DISTRIBUTION OF THE BEAM DENSITY AT THE TARGET OF SUBCRITICAL FACILITY “NEUTRON SOURCE”

NSC KIPT subcritical facility “Neutron Source” uses rectangular tungsten or uranium target of 6464 mm top cross-section. To generate maximum neutron flux, prevent overheating of the target and reduce thermal stress during the facility power operation one should provide uniform electron beam distribution at the target top surface. During the facility design three different possibilities of electron beam density redistribution above the target surface were considered. These were the fast beam scanning with two dimensional scanning magnets; the method of uniform beam distribution formation with linear focusing elements (dipole and quadrupole magnets) and nonlinear focusing elements (octupole magnets), when final required rectangular beam shape with homogeneous beam density is formed at target; and combined method, when one forms the small rectangular beam with homogeneous beam density distribution and scan it over the target surface with scanning magnets. In the paper the all three methods are considered and discussed taking into account the layout of the transportation channel of NSC KIPT subcritical facility “Neutron Source”. For the first stage of the facility start-up and pilot operation the fast scanning method was chosen, realised and tested. The results of the beam distribution measurements over the surface of the target during the facility adjustment and start up are presented.

Effective parameters in beam acoustic metamaterials based on energy band structures

We present a method to calculate the effective material parameters of beam acoustic metamaterials. The effective material parameters of a periodic beam are calculated as an example. The dispersion relations and energy band structures of this beam are calculated. Subsequently, the effective material parameters of the beam are investigated by using the energy band structures. Then, the modal analysis and transmission properties of the beams with finite cells are simulated in order to confirm the correctness of effective approximation. The results show that the periodic beam can be equivalent to the homogeneous beam with dynamic effective material parameters in passband.

Aeroelastic Tailoring of Helicopter Blades

The dynamic loads transmitted from the rotor to the airframe are responsible for vibrations, discomfort and alternate stress on components. A new and promising way to minimize vibration is to reduce dynamic loads at their source by performing an aeroelastic optimization of the rotor. This optimization uses couplings between the flapwise-bending motion and the torsion motion. The impacts of elastic couplings (composite anisotropy) and inertial couplings (center-of-gravity offset) on blade dynamic behavior and on dynamic loads are evaluated in this paper. First, analytical results, based on a purely linear modal approach, are given to understand the influence of these couplings on blade dynamic behavior. Then, a complete nonlinear aeroelastic model of the rotor, including elastic and inertial couplings, is derived. Finally, this last model is used to improve a simplified but representative blade (homogeneous beam with constant chord) and results are presented.

Swelling-induced and controlled curving in layered gel beams

We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method.