scholarly journals A Study on Fatigue State Evaluation of Rail by the Use of Ultrasonic Nonlinearity

2019 ◽  
Author(s):  
Bo Zhu ◽  
Jaesun Lee
Keyword(s):  
Longitudinal Wave ◽  
Second Harmonic ◽  
Early Stage ◽  
Wave Mixing ◽  
Third Harmonic ◽  
Longitudinal Waves ◽  
Testing Method ◽  
State Evaluation ◽  
Stress Fatigue ◽  
Train Safety

Nonlinear ultrasonic testing has been accepted as a promising manner for evaluating material integrity in an early stage. Stress fatigue is the main threats to train safety, railways examinations for stress fatigue are more significant and necessary. A series of ultrasonic nonlinear wave experiments are conducted for rail specimens extracted from railhead with different degree of fatigue produced by three-point bent loading condition. The nonlinear parameter is the indicator of nonlinear waves for expressing the degree the fatigue. The experimental results show that the sensitivity of a third harmonic longitudinal wave is higher than second harmonic longitudinal wave testing. As the same time, collinear wave mixing shows strong relative with fatigue damages than a second longitudinal wave NDT method and provides more reliable results than third harmonic longitudinal waves nonlinear testing method.

scholarly journals A Study on Fatigue State Evaluation of Rail by the Use of Ultrasonic Nonlinearity

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2698
Author(s):  
Bo Zhu ◽  
Jaesun Lee
Keyword(s):  
Longitudinal Wave ◽  
Second Harmonic ◽  
Early Stage ◽  
Wave Mixing ◽  
Third Harmonic ◽  
Longitudinal Waves ◽  
Testing Method ◽  
State Evaluation ◽  
Stress Fatigue ◽  
Train Safety

Nonlinear ultrasonic testing has been accepted as a promising manner for evaluating material integrity in an early stage. Stress fatigue is the main threats to train safety, railways examinations for stress fatigue are more significant and necessary. A series of ultrasonic nonlinear wave experiments are conducted for rail specimens extracted from railhead with different degree of fatigue produced by three-point bent loading condition. The nonlinear parameter is the indicator of nonlinear waves for expressing the degree the fatigue. The experimental results show that the sensitivity of a third harmonic longitudinal wave is higher than second harmonic longitudinal wave testing. As the same time, collinear wave mixing shows strong relative with fatigue damages than a second longitudinal wave nondestructive testing (NDT) method and provides more reliable results than third harmonic longitudinal waves nonlinear testing method.

scholarly journals Third harmonic autocorrelation and wave mixing in a thin film of poly(p-phenylenevinylene)

2003 ◽  
Vol 11 (15) ◽  
pp. 1787 ◽  
Author(s):  
Marek Samoc ◽  
Anna Samoc ◽  
Barry Luther-Davies
Keyword(s):  
Thin Film ◽  
Wave Mixing ◽  
Third Harmonic

High-power ultrafast thin-disk multipass amplifiers for efficient laser-based manufacturing

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Marwan Abdou Ahmed ◽  
Christoph Roecker ◽  
André Loescher ◽  
Florian Bienert ◽  
Daniel Holder ◽  
...  
Keyword(s):  
Harmonic Generation ◽  
State Of The Art ◽  
Second Harmonic ◽  
Average Power ◽  
Polycrystalline Diamond ◽  
Third Harmonic Generation ◽  
Thin Disk ◽  
Ultrafast Laser ◽  
Third Harmonic ◽  
Laser Systems

Abstract Thin-disk multipass amplifiers represent one of the most powerful approaches to scale the average and peak powers of ultrafast laser systems. The present paper presents the amplification of picosecond and femtosecond pulses to average powers exceeding 2 and 1 kW, respectively. Second-harmonic generation in lithium-triborate crystals with powers higher than 1.4 kW and 400 W at a wavelength of 515 nm with picosecond and femtosecond pulse durations, respectively, are also reported. Furthermore, third-harmonic generation was demonstrated with output powers exceeding 250 W at a wavelength of 343 nm. Finally, processing of silicon, metals, and polycrystalline diamond with fs pulses at an average power of 1 kW is presented to demonstrate removal rates that are improved by orders of magnitude as compared to state-of-the-art techniques.

scholarly journals Multiphoton Microscopy for Ophthalmic Imaging

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Emily A. Gibson ◽  
Omid Masihzadeh ◽  
Tim C. Lei ◽  
David A. Ammar ◽  
Malik Y. Kahook
Keyword(s):  
Harmonic Generation ◽  
Second Harmonic ◽  
Imaging Techniques ◽  
Multiphoton Microscopy ◽  
Tissue Imaging ◽  
Third Harmonic ◽  
Two Photon ◽  
Disease Mechanisms ◽  
Ophthalmic Imaging ◽  
Anti Stokes

We review multiphoton microscopy (MPM) including two-photon autofluorescence (2PAF), second harmonic generation (SHG), third harmonic generation (THG), fluorescence lifetime (FLIM), and coherent anti-Stokes Raman Scattering (CARS) with relevance to clinical applications in ophthalmology. The different imaging modalities are discussed highlighting the particular strength that each has for functional tissue imaging. MPM is compared with current clinical ophthalmological imaging techniques such as reflectance confocal microscopy, optical coherence tomography, and fluorescence imaging. In addition, we discuss the future prospects for MPM in disease detection and clinical monitoring of disease progression, understanding fundamental disease mechanisms, and real-time monitoring of drug delivery.

scholarly journals Shock impedance matching experiments in foam-solid targets and implications for “foam buffered ICF”

1999 ◽  
Vol 17 (3) ◽  
pp. 529-535 ◽  
Author(s):  
W. NAZAROV ◽  
D. BATANI ◽  
A. MASINI ◽  
A. BENUZZI ◽  
M. KOENIG ◽  
...  
Keyword(s):  
Streak Camera ◽  
Second Harmonic ◽  
Impedance Matching ◽  
Max Planck ◽  
Phase Zone ◽  
Third Harmonic ◽  
Shock Impedance ◽  
Al Foam ◽  
Pulse Energies ◽  
Mismatch Effect

We studied the influence of foams on laser produced shocks. Experiments were performed at LULI using a Nd laser converted to second harmonic, and at MPQ (Max Planck Institut für Quantenoptik) using the iodine Asterix laser converted to third harmonic. In both cases, sub-ns lasers with pulse energies of several tens of joules were focused on large focal spots (hundreds of microns) to reduce 2D effects. The laser beams were optically smoothed with phase zone plates (PZP) and directly focused on layered targets made of a foam layer on the laser side and a stepped Al layer on the other side. A visible streak camera was used to detect shock breakthrough at the base and at the step of the Al target, allowing shock velocity to be determined. Using the well known SESAME Al equation of state, we determined shock pressure. A stronger pressure increase was measured when foam was present, compared to what was obtained by focusing the laser beam directly on the Al target. This was due to the impedance mismatch effect at the Al-foam interface.

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