Experimental determination of plastic strain parameters at machining of metals

FIELD: machine building.

SUBSTANCE: coordinate marks are applied on specimen surface by pressing the tool there against, tool hardness exceeding that of the part material. Said tool represents an etching with sharp protruding elements shaped to tetrahedral pyramid that make a preset system of coordinate (reference) points. The latter are the points of intersection of analysed specimen with faces on indenter. Produced recesses are filled with non-solidifying luminescent dye not losing its properties at plastic strain. Now, said specimen is subjected to machining. Then, parameters of grating changed pattern are measured to calculate the plastic strain parameters.

EFFECT: higher pattern quality and accuracy of metal plastic strain parameter measurement.

3 dwg

 

The technical field

The invention relates to mechanical engineering and can be used to study the strain state of the processed material in the zone of plastic deformation during mechanical processing using a separating grid.

The level of technology

Known methods study strain state of a material with a separating grids, which allow to obtain the most complete information about the deformation process (Goldschmidt MG Strain and tension when cutting metals. - Tomsk: STT, 2001, - 180 C.). At the first stage of the sample of the material made the cut, then on the polished surface of the sample is applied with a certain step dividing the net. Then the prepared sample is subjected to energy impact pressure treatment or by cutting and measure geometrical parameters of the modified figure grid, which determine the parameters of plastic deformation of the sample. The net cause scratching and indentation in the surface of the conical indenter. The drawback of such methods is insufficient (poor) accuracy determination parameters of the strain state of the sample at large plastic strains, especially at high degrees of plastic deformation, such as cutting with before aeternum plastic deformation (SPD), etc.

The closest technical solution is a method of experimental determination of parameters of plastic deformation during the cutting of metals with the use of the method of obtaining the coordinate grid, including the application of the system of coordinate labels on the sample surface by pressing to the surface of the tool, the hardness of which is greater than the hardness of the sample material, as tool use metal plates with sharp protruding elements having the form of four-sided pyramids that make up a given system of coordinate points (Patent RF №2466813, IPC B21D 22/02, G01N 1/28 publ. 27.05.2011 year). The main disadvantage of this method is that enough reliable results define the parameters of plastic deformation are achieved with relatively small degrees of plastic deformation, when distinguishable coordinate (reference) mark grid, i.e. the boundaries of the recesses, after the process of plastic deformation. With increasing plastic deformation border labels, their location is increasingly uncertain due to deformation of the material (the formation of texture) on the surface of the sample, in which the deepening of the applied grid become almost indistinguishable, merging with the texture pattern. In this case, udaetsya quality clear picture of the field of deformation and, consequently, the ability to hold on to her exact measurements.

Disclosure of inventions

The objective of the invention is to improve the quality of the picture field deformation and increase the accuracy of measurement of parameters of plastic deformation of the sample material at the expense of a more precise definition of the labels of the grid.

The problem is solved due to the fact that in the method of experimental determination of parameters of plastic deformation in the machining of metals, including the application of the coordinate system (reference) marks on the sample surface by the clamping device to the surface of the tool, the hardness that exceeds the hardness of the material of the workpiece as the tool is used clichés with sharp protruding elements having the form of four-sided pyramids that make up a given coordinate system (reference) points formed deepening of fill returned device with a fluorescent dye that retains its properties during plastic deformation, and then mechanically treated sample, and then measure the parameters of the modified figure grid on which compute the parameters of plastic deformation.

List of figures

Figure 1 shows a micrograph of a deformed state of a rectangular dividing grid in the roots chip (increase K) when p is the timeframe steel SS (cutting with TTD).

Figure 2 shows a micrograph of a deformed state of a rectangular dividing grid in the roots chip (h) when cutting steel HT (cutting).

Figure 3 shows a micrograph of a deformed state of a rectangular dividing grid in the roots chip (h) when cutting steel HT (cutting with TTD).

The implementation of the invention

The implementation of the invention is carried out in several stages:

1. Thin sections of the samples of the investigated materials with a thickness of 3 mm.

2. Layout by way of scratching coordinate dividing grid on the polished surface of the samples, the grid spacing of 0.05 mm

3. The center punching holes in the corners of the grid cells using an indenter of microhardness tester PMT-3, the side of the square deepening of about 12 microns and education thus coordinate system (reference) points, which are points of intersection of the plane of the sample faces of the indenter.

4. Filling the recesses with a fluorescent dye FLC-01 by brush application and removing excess paint flexible spatula directly before the examination, not allowing the paint to dry (drying process about 2 hours).

5. The process of mechanical processing, in particular cutting. When cutting with TTD in the area before cutter set rolling deforming roller. The elements of the regime re the project, the material and geometrical parameters of cutting tools are selected in accordance with applicable standards.

6. Getting a picture of the modified grid using tool to instantly fix the cutting process (device instant stop), or by using high-speed microphoto and micrometeorite (using a microscope).

7. Measurement of geometric elements of the modified figure grid and determine based on this calculation, the parameters of plastic deformation of the material under investigation. Changing the position coordinate (reference) points plotted grid (for reference points take the point of intersection of the plane of the sample faces of the indenter) when deformation allows geometric ratios of the distances between them to determine the value of the relative shift of ε in the zone of chip formation. In terms of, for example, the cutting, the relative shift is associated with the intensity of deformation εiratio

εi=ε3.

Intensity of deformation in the assumption of the single curved flow is the magnitude of the deformation δi. In accordance with this changing picture of the grid allows the predelete stress-strain state δ iiat any point in the zone of chip formation.

The presence of a fluorescent dye under ultraviolet irradiation allows you to pinpoint the location coordinate (reference) points on a modified picture of the grid in the case when visually the position of these points becomes undetectable even at high magnification. Glowing the same paint particles show the location of reference points.

Using the proposed method allowed us to reproduce the real picture of deformations occurring in the cutting zone, and for the first time to give a mathematical dependences for calculation of the stress-strain state of the material in the cutting zone in time. Applying a coordinate grid in the study of stress-strain state of the cutting zone gave the possibility to determine the size of the zone of chip formation and to calculate the time course of deformation processes and the transition time of the original material in the material of the chip (10-4...10-7C).

The method is applicable for the analysis of plastic deformation when performing other operations associated with plastic deformation, such as sediment, forging, bending, cold extrusion, landing, stretching.

The method of experimental determination of parameters of plastic deformation under mechanical clicks the development of metals, including the application of the system of coordinate labels on the sample surface by the clamping device to the surface of the tool, the hardness that exceeds the hardness of the material of the workpiece as the tool is used clichés with sharp protruding elements having the form of four-sided pyramids that make up a given coordinate system (reference) points, which are points of intersection of the plane of the sample faces of the indenter, characterized in that the formed cavities fill returned device with a fluorescent dye that retains its properties during plastic deformation, and then mechanically treated sample, and then measure the parameters of the modified figure grid, which calculates the parameters of plastic deformation.



 

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