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The principal factors that affect the characteristics of contact problem between cam and follower vary enormously during the operating cycle of this mechanism. This includes radius of curvature, surface velocities and applied load. It has been found over the last decades that the mechanism operates under an extremely thin film of lubricant. Any practical improvement in the level of film thickness that separates the contacted surfaces represents an essential step towards a satisfactory design of the system. In this paper a detailed numerical study is presented for the cam and follower (flat-faced) lubrication including the effect of introducing an axial modification (parabolic shape) of the cam depth on the levels of film thickness and pressure distribution. This is achieved based on a point contact model for a cam and flat-faced follower system. The results reveal that the cam form of modification has considerable consequences on the level of predicted film thickness and pressure distribution as well as surface deformation.

This thesis reports experimental and theoretical analyses to study the heat generation and partition between contacting bodies under rolling/sliding elastohydrodynamic (EHL) point contact. A twin disk test rig was re-commissioned and used for the experimental work. 76 mm diameter crowned, super-finished test disks, fixed on parallel shafts, were used in the experimental EHL tests. In each disk, 6 thermocouples were installed to measure the temperature during sliding/rolling contact under EHL conditions. In addition, ceramic washers were fixed on the plane sides of each disk to minimize heat transfer over those surfaces. A Labview data acquisition system was built for acquiring data from the sensors installed on the rig. The EHL experimental results show the fast disk has significantly higher bulk temperature than the slow disk. A transient two dimensional numerical model was constructed to calculate the average circumferential temperature distribution within the disks using three thermocouples as a boundary condition. The heat partition factor,  , and convection heat transfer coefficient, h, were varied systematically in the model. A linear relationship between  and hf for the fast disk and 1- and hs for the slow disk were obtained. These two linear relations were related together by the variation of h with the rotational speed. Over the approximately steady state condition, the calculated  using this approach was in the range of 0.65 to 0.77 for 32 EHL tests at different loads and sliding speeds. This means that the majority of heat is conducted to the fast disk, which is compatible with the previous findings. In order to carry out transient modelling, the unloading mechanism was developed to ensure rapid disk separation. This improved the temperature trend in the cooling phase. In addition, a microswitch was used to give accurate monitoring of the disks contacting and separation. The thermocouple arrangement within the disks and their installation technique we

Experimental and theoretical analyses are reported to study the heat generation and partition in an elastohydrodynamic rolling/sliding point contact. Heat is generated within the lubricant in the Hertzian region by shearing and compression of the oil film. This heat is essentially conducted to the contacting surfaces as the amount convected from the Hertzian zone by the lubricant can be neglected due to the very low lubricant mass flowrate. A two-disk test rig was used for the experimental tests using crowned, superfinished 76.2 mm diameter disks fixed on parallel shafts. The disks was fitted with six thermocouples in two rows of three located 3 mm and 6 mm below the surface to measure the temperature distribution of the disks during the tests. In addition, the disks were insulated on both plane sides by ceramic washers to minimise heat transfer to the surroundings over those surfaces. A numerical model was developed to calculate the circumferential mean disk temperature variation in the outer 6 mm annular ring. The model was used to predict the temperature distribution for given values of the fraction of the total heat entering the fast disk, , and the heat transfer coefficient, h, for the disk running surfaces. These transient temperature solutions for specified values of  and h were compared with the recorded outer thermocouple temperatures to give a measure of error between the calculated and observed distributions. Error contours then show that the minimum error lies on a straight line in the (, h) plane so that  is essentially linearly related to hf for the error to be minimised. A similar relationship for the slow disk allows the value of  to be obtained for a given ratio hf /hs. Values of hf /hs obtained from the literature suggest that  lies in the range 0.65 to 0.78 for the experiments reported in the paper.

This thesis reports experimental and theoretical analyses to study the heat generation and partition between contacting bodies under rolling/sliding elastohydrodynamic (EHL) point contact. A twin disk test rig was re-commissioned and used for the experimental work. 76 mm diameter crowned, super-finished test disks, fixed on parallel shafts, were used in the experimental EHL tests. In each disk, 6 thermocouples were installed to measure the temperature during sliding/rolling contact under EHL conditions. In addition, ceramic washers were fixed on the plane sides of each disk to minimize heat transfer over those surfaces. A Labview data acquisition system was built for acquiring data from the sensors installed on the rig. The EHL experimental results show the fast disk has significantly higher bulk temperature than the slow disk. A transient two dimensional numerical model was constructed to calculate the average circumferential temperature distribution within the disks using three thermocouples as a boundary condition. The heat partition factor,  , and convection heat transfer coefficient, h, were varied systematically in the model. A linear relationship between  and hf for the fast disk and 1- and hs for the slow disk were obtained. These two linear relations were related together by the variation of h with the rotational speed. Over the approximately steady state condition, the calculated  using this approach was in the range of 0.65 to 0.77 for 32 EHL tests at different loads and sliding speeds. This means that the majority of heat is conducted to the fast disk, which is compatible with the previous findings. In order to carry out transient modelling, the unloading mechanism was developed to ensure rapid disk separation. This improved the temperature trend in the cooling phase. In addition, a microswitch was used to give accurate monitoring of the disks contacting and separation. The thermocouple arrangement within the disks and their installation technique we

Experimental and theoretical analyses are reported to study the heat generation and partition in an elastohydrodynamic rolling/sliding point contact. Heat is generated within the lubricant in the Hertzian region by shearing and compression of the oil film. This heat is essentially conducted to the contacting surfaces as the amount convected from the Hertzian zone by the lubricant can be neglected due to the very low lubricant mass flowrate. A two-disk test rig was used for the experimental tests using crowned, superfinished 76.2 mm diameter disks fixed on parallel shafts. The disks was fitted with six thermocouples in two rows of three located 3 mm and 6 mm below the surface to measure the temperature distribution of the disks during the tests. In addition, the disks were insulated on both plane sides by ceramic washers to minimise heat transfer to the surroundings over those surfaces. A numerical model was developed to calculate the circumferential mean disk temperature variation in the outer 6 mm annular ring. The model was used to predict the temperature distribution for given values of the fraction of the total heat entering the fast disk, , and the heat transfer coefficient, h, for the disk running surfaces. These transient temperature solutions for specified values of  and h were compared with the recorded outer thermocouple temperatures to give a measure of error between the calculated and observed distributions. Error contours then show that the minimum error lies on a straight line in the (, h) plane so that  is essentially linearly related to hf for the error to be minimised. A similar relationship for the slow disk allows the value of  to be obtained for a given ratio hf /hs. Values of hf /hs obtained from the literature suggest that  lies in the range 0.65 to 0.78 for the experiments reported in the paper.