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).
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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.
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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.
DESIGN AND OPTIMIZATION OF MECHANICAL SYSTEMS
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.
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.
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.
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)
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.