EFFECT OF FLUID VISCOSITY AND IRON -FLUID COMPOSITION ON DAMPING ABILITY OF MAGNETORHEOLOGICAL DAMPER DURING HARD TURNING PEOCESS

JMSD (2015) 1–13 © JournalsPub 2015. All Rights Reserved Page 1

International Journal of Mechanical Systems Design Vol. 1: Issue 1

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Effect of Fluid Viscosity and Iron-Fluid Composition on Damping

Ability of Magnetorheological Damper during Hard

Turning Process

D. Madhan1, P. Sam Paul

2*, R. Manikandan

1, Joyal Joseph

2

1 Department of Mechanical Engineering, Coimbatore Institute of Engineering and Technology,

Coimbatore (Tamil Nadu), India 2Department of Mechanical Engineering, Karunya University, Coimbatore (Tamil Nadu), India

Abstract

In manufacturing industry where metal cutting operation take place, tool vibration is an

undesirable phenomenon which affects surface finish of the work piece, tool life and cause

discomfort to human personal. In order to avoid tool vibration, the concept of

magnetorheological (MR) damper was considered in this study. When a magnetic field is

applied to the MR fluids, particle chains form and the fluid becomes a semisolid. This

transition is reversible and can be achieved in a few milliseconds. But the damping ability of

MR Damper is highly influenced by viscosity index of the fluid and composition of iron fluid

mixture. In this paper, the effect of viscosity of the fluid and iron-fluid mixture composition

on tool vibration and cutting performance was investigated during turning of hardened AISI

4340 steel. From the result, it was observed that tool vibration reduced effectively when

magnetorheological fluid had higher viscosity and higher iron-fluid composition. Also in this

paper, the turning tool holder was analyzed using ANSYS software with and without damping

effect. From the experimental and computational results, it was observed that the use of

magnetorheological damper reduces tool vibration effectively.

Keywords: Magnetorheological (MR) damper, tool vibration, viscosity, hard turning, surface

roughness, damping ratio, tool wear

*Author for Correspondence: Email ID: [email protected]

INTRODUCTION Vibration is a frequent problem in the

manufacturing industry where metal

cutting operations such as external and

internal turning, boring, milling etc., take

place. Excessive vibration will accelerate

tool wear, cause of poor surface finish,

may damage spindle bearings[1].

In order to

increase productivity, tool life and to

improve the quality of machined work

pieces, it is necessary to develop and

utilize methods which increase the stability

and restrain the tool vibration in metal

cutting. In many cases, the tooling

structure may be considered as a

bottleneck with regard to the achievable

accuracy imposed by static defections and

the cutting regimes, as well as surface

finish due to forced and self-excited

vibrations.

In this regard, many types of dampers have

been used in the past to reduce vibration.

Among them, rheological damper was

found to be effective in suppressing tool

vibration. MR fluid exhibits special

advantages as compared to typical ER

materials[2]

. Magnetorheological damper

provide excellent vibration control for

various applications including

Effect of Fluid Viscosity and Iron-Fluid Composition on Damping Ability Paul et al.

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manufacturing, automotive, aviation, and

civil industries without potentially

decreased reliability and added expense of

a fully active system. Magnetorheological

fluid dampers are a specific class of semi-

active suspension components that use an

electric current to generate a magnetic

field surrounding the piston of a damper,

which in turn changes the local viscosity

of the magnetic fluid, altering the damping

characteristics. MR Dampers also have the

additional benefits of very low power

consumption while maintaining the ability

to generate large forces, minimal

complexity, and the inherent ability to

function as a passive damper during a

failure mode.

P. L. Wong et al. (2001) investigated the

tribological performance of a

magnetorheological suspension and

observed that the performance in

magnetorheological was found to be good

for low MR particle concentration[3]

.

Deqing Mei et al. (2009) developed

magneto-rheological fluid controlled

boring bar for chatter suppression[4]

.

Andrzej Milecki et al. (2012) applied of

magneto rheological fluid in industrial

shock absorbers and it was found to be

capable of controlling the stopping process

of moving objects[5]

. Balamurugan and

Alwarsamy (2011) investigated the Chatter

suppression using magneto-rheological

Fluid Damper through Artificial Neural

Networks[6]

. A. Ashfak et al. (2009)

studied the rheology and theory behind

MR fluids and their use on vibration

control[7]

. Mohammad Hoseinzadeh and

Jalil Rezaeepazhand (2014) used smart

electro-rheological (ER) dampers to

reduce vibration in composite plates and

from the results they observed that ER

damper and laminate parameters have a

significant effect on vibration

suppression[8]

. Sam Paul et al. (2014)

analysed the effect of magneto-rheological

fluid on tool vibration and they observed

that tool vibration was reduced

effectively[9]

. In another study, they

observed that MR damper has significant

effect on tool wear[10]

.

In the present investigation, an attempt

was made to study the effect of viscosity

of the oil and iron fluid composition on

tool vibration using magneto rheological

damper during turning of AISI 4340 steel

of 45 HRC using hard metal insert with

sculptured rake face. When an electric

field is applied to the MR fluids, the fluid

becomes a semisolid and this transition is

reversible and can be achieved in a

few milliseconds.

When subjected to a magnetic field, the

fluid greatly increases its apparent

viscosity to the point of becoming a visco-

elastic solid. The effect of viscosity of the

fluid and iron-fluid mixture composition

on tool vibration and cutting performance

was investigated. From experimental

result, it was observed that tool vibration

reduced effectively when magneto-

rheological fluid used has high viscosity

and higher iron-fluid composition (80:20)

percent by weight.

SELECTION OF TOOL AND WORK

MATERIAL

AISI 4340 steel which was hardened to 45

HRC by heat treatment was used as work

piece in this study. It is general-purpose

AISI 4340 steel has a wide range of

application in automobile and allied

industries by virtue of its good harden

ability enabling it to be used in fairly large

sections[11]

. In this investigation, bar of

50 mm diameter and 380 mm length was

employed.

The chemical composition of AISI 4340

steel in weight percent is 0.41%C, 0.87%

Mn, 0.28% Si, 1.83% Ni, 0.72% Cr, and

0.20% Mo, Rest Fe[12]

. The tool holder

used had the specification PSBNR 2525

M12. Multicoated hard metal inserts with

sculptured rake face geometry with the

specification SNMG 120408 MT TT5100

from Taegu Tec were used as cutting tools



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in this investigation[13]

. Tool holder and

insert used in this study are shown in

Figure 1 and 2 respectively.

Fig. 1: PSBNR 2525 M12 Tool Holder.

Fig. 1: PSBNR 2525 M12 Tool holder.

Fig. 2: Tool Insert.

Fig. 2: Tool Insert.

COMPUTATIONAL ANALYSIS

The effect of damper on tool vibration

during turning of hardened AISI 4340 steel

was analyzed using ANSYS software.

PSBNR 2525 M12 tool holder along with

the insert and sim was modeled and

analyzed to determine the dynamic

characteristics.

Static Analysis

ANSYS software analysis had been made

on the geometry of the tool holder along

with the sim as shown in Figure 3. Solid

element of type 8 node Solid 185 was used

in this study.

Fig. 3: Geometric Model of Tool Holder.

Considering the tool holder as a cantilever

beam, the overhang length of 55 mm was

considered. Practically it is not possible to

perform the turning operation below

55 mm, due to interference between tool

and work piece. A point load of 578.6 N


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was applied on the tip of the tool holder in

vertical direction. Table 1 represents the

overhanging length and deflection values

for tool with or without damper. By

considering the tool without MR damper,

maximum deflection was found to be

00.04159 mm when comparing to

0.40316 mm. From the result, it was

observed that the tool deflection reduces

drastically.

Table 1: Tool Overhang Length Vs Deflection.

S. No. Overhang

Length(mm)

Deflection with MR

Damper(mm)

Deflection without MR

Damper(mm)

1 55 0.040316 0.04159

Fig. 4: Static Analysis without Damper.

Fig. 4: Static Analysis without Damper.

Fig. 5: Static Analysis with Damper.

Fig. 5: Static Analysis with Damper.

Harmonic Analysis

A sustained cyclic response will be

produced in a structural system when

subjected to any sustained cyclic load. To

verify whether the design is safe against

resonance, fatigue, and other harmful

effects of forced vibration, harmonic

response analysis is done. Harmonic



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response analysis is a technique used to

determine the steady state response of a

linear structure to loads that vary

sinusoidally with time. In this study, to

obtain the value of forced frequency a load

of 578.6 N is applied on the tip of the tool

holder. Damping ratio value for the tool

holder with and without damper was

calculated using half-power bandwidth

method and is tabulated in Table 2.

Harmonic analysis for tool with and

without damper is presented in Figure 6

and 7.

Table 2: Damping Ratio Values for Tool Holder with and Without Damper.

Tool Holder Natural Frequency(Hz) Damping ratio

Without MR Damper 11.94267 0.1333

With MR Damper 11.14649 0.0785

Fig. 6: Harmonic Analysis with Damper.

Fig. 6: Harmonic Analysis with Damper.

Fig. 7: Harmonic Analysis without Damper.

Fig. 7: Harmonic Analysis without Damper.


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FABRICATION OF

MAGNETORHEOLOGICAL FLUID

DAMPER

Magneto-rheological fluids belong to a

class of smart fluids which consist of a

fluid impregnated with iron particles. The

essential characteristic of these fluids is

their ability to reversibly change from a

free-flowing, linear, viscous liquid to a

semi-solid with controllable yield strength

in milliseconds when exposed to a

magnetic field. When exposed to a

magnetic field, the fluid develops the

characteristics of a semi-solid state. The

apparent viscosity and shearing stress can

be controlled by changing the intensity of

magnetic field. The viscosity of MR fluid

increases as the strength of the magnetic

field increases and when the applied

magnetic field vanishes, the MR fluid

reverts to its previous, more fluid state.

The transformation between the liquid to

the semi solid phase takes place very fast

i.e., within few milliseconds. Magneto-

rheological damper used in present

investigation consists of a conical plunger

which moves inside the cylinder

containing MR fluid. The other end of the

plunger will match with the thread cut on

the hole of the tool holder. MR fluid will

be magnetized by passing current through

the coil. A coil is wound around the outer

surface of the cylinder, where current is

applied. When the coil is energized, MR

fluid is activated and offers resistance to

the motion of the plunger, thereby

damping the tool vibration. Photograph of

the fabricated magnetorheological damper

is shown in Figure 8 and Figure 9

represents the assembly of MR damper

created using solid works. Also, the line

sketch of MR fluid setup is shown in

Figure 10.

Fig.8: MR Damper Model.

Fig. 8: MR Damper Model.

Fig. 9: Solid Works Model.

Fig. 9: Solid Works Model.

MR Damper

Core & coil



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Fig. 10: Line Sketch of MR Fluid Setup (Sam Paul et al, 2014).

EXPERIMENTATION A nine run experiment was designed based

on Taguchi Technique to study the

performance of magneto-rheological.

Three fluids with the specifications SAE

140, SAE 320 and SAE 15W40 were

considered based on the information

available from the literature. Particles of

size 25 µm were selected in preparing the

magnetorheological fluid. To magnetize

the magneto-rheological fluid, direct

current 30 V was used. Iron and fluid

composition used in magneto-rheological

damper has ratio of 70:30; 80:20 and 60:40

(% by weight). Since, higher supply

voltage may result in high temperatures

and can lead to safety problems; supply

voltage of maximum 30 V was used.

Cutting experiments were conducted on a

kirolskar turn master lathe. Photographs of

fabricated damper setup and experimental

setup are shown in Figure 11 and 12

respectively.

Fig. 11: Photograph of the Fabricated Magnetorheological Damper.

Vibrometer Pickup

Cutting Tool

MR Damper connected

with Tool Holder

AISI 4340 Steel


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Fig. 12: Experimental Setup.

During each experiment, the main cutting

force was measured using a Kistler type

9257B dynamometer, Surface roughness

was measured using Mar TR100 surface

roughness tester of type Mar Surf GD 25.

The average flank wear was measured

using a tool maker’s microscope and the

amplitude of tool vibration was measured

using a piezoelectric vibrometer pickup

mounted at the top of the tool holder.

Since the vibration in the radial direction,

is known to have a worst effect on the

machined surface, vibration in radical

direction was considered. Parameters

considered are shown in Table 3.

Table 3 Parameters of MR Fluid.

S. No. Parameter Level

1 Viscosity of fluid SAE 140

SAE 320

SAE 15W 40

2 Iron- Fluid composition 60:40

70:30

80:20

RESULTS AND DISCUSSION The relative significance of input

parameters on tool vibration is shown in

Figure 13 and 14 represents the relative

significance of input parameters cutting

force. Figure 15 and 16 represents relative

significance of input parameters on tool

wear and surface finish respectively. The

most prominent component of the cutting

force in turning operation is the main

cutting force and it acts in the downward

direction. The increase in the main cutting

force component during hard machining

can be considered as a measure of the



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cutting performance. Any system that can

oppose the movement of the tool in the

downward direction can provide better

damping. In this investigation, the main

cutting force component is reduced

effectively due to the presence of

magneto-rheological fluid which in turn

leads to a stable cutting operation with

reduced tool wear and improved surface

finish. In general, the best way to solve a

tool vibration problem is to increase the

stiffness of the system. The level of input

parameters for achieving minimum tool

wear, tool vibration, cutting force and

surface roughness are summarized in

Table 4. From the experimental results, it

can be observed that for minimizing tool

wear and for achieving better cutting

performance MR fluid must have high

viscosity and 80:20 iron fluid combination.

When the supply voltage is higher,

strength of the magnetic field will be high

and better will be the damping ability.

Moreover, higher supply voltage may also

result in high temperatures and can lead to

safety problems. Sam Paul, 2014[11]

analyzed the effect of magneto-rheological

fluid on tool vibration. A magneto-

rheological fluid made of oil with viscosity

index at (SAE 15W40) provided better

cutting performance as this oil can offer

higher resistance to the movement of the

plunger.

Fig. 13: Comparison of Tool Wear.

Fig. 14: Comparison of the Amplitude of Tool Vibration.


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Fig. 15: Comparison of Cutting Force.

Fig. 16: Comparison of Surface Roughness.

Table 4: Levels of Input Parameters for Getting Optimum Performance.

S. No Objective Composition of Iron-Oil

Mixture

Viscosity

Index of Oil

1 To minimize cutting force 80:20 SAE 15W40

2 To minimize Tool vibration 80:20 SAE 15W40

3 To minimize surface

roughness 80:20 SAE 15W40

4 To minimize Tool wear 80:20 SAE 15W40



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Finally, it is seen that magnetic particle in

the MR fluid should have certain

minimum size to offer better performance.

If the size of the particles in the MR fluid

is very small, there is a possibility of

magnetic materials sticking together to

form a solid mass when magnetized. But if

the size of the particle is sufficiently high

(75 µm), the tendency to form a solid

block reduces.

There will be a good distribution of the

magnetized particles with the fluid

occupying the region in between and this

distribution of magnetized particles in a

pool of the fluid provides better resistance

to the movement of the plunger which

leads to reduction in tool wear and

improvement in surface finish.

Cutting experiments were conducted with

the input parameters kept at levels as

indicated in Table 4 and the performance

was compared with the cutting

performance during conventional minimal

fluid application without magneto-

rheological fluid system and also with dry

turning operation. When iron particles of

75 µm size mixed with an oil of viscosity

index SAE 15W40 and magnetized with

direct current provided with a cone type

plunger, main cutting performance was

improved effectively.

Also, it was observed that the iron-fluid

mixture of the suspended particles affect

the change in properties of the MR fluid

when placed in a magnetic field. When the

iron-oil mixture is of 80:20% by weight

ratio and in the presence of a magnetic

field, the magnetic-responsive particles

become polarized and there by organized

into chains of particles or particle fibrils.

The particle chains increase the flow

resistance of the fluid, resulting in the

development of a solid mass and provide

better performance when compared to

60:30 and 70: 30 ratio. The effect of

viscosity of the fluid and iron-fluid

mixture composition on tool vibration and

cutting performance was investigated.

From experimental result, it was observed

that tool vibration reduced effectively

when magneto-rheological fluid used has

high viscosity and higher iron-fluid

composition (80%-Iron, 20%-Oil).

When this combination was used, cutting

force was reduced by 17.82%, tool wear

reduced by 46.80%, Tool vibration

reduced by 54.81%, and surface finish

reduced by 43.02%. This reduction in

cutting force reduces the total energy

required to perform cutting operation. The

damping force created by the effect of

magneto-rheological fluid increases the

rigidity of the tool which reduces the

amplitude of tool vibration.

Table 5: Confirmatory Experiment.

S. No. Parameters With Damper Without Damper % Reduction

1 Tool Vibration, mm 1.008 mm 2.231 mm 54.81%

2 Cutting force, N 441.5 N 537.35 N 17.82%

3 Tool Wear, mm 0.025 mm 0.047 mm 46.80%

4 Surface Roughness, mm 0.98 mm 1.72 mm 43.02%

In general, the increase in amplitude of

tool vibration increases the tool wear.

Amplitude of tool vibration caused by

waviness of work piece has a direct impact

on the surface finish of the work piece

degrades.


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Thus, the increase of tool vibration causes

poor surface finish and damage tool insert.

This factor will increase the average flank

wear and reduces tool life. Due to this, the

machine parts start vibrating further and if

frequency of forced vibrations approaches

the natural frequency of forced vibrations

of that part, the amplitude of vibration will

be quiet high and the part may even break.

Table 6: Comparison of Experimental and Computational Results with and without MR

Damper.

55 mm overhang without MR

damper 55 mm overhang with MR

damper

Parameters Computational Experimental Computational Experimental

Deflection 0.04159 mm 2.231 mm 0.04031 mm 1.008 mm

As shown in Table 6, the tool holder with

magneto-rheological damper has less

deflection when compared to tool holder

without damping effect. When tool was

connected to magneto-rheological fluid

damper, tool wear reduces due to the

increase in stiffness of tool holder. Also

the cutting operation which is quite free of

vibration when the tool is sharp may be

subjected to an unacceptable vibration

when the tool wears. As the tool wear

progresses, the surface finish produced in a

machining operation usually deteriorates.

CONCLUSION

In this investigation, the effect of viscosity

index and iron- fluid combination on tool

vibration was studied. Parameters such as

tool vibration, cutting force, tool wear and

surface finish were measured during

experimentation.

ANSYS software was also used to study

the effect of damper on vibration during

turning tool. The results obtained from

computational method reasonably matches

with the experimental result. From the

experimental results, the following

observation was made.

1. The damping force created by the

effect of magneto-rheological fluid

increases the stiffness of the tool which

in turn reduces the amplitude of tool

vibration.

2. Oil with high viscosity and higher

iron-fluid combination produces better

damping force and improves the

cutting performance.

ACKNOWLEDGEMENTS

The authors are grateful to the Department

of Mechanical Engineering and Centre for

Research in Design & Manufacturing

Engineering (CRDM) of the School of

Mechanical Sciences, Karunya University

for facilitating this research work. Also the

authors would like to thank Vibration and

Dynamics Laboratory staffs of Karunya

University for their help in this research

work. Special thanks to Mr. X. Ajay

Vasanth, Mr. G. Lawrance, Mr. Paul

Praveen, Mr. Jones Robin, Mr. Winston

and Mr. Sivasankaran for their help in

conducting experiments. Authors also

thank M/s. TageuTec India (P) Ltd. for

supplying cutting tools needed for this

investigation.

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EFFECT OF FLUID VISCOSITY AND IRON -FLUID COMPOSITION ON DAMPING ABILITY OF MAGNETORHEOLOGICAL DAMPER DURING HARD TURNING PEOCESS

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