Features of the processes of deformation of single-crystal titanium nickelide under the action of a comprehensive compression pulse

Using the example of single-crystal titanium nickelide, the importance of taking into account the volume compressibility anisotropy when calculating the processes of elastoplastic deformation in materials with cubic symmetry of elastic properties is shown. It is shown that the process of uniform volumetric deformation corresponds to the process of non-uniform stress state for materials with cubic symmetry of properties for some orientations of the calculated coordinate system relative to the directions of the main crystallographic axes. The index surface of volume compressibility (or the reciprocal of it - the compression modulus) has a non-spherical shape and is a function of Euler angles. This is shown for the first time by solving a model problem - determining the stress and strain states of a spherical body made of single-crystal titanium nickelide under the action of a comprehensive compression pulse. In the general case of orienting the calculated coordinate system relative to the directions of the main crystallographic axes, an initially spherical body of single-crystal titanium nickelide is deformed into a biaxial ellipsoid under the influence of a comprehensive compression pulse.

All-Fiber-Based All-Normal Dispersion Supercontinuum Source Using a Femtosecond Fiber Laser with Hollow-Core Fiber Pulse Compression

We develop and thoroughly characterize an all-fiber-based all-normal dispersion supercontinuum source pumped with a femtosecond fiber laser at 1036 nm using hollow-core fiber pulse compression. Pulse length, supercontinuum spectrum, and noise are measured.

Research on the compression properties of FC-3283 and FC-770 for generating pulse of hundreds picoseconds

This paper gives out two kinds of novel well-behaved stimulated Brillouin scattering (SBS) mediums, FC-3283 and FC-770. Numerical calculation and experimental measurements show these two mediums both having lower absorption, higher optical loads and short phonon lifetime, which making them good candidate mediums for high-energy high-power SBS. Using them as the mediums in the compacted two-cell SBS phase-conjugation mirror, it is easily to generate ultrashort phased-conjugated Stokes pulses just with hundreds picoseconds. When the incident light energy is beyond 200 mJ, the pulse width of 8 ns can be compressed to 200 ps or less in both mediums. Especially, the FC-770 is very suitable to be chosen for generating the SBS picosecond pulses with the narrowest compression pulse width of 109 ps and the highest energy reflectivity of 80%.

A study of the impulse waves discharged from convergent and divergent ducts

The present study describes experimental and computational works to investigate impulse waves that are generated by discharge of a compression pulse from the exit of convergent and divergent ducts. The objective of the present study is to compare the impulse waves discharged from a straight duct with those discharged from convergent and divergent ducts. Computational analysis is performed using the axisymmetric, unsteady, inviscid, compressible, Euler equations. A second-order total variation diminishing finite difference scheme is used to solve the governing equation system. Experiment is carried out in a simple shock tube with an open end. Convergent and divergent ducts are connected to the open end of the shock tube. Initial compression pulses with different overpressures and wavelengths are made at the entrance of the convergent and divergent ducts. The present computational method predicts the measured impulse waves well. The results obtained show that for a given duct the magnitude of the impulse wave decreases as the wavelength of the initial compression pulse increases and it is a weakly increasing function of the overpressure of the initial compression pulse. Compared with a straight duct, a convergent duct leads to a weaker impulse wave, while a divergent duct causes a stronger impulse wave. It is therefore believed that the convergent duct can be a passive control device used to reduce the magnitude of the impulse wave.