• Structural Engineering and Mechanics
• /
• 제46권1호
• /
• pp.39-51
• /
• 2013

An extremum method is presented to predict the wrinkling characteristics of the inflated cone in bending. The wrinkling factor is firstly defined so as to obtain the wrinkling condition. The initial wrinkling location is then determined by searching the maximum of the wrinkling factor. The critical wrinkling load is finally obtained by determining the ratio of the wrinkling moment versus the initial wrinkling location. The extremum method is proposed based on the assumption of membrane material of beam wall, and it is extended to consider beam wall with thin-shell material in the end. The nondimensional analyses show that the initial wrinkling location is closely related to the taper ratio. When the taper ratio is higher than the critical value, the initial wrinkles will be initiated at a different location. The nondimensional critical wrinkling load nonlinearly increases as the taper ratio increases firstly, and then linearly increases after the critical taper ratio. The critical taper ratio reflects the highest load-carrying efficiency of the inflated cone in bending, and it can be regarded as a measure to optimize the geometry of the inflated cone. The comparative analysis shows fairly good agreement between analytical and numerical results. Over the whole range of the comparison, the mean differences are lower than 3%. This gives confidence to use extremum method for bending-wrinkling analysis of inflated conical cantilever beam.

• 한국기계가공학회지
• /
• 제10권6호
• /
• pp.16-21
• /
• 2011

In machining operation, the quality of surface finish is an important factor for many turned products. In this paper, surface quality in turning machining considering angle variation has been investigated. To reach this goal, surface quality turning experiments are carried out according to cutting conditions with angle variation. The variable cutting conditions are cutting speed, feed rate and taper angle of workpiece. The surface roughness was measured and the effects of cutting conditions were analyzed by the method of analysis of variance (ANOVA). From the experimental results and ANOVA, it is found that a better surface roughness can be obtained as decreasing feed rate, increasing cutting speed. Taper angle variation has been more influenced by feed rate and cutting speed.

• 터널과지하공간
• /
• 제21권3호
• /
• pp.164-173
• /
• 2011

본 연구에서는 압축공기에너지 저장 공동의 콘크리트 플러그 최적 형상을 조사하기 위해 플러그 형상에 따른 저장 공동의 안정성을 수치해석적으로 평가하였다. 고려한 플러그 형상은 원통형, 암반에 근입된 원통형, 테이퍼형, 쐐기형이었고, 강도감소법에 의한 안전율과 압축 공기의 압력으로 인해 콘크리트에 발생하는 항복 영역의 부피비를 토대로 안정성을 분석하였다. 안정성 분석 결과, 암반에 근입된 원통형과 테이퍼형 플러그가 원통형과 쐐기형 플러그보다 역학적으로 더 안정한 것으로 분석되었다. 그러나 암반에 근입된 플러그의 경우 플러그와 암반이 접촉하는 부분에서 응력 집중이 발생하여 암반에 근입된 원통형 플러그보다는 테이퍼형 플러그 가 최적의 형상인 것을 확인하였다.

• EDISON SW 활용 경진대회 논문집
• /
• 제6회(2016년)
• /
• pp.101-105
• /
• 2016

Prandtl's Lifting-line theory is the classical theory of calculating aerodynamic properties. Though it is classical method, it predicts the aerodynamic properties well. By lifting-line theory, high aspect ratio is critical factor to decrease induced drag. And 'elliptic-similar' wing also makes the minimum induced drag. But due to the problem of manufacturing, tapered wing is preferred and have been utilized. In this Paper, by using Edison CFD, verifying the classical lifting-line theory. To consider induced drag only, using Euler equation as governing equation instead of full Navier-Stokes equation. Refer to the theory, optimum taper ratio which makes the minimum induced drag is 0.3. Utilizing the CFD results, plotting oswald factor over various taper ratio and investigating whether the consequences are valid or not. As a result, solving Euler equation by EDISON CFD cannot guarantee the theoretical values because it is hard to set the proper grid to solve. Results are divided into two cases. One is the values are decreased gradually and another seems to following tendency, but values are all negative number.

• 한국지반공학회논문집
• /
• 제24권12호
• /
• pp.13-22
• /
• 2008

지반조건과 말뚝의 테이퍼각도가 태야퍼말뚝의 지지력에 미치는 영향을 조사하기 위해서 원통형말뚝과 테이퍼각도가 다른 두 개의 메이퍼딸뚝을 이용해서 모형말뚝재하시험을 수행하였다. 시험결과에 띠르면 지반의 평균응력과 상대밀도가 커지면 테이퍼말뚝의 단위 선단지지력은 증가하였고, 말뚝의 테이퍼각도가 커집에 따라 느슨한 지반에서는 단위 선단지지력은 증가하였으나 조밀한 지반에서는 단위 선단지지력이 반대로 감소하였다. 그리고 테이퍼말뚝의 단위 주면마찰력은 지반의 수평 및 연직응력과 상대밀도, 말뚝의 테이퍼각도가 커짐에 따라 증가하는 것으로 나타났다. 한편, 모형말뚝재하시험의 결과에 근거해서 형상계수를 표함한 테이퍼말뚝의 지지력 산정식을 제안하였고, 이 제안식에서는 지반조건과 테이퍼각도가 말뚝의 지지력에 미치는 영향이 고려되였다. 제안한 지지력 산정식에 대한 정확도를 검증하기 위해서 점토질 모래지반에 설치된 중간규모의 원통형말뚝과 테이퍼말뚝에 대한 현장재하시험이 실시되었고, 이때 측정된 지지력이 제안식에서 얻은 예측치와 비교되었다. 그 결과 제안된 지지력 산정식은 테이퍼말뚝의 지지력을 비교적 정확하게 예측하는 것으로 나타났다.

• Steel and Composite Structures
• /
• 제51권6호
• /
• pp.601-617
• /
• 2024

This work aims to explore the static behaviour of a tapered functionally graded porous plate (FGPP) with even and uneven porosity distributions resting on two parametric elastic foundations. The plate under investigation is subjected to bi-sinusoidal loading and the edges of the plate are exposed to different combinations of edge restrictions. In order to examin the static behaviour, bending factors (BF) related to bending and normal stresses have been evaluated using classical plate theory. To achieve this, the governing equations have been derived employing the energy concept. And to solve it, the Rayleigh-Ritz method with an algebraic function has been utilised; it is simple, precise, and computationally intensive. After convergence and validation analyses, new findings are made available. The BF of the plate have been exhaustively examined to explain the influence of aspect ratios, material property index, porosity factor, taper factor, and Winkler and Pasternak stiffness. It is observed that the BF of an elastically supported FGPP are influenced by the index of material propery and the aspect ratio. Findings also indicate that the impact of porosity is more when it is spread evenly, as opposed to when it is unevenly distributed. Further, the deformed plate's structure is significantly influenced by the different thickness variations. Examination of bending characteristics of FGPP having different new cases of thickness variations with different types of porosity distribution under fifteen different mixed edge constraints is the prime novality of this work. Results presented are reliable enough to be taken into account for future studies.

• 대한기계학회논문집A
• /
• 제37권11호
• /
• pp.1323-1330
• /
• 2013

휠 로더는 다양한 작업이 가능한 건설장비 중의 하나로서, 기능적 다양성과 구조적 신뢰성 향상의 요구가 증대되고 있다. 휠 베어링은 로더의 수명을 결정하는 핵심부품 중 하나이며, 테이퍼 롤러 베어링이 사용되고 있다. 일반적인 베어링 수명은 하중과 회전속도로 계산되고 있다. 테이퍼 롤러 베어링의 초기 예압은 내구수명에 직접적인 영향을 미치는 중요한 인자이다. 본 논문은 테이퍼 롤러 베어링에 작용하는 하중, 회전속도, 열 변형에 따른 초기 예압량을 포함한 내구수명 및 예압특성 관계를 제시하였다. 사용온도가 $100^{\circ}C$라면, 상온에 비해 과다 예압 상태가 되며, 내구수명은 약 20.3% 감소하는 결과를 나타내었다.

• 한국정밀공학회지
• /
• 제23권9호
• /
• pp.127-133
• /
• 2006

Cold expansion method is used to protect a fatigue fracture from fastener hole in the structure and aerospace industry. Cold expansion is that an oversized tapered mandrel goes through the hole and produces a compressive residual stress as well as plastic deformation around the hole. Here, mandrel shapes are one of the factors which are influenced on the residual stress distribution by cold expansion method. This paper, according to mandrel shapes (diameter of mandrel, length of mandrel and length of taper), we are performed a finite element analysis of residual stress distribution by cold expansion method. From this study, it has been found that diameter of mandrel and length of taper are an important factor which was generated a low compressive residual stress surround of fastener hole by cold expansion method.

• Structural Engineering and Mechanics
• /
• 제55권3호
• /
• pp.605-638
• /
• 2015

It is intended to perform buckling analysis of steel gabled frames with tapered members and flexible connections. The method is based on the exact solutions of the governing differential equations for stability of a gabled frame with I-section elements. Corresponding buckling load and subsequently effective length factor are obtained for practical use. For several popular frames, the influences of the shape factor, taper ratio, span ratio, flexibility of connections and elastic rotational and translational restraints on the critical load, and corresponding equivalent effective length coefficient are studied. Some of the outcomes are compared against available solutions, demonstrating the accuracy, efficiency and capabilities of the presented approach.

• 한국도로학회논문집
• /
• 제15권6호
• /
• pp.135-141
• /
• 2013

PURPOSES : The lack of details of design guideline for zig-zag shaped section approaching central bus stop leads an traffic accident proneness. So, this study analysed the geometric elements of central bus stop area in terms of vehicle dynamics and suggested design alternatives. METHODS : The study analysed a dynamic behaviour of bus moving in and out of zig-zag shaped section using Auto-Turn under scenarios. Based upon dynamic analysis, the study found out the width of overtaking lane is the most influential factor for a safe moving at zig-zag alignment. RESULTS : The width of overtaking lane at design speed of 40, 50, and 60 km/h respectively was suggested given taper ratio of 1 to 10 required for Bus Rapid Transit (BRT), and the lane width is not wider than 4.0m which possibly makes two vehicles using the same lane. Also, the width of overtaking lane which mitigates the taper ratio was suggested with the same restriction about the maximum lane width. CONCLUSIONS : The results of the study can be used to prepare a design guideline on zig-zag shaped alignment of central bus exclusive lanes. The more stable moving is expected by applying the design alternatives suggested, therefore the lower rate of traffic crashes at the vicinity of central bus stops.