Smooth Contact Research Articles

Bending of a plate with circular rigid inclusion and system of cracks on the assumption of strip crack face contact

The article presents a solution to the bending problem for an infinite isotropic plate with a circular rigid inclusion and arbitrarily oriented straight through cracks. It is assumed that under the action of an external load at infinity, the faces of all cracks are in smooth contact along a region of constant width near the upper surface of the plate. The solution is obtained using methods of the theory of functions of complex variable and complex potentials and is reduced to a system of singular integral equations, which is numerically solved by the mechanical quadrature method. On the basis of numerical analysis, the graphical dependences of the contact force, forces and moments intensity factors are constructed at various parameters of the problem.

Rayleigh wave propagation in isotropic sandy layer sliding over isotropic sandy semi-infinite medium with sliding contact

The present study aims to investigate Rayleigh wave propagation in an isotropic sandy layer overlying an isotropic sandy semi-infinite medium, with interface considered to be imperfect (slide contact and dislocation like model). Expressions for displacement components are obtained using the variable separation method. The dispersion frequency equation for the Rayleigh wave propagating in sandy media is derived using suitable boundary conditions. Particular cases, such as when the interface is in smooth contact and when sandy media are replaced by elastic media, are also discussed. Using MATLAB software, the effects of the imperfectness parameter (slide contact and dislocation like model) and sandy parameter on the Rayleigh waves’ phase velocity are investigated and compared with the already obtained results of the dislocation like model. The present study may find useful applications in geophysics, civil engineering and soil mechanics.

Numerical Investigation of Presliding in Viscoplastic Spherical Contacts

AbstractPresliding contacts play an important role in stiffness, damping, and thus dynamic response of assembled structures. Load-dependent nonlinearities in presliding contacts still hinder predictive modeling. Classical models apply only to smooth elastic contacts and a small subset of materials. Recently, the authors tested high density polyethylene (HDPE) inside a scanning electron microscope (SEM) and observed that nonlinearity trends in tangential stiffness and damping deviate from the predictions of the classical models. This discrepancy was attributed to HDPE’s nonlinear viscoplastic response. The aim of this study is to model aforementioned experiments numerically and investigate the influence of nonlinear material response on the presliding response of spherical contacts. A finite element model of a rigid spherical indenter pressed and sheared on a nonlinear viscoplastic half-space is constructed. The indenter geometry and boundary conditions are set in accordance with the experiments, and the constitutive model is tuned to the measured indentation responses. The tuned model delivers a shear response in agreement with the experiments. Accumulated plastic deformations are also found to correlate well with the wear profiles. The model further reveals that nonlinear viscoplasticity dominates tangential stiffness and dissipation at high normal preloads. Our results confirm further that nonlinear material response contributes significantly to the load-dependent nonlinearities in viscoplastic presliding contacts.

Simulation of a pre-deformed plate compression by two indenters of complex shape

Within the framework of linearized formulation of the elasticity theory problems, the stress-strain state of a pre-deformed plate, which is modeled by a pre-stressed layer, is analyzed in the case of its smooth contact interaction with a two rigid axisymmetric indenters. The dual integral equations of the problem are solved by representing the quested-for functions in the form of a partial series sum by the Bessel functions with unknown coefficients. Finite systems of linear algebraic equations are obtained for determination of these coefficients. The influence of the initial strains on the magnitude and features of the contact stresses and vertical displacements on the surface of the plate is analyzed for the case of compressible and incompressible solids. In order to illustrate the results, the cases of the Bartenev – Khazanovich and the harmonic-type potentials are addressed.

A Novel Wearable Upper-Limb Rehabilitation Assistance Exoskeleton System Driven by Fluidic Muscle Actuators

This paper proposed a novel design using a torsion spring mechanism with a single fluidic muscle actuator (FMA) to drive a joint with one degree-of-freedom (DOF) through a steel wire and a proportional pressure regulating valve (PRV). We developed a 4-DOF wearable upper-limb rehabilitation assistance exoskeleton system (WURAES) that is suitable for assisting in the rehabilitation of patients with upper-limb injuries. This system is safe, has a simple mechanism, and exhibits upper-limb motion compliance. The developed WURAES enables patients with upper-limb musculoskeletal injuries and neurological disorders to engage in rehabilitation exercises. Controlling the joint is difficult because of the time-varying hysteresis properties of the FMA and the nonlinear motion between standard extension and flexion. To solve this problem, a proxy-based output feedback sliding mode control (POFSC) was developed to provide appropriate rehabilitation assistance power for the upper-limb exoskeleton and to maintain smooth and safe contact between the WURAES and the patient. The POFSC enables the overdamped dynamic of the WURAES to recover motion to be aligned with the target trajectory without a significant error overshoot caused by actuator saturation. The experimental results indicate that the proposed POFSC can control the designed WURAES effectively. The POFSC can monitor the exoskeleton system’s total disturbance and unknown state online and adapt to the exterior environment to enhance the control capability of the designed system. The results indicate that a single FMA with a torsion spring module exhibits a control response similar to a dual FMA configuration.

Robotic Arm Gripper Using Force Sensor for Crop Picking Mechanism

A dynamic gripper with qualities that resemble the human hand as closely as possible is sought after in the field of robotics. The idea of a robotic arm has been used in various cutting-edge technology fields, including agriculture, to assist people or farmers in carrying out regular tasks, such as gathering fruit, etc. The robot arm's end effector is one of the essential parts of the robot that we can configure based on their tasks, such as a spraying adaptor for fertilization function or a gripper for the picking mechanism. Since fruits have a delicate and fragile surfaces, it is vital to have a gripper with a smooth contact surface that can apply the right amount of force to pick the fruits without causing any bruising that can degrade the crop's quality. Hence, this paper proposes a robotic arm gripper design for the crop-picking mechanism using a force sensor as the main component of the Arduino Uno embedded system. The reliability result for the chili obtained is around 95% showing that this design is promising for designing an adaptive robotic arm gripper.

Admittance control design and system testing of industrial robot polishing operation

The control strategy is established with position control as the inner loop and admittance control the outer loop to solve the smooth contact force problem in faucet polishing operation. To avoid the excessive polishing, the parameter sensitivity is also introduced. Firstly, the system model and the controller are presented, the sensitivity of the parameter is calculated, and the effect of the admittance parameters on the output of the system is analyzed. Secondly, through the simulation of position control and admittance control, the change of the contact force between the robot end actuator and the external environment is analyzed, which shows that the proposed control strategy improves the accuracy of position control by 3.0% and guarantees that the contact force between the manipulator and the environment is close to the expected value. Finally, the polishing experiment is carried out on an industrial robot. The experimental results show that the control strategy can well control the contact force in the polishing process of the faucet.

The dynamical problem on acting distributed load on the elastic layer

The wave field of an elastic half-layer is constructed, when a dynamic normal load distributed over a rectangular area acts on upper face at the initial moment of time. The lower face of the half-layer is rigidly fixed to the foundation, and the side border is in the conditions of a smooth contact. The method of decomposing the system of motion equations into a system of equations and an independently solvable equation is used, this approach was proposed by Popov~G.~Ya. Laplace and Fourier integral transformations are applied directly to the motion equations and boundary conditions, which reduces the problem to a vector one-dimensional boundary value problem, which is solved by the matrix differential calculus method. The output displacements are obtained using inverse integral transformations. The case of steady oscillations was considered and the amplitude of vertical displacement occurring in the layer was analyzed depending on the shape of the distributed load section, the material of the layer medium and the values of the natural frequency of the layer oscillations.

Molecular dynamics simulation on friction performance of collision sliding contacts of soft metals in vibration environment

Soft metals are often used for space mechanism lubrication because of their low shear strength. In outer space, the vibration of spatial mechanism will occur when there is a small disturbance due to the effects of microgravity environment. Studies on the friction properties of soft metals in vibration environment could contribute to the application of space lubrication materials. Taking a clearance joint as an example, the relative motion between the shaft and the bearing is simplified to a sliding contact between a cylinder and two smooth contact bodies. A molecular dynamics model of the collision sliding contact between a rigid cylindrical indenter and an elastic substrate is established. The effects of sliding velocity, collision velocity and indenter radius on the friction properties of soft metals are studied. The results show that the Ag substrate and Au substrate present strong adhesion to the Fe indenter. The indenter and the substrate are always in a state of adhesive sliding contact. The larger the initial collision velocity of the indenter, the higher the friction force. The friction force shows great values as the sliding velocity increases. As the increase of indenter radius, the contact area is enlarged, which results in a high friction force. The adhesion of the Cu substrate to the Fe indenter is weak, so the friction force shows a low value, and the friction performance of Cu is the best, while the friction performance of Au is the worst.

Hybrid Polymer Electrolyte Encased Cathode Particles Interface‐Based Core–Shell Structure for High‐Performance Room Temperature All‐Solid‐State Batteries

AbstractA smooth interfacial contact between electrode and electrolyte, alleviation of dendrite formation, low internal resistance, and preparation of thin electrolyte (<20 µm) are the key challenging tasks in the practical application of Li7La3Zr2O12 (LLZO)‐based solid‐state batteries (SSBs). This paper develops a unique strategy to reduce interfacial resistance by designing an interface‐based core–shell structure via direct integration of Al‐LLZO ceramic nanofibers incorporated poly(vinylidene fluoride)/LiTFSI on the surface of a porous cathode electrode (HPEIC). This yields an ultrathin solid polymer electrolyte with a thickness of 7 µm. The integrated HPEIC/Li SSB with LiFePO4/C exhibits an initial specific capacity of 166 mAh g−1 at 0.1 C and 159 mAh g−1 with capacity retention of 100% after 120 cycles at 0.5 C (25 °C). The HPEIC/Li SSB with LiNi0.8Mn0.1Co0.1O2 cathode delivers a good discharge capacity of 134 mAh g−1 after 120 cycles at 0.5 C. The rational design of interface‐based core–shell structure outperforms the conventional assembly of solid‐state cells using free‐standing solid electrolytes in specific capacity, internal resistance, and rate performance. The proposed strategy is simple, cost‐effective, robust, and scalable manufacturing, which is essential for the practical applicability of SSBs.

Study on the Influence of Frozen Soil Change Characteristics on Pavement Materials in Cold Region

The challenge of constructing roads on frozen ground in cold climes has long been acknowledged on a global scale. As a result, particular requirements for pavement materials and structures have been developed to address the special construction and usage conditions for highway pavement. The influence of frozen soil change features on pavement materials in cold places is utilized to research the fluctuation law of subgrade temperature field under cement concrete and asphalt pavements because subgrade and pavement illnesses frequently occur in permafrost locations. The residual tensile strength of regular emulsified asphalt dropped to 50% after 7 days of continuous immersion, while that of high-performance modified emulsified asphalt only reached 75%. However, the residual tensile strength of water-borne epoxy resin emulsified asphalt remained over 90%. Regardless of how smooth or uneven the contact surface is, the results show that water-borne epoxy resin emulsified asphalt has good adhesive qualities. However, the water-borne epoxy resin emulsified asphalt still retained over 90% of its original tensile strength. Regardless of how smooth or uneven the contact surface is, the results show that water-borne epoxy resin emulsified asphalt has good adhesive qualities.

Assessment of pantograph-catenary interaction in a railway overlap section via a novel optical-based method

• Pantograph-catenary interactions at an existing overlap span are investigated. • A novel optical-based method is proposed and implemented at the overlap span. • Single- and double-pantograph train passages are obtained and studied. • Dynamic effects rendering high contact forces, contact loss and arcing are studied. • Peak contact force, transition distance and train speed show a strong correlation. Smooth pantograph-catenary contact is essential for regular train operation. However, catenary section overlaps are locations where peak contact forces occur, which significantly affects current collection quality. This work studies pantograph-catenary interaction and transition at an existing overlap span by using a novel optical-based measuring method. Image sequences of eleven single- and two double-pantograph train passages were processed to obtain wire displacement responses. The unsynchronised vibration of two contact wires was found, and the first contact wire exhibits different modal responses. The spatial motion paths of contact wires were obtained to estimate the pantograph-catenary interaction. Dynamic effects rendering high contact forces, contact loss and arcing were investigated. The results show that pantographs with a long transition distance and a high intersection gradient cause a serve impulse with the second contact wire, resulting in contact loss and arcing. Finally, this study successfully estimated the transition distance and found it has a strong positive correlation with peak contact forces and train speeds. The transition distance exhibits an increasing tendency with increasing train speed. The longer transition distance results in a higher peak contact force.

Coupling of an SPH-based solver with a multiphysics library

A two-way coupling between the Smoothed Particle Hydrodynamics-based (SPH) code with a multiphysics library to solve complex fluid-solid interaction problems is proposed. This work provides full access to the package for the use of this coupling by releasing the source code, completed with guidelines for its compilation and utilization, and self-contained template setups for practical uses of the novel implemented features, is provided here. The presented coupling expands the applicability of two different solvers allowing to simulate fluids, multibody systems, collisions with frictional contacts using either non-smooth contact (NSC) or smooth contact (SMC) methods, all integrated under the same framework. The fluid solver is the open-source code DualSPHysics, highly optimised for simulating free-surface phenomena and structure interactions, uniquely positioned as a general-purpose Computational Fluid Dynamics (CFD) software with a GPU-accelerated solver. Mechanical systems that comprise collision detection and/or multibody dynamics are solved by the multiphysics library Project Chrono, which uses a Discrete Element Method (DEM). Therefore, this SPH-DEM coupling approach can manage interactions between fluid and complex multibody systems with relative constraints, springs, or mechanical joints. Program summaryProgram title: DualSPHysics-ChronoCPC Library link to program files:https://doi.org/10.17632/g2cc37dw4f.1Licensing provisions: DualSPHysics and DSPHChronoLib under GNU Lesser General Public License (LGPL); Project Chrono under BSD-3-Clause License.Programming language: C++ and CUDANature of problem: The simulation of turbulent free-surface flows in interaction with complex fixed or floating structures is essential to address typical marine and coastal engineering problems. The Smoothed Particle Hydrodynamics (SPH) method is particularly suitable for solving this type of nonlinear problems. However, this type of application usually requires mechanical restrictions between the different structural elements (spherical joints, hinges, or springs), as well as the correct simulation of collisions between solid objects. In these cases, it is necessary to combine the SPH method with other numerical methods that allow performing these multiphysics simulations.Solution method: DualSPHysics-Chrono is a two-way coupling between an SPH solver and a multiphysics library that combines fluid simulation using a Lagrangian approximation and interactions between solids using Discrete Element Method (DEM). DualSPHysics solver is a GPU-optimized implementation of the SPH method that allows efficient simulation of fluid-structure interaction problems. Whereas Project Chrono is a DEM implementation for simulating multibody dynamics that includes collision detection and numerous mechanical constraints to solve complex mechanisms. The coupling of DualSPHysics and Project Chrono combines the capabilities of both models under a free software framework.Additional comments including restrictions and unusual features: The SPH solver includes a version implemented with CUDA (Compute Unified Device Architecture) to exploit the parallelism of NVIDIA graphics processing units (GPUs).

Leech‐Inspired Shape‐Encodable Liquid Metal Robots for Reconfigurable Circuit Welding and Transient Electronics

Deformability and self‐adaptability are important for soft robots to deal with uncertain and varying situations and environments during movement and navigation. Droplet‐based robots are great candidates to travel inside narrow and constrained spaces without damaging the interfaces due to their extreme deformability and liquid nature, which enables smooth contact between robots and target spaces. Here, magnetic liquid metal droplet robots, comprising liquid metal and carbonyl iron, that can perform reversible telescopic deformation, bending, and on‐demand locomotion are proposed. The magnetic liquid‐metal‐based robots can perform on‐demand and reversible coalescence and splitting by intricately applying magnetic fields. Importantly, the liquid metal robot can perform phase transition to fix the desired shape after programmable shape encoding. The liquid‐metal‐based soft robots can serve as dynamic and recyclable switches for complex circuits, and are capable of repairing damaged sections of microcircuits by remote actuation, controllable coalescence, and on‐demand circuit welding. This technology provides a new application scenario of droplet‐based soft robots for on‐demand circuit welding and transient recyclable electronics. A preprint version of the article can be found at: https://www.authorea.com/doi/full/10.22541/au.165167005.56125584.

Transient Elastohydrodynamic Lubrication of Rough Contact Surface for Intermittent Motion

The current study aims to study the characteristics of transient elastohydrodynamic lubrication of smooth and rough surface contacts subjected to intermittent motion for different inactive periods of motion and deceleration/acceleration periods to fulfill an identified need for such conjunction. In this case, the non-steady Reynolds’ equation, the film thickness equation with elastic deformation and taking into account the influence of surface roughness, and the load balance equation are simultaneously solved using the Newton-Raphson with Gauss-Seidel iterations method to determine the film profile and pressure distribution at various time steps. Surface contact of sinusoidal waves is presented with different amplitudes and wavelengths. The results indicated that surface waviness causes random oscillations in pressure and film profiles at different time steps. The greater the amplitude of the waviness, the more pressure and film profile variations occur. The magnitude of the pressure and film profile fluctuations becomes little noticeable as the wavelength of a wavy surface rises. The findings of this investigation also revealed that increasing the inactive duration for wavy surfaces results in zero minimum film thickness and surface contact. Squeezing action is ineffective in conveying loading capacity in this circumstance. The central and maximum pressure heights increase during the stop time interval as stop time increases. The centre film thickness increases at the end of the deceleration phase when the deceleration/acceleration period is reduced, but the minimum film thickness is unaffected. In fact, the minimum film thickness tends to be zero at the end of the deceleration phase, regardless of the deceleration/acceleration period. The central and maximum pressure increase during the stop time interval with the decrease of the deceleration/acceleration period. The difference between the results for smooth and wavy surface contacts is the appearance of fluctuations in film and pressure profiles, as well as the reduction of the film thickness and increase in pressure for the wavy surface when compared to contact with a smooth surface.

Tribological performance evaluation of slag waste filled phenolic composites for automotive braking applications

AbstractSlag waste‐filled phenolic resin‐based automotive brake friction composites were formulated, fabricated, followed by mechanical, physical characterization, and tribo‐evaluation. According to economic commission for Europe regulation, the tribological performance of the composites was evaluated on a Krauss friction‐testing machine. The increase in slag waste content led to increased physical properties such as density, porosity, ash contents, and compressibility, whereas hardness, acetone extraction, and shear strength increased with increased phenolic resin content. The fade and friction performance has been observed to be highly dependent on the slag waste content, that is, both followed a consistent decrease with the increase in the phenolic resin content, whereas the frictional fluctuations have been observed to decrease with the increase in slag waste content. In particular, the composites containing 65 wt% slag waste and 5 wt% phenolic resin showed the highest friction coefficient (0.406), lowest fade (20.44%) and frictional fluctuation (0.209), but the wear (10.80 g) and disc temperature rise (618°C) remains highest. Composite with the lowest slag waste content of 50 wt% combined with the highest phenolic resin of 20 wt% showed higher recovery performance (120.63%), lowest wear (4.45 g) and disc temperature rise (536°C), but exhibits lowest friction coefficient (0.315) and friction stability (0.79) along with highest friction variability (0.60) and fluctuations (0.238). Friction and wear data analysis revealed the predominance of the fade factor for friction performance while the fade factor and disc temperature‐induced results significantly influence the wear performance. The worn surface micrograph showed higher phenolic resin‐filled composites form smooth contact plateaus that successfully reduced wear.

Diversity of Ectomycorrhizal Fungi in Young Pedunculate Oak Stand from Morović, Serbia

Although oaks belong to the economically most important hardwood tree species in Europe, data on the diversity of ectomycorrhizal (ECM) fungi on pedunculate oak in the Republic of Serbia are deficient. The aim of our study was to give the first insight into the diversity of ECM fungi in the young stand of pedunculate oak in Morović, Serbia. The combination of morpho-anatomical characterization and molecular analysis was used for determination of ECM fungi on penduculate oak. Studied parameters included: (i) counting of vital ECM root tips, (ii) calculation of diversity indices and (iii) classification of morphotypes of ectomycorrhizae into the exploration types. Eighteen ECM fungal taxa were recorded in the studied young pedunculate oak stand. Seven of them were identified to the level of species, eight fungi to the genus, two to the family level, and one ECM fungus remained unidentified. ECM communities consisted of a small number of abundant taxa and a bigger number of rare taxa. The most abundant ECM fungi were Entoloma sp., Thelephoraceae sp., Russula cf. odorata and Russula lilacea, which made association with the majority of ECM root tips. Short-distance exploration type (ET) dominated, followed by medium-distance smooth ET and contact ET, while long-distance ET and medium-distance fringe ET were rare at the Morović site. Values of diversity indices obtained in the studied pedunculate oak stand were comparable to the ones recorded in different oak stands over Europe. In order to get a deeper insight into the diversity of ECM fungi on pedunculate oak there is a need to continue research on increased number of sites and also to include seasonal dynamics.

Ultrasonographic evaluation of contact configuration between flexor pollicis longus tendon and the volar prominence of volar plate in patients with distal radius fracture.

We classified the contact configuration between the volar prominence of volar locking plate (VLP) and flexor pollicis longus (FPL) tendon using ultrasound (US) into indentation contact and smooth contact, and investigated whether the contact configuration is associated with the flexor tendon attrition. Ninety-four patients who underwent VLP removal were included in this study. We assessed pain using visual analogue scale, grip strength, and Disabilities of the Arm, Shoulder and Hand score for clinical evaluations, radial inclination, palmar tilt, ulnar variance, and Soong classification for radiological evaluations, and contact configuration using US at 1year after VLP fixation. After these evaluations, we removed the VLP with observation for the presence of fibrillation or wear of FPL tendon substance. Subsequently, we classified the patients into either of FPL attrition and FPL intact group. Twenty-eight patients had indentation contact configuration and 66 patients had smooth contact configuration. The kappa value for inter-observer reliability for the contact configuration was 0.78. Twelve patients were included in the FPL attrition group and 82 in the FPL intact group. There was no significant difference in clinical outcomes and Soong classification between the groups. However, palmar tilt of the flexor tendon attrition group was significantly lower than that of the flexor tendon intact group and the FPL attrition group showed significantly higher indentation contact configuration rate than the FPL intact group. FPL tendon attrition was diagnosed using the contact configuration on US with a sensitivity of 100% and specificity of 80%. This study demonstrated that FPL tendon attrition was significantly associated with indentation contact on US with high sensitivity. Therefore, we recommend selective implant removal in patients with indentation contact configuration.

Myoendothelial junction heterogeneity enables phosphatidylserine regulation of Kir2.1‐mediated vasodilation

In resistance arteries, matrix‐devoid holes in the internal elastic lamina (HIEL) are presumably always the site of endothelial and smooth muscle contact (myoendothelial junction; MEJs). MEJs are signaling microdomains and we have previously demonstrated that specific protein localization regulates heterocellular communication. However, it is time consuming to localize proteins at the MEJ as it requires electron microscopy (EM) verification—it also lacks quantitative analysis for spatial localization both within endothelial cells and within the tissue. Thus, we wanted to determine if every HIEL was an MEJ without relying on any single protein marker. We first developed an in‐house MATLAB analysis program to obtain quantitative data from en face images of third order mesenteric arteries, including an evaluation of spatial distribution using Monte Carlo simulations, which revealed HIEL exhibit a random spatial distribution. We then converted these metrics from en face XY views to XZ views of TEM sections, where the presence of MEJs can unequivocally be detected. We predicted an incidence of 5 ‐ 17.5 HIEL per 1000um IEL length in TEM cross‐sections (corresponding to a 190.75 HIEL/um2 density in en face images), and the measured incidence was 11.97, where every detected HIEL contained cellular contents. We concluded every HIEL was an MEJ. Next, we wanted to investigate the spatial distribution and function of a novel lipid marker of the MEJ, phosphatidylserine, which we previously demonstrated was enriched within in vitro MEJs by mass spectrometry, but had not been demonstrated on intact tissue. It is well described that lipid species, like PIP2, have key roles in regulating the function of channels, and thus we hypothesized that PS may function in a regulatory capacity within these signaling microdomains. We first determined PS‐MEJ incidence and spatial distribution. Immunohistochemistry on en face third order mesenteric arteries revealed that PS comprised on average a 13.8% subset of total MEJs, indicating a heterogeneous nature to these microdomains. Within individual endothelial cells, an average of 9.89 MEJs were identified, and an average of 1.13 of these MEJs were PS positive. Monte Carlo analysis did not find unique PS‐MEJs spatial segregation to endoplasmic reticulum, nucleus, or interendothelial junctions. It wasn’t clear the biological rationale for the PS segregation in MEJs. However, recent in silico studies predicted that PS, in addition to PIP2, interacts with the inward rectifying potassium channel 2.1 (Kir2.1). Staining for Kir2.1, we found that it only localized to 1.5% of total MEJs, and yet remarkably, 83.3% of Kir2.1‐MEJs localized to PS‐MEJs. This contrasted with Cx40‐MEJs, where only 14.6% localized to PS‐MEJs. This observation led us to test the hypothesis that PS may regulate Kir2.1. Using pressurized third order mesenteric arteries, we performed dose response curves with NS309, a drug that can activate Kir2.1 channels. Application of either 1 uM or 10 uM exogenous PS demonstrated a significant reduction in dilation to the early range of NS309 doses comparable to arteries treated with the 3.6 uM ML‐133 and 30 uM Ba2+. In addition, direct application of 10 uM PS induced a significant constriction. Thus, we hypothesize PS may provide a mechanism for counteracting the dilatory effect of PIP2. Based on this data, we conclude MEJ heterogeneity may regulate vascular function.

Numerical Study of Transient Elastohydrodynamic Lubrication Subjected to Sinusoidal Dynamic Loads for Rough Contact Surfaces

Abstract The purpose of this paper is to study the behaviour of transient elastohydrodynamic contacts subjected to forced harmonic vibrations, including the effect of surface waviness for concentrated counterformal point contact under isothermal conditions. Profiles of pressure and film thickness are studied to reveal the combined effects of sinusoidal external load and surface roughness on the lubrication problem. The time-dependent Reynolds’ equation is solved using Newton–Raphson technique. The film thickness and pressure distribution are obtained at different snap shots of time by simultaneous solution of the Reynolds’ equation and film thickness equation including elastic deformation and surface waviness. It is concluded that the coupling effects of the transient sinusoidal external load and wavy surface would result in increase in modulations of the pressure and film thickness profile in comparison to the case where the smooth contact surfaces are subjected to sinusoidal external load.