Influence of localized microstructure evolution on second harmonic generation of guided waves

2014 ◽  
Author(s):  
Gloria Choi ◽  
Yang Liu ◽  
Clifford J. Lissenden ◽  
Joseph Rose
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Microstructure Evolution ◽  
Guided Waves ◽  
Second Harmonic

Cumulative Second Harmonic Generation of Ultrasonic Guided Waves Propagation in Tube-Like Structure

2016 ◽  
Vol 24 (03) ◽  
pp. 1650011 ◽  
Author(s):  
Weibin Li ◽  
Mingxi Deng ◽  
Younho Cho
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Polyvinylidene Fluoride ◽  
Guided Waves ◽  
Second Harmonic ◽  
Cumulative Effect ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Material Nonlinearity ◽  
Fundamental Wave

Second harmonic generation of ultrasonic waves propagating in unbounded media and plate-like structure has been vigorously studied for tracking material nonlinearity, however, second harmonic guided wave propagation in tube-like structures is rarely studied. Considering that second harmonics can provide sensitive information for structural health condition, this paper aims to study the second harmonic generation of guided waves in metallic tube-like structures with weakly nonlinearity. Perturbation method and modal analysis approach are used to analyze the acoustic field of second harmonic solutions. The conditions for generating second harmonics with cumulative effect are provided in present investigation. Flexible polyvinylidene fluoride comb transducers are used to measure fundamental wave modes and second harmonic ones. The work experimentally verifies that the second harmonics of guided waves in pipe have a cumulative effect with propagation distance. The proposed procedure of this work can be applied to detect material nonlinearity due to damage mechanism in tube-like structure.

QUASI-PHASE-MATCHED SECOND-HARMONIC GENERATION IN NONLINEAR OPTICAL POLYMER WAVEGUIDE

2004 ◽  
Vol 13 (03n04) ◽  
pp. 383-389 ◽  
Author(s):  
JUNG JIN JU ◽  
SEUNG KOO PARK ◽  
JUNG YUN DO ◽  
SUNTAK PARK ◽  
MIN-SU KIM ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Guided Waves ◽  
Second Harmonic ◽  
Device Fabrication ◽  
Polymer Waveguide ◽  
Material Development ◽  
Optical Polymer ◽  
Waveguide Design ◽  
Nonlinear Optical Polymer

We address issues related to quasi-phase-matched (QPM) second-harmonic generation (SHG) in nonlinear polymer waveguide for applying at optical communication. This field of research is very challenging because the high nonlinearity of polymers leads the device to operate at low pump power levels. However, key problems to this approach include difficulty of phase matching, the high propagation losses of the guided waves, and low nonlinearity contrast in the +/0 type QPM geometry. By optimizing these points on material development, waveguide design, and device fabrication, we demonstrate a QPM SHG with the best efficiency in polymer waveguide.

scholarly journals Bolted joint integrity monitoring with second harmonic generated by guided waves

2018 ◽  
Vol 18 (1) ◽  
pp. 193-204 ◽  
Author(s):  
Yi Yang ◽  
Ching-Tai Ng ◽  
Andrei Kotousov
Keyword(s):  
Finite Element ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Guided Waves ◽  
Second Harmonic ◽  
Fatigue Cracks ◽  
Bolted Joint ◽  
Contact Nonlinearity ◽  
Bolt Loosening ◽  
Joint Integrity

In this study, the second harmonic generation due to the contact nonlinearity caused by bolt loosening is studied experimentally and numerically using three-dimensional explicit finite element simulations. In particular, it is demonstrated that the magnitude of the second harmonic generation normally increases with the loosening of the bolted joint, and there is a reasonable agreement between the numerical simulations and experimental results. The finite element model, which was validated against the experimentally measured data, is further utilized to investigate an important practical situation when a loosened bolt is weakened by fatigue cracks located at the edge of the hole. The numerical case studies show that the contact nonlinearity and the change of the behaviour of the second harmonic generation with the tightening level are very different to the corresponding results with the fatigue cracks. This identified difference in the second harmonic generation behaviour can serve as an indicator of the bolted joint integrity and thus provide early warning for engineers to make decision on the necessity of carrying out further safety inspections. Overall, the findings of this study provide improved physical insights into second harmonic generation for bolt loosening, which can be used to further advance damage detection techniques using nonlinear guided waves.

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