• The korean journal of orthodontics
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• v.32 no.5 s.94
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• pp.343-353
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• 2002

This study was designed to investigate the stress distribution of alveolar bone in case of on masse retraction with lingual K-loop archwire using the 3-dimensional photoelastic stress analysis followed by stress freezing process. Lingual K-loop archwire which had loop in 15mm height was used and activated by retraction force of 350gm per each side. The results were as follows 1. Central incisor : As the closer side to crown, the larger tensile stress was distributed at both mesial and labial surfaces and the larger compressive stress was distributed at distal surface. As the closer side to root apex, the larger compressive stress was distributed at lingual surface. The compressive stress was distributed at root apex. 2. Lateral incisor : The tensile stress was distributed at the coronal side of mesial surface. The compressive stress was distributed at distal surface. As the closer side to crown, the larger tensile stress was distributed at labial surface. The tensile stress was distributed at coronal side and the compressive stress was distributed at apical side of lingual surface. The compressive stress was distributed at root apex. 3. Canine The tensile stress was distributed at coronal side and the compressive stress was distributed at apical side of mesial surface. The tensile stress was distributed at distal surface. As the closer side to crown, the larger tensile stress was distributed at both mesial and distal surfaces. The compressive stress was distributed at root apex. 4. Second premolar : The tensile stress was distributed at mesial surface. The compressive stress was distributed at coronal side and the tensile stress was distributed at apical side of distal surface. The compressive stress was distributed at coronal side of buccal surface. As the closer side to crown, the larger tensile stress was distributed at lingual surface. The compressive stress was distributed at root apex. 5. First molar . As the closer side to crown, the larger tensile stress was distributed at both mesial and distal surfaces. No stress was distributed at buccal surface and palatal root apex. As the closer side to crown, the larger tensile stress was distributed at both lingual surfaces. The compressive stress was distributed a4 buccal root apexes. 6. Second molar The compressive stress was distributed at all root apexes. As the closer side to crown, the larger compressive stress was distributed at both mesial and lingual surfaces, and the larger tensile stress at both distal and buccal surfaces. Transverse bowing effect was observed in on-masse retraction with lingual K-loop archwire, however vertical towing effect was not. Rather, reverse vortical bowing effect was developed.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.233-247
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• 2005

Most tunnel lining material which has been used in the domestic is a concrete. But many problems as the construction period, the cost, and the crack occurrence for the design, construction, and management were happened in the concrete lining. For this reason, many research institutes like the Korea Highway Corporation recognize the necessity of an alternate material development and grow on the interest for that. So in this study, the seismic behaviour characteristics for the application of the Corrugated Steel Plate Lining in cut-and-cover tunnel are evaluated as several conditions for the backfill height, the cutting slope, and the relative density of backfill soil are changed. The compressive stress which is calculated in the Corrugated Steel Plate Lining by the seismic load is decreased as the backfill height increases and the cut slope grows gentle. Also, the moment shows the tendency of decrease according to the increase of the backfill height. But in the case of the relative density of the backfill soil is small, the moment increases according to the increase of the backfill height and affects the dynamic behaviour characteristic. So it is considered that the relative density of the backfill soil is also the important point. As the result in analyzing the seismic response characteristics of the reinforcement spacing of the Corrugated Steel Plate, the variation in the compressive force is hardly happened, but the moment and the shear force increase on the reinforcement spacing being narrow.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.207-217
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• 2015

A concentrically braced steel frame is a very efficient structural system because it requires relatively smaller amount of materials to resist lateral forces. However, primarily developed as a structural system to resist wind loads based on an assumption that the structure behaves elastically, a concentrically braced frame possibly experiences the deterioration in energy dissipation after brace buckling and the brittle failure of braces and connections when earthquake loads cause inelastic behavior. Consequently, plastic deformation is concentrated in the floor where brace buckling occurs first, which can lead to the rupture of the structure. This study suggests reinforcing H-shaped braces with non-welded cold-formed stiffeners to restrain flexure and buckling and resist tensile force and compressive force equally.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.2
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• pp.101-110
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• 2007

This study was performed to find out hazardous factors in the loaded works of muscular skeletal disorders(MSDs) for four company attached to dining workers from October 2005 to June 2006. The results are summarized as follows. 1. 42.5% of workers in study group were 40-50 years old, and females were higher than males, and the average of body weight was 70kg, 57kg in males and females, respectively. Working time per day was mostly 7-9hours, and the rate of worker who had never education and training was 46%. 2. The upper part and right part of body were higher than lower part and left part in symptoms of muscular skeletal disorders. Body parts which complained of symptoms were the order of right shoulder(55%), right arm(54%), right hand,(40%) waist(35%), leg(25%), and neck(24%). 3. The results of evaluation in the loaded works of muscular skeletal disorders to cooking, dish supply, preparing side dish, and washing the dishes and cleaning the floor of cooking room using RULA and OWAS checklists was action level 4(potential hazards, needs of change workplace), and the result of evaluation using back compressive force needed control measures as 779.27 lbs~1,274.04 lbs. In a view point of the result of this study, large dining rooms should be designed by ergonomic technology for the work surface height, width, and depth. The height of carrying car should be lower to 70cm, and repetitiveness and handling weight should be reduced by mechanical means, and education and training also should be performed for all of workers positively.

• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.41-50
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• 2011

Three-dimensional(3D) numerical analyses have been conducted to study the behaviour of a single pile to adjacent tunnelling conducted in the lateral direction of the pile. In the numerical analyses, the interaction between the tunnel, the pile and the soil next to the pile has been analysed. The study includes the pile settlement, the relative shear displacement between the pile and the soil, the shear stresses at the soil next to the pile and the axial force on the pile. In particular, the shear stress transfer mechanism along the pile related to the tunnel advancement has been rigorously analysed. Due to changes in the relative shear displacement between the pile and the soil next to the pile during the tunnel advancement, the shear stress and the axial force distributions along the pile have been changed. Downward shear stress developed above the tunnel springline (Z/L=0.0-0.7~0.8), while upward shear stress is mobilised below the tunnel springline (Z/L=0.7~0.8-1.0) resulting in compressive force on the pile, where Z is the pile location and L is the pile length. Maximum compressive force of about $0.475P_a$ was developed on the pile after completion of tunnel advancement, where $P_a$ is the allowable pile capacity. Some insights into the pile behaviour to tunnelling obtained from the numerical analyses will be reported and discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.108-116
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• 2015

This study analytically reviewed the behavior of Steel Plate Concrete(SC) walls subjected to combined loads of axial force, flexural moment, and shear force to investigate the effects of shape and arrangement spacing of studs on the behavior of SC walls. To perform it, 9 cases of finite element analyses considering the different shape and spacing of studs in SC wall were carried out. The results showed that, for SC walls combined steel plate and concrete according to the Design Code, the compressive strength is higher than the tensile strength. Compared results from the finite element analyses of SC walls subjected to combined loads with Design Code showed that all cases were higher than the design strength. For KEPIC SNG, the moment and shear force were not influenced by the axial force of 0.1 to 0.2 times axial strength, however, from the analyses, it was found that the values were decreased as the axial force is increased.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.19-28
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• 2013

The longitudinal axial strain in the plastic hinge region of reinforced concrete (RC) columns influences on the structural behavior of RC structures subjected to reversed cyclic loading. This strain decreases the effective compressive strength of concrete and increases the lateral displacements between stories by causing the elongation of member length. This paper investigated the effects of the axial force on the elongation of a RC member by using a sectional analysis of RC members. The analytical and experimental results indicated that the axial force decreased the axial strain in the plastic hinge region of RC columns. In this study, a model was proposed to predict the axial strain of RC columns. The proposed model considering the effects of axial force ratio consisted of three path types ; Path 1-loading region, Path 2-unloading region, and Path 3-reversing cyclic loading region. The axal strains predicted by the proposed model were compared with the test results of RC columns with various axial force ratios, and agreed reasonably with the observed longitudinal strains.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.72-72
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• 2018

A dynamic fatigue characteristic of dental implant system has been evaluated with applying single axial compressive shear loading based on the ISO 14801 standard. For the advanced dynamic fatigue test, multi-directional force and motion needed to be accompanied for more information of mechanical properties as based on mastication in oral environment. In this study, we have prepared loading and motion protocol for the multi-directional fatigue test of dental implant system with single (Apical/Occlusal; AO), and additional mastication motion (Lingual/Facial; LF, Mesial/Distal; MD). As following the prepared protocol (with modification of ISO 14801), fatigue test was conducted to verify the worst case results for the development of highly stabilized dental implant system. Mechanical testing was performed using an universal testing machine (MTS Bionix 858, MN, USA) for static compression and single directional loading fatigue, while the multi-directional loading was performed with joint simulator (ADL-Force 5, MA, USA) under load control. Basically, all mechanical test was performed according to the ISO 14801:2016 standard. Static compression test was performed to identify the maximum fracture force with loading speed of 1.0 mm/min. A dynamic fatigue test was performed with 40 % value of maximum fracture force and 5 Hz loading frequency. A single directional fatigue test was performed with only apical/occlusal (AO) force application, while multi directional fatigue tests were applied $2^{\circ}$ of facial/lingual (FL) or mesial/distal (MD) movement. Fatigue failure cycles were entirely different between applying single-directional loading and multi-directional loading. As a comparison of these loading factor, the failure cycle was around 5 times lower than single-directional loading while applied multi-directional loading. Also, the displacement change with accumulated multi-directional fatigue cycles was higher than that of single directional cycles.

• The Journal of Korean Academy of Prosthodontics
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• v.18 no.1
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• pp.49-57
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• 1980

The adhesive mechanisms on the metal-ceramic restorations have been reported to be mechanical interlocking, chemical bonding, compressive force, and Van der Waal's force, etc. Of these, the mechanical interlocking and chemical bonding forces are thought to affect the adhesive force between Ni-Cr alloy and porcelain. This study investigates the adhesion of Ni-Cr alloy to porcelain according to surface treatment. For this purpose, the following experiments were made; The compositions of Ni-Cr alloy as cast by emission spectrograph, and the oxides produced on Ni-Cr alloy during degassing at $1850^{\circ}F$ for 30 minutes in air and in vacuum were analyzed by X-ray diffractograph. The metal phases of Ni-Cr alloy were observed according to porcelain-baking cyclic heat treatment by photo microscope and the distribution and the shift of elements of Ni-Cr alloy and porcelain and the failure phases between Ni-Cr alloy and porcelain by scanning electron microscope. The adhesive force between Ni-Cr alloy and porcelain was measured according to surface treatment with oxidization and roughening by Instron Universal Testing Machine. Results were as follows; 1. The metal phases of Ni-Cr alloy as cast and degassing state showed the enlarged and fused core, but when subjected to porcelain-baking cyclic heat treatment, showed a dendrite growing. 2. The kinds of metal oxides produced on Ni-Cr alloy during degassing were found to be NiO and $Cr_2O_3$. 3. The distribution of elements at the interface of Ni-Cr alloy and porcelain in degassing state showed demarcation line, but in roughening state, showed mechanical interlocking phase. 4. The shift of elements at the interface occurred in both states, but the shift amount was found to be larger in roughening than in degassing. 5. The adhesive force between Ni-Cr alloy and porcelain was found to be $3.45{\pm}0.93kg/mm^2$, in degassing and $3.82{\pm}0.99kg/mm^2$, in roughening. 6. The failure phase between Ni-Cr alloy and porcelain showed the mixed type failure.

• Steel and Composite Structures
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• v.39 no.5
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• pp.615-630
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• 2021

The main purpose of the present work was to study the dynamic instability of a three-layered, thick composite sandwich beam with the functionally graded (FG) flexible core subjected to an axial compressive follower force. Flutter instability of a sandwich cantilever beam was analyzed using the high-order theory of sandwich beams, for the first time. The governing equations in general for sandwich beams with an FG core were extracted and could be used for all types of sandwich beams with any types of face sheets and cores. A polynomial function is considered for the vertical distribution of the displacement field in the core layer along the thickness, based on the results of the first Frosting's higher order model. The governing partial differential equations and the equations of boundary conditions of the dynamic system are derived using Hamilton's principle. By applying the boundary conditions and numerical solution methods of squares quadrature, the beam flutter phenomenon is studied. In addition, the effects of different geometrical and material parameters on the flutter threshold were investigated. The results showed that the responses of the dynamic instability of the system were influenced by the follower force, the coefficients of FGs and the geometrical parameters like the core thickness. Comparison of the present results with the published results in the literature for the special case confirmed the accuracy of the proposed theory. The results showed that the follower force of the flutter phenomenon threshold for long beams tends to the corresponding results in the Timoshenko beam.