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

Table 4

Results of yield strength weighted analysis of variance.

Estimated effects and coefficients for avg. Ys (coded units)
Term		Effect	Coef.	SE coef.	T
Constant		—	346.718	3.953	87.71	0.0
rpm		−15.948	−7.974	3.004	−2.65	0.0045
s/mm		−17.026	−8.513	3.413	−2.49	0.0055
Ct Pt		—	8.469	4.903	1.73	0.45
		S = 0.533470	R^2 = 73.27%	R^2(adj) = 57.24%
Analysis of variance for avg. Ys (coded units)
Source	DF	Seq. SS	Adj. SS	Adj. MS	F
Main effects	2	3.051	3.709	1.855	6.52	0.040
Curvature	1	0.849	0.850	0.850	2.98	0.145
Residual error	5	1.423	1.422	0.285	—	—
Lack of fit	1	0.031	0.030	0.030	0.09	0.782
Pure error	4	1.393	1.392	0.348	—	—
Total	8	5.327	—	—	—	—
Estimated coefficients for avg. Ys using data in uncoded units
Term	Coef.
Constant	406.30
rpm	−0.019
s/mm	−64.01
Ct Pt	8.47