Detection of laser-induced nanosecond ultrasonic pulses in metals using a pancake coil and a piezoelectric sensor.

A piezoelectric sensor and a pancake coil sensor were used for broadband detection of laser-induced ultrasound in single-crystal aluminum and polycrystalline nickel. Pressure pulses with pronounced compression phases were induced by laser pulses of 5 ns duration from one side of the specimens and detected from the opposite side. A coupling layer of water was required for the piezoelectric method, whereas the pancake coil placed in the biasing permanent field of a cylindrical magnet ~0.

Attenuation of ultrasound in severely plastically deformed nickel.

Ultrasound attenuation was measured in nickel specimens of about 30 mm diameter prepared using the high pressure torsion technique. The cold working process produced an equivalent shear strain increasing from zero at the center up to 1000% at the edge of the specimen. The fragmentation of the grains due to multiple dislocations led to an ultrafine microstructure with large angle grain boundaries.

Nonlinear surface acoustic waves: silicon strength in phonon-focusing directions.

The anisotropy of the elastic properties of single-crystal silicon manifests itself in features of both the linear and nonlinear surface acoustic wave (SAW) propagation. Directions showing the phonon-focusing effect and strong nonlinearity were employed in contact-free and notch-free laser-based fracture experiments, yielding the intrinsic strength of silicon. The critical tensile stress values vary between 2.

Optoacoustic imaging of absorbing objects in a turbid medium: ultimate sensitivity and application to breast cancer diagnostics.

One of the major medical applications of optoacoustic (OA) tomography is in the diagnostics of early-stage breast cancer. A numerical approach was developed to characterize the following parameters of an OA imaging system: resolution, maximum depth at which the tumor can be detected, and image contrast. The parameters of the 64-element focused array transducer were obtained.