PVC-coated fabrics are widely used in tarpaulin applications due to their durability and flexibility. This study investigates the tearing behavior of PVC-coated fabric specimens containing central straight and inclined slits, sampled from S8210-type tarpaulins used in freight wagons. Uniaxial tensile tests were performed on both intact and slit specimens. Horizontal slits having lengths of 5, 10, and 20 mm, as well as inclined slits of 20 mm at 30°, 45°, and 60° angles, were analyzed. The results reveal two distinct fracture modes: progressive and abrupt failure. Inclined slits exhibited a progressive, Z-shaped crack propagation pattern while the horizontal slits lead to a more sudden failure. Key fracture parameters, including maximum fracture force, fracture energy, and the influence of slit geometry on fracture strength, were determined. A critical opening length beyond which the tarpaulin's repair is recommended was also identified. The paper translates the theoretical concepts of breaking energy in a directly measurable parameter (aech). This can be investigated directly on site by the maintenance personnel and based on the reading and proposed tables for this material, can make safety decisions.
This paper proposes an optimized control strategies for a dynamics 6-link robot manipulator using Model Predictive Control (MPC) and traditional Computed Torque Control (CTC). Two optimization methods are used for tuning of MPC controller, namely MPCbased Dandelion Optimization (DO) and MPCbased Genetic Algorithm (GA). The strategies are assessed in terms of performance indices based timedomain, settling time, rise time, overshoot percentage, and steady-state error (SSE). Simulation results depicted that traditional CTC suffers from higher control effort and slower transient response, mainly for links with high order. In contrast, MPC-based control strategy significantly improve dynamic performance and tracking accuracy. Among the tested approaches, MPCbased DO achieves minimal overshoot, smoother torque profiles, fastest convergence, and the lowest SSE across all six robotics links. The attained MATLAB/SIMULINK results confirm and prove that optimized MPC controller, especially MPCbased DO, offers an efficient and robust control solution for high DOF robotic manipulators.
Dynamic flexible job shop scheduling under machine tool breakdowns represents a complex and highly constrained combinatorial optimization problem in modern manufacturing systems. This research paper proposes an integrated optimization framework that simultaneously determines operation sequencing, machine tool assignment, tool selection, and tool orientation with the objective function of minimizing makespan. A unified multi-string solution representation is developed to simultaneously model all decision layers. Three biologically inspired metaheuristic algorithms, Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Hippopotamus Optimization (HO), are implemented using the proposed encoding scheme. A rescheduling strategy is introduced to preserve completed operations while rescheduling the affected operations after machine tool failures. Experimental verification demonstrates that the integrated framework effectively handles dynamic disturbances and significantly improves scheduling performance. Comparative analysis shows that the hippopotamus optimization algorithm achieves superior convergence behavior and better objective function values than the other approaches. The proposed method provides a robust framework for resilient scheduling under multiple resource constraints.
This study explores the use of soybean oil-based nanolubricants that incorporate hexagonal boron nitride (h-BN), multi-walled carbon nanotubes (MWCNTs), and their hybrid at a concentration of 0.15 wt% for minimum quantity lubrication (MQL) in the computer numerical control (CNC) milling of AISI 1045 steel. Nano-cutting fluids were prepared via a two-step process, involving stirring followed by ultrasonication, and were characterized for density, viscosity, thermal conductivity, and rheology. Machining responses comprised tool wear length, cutting temperature, surface roughness, chip morphology, and chip colors. All samples exhibited Newtonian behavior at 40 °C and 100 °C. The hybrid h-BN/MWCNT formulation delivered the best overall performance, achieving the lowest tool wear length (~0.067 mm), reduced cutting temperatures, and the smoothest surfaces relative to dry cutting and single-additive fluids. The improvements are attributed to a synergistic mechanism in which h-BN platelets form a boundary-lubrication tribofilm, while MWCNT act as nano-bearings and a thermally conductive network that stabilizes the cutting zone. Simple sedimentation observations indicated higher dispersion stability for MWCNT-containing nano-cutting fluids than for h-BN alone. These results suggest that hybrid nano-additives in plant-oil-based cutting fluids may offer practical benefits for MQL-assisted machining or, particularly by helping reduce tool wear, improve thermal management, and support more sustainable machining.
This paper presents a comprehensive framework for predicting the power requirements of high-speed craft, including semi-displacement, semi-planing, and planing hull forms, through the use of statistically-based mathematical models. These models belong to the class of reduced-order models, which streamline the inherently complex processes of modeling hull resistance, dynamic trim, and propeller efficiency, including the interactions of multiple design parameters. Model development has relied on various regression techniques and, more recently, artificial neural networks (ANN). These mathematical models often offer advantages over the CFD techniques that nowadays dominate professional journals and therefore deserve careful attention. This review presents the methodology in a structured way to facilitate its integration into power prediction and design-optimization workflows and adopts a user-focused perspective.
Effective utilization of high-ethanol fuels in spark-ignition (SI) engines requires injection configurations capable of accommodating significant variations in fuel properties. This study experimentally investigates the performance and emission characteristics of an SI engine fueled with gasoline-ethanol blends (E25, E50, E85, and E100) relative to baseline gasoline (E0), employing singleand dual-port fuel injection configurations. Experiments were conducted at a fixed engine speed of 6500 rpm over a range of load conditions. For consistent fuel-to-fuel comparison, gasoline-defined throttle settings were preserved while the injected fuel quantity and load were adjusted to sustain steady speed. Injector mass-flow characteristics were calibrated for each fuel to ensure accurate delivery. Results indicate that ethanol blends generally increased engine output but resulted in higher brake specific fuel consumption (BSFC) due to their lower heating value. At higher throttle openings (> 32%), gasoline exhibited superior performance. Under part-load conditions (< 28%), E25 combined with dual injection achieved brake power comparable to gasoline while improving brake thermal efficiency and reducing BSFC in both injection modes, reflecting enhanced mixture preparation enabled by ethanol-bound oxygen under low-throttle, low-airflow conditions. Increasing ethanol content significantly reduced CO, HC, NOx, and CO2 emissions, with dual injection providing additional emission benefits through shorter injection duration and improved mixture homogeneity. These findings demonstrate that dual-injector configurations can effectively enhance mixture preparation and reduce emissions when operating with high-ethanol fuels, offering their potential to improve part-load efficiency in SI engines.
This study presents the development of an innovative simulation-based model for analysing the accuracy of optical rotary encoders subjected to mechanical vibrations. The proposed approach establishes a digitally controlled environment that emulates real operational conditions, enabling systematic examination of dynamic effects on encoder performance. The model integrates essential components that allow the formation of a system capable of operating both within a digital simulation environment and under real experimental conditions with controlled generation of mechanical vibrations. By simulating diverse operating scenarios, the model provides detailed characterisation of measurement deviations and identifies variations in measurement error of the investigated encoder as a function of changes in input parameters. The resulting insights support predictive evaluation of measurement error behaviour and enable systematic assessment of encoder accuracy under varying vibration and operating conditions. Consequently, the proposed simulation method offers a reliable and reproducible tool for investigating vibration-induced measurement errors in advanced precision systems.
The use of Unmanned Aerial Systems is expanding rapidly across civil and military domains, with sustained growth anticipated in the coming decades. The X-tail UAV configuration, characterized by the absence of ailerons and higher wing loading, offers excellent maneuverability for loitering munition applications. However, the design requires extreme control derivatives to maintain flight quality, and the minimal air-speed is determined by both lift capability and the ability to counteract propulsion torque. This research systematically examines the latter factor. Brushless direct current motor was first characterized experimentally, followed by testing with five propeller types to evaluate maximum revolutions per minute and power input. Among the tested configurations, the 18×11-inch propeller achieved 6,390 revolutions per minute at peak power, demonstrating the most favorable trade-off between thrust and torque. Wind tunnel tests at zero airspeed and simulated take-off velocity validated the integrated propulsion performance, showing excellent agreements with the theoretical predictions. The results confirm the suitability of the chosen motor-propeller combination and establish a minimum launcher-assisted take-off speeds as a function of altitude for defined UAV mass. These findings provide a robust basis for propulsion optimization in similar UAV configurations, supporting reliable and efficient operational deployment.
It can generally be stated that successfully designed process, energy, and HVAC plants plants are characterized by both quality and quantity of the final product. Basic principle for every plant design state that every single piece of equipment must be sized as to perform its function in safe and efficient manner. To this end, due to many uncertainties, engineering design and construction often use the safety factor. Although this term is in everyday use in the engineering practice, the safety factor principle is often oversimplified and misunderstood. Paper presents a complete overview of application of safety factors in every aspect of plant and equipment design. Exhaustive literature review, coupled with authors' own extensive experience in plant and equipment design, serve not only to present the readers a clear background of basic principles and recommendations for safety factors, but also the help them understand all the complexities and aspects used in its formation. Examples provided in the dedicated section are meant to substantiate all the outlined concepts, while authors' own recommendations can guide the readers towards correct safety factor selection.
This study presents a numerical analysis of the airflow around a passenger vehicle (DrivAer model in the Notchback configuration) travelling across a viaduct, with the aim of investigating the influence of bridge protection elements on the vehicle's aerodynamic characteristics. CFD simulations were conducted in STAR-CCM+ using the RANS approach coupled with the k-ω SST turbulence model. Four geometric configurations were analysed: open flow without any protection, viaduct with a guardrail, viaduct with a solid windbreak, and viaduct with a porous windbreak. Each configuration was simulated under two flow scenarios, with and without a crosswind component. The CFD model was validated against experimental data obtained from the Technical University of Munich (TUM) wind tunnel, showing satisfactory agreement in the drag and pressure coefficients. The results indicate that the solid windbreaks increase side forces and rolling moments, whereas the porous windbreaks significantly reduce turbulent effects and improves aerodynamic stability. The analysis of the Q - criterion field and turbulent kinetic energy confirms that the porous barrier narrows the wake region and diminishes vortex structures behind the vehicle. It was further established that for passenger vehicles, a well-designed guardrail can achieve comparable or even superior effects to complex windbreak in terms of optimizing aerodynamic loads on the vehicle.
This study considers the ship Lucy Ashton, a benchmark case providing full-scale measurements of total ship resistance and boundary layer thickness. A series of CFD simulations was carried out for several different scales and Froude numbers, with the aim of reproducing experimental data on ship resistance and the boundary layer. The results showed agreement with the measurements, with ship resistance predictions within ±5% and realistic boundary layer profiles along the hull. Based on these findings, practical formulas for boundary layer thickness and base mesh cell size were derived. Although these formulas were developed considering only the Lucy Ashton case, they represent a promising basis for application to other ships, particularly at model scale. Further studies are recommended to confirm their reliability for different full-scale hull forms.
Overhead cranes are widely used in industry and transportation, but their operation is often affected by undesired payload oscillations that degrade maneuverability and safety. Although numerous control strategies have been investigated, most of them are relatively complex in both controller design and practical implementation. This paper proposes a hybrid control scheme that integrates Active Disturbance Rejection Control (ADRC) with a model reference-based input filter, where ADRC ensures accurate trolley positioning and the filter suppresses payload swings .reducing the need for precise system modeling and mitigating the impact of parameter uncertainties. Simulation results confirm that the proposed approach effectively eliminates payload oscillations while achieving the desired positioning, and experimental validations further demonstrate its robustness and practical feasibility for crane operations.
This paper presents analytical and experimental research on expendable turbojet combustion chamber with central-single vaporizer configuration. Expandable turbojet implies that engine is for single use and that simplicity and small size are dominant criteria. Because of these limitations it was considered that use of vaporizers instead of atomizers will save time needed for vaporization of the fuel. Most of empirical and experimental data related to combustion chambers origin from bigger engines and if we directly apply them to smaller combustors most likely we will overestimate their performances. That was one of important reasons for this research. Analytical analysis is based on ratio of vaporized fuel and ratio of residence time to droplet vaporization time with influence of geometry, working conditions and fuel type. Experimental analysis is focused on primary and secondary zone, its stability and efficiency. This paper combines analytical and experimental research of such space limited combustion chamber with central vaporizer.
Laser powder bed fusion (L-PBF) enables the creation of advanced metal parts that are difficult to manufacture conventionally. In this study, the model parameters of the Johnson-Cook (JC) constitutive relation and the damage parameters of the JC failure model for 1.2709 steel produced via L-PBF were determined. Constitutive parameters were identified from quasi-static uniaxial tensile tests conducted on smooth specimens. In contrast, stress triaxiality-dependent damage parameters were determined using tensile tests on notched round bar specimens in combination with FEM simulations. The load-displacement curves showed good agreement with the experimentally obtained data. The strain-rate-dependent failure model parameter was determined by correlating Charpy impact test results with numerical simulations. Reasonable agreement between the simulation and experimental results was achieved. The results demonstrate that the proposed experimental-numerical framework provides a reliable basis for modelling both the quasi-static and impact fracture behaviour of L-PBF-fabricated 1.2709 steel.
In this work, laminar mixed convection heating along a horizontal duct, formed by two concentric elliptical tubes under uniform and equal heat fluxes, is studied numerically using the finite volume method. The work focuses on the geometric effect of the duct passage section, where nine cases have been proposed, starting with the two cylinders case, followed by the case interior cylinder/exterior ellipse, then the opposite and finally the case with two ellipses. Re=100 is taken for Pr=100, While a Gr ranging from 0.0 to 5.0×10+5 is supposed. The results for the base case for a circular cross-sectional area -encountered in the food processing industryshow after some distance from the entrance the formation of thermal stratification between the top and bottom of a section where the hotter fluid risks being denatured, with a strong slowdown in the flow at the top, which degrades the convective heat transfer and favors conductive one, particularly at high Gr. The other cases tested show that the case with two ellipses offers the best thermal homogeneity and considerably reduces the problem of the flow slowdown. This result is proposed as a solution for the thermal stratification problem.
In this research, a multi-objective optimization study was conducted on the external cylindrical longitudinal grinding process of AISI 6150 alloy steel. The input variables examined for their influence included wheel speed, workpiece speed, feed, total depth of cut, number of passes, wheel grain size, and wheel porosity. Experimental research was carried out using a custom experimental design based on the I-criterion of optimality. Dimensional deviation was selected to quantify accuracy, surface roughness was used for quality assessment, and material removal rate was employed to measure productivity. The dimensional deviation values ranged from 0.0046 to 0.0144 mm, surface roughness values were between 0.4301 and 3.766 μm, and the material removal rate ranged from 9.375 to 112.5 mm³. Using the experimental findings, an analysis was performed to define the impact of input variables on output variables, and regression equations were developed. The goal was to optimize accuracy, quality, and productivity simultaneously while varying the weighting coefficients in the objective function. The reliability of the model and the optimal values of the variables were validated through confirmation experiments. The obtained absolute errors were acceptable, measuring between 0.0004 to 0.001 mm for dimensional deviation and 0.0102 to 0.0245 μm for surface roughness.
This study investigates the influence of disk edge geometry on the flow physics and pressure characteristics of a Multi-Row Disk Inlet Device (MRDID) operating at Mach 2 within the open cavity regime (L/D = 1). A detailed parametric analysis was conducted using 2D axisymmetric RANS simulations with the SST k-ω turbulence model and second-order MUSCL discretization, supported by supersonic wind tunnel experiments for validation. Two baseline geometries, the Flat Tip Disk (FTD) and Sharp Tip Disk (STD), were examined to understand the role of rear-wall stagnation and cavity shock interaction. Results show that FTD produces higher peak pressure ratios, compression, and drag due to a strong stagnation zone at the cavity rear wall, whereas STD reduces stagnation severity through its inclined surface. To explore passive flow control, two modified geometries-Rear Chamfered Tip Disk (RCTD) and Front Chamfered Tip Disk (FCTD)-were introduced. Rear chamfering improves wake recovery and reduces recompression shocks, while front chamfering transforms the detached bow shock into an attached oblique shock, significantly lowering peak pressure. The study establishes disk edge shaping as a critical passive design parameter for optimizing MRD inlet performance.
This paper presents the development of a low-cost, AI-enabled educational robotic platform designed to enhance hands-on STEM learning. The system consists of a 4-degree-of-freedom (DOF) robotic arm constructed from 3D-printed components, controlled by an ESP32-based circuit and integrated with both local and Web-based interfaces for flexible operation. Two control interfaces were developed: a local desktop GUI built with PyQt5 and a remote Web-based interface using the MQTT protocol. Both interfaces allow users to manually control robot joint angles, adjust movement step sizes, reset to default positions, and monitor real-time joint states. These interfaces provide intuitive interaction, enabling students to understand motion control in robotics. To integrate artificial intelligence and computer vision, three modules were implemented: face tracking, hand gesture control, and object detection. Face tracking translates facial position and size into 3D coordinates for real-time robot movement using inverse kinematics. Hand gesture recognition uses MediaPipe to interpret finger poses and execute corresponding robot actions. The object detection module employs a YOLOv12 model trained on classroom objects (pens, erasers, markers) to perform autonomous pick-and-place tasks on a simulated conveyor system. Experimental results validate the system's effectiveness in real-time tracking, gesture interpretation, and object manipulation. Real-time plots of joint angles and workspace coordinates illustrate the system's responsive behavior. This integrated platform enables students to explore AI, vision, and robotics in a unified environment. Through interactive exercises, they gain practical experience in programming, AI model development, user interface design, and robotic control, bridging theoretical knowledge and real-world applications.
Ti-6Al-4V has been widely used in the medical and dental fields due to its good biomechanical compatibility. Selective Laser Melting (SLM), an advanced metal powder-bed additive manufacturing method, offers versatility for tailoring part properties. However, further investigation is needed into the links between process parameters, volumetric energy density (VED), and resulting tribological performance. The present study focuses on the influence of varying VED levels on the porosity, surface finish, density, and wear behavior of Ti-6Al-4V. Five sets of samples were prepared at various VEDs. A higher VED results in densification, microhardness, and wear resistance, whereas a lower VED leads to increased porosity and roughness. The measured friction coefficient ranged from 0.266 to 0.63, and SEM observations identified smoother worn tracks in samples prepared under optimized conditions. These acid-etched results provide further, more direct evidence that VED must be closely controlled in SLM to enhance the durability and tribological properties of Ti-6Al-4V parts, thereby diminishing service life and expenditure in biomedical and industrial applications.
This paper covers the development and validation of a nonlinear mathematical model of an electromagnetic vibratory actuator used in vibratory conveyors. The motivation for this research stems from the need for a more detailed understanding of the electromechanical energy-conversion phenomena that occur during the operation of an electromagnetic vibratory actuator. Unlike previous mathematical models, which often use linear approximations or separately consider the mechanics and electrodynamics of the actuator, the proposed model integrates nonlinear electromagnetic effects with the dynamics of the electromagnet armature's relative motion, therefore establishing a dependence between the electrical quantities in the circuit and the dynamic characteristics of the moving element of the electromagnet. The newly developed mathematical model was simulated numerically, with the model parameters chosen based on a functional laboratory prototype. At the end, experimental validation is presented, demonstrating strong agreement with the simulation results.
