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).
The copyright for the articles in this journal is retained by the author(s) with the first publication right granted to the journal. The journal is licensed under the Creative Commons Attribution License 4.0 (CC BY 4.0).
Effect of Suction and Injection on the Time-Varying Flow Produced by an Oscillating Porous Disk and a Newtonian Fluid at Infinity Rotating about Parallel Axes
In this paper, the time-dependent flow of a Newtonian fluid generated by a porous disk performing oscillation without torsion and the fluid at infinity rotating about two different axes is considered. As the disk and the fluid at infinity are rotating in an eccentric form at the beginning of the oscillation motion, the disk initiates oscillations without torsion within its own plane. The exact solutions for the velocity and shear stresses within the fluid are presented and the influences of the suction and injection are analysed. It is observed that the application of suction leads to a decrease in the boundary layer thickness whereas it increases with the implementation of injection. Furthermore, a periodic solution is presented and it is shown that the elapsed time until the flow becomes periodic occurs shorter for both suction and injection cases.
Copyright (c) 2026 Mechanics https://creativecommons.org/licenses/by/4.0/
Study on the Rehabilitation Performance of 2-SPS-RRR Adjustable Hip Exoskeleton
Based on computer-aided ergonomics the paper proposes a hip joint rehabilitation exoskeleton utilizing a adjustable spherical parallel mechanism, specifically designed for rehabilitation training of individuals with impaired hip joint movement function. Initially, the screw theory is employed to determine the degrees of freedom of the parallel mechanism, revealing that it possesses three rotational degrees of freedom, enabling sagittal plane movements, frontal plane movements and transverse plane movements at the hip joint. The closed vector method is utilized to derive the inverse position solution, and the velocity Jacobian matrix is solved. Leveraging the inverse position solution and the constraint relationships between mechanisms, the reachable workspace of the mechanism is obtained using MATLAB software programming. Utilizing screw theory and velocity Jacobian matrix, the dexterity of the mechanism is analyzed. Ultimately, a human-robot integrated system is established in AnyBody software to verify its capability to achieve certain rehabilitation effects on human muscle groups. Research demonstrated that the hip joint parallel mechanism exhibits good stability and can effectively assist individuals with hip joint dysfunction in rehabilitation training.
Automated Temperature Control System for a Multi-Point Airflow Channel Using PID and MPC Controllers
This study compares MPC with PI and PID controllers for temperature control. While PI and PID are effective for simple and stable systems, MPC shows better performance in complex and dynamic conditions. Laboratory experiments confirm that MPC handles disturbances, airflow variations, and setpoint changes more accurately, with improved stability and reduced overshoot. The results highlight MPC as a more efficient and reliable solution for advanced temperature control applications, with strong potential for use in larger industrial systems.
DESIGN AND OPTIMIZATION OF MECHANICAL SYSTEMS
Research on Error Compensation of CNC Machine Tool Based on Multibody System Kinematics
This paper focuses on the error compensation of CNC machine tools based on the theory of multibody system kinematics. By abstracting the structure CNC machine tools into a multibody system composed of motion pairs and components, a complete spatial error model from driving input to tool execution is constructed using homogeneous coordinate transformation matrix which deeply reveals the generation, transmission, accumulation and coupling mechanism of various geometric errors. The article describes in detail the establishment of coordinate system in multibody system, the homogeneous coordinate method of points and vectors, and the process of constructing the zero-order kinematic equation, and on this basis, the general geometric error model with dual branches of "workpiece- tool" and "tool-machine tool" is established, and the mathematical expressions of position error and attitude error are derived, and the error compensation condition equation for realizing precision machining proposed. In the experimental verification, Renishaw ML10 dual-frequency laser interferometer is used to measure and compensate the error of Z-axis of VMC-500 CNC machine, the results show that the variance of error after compensation is significantly reduced from 6.4534 and 5.8352 before compensation to 3.61, the error fluctuation range is significantly narrowed, and the effectiveness and engineering applicability of the proposed model and compensation method are verified. The research provides systematic theoretical support and path for the precision improvement of CNC machine tools.
Optimization Design Method of High-Speed Angular Contact Ball Bearings
With the rapid development of high-speed rotating equipment technology, angular contact ball bearings (ACBBs) have been increasingly widely applied in industry. However, there is still a lack of systematic design theory support for their service performance under high-speed operating conditions. In existing engineering practices, the design of ACBBs often focuses only on a single performance index, such as rated dynamic load, spin-roll ratio, or static stiffness, with little consideration of the dynamic behavior changes caused by the ball ‘outward-thrown’ under high-speed operation. To fill the above research gaps, this paper innovatively introduces dynamic stiffness as a key design index and proposes a comprehensive design method integrating spin-roll ratio and rated dynamic load. By establishing the kinematic model of balls in the raceway, the analytical relationship of the spin-roll ratio under high-speed steady-state conditions is derived; the applicability of different dynamic load rating calculation models is systematically compared, and a mathematical model of dynamic stiffness is constructed along with a numerical solution strategy. On this basis, the intrinsic laws governing the evolution of rated dynamic load, spin-roll ratio, and dynamic (static) stiffness with key design parameters are revealed. This study clarifies the coupling mechanism of key design parameters under high-speed conditions and establishes a parameter design strategy based on collaborative optimization. It provides a theoretical basis and methodological support for solving problems in engineering applications of high-speed ACBBs, such as inaccurate parameter selection and difficulty in ensuring dynamic performance. The research results help to further improve the design system of high-speed ACBBs and have important guiding significance for enhancing the design quality and service reliability of bearing products.
Copyright (c) 2025 Mechanics https://creativecommons.org/licenses/by/4.0/
Investigation of The Use of Biodiesel Produced from Waste Cooking Oil as Fuel for a CI Engine Under Different Operating Parameters
The environmentally responsible disposal of waste cooking oil is a significant concern for numerous nations. One method to repurpose waste cooking oil is to employ it as diesel fuel. This approach diminishes both the expense of fuel feedstocks and the ecological repercussions of waste cooking oil. In this study, the use of waste cooking oil as fuel was achieved by converting it into biodiesel thru the transesterification method. The negative thermos-physical properties of biodiesel, due to its high density and viscosity, have been improved by increasing the injector injection pressure. Furthermore, the optimal injection advance value for engine torque was established, and combustion properties were enhanced. The impact of varying injection pressures and timings of biodiesel on engine performance, combustion characteristics, and exhaust emission parameters was examined in a three-cylinder, naturally aspirated direct injection diesel engine. Consequently, increasing both injection pressure and advance favorably affected combustion characteristics such as ignition delay, combustion duration, and the crank angle at which maximum pressure was achieved. Thanks to an increase in injection pressure, the specific fuel consumption improved by 6.74% and thermal efficiency by 10.14% compared to using biodiesel into regular engine parameters. The impact of injection advance was more significant in the exhaust emission parameters. Extra reductions of 7.92%, 5.79%, and 3.14% were established for CO, HC, and smoke opacity emissions, respectively. Enhanced combustion efficiency, leading to elevated end of combustion temperatures, resulted in a rise of up to 15.66% in NOX emissions.
Composite Nanofiltration Membranes for Water Treatment: Implementation and Educational Issues
This paper implements a Case Study Analysis method within the Mechanical engineering masters’ course Module T210M109 Microelectromechanical Systems Design at Kaunas University of Technology. This method guides students through experimental planning, fabrication, characterization, and interpretation, leading to deeper understanding of membrane composition and its structure, and relationship between properties and real-world engineering application areas. The paper examines the implementation and educational issues in design of composite nanofiltration membranes used in removal of microplastics (MPs) and nanoplastics (NPs) from water. It highlights both, the scientific challenges of membrane fabrication and the pedagogical value of integrating Case Study Analysis into engineering. Thus, students demonstrated improved ability to make technical decisions, analyze the cases of different microfabrication techniques and interpret the obtained results with the help of Case Study method.
Study on the Creep Deformation Characteristics of the Cylindrical Tubes under External Pressure
Cylindrical tubes are fundamental structural components across many engineering fields, particularly for bearing external loads. In pressurized water reactors (PWR), the metal cladding tube acts as the first safety barrier, containing radioactive materials under extreme conditions of external pressure, high temperature, and intense fast neutron flux. Accurate prediction of its creep deformation remains a critical challenge in nuclear engineering. This study analyzes the coupled thermal and irradiation creep behavior of cladding tubes using the commercial finite element code ABAQUS and its user subroutine CREEP. The results demonstrate that creep deformation mode and magnitude are highly sensitive to geometric and mechanical factors. Specifically, longer axial lengths correlate positively with greater creep deformation, while increased wall thickness reduces it. Cladding tubes with length-to-diameter ratios exceeding 21 can be treated as infinitely long structures. Furthermore, relaxed boundary conditions have an effect equivalent to increasing the tube’s effective length, thereby amplifying creep deformation. These insights are important for evaluating cladding performance and structural safety under long-term creep deformation.
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.
The Research on Horizontal Motion Axis Control System Error Prediction of the Gantry-Type Vertical Machining Center
As the cornerstone of high-end equipment manufacturing industry, the GVM Center breaks through the limitations of traditional processing through intelligent control technology, and has become a core equipment to promote the upgrading of precision manufacturing, which plays an irreplaceable role in enhancing the competitiveness of national high-end manufacturing. However, in the actual machining process of the GVM Center, due to the superposition of various factors, it is inevitable to produce complex machining errors. In order further improve the machining quality of the GVM Center, it is necessary to carry out error compensation technology research. HMM, as an important content in the field pattern recognition, has further developed its application scope with the rapid change of information data in recent years. Based on the data characteristics of HMM, the research on error compensation of the GVM Center is an innovative attempt. This research combines the theory of HMM dual stochastic process, deeply analyzes the motion error form of the horizontal moving axis X Y axis of the GVM Center, integrates the error lookahead prediction idea, describes the basic theory of HMM in detail, and embeds it into the g vertical machining center. It constructs a control error compensation model based on HMM, and analyzes the specific steps of HMM to implement error compensation. Based on the actualizing content, the error compensation effect of HMM with different training data is compared and analyzed, and the effectiveness of the research content is proved through data analysis before and after error. The research results provide theoretical support and engineering examples for the intelligent error control of high-precision CNC machine tools, and have important application value in the fields of aerospace-wall parts and precision mold processing.
Influence of Pressure Angle on the Dynamic Characteristics of Asymmetric Helical Gear Transmissions
To address the lack of research on the dynamic characteristics of asymmetric helical gears, this study systematically investigates their time-varying meshing stiffness and meshing impact characteristics based on the lumped-parameter method and nonlinear dynamic theory. An eight-degree-of-freedom dimensionless dynamic model is developed. Using the pressure angle on the driving side as the main variable, the dynamic characteristics of asymmetric and symmetric helical gears are compared, and the effects of different pressure angles on time-varying meshing stiffness, time histories, phase portraits, and Poincaré maps are analyzed. The results show that the asymmetric helical gear exhibits higher average meshing stiffness, smaller vibration amplitudes, and smoother responses than the symmetric gear. Within a driving-side pressure angle range of 30 to 35 degrees, the system achieves the best stability and periodicity, and the meshing impact amplitude is effectively suppressed. However, excessively small or large pressure angles lead to reduced system stability. This work clarifies the dynamic behavior of asymmetric helical gears and provides a theoretical basis for parameter design and high-performance transmission optimization.
Fail-Safe Mass Reduction of a Heavy-Duty Front Axle Using Topology Optimisation
A Topology Optimization and Design of Experiments (DoE) based mass reduction process for the rigid front axle of an in-use heavy commercial vehicle is summarized. Finite Element (FE) analyses were performed to determine the stress concentration regions of the axle beam for different loading conditions. Then, topology optimization was used to determine the regions where mass reduction is possible under critical loading condition. According to the results of the analyses, design parameters for the form and location of the holes were determined. A parametric study was carried out on the axle beam using the DoE-Response Surface Methodology (RSM) approach. The failure potential of these holes was evaluated with the help of Goodman-Haigh diagram. The results showed that the total mass can be reduced by 14.2% without creating a new failure mode. Considering the annual production capacity of the axle studied, it is seen that approximately 8,000 additional axle beams can be produced using the same amount of material.
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.
Research on Dynamic Load Identification Based on the Newmark-β Method and Novel Iterative Regularization Strategy
This work focuses on the dynamic load identification motivated by Newmark-β Method and regularization strategy. Given the ill-posed nature of load identification, an improved hybrid LSQR regularization strategy is proposed, which incorporates an adaptive correction mechanism by iteratively comparing the computed response with the measured response. For load identification problems with prior conditions, an augmented hybrid LSQR regularization strategy is further developed, which expands the Krylov subspace with prior information and combines the improved hybrid LSQR regularization strategies to ensure stable iteration. Simulation examples using a simply supported beam as a representative structure of continuous systems, involving different load types and noise levels, validate the stability and accuracy of the two methods. The results show that the improved hybrid LSQR algorithm exhibits superior stability and accuracy compared to the conventional LSQR algorithm and yields relatively favorable identification results. Moreover, the superposition load identification simulation indicates that the augmented hybrid LSQR algorithm further improves the accuracy of load identification when prior knowledge of the load is available.
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.
A Novel Fault Diagnosis Method for Rolling Bearings Based on ELTSA and CGWO-WGKELM
Fault diagnosis method for rolling bearings by using entropy-weighted distance-based local tangent space alignment and Weighted Gaussian Kernel extreme learning machine with Circle chaotic mapping-based grey wolf optimization (ELTSA-CGWGKELM) is presented in this paper. This study introduces two innovative methodologies for rolling bearing fault diagnosis. First, an entropy-weighted distance-based local tangent space alignment (ELTSA) technique is developed to address feature dimensionality reduction in rolling bearing data. This approach effectively resolves limitations associated with conventional Euclidean distance measurement while significantly enhancing critical data information preservation capabilities. Secondly, a weighted Gaussian kernel extreme learning machine optimized through circle chaotic mapping-enhanced grey wolf optimization (CGWGKELM) is proposed for fault classification. The Gaussian kernel implementation substantially improves nonlinear processing performance and robustness compared to traditional weighted ELM architectures. The circle chaotic mapping strategy integrated into the grey wolf optimization algorithm (CGWO) enables superior optimization of the weighted Gaussian kernel ELM training parameters, ensuring enhanced global search capability and convergence efficiency. The experimental results indicate the following fault diagnosis accuracy rates for rolling bearings: ELTSA-CGWGKELM achieves 99.5%, LTSA-WGKELM attains 95.5%, LTSA-ELM reaches 94%, and PCA-ELM attains 92%.It can be seen that ELTSA-CGWGKELM is the better fault diagnosis ability for rolling bearings than LTSA-WGKELM, LTSA-WGKELM, and PCA-ELM.
Research on Error Characteristics Analysis and Error Compensation Methods for High-Precision Angular Measurement Turntables
To address the issues of low calibration accuracy, complex system structure, and cumbersome detection processes in traditional angular measurement equipment, this study proposes an innovative Opto-Mechanical coupled high-precision angular measurement turntable solution based on the principle of reciprocal angular displacement measurement. By systematically analyzing the structural characteristics and error distribution patterns of the turntable, a comprehensive error mathematical model based on relative pose matrices was established, enabling quantitative characterization of the error characteristics in the high-precision angular measurement turntable system. The three-point reverse decoupling algorithm, combined with a systematic continuous error compensation strategy, effectively suppresses installation errors of the components under test on the turntable. Furthermore, by optimizing BP neural network parameters using an improved particle swarm optimization algorithm, the system's error compensation performance was significantly enhanced. Experimental results demonstrate that the compensated system achieves a calibration accuracy of 0.38″, meeting the sub-arcsecond precision calibration requirement. The post-compensation overall error distribution remains within ±0.5″, and the reliability and accuracy of the turntable system were thoroughly validated through multiple comparative experiments. This study provides a novel technical approach for high-precision angular measurement.
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.
The Effect of the Radius of Curvature on the Joint Strength in Butt-Curved Lap Joints
In this research, butt curved lap joints (BCLJs) were considered for the aluminum alloy plates exposed to tensile load, and the effect of the radius of curvature (RC) on the joint strength was investigated. For this purpose, butt-curved v joints were formed upon aluminum plates (AL2024-T3), and they were connected using an adhesive (DP810). Finite element analysis joint models were created three-dimensionally, and Cohesive Zone Materials Models (CHZMs) based on energy principles were used to estimate the strength of the adhesively bonded joint. In order to obtain numerical solutions, the parameters of the materials used in the joint model were determined experimentally. Furthermore, verification tests were performed to verify the numerical solutions. From the results obtained, it was understood that the radius of curvature has a important effect on the failure load and stress distributions in butt curved lap joints.
Numerical Simulation of a Binary Fluid Behavior Subjected to the Coupling Between Natural Convection and Thermodiffusion in a Partially Wavy Cavity
The current numerical study aims to analyze the hydrodynamic, thermal, and mass transport behavior of a binary fluid under natural thermal convection and thermodiffusion within a modified horizontal rectangular cavity. The cavity is heated either from the bottom or the top, with isothermal, impermeable, and partially wavy horizontal walls. The simulation is based on the finite element method applied to the differential equations governing the coupling of natural convection and thermodiffusion. The results reveal that partial wall undulations significantly affect the binary fluid flow, leading to species migration toward the perfectly insulated vertical walls. The numerical analysis of the mass field of the studied fluid clearly indicates that the lateral species separation intensifies with bottom heating, increased undulated length, and greater wave amplitude. These geometrical parameters also significantly impact heat transfer, as characterized by the Nusselt number.
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.
Effect of Adsorbed Layer on Methane Flow in Silicon Nano Slits for Different Channel Heights
The pressure-driven flow of methane in silicon nano slits is analytically studied by using Zhang’s multiscale scheme for the wide channel heights ranging between 8.6nm and 1444 nm when there is the intermediate (continuum or quasi-continuum) fluid film between the two adsorbed layers and no wall slippage occurs. The values of the characteristic parameters of the adsorbed layer required by Zhang’s approach was found from molecular dynamics simulation, and they are considered as independent on the channel height. According to the calculation results, the adsorbed layer encumbers the flow in the whole channel especially for the low channel heights which give the ratio of the thickness (hbf) of the adsorbed layer to the thickness (h) of the intermediate continuum fluid film no less than 0.1, and this makes the total volume flow rate through the channel about 35% smaller than the classical Hagen-Poiseuille equation calculation. The flow is not sensitive to the variation of the value of the ratio (q0) of the neighboring fluid molecule separations across the adsorbed layer thickness once the thickness of the adsorbed layer is fixed. With the increase of the channel height, the effect of the adsorbed layer is weakened. When hbf/h<=0.01, the reduction of the total flow rate through the channel owing to the adsorbed layer is no more than 5.5% and the effect of the adsorbed layer can be considered as negligible. These disciplines of the Poiseuille flow in nanochannels renders the great application values of the adsorbed layer in improving the load-carrying capacity of micro bearings with very low clearances.
Simulation on the Impact of Porosity on the Properties of Ceramic Par-ticles Reinforced Metal Matrix Composites
Although the porosity in Al/SiC metal matrix composites can be reduced, its presence is inevitable. This study aims to investigate the influence of porosity and pore size on the performance of SiC reinforced aluminum matrix composites that contain porosity. To achieve this, we consider both constant and variable diameters of pores, assuming a circular shape while maintaining the same volume fraction. Finite element analysis is conducted on a square matrix reinforced with nine particles subjected to a tensile test. The simulation employs a two-dimensional plane strain model along with square, hexagonal, and random distributions of multiple particles. The results indicate that, despite the presence of pores, the stress transfer from the softer matrix to the reinforcement remains effective. Moreover, the properties of the composite are found to be increasingly sensitive to porosity and pore size, particularly when the pore diameter increases and the distance to the particles decreases.
The Structure Design and Precision Improvement of Small Caliber Non-Spherical Surface Type Detector
Aspherical optical elements have significant advantages over traditional spherical elements, and have become the core technology for high-resolution imaging, intelligent devices, and precision instrument upgrades through optical performance, simplifying system structure, and reducing manufacturing costs. It has gradually promoted the development of optical systems towards high performance, lightweight, and high quality. However, the rapid development of aspheric optical elements is limited by the detection technology of aspheric surface profile. In order to solve the problems of detection principle error, low detection efficiency, expensive detection instruments and poor general performance in the current non-spherical optical elements shape detection technology, a new principle of non-spherical surface shape detection is proposed based on the theory of the closest circle, and the detection numerical model of non-spherical is constructed. At the same time, based on this, the overall structure design of small aperture non-spherical surface shape detection instrument is carried out, and the specific steps of detection instrument to implement small aperture non-spherical surface shape detection are analyzed. In order to further improve the detection accuracy of the small-caliber non-spherical surface profile detector, the detection technology of the geometric error of the is studied. The spatial geometric error detection of the moving axis of the small-caliber non-spherical surface profile detector is carried out by using the laser interferometer, and the compensation scheme of the small-caliber non-spherical surface profile detector is proposed through the analysis of the error compensation logic. In addition, the mathematical model of geometric error is established. The correctness of the research content is effectively verified by carrying out the geometric error compensation experiment on the moving axis of the small-caliber non-spherical surface profile, and the research on the accuracy improvement of the small-caliber non-spherical surface profile detector is completed.
Lightweight Design Of Ball Mill Cylinder Structure Based On Genetic Polymerization Agent Model
To address the issues of strong empirical dependence and low computational efficiency in traditional ball mill cylinder design, this study proposes a lightweight design methodology integrating multiple response surface models with finite element parametric simulation technology. Based on the equivalent density method, stress-strain characteristics are obtained through simplified cylinder structural modeling and finite element static analysis. Parametric finite element simulations are employed to generate sample data, The optimal response surface model is determined by comparing the goodness-of-fit (using evaluation metrics such as the coefficient of determination R², root mean square error RMSE, etc.) among neural network, Kriging, and genetic aggregation methods. Key structural parameters of the cylinder are identified through sensitivity analysis using data generated from the optimal response surface, enabling the construction of a lightweight mathematical model that is solved using a multi-objective genetic algorithm. Experimental validation on an MQY5585 ball mill demonstrates that the proposed method achieves an 8.04% reduction in cylinder mass and a 12.28% decrease in maximum deformation while maintaining equivalent stress within permissible safety limits.
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)