Mahatma Gandhi Mission's College Of Engineering and Technology

Noida, 2013012014-2015

Project PresentationOPTIMIZATION OF PROCESS PARAMETERS IN TIG

WELDING USING TAGUCHI METHOD AND REGRESSION ANALYSIS

Project Guide: Presented byMr. Abhijit A. Kulkarni Sukhendu Singh (1109540036) Varun Grover (1109540038) Vivek Bisht (1109540043)

INTRODUCTION

• TIG Welding is a non consumable electrode.• Arc produced between Tungsten electrode &

work piece.• Used for thin section jobs.• Metals that can be welded are MS, SS, &

Non-Ferrous like Aluminum etc.• Shielding gas prevents oxidation.• Filler material is optional.• Slower weld speeds with stronger welds.

OPTIMIZATION OF TIG WELDING PROCESS PARAMETERS

GOAL: Optimize process parameters for TIG welding.

• The purpose is to efficiently determine the optimum welding parameters for achieving the HIGHEST ULTIMATE TENSILE STRENGTH in the range of parameters.

• In order to meet the purpose in terms of both efficiency and effectiveness, TAGUCHI METHOD AND REGRESSION ANALYSIS are utilized.

NEED FOR OPTIMIZATIONENSURING

QUALITY

OF PRODUC

TREDUCING MANUFACTURING

COST

INCREASING PRODUCTIVITY

INCREASING TENSILE STRENGTH

Taguchi methods  are statistical methods developed by Genichi Taguchi to improve the quality of manufactured goods.

The data is collected & arranged as an “ORTHOGONAL ARRAY”.Experiments which gives most reduced variance for the experiment with optimum settings of control parameters are used.

Thus the merger of Design of Experiments with Optimization of Control parameters to obtain the most appropriate or optimized results is achieved by the Taguchi Method.

TAGUCHI METHOD

REGRESSION ANALYSIS

Regression analysis then chooses among all possible lines by selecting the one for which the sum of the squares of the estimated errors is at a minimum.

Regression analysis is a statistical process for estimating the relationships among variables. It includes many techniques for modeling and analyzing several variables, when the focus is on the relationship between a dependent variable and one or more independent variable.

Y = β0 + β1X1 + β2X2 + βnXn + ε

PARAMETERS INVOVLED

TIG WELDING

CURRENT

ELECTRODE DIA

GAS FLOW RATE

WELD STRENGTH

INPUT OUTPUT

ORTHOGONAL ARRAY• To investigate how different parameters

affect the mean and variance of a process performance characteristic.

• These designs can be used to estimate main effects using only a few experimental runs.

• For doing Experiment on TIG welding, we are using (L9) Orthogonal matrix method.

RUN COLUMNS

I II III IV

1 1 1 1 1

2 1 2 2 2

3 1 3 3 3

4 2 1 2 3

5 2 2 3 1

6 2 3 1 2

7 3 1 3 2

8 3 2 1 3

9 3 3 2 1

PARAMETERS(NOTATION)

VALUES

UNITS LEVEL 1 LEVEL 2 LEVEL 3

CURRENT (I)

A 90 120 150

ELECTRODEDIAMETER

(ED)

mm 1.60 2.10 2.40

FLOW RATE (F)

kg/cm² 5 6 7

ORTHOGONAL ARRAY NOMENCLATURE

RUN I ED F1 1 1 12 1 2 23 1 3 34 2 1 25 2 2 36 2 3 17 3 1 38 3 2 19 3 3 2

ORTHOGONAL INPUT ARRAY

EXPERIMENTAL WORK

EXPERIMENT RESULTCURRENT(A) ELECTRODE

DIA (B)FLOW RATE

(C)UTS S/N RATIO

90 1.6 5 397.95 51.996

90 2.1 6 324.24 50.217

90 2.4 7 422.00 52.506

120 1.6 6 512.39 54.192

120 2.1 7 579.90 55.267

120 2.4 5 638.64 56.105

150 1.6 7 320.46 50.115

150 2.1 5 523.97 54.386

150 2.4 6 534.60 54.561

DESIGN OF EXPERIMENT• Design of experiments is a series of tests in which purposeful

changes are made to the input variables of a system or process and the effects on response variables are measured.

• Design of experiments is applicable to both physical processes and computer simulation models

• Experimental design is an effective tool for maximizing the amount of information gained from a study while minimizing the amount of data to be collected.

• Factorial experimental designs investigate the effects of many different factors by varying them simultaneously instead of changing only one factor at a time.

WELDED WORKPIECE

Two work pieces of (100x50x3mm) are welded together to get the final work piece.

DIMENSIONS : 200x50x3 mm

TEST SPECIMENRECTANGULAR STRIP TYPE

DIMENSIONS : 200x28x3 mm

TEST SPECIMENS

S1 S2 S3

SPECIMEN AFTER TESTING

All the specimens failed at the weldment.

CRACK DEFORMATION MODES

Mode-I corresponds to fracture where the crack surfaces are displaced

normal to themselves. This is a typical tensile type of fracture.

SOLUTION BY MINITAB

DETERMINE OF RESPONSE TABLE

CALCULATION OF RANKCURRENT(A) ELECTRODE

DIAMETER (B)FLOW RATE(C) S/N RATIO

1 1 1 51.996

1 2 2 50.217

1 3 3 52.506

2 1 2 54.192

2 2 3 55.267

2 3 1 56.105

3 1 3 50.115

3 2 1 54.386

3 3 2 54.561

RESPONSE TABLE S/N RATIO OF UTS

LEVEL CURRENT(A) ELECTRODEDIAMETER (B)

FLOW RATE(C)

1 51.57 52.10 54.16

2 55.19 53.29 52.51

3 53.02 54.39 52.63

DELTA=MAX-MIN

3.61 2.29 1.65

RANK 1 2 3

MAIN EFFECT PLOTS FOR ULTIMATE TENSILE STRENGTH

ONE WAY ANOVA:S/N RATIO VS CURRENT

SOURCE ADJ SS DOF ADJ M.S F P

CURRENT 14.76 2 7.379 1.97 0.220

ERROR 22.51 6 3.752

TOTAL 37.26 8

ANOVA GRAPH FOR CURRENT

ANOVA GRAPH FOR CURRENT

ONE WAY ANOVA:S/N RATIO VS ELECTRODE

SOURCE ADJ

SS

DOF ADJ

M.S

F P

ELECTRODE

DIAMETER

7.867 2 3.934 0.80 0.491

ERROR 29.4011 6 4.9002

TOTAL 37.267 8

ANOVA GRAPH FOR ELECTRODE DIAMETER

ANOVA GRAPH FOR ELECTRODE DIAMETER

ONE WAY ANOVA:S/N RATIO VS GAS FLOW RATE

SOURCE ADJ SS DOF ADJ M.S F P

FLOW

RATE

1.824 2 0.9116 0.15 0.86

ERROR 35.443 6 5.9075

TOTAL 37.2677 8

ANOVA GRAPH FOR GAS FLOW RATE

ANOVA GRAPH FOR GAS FLOW RATE

ANALYSIS OF VARIANCE FOR S/N RATIO

All the three one-way ANOVA is calculated for S/N ratio and finally merged together to form a single ANALYSIS OF VARIANCE for S/N ratio.

Since the total of all the one-way ANOVA for current, electrode diameter and flow rate is same therefore it is taken as constant for the resultant in the ANOVA for S/N ratio which is marked with line in.

After applying the value of constant total value in the main ANOVA table, the error and finally F and P values of ANOVA table can be calculated according to those values, the calculated value is shown in table.

ANOVA FOR S/N RATIO COMBINATION OF ALL

SOURCE SEQ SS DOF M.S F P

CURRENT 14.756 2 7.3754 1.15 0.468* Significant

ELECTRODE

DIAMETER

7.866 2 3.933 0.61 0.620

FLOW RATE 1.8234 2 0.9117 0.14 0.875

ERROR 12.820 2 6.4100

TOTAL 37.264 8

NORMAL PROBABILITY PLOT OF RESIDUAL FOR UTS (Mpa)

PLOT OF RESIDUAL vs FITTED UTS VALUES

MATHEMATICAL MODEL

Using multiple linear regression and correlation analysis, mathematical models for Ra is obtained as follows

Ra = a0 + a1*x1 + a2*x2 + a3*x3

Where a0, a1, a2, a3 are constant coefficient

X1 = CurrentX2 = Electrode diameterX3 = Flow rate

RESULT

• Main effects plots revel that current and electrode diameter are the factors which has considerable influence on ultimate tensile strength. Flow rate has small / lesser influence.

• The optimum welding condition obtained by Taguchi method are:

CURRENT = 120 A

ELECTRODE DIAMETER = 2.4 mm

FLOW RATE = 5 kg/cm2

RESULT

The Regression Equation is :

ULTIMATE TENSILE STRENGTH = (1.882667 x Current) + (149.7731 x Electrode diameter) – (22.36 x Flow rate) + 176.385

The maximum strength in our case by using this equation is 649.96 MPa.

CONCLUSION

•From the ANOVA results, it is found that none the welding parameter current has effecting the ultimate tensile stress.

•Main effects plots revel that current and electrode diameter are the factors which has considerable influence on ultimate tensile strength. Flow rate has small / lesser influence.

•Confirmation test is confirms the improvement of the UL which also indicates the validity of the present optimization procedure by using Taguchi methodology.

CONCLUSION The strip specimens have simpler geometry and are easier to fabricate,

they are not a good choice for tensile testing because of large stress

concentration factors (as high as 1.84, for the materials properties used

in the analysis).

The dumbbell specimens with sharp junctions should also be avoided

because of the relatively high stress concentration factors (1.16–1.74,

for the materials properties used in the analysis).

The dumbbell specimens with rounded junctions are the preferred

specimen shape. The ratio of the radius of fillet to the gage width

should be maximized, so as to minimize stress concentration factors.

WELDING FIXTURE

SIMPLE FIXTURE MADE AFTER ANAZLYZING THE PROBLEMS FACED.

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