The paper presents results of measurements of surface roughness of holes reamed in steel and cast iron workpieces, when mineral industrial oil with and without liquid crystals additives was used as coolant for reaming. Four types of twisted nematic liquid crystals (cholesterol esters) were tested: cholesterol valerate, cholesterol caproate, cholesterol stearate and cholesterol oleate. The concentration of the liquid crystals in oil was 0.5% by oil volume. The dependence of average roughness Ra of the reamed surface on coolant composition was establishe

V. Mokshin

V. Vekteris

English

Journal of Vibroengineering

 367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B 
 
 
 VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716 
 
241 
367. Use of liquid crystals for metal machining   
 
 
V. Mokshin1,a, V. Vekteris1,b   
1Vilnius Gediminas Technical University,           
 J. Basanaviciaus str. 28, LT-03224, Vilnius, Lithuania 
E-mail: avadim@me.vtu.lt, bvekteris@me.vtu.lt 
 
(Received 22 May 2008; accepted 13 June 2008) 
 
 
 
 
 
 
 
 
 
Abstract 
The paper presents results of measurements of surface roughness of holes reamed in steel and cast iron 
workpieces, when mineral industrial oil with and without liquid crystals additives was used as coolant for reaming. Four 
types of twisted nematic liquid crystals (cholesterol esters) were tested: cholesterol valerate, cholesterol caproate, 
cholesterol stearate and cholesterol oleate. The concentration of the liquid crystals in oil was 0.5% by oil volume. The 
dependence of average roughness Ra of the reamed surface on coolant composition was established.  
 
Keywords: liquid crystals, coolant, mineral industrial oil, reaming. 
 
 
Introduction 
 
Coolants are widely used for many metal machining 
operations. They perform three very important functions in 
the tool-workpiece interface zone: lubrication, cooling and 
washing. The first function results in reduced cutting force, 
temperature, tool wear and height of the roughness of 
machined surface. The second function results in reduced 
temperature in the cutting zone and tool wear. Finally, 
good washing properties are necessary for effective chip 
removal from the cutting zone. Therefore, improvement of 
properties of the coolants is one of the possible ways to 
increase the tool life, dimensional accuracy and surface 
quality of machined parts and reduce the production costs. 
That can be achieved by using coolant additives. 
     Liquid crystals are an interesting solution in this field 
for two main reasons. At first, it is known [1-4], that liquid 
crystals additives to the various lubricants can significantly 
reduce the friction coefficient of lubricated friction pairs 
(in separate cases, when twisted nematic liquid crystals are 
used as additives, maximum reduction of the friction 
coefficient of friction pairs reaches 5 times [1], wear of 
friction surfaces – 20 times [1] and friction zone 
temperature – 2 times [2] in comparison with pure 
lubricants). Next, many of liquid crystals (especially 
twisted nematic liquid crystals – cholesterol esters) are 
surface-active substances and they can strengthen the      P. 
A. Rehbinder’s effect [5] and reduce the deformation 
resistance of the surface layer of the workpiece. 
Therefore, it may be presumed that liquid crystals can 
be used as effective additives for various coolants and can 
improve their lubrication properties, i.e. significantly 
reduce friction between tool and workpiece as well as tool 
wear, diminish temperature in the cutting zone resulting in 
improved  quality of machined surface and extended tool 
lifetime. They can be particularly effective for multipoint 
tools (drills, reamers, taps, etc), when the tool-workpiece-
chip contact area is comparatively large.                        
 
Research Object 
 
The mineral industrial oil I-40A (Table 1) with and 
without twisted nematic liquid crystals (cholesterol esters) 
additives was selected as an object of research. Molecular 
formula of the tested liquid crystals is presented in Fig. 1, 
the main properties are presented in Table 2. The research 
covered homologous series of twisted nematic liquid 
crystals, i.e.: valerian acid cholesterol ester (Val), capron 
acid cholesterol ester (Cap), stearine acid cholesterol ester 
(St). Oleine acid cholesterol ester (Ol) also was used as 
additive of industrial oil.   
 
 
 367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B 
 
 
 VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716 
 
242 
CH3 
CH3 
  
   
 
 
 
 
 
 
 
 
 
 
 
Fig. 1. The molecular formula of the studied twisted nematic liquid crystals: R is hydrocarbon radical of the saturated or unsaturated 
fatty acid (Table 2) 
 
 
           Table 1. Properties of industrial oil I-40A [6] 
 
Property Unit of measurement Value 
Density (20 °C) [kg/m3] 900 
Acid number [mg KOH/g] 0.05 (min.) 
Kinematic viscosity (40 °C) [mm2/s] 61-75 
Flash point [°C] 220 
Solidification temperature [°C] -15 
Ash content [%] 0.005 
 
 
 
Table 2. Properties of the tested twisted nematic liquid crystals 
 
Liquid crystals R=CmHn (Fig. 1) Melting point, [ºC] Molecular mass 
Valerian acid1 cholesterol ester (Val) C4H9 93.0 470.8 
Capron acid1 cholesterol ester (Cap) C5H11 99.5 484.8 
Stearine acid1 cholesterol ester (St) C17H35 83.0 653.1 
Oleine acid2 cholesterol ester (Ol) C17H33 48.0 651.1 
 
1saturated fatty acid; 2unsaturated fatty acid 
 
 
Research Methods 
 
Experiments were performed on vertical drilling 
machine. Steel 45 and cast iron СЧ-15 specimens were 
machined. First, the hole was drilled by twisted drill, then 
enlarged by core drill and finally, reamed by machine 
reamer (Table 3). Thus, in total 16 holes were machined in 
every workpiece: 1 hole, when no coolant was used for 
reaming, 3 holes, when pure industrial oil was used as 
coolant for reaming and 12 holes, when industrial oil with 
liquid crystals additives (Table 2) was used as coolant for 
reaming (3 holes × 4 types of the tested liquid crystals).   
The concentration of liquid crystals in industrial oil was 
0.5 % by oil volume. Industrial oil and liquid crystals 
mixtures were prepared as follows: industrial oil and liquid  
 
 
 
crystals were heated above melting temperature of the 
liquid crystals (Table 2), then melted liquid crystals were 
added to oil (0.5 % by oil volume) and, finally, the mixture 
was prepared and cooled down to room temperature. 
Subsequently it was poured into vessel and left for 3 days 
on purpose to examine the solubility of liquid crystals in 
oil, then tested as coolant for reaming in the low pressure 
flood application system of the drilling machine.  
The average roughness of the reamed surface Ra was 
chosen as an output parameter in the research. The Ra 
values of reamed holes were established by roughness 
indicator Talysurf 4 (Taylor & Hobson), and then average 
Ra value was calculated for every coolant. 
CH-CH2-CH2-CH2-CH 
 R-C-O 
O
 
 H  
CH3  
CH3  
CH3  
 367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B 
 
 
 VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716 
 
243 
Table 3. Cutting conditions 
 
Workpiece 
material 
Operation 
component Tool 
Feed, 
[mm/rev.] 
Cutting 
speed, 
[m/min] 
Rotational 
speed, 
[rev./min] 
Machine 
time, [min] 
Drilling Twisted drill ∅13 0.28 30.0 710 0.12 
Core drilling Core drill ∅15.75 0.56 17.6 355 0.12 Steel 45 
Reaming Machine reamer ∅16H9 1.12 2.26 45 0.46 
Drilling Twisted drill ∅13 0.28 30.0 710 0.21 
Core drilling Core drill ∅15.75 1.12 24.7 500 0.08 Cast iron 
СЧ-15 
Reaming Machine reamer ∅16H9  1.6 6.3 125 0.21 
 
 
 
Results of Research 
 
Results of experiments are presented in Fig. 2 and Fig. 
3 as relationships of average roughness of the reamed 
surface Ra on coolant composition. 
It should be mentioned, that all the tested twisted 
nematic liquid crystals completely melted in mineral 
industrial oil. 3 days after mixing all the oil and liquid 
crystals mixtures were clear and free from micelles of 
molecules of the liquid crystals, the visible changes of 
viscosity of mixtures were not observed.   
2,05
2,61
2,22 2,06 1,94
3,70
0
0,5
1
1,5
2
2,5
3
3,5
4
None Pure oil I-40A Oil I-40A +
Val
Oil I-40A +
Cap
Oil I-40A + St Oil I-40A + Ol
Coolant
 
Fig. 2. Average roughness Ra of reamed cast iron surface as function of coolant composition (presented average values of 9 Ra 
measurements (3 different measurement positions inside the hole × 3 reamed holes) when any coolant was used and average value of 3 
Ra measurements (3 different measurement positions inside the hole × 1 hole) when no coolant was used for reaming)  
 
2,372,48
2,733,013,18
4,27
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
None Pure oil I-40A Oil I-40A +
Val
Oil I-40A +
Cap
Oil I-40A + St Oil I-40A + Ol
Coolant
 
 
Fig. 3. Average roughness Ra of reamed steel surface as function of coolant composition (presented average values of 9 Ra 
measurements (3 different measurement positions inside the hole × 3 holes) when any coolant was used and average value of 3 Ra 
measurements (3 different measurement positions inside the hole × 1 hole) when no coolant was used for reaming) 
Ra, µm 
Ra, µm 
 367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B 
 
 
 VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716 
 
244 
Conclusions 
 
1. All tested twisted nematic liquid crystals positively 
influence the properties of coolant. Liquid crystals 
with the biggest molecular mass (stearine acid 
cholesterol ester and oleine acid cholesterol ester) are 
particularly effective. When they were used as 
industrial oil additives, the reduction of the Ra of 
reamed steel surface reached approx. 1.3 times as 
compared with additive-free oil. In case of cast iron 
workpiece, reduction of the average roughness was 
similar. 
2. All the tested twisted nematic liquid crystals are 
completely soluble in industrial oil at concentration of 
0.5 % by oil volume. This fact is very important for 
application of the liquid crystals in the coolant 
systems of the machines.     
3. Attempt to establish the dependence of the average 
roughness of reamed surface on the molecular mass of 
used liquid crystals was only partially successful since  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
the measuring errors were comparative with the variations 
of the Ra values. It can be only assumed that the 
dependence exists and as the molecular mass of the used 
liquid crystals increases, the average roughness of reamed 
surface slightly decreases. 
 
References 
 
[1] Kupchinov B. I., Rodnenkov V. G., Jermakov S. F. 
Introduction into tribology of the liquid crystals (IMMS 
ANB, Gomel, 1993). 
[2] Vekteris V., Mokshin V. Mechanika, No. 6(38) (2002), p. 
67-72. 
[3] Vekteris V., Mokshin V. Mechanika, No. 1(39) (2003), p. 
56-60. 
[4] Vekteris V., Mokshin V. and Buchinskas V. Proceedings of 
the 11th world congress in mechanism and machine science, 
Tianjin, China, vol. 5 (2004), p. 2320-2323. 
[5] Bhushan B., Gupta B. K. Handbook of tribology (McGraw-
Hill, 1991). 
[6] Kuznetsov A. V. Fuels and lubricants (Koloss, Moscow, 
2004). 


Use of liquid grystals for metal machining

Mokshin, V.

Vekteris, V.

Journal of Mechanical Engineering, Automation and Control Systems

 367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B    VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716  241 367. Use of liquid crystals for metal machining     V. Mokshin1,a, V. Vekteris1,b   1Vilnius Gediminas Technical University,            J. Basanaviciaus str. 28, LT-03224, Vilnius, Lithuania E-mail: avadim@me.vtu.lt, bvekteris@me.vtu.lt  (Received 22 May 2008; accepted 13 June 2008)          Abstract The paper presents results of measurements of surface oughness of holes reamed in steel and cast iron workpieces, when mineral industrial oil with and without liquid crystals additives was used as coolant for reaming. Four types of twisted nematic liquid crystals (cholesterol esters) were tested: cholesterol valerate, cholesterol caproate, cholesterol stearate and cholesterol oleate. The concentration of the liquid crystals in oil was 0.5% by oil volume. The dependence of average roughness Ra of the reamed surface on coolant composition was established.   Keywords: liquid crystals, coolant, mineral industrial oil, reaming.   Introduction  Coolants are widely used for many metal machining operations. They perform three very important functions in the tool-workpiece interface zone: lubrication, cooling and washing. The first function results in reduced cutting force, temperature, tool wear and height of the roughness of machined surface. The second function results in reduc d temperature in the cutting zone and tool wear. Finally, good washing properties are necessary for effective chip removal from the cutting zone. Therefore, improvement of properties of the coolants is one of the possible ways to increase the tool life, dimensional accuracy and surface quality of machined parts and reduce the production costs. That can be achieved by using coolant additives.      Liquid crystals are an interesting solution in this field for two main reasons. At first, it is known [1-4], that liquid crystals additives to the various lubricants can sig ificantly reduce the friction coefficient of lubricated friction pairs (in separate cases, when twisted nematic liquid crystals are used as additives, maximum reduction of the friction coefficient of friction pairs reaches 5 times [1], wear of friction surfaces – 20 times [1] and friction zone temperature – 2 times [2] in comparison with pure lubricants). Next, many of liquid crystals (especially twisted nematic liquid crystals – cholesterol esters) are surface-active substances and they can strengthen the      P. A. Rehbinder’s effect [5] and reduce the deformation resistance of the surface layer of the workpiece. Therefore, it may be presumed that liquid crystals c nbe used as effective additives for various coolants d can improve their lubrication properties, i.e. significantly reduce friction between tool and workpiece as well as tool wear, diminish temperature in the cutting zone resulting in improved  quality of machined surface and extended tool lifetime. They can be particularly effective for multipoint tools (drills, reamers, taps, etc), when the tool-wrkpiece-chip contact area is comparatively large.                  Research Object  The mineral industrial oil I-40A (Table 1) with and without twisted nematic liquid crystals (cholesterol esters) additives was selected as an object of research. Molecular formula of the tested liquid crystals is presented in Fig. 1, the main properties are presented in Table 2. The res arch covered homologous series of twisted nematic liquid crystals, i.e.: valerian acid cholesterol ester (Val), capron acid cholesterol ester (Cap), stearine acid cholesterol ester (St). Oleine acid cholesterol ester (Ol) also was used as additive of industrial oil.      367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B    VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716  242 CH3 CH3                 Fig. 1. The molecular formula of the studied twisted nematic liquid crystals: R is hydrocarbon radical of the saturated or unsaturated fatty acid (Table 2)              Table 1. Properties of industrial oil I-40A [6]  Property Unit of measurement Value Density (20 °C) [kg/m3] 900 Acid number [mg KOH/g] 0.05 (min.) Kinematic viscosity (40 °C) [mm2/s] 61-75 Flash point [°C] 220 Solidification temperature [°C] -15 Ash content [%] 0.005    Table 2. Properties of the tested twisted nematic liquid crystals  Liquid crystals R=CmHn (Fig. 1) Melting point, [ºC] Molecular mass Valerian acid1 cholesterol ester (Val) C4H9 93.0 470.8 Capron acid1 cholesterol ester (Cap) C5H11 99.5 484.8 Stearine acid1 cholesterol ester (St) C17H35 83.0 653.1 Oleine acid2 cholesterol ester (Ol) C17H33 48.0 651.1  1saturated fatty acid; 2unsaturated fatty acid   Research Methods  Experiments were performed on vertical drilling machine. Steel 45 and cast iron СЧ-15 specimens were machined. First, the hole was drilled by twisted drill, then enlarged by core drill and finally, reamed by machine reamer (Table 3). Thus, in total 16 holes were machined in every workpiece: 1 hole, when no coolant was used for reaming, 3 holes, when pure industrial oil was used as coolant for reaming and 12 holes, when industrial ol with liquid crystals additives (Table 2) was used as coolant for reaming (3 holes × 4 types of the tested liquid crystals).   The concentration of liquid crystals in industrial oil was 0.5 % by oil volume. Industrial oil and liquid crystals mixtures were prepared as follows: industrial oil and liquid     crystals were heated above melting temperature of the liquid crystals (Table 2), then melted liquid crystal  were added to oil (0.5 % by oil volume) and, finally, the mixture was prepared and cooled down to room temperature. Subsequently it was poured into vessel and left for 3 days on purpose to examine the solubility of liquid crystal  in oil, then tested as coolant for reaming in the low pressure flood application system of the drilling machine.  The average roughness of the reamed surface Ra was chosen as an output parameter in the research. The Ra values of reamed holes were established by roughness indicator Talysurf 4 (Taylor & Hobson), and then average Ra value was calculated for every coolant. CH-CH2-CH2-CH2-CH  R-C-O O  H  CH3  CH3  CH3   367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B    VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716  243 Table 3. Cutting conditions  Workpiece material Operation component Tool Feed, [mm/rev.] Cutting speed, [m/min] Rotational speed, [rev./min] Machine time, [min] Drilling Twisted drill ∅13 0.28 30.0 710 0.12 Core drilling Core drill ∅15.75 0.56 17.6 355 0.12 Steel 45 Reaming Machine reamer ∅16H9 1.12 2.26 45 0.46 Drilling Twisted drill ∅13 0.28 30.0 710 0.21 Core drilling Core drill ∅15.75 1.12 24.7 500 0.08 Cast iron СЧ-15 Reaming Machine reamer ∅16H9  1.6 6.3 125 0.21    Results of Research  Results of experiments are presented in Fig. 2 and Fig. 3 as relationships of average roughness of the reamed surface Ra on coolant composition. It should be mentioned, that all the tested twisted nematic liquid crystals completely melted in mineral industrial oil. 3 days after mixing all the oil and liquid crystals mixtures were clear and free from micelles of molecules of the liquid crystals, the visible changes of viscosity of mixtures were not observed.   2,052,612,22 2,06 1,943,7000,511,522,533,54None Pure oil I-40A Oil I-40A +ValOil I-40A +CapOil I-40A + St Oil I-40A + OlCoolant  Fig. 2. Average roughness Ra of reamed cast iron surface as function of coolant composition (presented average values of 9 Ra measurements (3 different measurement positions inside the hole × 3 reamed holes) when any coolant was used and average value of 3 Ra measurements (3 different measurement positions inside the hole × 1 hole) when no coolant was used for reaming)   2,372,482,733,013,184,2700,511,522,533,544,5None Pure oil I-40A Oil I-40A +ValOil I-40A +CapOil I-40A + St Oil I-40A + OlCoolant   Fig. 3. Average roughness Ra of reamed steel surface as function of coolant composition (presented average values of 9 Ra measurements (3 different measurement positions inside the hole × 3 holes) when any coolant was used and average valu  of 3 Ra measurements (3 different measurement positions inside the hole × 1 hole) when no coolant was used for reaming) Ra, µm Ra, µm  367. USE OF LIQUID CRYSTALS FOR METAL MACHINING. VADIM MOKSHIN1,A, VLADAS VEKTERIS1,B    VIBROMECHANIKA.  JOURNAL OF  VIBROENGINEERING.  JUNE   2008,   VOLUME  10,  ISSUE  2,  ISSN 1392-8716  244 Conclusions  1. All tested twisted nematic liquid crystals positively influence the properties of coolant. Liquid crystal with the biggest molecular mass (stearine acid cholesterol ester and oleine acid cholesterol ester) ar  particularly effective. When they were used as industrial oil additives, the reduction of the Ra of reamed steel surface reached approx. 1.3 times as compared with additive-free oil. In case of cast iron workpiece, reduction of the average roughness was similar. 2. All the tested twisted nematic liquid crystals are completely soluble in industrial oil at concentration of 0.5 % by oil volume. This fact is very important for application of the liquid crystals in the coolant systems of the machines.     3. Attempt to establish the dependence of the average roughness of reamed surface on the molecular mass of used liquid crystals was only partially successful ince                                       the measuring errors were comparative with the variations of the Ra values. It can be only assumed that the dependence exists and as the molecular mass of the used liquid crystals increases, the average roughness of reamed surface slightly decreases.  References  [1] Kupchinov B. I., Rodnenkov V. G., Jermakov S. F. Introduction into tribology of the liquid crystals (IMMS ANB, Gomel, 1993). [2] Vekteris V., Mokshin V. Mechanika, No. 6(38) (2002), p. 67-72. [3] Vekteris V., Mokshin V. Mechanika, No. 1(39) (2003), p. 56-60. [4] Vekteris V., Mokshin V. and Buchinskas V. Proceedings of the 11th world congress in mechanism and machine science, Tianjin, China, vol. 5 (2004), p. 2320-2323. [5] Bhushan B., Gupta B. K. Handbook of tribology (McGraw-Hill, 1991). [6] Kuznetsov A. V. Fuels and lubricants (Koloss, Moscow, 2004). 

JVE International

Journal of Mechatronics and Artificial Intelligence in Engineering

https://www.jvejournals.com/article/10198/pdf

Use of liquid grystals for metal machining

Abstract

Similar works

Full text

Available Versions

Journal of Vibroengineering

Journal of Mechanical Engineering, Automation and Control Systems

JVE International

Journal of Mechatronics and Artificial Intelligence in Engineering