• Structural Engineering and Mechanics
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• 제51권1호
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• pp.163-180
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• 2014

In the displacement based finite element analysis of composite beams that consist of two Euler-Bernoulli beams juxtaposed with a deformable shear connection, the coupling of the displacement fields may cause oscillations in the interlayer slip field and reduction in optimal convergence rate, known as slip-locking. In this study, the B-bar procedure is proposed to alleviate the locking effects. It is also shown that by changing the primary dependent variables in the mathematical model, to be able to interpolate the interlayer slip field directly, oscillations in the slip field can be completely eliminated. Examples are presented to illustrate the performance and the numerical characteristics of the proposed methods.

• 한국세라믹학회지
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• 제25권6호
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• pp.615-622
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• 1988

To develope good slip and microstructure of Si3N4 the knowledge of the interaction of particles in liquid systems is required. In this work polyethyleneimines was tested as a stabilizer for Si3N4-water system. The stability of slip dispersed with polyethyleneimines was good over a wide range of pH and concentrated slips with low viscosity could be cast. This work comprises a systematic investigation including determination of electrical mobility in order to estimate the particle surface charge, determination of sedimentation rate, as well as measurements of the viscosity as a function of dispersants, pH and shear rates. The influence of deflocculation on the microstructure of slip cast Si3N4 was discussed.

• Korea-Australia Rheology Journal
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• 제17권4호
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• pp.207-215
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• 2005

We present a finite difference solution for electrokinetic flow in rectangular microchannels encompassing Navier's fluid slip phenomena. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in the equation of motion. The basic principle of net current conservation is applied in the ion transport. The effects of the slip length and the long-range repulsion upon the velocity profile are examined in conjunction with the friction factor. It is evident that the fluid slip counteracts the effect by the electric double layer and induces a larger flow rate. Particle streak imaging by fluorescent microscope and the data processing method developed ourselves are applied to straight channel designed to allow for flow visualization of dilute latex colloids underlying the condition of simple fluid. The reliability of the velocity profile determined by the flow imaging is justified by comparing with the finite difference solution. We recognized the behavior of fluid slip in velocity profiles at the hydrophobic surface of polydimethylsiloxane wall, from which the slip length was evaluated for different conditions.

• 재활복지공학회논문지
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• 제8권3호
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• pp.169-175
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• 2014

본 연구에서는 전동휠체어 주행 시, 슬립 현상으로 인해 발생할 수 있는 경로 이탈 및 제어 불능에 대처할 수 있는 슬립 제어기에 관한 연구로 주요기능인 슬립 검출기를 제안하고자 한다. 전동휠체어에서 슬립의 검출은 주행과정에서 전동휠체어와, 모터의 상태를 검출하는 것으로, 이를 위해 6축 IMU 센서와 좌우 모터에 연결되어 있는 엔코더를 통해 산출된 정보를 슬립 검출 알고리즘을 이용하여 슬립율을 산출한다. 이렇게 산출된 슬립 비율은 전동휠체어의 안전성 향상을 위한 제어변수로 사용된다. 본 연구에서 제안한 슬림 검출기 실험 결과 제안된 경로에서의 슬립 현상을 확인 할 수 있었다. 실험 중 최대 슬립 율 검출 구간은 전동휠체어의 선회시 발생하는 것으로 확인 하였다.

• Journal of applied mathematics & informatics
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• 제39권5_6호
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• pp.813-823
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• 2021

In this work, we present the classical formulation for the antiplane problem of a eletro-viscoelastic materialswith total sliprate dependent friction and write the corresponding variational formulation. In the second step, we prove that the solution converges to the solution of the corresponding electro-elastic problem as the viscosity converges to zero.

• 한국자동차공학회논문집
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• 제15권6호
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• pp.120-127
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• 2007

This paper describes the development of a nonlinear observer for four wheel steer (4WS) vehicle. An observer is designed to estimate the vehicle variables difficult to measure directly. A brake yaw motion controller (BYMC), which uses a PID control method, is also proposed for controlling the brake pressure of the rear and inner wheels to enhance lateral stability. It induces the yaw rate to track the reference yaw rate, and it reduces a slip angle on a slippery road. The braking and steering performances of the anti-lock brake system (ABS) and BYMC are evaluated for various driving conditions, including straight, J-turn, and sinusoidal maneuvers. The simulation results show that developed ABS reduces the stopping distance and increases the longitudinal stability. The observer estimates velocity, slip angle, and yaw rate of 4WS vehicle very well. The results also reveal that the BYMC improves vehicle lateral stability and controllability when various steering inputs are applied.

• Korean Chemical Engineering Research
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• 제52권3호
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• pp.371-377
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• 2014

Characteristics of holdup and flow behavior of fluidized solid particles were investigated in a liquid-solid circulating fluidized bed ($0.102m{\times}3.5m$). Effects of liquid velocity ($U_L$), particle size ($d_P$) and solid circulation rate ($G_S$) on the solid holdup, overall particle rising velocity, slip velocity between liquid and particles and hydrodynamic energy dissipation rate in the riser were examined. The particle holdup increased with increasing $d_P$ or $G_S$ but decreased with increasing $U_L$. The overall particle rising velocity increased with increasing $U_L$ or $G_S$ but decreased with increasing $d_P$. The slip velocity increased with increasing $U_L$ or $d_P$ but did not change considerably with $G_S$. The energy dissipation rate, which was found to be closely related to the contacting frequency of micro eddies, increased with increasing $d_P$, $G_S$ or $U_L$. The solid particle holdup was well correlated with operating variables such as $U_L$, $d_P$ and $G_S$.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.181-188
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• 1994

Generally, the structural material shows rate dependent behaviors, which require to constitute different strain-stress relations according to strain rates. Conventional rate- independent constitutive equations used in general purpose finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate dependent constitutive equation for elastic-plastic material was developed. The plastic stretch rate was modeled based on slip model with dislocation velocity and density so that there is no yielding condition, and no loading conditions. Non-linear hardening rule was also introduced for finite strain. Material constants of present constitutive equation were determined by experimental data of mild steel. The constitutive equation was applied to uniaxile tension. It was appeared that the present constitutive equation well simulates rate dependent behaviors of mild steel.

• 열처리공학회지
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• 제16권6호
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• pp.315-319
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• 2003

Effect of nitriding on fatigue crack initiation and growth rate has been studied in Ni-Cr-Mo steel. Specimens were nitrided at $860^{\circ}C$ for 15 hr. The fatigue limit of nitrided specimens were superior to those ofannea1ed($860^{\circ}C$, 15 hr) specimens. Based on detailed observations of slip band and micro crack initiation, it is concluded that the excellent fatigue limit of nitrided specimens is attributed to improved slip initiation resistance by nitriding. The characteristic of fatigue crack growth rate of nitrided specimens was investigated by comparing with those of annealed specimens. It was found that the crack growth rate was markedly decreased and the threshold stress intensity factor range was improved by nitriding. It is concluded that the excellent fatigue limit of nitrided specimens is also attributed to improved fatigue crack growth rate and threshold stress intensity factor range by nitriding.

• 산업기술연구
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• 제23권A호
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• pp.3-7
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• 2003

Effect of nitriding on fatigue crack initiation and growth rate has been studied on SNCM. Specimens were nitrided for 15 hr at $860^{\circ}C$. The fatigue limit of nitrided specimens was superior to that of annealed($860^{\circ}C$, 15 hr) specimens. Based on detailed observations of slip band and micro crack initiation, it is concluded that the excellent fatigue limit of nitrided specimens is attributed to improved slip initiation resistance by nitriding. The characteristic of fatigue crack growth rate of nitrided specimens was investigated and compared with those of annealed specimens. It was found that by nitriding the crack growth rate was markedly decreased and the threshold stress intensity factor range was improved. It is concluded that the excellent fatigue limit of nitrided specimens is also attributed to improved fatigue crack growth rate and threshold stress intensity factor range by nitriding.