Vol 47, No 4 (2018)

A combined method for balancing of planar parallel structure mechanisms including a synthesis of mechanisms with decreased acceleration of the mass center and also balancing by redistributing the masses of moving links is presented in this study. This method is implemented in two stages: (1) optimal redistribution of the driving link masses for securing convergence of the gripping trajectory and the total mass center of the manipulator; (2) development of optimal control of grip acceleration according to the “bang-bang” law. Such control makes it possible to maximally decrease the acceleration of the mass center and the resultant vector of inertial forces. The method is applied to the planar 5R and 3RRR parallel structure manipulators. The efficiency of the method is illustrated by numerical simulations using the software ADAMS, where the inertial loads acting on the 5R manipulator’s base are decreased by 78% and those on the 3RRR manipulator’s base, by 60%.

The results of modeling and investigation of the stability of a continuous multicutter turning process are presented. The mathematical modeling is based on an equation for the formation of new surfaces, on equations of motion, and on the fractional-rational cutting law. The influence of the parameters of the technological system on the stability of the continuous cutting mode is analyzed.

A solution to the problem of realization of an acoustically transparent body in a far field is proposed using active quenching of the diffracted field by quenching means placed on the surface of the body.

The aspects of evaluating cyclical durability of screw joints are considered by the example of the main joint of the VVER-1000 nuclear reactor with a given record of operating load. Four variants of design are presented. The nonconservative essence of case three is noted. In the fourth case, the refined design requires additional in-service steps to guarantee the cyclic durability of the main joint pins.

In this paper, we present an algorithm for finite element calculation of thin shells with allowance for transverse shear deformations. In deriving the basic geometric relations, two options of counting the rotation angle of the normal to the middle surface were considered. In the first option, the reading of the rotation angle of the normal was carried out from its initial state. In the second option, the reading of the rotation angle of the normal was carried out from its position in the deformed state. A comparative analysis of the efficiency of two options of reading the rotation angle of the normal is performed based on calculating a thin elliptical cylinder shell rigidly pinched along the ends and loaded with an internal pressure of intensity q.

The features of wear of polytetrafluoroethylene and the filled composite F4K20 based on it during friction on the carbon and alloy steels with calculation of the contact temperatures according to the original method are studied. The ranges of the contact temperatures and loads corresponding to them, under which the wear coefficient increases sharply during friction of the polymer and its composite on steel containing nickel as one of the alloy additives, are defined. It is shown that the fluorides formed on the friction surface under these conditions contribute to the formation and development of cracks, which leads to replacement of the wear mechanism.

Laser shock-wave processing of materials is a modern technology for effective processing of metallic materials. In the near-surface region, the processing produces significant compressive residual stresses that contribute to increasing material strength and improving their tribological and operational characteristics. In this work, we performed finite element modeling of the laser shock-wave technology using the intrinsic deformation method. Specifically, using the intrinsic deformation method, we first solved the dynamic problem on the impact of a shock load and determined the distribution of stabilized plastic deformations (so-called “intrinsic deformations”) and then solved the static problem on the elastic response of the system to the intrinsic deformations induced into it. The level of the resulting compressive residual stresses arising upon laser shock-wave processing is determined. The obtained results correlated well with the known experimental data.

The list of authors should read as follows: U. Khasyanov^a, A. N. Romanov^a, D. U. Khasyanova^a,*, and M. M. Khrushchov^a