Wyniki wyszukiwania - BazTech

1

Impact of the Development of the Design of Firefighter Helmets on the Mechanical Shock Absorption Capacity

Walczak Agata, Pieniak Daniel, Lonkwic Paweł, Kupicz Włodzimierz, Ptak Szymon, Piątek Piotr, Wąsik Wiktor, Renkas Artur

Advances in Science and Technology. Research Journal

|

2023

|

Vol. 17, no 6

171--184

EN

A firefighter's helmet is used as a basic personal protective equipment item. The purpose of the helmet is to absorb a part of mechanical impact acting towards the rescuer's cervical spine, which may lead to its injury. The aim of the study was to determine the effect of changes in the helmet design on the threshold passive forces transferred to the firefighter's cervical spine. The test subjects were firefighter’s helmets compliant with the European standard for helmets used by fire brigades. The study was carried out under model conditions, using special equipment with a head model and an additional force sensor placed under it, where the cervical spine is anatomically located. The central impact energy was assumed to be 60 J. A semi-spherically ended beater was used. The experimentally determined force-displacement characteristics revealed two phases of force increase. Using polyurethane foam as a cushioning insert instead of the expanded polyester used in older designs reduced values of forces in the first phase of the characteristic. There were many cases where the critical passive force value was exceeded, which would have resulted in the cervical spine injury. Modifications in material selection and component manufacturing technology affect the protective capabilities of firefighter’s helmets and result in their improvement. Nevertheless, helmets that are currently in use are still affected by forces whose values exceed the ones that are considered to be safe for a firefighter.

2

Concrete impact strength as a measure of the resistance of a structure to external destructive energy

Fic Stanisław, Baryłka Adam, Jarosz-Hadam Monika

Inżynieria Bezpieczeństwa Obiektów Antropogenicznych

|

2022

|

Nr 3

1--9

EN

This paper presents authors’ own tests of the impact strength of concrete. The impact tests were carried out using a pendulum ballistic hammer, two types of concrete with natural aggregate: with pebble (river) gravel aggregate and medium-grained crushed granite aggregate. The concretes were tested on cubic specimens with varying W/C ratios (0.40; 0.45; 0.50; 0.55). The surface roughness of the grains in the aggregates used for the concretes was measured using a profilometer. Concrete impact strength was determined by the energy absorbed by the specimen until failure. Concrete impact strength (EA) was compared with compressive strength (fc), tensile strength (fct) and stress intensity factor (K1c).

3

Operating loads of impulse nature acting on the special equipment of the combat vehicles

Rybak P.

Eksploatacja i Niezawodność

|

2014

|

Vol. 16, no. 3

347--353

EN

Providing the combat vehicles with high operation effectiveness, safety and reliability during execution of complex tasks makes a priority. Therefore the armament and the military equipment have to meet very high requirements in that aspect when used in various conditions. This paper presents basic sources of dynamic loads affecting the combat vehicles. Attention is paid to the loads of impact nature as they mostly affect the effectiveness and reliability of a vehicle, electronic equipment and psychophysical condition of the combat vehicle crew. These loads result from off-road drives, firing the gun, the influence of the land mines or IED, hitting by enemy’s missile. As a result, some fragments of the experimental and model tests on combat vehicles are presented. Results of these tests can be helpful when designing internal vehicle equipment including special equipment. Particularly in the aspect of normative requirements for that class of vehicles and their special equipment.

PL

Zapewnienie wozom bojowym wysokiej skuteczności działania, bezpieczeństwa oraz niezawodności podczas realizacji złożonych zadań jest traktowane priorytetowo. A zatem uzbrojenie i sprzęt wojskowy musi spełniać bardzo wysokie wymagania w tym aspekcie podczas eksploatacji w różnych warunkach. W pracy przedstawiono podstawowe źródła obciążeń dynamicznych działające na wozy bojowe. Uwagę skupiono na obciążeniach mających charakter udarowy, gdyż one głównie wpływają na sprawność i niezawodność pojazdu, urządzeń wewnętrznych i stan psychofizyczny załogi. Obciążenia te wynikają z jazd terenowych, strzelania z armaty, oddziaływania miny lub IED, trafienia pociskiem przeciwnika. W rezultacie przedstawiono niektóre fragmenty z badań eksperymentalnych i modelowych wozów bojowych. Wyniki tych badań mogą być pomocne przy projektowaniu urządzeń wewnętrznych pojazdu w tym urządzeń specjalnych. Szczególnie w aspekcie wymagań normatywnych dla tej klasy pojazdów oraz ich urządzeń specjalnych.

4

Impact test analysis of dynamic mechanical parameters of a rigid-plastic material with linear strain hardening

Włodarczyk E.

Journal of Theoretical and Applied Mechanics

|

2011

|

Vol. 49 nr 1

159-173

EN

A simple engineering method to determine dynamic mechanical parameters of a rigid-plastic material with linear strain hardening is presented in this paper. For this purpose, Taylor's impact test, i.e., perpendicular impact of a long rod on a flat rigid target has been used. The rod is made of the tested material. The transcendental equations which explicitly determinate the dynamic yield stress and the plastic strain of the rod have been derived. The general trend of the obtained results is observation of the appearance of higher strengths at higher impact velocities, which is in agreement with expectations. The applied in literature approximation of dynamic properties of metals with strain hardening by means of a perfectly plastic material is far-reaching simplification disagreeing with reality.

PL

W pracy przedstawiono prostą inżynierską metodę określania dynamicznych parametrów mechanicznych sztywno-plastycznych materiałów z liniowym wzmocnieniem. Zastosowano do tego celu uderzeniowy test Taylora, tj. prostopadłe uderzenie pręta, wykonanego z testowanego materiału, w nieodkształcalną płytę. Wyprowadzono przestępne równania, z których można określić explicite dynamiczną granicę plastyczności Yw i odkształcenie plastyczne [epsilon]p materiału pręta. Uzyskano wzrost parametru Yw, wraz ze wzrostem prędkości uderzenia pręta, co jest zgodne z oczekiwaniem. Stosowana w literaturze aproksymacja dynamicznych właściwości metali modelem idealnie-plastycznym jest daleko idącym uproszczeniem, niezgodnym z rzeczywistością.

5

Experimental complex for material impact strength researches

Astanin V. V., Olefir G. O., Balalaey A. V.

Journal of KONES

|

2008

|

Vol. 15, No. 1

17-28

EN

The objective has been stated to investigate the capability of materials and structures to with stand to impact loading. Computerized research complex has been developed and manufactured to carry out experiments on impact interaction of specimen with an accelerated to a certain velocity piercer. The complex includes ,,GANCHEN"-type thermogas ballistic gun for piercer accelerating, piercer velocimeter, ballistic pendulum for measurement of integral energy datum of piercer-specimen interaction, and ,,ODD" device for measurement of residual deformation of the specimen. The experiment progress control, gaging equipment sensor signal processing and obtained information data storage are accomplished at researches. The elaborated system and research techniques permit carrying out a series of comparative check tests of specimens of different metal-composite constructions. Measurement of damages of a multilayer composite surface, the principal scheme of the thermal gas ballistic laboratory installation, basic and structural schemes of optical detector of deformations ODD-C, dependence of the optical gauge displacement, a screenshot of the developed software for the ,,ODD" device operation, the scheme of the contactless surface deformation damages scanning method, calculation algorithm of the scanned surface coordinates, appearance of the material samples after punching with a spherical piercer and computer representation of measurements of damaged zones, results of research of metal-plastic composites, increase of ability of samples to absorb the energy of the sphere, discrete character of deformation distribution are presented in the paper.

6

Analysis of stress-strain state of plates under impact loading

Astanin V. V., Borodachov M. M., Bogdan S. Y.

Journal of KONES

|

2008

|

Vol. 15, No. 1

5-15

EN

The problem concerning the stress-strain state of a plate under impact load with various intensity levels of collision momentum applying finite-element method was considered. The problem concerning transversal impact of a body in form of a mass point or a finite body to the sheet-formed structures of following type: a plate, a plate strengthened by ribs, a plate with damages was considered. Problem design diagram, design diagram of plate, fields of deflection intensities distribution w for plate central surface, stress distribution fields of the plate based layer, stress distribution fields of the plate based layer equivalent stresses sigma eq =f(m), relations for sigma eq = f(m) and w = f(m) at variation of impact initial velocity, impulse form of view, deflection and equivalent stress sigma eq intensity distribution diagrams in cross-section Kn depending on view form of impulse, the diagram of plate's deflections, the stress field sigma eq of the plate caused by impact body of finite dimensions, the field of deflection intensity distributions w for damage plate, the field of equivalent stress intensity distributions sigma eq for damage plate, the structure diagram of plate with stringers, the deflection field of plate with stringers, diagrams of equivalent stresses sigma eq of plate with stringers in central cross-section along axis x at damage deeps are presented in the paper.

7

Energetyczna metoda identyfikacji mechanicznych układów nieliniowych przy wymuszeniach impulsowych

Bocian M., Kulisiewicz M., Piesiak S.

Czasopismo Techniczne. Mechanika

|

2006

|

R. 103, z. 1-M

49-57

PL

Wyznaczanie własności dynamicznych elementów maszyn poddanych uderzeniom jest jednym z trudniejszych zagadnień identyfikacji. Rozwijana przez autorów metoda bilansu energii i bilansu mocy pozwala na identyfikację przy wymuszeniach okresowych. W niniejszej pracy zaproponowano sposób rozszerzenia działania tej metody także na wymuszenia impulsowe. Pociąga to za sobą pewne ograniczenia, które autorzy przedstawili w artykule. Praca opisuje działanie metody na przykładzie symulacji w programie Simulink, a następnie zastosowanie jej w układzie rzeczywistym. Opracowana metoda pozwala na identyfikowanie złożonych nieliniowości w układzie, bez konieczności stosowania wzbudników elektrodynamicznych do wzbudzania drgań okresowych.

EN

Estimation of dynamical properties of machine elements under impact loads is one of the more difficult identification problems. The developed by the authors the energy and power balance method enables to identify the dynamical system under periodic excitations. In this study the extension of the method for pulse excitations is proposed. The simulation of the method using the Simulink program was done too. The present method allows to identify the complex nonlinear of the system without the use shaker.

8

Wóz bojowy w warunkach oddziaływania obciążeń udarowych

Borkowski W., Rybak P., Hryciów Z.

Systems : journal of transdisciplinary systems science

|

2004

|

Vol. 9, No. sp. I

152-159

PL

Opisano zadania i warunki eksploatacji współczesnych wozów bojowych oraz zagrożenia na polu walki. Przedstawiono wyniki obliczeń numerycznych wytężenia elementów struktury nośnej wozu bojowego obciążonej udarem wygenerowanym wybuchem miny przeciwdennej.

EN

In paper there were described tasks and operating conditions of contemporary combat vehicles as well the battle-field threats. There were presented the results of numerical calculations of combined stress of combat vehicle supporting structure loaded with the strake generated by anti-bottom mine explosion.