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 The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage.

Abstract In this study, we have investigated the microstructural characteristics, the mechanical properties, and the dry sliding wear behavior of a ceramic coating consisting of zirconia (ZrO2) and alumina (Al2O3) deposited by flame spraying. A series of wear tests were carried out under a variety of loads and at two different sliding speeds. The evaluation included an examination of the coating microstructure, microhardness, coefficient of friction (COF), and wear resistance of the flame-sprayed coating. The results showed that the coatings had a perfectly structured micro-architecture and were metallurgically bonded to the substrate. The Al2O3 coating exhibited a fine granular structure with pores and oxides. The microstructure of Al2O3-10 wt.% ZrO2, on the other hand, showed a blocky structure with a uniform distribution of ZrO2 inclusions in the composite coating.

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 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 Vehicle vibration is the key consideration in the early stage of vehicle development. The most dynamic system in a vehicle is the powertrain system, which is a source of various frequency vibration inputs to the vehicle. Mostly for powertrain mounting system design, only the uncoupled powertrain system is considered. However, in real situations, other subsystems are also attached to the powertrain unit. Thereby, assuming only the powertrain unit ignores the dynamic interactions among the powertrain and other systems. To address this shortcoming, a coupled powertrain and driveline mounting system problem is formulated and examined. This 16 DOF problem is constructed around a case of a front engine-based powertrain unit attached to the driveline system, which as an assembly resting on other systems such as chassis, suspensions, axles, and tires.

Abstract Lubricant additives are the main means to improve the performance of lubricants. In this article, green and inexpensive layered kaolin were selected as lubricant additives, and the effects of the type of modifier, concentration, particle size of kaolin additives, and working temperatures on the tribological performance of lubricants were investigated. The results showed that the Span80 modifier can effectively improve the dispersibility and friction reduction effects of kaolin oil samples. Compared with kaolin oil samples without the modifier, the modified kaolin oil can reduce the friction coefficient by 40.9% and the wear spot diameter of the steel balls by 43.8%. The layered kaolin additive can significantly reduce the friction coefficient and wear of steel balls in lubrication, and the friction coefficient showed a trend of decreasing and then increasing with increasing kaolin additive concentration and particle size.

Abstract Articulated vehicles form an important part of our society for the transport of goods. Compared to rigid trucks, tractor-trailer combinations can transport huge quantities of load without increasing the axle load. The fifth wheel (FW) acts as a bridge between the tractor and trailer, which can be moved within the range to achieve rated front and rear axle loads. When the FW is moved front, it adversely affects the cab dynamics and cab suspension forces. Compared to the cab pitch and roll, yaw motion increases drastically. The current study tries to address this issue by providing reaction rod links in the rear cab suspension. In this study, a 4×2 tractor with a three-axle semitrailer is considered by keeping the FW at its frontmost position, which is the worst-case scenario for a cab. Three different cases of reaction rod arrangement and its influence on cab dynamics are studied in comparison with a model without reaction rods.

Abstract The present investigation has been conducted to study the tribological and adhesion properties of X10CrNi18-8 austenitic stainless steel (ASTM 301) coatings deposited on aluminum alloys such as AU4G by using the arc-spraying process. These coatings were made with and without a bond-coat layer, which is constituted by NiAl. The structure of the phases that are present in coatings was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The measurements of microhardness and tribological behavior at different loads were also performed on the surface of the coatings. Adherence test was also carried out using four-point bending tests. The SEM showed that the dense microstructures of coatings have a homogeneous lamellar morphology with the presence of porosities and unmelted particles. The main phase of coating corresponds to a solid solution as a face-centered cubic (fcc).

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 The use of converging-diverging (C-D) variable area nozzle (VAN) in military aeroengines is now common, as it can give optimal expansion and control over engine back pressure, for a wide range of engine operations. At higher main combustion temperatures (desired for supercruise), an increase in the nozzle expansion ratio is needed for optimum performance. But changes in the nozzle throat and exit areas affect the visibility of engine hot parts as the diverging section of the nozzle is visible for a full range of view angle from the rear aspect. The solid angle subtended by engine hot parts varies with change in visibility, which affects the aircraft infrared (IR) signature from the rear aspect. This study compares the performances of fixed and variable area nozzles (FAN and VAN) in terms of engine thrust and IR signature of the engine exhaust system in the boresight for the same increase in combustion temperature.

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 Computational fluid dynamics (CFD) simulation has been widely used in the automobile industry for design verification and validation. The article presents the axle oil vent expulsion results from particle-based CFD simulations, performed with a commercially available particle-based solver. The front axle houses a differential assembly which utilizes a pinion and ring gear. The ring gear is bolted onto the differential case in which the ring gear and differential case are spun as a whole. The turbulent flow field of the lube oil was simulated, and a free surface was detected. Probability density function (PDF) distributions of local lube oil volume fractions (VFs) were used to guide the identification of the stationary state for the simulated flow field. In the study of vent expulsion, the lube oil temperature was varied from −12°C to 149°C and the rotational speed of the pinion changed from 1000 rpm to 5000 rpm.

Abstract This article investigates the lateral dynamic behavior of a two-wheel axle bogie frame of an Indian railway vehicle. The influence of the different parameters of the vehicle on stability is investigated. The model is formulated by assigning 10 degrees of freedom (DoF) to the system with yaw and lateral DoF assigned to the bogie frame and vertical, lateral, roll, and yaw DoF assigned to each wheel axle. Linear creep force and moments suggested by Kalker’s linear theory of creep have been accounted for in the analysis. The stability analysis is carried out by transforming the second-order differential equations into first-order differential equations using state-space representation. The present model is validated by comparing the eigenvalues of the analytical model with the same obtained from the finite element (FE) model. The results obtained from the analytical and FE model are in good agreement.

Abstract The increased scope of active and passive safety in motor vehicles and the enforcement of approval requirements for individual parts and assemblies affect the design and parameters of a car’s motion. The tire, which transmits forces and torques onto the road’s surface is a particularly crucial element in the vehicle. Its structure, type of mixture, and operating conditions determine the safety of vehicle motion. The three-axial force system loads the tires of the car and affects both the tread and sidewall, as well as the suspension and steering system. Taking into account the controllability and stability of movement, the tire is subjected to dynamic and thermal loads, as well as to wear and random damage. This negatively impacts on the joints of composite layers. The sudden loss of pressure in the tire can lead to serious accidents, especially when moving at high speeds, due to changes in the rolling radius.

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.