• Title/Summary/Keyword: In-plane Deformations

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A Study on Residual Stress Measurements by Using Laser Speckle Interferometry (레이저 간섭법을 이용한 잔류응력 측정 방법에 대한 연구)

  • Rho, Kyung-Wan;Kang, Young-June;Hong, Seong-Jin;Kang, Hyung-Soo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.1
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    • pp.16-24
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    • 1999
  • Residual stress is one of the causes which make defects in engineering components and materials. And interest in the measurement of residual stress exists in many industries. There are commonly used methods by which residual stresses are currently measured. But these methods have a little demerits. time consumption and other problems. Therefore we devised a new experimental technique to measure residual stress in materials with a combination of laser speckle pattern interferometry, finite element method and spot heating. The speckle pattern interferometer measures in-plane deformations while the heating provides for very localized stress relief. FEM is used for determining heat temperature and other parameters. The residual stresses are determined by the amount of strain that is measured subsequent to the heating and cool-down of the region being interrogated. A simple model is presented to provide a description of the method. In this paper, the ambiguity problem for the fringe patterns has solved by a phase shifting method.

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Correlation between Oxygen Related Bonds and Defects Formation in ZnO Thin Films by Using X-ray Diffraction and X-ray Photoelectron Spectroscopy (XRD와 XPS를 사용한 산화아연 박막의 결함형성과 산소연관 결합사이의 상관성)

  • Oh, Teresa
    • Korean Journal of Materials Research
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    • v.23 no.10
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    • pp.580-585
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    • 2013
  • To observe the formation of defects at the interface between an oxide semiconductor and $SiO_2$, ZnO was prepared on $SiO_2$ with various oxygen gas flow rates by RF magnetron sputtering deposition. The crystallinity of ZnO depends on the characteristic of the surface of the substrate. The crystallinity of ZnO on a Si wafer increased due to the activation of ionic interactions after an annealing process, whereas that of ZnO on $SiO_2$ changed due to the various types of defects which had formed as a result of the deposition conditions and the annealing process. To observe the chemical shift to understand of defect deformations at the interface between the ZnO and $SiO_2$, the O 1s electron spectra were convoluted into three sub-peaks by a Gaussian fitting. The O 1s electron spectra consisted of three peaks as metal oxygen (at 530.5 eV), $O^{2-}$ ions in an oxygen-deficient region (at 531.66 eV) and OH bonding (at 532.5 eV). In view of the crystallinity from the peak (103) in the XRD pattern, the metal oxygen increased with a decrease in the crystallinity. However, the low FWHM (full width at half maximum) at the (103) plane caused by the high crystallinity depended on the increment of the oxygen vacancies at 531.66 eV due to the generation of $O^{2-}$ ions in the oxygen-deficient region formed by thermal activation energy.

Improvement of pavement foundation response with multi-layers of geocell reinforcement: Cyclic plate load test

  • Khalaj, Omid;Tafreshi, Seyed Naser Moghaddas;Mask, Bohuslav;Dawson, Andrew R.
    • Geomechanics and Engineering
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    • v.9 no.3
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    • pp.373-395
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    • 2015
  • Comprehensive results from cyclic plate loading at a diameter of 300 mm supported by layers of geocell are presented. The plate load tests were performed in a test pit measuring $2000{\times}2000mm$ in plane and 700 mm in depth. To simulate half and full traffic loadings, fifteen loading and unloading cycles were applied to the loading plate with amplitudes of 400 and 800 kPa. The optimum embedded depth of the first layer of geocell beneath the loading plate and the optimum vertical spacing of geocell layers, based on plate settlement, are both approximately 0.2 times loading plate diameter. The results show that installation of the geocell layers in the foundation bed, increase the resilient behavior in addition to reduction of accumulated plastic and total settlement of pavement system. Efficiency of geocell reinforcement was decreased by increasing the number of the geocell layers for all applied stress levels and number of cycles of applied loading. The results of the testing reveal the ability of the multiple layers of geocell reinforcement to 'shakedown' to a fully resilient behavior after a period of plastic settlement except when there is little or no reinforcement and the applied cyclic pressure are large. When shakedown response is observed, then both the accumulated plastic settlement prior to a steady-state response being obtained and the resilient settlements thereafter are reduced. The use of four layers of geocell respectively decreases the total and residual plastic settlements about 53% and 63% and increases the resilient settlement 145% compared with the unreinforced case. The inclusion of the geocell layers also reduces the vertical stress transferred down through the pavement by distributing the load over a wider area. For example, at the end of the load cycle of the applied pressure of 800 kPa, the transferred pressure at the depth of 510 mm is reduced about 21.4%, 43.9%, 56.1% for the reinforced bases with one, two, and three layers of geocell, respectively, compared to the stress in the unreinforced bed.

Creating Stick Figure Animations Based on Captured Motion Data (모션 캡쳐 데이터에 기초한 스틱 피규어애니메이션 제작)

  • Choi, Myung Geol;Lee, Kang Hoon
    • Journal of the Korea Computer Graphics Society
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    • v.21 no.1
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    • pp.23-31
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    • 2015
  • We present a method for creating realistic 2D stick figure animations easily and rapidly using captured motion data. Stick figure animations are typically created by drawing a single pose for each frame manually for the entire time interval. In contrast, our method allows the user to summarize an action (e.g. kick, jump) for an extended period of time into a single image in which one or more action lines are drawn over a stick figure to represent the moving directions of body parts. In order to synthesize a series of time-varying poses automatically from the given image, our system first builds a deformable character model that can make arbitrary deformations of the user's stick figure drawing in 2D plane. Then, the system searches for an optimal motion segment that best fits the given pose and action lines from pre-recorded motion database. Deforming the character model to imitate the retrieved motion segment produces the final stick figure animation. We demonstrate the usefulness of our method in creating interesting stick figure animations with little effort through experiments using a variety of stick figure styles and captured motion data.

Buckling and Postbuckling Behavior of Stiffened Laminated Composite Panels (보강된 복합적층 판넬의 좌굴 및 좌굴후 거동 연구)

  • Lee, In-Cheol;Gyeong, U-Min;Gong, Cheol-Won;Hong, Chang-Seon;Kim, Cheon-Gon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.10
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    • pp.3199-3210
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    • 1996
  • The buckling and postbuckling behaviors were sutdied analytically and experimentally for stiffened laminated composite panels under compression loading. The panels with I-, blade, -and hat-shapeed stiffeners were investigated. In the analysis, the stiffened panels were anlyzed using the nonlinear finite element method combined with an improved arc-length method. The progressive failure analysis was done by adopting the maximum stress criterion and complete unloading failure model. The effects of the fiber angles were investigated on the buckling and postbuckling behaviors. In the experiment, the web and the lower cap of each stiffener were formed by the continuous lay-up of the skin for cocuring the stiffened panels. Therefore, the separation between stiffener and skin was not found in the junction part even after postbuckling ultimate load and the stiffened panels had excellent postbuckling load carrying capacity. A shadow moire thchnique was used to monitor the out-of-plane deformations of the panels. The piezoelectric films were attached to the panels to get the failure characteristics of the panel. The analytical results on the buckling load, postbuckling ultimate load, and failure pattern showed good agreement with the experimental results.

Stability Analysis of Shear-Flexible and Semi-Rigid Plane Frames (전단변형효과를 고려한 부분강절 평면뼈대구조의 안정성 해석)

  • Min, Byoung Cheol;Min, Dong Ju;Jung, Myung Rag;Kim, Moon Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.1A
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    • pp.9-18
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    • 2011
  • Generally the connection of structural members is assumed as hinge, rigid and semi-rigid connections. The exact tangent stiffness matrix of a semi-rigid frame element is newly derived using the stability functions considering shear deformations. Also, linearized elastic- and geometric-stiffness matrices of shear deformable semi-rigid frame are newly proposed. For the exact stiffness matrix, an accurate displacement field is introduced by equilibrium equation for beam-column under the bending and the axial forces. Also, stability functions considering sway deformation and force-displacement relations with elastic rotational spring on ends are defined. In order to illustrate the accuracy of this study, various numerical examples are presented and compared with other researcher's results. Lastly, shear deformation and semi-rigid effects on buckling behaviors of structure are parametrically investigated.

Flexural and Buckling Analysis of Laminated Composite Beams with Bi- and Mono-Symmetric Cross-Sections (이축 및 일축 대칭단면 적층복합 보의 휨과 좌굴해석)

  • Hwoang, Jin-Woo;Back, Sung Yong
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.12
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    • pp.614-621
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    • 2019
  • A generalized laminated composite beam element is presented for the flexural and buckling analysis of laminated composite beams with double and single symmetric cross-sections. Based on shear-deformable beam theory, the present beam model accounts for transverse shear and warping deformations, as well as all coupling terms caused by material anisotropy. The plane stress and plane strain assumptions were used along with the cross-sectional stiffness coefficients obtained from the analytical technique for different cross-sections. Two types of one-dimensional beam elements with seven degrees-of-freedom per node, including warping deformation, i.e., three-node and four-node elements, are proposed to predict the flexural behavior of symmetric or anti-symmetric laminated beams. To alleviate the shear-locking problem, a reduced integration scheme was employed in this study. The buckling load of laminated composite beams under axial compression was then calculated using the derived geometric block stiffness. To demonstrate the accuracy and efficiency of the proposed beam elements, the results based on three-node beam element were compared with those of other researchers and ABAQUS finite elements. The effects of coupling and shear deformation, support conditions, load forms, span-to-height ratio, lamination architecture on the flexural response, and buckling load of composite beams were investigated. The convergence of two different beam elements was also performed.

An External Surfaces Modeling of Inlay/onlay Using Geometric Techniques (기하학 기술을 이용한 인레이/온레이의 외면 모델링)

  • Yoo kwal-Hee;Ha Jong-Sung
    • The KIPS Transactions:PartA
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    • v.12A no.6 s.96
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    • pp.515-522
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    • 2005
  • This paper presents a method for effectively modeling inlay/onlay prostheses restoring a tooth that are partially destroyed. An inlay/onlay is composed of internal surface adhering to an abutment, and external surface revealed to the outside sight. Internal surfaces are modeled using Minkowski sum expanding the grinded surface parts of abutments so that the internal surfaces can adhere to the abutments with closer contact. In modeling external surfaces, we exploit 3D mesh deformation techniques: DMFFD(direct manipulation free-form deformation)[19] and MWD(multiple wires deformation)[17] with three kinds of informations: standard teeth models, mesh data obtained by scanning a plaster cast of a patient's tooth, FGP(functionally guided plane) measuring the occlusion of the patients's teeth. The standard teeth models are used for building up the basic shapes of external surfaces, while the plaster fast and FGP data are used for reflecting the unique properties of adjacent md occlusal surfaces of the patients's teeth, which are slightly different to each other but very important for correct functioning. With these informations as input data, the adjacent and occlusal surfaces are automatically generated as mesh data using the techniques of DMFFD and m, respectively. Our method was implemented so that inlay/onlay prostheses fan be designed more accurately by visualizing the generated mesh models with requirements by dentists.

An Experimental Study on Geotextile Effects as Reinforcement and Vertical Drain Materials (보강재(補强材) 및 배수촉진재(排水促進材)로서 Geotextile 의 효과(効果)에 관한 실험적(實驗的) 연구(硏究))

  • Kim, Soo Il;Yoo, Ji Hyeung;Cho, Sam Deok
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.2 no.4
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    • pp.39-47
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    • 1982
  • Geotextile effects as reinforcement and vertical drain materials are studied through the laboratory model embankments on weak clays. The experiments are carried out in four stages; no woven fabrics between clay-crushed stone boundary, fabrics between boundary with no initial pretensioning of fabrics, and fabrics between boundary with two different initial pretensionings of fabrics. In all stages, vertical drains utilizing non-woven fabrics are installed in the clay layer in square pattern to accelarate the consolidation. The experimental model has plane dimensions of $32cm{\times}330cm$. The height for the clay container is 60 cm. The 47 cm height of crushed stone embankment is constructed over the 50 cm deep clay layer. The time dependent pore pressures are measured utilizing the 8 piezometers installed symmetrically on both sides of the wall at different heights. The time dependent deformations are measured utilizing the LED indicating lamp matrix inserted in the crushed stone embankment and the dialgauges put on top of the clay layer where the crushed stones are not laid. The measurements are carried out for 10 days which is equivalent to the time required for the primary consolidation. Through the experimental study, an analytical procedure is developed to predict the time dependent embankment settlement even if the top of the clay layer is reinforced with woven fabrics. This can be done through measuring the maximum pore pressures developed in the clay layer and comparing with the theoretical maximum pore pressures when no reinforcing fabrics are employed.

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Geological Structure of the Jirisan Metamorphic Complex of the Yeongnam Massif in the Hwagae Area, Korea (화개지역에서 영남육괴 지리산 변성암복합체의 지질구조)

  • Lee, Deok-Seon;Kang, Ji-Hoon
    • The Journal of the Petrological Society of Korea
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    • v.22 no.4
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    • pp.251-261
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    • 2013
  • Hwagae area, which is situated in the southeastern part of the Jirisan province, Yeongnam massif, Korea, is mainly composed of Precambrian Jirisan metamorphic rock complex (JMRC). Lithofacies distribution of the Precambrian constituent rocks mainly shows NS-trending tight fold and EW-trending open fold. This paper researched deformational phased structural characteristics of JMRC based on the geometric and kinematic features and the forming sequence of multi-deformed rock structures, and suggests that the geological structure of this area was formed through at least three phases of ductile deformation. (1) Most of structural elements related to the $D_1$ deformation were recognized as $S_{0-1-2}$ composite foliation which was transposed by the $D_2$ deformation. (2) The $D_2$ deformation occurred under the EW-directed tectonic compression, and formed the NS-trending $F_2$ fold and $D_2$ ductile shear zone which is (sub)parallel to the axial plane of $F_2$ fold. (3) The $D_3$ deformation occurred under the NS-directed tectonic compression, and partially reoriented the pre-$D_3$ structural elements into ENE or WNW direction. It indicates that the distribution of Precambrian lithofacies showing NS and EW-trending folds in the Hwagae area is closely associated with the $D_2$ and $D_3$ deformations, respectively.