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In order to address potential fatigue fractures at the valve stem-neck junction during engine operations, surface mechanical rolling treatment (SMRT) was introduced to enhance the rotary bending fatigue (RBF) performance of 4Cr14Ni14W2Mo engine valve steel in this study. The results indicate that the increasing number of rolling passes induces a modified surface layer characterized by refined grains and dislocations, increased hardness, and compressive residual stress (RS). SMRT specimens exhibited improved tensile strength but plasticity performance was decreased. At room temperature (RT) about 25 °C, the fatigue limit at 1 × 10 7 cycles of specimens treated with 10 rolling pass was increased from 437 MPa to 613 MPa (40.3%). At 400 °C, the fatigue limit of specimens treated with 10 passes was increased from 376 MPa to 425 MPa (13.0%) at 400 °C, but decreased at 650 °C. The enhanced fatigue performance is attributed to a modified surface layer, leading to the shift of the crack initiation to the subsurface. However, excessive rolling passes and high temperature (650 °C) significantly reduce the material plasticity, accelerating crack initiation and propagation, thus compromising performance.

The increasing concerns of air pollution and energy usage led to the electrification of the vehicle powertrain system in recent years. On the other hand, internal combustion engines were the dominant vehicle power source for more than a century, and they will continue to be used in most vehicles for decades to come; thus, it is necessary to employ advanced technologies to replace traditional mechanical systems with mechatronic systems to meet the ever-increasing demand of continuously improving engine efficiency with reduced emissions, where engine intake and the exhaust valve system represent key subsystems that affect the engine combustion efficiency and emissions. This paper reviews variable engine valve systems, including hydraulic and electrical variable valve timing systems, hydraulic multistep lift systems, continuously variable lift and timing valve systems, lost-motion systems, and electro-magnetic, electro-hydraulic, and electro-pneumatic variable valve actuation systems.

Reduction in friction ensures fuel economy, control on emissions and durability of components in internal combustion engines. A modern gasoline internal combustion engine was instrumented to determine the friction values at the cam–roller interface considering the effects of surface treatment and engine operating state. A series of tests under different operating speeds and lubricant inlet temperatures were undertaken using both an original surface roller and a Wonder Process Craft (WPC) surface-treated engine roller. The results clearly revealed a substantial reduction in friction magnitude for the WPC surface-treated engine roller in comparison to the original roller while operating under similar conditions, indicating their strong potential for employment in engines. An increase in friction with the rise in temperature was also observed for both types of rollers, whereas increased lubricant entraining velocity due to higher operating speed had the opposite impact. A considerable reduction in frictional drive torque ranging from 8% to 28% was observed by employing the WPC-treated roller in comparison to original/untreated roller at various operating conditions, which signifies the strong potential for employment of WPC surface treatment in the roller/follower valve train engines.

In order to improve the accuracy of engine valve clearance fault diagnosis, in this study, a fault identification algorithm based on wavelet packet decomposition and an artificial neural network is proposed. Firstly, the vibration signals of the engine cylinder head were collected, and different levels of noise were superimposed on the extended data sets. Then, the test data were decomposed into wavelet packets, and the power spectrum of the sub-band signal was analyzed using the autoregressive power spectrum density estimation method. A group of values were obtained from the power spectrum integration to form the fault eigenvalue. Finally, a neural network model was designed to classify the fault eigenvalues. In the training process, the test data set was divided into three parts, the training set, the verification set, and the test set, and the dropout layer was added to avoid the overfitting phenomenon of the neural network. The experimental results show that the wavelet packet neural network model in this paper has a good diagnostic accuracy for data with different levels of noise.

Due to their design, hollow cavity and filled sodium, hollow head and sodium filled engine valves (HHSVs) have superior performance to traditional solid valves in terms of mass and temperature reduction. This paper presents a new manufacturing method for 42Cr9Si2 steel hollow head and sodium filled valves. An inertia friction welding process parameter optimization was conducted to obtain a suitable process parameter range. The fatigue strength of 42Cr9Si2 steel at elevated temperatures was evaluated by rotating bending fatigue test with material specimens. Performance evaluation tests for real valve components were then carried out using a bespoke bench-top apparatus, as well as a stress evaluation utilizing a finite element method. It was proved that the optimized friction welding parameters of HHSV can achieve good welding quality and performance, and the HHSV specimen successfully survived defined durability tests proving the viability of this new method. The wear resistance of the HHSV specimens was evaluated and the corresponding wear mechanisms were found to be those classically defined in automotive valve wear.

The discs of the intake or exhaust valves are vital organs of internal combustion engines, being subjected to extreme operating conditions, thermal, mechanical and chemical types. One of the goals of researches in this area is related to thermal insulation of the combustion chamber of internal combustion engines, which could enhance their performance in operation. In this article we analysed the microstructural aspects of some coatings obtained from powders with thermal barrier role on specific materials for internal combustion engines valves. There were used as substrate samples of low alloy steels with Si and high alloyed steels with Cr, Ni and Mn. Using the facility SPRAYWIZARD 9MCE for atmospheric plasma spraying, two types of thermal barrier coatings were produced, from powders based on zirconia and alumina. The samples were analyzed in terms of microstructure using the QUANTA 200 3D scanning electron microscope and the X`PERT PROMD diffractometer. Observations were made both on the longitudinal surface of the coating in order to evaluate it and on the cross-section to evaluate the substrate-coating interface, the influence of deposition temperatures on the substrate and aspect/microstructure on its depth. XRD analysis revealed a cubic structure of aluminum oxide, respectively zirconium oxide. The identified morphology is a specific \"splat\" one for the ceramic coatings. Surface appearance shows tiny pores and cracks specific to the spraying method. The resulted coatings present a significant compactness and adherence to the substrate, which recommends them for further thermal behaviour testing.

The study presents a durability analysis of dies used in the first operation of producing a valve-type forging from high nickel steel assigned to be applied in motor truck engines. The analyzed process of producing exhaust valves is realized in the forward extrusion technology and next through forging in closed dies. It is difficult to master, mainly due to the increased adhesion of the charge material (high nickel steel) to the tool’s substrate. The mean durability of tools made of tool steel W360, subjected to thermal treatment and nitriding, equals about 1000 forgings. In order to perform a thorough analysis, complex investigations were carried out, which included: a macroscopic analysis combined with laser scanning, numerical modelling by FEM, microstructural tests on a scanning electron microscopy and light microscopy (metallographic), as well as hardness tests. The preliminary results showed the presence of traces of abrasive wear, fatigue cracks as well as traces of adhesive wear and plastic deformation on the surface of the dies. Also, the effect of the forging material being stuck to the tool surface was observed, caused by the excessive friction in the forging’s contact with the tool and the presence of intermetallic phases in the nickel-chromium steel. The obtained results demonstrated numerous tool cracks, excessive friction, especially in the area of sectional reduction, as well as sticking of the forging material, which, with insufficient control of the tribological conditions, may be the cause of premature wear of the dies.

In this research, the design of a new electromagnetic engine valve in the limited space of combustion engine is optimized by multidisciplinary simulation using MATLAB and Maxwell. An electromagnetic engine valve actuator using a permanent magnet is a new actuator concept for overcoming the inherent drawbacks of the conventional solenoid-driven electromagnetic engine valve actuator, such as high power consumption and so on. This study aims to maximize the vibration frequency of the armature to reduce the transition time of the engine valve. The higher performance of the new actuator is demonstrated by dynamic finite element analysis.

Engine exhaust valve are exposed to severe thermal loads and chemical corrosion. Exhaust valve opens and closes 2000 times per mile for passenger cars. Generally the material for manufacturing exhaust valve and exhaust valve seat insert have properties for working at high temperature continuously and resistance to corrosion due to their surrounding environment. Usually engine valve is made up of austenitic steels. This valve is to be replaced by a light weight dissimilar materials preferably by an Al6061 and FE 430 steel. In this paper, computational fluid dynamic analysis of such valve is presented. The flow characteristics and strength of the valve are assessed.

For the last several years, gamma titanium aluminide ( γ -TiAl)-based alloys, called “gammalloys,” in specific alloy-microstructure forms began to be implemented in civil aero-engines as cast or wrought low-pressure turbine (LPT) blades and in select ground vehicle engines as cast turbocharger rotors and wrought exhaust valves. Their operation temperatures are approximately up to 750°C for LPT blades and around 1000°C for turbocharger rotors. This article critically assesses current engineering gammalloys and their limitations and introduces eight strengthening pathways that can be adopted immediately for the development of advanced, higher temperature gammalloys. Intelligent integration of the pathways into the emerging application-specific research and development processes is emphasized as the key to the advancement of the gammalloy technology to the next higher engineering performance levels.