Stages Of Cycling Research Articles

Fatigue Process of a Heat Treated 0.45% C Steel in 3% NaCl Solution.

In order to clarify the corrosion fatigue process, rotating bending fatigue tests of heat treated 0.45% C steel smooth specimens were carried out in 3% NaCl solution. The emphasis is to perform successive observations by the plastic replica method. The results showed that corrosion pits are produced at the early stages of cycling, most of which then grow with further cycling until a crack initiates from each corrosion pit. The initiation of corrosion pits from slip bands was observed only in the case when the stress range is relatively large (in the range of stress under which slip bands are produced in air).

Fatigue damage and crack nucleation mechanisms at intermediate strain amplitudes

Polycrystalline copper was fatigued in rotary bending at constant intermediate surface strain amplitudes at 26 Hz under ambient conditions. The specimens were interrupted at various life fractions, their surfaces prepared metallographically and scrutinised to ascertain the types of fatigue damages, namely, short cracks which are confined to individual grains or isolated grain boundary facets, and their role in fatal crack formation. The results show that, at intermediate strain amplitudes, slip band and twin boundary crack damages predominate during early stages of cycling, while grain boundary crack damages remain relatively insignificant even at the stage when fatal cracks have developed. However, depending on the strain amplitude level, the transgranular crack damages may or may not be instrumental in fatal crack formation. At the lower amplitude end of the transition region, fatal cracks are formed by interlinkage of slip band and twin boundary damages. At the higher amplitude end, even though grain boundary damages are negligible initially, they degenerate rapidly on further cycling and eventually evolve into fatal cracks. The present findings show that some 0.05% plastic strain amplitude is required to propagate intergranular cracks. Once the above condition is met, cracks would propagate rapidly along the interface and the crack nucleation mode would change from transgranular to intergranular.

Implanted Probes Follow Changes in Electrolyte Composition in Cycling Zn / NiOOH Cells

Implanted probes in zinc electrodes within 150 Ah‐size zinc/nickel oxide cells were used to analyze the composition of electrolyte samples at different locations and stages of cycling. The probes had a negligible effect on the performance of the cells out to 300 cycles. Analyses of electrolyte density and dissolved zinc, and changes in and carbonate concentration, were used to investigate the shape change process, which was followed using an x‐ray radiography technique. It was found that the loss in cell capacity was directly related to the shape change of the zinc electrode. The data indicates that the shape change process involves several stages of development and that eventually the calcium zincate used to trap the dissolved zincate in solution and retard shape change loses its effectiveness, possibly through the formation of calcium carbonate in the electrode structure.

The Relationship Between Social Behavior and Genital Swelling in Captive Female Chimpanzees: Implications for Managing Chimpanzee (<em>Pan troglodytes</em>) Groups

This study was conducted as a portion of a project investigating relationships among reproductive cycling, aggression, and wounding in captive chimpanzees. Changes in behavior associated with the genital swelling of 11 adult female chimpanzees socially housed in four different groups were measured using 282 hours of data gathered within a 20-month period. The females' perineal swellings were rated daily using a five-point scale indicating level of tumescence. Behaviors recorded when the animals were detumescent were compared with behaviors when their sexual swellings were maximal. In addition to the subject's genital swelling rating, two factors, the male-to-female ratio in the groups and the presence or absence of a tumescent female other than the focal animal, were also included in the analysis. Multiple regression analysis revealed significant effects of each of the three factors. Significantly higher levels of sexual behavior and lower levels of submission were associated with the tumescent stage of cycling. Scores for affiliation, aggression, abnormal behavior, inactivity, locomoting, and being followed did not vary significantly with swelling phase. Group structure (male-to-female ratios) affected affiliation, locomoting, being followed, and aggression levels. Affiliation, submission, and locomoting were influenced by the presence of a tumescent female in the group. Proximity to other adult females increased during the tumescent stage of swelling, but proximity to adult males did not change. The group structure and whether or not a tumescent female was present affected various aspects of proximity to all age/sex classes of group members. Some findings from this study may be explained by the long-term stability of group membership in the colony studied, and implications for colony management are discussed.

Morphological changes in polymer electrolyte cells

Rechargeable solid state batteries utilizing lithium anodes, V 6O 13 composite cathodes and polymer electrolytes made from polyethylene oxide - LiCF 3SO 3 complex - were investigated at 100°C. The cells exhibited good cycling and reversibility. Optical and scanning electron microscopy were used to study the morphological changes taking place at the electrodes and electrolyte as a function of cycle number. Post-mortem examination of the cell materials indicated that the structures of lithium, electrolyte and cathode become finer grained and hence smoother. In addition the structures were more coherent. The cathode appeared to undergo a re-healing process during the early stage of cycling. The results indicate that the structures are consistent with one another and that long cycle life can be obtained with these types of cells.

異種金属電子ビーム溶接継手の高温低サイクル疲労破壊特性

Low cycle fatigue tests of the dissimilar metal electron beam welded joints between A387, Gr. 22 steel and SUS 405 steel (A387-SUS 405), and between A387, Gr. 22 steel and SUS 316 steel (A387-SUS 316) were carried out under the strain controlled cycling over the welded joints at a temperature of 839K. It was shown that the fatigue lives of the dissimilar metal welded joints were significantly shorter than those of base metals. In order to discuss the fatigue fracture behavior, the distribution of local strain and that of hardness were investigated. In A387-SUS 405, the strain concentration occurred on SUS 405 side during all strain cycling. While in A387-SUS 316, the uniform strain distribution was produced at the early stage of strain cycling, and thereafter the strain concentration occurred on A387 side. The change of strain distribution with strain cycling qualitatively corresponded to that of hardness. From the foregoing results, it was concluded that the shorter fatigue lives of the dissimilar metal welded joints resulted from the strain concentration which occurred on the base metal with lower deformation resistance.

The New IEEE-404 Test Specification for Joints Highlights the Importance of Connector Selection

On behalf of Hydro-Québec, IREQ undertook the evaluation of heat-shrinkable joints for 25-kV solid dielectric cable using the test schedule described in IEEE Standard 404-1986, a new specification containing higher performance requirements. Unexpectedly, the first batch of test samples failed. dramatically during the early stages of thermal heat and load cycling. Close examination of the joints followed by laboratory experiments, indicated thermal runaway of the connectors as the cause of failure, eventually attributed to faulty connector installation and compression. The experimental techniques and instrumentation used in this investigation are described in detail. The connector installation conditions were modified and the resulting satisfactory performance was demonstrated by testing samples for thermal stability under load-cycling conditions. New jointed-cable test samples were prepared and the splicing system successfully passed all the requirements of IEEE Standard 404-1986. It is now an accepted technique for the Hydro-Québec distribution system. This experience revealed that all aspects of a distribution system must be carefully considered when changes are made in the product performance requirements of any element. In fact all components of the system must be adjusted accordingly in order to provide the overall superior performance demanded by electrical utilities committed to reliable customer service.

ChemInform Abstract: Rechargeable Sodium Batteries. Part 6. Cycling Behavior of VS2, ′VCl3 + nS′ and NbS2Cl2 Cathodes in Molten NaAlCl4.

AbstractThe electrochemistry of V82, ′VC13 + nS′ and NbS2Cl2 has been investigated in relation to their usefulness as Cathodes for sodium batteries operating in the temp. range 160‐200°C. VS; reacts with NaAlCl4 during early stages of cell Cycling, and becomes VS2Cl showing a reversible capacity of z 2.8 electrons/vanadium.

Rechargeable sodium batteries—VI. Cycling behavior of VS 2, ‘VCl 3 + nS’ and NbS 2Cl 2 cathodes in molten NaAlCl 4

The electrochemistry of VS 2 in molten NaAlCl 4 has been investigated in relation to its usefulness as a reversible positive electrode for sodium batteries operating in the moderate temperature range of 160–200°C. VS 2 reacted with NaAlCl 4 during early stages of cell cycling, and became VS 2Cl showing a reversible capacity of ∼ 2.8 electrons/vanadium. The electrochemistry of mixtures of VCl 3 and S in molten NaAlCl 4 showed similarities to that of VS 2Cl. The VS x Cl y cathodes obtained via the two different routes exhibited excellent rechargeability as evidenced by the long-term cycling behavior of cells of the configuration, Na (l)/β″-Al 2O 3/NaAlCl 4(l), cathode material. When NbS 2Cl 2 was used as the cathode material it underwent a structural change in the first cycle to form what appeared to be NbS 2Cl 2, the Nb analog of VS x Cl y . The structurally modified niobium sulfur chloride cathode exhibited excellent rechargeability.

Capacity—cycle life behavior in secondary lithium cells

The practical utilization of high energy density rechargeable lithium cells is dependent upon maintaining high capacity for the duration of the required cycle life. However, a critical, yet generic problem with room temperature lithium systems is that the capacity often declines considerably during the early stages of cycling. We report the results of our studies on electrolyte degradation which we observe after cells have undergone 300 and 700 deep cycles with 3-methylsulfolane- and 2-methyltetrahydrofuran—LiAsF 6 electrolytes, respectively.

Thermal Cycling and Amorphous-Cyrstalline Transition in the Amorphous C60-Zr40 Alloy System

ABSTRACTThe transition behavior of the amorphous Cu60Zr40 alloy system during its transition to crystallinity by thermal cycling has been studied. A Differential Scanning Calorimeter (Perkin-Elmer model DSC-2) was used to record, in situ, the onset of thermal evolution of the sample during the course of transition. Analysis of DSC tracings reveal that: a. Transition occurs at a lower temperature than those transformed without thermal cycling, b. The amplitude of the exothermic rise decreases proportionally with increasing numbers of the thermal cycles and c. Details of the profile of the DSC tracing, i.e., the width of the exothermic rise and the presence of the secondary exotherm, are quite different from those transformed without thermal cycling. Preliminary high resolution electron microscopy of thermally cycled samples indicate random distribution of copper-rich precipitates at the early stages of cycling and their coalescence during the final stage of crystallization. For large number of cycles, however, the induced strains from thermal cycles contributes to the image contrast of the quenched solid thus allowing the assessment of the proposed atomic level stresses and strains, via technique of high resolution electron microscopy.

Influence of Mean Strain on Low-Cycle Torsional Fatigue Life of S45C Steel

Low-cycle torsional fatigue tests were carried out on annealed carbon steel of S 45 C and the results were examined by taking the mean strain as a parameter.The main conclusions obtained are summarized as follows:(1) The hysteresis energy per cycle is influenced by the mean strain at the beginning of strain cycling, but it saturates approximately to a constant value due to the rapid relaxation of mean stress after progressive strain cycling.(2) On the basis of hysteresis energy, an equation for estimating the effect of mean strain on the crack initiation life is proposed as follows;D=K0/K0=1/K0(We1/2+λ∫N'1/2Wedn)λ=N0'/N'where N' is the number of cycles to crack initiation when mean strain is applied, N0' is that when mean strain is zero, e and K0 are material constant and the average value of the constant K0 obtained from the equation 1/K0∫N0'0Wdn=1 when mean strain is zero, W1/2 and W are the hysteresis energies for the first half cycle and the subsequent cycles, respectively, when mean strain is applied, and dn is the infinitesimal increment of hysteresis energy cycle n.The test results confirms that this equation is well applicable to the estimation of crack initiation life.(3) Crack growth life is not influenced by mean strain, because mean stress is relaxed in a short period after the initial stage of strain cycling.

X-Ray Diffraction Study of Low Cycle Fatigue Damage in Plain Carbon Steel

An X-Ray diffraction analysis of low cycle bending fatigue was conducted on plain carbon steel (SAE 1008) in three conditions, as received (annealed) 20 percent prestrained, and strain aged. The decrease of the surface stresses at maximum and minimum strains, a reduction of the residual surface stress after unloading from the tension cycle, and a decrease of the half-value breadth during the first 20–30 cycles indicate rapid cyclic softening during the initial stages of strain cycling. After this initial period the microstructure of all specimens was found to be independent of the initial material condition. Similarly, the fatigue life as a function of strain range was also independent of the initial condition. X-Ray diffraction line analysis shows no changes for the major portion of the specimen life, from 0.1 Nf to 0.75 Nf. However, a linear relationship between half-value breadth and strain range is noted. It is suggested that this relationship can be utilized for monitoring and diagnostic purposes, particularly to determine the strain range to which a critical part has been subjected.

Application of Electron Spectroscopy for Chemical Analysis (ESCA) to the study of iron-based battery electrodes

Electron Spectroscopy for Chemical Analysis (ESCA) has been used in combination with X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDAX) to study the oxidation state, structure and morpholog of pure iron and iron-cadmium electrodes in various stages of cycling. The electrodes have only been studied in their discharged state. Cycling produces particle coarsening and a change in phase composition of the iron compounds from Fe3O4 toα-Fe. ESCA spectra suggest that a thin cadmium-rich surface film of poor electronic conductivity forms on the surface of the particles after prolonged cycling.

Zinc Electrode Shape Change in Secondary Cells

Shape change, the reduction in zinc electrode area with cycling, is a limiting factor in the life of most secondary zinc batteries. This investigation was an attempt to elucidate the mechanism of shape change by monitoring the pattern of current and potential distribution over the surface of a zinc electrode during cycling. This was done while keeping all electrode and cell parameters similar to those found in conventional cells. Differences in the secondary current distribution during charge and discharge result in exhaustion of the reducible zinc species at the plate periphery in the early stages of cycling. This generates a concentration cell which corrodes zinc off the plate edge and deposits it in the plate center. Shape change is a result of these concentration cell effects and the transfer of zincate from the plate periphery to the plate center in the early stages of discharge. Many other hitherto unexplained phenomena related to shape change were rationalized on the basis of these findings and mechanism.

The Long-Range Planning Function as Related to Katy Field Gas Sales

Devising an Optimum depletion plan for the fourth largest gas field in the United States required a detailed volumetric study for each of the twelve Katy reservoirs. All of the reservoirs have different water drive strengths, so the erect of producing rate on ultimate recovery is different for each reservoir. This is a key consideration in total-field optimization. Introduction The Katy gas field is presently under a 20-year gas sales contract, begun in 1967, and is in the last stages of gas cycling, begun in 1943. The field is located 35 miles west of downtown Houston, covers an areal extent of 50 sq miles, and comprises 12 reservoirs in the Cockfield formation, located at depths ranging from 6,000 to 7,400 ft subsea. Each reservoir has a different water-drive strength, depending on rock permeability, sand thickness, ratio of aquifer radius permeability, sand thickness, ratio of aquifer radius to reservoir radius, and reservoir geometry in general. Thus, the effect of the producing rate on ultimate recovery is different for each reservoir, and is a key consideration for total field optimization. Reservoirs with weak water drives exhibit high recoveries as a result of the combined action of pressure depletion and water influx over a long production life. Reservoirs with strong water drives are more sensitive to the producing rate, and should be depleted very quickly in order to maximize ultimate recovery. To determine the optimum production and investment schedules for the entire Katy gas field it was first necessary to develop mathematical models for each reservoir from pressure-production performance over the past 27 years. Anomalies caused by interreservoir communication and pressure interference from other fields producing from the Cockfield formation were considered in developing these models so that reasonably accurate predictions could be made regarding future reservoir pressure and well deliverability. Water influx data for reservoirs that have already undergone a significant amount of blowdown was determined by volumetric balance calculations. For the reservoirs that have experienced little or no depletion, however, these factors had to be estimated. After reasonable reservoir models were determined, it was necessary to impose certain constraints on the long-range blowdown scheduling. Two of the reservoirs have an associated thin rim-type oil column that must be essentially depleted before full-scale gas blowdown can occur. In addition, certain reservoirs are separated by very thin shale barriers and therefore must be depleted simultaneously to prevent large pressure differentials across these thin barriers. This precaution minimizes potential interreservoir communication and thus conserves potential interreservoir communication and thus conserves reservoir energy. Since most of the existing wellbores penetrate the productive areas of all the Katy reservoirs, it was productive areas of all the Katy reservoirs, it was necessary to develop models for estimating, the time at which wells water out and are available for recompletion to other zones. Wells now used for gas cycling in four of the upper reservoirs are also made available for recompletion as they drop out of the cycling program. Other factors to be considered for total field optimization are liquid recovery factors for each reservoir and development of sufficient deliverability to meet contract sales rates and peaking requirements. peaking requirements. JPT P. 145

The desorption of oxygen from silver powder

Desorption of oxygen from silver powder has been studied with a microbalance during and after using a thermochemical surface preparation technique. The powder was exposed cyclically to outgassing, oxygen adsorption at 5 Torr, outgassing and carbon monoxide reduction at 5 Torr (OAOR cycling) at a constant temperature chosen from the range 300–400°C. The microbalance was used to measure the rate and amount of oxygen desorbed from the powder at various stages of cycling by the techniques of thermal desorption and isothermal desorption. The data were analyzed for E and v by assuming that the rate of desorption follows the relation: − dθ s dt = v nθ s n exp − E RT , where n is the order of the process and is either one or two, E is the activation energy of desorption, v is the frequency factor, and θ s is the fractional coverage of a chemisorbed state. For a surface cycled at 325–400°C, the desorption parameters E and υ changed during the first five cycles and then remained constant with additional OAOR cycling. The desorption of oxygen was found to be a second-order process and E nearly independent of coverage when oxygen was adsorbed at 154°C and 5 Torr. The same result was obtained when oxygen was adsorbed at the cycling temperature and 5 Torr, and then cooled to 154°C in the ambient oxygen. The values of E and υ obtained are: E = 34.5 ± 3.5 kcal/mole and v = 2 × 10 11 to 2 × 10 14 sec −1 from thermal desorption data and E = 41.8 ± 3.5 kcal/mole and v = 3 × 10 13 to 5 × 10 16 sec −1 from isothermal desorption data. It can be concluded from these results that the adsorbed state at 154°C consists of weakly localized adsorbed oxygen atoms that recombine prior to desorption. For a sample cycled at 300°C, the amount of oxygen desorbed was insufficient to determine the parameters with any meaning even after extended cycling.

熱サイクルによる原子炉用金属材料の変形について

In order to clarify the basic characteristics on the thermal fatigue strength of metals, the authors have investigated on the changes in dimension, deformation, hardness, specific gravity, microstructure, temperature distribution and yield strength at elevated temperatures during simple thermal cycling of the various metals and alloys for reactor use, and the following results were obtained:(1) Armco iron and 304L stainless steel elongated in longitudinal direciton, but carbon steel having various carbon contents, 21/4Cr-1 Mo steel and four kinds of Fe-Al-Cr alloy contracted after the thermal cycling.(2) The grain growth due to thermal cycling of both 304L stainless steel and Fe-7.5 Al-6 Cr alloy containing 0.5% Ti and 1% Nb which suppressed the contraction was faily small. But in both alloys, surface crack occurred in the early stage of thermal cycling and propagated to the interior of samples. In the other Fe-Al-Cr alloys which displayed contraction by thermal cycling remarkable grain growth occurred and, in these cases, crack initiated only on the surface layer of sample at later stages than in 304L stainless steel, where that did not propagated. Therefore the grain growth itself could not be seemed as the essential cause of dimensional changes, because thermal stresses due to thermal cycling are relieved during the grain growth and not to promote but to retard the dimensional changes.(3) The temperature and yield strength distributions in sample during thermal cycling of 304L stainless steel and two kinds of Fe-Al-Cr alloy (8% Al and 12% Al) were measured. For latter alloys the intense decrease of the yield strength was observed at higher temperature than 500-550°C but for former alloy such marked change of yield strength was not observed through a temperature range up to 750°C. From these results, the authors concluded that the essential cause of the dimensional changes in such metals and alloys having simple phase as armco iron, 304L stainless steel and Fe-Al-Cr alloys depends generally upon the amount of thermal strain due to temperature gradient and the change in yield strength.Besides, the authors suggested that whether elongation or contraction was dependent apparently upon the existence of the marked decrease of yield strength within the cycling temperature range. However, the critical values could not be decided quantitatively because of lack in data. The authors will study further quantitatively to clarify the mechanism of the above mentioned phenomena.