• Computers and Concrete
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• 제8권3호
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• pp.279-292
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• 2011

The main purpose of this study includes investigation of the rheological properties of fresh self consolidating cement paste containing chemical and mineral additives using Artificial Neural Network (ANN) model. In order to develop the model, 200 different mixes are cast in the laboratory as a part of an extensive experimental research program. The data used in the ANN model are arranged in a format of fourteen input parameters covering water-binder ratio, four different mineral additives (calcium carbonate, metakaolin, silica fume, and limestone), five different superplasticizers based on the poly carboxylate and naphthalene and four different Viscosity Modified Admixtures (VMAs). Two common output parameters including the mini slump value and flow cone time are chosen for measuring the rheological properties of fresh self consolidating cement paste. Having validated the model, the influence of effective parameters on the rheological properties of fresh self consolidating cement paste is investigated based on the ANN model outputs. The output results of the model are then compared with the results of previous studies performed by other researchers. Ultimately, the analysis of the model outputs determines the optimal percentage of additives which has a strong influence on the rheological properties of fresh self consolidating cement paste. The proposed ANN model shows that metakaolin and silica fume affect the rheological properties in the same manner. In addition, for providing the suitable rheological properties, the ANN model introduces the optimal percentage of metakaolin, silica fume, calcium carbonate and limestone as 15, 15, 20 and 20% by cement weight, respectively.

• 대한기계학회논문집A
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• 제30권7호
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• pp.757-764
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• 2006

Isothermal cyclic stress-strain deformation and thermomechanical deformation (TMD) of 429EM stainless steel were analyzed using a rheological model employing a bi-linear model. The proposed model was composed of three parameters: elastic modulus, yield stress and tangent modulus. Monotonic stress-strain curves at various temperatures were used to construct the model. The yield stress in the model was nearly same as 0.2% offset yield stress. Hardening relation factor, m, was proposed to relate cyclic hardening to kinematic hardening. Isothermal cyclic stress-strain deformation could be described well by the proposed model. The model was extended to describe TMD. The results revealed that the hi-linear thermomechanical model overestimates the experimental data under both in-phase and out-of-phase conditions in the temperature range of $350-500^{\circ}C$ and it was due to the enhanced dynamic recovery effect.

• Smart Structures and Systems
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• 제2권1호
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• pp.61-80
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• 2006

The concept of structural vibration control is to absorb vibration energy of the structure by introducing auxiliary devices. Various types of structural vibration control theories and devices have been recently developed and introduced into mechanical systems. One of such devices is damper employing controllable fluids such as ElectroRheological (ER) or MagnetoRheological (MR) fluids. MagnetoRheological (MR) materials are suspensions of fine magnetizable ferromagnetic particles in a non-magnetic medium exhibiting controllable rheological behaviour in the presence of an applied magnetic field. This paper presents the modelling of an MRfluid damper. The damper model is developed based on Newtonian shear flow and Bingham plastic shear flow models. The geometric parameters are varied to get the optimised damper characteristics. The numerical analysis is carried out to estimate the damping coefficient and damping force. The analytical results are compared with the experimental results. The results confirm that MR damper is one of the most promising new semi-active devices for structural vibration control.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.251-252
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• 2009

국내에서 생산되는 시멘트, 골재 및 SP 혼화제를 대상으로 하여 배합조건에 따른 유동 콘크리트의 레올로지 특성 시험을 수행하였다. 이로부터 물시멘트비와 SP제의 영향을 고려 한 유동 콘크리트의 레올로지 정수 추정에 관한 예측모델을 제시하였다.

• 한국자동차공학회논문집
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• 제2권3호
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• pp.62-74
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• 1994

This paper addresses on the model synthesis and performance analysis of an engine mount featuring electro-rheological(ER) fluids which undergo a phase change when subjected to electric fields. A novel type of ER fluid-filled engine mount is devised and its hydraulic model is constructed. An equivalent mechanical model is subsequently obtained from the governing equation of the hydraulic model. The model parameters associated with the ER fluids are distilled from experimental investigations on the Bingham properties of the fluids. The distilled data are then incorporated into the governing model to undertake feasible work through computer simulations,. It is shown that the proposed engine mount has an inherent capability of controlling both the damping force and the resonance frequency. Other superior performance characteristics accrued from the proposed methodology are also evaluated.

• 한국식품과학회지
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• 제34권4호
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• pp.583-589
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• 2002

펙틴에서 곁사슬의 정도가 다르게 제조된 사과펙틴과 토마토펙틴을 이용하여, 낮은 층밀림속도에서부터 높은 층밀림속도까지 적용이 가능한 유변학적 모델을 구하고자 하였다. 지수법칙모델, Cross 모델, Carreau 모델을 실험값에 비교하여 본 결과, Carreau 모델이 가장 적합하였다. 모델식에서 얻어진 층밀림속도 0에서의 점도$({\eta}_0)$는 곁사슬의 정도가 큰 사과펙틴의 경우에는 곁사슬이 많은 sample II가 적은 sample I보다 크게 나은 반면에 곁사슬이 적은 토마토 펙틴은 큰 차이를 보이지 않았으며, 그 값은 사과펙틴보다 크게 나타났다. 모델식의 계수를 펙틴농도에 대한 지수함수로 표현하여 펙틴에서 곁사슬의 영향을 살펴보았다. 즉, 곁사슬이 많은 사과펙틴은 토마토펙틴에 비해 유변학적 성질이 큰 차이를 보이고 있으며 모델로 설명할 수 있다.

• 식품보건융합연구
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• 제8권5호
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• pp.11-20
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• 2022

Honey was diluted with different percentages of water and was analysed rheologically at room temperature of 27℃. The rheological profiles of pure and impure honey samples were measured at low shear rates (0.01-4.16s^-1). This work developed a structural kinetic model, which correlated well with the rheological data. The new model was used to categorise honey samples using their average molecular weights as one of the distinctive properties. Also, the kinetics order in the new model predicts the number of active components in the "honey" undergoing deformation. Honey produced third order kinetics to depict the monomers, oligomers and water content in honey. Pure honey exhibits peculiar non-Newtonian rheological behaviour. The behaviour of water is Newtonian. Dilution of honey with different percentages of water turns the resulting fluid Newtonian from 10% dilution with water. This study analysed the antibacterial activities of honey and serially adulterated samples against Staphylococcus aureus and Pseudomonas aeruginosa. The antibacterial analyses of honey were conducted using Kirby Bauer's well diffusion method. The results indicated that pure honey exhibited a zone of inhibition against both organisms. Also, the diameter of the zone of inhibition decreased with increasing dilution of honey, suggesting a correlation with the rheological method.

• Computers and Concrete
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• 제2권2호
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• pp.97-110
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• 2005

Rheological behaviour of fresh concrete is an important factor in controlling concrete quality. It is recognized that the measurement of the slump is not a sufficient test method to adequately characterize the rheology of fresh concrete. To further understand the slump measurement and its relationship to the rheological properties, an elasto-viscoplastic, 2-D axisymmetric finite element (FE) model is developed. The FE model employs the Bingham material model to simulate the flow of a slump test. An experimental program is carried out using the Slump Rate Machine (SLRM_II) to evaluate the finite element simulation results. The simulated slump-versus-time curves are found to be in good agreement with the measured data. A sensitivity study is performed to evaluate the effects of yield stress, plastic viscosity and cone withdrawal rate on the measured flow curve using the FE model. The results demonstrate that the computed yield stress compares well with reported experimental data. The flow behaviour is shown to be influenced by the yield stress, plastic viscosity and the cone withdrawal rate. Further, it is found that the value of the apparent plastic viscosity is different from the true viscosity, with the difference depending on the cone withdrawal rate. It is also confirmed that the value of the final slump is most influenced by the yield stress.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.433-436
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• 2003

This paper proposes rheological creep and shrinkage model of FCM bridges made for HPC about 40Mpa. The proposed model separates time dependent part with characteristic material part and regards main variable as elastic modulus, which represents material characteristic and history. To find parameters of the model, we had creep, shrinkage and basic material tests about four FCM bridges. All specimens were tested with same condition, after 3days, 28days and 90days of curing. Also, exposed condition and closed condition were separately given to compare the data of each bridge. Finally, all creep data of four FCM bridges were compared to proposed rheological model and other proposed world code models, AASHTO, ACI, CEB-FIP, JSCE and etc.

• Journal of Biosystems Engineering
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• 제19권2호
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• pp.138-147
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• 1994

The stress relaxation and creep characteristics of fruits have usually been fit to an exponential expression based on a generalized Maxwell model and Burger's model. It is known that two to three terms in the expansion of those models are necessary to obtain a satisfactory fit to the rheological characteristics of fruits. Since four to six constants appear in the models, it is very difficult to determine their physical meaning according to the experimental conditions and levels. Therefore in order to ease the comparison of data, this study was conducted to develop the linearized rheological model of the fruit from the previous studies of stress relaxation and creep characteristics of fruits. Stress relaxation and creep characteristics were able to normalize and presented in the linear form of $t/S(t)=K_1+k_2t$ and $t/C(t)={K_1}^{\prime}+{K_2}^{\prime}t$, respectively. It was possible to compare the effects of experimental conditions and levels much easier from the linearized models developed in this study than from the generalized Maxwell model and Burger's model.