Action Of External Forces Research Articles

Macro-Rheology Characterization of Gill Raker Mucus in the Silver Carp, Hypophthalmichthys molitrix.

The silver carp, Hypophthalmichthys molitrix, is an invasive planktivorous filter feeder fish that infested the natural waterways of the upper Mississippi River basin due to its highly efficient filter feeding mechanism. The characteristic organs called gill rakers (GRs), found in many such filter feeders, facilitate the efficient filtration of food particles such as phytoplankton that are of a few microns in size. The motivation to investigate the rheology of the GR mucus stems from our desire to understand its role in aiding the filter feeding process in the silver carp. The mucus-rich fluid, in a 'thick and sticky' state may facilitate the adhesion of food particulates. The permeation and transport through the GR membrane arefacilitated by the action of external shear forces that induce varying shear strain rates. Therefore, mucus rheology can provide a vital clue to the tremendous outcompeting nature of the silver carp within the pool of filter feeding fish. Based on this it was posited that GR mucus may provide an adhesive function to food particles and act as a transport vehicle to assist in the filter feeding process. The main objective of the protocol is to determine the yield stress of the mucus, attributed to the minimum shear stress required to initiate flow at which irreversible plastic deformation is first observed across a structured viscoelastic material. Accordingly, rheological properties of the GR mucus, i.e., viscosity, storage, and loss moduli, were investigated for its non-Newtonian, shear-thinning nature using a rotational rheometer. A protocol presented here is employed to analyze the rheological properties of mucus extracted from the gill rakers of a silver carp, fished at Hart Creek location of the Missouri River. The protocol aims to develop an effective strategy for rheological testing and material characterization of mucus assumed to be a structured viscoelastic material.

Instantaneous radiation from time-varying electric and magnetic dipoles

Radiation from magnetic and electric dipole moments is a key subject in theory of electrodynamics. Although people treat the problem thoroughly in the context of frequency domain, the problem is still not well understood in the context of time domain, especially if dipole moments arbitrarily vary in time under action of external forces. Here, we scrutinize the instantaneous power radiated by magnetic and electric dipole moments, and report findings that are different from the conventional understanding of their instantaneous radiation found in textbooks. In contrast to the traditional far-field approach based on the Poynting vector, our analysis employs a near-field method based on the induced electromotive force, leading to corrective terms that are found to be consistent with time-domain numerical simulations, unlike previously reported expressions. Beyond its theoretical value, this work may also have significant impact in the field of time-varying metamaterials, especially in the study of radiation from subwavelength meta-atoms, scatterers and emitters that are temporally modulated.

Nanoengineering of transparent polypropylene containing sorbitol-based clarifier

In this work, 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol (TBPMN) was conscripted as the clarifying agent, the influence of the injection pressure on optical properties of PP were investigated, and results documented that increasing the injection pressure could not improve the transparency of the transparent PP. Thereafter, the crystallization behavior and morphological changes of transparent PP in condensed structure under different injection pressures were studied by the differential scanning calorimetry (DSC), the scanning electron microscopy (SEM) and the dynamic thermomechanical analysis (DMA), respectively, and results presented that change in injection pressure influence crystallization properties significantly. Besed on analyzing of the relationship between structure and optical properties, the effect of pressure on the optical properties was explained as follows: low injection pressure would be facilitated to the transparency of transparent PP, because under low injection pressure, the clarifier fiber could be dispersed uniformly and the network structure was formed and preserved well, and molecular chains of transparent PP was crystallized to the nanometer-level fiber on the surface of nucleation sites, which greatly reduces the scattering of light. However, increasing the injection pressure would promote the fiber itself accumulation into a scatterer point, which not only reduces the effect of the clarifier, but also causes the preferential arrangement of the PP molecules to produce an oriented structure due to strong external force and shearing action, thereby increasing light scattering.

Study on the Deformation behaviour of Non–Hardenable Ferritic Stainless Steel (grade X6Cr17) by Hot Torsion Tests

The knowledge about the characteristics of deformability (deformation resistance and plasticity) has for the technologist, as well as for the designer and researcher, a great practical significance, because they are important elements in establishing a correct technological process. The change of deformation conditions existing in the industrial process, such as the temperature and rate of deformation, are difficult to consider for correcting the deformability determined by testing. The chemical composition of the material influences the plasticity and its deformation resistance both by the nature and distribution of the alloying elements and by the phase transformations they produce. In this paper, through "deformability", we cover all properties characterizing the deformation behaviour of alloys. In this sense, "deformation resistance" is expressed through the unit strain required to produce a certain degree of plastic deformation, under the conditions of a particular diagram of tensions, deformations and deformation rates, in the absence of external friction forces. Plasticity, being the ability of metallic materials to deform plastic under the action of external forces, is influenced by a number of material characteristics (chemical composition, structure) and other factors characteristic of the deformation (temperature, degree and speed of deformation, applied mechanical scheme). Plasticity is characterized, in the torsion test, by the number of rotations made by the specimen until breakage. A number of methods have already been used for the study of deformability. This study includes the results of hot torsion tests conducted to find the plasticity and deformability characteristics of ferritic stainless steel (non–hardenable stainless steel, grade X6Cr17), which is a flexible grade of the stainless steel family with properties closely matching those of the more popular and expensive austenitic grade.

PVA-co-PE nanofibers synergistically reinforced composite film with high transparency and flexibility

With the rapid development of electronic information technology, flexible transparent materials have been widely concerned and studied by researchers. Traditional transparent films have some problems in flexibility, transparency, or preparation method, which restrict their further development in scale production and application. Herein, we have developed a simple method by embedding the mass produced PVA-co-PE nanofibers into the PVP polymer matrix through photopolymerization method to produce a Polyvinyl Pyrrolidone/PVA-co-PE (PVP/NFs) composite film with high flexibility and transparency. Due to the nanoscale size and small refractive index contrast between nanofiber and PVP, the PVP/NFs composite film showed high light transmittance of 85.87%. In addition, the filling of PVA-co-PE nanofibers had a synergistic enhancement effect on the mechanical properties and thermal stability of PVP/NFs composite film. The tensile stress was as high as 16.6 MPa with a nanofiber content of 37.67 wt%, which was 4.05 times higher than that of the pure PVA-co-PE nanofiber film, and 2.81 times higher than that of the pure PVP film. Furthermore, the excellent flexibility of the PVP/NFs composite film enabled it to withstand a large-scale bending deformation under the action of external forces. The high flexibility, optical transparency and fast preparation made the PVP/NFs composite film a great application prospect in the intelligent electronic equipment and smart buildings.

Обґрунтування впливу робочих органів зернозбиральних комбайнів на пошкодження і якість насіння

Goal. To justify the possibility of improving seed quality due to the reduction of damage at all stages of the process of collecting, processing, preparation, and planting; to develop the equipment for implementing these processes in production. Methods. Theoretical studies and calculations were performed using mathematical modeling of the technical means and technological processes. They used basic laws of mechanics and modern methods of computer calculations. Experimental studies were carried out in laboratory and manufacturing conditions using full-scale specimens and equipment according to the developed and standard methods. Results. They studied the strength and destruction, that is, macro-trauma of grains, depending on the mechanical influence, strain and stress. The influence of external means was studied on the occurrence and the distribution of deformations and cracks, as well as how many of them at a certain load reaches the critical length. The origin and direction of cracks and their number in most cases depended on the direction of the action of external forces and internal biological characteristics of corn. The strength of the grain, in addition to cracks, also has a significant impact of micro-trauma of the embryo, endosperm and seed and flower shells. As independent parameters, which optimize the energy acceleration of the grain to minimize deformations and micro-trauma of seeds, they took angular and linear acceleration of deformation of the volume of the grain and angular acceleration at the point of impact of the grain with the spherical surface of the working body. Theoretical calculations were made, and the influence of drum and rotary threshing devices was substantiated on deformation and damage to the seed. Conclusions. Calculation and graphic dependencies confirm the conclusion of experimental-manufacture research: macro- and especially micro-trauma of seeds of winter wheat and rye at harvesting with rotary threshing apparatus is much less than at use of drum one, which significantly influences the quality of seed.

Quantitative analysis of bond and splice strength of steel cord conveyor belt

Steel cord conveyor belt has the advantages of high tensile strength, high friction resistance and strong impact resistance. It is widely used in coal, mining, port, electric power and other fields. The splice area is the weakest link in the whole steel cord conveyor belt, and the splice deformation often occurs. In order to prevent a serious belt breakage accident, we need know the quantitative relationship between splice deformation and splice strength clearly. In this paper, the finite element simulation analysis is carried out on the relationship between deformation and strength of steel cord conveyor belt splices. The change of the bond strength between steel cord and rubber under the action of external force is mainly studied. The emphasis is on the influence of length, number and diameter of steel cords. In these three different factors, the value of A is different. At the same time, we have also analyzed each situation accordingly. Finally, the quantitative relationship between the splice deformation and the overall strength of the splice was summarized. The research results can provide theoretical basis for safety inspection, splice performance analysis, maintenance and renewal of steel cord conveyor belt.

Temporal regularities of changing magnetic field generation modes in the model of the αΩ-dynamo

In the dynamic model aΩ-dynamo the change in the intensity of the a-generator under the action of external forces is considered as a result of synchroniza-tion of higher modes of the velocity field and the magnetic field and is regulated by the function Z(t) with an exponential-power kernel J(t). Depending on the choice of the exponent and the scale factor of the kernel determine its temporal characteristics: delay time and waiting time. The question of changing the modes of magnetic field generation depending on the temporal characteristics of the function’s kernel is investigating. In the dynamic model aΩ-dynamo the change of the a-generator intensity under the action of external forces is considered as a result of synchronization of higher modes of the velocity field and the magnetic field and is regulated by the function Z(t) with an exponential-power kernel J(t). Depending on the choice of the exponent and the scale factor of the kernel J(t) determine its temporal characteristics: delay time and waiting time. The question of changing the modes of magnetic field generation depending on the temporal characteristics of the function’s kernel is investigating.

Экспериментальное исследование поверхностного натяжения ферроколлоида в магнитном поле

Direct measurements of surface tension, viscosity and surface elasticity under the action of external forces are often impossible. In many tasks, the magnetic fluid surface tension is considered to be independent of the magnitude of the applied magnetic field and is determined by the properties of the base fluid. The anisotropy of the magnetic properties at the interface due to the jump in the fluid’s magnetization suggests the dependence of the surface tension tensor on the magnetic field. In this paper, we propose a new experimental method for studying the surface tension of a magnetic fluid in an external uniform magnetic field, depending on the orientation of the magnetic field intensity towards the liquid-gas interface. The study was carried out with the help of modified capillary wave method in a magnetic field orthogonal to the liquid surface and with the ring detachment method in the case of a longitudinal field. It was shown experimentally that the surface tension of a ferrocolloid fluid base (kerosene) does not depend either on the frequency of capillary waves excitation or on intensity of an applied external magnetic field, and corresponds to the value determined with the help of a commercial tensiometer by the standard method of ring detachment. The surface tension of the ferrofluid decreases with increasing intensity of the orthogonal magnetic field interface and with increasing frequency of acoustic vibrations. However, an increase in the field strength longitudinally directed to the interface, provokes an increase in the surface tension of the magnetic fluid. The experimental results are in qualitative agreement with theoretical predictions by A. V. Zhukov: the eigenvalues of the surface tension tensor monotonically increase with the tangential magnetic field component and monotonically decrease with an increase in its normal component.

Effect of Guar Gum on Texture and Rheology Property of Potato-Wheat Dough

In this paper,the influence of guar gum 0(control group),[(0.3%,0.6%,0.9%,1.2% and 1.5%)]on the textural and rheological properties of the mixed dough with 35% potato content were investigated. The results showed that the modified dough was a pseudoplastic fluid with shear thinning characteristics. The addition of guar gum could reduce the hardness of dough,improve the tensile properties,increase the modulus of elasticity and viscosity,reduce the tangent value of loss angle,strain value and creep compliance,increase the content of high polymer in dough and the degree of polymerization. Among them,the mixed dough with 0.9% guar gum had a moderate hardness and the largest tensile distance. The elastic modulus and viscosity modulus were close to the control group with good viscoelasticity. The strain value,creep change rate and creep compliance were the least,indicating that the dough has high internal strength and strong resistance to deformation under the action of external forces. The creep recovery rate and resilience flexibility of dough were the highest,and the dough had strong recovery ability after removing external forces. Therefore,the mixed dough with 0.9% guar gum was suitable for potato staple products.

Rheometric flows of concentrated suspensions of solid particles

Publications on experimental and theoretical studies of the rheological properties of concentrated suspensions of solid particles have been analyzed. According to the currently accepted ideas, the rheology of suspensions is considered as a result of contact interaction of their constituent particles caused by the action of external forces, the formation and destruction of various types of conglomerate structures. A new rheological model of a highly concentrated suspension of solid particles in a Newtonian fluid is proposed, which describes both a continuous and discontinuous increase in the effective viscosity with a uniform increase in shear stresses. Accurate analytical formulas are obtained for the velocity profiles of suspensions in rotational viscometers “cone-plane” and “cylinder-cylinder”, as well as in a slit viscometer. The proposed model is modified to take into account the non-Newtonian properties of a dispersion medium, which exhibits pseudoplastic properties at low strain rates, and dilatant properties at large strain rates. The effective viscosity of such a suspension is presented as the sum of the contributions from the dispersion medium and the solid particles of the dispersed phase. To describe the rheology of the dispersion phase, the Ellis model was used. The velocity profiles in a pressure driven flat channel are obtained numerically by the finite element method. It is shown that, depending on the parameters of the model, the velocity profiles in a flat channel can take various complex forms.

Експериментальні дослідження деформаційних характеристик охоронних споруд гірничих виробок

The purpose of the article. Studying deformation characteristics of protective structures under the influence of external loads used to maintain lateral rocks in the coal massif behind the production face. Methods. To achieve this goal, laboratory studies of the deformation characteristics of security structures under uniaxial compression were performed. Results. As a result of the research it has been established that at uniaxial compression of wooden protective constructions in the form of rolling fires from sleepers or bushes from risers, change of their rigidity is caused both by differences in properties of wood at action of external force along or across fibres, and design features. In cases where a constant compressive force is applied to the experimental sample across the fibres (rolling fires from sleepers), the change in stiffness is quadratic and reaches minimum values when the deformation of the model by 30-35%, and with a further increase in deformation to 50% stiffness increases. This indicates an increase in the resistance of rolling fires to external loads after their compression, without losing the strength of the structure. Under the action of compressive force along the fibres (bushes of risers), the stiffness of the experimental samples increases until the moment of destruction, when there is a loss of strength of the structure. The change in the stiffness of embedded arrays of crushed rock, if possible, their lateral expansion occurs due to the compaction of embedded material, i.e. recomposition of particles of crushed rock of different fractions in the total volume. Novelty. The nature of the deformation of security structures considered as prefabricated structures can be described by the change in the specific potential deformation energy spent on changing the shape and/or volume of the protective structures. Practical meaning. To ensure the stability of the side rocks in the coal massif containing the workings, it is necessary to focus on the use of flexible protection structures located above the retractable roadway.

Road holding ability I.P. of machine-tractor unit during plowing

The discrepancy between the working width of the plow and the width of the tractor leads to asymmetry of the arable units. The geometry of the share surface of the reversible plow contributes to the generation of lateral forces on the working tool. All this contributes to the imbalance of the working body and the deviation of the tractor from straight-line movement during plowing. To maintain a straight line, the driver has to correct the vehicle movement every 5-10 meters, which makes him more tired. To study the causes of lateral slip of the plowing unit, a mathematical model was built. It consists of the equations of controlled motion and equations of uncontrolled shift of the tractor under the action of external forces from the plow. The description of the force interaction of the propeller with the ground is based on the mathematical theory of friction, taking into account anisotropy and elastic properties in contact. On the basis of the passive shear model, the hodograph of the maximum force shifting the tractor from the side of the working tool is constructed. It has been established that the shear force reaches its maximum adhesion value only in the case of translational shear, when its line of action passes through the center of gravity of the tractor. In all other cases, the shift (pull) of the tractor is carried out by a force of a lower value. The features and assumptions of the model are formulated in relation to the tracked and wheeled tractors. As a result, it was found that regardless of the direction of the lateral displacement of the plow draft resistance, the tractor is pulled towards the plowed field. The result of the numerical experiment showed that the main reason for the drift of the wheeled arable unit is the different type of soil along the sides of the tractor, but not the displacement of the plow traction resistance.

Experimental Study on Deformation and Acoustic Emission Characteristics of Arch Roadway under Different Unloading Rates

The essence of roadway excavation is a process of unloading at the periphery, and the influence of unloading paths on surrounding rock damage is directly related to the selection of support design and construction technology. The real stress state of surrounding rock is often affected by different excavation conditions in the actual construction process. Therefore, a testing system of excavation and unloading model was developed to simulate the unloading process of the arch roadway under different excavation conditions. Small hollow cylindrical specimens used in this experiment were made of cement mortar. The load at the inner cavity of specimens was removed under the constant action of external pressure and axial force to simulate the real excavation unloading process. The deformation, the failure modes, and the acoustic emission evolution characteristics at the inner of specimens were obtained under unloading conditions using the strain and acoustic emission monitoring systems. The experimental results indicate that deformation laws of surrounding rock were similar under different unloading rates and initial geostresses, but failure modes and acoustic emission characteristics were quite different. Compared with that of slow unloading, the damage of surrounding rock under rapid unloading mainly accumulated after unloading, and it is easier to induce rockburst after unloading. As initial geostress increased, the occurring time of the main fracture may be delayed relatively, and the phenomenon that the distribution range of peak frequency expanded and the amplitude rose gradually can be regarded as the precursor information of the main fracture occurring. This study can be used to provide experimental support for the failure and supporting design of surrounding rock in deep underground engineering.

Motion of a Smooth Foil in a Fluid under the Action of External Periodic Forces. II

Motion of a Smooth Foil in a Fluid under the Action of External Periodic Forces. II

Piezochromic luminescence in all-inorganic core-shell InP/ZnS nanocrystals via pressure-modulated strain engineering.

Piezochromic materials alter their photoluminescent (PL) colors in response to the action of external force. Such materials have attracted much attention owing to their promising applications in pressure-sensing, optoelectronic memory and anticounterfeiting. However, almost all the reported piezochromic materials were limited to the organic matters or compounds containing organic components. Here we present piezochromic materials and pressure-induced optical response based on all-inorganic core/shell InP/ZnS nanocrystals (NCs). The InP/ZnS NCs exhibit noticeable PL color changes, shifting from orange (2.08 eV) to green (2.25 eV), with the PL intensity showing slight enhancement below an applied pressure of 2.5 GPa. Further compressing to fluorescence quenching produces an ultrabroad energy tenability range up to 400 meV. Structural and time-resolved PL lifetime studies, together with first-principle calculations, reveal the weakening of strain-induced defect states in the low pressure regime, which contributes to effective excition recombination, thus ensuring high fluorescence emission of InP/ZnS NCs. This work provides a promising strategy to prepare piezochromic materials of all-inorganic semiconductors, thereby greatly increasing the choice of materials for new applications.

Experimental Study on Manufactured Sand-Soil Bearing Capacity W-T-BC Model Based on Mechanical Response of Rotary Penetration

Studies are lacking in establishing the quantitative relationship between the mechanical response and the rock and soil mechanical parameters by digital rotary penetration. In this study, based on the custom-built rock and soil strength parameter test device and the three-dimensional flexible boundary loading device, we conducted an experimental study of the manufactured sand-soil model with moisture contents of 5%, 10%, and 15% under different confining pressures (0, 0.12, 0.18, 0.24, and 0.42 MPa). Analysis was conducted on the influencing factors and laws of water content on the experimental results, and a quantitative relationship model (W-T-BC model) between the drilling torque and the bearing capacity of manufactured sand-soil under the condition of different water contents was established. Through failure detection verification on the manufactured sand-soil-filled subgrade of the Taihang Mountains Expressway in Beijing, the average conformity between the calculated value of the bearing capacity of the W-T-BC model and the standard experimental bearing capacity was 93.23%, which proved the validity and accuracy of the model. Finally, the rigid-soft interface grid body of sand-soil particles was analyzed. The reason why the manufactured sand-soil exhibited better stability than homogeneous soil under the action of external force in microcosmic aspect was expounded. The establishment of the W-T-BC model provided a scientific basis and important reference for further study of the relationship between mechanical response and force parameters under different conditions of different materials.

Improvement of fretting wear resistance of blade root made of polymer composite material

Polymer composite materials (PCM) are being increasingly used in aircraft engine industry. Development of PCM fan blade manufacturing technology that meets all the necessary strength requirements is an important task in creating Russian-made latest-generation engines. One of the problems to be faced is the wear of the blade root caused by cyclic micro-displacements in the interlock under the action of external forces. There are several engineering solutions to control surface wear of blade roots made of PCM that can basically be divided into three groups: manufacture of metal roots and the use of known methods of metal fretting prevention, use of replaceable special inserts placed between the contact surfaces of the root and the disk slot, application of elastic and damping elements. In this paper, we consider another method of controlling wear, the principal feature of which is stitching the blade pre-form with aramid thread that forms a layer with higher wear resistance on the root surface. In order to verify the efficiency of the proposed approach, model blades were made and tests were carried out on an electrodynamic shaker.

Обоснование условий устойчивости откаточных штреков в глубоких шахтах

Purpose. The purpose of the study is to justify the conditions of stability and features of manifestations of rock pressure on the circuit of local preparatory workings with different methods of protection in deep mines.Research Methods. An integrated approach is used, including analysis and generalization of theoretical and experimental studies on the problem of the stability of excavation preparatory workings, with different methods of protection, in mines developing steeply and steeply bedded layers at great depths.Results. As a result of the experimental and analytical studies, it was found that when guarding haulage drifts by compliant security structures (rolling fires from wooden sleepers), the load on the lining of the preparatory mine over time, as the lava moves, tends to a finite value in hyperbolic dependence. In this case, there is a change in its growth, and the displacements of the lateral rocks on the contour of the recoil drift take the greatest values in the initial period of time after coal extraction. However, when protecting the production by fragile security structures, the pillars of coal, a change in the load growth on the lining per unit time occurs according to a linear law, which leads to a deterioration in the stability of the recoil drift behind the face, associated with the loss of the bearing capacity of the lining, designed to support the preparatory development.Scientific novelty. The stability conditions of the recoil drift are based on the representation of the lining installed in the excavation excavation, in the form of a geometrically unchanged system, individual elements of which experience bending deformations from the action of external forces that appear when unloading the coal-bearing massif as a result of mining operations.Practical significance. To improve the safety of miners in deep mines, it is necessary to use compliant structures or laying out worked out space to protect recoil drifts, based on increasing their stability, which ensures their operational state behind the face.

Motion of a Smooth Foil in a Fluid under the Action of External Periodic Forces. I

This paper considers the plane-parallel motion of an elliptic foil in a fluid with a nonzero constant circulation under the action of external periodic forces and torque. The existence of the first integral is shown for the case in which there is no external torque and an external force acts along one of the principal axes of the foil. It is shown that, in the general case, in the absence of friction, an extensive stochastic layer is observed for the period advance map. When dissipation is added to the system, strange attractors can arise from the stochastic layer.