AiMT Volume 9 (2014), Issue 2

Safety Concept and Partial Factors for Bridge Assessment under Military Loading

Lenner R., Keuser M. and Sykora M.

The use of civilian bridges by military vehicles is in the NATO countries regulated and governed by STANAG 2021. This standard, however, does not fully deliver some of the essential aspects important for safe and reliable crossing of military vehicles over existing bridges. This paper aims at investigating the military loads and at developing partial factors that can be utilized during the assessment of bridges for military traffic. A number of factors must be taken into account including target reliability index and uncertainties related to dynamic amplification factor, static load due to military vehicle and applied model for load effect. The results show that the military partial factors can be generally considered in a range close to or smaller than those values given in civilian codes.

Keywords: Bridge assessment, military traffic, load simulation, safety concept

Pages: 5 - 20

Verification of Accuracy of the New Generation Elevation Models

Hubacek M., Brenova M., Ceplova L. and Zerzan P.

Military and civil applications use more and more often digital elevation models (DEM) in order to get terrain spatial information. During last two decades in the Czech Republic there were used several DEMs. The accuracy and details of the models are no longer meeting current requirements, so in 2008 there was worked out the project of forming the new altimetry of the Czech Republic for 2009-2015. It is based on a modern technology of airborne laser scanning. On the basis of laser data there are gradually formed new elevation models – Digital terrain model of the 4th generation and the 5th generation (DMR 4G, DMR 5G) and Digital surface model (DMP). This paper deals with aerial laser scanning of the Czech Republic and the accuracy verification results of continuously formed DMR 4G and DMR 5G.

Keywords: DTM (digital terrain model), DEM (digital elevation model), aerial laser scanning (ALS), accuracy analysis

Pages: 21 - 32

Material Characteristics of Plastic Deformation in High-Strength Steel

Binar T., Dvořák I., Kadlec J., Sukáč J., Rolc S. and Křesťan J.

The paper is concerned with material characteristics of plastic deformation, relating to the occurrence and development of plastic deformation, proof stress and strain hardening exponent with changing testing temperature, in high-strength low-alloy steels. The material characteristics of plastic deformation were measured experimentally by means of a tensile test in the temperature range from –80 °C to +100 °C; subsequently, a fractographic analysis of fracture surfaces was carried out in order to evaluate failure mechanisms of the steels studied.

Keywords: high-strength low-alloy steel, proof stress, strain hardening exponent, fractographic analysis, transcrystalline ductile failure

Pages: 33 - 39

Principles of a Defect Localisation in Nonlinear Ultrasonic Mixing Impulse Spectroscopy

Hajek K. and Nenakhova V.

Principles of nonlinear ultrasonic mixing impulse spectroscopy (NUMIS) show great potential advantages in comparison with other nonlinear ultrasonic methods. It is first of all from the point of view of sensitivity and possibility of quick, simple and precise localization of a defect. This paper elaborates on the principles and algorithms of calculation of the defect place for this method. The point idealization of ultrasonic transducers and receivers are supposed for this aim. With the successive increase in delay of the second excitation pulse to the first one it can be obtained distribution of image defects on test subjects in a 2D plane within seconds.

Keywords: nonlinear ultrasonic mixing spectroscopy, sensitivity, impulse excitation, localization

Pages: 41 - 48

Sound Effect of RPG-7 Anti-Tank Grenade Launcher for Shooting Training

Mai Q. H., Horák, V. and Do Duc L.

The purpose of this research is to use the released energy of the liquid carbon dioxide for the PET bottle to burst, which can simulate safely and cheaply the combat sound effects. This article deals with the mathematical modelling of the problem, which is the base for the design of this device that would simulate the sound effects of the RPG-7 launching and that can be used for the RPG-7 hand-held anti-tank grenade launcher in combat shooting training. The prototype of this device has been extensively tested and has shown to be suitable for military use.

Keywords: Sound effect, shooting training, practice grenade, RPG-7

Pages: 49 - 60

Investigation of Airflow in Internal Recirculation Channel of Centrifugal Compressor

Poledno M., Kmoch P. and Jílek A.

Contemporary high pressure ratio centrifugal compressors have a narrow stable operating. In order to achieve a wider stable operating region, some anti-surge measures can be used, such as an internal recirculation channel (IRC). This article presents a study of the airflow in IRC of a centrifugal compressor. A model of such channel was designed and manufactured in order to investigate the influence of various IRC inlet slot geometry on air flow parameters. Numerical simulation of the airflow for selected variants was also performed. Results of the simulation together with results of the experiment enable us to analyse the airflow in the area of the inlet slot and to find out its most suitable geometry.

Keywords: Centrifugal compressor, internal bleed system, internal recirculation channel, stable operating region

Pages: 61 - 76

Technical Characteristics of Shells Conveyer

Balla J. and Krist Z.

The purpose of this article is to familiarize with new attitude to finding technical characteristics of the shells and charges conveyers used in heavy guns. The results are values of the hydraulic capacities, damping coefficient, and hydraulic resistances in the hydraulic circuits derived from own technical experiments. The kinematical parameters as are the conveyer velocity and conveyer acceleration are derived from the measured conveyer displacement. They enable with the measured input and output pressures, and the angular velocity of the hydraulic motor give expert opinion about conveyer operation as whole. The results are used for validation of the dynamic model, and they can be used as diagnostics data of the loading systems, and whole procedure as an example of the practicable technique in the higher military repair.

Keywords: conveyer acceleration, conveyer velocity, conveyer displacement, damping coefficient, hydraulic capacity, hydraulic resistance, pressures in hydraulic motor, pressure derivative, Maltese cross

Pages: 77 - 89

Experimental Studies of Stereoscopic Vision for Command and Control Operations

Wolfe B., Kim B., Aeschliman B. and Sedlmeyer R.

3D stereoscopic vision is used in many applications, but the level of benefit to the user differs depending on the particular application. We studied its benefits for command and control applications such as battlefield visualization or disaster response. We conducted experiments where the subjects completed some simple military planning exercises both with and without 3D vision. 3D users had lower error in general, particularly when judging line of sight between two points. Furthermore, survey results show that most subjects preferred 3D. However, 3D took longer for completing the tasks. We also compared two ways of rendering military symbols in the virtual environment, finding that billboard style visualization boosted the subjects’ efficiency when compared with draping the symbol on the terrain.

Keywords: 3D stereoscopic vision, virtual environment, command and control, visualization

Pages: 91 - 104

A Universal Mobile Packaging Line and its Operating Capability Simulation

Rejzek M., Šmerek M. and Vlkovský M.

The paper presents a universal mobile packaging line prototype as the outcome of a defence development project assigned by the Ministry of Defence of the Czech Republic. It is a facility designed for disassembling military as well as other material, and assembling supply units on standard-size disposable pallets suitable for road and air transportation. In the practical part, basic tactical-technical data of the universal mobile packaging line and its operating capabilities are determined using simulation software and the queuing theory.

Keywords: Container ISO 1C, configured load, mounted hall, pallet unit, queuing theory, simulation

Pages: 107 - 114