Theoretical studies of the force interaction of a three-axle vehicle with a stand with single rollers

The article discusses the issues of modeling conditions for obtaining diagnostic information about complex objects. Checking the braking and traction properties of three-axle trucks on a roller stand is considered as an example. As shown by many studies, in particular, which were carried out at the Department of Technical Operation and Service of Automobiles of the KhNADU (HADI), inertial stands provide more reliable information about the technical condition of the car. Such stands allow you to reproduce the real speed and thermal conditions of the brakes. To improve the accuracy of diagnosing a car on a roller stand, it is necessary to have an idea of the nature of the interaction of the car's wheels with the rollers. The study of the rolling of the wheels of a three-axle car bogie on the stand rollers was carried out at the Department of Technical Operation of Cars, KhNADU. However, all these studies were carried out on biaxial stands, where each bogie wheel rests on a pair of rollers. In order to exclude wheel slippage, partial braking is recommended, that is, a mode when partial force on the pedals (or pressure) is created in the system and, as a result, incomplete braking force develops in the braking mechanisms (or deceleration reaches some partial value from the full one). It is necessary to analyze the possibility of implementing full brake test modes on a roller stand by improving the layout and geometrical scheme of the stand. A power model of the system of interaction between a car and a stand has been developed, taking into account the design features of the stand and the design features of the suspension of a three-axle car. The power model of this system includes the equations of equilibrium of the body and two axles, as well as the equations of motion for the rollers and wheels of the car. Based on the results of the analysis of the acting forces in the "car-stand" system, the coefficients of the use of the load q during the brake tests of a three-axle car were determined, and the longitudinal stability of the car was also analyzed. The obtained research results allowed to improve the theory of interaction of the wheels of three-axle vehicles with single rollers of the diagnostic stand.

RELAP5-3D Three-Dimensional Analysis Based on PHÉNIX Dissymmetric Transient Test

Before the final shutdown of the PHÉNIX fast reactor, the CEA carried out a final set of experimental tests to gather data and additional knowledge on relevant sodium fast reactors (SFR) operation and safety aspects. One of these experiments conducted was the dissymmetrical configuration test, which was selected as benchmark transient within the H2020 SESAME project. ENEA and Sapienza University of Rome are participating in the benchmark using the RELAP5-3D© code. The thermal hydraulic analysis focuses on adequate core cooling prediction in accidental scenario. With the goal of investigating asymmetric thermal hydraulic behavior inside of the reactor pool, two different nodalization approaches have been applied for the RELAP5-3D model, which adopt the same geometrical scheme for the primary flow path, with the exception of the hot and cold pools and the core bypass. The first scheme has been developed using vertical parallel pipes with cross junctions for the hot and cold pools and an equivalent pipe to reproduce the core bypass. The second model includes a multidimensional (MULTID) component, which simulates the pools and provides a detailed nodalization of the core bypass. This study aims at assessing whether the two modeling approaches are equally capable to predict the asymmetrical temperature evolution over the test, caused by the azimuthal asymmetry of the boundary conditions. Blind calculation results are presented and discussed. The paper will be a first step toward the RELAP5-3D code assessment against the experimental results collected as part of the PHÉNIX dissymmetric test.

Hopf Bifurcation of a Type of Neuron Model with Multiple Time Delays

By applying a geometrical scheme developed to tackle the eigenvalue problem of delay differential equations with multiple time delays, Hopf bifurcation of Hopfield neuron model is analyzed in two-parameter space. By the introduction of two new angles, the calculation of imaginary roots is carried out analytically and effectively. By increasing the parameter to cross over the Hopf bifurcation lines, the stability switching direction is confirmed. The method is a useful tool to show the partition of stable and unstable regions in two-parameter space and detect double Hopf bifurcation further. The typified dynamical behaviors based on nearby double Hopf points are analyzed by applying the normal form technique and center manifold method.

Building constructions modelling problems in modern cae-systems

This article is about choosing building structure analysis model question. Construction analysis model type choice affects result of counting. Result accuracy and reliability depends on analysis scheme choice. Using modern computers, there is a lot of alternative abilities of creation construction analysis model. This article is made to understand these analysis models features and their influence on result. An example of counting beam in six independent CAD systems is shown. Engineering simulation and design software, which base on finite elements method, were chosen for analysis. These counting models differ from each other only by geometrical scheme. Beam geometry modeling is performed using beam elements, shell elements and solid elements. The comparison of beam calculation results with its beam, shell and solid elements analysis scheme modelling was performed. The analysis of single factor (geometric scheme) influence on the results of beam calculation is shown. It was defined, that the choice of calculation complex does not affect the calculation result, if the geometrical counting models are completely identical. It was defined, that in case creating construction with various types finite elements there are differences in the calculation results. Difference in calculation results, using different geometrical models, is seen in using the same complex and in comparison of different complexes. It was defined, that difference in calculating internal forces and moments in beam for different geometrical models can be more than 10%.

The creation of a computational model of corrugated beams using the author’s program “GOPRO”

The program «Gofro» is intended for the automated generation of data on the geometrical scheme of the beam with corrugated or plane web for further use in design complexes. The program has got a window interface, and it consists of one module for the input of feed da-ta, for calculation and for the display of its results in txt file format. The program offers a possibility to choose the outline of the structure, the profile of the web, the type of cross-section, and to set other parameters of the structure. When building up the model with the help of the author program «Gofro» and GMSH preprocessor for the automatic genera-tion of finite element mesh, the correctness of geometrical shape of elements is monitored by the algorithms that are input in the preprocessor. The author compares the time re-quired to create the models using the author program and GMSH preprocessor and using the standard resources of «Lira» software system. The authors performed numerical studies of various I-beams created in the program «GOPRO».