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Master's degree DonNTU Sartibaev D.Y.

Sartibaev Dilshod Yulbarsovich

The abstract of the master's thesis on the theme:

"Optimization of parameters of process for the flat polishing of construction ceramics"

Scientific Leader: Ph.D. technical sciences Molchanov Aleksandr Dmitrievich




    

        Performance parts, along with working conditions (pressure adjoin table surfaces, the speed of their relative movement, a kind of friction and lubrication, etc.) and parameters characterizing the composition, structure and mechanical properties of interacting surfaces, defined by the parameters characterizing the state of the surface layer of parts to evaluate the quality of the surface layer used: geometric parameters (deviations from a given geometric shape, waviness parameters, characteristics of roughness, the direction of the traces of processing). From the geometric parameters of the details of the most studied impact on its performance indicators of surface roughness, which is simple and reliable criterion for assessing the state of the technological process of machining and operating conditions. The recommended parameters of working surfaces of machine parts is the arithmetical mean deviation of roughness profile, Ra, smoothing height profile from the height of a small projection Rr, the average step roughness profile Sm, relative bearing length profile tp and greatest height Rmax. The amount of wear parts for the period of bedding depends on the initial roughness is different from the optimal, and can reach 20-30% of the limit of its wear. The significance of intensity of wear depends on the initial roughness, on how it differs from the equilibrium. Therefore, the details of working in the hospital, it is important to decrease and the decrease in their bedding. Thus, it is necessary to ensure a technologically optimal structure of surface layer of working surfaces of friction pairs. The use of mathematical models to calculate the parameters of micro relief surface allows, without lengthy and expensive experimental studies to choose good from the standpoint of operation characteristic of the diamond range of products and modes of processing of structural ceramics.
    Random nature of the relief is the dominant terms in the formation of surface roughness with grinding details. To describe the micro-surface details of commonly used theory of probability and random processes.    This is due to participate in the process of cutting multiple cutting edges with uncertain geometry and varying different elevation on the working surface of the circle, as well as various forms of cut, leaving after diamond grain. A single cross-section, the resulting force of interaction of diamond grains and the surface layer of ceramics, will differ from the ideal shape, that would have occurred with the full copy of grain shape.  A typical result of the destruction of a side and chipped extract groups of grains from the surface layer of a workpiece as pockets of destruction, which have the greatest influence on the roughness of the surface layer. The influence of brittle fracture in the form of a single cut-off is not accurate analytical prediction. The degree of influence of major destruction allowances to the formation of a micro relief surface layer, taking into account the probabilistic nature of grain ceramics extracts group has so far not been studied deeply.
      The purpose of this work is to develop a mathematical model of the formation of a micro relief surface structural ceramics with diamond grinding. In developing the mathematical model must take into account the random nature of brittle fracture in the form of pockets of devastation.

        The mathematical model of the surface micro relief CC has been developed in relation to a scheme of flat grinding periphery circle. The process of marginalization of plastic ceramic cutting with diamond grains in the model may be neglected because it plays a significant role only under ultra-high speed cutting and grinding with a very small depths of cut. The processing of ceramics, along with inside the crystal deformation proceeds and between crystal strain - the relative sliding and rotation of grains, splitting them into separate blocks, the destruction of grain boundaries and their units.   So that the formation of surface layer on a ceramic workpiece as a result of material removal allowance when copying the form of diamond grains range of groups and how many grains of ceramics in the epicenter of destruction. Regardless of the type of ceramics at the treated surface, there field foci of destruction in the form of chips resulting from the accidental destruction of stock diamond grains (Fig. 1). For this field is characterized by the phenomenon of ordinariness chips, as they appear one by one, not two, three, etc. The probability of getting any number of chips in a flat shape does not depend on how many chips fall into any other disjoint with her figure. Thus, the condition of the absence of interaction between chips.


Figure 1 – Modèle informatique de shunt à tube régulateur de tension

Fig. 1. The surface of the ceramic sample (Al2O3) after diamond grinding. Flat grinding the periphery of the circle


    

FINDINGS



    Thus, the presented model of brittle fracture surface of ceramics with diamond grinding to adequately reflect the real mechanism of formation of the roughness. This model is implemented as a universal system of mathematical calculations MatCAD and can be used to predict all the parameters of the roughness of the treated surface of ceramics with diamond grinding.

 

BIBLIOGRAPHIE


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