International Journal of Automotive and Mechanical Engineering

A Review of Recent Improvements, Developments, Influential Parameters and Challenges in the Friction Stir Welding Process

2024-03-19T08:51:26+00:00

Friction Stir Welding (FSW) is an innovative and reliable welding technique. Since this method is environmentally beneficial, it has received much attention and development over the past few decades. This study aims to revise the conceptual facts of FSW and evaluate the most recent improvements and developments in its applications. This review also assesses the influences of design parameters such as rotational and welding speeds on weld quality and joint efficiency. Existing challenges associated with applying FSW in various contexts, as well as the potential advantages that might lead to further study and broader FSW applications, are addressed. It has been concluded that FSW allows for optimising the rotating speed based on the preferred welding speed to achieve the greatest tensile strength in the welded materials. Despite FSW being established as effective in laboratory and small-scale applications, utilising FSW for large structures poses challenges. These challenges include maintaining consistent weld quality, controlling heat dissipation, and ensuring joint integrity during FSW. Consequently, further research is required to resolve these challenges and make FSW a promising welding method in contemporary production sectors.

Modeling and Simulation of a Battery/Supercapacitor Hybrid Power Source for Electric Vehicles

2023-09-05T07:28:32+00:00

Environmental protection and energy conservation have become highly concerning themes. In the transportation field, green electric vehicles (EVs) are rapidly being promoted and applied, and power sources, as one of the core technologies, greatly affect the working performances of EVs. Currently, a single battery power supply is the mainstream configuration for EVs, but the instantaneous/short-term high-power output required by the battery for vehicle working conditions has a serious impact on the service life of the battery. As an effective solution, the battery/super-capacitor (SC) hybrid power source (HPS) has attracted increasing attention. This article proposes an improved semi-active battery/SC HPS, which can achieve multiple operating modes and fully utilize the advantages of the two power sources to effectively protect the battery. A fitness function is established with the optimization objective of minimizing the HPS cost and the number of cells in SC and battery as control variables. A genetic algorithm (GA) is adopted to optimize the HPS configuration based on the power required of the New European Driving Cycle (NEDC) working condition. The optimized number of battery cells is 777, much smaller than the 1191 calculated based on theoretical formulas. Additionally, a logic threshold strategy is introduced to flexibly control the collaborative work of the two power sources and achieve effective energy management. The availability of the presented control method of HPS in various working modes is verified through MATLAB/Simulink-based modeling and simulation. This work provides a theoretical reference for the application research of HPS in EVs.

Aerodynamic Effects of High-Speed Train Positions During Tunnel Exit Under Crosswind Conditions Using Computational Fluid Dynamics

2023-07-04T02:38:24+00:00

Strong crosswinds can cause catastrophic accidents like overturning and derailment in extreme circumstances, therefore the train's capacity to tolerate their impacts is crucial. Despite the significance of this issue, there exists a notable research gap in understanding the specific effects of various positions of a high-speed train within a tunnel on its aerodynamic loads and flow structure under different crosswind conditions. To address this gap, numerical simulations were performed using computational fluid dynamics. The crosswind angles (Ψ) were 15°, 30°, 45°, and 60° and the number of coaches exiting the tunnel was one to three coaches, respectively. The incompressible flow around the train was simulated using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations in conjunction with the k-epsilon (k-ε) turbulence model. The Reynolds number employed in the simulation was 1.3 x 10⁶, calculated based on the height of the train and the freestream velocity. With regard to aerodynamic performance due to the crosswind, force coefficients such as drag, side, and lift and moment coefficients of rolling, pitching, and yawing were measured. The higher crosswind angles including ψ = 45° and ψ = 60° cases produced the worse results of aerodynamic load coefficients compared to the lower crosswind angles of ψ = 15° and ψ = 30°. For instance, the highest side force coefficient (C_s) was recorded at a crosswind angle of ψ = 45°, with a value of 23.6. Meanwhile, the flow structure revealed that the leading coach of the train experienced intricate flow patterns during crosswinds, characterized by vortices and flow separation. These findings indicate that aerodynamic instabilities can potentially affect the overall performance of the train. Additionally, this increases the risk of derailment or overturning to be high, particularly when the majority of coaches are exiting the tunnel under strong crosswind conditions.

Investigation of Static Aeroelastic Analysis and Flutter Characterization of a Slender Straight Wing

2024-02-16T09:11:35+00:00

This research aims to investigate the static aeroelastic characteristics of a slender straight 2D wing using aerodynamic strip theory. The finite element method is employed to determine the wing's divergence speed and aileron effectiveness, while Galerkin's method, based on the principle of virtual work is used to obtain the influence coefficient of the straight wing. The application of aerodynamic strip theory and finite span correction is utilized to establish a correlation between elastic twist and lift coefficient. Subsequently, a computational tool in MATLAB is formulated to derive an approximate solution for the static aeroelastic equilibrium equations concerning slender straight wings. An investigation is conducted into the impact of various elastic axis positions on the divergence speed and its implications for structural integrity are analyzed. It was observed in the study that the incorporation of finite span correction into the strip theory led to a 15% augmentation in the divergence speed of the slender wing. Validation of the mathematical model of the slender wing is performed through computational analyses conducted using ANSYS software. The flutter analysis examines parameters such as the distance between the elastic and aerodynamic axes, the sweep position, and the wing span. A MATLAB code is presented in the research article to explore the influence of these parameters on the flutter speed of a slender wing. Through an investigation of the interplay between these parameters and the flutter speed, the study strives to enhance comprehension of the fundamental mechanisms governing flutter occurrence in slender wings. The current research reveals that the flutter speed is notably affected by both the eccentricity and span of the wing. Specifically, a reduction in eccentricity leads to a 1.5% enhancement in flutter speed, while increasing the sweep angle from 15 to 30 degrees for a wing with a 15ft span results in a 2.54% increase in flutter speed. Moreover, wings spanning from 5ft to 15ft exhibit a 5% rise in flutter speed. These findings offer valuable insights for the design of more efficient and stable wings.

Hydrodynamic Analysis of Integrated Interceptor-Stern Flap for Trim Control on High-Speed Planing Vessel

2023-09-26T10:19:19+00:00

In a planing vessel, an interceptor is used to exercise control trim at a limited speed, which can result in excessive drag and bow trim at high speed. Previous studies have combined interceptors with stern flaps to achieve optimal hydrodynamic performance on planing hulls. This study investigated the hydrodynamic characteristics of a planing hull with an integrated interceptor-stern flap. The integrated interceptor-stern flap is a form of integration between the interceptor, which is mounted downwards and vertically on the transom, and the stern flap at the end. At high speed, the same interceptor (i) height converted to an integrated interceptor-stern flap can produce better results. Different flap angles were considered to affect interceptor performance. The fluid flow around the ship model was solved using the Reynolds-Average Navier-Stokes equation and the realizable k-epsilon turbulence model technique. The total number of meshes was determined using mesh independence. In conclusion, while the interceptor showcased significant reductions in resistance and trim across various Froude numbers, its effectiveness was compromised at high speeds due to increased drag and trim height, necessitating caution in its application. Furthermore, integrating stern flaps with the interceptor, particularly with a 5° angle, proved promising in further reducing drag and trim, highlighting the importance of interceptor design considerations for enhancing ship performance.

Implementation of a Semi-active Auxiliary Axle for Lateral Stability of Articulated Heavy Vehicles at Extreme Loss of Control Limit

2023-09-06T02:47:22+00:00

Articulated heavy vehicles (AHVs) play a vital role in the economy of freight transport. Lateral stability control of AHVs during the immediate vicinity to loss of control (LOC) is a significant issue that has not been effectively addressed in the literature. This paper presents a novel approach to the lateral stability control of tractor semi-trailers under conditions leading to LOC. An active auxiliary axle is proposed to prevent trailer swing and snaking during severe lane change maneuvers. A linear 3-DOF model was developed to represent the effectiveness of the active auxiliary axle and tire cornering stiffness in yaw-rate control to provide an analytical basis. Nonlinear modeling of the axle and vehicle system was performed in TruckSIM. A Fuzzy Logic Controller (FLC) was developed to identify the required rate (magnitude per unit time) of actuation force, and a PID controller was introduced to regulate the magnitude of actuation force at the axle-wheel interface. Co-simulation was performed in MATLAB/SIMULINK in combination with TruckSIM. To simulate an LOC on a dry road with a coefficient of friction of 0.85, a double lane change (DLC) maneuver at 90 km/h was conducted. This resulted in a combined state of relative roll-over and trailer swing, facilitating the evaluation of the semi-active auxiliary axle's performance in regaining stability and eliminating transient overshoots in the vehicle combination's lateral response. Yaw rate rearward amplification was effectively controlled, and articulation angle oscillations were significantly diminished. This approach suggests a systematically minimal yet practicable retrofit to the trailer, contributing to a remarkable improvement in the traffic safety of AHVs.

Computational Fluid Dynamics Evaluations on New Designs of the Delta-Shaped Blade Darrieus Hydrokinetic Turbine

2024-04-04T04:58:40+00:00

In this research, the computational fluid dynamics (CFD) approaches using ANSYS Fluent solver was employed to evaluate new designs of the delta-shaped bladed Darrieus hydrokinetic turbines (DHKT) employing NACA0012 hydrofoils. The 2-bladed models with four different designs (MD1-MD4) of varying blade characteristics and cross-sectional areas were simulated. The models were positioned fully submerged inside a water flow domain and were forced to rotate with different rotational speeds by utilizing the sliding mesh technique under a constant upstream velocity of 1.5 m/s. The results using a Shear Stress Transport (SST) k-w turbulence model were compared with previous studies. The optimum model designs were shown to be the models with twisted blades and reduced and constant cross-sectional areas (MD3 and MD4). The 3-bladed models with similar blade characteristics (MD7 and MD8) were continuously tested and compared with the 2-bladed models. The 2-bladed models performed better during the higher range of tip speed ratio (l), whereas 3-bladed models were outstanding at the lower range. Based on the work using CFD approaches in this paper, the MD4 model was shown to be the most appropriate design to operate under the specified conditions.

Particle Swarm Optimization-Based Model-Free Adaptive Control for Time-Varying Batch Processes

2024-03-05T02:25:09+00:00

The batch process is a production process with strong nonlinearity, which usually suffers from time-varying parameters and uncertainty of disturbances. Concerning the mentioned problems, this study proposes to investigate the application of the particle swarm optimization-based model-free adaptive control (PSO-MFAC) method for time-varying batch processes. Model-Free Adaptive Control (MFAC) is a data-driven control method, which is one of the promising methods to solve the nonlinear process. Firstly, a Full Form Dynamic Linearization Model-Free Adaptive Control method has been adopted for the control of batch processes. Further, considering that the adopted model-free adaptive control involves seven control parameters, such as cognitive scaling factor (φ₁), social scaling factor (φ₂), inertia weight (φ₃), learning rate (η), control parameter update rate, exploration rate and learning rate for MFAC obtained by a particle swarm optimization (PSO) algorithm in combination with a criterion function performance index. Finally, by comparing it with the existing methods, a typical batch fermentation was applied to verify that PSO-MFAC had a good control effect. The findings indicate that the PSO-MFAC controller exhibits a preference for exploiting the optimal option due to its φ₃ value less than 0.1. The efficacy and feasibility of the PSO-MFAC control effect have been proven by obtaining the lowest integral square error (ISE) value of 1.1192 regarding the nonlinearity of the batch process due to time-varying challenges.

Characteristics of Mechanical Strength of Hybrid Reinforced Plastic Waste Mixed with Wood Waste

2024-04-05T03:41:21+00:00

Commercial products made of plastics or wood have always been in high demand until now. Consequently, waste from these products has increased, accumulated, and catastrophically impacted the environment. Through recycling, waste products are not only reduced but will also be easily available for improvement or manufacturing new products. This research focused on the fabrication of lightweight composites using plastic waste (PW) and wood waste (WW) as reinforcement and epoxy as a matrix suitable for tile applications. It was revealed that the density of PW-WW polymer composite increased with increasing PW loading up to a 4.0 ratio at 1.070 g/cm³ with a porosity of 0.05%. Optical microscope analysis at 100X magnification showed good bonding between the reinforcements (PW and WW) and matrix (epoxy). With a maximum bending strain of 2.41%, the 3.0 ratio achieved the highest bending strength of 2069.20 N, followed by the bending stress at 8.28 MPa. The PW-WW polymer composite with a composition ratio of 3.0 showed a maximum tensile force of 313.8 N and a tensile strength of 1.79 MPa. The composite with a 4.0 ratio had the greatest impact strength (1.67 kJ/m²), followed by the composite with a 3.0 ratio (1.44 kJ/m²). In summary, a 3.0 ratio is the best polymer composite composition for tile applications.

Numerical Study on the Effect of Incorporating Phase Change Materials in a Wall

2024-04-04T05:15:15+00:00

Integrating phase-change materials (PCMs) into the structure of a building can significantly improve its heat storage capacity and thermal performance. Thanks to their phase-change properties, PCMs can absorb, store and release large amounts of energy in the form of latent heat within a narrow temperature range. This study examines the thermal behavior of a housing wall that incorporates PCM to increase its thermal inertia. Simulations using Ansys Fluent 14.0 software compare a standard wall with a wall incorporating layers of PCM of different thicknesses and positions. Three types of PCM - RT28 kerosene, C .6 O wet salt and A26 - are evaluated. The results show that positioning the PCM layer on the interior surface adjacent to the indoor environment can reduce internal heat flow by around 50% compared with a standard wall. In addition, the study identifies an optimum PCM layer thickness of between 10 and 15 cm.

A Comparative Study of Dry Turning Performance of 4340 Alloy Steel with As-Received and Cryogenically Treated Coated Cermet Cutting Tools

2024-04-29T06:56:48+00:00

Cryogenic treatment has been shown to significantly improve the cutting performance of inserts. Alloy steel grade 4340, renowned for its high impact and abrasion resistance, has extensive application in aircraft landing and high-power transmission gears. In this study, a comparative characterization (microhardness and XRD profile) and dry turning performance evaluation (turned surface roughness and insert wear) of alloy steel grade 4340 were performed using as-received and cryogenically treated coated cermet cutting inserts. The turning operation was carried out with various cutting velocities ( 55, 90, and 150 m/min) and a constant feed and cutting depth (0.111 mm/rev and 1 mm) under dry cutting conditions. The cryogenically treated insert obtained A reduced R_a value compared to untreated conditions at all cutting speeds. In addition, R_a value was reduced to a maximum of 29%. A lower level of insert wear and chip particle deposition at the cutting point was observed with cryo-treated inserts. Finally, it was revealed that the better machining characteristics in terms of reduced R_a values and insert wear with cryo-treated conditions were due to the enhanced wear resistance over the untreated conditions.

Impact of Dry and Cryogenic Cutting Medium on Shear Angle and Chip Morphology in High-speed Machining of Titanium Alloy (Ti-6Al-4V)

2024-03-31T04:21:33+00:00

Ti-6Al-4V, a titanium alloy, is widely employed in various engineering sectors due to its attractive combination of strong corrosion resistance and specific strength. However, titanium alloys frequently result in serrated chips, which present considerable machinability issues compared to other materials. The cutting medium plays a vital role in the chip formation mechanism, further affecting the machined part integrity and thermo-mechanical properties. Chip morphological parameters such as shear angle, compression ratio, and segmentation degree are essential aspects of estimating machined part surface roughness, tool wear, cutting forces, and energy consumption. Therefore, it is important to understand the entire mechanism of chip formation in terms of chip morphology in high-speed cutting. This fundamental research aims to analyze and compare the shear angle model and chip formation of titanium alloy Ti-6Al-4V for cutting speeds ranging from 50 m/min to 150 m/min and feed rates ranging from 0.12 mm/rev to 0.24 mm/rev under dry and cryogenic cutting environments. Single-point turning experiments were conducted on Ti-6Al-4V workpieces with uncoated tungsten carbide inserts (without chip breakers), which are advantageous for heat transfer. After the chip analysis, it was observed that the shear angle obtained practically with model-4 is the most appropriate model for shear angle calculation, and the cryogenic cutting medium is suitable for Ti-6Al-4V machining. At the feed rate of 0.12-0.24 mm/rev and cutting speed of 50-150 m/min, the shear angle in dry-medium machining ranges from 32° to 42°, while in cryogenic medium machining, it ranges from 34.6° to 44.6°. Overall, a larger shear angle has been observed in cryogenic turning compared to dry turning, which is advantageous for reduced cutting forces owing to a lesser shear plane. The tool-chip contact length, which is the intimate contact between the tool face and chip surface, significantly decreases under cryogenic media. A smaller tool-chip contact length results in an elevated shear angle, which improves process sustainability and economy during cryogenic turning, as described.

Motorcycle Engine Performance Comparison Between Laser Ignition System and Conventional Ignition System Through Simulation

2024-02-12T03:13:35+00:00

In many countries, motorcycles have become a primary and popular mode of transportation, driven by increasing demand due to their convenience. However, as fossil fuel sources deplete, there's a pressing need to enhance engine performance, efficiency, fuel economy, and reduce emissions. Improving ignition systems is crucial in achieving these goals. This study compares the performance of the Honda Future FI 125cc engine between a laser ignition system (LIS) and a conventional ignition system (CIS) using simulation. CATIA software was utilized to design the engine's intake manifold, ANSYS Fluent software for simulating and determining the optimal swirl and tumble ratio, and Matlab/Simulink for modeling and simulating engine performance with both LIS and CIS. Detailed discussions and comparisons were made on parameters such as cylinder air mass, ignition energy, engine power and torque, specific fuel consumption (SFC), and mass fraction burned (MFB) between LIS and CIS. Overall, LIS demonstrated superior engine performance compared to CIS. This finding is significant for evaluating the advantages of LIS in motorcycles, especially in the Honda Future FI 125cc engine.

Effects of a Hybrid Additive of Ethanol-Butanol and Magnetite Nanoparticles on Emissions and Performance of Diesel Engines Fueled with Diesel-Biodiesel Blends

2024-01-25T14:53:35+00:00

This study concentrates on investigating the impact of hybrid additives of ethanol and butanol with magnetite (Iron oxide nanoparticle) added at 100 ppm each to the biofuels, 10% of the resulting nano-biofuel (5% ethanol and magnetite; 5% butanol and magnetite) was then blended with 90% pure palm oil biodiesel (B100). A single-cylinder Yanmar L70N engine was used in the experiment with the resulting fuel. The engine test results indicated that the addition of magnetite nanoparticles in conjunction with the two biofuels significantly reduced brake-specific fuel consumption (BSFC) up to 15.68% (8.8 gm/kW-hr) compared with B100 (10.4 gm/kW-hr) at peak brake power. The break thermal efficiency (BTE) also improved by 4.26% and 9.71% at tested minimum and maximum brake power, respectively. The emission of hydrocarbon (HC), Carbon Oxide (CO), smoke and nitrogen oxide (NOx) were reduced obviously by 14.45%, 11.98%, 7.25% and 5.77% respectively, compared to pure B100 use at peak load. In general, the application of the dual additive approach of combining biofuels and nanoparticles yields positive results due to the improved surface-to-volume ratio of the nanoparticles and good physicochemical attributes of the biofuels, which enhanced the performance of the B100 fuel; thus, more areas should be exploited in these regards.

A New Blade Design for Municipal Solid Waste Bag Opener Machines: A Static and Fatigue Finite Element Analysis Study

2024-02-27T03:36:33+00:00

Municipal solid waste (MSW) presents a global challenge, carrying health and environmental risks without proper recycling and disposal methods. Mechanical-biological treatment (MBT) emerges as a promising solution capable of recycling MSW and reducing landfill volumes. However, the efficiency of MBT heavily relies on the bag opener machine, which extracts waste from bags. Therefore, enhancing the bag opener machine's performance is crucial for optimizing the MBT process. This paper introduces four blade models (A, B, C, and D) with different cutting angles (60°, 50°, 45°, and 30°, respectively) aimed at achieving high efficiency, low power consumption, minimal maintenance costs, and extended service life. The blade design was developed using the 3-D modeling software, SOLIDWORKS. Additionally, the paper presents primary calculations of the bag opener machine, which were informed by a review of MSW characterization studies. Static and fatigue finite element analyses (FEAs) were conducted under a pressure of 1 MPa to assess blade strength, performance, and durability. The results indicate that the proposed design can handle a capacity of approximately 30 tons/hr with a power consumption of 22 kW. Notably, blade model D, featuring the minimum cutting angle of 30°, exhibits the lowest Von Mises maximum stress at 15.18 MPa and the minimum factor-of-safety (FOS) at 18.12. Fatigue stress analysis reveals a life expectancy of 10⁶ cycles for all blade models. In conclusion, model D demonstrates superior strength, FOS, and durability, making it the optimal choice for the bag opener machine.

Performance and Emission Characteristics of a High-Speed Diesel Engine Using a 20% Palm Oil Ester and Ethyl Alcohol Blend

2024-02-24T02:42:42+00:00

The issue of diesel engine exhausts is expanding to affect human health, while oxygenated fuels have been continuously studied for a healthier environment. Palm oil ester (POE) is applied in Thailand to reduce exhaust products, but its viscosity is thicker than diesel fuel, which may cause injection systems. It has been improved by mixing with diesel, and diesel blended with 20% POE (POE20) is surveyed as an alternative fuel to reduce viscosity. Currently, ethyl alcohols combined with this blend have gained a lot of attention due to improved fuel properties and the alleviation of exhaust products. Therefore, this research studies a diesel engine's performance parameters and pollution products at high speed at 3,000 rpm and various powers when operated with POE20 and combinations of POE20, 5% ethyl acetate, and ethyl alcohol up to 20%. The results indicate that the POE20 had lower engine performance but higher carbon dioxide and nitric oxide than regular diesel. The 10% ethyl alcohol blended with POE20 improved the brake thermal efficiency, similar to regular diesel. However, POE20 mixed with ethyl alcohols by more than 10% remarkably changed performance parameters and pollution products compared with regular diesel and POE20.

Comparison of Velocity Profiles in Stented Carotid Artery Bifurcation Between Computational Fluid Dynamics and Particle Image Velocimetry Measurements

2024-05-29T01:52:53+00:00

Cardiovascular disease remains the leading cause of morbidity and mortality globally, necessitating extensive research into the hemodynamics of blood flow under pathological conditions, such as atherosclerosis in carotid arteries. In vitro studies, particularly Computational Fluid Dynamics (CFD), are crucial for advancing our understanding of arterial blood flow and predicting pathological states. However, the accuracy of CFD simulations relies heavily on their validation against empirical data, such as those obtained from Particle Image Velocimetry (PIV). This study focuses on the comparative analysis of CFD predictions and PIV measurements of blood velocity vectors in a stented carotid artery bifurcation model under steady flow conditions derived from patient-specific data. The methodology involves simulating blood flow within a CFD framework and conducting PIV experiments using a blood-mimicking fluid seeded with particles in a carotid artery bifurcation phantom. The results indicate a reasonable agreement between the axial velocity vector profiles obtained via PIV and those predicted by CFD, with CFD predicting 10% higher than that recorded by PIV, especially in terms of recirculation areas and velocity values, despite some discrepancies in the velocity contours distribution, highlighting potential differences in how each method captures flow separation or recirculation areas. Despite some discrepancies in velocity contour distribution, which highlight potential differences in capturing flow separation or recirculation areas, the findings confirm that CFD simulations can effectively replicate the hemodynamics observed in carotid arteries and potentially other arterial segments. This study emphasizes the importance of integrating CFD simulations with experimental PIV data to validate and refine our understanding of arterial flow dynamics, significantly contributing to cardiovascular research and the development of interventions for arterial diseases.

Application of Passive Technique to Cocoa Beans Batch Dryer and Assessment of Thin Layer Models

2024-04-08T01:38:30+00:00

The objective of this work was to develop a hot air production system using twisted tapes (TT) for the specific purpose of drying cocoa. The study also aimed to analyze the drying characteristics and kinetics of cocoa beans under the specific conditions that were investigated. TTs were inserted into the pipes of the shell and tube heat exchanger with multiple tube passes (STHEX). A modified rocket stove was used to burn biomass. Insertion levels of typical TT are 0%, 17.24%, 34.48%, and 60.63%, representing A (plain tube), B, C, and D, respectively.TT with a higher insertion level results in increased heat transfer. However, this also leads to an increase in pressure loss, which in turn affects the fan power consumption required to maintain the desired flow rate. The insertion level of D was the best in this work. It was used to produce a hot air supply to the drying room. After fermentation, the initial moisture content (MC) of 5 kilograms of the cocoa beans was 56.48% (wet basis; wb). The cocoa beans were dried in a drying room at an airflow rate of 4.5 m³/min. The MC declined from 56.48% to 5.13% (wb) within 14 hours. The present study only detected a falling rate period in cocoa bean drying. The Overhult model is the most effective model for this drying process. It has the potential to serve as a useful tool for engineering applications.

Investigation of Brake Pad Wear Impact on Autonomous Emergency Braking Pedestrian Performance on Wet Road Conditions

2024-03-26T06:50:06+00:00

This study presents an investigation of autonomous emergency braking pedestrian (AEB-P) system performance during harsh braking on wet road pavement. The system was designed to consider a pedestrian walking in front of the host vehicle. The performance of the AEB-P system would degrade immediately as the pads on the brakes become worn, and the vehicle continues to brake on a wet road surface. The vehicle conditional artificial potential field (VC-APF) is an innovative approach for motion planning in the AEB-P introduced in this work. The simulation was performed to explore the impact of brake pad degradation on VC-APF effectiveness on wet road pavement. The first evaluation involved a test to evaluate the effectiveness of the risk assessment in the AEB-P system when encountering a moving obstacle (pedestrian). The second test evaluated VC-APF performance, for instance, the vehicle's safety distance when the vehicle performed hard braking at 0.4, 0.35, and 0.24 brake pad friction coefficients. The third evaluation focused on the vehicle’s speed behavior during deceleration at various brake pad friction coefficients. The simulation results showed that while braking at 0.4 and 0.35 brake pad friction coefficients, the vehicle maintained a minimum safety distance of 1.5 m and 0.69 m from a pedestrian on wet road pavement, respectively. However, the brake pad friction coefficient of 0.24 failed to prevent the vehicle from crashing. The findings indicate that an exhausted brake pad reduces the vehicle's safety.

Influence of Friction Stir Processing on the Hardness and Tribological Properties of Aluminium-Magnesium Alloys

2023-10-06T07:16:55+00:00

In this study, we have employed friction stir processing to strategically modify the microstructure of AA-Mg alloys, resulting in a direct enhancement of their mechanical properties. The experiments encompassed a range of tool speeds ranging from 800 to 1600 rpm and feed rates ranging from 20 to 80 mm/min. Employing a single-pass approach across all combinations, samples were extracted from the stir zone region to evaluate hardness and wear characteristics. The evaluation involved Vickers hardness tests to quantify hardness and pin-on-disc tests to examine the tribological attributes of the specimens. The worn-out surfaces of the specimens were examined using scanning electron microscope imagery. There is a substantial increase in hardness when compared with the base material, i.e., 78 HVN is up to 96 HVN for 20 mm/min at 1200 rpm, 98 HVN for 20 mm/min at 800 rpm, 106 HVN for 60 mm/min at 1600 rpm and 96 HVN for 80 mm/min at 1600 rpm. Furthermore, the coefficient of friction increased from 0.341 for base materials to a maximum of 0.635, 0.667, 0.604, and 0.646 for the same combination of speed and feed rate, respectively. The maximum change in percentage is 26% in hardness and 49% in wear coefficient.