PSI - Issue 23

Jozef Majerík et al. / Procedia Structural Integrity 23 (2019) 541–546

542

Jozef Majerík et al. / Structural Integrity Procedia 00 (2019) 000 – 000

2

Nomenclature H

nanohardness [GPa]

E r

reduced Young modulus [GPa]

P h F

load [N]

displacement [N] load force [μN]

t

time [s]

v c v o

cutting speed [m.min workpiece speed [m.min -1 ] -1 ] feed rate [mm.rev -1 ] depth of cut [mm] tensile strength [MPa] limit of proportionality [MPa]

f

a p R m R E

KCU

toughness [J] elongation [%]

A 5

1. Introduction In the mechanical engineering industry, it is now possible to observe constant efforts to increase efficiency as well as productivity as well as to continually improve product quality and lifetime. Due to new designs and innovative types of CNC machine tools, their control systems as well as new types of cutting tools and new types of coatings are implemented into the production process to increase dimensional accuracy and surface quality.. With regard to the constant trend of increasing the quality of the production process, it is necessary to ask whether the ever higher application of cutting conditions, which are used in the machining process, also has an impact on the properties of the resulting machined surface. However, the results of the scientific research carried out by many authors, together with practical knowledge, point to their significant impact. At present, it is necessary to examine not only the micro-geometrical characteristics of the machined surfaces, but also the changes in structure and properties within the surface of the workpiece after application of the finishing method. As a result of such changes, usually caused by both deformation and temperature processes during machining, it can result in a negative effect on the functional operation of such functional surfaces of the components produced. It has also been statistically confirmed that the initiation of damage to the functional surfaces of components during their service life occurs to a large extent on the surface or just below the machined surface. These findings therefore confirm the need to investigate the state of such a surface layer in cases where such component surfaces are highly stressed during their own operation. The research results that have been published in the articles of authors Barényi et al. 2019 and Pokorný et al. as well as knowledge obtained directly from industrial practice show us the need to evaluate the state of the machined surface of such types of components as the result of the applied particular type of technological process depending on the particular functional surface conditions in service. Just such a view of the evaluation of the machined surface is nowadays called surface integrity. Also, according to the authors Braga et al., Sedlák et al. , and Ranjan Das et al., it is now possible to define the term surface integrity as an overall summary of the given conditions under which the functional surface is created in the finishing process. In this process, the consequences of the action of the individual technological methods on the final quality of the machined surface of the manufactured parts are taken into account. It is in practice possible to generally assess the quality of component surfaces according to dimensional accuracy, shape accuracy, as well as the texture of the machined surface and also the properties of the surface layer. As already defined in the articles of some authors, the most frequently evaluated surface integrity parameters include qualitative indicators such as microgeometry of the machined surface, hardening of the surface layer after machining, as well as structural changes in the surface layer of components. In addition to studying the properties of machined surfaces, it is important to start with finishing technology. It is also necessary to explain the emergence of a new functional surface, as machining technology is most involved in completing such components. This has a very significant effect on the final state of the machined surface. It is the