42 research outputs found
Experimental study on circular eccentric cam-follower pairs
No full textExperimental verifications of cam-follower contacts are very important because of the difficulties for a reliable simulation due to the continuous variation of load, speed and geometry of the lubricated contact. Some experiments have been carried out with a new apparatus, specifically designed and realised for investigation on cam-follower and gear teeth contacts, in order to test its capability to measure film thickness and contact forces. Circular eccentric cams have been used because they feature lower transient effects and comparison of the results with the theoretical/numerical ones is easier. The tests have been performed using cams with two different eccentricities and surface roughness, and two different followers, one made of steel and one made of glass.
The behaviour of the cam-follower contacts at several different rotational speeds, ranging from 50 to 500 rpm, and different pre-loads have been investigated. Lubrication regimes ranged from boundary to complete, being most of the tests performed under mixed lubrication conditions. Localised wear has occurred during some tests. Data of all contact force and moment components as well as of the cam shaft driving torque have been acquired at high acquisition frequency. Some methodologies for numerical data elaboration have been identified. Optical interference images have been correctly recorded at the desired frequency. The trends of the normal and friction forces measured in the different tests are presented in the paper, as well as the evaluated trends of the friction coefficient. Some sample optical interference images are also shown. The results furnish encouraging indications about the capabilities of the experimental apparatus
Investigation on plain journal bearings for severe working conditions
No full textIn this paper a theoretical and experimental work for design of plain journal bearing able to work up to severe conditions is reported.
The mathematical model and the numerical methods on which a purposely developed computer program is based are firstly described. The program is aimed to the evaluation of the behaviour of hydrodynamic plain journal bearings under heavy static loads, considering the elastic deformation of the bearing members, geometrical errors such as the axis misalignment and thermal effects.
The experimental apparatus designed and set up for testing plain bearings in several working conditions, by varying speed, load and oil supply up to extremely critical situations, is then briefly described.
Theoretical and experimental results obtained at different load, speed and oil flow rate conditions are finally compared showing a good agreement
Experimental study of engine cam-followers
No full textThe cam-follower pair is a very complex lubricated contact because its continuous variation of load, speed and radius of curvature. Experimental verification are necessary but very difficult to perform. After a literature review of the existing test rigs for cam-follower simulation, the main aspects of a new versatile apparatus are presented. Several design variations are presented, each one with its advantages and drawbacks. The final project will take into account some of the presented design solutions and the results of dynamic simulations of the rigs currently under elaboration
Wear and elastohydrodynamic lubrication studies of cams and followers
No full textThe concentrated non-conformal contact between the cam and the follower is one of the most severe working tribological components in the internal combustion engine. Due to the continuous variation of load, speed and geometry, this contact is very difficult to be investigated.
This work is mainly devoted to review the wear and elastohydrodynamic film thickness studies related to this important engine mechanism and is divided into two parts.
In the first part a review is made of theoretical/numerical studies addressed to predict the film thickness, pressure distribution and their relations with the most common surface failures as pitting and scuffing.
The second part is committed to show the experimental efforts that have been carried out to estimate the real film thickness and the force friction in order to improve the durability of mating cam/follower surfaces under elastohydrodynamic lubricating regimen. A new versatile experimental apparatus under development is also presented
