Search Results

Abstract This study aims to explore the wear characteristics of fused deposition modeling (FDM) printed automotive parts and techniques to improve wear performance. The surface roughness of the parts printed from this widely used additive manufacturing technology requires more attention to reduce surface roughness further and subsequently the mechanical strength of the printed geometries. The main aspect of this study is to examine the effect of process parameters and annealing on the surface roughness and the wear rate of FDM printed acrylonitrile butadiene styrene (ABS) parts to diminish the issue mentioned above. American Society for Testing and Materials (ASTM) G99 specified test specimens were fabricated for the investigations. The parameters considered in this study were nozzle temperature, infill density, printing velocity, and top/bottom pattern.

Abstract With the use of the stepped surface of the friction pairs of the stepped bearings (SB) in the high-speed centrifugal pumps, its liquid film thickness is suddenly changed and it was discontinuously distributed in the direction of motion of pump. To ensure the continuity of the liquid film thickness and enhance the lubrication efficiency of the pump, based on the lubrication model of the SB, two other structures of the inclined surfaces [inclined bearings (IB)] and curved surfaces [curved bearings (CB)] used to replace stepped surfaces of the SB are investigated, respectively. Under the same conditions of the minimum thickness of the liquid film and initial dimensions of the sliding friction pairs, the influence of both the thickness ratio (α) of the liquid film and dimension ratio (β) in the direction of motion of SB, IB, and CB on the bearing capacity and friction coefficient of the liquid film are simulated and analyzed, respectively.

Abstract In view of the combustion efficiency and emission performance, various new clean combustion modes put forward higher requirements for the performance of the fuel injection system, and the cavitating two-phase flow characteristics in the injector nozzle have a significant impact on the spray atomization and combustion performance. This article comprehensively discusses and summarizes the factors that affect cavitation and the effectiveness of cavitation, and presents the research status and existent problems under each factor. Among them, viscosity factors are a hot research topic that researchers are passionate about, and physical properties factors still have the value of further in-depth research. However, the importance of material surface factors ranks last since the nozzle material was determined. Establishing a more comprehensive cavitation–atomization model considering various factors is the focus of research on cavitation phenomena.

Abstract The European Union’s pro-ecological policy imposes a requirement to use biofuel additives in diesel fuel which is supposed to support the sustainable development of transport and limit its negative impact on the natural environment. The study presents an analysis of the exhaust gas components and the amount of solid particles carried out for internal combustion engines fueled with mixtures of diesel fuel and fatty acid methyl esters. Additionally, the computer software of the tested power units was modified by changing the amount of fuel to be supplied and the air intake. The goal of the tests was to find out how the fuel mixture and reprogramming of the computer control systems would impact the emission of exhaust gas components. Based on the tests, it was found that an additive of fatty acid methyl esters to diesel does have an influence on the tested unit parameters.

Abstract Pre-chamber jet ignition technologies have been garnering significant interest in the internal combustion engine field, given their potential to deliver shorter burn durations, increased combustion stability, and improved dilution tolerance. However, a clear understanding of the relationship between pre-chamber geometry, operating condition, jet formation, and engine performance in light-duty gasoline injection engines remains under-explored. Moreover, research specifically focusing on high dilution levels and passive pre-chambers with optical accessibility is notably scarce. This study serves to bridge these knowledge gaps by examining the influence of passive pre-chamber nozzle diameter and dilution level on jet formation and engine performance.

Abstract The secure boot has successfully protected systems from executing untrusted software (SW), but low-power controllers lack sufficient time to check every memory cell while satisfying real-time functional safety requirements. Automotive controllers need to maintain security through multiple cycles of remote, unsupervised operation and safely reach a secure state when an anomaly is detected. To accelerate the boot time, we propose Sliced Secure Boot: build fingerprints by slicing orthogonally through memory blocks, protect each cell with a reusable fingerprint using a reproducible pattern with sufficient entropy, and randomly check one fingerprint pattern during boot. We do not claim that sampling offers equivalent protection to exhaustive checks but demonstrate that careful sampling can provide a sufficient level of detection while maintaining compatibility with both startup time and functional safety requirements.

Abstract Autonomous driving faces the difficulty of securing the lowest possible software execution times to allow a safe and reliable application. One critical variable for autonomous vehicles is the latency from the detection of obstacles to the final actuation response of the vehicle, especially in the case of high-speed driving. A prerequisite for autonomy software is that it enables low execution times to achieve superhuman reaction times. This article presents an in-depth analysis of a full self-driving software stack for autonomous racing. A modular software stack especially developed for high-speed autonomous driving is used and the latency of the software is analyzed in four main autonomy modules: perception, prediction, planning, and control. With the help of a trace point measurement method, it is possible to investigate the end-to-end latency and runtimes of the individual modules.

Abstract Optimization is essential in real-life mechanical engineering problems that mostly are nonlinear, depend on mixed decision variables, and are usually subject to constraints. However, most of the studied problems are modelled assuming continuous variables. A limited number of studies have been devoted to cases with mixed variables. Moreover, there is a lack of algorithm treating mixed variable problems properly. This article introduces a hybrid algorithm that can handle constrained problems depending on continuous or mixed variables. The proposed algorithm combines two meta-heuristics, Jaya and particle swarm optimization (PSO). PSO is one of the most popular methods to solve nonlinear problems, and Jaya is a novel parameter-free optimization algorithm. This new hybrid optimization algorithm is proposed in order to improve the convergence speed and to investigate what improvements it will bring to optimization problem solutions.

Abstract Under the influence of the interactions between the vibratory drum/wheel and deformable terrains, the ride comfort of the soil compactors is greatly affected. Therefore, the isolation systems of the cab and driver’s seat of the soil compactors have been researched and developed to improve ride comfort. Based on the existing research results, this study provides an overview of the development of the isolation systems of the cab and driver’s seat of the soil compactors. The research result shows that the cab isolations used by the semi-active hydraulic mounts (SHM) or semi-active hydraulic-pneumatic mounts (SHPM) can greatly improve the driver’s ride comfort and control the cab shaking, whereas the driver’s seat suspension embedded by the negative stiffness structure (NSS) strongly improves the driver’s ride comfort.

Abstract Gasoline compression ignition (GCI) is a promising combustion technology that can help the commercial transportation sector achieve operational flexibility and meet upcoming criteria pollutant regulations. However, high-pressure fuel injection systems (>1000 bar) are needed to enable GCI and fully realize its benefits compared to conventional diesel combustion. This work is a continuation of previous durability studies that identified three key technical risks after running gasoline-like fuel through a heavy-duty, common rail injection system: (i) cavitation damage to the inlet check valve of the high-pressure pump, (ii) loss of injector fueling capacity, (iii) cavitation erosion of the injector nozzle holes. Upgraded hardware solutions were tested on a consistent 400- to 800-hour NATO durability cycle with the same gasoline-like fuel as previous studies. The upgraded pump showed no signs of abnormal wear or cavitation damage to the inlet check valve.

Abstract The objective of this work is to analyze the signal of a piezoelectric washer installed under the spark plug and to compare the combustion metrics evaluated with such signal to the indexes from a standard piezoelectric sensor for the in-cylinder pressure measurement, considered as the reference. In the first part of the article, the spectrum analysis of the piezoelectric washer pressure trace is proposed. It is demonstrated how such a signal can be used to measure the main combustion and knock indexes. Nevertheless, due to the intrinsic characteristics of the system, the knock index evaluated from the raw pressure trace cannot be directly used to estimate the instantaneous knock intensity. For this reason, a model-based algorithm for Real-Time (RT) application is developed to calculate a corrective factor of the high-frequency content of the signal.

Abstract Fretting is a surface damage phenomenon and is typically observed at the contact interfaces such as bolted, gasketed joints, and the like. It occurs due to the combined effect of normal and tangential loads, which produces a small-amplitude relative sliding between two components that are held together using clamping forces. Fretting-related failures are also observed in multiple components of an internal combustion engine. This article presents the fretting fatigue damage evaluation of a single layer head gasket using a relative new approach, i.e., deviatoric strain amplitude-based method, further combined with the Ding’s empirical parameter D fret2. Corresponding fretting damage results are compared with the traditional approach based on the Ruiz’s parameter F1.

Abstract The gear whine in the electric drive system of an electric vehicle is important and remains a challenge in developing novel electric vehicles. A gearbox dynamic model is established, and the effects of modification parameters on the sound pressure level, transmission error, and contact stress of the gear pair are introduced to reduce the gear whine. A multi-objective optimization study of four modification variables under multiple torque conditions is carried out by using transmission error and maximum contact stress as the objective functions. The eclectic programming method is imported to solve the convergence problem of multi-objective optimization. The influence of modification variables on objective functions is studied by establishing an approximate model of the optimal Latin hypercube design.

Abstract In real-life mechanisms, the design parameters differ from their theoretical values. This difference is due to the manufacturing tolerances of link dimensions and revolute joints of mechanisms. In this article, the effect of link dimensions manufacturing tolerances and joints clearance on the kinematic and dynamic performances of a planar mechanism is studied. A slider-crank mechanism with two joint clearances is considered as a case study. Furthermore, an analytical method based on the partial derivatives is used to determine the mathematical equation representing the kinematic errors of the mechanism. This error depends on the manufacturing tolerances of link dimensions and revolute joints of the mechanisms. The Lagrangian equation is adopted to define the mathematical expression of the mechanism motion. Two objectives are considered regarding the acceleration error and the dynamic performance.

Abstract Vehicular communications face unique security issues in wireless communications. While new vehicles are equipped with a large set of communication technologies, product life cycles are long and software updates are not widespread. The result is a host of outdated and unpatched technologies being used on the street. This has especially severe security impacts because autonomous vehicles are pushing into the market, which will rely, at least partly, on the integrity of the provided information. We provide an overview of the currently deployed communication systems and their security weaknesses and features to collect and compare widely used security mechanisms. In this survey, we focus on technologies that work in an ad hoc manner. This includes Long-Term Evolution mode 4 (LTE-PC5), Wireless Access in Vehicular Environments (WAVE), Intelligent Transportation Systems at 5 Gigahertz (ITS-G5), and Bluetooth.

Abstract Due to their high strength and good flexibility, wire ropes are widely used in various intense applications. A wire rope will present complex wave mechanics, especially under impact conditions. In this article, wire ropes (steel core rope and hemp core rope alternately twisted) were used to study the wave dynamic response of steel wire ropes with preload shock. The transmission law of wire rope shock waves was obtained through actual measurements. The results showed that the compression wave and shear wave were generated and propagated along the rope after impact. The conduction of shear waves had significant reflection characteristics, and the reflected waves overlapped with each other. The conduction velocity of the impact shear wave of the steel core wire rope increased with increasing pretension. The peak tension caused by impact decayed exponentially.

Abstract Stress-based sheet metal fatigue near nuts welded to thin sheets is one of the necessary design processes for car bodies. In this investigation, the influence of the attachment contact on the localized fatigue mechanism is examined through finite element (FE) models and controlled fatigue experiments. First, a fatigue experimental setup, which includes a thin-sheet closed-hat section with a weld nut bolted to a thick attachment piece, is designed to minimize the uncertainty of the influence of the fixtures on the experimental results. The experiments are carried out on 0.9- and 1.0-mm thick hat sections with a square weld nut under force control conditions with complete reversed loading. Due to the contact, the test specimen performs as a bilinear spring that has a lower stiffness in the upstroke direction when compared to the downstroke direction where full contact of the attachment occurs with the hat section.

Abstract The thermal error of ball screw is the main factor affecting the accuracy of machine tool. Establishing an accurate thermal error model of ball screw is the key to compensate the error of machine tool. The ultimate goal of the research work in this article is to develop a comprehensive modeling method that can predict the temperature rise and thermal error of ball screw. In view of the problem that the reciprocating motion of ball screw nut was ignored in the traditional thermal error model, a transient thermal-structural coupling model considering the actual working conditions was proposed. ANSYS parametric design language (APDL) was used to set the ball screw nut as the moving heat source load, and the displacement-time relationship between the ball screw nut and the ball screw was defined. The temperature and thermal deformation distribution of the ball screw under the action of the bearing and the heat source of the ball screw nut were simulated.

Abstract A new approach of the crankpin bearing (CB) surface designed by different partial textures (PTs) with spherical dimples (SDs), conical dimples (CDs), or circular-cylindrical dimples (CCDs) is proposed to enhance the lubrication performance and reduce the friction power loss of engines. To assess the effect of the geometric dimensions of different PTs, such as the distribution density, depth, and shape of dimples on the lubrication performance and friction power loss (LP-FPL), a hydrodynamic model of the engine’s CB lubrication is then built. Then a genetic algorithm (GA) developed in MATLAB software is applied for optimizing the geometric dimensions of the PTs to further improve the LP-FPL. Both the oil film pressure and friction force of the CB are chosen as the objective functions to evaluate the LP-FPL of engines.

Abstract In today’s era, due to increasing energy demands, it is necessary to make vehicles lightweight without affecting their strength. In order to achieve this, the subassemblies of the automobile should be optimized. Optimizing the product not only saves energy consumption but also reduces the material required for manufacturing and increases the overall performance of the product. Taking the same as the base, this article focuses on optimization of a straight bevel gear pair used in automotive differential and performing finite element analysis (FEA) to validate its results. FEA is carried out on the optimized bevel gear to check its durability, and topology optimization is performed on the optimized gear to reduce the mass. Finally, the optimized gear is checked for fatigue. For design optimization, nonlinear multi-objective problem is formulated with a number of teeth and modules as the design parameters.