**5. Summary**

The work refers to different aspects of research methodology and the difficulties in the interpretation of the durability and reliability of the bearings. The proposition of own methods of research and empirical descriptions was done. The material presented in the work was divided into four separate subsections: on research methodology, work, geometry, and the impact of these elements on the friction and wear. All tests were performed for three replicates at each point. The investigations were conducted with using different tribological testers and tribological stands. Should add that all of the test, later in this chapter bearings are factory items and their designations are in accordance with PN, PN-EN and ISO standards. All tests were performed for three replicates at each point.

Performance Evaluation of Rolling Element Bearings Based on Tribological Behaviour 47

characterized by specific properties which influence the durability of the elements of the friction pair. This means that the materials meant for friction pairs should be properly selected and their geometry carefully analyzed. While examining the shaft neck wear in the function of initial clearance, the conditions of movement from the normal wear to the pathological one were established by means of setting up the critical parameters: the clearance, the intensity of wear in the function of load. It has been observed that the movement from the normal wear to adhesion is characterized by a gradual increase of the intensity of the elements wear. The examination was carried out for the nominal clearance of 0.065 mm and other clearances achieved as a sum of the nominal one and the value of reduction of the shaft neck diameter. The associations received in this way made it possible to examine the process of friction with clearances of 0,1, 0,2, 0,3, 0,4, 0,5 [mm] respectively. A hundred-hour examination was carried out for each value of clearance in bearing; next, the micro-structure of the friction surface was examined under an optic microscope with magnification ×300, which lead to the distinction of three different surfaces of wear characteristic for normal, mechano-chemical and pathological wearing (Fig. 10 b). On the basis of the results received is can established that the enlargement of clearance between the elements in the friction pair leads to a considerable enlargement of the intensity in the shaft neck wear, which, in turn, results in the worse durability of the connection. Fig. 10 a shows the wear of the shaft neck understood as function of the initial clearance. Point A as a critical clearance with which the friction pair works in the conditions of normal wear was achieved as a result of crossing the tangents led to the curve of wear in areas I and III (Nachimowicz et al., 2007). In real conditions, when the surfaces of the bodies in direct contact are uneven, and anisotropy of top layer occurs, the problem of body contact becomes a more complicated one. Further examination will focus on the analysis of friction surface of the needle bearing elements in real conditions, in the lubricated environment and under kinematic load.

**Author details** 

Jerzy Nachimowicz

Marek Jałbrzykowski\*

**6. References** 

1986, 233-240.

Corresponding Author

 \*

*Department of Building and Exploitation of Machines,* 

*Department of Materials and Biomedical Engineering,* 

tribological research, Publisher ITE Radom, 1997.

*Mechanical Faculty, Bialystok University of Technology, Bialystok, Poland* 

*Mechanical Faculty, Bialystok University of Technology, Bialystok, Poland* 

[1] Szczerek M.: The methodological problems of systematization of experimental

[2] Budzoń P., Lenkiewicz W., Olesiak Z.: Standardization of documentation of tribological research on the example of rolling friction, The Problems of machine Exploitation 1,

On the basis of the test results the following conclusions have been made:

The results of tribological tests indicate different friction characteristics of the evaluated elements. Bigger resistance to motion is noticed at the beginning of the test. Afterwards it becomes stable – at minimal level, at the end of the process. The data included in this section indicate entirely different test results obtained with two different methods. This may lead to totally different conclusions concerning the tribological properties of tested elements. The data presented in fig. 2, 3 and 4 clearly indicate the lack of correlation between MB-1 and MB-2 methods applied in the tests. This means that conducting a scientifically reliable evaluation of tribological properties of such elements requires applying one method. However, the results obtained with this method may not reflect the actual friction nodes when one is unable to faithfully reproduce their actual working conditions. The conducted examination and simulations have demonstrated the changes in the contact area of friction pair elements when two rollers with parallel axes (i.e. the needle roller and the shaft neck) press against each other. Examination of the factors that can have an influence on the contact area of cooperating elements, i.e.: changes in the needle roller diameter and the change in the shaft diameter, are of particular importance because the contact area alters the resistance moment of motion in the bearing. The suggested mathematical model and the examination on a stand help to estimate the extent to which the bearing friction and the sliding friction matter in the overall balance of motion resistance. While examining the shaft neck wear in the function of initial slackness, the conditions of movement from the normal wear to the pathological one were established by means of setting up the critical parameters: the slackness, the intensity of wear in the function of load. It has been observed that the movement from the normal wear to adhesion is characterized by a gradual increase of the intensity of the elements wear. The conducted examination and simulations have demonstrated the changes in the contact area of friction pair elements when two rollers with parallel axes (i.e. the needle roller and the shaft neck) press against each other. Examination of the factors that can have an influence on the contact area of cooperating elements, i.e.: changes in the needle roller diameter and the change in the shaft diameter, changes in the value of Young's modulus, Poisson's ratio of the materials used and changes of load are of particular importance because the contact area alters the resistance moment of movement in bearing. The analysis of the above-mentioned relations in the energetic perspective made it possible to conclude that deformed areas of friction surfaces are characterized by specific properties which influence the durability of the elements of the friction pair. This means that the materials meant for friction pairs should be properly selected and their geometry carefully analyzed. While examining the shaft neck wear in the function of initial clearance, the conditions of movement from the normal wear to the pathological one were established by means of setting up the critical parameters: the clearance, the intensity of wear in the function of load. It has been observed that the movement from the normal wear to adhesion is characterized by a gradual increase of the intensity of the elements wear. The examination was carried out for the nominal clearance of 0.065 mm and other clearances achieved as a sum of the nominal one and the value of reduction of the shaft neck diameter. The associations received in this way made it possible to examine the process of friction with clearances of 0,1, 0,2, 0,3, 0,4, 0,5 [mm] respectively. A hundred-hour examination was carried out for each value of clearance in bearing; next, the micro-structure of the friction surface was examined under an optic microscope with magnification ×300, which lead to the distinction of three different surfaces of wear characteristic for normal, mechano-chemical and pathological wearing (Fig. 10 b). On the basis of the results received is can established that the enlargement of clearance between the elements in the friction pair leads to a considerable enlargement of the intensity in the shaft neck wear, which, in turn, results in the worse durability of the connection. Fig. 10 a shows the wear of the shaft neck understood as function of the initial clearance. Point A as a critical clearance with which the friction pair works in the conditions of normal wear was achieved as a result of crossing the tangents led to the curve of wear in areas I and III (Nachimowicz et al., 2007). In real conditions, when the surfaces of the bodies in direct contact are uneven, and anisotropy of top layer occurs, the problem of body contact becomes a more complicated one. Further examination will focus on the analysis of friction surface of the needle bearing elements in real conditions, in the lubricated environment and under kinematic load.
