[Retracted] Nonlinear Lamb Wave for Structural Incipient Defect Detection with Sequential Probabilistic Ratio Test

Table 1

Main components of 2A12 aluminum alloy.

Chemical composition	Cu	Si	Fe	Mn	Mg	Zn	Cr	Ti	Al
Scale scores	3.8–4.9	0.5	0.5	0.3–0.9	1.2–1.8	0.3	—	0.15	Remaining