Tribological performance of multi-scale micro-textured H62 brass surface fabricated by micro-milling and wet micro-blasting

The cylinder block/valve plate interface in the axial piston pump has been proven to be easily worn out, which will increase power loss and reduce its efficiency. The valve plate surface is required to be manufactured with low viscous friction and wear. Multi-scale micro-texture has been proven to improve surface tribological properties. However, there are few types of research in the effect of surface topography on the tribological performance of multi-scale micro-textured surfaces. The purpose of this study is to explore how the multi-scale micro-texture on H62 brass affects its sliding friction behavior on 38CrMoAl. Based on micro-milling and wet micro-blasting, the multi-scale micro-textured surface was manufactured on H62 brass. The wet micro-blasting was applied in the H62 brass after the surface micro-texturing. The surface topography of multi-scale micro-textured samples processed by three abrasive grit sizes accompanied by two processing times was comprehensively measured in terms of height, feature, functional, and functional volume parameters. The tribological performance of multi-scale micro-textured H62 brass was characterized by disk-on-disk frictional experiments. Through analyzing the relationship between surface morphology and tribological properties, the anti-friction mechanism of the multi-scale micro-textured surface was analyzed from the perspective of 3D surface roughness parameters. The friction coefficient of the multi-scale micro-textured surface processed by the combination of micro-milling and wet micro-blasting decreased with the increasing grit size and micro-blasting time.

Theoretical assessment of the stress-strain state of the cylinder sleeve of a marine diesel engine from the effects of variable moving gas loads

Цилиндровые втулки относятся к наиболее нагруженным деталям судовых дизелей. Оценка их напряженно-деформированного состояния показывает, что последовательное форсирование дизелей по среднему эффективному давлению требует существенного пересмотра некоторых положений конструирования этих деталей. Это касается конструктивного оформления наружных поверхностей втулок, а также их закрепления в блоке цилиндров. В статье рассматривается влияние условий закрепления верхнего торца втулки и промежуточных опор-уплотнителей на деформирование цилиндровой втулки газовыми нагрузками. Показано, что для выбора оптимального места установки кольца-уплотнителя по длине втулки целесообразно исходить из минимизации воздействий на него со стороны подвижных газовых нагрузок. Предлагается расчётная методика, которая позволяет определить то место установки промежуточной опоры, где она практически не влияет на параметры напряженно-деформированного состояния цилиндровой втулки судового дизеля с учётом особенностей закрепления её верхнего торца в цилиндровом блоке. Применение данной методики позволяет с учётом особенностей конкретного двигателя обоснованно решить вопрос размещения дополнительных опор-уплотнителей. Cylinder bushings are among the most loaded parts of marine diesel engines. Evaluation of their stress-strain state shows that the sequential forcing of diesel engines according to the average effective pressure requires a significant revision of some provisions for the design of these parts. This applies to the design of the outer surfaces of the bushings, as well as their fastening in the cylinder block. The article examines the influence of the conditions for fixing the upper end of the sleeve and intermediate support-seals on the deformation of the cylinder sleeve by gas loads. It is shown that in order to select the optimal place for installing the seal ring along the length of the sleeve, it is advisable to proceed from the minimization of the effects on it from the movable gas loads. A calculation method is proposed that allows you to determine the place of installation of the intermediate support, where it practically does not affect the parameters of the stress-strain state of the cylinder liner of a marine diesel engine, taking into account the peculiarities of fixing its upper end in the cylinder block. The use of this technique allows, taking into account the characteristics of a particular engine, to reasonably solve the issue of placing additional support-seals.

Tribological Properties of Cylinder Block/Valve Plate Interface of Axial Piston Pump on the Tribometer

The tribological properties of cylinder block/valve plate is an important consideration in the design of axial piston pump. The effect of materials and heat treatment on friction and wear properties has been studied in depth. Engineering experiences show that the speed and load also affect the tribological properties, but these have not been systematically analyzed. The purpose of this paper is to evaluate the tribological properties of the commonly used materials (CuPb15Sn5 and 38CrMoAl/42CrMo) for cylinder block/valve plate with different heat treatment and contact pressure at different speed. During the test, tribometer is used to simulate the contact pattern between the valve plate/cylinder block in axial piston pump, the friction coefficient, wear rate and surface topography are analyzed to evaluate the tribological properties of different types of friction samples at different speed. Results indicate that: (1) contact surface of the samples at 1800 r/min is more prone to adhesive wear than those at 500 r/min; (2) in the terms of wear resistance, quench-tempered and nitrided 38CrMoAl (38CrMoAl QTN for short) is better than quench-tempered and nitrided 42CrMo, although they are all commonly used materials in the axial piston pump; (3) 2.5 MPa is the critical contact pressure of the interface between valve plate made of 38CrMoAl QTN and cylinder block made of CuPb15Sn5 on the tribometer, which implies the pressure bearing area at the bottom of the cylinder block should be carefully designed; (4) the valve plate/cylinder block made of 38CrMoAl QTN/CuPb15Sn5 exhibits good tribological properties in a real axial piston pump. This research is useful for the failure analysis and structural optimization design of the valve plates/cylinder block.

Effect of stir casting parameters and mono/hybrid reinforcements on aluminium metal matrix composite–A review

Aluminum metal matrix composites are a new class of materials that have gathered more attention from many materialists. Especially, the automotive components like a piston, cylinder block, brake drum, etc., fabricated by different reinforcement, which has exposed better performance over conventional engineering materials. Aluminum composites are generally fabricated by stir casting technique due to simplicity in operation and adaptive to mass or job order production. The paper provides a background for the readers interested in the production of metal matrix composites through stir casting. Based on the literature assessment, the special attentions taken by the researchers to enhance the uniform distribution of particle to avoid agglomeration are discussed. The composite performances mainly depend on the aluminum matrix, particle size, the quantity of reinforcement, preheating temperature of reinforcement, and processing parameters such as stirring speed, stirring time, and wetting agents. The selection of two reinforcements and their suitable parameters for wetting are attaining interest by many researchers and maybe opted as future scope.

Investigating the Condition Monitoring Potential of Oil Conductivity for Wear Identification in Electro Hydrostatic Actuators

To meet future goals of more electric airplanes conventional hydraulic airplane control systems, consisting of redundant centralized pumps within the airplane’s fuselage, need to be substituted for compact electro-hydraulic actuators (EHA). The capsulated architecture of EHAs results in higher safety due to separate hydraulic circuits, simple practicability of redundancy, decreased maintenance because of simplified error location detection as well as an overall reduction in weight and complexity of the airplane control system. Currently, EHAs are only used as backup devices as the reliability does not achieve normative requirements for a frontline application. Thus, recent studies aim to increase the reliability. The axial piston pump of current EHA is the source of most failures. High dynamic requirements and challenging operation points and environments result in wear of contact pairs such as swash plate/piston shoes, pistons/cylinder block and cylinder block/valve plate. In the scope of the project MODULAR at ifas one goal is to increase the robustness of the contact surfaces. A second goal addresses the topic of developing a condition monitoring approach to constantly track the pumps’ health status. Next to signals such as pressures and temperatures, acceleration and oil status signals describing the actual particle contamination are needed. In this contribution different methods of oil status detection are explained and the method of electric conductivity analysis for condition monitoring is further investigated. Filtered HLP46 is used and impurities in form of metallic powders are added. Furthermore, degraded oil of a disc-on-disc Tribometer test bench is measured and compared.

A Novel Positive Displacement Axial Piston Machine With Bent Cylinder Sleeves

In this paper, an investigation of a novel positive displacement axial piston machine using a bent cylinder sleeve configuration is presented. The proposed design eliminates the side moments on the piston/cylinder interface, therefore, reduces the frictional loss and improves the total energy efficiency. A multi-physics elastohydrodynamic lubrication model was used to aid the design of the piston/cylinder and the cylinder block/port block interface. Then, a lumped parameter model was used to optimize the port block geometry. Groove geometry was chosen primarily to reduce flow ripple, tilting moment, and cavitation risk. To improve the housing stiffness, the lumped parameter model was combined with a finite element analysis. This ensured safety for the testing. In the end, steady-state experiments were performed on the prototype based on the ISO4409 normative. The unit’s speed was set to 500 rpm, then increased by 500 rpm until it reached 3000 rpm. The supply pressure was set to 20 bar. The outlet pressure was set to 70 bar at first, then increased by 50 bar until it reached 220 bar. The results show a remarkable volumetric efficiency with a peak of 99.5%. It is however noted that due to some of the issues with the initial iteration of the current design, there is a reduction in mechanical efficiency. The causes and possible future solutions to these issues are discussed in the manuscript.

Analysis of Cavitation Characteristics of High Temperature Fuel Piston Pump in the Process of Suction and Discharge

The fuel piston pump is the core power component of the aircraft engine fuel control system. The key technology of improving the reliability of the pump is the suppressing of the cavitation at the interface between the valve plate and the cylinder block. This article aims to solve the problem of cavitation caused by high temperature in the process of suction and discharge. The theoretical model of cavitation related to the interface is established. The influence of different working conditions and valve plate structures are considered, and the performance such as gas volume fraction and pulsation are analyzed separately. A new valve plate with combined damping groove is proposed. A hydraulic system test rig to verify the performance of the pump is built. In summary, the results of simulation and test show that the new combined damping groove effectively suppress the cavitation at the interface under high temperature. The non-cavitation time of the fuel piston pump is extended from 20h to 450h, which significantly improves its reliability.