Low Displacement Rates Research Articles

R-curves of an yttria- and alumina-doped hot-pressed silicon nitride ceramic at 1200°C and room temperature

An energy approach has been utilized to measure theR-curves of an Y2O3~A⪿3-doped hot-pressed silicon nitride ceramic at 1200‡C in an argon atmosphere in three-point bending. In order to evaluate theR-curves at 1200‡C, a low constant displacement rate of\(\dot \delta \)=5 Μm min−1 was applied in cyclic loading to obtain the cyclic loading/ unloading-displacement curves during controlled-crack propagation. Propagated crack lengths were measured directly by a microscope and they were compared to compliance-calculated crack lengths. After digitizing the cyclic load-displacement and crack length-displacement curves, crack-resistance parameters,R-curves andK-curves, were calculated by computer. At 1200‡C this material behaved non-elastically and the crack parameters, obtained here, represent the non-elastic ones. For comparison, at room temperature, continuous loading was applied to obtain the load-displacement curves. At room temperature, linear-elastic fracture mechanics behaviour was observed.

Influence of helium generation rate and temperature history on mechanical properties of model Fe-Cr-Ni alloys irradiated in FFTF at relatively low displacement rates

In agreement with earlier studies conducted at higher displacement rates, the evolution of mechanical properties at room temperature of model Fe-Cr-Ni alloys irradiated at lower displacement rates in the 59Ni isotopic doping experiment does not appear to be strongly affected by large differences in helium generation rate. This insensitivity to helium/dpa ratio is exhibited during both isothermal and non-isothermal irradiation. The overall behavior of the model alloys used in this study is dominated by the tendency to converge to a saturation strength level that is independent of thermomechanical starting state and helium/dpa ratio, but which is dependent on irradiation temperature and alloy composition.

An evaluation of low temperature radiation embrittlement mechanisms in ferritic alloys

Investigations underway at Oak Ridge National Laboratory (ORNL) into reasons for the accelerated embrittlement of surveillance specimens of ferritic steels irradiated at 50°C at the High Flux Isotope Reactor (HFIR) pressure vessel are described. Originally, the major suspects for the precocious embrittlement were a highly thermalized neutron spectrum, a low displacement rate, and the impurities boron and copper. Each of these possibilities has been eliminated. A dosimetry experiment made at one of the major surveillance sites shows that the spectrum at that site is not thermalized. A new model of matrix hardening due to point defect clusters indicates little effect of displacement rate at low irradiation temperature. Boron levels are measured at 1 wppm or less, which is inadequate for embrittlement. Copper and nickel impurities are shown to promote radiation strengthening at high doses but not at the low doses pertinent to the surveillance data. It is shown that a copper embrittlement scenario has other drawbacks, and it is argued that copper impurity is not responsible for the accelerated embrittlement of the HFIR surveillance specimens. The dosimetry experiment revealed unexpectedly high levels of reaction products in some of the fast flux monitors, which are found to be caused by an exceptionally high ratio of gamma ray flux to fast neutron flux at the pressure vessel. Gamma rays can also induce atomic displacements, leading to the suggestion that the accelerated embrittlement may be provoked by gamma irradiation.

Geometric and numerical model of progressive limb rotation in detachment folds

A simple, area-balanced, geometric model of progressive limb rotation in detachment folds allows the quantification of displacement, uplift, and rotation and the assessment of their effect upon growth strata geometries. Translation of this geometric model into a velocity model of deformation allows the modeling of associated growth strata resulting from background sedimentation and local erosion, transport, and deposition. We show that with constant displacement and sedimentation rate, this model predicts a progressive unconformity, indicating the onlap and eventual overlap of the fold limb caused by a decreasing uplift rate. This decrease is a consequence of the kinematics of progressive limb rotation. Increases in displacement rate, with sedimentation rate kept constant, can lead to offlap and angular unconformities, although subsequent onlap does not necessarily reflect a return to a lower displacement rate. Modeled growth strata geometries exhibit many of the features reported from the literature.

On the mechanical properties of synthetic kaolinite/quartz fault gouge

SUMMARYThe mechanical properties and microstructures of mixed kaolinite/ quartz fault gouge have been studied by means of triaxial tests, wherein a 1 mm thickness of fault gouge was sheared between rigid, sintered alumina sliders. Test conditions ranged up to 200 MPa confining pressure, 175 MPa pore water pressure and temperatures to 600°C. Constant displacement rate tests were carried out at 5×10‐4 mm s‐1, and the stress relaxation technique was used to access a wide range of lower displacement rates down to 10‐10 mm s‐1. The effects of different ratios of clay: quartz were studied, and some experiments were cafried out using crushed Tennessee sandstone gouge and pre‐faulted cylinders of Tennessee sandstone. Deformation‐induced microstructures were studied by optical, scanning and transmission electron microscopy, and mineral chemistry changes were identified using EDS analysis in the STEM.The most important factor determining the strength of these gouges is effective confining pressure, and the effective stress law was obeyed at all test conditions. Increasing the proportion of quartz in the gouge slightly increases the strength, as does increase of temperature. Under all test conditions the gouges deformed by strain‐hardening stable sliding. At 2 mm displacement the friction coefficient is similar to that for rock and rock sliding (μ= 0.85).Over wide ranges of strain‐rate and temperature the strength of these gouges is little affected if the effective pressure is high, but strength drops rapidly with decreasing strain‐rate if effective pressure is low (or if pore water pressure is high).Reloading of the gouge after stress relaxation at high temperatures demonstrated hardening arising from hydrothermal cementation during stress relaxation, which led to sudden rupture of the cemented gouge. This phenomenon may be responsible for cyclic rupture of natural faults.New mineral phases were produced in these experiments only at 600°C. At 400°C, anticipated production of pyrophyllite from kaolinite plus quartz was not found, but recrystallization of kaolinite is believed to have occurred and evidence of healing of cracks in quartz was seen. Microstructural studies revealed the ubiquitous development of P and R1 foliations and other features, which are identical to those found in natural clay‐bearing fault zones. Microstructural evolution is associated with the strain‐hardening, and apparent hardening is strongly associated with the stress path during loading.

Effects of temperature and rate on fracture toughness of short-alumina-fibre-reinforced epoxies

The failure mechanisms of two short-alumina-fibre-reinforced epoxy resin composites (with and without rubber) have been investigated over a range of temperatures (−70°C to 100°C) and displacement rates (5 × 10 −2 mm/min to 1·8 × 10 5 mm/min.). The fracture toughness, K IC , of these materials is highly rate dependent but is insensitive to temperature below 50°C. Addition of alumina fibres to the epoxy matrix significantly improves the low-temperature fracture toughness. High displacement rates and low temperatures tend to promote brittle fracture with little fibre debonding and fibre pull-out. However, low displacement rates and high temperatures lead to the formation of highly non-planar fracture surfaces with extensive fibre debonding, fibre pull-out and substantial plastic shear flow of the matrix material. A qualitative model in terms of residual stresses at the fibre-matrix interface is presented to describe the temperature-dependent failure mechanisms in these composite materials.

Tensile behavior and swelling of ternary austenitic alloys irradiated in different neutron spectra

Two nominally identical experiments were designed to study the effects of nickel, chromium, cold work and helium generation rate on neutron-induced swelling and changes in tensile properties of simple Fe-Cr-Ni alloys. One was conducted in the Oak Ridge Research Reactor (ORR) at higher He/dpa ratios and lower displacement rates than the other, conducted in the Experimental Breeder Reactor II (EBR-II). The ORR results are at higher dpa levels and show substantially more strengthening and a different temperature range of swelling.

On mechanisms by which a soft neutron spectrum may induce accelerated embrittlement

Both low displacement rates and softened neutron spectrum favor survival of a higher fraction of point defects per displacement for producing micro-structural changes leading to hardening and embrittlement. Low displacement rate results in low bulk recombination rate. A high thermal to fast neutron flux ratio results in a large fraction of point defects produced in small cascades from (n,γ) and (n,α) reactions. Defects from such cascades generally avoid in-cascade recombination, while most of the defects created in large cascades produced by fast neutrons are lost to in-cascade recombination. Thus thermal neutrons produce more available defects per unit displacement dose. It is argued that the spectral effect may dominate the accelerated embrittlement observed in ferritic steels at the High Flux Isotope Reactor (HFIR) pressure vessel location. The rate effect is expected to be a secondary factor at temperatures as low as 50°C, where the HFIR data were obtained. Our analysis suggests generally that components subject to neutron environments with high thermal-to-fast ratios and irradiated at low temperatures may be subject to accelerated radiation effects.

APPLICATION OF FRACTURE MECHANICS TECHNIQUES TO THE ENVIRONMENTALLY ASSISTED CRACKING OF ALUMINIUM 2024

Abstract— Stress corrosion cracking of 2024 T351 aluminium alloy in an aqueous 3.5% sodium chloride solution was investigated using three fracture mechanics based testing techniques: constant load, constant displacement, and constant displacement rate. In spite of their different loading characteristics, all three test methods yielded approximately the same Klscc value. Crack growth rates in the plateau region, as measured from bolt loaded DCB specimens and from CT specimens tested at low constant displacement rates are similar. The tests at constant displacement rate not only provide results in a much shorter time, but produce additional information in terms of crack growth resistance curves as a function of the displacement rate. Linear elastic as well as elastic‐plastic fracture mechanics test evaluation procedures are applied and discussed in view of an assessment of criteria for the accelerated evaluation of SCC parameters such as Klscc, Jlscc, and δlscc.

Parabolic distribution of circumeastern Snake River Plain seismicity and latest Quaternary faulting: Migratory pattern and association with the Yellowstone hotspot

The Intermountain and Idaho seismic belts within Idaho, Wyoming, and Montana form an unusual parabolic pattern about the axis of the aseismic eastern Snake River Plain (SRP). This pattern is also reflected in the distribution of latest Quaternary normal faults. Several late Cenozoic normal faults that trend perpendicular to the axis of the eastern SRP extend from the aseismic region to the region of latest Quaternary faulting and seismicity. A study of the late Miocene to Holocene displacement history of one of these, the Grand Valley fault system in southeastern Idaho and western Wyoming, indicates that a locus of high displacement rates has migrated away from the eastern SRP to its present location in southern Star Valley in western Wyoming. In Swan Valley the studied area closest to the eastern SRP, isotopic ages, and paleomagnetic data for over 300 samples from 47 sites on well‐exposed late Cenozoic volcanic rocks (the tuff of Spring Creek, the tuff of Heise, the Huckleberry Ridge tuff, the Pine Creek Basalt, and an older tuff thought to be the tuff of Cosgrove Road) are used to demonstrate differences in the displacement rate on the Grand Valley fault over the last ∼10 m.y. Tectonic tilts for these volcanic rocks are estimated by comparing the results of paleomagnetic analyses in Swan Valley to similar analyses of samples from undeformed volcanic rocks outside of Swan Valley. Basin geometry and tilt axes are established using seismic reflection profiles and field mapping. Combining these data with the tilt data makes it possible to calculate displacement rates during discrete temporal intervals. An average displacement rate of ∼1.8 mm/yr is calculated for the Grand Valley fault in Swan Valley between 4.4 and 2.0 Ma. In the subsequent 2.0‐m.y. interval the rate dropped 2 orders of magnitude to ∼0.014 mm/yr; during the preceding 5.5‐m.y. interval the displacement rate is ∼0.15 mm/yr, or about 1 order of magnitude less than the rate between 4.4 and 2.0 Ma. Mapping of fault scarps and unfaulted deposits along the Grand Valley fault system shows that latest Quaternary fault scarps are restricted to the portion farthest from the eastern SRP, the southern part of the Star Valley fault. Surface displacements estimated from scarp profiles and deposit ages estimated from soil development suggest a latest Quaternary displacement rate of 0.6–1.2 mm/yr for the southern portion of the Star Valley fault. Morphologic evidence suggests that this displacement rate persisted on the Star Valley fault throughout most of the Quaternary. The latest Quaternary displacement rate calculated for the southern portion of the Star Valley fault is similar to the rate calculated for Swan Valley during the interval from 2.0 to 4.4 Ma. This similarity, together with evidence for a low Quaternary displacement rate on the fault system in Swan Valley, suggests that the location of the highest displacement rate has migrated away from the eastern SRP. Other normal faults in southeastern Idaho, northwestern Wyoming, and southwestern Montana, while less well described than the Grand Valley fault system, exhibit a similar outward migrating pattern of increased fault activity followed by quiescence. Furthermore, a temporal and spatial relationship between fault activity and the 3.5 cm/yr northeastward track of the Yellowstone hotspot is observable on the Grand Valley fault system and on other north‐northwest trending late Cenozoic faults that border the eastern SRP. The temporal and spatial relationship of Miocene to present high displacement rates for other circumeastern SRP faults and the observable outwardly migrating pattern of fault activity suggest that a similar parabolic distribution of seismicity and high displacement rates was symmetrically positioned about the former position of the hotspot. Moreover, the tandem migration of the hotspot and the parabolic distribution of increased fault activity and seismicity are closely followed by a parabolic‐shaped “collapse shadow,” or region of fault inactivity and aseismicity. We suggest that the outwardly migrating pattern of increased fault activity (active region) results from reduced integrated lithospheric strength caused by thermal effects of the hotspot. Conversely, the outwardly propagating quiescent region is the result of a reduction or “collapse” of crustal extension rates caused by increased integrated lithospheric strength. Lithospheric strength in this region is increased by addition of mafic materials at the base of the crust and at midcrustal levels. Although the strength of the mantle portion of the lithosphere is reduced, the increased strength of the crust results in a total integrated increase in lithospheric strength. Paradoxically, the surface heat flow data suggest that the region within the interior parabola has a higher heat flow (after accounting for the cooling effects of the eastern SRP aquifer) than the adjacent regions, yet the interior region exhibits significantly lower extension rates. It appears that in this region the surface heat flow is not a good predictor of rates of lithospheric extension.

Neutron Irradiated Uranium Silicides Studied by Neutron Diffraction and Rietveld Analysis

Uranium silicides have been considered for use as reactor fuels in both high power and low enrichment applications. However, U3 Si was found to become amorphous under irradiation [1] and to become mechanically unstable to rapid growth by plastic flow [2,3]. U3Si2 appears to be stable against amorphization at low displacement rates, but the extent of this stability is uncertain. Although the mechanisms responsible for plastic flow in U3Si and other amorphous systems are unknown, as is the importance of crystal structure for amorphization, it may not be surprising that these materials amorphize, in light of the fact that many radioactive nuclide - containing minerals are known to metaminctize (lose crystallinity) under irradiation [4]. The present experiment follows the detailed changes in the crystal structures of U3Si and U3Si2 introduced by neutron bombardment and subsequent uranium fission at room temperature. U-Si seems the ideal system for a neutron diffraction investigation- since the crystallographic and amorphous forms can be studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering analysis [5] of the non-crystalline scattering component.

Fractal Flow in Porous Media

The flow of fluids in porous media leads to displacement fronts that are fractal in many situations. We discuss results obtained in experiments on well defined models. The dispersion of tracers, the invasion percolation at low displacement rates and the viscous fingering at high displacement rates are discussed in detail.

Salt-Free Cement An Alternative to Collapsed Casing in, Plastic Salts(includes associated papers 12952 and 13012 )

Summary The high incidence (20 to 25%) of collapsed ordoglegged casing in the Williston basin led to an investigation of cementing systems and practices employed in that area. The vast majority of the collapse problems are occurring across the Charles formation. The Charles contains numerous salt sections over a 600- to 700-ft [183- to 213-m] gross interval. These salt sections exhibit plastic tendencies when exposed to aqueous drilling fluids-i.e., the saltsections flow. Under plastic conditions, the saltsections flow against the casing before the cementsheath can attain sufficient compressive strength toprotect the casing. These salt sections can be seen on conventionally cemented casing strings as 100% bondedsections in what otherwise appears to be poorlycemented intervals. The plastic salt exhibits a horizontal stress against the casing equivalent to the overburdenstress (about 1 psi/ft [22.6 kPa/m] of depth). The use of high concentrations (20) t(37.2%)of saltin cement slurries exhibit a retarding effect on thickening time and the rate of compressive strength development. These excessive development times appear to be contributing to the collapse problems defined. Laboratory investigation of salt dissolution rates in cement slurries, at various annular velocities show that salt-free cementslurries can be placed across the salt sections with finalsalt concentrations of less than 10% as a result of saltdissolution. This prompted an investigation involving the possible use of salt-free cement slurries, which exhibit controlled thickening times and much faster compressive strength development, across the Charles. To date, the wells that have been cemented in the Willistonbasin with the salt-free cement systems have shown no incidence of casing collapse, except as listed in the last paragraph under Field Experience. Introduction The use of salt in oil well cementing has been practiced for several years, especially for cementing casing with salt domes along the U.S. gulf coast, and has been included in cement slurries for various other reasons. Saltis used in cement slurries to obtain bonding to acrystalline salt, such as that existing in a salt dome. This practice has been extended to using salt slurries acrossany salt section, including those encountered in the Williston basin. Several salt-bearing formations are encountered in the Williston Basin-e.g., the Prairieevaporite, the Charles, the Pine, and the Dunham salts. Investigation of cementing practices in the Williston basin indicated a severe problem with collapsed ordoglegged casing in the Charles salt zones, with some instances of collapse reported in the Pine and Prairie salts as well. These collapse problems can occur within a timeframe of 4 weeks to 3 years. The salt sections creating the collapse problems exhibit plastic tendencies when exposed to aqueous fluids for extended periods of time. They can generally be seen on bond logs (Fig. 1) as four to six separate sections of apparent 100% bond in what otherwise appears to be a poorly bonded interval. These plastic salt sections apparently move against the casingprior to development of a competent cement sheath, subsequently exhibiting a horizontal stress against the casing equivalent to the overburden stress (about 1 psi/ft[22.6 kPa/m] of depth). The prevalent cementingslurries are composed of 50/50 or 65/35 pozzolanic cementscontaining varying amounts of gel (bentonite), 85 to95% mix water, and 18 to 37.2%salt. A comparison ofthe compressive strength development of a 65/35 Pozzolan system and Class G cement is given in Fig. 2. Laboratory Investigation The effects of varying salt concentrations on cementslurries have been demonstrated. As the salt concentration increases in a cement slurry(2 to 8%), it acts as an accelerator. Ten to 18% salt is a transition zone exhibiting no appreciable effect on the slurry. However, at concentrations greater than 18%, an increasingly greater retarding effect is exhibited on both setting time and the rate of compressive strength development (Fig. 3). Laboratory investigations were conducted to determine the dissolution rates of salt by cement slurries atlaminar and plug flow annular velocities. Reynold'snumbers of 100 for plug flow and 3,000 for turbulent flow were used in the annular velocity calculations. The test apparatus consists of a centrifugal pump capable of circulating a cement slurry through a 1-in.[2.54-cm] line and then through a compressed salt block. The pump is capable of achieving high or low displacement rates, depending on the flow characteristics desired for testing(plug, laminar, or turbulent flow). These flow rates are regulated by a rheostat control and valve system. The apparatus, being a closed system, circulates a known volume of cement in a loop from a reservoir tank across the salt section and back into the reservoir (see Fig. 4). JPT P. 320^

Selected buffer systems for moving boundary electrophoresis on gels at various pH values, presented in a simplified manner

AbstractMoving boundary electrophoresis on gels is useful for 4 purposes: (1) As an automatic concentration method to produce concentrated starting zones of proteins* for analytical and preparative resolving gels; (2) to provide a sharply defined reference zone in the resolving gel for Rf measurement; (3) for the preparative electrophoretic extraction of proteins from gel slices; (4) for high load preparative “charge fractionations” of relatively simple mixtures of proteins. It requires buffer systems at various pH values which are capable of setting up moving boundaries with numerically known leading and trailing ion mobilities. Moreover, since protein migration is slow compared with that of buffers, these moving boundaries have to have low displacement rates if they are to concentrate and align the proteins in order of mobility. Ten years ago, the authors made available in form first of magnetic tapes, then of microfiche, a collection of buffer systems for that purpose. But, in spite of the large number, over 4000, of these buffer systems, biochemists have not taken advantage of them widely. This appears in part due to the terminological complexity of the presentation needed to give an exhaustive physical‐chemical description of the systems. In part, it was due to the confusion about which of the various forms and techniques of moving boundary electrophoresis, known under a variety of names, these buffer systems applied to. Also, among the many buffer systems, only relatively few exhibited sufficiently low moving boundary displacement rates to allow slowly migrating proteins to migrate within the moving boundary. Finally, it proved difficult for potential users to interpret the magnetic tapes and microfiche; also tapes were excessively expensive. To remedy all these problems, and to allow biochemists to benefit more widely, both analytically and preparatively, from moving boundary electrophoresis at any pH, we have selected a small number of buffer systems capable of concentrating proteins within moving boundaries set up at various pH values, with low displacement rates, and with either anodic or cathodic displacement. These are presented in simplified format and terminology.

Non-random mating by size in American toads, Bufo americanus

Male American toads, Bufo americanus, captured in amplexus at least once during the season were significantly longer than males captured only singly in the same breeding population in all three cases studied. Absence of any correlation between the body lengths of the members of amplexing pairs argues against selection for optimal relative size. Males successful at breeding were those that (1) were larger, (2) were at the pond more nights, and (3) spent more time calling than unsuccessful males. Residency, per se, did not enhance breeding success, however, as on any given day successful males were equally likely to come from recaptured males previously present at the pond and unmarked males presumed new to the pond. Amount of movement about the pond did not vary with breeding success; all males tended to remain in one area on any given night and to change areas between nights. A very low displacement rate (about 7%) of males in amplexus argues against primacy of this form of male-male competition in producing differential mating by size. Rather it appears that some combination of other forms of intrasexual competition and female choice caused the mating pattern seen.

Low-flux radiation-induced precipitation

Precipitation of Ni3Si in undersaturated NiSi solid solutions is shown to be triggered by high-energy electron irradiations at very low displacement rates. The results are compared to those previously obtained under high-flux irradiations. A simple interpretation is proposed for the temperature shift of the dose rate threshold for radiation-induced precipitation in this system.

Vibration damper with variable spring rate and damping friction

A torsional vibration dampener assembly having resilient means to provide a variable torque output in conjunction with variable damping friction torque. The assembly utilizes a first set of torsion springs to provide a low deflection or displacement rate for a first stage of travel between the input and output members and a second set of springs providing an increased deflection rate for a second stage of travel, and a cooperating cam construction which can be arranged to provide an increase or decrease in damping friction as required in relation to the transmitted torque.

Radiation-induced solute segregation and precipitation in alloys

Solute segregation and precipitation in dilute alloys during irradiation have been studied by means of the Johnson-Lam kinetic model. The model is based on a combination of chemical reaction rates and diffusion equations for free defects, solutes, and bound defect-solute complexes. The enrichment of solute at sink surfaces and solute depletion in the matrix have been calculated as functions of temperature, damage rate, defect-solute bind-ing energy, and initial solute concentration. Using parameters appropriate for Be in Ni, significant solute segregation is found in the temperature range from 0.2 to 0.7 Υm. The temperature for maximum segregation is higher for the high displacement rates typically used in charged-particle bombardment experiments than for the low displacement rates used in fast-reactor irradiations. The solute concentration at the sink surface builds up at high temperatures, without surpassing the solubility limit, until a steady state is at-tained. However, at lower temperatures solute enrichment at sinks becomes larger and the solubility, in general, becomes lower. Precipitation will occur when the local solute concentration reaches that of the phase boundary. The solute concentration at the precipi-tate-matrix interface is determined by the solubility limit, and precipitation continues until the matrix is sufficiently solute-depleted to achieve a steep concentration gradient that will balance the defect-induced solute flow by back-diffusion. Hence, the steady-state matrix composition is determined by radiation conditions and is independent of the initial alloy composition when precipitation occurs. The solute depletion at steady state is more severe at low displacement rates than at high rates. The calculations are quali-tatively compared with recent experimental observations of the temperature and com-positional dependence of solute precipitation in the Ni-Be system.

Effect of mobile helium on void nucleation in materials during irradiation

The steady-state rate of void nucleation is calculated for irradiated materials containing mobile helium. At the low displacement rates typical of a fast-breeder reactor a concentration of less than 10 −10 atom fraction helium can cause a 10 20 increase in nucleation rate. The helium is less effective at the high displacement rates typical of accelerator experiments, but can increase the void-nucleation rate by 10 4 at a helium concentration of 10 −8. The calculated void-nucleation rates for low displacement rates and without helium are too low to explain the void number densities observed in breeder-reactor irradiated materials. Therefore, void nucleation in reactor environments is helium-assisted. Accelerator experiments intended to simulate void nucleation under reactor conditions must be carefully designed to observe gas-assisted rather than homogeneous void nucleation.

Certain Wettability Effects on Electrical Resistivity in Porous Media

ABSTRACT A laboratory study was made on the relation of wettability and wetting equilibrium to electrical resistivity, particularly under dynamic conditions. Teflon cores and synthetic fluids as well as reservoir cores and fluids wereused. Resistivities were measured by a four-electrode system. Under static conditions and with the wetting equilibrium prevailing, exponents as high as 9 were calculated from Archie's Equation when the interstitial conductive liquid was the non-wetting phase. When it was the wetting phase, saturation exponents ranged from 2 to 3 for the same core. This means that in laboratory measurements of Archie's saturation exponents on reservoir cores, the corewettability must represent the wettability of the reservoir. Otherwise, thecalculated connate water saturations will be in error. Under dynamic conditions, wetting equilibrium prevails only for very low displacement rates. At high flow rates the rate has an important bearing on the measured resistivity, indicating non-equilibrium fluid distribution in some experiments, the porous medium was saturated with the non-wetting liquid first. It was shown that, in these tests, the wetting equilibrium is either notobtained at all or it is obtained extremely slowly. These laboratory resultsare explained in terms of fluid distribution in porous media. A qualitative discussion is given on the implications of this work in electrical loginterpretation and the recovery of crude oil by chemical waterfloods. INTRODUCTION HYDROCARBON-BEARING FORMATIONS are generally identified through themeasurement and interpretation of their electrical properties by well logging. The empirical equation used in the estimation of the hydrocarbon saturations from resistivity data is: {See equation in full paper}, In this equation, S, is connate water saturation, R. is the resistivity ofthe 100 per cent water-saturated formation, Rt is the resistivity of the formation containing both water and hydrocarbon, and n is the saturation exponent. The true resistivity, R, of the un-invade zone and R. are obtained from the logs; n is found from laboratory measurements on reservoir cores. Implicit in the above approach are the assumptions that:the saturation-resistivity relationship is unique,laboratory-derived n valuesapply to the reservoirn is constant for a given porous medium andall of the water contributes to the flow of the electric current. Numerous studies on the electrical resistivities of cores partly saturated with sodium chloride solution have shown that the above assumptions are notnecessarily invalid. For the same saturations, the resistivity of cores hasbeen found to vary significantly with wetting conditions, clay content, textureand salinity. To find the effect of wettability on resistivity, some studieshave been performed on natural or synthetic cores in which the wettability waschanged through a chemical reaction, i.e. hot solvent extraction, oxidation or coating the surfaces with a chemical. There are some complicating factors insuch an approach; namely, the resulting core wettability is not uniform, and cannot be described or measured, and exchangeable ions from natural mineral scan change the resistivity of the electrolyte filling the pores. Also, the porosity of the core, particularly the effective porosity, can change.