• Structural Engineering and Mechanics
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• 제36권6호
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• pp.669-678
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• 2010

In general means, the stress concentration problem of elastic plate with a rectangular hole can be investigated by numerical methods, and only approximative results are derived. This paper deduces an analytical study of the stress concentration due to a rectangular hole in an elastic plate under bending loads. Base on classical elasticity theory and FEM applying the U-transformation technique, the uncoupled governing equations with 3-DOF are established, and the analytical displacement solutions of the finite element equations are derived in series form or double integral form. Therefore, the stress concentration factor can then be discussed easily and conveniently. For the plate subjected to unidirectional bending loads, the non-conforming plate bending element with four nodes and 12-DOF is taken as examples to demonstrate the application of the proposed method. The inner force distribution is obtained. The solutions are adequate for the condition when the hole is far away from the edges and the thin plate subjected to any transverse loadings.

• 산업기술연구
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• 제20권A호
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• pp.169-178
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• 2000

The 4-point bending tests have been performed In order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strengths of as-welded specimens have satisfied the grade of fatigue strength prescribed in specifications of korea, AASHTO and JSSC. Fatigue strength at 2 million cycles of TIG-dressing specimens have increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks occurred at several points, where the radius of curvature and flank angle in the weld bead toes were low, and grew as semi-elliptical cracks, then approached to fracture. As a result of finite element analysis, stress concentration factor in weld bead toes has closely related to the flank angle and radius of curvature, and between these, the radius of curvature has more largely affected in stress concentration factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has largely affected on stress gradient correction factor in case a/t is below 0.4. From the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.

• 한국산학기술학회논문지
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• 제12권3호
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• pp.1078-1084
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• 2011

스포츠화의 설계에서 신발 앞축 부분의 굽힘강성은 매우 중요한 설계인자이지만, 측정하기가 어렵다. 본 논문은 이러한 굽힘강성을 측정하는 장비를 소개한다. 장비는 알루미늄 프레임 구조와 AC 모터, 2개의 로드셀, 엔코더와 제어용 하드웨어로 구성되어있으며, 신발의 굽힘 모멘트를 측정하는 메카니즘을 소개하였다. 유용성을 입증하기 위하여, 신발의 소재와 디자인이 굽힘강성에 미치는 영향을 관찰하는데 사용되어 졌다. 실험을 위하여 신발 중창소재의 경도와 두께를 달리하여 완성신발 시편을 제작하였다. 이들 시편으로 굽힘실험을 수행하고, 최소자승법을 사용하여 굽힘강성을 구하였다. 실험결과 PU 중창으로 만든 신발이 PH 중창으로 만든 신발보다 굽힘강성이 높았으며, 중창의 두께가 중창의 경도보다 굽힘강성에 미치는 영향이 크다는 것을 알아낼 수 있었다. 따라서, 이러한 실험결과를 바탕으로, 본 측정장비는 유용한 실험결과를 도출할 수 있었으며, 이 장비를 통하여 측정된 신발의 굽힘강성은 신발 설계의 유용한 설계인자로 활용될 수 있다고 사료된다.

• 한국의류학회지
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• 제20권6호
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• pp.1116-1124
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• 1996

The factors to presume the shapes of bending and draping were examined in this study, by applying the similar phenomenon and theory of analysis. The findings were as followings: 1. The value of deflection angle (f) of deflection curve were almost consistent with those of K number and the shapes of deflection curve were congruent, under the condition of that the values of EI/w are almost similar and the lengths of samples are consistent. 2. The values of drape area, drape coefficient, mean of deflection angle, and $\pi$ number were consistently estimated and the shapes of drape were almost the same, under the condition of that the values of EI/w are similar and the diameter of samples are consistent. 3. In using the samples with different values of EI/w, scale factor, kl, was obtained from the formula, the shapes of bending of the referent samples and compsactive smaples was geometrically similar, which the lengths of samples were 1,1'and were satisfied with the formula, hi: L'11, and their $\pi$ number were also consistent. 4. In applying the samples with different values of Rllw, scale factor (kl) was obtained and then, when semidiameter of samples was adjusted to be satisfied with the formula, k1=L/L, the shapes of draping of referent samples and comparative samples were geometrically similar. Furthermore, their $\pi$ number was also consistent. 5. The shares of bending and draping could be changed in terms of three factors such as the lengths of samples, bending ridigity, and weigths per unit area. $\pi$ number was obtained from theory of similar phenomenon, which was index to presume shapes of bending and the shapes of draping getting from the three factors.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.71-74
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• 2005

In manufacturing automotive parts, such as engine cradles, frame rails, subframes, cross-members, and other parts from circular tubes, pre-bending and pre-forming operations are often required prior to the subsequent tubular hydroforming process. During some pre-forming operations, the cross section of a bent circular tube is crushed into an oval-like shape to ensure proper geometry and sufficient clearance in the hydroforming dies. For such applications, the use of oval Instead of circular tubes could be an effective means of eliminating the pre-forming step. The oval tube could also be produced with less thinning and with less strain on the outside of the bend when controlled by a booster system without the use of mandrel. Hence, the understanding of the issues that occur in the bending of oval tubes is worthy of Investigation. This paper presents parametric studies on the bending of oval tubes without a mandrel. The finite element modeling technique is used to examine the deformation characteristics for both circular and oval tubes. In the simulations, the bending process parameters of bend radius, aspect ratio of the tube ovalness, and tube wall thickness are varied. Observations are made to obtain a hoop-buckle limit diagram in terms of a non-dimensional shape degradation factor. Suggestions based upon developed criteria are made on the acceptability of bend tubes suitable for hydroforming applications without the need ofa pre-forming step or the used of a mandrel.

• Steel and Composite Structures
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• 제21권6호
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• pp.1327-1345
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• 2016

$Al_2O_3$/SiC particulate reinforced (Metal Matrix Composites) MMCs which were produced by using stir casting process, bending strength and hardening behaviour were obtained using an analysis of variance (ANOVA) technique that uses full factorial design. Factor variables and their ranges were: particle size $2-60{\mu}m$; the stirring speed 450 rpm, 500 rpm and the stirring temperature $620^{\circ}C$, $650^{\circ}C$. An empirical equation was derived from test results to describe the relationship between the test parameters. This model for the tensile strength of the hybrid composite materials with $R^2$ adj = 80% for the bending strength $R^2$ adj = 89% were generated from the data. The regression coefficients of this model quantify the tensile strength and bending strengths of the effects of each of the factors. The interactions of all three factors do not present significant percentage contributions on the tensile strength and bending strengths of hybrid composite materials. Analysis of the residuals versus was predicted the tensile strength and bending strengths show a normalized distribution and thereby confirms the suitability of this model. Particle size was found to have the strongest influence on the tensile strength and bending strength.

• Journal of Mechanical Science and Technology
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• 제15권1호
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• pp.44-51
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• 2001

One of the recent issues in design of the spot-welded structure such as the automobile body is to develop an economical prediction method of the fatigue design criterion without additional fatigue test. In this paper, as one of basic investigation for developing such methods, fracture mechanical approach was investigated. First, the Model I, Mode II and Mode III, stress intensity factors were analyzed. Second, strain energy density factor (S) synthetically including them was calculated. And finally, in order to decide the systematic fatigue design criterion by using this strain energy density factor, fatigue data of the ΔP-N(sub)f obtained on the various in-plane bending type spot-welded lap joints were systematically re-arranged in the ΔS-N(sub)f relation. And its utility and reliability were verified by the theory of Weibull probability distribution function. The reliability of the proposed fatigue life prediction value at 10(sup)7 cycles by the strain energy density factor was estimated by 85%. Therefore, it is possible to decide the fatigue design criterion of spot-welded lap joint instead of the ΔP-N(sub)f relation.

• 한국정밀공학회지
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• 제14권9호
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• pp.80-89
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• 1997

Die sinking electrical discharge machining(EDM) was conducted for ceramic composite of 33 weight percent TiC based on AI$_{2}$O$_{3}$ ceramic matrix according to the change of current and duty factor(DF). Material removal rate(MRR) was increased as the current and the duty factor increased, but better surface mor-pholoty was obtained in the region of lower current and duty factor. From the scanning electron microscopy(SEM) photographs and the energy dispersive X-ray spectroscopy(EDX) of the EDMed surface, EDM trace formed by one discharge spark was analyzed. Although the bending strength after EDM was highly decreased, reliability obtained by weibull analysis was increased twice. The bending strength was recovered or more by barrel polishing after EDM. From the FEM analysis of temperature for one spark, the possible melting region of AI$_{2}$O$_{3}$and TiC was obtained.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.92-97
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• 2004

The aim of this study is to estimate the strength of injection molded plastic stepped gear. We considered stepped gear as plate model which are fixed by two edges. While, on the other sides are free. Normal gear is calculated by Lewis formula which can be derived quite simply from the equation for the stress at the root of a cantilever beam. Stress ratio(step factor) is represented for the ratio of the bending stress of normal and the bending stress of stepped gear, and it is plotted by face width factor. This study is propose the step factor added in Dupont equation which are strength estimation of step gear

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.585-590
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.