Small Number Of Cycles Research Articles

OS1301-376 対称アングルプライCFRP積層板の高温におけるサイクル軟化挙動

Strain-controlled cyclic behavior of angle-ply CFRP laminates [±θ] at high temperature has been studied. Strain-controlled symmetric tension-compression cyclic tests for different strain amplitudes were carried out on coupon specimens with different fiber orientations (θ = 30°, 35° and 45°), respectively. On the basis of the cyclic tests, the changes of stress amplitude, mean stress, non-elastic strain amplitude, maximum and minimum stress levels and loading and unloading tangent moduli with cyclic straining are examined. The experimental results showed that hysteretic stress-strain response to cyclic straining appears, regardless of the fiber orientation. The stress amplitude decreased with increasing number of cycles, and accordingly the non-elastic strain amplitude increased with cyclic straining. These observations reveal that the cyclic softening occurs in the angle-ply CFRP laminates tested in this study. The cyclic softening terminates rapidly in a small number of cycles, and a cyclic saturation stage is reached in all the strain-controlled cyclic tests, except some cases of large strain amplitude or small fiber orientation angle.

Evaluation of the performances of self-compacting concretes based on byproducts subject to freeze thaw in local conditions

The evaluation of freeze-thaw resistance of self-compacting concrete containing by-products is a major issue for the construction of durable concrete structures and raises many questions among researchers. This work aims to study the behavior of self-compacting concrete-based on local by-products subjected to freeze/thaw cycles starting at 14 days, of air and watercuring, where the concrete has reached more than half of its strength. For this purpose, a comparative study was conducted on a reference SCC with limestone’s filler (LP) which was replaced by marble powder (MP) and granulated blast furnace slag (GBFS). Freezing and thawing was performed according to ASTM C666 standard procedure B, air freezing and water thawing by adapting the freeze-thaw test to the Algerian context using a small number of cycles and without salt deicer. The test methods used to evaluate durability were weight change, length change, compressive and tensile strength loss. The results show that the curing condition and the by-product type have a combined influence on freeze-thaw resistance of self-compacting concrete. The moisture resistant mixture to freeze-thaw was the SCC obtained with granulated blast furnace slag. While SCC with marble powder present characteristics very comparable with those of SCC mixture with limestone powder. It appears that the mixture with the best characteristics is the most resistant to the freeze thaw action. Keywords : Self-compacting concrete, by-products, freeze/thaw resistance, granulated blast furnace slag, marble powder.

Modification of Crystal Shape through Deep Temperature Cycling

The evolution of particle shape is an important consideration in many industrial crystallizations. This article describes the design of temperature-cycling experiments (between alternating positive and negative supersaturations) to substantially change crystal shape with only a small number of cycles. The growth and dissolution of monosodium glutamate crystals of varying shapes were monitored using in-process attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), focused beam reflectance measurement (FBRM), particle vision and measurement (PVM), and off-line optical microscopy. The growth and dissolution kinetics were estimated in a multidimensional population balance model based on solute concentration and crystal dimension measurements. This model fitted the experimental data with a limited number of parameters of small uncertainty. In addition, with the estimated kinetic parameters, the model predicted the crystal size and shape distribution in a different temperature-cycling e...

New Combined Process “Pressing-drawing” and Impact on Properties of Deformable Aluminum Wire

The aim of this work is to study the influence of the combined process of “pressing-drawing” on the microstructure and mechanical properties of aluminum wire. Analysis of the results of the research has shown that the proposed combined method of deformation “pressing-drawing” has a significant advantage over the existing technology of production of aluminum wire. This method of deformation due to combination of two ways: by severe plastic deformation in equal channel step die and the process of drawing through a drawing die, allows obtaining aluminum wire with ultrafine-grained structure and a high level of mechanical properties, required size and shape of the cross section at a small number of cycles of deformation. Also would like to mention that this method of deformation in implementing it in production does not require significant economic investments, and substantial refitting of existing drawing mills.

Studying the parameters of acoustic emission signals during inspection of cast parts of a freight car truck

The main parameters of acoustic emission (AE) signals, viz., the energy, the total number, and the activity, were studied under a static and a subsequent cyclic loads during strength testing of cast parts (solebars and bolsters) of a freight car truck. It was shown that loading with a small number of cycles made it possible to obtain additional data, which extended the information on the state of the parts under study.

Low cycle fatigue and cyclic softening behaviour of martensitic cast steel

The paper presents the results of research on fatigue properties in a small number of cycles to failure of high-chromium martensitic GX12CrMoVNbN9-1 (GP91) cast steel designed for the casts working under the so-called supercritical parameters. The tests of fatigue life were carried out at three temperatures: room temperature, 550°C and 600°C, for five levels of controlled amplitude of total strain ɛac: 0.25%; 0.30%; 0.35%; 0.50% and 0.60%. Cyclic softening was observed in the fatigue tests at all temperatures without a stabilization period. The fatigue lifetime curves at each temperature were obtained based on Basquin and Coffin–Manson equations. It has been shown that the influence of temperature on fatigue life depends on the level of strain and is the biggest for the lowest levels of strain covered in the research. The results of fatigue tests are connected with the quantitative changes in the microstructure of the cast steel. Quantitative tests were carried out using thin foils by means of TEM. Disappearance of martensitic laths, increase in the subgrains size, decrease in the dislocations density and coagulation of carbides were observed after low cycle fatigue. The scale of these changes in the microstructure is dependent on the temperature and level of strain.

Tangential load–deflection behaviour at the contacts of soil particles

This paper describes a laboratory investigation of the response of coarse-grained soil particles at their contacts. The tests were carried out in a newly developed micromechanical inter-particle loading apparatus capable of imposing and measuring loads and deflections at the contacts of non-conforming (i.e. non flat-to-flat) surfaces. The apparatus was designed to investigate the behaviour at contacts over a range of load levels from the initial contact stiffness to failure under sliding. The paper presents tests on a variety of particle contacts, investigating the effects of test conditions as well as particle properties and quantifying the particle roughness using an interferometer microscope. The initial tangential load–deflection behaviour is shown to be highly non-linear and predominantly plastic. The stiffness depends on the normal load applied and the particle type, but does not degrade with small numbers of cycles. Shearing led to a significant decrease in the amplitude of the surface roughness of the particles, mostly through the removal of asperities, which shows that the tangential stiffness might not be significantly affected by the amplitude of surface roughness.

Fatigue reliability analysis of steel bridge details based on field-monitored data and linear elastic fracture mechanics

This article presents the fatigue reliability analysis of welded details of a 40-year old steel box-girder bridge, based on the linear elastic fracture mechanics (LEFM) and the long-term stress monitoring. The fatigue crack growth is described by using the LEFM, based on which the ultimate limit state is established as a function of the crack size. Effective stress ranges are obtained from daily stress range histograms, and lognormal probability density functions (PDFs) are used to model the uncertainties in stress data. Details at discontinuous backing bar splices, which have not been explicitly listed in the American Association of State Highway and Transportation Officials (AASHTO) specification, and the welded details at the base of bridge bents are evaluated on their fatigue reliabilities. It is found that the backing bar splice detail may have high fatigue reliability, considering that low stress ranges and small number of cycles occurred in the monitoring period. For the weld detail at the base of bent, stress ranges higher than the constant amplitude fatigue limit (CAFL) existed, and currently the reliability indexes are all below the target value, showing that maintenance or retrofit actions may be required. For the details at the upper base of bridge bents, sufficient reliabilities are expected throughout the service life.

CO2 multicyclic capture of pretreated/doped CaO in the Ca-looping process. Theory and experiments

We study in this paper the conversion of CaO-based CO2 sorbents when subjected to repeated carbonation-calcination cycles with a focus on thermally pretreated/doped sorbents. Analytical equations are derived to describe the evolution of conversion with the cycle number from a unifying model based on the balance between surface area loss due to sintering in the looping-calcination stage and surface area regeneration as a consequence of solid-state diffusion during the looping-carbonation stage. Multicyclic CaO conversion is governed by the evolution of surface area loss/regeneration that strongly depends on the initial state of the pore skeleton. In the case of thermally pretreated sorbents, the initial pore skeleton is highly sintered and regeneration is relevant, whereas for nonpretreated sorbents the initial pore skeleton is soft and regeneration is negligible. Experimental results are obtained for sorbents subjected to a preheating controlled rate thermal analysis (CRTA) program. By applying this preheating program in a CO2 enriched atmosphere, CaO can be subjected to a rapid carbonation followed by a slow rate controlled decarbonation, which yields a highly sintered skeleton displaying a small conversion in the first cycle and self-reactivation in the next ones. Conversely, carbonation of the sorbent at a slow controlled rate enhances CO2 solid-state diffusion, which gives rise, after a quick decarbonation, to a highly porous skeleton. In this case, CaO conversion in the first cycle is very large but it decays abruptly in subsequent cycles. Data for CaO conversion retrieved from the literature and from further experimental measurements performed in our work are analyzed as influenced by a variety of experimental variables such as preheating temperature program, preheating exposition time, atmosphere composition, presence of additives, and carbonation-calcination conditions. Conversion data are well fitted by the proposed model equations, which are of help for a quantitative interpretation of the effect of experimental conditions on the multicyclic sorbent performance as a function of sintering/regeneration parameters inferred from the fittings and allow foreseeing the critical conditions to promote reactivation. The peculiar behavior of some pretreated sorbents, showing a maximum conversion in a small number of cycles, is explained in light of the model.

Poisson survival model of quantum entanglement signaling network and fidelity analysis

Quantum signaling states have decoherence because of the environment during the transmission. It causes signaling damage and thus will have impact on building high survivability quantum entanglement signaling network. In order to study the influence deeply, Poisson damage model of quantum signaling network is established. First, disaster magnitude is defined base on signaling fidelity. Second, average damage signaling quantum bits and survival function of quantum signaling network is put forward by basic quantum theory. At last, research on the signaling damage repair strategy and simulation is analyzed. Simulation results show that increasing of disaster magnitude will greatly reduce the signaling network survivability. However, increasing the nodes and controlling signaling damage caps may improve survivability. The repair strategy which costs small number of cycles can rapidly increase the signaling fidelity from 0.6 to 0.9 and the survival function of the signaling network from 0.4 to 0.9.

Time to pregnancy: a computational method for using the duration of non-conception for predicting conception.

An important problem in reproductive medicine is deciding when people who have failed to become pregnant without medical assistance should begin investigation and treatment. This study describes a computational approach to determining what can be deduced about a couple's future chances of pregnancy from the number of menstrual cycles over which they have been trying to conceive. The starting point is that a couple's fertility is inherently uncertain. This uncertainty is modelled as a probability distribution for the chance of conceiving in each menstrual cycle. We have developed a general numerical computational method, which uses Bayes' theorem to generate a posterior distribution for a couple's chance of conceiving in each cycle, conditional on the number of previous cycles of attempted conception. When various metrics of a couple's expected chances of pregnancy were computed as a function of the number of cycles over which they had been trying to conceive, we found good fits to observed data on time to pregnancy for different populations. The commonly-used standard of 12 cycles of non-conception as an indicator of subfertility was found to be reasonably robust, though a larger or smaller number of cycles may be more appropriate depending on the population from which a couple is drawn and the precise subfertility metric which is most relevant, for example the probability of conception in the next cycle or the next 12 cycles. We have also applied our computational method to model the impact of female reproductive ageing. Results indicate that, for women over the age of 35, it may be appropriate to start investigation and treatment more quickly than for younger women. Ignoring reproductive decline during the period of attempted conception added up to two cycles to the computed number of cycles before reaching a metric of subfertility.

RF-sputtered LiCoO2 thick films: microstructure and electrochemical performance as cathodes in aqueous and nonaqueous microbatteries

Films of LiCoO2 are prepared on metallized silicon substrates using RF-magnetron sputtering technique. The microstructural properties of the films are investigated by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The films deposited at a substrate temperature of 250 °C with subsequent annealing at 650 °C exhibited hexagonal layered structure with R $$ \overline 3 $$ m symmetry. The kinetics of lithium ions in LiCoO2 film cathode host matrix and its cycleability are studied in aqueous Pt//LiCoO2 and nonaqueous Li//LiCoO2 cell. Both the electrochemical cells at same current density of 50 μA cm−2 delivered the same initial discharge capacity of about 60 μA h cm−2 μm−1 with a chemical diffusion coefficient of ca. 10−11 cm2 s−1 for Li+ ions. The capacity fade rates for the Pt//LiCoO2 and Li//LiCoO2 cells, in average are 3.0 and 0.15 % per cycle, respectively, for the first 20 cycles. The Pt//LiCoO2 cell is found to be advantageous for small number of cycles and is cost effective than the Li//LiCoO2 cell.

DEVELOPMENT OF SIMPLE FREEZING AND THAWING TEST USING LIQUID NITROGEN

In this research, an apparatus for a simple freezing and thawing test using liquid nitrogen that enables measurement to be carried out even in actual structures has been developed based on existing research studies as a new testing method replacing the freezing and thawing test of concrete defined in the Japanese Industrial Standards (JIS), and a reviews was made of its practicality. The results indicated that, when used in conjunction with ultrasonic measurement equipment, the apparatus for a simple freezing and thawing test using liquid nitrogen was capable of evaluating the degradation of concrete surfaces part after only a small number of cycles and was greatly effective in practical application.

Fuzzy FES controller using cycle-to-cycle control for repetitive movement training in motor rehabilitation. Experimental tests with wireless system

A prototype of wireless surface electrical stimulation system combined with the fuzzy FES controller was developed for rehabilitation training with functional electrical stimulation (FES). The developed FES system has three features for rehabilitation training: small-sized electrical stimulator for surface FES, wireless connection between controller and stimulators, and between controller and sensors, and the fuzzy FES controller based on the cycle-to-cycle control for repetitive training. The developed stimulator could generate monophasic or biphasic high voltage stimulus pulse and could output stimulation pulses continuously more than 20 hours with 4 AAA batteries. The developed system was examined with neurologically intact subjects and hemiplegic subjects in knee joint control. The maximum knee joint angle was controlled by regulating burst duration of stimulation pulses by the fuzzy controller. In the results of two experiments of knee extension angle control and knee flexion and extension angle control, the maximum angles reached their targets within small number of cycles and were controlled stably in the stimulation cycles after reaching the target. The fuzzy FES controller based on the cycle-to-cycle control worked effectively to reach the target angle and to compensate difference in muscle properties between subjects. The developed wireless surface FES system would be practical in clinical applications of repetitive execution of similar movements of the limbs for motor rehabilitation with FES.

A Novel Method for Rapid and Accurate Detection of Ovulation in Macaca fascicularis.

Precise knowledge of the day of ovulation is a critical component to nonhuman primate (NHP) assisted reproduction technology (ART) programs and peaks in luteinizing hormone and estrogen levels are considered the gold standard for ovulation detection. Conventional assays (RIA, ELISA) for gonadotrophins and steroid hormones are often time consuming and costly with respect to equipment and reagents, particularly when small numbers of cycles are being monitored. Estrone conjugates are common in a number of primate species including humans and are well known markers of ovulation that correlate with peak estrogen levels. Rapid estrone conjugate assays (Dip Sticks) are employed in many human urinary fertility tests and rely on a color density function to determine hormone levels. Given the similarities of estrone conjugates in primates our aim was to develop a novel ovulation detection system using human fertility Dip Sticks and a color density function analysis. Overnight urine samples were collected daily between 0700-0800 hours and the volume recorded. A 1 ml sample of the urine was centrifuged at 10,000 rpm for 1 minute and a Dip Stick (Clearblue Easy) was immersed in the supernatant according to manufactures instructions. The Dip Sticks were subjected to color density analysis using a digital masking procedure in Adobe Photoshop. The Dip Sticks displayed a concentration-related shift in red color density in relation to increasing concentrations (0-1000 nM) of estrone conjugate controls. Tests for parallelism indicated that the minima, maxima, slope and EC50 values were not different across three batches of Dip Stick. Control concentration-response data was combined and fit by a four-parameter logistic function to establish a control curve. A total of 27 cycles from 18 females were examined for peak red color shifts. Eighty-one percent of cycles (22/27) from 94% of the animals (17/18) exhibited mid cycle red color shift peaks. Estrone conjugate estimates (E1C) derived from the control curve indicated peak E1C values that were greater than 2-fold higher than mid-follicular (day 7-9) levels. Serum estrogen levels correlated significantly and positively with E1C estimates derived from the color shift data. Significant positive correlations were derived for day of peak E1C estimate and the expected day of ovulation derived from the day of ovulation:cycle length (DO/CL) ratio method for both the last cycle and the average cycle length of the previous three cycles. However, in a non-surgical embryo transfer model use of the Dip Stick resulted in accurate determination of ovulation and subsequent implantation window (Estrogen ≤100 pg/ml, Progesterone ≥2 ng/ml) in 91% of cycles (10/11) and pregnancy rates of 36.4% (4/11) of transfer cycles, respectively compared to 32% of cycles (8/25) with pregnancy rates of 16% (4/25) of transfer cycles based on the DO/CL ratio method alone. This novel, rapid, accurate and low-cost method of ovulation detection may be of utility for NHP ART and assisted breeding programs. This work was supported by NIH 000166. (platform)

Stress and fatigue in the magnets in DEMO in pulsed and steady-state operation using geometric scaling factors

One of the most important lifetime-limiting effects for a pulsed tokamak reactor, the effect due to pulsing the magnets, is addressed here. Pulsed operation imposes stresses with significant alternating components on all the coils. This paper analyses the effects of fatigue on the coils. (Fatigue of the superconductor itself is not discussed.) Initial work has concentrated on the TF coils. The form of the finite element model is simple to permit parametrisation so that the results can be used in systems studies using codes such as PROCESS. The parameters used so far are geometric scaling factors describing the TF and CS coils only. Once sufficient parameters have been introduced, the resulting equations for stress can give realistic results in a systems code, which allows for the interdependence of all the variables. The magnetic field in the TF coil winding pack due to all the coils is calculated using the Biot–Savart law. This gives the Lorentz force in the winding pack, which is then used for the stress–strain calculation. The alternating stress is calculated by subtracting the stress tensors between two different load cases. In order to meet the lifetime fatigue goal the coil support structure needs to be made stronger than the structure intended for the small number of cycles of a steady-state reactor design, which will add to its radial build. We have quantified these requirements, allowing systems codes to estimate the additional costs.

2-Walk linear graphs with small number of cycles

A graph has exactly two main eigenvalues if and only if it is a 2-walk linear graph. In this paper, we show some necessary conditions that a 2-walk (a, b)-linear graph must obey. Using these conditions and some basic theorems in graph theory, we characterize all 2-walk linear graphs with small cyclic graphs without pendants. The results are given in sort on unicyclic, bicyclic, tricyclic graphs.

Failure mode shifts during constant amplitude fatigue loading of GFRP/foam core sandwich beams

This paper presents fatigue results for sandwich beams that exhibit a transition in failure mode, from core shear failure to face laminate tensile failure, as function of load amplitude only. The basis of this are fatigue tests of foam cores in shear and tensile tests on composite laminates. These results show that the slopes of the stress–life (S–N) relation are different for the core and laminates. By using the obtained stress–life relations, a simple design scheme is given for sandwich beams which are anticipated to have a transition of failure mode for a particular load level. Two designs are manufactured and tested in fatigue under constant amplitude loading. The results clearly show the aim of investigation with transitions in failure modes giving a structural stress–life diagram a bi-linear shape. For high load and small number of cycles to failure, the beams fail by core shear fracture while for lower loads, and large number of cycles to failure the beams fail by face sheet tensile failure.

Making Sense by Building Sense: Kindergarten Children’s Construction and Understanding of Adaptive Robot Behaviors

This study explores young children’s ability to construct and explain adaptive behaviors of a behaving artifact, an autonomous mobile robot with sensors. A central component of the behavior construction environment is the RoboGan software that supports children’s construction of spatiotemporal events with an a-temporal rule structure. Six kindergarten children participated in the study, three girls and three boys. Activities and interviews were conducted individually along five sessions that included increasingly complex construction tasks. It was found that all of the children succeeded in constructing most such behaviors, debugging their constructions in a relatively small number of cycles. An adult’s assistance in noticing relevant features of the problem was necessary for the more complex tasks that involved four complementary rules. The spatial scaffolding afforded by the RoboGan interface was well used by the children, as they consistently used partial backtracking strategies to improve their constructions, and employed modular construction strategies in the more complex tasks. The children’s explanations following their construction usually capped at one rule, or two condition-action couples, one rule short of their final constructions. With respect to tasks that involved describing a demonstrated robot’s behavior, in describing their constructions, explanations tended to be more rule-based, complex and mechanistic. These results are discussed with respect to the importance of making such physical/computational environments available to young children, and support of young children’s learning about such intelligent systems and reasoning in developmentally-advanced forms.

Effect of retained austenite on high cycle fatigue behavior of carburized 14NiCr11 steel

Two vacuum carburizing treatments were applied to ductile steel 14NiCr11 to obtain equivalent hardened layers with retained austenite contents of 25% and 41%. The properties of the carburized surfaces were examined and characterized before fatigue tests and during cyclic loading. Transformation of retained austenite into martensite during loading, was evaluated by dispersive X-ray diffraction method. The effects of this transformation on the residual stresses have been measured by X ray diffraction in martensite and in retained austenite structures. It was shown that the cyclic retained austenite transformation caused a redistribution of the compressive residual stresses and an increased surface hardness that stabilized after a small number of cycles. The dependence of fatigue behavior on surface properties was determined, and a relationship between the stabilized state and the fatigue limit is suggested. A phenomenological approach is proposed to correlate the influence of surface hardening and the stabilized residual stresses on fatigue limit of carburized specimens. The Crossland, Dang Van and Findley-Matake, multiaxial high cycle fatigue criteria were used in this approach and results have shown a good agreement with experimental data.