• Advances in materials Research
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• 제13권1호
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• pp.1-18
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• 2024

The present experimental investigation focuses on finding optimal parametric data-set of laser micro-drilling operation with minimum taper and Heat-affected zone during laser micro-drilling of Carbon Nanotube/Epoxy-based composite materials. Experiments have been conducted as per Box-Behnken design (BBD) techniques considering cutting speed, lamp current, pulse frequency and air pressure as input process parameters. Then, the relationship between control parameters and output responses is developed using second-order nonlinear regression models. The analysis of variance test has also been performed to check the adequacy of the developed mathematical model. Using the Response Surface Methodology (RSM) and an Accelerated particle swarm optimization (APSO) technique, optimum process parameters are evaluated and compared. Moreover, confirmation tests are conducted with the optimal parameter settings obtained from RSM and APSO and improvement in performance parameter is noticed in each case. The optimal process parameter setting obtained from predictive RSM based APSO techniques are speed=150 (m/s), current=22 (amp), pulse frequency (3 kHz), Air pressure (1 kg/cm²) for Taper and speed=150 (m/s), current=22 (amp), pulse frequency (3 kHz), air pressure (3 kg/cm²) for HAZ. From the confirmatory experimental result, it is observed that the APSO metaheuristic algorithm performs efficiently for optimizing the responses during laser micro-drilling process of nanocomposites both in individual and multi-objective optimization.

• Computers and Concrete
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• 제24권2호
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• pp.103-115
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• 2019

In this study, the strength and stiffness (EI) of wood-concrete composite beams for bridges with T-shaped cross section were evaluated. Two types of connectors were used: connectors bonded with epoxy adhesive and connectors attached to the wood just by pre-drilling (without adhesive). The connectors consisted of common steel bars with a diameter of 12.5 mm. Initially, the strength and stiffness (EI) of the beams were analyzed by bending tests with the load applied at the third point of the beam. Subsequently, the composite beams were evaluated by numerical simulation using ANSYS software with focus on the connection system. To make the composite beams, Eucalyptus citriodora wood and medium strength concrete were used. The slip modulus K and the ultimate strength values of each type of connector were obtained by direct shear tests performed on composite specimens. The results showed that the connector glued with epoxy adhesive resulted in better strength and stiffness (EI) for the composite beams when compared to the connector fixed by pre-drilling. The differences observed were up to 10%. The strength and stiffness (EI) values obtained analytically by $M{\ddot{o}}hler^{\prime}$ model were lower than the values obtained experimentally from the bending tests, and the differences were up to 25%. The numerical simulations allowed, with reasonable approximation, the evaluation of stress distributions in the composite beams tested experimentally.

• Computational Structural Engineering : An International Journal
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• 제3권1호
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• pp.19-29
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• 2003

In the present study, finite element linear buckling analysis is performed for grid-stiffened composite plates. A hybrid element with drilling degrees of freedom is employed to reduce the effect of the sensitivity of mesh distortion and to match the degrees of freedom between skins and stiffeners. The preliminary static stress distribution is analyzed for the determination of accurate load distribution. Parametric study of grid structures is performed and three types of buckling modes are observed. The maximum limit of buckling load was found at the local skin-buckling mode. In order to maximize buckling loads, stiffened panels need to be designed to be buckled in skin-buckling mode.

• 한국공작기계학회논문집
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• 제12권6호
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• pp.8-13
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• 2003

CFRP composite has a lot of merits such as mechanical characteristic, light weight and thermal resistance. For these merits CFRP is applied to so many industrial area. In order for the composite materials to be used in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joints must be provided, which require precise machining. In this paper, the relationship between the stack thickness and drill diameter is examined from the drilling experiment, which is the drilling of 16, 32, 48p1ies specimen with the ${\phi}8$, ${\phi}10$, ${\phi}12mm$ cemented carbide drill. The results are analyzed with consideration of cutting force, stack thickness and drill diameter.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.168-173
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• 2005

Composite material is combined with two or more chemical ingredient and different components. FRP has been widely used for the structure of aircraft, ships, automobiles, sporting goods and other machines because of their high specific strength, high specific stiffness and excellent fatigue strength. Recently, the development of machine tool and cutting tool greatly relies on high speed process to satisfy high precision, high efficient machining, shortened process time to maximize material removal rate (MRR) through high cutting speed and feed speed. The research molded CFRP, GFRP as stacking sequence methods of two direction (orientation angle $0^{\circ}\;and\;0^{\circ}/9^{\circ}$) hand lay-up, drilled molded plates using cemented carbide drill and examined chip shapes, surface roughness properties.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.39-44
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• 2002

A three node triangular element with drilling rotations incorporating Improved Layerwise Zig-zag Theory(HZZT) is developed to analyze the vibration of spinning pretwisted composite blades with embedded damping layer. Matching conditions at the interfaces between the damping material and the border material are enforced by setting the shear forces matched and different shear strains along the interfaces. The natural frequencies and modal loss factors of cantilevered pretwisted composite blade with damping core are calculated with the present triangular element enforcing the matching conditions and compared to experimental results and MSC/NASTRAN results using a layered combination of plate and solid elements.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.190-195
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• 2003

CFRP composite has a lot of merits such as mechanical characteristic, light weight, and thermal resistance. For these merits CFRP is applied to so many industrial area. In this paper, the relationship between the stack thickness and drill diameter is examined from the drilling experiment, which is the drilling of 16, 32, 48 plies specimen with the $\phi$8, $\phi$10, $\phi$12mm cemented carbide drill. The results are analyzed with consideration of cutting force, stack thickness and drill diameter.

• Steel and Composite Structures
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• 제15권4호
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• pp.425-438
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• 2013

A new-styrofoam-concrete composite sandwich slab with function of heat insulation is designed. Four full-scale simply supported composite sandwich slabs with different shear connectors are tested. Parameters under study are the thickness of the concrete, the height of profiled steel sheeting, the influence of shear connectors including the steel bars and self-drilling screws. Experimental results showing that four specimens mainly failed in bending failure mode; the shear connectors can limit the longitudinal slippery between the steel profiled sheeting and the concrete effectively and thus guarantee the good composite action and cooperative behavior of two materials. The ultimate sagging bending resistance can be determined based on plastic theory. This new composite sandwich slab has high sagging bending resistance and good ductility. Additionally, these test results help the design and application of this new type of composite sandwich slab.

• Composites Research
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• 제23권6호
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• pp.55-60
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• 2010

본 연구에서는 열가소성 복합재료인 유리섬유/폴리프로필렌 복합재료를 이용한 복합재료 고정판의 적절한 성형조건을 찾기 위해 다양한 성형조건으로 제작된 시편의 인장실험과 굽힘실험을 수행하여 성형조건에 따른 기계적 거동을 비교하였다. 실험 결과 성형온도와 압력이 각각 $230^{\circ}C$, 3MPa일 때 가장 우수한 기계적 특성을 가짐을 확인하였다. 성형실험을 통해 결정된 성형조건을 이용한 복합재료 고정판의 성형방법으로는 고정판의 스크류 구멍을 한번에 성형하는 정형성형방법과 스크류 구멍을 후가공하는 방법을 사용하였으며, 성형실험과 굽힘실험 결과 스크류 구멍을 후가공 하는 경우 우수한 굽힘특성을 가지는 것을 확인하였다. 본 논문에서는 복합재료 고정판의 적절한 성형을 위해 유리섬유/폴리프로필렌 복합재료의 기초 성형정보와 그에 따른 고정판 성형에 대한 연구를 수행하였으며, 이 결과는 해당재료를 이용한 구조물 성형에 중요한 정보를 제공할 것으로 기대된다.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.100-105
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• 2008

Cross-drilling on the brake disc is generally known as a way of improving cooling efficiency. In other theories, cross-drilled holes act like a path of gas or water and are also known that they can reduce fading and wetting of brake rotors. However, in disc rotors with cross-drilling, thermal crack phenomena have been reported more frequently and more manufacturing cost should be paid than non cross-drilled disc rotors. In this study, to examine various effects of cross-drilling on the brake disc, two kinds of brake disc rotors, cross-drilled and non cross-drilled, were used in computational fluid dynamic analyses and dynamometer tests.