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2 Scientific Problems of Machines Operation and Maintenance

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The lubricant and implants influence above tribological behaviour at three cone bits bearings

Ripeanu R. G., Tudor I., Zidaru I., Drumeanu A. C.

Scientific Problems of Machines Operation and Maintenance

2010

Vol. 45, nr 1

25-32

Sliding bearings at three cone bits are lubricated in heavy conditions. To improve tribological behaviour, samples of bearing materials were made with implants with antifriction materials having different rapports between the implant and free base material in the presence of different greases. Tests made on a CSM microtribometer and on an Amsler A135 were to establish the proper implant rapport, measuring friction coefficient, and wear. The behaviour of the greases containing P.T.F.E was also established. In a second phase of the tests was designed and realised a device for testing three cone bits bearings at real axial loads. A SPIDER 8 device and inductive traducers were used to establish the friction coefficients and the temperature on the friction surface, depending on implants' dimensions and grease lubricant type.

Specific phenomena that characterize thermal fatigue wear of the forging die steels

Drumeanu A. C., Parschivoiu S. T., Tudor I., Ripeanu R. G.

Scientific Problems of Machines Operation and Maintenance

2009

Vol. 44, nr 4

13-20

Thermal fatigue wear is a kind of degradation, which characterises the metallic element friction surface of some couples, like forging dies, fire guns, heavy-duty mechanical brakes, etc. During the drop forging process, the die surfaces are heated. Because this heating has a variable or almost cyclic character, the thermal stresses and strains effects are similar to that, which characterise the low cycle, fatigue. The paper presents the experimental results concerning specific aspects, which characterise thermal fatigue wear of the steels used in forging dies construction e.g. equations which emphasise the cyclic durability and cyclic strengthening or softening phenomena of the die steels. These data can be used both in designing and exploitation of the forging dies.