**4. Discussion**

The coupled analysis between the evolution of the coefficient of friction and the structure of the interface allows us to establish the tribological scenario next (**Figure 17**).

The very low coefficient of friction observed at the beginning of the test corresponds to an interface involving the native oxides (A). Very quickly, the layer of oxides is eliminated and there is a sharp increase in the coefficient of friction related to activation of interactions metal/metal (B). The interactions metal/ metal generalize and generate a maximum shear in the interface (C). The very high stresses generated in the interface lead to formation of debris that oxidize. The interface is more accommodative and the coefficient of friction tends to decrease (D).

**111**

*Tribological Study of the Friction between the Same Two Materials (RAD Steel)*

The training of cohesionless debris generalizes and finally écrante interactions metal/metal. Fully accommodated by a third body, very cohesionless, divided on the periphery of the contact, the interface then presents a second minimum of its

*Traces of wear on the samples after 6000 cycles. (a) Image under the microscope perspective of the SPHERE* 

Under the mechanical action of the loading of fretting, the bed of debris then tends to be compressed. It becomes more adherent and generalizes on the whole of the interface. Less complacent than the bed cohesionless debris (Step e), it presents a coefficient of friction higher (F) of the order of (μ = 0.8). If the evolution between the steps a and e is classically described in the literature, the transition between E and F that we have analyzed clearly shows the influence of rheology in

Having analyzed the response of the friction coefficient of the dry contact, we

The objective of this study was to analyze the behavior in fretting of the steel contact. The expertise of the industrial systems in fact appear of slip conditions, total inducing large amplitudes of slip, thus favoring the degradation of the assembly by wear. There is a real need in the industry to have predictive methods about the mechanisms of wear, to limit maintenance inspections while ensuring an

For the first time, the coupled analysis of the evolution of the coefficient of friction and the structure of the interface allows us to divide the evolution of the coefficient of friction into six phases, appointing A, B, C, D, E, and F and describing the scenario of the evolution of the interface as well as the role of the debris and oxides in

The elimination of the layer of native oxides (A and B) generates the interactions of metal/metal, which promotes a maximum shear in the interface (C). The training of debris that oxidize tends to decrease the coefficient of friction (D and E). Under the mechanical action of the loading of fretting, the bed of debris then tends to be compact and becomes more adherent, and it generalizes on the whole of the interface. This third compacted body, less complacent than the bed of the cohesionless

will discuss in the next chapter, the response by report to the wear.

debris, may cause an elevation of the coefficient of friction (F).

*DOI: http://dx.doi.org/10.5772/intechopen.93478*

coefficient of friction (E).

*and (b) zoom of the trace of wear [10].*

the interface.

**Figure 16.**

**5. Conclusion**

the contact.

optimum level of security.

*Tribological Study of the Friction between the Same Two Materials (RAD Steel) DOI: http://dx.doi.org/10.5772/intechopen.93478*

**Figure 16.** *Traces of wear on the samples after 6000 cycles. (a) Image under the microscope perspective of the SPHERE and (b) zoom of the trace of wear [10].*

The training of cohesionless debris generalizes and finally écrante interactions metal/metal. Fully accommodated by a third body, very cohesionless, divided on the periphery of the contact, the interface then presents a second minimum of its coefficient of friction (E).

Under the mechanical action of the loading of fretting, the bed of debris then tends to be compressed. It becomes more adherent and generalizes on the whole of the interface. Less complacent than the bed cohesionless debris (Step e), it presents a coefficient of friction higher (F) of the order of (μ = 0.8). If the evolution between the steps a and e is classically described in the literature, the transition between E and F that we have analyzed clearly shows the influence of rheology in the interface.

Having analyzed the response of the friction coefficient of the dry contact, we will discuss in the next chapter, the response by report to the wear.

## **5. Conclusion**

The objective of this study was to analyze the behavior in fretting of the steel contact. The expertise of the industrial systems in fact appear of slip conditions, total inducing large amplitudes of slip, thus favoring the degradation of the assembly by wear. There is a real need in the industry to have predictive methods about the mechanisms of wear, to limit maintenance inspections while ensuring an optimum level of security.

For the first time, the coupled analysis of the evolution of the coefficient of friction and the structure of the interface allows us to divide the evolution of the coefficient of friction into six phases, appointing A, B, C, D, E, and F and describing the scenario of the evolution of the interface as well as the role of the debris and oxides in the contact.

The elimination of the layer of native oxides (A and B) generates the interactions of metal/metal, which promotes a maximum shear in the interface (C). The training of debris that oxidize tends to decrease the coefficient of friction (D and E). Under the mechanical action of the loading of fretting, the bed of debris then tends to be compact and becomes more adherent, and it generalizes on the whole of the interface. This third compacted body, less complacent than the bed of the cohesionless debris, may cause an elevation of the coefficient of friction (F).

**Figure 17.**

*Illustration of the scenario describing the evolution of the interface and that associated to the coefficient of friction.*

By that result, we sought to quantify the kinetics of wear. The successive damage the contact has been formalized through the approaches of Archard and the dissipated energy. The evolution of the coefficient of friction for different sizes of contact shows that the more the contact, the lower the coefficient of friction of the stabilized phase (F). It can assume that larger contact facilitates the trapping of oxidized debris in the contact.

The interface will be more accommodative and will induce a coefficient of friction that is more low. By elsewhere, a greater amount of energy will be dissipated in the third body and not to the level of the first body for the creation of new debris so that the kinetics of wear will also be lower for the great contacts.

**113**

**Author details**

D. Kaid Ameur

Universitaire de Relizane, Bormadia, L'Algérie

provided the original work is properly cited.

\*Address all correspondence to: djilalikaidameur@gmail.com

*Tribological Study of the Friction between the Same Two Materials (RAD Steel)*

Laboratoire de Génie Industriel et du Développement Durable (LGIDD), Centre

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*DOI: http://dx.doi.org/10.5772/intechopen.93478*

*Tribological Study of the Friction between the Same Two Materials (RAD Steel) DOI: http://dx.doi.org/10.5772/intechopen.93478*
