Analytical and Experimental Study of Fatigue-Crack-Growth AE Signals in Thin Sheet Metals

Abstract

The acoustic emission (AE) method is a very popular and well-developed method for passive structural health monitoring of metallic and composite structures. AE method has been efficiently used for damage source detection and damage characterization in a large variety of structures over the years, such as thin sheet metals. Piezoelectric wafer active sensors (PWASs) are lightweight and inexpensive transducers, which recently drew the attention of the AE research community for AE sensing. The focus of this paper is on understanding the fatigue crack growth AE signals in thin sheet metals recorded using PWAS sensors on the basis of the Lamb wave theory and using this understanding for predictive modeling of AE signals. After a brief introduction, the paper discusses the principles of sensing acoustic signals by using PWAS. The derivation of a closed-form expression for PWAS response due to a stress wave is presented. The transformations happening to the AE signal according to the instrumentations we used for the fatigue crack AE experiment is also discussed. It is followed by a summary of the in situ AE experiments performed for recording fatigue crack growth AE and the results. Then, we present an analytical model of fatigue crack growth AE and a comparison with experimental results. The fatigue crack growth AE source was modeled analytically using the dipole moment concept. By using the source modeling concept, the analytical predictive modeling and simulation of the AE were performed using normal mode expansion (NME). The simulation results showed good agreement with experimental results. A strong presence of nondispersive S0 Lamb wave mode due to the fatigue crack growth event was observed in the simulation and experiment. Finally, the analytical method was verified using the finite element method. The paper ends with a summary and conclusions; suggestions for further work are also presented.

Crack-Length Estimation for Structural Health Monitoring Using the High-Frequency Resonances Excited by the Energy Release during Fatigue-Crack Growth

“…A 1/3 mm element size for the length and thickness of the model was used for the finite element meshing. The dipole moment excitation concept [ 27 , 42 ] was used for the modeling of a fatigue-crack growth source cause by a crack growth event. In this approach, the AE source caused by a fatigue-crack growth event was considered to be self-equilibrating dipole forces (M11 moment tensor) acting at the crack tip.…”

“…In this approach, the AE source caused by a fatigue-crack growth event was considered to be self-equilibrating dipole forces (M11 moment tensor) acting at the crack tip. In previous research, this source definition has been implemented for fatigue-crack growth AE numerical prediction and sensing using a PWAS sensor, and validated using experimental investigation [ 42 ]. Figure 3 a,b present the modeling details of the dipole force.…”

Passive Wireless Dual-Tag UHF RFID Sensor System for Surface Crack Monitoring

“…In civil machinery and aviation systems, the failure and fatigue of metallic objects may cause economic loss and endanger personal safety [ 2 ]. Therefore, the detection of stress and fatigue cracks are important aspects of in-depth evaluation of sensitive metallic structures [ 3 ]. We can detect failures by embedding compact and portable sensors in the structure.…”

Application of Laser Vibrometry to Assess Defects in Ship Hull’s Welded Joints’ Technical Condition

“…NDT testing techniques are well researched and give results with usually sufficient reliability [ 10 , 11 , 12 , 13 , 14 ]. However, they have a fundamental disadvantage—they are carried out periodically.…”