Showing papers in "Journal of The Brazilian Society of Mechanical Sciences and Engineering in 2021"

An analytical solution for the free vibration of FG nanoplates

Abstract: In the present work, an analytical solution for the free vibration of nanoplates made of functionally graded materials (FGMs) under various boundary conditions is provided. In this context, a new refined plate theory with four variables based on the theory of non-local elasticity including the small-scale influences is adopted. Using the rule of mixture, the material properties of nanoplates are supposed to vary continuously across the thickness direction. Based on Eringen’s non-local elasticity theory, the equations of motion of functionally graded (FG) nanoplate are derived using Hamilton's principle, and the obtained equations are solved analytically. Here, the number of unknowns and governing equations of the present model are reduced to four separating the vertical displacement into shear and bending components, and so the number of unknowns has become less than the other alternative theories. The influences of the different parameters such as vibration mode, the aspect ratio, boundary conditions, power-law index, and non-local parameter on the natural frequencies of the FG nanoplate are discussed, in detail. Finally, it is decided that the considered parameters have major influence on the natural frequencies of the FG nanoplates. Furthermore, the proposed solution method not only satisfactorily handled the present problem and yielded successful results but also it supplied ease in the examination of non-local free vibration of FG nanoplates.

A combined backstepping and adaptive fuzzy PID approach for trajectory tracking of autonomous mobile robots

Abstract: A combined backstepping and adaptive fuzzy PID approach for a nonholonomic autonomous mobile robot to follow the desired path is proposed in this paper. Two adaptive fuzzy PID controllers are adopted at the dynamic control level for velocity tracking and steering control of the robot. The fuzzy PID controller consists of a PID controller which is designed by a trial-and-error approach, optimized using the cross-entropy method, and a fuzzy controller based on relational models with two inputs and three outputs. Adaptive adjustment of the PID controllers is implemented by means of the fuzzy controllers. The pose deviations of the robot when trajectory tracking will be eliminated by the backstepping control technique at the kinematic level using a kinematic model. The simulation validation results demonstrate that the proposed control system can offer good performances for the robot in terms of small distance error, rapid response, high stability, and trajectory tracking more accuracy.

Influence of fillers on polymeric composite during conventional machining processes: a review

Abstract: Nowadays, polymeric composites have emerged as a material highly in demand for advanced structures in various sectors, such as automotive, aerospace, and marine industries, due to their specific mechanical and physical properties. Functional efficiency of these composites significantly depends on their machinability. This encouraged the researchers to present a wide study and research work on polymeric composite. The present paper reviews the research progress on conventional machining of different filler-loaded polymeric composites. It delves into integrated functions in terms of its mechanism and machining responses. This includes aspects such as various weight percentage of filler on the machining responses. It also shows the proper filler loading for the improvement of mechanical properties (i.e., strength and stiffness) and fracture toughness for both intralaminar and interlaminar perspectives. Machining procedure and performance capabilities have been reviewed and depicted in detail as well. A comprehensive summary of the findings along with future perspectives has been included at the end, which might contribute to a greater development of this machining process in the future.

Modelling of the flexoelectric effect on rotating nanobeams with geometrical imperfection

Abstract: Flexoelectricity is the phenomenon of electric polarization caused by the strain gradient, which usually has a huge effect on nanoscale structures. This paper firstly combines the finite element method (FEM) with a novel third-order shear deformation beam theory (TSDT) to simulate the static bending and free vibration responses of rotating (around one fixed axis) piezoelectric nanobeams with geometrical imperfection considering flexoelectric effects, where the structures are placed on the Pasternak’s elastic foundations. Based on two-node beam elements, the Lagrange and Hermit interpolation functions, the proposed approach shows high accuracy through the comparative results of this work and published references. A wide range of parameter studies is conducted such as the rotational speed, shape imperfection, flexoelectric effect, and so on to evaluate the influences on the static bending and free vibration behaviors of the structures. The novel investigation points out that when the beams are rotating around one fixed axis, the mechanical responses, in this case, are not similar to those of normal cases when the rotational speed is zero. This is a new study that can be referenced when designing nanoscale beam structures in practice.

Analysis of residual stresses in rails during the straightening process

Abstract: The straightening process is the main cause of residual stresses in the manufacture of rails. It is a non-trivial process with cyclic plastic loads, solid–solid contact and complex geometry, which computational simulation is often complex and time-consuming. In this work, a new methodology was developed by means of a quasi-static modeling instead explicit dynamic. This methodology was proved to be effective and fast. Sixteen cases were simulated, and a C-shaped pattern for longitudinal stress, as seen through the literature, was obtained in the most of them, even with large variations between the main parameters: the yield strength, the tangent modulus and the initial curvature of the rail. The longitudinal normal residual stresses were higher than the transversals ones, as expected. The results obtained by simulations were the basis for the use of a Gaussian process regressor to predict the residual stresses from any initial parameters. This tool confirmed that the parameters that more affect the final state of residual stresses are, in this order, yield strength, tangent modulus and curvature. This is relevant information, since the hardest data to obtain in practice are the initial curvature of rail. Both simulation methodology and the statistical Gaussian process tool could be useful to perform life fatigue analysis in rails, since this needs the initial state of residual stresses to be more reliable.

A review on microdroplet generation in microfluidics

Abstract: Micro-nanofluidic technology is widely used in food safety testing, drug screening, new material synthesis and bioengineering. Droplet microfluidic technology is an important branch of micro-nanofluidic technology. The microdroplet technology can produce high-throughput monodisperse droplets. The droplet technology overcomes many problems of continuous flow, such as small sample reagent volume, no cross-contamination, and rapid chemical reaction. So microdroplets have an important position in the fields of single cell analysis, gene sequencing, and real-time diagnosis. This review focuses on the different methods and applications of microdroplet generation in microfluidics. The droplet generation methods are passive and active methods. The passive method does not require external force, while the active method requires external force such as external electric field, magnetic field, acoustic field, and laser field. It is predicted that the quantitative generation of droplets on demand in microfluidics will be the important direction for future research. This review provides new ideas for the applications of the quantitative generation of microdroplets on demand in microfluidics.

Electric vehicle battery-ultracapacitor hybrid energy storage system and drivetrain optimization for a real-world urban driving scenario

Abstract: A battery has normally a high energy density with low power density, while an ultracapacitor has a high power density but a low energy density. Therefore, this paper has been proposed to associate more than one storage technology generating a hybrid energy storage system (HESS), which has battery and ultracapacitor, whose objective is to improve the electric vehicle (EV) driving range. The HESS parameters have been evaluated in a configuration of EV powered by two in-wheel electric motors, coupled straight into the front wheels, and by a unique EM, connected to a differential transmission to drive the rear wheels. Moreover, this paper considers a real-world drive cycle based on the urban driving behavior of Campinas city, one of the most populous cities in Brazil. Aiming to minimize the HESS size and enhance the EV driving range, an optimization problem was formulated and solved using a genetic algorithm technique, in which the EV drivetrain parameters and HESS components and control are optimized. Finally, the obtained Pareto frontier defines the optimum EV configurations, in which the best-selected configurations were able to perform up to 188 km with a 418 kg HESS (maximum drive range solution), or 82.75 km with a 146.58 kg HESS (minimum HESS solution) and 319 km with a 188.43 kg HESS (best trade-off solution), without presenting performance losses.

Effect of deep cryogenic treatment on tool life of multilayer coated carbide inserts by shoulder milling of EN8 steel

Abstract: High-strength materials are hard to machine with ordinary tools and necessitates tool inserts of high strength and hardness to machine them. One of the methods to improve the physical properties of an insert material is cryogenic treatment which involves the treating of materials at low temperatures. In the current experiments, two multilayer carbide tool inserts WS40PM and F40M were analyzed by cryogenically treating them. Three class of cutting tool inserts were taken for comparison: untreated, cryogenically treated and cryogenically treated and tempered (CTT). The microstructural changes were observed through scanning electron microscopy, and the change in microstructure of all classes of tool inserts was compared and contrasted. Hardness of the tool inserts was measured using Vickers microhardness tester, and the variation of crystallite size in tool inserts was examined through X-ray diffraction studies. Rate of tool wear (through flank wear) was observed by performing shoulder milling operation on the mild steel EN8 grade steel at constant velocity in a CNC vertical machining center using treated and untreated tool inserts. The results showcased the increase in insert hardness, microstructure and tool life of treated tools when compared with untreated tool inserts. Highest hardness was achieved for CTT tool inserts and was found to be 1142 HV for WS40PM and 1483 for F40M inserts, respectively. From the flank wear studies, F40M inserts experienced a wear of 203 µm and WS40PM inserts experienced 269 µm upon machining EN8 grade steel.

Performance enhancement of rotary tool near-dry EDM process through tool modification

Abstract: The performance enhancement of the rotary tool near-dry electrical discharge machining (RT-ND-EDM) process by modifying the tool electrode geometry was explored in the present work. The experiments were performed using the tubular tool, slotted tools, and helical tools. The number of slots in slotted tool electrodes and the number of starts in the helical tool electrodes were selected based on the experimental results. Also, the performance of the selected tool electrodes was compared with that of the basic tubular tool electrode. The effects of input parameters (tool rotation speed, current, pulse on time, gas pressure, and the LFR) on the performance of the RT-ND-EDM process are assessed for selected tool electrodes. This research established the efficacy of introducing slotted and helical features into rotating cylindrical tools to enhance the performance of the RT-ND-EDM process. The flushing of the inter-electrode gap is of decisive importance with respect to material removal rate, geometric accuracy, and surface quality of work material during the RT-ND-EDM process. The results revealed that a double-start helical-shaped tool electrode resulted in better process performance among all the selected shape electrodes.

Innovation of thermoplastic polymers and metals hybrid structure using friction stir welding technique: challenges and future perspectives

Abstract: Friction stir welding (FSW) is an innovative technique to produce a hybrid joint of thermoplastic polymers and metals in the recent past. A review of the friction stir welding processes and fabrication of polymer-based nanocomposites was developed to meet the challenges of the industry’s needs in the twenty-first century. These hybrid structures predominantly will play a vital role in future innovations. In the recent past, it is widely used in the automobile and aerospace sectors. It is due to its lightweight and high strength-to-weight ratio. This article focuses on the recent development that has been made in the joining of thermoplastic polymers and metals through the friction stir welding technique and friction stir processes. This article provides a comprehensive study of the influences of various process parameters on weld performance. The effect of surface pretreatment on the adhesive mechanisms is presented. Finally, mechanical behavior like hardness and tensile strength of joints, and the microstructural features of joints are presented. Based on the detailed survey, this paper consolidated the way to improve the thermoplastic polymers and metals joints through FSW.

Sustainability improvement of WEDM process by analysing and classifying wire rupture using kernel-based naive Bayes classifier

Abstract: The current work aims to improve the sustainability of wire electric discharge machining by predicting the wire breakages. Wire breakages are process interruptions which increase the machining time, energy wastage and material consumption. The study is a novel approach to predict process continuity by binomial classification of machining outcomes using kernel-based naive Bayes algorithm. The two classes are labelled as wire breakages and continuous machining. Training dataset consists of 31 experiments according to central composite design of response surface methodology, and wire breakage instances are recorded as response. The input dataset contains four machining parameters, namely pulse on time, pulse off time, servo voltage and wire feed rate, whereas mean gap voltage variation is derived from in-process data. The trained model was 96.7% accurate in wire breakage predictions. Further, nine confirmation tests were conducted to check model adequacy in real-world situations. The model predicted all instances of wire breakages accurately. The stages of wire wear up to wire rupture were studied by conducting microstructural analysis.

Correction to: Isogeometric small-scale-dependent nonlinear oscillations of quasi-3D FG inhomogeneous arbitrary-shaped microplates with variable thickness

Abstract: The current investigation deals with proposing a numerical analysis for the geometrically nonlinear large-amplitude vibrations of arbitrary-shaped microplates having variable thickness with various patterns in the presence of couple stress type of microstructural size dependency. To accomplish this purpose, the isogeometric analysis (IGA) is employed to achieve exact geometrical description as well as higher-order efficient smoothness with no meshing difficulty. On the other hand, the modified couple stress continuum mechanics is applied to a refined quasi-3D plate model having the capability to take the thickness stretching into consideration with only four variables. The microplates are assumed made of functionally graded (FG) composites, the material properties of which are changed continuously through the variable thickness. The variation of microplate thickness obeys three different schemes including linear, concave, and convex ones. It is highlighted that by changing the pattern of the thickness variation from convex type to linear one, and then from linear type to concave one, the both classical and couple stress continuum-based nonlinear frequency of the microplates having different shapes increases due to a higher value of the average plat thickness. On the other hand, by considering this change in the thickness variation pattern, it is seen that the significance of the couple stress size effect increases. For this reason, the significance of the stiffening scheme associated with the gradient of rotation gets lower through increment of the material gradient index of a FG composite microplate.

Multiobjective crashworthiness optimization of graphene type multi-cell tubes under various loading conditions

Abstract: Nature is an important source of inspiration for researchers to create better designs. In this study, graphene type multi-cell tubes is inspired by graphene due to its strong and lightweight mechanical properties. Peak crushing force (PCF), energy absorption (EA) and crushing force efficiency crashworthiness indicators have been taken into consideration under different loading angles, and the complex proportion assessment (COPRAS) which is a multicriteria decision-making method has been used to determine the best model. The best model is found to be GTMT5 (second-order and third-order hollow cylinders in the graphene type multi-cell tube) by the COPRAS selection method. The multiobjective optimization, whose objective is to minimize PCF and maximize EA, is applied on the GTMT5 using the multiobjective particle swarm optimization and non-dominated sorting genetic algorithm II methods, and the techniques are compared. The optimization study is carried out on the radial basis function metamodels. This study shows that circular structures placed in multi-cell tubes have a significant effect on the crashworthiness performance.

Functional grading of surfaces through hybrid ultrasonic, abrasive water jet, and electric discharge machining processing

Abstract: The present study investigated a hybrid electrical discharge machining (h-EDM) process for producing functionally graded titanium surface. Herein, a stream of hydroxyapatite/titanium oxide abrasive slurry jet has been supplied, through a specially designed tool, to the ionized zone created by the EDM process, and the abrasive particles were finally directed towards the melted region of titanium through ultrasonically produced kinetic energy. The finally produced functionally graded surfaces have been characterized through microscopic analysis to assess the efficacy of the as-produced surfaces. The results highlighted that the abrasive particles have been successfully embedded into the surfaces. The proposed hybrid technology could be used for various engineering applications, including automotive and biomedical sectors.

Numerical study of coupled flow in blocking pulsed jet impinging on a rotating wall

Abstract: In order to study the complex unsteady flow characteristics of pulsed jet impinging on a rotating wall, the Wray–Agarwal turbulence model was adopted. The following conditions were used to simulate the internal flow mechanism, namely: jet with Re = 10,000; rotational speed n = 500 rpm; impinging height H/D = 5; pulse period T = 0.5 s + 0.5 s. The results show that: (1) The flow field structure of pulsed jet impinging the rotating wall is symmetrical about the jet axis. With the development of time, a pair of entrainment vortices and rotating vortices are formed on both sides of the jet and on the rotating wall, respectively. (2) In the vicinity of the jet outlet, the radial distribution of the velocity V gradually becomes non-uniform as time progresses and eventually coincides with the velocity at steady state. (3) During 0 s ≤ t < 0.5 s, the velocity at nozzle-exit increases with time, and the V/Vj along the axis coincides with the steady state. During 0.5 s ≤ t < 1 s, the nozzle-exit velocity V/Vj decreases to 0, along the axis direction, the V/Vj increase first and then decrease. (4) The impact pressure of pulsed jet on the impact wall is greater than that of continuous jet on the impact wall in a certain period when water hammer effect occurs.

Machinability of AA6061 aluminum alloy and AISI 304L stainless steel using nonedible vegetable oils applied as minimum quantity lubrication

Abstract: In the present investigation, the machinability and rheological properties of the modified vegetable oils like pongam (Pongamia pinnata), jatropha (Jatropha curcas), neem (Azadirachta indica), and mahua (Madhuca indica) are carried out. Experiments are conducted by applying prepared oils for turning and drilling of AA 6061 aluminum alloy and AISI 304L stainless steel as cutting fluids. Tool flank wear, cutting force, and surface roughness are evaluated using mineral, raw, and modified vegetable oils. The fatty acid composition and results of the copper corrosion test for all vegetable oils show that they are better candidates for cutting fluid formulation than mineral oil. The results indicate lower coefficient of friction and better surface roughness values for vegetable oils in contrast with mineral oil. Finally, it can be concluded that a lesser environmental impact and satisfactory metal cutting performance can be achieved using a vegetable oil-based metal cutting fluids.

Recent trends and challenges in predictive maintenance of aircraft’s engine and hydraulic system

Abstract: Predictive maintenance (PM) strategies are based on real-time data for diagnosis of impending failure and prognosis of machine health. It is a proactive process, which needs predictive modeling to trigger an alarm for maintenance activities and anticipate a failure before it occurs. Various industries have adopted PM techniques because of its advantage in increasing reliability and safety. But in the aviation industry, expectations for safety are increased due to its high cost and danger to human life when an aircraft fails or becomes out of service. Flight data monitoring systems are regularly implemented in commercial operations using artificial intelligence (AI) algorithms, but there is limited work specific to safety critical systems such as engine and hydraulic system. This paper provides a survey of recent work on PM of aircraft's’ hydraulic system and engine, identifying new trends and challenges. This work also highlights the importance of PM and state-of-the-art data pre-processing techniques for large datasets.

A review on the corrosion fatigue strength of surface-modified stainless steels

Abstract: Materials are often exposed to simultaneous actions of corrosive environment and repeated stress, which sometimes leads to a significant decrease in corrosion fatigue strength. Several attempts have been made in the past to investigate the fatigue cracks initiation and propagation process across different materials. However, the current knowledge is insufficient to address the combined response of corrosion reaction and repeated stress on the fatigue properties of stainless steels (SS) especially when they are subjected to surface treatments. The present paper reviews the relevant past work done to date on the fatigue and corrosion fatigue strengths of nanostructured SS. The corrosion fatigue strengths of SS can be improved by the combined effects of surface treatments and the associated compressive residual stresses. The corrosion fatigue mechanism reviewed in this paper explains in detail the major factors involved in predicting the fatigue life behaviour including residual stress, loading frequency, microstructures, work-hardening, surface topography, surface treatment processing parameters, and fracture surface. For future works, the factors that could improve the corrosion fatigue behaviour of nanostructured SS were also discussed in detail.

Abrasive water jet machining techniques and parameters: a state of the art, open issue challenges and research directions

Abstract: Recently, different problems in manufacturing operations namely lower product time, secondary operations, waste reduction, miniaturization, high-level precision ability, better surface, complex-shaped profiles and high strength material machining are solved with the usage of superior machining methods The abrasive water jet machining (AWJM) process is further established based on various advanced machining techniques by the researchers In the manufacturing industries, the AWJM process is used to determine extensive use for a wide range of machining materials This survey is categorized into different kinds of AWJM processes based on certain parameters to be precise which are factor influences, work materials and modeling process of AWJM AWJM influences parameters are categorized into subparameters which include mixing parameters, hydraulic parameters, cutting parameters and abrasive parameters Additionally, we investigated a few modeling processes in AWJM such as dimensional analysis, statistical model, differential equation, neural network model, numerical model and analytical model The review papers were collected from the year 2009 to 2019, and approximately 78 papers are used for this examination Additionally, the comparative analysis is carried out between the different numbers of papers chosen for each experiment and their performances were established in this work Several open issues challenges namely low material removal rate, low depth of penetration, etc with its future scopes are addressed

Effect of multi-infill patterns on tensile behavior of FDM printed parts

Abstract: Fused Deposition Modeling (FDM) is an extrusion-based additive manufacturing technique which growing rapidly due to its ability to fabricate complex parts directly from CAD models. In conjunction with its growing applications, the mechanical behavior of the FDM printed part needs thorough investigation for effective application as an end use functional part in various industries such as aerospace, automobile, mold and die, biomedical. Functional applications of FDM printed parts are affected due to their lower mechanical properties compared to injection molded parts. The assessment of the mechanical behavior of the FDM printed part is proved as challenging task due to the wide variety of the process parameters. In the present work, an attempt has been made to experimentally investigate the tensile behavior of FDM printed parts having multi-Infill patterns and different stacking of layer arrangements for different Infill density and raster orientations. Combined patterned parts are printed from two thermoplastic materials, viz. PLA and ABS having six different stacking sequences at three different levels of Infill density (i.e., 30%, 60% and 90%) and two different raster arrangements (i.e., 0° and 45°) and those are mechanically tested to obtain tensile properties. Further, the fractographic analysis was carried out to study various aspects of tensile failure modes for FDM printed multi-infill pattern samples. Combining two different infill patterns and layer stacking sequence improves tensile strength for 45° raster orientation samples and decreases tensile strength for 0° raster orientation samples when compared to a single pattern throughout. For 0° raster orientation, stacking sequence with all the layers are deposited parallel to loading direction offers more strength than multi-infill pattern samples. Whereas for 45° raster orientation, stacking sequence with all the layers parallel to loading direction offers lower strength than multi-infill pattern samples.

Experimental modeling and optimization of surface quality and thrust forces in drilling of high-strength Al 7075 alloy: CRITIC and meta-heuristic algorithms

Abstract: Al 7075 is a renowned high-strength engineering material used in automotive and aerospace applications, wherein many functional cylindrical parts are subjected to internal or external loads. Engineered parts with form errors (cylindricity CE and circularity error Ce) result in undesirable vibration and high deformation in rotating parts. In addition, reduced surface roughness (SR) and thrust forces (TF) are essential to limit the secondary process (namely, polishing) and power consumption. Experiments are performed based on central composite design considering drilling parameters (point angle, cutting speed, and feed rate) as inputs and output performances as CE, Ce, TF, and SR. It is noted that, except feed rate for Ce, all other parameters are found significant toward the output performance. Also, prediction accuracy with ten random experimental cases resulted with the percent error of 8.4% for SR, 5.41% for TF, 10.64% for Ce, and 10.35% for CE, respectively. Continuous ribbon-like chips at higher cutting speed, loose fragmented chips at higher feed rate, and increased arc length and radius at higher point angle were observed from the chip morphology analysis. Criteria importance through inter-criteria correlation (CRITIC) method applied to determine the weight fractions for Ce, CE, TF, and SR was found equal to 0.2802, 0.1991, 0.3293, and 0.1914, respectively. Four algorithms (genetic algorithm GA, particle swarm optimization PSO, teaching learning-based optimization TLBO, and JAYA algorithm) were applied to determine the optimal drilling conditions. JAYA algorithm determined optimized drilling conditions ensure predicted output values found close to experimental values with an acceptable percent error of 10.8% for Ce, 8.9% for CE, 6.73% for SR, and 3.51% for TF, respectively.

Laser transformation hardening of various steel grades using different laser types

Abstract: Laser surface hardening has become a promising replacement technique for conventional heat treatment. The laser is a heat source, deployed with optics to modify the surface along with the desired geometry. Laser density and its interaction time can be controlled and varied depending upon the final requirement at the surface. Increased hardness, diffusion-less phase transformation, self-quenching, uniform case depth over the entire scanned area are the reasons for laser-assisted hardening to become very popular and successful. Another reason for its success is that there is no bulk transformation of the material; only selected regions are subjected to laser irradiation for better surface improvements. This paper is a precis of various investigations done with a gas type CO2 laser, a solid-state Nd: YAG laser, high-power diode laser and fiber laser (only Continuous Wave mode) over a variety of steel grades. Laser wavelength, power intensity, transverse/scanning speed, focal plane distance, surrounding atmosphere, pre-treated surface and surface absorptivity are parameters involved in laser surface hardening technique. By varying these independent variables, the desired surface property is achieved on the substrate subjected. A significant analysis of various experimental investigations done in this area is provided. Particular reference is made to surface hardening using different lasers as mentioned above. Although laser hardening is a potential technique for enhancing the surface properties, multi-track hardening/back tempering of the large surface area is still a concern and needs some attention. The main reason is a decrease in hardness in the overlap region. Various studies indicate that a single-track laser hardened region results in 3- or 4-times higher hardness than that of the original or base metal hardness. In contrast, in the overlapped region, the hardness value decreases, i.e., the difference between the hardness values at the single-track hardened region and an overlapped region is around 100–400 HV. This article reviews the chronological development of laser transformation hardening method explicitly by outlining the effect of process parameters on hardened depth and width, hardening influence in wear and corrosion resistance, numerical simulation and experimental validation techniques. Particular reference is made to CW (continuous wave) type laser hardening.

A novel technique of harvesting cortical bone grafts during orthopaedic surgeries

Abstract: The harvesting and implanting of bone graft is a complicated and expensive orthopaedic procedure. This study introduces a unique designed hollow drill bit and a novel technique of rotary ultrasonic drilling of porcine bone to get a precise hole for screw insertion and can harvest cortical bone graft with the least bone debris generation. The new diamond impregnated hollow drill bit is compared with the conventional surgical drill bit with and without providing the ultrasonic vibrations. Also, variation in diamonds grit sizes (fine 70 µm, medium 155 µm, coarse 250 µm) and various process parameters like rotational speeds (500 rpm, 1500 rpm, 2500 rpm), feedrate (10 mm/min, 30 mm/min, 50 mm/min) and amplitude (4 µm, 12 µm, 20 µm) were optimised for enriched graft quality of bone. The diamond hollow tool provides a cylindrical bone graft as per the geometry of hollow bit whereas the surgical drill gives dense spiral-shaped bone debris. While providing no ultrasonic vibrations to hollow bit, segmented bone grafts were observed. The optimised parameters for a continuous uniform rod-shaped bone graft with the least graft deformity are obtained with drilling at rotational speed of 2500 rpm, feedrate of 10 mm/min, using fine (70 µm) diamond abrasives and amplitude of 4 µm. Rotary ultrasonic bone drilling is a better alternative method to reduce the bone debris formation and is capable of providing solid cylindrical rod-shaped cortical bone graft using a fine (70 µm) diamond coated hollow drill tool. This first successful trail-based in-vitro study relates the chip morphology of bone debris with the graft quality of bone obtained during the surgery.

Performance improvement of the sanitary centrifugal pump through an integrated approach based on response surface methodology, multi-objective optimization and CFD

Abstract: Performance improvement of the pumps leads to the reduction in power consumption of industrial pumping systems. This paper presents an effective approach for the enhancement of the performance of a sanitary centrifugal pump by adopting computational fluid dynamics and response surface methodology with a multi-objective optimization algorithm. An experimental apparatus with a closed loop is set up in laboratory to measure the pump performance and then to valid it with the numerical results. In this study, three input design parameters, namely blade outlet angle, blade wrap angle and blade outlet width, are investigated for the simultaneous optimization of pump head and efficiency. Twenty-five samples of impeller are generated with the help of the Latin hypercube sampling method. All impellers in the design space are numerically simulated. The multi-objective optimization algorithm is used to get the Pareto optimal solution between head and efficiency. Looking at the results, 9.154% and 10.15% improvement in head and efficiency are observed at the design point as compared to initial pump. Further, the effect of the three design variables on head and efficiency is also studied. The results indicate that the blade outlet width and blade wrap angle are most significant parameters that affect the efficiency of the pump.

Tribological characteristics and drilling performance of nano-MoS2-enhanced vegetable oil-based cutting fluid using eco-friendly MQL technique in drilling of AISI 321 stainless steel

Abstract: The implementation of sustainable manufacturing techniques to make machining operations more eco-friendly is a demanding issue that has gained attention from academic and industrial sectors. In some machining operations, a large quantity of machining fluids is wasted to make machining easier, especially during the machining of difficult-to-machine materials such as stainless steel. In such circumstances, many researchers are investigating eco-friendly techniques. Therefore, in this study, effects of minimum quantity lubrication (MQL) with MoS2-enhanced vegetable-oil-based cutting fluid on the drilling characteristics of AISI 321 stainless steel are investigated. The main aim of this study is to analyse the machining performance of various coolant–lubricant strategies, namely dry, flood, pure MQL, and three nanofluid MQL (NFMQL) with regard to thrust force and torque, surface roughness, friction coefficient, chip morphology and tool wear mechanism in drilling of stainless steel (AISI 321). Research findings indicated that NFMQL drilling conditions have given excellent drilling performance by improving drilling characteristics than pure MQL, dry and flood drilling. Among the NFMQL drilling conditions, 1.5 wt.% nano-MoS2 in sunflower oil-based MQL condition provided better cooling–lubrication effect and improved the drilling characteristics followed by 1.0 wt.% and 0.5 wt.% nano-MoS2 in sunflower oil-based MQL conditions. The 1.5 wt.% nano-MoS2 in sunflower oil-based MQL drilling had resulted in 43.2%, 68.9%, 56.8% and 41.6% reduced values of thrust force, torque, surface roughness and COF, respectively, at the 30th hole in comparison with flood drilling. Moreover, noticeable improvement in the chip morphology and tool wear rate has been achieved while drilling under NFMQL environments. The better drilling performance of nanofluid MQL may be attributed to the fact that nanoparticles (MoS2) in sunflower oil offer excellent cooling–lubrication features and provide strength to the oil film at the tool–workpiece interface. In addition, nano-MoS2 particles have high surface activity and are easily adsorbed onto the contacting surfaces, thereby maintaining the lubrication effect.

High-velocity impact behavior of hybrid fiber-reinforced epoxy composites

Abstract: In this study, non-hybrid and hybrid (Kevlar, carbon and glass) fabric epoxy composite laminates were fabricated with different stacking sequences by hand lay-up followed by hot-compression molding. Experimental tests were conducted to investigate tensile, flexural, and hardness characteristics. It was found that the stacking sequence did not significantly affect the tensile strength and hardness values of the composites; however, it affected their flexural strength. Damage morphology of the specimens through SEM images showed that the major damage mechanisms in the composites were delamination, fiber breakage, pull-out, and matrix cracking. Based on the static experimental results, the high-velocity impact behavior was investigated through simulation study using LS-DYNA finite element analysis (FEA) software. To study the ballistic impact, a steel projectile with a hemispherical penetrating edge at impact velocities of 100 m.s−1, 250 m.s−1, and 350 m.s−1 was considered. Among non-hybrid fabric epoxy composite specimens, Kevlar/epoxy specimen was found to have the highest impact energy absorption followed by carbon/epoxy and glass/epoxy, respectively. Regarding the hybrid fabric epoxy composite specimens, the ones with Kevlar plies in the rear face exhibited better energy absorption compared to other stacking sequences. The non-hybrid glass/epoxy specimen had the lowest energy absorption and highest post-impact residual velocity of projectile among all specimens. From the FEA results, it was noted that impact resistance of hybrid composites improved when Kevlar fabric was placed in the rear layer. Thus, the stacking sequence was observed to be of substantial importance in the development of fabric-reinforced composite laminates for high-velocity impact applications.

Multi-objective optimization of piezoelectric vibrational energy harvester orthogonal spirals for ore freight cars

Abstract: Heavy haul freight car cargo capacity and speed have both been increased over time, aiming to boost overall rail transportation efficiency. These trains are often long and operated by a single person, who may not notice failures, especially in the wagons located far from the main locomotive. Sensors to measure the in-train forces have emerged as a feasible solution to assist the driver, indicating possible failures, avoiding accidents and derailments. However, the vast majority of freight cars used in commodity transportation do not have any electric power source, requiring some kind of energy harvester. Vibration energy harvesters (VEH) present some advantages compared to batteries, which need to be charged or replaced periodically. Among VEH designs, the piezoelectric orthogonal spiral (OSo) multibeam has proven to be adequate in reducing environmental frequencies that are typical of these vehicles, for both the well-defined loaded and unloaded conditions. This paper searches for the best set of characteristics for an OSo device for freight car sensors, aiming to enhance the output power in both wagon conditions, as well as ensuring its safety against structural failures. For an aluminum structure and lead zirconate titanate (PZT) ceramics, the best configuration leads to an overall factor of safety of 1.51 and generates up to 2.73 mW (loaded) and 16 mW (unloaded), which is sufficient to feed most of the low power sensors.

Path planning for autonomous ground vehicles based on quintic trigonometric Bézier curve

Abstract: Path planning is one of the essential steps for autonomous ground vehicles or even wheeled mobile robots. This paper proposes a general framework for the path planning using quintic trigonometric Bezier curve with two shape parameters and $$C_{3}$$ continuity. We express that when there are obstacles, predefined path can be adjusted by only using shape parameters without altering any obstacle. Additionally, the velocity, lateral acceleration, longitudinal and lateral jerks of the predefined cubic and quintic Bezier, and cubic and quintic trigonometric Bezier paths are compared. Also, a path surface for autonomous ground vehicles can be generated using developable surfaces.

An adaptive extreme learning machine based on an active learning method for structural reliability analysis

Abstract: The metamodel-assisted reliability method opens a promising way to achieve efficient structural reliability assessment for structures with expensive-to-evaluate simulations. The advances in machine learning promote the development of the metamodel technique over the last decades. In this study, an active learning reliability method is presented by the combination of the extreme learning machine(ELM) and an efficient sequential sampling method with the framework of the Bayesian optimization theory. To determine the hyperparameters of ELM automatically, an adaptive extreme learning machine is introduced to approximate the performance function for reliability analysis. Furthermore, a novel active learning function inspired by the ensemble learning strategy is established to select the next best sample for approximation model refinement. Correspondingly, an effective stopping criterion on the cross-validation technique is built to terminate the active learning process timely. Four problems including numerical examples and practical engineering structures are analyzed. The test results show that the proposed method provides a satisfactory failure probability estimation with fewer performance function evaluations for these different reliability problems.

A review of the relationship between design factors and environmental agents regarding adhesive bonded joints

Abstract: Fiber-reinforced polymers (FRPs) combine characteristics of polymers and fibers to obtain a material with high mechanical strength and stiffness together with low specific mass and good corrosion resistance. The use of FRPs is growing as an alternative to metals in the automotive, aerospace and civil construction industries. Since adhesive bonded joints are an excellent way of joining materials due to the better load distribution, the use of FRPs for this purpose has been the objective of many studies about durability and structural safety. In service, environmental factors, including temperature, humidity, UV exposure and salt spray, can degrade materials, leading to unexpected failures. Since joints in service are subject to these multiple and uncontrolled adverse conditions, FRP adhesive bonded joint degradation has been studied by experiments that simulate these adverse environmental conditions. The combined analysis of the effect of environmental factors on the joint and the materials of each component allows predicting the system performance. In addition, optimal design parameters, such as the thickness of the adhesive, overlap length, materials and manufacturing processes, may be different according to the target application of the joint. Therefore, the achievement of optimal design parameters depends on the understanding of joint behavior in service. Based on analysis of the contribution of researchers in the specialized literature on adhesive joints and FRPs, this article reviews the main findings on degradation of adhesive joints and their components. Research topics for optimization of adhesive joint systems are also discussed.