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Parts made from carbon fiber reinforced polyetherketoneketone (CF/PEKK) primarily use mechanical connections during assembly, where the quality of hole processing directly impacts the connection strength. However, defects like delamination, burrs, and fiber pull‐out frequently occur during drilling. While existing research focuses on optimizing conventional drilling (CD) and helical milling (HM), ultrasonic vibration‐assisted drilling (UVAD) shows superior performance in reducing thrust force and defects. This study experimentally evaluates the hole‐making performance of CF/PEKK using the UVAD method. It examines the effects of ultrasonic vibration on thrust force, drilling temperature, processing damage, chip morphology, and surface microstructure, and discusses the damage suppression mechanism. The results show that the UVAD method significantly reduces thrust force and drilling temperature compared to the CD method, with similar trends in delamination and burr damage. This study demonstrates that using the UVAD method for drilling CF/PEKK laminates effectively reduces thrust force, drilling temperature, and machining damage, thereby significantly improving processing quality. The material removal mechanism of UVAD was analyzed, offering substantial insights and practical guidance for the efficient drilling of CF/PEKK laminates. Highlights: The drilling performance of CF/PEKK was studied.The drilling quality of UVAD and CD is compared by experiments.UVAD has a lower thrust force and drilling temperature.UVAD can reduce machining damage and improve machining quality. [ABSTRACT FROM AUTHOR]

The anisotropic characteristics of rock have important value for construction safety and evaluation of rock properties. The purpose of this article is to study the variation law of drilling parameters in different rocks and their anisotropy characteristics. This article investigates drilling characteristics by conducting digital drilling experiments on six different types of rocks in three different directions. The variation law of drilling parameters (drilling speed, torque, rotational speed, thrust force) and the special energy with drilling depth are analyzed as well as the anisotropy variation of six types of rocks. The influence of anisotropy on the specific energy of six types of rocks is investigated. A special energy index f is proposed to characterize the anisotropy for evaluating different rocks. The test results show that the anisotropy of granite, slate, gneiss, red sandstone, argillaceous sandstone, and sandstone is weakened accordingly by using the special energy index f. The specific energy index after data normalization can better judge the anisotropy difference for different rocks, such as granite, slate, gneiss, and red sandstone. [ABSTRACT FROM AUTHOR]

During drilling CFRP composite plates, the direction pointing to the hole wall along the length can be considered the forward direction of the carbon fiber. The angle between the forward direction of the cutting speed and the forward direction of the carbon fiber is regarded as the main cutting angle of the major cutting edge. If the main cutting angle is an acute angle, the cutting is called as forward cutting. If the main cutting angle is an obtuse angle, the cutting is called reverse cutting. From the above concepts, the forward cutting zone and the reverse cutting zone can be defined. Based on viscoelastic mechanics and foundation beam theory, the carbon fiber among CFRP composite plate is regarded as an infinite or semi-infinite foundation beam with equal section on elastic foundation. The calculation model of equivalent stiffness modulus is derived, and the thrust force model of the major cutting edge is established. The research shows that when the drill bit turns for a revolution, the forward cutting and reverse cutting alternately change twice, and the main cutting angle and thrust force of the major cutting edge change 2 cycles. The cutting mode of the major cutting edge is the fundamental reason which brings about the periodic change of the thrust force and the defects of the entrance or exit. The reliability of the thrust force model of the major cutting edge is proved by drilling experiments. This study can provide theoretical support for improving the drilling process of CFRP composite plates. [ABSTRACT FROM AUTHOR]

Drilling of aluminum matrix composite of silicon carbide materials is analyzed using cryogenically treated drills under cryogenic conditions. Vibration acceleration, thrust force, geometrical aspects of drilled workpiece like hole quality, surface roughness, tribology properties of drill wear and chip morphology are evaluated at various drilling parameters such as spindle speed and feed rate. Experimental results showed that impact of spindle speed is considerably higher than impact of feed rate on vibration acceleration, whereas thrust force is influenced by spindle speed as well as feed rate. The maximum vibration acceleration obtained at the highest feed rate is 74.48 m/s2 and 81.34 m/s2 at the spindle speed of 3,000 rpm and 4,500 rpm. The hole diameter variation is 0.139 mm than original drill diameter and observed entry side hole diameter is slightly larger than that of exit side. Moderate spindle speed i.e., 3,000 rpm and 4,500 rpm produced better geometrical aspects of drilled workpiece and it is recommended for smooth drilling operation under cryogenic drilling condition. Adhesive wear is found to be prominent specially at the higher spindle speed. Smaller and smooth chips are observed at the lower spindle speed while short and curly shape chips are found at higher spindle speeds. [ABSTRACT FROM AUTHOR]

In this study, the effects of reinforcement ratio, drill bit material, and drilling process parameters on the cutting forces generated during the drilling of glass sphere‐reinforced polypropylene composites were investigated experimentally. Test specimens were produced by conventional injection‐moulding of glass sphere reinforced polypropylene composite materials at 5 %, 10 % and 20 % wt. ratios. High speed steel, titanium‐coated high‐speed steel, and carbide drill bits with 4 mm diameter were preferred for drilling. In addition, the drilling process was carried out on a 3‐axis computer numeric control milling machine. Three different feed rates of 0.05 mm/rev, 0.10 mm/rev, and 0.15 mm/rev and cutting speeds of 12 m⋅min−1, 16 m⋅min−1, and 20 m⋅min−1 were determined for the drilling process. In addition, Taguchi experimental optimization method, analysis of variance and scanning electron microscopy were used to investigate the morphology of the drilled surface and the wear mechanisms occurring on the drill bit due to the drilling process. The test findings showed that the maximum torque value was 54.64 N⋅mm and the maximum thrust force was 100.43 N. The optimum test parameter for cutting forces was observed as C1D3FR1CS3. Drill parameter had an effect of 40.96 % on thrust force and 36.11 % on torque. [ABSTRACT FROM AUTHOR]

Real service requirements of the assembly performance and joining properties of design components are critical for composite usage in the aerospace industry. This experimental study offers a novel and comprehensive analysis of dry drilling optimization for glass-reinforced, high-performance epoxy matrix composites used in aerospace structures, focusing on thrust force and delamination. The study presents a first-time investigation into the combined effects of spindle speed (1000, 2250, 4000 and 5750 rpm), feed rate (0.2, 0.4, 0.6 and 0.8 mm/rev) and tool diameter (3 and 5 mm) using a custom-designed drill tool specifically developed for this application, filling a gap in the current literature. By employing the Taguchi design of experiments, the study identified that medium spindle speeds (2250–4000 rpm), lower feed rates (0.2 mm/rev) and smaller tool diameters (3 mm) provided optimal conditions for minimizing thrust force and delamination. These results present actionable insights into improving the structural integrity and performance of drilled aerospace-grade composite components, offering innovative advancements in both the aerospace and defense industries. [ABSTRACT FROM AUTHOR]

Thermoplastic carbon fiber reinforced polyetheretherkrtone (CF/PEEK) and thermoset carbon fiber reinforced epoxy (CF/epoxy) composites are being widely applied in aviation and aerospace fields for their excellent performance. To compare the drilling characteristics of two typical carbon fiber reinforced composites under varying feed speeds, drilling experiments were carried out using three different special drills involving twist, brad, and dagger drills. The drilling performance of CF/epoxy and CF/PEEK composites was analyzed in terms of chip morphology, drilling temperature, thrust force, delamination damage, and surface morphology. The results show that CF/PEEK composites produced continuous chips, so that CF/PEEK composites generated higher drilling temperature and thrust force than that of CF/epoxy composites. CF/epoxy composites showed larger delamination damage and poorer machined surface than CF/PEEK composite due to its poor interlaminar toughness. Burrs produced agglomeration and crimping at the hole edges of the CF/PEEK composites due to PEEK resin is softened by heat, matrix plastic deformation. Brad drill revealed fewer burrs and merely a tearing damage at the exit. Dagger drill showed more burrs. The hole wall damage is minimal for brad drill. The results provide guidance for drilling of high quality thermoset and thermoplastic composites. [ABSTRACT FROM AUTHOR]

This attempt covers an investigation of cutting temperature at interfaces of Fiber Metal Laminates (FMLs) made of glass fiber-reinforced polymer (GFRP) stacked with an Al2020 alloy. GFRP/Al/GFRP and Al/GFRP/Al composite stacks are both investigated to highlight the effect of stacking arrangement on thermal behavior within the interfaces. In a first test series, temperature history is recorded within the metal/composite stack interfaces using preinstalled thermocouples. In a second test series, a wireless telemetry system connected to K-type thermocouples implanted adjacent to the cutting edge of the solid carbide drill is used to record temperature evolution at the tool tip. Focus is put on the effects of cutting speed and stacking arrangement on the thrust force, drilling temperature, and delamination. From findings, the temperature histories show high sensitivity to the cutting speed. When cutting Al/GFRP/Al, the peak temperature is found to be much higher than that recorded in GFRP/Al/GFRP and exceeds the glass transition point of the GFRP matrix under critical cutting speeds. However, thrust force obtained at constitutive phases exhibits close magnitude when the stacking arrangement varies, regardless of cutting speed. Damage analysis is also discussed through the delamination factor at different stages of FML thickness. [ABSTRACT FROM AUTHOR]

Questions related to the research of the model of functional dependence of the engine thrust on their operating parameters to reduce the asymmetry of the aircraft thrust due to the different thrust of its engines are considered. The aim of this study is to control the rotor speeds of aircraft engines on the basis of a three-dimensional model of the dependence of the engine thrust on their rotor speeds of turbine rotors of low-pressure compressors and high-pressure compressors. Methods of mathematical statistics and hardware-software modeling are used in the study. The results of the study show and confirm the possibility of balancing the thrust of aircraft engines when controlling the rotor speeds of its engines in flight. A three-dimensional model of the engine thrust's dependence on the values of rotational frequencies of its two rotors is developed. This model allows providing the control of the rotation frequencies of both rotors of the engine by the additional fuel supply to them for the formation of new values of these frequencies according to the results of comparative estimation of their values, taking into account the values of their first derivatives as sign-variable special corrections providing automatic control of the speed and direction of change of the controlled frequencies values. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Threading with taps is a method frequently used in machining. Since this process takes place in a closed area due to its nature, some difficulties are encountered. In this study, the results of a previous experimental work were compared with the results of a simulation program. In the experimental work, the tapping process was performed using M10 taps with three different geometries for the drilled holes on AISI 1050 material. Tapping operations were carried out with uncoated and TiN coated HSS tools. For the simulation program, the 3D CAD models of the tested taps were created by reverse engineering method and then imported into a simulation program, called Third Wave AdvantEdge program. The CAD models were evaluated by Third Wave AdvantEdge program based the finite element method. The thrust force, torque, chip formation occurring during the threading process were examined. It was concluded that the simulation and the experimental results were quite compatible. [ABSTRACT FROM AUTHOR]

This study addresses the pressing need for enhancing the machining performance and hole quality of castamide by investigating the effects of solid lubricant addition and drilling parameters. Castamide, a highly crystalline polyamide synthesized via anionic ring‐opening polymerization, offers superior mechanical, physical, and chemical properties compared to conventional polyamide 6. However, its machining process, particularly drilling, remains a critical challenge due to its viscoelastic nature and sensitivity to heat generation. Using experimental investigations, thrust forces, drilling temperatures, hole geometry, and quality parameters are systematically analyzed and discussed. Notably, the study introduces Kestlub, a modified version of castamide with solid lubricant, and evaluates its drilling performance, a previously unexplored area in the literature. The research employs response surface methodology to model experimental data, considering both linear and quadratic effects of drilling parameters. Additionally, the significance of each parameter is assessed using ANOVA tables and Pareto charts, offering valuable insights into optimizing the drilling process for enhanced hole quality in castamide. It found that optimal drilling conditions occur at low rotational speeds and high feed rates, but thermal damage, influenced by factors like thermal conductivity and transition temperature, affects hole geometry and burr formation. Highlights: Drilling performances of solid lubricant reinforced castamides were investigated.Drilling temperatures were recorded with a thermal camera and differential scanning calorimeter and thermal gravimetric analyses were performed.Drilling properties were analyzed statistically according to the response surface method.It found that optimal drilling conditions occur at low rotational speeds and high feed rates. [ABSTRACT FROM AUTHOR]

AbstractAdvancements in technology and the compulsion to use environment-friendly materials have been challenging tasks for researchers for the past two decades. Researchers have been focusing on the utilization of plant fibers to produce good quality fiber-reinforced polymer/polyester composites for automobile, structural, and building applications. Researchers have been looking for high-quality and cost-effective drilling processes. The primary goal of this study is to identify optimal drilling conditions for CCFRP composite laminates, affecting thrust force and torque. This is achieved by manipulating drilling process variables using Taguchi’s Design of Experiments (TDOE), Analysis of variance (ANOVA), Response Surface Methodology (RSM), Desirability Function Analysis (DFA) and Artificial Neural Network (ANN). From the results, it was observed that the spindle speed of 2000 rpm, feed of 15 mm/min, point angle of 90°, fiber length of 6 mm, fiber volume of 30%, and fiber diameter of 7 microns gave the optimum results for obtaining minimum thrust force and torque. Further RSM revealed that an increase in fiber vol % and a decrease in spindle speed resulted in an increase in thrust force and torque. From DFA optimization results, the minimum thrust force of 24.0042 N and minimum torque of 0.8001 N-m was obtained. Finally, the experimental values of thrust force and torque were compared with the corresponding values predicted by the MLP-ANN model. The average error percentage for thrust force and torque was 1.75% and 6.56% respectively.

The exterior layer of the fuselage skin structure is made of Glass-Reinforced Fiber Metal Laminates (GLARE-FMLs). Hole quality is impacted by various force components during the drilling process. The process variables of drilling are optimized to obtain quality holes by controlling such force components. Because of the very limited works on optimizing the significant input process variables in getting quality drilled holes on FML plates, the present investigation is aimed to analyze the impact of varying the significant drilling process variables referred from the literature study and the wt.% of Layered Double Hydroxide (LDH) mixed with the epoxy, on the force components generated during the drilling process. The FML plates proposed in the study have been drilled based on the test plan prepared by Taguchi's DOE. Grey Relational Analysis has been used for discovering the best combination of process variables leading to good quality holes. Further, grey-fuzzy modeling technique has been employed to check the results of GRA. From the results, it is identified that 1000 rpm spindle speed, 20 mm/min feed rate and 4 wt.% inclusion of LDH to the epoxy resin combination within the considered range of input process variables were found to be the best input parameter combinations resulting in comparatively better output responses. Artificial Neural Network (ANN) model has been generated to bridge the input variables with the outputs measured. The fitness of the generated ANN model has been checked and reported. The effect of varying the process variables on obtaining the quality drilled holes has been revealed using Main Effect Plots (MEPs). [ABSTRACT FROM AUTHOR]

Flax reinforced epoxy (F-Ep) composites were prepared by the compression moulding technique, varying the fiber content (0, 25, 35 and 45 wt%). The free vibration test was performed on the neat epoxy and F-Ep composites to understand their dynamic characteristics, and results showed that natural frequency and damping factor of the F-Ep composites increased with an increase in the fiber content. The F-Ep composite (45F-Ep) that exhibited better damping was selected for performing the drilling operation. Factors such as spindle speed (rpm), feed rate (mm/min) and drill point angle (degree) were chosen as input parameters and the tabulated set of experiments were in accordance with Taguchi's design of experiment. The response measured was thrust force and the obtained values were found in the range of 19.66 to 50.75 N. The minimum value of thrust force was achieved when the F-Ep composite was drilled at high spindle speed (3000 rpm), with a feed rate of 75 mm/min using the drill point angle of 118°. ANOVA analysis showed that the developed regression model was significant and thrust force was mainly influenced by the spindle speed. Mathematical models were developed for drilling F-Ep composite using response surface methodology (RSM) and adaptive neuro fuzzy inference system (ANFIS) and compared for their efficacy. [ABSTRACT FROM AUTHOR]

In the modern aviation environment, research on unmanned aerial vehicles is attractive in many aspects. Integrating efficient propellers into the unmanned aerial vehicle structure helps to enhance the performance factors such as endurance, range, distance to take-off and payload carrying capacity. This paper numerically investigates the configured propeller blades to enhance aerodynamic efficiency and performance parameters. The design parameters such as diameter, pitch, number of blades, and blade shape were configured with highly efficient propellers. The E62 airfoil opted to configure bi-blade, tri-blade, and modified nozzle-shaped ducted propellers and subjected to a computational fluid dynamic process for the varying rotational velocity. The thrust component, lift, drag and aerodynamic efficiency of the propeller blades were studied for the different operating speeds. The performance of E62 airfoil-based propeller was more efficient whereas the ducted blade profile generates the maximum thrust of 7.07N at the maximum angular velocity. [ABSTRACT FROM AUTHOR]

The current research investigation aims to use and compare three different population-based optimization approaches to optimize the operating factors of drilling process to reduce thrust force (TF) and subsequently delamination in flax/PP laminates. Five different tool point geometries and three levels of spindle speed (SS) and feed rate (FR) were considered. Analysis of variance indicated that drill point geometry was most significant parameter affecting the TF, whereas SS had the most negligible impact. Moreover, the lowest and maximum TF and delamination factor (DF) were recorded for the U-shape drill bit and 135°- point angle twist drill bit, respectively. The outcome of the experimental investigation revealed that a low FR value (0.05 mm/rev) and medium-range SS value (1500–1800 RPM) were optimum parameters for each drill geometry. Although all optimization techniques provided almost the same optimum values, but TLBO (teaching learning-based optimization) technique's convergence rate was fast compared to others. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the cutting behavior of optical glassy polymers in order to identify the shape defects induced by the micro-machining processes. Polycarbonate (PC), Allyl Diglycol Carbonate (CR39), and polythiourethane (MR7) polymers are considered in this study to perform micro-machining experiments using the orthogonal cutting configuration. The comparative analysis is carried out by conducting the cutting experiments on hybrid samples that are composed of two types of polymers (MR7-PC, CR39-PC, and MR7-CR39) and then comparing the topographic state of the machined hybrid surfaces. Results show that PC is by far the polymer that generates the most shape defects because of its high rate of spring-back. This finding has been validated by nanoindentation experiments that reveal the highest mechanical reaction of PC at the time of nanoindentation unloading. This study demonstrates also that the measured thrust forces could be an indicator for predicting the spring-back defects induced by micro-machining. [ABSTRACT FROM AUTHOR]

Copyright of Dokuz Eylul University Muhendislik Faculty of Engineering Journal of Science & Engineering / Dokuz Eylül Üniversitesi Mühendislik Fakültesi Fen ve Mühendislik Dergisi is the property of Dokuz Eylul Universitesi Muhendislik Fakultesi Fen ve Muhendislik Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In many industrial, automobile, and defence products, there is a need to produce holes of a diameter larger than 25 mm. This requires the use of heavy machines, which requires more time and produces higher cutting forces. The cutting time and cutting forces can be considerably reduced by using trepanning in place of conventional drilling operations. Though a few trepanning tools are available commercially, they are costly, and not much literature is available on the design of such tools. Conventional design approach and manufacturing, and then experimental validation if the tool is costly and time-consuming. Hence, this research work follows finite element analysis and simulation for the tool design, followed by experimental validation of the performance. The developed trepanning tool uses two carbide parting inserts to produce holes of 40 mm in diameter in a 40 mm thick stainless steel 304 work-piece. The effects of machining parameters, cutting speed and feed rate, on the torque and thrust force were studied. The experimental and simulation results for the torque and thrust force were found to be in good agreement and the percentage error was less than 7% and 15%, respectively. The average thrust forces of 344 N and 258 N and average torque of 18.87 Nm and 6.97 Nm were observed for the two levels of cutting speed and feed rate chosen for machining trials. This simulation-based design approach can be used for developing similar cutting tools. The proposed methodology of CAD design, analysis, physical tool development, and then its performance validation could lead to an increase in innovation and a time and cost reduction during the development process of any tool used for machining. [ABSTRACT FROM AUTHOR]

Monitoring thrust during drilling operations is critical to optimizing drilling parameters and ensuring safe and efficient drilling. In this study, we will monitor variations in thrust force during the drilling process using a sensor coated with carbon black. These sensors measure changes in electrical resistance when the sensor is subjected to a mechanical load, such as drilling force. Carbon black at 5 wt% was used, which was embedded in a fiberglass composite. For this study, an orthogonal arrangement of Taguchi's L27 sequence was used, with drill diameter D, feed rate F, and spindle speed S as machining parameters. The thrust force was measured with a force dynamometer and the resistance change was measured simultaneously with the developed new system. Analysis of variance was used to find the optimal parameters, and in this study, a mathematical model was proposed to measure the thrust force directly using the electrical resistance detected. NSGA-II algorithm was used to predict solutions for the given parameters for comparison. A comprehensive way of drilling process and data-driven decisions to improve drilling performance and safety was studied, and a correlation between actual thrust and calculated thrust of 0.91 was found. The proposed system was able to monitor and continuously record thrust force in real time during drilling, with electrical resistance as the most important factor with an error percentage of less than 8% compared to the NSGA-II predictions of less than 5%. [ABSTRACT FROM AUTHOR]

In this study, micro‐drilling tests were carried out on composite laminates reinforced with hybrid (aramid‐carbon) and carbon fibers. Thrust force, hole quality, tool wear, and temperature parameters were measured and assessed following each drilling test. The quality of holes includes circularity, overcut, hole damage factor (HDF), and taper ratio. Micro‐drilling was performed on a CNC milling machine using 0.6 mm drill diameter, 7500 rpm, and 0.5 mm/min feed parameters. The plates are 3.05 mm (carbon fiber) and 3.45 mm (hybrid) thick. According to the results, the maximum thrust force (29.8 N) was measured in the hybrid composite due to the high fracture toughness of the aramid. In addition, it was determined that the thrust force and drill wear were related. The increase in thrust force during drilling caused an increase in drill wear values. While the average wear of the drill in carbon composite was 0.013 mm, the average wear of the drill in hybrid composite was 0.021 mm. Thrust force and tool temperatures were found to have a similar trend. The highest tool temperature was measured as 86.7°C in the hybrid composite. Hole quality results showed that drilling in carbon composite was more successful than in hybrid composite. Holes drilled in carbon composite have lower values for overcut (0.017 mm), HDF (1.028), and taper ratio (0.008). It has been understood that hole quality depends on thrust force and damage formation. Highlights: Carbon and hybrid (carbon‐aramid) composites were produced with a vacuum infusion process (VIP).Micro‐drilling of composites was investigated focusing on thrust force, tool temperature, and hole quality.Hybrid composites exhibited greater thrust forces due to their higher toughness compared to carbon composites.Hybrid composites showed higher maximum tool temperatures compared to carbon composites.The carbon composites exhibited better hole quality compared to the hybrid composites. [ABSTRACT FROM AUTHOR]

As a maraging steel, Corrax, is used in many engineering applications in the manufacturing, aerospace, and medical industries thanks to its properties such as high strength, hardness and corrosion resistance. However, these high specifications can cause some issues for manufacturing operations such as forging, machining, grinding. In addition to that, using heat treatment applications changes materials' mechanical specifications, affecting the material's behavior during machining. Therefore, it is important to characterize the influences of different heat treatment conditions on the material's property and behavior. In this study, the effects of heat treatment process on the mechanical properties, drilling machinability and corrosion resistance of Corrax steel were experimentally investigated with the samples of solution heat treated and aged at 400 °C, 525 °C, 600 °C, and 700 °C. The machinability was evaluated based on thrust force, chip morphology, hole quality, and tool wear. The results showed that the thrust force, torque and hole quality depend on feed rate, cutting speed, and mechanical properties affected by aging treatment. The highest hardness (47.4 HRC), ultimate tensile strength (1720 MPa), maximum elongation (33%), and toughness (198 jm-3) were obtained for the sample which aged at 525 °C for four hours, consequently the highest cutting force and surface roughness results were measured for this sample. Better hole surface quality and less burr formation were observed in the samples aged at 600 °C and 700 °C, and not-aged. On the other hand, while the highest value of corrosion potential were measured in the sample aged at 400 °C, the lowest corrosion potential value were measured in the sample aged at 700 °C. [ABSTRACT FROM AUTHOR]

The operational procedure of the helicopter requires the maintenance of a consistent velocity to ensure that the rotor blade tip remains within the subsonic threshold during forward flight. However, this approach leads to the drawback of heightened energy consumption. This research was designed to confront this challenge head-on, with the aim of augmenting energy efficiency by enhancing the helicopter performance in both hovering and forward flight scenarios. In order to realize this objective, the focus is on optimizing the rotor structure, particularly the rotor blades, with the aim of enabling dynamic adjustments to the rotor diameter. In order to validate the feasibility of this variable diameter adjustment mechanism, the study begins with a theoretical approach. Subsequently, simulations were conducted employing numerical mechanical analysis. The ultimate goal of these approaches is to compare the equivalent stress experienced by the tool material with its elastic limit. The outcomes stemming from both the theoretical and simulationbased methodologies have culminated in a comparative evaluation of the tool performance. This assessment allowed us to validate successfully the suitability and effectiveness of the chosen approach. [ABSTRACT FROM AUTHOR]

This paper presents an analytical approach for estimating frictional resistance to pipe movement at soil and external pipe surface of buried coated pressurized steel pipes relative to the internal thrust force. The proposed analytical method was developed based on 36 experiments, which involved three coating types (cement mortar (CM), polyurethane type-I (PT-I), prefabricated plastic tape (PPT)) on pipes' surfaces, three different soils (pea-gravel (PG), sand (S), silty-clay (SC)), and four simulated over burden depths above the pipe's crown. Investigation showed frictional resistance decreased with increasing over burden depth above the pipe's crown. The degree of frictional resistance at the pipe-soil interface was found to be in the order of PG > SC > S for all coating variations and overburden depths. CM coated pipe buried in all three types of soil produced significantly higher frictional resistance as compared to other coating types. Based on experimental data, the developed analytical introduced a dimensionless factor "Z", which included effects of types of coatings, soil, and overburden depths for simplified rapid calculation. Analysis showed that the method provided a better prediction of frictional resistance forces, in comparison to previous analytical methods, which were barely close in predicting friction resistance for different coating variations, soil types, and overburden depths. Friction resistance force values reported herein could be considered conservative. [ABSTRACT FROM AUTHOR]

Zirconium-based metallic glass (Zr-based MG) explores extensive applications in biomedicine and micro/nanomaterial fabrication owing to its remarkable combination of high specific strength and excellent corrosion resistance. In order to solve the difficulty of drilling micro-machining Zr-based MG, the longitudinal-torsional ultrasonic-assisted drilling (LTUAD) technique was employed for processing. Through experiments, its feasibility and effectiveness were explored in comparison with traditional drilling (CD). Firstly, in accordance with the Mohr–Coulomb yield criterion, the model for the mean thrust force under ultrasonic vibration assistance was developed, taking into account both the temperature effect and the tension–compression asymmetry of Zr-based MG. Secondly, the study examined the impacts of spindle speed, feed rate, and ultrasonic amplitude on the thrust force, while also discussing the characteristics of the hole exit and hole wall morphology. Finally, the impact of ultrasonic vibration on suppressing crack initiation and propagation was explored based on the free volume theory. Experimental results showed that the mean thrust force in LTUAD Zr-based MG decreased by 3.95–29.12% compared with that in CD, and the deviation of the experimental results from the model was 17.52%. Compared with CD, LTUAD technology significantly reduced the thickness and diameter of the exit round cap and effectively the number of pits caused by material chipping. [ABSTRACT FROM AUTHOR]

In this research, the idea of combining the genetic algorithm and adjoint method was proposed to leverage the benefits of both approaches to improve the accuracy of thrust nozzle shape optimization. Although the genetic algorithm can search the entire design space to approach the global optimum, its computational cost increases considerably with the number of design variables. Meanwhile, the adjoint method is unaffected by the design variables, but it cannot achieve the global optimum directly and relies on the initial guess geometry. To address these challenges, a genetic algorithm was initially employed to approximate the global optimal geometry of a thrust nozzle with a conical center body parameterized by a Bezier curve. A MATLAB code integrated the geometry parameterization, genetic algorithm, and Fluent R2 2021 flow solver. The resulting geometry was then considered as the initial guess for the adjoint method, which accurately achieved the final optimal geometry with increased control points. The genetic algorithm aimed to maximize the thrust coefficient as the objective function, while the adjoint solver aimed to minimize the axial velocity variance at the nozzle outlet as the cost function. Three distinct constraints were incorporated in the optimization process, and the influence of the center body shape on the results was thoroughly examined to consider all possible geometries throughout the optimization procedure. The findings revealed that the conical center body effectively adjusted the flow angle at the exit, significantly affecting the thrust force. Both optimization steps reduced the average velocity and increased the average pressure at the nozzle exit, enhanced the mass flow rate, and finally increased the thrust force. The genetic algorithm and adjoint method contributed to 3 % and 0.6 % increases, respectively, in the thrust force, resulting in a thrust coefficient of 96.15 % for the final optimized nozzle.

The controlled motion of an inertial object during a high-speed maneuver in a vertical plane is investigated. The generated thrust is limited in magnitude, the control is the angle that sets its direction, the initial velocity is generally non-zero, and external forces are not considered. The goal is to maximize the horizontal velocity projection at a given final moment of time with the simultaneous fulfillment of two terminal conditions: bringing the object to a given height and damping the vertical velocity projection. Similar tasks often arise when controlling mechanical objects with modulo-limited thrust. The research is relevant, as it is aimed at ensuring both the efficiency of the desired algorithm and the simplicity of its calculation and implementation. In this case, the methods of the mathematical theory of optimal control are used. As a result, a solvability condition for the problem posed is obtained, which is related to the minimum possible time of motion in the dual timeoptimal control problem. In the law of optimal control, based on the so-called law of fractional linear tangent, an analytical relationship between two integration constants is found, which makes it possible to reduce the procedure for determining these constants to the numerical solution of only one transcendental equation. An appropriate comparative analysis of the trajectories was carried out and conclusions were drawn that one of the proposed suboptimal strategies is more effective.

Conventional mechanical drilling of thick carbon fiber reinforced plastic (CFRP) composite laminates is prone to machining-induced defects such as burrs, delamination, and severe tool wear. However, pulsed laser drilling as an improved strategy results in hole taper and the formation of a heat-affected zone (HAZ). Herein, a new laser-mechanical composite drilling process is proposed, which combines the advantages of pulsed laser drilling for avoiding tool wear and twist drilling for achieving high dimensional accuracy, significantly improving the drilling quality of thick CFRP laminates. The evolution mechanism of the hole taper and HAZ with processing conditions in pulsed laser drilling is investigated. Furthermore, a theoretical model is established to reveal the material removal mechanism during the reaming process. The thrust force variation, drilling quality and tool wear are analyzed and verified by comparative experiments. The results show that due to the shielding effect from the surface materials, the maximum hole taper and HAZ at the hole exit reach up to 37.5° and 650 μm, respectively, which can be removed effectively by subsequent reaming operations. Due to its small amount of material removal, the peak thrust force and the average thrust force in laser-mechanical drilling are only 53.8 % and 37.6 % of the critical thrust force of delamination, respectively, which can effectively inhibit delamination. Compared with direct twist drilling, the average wear of the main cutting edge in laser-mechanical drilling is decreased by 60.87 %, which greatly reduces the size of the delamination by 55 %.

The increase in environmental awareness, energy saving, and carbon reduction means that demand for advanced materials for high-tech industries is increasing. Composite materials are widely used in structural components for various industrial applications because they feature light weight, high strength, corrosion resistance, and high durability. For final assembly processes for these composite material structural components (CMSCs), hole-drilling using a twist drill (TD) is a fast and inexpensive process. A step elliptical sphere-core drill (SESCD), which is a special compound drill, is composed of a TD and an elliptical sphere-core drill (ESCD). It prevents chip jamming and reduced thrust force (non-edge thrust) at the exit hole better than a step sphere-core drill (SSCD). Studies also show that CMSCs can delaminate during drilling if the thrust force is too great. This study determines the difference in the critical thrust force (CTF) for a SESCD and a TD for drilling composite materials. The results show that the CTF for a SESCD is increased by ~ 75% if s > 0.84 over that for a TD for various values of β (the ratio between the thickness of the ESCD (t) and the radius of the ESCD (c)). This design for a SESCD increases the drilling quality of composite materials and provides direction for future tool innovation. [ABSTRACT FROM AUTHOR]

Natural fiber composites are gaining popularity in manufacturing due to their cost-effectiveness, sustainability, reusability, and eco-friendly nature. Kenaf fiber is increasingly used as a reinforcing component in organic fiber-strengthened polymers for engineering purposes. Drilling is a crucial machining process used to create holes in composite constructions for the easier assembly of complex parts. Limited research has focused on drilling organic fiber-strengthened materials, as indicated by literature surveys. Consequently, this study investigates the drilling of weaved kenaf fiber-augmented polymeric composites. The study assesses the impact of drill bit varieties and cutting settings on delamination size and thrust force in poly (lactic acid) (PLA) composites supplemented with kenaf fibers. The investigation revealed that drill bit selection significantly influences surface finish and delamination index. Feed is the cutting variable that, when drilling kenaf fiber-reinforced materials, has the most impact on the thrust force for every drill bit. When using an HSS twisting drill with the Coro Drill-856 (CD-856), the thrust force produced is less than when using the Coro Drill (CD-854) design. [ABSTRACT FROM AUTHOR]

The current project uses computational studies to design and improve a new type of small propeller used in unmanned aerial vehicles. The design process started with selecting the appropriate airfoils for the new propeller and then investigating the effects of changing the airfoil, angle of attack and rotational speed on its aerodynamic performances. The numerical simulation of the turbulent flow produced by the propeller's rotation is carried out using the commercial calculation code ANSYS Fluent 14.0. Numerical results show that the newly developed propeller has a 116% improvement in thrust force compared to the commercial propellers used in today's UAVs. Furthermore, the values of the critical angles strongly depend on the propeller's rotational speed. Higher critical angles of attack could be reached (without the boundary layer getting separated) in low RPMs than in high RPMs. On the other hand, the thrust force increases when the rotation speed increases. Therefore, the selection of the angles of attack strongly depends on the rotation speed range desired. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been paid to the development of plasma aerodynamics. Among the main tasks to be solved in this area are an increase in thrust force, induced velocity and efficiency of operation of multi-discharge actuator systems used to control air flows. This work presents the results of experimental studies of the dependencies of the characteristics (thrust force, speed of the created air flow, power consumption) of such systems on the parameters of the power mode (voltage, frequency, pulse front duration) with unipolar high-voltage pulses with a bias voltage and comparison of these characteristics when working with other power modes. • High-voltage power supply system provides DC bias voltage to MAS electrodes in combination with repeated unipolar pulses. • High-voltage power supply system with rectangular voltage pulses for multi-discharge actuator system is created. • Electric discharge and gas dynamic characteristics of MAS under various power supply modes were investigated. • At optimal actuator system power supply modes comparable values of thrust force and airflow rates are achieved. [ABSTRACT FROM AUTHOR]

Marine propellers are frequently exposed to the corrosive effects of seawater, which can significantly reduce their performance and durability. As a result, high corrosion-resistant materials are used in the fabrication of the propellers. Fiber-reinforced polymers (FRPs) have recently taken over as the material of choice when it comes to creating corrosion-resistant structure. To get the desired mechanical properties and performance, it is necessary to combine FRP composites with other materials, such as steel or aluminum. The present work deals with evaluating the bond strength between Aluminum hub and carbon fiber reinforced polymer (CFRP) propeller blade profile. Araldite 2011 adhesive was used to establish the bond between the aluminum hub and CFRP propeller blade profile. A universal testing machine(UTM) was used to evaluate the bond strength of CFRP propeller blade profile-Al hub bonded joint specimens. The Al hub and CFRP propeller blade profile were subjected to axial thrust conditions. The surface interaction values obtained from the experiments were given as input data in Finite Element (FE)-model for complex geometry. The von-Mises stress criterion was used to assess the bond strength between Al hub and CFRP blade profile. In addition, bonded joint specimens were also subjected to cyclic aging at intervals of 0, 30, 60, and 90 days, respectively. The cyclic aged specimens were mechanically characterized using UTM. The Fourier transform infrared (FTIR)spectrum was used to analyze the aging behavior of adhesive (Araldite 2011), and the surface of the fractured specimens was analyzed using scanning electron microscopy (SEM). The extended aging period affects the Al hub/adhesive interface in bonded joints, leading to lower load joint failure. [ABSTRACT FROM AUTHOR]