Rheological and Tribological Characteristics of the Synthesized Lubricants Derived from Vegetable Oils

The double bonds in the vegetable oils can be conjungated and Diels-Alder react when they are heated in the existence of the catalyst. The percent of the double bond will decrease and the oxidative stability of the vegetable oils can be ameliorated. Dimmer acid can react with different carbon chain length of alcohols to form dimmer acid esters. A series of dimmer acid esters were synthesized and their rheological characteristics （viscosity, viscosity index, pour point） and tribological characteristics （the coefficient of friction at different load, the characteristic of extreine pressure （ PB ）, the wear scare diameter （ D30min^196N ） were evaluated and analyzed. The results showed that the characteristics of Di-iso-octanol dimmer acid ester were the best among the synthesized dimmer esters. It＇ s a lubricant with good properties（the viscosity is 94.5 mm^2/s, the viscosity index is high up to 141 and the pour point is - 49℃ ）. It is a kind of newly interesthing ester type lubricant. Its rheological and tribological characteristics are even better than those of the slap-up synthesized lubricant--pentaerythritol esters （C7-9 acidate）. The FT-IR spectrophotometer was used to analyze the structure of the synthetic esters. Their IR spectra are the same as the typical IR spectrum of ester. The test indicated that Di-iso-octanol dimmer acid ester could be used as a kind of base lubricant with excellent quantity.

Rheological characteristics of soft rock structural surface

There are two mechanisms of the coarse surface asperity resistance effect and rubbing resistance effect in the course of the soft rock structural surface creep,of which the former plays a dominant role in hindering the deformation in the starting creep phase,so that the structural surface creep usually displays the strong surface roughness effect,and so does the latter when the asperities in the coarse surface were fractured by shearing.Under the low stress condition,there are only two phases of the decelerating creep and the constant creep for the soft rock structural surface,and as the stress increases and overcomes the rubbing resistance,the accelerating creep failure of the structural surface will happen suddenly.Therefore,a multiple rheological model,which combines the nonlinear NEWTON body(NN) of a certain mass and the empirical plastic body(EM) with the classical SAINT VENANT body,NEWTON body,KELVIN body and HOOKE body,could be used to comprehensively describe the creep characteristics of the soft rock structural surface.Its mechanical parameter values will vary owing to the different surface roughness of the structural surface.The parameters of GH,GK and ηL are positively linearly correlative to the surface roughness.The surface roughness and m are negative exponential function correlation.The long-term strength τS is positively correlative to the surface roughness.

Effects of pH on rheological characteristics and stability of petroleum coke water slurry

In this study, the effects of pH on slurrying properties of petroleum coke water slurry（PCWS） were investigated. The slurrying concentration, rheological characteristics and stability of PCWS were studied with four different types of additives at pH varying from 5 to 11.The results showed that the slurrying concentration, rheological characteristics and stability of PCWS all increased at first and then decreased with increasing pH from 5 to 11,and a pH of around 9 was found to be the most favorable acid–alkali environment to all these three slurrying properties. It was also indicated that only in a moderate alkaline environment can the additives be active enough to react with particle surfaces sufficiently to obtain good slurrying concentration and form a stable three-dimensional network structure, which can support strong pseudoplastic characteristics and good stability. An acid environment was a very unfavorable factor to the slurrying properties of PCWS.

Evaluation Indices of Interaction Ability of Asphalt and Aggregate Based on Rheological Characteristics

In order to find a parameter as the evaluation index that can capture the effect of the interaction between asphalt and aggregate, the rheological properties of asphalt mastics using two kinds of asphalts and four kinds of aggregates under different filler-asphalt ratios were measured by a dynamic shear rheometer （DSR）. Moreover, four rheological parameters of K.Ziegel-B, Luis Ibrarra-A, complex shear modulus ΔG＊and complex viscosity Δη＊ for evaluating the interaction ability were studied. Results indicate that all the four parameters can characterize the interaction ability of asphalt and aggregate correctly and feasibly. Through the comparison of sensitivities and physical meanings of the four parameters, K.Ziegel-B with high sensitivity and exact physical meaning is finally selected as the evaluation index for interaction ability of asphalt and aggregate.

Review of Non-Newtonian Mathematical Models for Rheological Characteristics of Viscoelastic Composites

This study presents an overview of viscoelastic characteristics of biocomposites derived of natural-fibre-reinforced thermoplastic polymers and predictive models have been presented in order to understand their rheological behavior. Various constitutive equations are reviewed for a better understanding of their applicability to polymer melt in determining the viscosity. The models to be investigated are the Giesekus-Leonov model, the Upper Convected Maxwell (UCM) model, the White-Metzner model, K-BKZ model, the Oldroyd-B model, and the Phan-Thien-Tanner models. The aforementioned models are the most powerful for predicting the rheological behavior of hybrid and green viscoelastic materials in the presence of high shear rate and in all dimensions. The Phan-Thien Tanner model, the Oldroyd-B model, and the Giesekus model can be used in various modes to fit the relaxation modulus accurately and to predict the shear thinning as well as shear thickening characteristics. The Phan-Thien Tanner, K-BKZ, Upper convected Maxwell, Oldroyd-B, and Giesekus models predicted the steady shear viscosity and the transient first normal stress coefficient better than the White-Metzner model for green-fibre-reinforced thermoplastic composites.

Rheological characteristics of aged asphalt binder

Different aging levels(RTFOT,PAV-10h,PAV-20h and PAV-30 h) of asphalt binders with various mass ratios of mineral powder to asphalt(0,0.4,0.8,1.2,1.6,2.0) were used to investigate the rheological properties of aged asphalt binders with respect to their short and long terms aging characteristics.Viscosity test,dynamic shear test and creep test were conducted.The test results indicate that the viscosity of aged asphalt binder increases sharply with the extension of aging period.Complex shear modulus of aged asphalt increases,which indicates that the stiffness of asphalt binders can increase.The phase angle for aged asphalt binders reduces,which indicates that the elastic portion for viscoelastic property of asphalt binders increases.|G*|·sin δ increases after aging procedure which means that the fatigue resistance becomes poor.The creep test results show that creep strain curves varies remarkably for virgin and aged asphalt binders.The total strain during loading period and the permanent strain decreases significantly for aged asphalt binders,which implies that the elastic portion increases and the viscous portion decreases.

Study on Rheological Characteristics of a Grease Used in High Speed Bearing

On a self-made super-high shear strain rate rheometer, the rheological characteristics and apparent viscosity curves of a high-speed bearing grease were obtained under different working conditions. A new grease rheological model suited to a shear strain rate range of 0—3.5×10~6s^(-1) was presented. The results showed that the shear stress increased linearly at first and then increased nonlinearly with the increase in shear strain rate up to 1.5×10~6s^(-1), and finally the shear stress decreased slightly with the successive increase in shear strain rate. The shear stress increased with a decreasing rolling speed and an increasing contact pressure. The apparent viscosity decreased rapidly with the increase of shear strain rate at beginning and could approach the viscosity of the base oil if the shear strain rate surpassed 1.5×10~6s^(-1). The fits between the test data and the predicted values by the new model were fairly good.

Analysis on damage and rheological characteristics of deep surrounding rock of shaft engineering

According to the characteristics of deep engineering surrounding rock main shaft of No.3 mining district in Jinchuan, electron microscope scanning and rock mechanics test were adopted to analyze the damage features of rock. The software of FLAG3D and Burgers body （Kelvin-Maxwell model） were used to research on rheological theory, and rheological model was modified. The results indicate that the damage of rock mass is very serious, and the rheological characteristics also outstanding; rheological behavior of deep surrounding rocks of the shaft can be taken as superposition of transient and stable rheology; and there exist the most dangerous zone on 100 m higher than 1 063 m level, so it is necessity that works of monitor and corresponding reinforcement should strengthen.

Modeling the Rheological Characteristics of Flexible High-Yield Pulp-Fibre-Reinforced Bio-Based Nylon 11 Bio-Composite

The aim of this work was to develop a mathematical model to investigate the rheological characteristics of viscoelastic pulp-fibre composite materials. The rheological properties of High-Yield Pulp (HYP) reinforced bio-based Nylon 11 (Polyamide 11) (PA11) composite (HYP/PA11) were investigated using a capillary rheometer. Novel predicted multiphase rheological-model-based polymer, fibre, and interphasial phases were developed. Rheological characteristics of the compo-site components influence the development of resultant microstructures;this in turn affects mechanical characteristics of a multiphase composite. The main rheological characteristics of polymer materials are viscosity and shear rate. Experimental and theoretical test results of HYP/PA11 show a steep decrease in apparent viscosity with increasing shear rate, and this melt-flow characteristic corresponds to shear-thinning behavior in HYP/PA11. The non-linear mathematical model to predict the rheological behavior of HYP/PA11 was validated experimentally at 200°C and 5000 S-1?shear rate. Finally, predicted and experimental viscosity results were compared and found to be in a strong agreement.

Steady State Rheological Characteristic of Semisolid Magnesium Alloy

Isothermal compressive experiments at different temperatures, strain rates and holding time for semisolid AZ91D, Zr modified AZ91D and MB15 alloy with higher solid volume fraction were carried out by using Gleeble-1500D simulator and the true stress-strain curves were given directly. The relationship of apparent viscosity vs temperature, shear rate and holding time of the three kinds of semi-solid magnesium alloys, as well as isothermal steady state rheological characteristic and mechanical behavior were studied. The results show that the three magnesium alloys had the characteristic of shear-thinning. The rheological characteristic of the semi-solid MB15 is different from that of semi-solid AZ91D. The semi-solid MB15 has higher apparent viscosity and deformation resistance.

Dynamic characteristics of the planetary gear train excited by time-varying meshing stiffness in the wind turbine

Wind power has attracted increasing attention as a renewable and clean energy. Gear fault frequently occurs under extreme environment and complex loads. The time-varying meshing stiffness is one of the main excitations. This study proposes a 5 degree-of-freedom torsional vibration model for the planetary gear system. The influence of some parameters(e.g., contact ratio and phase difference) is discussed under different conditions of a single teeth pair and double pairs of teeth. The impact load caused by the teeth face fault, ramped load induced by the complex wind conditions, and the harmonic excitation are investigated. The analysis of the time-varying meshing stiffness and the dynamic meshing force shows that the dynamic design under different loads can be made to avoid resonance, can provide the basis for the gear fault location of a wind turbine, and distinguish the fault characteristics from the vibration signals.

Efficient computation for dynamic responses of systems with time-varying characteristics

Based on Neumman series and epsilon-algorithm, an efficient computation for dynamic responses of systems with arbitrary time-varying characteristics is investigated. Avoiding the calculation for the inverses of the equivalent stiffness matrices in each time step, the computation effort of the proposed method is reduced compared with the full analysis of Newmark method. The validity and applications of the proposed method are illustrated by a 4-DOF spring-mass system with periodical time-varying stiffness properties and a truss structure with arbitrary time-varying lumped mass. It shows that good approximate results can be obtained by the proposed method compared with the responses obtained by the full analysis of Newmark method.

Evaluation of the Influence of Fibre Aspect Ratio and Fibre Content on the Rheological Characteristic of High Yield Pulp Fibre Reinforced Polyamide 11 “HYP/PA11” Green Composite

The rheological behavior of composites made with low-density polyamide 11 (PA11) and high yield pulp fibre (HYP) is evaluated. The rheological properties of high-yield, pulp-reinforced bio- based Nylon 11 HYP/PA11 composite were investigated using a capillary rheometer. The rheological tests were realized in function of the shear rate for different temperature conditions. The experimental results showed that identically for fibre content and aspect ratio, the shearing effects decreased as the temperature increased;that is, the HYP/PA11 became more non-Newtonian in the higher temperature region, which corresponds to the high pseudoplasticity of the HYP/PA11. At low HYP content, the shear viscosity is expected to increase rapidly with increasing concentrations of the fibres because of the rapidly increasing interactions between particles as they become more closely packed. However, at very high fibre content, random anisotropic structure of the fibres in polymer melts is created. The increase in shear viscosity is greater at lower shear rates, where fibre and polymer molecules are not completely oriented.

Comparison of Different Dough Rheological Measurement and Path Coefficient Analysis of Bread Quality

Farinograph, extensograph and mixograph are the special instruments used to determinedough rheological characteristics. In this study, twenty-seven wheat cultivars ofdifferent gluten strength were used to study the correlations among each rheologicalparameter determined by above instruments. Multiple linear regression analysis and pathcoefficient analysis were used to study the direct and indirect effects of 11 doughrheological characteristics on bread quality. The results showed significant correlationsamong the principal parameters. There were significantly or extremely significantlypositive correlations among development time (DT), stability time (ST), farinographquality number (FQN) of farinograph, area, maximum resistance (Rmax), viscoelastic ratio(Rmax/E)of extensograph and mixing time (MT), 8-minute-curve-tail (8MCT) of mixograph.These indexes affected bread-making quality either directly or indirectly. Of all theindexes, ST, maximum Rmax, MT and FQN were the most important ones.

Quadrant characteristics of earthquake precursors and its theoretical analysis

On the basis of quadrant features of the precursors in geo-electricity and deformation in the case of Tangshan earthquake and Datong earthquake in North China, the same feature of geo-electricity and deformation precursors before the Zhangbei earthquake has also been found. It seems that the existence of the quadrant behavior is not accidental, which might be related to existence of the earthquake generations. It is known in terms of rock experiment and theoretical analysis that there exists actually quadrant feature in earthquake-generating process with the range of quadrant spatial distribution unfixed, showing features of (gradual increasing ? maximum ? lessening slightly(, showing that the increasing zone and the decreasing one (or compressing zone and expanding one) of the quadrant in the near-source region could be different from that in the far-source region. Based on the knowledge of quadrant characters of earthquake precursors, we analyze space distributions of different types of precursor anomalies which may be a useful reference for one to predict the location of a strong earthquake occurrence.

GENERALIZED ASYMMETRIC HYSTERESIS MODEL OF CONTROLLABLE MAGNETORHEOLOGICAL DAMPER FOR VEHICLE SUSPENSION ATTENUATION

A generalized model is synthesized to characterize the asymmetric hysteresisforce-velocity (F-v) properties of the magneto-rheological (MR) fluids damper. The model isrepresented as a function of the command current, excitation frequency, and displacement amplitude,based on the symmetric and asymmetric sigmoid functions. The symmetric hysteresis damping propertiesof the controllable MR-damper and properties of the conventional passive hydraulic damper can alsobe described by the proposed model. The validity of the model is verified by experiments, which showthat the results calculated from the model are consistent with the measured data. In addition, itis shown that the model applies to a wide vibration frequency range. The proposed model haspotential application in vehicle suspension design employing the symmetry MR-damper, and also indeveloping the asymmetry MR-damper especially for the vehicle suspension attenuation.

GENERATION OF ASYMMETRIC F-v CHARACTERISTICS FOR SYMMETRIC MR DAMPERS

An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological （MR） dampers. The command current is formulated in an asymmetric manner to excite the symmetric MR dampers by employing the “on-off” control law in response to the direction of velocity, and a smooth modulation function is developed without phase shift to suppress strong transients in the damping forces caused by the current-switching discontinuity. The effectiveness of the proposed algorithm is evaluated by analyzing the dynamic responses of a quarter-vehicle suspension system with a symmetric MR-damper by modulating the command current into the asymmetric manner. The simulation results show that the proposed algorithm could achieve a better compromise between the conflicting requirements of the asymmetric damping force ratio and the force-velocity curve smoothness, and the asymmetric damping MR-suspension design can ideally improve the road holding and ride performances of vehicle motion. The proposed algorithm can be generally incorporated with a controller synthesis to realize an intelligent vehicle suspension design with the symmetric MR dampers.

Effect of Lithium Chloride on the Fibre Length Distribution, Processing Temperature and the Rheological Properties of High-Yield-Pulp-Fibre-Reinforced Modified Bio-Based Polyamide 11 Composite

The aim of this work was to investigate the effect of lithium chloride (LiCl) on the fibre length distribution, melting temperature and the rheological characteristics of high yield pulp fibre reinforced polyamide biocomposite. The inorganic salt lithium chloride (LiCl) was used to decrease the melting and processing temperature of bio-based polyamide 11. The extrusion method and Brabender mixer approaches were used to carry out the compounding process. The densities and fibre content were found to be increased after processing using both compounding methods. The HYP fibre length distribution analysis realized using the FQA equipment showed an important fibre-length reduction after processing by both techniques. The rheological properties of HYP-reinforced net and modified bio-based polyamide 11 “PA11” (HYP/PA11) composite were investigated using a capillary rheometer. The rheological tests were performed in function of the shear rate for different temperature conditions. The low-temperature process compounding had higher shear viscosity;this was because during the process the temperature was low and the mixing and melting were induced by the high shear rate created during compounding process. Experimental test results using the extrusion process showed a steep decrease in shear viscosity with increasing shear rate, and this melt-flow characteristic corresponds to shear-thinning behavior in HYP/PA11, and this steep decrease in the melt viscosity can be associated to the hydrolyse reaction of nylon for high pulp fibre moisture content at high temperature. In addition to the low processing temperature, the melt viscosity of the biocomposite using the Brabender mixer approach increases with increasing shear rate, and this stability in the increase even at high shear rate for high pulp moisture content is associated to the presence of inorganic salt lithium chloride which creates the hydrogen bonds with pulp during the compounding process.

Improving slurryability, rheology,and stability of slurry fuel from blending petroleum coke with lignite

Petroleum coke and lignite are two important fossil fuels that have not been widely used in China. Petroleum coke-lignite slurry （PCLS）, a mixture of petro- leum coke, lignite, water, and additives, efficiently utilizes the two materials. In this study, we investigate the effects of the proportion （7） of petroleum coke on slurryability, rheo- logical behavior, stability, and increasing temperature characteristics of PCLSs. The results show that the fixed- viscosity solid concentration （COo） increases with increasing 7. The ~Oo of lignite-water slurry （LWS, ~ = 0） is 46.7 %, compared to 71.3 % for the petroleum coke-water slurry （PCWS, c~ --- i00 %）, while that of PCLS is in between the two values. The rheological behavior of PCLS perfectly fits the power-law model. The PCWS acts as a dilatant fluid. As decreases, the slurry behaves first as an approximate Newtonian fluid, and then turns into a pseudo-plastic fluid that exhibits shear-thinning behavior. With increasing ct, the rigid sedimentation and water separation ratio （WSR） increase, indicating a decrease in the stability of PCLS. When α is 60-70 %, the result is a high-quality slurry fuel for industrial applications, which has high slurryability （ω0 = 57-60 %）, good stability （WSR 〈 2 %）, and superior pseudo-plastic behavior （n = 0.9）.