Depth Detection of Material Surface Defects Based on Laser Thermography

Jiaqi Liu; Zhijie Zhang; Zhenyu Lin; Wuliang Yin

doi:10.3788/LOP202158.0411002

Journals >Laser & Optoelectronics Progress >Volume 58 >Issue 4 >Page 0411002 > Article

Laser & Optoelectronics Progress
Vol. 58, Issue 4, 0411002 (2021)

Depth Detection of Material Surface Defects Based on Laser Thermography

Jiaqi Liu¹, Zhijie Zhang^1、*, Zhenyu Lin¹, and Wuliang Yin^1、2

Author Affiliations

¹Key Laboratory of Instrumentation Science & Dynamic Measurement of Ministry of Education, North University of China, Taiyuan,Shanxi 0 38507, China;

²School of Electrical and Electronic Engineering, University of Manchester, Manchester M139PL, UK

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DOI: 10.3788/LOP202158.0411002 Cite this Article Set citation alerts

Jiaqi Liu, Zhijie Zhang, Zhenyu Lin, Wuliang Yin. Depth Detection of Material Surface Defects Based on Laser Thermography[J]. Laser & Optoelectronics Progress, 2021, 58(4): 0411002 Copy Citation Text

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Fig. 1. Schematic of laser heating

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Fig. 2. Schematic of proposed system

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Fig. 3. Schematic of material characteristics

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Fig. 4. Infrared images of defects

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Fig. 5. Change of gray value at different defects. (a) No. 5 defect; (b) No. 10 defect; (c) No. 15 defect

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Fig. 6. Relationship between temperature and defect depth

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Fig. 7. Fitting curve between temperature of point B and defect depth when temperature of point A is 322.15 K

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Defect depth /mm	Gray value	Temperature /K
0.13	124	320.20
0.26	119	317.60
0.39	117	316.50
0.52	112	313.70
0.65	110	312.60
0.78	109	312.00
0.91	108	311.40
1.04	108	311.40
1.17	106	310.30
1.30	105	309.65
1.43	103	308.50
1.56	100	306.70
1.69	98	305.05
1.82	98	305.05
1.95	96	304.50
2.08	90	300.85
2.21	89	299.85
2.34	87	298.50
2.47	83	295.83

Table 1. Change of gray value and temperature of point B

Fitting curve	Fitting equation	SSE	RMSE
Exponential equation	T_B=345-26.28exp(0.25d_depth)	19.79	1.112
Linear equation	T_B=320.1-8.97d_depth	23.74	1.18
Quadratic equation	T_B =-0.93d_{depth 2}-6.56d_depth +319	20.42	1.13

Table 2. Parameters of fitting equations

Defect depth /mm	0.13	0.26	0.39	0.52	0.65	0.78	0.91	1.04	1.17	1.30
‖e‖	0.22	0.21	0.13	0.20	0.24	0.19	0.14	0.01	0.03	0.02
Defect depth /mm	1.43	1.56	1.69	1.72	1.95	2.08	2.21	2.34	2.47
‖e‖	0.01	0.04	0.04	0.08	0.09	0.10	0.02	0.01	0.05

Table 3. Residuals between fitting equation and measured data

Various parameters of fitting curve when temperature of A is 320.15 K
Fitting curve		Fitting equation		SSE		RMSE
Exponential equation		T_B=321.7-3.81exp(0.51d_depth)		4.53		0.53
Linear equation		T_B=318.9-3.88d_depth		7.94		0.68
Quadratic equation		T_B =-0.89d_{depth 2}-1.56d_depth +317.9		4.85		0.55
Various parameters of fitting curve when temperature of A is 317.15 K
Fitting curve		Fitting equation		SSE		RMSE
Exponential equation		T_B=321.8-6.45exp(0.33d_depth)		4.25		0.51
Linear equation		T_B=316-3.29d_depth		5.61		0.57
Quadratic equation		T_B =-0.58d_{depth 2}-1.77d_depth +315.3		4.27		0.52
Various parameters of fitting curvewhen temperature of A is 314.15 K
Fitting curve	Fitting equation		SSE		RMSE
Exponential equation	T_B=317-4.33exp(0.39d_depth)		3.96		0.49
Linear equation	T_B=313.3-2.91d_depth		4.21		0.50
Quadratic equation	T_B =-0.26d_{depth 2}-2.23d_depth+313		3.98		0.50

Table 4. Parameters of fitting equations

Jiaqi Liu, Zhijie Zhang, Zhenyu Lin, Wuliang Yin. Depth Detection of Material Surface Defects Based on Laser Thermography[J]. Laser & Optoelectronics Progress, 2021, 58(4): 0411002

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