Rapid and accurate assessment of aerodynamic performance is essential for aircraft design. Key factors affecting aerodynamic performance include pressure and skin friction forces, which are critical distributed loads in aerodynamic shape optimization and structural analysis. Traditional methods for determining these loads rely heavily on numerical simulations, which are time-consuming and highly sensitive to mesh quality and turbulence modelling choices. Conventional machine learning methods, on the other hand, often require a large amount of training data and may suffer from poor generalization. To address these limitations, this paper presents a machine learning framework that integrates solutions from the Euler equations to predict wall aerodynamic forces. By embedding inviscid flow characteristics into the machine learning model, this approach leverages the inherent physical knowledge of Euler solutions to enhance both accuracy and generalizability, even with a modest dataset. The effectiveness of this method is demonstrated through tests on standard 2D aerofoil and 3D wing geometries under subsonic and transonic flow conditions, showing strong extrapolation capabilities for cases with varying flow states and geometries. This hybrid modelling approach not only achieves high accuracy with a significantly reduced dataset but also effectively reduces prediction error, keeping drag error within approximately 3%.

The present study investigates the design of controllers to stabilize an armed turret mounted on a moving platform on uneven ground. Including kinematic joints and contact constraints resulting from interactions with its surroundings, the turret-vehicle system is described as a constrained multibody system. A Linear Complementarity Problem (LCP) method was used to represent the non-smooth dynamics, such as impacts and contacts with friction forces. Essential factors, including the suspension of the vehicle, the recoil forces from shooting, and the control inputs used to maintain turret stability, are also incorporated in the model. Using an external ballistic model, the path of the bullet from the time it leaves the barrel until it reaches its target was modeled and used to identify the exact elevation angle to hit the target and also to calculate the hit probability after many shots. We investigated many control techniques including Proportional-Integral-Derivative (PID), Linear Quadratic Regulator (LQR), and Sliding Mode Control (SMC) to guarantee stability even against disturbances such as firing and operational conditions. By comparing different techniques, it was found which one is more efficient in reducing disturbances and maintaining turret stability. Simulations across multiple vehicle speeds and terrain scenarios consistently showed that SMC achieved the best stabilization and hit probability performance compared to PID and LQR, demonstrating its robustness under varying operating conditions. Numerical simulations demonstrate that a more realistic and accurate depiction of the behavior of the system arises from adopting a non-smooth dynamics model, hence guiding the choice of stabilization technique and its parameters.

Research of Russian large livestock complexes (1,000 heads or more) was revealed that "Karusel" rotary conveyor-and-milking machines of various capacities are the most widely used in milking parlors. To rotate the milking platforms, they use gear motors with drive wheels that frictional contact with a movable providing, curved circular rail on which the platform being driven rests, or with an edged curved strip at the end of the platform locating. When a levitating milking platform creating, the drive power will be significantly lesser due to the friction forces’ actual absence due to magnetic suspension’s technology. The most appropriate option is an open type friction transmission using. The advantages of friction gears include: simplicity of design, quietness and smooth running, automatic overload protection due to wheel slip. A mathematical model has been developed that defines the main parameters of an energy saving electric drive based on the of rotational motion dynamics’ equation for an annular platform. The total moment of milking platform and the animals’ inertia on the torques on the driving and driven wheels, and their dependence of the platform’s angular acceleration on time are determined. The friction transmission was calculated, and the main analytical dependences were obtained making it possible determining: the driving and driven wheels’ diameters, these wheels’ calculated downforce, the wheels’ circumferential force, the specific force at wheel contact, and the gear ratio. The gear motor for the platform drive selection was carried out in according to the maximum torque (259 N*m) and the drive wheel rotation’s speed (3,6 rpm). A 3-MP-40 three stage planetary gear motor with an output shaft’s speed of 3.55...4.4 rpm, a torque of M1 =375 Nm and an electric motor power of N=0,18 kW was selected. To create a controlled mode, it is advisable the electric milking platform with a Vesper E4-8400-SP5L frequency converter equipping. Due to the magnetic suspension’s technology, that made it possible the propellers’ wheelsets resistance moment eliminating, the electric drive’s power consumption from 3 kW (two 1,5 kW drives for a 40-seat "Carousel") to 0,18 kW with one drive decreasing.

The inerter is a vibration control element related to the acceleration between its two ends, which can increase inertia through a speed-increasing mechanism. Applying the inerter to a vibration isolator can enhance its low-frequency vibration isolation performance. Frictional force always exists in the high-speed mechanism of the inerter. Even if it is not large, its influence on the dynamic performance of the low-speed end cannot be ignored. This study analyzes the force of a ball-screw inerter using the kinetic energy theorem. The inerter force is then expanded into the first-order Taylor approximation, from which the inerter coefficient and apparent friction coefficient are determined. Based on the approximate formula of the inerter force, the nonlinear dynamic model and its corresponding dynamic equation for the inerter vibration isolator under base excitation are established. The nonlinear dynamic equation is then solved by averaging method, and the approximate analytical solutions for the relative displacement, absolute displacement, and displacement transmissibility are obtained. The analysis results show that a larger apparent friction coefficient reduces the resonance peaks of the displacement transmissibility and relative displacement amplitude, but it slightly increases the initial vibration isolation frequency, as well as the resonance and valley frequencies of the displacement transmissibility and relative displacement. Increasing the inerter-mass ratio can reduce the resonance frequency and initial vibration isolation frequency, thereby broadening the vibration isolation frequency domain. When friction is considered, increasing the inerter-mass ratio can suppress the resonance peaks of the displacement transmissibility and relative displacement.

Guided by principles of symmetry to achieve a proper balance among model consistency, accuracy, and complexity, this paper proposes a new approach for identifying the unknown parameters of nonlinear one-degree-of-freedom mechanical systems using nonlinear regression methods. To this end, the steps followed in this study can be summarized as follows. Firstly, given a proper set of input time histories and a virtual model with all parameters known, the dynamic response of the mechanical system of interest, used as output data, is evaluated using a numerical integration scheme, such as the classical explicit fixed-step fourth-order Runge–Kutta method. Secondly, the numerical values of the unknown parameters are estimated using the Levenberg–Marquardt nonlinear regression algorithm based on these inputs and outputs. To demonstrate the effectiveness of the proposed approach through numerical experiments, two benchmark problems are considered, namely a mass-spring-damper system and a simple pendulum-damper system. In both mechanical systems, viscous damping is included at the kinematic joints, whereas dry friction between the bodies and the ground is accounted for and modeled using the Coulomb friction force model. While the source of nonlinearity is the frictional interaction alone in the first benchmark problem, the finite rotation of the pendulum introduces geometric nonlinearity, in addition to the frictional interaction, in the second benchmark problem. To ensure symmetry in explaining model behavior and the interpretability of numerical results, the analysis presented in this paper utilizes five different input functions to validate the proposed method, representing the initial phase of ongoing research aimed at applying this identification procedure to more complex mechanical systems, such as multibody and robotic systems. The numerical results from this research demonstrate that the proposed approach effectively identifies the unknown parameters in both benchmark problems, even in the presence of nonlinear, time-varying external input actions.

Modern industry requires high-precision control of vibrating electromechanical systems, which are widely used in many industries. Variable load modes require the drive to have good control properties while maintaining the necessary energy parameters of the technological process. The presented work substantiates the strategy for controlling a three-phase vibrating linear motor based on back electromotive force estimation, which ensures the improvement of its control properties due to an increase in the amplitude of mechanical vibrations. The operation of the motor control system is studied using a multi-physics model that combines the calculation of electric and magnetic circuits, as well as the determination of the law of mover motion depending on the forces applied to it. The mechanical scheme is represented by a lumped mass that oscillates relative to the position of mechanical equilibrium under the action of the motor electromagnetic force. Conservative and dissipative forces are represented by the corresponding stiffness and viscous friction coefficients. The load force characteristic is given by the sum of the elastic component, proportional to the mover displacement, and the viscous friction force, proportional to its velocity. The solution of this problem was carried out by the finite element method in the axisymmetric formulation, using a moving type of computational mesh, based on the equations of a quasi-stationary magnetic field in the time domain. The control system operation was simulated in two operating modes - with rectangular and sinusoidal modulation, and the electromechanical processes of the motor in a steady-state mode were calculated.

Samples of M78 sack paper coated with agar-agar (a biodegradable polymer produced from brown and red algae) with a thickness of 15–70 μm have been obtained. It has been shown that when an aqueous solution, containing agar-agar is applied to sack paper, a continuous elastic coating is formed, with part of the polymer penetrating into the volume of the paper, filling the interfiber space and, possibly, the macro- and micropores of the fibers themselves. As the thickness of the polymer coating grows, the drip absorbency of the material increases and then reaches a certain stable value (taking into account the experimental error). It has been found that the thickness of the agar-agar coating of 40 μm is sufficient to impart barrier properties to sack paper with respect to the action of moisture. In this case, the drip absorbency of coated paper will be equal to ~1000 s, and the absorbency at full immersion will be ~40 %. To evaluate the mechanical properties of pulp and paper materials, a method is proposed for determining the strength properties of the obtained samples, implying a comprehensive deformation of the samples, allowing for anisotropy to be neglected. It has been shown that the tangential stiffness values of sack paper coated with agar-agar is 15–20 % higher than that of the original paper. A mechanism for this strengthening has been developed, which consists in the following. When a load is applied to the paper material, its destruction occurs due to both the rupture of cellulose fibers and the separation of fibers from each other. In case of a lack of binder, the load is transferred from fiber to fiber only by means of friction force. In paper, the surface layer of which is impregnated with agar-agar, the load from fiber to fiber goes through the polymer, therefore the deformation and strength properties increase. The nature of cellulose fibers and agar-agar ensures the manifestation of good adhesion between them. It has been concluded that agar-agar coated sack paper is environmentally friendly, since both of its components are biodegradable.

The relevance of this work stems from the need to use a simple and reliable dry friction model in the study of relay control systems for positional electric drives. The discontinuity condition of the simplest dry friction characteristics coincides with the condition for the existence of a sliding mode position controller for such systems, which negatively impacts the quality of their modeling results. The goal of this work is to substantiate an analytical characteristic of the reactive torque that does not require detailed information regarding the mechanism's structural elements but is capable of reproducing typical manifestations inherent in friction forces in a relay control system model. The development is focused on the use of such characteristics for tasks involving the general assessment of the dynamics of electromechanical systems operating under the control of relay controllers through their mathematical modeling. The solution proposed in this work consists of using a friction force model in the form of a continuous analytical function whose inflection points are related to the amplitude of velocity pulsations in the sliding mode. A well-founded characteristic form and parameters matched to the current pulsation amplitude during sliding of relay controllers prevent the occurrence of erroneous self-oscillations in the mathematical model of an automatic position control system. The proposed dry friction characteristic enables modeling of a positioning electric drive in typical static and transient modes for both academic and research applications. The advantages of the results include consideration of the specificity of sliding modes when determining the parameters of the reactive resistance characteristic and the simplicity of its setup procedure, which expands the range of possible applications of the developed model. Further development of the obtained results, focusing on their use in studying the influence of sliding modes on the course of frictional self-oscillations in electric drives, taking into account viscous friction forces, appears promising.

The article discusses the application of the discrete element method (DEM) for modeling the behavior of spherical particles in granular media. Key aspects of particle contact interactions, including frictional forces, elasticity, coordination number, and the shape factor of spherical particles, are analyzed and investigated. It is worth noting that the proposed methodology enables the study of the mechanical properties of systems with particles of various sizes and compositions, as well as the modeling of their behavior in confined spaces and under dynamic influences. The modeling results demonstrate the high accuracy and versatility of the DEM for analyzing processes in bulk materials, particularly transportation, mixing, and granulation. The findings underscore the effectiveness of using DEM to solve complex problems and highlight prospects for its further improvement.

We report the results of molecular dynamics simulations of the frictional behavior of a Lennard–Jones fluid confined between two solid crystalline walls. To study the effects of commensurability on friction, different ratios of interatomic distances in walls and fluid were considered. In particular, numerical experiments with the same fluid confined between walls with five different lattice parameters were performed. System behavior was examined by analyzing calculated time dependencies of the friction force between fluid and solid walls and distributions of the velocities of fluid particles. Friction coefficients and slip length parameters were obtained as numerical characteristics of commensurability effects. Fluid behavior near the solid interface was analyzed through visualization of the atomistic configurations and calculation of radial distribution functions. In the performed simulations, a pronounced reduction in friction was observed for highly incommensurable configurations, when the ratio between fluid and wall interatomic distances is around 1.62.

Thermal spray coatings have emerged as a pivotal technology in materials engineering, primarily for augmenting the characteristics related to wear and tribology of metallic substrates. This study aims to develop into applying High-Velocity Oxygen Fuel (HVOF) thermalsprayed WC-Co nanocoatings on Titanium Grade-5 alloy (Ti64). The coating process, utilizing nano-sized WC-Co powder, undergoes systematic optimization of HVOF parameters, encompassing the flow rate of carrier gas, powder feed rate, and nozzle distance. Experimental assessments via Pin-on-Disc (PoD) tests encompass Loss of Wear (WL), Friction Coefficient (CoF), and Frictional Force (FF). Later, an exhaustive optimization of responses is conducted using the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) method and the golden jack optimization algorithm (GJOA). Outcomes show a substantial increase in WL, CoF, and FF with a rise in the carrier gas and powder feed rate. However, with increasing spraying distance of powder, the WL, CoF, and FF tend to lower due to higher bonding, which leads to increased wear resistance. The ideal parametric settings achieved from TOPSIS and GJOA are 245 mm of spray distance, 30 gpm rate of powder feed, and 11 lpm of carrier gas flow rate. The powder feed rate contributes 88.99% to the control action, as seen from ANOVA. The confirmation experiment presents that the WL, CoF, and FF output responses are 42.33, 27.97, and 9.38% less than the mean of experimental data. These results highlight the HVOF process in spraying WC-Co nanocoatings to fortify the durability and performance of Ti64 alloy that can be patented for diverse engineering applications.

Distinct viscosity and gel hardness obtained by ball-milled konjac flour: Insights into physicochemical properties, structure and gel properties.

This research investigated the polishing treatment of silicon wafer rough surfaces using molecular dynamics simulations. The material removal behavior of tangential vibration polishing and linear polishing was analyzed in detail. A molecular dynamics geometric model of tangential vibration polishing for silicon wafers was constructed. The environmental setup and simulation methods were clarified, and the Tersoff, Stillinger–Weber (SW), and Lennard-Jones (LJ) potential functions were used for the simulation. A comparison of the two polishing methods revealed that tangential vibration polishing has significant advantages in material removal. The amount of debris generated in tangential vibration polishing increases by about 35% and is more uniformly distributed. The polishing efficiency is higher, the polishing range expands by about 20%, and surface damage is reduced. In terms of material mechanical properties, tangential vibration polishing caused frictional forces to change periodically, reduced local stress concentration, improved material cohesion, decreased shear strain, and optimized atomic bond structure. Dislocation analysis shows that the peak total dislocation length in tangential vibration polishing is only 20%–25% of that in linear polishing, and no obvious 1/2⟨110⟩ dislocation loops appear. This method can more effectively suppress the generation and development of dislocations. The results provide a theoretical basis for optimizing silicon wafer polishing processes and improving polishing quality.

Multi-objective optimisation of vibration-assisted electrode insertion parameters for DBS using hybrid approach of grey-orthogonal coupled response surface methodology.

This study analyzes gas dynamics and heat transfer behind shock waves, incorporating complex parameters, making it essential for improving the performance and stability of systems requiring precise control over shock waves, thermal management, and non-ideal gas behavior. This explores the impact of shock wave intensity, slippage, dissipation, van der Waals constants, the Prandtl number, the Knudsen number, the Brinkman number, and the magnetic field on the flow's dynamic and thermal behavior, including frictional forces and heat transfer characteristics, while considering the temperature ratio between the flow and the wall. Self-similar transformation variables were employed to transform the governing equations into ordinary differential equations, which were subsequently solved using MATLAB's boundary value problem (BVP4c) solver and cross-verified through artificial neural networks (ANN). The study revealed that increasing the Knudsen number enhances the velocity gradient and broadens the boundary layer, while a stronger magnetic field suppresses flow velocity and increases temperature uniformity. Higher Eckert numbers result in greater viscous dissipation and temperature rise near the wall, while van der Waals forces significantly reduce skin friction and heat transfer. The ANN model achieved over 95% prediction accuracy, and sensitivity analysis indicated that a 10% increase in the Knudsen number led to a 15% rise in the velocity gradient, with variations in the magnetic field causing a 20% change in temperature profiles. This model is applicable in microfluidics, magnetohydrodynamics, thermal management, and high-speed fluid dynamics, where precise control of friction and heat transfer is crucial.

The design and installation of conductor pipe in deepwater environments are crucial for ensuring stable soil penetration and maintaining structural integrity. This study aims to establish a comprehensive understanding of the interdependencies among key parameters—bearing capacity, soil recovery coefficient, water jet force, side friction force, and running speed—to determine optimized jetting conditions. Utilizing numerical analysis through an empirical model and optimization techniques implemented in MATLAB, this research provides insights into efficient and stable conductor installation. Our findings indicate that soil recovery is most significant within the initial 3 hours post-jetting, with diminishing returns thereafter, suggesting that optimal soaking times are critical. The study further reveals that maximizing water jet force is achieved at smaller angles of reflection, underscoring the importance of precise jet nozzle orientation for effective soil penetration. Additionally, increased weight on the bit effectively reduces side friction, leading to smoother penetration. The investigation yielded optimized jetting parameters: bit stick-out of 0.145 ft, running speed of 16.4 ft/h, and soaking time of 4 hours. These parameters are demonstrated to ensure high efficiency while minimizing operational risks. The outcomes of this research offer valuable practical knowledge for maximizing jetting operations, reducing installation duration, and enhancing overall drilling efficiency in deepwater settings. While these findings are derived from numerical simulations, they provide a robust theoretical framework for future empirical validation.

In this study, we utilized a molecular dynamics simulation approach to understand the adhesion and friction behavior of cross-linked polymer networks. We used a breakable quartic bond to model cross-linked polymers. We explored the structural characteristics and evaluated the coefficient of friction (CoF) as a function of cross-linked monomer fraction (cross-linking bond density) in 4-fold cross-linked polymer networks. To estimate the CoF, a rigid indenter was inserted to different depths of indentation. Subsequently, a constant sliding speed was applied, while keeping the depths of indentation fixed. Normal and friction forces were calculated at each depth to estimate CoF through linear curve fitting. For adhesion studies, using the force versus displacement curve, we quantified adhesion through the forces during the separation of the rigid indenter from surface of cross-linked polymeric materials while unloading after indentation into the sample. The results indicate that as the fraction of cross-linked monomers increases, the stiffness of the cross-linked network increases while the force of adhesion and CoF decrease. Additionally, increasing the depth of indentation during friction leads to higher frictional forces.

Accurately predicting human perception of tactile roughness remains challenging because previous models often used limited mechanical properties, small sample sizes, and insufficient validation methods. To address these limitations, we developed a predictive model integrating multidimensional mechanical properties and subjective evaluations of tactile perception, using 50 commercially available synthetic fiber samples, including polyester, spandex, nylon, and their blends. Twelve mechanical properties were measured across four categories: geometric roughness, frictional force, hardness, and tensile strength. Tactile perception of smoothness/roughness was evaluated by 37 participants using a 5-point scale, with lower values indicating smoother textures and higher values indicating rougher textures. Correlation analysis identified kinetic friction coefficient (KF, ρ = -0.67), arithmetic mean roughness (Ra, ρ = 0.44), mean width of profile elements (RSm, ρ = 0.42), maximum load (ML, ρ = -0.41), and root mean square slope (Rdq, ρ = 0.31) as key predictors. Among six regression models, Gaussian process regression showed the highest predictive accuracy (cross-validated R2 = 0.71). Comparisons between non-cross-validated and cross-validated results revealed substantial performance drops in cross-validation, underscoring the risk of performance overestimation without rigorous validation. The proposed framework provides a robust, generalizable approach applicable to broader tactile dimensions, benefiting material evaluation, product development, and haptic technologies.

The dynamical friction force acting on a spatially extended probe (globular clusters and dwarf galaxies) moving in the environment of ultralight bosonic dark matter in the state of the Bose–Einstein condensate is determined. Modelling the probe as a r sphere of radius lp, the radial and tangential components of the dynamic friction force are found in an analytic form, which reduces in the limit lp → 0 to the corresponding analytic expressions obtained in the literature in the case of a point probe. The dependence of dynamical friction force on boson particle mass was analyzed and found to be non-monotonous in the interval 10−23÷10−21 eV.

The processing of bulk amorphous alloys is typically realized through superplastic deformation in the supercooled liquid region, and current research efforts predominantly focus on enhancing formability by optimizing processing parameters such as temperature and duration. However, excessive temperatures or prolonged exposure times can induce crystallization, which severely compromises the mechanical and functional properties of the alloy. This study presents the design of an ultrasonic vibration (UV)-assisted metal hot-forming apparatus that integrates an ultrasonic vibration field into the superplastic flow deformation of amorphous alloys. High-temperature compression experiments were conducted on Zr55Cu30Al10Ni5 amorphous alloy, and finite element simulations were performed to model the experimental process. Results show that ultrasonic vibration reduces the flow stress of the amorphous alloy, thereby enhancing its superplastic deformation capability. Simulation analysis reveals that surface effects arise from periodic interface separation between the pressure plate and the specimen caused by ultrasonic vibration, leading to a cyclic disappearance of friction forces, which manifest macroscopically as a reduction in effective friction. On the other hand, vibration introduces additional strain rates. Since the undercooled liquid of amorphous alloys exhibits non-Newtonian fluid behavior characterized by shear-thinning, ultrasonic vibration assistance can effectively reduce the apparent viscosity, thereby improving their filling capacity.