High Pressure Rheology Research Articles

Presentation of the 2012 Roebling Medal of the Mineralogical Society of America to Harry W. Green II

Mr. President, Colleagues, and Guests: It is with great pleasure that I introduce Harry W. Green II, as recipient of the Mineralogical Society of America’s highest honor, the Roebling Medal. The Roebling Medal is awarded “for outstanding original research in mineralogy...defined broadly”—a description that completely fits Harry Green’s distinguished scientific career. Harry’s research activities have focused on the rheology of geological materials in mantle conditions, and how stress and deformation interact with metamorphism and phase transformations. Now, Harry calls this direction “Mineralogy in Action,” that is, indeed, a bridge between “Phase Transformations and Earth’s Dynamics.” Throughout his career of more than 40 years, Harry has made seminal advances in mineralogy-based disciplines using the physical properties of minerals, mineral reactions, and their connections with the microstructures of minerals and rocks. All of his numerous publications are done in provocative and creative ways, and Harry remains today on the scene as one of the most influential, world-leading scientists in high-pressure rheology and mineralogy. He has done so through innovative high-pressure experiments and exhaustive interrogation of natural minerals and their experimental counterparts down to the smallest scales by electron microscopy. Before putting in context Harry’s main achievements, I would like to highlight “Where Harry was first at the beginning of his career?” His first major impacts in the 1960s to the 1980s included research on understanding extreme preferred orientation of quartz caused by annealing; on deformation microstructures in mantle xenoliths connected to generation of …

Viscosity of Alaska Heavy Oil Saturated with Methane

Viscosity, μ, of Ugnu heavy oil (North Slope of Alaska, USA) saturated with methane was measured at temperatures from 0 to 60 °C, pressure from 15 to 1800 psi, and shear rate of 0.1–500 s–1 using a high-pressure rheology apparatus constructed for this work. Under all saturated conditions, the oil behaves as a Newtonian fluid. The influence of temperature, pressure, and methane concentration was analyzed, and important regularities in the viscosity were established. A two-variable Antoine-type correlation, μ = f(T, p), with 6 fitting parameters was developed using 48 points on a p,T,μ-diagram for Ugnu oil. Since produced oil is accompanied by sand and water, their influence on the viscosity of Ugnu oil saturated with methane at 1500 psi was also studied. The relative viscosity of the Ugnu oil + water emulsions at temperatures from 2 to 60 °C increased linearly with increasing water concentration from 0 to 20 wt % following the Einstein viscosity model for dilute suspensions. Although possible in the time s...

High-Pressure Rheology of Hydrate Slurries Formed from Water-in-Oil Emulsions

A unique high-pressure rheology apparatus is used to study the in situ formation and flow properties of gas hydrates from a water-in-crude oil emulsion. Viscosity and pressure of the hydrate slurry are measured during hydrate formation, growth, aggregation, and dissociation. The rheology of the hydrate slurries varies with time, shear rate (1–500 s–1), water content (0–50%), and temperature (0–6 °C). Hydrate slurry viscosity increases rapidly with time when hydrates form and then decays after going through a maximum as hydrate aggregates breakup or rearrange. Yield stress increases with annealing time up to 8 h and then remains constant. Hydrate slurry viscosity decreases with an increasing shear rate (i.e., they are shear thinning). Viscosity and yield stress both increase with an increasing water content. During dissociation, the viscosity increases just before the hydrate equilibrium temperature. Finally, transient viscosity measurements at varying temperatures suggest that mechanisms, such as cohesion forces and shear forces, competitively affect hydrate slurry viscosity.

Effect of high-pressure rheology of lubricating oils on boundary lubrication

High-pressure rheology of lubricating oil was determined using different experiments, and the phase diagram was drawn. The four-ball wear tests were used to evaluate anti-wear characteristics of oils in boundary lubrication condition. The bridged ring compound oils showed the minimum wear scar in the four-ball wear tests. The diameter of wear scar decreases with increasing the elastohydrodynamic film-forming capability. Next, we considered the molecular packing parameter T VE −T at the four-ball wear test. The T VE −T values of bridged ring compound oils were in the range 250–360 and oils were elastic-plastic solid. It is concluded that the solidified oil film under boundary lubrication conditions has the anti-wear action.

Studies on the interactions of CO 2 with biodegradable poly( dl-lactic acid) and poly(lactic acid- co-glycolic acid) copolymers using high pressure ATR-IR and high pressure rheology

Amorphous poly( dl-lactic acid) (P dl LA) and poly(lactic acid- co-glycolic acid) (PLGA) polymers have been used to fabricate porous scaffolds for tissue engineering applications via a supercritical foaming technique. The chemical composition of the polymers and the morphology (pore size, porosity and interconnectivity) of the scaffolds are crucial because they influence cell filtration, migration, nutrient exchange, degradation and drug release rate. To control the morphology of supercritical foamed scaffolds, it is essential to study the interactions of polymers with CO 2 and the consequent solubility of CO 2 in the polymers, as well as the viscosity of the plasticized polymers. In this paper, we are showing for the first time that well known and useful biodegradable polymers can be plasticized easily using high pressure CO 2 and that we can monitor this process easily via a high pressure attenuated total reflection Fourier transform infrared (ATR-IR) and rheology. High pressure ATR-IR has been developed to investigate the interactions of CO 2 with P dl LA and PLGA polymers with the glycolic acid (GA) content in the copolymers as 15, 25, 35 and 50% respectively. Shifts and intensity changes of IR absorption bands of the polymers in the carbonyl region (∼1750 cm −1) are indicative of the interaction on a qualitative level. A high pressure parallel plate rheometer has also been developed for the shear viscosity measurements of the CO 2-plastisized polymers at a temperature below their glass transition temperatures. The results demonstrate that the viscosities of the CO 2-plasticized polymers at 35 °C and 100 bar were comparable to the values for the polymer melts at 140 °C, demonstrating a significant process advantage through use of scCO 2. The data from the high pressure rheology and high pressure ATR-IR, combined with the sorption and swelling studies reported previously, demonstrate that the interaction and the solubility of CO 2 in PLGA copolymers is related to the glycolic acid content. As the glycolic acid ratio increases the interaction and consequent solubility of CO 2 decreases. The potential applications of this study are very broad, from tissue engineering and drug delivery to much broader applications with other polymers in areas that may range from composites and polymer synthesis through to injection moulding.

High pressure rheology and the impact on process homogeneity

The impact of different viscous substances on homogeneous thermal treatment during high pressure processes is exemplified for a cylinder piston system. Therefore, the relevant equations of thermofluid dynamics have been examined and conditions for homogeneous thermal processing have been set up. Furthermore, the analysis of an n-order inactivation kinetic delivers criteria for insensitivity of reactions to spatial temperature heterogeneities. The findings have been applied to a short time high pressure process and compared with results of numerical simulations. Good agreement could be achieved.

Effect of high-pressure rheology of lubricants upon entrapped oil film behaviour at halting elastohydrodynamic lubrication

The steady-state elastohydrodynamic lubrication (EHL) is now quite well understood both computationally and experimentally. However, many practical machine elements such as rolling element bearings and traction continuously variable transmission (CVT) operate often under the halting of machine, the suspension of long time and start of machine. It is often in such operating condition that breakdown of lubrication films occurs, which eventually gives rise to fail of the lubricated surfaces. This paper describes an experimental study of EHL film thickness at halting of operation and a change by the time of an entrapped film thickness. The film thickness is investigated with some different type of lubricating oil, which a phase diagram is known by high-pressure density measurements. The results demonstrate an entrapped oil film thickness at EHL halting is dependant on αηa, where α is the pressure-viscosity coefficient, η is the dynamic viscosity, a is the deceleration, and squeeze out time of entrapped oil film is dependant on a phase diagram parameter TVE - T, where TVE is the viscoelastic solid transition temperature at Hertzian pressure, and T is the oil temperature.

Do Reuss and Voigt bounds really bound in high-pressure rheology experiments?

Energy dispersive synchrotron x-ray diffraction is carried out to measure differential lattice strains inpolycrystalline Fe2SiO4 (fayalite) and MgO samples using a multi-element solid state detector during high-pressuredeformation. The theory of elastic modelling with Reuss (iso-stress) and Voigt(iso-strain) bounds is used to evaluate the aggregate stress and weight parameter,α (0≤α≤1), of the two bounds. Results under the elastic assumption quantitativelydemonstrate that a highly stressed sample in high-pressure experimentsreasonably approximates to an iso-stress state. However, when the sampleis plastically deformed, the Reuss and Voigt bounds are no longer valid(α becomes beyond 1). Instead, if plastic slip systems of the sample are known (e.g. in the caseof MgO), the aggregate property can be modelled using a visco-plastic self-consistenttheory.

High-pressure behavior of toroidal CVT fluid for automobile

Practical toroidal-type continuously variable transmission (t-CVT) is subjected to extremely severe operating conditions, viz., maximum contact pressure is very high at 4 GPa, rolling speed exceeds over 30 m/s and lubricant temperature goes up over 140 °C. Traction measurements were recently made at wide range of contact pressures, oil temperatures and rolling speeds by USCAR Group. The objective of this research is to investigate high-pressure rheology of the traction characteristics at extremely severe EHL contact conditions. The effects of contact pressure and temperature on maximum traction coefficient were evaluated using the phase diagram and the liquid/solid transition lubrication diagram.

Influence of pressure and temperature on the flow behaviour of heavy fuel oils

Transportation and consumption of petroleum products around the world have created a potential risk for oil spills in the environment. Knowledge of high-pressure rheological behaviour of heavy crude oil fractions, which are usually transported in oil tankers, is very important to design deep recovering operations of the oil remaining in the tanks after an accident. The effect of pressure on the viscosity of these materials is not well understood, this is mainly due to experimental constraints involving high-pressure rheology measurements at low shear rates. Consequently, the overall objective of this work is to model the temperature–pressure–viscosity dependence of a selected heavy fuel oil in a wide range of pressure and temperature. With this aim, viscous flow tests at different temperatures and differential pressures and modulated differential scanning calorimetry tests were carried out on the heavy fuel oil selected. A temperature–pressure–viscosity model (FMT model) fits fairly well the experimental results obtained in the whole differential pressure range studied. However, viscosity values at temperatures lower than 10°C cannot be predicted due to microstructural changes associated with the solidification process of the heaviest components of the fuel oil tested.

The High Pressure Rheology of Mixtures

The Newtonian mixing rules for several binary systems have been experimentally investigated. Some systems show non-ideal mixing response and for some systems the non-ideal response is pressure-dependent, yielding an opportunity for manipulation of the pressure-viscosity behavior to advantage. The mixing of differing molecular weight “straight cuts” can produce very different pressure-viscosity response. This behavior underscores the difficulty in predicting the pressure-viscosity coefficient based upon chemical structure and ambient viscosity since the molecular weight distribution is also important, but it also provides another opportunity to control the high-pressure response by blending. The first experimental observation of double shear-thinning within a single flow curve is reported. Blending then provides the capability of adjusting not only the Newtonian viscosity but also the non-Newtonian shear-thinning response as well.

Dislocation creep in MgSiO3 perovskite at conditions of the Earth's uppermost lower mantle.

Seismic anisotropy provides an important observational constraint on flow in the Earth's deep interior. The quantitative interpretation of anisotropy, however, requires knowledge of the slip geometry of the constitutive minerals that are responsible for producing rock fabrics. The Earth's lower mantle is mostly composed of (Mg, Fe)SiO3 perovskite, but as MgSiO3 perovskite is not stable at high temperature under ambient pressure, it has not been possible to investigate its mechanical behaviour with conventional laboratory deformation experiments. To overcome this limitation, several attempts were made to infer the mechanical properties of MgSiO3 perovskite on the basis of analogue materials. But perovskites do not constitute an analogue series for plastic deformation, and therefore the direct investigation of MgSiO3 perovskite is necessary. Here we have taken advantage of recent advances in experimental high-pressure rheology to perform deformation experiments on coarse-grained MgSiO3 polycrystals under pressure and temperature conditions of the uppermost lower mantle. We show that X-ray peak broadening measurements developed in metallurgy can be adapted to low-symmetry minerals to identify the elementary deformation mechanisms activated under these conditions. We conclude that, under uppermost lower-mantle conditions, MgSiO3 perovskite deforms by dislocation creep and may therefore contribute to producing seismic anisotropy in rocks at such depths.

High‐pressure rheology of eight synthetic lubricants based on phase diagrams

AbstractNew sets of equations have been constructed from the density‐pressure‐temperature and viscosity‐pressure‐temperature relationships to determine the rheology of synthetic lubricants at high pressure. A phase diagram was first plotted for the oils up to a pressure of 1.2 GPa and temperatures from 303 to 353 K using high‐pressure density experimental results and others. For the oils at temperatures of 313, 333, and 353 K, the high‐pressure viscosity experiment was done up to a viscosity of 104 Pa s and up to a pressure of 0.4 GPa. A relationship, based on free volume theory, between pressure and temperature with varying density and viscosity was proposed. It was found that the new equations from these relationships could predict the high‐pressure rheology more closely than those of previous researchers. Moreover, it was shown that the Ehrenfest equation or the gradient of the phase diagram is closely related to the expansion coefficient of free volume.

The high pressure rheology of polymer-oil solutions

We present perhaps the most comprehensive work on the high-pressure shear-thinning of polymer-blended mineral oil. Three solutions of commercial polymer VI improver in mineral oil are characterized for the effect of pressure and shear rate on viscosity. We show that the film thinning measured in concentrated contact can be explained by ordinary shear-thinning of the power-law type. We present extended high-pressure flow curves for a model polybutene-mineral oil blend that has been previously studied and show the possibility of two shear-thinning transitions; one for the polymer and one for the base oil. Solutions of well-characterized, narrow distribution polyisobutylene in squalane were prepared. The high-pressure mixing rule was determined and Carreau parameters were extracted from flow curves and compared to existing models for calculating characteristic times from molecular weight and concentration.

806 t-CVT 停止時の閉じ込め EHL 油膜厚さに及ぼす潤滑油高圧物性の影響

806 t-CVT 停止時の閉じ込め EHL 油膜厚さに及ぼす潤滑油高圧物性の影響

Effect of Lubricating Oils on Cage Failure of Ball Bearings

Ball Speed Variation (BSV) and cage clearances affect the cage life of ball bearings. Vibration and impact of the moving surfaces of a bearing under high pressure conditions also affects the cage life. Moreover, large forces at the cage-ball and cage-race contacts cause cage failure. Therefore, cage design is improved by increasing the looseness at the ball pocket and race. However, in many cases, cage failure still is occurring. To investigate the causes of cage failure, thrust ball bearing life testing was done using eight kinds of lubricant. The general feature found was that bearing life with synthetic naphthenic oils, polybutene and fluoro silicon oil increases with increasing film parameter in the ball-race contacts. Flaking occurred in the inner and outer ring and ball. In the case of dimethyl silicon oil that has mechanical shear thinning (permanent viscosity loss), poor oil film formation and poor boundary lubrication performance, all stoppage of the experiments occurred due to cage damage. Cage-ball contact fluid film characteristics were investigated by testing the high pressure rheology of the lubricants under the impact of a ball on a lubricated surface. Impact indentations were analyzed and compared with the bearing life experiment results. It was found that abrasion of the cage at the ball-cage contact was not the only determining factor. Surface chemistry also had a great influence on the cage failure. Presented at the 58th Annual Meeting in New York City April 28–May 1, 2003

The high pressure rheology of some simple model hydrocarbons

The variation in viscosity with pressure and shear rate is required for modelling of film thickness and traction in elastohydrodynamic contacts. Two examples are presented with supporting data for lubricants. Then, five well-characterized simple, low molecular weight hydrocarbon liquids are investigated in detail. The effect of structure on the pressure-viscosity response and non-Newtonian response is discussed. A favourable comparison can be made with non-equilibrium molecular dynamics simulations on squalane.

High-pressure rheology of polystyrene melts plasticized with CO2: Experimental measurement and predictive scaling relationships

A high-pressure extrusion slit die rheometer was constructed to measure the viscosity of polymer melts plasticized by liquid and supercritical CO2. A novel gas injection system was devised to accurately meter the follow of CO2 into the extruder barrel. Measurements of pressure drop, within the die, confirm the presence of a one-phase mixture and a fully developed flow during viscosity measurements. Experimental measurements of viscosity as a function of shear rate, pressure, temperature, and CO2 concentration were conducted for three commercial polystyrene melts. The CO2 was shown to be an effective plasticizer for polystyrene, lowering the viscosity of the polymer melt by as much as 80%, depending of the process conditions and CO2 concentration. Existing theories for viscoelastic scaling of polymer melts and the prediction of Tg depression by a diluent were used to develop a free volume model for predicting the effects of CO2 concentration and pressure on polymer melt rheology. The free volume model, dependent only on material parameters of the polymer melt and pure CO2, was shown to accurately collapse the experimental data onto a single master curve independent of pressure and CO2 concentration for each of the three polystyrene samples. This model constitutes a simple predictive set of equations to quantify the effects of gas-induced plasticization on molten polymer systems. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3168–3180, 2000

Impact of Molecular Architecture on the High-Pressure Rheology of Hydrocarbon Fluids

Molecular dynamics simulations are conducted on three C18 poly-α-olefin isomers under extreme conditions typical of traction fluids or lubricants under elastohydrodynamic lubrication conditions. The viscosity, self-diffusivity, and rotational relaxation times of the molecules are computed at pressures ranging from atmospheric to as high as 1 GPa. The dynamics of all three isomers are slowed as pressure increases, but a highly branched isomer shows a more dramatic reduction in mobility with pressure than does a linear or singly branched isomer. In particular, the viscosity of the highly branched molecule exhibits a much larger increase with pressure than does the viscosity of the other isomers, indicating that the highly branched molecule should exhibit more favorable traction properties than the other isomers. An explanation for the differences in dynamic properties between the isomers is given in terms of a reduction in liquid void volume coupled with the greater backbone stiffness of the highly branched...

High-pressure rheology of lubricants and limitations of the Reynolds equation

A review of high pressure rheology leads to the conclusion that the results from rheometers may be used to generate empirical rate equations which are useful in modelling elastohydrodynamic traction. However, an analytical treatment of piezoviscous liquids reveals that the Reynolds equation adequately captures the mechanics of the piezoviscous liquid only when the shear stress is much less than the reciprocal of the pressure viscosity coefficient. Otherwise the cross film pressure gradient may be significant and secondary flows result.