An Impact-Echo Experimental Approach for Detecting Concrete Structural Faults

Table 3

Peak frequency.

Number	Plate thickness frequency			Defect frequency
	ftheory	fcalculate	ᅀf (%)	Ftheory	Fcalculate	ᅀF (%)
1–1	6206.3	4988.0	19.6	16296.4	16420	3.0
2–1		5072.0	18.3	16296.4	16542	2.3
3–1		5233.0	15.7	16296.4	16485	2.6
4–1		6080.0	2.1	/	/	/
1–2		4673.0	24.7	16296.4	16180	4.4
2–2		4821.0	22.3	16296.4	16277	4.1
3–2		4904.0	20.9	16296.4	16331	3.5
4–2		6053.0	2.5	/	/	/
5		5581.0	10.1	16477	16025	2.7
6		5883.0	5.2	16477	15810	4.1
7		6334.0	−2.1	/	/	/
8		6334.0	−2.1	/	/	/
9		5306.0	14.5	13299.2	12768.5	3.8
10		5306.0	14.5	16926.4	16255.0	3.9

Notes. (1) 1–1 in the table is a corrugated metal pipe; 1–2 is the PVC corrugated pipe; the rest are similar. The rest of the number corresponds to the working conditions in Table 2. (2) “/” in the table indicates that there is no such content, and the above frequency unit is kHz. (3) ᅀf = (f_theory − f_calculate)/ f_theory; ᅀF = (F_theory − F_calculate)/F_theory; ᅀF takes absolute value.