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

Table 7

Results of ultimate strength weighted analysis of variance.

Estimated effects and coefficients for avg. US (coded units)
Term		Effect	Coef.	SE coef.	T
Constant		—	442.97	2.973	148.99	0.0
rpm		−48.23	−24.12	1.860	−12.96	0.0
s/mm		−43.49	−21.75	2.798	−7.77	0.001
Ct Pt		—	34.26	3.629	9.44	0.0
		S = 0.3170	R^2 = 97.93%	R^2(adj) = 96.68%
Analysis of variance for avg. US (coded units)
Source	DF	Seq. SS	Adj. SS	Adj. MS	F
Main effects	2	14.7680	23.677	11.838	117.76	0.0
Curvature	1	8.9605	8.9605	8.9605	89.13	0.0
Residual error	5	0.5027	0.5027	0.1005	—	—
Lack of fit	1	0.0464	0.0464	0.0464	0.41	0.558
Pure error	4	0.4563	0.4563	0.1141	—	—
Total	8	24.2317	—	—	—	—
Estimated coefficients for avg. US using data in uncoded units
Term	Coef.
Constant	611.11
rpm	−0.057
s/mm	−163.52
Ct Pt	34.26