Measurement of Interfacial Fracture Toughness of Surface Coatings Using Pulsed-Laser-Induced Ultrasonic Waves

Journal Article · Thu Mar 15 04:00:00 EDT 2018 · Journal of Nondestructive Evaluation

DOI:https://doi.org/10.1007/S10921-017-0456-Y· OSTI ID:22810167

Watanabe, Yousuke; Yonezu, Akio ^[1]; Chen, Xi ^[2]

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1. Chuo University, Department of Precision Mechanics (Japan)
2. Xi’an Jiaotong University, International Center for Applied Mechanics, SV Lab, School of Aerospace (China)

This research develops a new technique for the measurement of interfacial fracture toughness of films/surface coatings using laser-induced ultrasonic waves. Using pulsed laser ablation on the bottom substrate surface, strong stress waves are generated leading to interfacial fractures and coating delamination. Simultaneously, a laser ultrasonic interferometer is used to measure the normal (out-of-plane) displacement of the top surface coating in order to detect coating delamination in a non-destructive manner. We can thus determine the critical laser energy for delamination, yielding the critical stress (that is, the interfacial strength). Subsequently, to examine the interfacial fracture toughness, additional pulsed laser irradiation is applied to a pre-delaminated specimen to show that the delamination area expands. This type of interfacial crack growth can be visualized using laser ultrasonic scanning. Furthermore, the calculation of elastic wave propagation was carried out using a finite-difference time-domain method) in order to accurately estimate the interfacial stress field. In this calculation, the stress distribution around the initial delamination is calculated to obtain the stress intensity factor. Based on the experimental and computational results, interfacial fracture toughness can be quantitatively evaluated. Since this technique relies on a two-laser system in a non-contact approach, it may be useful for a quantitative evaluation of adhesion/bonding quality (including both interfacial fracture strength and toughness) in various environments.

• OSTI ID: 22810167
• Journal Information: Journal of Nondestructive Evaluation, Journal Name: Journal of Nondestructive Evaluation Journal Issue: 1 Vol. 37; ISSN 0195-9298; ISSN JNOED5
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
BONDING
COATINGS
CRACK PROPAGATION
FRACTURE PROPERTIES
FRACTURES
INTERFACES
INTERFEROMETERS
LASER RADIATION
LASERS
STRESS INTENSITY FACTORS
STRESSES
SURFACE COATING
ULTRASONIC WAVES
WAVE PROPAGATION