, used in box type girder and other welding structure, was investigated by stress analysis and bending fatigue test without edge preparation, with variation of joint shape. The purpose of this study is to give the welding condiltion and design standard on manufacturing one side fillet welded T-joint. As a result, the following conclusions were obtained. 1) In one side fillet welded T-joint, the larger the leg length and the penetration depth, the greater the bending fatigue strength because reduction of stress and strain on toe and root. The increase of the longitudinal leg length rather than vertical leg length contributed to the increase in bending fatigue strength. 2) In one side fillet welded T-joint without edge preparation, both general manual welding and general automatic welding were carried out with same condition. In this case, automatic welding showed deeper penetration and more increased longitudinal leg length than manual welding, so that automatic welding offers greater bending fatigue strength. 3) For one side fillet welded T-joint without edge preparation with automatic welding, the ratio(h/t) of the leg length(h) and the main plate thickness(t) in which toe crake can occur was 1.0 over.

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Effect of Siloxane Oligomer on Thermal Stability and Internal Stress of Epoxy Resins (실록산 올리고머가 에폭시 수지의 열안정성 및 내부응력에 미치는 영향)

  • Kwak, Geun-Ho;Park, Soo-Jin;Park, Jun-Ha;Kim, Kong-Soo
    • Applied Chemistry for Engineering
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    • v.10 no.5
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    • pp.701-706
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    • 1999
  • The effect of siloxane oligomer content on thermal stability and internal stress of DGEBA epoxy resin was investigated. Siloxane-epoxy polymers having terminal epoxy group were prepared by reaction of siloxane-DDM prepolymer with DGEBA epoxy resin. Thermal stability was studied in terms of the initial decomposition temperature(IDT), temperature of maximum rate of weight loss($T_{max}$), integral procedural decomposition temperature(IPDT), and decomposition activation energy($E_t$) using TGA data. The thermal stability increased with increasing the siloxane oligomer content and showed a maximum value in the case of 5 wt% siloxane oligomer content in the blend system. While, the coefficient of thermal expansion(${\alpha}_r$) and the flexural modulus($E_r$) allowed us to study internal stress of the blend system. As the content of siloxane oligomer increases, the internal stress systematically decreases as decreasing both ${\alpha}_r$ and $E_r$.

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Prediction of Fretting Fatigue Life on 2024-T351 Al-alloy (2024-T351 알루미늄 합금판 프레팅 피로수명 예측)

  • Kwon, Jung-Ho;Hwang, Kyung-Jung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.7
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    • pp.601-611
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    • 2007
  • Most of mechanically jointed aircraft structures are always encountered the fretting damages on the contact surfaces between two jointed structural members or at the edges of fastener holes. The partial slip and contact stresses associated with fretting contact can lead to severe reduction in service lifetime of aircraft structures. Thus a critical need exists for predicting fretting crack initiation in mechanically jointed aircraft structures, which requires characterizing both the near-surface mechanics and intimate relationship with fretting parameters. In this point of view, a series of fretting fatigue specimen tests for 2024-T351 Al-alloy, have been conducted to validate a mechanics-based model for predicting fretting fatigue life. And included in this investigaion were elasto-plastic contact stress analyses using commercial FEA code to quantify the stress and strain fields in subsurface to evaluate the fretting fatigue crack initiation.

A Study on the Mathematical Modeling of Human Pharyngeal Tissue Viscoelasticity (인두조직의 점 탄성특성의 수학적모델링에 관한 연구)

  • 김성민;김남현
    • Journal of Biomedical Engineering Research
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    • v.19 no.5
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    • pp.495-502
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    • 1998
  • A mathematical model of viscoelasticity on the material property of human pharyngeal tissue utilizing Y.C. Fung's Quasi-linear viscoelastic theory is proposed based on cyclic load, stress relaxation, incremental load, and uniaxial tensile load tests. The material properties are characterized and compared with other biological materials' results. The mathematical model is proposed by combining two characteristic functions determined from the stress relaxation and uniaxial tensile load tests. The reduced stress relaxation function G(t) and elastic response function S(t) are obtained from stress relaxation test and uniaxial tensile load test results respectively. Then the model describing stress-time history of the tissue is implemented utilizing two functions. The proposed model is evaluated and validated by comparing the model's cyclic behaviour with experimental results. The model data could be utilized as an important information for constructing 3-dimensional biomechanical model of human pharynx using FEM(Finite Element Method).

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