Military Academy

About: Military Academy is a based out in . It is known for research contribution in the topics: Population & Fuzzy logic. The organization has 2478 authors who have published 3003 publications receiving 33188 citations.

The observation and analysis of the dislocation morphology of fatigue crack tips at steady state propagation rates subject to a single peak load

Abstract: During fatigue crack propagation there is large interaction effects of the fatigue cycle for different loading amplitudes. Two examples are the retarding effect of overload and the accelerating effect of underload on the crack propagation. In the former, the result is explained in terms of residual stress effects associated with the overload, and in the latter, the underload partially annihilates the residual stress built up by the positive load. However, at the microstructure level of material under fatigue, the crack propagation is caused by dislocation action. Assuming this, this paper reports studies of the crack propagation interaction effect by using microstructural examination of crack tips. Observations were made with the Back Electron Images (BEI) of the Scanning Electron Microscope (SEM). The results are: (1) the microstructure of cells close to the crack tips formed into vein or loop patch structures upon the overload, so that the crack propagation was reduced. (2) The region of cells s close to the crack tips become enlarged on the underload and the scale of the other microstructure (such as PSB, vein and loop patch) were also enhanced too, so that the crack propagation was accelerated.

Polarization Direction Finding Method of Interfering Radio Emission Sources

Abstract: Rapid growth of radio emission sources (RES) leads to the interference of signals from various transceivers and thus complicates its positioning based on direction finding (DF). Traditional DF use structural-statistical redundancy to resolve multi-signal and multipath situations, which makes impossible to implement it in compact direction finders. The aim of current work is to investigate possibilities of polarization DF accounting interference conditions. It is proposed to use frequency and phase differences of received rays in the interference mixture of signals in tri-orthogonal antenna system (TOAS). The solution to polarization DF task of RES during interference utilize methods of search for normals to planes that are envelopes from a family of curves, which use the resultant field, induced in TOAS. The novelty of presented solution is in the realization of the idea that in the case of RES interference with frequency or phase differences in TOAS, the resulting field vector forms three-dimensional shape, which contains spatial parameters of the rays. Contribution of current investigation validates the use of relatively simple DF techniques in a complex interference environment, both for several sources and separation of rays from one source.

Development of dynamic-mathematical model of hydraulic excavator

Abstract: This work deals with analysis of dynamic behaviour of hydraulic excavator on the basis of developed dynamic-mathematical model. The mathematical model with maximum five degrees of freedom is extended by new generalized coordinate which represents rotation around transversal main central axis of inertia of undercarriage. The excavator is described by a system of six nonlinear, nonhomogenous differential equations of the second kind. Numerical analysis of the differential equations has been done for BTH-600 hydraulic excavator with moving mechanism with pneumatic wheels.