Force Hysteresis Research Articles

Onset of sliding motion in sessile drops with initially non-circular contact lines

The onset of motion of a drop with an initially non-circular three phase contact line was studied experimentally and numerically. Two drops of volume 10 μl were made to coalesce and form a composite 20 μl drop. The contact line of this drop was approximately elliptical and the local contact angle along the contact line was not a constant (as would have been the case with a circular contact line). The orientation of the drop to the impending direction of motion was varied. Inclined plate experiments were performed and the moving and sliding angles were noted in each case. It was observed that the moving and sliding angles of the drop were strongly dependent on this orientation. Specifically, the local conditions on the contact line at the front and back edges of the drop as well as the drop profile width were found to be the determining parameters. Surface evolver simulations were performed to understand the results of the experiments. It was found that the evolution of the contact line for non-circular drops was rather counter-intuitive when compared to the results from a drop with a circular contact line and resulted from a competition between gravity and the local contact angle hysteresis forces.

Non-textured laser modification of silica glass surface: Wettability control and flow channel formation

Local wettability of silica glass surface is modified by infrared laser irradiation. The silica glass surface exhibits hydrophobic property in the presence of CF3 or (CH3)2 terminal functional groups, which are decomposed by thermal treatment, and degree of the decomposition depends on the applied heat. Laser irradiation can control the number of remaining functional groups according to the irradiation conditions; the contact angle of deionized water on the laser modified surfaces range from 100° to 40°. XPS analysis confirms that the variation in wettability corresponds to the number of remaining CF3 groups. The laser irradiation achieves surface modification without causing any cracks or damages to the surface, as observed by SEM and AFM; moreover, surface transparency to visible light and surface roughness remains unaffected. The proposed method is applied to plane flow channel systems. Dropped water spreads only on the hydrophilic and invisible line modified by the laser irradiation without formation of any grooves. This indicates that the modified line can act as a surface channel. Furthermore, self-transportation of liquid is also demonstrated on a channel with gradually-varied wettability along its length. A water droplet on a hydrophobic side is self-transported to a hydrophilic side due to contact-angle hysteresis force without any actuators or external forces.

Asymmetric and Speed-Dependent Capillary Force Hysteresis and Relaxation of a Suddenly Stopped Moving Contact Line.

We report on direct atomic-force-microscope measurements of capillary force hysteresis (CFH) and relaxation of a circular moving contact line (CL) formed on a long micron-sized hydrophobic fiber intersecting a water-air interface. The measured CFH and CL relaxation show a strong asymmetric speed dependence in the advancing and receding directions. A unified model based on force-assisted barrier crossing is utilized to find the underlying energy barrier Eb and size λ associated with the defects on the fiber surface. The experiment demonstrates that the pinning (relaxation) and depinning dynamics of the CL can be described by a common microscopic framework, and the advancing and receding CLs are influenced by two different sets of relatively wetting and nonwetting defects on the fiber surface.

Current Sensor Based on Nanocrystalline NiFe/Cu/NiFe Thin Film

The nanocrystalline NiFe/Cu/NiFe thin films were fabricated via a facile sputtering method in order to improve the current sensor performance. Further, the resulting thin films were characterized by means of X-ray diffraction, Field emission scanning electron microscopy, Atomic force microscopy and Hysteresis techniques for their structure, morphology and magnetic properties. In the present work NiFe/Cu/NiFe thin film based current sensor device length is varied and the influence of device length on current sensor performance and sensitivity were investigated. The length of device is varied from 2 to 8mm and current sensor performance increases because of mean free path length goes on decreasing and electron may be reach the boundary of material and scattered. The highest sensitivity for the device is found to be 0.76 ΩOe1.

Magnetic nanocomposites based on mesoporous silica for biomedical applications

In the present work we report the synthesis procedure of magnetic mesoporous SBA-15 silica materials with controlled morphology as potential composites for biomedical applications, mainly as scaffolds for bone tissue engineering. Different procedures and synthetic parameters are varied to control the physico-chemical, textural and magnetic properties of these materials. Our results show that magnetic mesoporous silica presents two-dimensional hexagonal symmetry with the presence of mesoporous cylindrical geometries, open at both ends, with magnetite nanoparticles in the channels as shown by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) micrographs. Determined by the Brunauer-Emmett-Teller (BET) method, these materials show a surface area above 150 m2/g, which assures a loading capacity higher than conventional ceramics. The presence of crystalline magnetite is corroborated by X-ray diffraction (XRD). The magnetisation cycles show no hysteresis or coercive forces, evidencing their superparamagnetic (SPM) behaviour, which is highly desirable for biomedical applications to avoid magnetic agglomeration of particles.

Forces generated during stretch in the heart of the lobster Homarus americanus are anisotropic and are altered by neuromodulators.

Mechanical and neurophysiological anisotropies mediate three-dimensional responses of the heart of ITALIC! Homarus americanus Although hearts ITALIC! in vivoare loaded multi-axially by pressure, studies of invertebrate cardiac function typically use uniaxial tests. To generate whole-heart length-tension curves, stretch pyramids at constant lengthening and shortening rates were imposed uniaxially and biaxially along longitudinal and transverse axes of the beating whole heart. To determine whether neuropeptides that are known to modulate cardiac activity in ITALIC! H. americanusaffect the active or passive components of these length-tension curves, we also performed these tests in the presence of SGRNFLRFamide (SGRN) and GYSNRNYLRFamide (GYS). In uniaxial and biaxial tests, both passive and active forces increased with stretch along both measurement axes. The increase in passive forces was anisotropic, with greater increases along the longitudinal axis. Passive forces showed hysteresis and active forces were higher during lengthening than shortening phases of the stretch pyramid. Active forces at a given length were increased by both neuropeptides. To exert these effects, neuropeptides might have acted indirectly on the muscle via their effects on the cardiac ganglion, directly on the neuromuscular junction, or directly on the muscles. Because increases in response to stretch were also seen in stimulated motor nerve-muscle preparations, at least some of the effects of the peptides are likely peripheral. Taken together, these findings suggest that flexibility in rhythmic cardiac contractions results from the amplified effects of neuropeptides interacting with the length-tension characteristics of the heart.

Analysis of the Pavement Surface Texture by 3D Scanner

Interaction between vehicle and the pavement surface has the primary effect to the road safety. This phenomenon including adhesive and hysteresis forces influences the contact stresses which are responsible for appropriate interaction between tyre and pavement. Skid resistance of the pavement surface is evaluated by measurements of texture characteristics (depth of texture, morphology) and physical (sliding friction). World Road Association indicates that the friction coefficient decreased on the road below 0.45 will increase the risk of accident 20 times; when it goes below 0.30 the risk is 300 times higher.The macro-texture measuring is realised at present by non-contact profilometers evaluated texture of surface as a mean profile depth – MPD; and by volumetric method evaluated texture by mean texture depth – MTD. The micro-texture measuring can be realised by direct methods by using of microscope or another equipment with high resolution. However, these methods are used very rarely, indirect methods by pendulum tester is used more frequently. University of Žilina (UNIZA) uses for skid resistance measuring the own equipment TWO that measures the coefficient of longitudinal friction with 17.8% slide.Slovak Road Administration operated 23 long-time observed road sections for analysis of the pavement serviceability parameters. Friction coefficient is measured by Skiddometer BV11, texture with using one separately laser installed on measurement beam of Profilograph GE. Measuring of texture is along with analysis of surface unevenness. Evaluation of measured data suggests problems with reliability and repeatability of measurements, measuring of texture depth above all.Concerning these problems new possibilities of texture analysis are tested in UNIZA. Friction coefficient is measured by Traction Watcher One equipment. 3D scanners are tested for texture evaluation, mainly the ZScanner®800. ZScanner is high resolution equipment and measuring of surface texture enables evaluation of the amplitude and wave length of the surface irregularities. All the measured data are processed by algorithm created in MATLAB and compared with results obtained by standardized measuring methods. 3D scanner has a very important characteristic compared with 2D scanners that provides the analysis and following evaluation of more parameters (not MPD only). On the other hand the time-consuming of measuring process is a big disadvantage. Request for big data processing is a second problem of 3D scanners, but actual level of hardware and software possibilities can eliminates it.

Effects of silane coupling agents on tribological properties of bentonite/nitrile butadiene rubber composites

In this work, effects of silane coupling agents on the tribological properties of bentonite/nitrile butadiene rubber (NBR) composites were investigated. The composites were fabricated with a facile method. Three silane coupling agents, (3‐mercaptopropyl)trimethoxysilane (MPTMS), bis[3‐(triethoxysilyl)propyl]tetrasulfide (TESPT) and [3‐(2‐aminoethylamino)propyl]triethoxysilane (AEAPTMS) were employed in our research. The short sulfur bonds formed between MPTMS and macromolecules in the matrices limited the extension of the contact interface between rubber matrices and glass plate, which contributed to the reduction in friction coefficient. With TESPT and AEAPTMS, the adhesion force of the composites was remarkably reinforced, further leading to the increase in friction coefficient. In the wear test, bentonite/silane/NBR composites showed better wear resistance compared to the specimens fabricated without silanes. By investigation on the morphological features of the worn surfaces, different wear mechanisms for composites with/without silane coupling agents were illustrated in detail. Generally, the effects of silanes to adhesion force, hysteresis loss ratio, and hardness all contributed to the friction coefficients of the composites. In wear test, the effects of the silanes on hysteresis force were prominent. Incorporated with MPTMS, the composite showed poor wear resistance due to its high hysteresis loss ratio. POLYM. COMPOS., 38:2347–2357, 2017. © 2015 Society of Plastics Engineers

Fingertip Three-Axis Tactile Sensor for Multifingered Grasping

A fingertip three-axis tactile sensor system with the capability of measuring both normal and shear force distribution using quantum tunneling composites is presented. The practical design and fabrication of a tactile sensor for the robot fingertip are described in detail. Also, an integrated fingertip-shaped tactile sensor with 13 tactile cells is developed. The tactile sensor is mounted on a multifingered robotic hand fingertip, and its effectiveness is validated with experimental results. The fabricated fingertip tactile sensor shows that the full-scale range of detectable force are about 10, 10, and 20N for the x -, y -, and z -directions, respectively. Each detector response was proportional to the magnitude of the applied stress. The fingertip tactile sensor showed a high repeatability, low hysteresis, and minimal three-axis force crosstalk. Experiments are conducted with dynamic grasping force control, based on fingertip three-axis sensor feedback. The grasping force of the finger is adjusted adaptively to the three-axis tactile feedback, such that the force on each fingertip is restricted inside the friction cone without any undesired slip or detaching from the object when grasping it.

Applying “the upgraded Berg model” to predict hysteresis free reactive sputtering

Reactive sputtering is a popular process to deposit oxides, nitrides, and several other compounds. Unfortunately, this process mostly exhibits a hysteresis effect. The hysteresis causes a delicate choice of either a high deposition rate but not a fully oxidized/nitrided film or a fully formed compound film but at a significantly lower deposition rate. For high reactivity target material/reactive gas systems, the hysteresis forces the process to flip quite abrupt between these two conditions. Process control may therefore be quite critical.In this work we will use the original “Berg model” as well as the newly published “upgraded Berg model” to illustrate how hysteresis is generated. We have selected one simple graph (reactive gas flow vs. partial pressure) that gives clear indications of how the process may be affected in such a way as to decrease or even eliminate the hysteresis. Specific values of target size and composition, gas mixture as well as total pressure and pumping speed are processing parameters that may be selected in a way to eliminate hysteresis. We will show that this behavior is predicted by the simulations and also refer to experimental evidence for such behavior.

The influence of saccharin on the electrodeposition and properties of Co–Ni alloy thin films

Co–Ni alloys thin films were electrodeposited on Ru substrates from a chloride-saccharin bath at pH 3.8 and the effects of adding saccharin to the bath on the electrochemical deposition, corrosion resistance, chemical composition, physical and magnetic properties of the deposits were investigated. The analytical techniques of cyclic voltammetry (CV), potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), atomic absorption spectroscopy (AAS), atomic force microscopy (AFM), X-ray diffraction and hysteresis curves were applied to assess the codeposition process, and determine corrosion resistance, composition, morphology, nanocrystallinity and magnetic properties. Effectively, CV measurements revealed that the addition of saccharin in the electrolytic bath modifies the deposition process and an anomalous codeposition takes place; this enhanced the Co percentage in the Co–Ni deposits. Saccharin addition also increases the double layer capacitance and decreases the charge transfer resistance. On the other hand, the Tafel plots show a higher corrosion resistance for the deposits obtained from a bath with saccharin than those obtained from a bath without it. Furthermore, the presence of the saccharin in the bath also causes notable changes in the morphology and structure characteristics of deposits. In addition, it was found that the additive influences the magnetic properties of Co–Ni alloy thin films. The coercivity and magnetisation saturation are diminished for Co–Ni films prepared from electrolytes with addition of saccharin.

Radial wettable gradient of hot surface to control droplets movement in directions.

A radial wettable gradient was fabricated on the surface of graphite plate by a simple one-step anodic oxidation process. It was found that the direction and value of the wettable gradient could be easily controlled by adjusting current and oxidation time gradient. With the increase of surface temperature, droplets on surface not only exhibited the transition of boiling mode, but also showed the controlled radial spreading, evaporation and movement behaviors. These phenomena could be attributed to the cooperation of wettability force, hysteresis force and vapor pressure (Leidenfrost effect). Especially, the controlled radial convergence or divergence of droplets with high velocity were realized on the surfaces with either inside or outside radial gradient, which would have crucial applications in the design of microfluidic devices and the exploration of the biotechnology.

Thermoelastic Behaviour, Hysteresis, and Dissipative Forces in Thermodynamics of Martensitic Transformations

Thermoelastic Behaviour, Hysteresis, and Dissipative Forces in Thermodynamics of Martensitic Transformations

A Modified Comprehensive Model for Piezoelectric Stack Actuators and Corresponding Parameter Identification Method

In order to accurately model the hysteresis and dynamic characteristics of piezoelectric stack actuators (PSAs), consider that a linear force and a hysteresis force will be generated by piezoelectric wafers under the voltage applied to a PSA, and the total force suffering from creep will result in the forced vibration of the two-degree-of-freedom mass-spring-damper system composed of the equivalent mass, stiffness, and damping of the piezoelectric wafers and the bonding layers. A modified comprehensive model for PSAs is put forward by using a linear function, an asymmetrical Bouc-Wen hysteresis operator, and a creep function to model the linear force, the hysteresis force, and the creep characteristics, respectively. In this way, the effect of the bonding layers on the hysteresis and dynamic characteristics of PSAs can be analyzed via the modified comprehensive model. The experimental results show that the modified comprehensive model for PSAs with the corresponding parameter identification method can accurately portray the hysteresis and dynamic characteristics of PSAs fabricated by different layering/stacking processes. Finally, the theoretical analyzing on utilizing the modified comprehensive model to linearize the hysteresis characteristics and design the dynamic characteristics of PSAs is given.

Performance Evaluation on Transmission Tower-Line System with Passive Friction Dampers Subjected to Wind Excitations

The vibration control and performance evaluation on a transmission-tower line system by using friction dampers subjected to wind excitations are carried out in this study. The three-dimensional finite element (FE) model of a transmission tower is firstly constructed. A two-dimensional lumped mass model of a transmission tower is developed for dynamic analysis. The analytical model of transmission tower-line system is proposed by taking the dynamic interaction between the tower and the transmission lines into consideration. The mechanical model of passive friction damper is presented by involving the effects of damper axial stiffness. The equation of motion of the transmission tower-line system incorporated with the friction dampers disturbed by wind excitations is established. A real transmission tower-line system is taken as an example to examine the feasibility and reliability of the proposed control approach. An extensive parameter study is carried out to find the optimal parameters of friction damper and to assess the effects of slipping force axial stiffness and hysteresis loop on control performance. The work on an example structure indicates that the application of friction dampers with optimal parameters could significantly reduce wind-induced responses of the transmission tower-line system.

Superwetting Surfaces under Different Media: Effects of Surface Topography on Wettability.

Superwetting surfaces in air, such as superhydrophobic and superoleophobic surfaces that are governed by surface chemical compositions and surface topographies, are one of the most extensively studied topics in this field. However, it is not well-understood how surface topographies affect the behaviors of immiscible liquids and gases under other kinds of media, although it is significant in diverse fields. The main aim of this work is to systematically investigate the wetting behaviors of liquids (water and oil) and gas (air) on silicon surfaces with different topographies (i.e., smooth, micro, nano, and micro-/nanostructures) under various media (i.e., air, water, and oil). The contact angles, as well as contact-angle hysteresis, sliding angles, and adhesive forces, were utilized to evaluate the wettability of these surfaces. As a result, the microstructured surfaces typically exhibit high contact-angle hysteresis, high sliding angles, and high adhesive forces, whereas the micro-/nanostructured surfaces display low contact-angle hysteresis, low sliding angles, and low adhesive forces, even if they have high (>150°) and similar contact angles. Furthermore, when transferring the same surface from one kind of medium to another, different superwetting states can be reversibly switched.

The effect of the thickness ratio of magnetic layers on the microstructure and magnetic properties of (CoCrPt)97.5Nb2.5/Co75Cr13Pt12/Cr thin films

A Co75Cr13Pt12 intermediate magnetic layer was deposited between the (CoCrPt)97.5Nb2.5 upper magnetic layer and chromium underlayer by the magnetron sputtering technique. The effect of the thickness ratio of two magnetic layers and post-annealing treatment on the microstructure and magnetic properties of the films were investigated. The magnetic characteristics of the films were obtained by magnetic force microscopy, hysteresis loops and switching field distribution curves. Although annealing had no significant effect on the layer roughness, it rotated the easy axis of the magnetic layer towards the film plane, thereby enhanced the coercivity. The results showed an impressive effect of the magnetic intermediate layer thickness and post-annealing on the improving of coercivity through isolation of the magnetic grains. Formation of a non-magnetic halo around the magnetic grains reduced the inter-granular magnetostatic interaction.

Stress-relaxation and fatigue behaviour of synthetic brow-suspension materials

Ptosis describes a low position of the upper eyelid. When this condition is due to poor function of the levator palpebrae superioris muscle, responsible for raising the lid, “brow-suspension” ptosis correction is usually performed, which involves internally attaching the malpositioned eyelid to the forehead musculature using brow-suspension materials. In service, such materials are exposed to both rapid tensile loading and unloading sequences during blinking, and a more sustained tensile strain during extended periods of closure. In this study, various mechanical tests were conducted to characterise and compare some of commonly-used synthetic brow-suspension materials (Prolene®, Supramid Extra® II, Silicone rods (Visitec® Seiff frontalis suspension set) and Mersilene® mesh) for their time-dependent response. At a given constant tensile strain or load, all of the brow-suspension materials exhibited stress-relaxation or creep, with Prolene® having a statistically different relaxation or creep ratio as compared with those of others. Uniaxial tensile cyclic tests through preconditioning and fatigue tests demonstrated drastically different time-dependent response amongst the various materials. Although the tests generated hysteresis force–strain loops for all materials, the mechanical properties such as the number of cycles required to reach the steady-state, the reduction in the peak force, and the cyclic energy dissipation varied considerably. To reach the steady-state, Prolene® and the silicone rod required the greatest and the least number of cycles, respectively. Furthermore, the fatigue tests at physiologically relevant conditions (15% strain controlled at 6.5Hz) demonstrated that the reduction in the peak force during 100,000 cycles ranged from 15% to 58%, with Prolene® and the silicone rod exhibiting the greatest and the least value, respectively.Many factors need to be considered to select the most suitable brow-suspension material for ptosis correction. These novel data on the mechanical time-dependent performance could therefore help to guide clinicians in their decision-making process for optimal surgical outcome.

Comparison of magnetoelastic properties between the 〈110〉 oriented TbxDy1-xFe1.95 polycrystalline alloys with different Tb/Dy composition ratio under magnetomechanical loading

This paper presents comparison of magnetoelastic properties between the 〈110〉 oriented Tb x Dy 1-x Fe 1.95 polycrystalline alloys for x = 0.27, 0.3, 0.45 under coupled loading of magnetic field and compressive stress. The simultaneously measure are investigated for the magnetization and magnetostriction under applied magnetic field from -200 to 200 kA/m and compressive stress from 0 to 50 MPa along the rod axis at room temperature. The results show that, according to the increase of Tb concentration and compressive stress, the hysteresis, coercive force and magnetostriction hysteresis loops of Tb x Dy 1-x Fe 1.95 alloys increase rapidly and the distortion of the hysteresis loops occurs at higher compressive stress, especially Tb 0.45 Dy 0.55 Fe 1.95 alloys, while the maximum relative permeability of Tb x Dy 1-x Fe 1.95 alloys monotonously decrease. Meanwhile, the higher the Tb concentration the stronger is magnetostrictive "jump" effect. For these experimental results, the effect of compressive stress and Tb / Dy ratio on magnetoelastic properties of Tb x Dy 1-x Fe 1.95 alloys are coupling and remarkable. A tradeoff and optimization are very important for many engineering designs and applications.

Research on modeling of nonlinear vibration isolation system based on Bouc–Wen model

Abstract A feedforword neural network of multi-layer topologies for systems with hysteretic nonlinearity is constructed based on Bouc–Wen differential model. It not only reflects the hysteresis force characteristics of the Bouc–Wen model, but also determines its corresponding parameters. The simulation results show that restoring force–displacement curve hysteresis loop is very close to the real curve. The model trained can accurately predict the time response of system. The model is checked under the noise level. The result shows that the model has higher modeling precision, good generalization capability and a certain anti-interference ability.