Papers by Keyword: Viscoelasticity

Abstract: Because of alkaline declining the sweep efficiency, causing scale formation problem in the reservoir and the well bottom and the tubular pipes, so polymer/surfactant compound flooding technology is the emphasis in the research of enhanced recovery. So the articles study the regulation of different kinds of surface active agents at different temperature by MARS Rheometer. The testing result showed that the variation of viscocity under the interaction between the surface active agent and association polymer according to “three stage” model .The linear viscoelastic region of stress decrease when different surface active agents are put into polymer liquor, and the higher frequency, the better elasticity of polymer liquor. The hydrophobic association between the surface active agents and polymer decrease with a higher temperature, but the ionic surfactant is aggravate. The systematic study of binary system rheology can contribute to correctly understand and apply binary system.

Abstract: The mechanical stimulation can affect the biological function of lung cells, but little is known about the effects on biomechanical properties of lung fibroblasts. In this paper, the human lung fibroblasts (MRC-5) were subjected to cyclic stretch (5% and 10% elongation amplitude) by FX-4000 Tension System. The micropipette aspiration technique was used to investigate the viscoelasticity of MRC-5. The results: for 5% stretch group, the viscoelastic parameters of MRC-5 were significantly lower than static group at 72 h; for 10% stretch group, the viscoelastic parameters of MRC-5 were significantly lower than static group at 48 h and 72 h, there was no difference of the viscoelastic parameters between 48 h and 72 h. The changes of viscoelasticity suggest that the lung fibroblast have different response to different mechanical stimulation and the mechanical stimulation plays an important role in regulating the viscoelasticity in the process of the growth and development.

Abstract: Abrasive medium plays an important role in the application of abrasive flow machining (AFM), a process that finishes complex internal and external geometries. A new abrasive medium needs to be fabricated due to a lack of literature on it. In this work, a new abrasive medium was fabricated by using styrene butadiene rubber (SBR) as carrier and DF-101S was used to study its characterization. Results showed that new abrasive medium with good fluidity and temperature stability was obtained. Processing experiments have also been carried out by using new abrasive medium and MLLD60, and ZYGO was used to study the surface characteristics of the work-piece. Experimental results indicate that the new abrasive medium is applicable to AFM process.

Abstract: This paper presents the results of an experimental and numerical investigation of the tensile behaviour of glass fibre reinforced epoxy composite for incremental and cyclic creep-recovery load conditions. The proposed constitutive model incorporates linear viscoelasticity coupled with damage and viscoplasticity for prediction of the creep-recovery responses. The material parameters are determined by fitting the experimental results. Scanning electron microscopy (SEM) of composite fracture surfaces is performed to explain the failure mechanisms. A computational algorithm for the integration of the proposed constitutive model at the material point level is derived and implemented into the finite element code ABAQUS. The model predictions are found to be in good agreement with the experimental data.

Abstract: The present paper is concerned with an experimental research and numerical modelling of the viscoelastic-viscoplastic-damage behaviour of bovine cortical bone. A one-dimensional constitutive model is proposed to predict the experimental behaviour under creep-recovery load conditions. The material parameters are determined by fitting experimental results. The derived algorithm for the integration of the proposed constitutive model is implemented into finite element formulation. The computational algorithm shows an excellent capability to describe the tensile behaviour of bovine cortical bone for the specific mechanical conditions analyzed.

Abstract: Polyacrylamide (polymer) solution which has different relative molecular mass and mass concentration in porous media has been studied in seepage flow experiment. Due to differences in pressure drop at different seepage velocities, the effective viscosities of different polymer solutions are calculated. Rheological behaviors of polymer solution changes in different mass concentration and relative molecular mass in porous media are analyzed. It is indicated that in the range of Darcy seepage velocity, acceleration is increasing during the process of pressure drop on both sides of core is resulted from the increase of flow rate during percolation, its effective viscosity first decreased, then increased with the increases of shear rate at range of Darcy velocity. Higher the relative molecular mass and mass concentration lead greater the effective viscosity.

Abstract: A novel kind of activated polymer flooding (APF) composing activated agent and polymer components designed for the target reservoir is studied for the first time. Interactions between the activated agent and natural surfactant from heavy oil, and the synergistic effect between the activated agent and polymer are existed. APF could enhance more oil recovery with less investment, compare to polymer-surfactant flooding (PSF) in the offshore heavy oilfield. The optimum formulation of APF is 1200mg/L polymer + 500mg/L activated agent. Experimental results implies that (1) the contained amide groups and sulfonic groups in APF can form hydrogen bonds with-NH₂ groups contained in PM, (2) the apparent viscosity of APF was higher than PM along with the increase of shear rate, (3) the viscoelasticity, deformation capability and solubility of APF were much better than PM.

Abstract: A finite volume method for the numerical solution of viscoelastic flows is given. The flow of a differential Phan-Thien-Tanner (PTT) fluid through an abrupt expansion-contraction channel has been chosen as a prototype example. Through the results of numerical simulations, the contours of velocity and stream function are drawn. Numerical results show that the viscoelasticity of polymer solutions is the main factor influencing the sweep efficiency. With increasing elasticity, the flowing area in the channel is enlarged significantly, thus the area with immobile zones becomes smaller, the microcosmic sweep efficiency increases. The visco-elastic nature of the displacing polymer fluids can ingeneral improve the displacement efficiency in pores compared to using Newtonian fluids. This conclusion should be useful in selecting polymer fluids and designing polymer flooding operations.

Abstract: The dynamic property of carbon filled rubber materials is related to pre-load, excitation frequency and amplitude etc. A model by superimposing an elastic model, a viscoelastic model and an elastic-plastic model is presented to model the dynamic property of a rubber isolator. In this paper, this approach is adopted to calculate the dynamic property of a rubber isolator. It is shown that the presented model can predict the amplitude and frequency dependency of a rubber isolator with small relative errors. The validity of this model is verified by experiment. The approach described in this paper can be used in the design and calculation for rubber isolators.

Abstract: The numerical simulation of the static response of viscoelastic materials with the finite element method is presented in this paper. In particular, elastomeric solids which are of essential engineering interest are discussed. A rubbery elastic manner is assumed to be modeled with an Ogden-type strain energy function. A Prony series represents the relaxation moduli is exploited. By using a general finite element software ANSYS, numerical examples illustrate relaxation and creeping phenomena.