Diamond/CBN Abrasive Wheels with Adaptive Abrasive Composite Technology

for Ultra-High Capacity and Precision Finishing Machining of Hard-to-Machine Materials

Mr. N. IgnatovMr. Y. Pashchenko

Aignesco Abrasive Systems Co.Canada

The traditional response to the challenges of the cutting zone is the determination to maximize

the bond stability under highly unstable conditions.

The alternative may be the development of adaptive, self-organizing abrasive composites.

0 2 4 6

2 - elastic modulus of adaptive composite

3 - elastic modulus of traditional composite

ultra

so

un

d p

ow

er,

arb

itra

ry u

nits

ela

stic m

od

ulu

s, a

rbitra

ry u

nits

, seconds

1 - ultrasound power

Fig.1 The change of elastic modulus of the adaptive (1)

and traditional (2) composites under variable intensity of

ultrasound impact on the sample.

In the adaptive composites the growth of

the contact forces causes its reversible

structural transformation into a more rigid

state.

A new criterion for the behaviour of polymer-bonded

abrasive composites – the adaptive capacity:

1

2lnE

EE

ΔτΔЕ = Е2 – Е1,

0,0 0,2 0,4 0,6 0,8 1,0 1,2

0,0

0,1

0,2

0,3

0,4

0,5

sp

ectr

al d

en

sity, a

rbitra

ry u

nits

Hz

1

2

Fig. 2 Spectral density of vibrations generated in the cutting area by the

traditional (1) and adaptive (2) composites while grinding the hard alloy.

The application of the adaptive composites results in significant

narrowing of the width of the density of spectral distribution for

the vibrations generated during the grinding process.

Where, α – the index of adaptive capacity of the composite

based on polymeric bond,

Е1, Е2 – elastic modulus for less rigid and more rigid states of

the composite,

– transition period.

Two compositions of the traditional composites and three adaptive composites with different

proportions of the components were tested.

1,2 – olygoamidoimide + silicon carbide

3,4 – hybrid epoxy-siloxane + modified clay

5,6,7 – adaptive composite

Δ

Composition 1 2 3 4 5 6 7

Elastic modulus, МPa 1900 2250 2280 2380 1715 1980 2130

Adaptive capacity, MPa·c-1·10-6 0,002 0,004 0,007 0,010 0,580 0,980 1,720

1600 1800 2000 2200 2400

7

6

5

4

3

E, MPa

1

a b

0,0 0,6 1,2 1,8

6

7

8

9

5

0 1

0

-5, H

z

10

6

7

8

9

7

65

43

22

1

5

0 1

0

-5, H

z

MPa sec

-1

10

6

7

8

9

5

0 1

0

-5, H

z

10

Fig. 3 The correlation of halfwidth of spectral density 50 of vibrations in the cutting area by the adaptive and

traditional composites with elastic modulus (a) and the adaptive capacity of the composites (b)

1…7 – order of specimens according to Table 1

Table 1

The mentioned composites demonstrated comparable results on G ratio and surface roughness.

The significant difference appeared in 2 indicators, namely:

ΔFig. 4 The relation of the polishing time till Rа 2,2 nm (а) and the bearing surface (b) of the monocrystalline sapphire samples

at the halfwidth of spectral density of vibrations 50, generated during grinding with different composites.

• the bearing face of the machined workpieces,

• the operational time for polishing to the final roughness Rа 2,2 nm

0

2

4

6

6 8 106 8 10

Cycle

of p

oly

sh

ing

, a

rbitra

ry u

nits

50

10 -5

, Hz

78

80

82

84

86

88

90

92

94

96

98

be

ari

ng

fa

ce

, %

50

10 -5, Hz

a b

The adaptive capacity has a direct impact on the spectrum of vibrations generated in the

process of grinding. In turn, it determines the bandwidth of the energy exchange channels

between the abrasive composite and the workpiece.

The surface formed by grinding may be compared

not only by the geometrical parameters of

roughness. It is complemented by the

characteristic of a surface microrelief defined in the

process of its deformation.

Fig.5 Spectral density of indenter vibrations by scanning

the hard alloy surface machined with traditional (a) and

adaptive (b) composites

1,2,3 (a) – consecutive scanning on one track

The data prove that the architecture of the surface

grinded by the traditional composite is formed by a

large number of independent overlapping systems

of roughness.

These systems tend to evolve independently

under external influence.

3

2

0 2 4

sp

ectr

al d

en

sity, a

rbitra

ry u

nits

Hz

1

0 1 2 3 4 5

Hz

2

1

sp

ectr

al d

en

sity, a

rbitra

ry u

nits

The surface of the hard alloy formed by the

adaptive composite demonstrates a qualitatively

different behaviour.

Fig.5 Spectral density of indenter vibrations by scanning

the hard alloy surface machined with traditional (a) and

adaptive (b) composites

1,2 (b) – consecutive scanning on one track

The adaptive abrasive composites pave the way to the

formation of another large class of surface structures

which behaviour does not fit the traditional view.

Being stochastic by the geometry, they are able to self-

organizing.

Such surfaces acquire an unusual property that could

be named the “fractal capacity”.

The tool creates a hierarchy of structural “spare

positions”.

a

b

Under more intensive deforming influence, the

ensemble of surface microroughnesses formed by

the adaptive composite organizes and reproduces

itself on a new scale level.

These structural differences in the surfaces with

the equal Ra machined with adaptive and

traditional composite essentially effects the wear

resistance of the workpieces.

Fig. 6. The wear of hard alloy cutter on back surface for steel,

1- cutter machined by an adaptive abrasive wheel,

2- machined by a traditional grinding wheel.

The effect of the self-organization of the surface

layer of the workpieces is truly evident not only with

single samples, but with the groups of aggregated

components in the integrated mechanisms.

Fig.7. Wear of bearings aggregated in one mechanism up to

failure:

а – rolling paths machined with the traditional composite

b – rolling paths machined with the adaptive composite

For the groups of 6 bearings with the rolling paths

formed by the adaptive composite the time to failure

in overload was 25-40% longer in comparison with

the products machined by the traditional analogue.

The aggregate of 6 bearings was still able to operate

at the total wear much greater than it was for the

same group machined with the traditional composite.

0 30 60 90

0,0

0,5

1,0

1,5

2,0

fla

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ace

we

ar,

mm

t, min

1

2

1 2 3 4 5 6

0

1

2

We

ar,

arb

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bearings order

a

1 2 3 4 5 6

0

1

2

We

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bearings order

b