Unloading Behavior of Elastic-power-law Strain Hardening Materials Indented by Elastic Indenter

Both strain hardening and indenter elastic deformation usually cannot be neglected in engineering contacts. By the finite element (FE) method, this paper investigates the unloading behavior of elastic-power-law strain-hardening half-space frictionlessly indented by elastic sphere for systematic materials. The effects of strain hardening and indenter elasticity on the unloading curve, cavity profile during unloading and residual indentation are analyzed. The unloading curve is observed to follow a power-law relationship, whose exponent is sensitive to strain hardening but independent upon indenter elastic deformation. Based on the power-law relationship of the unloading curve and the expression of the residual indentation fitted from the FE data, an explicit theoretical unloading law is developed. Its suitability is validated numerically and experimentally by strain hardening materials contacted by elastic indenter or rigid flat.

GYROTRONES WITH CONE-SHAPED RESONATORS

In this paper we compared the efficiency of the cylindrical, conical, and biconical types of gyrotron resonators. Based on the results of comparing the three studied variants of gyrotron profile, it was concluded that the regular-type profile is the least efficient. This type of a resonator made it possible to achieve the level of efficiency of only 23 %, which can be increased in the regular-waveguide gyrothrons only through several modes or by recovering the electrons on the collector. The medium efficiency option is the biconical profile of the resonator. Its efficiency accounted for 42 %. Through a scientific study we revealed an increase in the efficiency for gyrotrons with conical resonators from 23 to 50 % in the TE01 wave. It is worth mentioning that obtaining such efficiency requires phase grouping of the electrons in an increasing high-frequency field by means of an electromagnetic field with further selection of energy from the electron beam in a strong decaying electromagnetic field. The efficiency of 50 % exceeds significantly that of a gyrotron with a regular cavity profile of ~30 %. The gyrotron efficiency for a waveguide profile with a conical resonator and with recovery on the collector can reach 80 %. To carry out the calculations, the KEDR software package was used, and the optimization of the gyrotron parameters, in particular, was carried out using the GYRO-K software. This software has several advantages over other similar options based on the “PIC” code. GYRO-K makes it possible to obtain a high convergence rate when solving boundary value problems, as well as to solve the problem of optimizing the waveguide profile of gyroresonance devices with an acceptable computational burden. Conical cavity gyrotrons can be widely used in industry to create effective gyrotrons for spectroscopy, diagnostics of various media, and for technological needs.

A new generatrix of the cavity profile of a diaphragm compressor

The small flowrate and the diaphragm’s short life are two shortcomings of the diaphragm compressor. This paper presents a new generatrix of the cavity profile of a diaphragm compressor to increase cavity volume and decrease diaphragm's radial stress. To verify the design theory, the radial stresses on the oil side of the diaphragm in the cavities with the new and traditional generatrices were tested, and the experimental radial stresses agreed with the theoretical values. As the most important evaluation criteria of the cavity profile, the volumes of the cavities with different generatrices and the radial stress distribution of the diaphragm within were investigated under various design conditions. The results showed that the volume of the cavity with the new generatrix was about 6.5% larger than that with the traditional generatrix under the same design condition. Otherwise, with the same cavity volume and radius, the maximal radial stress of the diaphragm in the cavity with the new generatrix decreased by 10.3% stably, compared to that in the cavity with a traditional generatrix. Likewise, in the diaphragm’s centric region where the additional stress caused by the discharge holes occurred, the maximal radial stress of the diaphragm in the cavity with the new generatrix decreased about 11.5%.