Research Article

Mechanical Properties Optimization of Friction Stir Welded Lap Joints in Aluminium Alloy

Table 9

Results of elongation analysis of variance (nugget zone).

Estimated effects and coefficients for avg. El (coded units)
TermEffectCoef.SE coef.T
Constant19.4170.561234.600.018
rpm−19.500−9.7500.5612−17.370.037
s/mm−3.500−1.7500.5612−3.120.198
rpm ∗ s/mm0.8330.4170.56120.740.593
Ct Pt9.8501.0899.040.070
S = 0.619324R2 = 99.82%R2(adj) = 99.09%

Analysis of variance for avg. El (coded units)
SourceDFSeq. SSAdj. SSAdj. MSF
Main effects2179.25149.8074.90195.260.051
2-Way interactions10.2560.2110.2110.550.593
Curvature131.3731.3731.3781.800.070
Residual error10.3840.3840.384
Pure error10.3840.3840.84
Total5211.26

Estimated coefficients for avg. El using data in uncoded units
TermCoef.
Constant71.56
rpm−0.026
s/mm−23.51
rpm ∗ s/mm0.0074
Ct Pt9.85