Mechanical faculty
"Metal-cutting machine-tools and toolware"
Speciality "Metal-cutting machine-tools and systems"
Theme of master's work:
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Voitov Mihail Mechanical faculty "Metal-cutting machine-tools and toolware" Speciality "Metal-cutting machine-tools and systems" Theme of master's work: |
Of paramount importance for the acceleration of technological progress and equip all sectors of the economy a new technique has the further rapid development of modern engineering industries.
Grinding, as one of the most productive methods of processing metals, provides a low height of roughness parameters of treated surface, the high accuracy of shape and size of parts. Sanding can handle almost all materials.
In connection with this very important and promising area is the development of elborovyh circles on the metal binder. These grinding wheels with high cutting capacity, a large period of resistance, but require constant editing electroerosion impact on the link range.
Goals and Objectives of the master's work When the master's work was given the following core objectives:
- Perform literature review on the destination regime grinding CNB community;
- Investigate the impact of the provisions of the terms of grinding on the workpiece with a flat grinding surface at a temperature in the environment "ANSYS";
- Modernize intragrinding machine for electric discharge editing and polishing the terms of the elastic pattern;
- Determine the strength application range to the sample to test the strength of grain;
- Appoint a grinding regimes were R6M5F3 CNB range;
- Explore the instantaneous cutting ability in the inner circle of elastic grinding R6M5F3 scheme;
- Determine the mechanical treatment and electric discharge impacts with internal grinding R6M5F3.
The aim of this paper is a literature review on the grinding and CNB study of HQ on the surface of the workpiece in order temperature means "ANSYS".
Abrasive material elbor comprises cubic boron nitride - BN (91 - 95%) and related impurities: hexagonal boron nitride BN (1 - 2.5%), silicon (0,05 - 0,15%), iron (0, 07 - 0,10%), aluminum (0,05 - 0,25%), calcium (0,05 - 0,20%), magnesium (1 - 1.5%) and free carbon (0.6 - 1 %).
Studies on the abrasive grains of cubic boron nitride, the size of grains of the main faction of which changes from (-5 +3) to (-250 +200), MC showed that the concentrated and diluted acids (hydrochloric, sulfuric, nitric, phosphoric, hydrofluoric), a mixture of concentrated sulfuric acid with potassium sulphate, oxidants (pergidrolya mixture with nitric acid and aqua regia) as well as the solutions of alkali did not have chemical effects on the cubic boron nitride. Chemical resistance was observed at temperatures of boiling acid excerpt from 1 to 24 h.
It was found that isometric grains elbora higher than a diamond and elektrokorunda [4]. It is connected with the specifics of grinding grains and polycrystalline structure. The average value of shape factor of grains, representing the ratio of length of grain to its width (l: b), when observing under a microscope for diamond ADF 16 - 25 equals 1.44 - 1.50, elektrokorunda DL 32 - 50 - 1,47 - 1, 48 and elbora L12 - 1.38.
Changes in the physical characteristics of the STM, depending on the synthesis parameters and external influences, such as thermal annealing or exposure associated with the transformation of defect structure of these materials, which establish the physical principles of designing STM-directed changes of defect structure, correlating with the change less hanicheskih performance materials. On these principles a number of Ori-ginalnyh technologies that significantly increase the strength characteristics of diamond and BNK.
A nature relatively resistant to annealing peak of internal friction at 360 K BNK, caused a shift divakansy boron in an alternating field of elastic stresses on the type of relaxation parauprugoy Zinera. We show that the nature of the temperature dependence of the coefficient of linear expansion BNK, from the set of resonance measurements, depends on its defect structure. Revealed the existence of amplitude dependence of internal friction in BNK and show that at room temperature the motion of dislocations controlled by Peierls mechanism. At elevated temperatures the motion of dislocations is determined by their interaction, at least two types of establishing centers of vakansionnye a range of different structures.
Tools of CNB released on ceramic, organic and metallic bundles. The creation of special ceramic ligaments largely predetermined effective use elbora as abrasive material in the instrument.The structure of the instrument elbora in ceramic bundles characterized elbora and content of filler in the unit volume of work (elborosoderzhaschey) of the circle, expressed as a percentage, and is designated a certain number (from number 6 to number 12), depending on the granularity of elbora. The higher the number of structures, the more links and fewer grains per unit volume of the tool with the same firmness. In the total production of tools from elbora in ceramic bundles accounted for 60%.
Regularities of the influence of the characteristics of the circle and cutting regimes on the quantity of residual austenite are similar to patterns obtained for the temperature grinding. Above it was shown that, when grinding circles of elbora temperature, resulting in the surface layer, much less than when I am grinding abrasive diamond circles. In this regard, when elborovom grinding reduces the risk of structural changes in the surface layer of parts and tools.
The experiments showed that in the process of diamond grinding and kubonitovogo observed disintegration of residual austenite, education martensita and fine carbides. The exact number of remaining austenite decreases, while in the surface layers of no-troosto sarbitnaya (steel 40X) and troosto-martensitic (Steel 111X15) zone.
In general, there are two kinds of methods for determining the temperature at the surface, namely, the theoretical and experimental. Each of them has a re-revagy and disadvantages.
The task of theoretical research is to determine the general patterns of occurrence and distribution of heat in the process of grinding and temperature, which has evolved. The theoretical calculation of the temperature of grinding basically boils down to a solution of the Fourier transform.
Modern thermophysics grinding temperatures have contributed to theoretical research, which evolved through friction. A J. Iegera considered two main cases of calculating the temperature in the friction at a constant speed. In the first case, it was assumed that the surface (source), the friction has the form of stripes, while the second case - the form of a rod of square cross section. The resulting formula, with a given approximation, given the opportunity to determine the average temperature in the growing friction.
Appointment of grinding regimes must ensure the achievement of the required processing accuracy and quality shlifuemogo surface details. Lack. The absence of defects in the surface layer (prizhogiv and microcracks) is essential for the successful implementation of grinding in the production. Requirements guarantee the bezdefektnoy deep grinding process with identified during the comprehensive study of the surface layer of parts.Consider the question of the proportion of heat that goes in the lap. This problem should be solved from the proposal and the terms of the discreteness of the contact details. If shlifuemoy surface of rapidly changing thermal pulse on the most active beans poured into a continuous background, the range of grinding contact is always discrete, which operates over multiple time, which depends on the speed range. Priority heat on the grains as compared to the ligament, makes it possible to simulate every grain in half with a contact at a small station in the second half, moving on the first at the periphery of the circle. The question of the distribution of heat between the half-solved on the basis of raventsva average contact temperatures. This condition, after minor changes lead to a formula for determining the ratio of input, indicating which part of the heat leaves in half (in this case in detail).
After the experience of seeing the details of temperature, while the source of heat at the beginning and the middle part, exceeds 33% and this should be taken into account in the assigned treatment, as this may affect the quality of treated surface.
It is important to investigate how this difference in temperature will affect the accuracy of processing. We already know that the maximum temperature difference occurs when the heat source in the early and middle parts, so the study of thermal deformations hold for these two provisions. For this analysis, sets out detail on the bottom surface of the movement in all directions, ie simulates a magnetic plate.
After the study find that the difference between the maximum temperature deformation of 9%, which may vizyvat a small convex surface, as well as in places with maximum deformation will cut more metal, and after cooling in these areas will reduce the line size.
1. The temperature at the beginning and end parts exceeds the temperature in the middle parts of 33%
2. Thermal strain in early and late parts exceed the temperature of deformation in the middle part, which leads to the convexity of processed parts.
3. In determining the critical temperature at the surface, at the time of appointment regimes should be taken into account the temperature, which occurs near the end of the length of the details.