Research article

Evaluation of temperature and propertiesat interface of AISI 1040 steels joined

by friction weldingHilmi Kuscu

Department of Mechanical Engineering, Faculty of Engineering and Architecture, Trakya University, Edirne, Turkey

Ismail BecenenHigh Vocational School, Faculty of Engineering and Architecture, Trakya University, Edirne, Turkey, and

Mumin SahinDepartment of Mechanical Engineering, Faculty of Engineering and Architecture, Trakya University, Edirne, Turkey

AbstractPurpose – The purpose of this paper is to evaluate temperature and properties at interface of AISI 1040 steels joined by friction welding.Design/methodology/approach – In this study, AISI 1040 medium carbon steel was used in the experiments. Firstly, optimum parameters of thefriction welding were obtained by using a statistical analysis. Later, the microstructures of the heat-affected zone are presented along with microhardness profiles for the joints. Then, the temperature distributions are experimentally obtained in the interface of the joints that is formed during thefriction welding of 1040 steels with the same geometry. This study was carried out by using thermocouples at different locations of the joint-interface.The results obtained were compared with previous studies and some comments were made about them.Findings – It was discovered that temperature had a substantial effect on the mechanical and metallurgical properties of the material.Research limitations/implications – The maximum temperature in the joint during frictional heating depends not only on the pressure, but also onthe temperature gradient which depends on the rotational speed in particular. It is important to note that the measurement process was successfullyaccomplished in this study although it was particularly difficult to obtain temperature due to the large deformations at the interface. Future work couldbe concentrated on the temperature measurement of the joined materials.Practical implications – Temperature is one of the most important of all physical quantities in industry. Its measurement plays a key part in industrialquality and process control, in the efficient use of energy and other resources, in condition monitoring and in health and safety. This paper contributes tothe literature about temperature measurement in welded, brazed and soldered materials.Originality/value – The main value of this paper is to contribute and fulfill the influence of the interface temperature on properties in welding ofvarious materials that is being studied so far in the literature.

Keywords Friction welding, Temperature measurement, Steels

Paper type Research paper

1. Introduction

In the process, heat is generated by the conversion of mechanicalenergy into thermal energy at the interface of the work piecesduring rotation under pressure. Some advantages of frictionwelding are that, it is economical as regards material, it requireslow production time and it offers greater possibilities when itcomes to thewelding of differentmetals or alloys. Frictionweldingcan also be used in order to join components that have circular ornon-circular cross-sections. The most interesting parameters infriction welding are friction time, friction pressure, upset time,upset pressure and rotation speed (Vill, 1962).

In general, friction welding is divided into two methods:

continuous drive friction welding and inertia friction welding.In the continuous drive method, one of the components is

rotated at constant speed (s),while the other is pushed towards the

rotated part by a sliding action under a predetermined pressure-

friction pressure (Pf). Friction pressure (Pf) is applied for a certain

friction time (tf). Then the drive is released and the rotary

component is quickly stoppedwhile axial pressure is increased to a

higher predetermined upset pressure (Pu) for a predetermined

time (tu). The layout of the welding method is shown in Figure 1.

Parameters of the method are shown in Figure 2.Many studies have been published in this area and these are

given below:Vill (1962) directed a study on the friction welding of

metals. Rich and Roberts (1971) presented an analytical

temperature solution based upon a finite welding piece and

The current issue and full text archive of this journal is available at

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28/4 (2008) 308–316

q Emerald Group Publishing Limited [ISSN 0144-5154]

[DOI 10.1108/01445150810904468]

The authors would like to thank Trakya University/Edirne–Turkey for thehelp provided in this research.

308

ambient temperature chuck ends. They discussed the

establishment of the boundary conditions using the

continuous drive method to join AISI 4140 steel tubes.

Imshennik (1971) examined the heating properties in friction

welding. Healy et al. (1976) carried out an analysis of

frictional phenomena in the friction welding of mild steel.

Kinley (1979) directed a study on the friction welding set up.

Sluzalec (1990) developed a finite element model to simulate

this process and to represent the work pieces and surface

contact conditions. The predictions of the temperature

distribution, thermal expansion and thermo-plastic stresses

were obtained from this model. The comparison of the

analytic results to the test data were presented and discussed

by the author. Nentwig (1996) investigated the effect on cross

section differences of components on the joint quality of

friction welding and stated that friction pressure, upset

pressure and rotation speed must be changed in the friction

welding of the different cross-sections. Bendzsak et al. (1997)

investigated a numerical model in friction welding. Fu and

Duan (1998) carried out an analysis of the coupled thermo-

mechanical problem during friction welding by using a finite

element method, according to the constitutive relation of a

large elasto-plastic deformation and the principle of the

virtual work in their studies. Then, the heat flow and stress-

strain process at the heating stage of the friction welding were

simulated, and the law of the variation of temperature, stress

and the strain fields during friction welding were

systematically investigated by the authors. Balasubramanian

et al. (1999) presented the results of a combined experimental

and a numerical study of the continuous drive friction welding

of the 1045 steel. A new friction law was proposed for the

estimation of the apparent coefficient of the friction during

direct drive friction welding. Temperature distributions were

empirically and numerically predicted in the heat-affected

zone (HAZ) that is formed during the direct drive friction

welding of 1045 steel to 1045 steel. The temperature

measurements were made at different locations using

thermocouples. A finite element model was used to

determine the appropriate coefficient of the friction to fit

the experimental data. The predictions of the coefficient of

the friction were in close agreement with the experimental

results obtained from the direct drive friction welding trials on

the 1045 steel. The current results suggest that the new

friction law may be used to determine the effects of friction

welding parameters on friction coefficients in other material

systems. Sahin (2001) investigated the effects of the work-

piece dimensions and the plastic deformation on the friction

welding method. Then, Sahin and Akata(2001) examined an

experimental study on the application of friction welding for

parts with different diameters and width. D’Alvise et al.(2002) studied the finite element modelling of the inertia

friction welding process between dissimilar materials. Sahin

and Akata (2003) carried out the joining of plastically

deformed steel with friction welding by using a statistical

analysis. Akata and Sahin (2003) directed research on the

effect of dimensional differences in the friction welding of the

AISI 1040 specimens. Lambrakos et al. (2003) directed a

study on analysis of friction stir welds using thermocouple

measurements. The friction stir welding process was analysed

via an inverse problem approach, using experimentally

obtained thermocouple information to constrain the thermal

field of the model in their studies. Triantafyllidis et al. (2003)investigated comparison of high power diode laser and

Nd:YAG laser microwelding of k-type thermocouples. Ferro

et al. (2005) carried out investigation of electron-beam

welding in wrought Inconel 706–experimental and numerical

analysis. Moreira et al. (2007) examined the temperature field

acquisition during gas metal arc welding using

thermocouples. The paper presents and compares

measurements made in welded plates of aluminium alloy

6082-T6. Tests were performed in both plate surfaces and a

good agreement between the three techniques was found.In this study, AISI 1040 medium carbon steel was used in

the experiments. Firstly, the optimum parameters of friction

welding were obtained by using a statistical analysis. Later,

the microstructures of the HAZ are presented along with the

micro hardness profiles for the joints. Then, the temperature

distributions are experimentally obtained in the interface of

the joints that is formed during the friction welding of the

1040 steels with the same geometry. This study was carried

out by using thermocouples at different locations of the joint-

interface. The results obtained were compared with previous

studies and comments were made.

2. The experimental procedure

2.1 The experiment set up

The friction welding set up designed and constructed for

experimental part of the present study is shown in Figure 3.

Figure 1 Layout of continuous drive friction welding

1 2 3 4 7

5 6

1 Motor2 Brake3 Rotating Chuck4 Unrotating Chuck5 Rotating Work-piece6 Unrotating Work-piece7 Hydraulic Cylinder

Figure 2 Parameters on continuous drive friction welding

Starting

Friction Pressure (Pf)

Rotational Speed (s)

Friction Time (tf)

Torque (T)

Braking

Waiting

Shortening

Upset Pressure (Pu)

Time

Upset Time(tu)

Evaluation of temperature and properties

Hilmi Kuscu, Ismail Becenen and Mumin Sahin

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Volume 28 · Number 4 · 2008 · 308–316

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The set-up was designed and constructed according to theprincipals of continuous drive weldingmachines. A drivemotorwith 4 kWpower and 1410 rpmwas selected as adequate for thetorque capacity in the friction welding of the steel bars within10mm diameter taking into account the friction and the upsetpressures. The friction and the upsetting pressures can be seenon number 2 pressure indicator, and the stages of the weldingsequences are controlled by number 3 solenoid valve driven byan external timer.

2.2 Test parts and geometry of parts

The chemical composition of the AISI 1040 steel is given inTable I (Stahlschlussel, 1995).The experiment specimens were machined from AISI 1040

steel on the geometry below. The geometry of parts is given inFigure 4.It is thought that friction time and friction pressure has a

direct effect on the tensile strength of the joints. Therefore, inthe last years, the statistical analysis which has been used inorder to discover the effects of the parameters that have asignificant role on the results in such studies (Draper andSmith, 1981; Akata and Sahin, 2003; Sahin and Akata, 2003)was also used in this study. Besides this, on thinking that theparameters affect the results directly, the linear style was usedin the statistical analysis. The statistical analysis in this studyis given in section 2.3.

2.3 Selection of the optimum parameters

Firstly, tests were conducted to determine the optimumparameters for a convenient joint. The optimum parameterswere determined by using statistical analysis with 10mmspecimens having an equal diameter. The weldingexperiments were directed to obtain an optimum frictiontime and friction pressures by using the upset time (20 sec)and the upset pressure (110MPa).

The basis of this approach is the assumption of a simplified

linear model for the optimization parameter h given by

h ¼ b0 þ b1x1 þ b2x2 þ . . . , where x1, x2 . . . , etc. are the

factors which h depends on and b0, b1, b2 . . . , etc. represent

the “true” values of the corresponding unknowns. From the

results of an experiment comprising a finite number of trials,

one can arrive at sample estimates of the coefficients, b, which

are then usually fitted into a linear regression equation of the

type y ¼ b0 þ b1x1 þ b2x2 þ . . . , where y is the response

function and the bs are the “estimated” values of the bs. In

simple terms, each coefficient represents the influence of the

corresponding factor on the quality of the weld expressed by

the optimization parameter.The statistical analysis involves two steps. The first step is

the adequacy of the model tested. A suitable method is based

on the Fischer or “F” ratio, which can be used to confirm if

the terms in the assumed linear function are statistically

significant. The second step is to obtain optimal estimates of

the regression coefficients for the significant factors, which

may be carried out by using the method of the fewest squares

(Sahin and Akata, 2003; Draper and Smith, 1981). The

parameter optimization was carried out by using the factorial

design of the experiments. In the present study, the friction

time and friction pressure were chosen as the two factors. The

other parameters such as upset time, upset pressure and

rotational speed were kept constant. Experimental results are

given in Table II.Firstly, the optimal estimates of the regression coefficients

were obtained by using the method of the Fisher ratio. The

resulting equation is also given below:

y ¼ 14; 1462 32; 533x1 þ 45; 067x2

However, if the correlation coefficient is examined in the

resulting equation, it is quantitatively shown that the effects of

friction time and friction pressure on the tensile strength are

as significant as expected.Later, the parameters having the least error by using the

method of fewest squares were taken as the optimum welding

parameters. Hence, the optimum parameters were found

(30MPa) for friction pressure and (5 sec) for friction time.

The parameters used in the friction welding experiments are

given in Table III.The effects of friction time and friction pressure on the

welding strength of the joints were examined in the welding of

the parts with an equal diameter. Results of the two sets of the

welding experiments, keeping the upset time and the upset

pressure constant, respectively, as 20 sec and 110MPa, are

shown in the diagrams of Figures 5 and 6.As seen in Figures 5 and 6, the tensile strengths of the joints

increase as friction time and friction pressure increase.

However, after a value where the maximum tensile strength is

obtained, the joints become over-deformed and the joint-

interface loses its property. Consequently, those friction time

and friction pressure values which increase after that

maximum value decrease the tensile strengths of the joints.

Figure 3 Continuous drive friction welding set-up

M: MotorP: PressureT: Tank exit1: Return Valve2: Pressure Indicator3: Solenoid Valve

HydraulicGroup

FrictionPressureControl

UpsetPressureControl

1

Drive

Chuck BearingsClutch

Work-pieces Sliding Guide

Clamps

M

TP

TP

Oil Tank

2

3 T

Table I Chemical compositions of test part

Material C (percent) P (percent) S (percent) Mn (percent) Si (percent) Ni (percent) Cr (percent) Tensile strength (MPa)

AISI 1040 0.35 0.44 ,0.04 ,0.05 0.75 0.20 – – 800

Evaluation of temperature and properties

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Subsequently, temperature measurement is of great

importance at the interfaces of the parts because of friction

in friction welding. Although it is difficult to obtain the

temperature measurements versus time, this was carried outin the present study.The temperature measurements were made by using

thermocouples at different locations of joint-interface in this

study.

2.4 The measurement of the temperature

Thermocouples which are one of the most frequently used

temperature sensors have become standard in the industry as

a cost effective method for measuring temperature. The

standards community together with modern metallurgy has

developed special material pairs specifically for use asthermocouples. Most of practical temperature ranges can be

measured using thermocouples; even though, their output

full-scale voltage is only millivolts with sensitivities in the

microvolt per degree range and their response is non-linear.In this study, four pieces of f 1mm diameter holes to part

having f 10mm diameter were machined with the wire

electrical discharge machining method to perform the

temperature measurement in the friction welding

experiment. The position of the thermocouples is shown

schematically in Figure 7.In order to measure the temperature variation at the points

shown in Figure 7 (R1, R2, R3 and R4), thermocouples,

whose wire diameter is 0.20mm, are inserted into four holes

with 1mm diameter one by one after being isolated.

The temperature variations, which would be measured, were

kept at a small value in order to give the nearest result in a

solid object. The thermocouples whose holes diameters are

1mm were inserted into these holes in the experiments. But,

as the holes into which the thermocouples will be inserted are

relatively small, there comes out the risk of a short circuit.

In order to avoid this risk, the isolation which avoids the short

circuit between the thermocouples and the metal, was made

from bobbin wire resin which can stand high temperatures.To the each of these holes, thermocouples made from thin

wires, which have two different compositions, were inserted

from the back of the specimen to the welding surface.

Electrical insulation was obtained with a slow-drying adhesive

so as not to cause a short circuit between the thermo-element

wires, inserted to the thin hole, and the metal rod. One end of

the thermo-element couple was connected to an environment

with the same type thermo-element, at the identified

temperature and taken as reference, in order to carry out

temperature compensation. After this temperature

compensation, the obtained value from the thermo-element

in the test specimen was instructed by a 4-channelled data

logger and was then registered to a database to obtain data at

every second for each channel with time dependence.

A GreenLine type HOBO U12 data register was used for

these registering processes. The photos of the data-logger, the

detail from the software form and the data-logger connected

to the computer and the thermocouple in the welded parts are

shown in Figures 8-10.

Table II Experimental results for factors

Trial no

Friction pressure x1(MPa)

Friction time x2(sec)

Tensile strength

(MPa)

1 30 3 270

2 35 4 760

3 30 5 764

4 35 6 650

5 40 7 225

Table III Parameters used in the friction welding experiments

Diameter

of

rotating

work-

piece D(mm)

Diameter

of axially

sliding

work-

piece d(mm)

Friction

time tf(sec)

Friction

pressure

Pf(MPa)

Upset

time tu(sec)

Upset

pressure

Pu(MPa)

10 10 5 30 20 110

Figure 5 The effect of friction time on the tensile strength

AISI 1040 D = 10mm. , d = 10mm. (Pf = 30 MPa. Pu = 110 MPa. tu = 20sec)

0

100

200

300

400

500

600

700

800

900

1,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Friction Time (tf - sec.)

Ten

sile

Str

engt

h (M

Pa.)

Figure 4 Part dimensions used in the experiments

Pf (MPa),tf (sec)

s (rpm)D=10 (mm) d=10 (mm)

AISI 1040 AISI 1040

Evaluation of temperature and properties

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Volume 28 · Number 4 · 2008 · 308–316

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Friction welding was carried out in the continuous drive

friction machine. When the experiment was started, the

friction welding machine was first operated for about 5 sec.

The two parts were then pressed together under an applied

pressure (30MPa), and the temperature changes in the

interface of joints were monitored using the thermocouples

installed in the specimens. The temperature data was

acquired through a data-logger. After the motor stopped,

pressure was increased to 110MPa. The latter pressure was

maintained until the parts cooled down (20 sec). The

temperature changes in the interface of joints were

monitored until the temperature decreased to the levels

below room temperature.

3. Results and discussion

3.1 Micro-photo and hardness measurement of welded

parts

Microstructures of the base metal and weld interface after

being etched in picral are shown, respectively, in Figure 11 (a)

and (b).The base metal consists of large pearlite grains surrounded

by a ferrite network. The microstructure taken from the weld

interface also consists of pearlite and a broken-down ferrite

network.Hardness variations of the joints were obtained by the

Vickers hardness testing and measuring locations. The

hardness variations on the horizontal direction of the welded

parts are shown in Figure 12.The maximum hardness values are obtained from the

welding interface. The hardness values increase due to the

heating and the cooling effect. The hardness values that

are equal to the normalized hardness of the test material are

raised to higher levels within the HAZ by the process. The

hardness along the horizontal distance increases to a

maximum at the welding centre as can be seen in Figure 12.As seen in the microstructure photographs, while the

microstructure of the base metal is a bigger grain, the grains in

the welding metal become smaller because of the cooling

affect of the material and the great deformation in the

interface. This condition is shown as the great hardness

increase in the interface when the hardness figure is

examined.

3.2 Measured temperature values

The sensor of the data register was changed with the thermo-

elements and calibrated according to sensors relatively. This

Figure 6 The effect of friction pressure on the tensile strength

Friction Pressure (Pf- MPa)

0 10 20 30 40 50 60 70 80 90

AISI 1040 D = 10mm., d = 10mm.(tf = 5sec. tu = 20sec. Pu = 110 MPa.)

0

100

200

300

400

500

600

700

800

900

1,000

Ten

sile

Str

engt

h (M

Pa.)

Figure 7 Schematic illustrating of locations and orientation of thermocouples

R1

R3R2

Ø10 mm, R

Pf (MPa),tf (sec)

Sliding work-piece

Locations of thermocouplesat front-face of parts

R4 (Centre of Part)

Evaluation of temperature and properties

Hilmi Kuscu, Ismail Becenen and Mumin Sahin

Assembly Automation

Volume 28 · Number 4 · 2008 · 308–316

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calibration work was carried out by a sensitive digital gauged

thermo furnace at the Mechanical Engineering Department

Laboratories of Trakya University. The friction welding

specimens that will be used in the friction welding and into

which the thermo-element was located were connected to the

data register computer. The values which have intervals of

1008C beginning from room temperature were read from the

monitor. With the help of interpolation and by using those

calibration values, this gave an opportunity to read higher

temperature values occurring in the friction welding. While

making a measurement with thermocouples, the reference

point temperature (usually, 08C in the melted ice is taken as

the reference point) is known from various sources. While

carrying out these experiments, the cold end of the

thermocouples was kept in the 188C which is room

temperature, and some corrections in the results were

carried out by taking this temperature as the reference

point. The obtained temperature values in the experiments

are given in Table IV.Consequently, because of the separate registration for these

values of each channel for each second, the temperature

variation graphic obtained from the datum is given in

Figure 13.The high temperature that comes out during friction of

parts while making the temperature variation measurements

has caused some short circuits (errors) between the

thermocouples and the work-piece. For this reason, the

experiments were repeated with some experiment materials

until the measurement results in the Figure 13 were obtained.The temperatures rise up to a maximum value during a

time period of 5 sec. of the frictional contact. They then

remain at a somewhat steady state level at the end of the

heating stage and during the forging stage. Thus, steady

conditions are approached during the deformation stage. The

measured temperature values are harmonious with the prior

experimental studies as demonstrated (Sluzalec, 1990; Fu and

Duan, 1998; Balasubramanian et al., 1999).

Figure 9 A detail from software form of the data-logger

Figure 8 The photo of GreenLine HOBO U12 data-logger Figure 10 Data-logger connected to computer and thermocouple inwelded parts

(b)

(a)

Evaluation of temperature and properties

Hilmi Kuscu, Ismail Becenen and Mumin Sahin

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Volume 28 · Number 4 · 2008 · 308–316

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4. Conclusions

. In this study, temperature variations were measured at

different points by thermocouples. Even though the small

amounts of changes in the room temperature are

negligible, some measurement errors can be seen during

the measurements. Hence, to use some varnishes or

special solutions which can stand high temperatures and

form an isolation layer by solidifying at those high

temperatures can be useful in order to avoid the short

circuits during the experiments.. The variations in the welding pressures primarily affect the

rate of the deformation of the rubbing surfaces and

the temperature gradient. The maximum temperature in

the joint during frictional heating depends not only on the

pressure, but also on the temperature gradient which

depends on the rotational speed in particular.. Temperature has a substantial effect on the mechanical

and metallurgical properties of the joint.. The tensile strengths of the welded parts are about

95 percent of those of the AISI 1040 parts which are the

base metal. As can be seen in Figures 5 and 6, the

changing of the friction time and the friction pressure

results in the changing of the welding strengths of the

joints. For the lower values of the friction time or the

friction pressure in Figures 5 and 6, welding strengths

increase with increasing friction time and pressure. As

expected, the welding strength reaches a maximum value

and turns down. Beyond the maximum point, the

produced heat causes regional melting, which decreases

the welding strength.

Figure 12 Hardness variations along the horizontal distance

AISI 1040 JointsD = 10mm - d = 10mm

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750

–4 –3 –2 –1 0 1 2 3 4

Horizontal Distance (mm)

Vic

kers

Har

dnes

s (H

V)

HorizontalDistances (x)

Sliding PartRotating Part

Weld-Center

Figure 11 Microstructures of the joint

25 µm

(a) Microstructure of basemetal

(b) Microstructure of weld interface

25 µm

Evaluation of temperature and properties

Hilmi Kuscu, Ismail Becenen and Mumin Sahin

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Table IV Temperature values obtained in the experiments

Temperatures (08C)

Time (sec) R1 5 2R/3 R2 5 R/2 R3 5 R/3 R4 5 0

0 0 0 0 0

1 269.2913386 153.8057743 0 115.4855643

2 307.6115486 230.7086614 38.58267717 115.4855643

3 576.9028871 346.1942257 153.8057743 384.5144357

4 769.0288714 807.3490814 538.32021 501.365

5 1,368 1,191.863517 812.472 1,001.858

6 1,076.251969 922.4461942 513.493 667.824

7 999.3490814 783.8635171 423.5144357 571.356

8 922.4461942 745.5433071 385.1942257 545.989

9 845.5433071 706.9606299 346.6115486 473.652

10 806.9606299 652 346.6115486 416.9317585

11 768.6404199 630.0577428 308.2913386 378.8740157

12 730.0577428 591.7375328 308.2913386 378.6115486

13 691.7375328 553.1548556 308.2913386 378.8740157

14 653.1548556 484 269.7086614 340.0288714

15 614.8346457 464 308.2913386 378.8740157

16 576.2519685 421.523 269.7086614 340.0288714

17 499.3490814 425.871 269.7086614 301.7086614

18 461.0288714 400.982 231.3884514 263.3884514

19 422.4461942 365.254 231.3884514 263.3884514

20 384.1259843 347.281 231.3884514 263.3884514

21 384.1259843 345.5433071 235.414 301.9711286

22 345.5433071 307.2230971 231.3884514 283.653

23 307.2230971 282 192.8057743 224.8057743

24 268.9028871 268.9028871 192.8057743 224.8057743

25 268.9028871 230.32021 192.8057743 263.3884514

26 230.32021 230.32021 192.8057743 224.8057743

27 192 192 192.8057743 206.8355206

28 192 191 192.8057743 192.5273091

Figure 13 Measured temperature values in friction welds

0

200

400

600

800

1,000

1,200

1,400

1,600

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Time (s)

Tem

pera

ture

(°C

)

R1=2xR/3

R2=R/2

R3=R/3

R4=0

Evaluation of temperature and properties

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. In this study, the effect of the welding optimum valuesachieved with the help of the statistical analysis on thejoining quality was important, and helped in the case ofcarrying out experiments in a short time and obtainingresults.

. As it can be seen from the microstructures, although thesizes and forms of the pearlite and ferrite grains werechanged, all the structures consisted of pearlite and ferrite.For that reason, the strength of the joints is nearly thesame as that of the original material strength.

. Subsequently, the maximum hardness values are obtainedfrom the weld interface because of the increasingtemperature and the rapid cooling at the joint-interfaceas seen from the temperature measurement. Then, thedeformation at the interface causes a strong decrease inthe grain size, which leads to a hardening in the region ofthe interface. Therefore, it can be observed that hardnessat the weld interface is increased by deformation.

. It is important to note that the measurement process wassuccessfully accomplished in this study although it wasparticularly difficult to obtain a temperature measurementdue to the large deformations at the interface.

References

Akata, H.E. and Sahin, M. (2003), “An investigation on theeffect of dimensional differences in friction welding of AISI1040 specimens”, Ind. Lub. & Tribo., Vol. 55 No. 5,pp. 223-32.

Balasubramanian, V., Li, Y., Stotler, T., Crompton, J.,Soboyejo, A., Katsube, N. and Soboyejo, W. (1999),“A new friction law for the modelling of continuous drivefriction welding: applications to 1045 steel welds”, Mat. andMan. Proc., Vol. 14 No. 6, pp. 845-60.

Bendzsak, G.J., North, T.H. and Li, Z. (1997), “Numericalmodel for steady-state flow in friction welding”, ActaMatellurgica, pp. 1735-45.

D’Alvise, L., Massoni, E. and Walloe, S.J. (2002), “Finiteelement modelling of the inertia friction weldingprocess between dissimilar materials”, J. Mat. Proc. Tech.,Vol. 125-126, pp. 387-91.

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Corresponding author

Mumin Sahin can be contacted at: mumins@trakya.edu.tr

Evaluation of temperature and properties

Hilmi Kuscu, Ismail Becenen and Mumin Sahin

Assembly Automation

Volume 28 · Number 4 · 2008 · 308–316

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