• 한국정밀공학회지
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• 제14권6호
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• pp.15-21
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• 1997

This study is performed for investigating the effects of stripping and counter punching forces on shearing characteristics in fine blanking of T-shaped products, such as camber, burr-height and dimensional accuracy, etc by experiments. Conventional hydraulic press is used for experiments so that both the stripping force and counter punching force can be arbitrarily adjusted by another hydraulic unit connected to the fine blanking die. Specimens are selected as hot rolled steel sheet and carbon steel sheet commonly used in auto- mobile company. Based on the experimental results, both the dimensional accuracy and the burr height are not influenced by the stripping and counter punching forces, wherease the camber height representing dish- shaped deflection is much influenced by them, it can be seen through this study that the finely cut surface of T-shaped blank can be obtained even in conventional hydraulic press if additional equipments and specially designed die are employed.

• Korea-Australia Rheology Journal
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• 제15권2호
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• pp.55-61
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• 2003

The steady shear flow properties of vaseline generally used as a base of the pharmaceutical dosage forms were studied in the consideration of wall slip phenomenon. The purpose of this study was to show that how slip may affect the experimental steady-state flow curves of semisolid ointment bases and to discuss the ways to eliminate (or minimize) wall slip effect in a rotational rheometer. Using both a strain-controlled ARES rheometer and a stress-controlled AR1000 rheometer, the steady shear flow behavior was investigated with various experimental conditions ; the surface roughness, sample preparation, plate diameter, gap size, shearing time, and loading methods were varied. A stress-controlled rheometer was suitable for investigating the flow behavior of semisolid ointment bases which show severe wall slip effects. In the conditions of parallel plates attached with sand paper, treated sample, smaller diameter fixture, larger gap size, shorter shearing time, and normal force control loading method, the wall slip effects could be minimized. A critical shear stress for the onset of slip was extended to above 10,000 dyne/$\textrm{cm}^2$. The wall slip effects could not be perfectly eliminated by any experimental conditions. However, the slip was delayed to higher value of shear stress by selecting proper fixture properties and experimental conditions.

• Design & Manufacturing
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• 제15권4호
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• pp.51-56
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• 2021

Piercing is the process of shearing a circular hole in sheet metal, whose high shear force makes it difficult to secure the durability of tools. In addition, uneven clearance between tools due to poor alignment of the piercing punch causes accelerated die wear and breakage of the tool. This study reviewed the feasibility of in-situ determining alignment failure during the piercing process by analyzing the signal deviation of a bolt-type piezo sensor installed inside the tool whose alignment level was controlled. Finite element analysis was performed to select the optimal sensor location on the piercing tool for sensitive detection of process signals. A well-aligned piercing process results in uniform deformation in the circumferential direction, and shearing is completed at a stroke similar to the sheet thickness. Afterward, a sharp decrease in shear load is observed. The misaligned piecing punch leads to a gradual decrease in the load after the maximum shear load. This gradual decrease is due to the progressive shear deformation that proceeds in the circumferential direction after the initial crack occurs at the narrow clearance site. Therefore, analyzing the stroke at which the maximum shear load occurs and the load reduction rate after that could detect the misalignment of the piercing punch in real-time.

• 산업기술연구
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• 제3권
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• pp.103-116
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• 1983

Recent developments in multi-storey buildings for residential purpose have led to the extensive use of shear walls for the basic structural system. When the coupled shear wall system is used, joined together with cast-in-place concrete or mortar (or grout), the function of the continuous joints is a crucial factor in determining the safety of L.P. Precast concrete shear wall structures, because the function of the continuous joints(Vertical wall to wall joints) is to transfer froces from one element(shear wall panel) to another, and if sufficient strength and ductility is not developed in the continuous joints, the available strength in the adjoining elements may not be fully utilized. In this paper, the influence of the stiffness of vertical joints(wet vertical keyed shear joints) on the behaviour of precast shear walls is theoretically investigated. To define how the stiffness of the vertical joints affect the load carrying capacity of L.P.Precast concrete shear wall structure, the L.P.Precast concrete shear wall structure is analyzed, with the stiffness of the vertical joints varying from $K=0.07kg/mm^3$(50MN/m/m) to $K=1.43kg/mm^3$(1000MN/m/m), by using the continuous connection method. The results of the analysis shows that at the low values of the vertical stiffness, i.e. from $K=0.07kg/mm^3$(50MN/m/m) to $K=0.57kg/mm^3$(400MN/m/m), the resisting bending moment and shearing force of precast shear walls, the resisting shearing force of vertical joints and connecting beams are significantly affected. The detailed results of analysis are represented in the following figures and Tables.

• 대한기계학회논문집
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• 제5권2호
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• pp.88-93
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• 1981

The three force components of shear spinning are calculated by a newly proposed deformation model. The spinning process is understooed as shearing deformation arter uniaxial yuelding by ending, and shear stress .tau.$\sub$rz/ becomes .kappa. the yueld limit in pure shear, in the deformation zone. The tangential forces are calculated and then the feed forces and normal foeces are obtained by assuming a nuiform distribution of roller pressure on the contact surface. An optimum contact area is obtaned by minimizing the bending energy required to obtain the assumed deformation mechanism. The calculated forces are compared with experimental data form published literature and present experiments. Good agreement cetween calculated and experimental values for working forces is obtained over a wide range of process variables.

• 소음진동
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• 제9권4호
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• pp.828-834
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• 1999

The paper describes the vibration and the stability of nonuniform tapered beams resting on two-layered elastic foundations. The two-layered elastic foundations are constructed by discributed Winkler springs and shearing layers as ofen used in oil models. Governing equations are derived from energy experssions using Hamilton's Principle. The associated eigenvalue problems are solved to obtain the free vibration frequencies or the buckling loads. Numerical results for the vibration and the stability of beams under an axial force are presented and compared with other available solutions. Finally, vibration frequencies and critical forces are investigated for various thickness ratios, shear foundation parameters, Winkler foundation parameters, and boundary conditions of tapered beams.

• 대한기계학회논문집
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• 제9권2호
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• pp.181-189
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• 1985

본 연구에서는 단순유로인 단면이 장방형인 각통을 그것에 수직한 축둘레에 회전시켜서 유로의 압력측 및 부압측에서의 속도 및 변동속도성분의 거동을 실험적으 로 조사함으로서 코리올리힘이 난류경계층 내의 유동에 미치는 영향을 구명하였다.

• 한국시뮬레이션학회논문지
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• 제8권2호
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• pp.111-122
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• 1999

The paper presents a stability analysis of uniform Timoshenko beams resting on two-parameter elastic foundations. The two-parameter elastic foundations were considered as a shearing layer and Winkler springs in soil models. Governing equations of motion were derived using the Hamilton's principle and finite element analysis was performed and the eigenvalues were obtained for the stability analysis. The numerical results for the buckling stability of beams under axial forces are demonstrated and compared with the exact or available confirmed solutions. Finally, several examples were given for Euler-Bernoulli and Timoshenko beams with various boundary conditions.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.806-818
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• 2006

The shear spinning process, where the plastic deformation zone is localized in a very small portion of the workpiece, shows a promise for increasingly broader application to the production of axially symmetric parts. In this paper, the three components of working force are calculated by the newly proposed deformation model in which the spinning process is understood as shearing deformation after uniaxial yielding by bending, and shear stress, $\tau_{rz}$ becomes $\kappa$, yield limit in pure shear, in the deformation zone. The tangential forces are first calculated and the feed forces and the normal forces are obtained by the assumption of uniform distribution of roller pressure on the contact surface. The optimum contact area is obtained by minimizing the bending energy required to get the assumed deformation of the blank. The calculated forces are compared with experimental results. A comparison shows that theoretical prediction is reasonably in good agreement with experimental results.

• 한국식품조리과학회지
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• 제17권5호
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• pp.483-489
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• 2001

본 연구의 목적은 김치의 장기간 저장숙성이 김치 또는 동결건조/복원 제품의 품질에 미치는 영향을 조사하는 것이다. 김치를 $0^{\circ}C$에 120일간 숙성시키면서 10일 간격으로 일정량씩 취하여 동결건조한 후 복원하여 젖산균수, pH, 전단력, 관능적 특성 및 형태를 관찰하고, 동일한 조건하에서 숙성된 김치의 품질과 비교하였다. (1) $0^{\circ}C$에서 120일간 숙성시킨 김치(Raw시료)의 젖산균수는 다소 감소하는 경향을 보였으며, pH는 점차 저하하였다. 이러한 경향은 F/D시료의 경우도 유사하였으며, 젖산균수가 동결건조에 의하여 Raw시료의 6~l6%로 감소하였다. (2) 120일의 숙성으로 김치시료의 전단력은 영향을 받지 않았으나 동결건조에 의하여 김치의 전단력이 현저하게 증가하였다. (3) 120일의 숙성기간 동안에 Raw시료와 F/D시료의 전반적인 기호성과 맛은 변화, 즉 저하하였으나, 저하하는 정도는 Raw시료의 경우가 F/D시료의 경우보다 다소 높았다. Raw시료와 F/D시료의 냄새는 120일의 숙성기간 동안에 저하하였으나 70일 이후에는 두 시료 사이의 차이가 그다지 크지 않았다. Raw시료와 F/D시료의 Moistness는 120일의 숙성기간 동안에 비교적 일정한 수준을 유지하였다. Raw시료의 저작성은 120일의 숙성기간 동안에 저하하였으나 F/D시료는 120일의 숙성에 의하여 큰 영향을 받지 않았다. Raw시료와 F/D시료의 색상은 120일의 숙성기간 동안에 변화하였으나 두 시료 사이의 차이는 크지 않았다. 이상의 결과로부터 얻은 결론은 다음과 같다. 즉, 김치를 120일간 숙성하면서 동결건조한 시료(F/D시료)와 숙성만 시킨 시료(Raw시료)를 비교하여 볼 때, 장기간의 숙성에 의하여 두 시료의 젖산균수, pH, 전단력이 변화하는 경향은 큰 차이가 없었으나 관능적 특성, 특히 전반적인 기호성, 맛, 저작성이 변화하는 경향은 두 시료 사이에 차이가 있는 것으로 생각된다.