• 대한기계학회논문집
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• 제5권2호
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• pp.110-121
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• 1981

In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

• Korea-Australia Rheology Journal
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• 제15권3호
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• pp.151-156
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• 2003

In this research, experimental studies were performed to examine the rheological behavior of equimolar solutions of cetylpyridinium chloride (CPyCl) and sodium salicylate (NaSal) solutions with concentration. The surfactant solutions were prepared by dissolving 2 mM/2 mM - 80 mM/80 mM of surfactant/counterion in double-distilled water. It has been observed that the zero shear viscosity shows abrupt changes at two critical values of C^*$ and C^{**}$. These changes are caused by the switching of relaxation mechanism with concentration of CPyCl/NaSal solutions at those concentrations. The wall slip velocities of dilute and semidilute CPyCl/NaSal solutions show a dramatic increase with shear rate where the shear viscosity exhibits shear thickening behavior for dilute solutions and shear thinning behavior for semi-dilute solutions, respectively. Considering that the dramatic increase in wall slip velocity should be related to the formation of shear-induced structure (SIS) in the surfactant solution, the shear thickening behavior of semi-dilute solutions is caused by elastic instability unlike the case of dilute solutions.

• Advances in concrete construction
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• 제15권5호
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• pp.303-312
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• 2023

The present study investigates the effects of Cattaneo-Christov thermal effects of stagnation point in Walters-B nanofluid flow through lubrication of power-law fluid by taking the slip at the interfacial condition. For the solution, the governing partial differential equation is transformed into a series of non-linear ordinary differential equations. With the help of hybrid homotopy analysis method; that consists of both the homotopy analysis and shooting method these equations can be solved. The influence of different involved constraints on quantities of interest are sketched and discussed. The viscoelastic parameter, slip parameters on velocity component and temperature are analyzed. The velocity varies by increase in viscoelastic parameter in the presence of slip parameter. The slip on the surface has major effect and mask the effect of stagnation point for whole slip condition and throughout the surface velocity remained same. Matched the present solution with previously published data and observed good agreement. It can be seen that the slip effects dominates the effects of free stream and for the large values of viscoelastic parameter the temperature as well as the concentration profile both decreases.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.632-637
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• 2004

In the shrink or press fitted shaft such as railway axle, fretting can occur by cyclic stress and micro-slippage due to local movement between the shaft and the hub. When the fretting occurs in the press fitted shaft, the fatigue strength remarkably decreases compared with that of without fretting. In this paper, the analysis of contact stresses in a press fitted shaft in contact with a hub was conducted by finite element method and the micro-slip according to the bending load was analyzed. It is found that the largest stress concentration and maximum slip amplitude of shrink fitted shaft are found at the edge of the interface and the distribution of contact stresses at the contact edge has largely influenced and coefficient of friction.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.497-502
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• 2003

This study intends to provide the analytical and experimental damping characterization of carbon nanotube/epoxy composites. A constitutive model based on continuum mechanics is employed to describe epoxy and the perfectly bonded and partially bonded nanotubes. An interfacial stick-slip between the nanotubes and epoxy is considered to characterize the damping of the composites. For experimental estimation, beam-type specimens are prepared with a variation of nanotube concentration from 0.5% to 2% in weight. An ultrasonic agitation method is employed for enhancing the nanotube dispersion within epoxy. Damping of the composites is characterized in terms of the strain and the nanotube concentration. Results show that the nanotube concentration significantly affects the damping characteristics of the nanocomposites. A good correlation is found between the analytical prediction based on the stick-slip and the experimental measurements.

• 한국안전학회지
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• 제27권6호
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• pp.78-83
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• 2012

In this study, some experimental results of the peroxide-degradation process of polypropylene(PP) in a co-rotating twin-screw extruder to produce controlled rheology polypropylene(CRPP) are presented. The peroxide was dicumyl peroxide(DCP) and the concentration of DCP was in the range 0-0.3 wt%. It was found that the rheological properties of PP change significantly during reactive extrusion. Melt flow index(MFI) increased with DCP concentration. Intrinsic viscosity decreases with increasing DCP concentration. From dynamic rheological data, number average molecular weight(Mn), weight average molecular weight(Mn) and molecular weight distribution(MWD) were calculated. Results indicated that Mw decreases and MWD becomes narrower with increasing peroxide concentration. Especially, particle size distribution of CRPP decreases with increasing DCP concentration by chemical powdering process, and anti-slip floor paint, CRPP(DCP 0.2 wt%) powder by 10phr was friction coefficient 2.15 ${\mu}$, abrasion resistance 511.18%.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권4호
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• pp.333-354
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• 2016

The present investigation deals, heat and mass transfer characteristics with the effect of slip on the hydromagnetic pulsatile flow through a parallel plate channel filled with saturated porous medium. Based on the pulsatile flow nature, exact solution of the governing equations for the fluid velocity, temperature and concentration are obtained by using two term perturbation technique subject to physically appropriate boundary conditions. The expressions of skin friction, Nusselt number and Sherwood number are also derived. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall.

• 한국세라믹학회지
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• 제36권2호
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• pp.178-185
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• 1999

Si3N4 겔캐스팅공정 제어를 위하여, 슬립 조성의 영향이 슬립의 점성특성과 성형체의 기계적 특성 및 소결체의 밀도에 미치는 영향에 대하여 조사하였다. 아크릴아마이드 모노머, 고분자전해질, 그리고 질화규소의 혼합물을 어트리터에 예비혼합한 후 볼밀링하여 슬립을 제조하였다. 개시제가 혼합된 슬립을 진공탈포하고 몰드에 주입하고 중합을 진행하였으며, 겔화된 슬립을 건조하여 성형체를 얻었다. 슬립의 특성과 성형체의 기계적 특성을 평가하기 위해, 슬립의 점도 측정과 직경방향 압축시험을 행하였다. 그 결과, near net shaping을 위한 낮은 점도를 갖는 46 vol%의 고농도 질화규소 슬립의 제조가 가능하였다. 성형체가 기계적 특성은 주로 모노머의 농도에 비례하여 증가하였다. 또한, 겔캐스트 성형체의 인장강도가 약 3MPa이 넘으면 기계적 가공이 가능하였으며, 겔캐스팅 성형체를 176$0^{\circ}C$, 3시간 상압소결하여 약 98.5%의 상대밀도를 얻을 수 있었다.

• 한국세라믹학회지
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• 제34권4호
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• pp.394-398
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• 1997

Mn-Zn ferrite powders were prepared by alcoholic dehydration, using coprecipitation method. Then the effects of organic dispersant and polymeric binder concentration on stability and casting of slurry were discussed. Citric acid, the organic dispersant and polyvinylacohol(PVA), the non-ionic binder, were selected as additives of slurry. With variation of concentration of water, citric acid and polyvinylalcohol(PVA), optimum forming conditions were determined from viscosity and density. To compare with dry process, density and microstructure of sintered body formed by uniaxial die pressing were observed.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.37-43
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• 2000

The effect of the alignment of the contacting bodies is concerned. Tilting of a body (indenter) is regarded as a mis-alignment. Recently developed method fur evaluating the contact normal traction is introduced and discussed, in which piecewise parabolic profile is considered as a generalized contact profile. Indentation by a wedge with rounded apex is solved as an example problem. In the case of partial slip regime, the variation of shear traction is examined during the closed path of shear force by using the efficient numerical technique. Concentration of the slip region is also investigated. By evaluating the energy dissipation from the contact surface, the effect of the mis-alignment-alignment on wear is discussed.