The viscosity behaviour of the reopectic abrasive mediums in the nanoprocessing processes by abrasive flow machining.

Avramescu, Valeriu ; Avramescu, Norvegia ; Ionescu, Nicolae 等

1. INTRODUCTION

Within the concerns aiming at developing the non-traditional technologies, a highly efficient ecological procedure emergent nowadays is Abrasive Flow Machining (A.F.M.), as it is known in the speciality literature. Abrasive Flow Machining finishes surfaces and edges by extruding viscous abrasive media through or across the work piece (Hase et al., 1998). Abrasion occurs only where the flow of the media is restricted; other areas remain unaffected.

The studies regarding the abrasive flow machining (Miller et al., 1994) showed that through this finishing procedure it is possible to accomplish operations such polishing, trimming and edges rounding for work pieces within a very wide dimensions range, performed in places difficult of access.

Using this procedure we may polish orifices of over 0,15 mm, diameter, cavities and complex surfaces in a wide domain of dimensions.

A variety of finishing results can be achieved by changing the process parameters and also by choosing a proper abrasive fluid (AF) which is of major importance.

2. EXPERIMENTAL

Technological elements of AFM system

By repeatedly extruding the media from one cylinder to the other and abrasive action is produced as the abrasive media enter a restrictive passage and travel through or across the work piece (Perry et al., 2000).

The machining action is similar to a grinding or lapping operation as the abrasive media gently polish the surfaces or edges.

When forced into a restrictive passage, the polymer carrier in the media temporarily increases viscosity.

This holds the abrasive grains rigidly in place and abrades the passages only when the abrasive fluid is in viscous state.

Abrasive fluids (AF) Materials

In the frame of this work a main aim is the obtaining the suitable fluids using ecological, safe and efficient materials. Keeping these criteria we used the following chemicals and materials.

[FIGURE 1 OMITTED]

Fluid component:

O--oleine contain mainly oleic acid with formula: C[H.sub.3][(C[H.sub.2]).sub.7]CH=CH(C[H.sub.2])COOH;

ODT--diethanolamide of oleic acid containning about 20%

TEA--triethanolamine N[([C.sub.2][H.sub.5]OH).sub.3] with OD--amide, resulting from reaction of condensation of D- dietanholamine HN[([C.sub.2][H.sub.5]).sub.2] with oleic acid, with water elimination as follows: [([C.sub.2][H.sub.5]OH).sub.2] NH + HOOC[(C[H.sub.2]).sub.7]CH=CH[(C[H.sub.2]).sub.7]C[H.sub.3] [right arrow] [right arrow] [([C.sub.2][H.sub.5]OH).sub.2] NCO[(C[H.sub.2]).sub.7]CH=CH[(C[H.sub.2]).sub.7]C[H.sub.3] + [H.sub.2]O The ODT product imparts many useful properties for AF fluid like increasing viscosity, emulsifying corrosion inhibition and lubrificating.

O-PPG and O-MPG are two esters of acid oleic O with polypropylene glycol PPG short chain polymer of MPG mono propylene glycol of formula: C[H.sub.3]-CHOH-C[H.sub.2]OH.

[H.sub.2]0--water in some circumstances is an useful additive to enhance the viscosity and reopecticity of the fluid.

Beside of those main components can used also another minor additives.

Abrasive materials used in these preliminary samples of AF are for the beginning only three:

* Alumina, aluminium oxide [Al.sub.2][O.sub.3], fine power grains of 3 - 70[micro]m;

* Silicone carbide SiC, fine power grains of 6 - 63[muicrom;

* Silica, silicium dioxide Si[O.sub.2], fine power grains of 48[micro]m;

The hardness values of abrasive powders used are very high in the Mohs scale: [Al.sub.2][O.sub.3] - 9, SiC - 9 and Si[O.sub.2] - 9.

The highest value in this scale is the hardness 10 for the diamond.

In the next extended research we intend also to use other abrasive materials in order to increase the value of the nanofinishing work.

3. RESULTATS AND DISCUSSION

Composition of AF samples

Using the chemicals and materials presented above we tried to obtain several abrasive fluids for AFM method.

The mixtures of those components in different ratios, is obtained under high stirring.

The effect of great interest is the reopecticity of the viscous AF resulted fluid (SC ICTCM SA, 2006).

The reopecticity is crucial for nanofinishing, because it means the increase of viscosity of the fluid under mechanical force; the abrasive grains abrade only in this viscous state where they hold rigidly in place.

The viscosity of the fluid returns to initial state when it exits the restrictive passage.

The preliminary abrasive fluid obtained considering the above stated principles are presented the next two tables.

In table 1 was used as main component the carboxyamide OD with TEA--triethanolamine added ODT and in the table 2 was used as main component the ester O-PPG.

The next samples of AF show a different composition because both main ODT components and O-PPG were used in all samples and only one abrasive; calcinated alumina with finest grain of 2,9-3,1[mu]m.

These samples are presented in the table 3.

It must notice that the ester O-MPG (mono propylene glycol is very similar with the previous O-PPG (polypropylene glycol) used in samples of table 1 and table 2 and is easier to obtain at a reproducible chemical structure.

Characteristic of abrasive fluids (AF)

Due to the complexity of AF samples their characterization is very difficult as well as the correlation of composition with efficiency in the nanofinishing (Rhoodes et al., 1997).

In this preliminary work the main characteristics of the samples were determined as follows:

* Stability and the homogeneity

The stability is good in time between several weeks to several months when the sample does not present the phases separation. After separation the sample returns at initial state. The homogeneity is good by visual observation but in the future a better microscopic analysis of structures will be correlated with the nanofinishing process.

* Viscosity

Viscosity is also difficult parameter to determine because, as it is was before explained it is variable during homogenisation due the reopecticity. The values given in the tables 1-3 for initial viscosity are only approximate.

* Viscosity dependence with temperature

Viscosity dependence with temperature is also very important, because it does be as small as possible. The most of samples are quite stable with the temperature increasing until 70[degrees]C--when they became more fluid but after they return at initial values by decreasing temperature.

* Reopecticity

Reopecticity is the increase of fluid viscosity under mechanical pressure, it depends essentially of the mechanical parameters of the AFM machine and so can be evaluated quantitative during de nanofinishing process.

4. CONCLUSIONS

In spite of the preliminary character of these results they reveal many possible formulations for the abrasive fluid compositions.

This will allow choosing the most suitable AF fluids for any specific application.

The base for the future development of AFM nanofinishing unconventional method is ensured by the abrasive fluids as they are here presented.

5. REFERENCES

Hase, C. et al. (1998). German patent no. WO/17774

Miller et al. (1994). Patent USA No. 5363603, 15 November

Perry, W.B. et al. (2000). Patent USA no. 6132484

Rhoodes, L. J. et al. (1997). Patent USA No. 5679058

SC ICTCM SA. (2006). Researches regarding the achievment of the work mediums at the nanofinishing process by abrasive flow machining with reopectic mediums / Cercetare privind realizarea mediilor de lucru la nanofinisarea prin curgere abraziva cu medii reopectice. Contract CEEX-REOFIN 296/2006, ICTCM

Tab. 1. Abrasive Fluids (AF), on ODT base

Component ODT O Abrasive [H.sub.2]O
 /Sample (%) (%) (%) (%)

 1a 25 25 10 40
 1a 40 10 10 40
 1b 20 22 8 46
 1b 20 24 8 46
 1c 40 30 10 --
 1c 40 40 10 --

Component [[eta].sub.i]
 /Sample PPG (poise)

 1a -- ~16
 1a -- ~25
 1b 4 ~14
 1b 2 ~20
 1c 20 ~12
 1c 10 ~16

Component Abrasive's
 /Sample nature

 1:1
 1a SiC /
 Silica
 1:1
 1a SiC /
 Silica
 1:1
 1b Silica /
 [Al.sub.2][O.sub.3]
 1:1
 1b Silica /
 [Al.sub.2][O.sub.3]
 1c [Al.sub.2][O.sub.3]
 1c [Al.sub.2][O.sub.3]

Tab. 2. Abrasive Fluids (AF), on O-PPG base

Component/ O-PPG Abrasive [H.sub.2]O
 Sample (%) O (%) (%) (%)

 2a 35 20 10 25
 2a 35 30 10 15
 2b 30 20 10 30
 2b 40 25 10 10
 2c 25 35 10 20
 2c 30 35 10 15

Component/ TEA [[eta].sub.i]
 Sample (%) (poise)

 2a 10 ~12
 2a 10 ~20
 2b 10 ~10
 2b 15 ~25
 2c 10 ~10
 2c 10 ~15

Component/ Abrasive's
 Sample nature

 2a 1:1
 SiC/ Silica
 2a 1:1
 SiC/ Silica
 2b 1:1
 Silica /
 [Al.sub.2][O.sub.3]
 2b 1:1
 Silica /
 [Al.sub.2][O.sub.3]
 2c [Al.sub.2][O.sub.3]
 2c [Al.sub.2][O.sub.3]

Tab. 3. Abrasive Fluids (AF), on ODT and MPG base

Component/ ODT O Alumina PPG O-MPG [[eta].sub.i]
 Sample (%) (%) (%) (%) (%) (poise)

F1 30 30 5 10 25 15
F2 25 35 10 5 25 12
F3 25 45 5 -- 25 10
F4 25 35 10 -- 30 14