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A detailed investigation has been carried out to understand the effect that soot has on the properties of automotive lubricants. The paper builds on previous work, through testing of different lubricants and increased levels of soot contamination. The objective of the work was to increase the understanding of the wear mechanisms that occur within the contaminated contact zone, to help in future development of a predictive wear model to assist in the valve-train design process. Testing has been carried out using specimens operating under realistic engine conditions, using a reciprocating test-rig specifically designed for this application, where a steel disc is held in a heated bath of oil and a steel ball (replicating a valve train contact) is attached to a reciprocating arm. Detailed analysis of the test specimens has been carried out using scanning electron microscopy (SEM) to identify wear features relating to the proposed wear mechanisms.

The measurement of pressure at a contact in engine parts is important, because it is frequently contact stresses that lead to failure by seizure, wear, or fatigue. Whilst an interface might appear smooth on a macro-scale, it consists of regions of asperity contact and air gaps on a micro-scale. The reflection of an ultrasonic pulse at such a rough contact can be used to give information about the contact conditions. The more conformal the contact, the lower the proportion of an incident wave amplitude that will be reflected. In this paper, this phenomenon has been used to produce maps of contact pressure at three automotive component contacts: a cam/follower interface, a valve tip contact and a tripode drive joint. An ultrasonic pulse is generated and reflected at the interface, to be received by the same piezo-electric transducer. The transducer is scanned across the interface and a map of reflected ultrasound (a c-scan) is recorded.

A study has been carried out to investigate the influence of soot contaminated automotive lubricants in the wear process of engine valve train contacts. Previous research on this topic has been performed from a purely generic and theoretical point of view. Testing has been carried out using standard testing techniques with very little relevance to real engine conditions or components. In this study the conditions under which wear occurs was investigated using tests with actual valve train components. The objective of the work was to develop a knowledge base of wear data for a variety of lubricated reciprocating valve train components. This will increase the understanding of the wear mechanisms that occur within a contaminated contact zone, which will be used in the future development of a predictive valve train wear model.

Wear problems will continue to occur with engine components even with changing design and the introduction of novel materials. Very few wear models for engine components exist, however, so it is difficult for engineers to easily establish how materials and components will perform and costly engine testing programs have to be carried out. Those models that do exist are often complex, difficult to use and written in software that is not available within many organisations. The use of browser-enabled software applications is becoming increasingly common in large, multi-location organisations to make the delivery and support of engineering tools more efficient, so it would be beneficial if wear modelling software was available in this format. In this project, work has been carried out to further the development of an existing valve recession model to provide an easy to use variant for use in industry.

The paper presents a novel method for the measurement of lubricant film thickness in the piston-liner contact. Direct measurement of the film in this conjunction has always posed a problem, particularly under fired conditions. The principle is based on capturing and analysing the reflection of an ultrasonic pulse at the oil film. The proportion of the wave amplitude reflected can be related to the thickness of the oil film. A single cylinder 4-stroke engine on a dyno test platform was used for evaluation of the method. A piezo-electric transducer was bonded to the outside of the cylinder liner and used to emit high frequency short duration ultrasonic pulses. These pulses were used to determine the oil film thickness as the piston skirt passed over the sensor location. Oil films in the range 2 to 21 μm were recorded varying with engine speeds. The results have been shown to be in agreement with detailed numerical predictions.

A photoelastic stress analysis technique has been used to determine the contact stresses in an automotive chain drive tensioner. The tensioner in normal operation is subject to high magnitude, short duration impact stresses. These stresses are known to cause surface damage, wear, and surface pitting. In order to adequately design the drive system layout, a means for stress quantification is needed. A replica tensioner was made from epoxy resin and tested in a variety of configurations. A simple model has been created to relate the chain link load to the resulting tensioner sub-surface stress field. This model has been used to correlate the observed and predicted location of isochromatic fringes, and hence to evaluate the chain link load from the photoelastic fringe pattern. A series of static load tests were performed to calibrate the apparatus. The tensioner specimen was then assembled in a chain drive test facility.

Although new materials and production techniques are being developed to reduce valve and seat wear, these advances have been outpaced by demands for increased engine performance. At present no rules exist to arrive at a satisfactory valve life. Each wear problem, therefore, has to be investigated, the cause isolated and remedial action taken. The objective of this work was to develop design and failure analysis tools for use in industry to assess the potential for valve recession and solve problems that occur more quickly. A semi-empirical wear model for predicting valve recession has been developed based on data gathered from laboratory simulation experiments. A software program, RECESS, was developed to run the model. Model predictions are compared with engine dynamometer tests and bench tests.

The aim of this work was to investigate the wear mechanisms occurring in passenger car diesel engine inlet valves and seat inserts using a bench test-rig designed to simulate the loading environment and contact conditions to which the valve and seat are subjected. The investigation has shown that the valve and seat insert wear problem involves two distinct mechanisms: impact of the valve on the seat insert on valve closing and sliding of the valve on the seat insert under the action of the combustion pressure. The prevailing wear mechanisms have been shown to be related to critical operating conditions such as valve closing velocity, combustion load and valve misalignment relative to the seat insert and valve and seat insert material choice.