Bore polishing — identification and simulation

Bore polishing resulting from the abrasive wear of the bore of diesel engines has become more evident with the introduction of turbo-charging and consequent high mileage. This paper identifies the principal characteristics of bore polish, suggests causes and records the examination of a particular used liner. A laboratory wear machine was then used to simulated bore polish conditions. The results are analysed and discussed.     

Cavitation effects on textured compression rings in mixed lubrication

Thin lubricant films and cavitation to ring–bore contact have a directly correlation between wear and emissions output of internal combustion engines. Thus, there is a need to develop innovate engineering solutions such as surface texturing. In particular, micro textures are manufactured in order to keep more lubricant in weakly lubricated contact. An isothermal mixed‐hydrodynamic analysis was developed for textured compression rings, which utilised the effects of two‐phase flow using Navier–Stokes equations, vapour transport and asperity interaction. Realistic boundary conditions are used from a real motorbike engine. This paper employs a computational model including multiphase flow of the ring–bore conjunction in order to predict the effects of surface texturing of the barrel face ring around the dead centres. The model is validated using numerical and experimental results from the literature. Additionally, flow simulations have been performed, on how micro‐dimples shape and depth on the ring liner affect on the total friction and minimum lubricant film. Copyright © 2016 John Wiley & Sons, Ltd.     

Quantification of the cold worked material inside the deep honing grooves on cylinder liner surfaces and its effect on wear

The increased presence of cold work material on cylinder liners due to the introduction of the diamond honing is undesirable as it seals the oil-bearing honing grooves. The most of it is a smeared metal inside the deep honing grooves (blechmantel) that may break and act as abrasive wear particles increasing the bore wear. An attempt has been made to estimate the extent of removal of blechmantel for different wear regimes present at the middle and top region (near the top dead centre) of the liner surface using the least worn bottom region as a reference for comparison. A number of truck grey iron cylinder liners were axially sectioned after varying periods of engine running under similar conditions of load, engine speed and lubrication. 3D surface measurements were taken at the three regions and a range of standard parameters was extracted. Combining the profile and image analysis, an algorithm was developed to identify and quantify the blechmantel. The algorithm has successfully identified/quantified the blechmantel and can be used for automatic surface quality and process control. It was found that the amount of the blechmantel in the middle section was approximately the same (though slightly lower) as that in the bottom section, while there was a considerable dislocation and removal of blechmantel in the top section and thereby it represents one of the possible causes for wear. Axial wear scratches of different size and distribution were observed not only through the whole stroke area, but also in the bottom region. All engines and liners performed well throughout the tests, and the observed quantities of blechmantel and axial scratches are acceptable for the time being.     

Composition of lubricating oil in the upper ring zone of an internal combustion engine

It is demonstrated that the composition of lubricating oil obtained from the top ring zone of a spark ignition, natural gas, internal combustion (i.c.) engine at top dead centre (TDC) is very much different from that of the oil in the sump. The implications of this observation for wear in the bore of i.c. engines and piston fouling are briefly discussed.     

Corrosive wear of diesel engine cylinder bore

Deleterious wear of the cylinder bore in diesel engines can be aggravated by alteration of combustion conditions, such as that brought about by use of Exhaust Gas Recirculation (EGR) equipment and consequent high mileage. This paper describes the influence of combustion products — i.e. sulphuric acid and carbon soot, which can be primarily concerned in corrosive wear — on lubrication under reciprocating sliding of a piston ring and on the bore wear.     

Condition monitoring of aircraft by quantitative filter debris analysis

Various condition monitoring techniques are used collectively to monitor the health of aircraft engines and transmission, a concept known as Integrated Health Monitoring (IHM). A well-established quantitative technique is Aircraft Oil Analysis (AOA), in which spectroscopic techniques such as Rotating Disk Electrode Atomic Emission Spectroscopy (RDE-AES) are employed to analyse periodic oil samples for wear debris. Usually, no sample preparation is undertaken, as the oil sample containing both dissolved and suspended metallic wear debris is analysed directly. AOA works well for oil-lubricated systems with relatively coarse filtration that allow circulation of the debris and its subsequent abrasive contact with moving components. To avoid this secondary wear, finer filtration is employed on both new and older aircraft. Less wear debris, and thus information, is available in the oil. A technique that quantitatively analyses the wear debris caught on the filter has been developed and is termed Quantitative Filter Debris Analysis (QFDA). Actual oil filters from CF88 Challenger ALF 502L-2C and Hornet F404 engines were obtained in sequence, when possible, prepared by the developed procedure, and analysed with AOA instrumentation. With sufficient results, both normal and abnormal levels of wear rates emerged, as has been recorded and used for AOA. Moreover, trending of the data for sequential samples has demonstrated the capability of GFDA for condition monitoring.     

不同活塞销孔衬套-活塞销摩擦副匹配性能研究

活塞销孔衬套-活塞销是柴油机重要的摩擦副之一,其匹配性能的优劣直接影响使用寿命和动力特性。为探讨不同制备工艺的活塞销孔衬套与柴油机在用活塞销的匹配性能,将分别采用挤压和旋压工艺制备的活塞销孔衬套,以及进口衬套分别与柴油机在用活塞销匹配,在摆动摩擦副摩擦磨损试验台进行承载、抗咬合和耐磨损性能试验。试验结果表明：制备工艺对摩擦副匹配性能具有一定的影响;从摩擦扭矩、摩擦温度、宏观形貌和磨损量4个方面分析,相同工况下挤压衬套承载极限、抗咬合性能和耐磨损性能均优于旋压衬套,具备对标进口衬套的能力,可为国内活塞销孔衬套的选配提供参考。     

12150发动机磨损分析与油液监测机理研究

本文对12150发动机的磨损情况进行了详细的分析与讨论,总结了该发动机的磨损类型与磨原因,文中针对基于油液分析的12150发动机磨损故障监测方法进行研究,给出了油液监测机理。     

The effect of a friction modifier on piston ring and cylinder bore friction and wear

The addition of friction modifiers to crankcase lubricants has been shown to significantly reduce the mechanical losses of critical components in internal combustion (ic) engine; thereby improving fuel economy.In this study the friction and wear of a piston ring/cylinder bore material combination was studied using a pin-on-plate laboratory tribo-test machine developed to reproduce the wear mechanisms encountered in an ic engine. Two lubricants were evaluated: (i) a standard SAE 30 grade diesel formulation, and (ii) the same formulation with the addition of a 5% soluble MoS₂ friction modifier.Analysis of the wear results identified three periods of wear: (1) running-in, (2) transient wear and (3) terminal wear. Throughout this study particular emphasis has been placed on the simulation of the wear mechanisms occurring within engines. Surface analysis confirmed that both abrasive wear and delamination wear was produced.Friction benefits attributable to the addition of MoS₂ friction modifier were obtained. However, under specific conditions the wear rate increased due to increased abrasion of the plate.     

Temperature—friction characteristics of cylinder lubrication in large,slow, cross‐head marine diesel engines under boundary lubrication conditions

In large, slow, cross‐head marine diesel engines research has increasingly shown that the lubrication regime between piston rings and cylinder liner at top dead centre is of the boundary lubrication type due to the high gas pressure, low sliding speed, and high temperature. This means that the tribological properties of piston ring, cylinder liner, and cylinder lubricant in these types of engine under boundary lubrication conditions should be considered simultaneously when friction and wear between the piston ring and cylinder liner are studied. Until now there has been no standard method to evaluate boundary lubrication performance. There are a few traditional methods used in lubricant research, but their results are not correlated with service conditions. It is important to find a suitable method to evaluate the boundary lubrication performance of lubricants at the laboratory testing stage or before the engine testing stage. The important parameters, such as sliding speed, normal load, materials of the contacting pairs, and lubricant, need all to be controlled. In this paper a systematic experimental procedure, the ‘five times heating and cooling test’, is introduced to assess lubricant properties under boundary lubrication conditions. Most of the parameters mentioned above are controlled. The model contact, of pin‐on‐plate form, is made from the actual piston and liner materials used in a large‐bore, slow, cross‐head marine diesel engine. The temperature characteristics of different blends of lubricants are investigated under boundary lubrication conditions using a pin‐on‐plate reciprocating test rig. These blends of lubricants have the same additives but different base fluids; they nevertheless fulfil the physical and chemical requirements of a real marine diesel engine. The test temperature range is from room temperature to the working temperature of the top piston ring. The experiments show that there are different temperature—friction characteristics for lubricants with different bases and the same additive package and there are also different temperature—friction characteristics during heating up and cooling down for each blend. Single‐base lubricants have more promising temperature—friction characteristics than those of a blend of a high‐viscosity base and a low‐viscosity base at high temperature.     

Application of grey modeling method to fitting and forecasting wear trend of marine diesel engines

Oil monitoring is an important and useful method for predicting wear failure, and has been used in diesel engines successfully. The diesel engine is the key power equipment in ships and it is a complicated tribological system with uncertainty and indetermination. Grey system theory is suitable for systems in which some information is clear and some is not, so it is feasible to study the wear process of diesel engines with this theory. The unequal interval revised grey model (UIRGM) (1,1) is presented in this paper, which is applicable to original series with unequal intervals and sharp variation. The model that is built is applied to fit and predict element concentration as determined by oil spectrometric analysis. It is proved that UIRGM (1,1) determines the exact turning point, and the fitting and prediction results are acceptable.     

Numerical evaluation of the potential for fuel economy improvement due to boundary friction reduction within heavy-duty diesel engines

Advanced surface treatments have been developed by a number of research institutes as an approach to reduce friction at sliding interfaces. Laboratory tests have shown that some of these surface treatments can result in boundary friction reductions approaching an order of magnitude [1], [2] and [3]. While there are many potential applications for such surface treatments, friction reduction in internal combustion engines is of particular interest due to the apparent fuel savings potential. Ricardo, Inc. has performed simulations to estimate potential fuel economy improvements due to the application of such treatments at key interfaces within engines typical of those used in large trucks. The results show that fuel economy improvements in excess of 4% can be achieved from combined application of a surface treatment and reduction in lubricant viscosity, if the surfaces can be protected against wear.     

Scuffing detection of TU3 cam–follower contacts by electrostatic charge condition monitoring

The increasing costs associated with lubricant development and qualification has driven the need for condition monitoring techniques to be deployed on test engines to maximise information gained from expensive testing programmes. This paper discusses the results from a motorised TU3 engine with electrostatic sensors focused on the cams. System characterisation tests and an oil starvation test were used to decouple charge mechanisms associated with a lubricated wear test, accelerated through the use of carbon black. Cross-correlation of various charge signal processing techniques, scanning electron microscopy and profilometry revealed that tribocharging dominated during running-in/mild wear and contact potential difference (CPD) dominated during the progression of severe adhesive wear. Tribocharging (the charge generated by a low conductivity fluid) has been shown to be affected by oil temperature, cam rotation speed and the presence of charged species within the lubricant. Contact potential differences was principally generated by the work function difference between oxidised and nascent regions associated with adhesive wear on the cam surface. Electrostatic monitoring which is sensitive to lubricant chemistry and wear, and can be implemented in an industry standard engine, has great potential for the lubricant industry.     

Modeling of Abrasive Wear in a Piston Ring and Engine Cylinder Bore System©

Engine-related improvements such as more efficient engine components, improved engine oils, and high-performance coating materials, need to be verified in terms of their effects on the tribological performance of the piston ring/cylinder bore system. The main purpose of this research is to develop an abrasive wear model for the piston ring/cylinder bore system during steady-state operation by considering the effects of temperature, load, oil degradation, surface roughness, and material properties. The model can be used either in theoretical modeling or integrated with finite element analysis. Based on a laboratory simulator, a three-body abrasive wear model has been developed to model the wear progression of the piston ring/cylinder bore system during steady state operation. The proposed novel abrasive wear model addresses the effects of temperature, load, oil degradation, surface roughness, and material properties. The feasibility of the proposed model is illustrated by a numerical example.     

Bench Wear Testing of Common Gasoline Engine Cylinder Bore Surface/Piston Ring Combinations

In this study, two bench wear tests, the Cameron-Plint modified lest (C-P) and the Electro-Mechanical test (LS9), have been used to evaluate common internal combustion engine cylinder bore surface/piston ring pairs. Bore, materials tested include cast iron, 390 aluminum, and Nikasil. Piston rings tested include chromium-plated, plasma-sprayed molybdenum, and gas-nitrided stainless steel. Both the C-P and LS9 bench wear tests showed the same general trends. Gas-nitrided stainless steel rings provide the lowest overall ring wear and the lowest cast iron bore wear. 390 bore wear is higher than that of cast iron or Nikasil. Chromium-plated or gas-nitrided stainless steel rings provide the best balance of ring and bore wear against 390 aluminum, while molybdenum rings against 390 produce the worst combined wear. Differences in wear rates for 390 aluminum are related to variations in temperature and lubrication rate between the two testers. Bore wear measurement accuracy is quantified and an improved measurement technique is introduced. An initial study of surface finish effects shows that an increase in roughness increases the friction coefficient.     

Bio-Fuel-Contaminated Lubricant and Hardening Effects on the Friction and Wear of AISI 1045 Steel

A study has been made on the wear and friction of hardened AISI 1045 steel using a tri-pin-on-disc type of friction and wear apparatus. During the investigation the linear pin wear, coefficient of friction and rise in pin specimen temperature were monitored and wear and friction curves plotted. Wear surfaces and mechanisms were investigated by means of optical microscopy. Analysis of used lubricating oil was performed using FTIR spectroscopy.

It was shown that the wear rate, type of wear and friction coefficient were influenced by contaminating the lubricant with bio-fuel as well as the surface hardening treatment. Corrosive wear and pits on the specimen surface were found when plain bio-fuel was used as lubricating oil. The results also confirmed that better wear resistance was obtained from the surface-hardened steel specimen with 4 % bio-fuel-contaminated lubricant.

Results from this study will be useful in material selection for tribological components in diesel engines running on vegetable fuel.     

Wear of projectile rotating bands

Rotating or driving bands are bands of relatively soft materials surrounding a projectile. They have a number of functions the chief of which is probably that they produce stabilizing rotation of the projectile when they are “engraved” or keyed into the rifling. These bands are used on spinstabilized projectiles as small as 20 mm caliber, but this discussion concerns especially the larger cannon, i.e. in excess of 105 mm. Excess wear of projectile rotating bands has a number of important negative consequences including inaccuracy and “short rounds”. There are two distinctly different mechanisms of wear. At low speeds near the beginning of motion, wear is by adhesion, abrasion and even, under some conditions, scuffing. After a few centimeters of sliding, a thin surface film of molten band material is formed and the remainder of the sliding is melt lubricated. While metal-on-metal sliding is limited to the first few centimeters, it is very important and can result in serious wear problems down bore. The exact wear of rotating bands depends on the motion of the projectile in the bore of the cannon. Therefore, this motion can be inferred from the wear.     

Kinematics and wear patterns of cam and finger follower automotive valve gear

The kinematics and geometry of the finger follower valve gear used in three engines on the European market have been analysed. The results of the analyses disclose some features that are common to all the designs and which may be related to features in the patterns of wear observed in the engines. The effects of various changes in the geometry of one of the engines have been investigated.     

Tribological evaluation of oil pump relief valve coatings compatible with an aluminum oil pump body

Wear can cause automotive relief valves to jam. In order to evaluate and screen candidate coatings for oil pump relief valves for reduction of aluminum pump cylinder bore wear and wear-related sticking, a laboratory reciprocating wear test using production parts has been developed. The coatings on valves include impinged and physical vapor deposited (PVD)-coated molybdenum disulfides, electroplated nickel–phosphorous with polytetrafluoroethylene (Ni–PTFE), electroplated bronze, and electroplated nickel–phosphorous–boron nitride (Ni–P–BN).

The test results showed that the electroplated bronze coating demonstrated the best wear resistance against 380 aluminum pump bores while Ni–PTFE ranked second, PVD-coated MoS₂ third, and Ni–P–BN ranked last. It was observed that the electroplated bronze coating showed only mild oxidative or abrasive wear after 20 h wear test. The Ni–P–BN coating gave the worst wear resistance due to severe abrasive wear, surface scoring, and coating abrasion during the wear test. The major wear mechanisms for valve bore/relief valve can be classified at different levels from mild wear (oxidative wear or surface delamination) to abrasive wear (scoring, scuffing, and ploughing). This paper also reviewed the rooted wear mechanisms of production pump relief valves against aluminum bores based on metallographic observations of worn surfaces after field tests. This tribological investigation of valve coatings has provided insights into the fundamental wear mechanisms which depend on the compatibility of two sliding materials, protective coating composition, hard particle content, and surface interaction. The information will be useful in preventing oil pump relief valves from jamming.     

Friction and wear bench tests of different engine liner surface finishes

Six different bore finishes of combustion engines were bench-tested against PVD-coated rings. Ring and liner specimens were removed from actual Heavy-Duty Diesel engine. The test was conducted in a CETR UMT-2 reciprocating tester. Current bore honings, e.g. slide honing, as well as recently developed structured laser were tested.For friction bench tests, the specimens were tested at different reciprocating speeds and loads. When lubricant condition approached the boundary regime (speed/load tending to zero), most of the finishes showed the usual boundary friction coefficient 0.11. When the conditions tended to the hydrodynamic regime, the specimen removed from the non-laser region of the laser-structured finish showed a remarkably low friction coefficient, followed by the laser-structured ones.For wear bench tests, the lubricant was doped with hard particles, and higher load and speed were used to accelerate the wear rate. Wear tests ran for 4 h and, as expected, friction coefficient reduced during the wear test due to break-in. In general, friction during the wear test followed the friction test ranking. The remarkable exception was the UV laser finish, which initially presented one of the highest coefficient and after 0.5 h of testing turned to be one of the lowest. Liner and ring wear was measured post-test by profilemeter. In general, the smoother surfaces presented lower ring and bore wear.Greenwood asperity parameters and Patir and Cheng flow factors were calculated from two measured surfaces. A computer model was applied to calculate the oil film thickness and friction for the different speed and load conditions. The calculated friction results showed good adherence to the measured data.