• The korean journal of orthodontics
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• v.41 no.3
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• pp.184-190
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• 2011

Objective: The purpose of this study was to investigate the relationship between the enamel thickness of proximal surfaces and the morphologic features of mandibular incisors. Methods: Mesiodistal/faciolingual (MD/FL) index, MD width, and height of contour width/cervical width ratio were measured in 40 incisors extracted from Koreans. For determining the height of contour width/cervical width ratio, the cervical width was measured as the distance between proximal cementoenamel junctions. Then, the labial surface was ground to the height of the contour level to measure enamel thickness. Pearson correlation analysis was used to investigate the correlation between enamel thickness and morphologic features. Results: Enamel thickness was $0.75{\pm}0.07mm$ per side, and MD width was $5.56{\pm}0.40mm$. Enamel thickness and MD width were significantly correlated. However, a significant relationship was not observed between enamel thickness and MD/FL index or the height of contour width/cervical width ratio. Conclusions: The results suggest that enamel thickness is affected only by MD width. Therefore, if the MD width is the same for mandibular incisors with a large MD/FL index or triangular shape and mandibular incisors with normal shape, then the limit of enamel reduction for reproximation will be the same.

• Steel and Composite Structures
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• v.45 no.6
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• pp.819-830
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• 2022

This paper presented an experimental study of the bond-slip behavior of reactive powder concrete (RPC)-filled square steel tube. A total of 18 short composite specimens were designed forstatic push-out test, and information on their failure patterns, load-slip behavior and bond strength was presented. The effects of width-to-thickness ratio, height-to-width ratio and the compressive strength of RPC on the bond behavior were discussed. The experimental results show that:(1) the push-out specimens remain intact and no visible local buckling appears on the steel tube, and the interfacial scratches are even more pronounced at the internal steel tube of loading end; (2) the bond load-slip curves with different width-to-thickness ratios can be divided into two types, and the main difference is whether the curves have a drop in load with increasing slip; (3) the bond strength decreases with the increase of the width-to-thickness ratio and height-width ratio, while the influence of RPC strength is not consistent; (4) the slippage has no definite correlation with bond strength and the influence of designed parameters on slippage is not evident. On the basis of the above analysis, the expressions of interface friction stress and mechanical interaction stress are determined by neglecting chemical adhesive force, and the calculation model of bond strength for RPC filled in square steel tube specimens is proposed. The theoretical results agree well with the experimental data.

• Steel and Composite Structures
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• v.36 no.2
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• pp.187-196
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• 2020

Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.

• Transactions of Materials Processing
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• v.4 no.2
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• pp.151-158
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• 1995

In this study, the width spreads of spring steel including Mn-Cr steel(SUP 9A), Mn-Cr-V steel(SUP 11A), and Si-Cr steel(SAE 9254) and were investigated under different reduction ratios and thickness-width ratios friction coefficients. The experimental results were compared with the theoretical prediction by the Ekelund equation, Geuze equations, etc. The width spreads of the three spring steels were found to be 10-15% larger than mild steel, and the optimal reduction ratio for the spring steel was found in a range from 20 to30%. Among the spring steels, the width spread of Mn-Cr-V steel was measured to be the largest followed by those of Si-Cr steel and Mn-Cr steel. It was found that the width spread increased with friction coefficient, width-thickness ratio and reduction ratio as predicted. However, the theoretical predictions revealed smaller width spread than the experimental results. This finding indicates that the coefficients of the width spread of the theoretical models need to be modified in order to predict the actual behavior of the width spreading of the spring steels. In this study, the coefficients of width spread of the Geuze equation were determined from the experimental results.

• Tribology and Lubricants
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• v.29 no.1
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• pp.13-18
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• 2013

Slider bearing is a widely used load-carrying element in the industry. While a large number of studies have investigated the effect of overall surface curvature, very few have considered sinusoidal surface. Recently, consideration of surface roughness/waviness or intentional wave design has been identified as an important issue in the manufacture of hard disk driver, mechanical seal, hydraulic machine, and etc. This study investigated the load-carrying capacity of a finite-width slider bearing with a wavy surface. Film thickness ratios, length-width ratio, ambient pressure, amplitude, and partial distribution were selected as the simulation parameters. The calculation results showed that the load-carrying capacity rapidly varied at small film thickness ratio, but the waviness near the area of minimum film thickness made much more influence with an increase in film thickness ratio. As the length-width ratio of bearing was increased, ambient pressure became more influential at small film thickness ratios. Furthermore a particular partial distribution of the wavy area led to higher load-carrying capacity than did the whole distribution. Consequently, the results of this study are expected to be of use in surface micro-machining of finite-width slider bearings.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.2
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• pp.112-120
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• 1993

Variable thickness plates are commonly encountered in the majority of mechanical/structural components of industrial applications. And, as a result of the unsymmetry of the structure or the load and the anisoptropy of the materials, the cracks in engineering structures are generally subjected to combined stresses. In spite of considerable practical interest, however, a few fracture mechanics study on combined mode crack in a variable thickness plate have carried out. In this respect, combined mode 1/3 stress intensity factors $K_{1}$ and $K_{3}$ at the crack tip for a variable thickness plate were obtained by 3-dimensional finite element analysis. Variable thickness plates containing a central slant crack were chosen. the parameters used in this study were dimensionless crack length .lambda. crack slant angle .alpha, thickness ratio .betha. and width ratio .omega. Stress intensity factors were calculated by crack opening displacement(COD) and crack tearing displacement(CTD) method proposed by Ingraffea and Manu. The effect of thickness ratio .betha. on $K_{1}$ is relatively great in comparison to $K_{3}$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.952-956
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• 1997

This paper describes the method that can expand the forming limit of T type forging products used in aircraft and automotive forged products. The forming limitis determined by the ratio of web thickness to rib width in T type and the reduction in height of workpiece and especially depends on the ratio of web thickness to rib width. For this method, the geometric condition that consists of triangle type was introduced and FEM simulations and model exoeriments were carried out and compared with each other. The objective of this paper is to give the method not only that sink mark and folding phenomenon are eliminated but also that the forming limit and the structural strength of rib and web is increased.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.132-144
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• 1987

This paper presents the theroetical analysis of the crack tip stress intensity factor for a center crack in a finite width plate with variable thickness. The analyses were based on Laurent's expansions of complex stress potentials where the expansion coefficients are determined from the boundary conditions. The perturbation method was employed in numerical calculations. The correction factor F(.lambda.)is given in the form of power series of .lambda. [a numerical formula] where .lambda.=a/w$^{1}$; Dimensionless crack length, .betha.=t$_{2}$/t; Thickness ratio .omega.=w$_{2}$/w$_{1}$; width ratio The correction factor values vary with the width ratio .omega. and the maximum variation occurs around .betha.=1. For the case of .betha.=1 or .betha.=0 (uniform thickness plate0, the correction factor values agree well with Feddersen's formula. In all cases, as .lambda. approaches to 1 (thickness interface), the correction factor values are decreased rapidly for .betha.>1, and increased rapidly for .betha.<1.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.32-39
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• 2015

So far, square concrete filled tubular(CFT) columns have been used in a limited width thickness ratio. The reason is that local buckling occurs in steel tube easily. Once the local buckling occurs, the confinement effect of steel tube on concrete disappears. In this study, we developed welded built-up square steel tube with reinforcement which are placed at the center of the tube width acts as an anchor. 3 specimens of slender welded built-up square CFT columns and 3 specimens of slender welded built-up square steel tube columns were manufactured with parameters of width(B) of steel tube, width thickness ratio(B/t). we conducted a experimental test on the 6 specimens under eccentric load, and evaluated the structural resistance and behavior of 6 specimens.

• Journal of Crop Science and Biotechnology
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• v.11 no.2
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• pp.151-156
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• 2008

The objective of this study is to identify main-effect QTLs, epistatic QTLs, and the interactions between QTL and the environment associated with grain appearances of brown rice. A genetic linkage map was created with 172 DNA markers spanning 12 rice chromosomes based on 120 DH lines, which derived from a cross between 'Samgang'(Tongil) and 'Nagdong'(Japonica). One thousandgrain weight, length, width, length-to-width ratio, and thickness were evaluated regarding the DH population. Twenty independent QTLs and fourteen epistatic QTLs were identified in using CIM by two programs, known as WinQTLcart2.5 and QTLMAPPER. The QTLs of qgw9.1 in an interval of RM434-RM242 on chromosome 9 and qgw11.1 at a peak marker of RM287 on chromosome 11 for one thousand-grain weight, qgwi2.2 for grain width at a peak marker of RM450, qlw2.1 for length-to-width ratio flanked by RM492 and RM324, and qgt2.1 for thickness flanked by 2009 and RM492 on chromosome 2 were detected over two years, which can be considered as stable QTLs. The epistatic effect might be an important component for genetic basis of one thousand-grain weight and width. The main-effect QTLs of grain width and length to width ratio were easily influenced by environments.