Form Of Hysteresis Loop Research Articles

Estimation of CLARK Y-14 Airfoil’s Lift Hysteresis in Low-Speed Flow

A phenomenon called hysteresis is responsible for the difference in the separation and the reattachment angles of an airfoil which is seen within the vicinity of the stalling angle of attack. The reason for this is the difference in the expected lift distribution of an airfoil for a particular angle of attack when recovery from stall is achieved. This leads to asymmetric flow parameters around a body even when the boundaries remain symmetric. Empirical results were obtained for a two-dimensional Clark Y-14 airfoil by varying the angle of attack for different Reynold’s numbers in order to estimate how lift characteristics are affected by the formation of hysteresis loops at different Reynolds numbers. It was seen that the extent of the clockwise hysteresis loops of the Clark Y-14 increased with the increase of the Reynolds number up to the Reynolds number of 134072 before starting to decrease again. The stalling angles followed a similar pattern before starting to decrease at a Reynolds number of 164543. These trends observed for the Clark Y-14 airfoil is similar to that of the Eppler 591 and NACA 0018 by Lance W.Traub and W.A Timmer respectively (Timmer, 2008), (Traub, 2016). When analyzing the coefficient of pressure variation for the Clark Y-14 airfoil at a particular Reynolds number, it was seen that a laminar separation bubble was formed for the forward stroke which shifted towards the leading edge of the airfoil which was common for all the Reynolds numbers. In the forward stroke, it could be seen that a laminar separation bubble was formed whereas for the backward stroke no such laminar separation bubble was formed for the same angle of attack which gave rise to the hysteresis loops of the Clark Y-`14 airfoil. It was observed that the laminar separation bubble had a direct impact on the formation of the hysteresis loops giving rise to static stall hysteresis as mentioned in previous research published by various authors. The empirical results obtained were further validated using Computation Fluid Dynamics.

Сomputational approach to thermal-stressed state modeling of tire based on the algorithm of its self-heating analysis. Part 2 – Practical results of applying the approach

Elastomers and their composites are widely used in modern innovative technology: for the production of aviation and automobile tires, anti-vibration elements (rubber, rubber-metal springs), dampers, elastomeric bearings. Also they are used in shaft suspensions, as spacers between structural parts, supporting parts and fasteners. Elastomeric elements of structures have a high dynamic load, in particular of a cyclic nature, which is accompanied by the formation of hysteresis loops and, as a result, the occurrence of the phenomenon of self-heating. An increase in temperature in the middle of materials causes significant changes in their mechanical properties, reduces strength characteristics, accelerates aging and degradation processes, and has a significant impact on fatigue processes. In addition, an increase in temperature causes an additional thermal stress state, capable of significantly changing the qualitative picture of the structure's deformation characteristics' distribution. Thus, the purpose of this study is development of approach to assessing the thermal stress state of structures made of elastomeric materials for the possibility of further analysis of its influence on the structure work as a whole. The appropriate approach was built on the basis of numerical modeling of thermal and deformation processes which takes place into the structure during operation. The proposed approach includes several related calculations by using FEM and is based on the fundamental approaches of the theories of elasticity and viscoelasticity, thermal conductivity and thermo-elasticity. Thus, the article presents an approach to the analysis of the thermal stress state of structural elements under operating conditions. This approach was applied to determine the thermo-strain-stress characteristics of a pneumatic tire and corresponding pictures of its distribution were obtained.

Hysteresis Phenomena in the Relationship between the Cosmic Ray Cutoff Rigidity and Parameters of the Magnetosphere during a Storm on May 15, 2005

Variations in the cutoff rigidities of cosmic rays (ΔR) depending on the parameters of the solarwind, the interplanetary magnetic field (IMF), and geomagnetic activity were studied at different phases ofthe strong magnetic storm on May 15, 2005. We found that the trajectories ΔR, i.e., the successive values thatΔR takes depending on the parameters under study during the main phase of the storm did not coincide withthe trajectories in the recovery phase, which led to the formation of hysteresis loops. The clearest hysteresisloops are formed for the relationship between ΔR and the Bz component of the IMF, the density and pressureof the solar wind, and the Dst index of geomagnetic activity. The area of the hysteresis loops increases withthe latitude of the cosmic ray observation station.

Computational approach to thermal-stressed state modeling of tire based on the algorithm of its self-heating analysis . Part 1 – Theoretical basics of the approach

Elastomers and their composites are widely used in modern innovative technology: for the production of aviation and automobile tires, anti-vibration elements (rubber, rubber-metal springs), dampers, elastomeric bearings. Also they are used in shaft suspensions, as spacers between structural parts, supporting parts and fasteners. Elastomeric elements of structures have a high dynamic load, in particular of a cyclic nature, which is accompanied by the formation of hysteresis loops and, as a result, the occurrence of the phenomenon of self-heating. An increase in temperature in the middle of materials causes significant changes in their mechanical properties, reduces strength characteristics, accelerates aging and degradation processes, and has a significant impact on fatigue processes. In addition, an increase in temperature causes an additional thermal stress state, capable of significantly changing the qualitative picture of the structure's deformation characteristics' distribution. Thus, the purpose of this study is development of approach to assessing the thermal stress state of structures made of elastomeric materials for the possibility of further analysis of its influence on the structure work as a whole. The appropriate approach was built on the basis of numerical modeling of thermal and deformation processes which takes place into the structure during operation. The proposed approach includes several related calculations by using FEM and is based on the fundamental approaches of the theories of elasticity and viscoelasticity, thermal conductivity and thermo-elasticity. Thus, the article presents an approach to the analysis of the thermal stress state of structural elements under operating conditions. This approach was applied to determine the thermo-strain-stress characteristics of a pneumatic tire and corresponding pictures of its distribution were obtained.

Structural and Electrical Properties of Pure and Samarium Doped MgFe<sub>2</sub>O<sub>4</sub> Nanoparticles for Resistive RAM Applications

Spinel ferrites nanoparticles have attracted the attention of researcher for memory storage devices. We have synthesized MgFeO4 pure sample and MgFe1.8Sm0.2O4 doped sample via solgel technique. The study of structural, electrical, dielectric, and I-V properties were studied of synthesized spinel magnesium ferrites nanoparticles. X-ray diffraction (XRD) confirmed the spinel structure of both compositions. The frequency dependent AC conductivity, dielectric constant, dielectric tangent loss, was studied in the range of 20Hz to 3MHz. I-V measurements has been done for the resistive switching properties. I-V curves of both compositions in the current study exhibits the formation of hysteresis loop. The hysteresis loop behavior shows that with the addition of samarium the trend of loop increases which plays crucial role as a Resistive Random-Access Memory (ReRAM) application in switching memory storage devices.

Сomparative analysis of methods for calculating stamp modules of soil deformation

Introduction. The purpose of the article is a comparative analysis of methods for calculating stamp modules of soil deformation regulated by various standards of the Russian Federation.Materials and methods. The experimental determination of the deformation modules for the soil of the roadbed was performed using stamp tests. The tests were carried out in a soil tray by loading and unloading a soil base compacted to the required compaction coefficient of 0.98. The load was applied by steps, and the stamp draft was measured after completion of deformation stabilization from each step. The criterion for stabilizing the deformation was a decrease in the speed to 0.02 mm / min and the time of application of the load, which should be at least 120 s. After measuring the elasto-plastic draft of the soil, the model was unloaded. Unloading is also carried out by steps. As a result, the dependences of the elasto-plastic and elastic draft of the soil model of the roadbed from the pressure in the form of hysteresis loops are constructed.Results. The calculations of the soil deformation modulus were performed according to the various methods regulated by the standards of the Russian Federation. The calculation results are grouped into data samples that are processed by mathematical statistics methods. When processing data, each sample is checked for the presence of gross errors. The data samples are checked for belonging to one general population. To check whether three samples belong to one general population, the Kruskal W. H. and Wallis W. A. criterion was applied. Based on this comparison, we made judgments about the significance of differences in the samples.Discussion and conclusions. To determine the deformation modulus of soil and road pavements made of granular materials, a method for calculating the modulus of deformation using a method that assumes a nonlinear dependence of deformations on pressures, described by a second-degree polynomial is recommended.

Study on the thixotropy and structural recovery characteristics of waxy crude oil emulsion

Waxy crude oil emulsion has thixotropic properties at the temperature near gel point, which is a macro-mechanical characterization of the structure failure and recovery of waxy crude oil emulsion. In this paper, the thixotropic behaviors of waxy crude oil emulsion near gel point were studied using hysteresis loop formed by stress linear increase and decrease, as well as the structural recovery characteristics. The influence of the loading conditions and water content on the thixotropy of waxy crude oil emulsion were analyzed with hysteresis loop area. The concept of “structural recovery” was introduced to study the degree of structural recovery after different stewing, and influencing factors were taken into account. Results have shown that for waxy crude oil emulsion, the failure to fully restore of the structure after lysis is the cause of the formation of hysteresis loop, and the loading conditions will not affect the strength of thixotropy and the degree of structural recovery. Additionally, the dispersed phase droplets weaken the thixotropy and structure recovery characteristics of waxy crude oil emulsion, and the greater the water content, the weaker the thixotropy. The findings can help to better understand the safe and economic operation of waxy crude oil-water pipeline transportation.

Synthesis and magnetic properties of stable cobalt nanoparticles decorated reduced graphene oxide sheets in the aqueous medium

We have synthesized cobalt nanoparticles-reduced graphene oxide (Co-RGO) nanocomposites. The Co NPs achieve shape variation in different nanocomposites due to the strategic use of variety in the preparation techniques. The transmission electron microscope image of composites confirms the decoration of different shapes of Co NPs on RGO sheets. The magnetic study with the variation of temperature indicates a change in the form of hysteresis loops. This is due to the transition from ferromagnetic to superparamagnetic behavior. We found that cubic-shaped Co NPs while decorating RGO show the highest values for some critical magnetic parameters. Coercivity, magnetic moment, and squareness ratio are these parameters. Besides, the nanocomposite-impregnated aqueous sols are found to be quite stable and could be a potential candidate for inkjet printing and ferrofluid as the squareness ratio (Mr/MS) is very small.

Cupper doping effect on the electrical characteristics of TiO2 based Memristor

Nanostructures as a starting point to solve the scaling problems of the CMOS technologies, have been concerned the attention of numerous researchers. By strong demanding for nonvolatile memory technology, resistive memories based on metal oxide has been common due to several advantages, such as low-power consumption, good scalability and fast switching speed. Even though high-temperature fabrication process has a large area limitation by their material characteristics. Metal oxide thin films are respectable candidate to fabricate at nano scale solid state electronic device. Metal/Metal-Oxide/Metal structure is employed to several devices such as Non-volatile able memories, RRAMs, resistance switching based devices and memristor. The foundation of the primary TiO2 based memristor served a number of consequences for understanding the conduction mechanisms during the formation of hysteresis loop. Also, the current-voltage characteristics (hysteretic loop) which is formed by mobile anions or oxygen vacancies motion in the set and reset process, is clarified the resistive switching behavior by swapping the resistance of TiO2 thin film. Here, the effect of Cu doping into TiO2 based memristor by focused on the hysteresis loop characteristics is considered. Similarities of hysteresis loop form in Cu doped devices are explored. Hysteresis loop is symmetric for structures having pure TiO2; however, asymmetric character appears after Cu doping. After the formation process hysteresis loop of the Cu doped devices shown higher conductance path on (I-V) characteristic than the initial forming process loop in positive cycle loop as the un-doped TiO2. Also, in spite of un-doped TiO2, this (I-V) hysteresis loop character shown lower path conductance than primary forming process in the negative cycle loop. Surface roughness of 30nm thick TiO2 is increased from 0.3nm to 0.77nm as Cu doping increased from %10 to %30. Unfortunately, XRD results cleared that there is no exchange in crystallinity but optical band gap decreased as Cu doping increased.

A new approach for the determination of the Iwan density function in modeling friction contact

Friction between interfaces seriously affects the dynamics of structures with joints. An accurate description of the friction behavior, usually given in the form of hysteresis loops, is then a prerequisite for a successful prediction of the dynamics of joint structures. Driven by this demand, this paper proposes a new approach in the framework of the Iwan model to better simulate the nonlinear constitutive relationship of joints. The approach derives the Iwan density function from the contact pressure distribution on the joint interface, without having to assume it like traditional Iwan-type models. Following this, the corresponding force-displacement expressions can be obtained. The proposed approach is applied to two different contact geometries: sphere-on-sphere and flat-on-flat. For the spherical contact, comparisons between the simulated results and the analytical solutions available in the literature show perfect agreement. Moreover, the effectiveness of the approach in flat-to-flat contact is validated by comparing the simulated hysteresis loop with the experimental counterpart.

Successful electrospinning fabrication of ZrO2 nanofibers: A detailed physical – chemical characterization study

Electrospinning fabrication of Zirconia nanofibers was successfully achieved, followed by different thermal treatment. A careful physical characterization study was performed based on the calcination temperature effect, which was confirmed by a wide range of analysis such as SEM, TG-DT analysis, XRD, FT-IR, DRS, VSM, and PL spectra. The morphological characterization of both polymer and ceramic nanofibers was achieved by SEM images through an image analyzing software. The average diameter of the produced nanofibers was estimated below 100 nm after rising thermal treatment temperature. The thermal behavior of the as-spun ZrO2 nanofibers was studied using thermogravimetric analyses (TGA). The whole powder pattern modeling (WPPM) approach using the PM2K package and the Rietveld refinement approach were applied on the X-ray diffraction pattern to get insight into the effect of calcination temperature on the microstructure parameters of nanostructured zirconia fibers. A comprehensive study was done on the chemical properties of the fabricated samples based on the absorption bands using FT-IR spectroscopy. Chemical study shows a good correlation between the XRD and FT-IR findings. The optical properties were investigated using diffuse reflectance spectroscopy and room-temperature photoluminescence spectra. An enhancement of PL intensity of the ZrO2 calcined at 800 °C could be due to its high crystal quality. The magnetic properties of zirconia nanofibers were investigated by a vibrating sample magnetometer (VSM). Room temperature magnetization results showed a hysteresis loop formation, indicating the ferromagnetic behavior of samples.

Anelasticity in cast Mg-Gd alloys

Cyclic loading-unloading tests in tension and compression were carried out on pure Mg and alloys with 0.4, 1.5 and 4.2at% Gd, over a range of grain sizes, to quantify the solute and strain dependence of the materials anelasticity in the form of hysteresis loops. For a given grain size, the anelastic effect was more pronounced, i.e., the loops were wider, for pure Mg, and it decreased rapidly with the Gd concentration. The effect was larger for the finer grains in all materials, and in compression for the pure Mg and the 0.4Gd alloy. No difference between tension and compression was observed for the 1.5Gd alloy, whereas the loops were wider in tension than in compression for the 4.2Gd alloy. In comparison with existing studies in Mg-Al and Mg-Zn alloys, for a given solute concentration, Gd was more effective in reducing the magnitude of the effect than either Zn or Al, in that order. The overall behavior is discussed in terms of the hardening effects of short range order of the alloys on {101¯2} and {101¯1} twinning.

Multiferroic behavior of heterostructures composed of lanthanum and bismuth ferrite

Heterostructured thin films of lanthanum ferrite (LFO) and bismuth ferrite (BFO) with different thicknesses were successfully obtained by a soft chemical method. The films were deposited by spin-coating and annealed at 500°C for 2h. The XRD pattern confirmed the purity of the thin films, where no additional peaks associated with impurity phases were present. The morphology analysis showed spherical grains with a random size distribution. The grain sizes increased with the number of BFO layers. The average grain size varied from 43nm to 68nm. The best dielectric results were obtained for the film with 6 LFO sublayers and 4 BFO top layers, in which the dielectric constant showed low dispersion. Since the capacitance-voltage curve for the film 6-LFO/4-BFO is symmetrical around null voltage, it can be inferred that this heterostructure has few mobile ions and accumulated charges on the film-substrate interface. In this film, polarization remains almost constant during 1012 cycles before the onset of degradation, which shows the very high resistance of the films to fatigue. Magnetoelectric coefficient measurements of the films revealed the formation of hysteresis loops, and a maximum value of 12V/cmOe was obtained for the magnetoelectric coefficient in the longitudinal direction; this value is much higher than that previously reported for pure BFO thin films.

Influence of Annealing Process on the Structure and Magnetic Behavior of Ba0.5Co0.5Fe2O4 Nanoparticles

The structure and magnetic properties of Ba0.5Co0.5Fe2O4 nanoparticles were investigated for as-synthesized and for samples annealed at temperatures of 300°C, 400°C, 500°C and 600°C. The phase structure was studied by means of X-ray powder diffraction (XRD). The XRD results reveal that the annealing effect up to 500°C decreases the sample microstrain and increases the crystallinity. Fe distribution and hyperfine parameters at tetrahedral (A) and octahedral (B) sites for the samples were studied using room temperature Mössbauer spectroscopy. The hyperfine fields increased with annealing temperature (TA). The values of the isomer shifts show only existence of Fe3+ cations on both A and B sites. We report magnetization measurements in the form of hysteresis loops in temperature range 4-300K and magnetic fields up to 5 Tesla. The results show effects of spin freezing. The values of the remanence (Mr) at 4K decreases as TA increases, whilst at 300K, Mr increases with increase in TA. The measurement of Mr at low temperature reveals evidence of cubic anisotropy.

On Traffic Relaxation, Anticipation, and Hysteresis

Traffic oscillations, an unpleasant form of traffic congestion, have attracted the attention of researchers for years. When viewed in the so-called flow–density or speed–density phase plane, oscillatory traffic states often present themselves in the form of hysteresis loops. In this paper, the impacts of driver relaxation and anticipation on traffic flow are examined, and their link to traffic hysteresis is sought. Through an analysis of the trajectory data from NGSIM and a theoretical analysis of car-following models, it is revealed that traffic hysteresis is generated by an imbalance in driver relaxation and anticipation. Changing the strength of relaxation and anticipation can reproduce positive, negative, and double hysteresis loops, as well as aggressive and timid driving behavior. It is further shown that the relative positions of acceleration and deceleration phases with respect to the equilibrium state are not unique and are determined by the comparative strength of relaxation and anticipation in different traffic conditions. This study suggests that traffic hysteresis can be suppressed by balancing driver relaxation and anticipation, and stop-and-go traffic can be smoothed by eliminating aggressive driving in congested traffic.

Continuum models in dynamics of granular media. Review

Mechanical models and equations of state used for solving dynamic problems in mechanics of granular media are reviewed. We study elastic, hypoelastic, hyperelastic, elastoplastic, and hydrodynamic models. Within the framework of hyperelasticity several generalized models, including the modified Arruda-Boyce model and some other hyperelastic models, are examined to investigate the formation of hysteresis loops during cyclic loading. We find that due to the switching mechanism the hysteresis loops can also be studied using the concept of hyperelasticity. The elastic-plastic models with one or several plastic flow surfaces, as well as the models with continuously distributed flow surfaces (microplasticity), are analyzed. Some newly developed models without plastic flow surfaces are considered (hypoplasticity, barodesy). Special attention is given to the elastic-plastic models with isotropic hardening and the models used to analyze the formation of hysteresis loops. The elastic-plastic models for studying non-degenerate hysteresis loops under cyclic loading conditions are examined as well. The comparative analysis of elastic, hyperelastic, hypoelastic and various elastic-plastic models reveals that under quasistatic cyclic loading conditions the cam-clay and other critical state models that take into account both the hardening and softening phenomena in real granular materials appear to be the most suitable ones for modeling hysteresis loops in cohesionless granular materials. However, the study of non-stationary dynamical processes requires finding appropriate models. For such problems, the combination of hyperelastic and hypoelastic models provides a simple adequate tool for taking into account the nucleation effects associated with the formation of local discontinuities. This is mainly due to the capabilities of hyper- and hypoelastic models to account for variations in elastic parameters and, consequently, in elastic wave velocities under wave propagation. In the future we plan to combine hyper- or hypo-elastic models with cam-clay or other critical state models.

Structural investigation of cobalt-doped silica derived from sol–gel synthesis

This work investigates the structural properties of cobalt doped silica samples prepared by sol–gel synthesis. Air calcination led to the formation of Co3O4 particles as evidenced by XRD and FTIR tests, although these features were no longer apparent for hydrogen-reduced samples. This behavior suggests the formation of metallic Co and CoO in the reduced samples. The variation of the cobalt content embedded in the silica matrix resulted in a change in texture of the prepared materials from microporous to mesoporous. This was attributed to the agglomeration of particles as observed in TEM micrographs, which led to larger particles and pores. The latter was associated with the formation of hysteresis loop in the nitrogen adsorption isotherms as a function of the [Co/(Si+Co)] molar ratio. This effect was more remarkable for reduced samples, leading to a further broadening of the hysteresis loop that stemmed from the reduction or loss of oxygen from cobalt oxide particles.

Ferromagnetism, hysteresis and enhanced heat dissipation in assemblies of superparamagnetic nanoparticles

In this paper, we develop theoretical frameworks to explain the emergence of ferromagnetism in suspensions and agglomerates of superparamagnetic (SPM) nanoparticles. In the limit of strong anisotropy, the super moments can be treated as a collection of two-state Ising spins. When adequate in number, they interact via dipole-dipole coupling to produce a dipolar field and subsequently a permanent dipole moment. As a result, this effectual ferromagnet exhibits hysteresis on the application of an oscillating magnetic field yielding heat dissipation that is several orders of magnitude larger than in a paramagnet. Using our frameworks, we provide a design for a magnetite-blood suspension that yields heat dissipation in the mW range. Its important physical application is in remedial procedures for destroying tumor and cancer cells. We are also able to explain many experiments reporting manifestations of ferromagnetism in the form of hysteresis loops, return point memory and large heat dissipation in suspensions and aggregates of SPM nanoparticles. Our frameworks can be used to manipulate heat dissipation in variety of combinations of particles and their embedding mediums. They impart a basis to the often used ad-hoc methodologies in this subject.

Anelastic Phenomena in Mg-Al Alloys

Cyclic loading-unloading in tension and compression has been used to quantify the anelastic behaviour, in the form of hysteresis loops, of pure Mg and three Mg-Al alloys (0.5, 2, and 9 at.% Al). The effect reached a maximum at a plastic strain of approximate to 0.02 for all of the materials, and decreased at higher strains. The amount of anelasticity at any given strain was smaller for the dilute alloys in comparison with the pure Mg whereas it increased above that of pure Mg for the most concentrated alloy. Possible reasons for this behaviour are discussed in terms of reversible twinning, solid solution softening, and hardening and short range order.

Change in the magnetic properties of polycrystalline thin-film magnetite upon introduction of an iron sublayer

The field dependences of the magnetic moment of polycrystalline magnetite films formed by pulsed laser deposition on a silicon substrate with the addition of an iron sublayer have been investigated. The influence of the sequence of layers Fe/Fe3O4 and Fe3O4/Fe on the magnetic characteristics of these structures has been analyzed. It has turned out that an increase in the saturation magnetization and the formation of a rectangular hysteresis loop with the coercive force acceptable for applications of thin-film magnetite as a hard magnetic electrode of the magnetic tunnel junction are observed only for the sequence of layers Fe/Fe3O4. The effect of the vacuum annealing temperature on the magnetic properties of polycrystalline samples of the Fe/Fe3O4 structure has been studied. It has been found that the best result is achieved at an annealing temperature of 500°C. The phenomenological model describing the magnetic properties of the polycrystalline two-layer magnetic structure Fe/Fe3O4 has been formulated. The results of numerical calculations have demonstrated that the introduction of only two phenomenological anisotropic interactions into the expression for the energy of the film provides a qualitative description of the observed experimental data in the form of hysteresis loops.