Mechanika (ISSN: 1392-1207, eISSN: 2029-6983) journal publishes theoretical and practice oriented papers, dealing with problems of Mechanics of Solid Bodies, Mechanics of Fluids and Gases, Dynamics of Mechanical Systems, Design and Optimization of Mechanical Systems, Mechanical Technologies. Impact Factor: 0.7 (2024); 5 Year Impact Factor - 0.7 (2024) according to Journal Citation Reports (Clarivate, 2025).
Application of Worm Optimization Algorithm to Design Challenges: A Focus on Pressure Springs
Meta-heuristic algorithms are approximate algorithms that are used in situations where traditional optimization techniques cannot achieve acceptable results. Specifically, they are widely used to achieve optimum design of machine elements. Designing springs according to minimum weight or volume is one of the most basic problems in this field. In this study, a bio-inspired meta-heuristic Worm Optimization Algorithm (WOA) inspired by the contribution of worms to nature was used to solve the problem. The results obtained were compared with those obtained by other algorithms and it was seen that similar data was obtained recently. As a result, it was determined that this algorithm can be used for optimum design of mechanical structures.
DESIGN AND OPTIMIZATION OF MECHANICAL SYSTEMS
Copyright (c) 2025 Mechanics https://creativecommons.org/licenses/by/4.0/
Research on Many-Objective Scheduling Optimization Method for the Large-Scale Hybrid System
For the many-objective collaborative optimization problem of high performance alloy casting manufacturing process, how to achieve high efficiency, low energy consumption and intelligent scheduling process is an urgent problem to be solved. Firstly, a multi-objective pro-duction scheduling model of the whole process was established according to the production characteristics, process flow and production constraints. Meanwhile, a new high-dimensional multi-objective strong dominant optimization algorithm was proposed to solve the production scheduling model of high-performance alloy melting casting production line. The proposed algorithm is designed by combining strong domination algorithm and large neighborhood search algorithm. The proposed algorithm method implements deep exploration of solution space through cyclic destruction-repair operation. Its dynamic neighborhood characteristics can effectively escape the local optimal. Based on the industrial data set of alloy casting production line, the performance of the model and the proposed algorithm are tested. Experimental results substantiate the effectiveness and comparative advantages of the many-objective scheduling model and the proposed algorithm method.
Design and Parametric Study of Lightweight Aluminium Alloy Bumper Beams for Enhanced Crashworthiness Using the Finite Element Method
The study focuses on improving the performance and efficiency of a vehicle bumper beam by addressing limitations in the baseline design, which uses Steel 350MC material with a thickness of 3 mm. The baseline design, though robust, is bulky, absorbs limited crushing energy during high-speed impacts, and contributes to reduced fuel efficiency due to its heavy weight. To address these challenges, a three-point bending test was employed to evaluate stiffness and energy absorption characteristics at the component level. Based on numerical simulations, three novel bumper beam designs were developed using aluminum alloy materials to achieve weight reduction while maintaining performance. Design of Experiments (DOE) was utilized to validate these designs through iterative three-point bending tests, identifying the optimal configuration using AA6056 material. The optimized bumper beam demonstrated a 61.29% reduction in mass, an 8.8% improvement in energy absorption, and no compromise in stiffness compared to the baseline. Furthermore, the optimized design was validated in a slow-speed RCAR (Research Council for Automobile Repairs) numerical simulation to ensure compliance with crashworthiness standards. Results confirmed the optimized bumper beam meets RCAR requirements, highlighting its suitability for real-world application. This research provides automakers with a lightweight, high-performance bumper beam design that enhances crashworthiness, reduces vehicle mass, and improves fuel efficiency, contributing to sustainable automotive innovation.
Research on Efficient Dynamics Simulation Technology for Artillery Equipment
In response to the efficiency bottleneck in the overall design phase of artillery, this paper proposes an agile design tool for artillery based on the RecurDyn solver, IAOD. This tool achieves rapid evaluation and optimization design of artillery dynamics simulation models through parametric modeling and integration of shooting test data. The IAOD system adopts a fully parameterized driven template model, combined with machine learning, parameter identification, and multi-level optimization algorithms, significantly improving the design efficiency of large caliber self-propelled artillery. The system innovatively applied a sparse single hidden layer neural network proxy model and a simulation parameter identification method based on test data, achieving multi-objective collaborative optimization. The effectiveness and practicality of the IAOD system have been verified through the practical application of a vehicle mounted artillery design case, demonstrating its potential for application in the field of artillery design. This study has significant military and defense value in improving the efficiency and quality of artillery equipment development.
Analysis of Material Optimization and Performance Parameter Difference of Expandable Sand Screen
Sand control technology of expansion sand screen is one of the effective methods to solve the sand problem in oil wells, due to its unique working mode, which has significant benefits in improving production and reducing costs, and has been widely used in the oilfield field. However, the operational conditions that expansion sand screens are subjected to, such as high temperatures, high pressure and high corrosion, exert greater demands on the material performance of the expansion sand screens. The advancement of this technology is predominantly constrained by the intrinsic characteristics of the material in question. In this study, five materials were selected as the base tube materials of the expansion sand screen, namely stainless steel 654SMo, stainless steel Incoloy 27-7Mo, stainless steel 2507, stainless steel Incoloy 625 and stainless steel 316L. These materials were chosen based on their performance requirements in relation to the expansion sand screen. The impact of diverse materials on the expansion performance of base tubes was investigated through a multifaceted approach, integrating tensile experiments, prototype expansion experiments, and finite element analysis. The experimental results demonstrate that stainless steel 316L is a more suitable base tube material under the condition of relatively low requirements for temperature and corrosive environment. Conversely, stainless steel Incoloy 27-7Mo is a more suitable base tube material in more demanding deep well environments. Finally, stainless steel Incoloy 625 is a more suitable base tube material for working conditions with higher requirements for corrosion resistance and mechanical properties. A comparison of the results of the finite element analysis with those of the prototype expansion experiment indicates that the volume percentage of the high stress region is a useful indicator of the expansibility of the base tube to a certain extent. The findings of this study provide a novel evaluation metric for the optimisation of parameters and the selection of materials for expandable sand screen. This has the potential to reduce costs and time during the research process.
Multi-Objective Optimization and Design of Hydraulic and Hemolysis Performance of Micro-Axial Heart Pump
In order to optimize the hydraulic performance of the heart pump and reduce blood damage, the effects of the main structural parameters on efficiency, head and hemolysis values was studied by CFD, outlet impeller diameter, inlet impeller blade angles, outlet impeller blade angles and blade thickness were selected as design variables using OFSD method, the efficiency, head, and hemolytic performance of the pump were taken as objective functions, the response surface method is used to fit the multivariate regression model of design variables and objective functions. Finally, the multi-objective optimization is carried out with NSGA-II genetic algorithm, one of the qualified structural parameter combinations was selected according to actual needs as the final solution of the optimization. The outlet impeller blade angles is β2=30°, the outlet impeller diameter is D2 =20 mm, the outlet impeller blade angles is β1=12.5°, and the blade thickness is δ = 1 mm. Efficiency is 74.5% , head is 96.3 mmHg, the hemolytic value is 0.0172 g/100L. The study results can provide a reference for the structural optimization of heart pumps.
Effect of Dimensions in Laser Surface Texturing on Cutting Tools
A significant part of the costs the companies that produce with the machining method is the cost of the cutting tool. The high cost and the continuous increase in the competition in the sector have pushed the companies operating in this field to work to extend the life of cutting tools. In this study, laser patterning was applied to the surfaces of silicon nitride-based cutting tools, and the most ideal combination was determined by changing the dimensions of the patterning. Before the laser patterning process, an experimental design was created using the Taguchi method and the L9 orthogonal array. The experiments were carried out on a Doosan Puma V550 turning machine, and the chip removal process was carried out dry. Material conforming to the GG25 standard is processed on the turning machine. In the experiments, the widths of the patterns, the spaces between the patterns, and the angles between the lines of the patterns were varied. The wear number of the cutting tools was observed using an Axio Zoom V16 microscope. After all these examinations, the data were collected and the results were compared using the signal-to-noise ratio method. With this comparison, it was seen that the most efficient pattern was 20 μm-300 μm-30°. In addition, it was determined that the most influential factor on cutting tool performance was the angle of the patterns.
Investigation of Robotic System Parameters for 3D Scanning Human Limbs
This paper presents the investigation of motion speed effect on scan accuracy and in turn, automation benefits for a semi-automated 3D human limb scanning system. The robot arm ABB IRB 1200 was used in combination with HandyScan 700 handheld scanner to scan a human hand replica, achieving average noise of 0.0277 mm. It was found that for each resolution setting of a scanner, there is an ideal motion speed that maximizes accuracy. In this case, resolutions of 0.2, 0.6, 1.0 and 2.0 mm were tested at max toolhead speeds 100, 300, 500, 800, 1000, 1500 and 3000 mm/s, where minimal standard deviation values were found at 100, 300, 500, 1000 mm/s speeds for each resolution respectively. Further development is needed in order to adapt such a system for real human limb scanning, such as longer robot reach, human safety measures, improved supports.
Failure Analysis of Deep-Drawn Single Piece Pressure Vessels
This study presents a comprehensive failure analysis of fully deep-drawn, thin-walled pressure vessels used in fire extinguisher applications, focusing on the effects of deep drawing and welding processes. Hydrostatic burst pressure testing, tensile and microhardness measurements, microstructural evaluations, and coupled thermomechanical finite element analysis (FEA) were performed to identify the root causes of failure and assess the influence of weld-induced residual stresses. The experimental results revealed that the weld heat-affected zone (HAZ), particularly at the curved head section of the vessel, exhibited reduced microhardness and structural integrity due to recrystallization and grain refinement. Hydrostatic testing confirmed that failure typically initiated in this thinned, weld-affected region, where residual tensile stresses were also found to be concentrated. Numerical simulations further substantiated the experimental observations. Thermal-mechanical FEA demonstrated the presence of tensile residual stresses in the HAZ and identified stress concentrations aligned with experimentally observed crack zones. A two-stage FEA approach, incorporating both thermal and structural analyses, was used to simulate weld heat input and internal pressure loading. The resulting stress distributions and crack propagation patterns, evaluated using a semi-elliptical crack model, revealed that Mode I crack opening was dominant, especially at the head section. Comparative analysis of critical stress intensity factors between the shell and head sections showed that the head region had a significantly lower threshold, explaining its susceptibility to catastrophic fracture. The numerical predictions showed strong correlation with experimental hydrostatic burst test results, validating the use of FEA in predicting failure mechanisms in deep-drawn welded vessels. Overall, the study highlights the critical role of weld-induced residual stresses and geometric thinning in determining failure zones in pressure vessels. The integration of experimental and numerical techniques offers a robust framework for evaluating structural integrity and improving the safety of welded deep-drawn pressure vessels in industrial applications.
Motion Control of AUV Vertical Plane Based on RBF Neural Network Backstepping Sliding Mode
Aiming at the vertical plane motion issue of autonomous underwater vehicle (AUV) with modeling uncertainty and external perturbation, a backstepping sliding mode control algorithm is proposed on the base of multiple radical basis function (RBF) neural networks. Firstly, the kinematics and dynamics equations of AUV are established. Secondly, according to the second method of Lyapunov, a robust sliding mode controller on the base of backstepping control algorithm is designed to eliminate the errors of states and improve the response speed. At the same time, multiple RBF networks are adopted to adaptively compensate for the uncertainty or nonlinear term in the AUV motion equation and external perturbation. Finally, the stability analysis for the AUV control system is given based upon the second method of Lyapunov. The simulation results demonstrate that: The presented controller can enable the AUV to reach the desired depth at a quick speed and high accuracy. In comparison to the traditional sliding mode controller, the given method possesses higher adaptability and better dynamics performance.
radical basis function neural network (RBFNN)
Vibration Characteristics Analysis of Rotor System with Permanent Magnet Drive Considering Misalignment and Unbalance
Misalignment and unbalance are two major mechanical faults in rotating machinery. In recent years, with the increasing application of permanent magnet coupling in rotating machinery, it is necessary to study the misalignment and unbalance of rotor system with permanent magnet drive. In this paper, the vibration characteristics of centrifugal pump rotor system driven by asynchronous disc permanent magnet coupling（ADPMC）considering misalignment and unbalance faults will be discussed. First, the three-dimensional models of ADPMC with axial and radial misalignments are established respectively, and the axial and radial unbalanced magnetic pull of ADPMC are solved. Second, the axial force of angular contact ball bearing and radial force of cylindrical roller bearing are calculated under different operating conditions. Further, the radial support stiffness of each bearing is obtained. Third, the modal analysis of rotor system driven by ADPMC is carried out to obtain the natural frequencies and modal shapes. Finally, the radial unbalanced magnetic pull of ADPMC and unbalanced force caused by mass eccentricity of impeller are taken as the excitation sources, and the harmonic response of rotor system are calculated. The results show that the axial misalignment of ADPMC will cause a larger unbalanced magnetic pull, and the radial misalignment of ADPMC will lead to a smaller unbalanced magnetic pull. When ADPMC has different misalignment faults, the natural frequencies of same modal order of rotor system are basically the same. In the vicinity of the operating frequency, the vibration displacement at two journal of the rotor system excited by dual excitation sources are both small. Therefore, large radial misalignment of ADPMC can be allowed in rotor system, and ADPMC has good vibration isolation characteristics between the driver shaft and the driven shaft. The results provide important engineering references for the application of ADPMC in rotating machinery.
Experimental Investigation of Suspended Water, Ethanol and Acetone Droplets Transient Phase Change Regimes in the Heated Airflow
This paper presents an experimental investigation into the use of water, ethanol, and acetone using the suspended droplet method. The influence of atmospheric air temperatures on droplets in the transient phase change is analysed. Experimental results are presented, including thermograms that characterise the droplet's thermal state and diameter monograms that define the variation in droplet size. These data are processed according to the droplet liquid volume change rate parameter. The experimental results confirm that the airflow temperature leads to intensified heat exchange and phase change processes during the droplet transition stages, resulting in the droplet's heating to a higher thermal equilibrium evaporation state. For all the fluids studied, the impact of airflow temperature on the droplet temperature and liquid volume change rate of different liquids is qualitatively similar. Still, the strength of the influence varies depending on the nature and properties of the liquid. In heated air up to 50 °C, the droplet equilibrium temperatures are approximately 8.5 °C for acetone, 22.2 °C for ethanol and 28.3 °C for water. In 100 °C air, these values become approximately 17.8 °C, 32.3 °C and 43.4 °C, respectively. The estimated volume change in the liquid droplet's size shows that acetone, which has the most volatile properties and lowest boiling temperature, evaporates most intensely from the liquids tested in the initial stage.
Mechanical Behaviour Analysis of Bio-Inspired Joints with Notched Flexure Hinges
This study derives the analytical calculation formula for the output compliance of a notched flexure hinge-based bio-inspired joint linkage mechanism in flexible gripping mechanism. Finite element analysis (FEA) was conducted to investigate the compliance characteristics of three distinct notch-type 3-RRR flexible link. The correctness of the analytical solution was validated by comparing it with the finite element solution. Further investigation into the influence of structural parameters on the performance characteristics of 3-RRR flexible link was conducted, establishing correlation curves between geometric parameters and both compliance and stress-strain characteristics. Through comprehensive comparison, the notch configuration demonstrating optimal overall performance in 3-RRR flexible link was identified.
Research on the Rotational Accuracy of Aerostatic Spindle Under Variable Load Conditions
This study aimed to study the influence of variable load conditions on the rotational accuracy of the aerostatic spindle. The dynamic model of aerostatic spindle was established considering the gravity of the spindle, nonlinear air film force, and external applied loads. By solving the dynamic model, the motion trajectory of the spindle axis was obtained. Finally, a quantitative explanation was provided for the rotational accuracy laws of the aerostatic spindle. As the speed and eccentricity of the spindle increase, the vibration of the spindle in the x and y directions gradually increased, and the rotational accuracy of the spindle decreased. The periodic load of simulating cutting load was superimposed on the spindle, which increased the amplitude of spindle vibration and reduced the rotational accuracy of the spindle, but did not affect the balance position of the spindle. The impact load changed the balance position of the spindle without generating rotational errors.
Experimental Investigation on Fatigue Crack Propagation Under Mixed Mode Loading on Aluminum Alloy AA3033
The phenomenon of fatigue-crack propagation is a permanent concern for designers, manufactures and users in order to ensure the integrity of structures subjected to cyclical stresses during their operational service. The concept of damage tolerance (DT) is the most commonly used for the design of structures with the prediction of fatigue life crack propagation. Most researchers have focused on studying fatigue crack propagation under mode I loading conditions. However, these structures in service are often subject to complex constraints and combined stresses that can generate local loadings in mixed modes I, II and mode III. In this regard this paper presents a study of fatigue crack propagation in mixed mode (I+II) using CTS (compact-tension-Shear) specimens for three loading angles (45°, 60°, and 90°) respectively. The mixed-mode fatigue crack propagation tests were carried out in modes I and II using the CTS specimen and Arcan loading device specially designed and constructed by our laboratory based on the Richards principle. The experimental results show that the loading angle has a significant effect on the crack growth rate and consequently on the fatigue life prediction of mechanical structure under fatigue loading.
Study of Air Volume Fraction in Water Flow: An Experimental Approach
The spillway system plays a crucial role in maintaining uniform flow conditions in open channel streams, ensuring consistent water levels according to the flow rate. However, the design of the spillway weir crest can lead to flow deviations and non-uniform velocity distributions, causing the formation of air bubbles in the water. This study investigates the impact of flow uniformity device length and spillway profiling on air entrainment in water flow. Various flow uniformity device lengths (100%, 50%, 25% and 12.5%) were modeled and tested in a laboratory setup. Water velocity was measured using an anemometer and air characteristics were studied using different spillway profiles, including concave surfaces, grooved surfaces and roughened surfaces. The air entrainment was assessed using a quick entrained air tester and water thickness was measured with ultrasonic sensors. Results showed that concave and punched surfaces produced the least air bubble formation. The 100% flow uniformity device resulted in consistent velocities, validated by analytical data. The study also verified that for a 600 mm uniformity device with 38.2% permeability, the flow remained laminar. The impedance probe method was used to accurately measure the volume fraction of air (VOF) in the water.
Predictive Maintenance of Rotating Machines, Application to the DHB Semolina Decorticator
Real industrial machinery is never perfect. We encounter manufacturing defects, operating clearances, and more effects and parameters: temperature, rotation speeds, etc. The analysis of vibration is to provide information on the condition of equipment in order to ensure the planning of operations of maintenance. This study examines condition-monitoring strategies for Semolina Decorticator DH 201.This machine exhibits several simultaneous mechanical faults. including imbalance rupture. bearing defects. and wear. Experimental and numerical results for the detection and identification of numerous faults that may occur in various mechanical components are presented. To achieve this. various fault indicators are detected or calculated using a vibrational analysis method. We programmed the vibration of measurement points using vibration analysis software. Subsequently. vibration measurements were conducted using a data collector. The results of theoretical simulations were compared with experimental measurements to determine the severity of mechanical faults and establish an appropriate vibrational prognosis. This work is enriched by the proposed technological solution and potential tests.
Effect of Surface Thermoelastic Deformation on the Performance of the Hydrodynamic Big-Size Step Bearing
The multiscale lubrication analysis is presented for estimating the performance of the hydrodynamic big-size step bearing by incorporating the effects of the surface thermoelastic deformation and the lubricant molecule layers physically adsorbed to the bearing surface. The numerical calculation results show that in the condition of heavy loads and high sliding speeds, the effect of the surface thermoelastic deformation can reduce the minimum surface separation by 1 to 2 orders, while the effect of the physically adsorbed layer on the bearing surface significantly increases the minimum surface separation especially for the strong fluid-bearing surface interaction; The effect of the surface thermoelastic deformation largely modifies both the film pressure profile and the surface separation profile in the bearing; It also obviously changes the friction coefficient of the bearing. The effect of the physically adsorbed layer significantly influences the friction coefficient of the bearing only in the condition of heavy loads and high sliding speeds, which yields very low surface separations.
Study of Insert Flank Wear and Surface Roughness Evolutions During Turning of Stellite 6 Based on RSM and Desirability Approaches
In this research, turning experiments on Co-Cr-Mo, cobalt-based alloy Stellite 6 were carried out to examine the effect of four machining factors (tool tip radii, feed rate, cutting depth and cutting speed) on insert flank wear and surface roughness. On the basis of a design Taguchi plan (L18), the experiments were conducted. The response surface methodology (RSM) was employed to develop mathematical modelling of flank wear and surface roughness evolutions. The contribution of each individual parameter to process responses was assessed using ANOVA analysis. Predicted models in relationship with flank wear and surface roughness evolutions were obtained from the regression equation. These models show good correlations with experimental results. A maximum error of 13.82% and 10.90% of flank wear and surface roughness was observed between simulated and experimental results, respectively. The optimization of processing parameters was investigated in order to achieve both the minimum values of flank wear band and surface roughness.
Development and Research of the Laser Engraving Process in Packaging Manufacturing Technology
The areas of application of carbon dioxide lasers in the printing industry are given. A technological process for laser engraving of packaging made of wood-fiber materials has been developed. Experimental studies of the influence of the parameters of CO2 laser radiation on the engraving process of HDF material, which is widely used in the packaging industry, have been conducted. The dependence of the engraving depth on changes in the speed and power of laser radiation has been studied. Based on the experimental studies conducted, the main operating, technological and operational factors affecting the quality of engraving have been identified.
Investigation on Energy Output Performance of IPMC Optical-Controlled Composite Driving Based on PLZT Ceramic
Ionic polymer-metal composite (IPMC), as an intelligent material, exhibits advantages such as rapid responsiveness, large deformation angles, and high flexibility, leading to its extensive application in biomimetic machinery, biomedicine and other fields. In this paper, based on the previous proposed IPMC optical-controlled composite driving method under lanthanum-modified lead zirconate titanate (PLZT) ceramic configuration, the output energy characteristic is analyzed by establishing a novel model and conducting a series of experiments. The analysis and experimental results show that under different light intensities, the driving force and output deformation of IPMC with varying dimensions exhibit similar trends, both increasing gradually and reach a maximum value. Furthermore, the deformation curves of IPMC driven by light source are consistent with those driven by direct current, confirming that IPMC under light excitation also possesses stable and excellent energy output properties. Therefore, the research on the energy output of IPMC optical-controlled composite driving not only provides deeper theoretical guidance for its application in flexible driving area, but also promotes the vigorous development of IPMC in other innovative technological fields.
Combined Effects of Surface Adhering Layer and Surface Elastoplastic Deformation in Hydrodynamic Lubricated Line Contacts with Long-Chain-Molecule Fluids
In a line contact, when the surface separation is smaller than one hundred times of the thickness of the adsorbed boundary layer on the contact surface, the hydrodynamics should be considered as multiscale and consisting of both the adsorbed layer flows and the intermediate continuum fluid flow. However, for the fluids with long-chain molecules, there may be only one or several fluid molecule layers on the contact surface, which can be considered as a solid layer. The multiscale hydrodynamic film thickness was calculated for such fluids in the line contact which is respectively elastic or fully plastic under different loads. The results show that in the micro line contact with small equivalent curvature radii (R) such as on the 10 micrometer scale like the surface asperity contact, the adsorbed boundary layer has a very strong effect on the hydrodynamic behavior, while in the macro line contact such as with R on the 10 mm scale the adsorbed layer effect is eliminated and it is significant only for small rolling speeds or/and heavy loads.
A Comparative Study of Metaheuristic Optimization Approaches to Optimize Laser Welding Process Parameter with Pre-Set Weld Size Magnitude for AISI 416 and AISI 440 FSe Stainless Steels
Optimization methods are used to accurately predict laser welding process parameters, helping to save material effort and time in determining the desired output variables. Based on a mathematical model, parameter selection is considered a binding optimization problem. The work involved is closely related to evolutionary optimization algorithms. This article proposes highly effective meta-heuristic methods: the GA (Genetic Algorithm), the JAYA optimization algorithm, and the MDE (Modified Differential Evolution) algorithm, which optimize the parameters of the laser welding to achieve the desired size for the weld. The performance of these three methods is evaluated on laser welds for AISI 416 and AISI 440 FSe stainless steels. With the same initial conditions, the MDE algorithm outperforms the other algorithms, GA and JAYA algorithms, regarding the best fitness value after ten runs. Thus, the MDE algorithm is used to optimize three parameters: Laser Power (LP), Welding Speed (WS), and Fiber Diameter (FD) to achieve two desired welding dimensions: the Width of the Weld Zone (WWZ) and the Penetration Depth of the Weld (PDW) for laser welds.
AISI 416 and AISI 440 FSe stainless steels
Modified Differential Evolution (MDE) algorithm
Less Channel Hitting Measuring System for Table Tennis Monitoring
Sports play a crucial role in daily life, and precise monitoring of muscle states during sports is valuable for guiding training programs, preventing injuries, and detecting fouls. Despite significant advancements in monitoring technologies, there are still unexplored areas in detecting various sports actions and processing the associated data. In this study, we present a method to reduce communication channels in a table tennis racket sensor array and use the fabricated monitoring system to detect the player's status through signal analysis and machine learning algorithms. The system includes a flexible piezoelectric PVDF sensor array, Bluetooth chip, and battery. Unlike conventional designs that assign an individual communication channel to each sensor, this approach uses a single striped sensor on each row and column. By analyzing the axis of the sensor with signal, the hitting position and force are determined. After that, a kNN classification algorithm is built with the help of electromyography (EMG) test, aiming to assess the player's status based on their hitting input. The system effectively differentiates various player statuses with an accuracy exceeding 90%. The hardware innovation and signal processing techniques also have potential applications in other wearable sensing fields.
Real-Time Swing-up of a Linear Inverted Pendulum Using Reinforcement Learning
This study focused on applying and enhancing the Deep Deterministic Policy Gradient (DDPG) algorithm to effectively control a Single Inverted Pendulum (SIP) system. The primary objective was to improve the algorithm's performance by addressing common challenges such as overestimation of Q-values and convergence to local optima. The system's behaviour was analyzed through simulation and real-world experiments, showcasing the algorithm's ability to offer faster responses, enhanced stability, and reduced pendulum displacement. The research introduced key modifications to the experience replay mechanism and the Critic network, which played a significant role in improving the efficiency of the learning process and the robustness of the control strategy. By combining Reinforcement Learning with traditional control methods, this approach successfully managed the nonlinear dynamics of the SIP system. Nevertheless, certain challenges persist, particularly in terms of the efficiency of deep reinforcement learning algorithms and their stability in real-world environments. These findings suggest that future research should focus on further refining DRL algorithms to increase their practical application in physical control systems. In conclusion, the research highlights the potential of combining DRL techniques with conventional control strategies for tackling complex control problems. The success achieved in controlling the SIP system indicates a promising direction for further exploration and development in this field.
A Novel Principle Stress Model to Predict the Stress and Load in Sheet Drawing
The solution of stress and load of metal sheet deep drawing serves as a primary basis for guiding production, verifying strength of dies, and optimizing technology parameters. Based on the differential equations, boundary conditions, theory simplification and solution equations, an principle stress model (PSM) to predict the stress distribution and deformation load in drawing processes with a blank holder were proposed, and then the results were compared with the predicted value by finite element method (FEM) under the same conditions. Due to the thickness of the flange in deformation zone remains basically unchanged under the action of blank holder, it is reasonable to simplify the solution of deformation to plane strain problem. The PSM and FEM predict that the radial tensile stress and circumferential compressive stress in the flange zones remain basically consistent trends, and the relative error of most of predicted results is less than 5%. The influence of the die fillet bending on the stress state of inner and outer sides is not consider, leads to the calculated stress and load by PSM slightly higher than those of FEM. The solution of stress and load solution by PSM is reliable and convenient, and the FEM predicts more detailed and accurate results but need consume much larger calculating time. This research is of great significance for improving the solution efficient and engineering applications of plastic mechanics in sheet deep drawing deformation.
Mixed Elastohydrodynamic Lubrication in Micro Wedge-Platform Thrust Bearing Involving Adsorbed Layer
The film pressure and film thickness distributions, carried load and friction coefficient of the hydrodynamic lubricated micro wedge-platform thrust bearing were numerically calculated when the effects of the surface roughness, the surface elastic deformation and the physically adsorbed layer on the bearing surface were incorporated. The bearing clearance is so small that the effect of the adsorbed layer is significant but in the whole lubricated area there is the continuum fluid film. The flow in the bearing is multiscale and the solution is sought from the multiscale approach. The obtained results show that for the given load, sliding speed and surface roughness, the surface elastic deformation modifies both the film pressure and film thickness distributions, it makes the total lubricating film thickness increased but reduces the maximum film pressure; For the given minimum bearing clearance and sliding speed, the increase of the surface roughness increases both the film pressure and carried load of the bearing but the surface elastic deformation reduces this surface roughness effect especially when the fluid-bearing surface interaction is strong; The surface elastic deformation, the increase of the surface roughness and the increase of the interaction strength between the fluid and the bearing surface all result in the reduction of the friction coefficient of the bearing.
Failure Analysis and Optimization of Crosshead-Cylinder Hole Tribo-Pair in a Reciprocating Plunger Pump
In this paper, the failure of the crosshead-cylinder hole tribo-pairs in a reciprocating pump is reported. The crank-connecting rod-crosshead mechanism was analyzed to obtain the velocity of the crosshead. The material, hardness, and roughness of the new crosshead and cylinder holes were determined. Macroscopic observations, material properties and roughness analyses, scanning electron microscopy (SEM) analyses, energy dispersive spectrometry (EDS) analyses, and lubricating oil quality analysis were conducted to clarify the potential reasons for the failure of the crosshead-cylinder hole tribo-pairs. Lubrication oil degradation is likely to cause the failure of the crosshead-cylinder hole tribo-pairs. The effects of the oil supply system design and surface roughness on the anti-wear behaviors of the crosshead-cylinder hole tribo-pairs are discussed.
Optimization of Static Three-Dimensional Stiffness of Non-Pneumatic Tire with Composite Spokes Based on Response Surface Method
This study aimed to investigate the relationship between the static stiffness of non-pneumatic tires (NPTs) and the design parameters of composites spokes and shear bands using the finite element (FE) method. The stress–strain curve of the rubber material was fitted using the neo-Hookean constitutive model. Subsequently, key design parameters, including the reinforcement plate thickness and constitutive parameters of the spoke and shear band materials, were selected based on the NPT structure. FE simulations were performed on multiple sets of different parameter design schemes for the NPTs, and polynomial models for the vertical, lateral, and longitudinal stiffnesses were established using response surface analysis. The sensitivity analysis results indicated that the thickness of the reinforcement plate significantly influenced the three-dimensional stiffness, whereas the constitutive parameters of the spoke and shear band materials had a relatively minor impact. Finally, multi-objective optimization was employed to determine a design scheme with maximum longitudinal stiffness while ensuring vertical load-bearing capacity. Under the premise of ensuring the vertical load-bearing capacity, the longitudinal stiffness increased by 39.1% and 32.9% in the forward and backward directions, respectively. This method can be used to predict the three-dimensional stiffness of NPTs under different design parameter schemes or to optimize the setting parameters of NPTs based on the desired target stiffness, facilitating the rapid design of the three-dimensional stiffness of NPTs.
Development and Research of Technologies and Methods of Electro-flocking in the Decoration of Packaging Products
The aim of this work is to analyze the modern electroflocking technology and to develop a new method for printing a color image on white flocked material. For packaging material, High Density Fiberboard (HDF) with a 3 mm thick white painted coating was chosen. Printing was carried out using DTI InkTec sublimation inks on an Epson L132 inkjet printer, followed by image transfer in an Amazon MAX 400C heat press. The image was applied to a 0.5 mm thick SEF FiberPlus thermal transfer sublimation flock film, which contains exclusive polyester microfibers and 100% polyurethane resins. Cutting of the packaging components was performed using a TS1390 CO2 laser cutting machine with a wavelength of 10.6 µm. Image quality was evaluated using operational control scales. Microscopic photographs were taken at 60x magnification. Image fixation in the heat press was done using the following parameters: transfer temperature 170°C, transfer time 40 seconds, and pressure 3.0 bar. As shown by microscopic studies, the reason for the reduced optical density of the printed image with sublimation inks on flocked film is its high porosity. Therefore, to enhance the decorative effect and give the packaging an attractive velvety appearance, it is advisable to use a combination of printing on flocked material with cutting out several differently shaped and colored images from the flocked material.