The introduction of overhead camshaft valve train systems some 25 years ago has resulted in improved engine performance and efficiency, this in turn however, has caused increased wear problems. In order to understand the tribological behaviour of overhead camshaft systems, test engines and dynameter test methods have been extensively used. These are however, time consuming and expensive, a cheaper and quicker method of camshaft material and lubricant appraisal is therefore required and this has resulted in the design and construction of a simulative overhead camshaft test rig. A range of commercially available camshaft and follower materials have been tested using both a fully formulated and a -mineral base -equivalent. The most commonly encountered cam and follower wear failures of scuffing, pitting and polishing were reproduced. Results showed scuffing wear to be associated with all of the camshaft materials using the mineral base oil under high load, boundary lubrication conditions. Scuffing also occurred under low load, mixed lubrication conditions using the case-hardened steel cam and chilled white iron follower combinations. The remaining cam materials, carbonitrided and induction hardened grey flake iron did not fail under similar test conditions due to the presence of free graphite in the icrostructure. The fully formulated oil generally suppressed the onset of scuffing under all test conditions due to the presence of the zinc-dialkyldithiophosphate (Z.D.D.P) anti-wear additive in the oil. Pitting failure was associated with the chilled white iron follower using the fully formulated oil under high load conditions. This failure could have been initiated by either a surface, sub-surface or stress - corrosion mechanism. Analysis of this type of failure is complicated by the difference in both chill depth and hardness and also the presence. of cracks within, samples prior to examination and testing. Standardisation of chilled white irons therefore needs to be carried out in order to understand fully the wear behaviour of such materials. Polishing wear was associated with the fully formulated oil at low loads, and appeared to occur by a chemical reaction between the contacting surfaces and the additives present in the oil. The use of the acetate replica technique proved a satisfactory method of analysing the change in surface topography of cam surfaces. Using the fully formulated oil the cam surface 'ran in' satisfactorily, by a process of plastic deformation and fracture, whilst the mineral base oil caused instanteous scuffing of the cam surface. Once the surfaces had 'run in' satisfactorily by using either the additives in the oil or by a diamond lapping operation, the cams continued to run without scuffing in the mineral base oil under continuous, non stop test conditions. An intermittent, stop/start operating cycle however results in eventual scuffing due to additive film depletion and repeated surface interaction under boundary lubrication conditions. From a range of 'new' materials tested for follower application the ceramics, with the exception of the toughened zirconia, exhibited the best wear characteristics using a case hardened steel cam as a standard and tested under mineral base oil conditions. The silicon carbide and sialon ceramics both exhibited a low frictional resistance and wear rate, whilst the metallic follower materials of cobalt and nickel base hard facing alloys and a ceramic fibre reinforced aluminium/silicon alloy all suffered some form of material.

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The paper presents a computer-based guide of the effect of layout and loading (tension and torque) on the timing belt life and uses it to show the sensitivity of life to changed conditions in an automotive camshaft drive. The predictions are in line with experience. The guide requires belt property information, such as the tooth and tension member stiffness, the friction coefficient between the belt lands and pulleys and the pitch difference from the pulley, in order to calculate the tooth deflections caused by the belt loadings on the various pulleys in the layout. It also requires information on how the belt life depends on the tooth deflections. Experimental data are presented on the life±deflection relations of a commercial automotive timing belt tested between 100 and 140 8C, although the bulk of the data has been obtained at 120 8C. Four different life laws have been found, depending on whether the failure-initiating deflection occurred on a driver or a driven pulley, and whether at entry to or exit from the pulley. Theoretical analysis of the tooth loading in the partial meshing state shows that, in three cases out of the four, the different life±deflection laws transform to a single relation between the life and the tooth root strain. The exception is failure caused by driven entry conditions; work is continuing to understand better the causes of failure in this circumstance

Vibrations are very common phenomenon. It influences structures and generates acoustic noise which might be harmful to human beings. The vibration isolator was invented to reduce the effect from vibrations. However, the behavior of rubber material, which many vibration isolators are made of, is hard to predict. Consequently, vibration tests are needed to obtain the dynamic properties of rubber isolator.In this case, a six-year old LORD 2204-5 rubber isolator provided by Atlas Copco was tested. The aim of this paper is to obtain the FRF (Frequency Response Function) diagram which can describe the property of the rubber material. Moreover, the influence of aging of rubber material on the dynamic properties was studied.As the vibration test should simulate the working environment of the isolators that are both a static load from the structure and a dynamic force from the engine, a new excitation method was designed. The camshaft with the shape of an epitrochoid induced the sinusoidal signal of the isolator and the frame transferred the static load from the hydraulic machine. The artificial aging was performed in a hot air oven in 90°C for 42 hours, which according to Arrhenius equation should be equivalent to six years of natural aging. The vibration isolator was tested again after being aged.The obtained data showed that the aging process decreased the stiffness of the material. The results were corresponding with other studies regarding aging of rubber.

One of the products produced by Motorpal a.s. is a camshaft. Recently, the company signed a contract with Bosch company to produce new types of camshaft. The analysis of the impact of the contract on the production was made by simulation. To perform the simulation it was necessary to map the whole process. The simulation of the current state was made in the first phase. The results shew many uneffectivnesses in the process and lack of capacity of some workplaces. Some changes in the process were suggested and tested with the aid of the simulation. The best results were achieved when the single-item flow was used. In the second phase the production of a new type of camshaft was added to the simulation. Analysis of these results was divided into two parts. The new production was analysed in the first part and it was discovered that the planned capacites are very deficient. The impact of the new production on the current one was analysed in the second part. It shew that this impact is negativ, especially on the duration of production.

No / This paper presents a calibration optimization study for a Gasoline Direct Injection engine based on a multidisciplinary design optimization (MDO) framework. The paper presents the experimental framework used for the GDI engine mapping, followed by an analysis of the calibration optimization problem. The merits of the MDO approach to calibration optimization are discussed in comparison with a conventional two-stage approach based on local trade-off optimization analysis, focused on a representative emissions drive cycle (NEDC) and limited part load engine operation. The benefits from using the MDO optimisation framework are further illustrated with a study of relative effectiveness of different camshaft timing control strategies (twin independent Versus fixed timing, exhaust only, inlet only and fixed overlap / dual equal) for the reference GDI engine based on the part load test data. The main conclusion is that the MDO structure offers an effective framework for the GDI steady state calibration optimization analysis.

An analytic treatment of stresses and temperatures generated during grinding is presented from an elasticity approach. A two-dimensional heat conduction model employs an energy partition scheme in the grinding zone to produce realistic temperature profiles. By using the basic equations of thermoelasticity, the temperature profiles yield thermal stresses. An extension of the Hertzian contact theory yields mechanical stresses, which are then superimposed on the thermal stresses. Approximate plasticity corrections are used to approximate the deformation as the grinding wheel passes over the workpiece. Subsurface results are qualitatively consistent with those found experimentally. However, they still do not agree with near-surface experimental results. Possible explanations and areas of further research are discussed. / Master of Science

The aim of this thesis is a comparing single valve train motion (SVT) and complete valve train motion with a flexible camshaft focused on dynamic characteristics. In this thesis is also performed kinematics analysis in the VALKIN software. Dynamic analysis is solved in the MBS software Virtual Engine. Influences to the valve train motion are described in the conclusion

Nondestructive evaluation techniques were employed to fully characterize three 2.3L camshafts tested in an engine simulator for an equivalent of 100,000 miles. Optical microscopy, acoustic microscopy (SAM), and profilometry were used to characterize wear and fatigue, crack depth, and surface roughness, respectively. Results show cracking to occur mainly in the opening ramp of the most abusively ground cam lobes. No clear evidence was found for subsurface cracking at depths as great as 200 μm from the lobe's surface. Profilometry results show no evidence of any major tribological effect due to the sliding friction of the follower. Fractography studies show a difference between fracture surfaces among the cracks examined; straight cracks exhibit features resembling fatigue propagation, while fracture surfaces from pitted cracks show a more brittle behavior. Small grinding cracks (approximately 300 μm in length) were found in the opening ramps of the most abusively ground lobes prior to testing. Knoop and Nanoindenter microhardness indicate a near-surface rehardening for the most abusively ground lobe (confirmed by metallography), and temper burn for the remaining lobes. X-ray residual stress results made in the opening ramp of the tested lobes show evidence of residual stress relaxation. X-ray line width data as a function of depth does not correlate with residual stress. / Master of Science

Im Vortrag wird die Vorgehensweise zur Modellierung des Ventiltriebs eines Einzylinder-Motorradmotors beschrieben. Dieser setzt sich aus zwei gebauten, wälzgelagerten Nockenwellen zusammen. Die Ventile werden über Schlepphebel betätigt. Das Hauptaugenmerk liegt dabei auf den Pressverbindungen zwischen Nocken und Welle sowie auf den Wälzlagerungen. Um die Belastungszustände zu ermitteln ist eine detaillierte Simulation nötig. Diese Mehrkörpersimulation wird in Mathcad mit Hilfe eines eigenen Lösers durchgeführt.