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a technique of carrying out of experimental researches

Experiment mapping out allows to receive optimum values of target parametres at a minimum quantity of experiences. Thus it is necessary to select the most essential factors influencing accuracy and quality of the processed surface of the worn out pin of a mill not to complicate labour-intensive process of carrying out of experiment and processing of results of experimental data [6, 123].

For reception of a cylindrical surface of an accuracy requirement and quality, the design of a rotational cutter should provide corresponding character of processing. In the second chapter the basic characteristics of rotational cutting have been established, changing which in the set limits, it is possible to receive a surface of the better sample and as design features of a rotational cutter for impact realisation on necessary parametres of accuracy and quality of a surface are defined.

During carrying out of experiments it is necessary to investigate influence of technological parametres of a rotational cutter for processing of a working surface of pins of mills at a variation of parametres. The decision of the given problem gives the chance to define rational constructive and preferable technological parametres for reception of peak efficiency of processing.

By target parametres for definition of accuracy and quality of the processed cylindrical surface of a pin of a mill with application of the added machine tool, under operating conditions, are selected - the area of a cut off layer 8ср, мм2и coarseness Ra, a micron.

As the basic plan for experiment carrying out the central composite orthogonal plan polnofaktornogo experiment PFE TSKOP 24 [123] has been selected. Advantage of the given plan is simplicity of the decision of calculations of systems of the equation otsenivanija varied parametres and redundancy of quantity of the measurements reducing influence of errors of measurements on an estimation of parametres of processing [31, 49].

As the factors defining impact on function of the response in the course of processing of a pin of a mill which answer a number of shown requirements: universality and expression possibility in a quantitative sort are selected:

- x1 - A forward corner γ, hailstones.;

- х2 - An installation corner ω, hailstones.;

- х3 - A turn corner φ, hailstones.;

- х4 - Radius of a cutting cup of a cutter r, mm.

The general number of experiences TSKP at k factors [51] will make

Where 2k - number of "star" points;

rn0 - Number of experiences in the plan centre.

At drawing up of a negative mould of mapping out of experiment the central composite orthogonal plan provides carrying out only one experience which conditions corresponds to initial values of all considered factors, i.e. m0 = 1. Therefore for TSKOP expression 3.1 will become

і

That is for a model of investigated process negative mould TSKOP of 2nd order at 4 factors N = 25.

Influence of factors on response functions can depend on level on which there is other factor, or from a combination of levels of several factors.

As a priori it is not known, that such dependence between factors is not present, we will construct the developed negative mould of mapping out,
Considering not only factors, but also their interactions. Thus signs in columns for interactions we receive multiplication of signs on interplaying factors (table 3.1). Negative mould TSKOP of numerical values of functions possesses following property

Where i, j - numbers of columns,

p - number of a line of a negative mould (experience number).

Table 3.1 - the Negative mould of mapping out PFE TSKOP 24

№ p/p *1 *2 *3 х4 Order of carrying out of experiences
1 - - - - 1
2 + - - - 11
3 - + - - 24
4 + + - - 9
5 - - + - 5
6 + - + - 15
7 - + + - 18
8 + + + - 23
9 - - - + 7
10 + - - + 6
11 - + - + 20
12 + + - + 8
13 - - + + 14
14 + - + + 3
15 - + + + 10
16 + + + + 19
17 +1,414 0 0 0 13
18 -1,414 0 0 0 25
19 0 +1,414 0 0 4
20 0 -1,414 0 0 22
21 0 0 +1,414 0 21
22 0 0 -1,414 0 2
23 0 0 0 +1,414 12
24 0 0 0 -1,414 16
25 0 0 0 0 17

According to a negative mould of mapping out PFE TSKOP 24установлены levels of a variation of factors:-1,414 and +1,414 - star,-1 - bottom, 0 - average, +1 - top.

Levels of a variation of parametres are resulted in table 3.2.

Table 3.2 - Investigated factors and levels of a variation of independent variables PFE TSKOP 24

Investigated factors The coded value Variation levels
-1,414 -1 0 +1 +1,414
Forward corner γ, hailstones.; *1 15 23 43 63 70
Installation corner ω, hailstones.; х2 0 4 15 26 30
Turn corner φ, hailstones.; х3 5 15 38 61 70
Radius of a cutting cup of a cutter r, mm. х4 10 13 20 27 30

The analytical equation of regress of the function, being a mathematical model of process of processing of experimental data, is described by following expression [51, 62]

i ≠∕

Where at - the function of the response expressed through coded values of the factor; xi, Xj-varied factors; b0 - a free member of the equation of regress; bi - factors of linear dependence; bij - factors of pair interaction of factors; bii - factors of square-law dependence.

For calculation of factors we will take advantage of a method of the least foursquares under mentioned below formulas [49].

The free member of the equation of regress is calculated under the formula

Factors of linear dependence are calculated starting with

Factors of pair interaction of factors it is calculated under the formula

Factors of square-law dependence:

Check of the statistical importance of the received factors of the equations of regress includes calculation of a dispersion of reproducibility (an error of experience Sy), an estimation of the importance of all factors of the received mathematical model by criterion Stjudenta, calculation of the residual sum of foursquares (Socm) and numbers of degrees of freedom (fad), adequacy dispersions (Sad), check of adequacy of the equation of regress by Fisher's criterion at a significance level of 5 % [123].

3.4.

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A source: Bestuzheva Olga Vasilevna. Perfection of technology of restoration of pins of mills under operating conditions with application of the added machine tool. The dissertation on competition of a scientific degree of a Cand.Tech.Sci. Belgorod - 2017. 2017

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