Improvement of tensile strength of butt welded joints prepared by vibratory welding process

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –

6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

53

IMPROVEMENT OF TENSILE STRENGTH OF BUTT WELDED JOINTS

PREPARED BY VIBRATORY WELDING PROCESS

P. Govindarao1, Dr. P. Srinivasarao

2, Dr. A. Gopalakrishna

3 and C V sriram

4

1Associate Professor, Dept. of Mechanical Engineering, GMRIT, Rajam, Andhra Pradesh,

2Professor, Dept. of Industrial Engineering, GITAM University, Vishakhapatnam, Andhra Pradesh

3 Professor, Dept. of Mechanical Engineering, JNTU Kakinada, Andhra Pradesh

4 Dept. of Mechanical Engineering, Andhra University, Andhra Pradesh

ABSTRACT

Vibration techniques have been used in welding for improving the mechanical properties of

metals in the last few decades. In the present work vibratory setup has been used for inducing

mechanical vibrations into the weld pool during welding. The designed vibratory setup produces the

required frequency with the amplitude and acceleration in terms of voltages. An increase in the

tensile strength of the weld pieces in to the heat affected zone (HAZ) has been observed. The

increase in mechanical properties is attributed to, as the weld pool solidifies, grains are not only

limited in size but also dendrites are broken before they grow large in size. Refined microstructure

has been observed. The above mechanism is responsible for the improvement in tensile strength of

weld pieces welded with vibratory setup compared to without vibration during welding.

I. INTRODUCTION

In manual metal arc welding (MMA) process, an arc is drawn between a coated consumable

electrode and the work piece. The metallic core-wire is melted by the arc and is conveyed to the weld

pool as molten drops. The electrode coating is also melting to form a gas shield around the arc and

the weld pool. Slag is formed on the surface of the weld pool, and the slag must be removed after

each layer. Manual Metal Arc welding is still a widely used hard facing process. Due to the low cost

of the equipment, the low operating costs of the process and the ease of transporting the equipment,

this flexible process is ideally suited to repair work benefits of MMA Welding are: Flexible, Low

Cost, and ease of Repairs. Butt welding is used to connect parts which are nearly parallel and don't

overlaps. It can be used to run a processing machine continuously, as opposed to having to restart

such machine with a new supply of metals. Butt-welding is an economical and consistent way of

joining process without using supplementary components. Usually, a butt-welding joint is made by

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ISSN 0976 – 6340 (Print)

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slowly heating up the two weld ends with a weld plate and then combine them under specific

pressure. This process suitable for prefabrication and manufacturing special fittings afterward, the

material is usually ground down to a smooth finish and either sent on its way to the processing

machine, or sold as a completed product.

Lakshminarayanan A.K. and Balasubramanian. V [1] described about improvement in tensile

properties of 409M ferritic stainless steel welded joints in comparison with base metal. Ductility and

impact toughness of welded joints also tested for the welded joints.

Lu Qinghua, Chen Ligong and Ni Chunzhen [2] discussed about the applications of vibration

during submerged arc multi-pass welding to improve welded valve quality. The reduction in residual

deformation and stress due to vibratory weld conditioning is discussed. The enhancement of the

impact property in the weld metal due to vibratory weld conditioning is described.

Munsi A S M Y, Waddell A J and Walker C A[3] discussed about the effect of vibratory

stress on the welding microstructure and residual stress distribution of steel welded joints. The 25

percent improvement in hardness of weld joint is also discussed.

Shigeru Aoki, Tadashi Nishimura and Tetsumaro Hiroi [4] discussed about a method for

reducing the residual stress using random vibrations during welding. The residual stress in the

quenched butt-welded joint is measure by paralleled beam X-ray diffractometer with scintillation

counter.

Tewari S P and Shanker A.[5] described about improvements on yield strength, ultimate

tensile strength and breaking strength on shielded metal arc welded joints due to vibratory conditions

like longitudinal vibration and frequency. The drop in percentage of elongation due to the vibratory

conditions is discussed.

Weglowska. A, and Pietras A [6] described the influence of the welding parameters on the

mechanical properties of vibration welded joints such are tensile properties and microscopic

behaviour of dissimilar grades of nylons.

II EXPERIMENTAL WORK

The MMA welding process is an arc welding process which produces coalescence of metal

by heating them with an arc between a covered metal electrode and the work. Shielding is obtained

from decomposition of the electrode covering. Pressure is not used during the operation and the filler

metal is obtained from the electrode. The MMA welding process can be used for welding most

structural and mild steels. These include low-carbon or alloy steels; low-alloy, heat treatable steels;

and high-alloy steels such as stainless steels. This welding process can be used in all positions flat,

vertical, horizontal and requires only the simplest equipment. Thus, MMA welding lends itself very

well to field work

Material Used: Mild Steel, It is composed of (in weight percentage) 0.9% Carbon (C), 7.5-10.0% manganese

(Mn), 1.00% Silicon (Si), 17.0-19.0% Chromium (Cr), 4.0-6.0% Nickel (Ni), 0.06% Phosphorus (P),

0.03% Sulphur (S), and the base metal Iron (Fe). Fig.1. shows a typical specimen used in the current

study.

Fig 1 Specimen piece



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Equipment Used: Fig 2 shows the experimental setup of the vibrator machine, its properties and welding

process used for laying down the vibratory welding bead

Fig.2 Experimental setup

Vibratory Setup for Welding

With an aim of improving the mechanical properties of weld joints through inducing of

favourable changes in the weld microstructures, an auxiliary vibratory set up capable of inducing

mechanical vibrations into the weld pool during manual metal arc welding is designed and

developed. Different frequencies and with different amplitude are applied along the weld length,

just trailing behind the welding arc so that weld pool could be mechanically stirred in order to induce

favourable micro structural effects. This setup produces the required frequency with the amplitude

in terms of voltages.

Butt welding by MMA welding Process

In the current investigation, 5 mm thick mild steel butt joints are used. Low and high heat

input combinations are used to study the effect of mechanical vibrations. Figs.3 and 4 depict the

joining of two mild steel strips during and after the welding process.

Fig.3 During welding



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Fig.4 After welding

Butt Welded Joint at different voltages of Vibromotor: The prepared butt welded joints are under the low heat input (90-110 Amp).There are 2

umber of passes to fill the gap, in which 1 main passes and 1is root pass. During the root pass there

is no role of vibratory setup. After the root pass, vibratory setup come into action and moved just

behind the arc and make a disturbance during the solidification of weld bead. Table 1 and Table 2

illustrate the parameters variation with respect to acceleration & amplitude during the process

Table 1 Parameters variation with respect to acceleration during the analysis

Table 2 Parameters variation with respect to amplitude during the analysis

Tensile Testing: Tensile test has been conducted in UTM for Different test Specimens which are

prepared under the influence of mechanical vibration. Following fig. 4 and 5 shows the line diagram

and sample of actual tensile test specimen respectively.

Voltage Input to the

Vibromotor (Volts)

70 V 150 V 230 V

Accelerations of the tip

of the specimens (m/s2)

18.3 32.6 49.1

16.4 31.1 49.7

19.9 30.4 48.7

17.7 28.4 45.3

18.6 28.3 51.9

19.3 29.7 50.8

RMS Value 18.4 30.33 49.29

Voltage Input to the

Vibromotor (Volts)

70 V 150 V 230 V

Amplitude at the tip of

the specimen (mm)

0.238 0.274 0.350

0.233 0.269 0.348

0.230 0.266 0.347

0.235 0.270 0.349

0.242 0.275 0.352

0.240 0.273 0.351

RMS Value 0.236 0.273 0.350



57

Fig. 4 Line diagram of a tensile test specimen

Figure 5 Tensile Test Specimen before testing in UTM

Figure 6 Tensile test specimen (without vibration) after testing in UTM

Figure 7 Tensile test specimen (with vibration at 70 Volts input to the vibromotor) after testing


International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976

6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July


III RESULTS AND DISCUSSION

Tensile strength of a welded joint is increased with respect to the

and acceleration of the specimens in terms of voltage input to the vibromotor. And also tensile

strength of welded joints prepared with vibration is more compared to wi

and graphs 1, 2 and 3 shows about the

acceleration in terms of voltage input to the vibromotor

Tensile testing Results are shown in following table

Voltage input to the

vibromotor

Amplitude in mm

(RMS)

Acceleration in m/s

(RMS)

Tensile Strength

Mpa

Graphs:

Voltage input to

Graph. 1 Variation of Tensile Strength with respect to Voltage input to vibromotor

500

550

600

650

700

0

Te

nsi

le S

tre

ng

th (

Mp

a)

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976

6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

58

(with vibration at 230 Volts input to the vibromotor) after testing

III RESULTS AND DISCUSSION

e strength of a welded joint is increased with respect to the increase in the amplitude


strength of welded joints prepared with vibration is more compared to without vibration. The table 3

about the variation of tensile strength with respect to the amplitude and

acceleration in terms of voltage input to the vibromotor.

shown in following table 3

input to the

Without

Vibration

70 V 150 V 230 V

in mm 0 0.236 0.273 0.350

in m/s2 0 18.4 30.33 49.29

Tensile Strength

530

596.7

620.25

651

Voltage input to the Vibromotor (Volts)

Variation of Tensile Strength with respect to Voltage input to vibromotor

70 V 150 V 230 V


August (2013) © IAEME

(with vibration at 230 Volts input to the vibromotor) after testing

increase in the amplitude


thout vibration. The table 3

with respect to the amplitude and

Variation of Tensile Strength with respect to Voltage input to vibromotor



59

Graph. 2 Variation of Tensile Strength with respect to the amplitude of the specimen

Graph.3 Variation of Tensile Strength with respect to the Acceleration of the specimen

IV METALLURGICAL STUDY OF SPECIMENS

Metallographic study shows that during conventional butt welding the uniform long

dendrites which show that a uniform solidification process took place with uniform dendrites shown

in the fig.10 and fig.11 with acceleration and amplitude kept constant during welding current

respectively. Long dendrites show Corse structure of the weld joint. The microstructure shows the

uniform solidification process. Under vibratory conditions with acceleration and amplitude kept

changing, the microstructure of vibratory butt-weld joints, long dendrites get fragmented and

break in to small dendrites and forms a new nucleation sites. Here dendritic fragmentation took

place due to which fine structures form. This enhances the hardness and tensile strength of weld

joints

500

520

540

560

580

600

620

640

660

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Ten

sile

Str

en

gth

(M

pa

)

Amplitude of the Specimen

Tensile Strength Vs Amplitude

500

520

540

560

580

600

620

640

660

0 5 10 15 20 25 30 35 40 45 50

Ten

sile

Str

en

gth

(M

pa

)

Acceleration of the Specimen

Voltage Vs Acceleration



60

Fig 10: Microstructure of manual

metal arc welding Without vibration.

Fig 11: Microstructure of manual metal

arc welding With vibration.

V CONCLUSIONS

Tensile strength of the welded joints prepared under the influence of mechanical vibrations is

found to be more compared to welded joints prepared without vibration. This is attributed to, as the

weld pool solidifies, grains are not only limited in size but also dendrites are broken up before they

grow large in size. The microstructure of the weld metal is observed to be improved. Therefore the

tensile strength and hardness are improved in welded joints prepared under the influence of vibration

compared to without vibration. Further, the tensile strength of welded joint has also been increased

with respect to the increase in the voltage input to the vibromotor. There is also an improvement in

the tensile strength with the increase in the acceleration and amplitude of the specimens.

REFERENCES

1) Lakshminarayanan A.K. and Balasubramanian. V (2010) an assessment of microstructure

hardness, tensile and impact strength of friction stir welded ferritic stainless steel joints, 31,

pp 4592-4600.

2) Lu Qinghua, Chen Ligong and Ni Chunzhen (2006) Improving welded valve quality by

vibratory weld conditioning, Materials Science and Engineering A 457, pp246-253.

3) Munsi, A.S.M.Y. and Waddell, A.J. and Walker, C.A. (2001) the effect of vibratory stress on

the welding microstructure and residual stress distribution. Proceedings of the Institution of

Mechanical Engineers, Journal of Materials: Design and Applications, 215 (2). pp. 99-111.

4) Shigeru Aoki, Tadashi Nishimura and Tetsumaro Hiroi (2005) Reduction method for

residual stress of welded joint using random vibration, Nuclear Engineering Design,

235,pp1441-1445.

5) Tewari, S. P. and Shanker (1993), A. Effect of longitudinal vibration on the mechanical

properties of mild steel weldments. Proc. Instn Mech. Engrs, Part B, Journal of Engineering

Manufacture, 207(B3), 173–177.



61

6) Weglowska. A. and Pietras. A. (2012), Influence of the welding parameters on the structure

and mechanical properties of vibration welded joints of dissimilar grades of nylons. Archives

of civil and mechanical engineering 12, pp198-204.

7) P. Govinda Rao, Dr. C L V R S V Prasad, Dr.D.Sreeramulu, Dr.V. Chitti Babu And

M.Vykunta Rao, “Determination Of Residual Stresses Of Welded Joints Prepared Under The

Influence Of Mechanical Vibrations By Hole Drilling Method And Compared By Finite

Element Analysis” International Journal of Mechanical Engineering & Technology (IJMET),

Volume 4, Issue 2, 2013, pp. 542 - 553, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

8) U.S.Patil And M.S.Kadam, “Effect Of The Welding Process Parameter In Mmaw For Joining

Of Dissimilar Metals And Parameter Optimization Using Artificial Neural Fuzzy Interface

System” International Journal of Mechanical Engineering & Technology (IJMET), Volume 4,

Issue 2, 2013, pp. 79 - 85, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

9) P.Govinda Rao, Dr.Clvrsv Prasad, Dr.S.V.Ramana And D.Sreeramulu,“Development Of

Grnn Based Tool For Hardness Measurement Of Homogeneous Welded Joint Under

Vibratory Weld Condition” International Journal Of Advanced Research In Engineering &

Technology (IJARET) Volume 4, Issue 4, 2013, pp. 50 - 59, ISSN Print: 0976-6480, ISSN

Online: 0976-6499.

10) ravi butola, shanti lal meena and jitendra kumar, “Effect Of Welding Parameter On Micro

Hardness Of Synergic Mig Welding Of 304l Austenitic Stainless Steel” ” International

Journal of Mechanical Engineering & Technology (IJMET), Volume 4, Issue 3, 2013, pp.

337 - 343, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

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Improvement of tensile strength of butt welded joints prepared by vibratory welding process