Wyniki wyszukiwania - BazTech

1

Zastosowanie techniki dzielonego pręta Hopkinsona do badania wpływu skrępowania bezwładnościowego na dynamiczną odpowiedź mechaniczną betonu

Pająk Małgorzata, Janiszewski Jacek, Baranowski Paweł, Pytlik Mateusz

Inżynieria i Budownictwo

|

2023

|

R. 79, nr 9-10

547--551

PL

W pracy przedstawiono wyniki dynamicznych badań wytrzymałościowych próbek betonowych skrępowanych tuleją ołowianą z wykorzystaniem techniki dzielonego pręta Hopkinsona. Przeanalizowany zakres dużych szybkości odkształcenia wynosił od 80 s-1 do 194 s-1. Wykazano przyrost wytrzymałości betonu wynikający nie tylko z wrażliwości badanego betonu na szybkość odkształcenia, ale także ze skrępowania, które w warunkach dynamicznego obciążenia wywołuje dodatkowe efekty bezwładnościowe.

EN

In the paper, the results from the SHPB tests of concrete specimens confined with the lead covers are presented. The analysed high strain rate was from 80 s-1 to 194 s-1. The increase of the compressive strength was noted due to strain rate sensitivity of concrete but also to confinement which caused additional inertial effects.

2

Experimental study on the dynamic tensile mechanical properties of marble under water and oil conditions

Li Chaoxin, Liu Dongyan, Zhu Yunhui

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

317--330

EN

To investigate the dynamic tensile properties and energy dissipation characteristics of marble in three different conditions: dry, water-saturated, and oil-saturated, a Brazilian disk splitting test was conducted using a 50 mm diameter Hopkinson pressure bar (SHPB) device. The findings indicate that the peak strain and dynamic tensile strength of the three conditions increase with strain rate, exhibiting a clear strain rate effect. Additionally, lubricating effects of water and oil weaken internal shear sliding friction, thus promoting crack expansion. Furthermore, immersion of fluid in marble weakens the cementation of internal mineral particles, leading to lower tensile strength of marble saturated with water and oil compared to dry marble under dynamic impact. When analyzing the energy dissipation of marble, both the absorption energy and dissipation energy density increase with oil strain rate, indicating a positive correlation. Moreover, numerical results obtained from ANSYS/LS-DYNA correspond well with experimental data, thus verifying and interpreting the experimental outcomes.

3

Critical appraising of Hopkinson bar techniques for calibrating high g accelerometers

Miao Yinggang

Metrology and Measurement Systems

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2019

|

Vol. 26, nr 2

335--343

EN

The Hopkinson pressure bar has been developed to calibrate and assess high g accelerometers’ capacity. The extreme caution is indispensable for performing calibration of severe characteristics, like the bearable super-high overload peak and wide duration of stress. In the paper, the Hopkinson bar calibrating system is being critically appraised. A limiting formula is deduced based on the stress wave theory. It indicates that the overload peak and duration of stress are limited by the elastic limit and wave speed of Hopkinson bar material. Both stress wave configurations in the form of linear ramp and cosine functions were designed theoretically to meet typical calibrating requirements. They were confirmed experimentally with the aid of the pulse shaping technique. Their corresponding calibration characteristics were analysed critically, and it was found that the cosine stress wave can achieve the values of acceleration peak or duration by π/2 times greater than those obtained with the linear stress wave. Finally, some suggestions are proposed for more extreme calibration requirements.

4

Behavior of concrete reinforced with fibers from end-of-life tires under high compressive strain rates

Pająk Małgorzata, Janiszewski Jacek, Kruszka Leopold

Engineering Transactions

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2019

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Vol. 67, iss. 1

119--131

EN

The behavior of concrete reinforced with the fibers obtained from the end-of-life tires under high compressive strain rates was the scope of this research. The laboratory investigations were performed using the Hopkinson Pressure Bar with a diameter of 40 mm. The waste fibers with untypical geometrical parameters were applied to concrete with a dosage of 30 kg/m3 . The pronounced increase of compressive strength of the RSFRC, when subjected to high strain rates, was observed. The strain rate sensitivity of the RSFRC expressed by DIF was comparable to the other results presented in the literature.

5

Influence of Anisotropy on the Viscoplastic Properties of a Hot Rolled Ti6Al4V Titanium Alloy

Moćko W., Kostrzewski C., Brodecki A.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

403--411

EN

In this work, the influence of strain rate on the anisotropy of the Ti6Al4V titanium alloy has been analyzed. Tensile tests of notched specimens were carried out in three loading orientations (0°, 45°, and 90°) with respect to the rolling direction, using the servo-hydraulic testing machine and Hopkinson bar. Investigation was supported by the digital image correlation analysis of strain distribution on the specimen surface and assessment of the fracture mechanism. The Ti6Al4V titanium alloy reveals a typical strain rate hardening behavior; however, strain rate sensitivity is independent of the loading orientation. Increases of the loading orientation results in material softening, observed as lowered yield stress, whereas plastic strain exponent and modulus remain unaffected. Fracture strain decreases with loading orientation at quasi-static and dynamic loading conditions.

6

Eksperymentalna metodyka oceny wrażliwości stopów na szybkość odkształcania

Moćko W.

Transport Samochodowy

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2017

|

z. 2

69--86

PL

W pracy omówiono podstawowe metody badawcze, wykorzystujące koncepcję pręta Hopkinsona, wykorzystywane do wyznaczania krzywych ściskania materiałów konstrukcyjnych w warunkach obciążeń udarowych. Ponadto zaprezentowano opracowane i wykonane w Instytucie Transportu Samochodowego stanowisko stosowane do badania charakterystyk mechanicznych materiałów przy dużych szybkościach odkształcania. Opisana aparatura posłużyła do wyznaczenia charakterystyk naprężenia w funkcji odkształcenia wybranych stopów. Na podstawie otrzymanych wykresów można ocenić wrażliwość badanych materiałów na szybkość odkształcania.

EN

Basic experimental methods based on the Hopkinson bar concept were discussed in this paper. The methods are used to determine compressive curves of materials under impact loading conditions. Moreover, the testing stand designed and fabricated in the Motor Transport Institute was introduced. The testing stand is used to analyse mechanical behavior of a materials at a high strain rates. Described equipment was applied to estimate stress-strain curves of selected structural materials. On the basis of the obtained characteristics strain rate sensitivity may be investigated.

7

Anisotropic fracture criterion of Ti6Al4V titanium alloy under wide range of strain rates

Moćko W., Kostrzewski C.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 2

741—745

EN

The new fracture criterion taking into account stress triaxiality, strain rate and anisotropy is introduced in this paper. The model is capable to predict the influence of the loading direction on the fracture strain. The equation is applied to estimate the fracture locus of Ti6Al4V titanium alloy under quasi-static and dynamic loading regimes.

8

Analysis of the composite material behaviour subjected to dynamic bending using the hopkinson bar

Massaq A., Rusinek A., Klósak M., Boulouz A., Koutti L.

Engineering Transactions

|

2016

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Vol. 64, iss. 1

115--131

EN

The aim of this study is to propose an experimental approach supported by an analytical analysis for polymer materials under dynamic loading. The experimental technique of Hopkinson split pressure bar is used which allows for high impact velocities. The specimens are subjected to the three-point bending and the efficiency of the experimental technique is proved. During quasi-static and dynamic bending tests, the rupture mode is described and the evolution of the energy and the ultimate stresses as a function of the initial impact velocity is discussed. In addition, the critical impact velocity estimated above an important change in the rupture mode is observed. In order to better describe the physical phenomena encountered during the three-point bending impact, the analysis is supported by a rheological model based on a mass-spring system.

9

Zastosowanie procesu wyciskania w projektowaniu urządzeń pochłaniających energię uderzenia

Ryzińska G., Gieleta R.

Rudy i Metale Nieżelazne Recykling

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2015

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R. 60, nr 11

593--600

PL

W artykule przedstawiono wyniki badań eksperymentalnych wykonanych z zastosowaniem pręta Hopkinsona oraz obliczenia numeryczne procesu wyciskania przeciwbieżnego aluminium w gatunku 1050A z prędkością 36 km/h .Elementy teorii wyciskania zastosowano w procesie projektowania urządzenia pochłaniającego energię uderzenia. Zaprezentowane obliczenia obejmowały trzy warianty układu geometrycznego. Uzyskane wyniki pozwoliły na odpowiedni dobór parametrów geometrycznych urządzenia, dla którego został spełniony warunek odpowiedniej ilości pochłoniętej energii.

EN

Experimental obtained results using Hopkinson bar and numerical results of 1050 aluminum backward extrusion at 36 km/h tool speed are presented in this paper. Engineering applications concern the use of extrusion technology in the design of energy absorbing devices. Devices of this type must comply some requirements which mainly represent constant force versus displacement of the piston and objective absorbed energy amount. Presented calculations included three variants of the geometry. Obtained results allowed the proper selection of geometric parameters of the device for which it was complied with the requirements.

10

Wpływ szybkości deformacji oraz temperatury na lepko-plastyczne właściwości komercyjnie czystego tytanu oraz stopu Ti6Al4V

Moćko W.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2015

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Vol. 6, Nr 2 (20)

99-112

PL

W publikacji przedstawiono wyniki badań dotyczących lepko-plastycznych właściwości komercyjnie czystego stopu tytanu oraz stopu Ti6Al4V. Analiza została przeprowadzona dla szerokiego zakresu szybkości odkształcania od 2 × 10⁻⁴s⁻¹ to 2 × 10³s⁻¹ z wykorzystaniem maszyny wytrzymałościowej oraz pręta Hopkinsona, odpowiednio w quasi-statycznym i dynamicznym zakresie obciążeń. Wpływ temperatury na krzywe ściskania został wyznaczony w zakresie temperatur od 23 do 400°C przy wykorzystaniu pręta Hopkinsona wyposażonego w piec. Na podstawie otrzymanych wyników przeprowadzono kalibrację współczynników modelu Johnsona–Cooka (J–C) opisującego lepko-plastyczne właściwości badanych materiałów. Badania właściwości mechanicznych zostały poparte analizą mikrostrukturalną, w celu określenia wpływu temperatury i szybkości odkształcania na mechanizm odkształcania.

EN

The paper presents results of tests concerning visco-plastic properties of commercially pure titanium and Ti6Al4V titanium alloy. The analyses were carried out at wide range of strain rates from 2 × 10⁻⁴s⁻¹ to 2 × 10³s⁻¹ using servo-hydraulic testing machine and Hopkinson bar at quasi-static and dynamic range of loadings, respectively. The influence of temperature on the compressive curves was determined within the range of temperatures from 23°C to 400°C applying Hopkinson bar equipped with temperature chamber. Taking into account obtained results, the coefficients of Johnson–Cook (JC) constitutive model were calibrated. Mechanical investigations were accompanied by microstructural analysis in order to determine influence of temperature and rate of deformation on the plastic deformation mechanisms.

11

An application of longitudinal elastic waves for investigation of materials under high strain rates using the Hopkinson bar

Szolc T., Kowalewski Z. L.

Vibrations in Physical Systems

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2014

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Vol. 26

305--310

EN

In the paper there is presented a discrete-continuous model of the Split Hopkinson Pressure Bar (SHPB) for numerical simulations of a dynamic behaviour of material specimens under high strain-rates. For this purpose several material theories describing visco-elasto-plastic properties of the tested specimens can be applied. Using this model impact-type dynamic responses are sought by means of the longitudinal elastic wave analytical solution of the d’Alembert type. The proposed model enables us theoretical strength investigations for various elasto-plastic materials under great deformation velocities as well as structural parameter determination of the real SHPB designed to play a role of the laboratory test-rig.

12

New Experimental Technique for Dynamic Bending of Composite Materials

Massaq A., Rusinek A., Klósak M.

Engineering Transactions

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2014

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Vol. 62, iss. 3

269–-289

EN

The paper is reporting a new experimental technique to study the dynamic behaviour of composite materials subjected to bending direct impact. It is based on the Hopkinson bar system allowing to observe material behaviour at very high impact velocities. The material used to perform the tests is a woven glass-fibre-reinforced Polyamide 6.

13

Analysis of the impact of the frequency range of the tensometer bridge and projectile geometry on the results of measurements by the split Hopkinson pressure bar method

Moćko W.

Metrology and Measurement Systems

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2013

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Vol. 20, nr 4

555--564

EN

The paper presents the results of the analysis of the striker shape impact on the shape of the mechanical elastic wave generated in the Hopkinson bar. The influence of the tensometer amplifier bandwidth on the stress-strain characteristics obtained in this method was analyzed too. For the purposes of analyzing under the computing environment ABAQUS / Explicit the test bench model was created, and then the analysis of the process of dynamic deformation of the specimen with specific mechanical parameters was carried out. Based on those tests, it was found that the geometry of the end of the striker has an effect on the form of the loading wave and the spectral width of the signal of that wave. Reduction of the striker end diameter reduces unwanted oscillations, however, adversely affects the time of strain rate stabilization. It was determined for the assumed test bench configuration that a tensometric measurement system with a bandwidth equal to 50 kHz is sufficient.

14

Properties of AW8S-V Polyester Composite under Various Loading Conditions

Moćko W., Szymczak T., Kowalewski Z. L.

Engineering Transactions

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2013

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Vol. 61, iss. 4

289–-300

EN

This article presents the results of an analysis of the mechanical properties of the AW8S-V polyester composite reinforced by a roving fabric under tensile loading. The stress-strain curves show an increase of the maximum stress and elastic modulus with increasing strain rate. By contrast, an increase of the temperature led to decrease of the maximum stress and elastic modulus. It is also shown that, failure mechanisms are dependent on the loading type. Shear cracks occurred in the specimens under quasi-static loading whereas composite layers damage was observed under dynamic loading. Temperature increase resulted to stronger fragmentation of the specimens.

15

Method for Determination of the Dynamic Elastic Modulus for Composite Materials

Massaq A., Rusinek A., Klósak M.

Engineering Transactions

|

2013

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Vol. 61, iss. 4

301--315

EN

Majority of polymer matrix composite materials, a marked viscoelastic behavior and faculties of dissipation of energy, it thus proves necessary to know the viscoelastic properties, as the dynamic Young modulus. In this work, we will present a new experimental technique for determining the dynamic elastic modulus at high strain rates of polymer matrix composites materials by a statistical method demanding a large number of tests. This new technique is based on the split Hopkinson pressure bar. Further, we study the effect of strain rate on dynamic elastic modulus of a woven Polyamid 6 – glass fibre reinforced.

16

Temperature increase associated with plastic deformation under dynamic compression: application to aluminium alloy AL 6082

Perez-Castellanos J.-L., Rusinek A.

Journal of Theoretical and Applied Mechanics

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2012

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Vol. 50 nr 2

377-398

EN

The temperature increase associated with plastic deformation of a material under loading may be measured using several techniques such as infrared thermography (IRT). The present work investigates the temperature increase at different high strain rates and initial test temperatures, using an aluminium alloy Al 6082. A Split Hopkinson Pressure Bar (SHPB) was applied to induce high strain rates to the material and an infrared camera was used to measure the temperature increase. Numerical simulations of dynamic tests were performed to calculate the temperature increase and to gain a better understanding of the process by local measurements. Thus, a detailed finite-elements model was developed to simulate the dynamic compression test. The fraction of plastic work converted into heat was estimated using the Zehnder model. Numerical results in terms of the strain rate and initial temperature effect on the material temperature increase are reported and compared with experiments.

PL

Wzrost temperatury w materiale związany z plastycznym odkształcaniem może być rejestrowany różnymi metodami, w tym m.in. techniką termografii podczerwieni (IRT). Prezentowana praca poświęcona jest badaniom wzrostu temperatury przy różnym tempie odkształceń i temperatury początkowej próbek wykonanych ze stopu aluminium Al 6082. W eksperymentach użyto zmodyfikowanego pręta Hopkinsona do generowania szybko-zmiennych odkształceń w materiale i jednocześnie dokonywano pomiarów temperatury za pomocą kamery termowizyjnej. Przeprowadzono także symulacje numeryczne przebiegu przyrostu temperatury pozwalające na lepsze zrozumienie zachodzących procesów na podstawie lokalnych pomiarowym. W tym celu zbudowano szczegółowy model bazujący na metodzie elementów skończonych, który przeanalizowano pod kątem dynamicznego ściskania. Część pracy odkształcenia plastycznego zamienianego w ciepło oszacowano za pomocą modelu Zehndera. Wyniki obliczeń uwzględniających tempo odkształceń i temperaturę początkową na jej przyrost w badanym materiale zweryfikowano z rezultatami doświadczeń.

17

Badania właściwości mechanicznych staliwa LH556 i stali VP159 pod kątem zastosowania w osłonach balistycznych

Moćko W., Kowalewski Z. L., Wojciechowski A., Rudnik D.

Biuletyn Wojskowej Akademii Technicznej

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2012

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Vol. 61, nr 2

449-462

PL

Praca przedstawia charakterystyki naprężenie-odkształcenie stali austenitycznej VP159 oraz staliwa austenitycznego LH556, o dużej zawartości azotu, przy różnych prędkościach odkształcania. Do badań w zakresie obciążeń statycznych zastosowano serwohydrauliczną maszynę wytrzymałościową, natomiast w zakresie obciążeń dynamicznych metodę pręta Hopkinsona. Otrzymane rezultaty przedstawiono w formie wykresów naprężenia rzeczywistego w funkcji odkształcenia rzeczywistego. Na podstawie statycznej próby rozciągania wyznaczono również podstawowe parametry badanych materiałów, takie jak: E, R0,05, R0,2, Rm. Na podstawie badań stwierdzono, że stal VP159 ma znacznie lepszą ciągliwość niż staliwo LH556, natomiast pozostałe parametry i charakterystyki były zbliżone. Otrzymane wyniki można wykorzystać do wyznaczenia parametrów równań konstytutywnych opisujących termomechaniczne właściwości materiałów na potrzeby symulacji komputerowych.

EN

This work presents the stress-strain curves of the VP159 steel and LH556 cast alloy of high nitrogen content, at wide range of strain rates. At quasi-static deformation regime, the servohydraulic testing machine was applied, whereas for dynamic tests the Hopkinson bar was used. The results were presented as a true stress - true strain diagrams. The basic mechanical properties of materials, i.e., E, R0.05, R0.2, Rm were determined. The tests show that the VP159 steel exhibits a much better ductility than the LH556 cast alloy, whilst the other parameters were similar for both materials. The results create a base for determination of parameters appearing at different constitutive equations describing thermo-mechanical behavior of materials within finite element method codes.

18

Numerical modeling of wave propagation and interaction in bars

Jankowiak T., Klepaczko J., Łodygowski T.

Foundations of Civil and Environmental Engineering

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2006

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No. 7

187-199

EN

In the first part, the paper presents analytical solution of symmetric longitudinal impact of a semi-infinite circular bar. In the second part the Maple code is used in order to solve the differential equations, derived and solved by Skalak [1]. Based on this analytical solution, a verification is performed by Finite Element code. The calibration of parameters like the artificial viscosity and the mesh size is done. The initial FE calibration is used, together with cumulative fracture criterion, to verify the laboratory test results presented by Klepaczko [2,3,4,7]. The finite element solution is focused on the new experimental technique to test semi-brittle materials in dynamic tension via spalling. The technique which is based on Hopkinson pressure bar has been developed in LPMM-Metz [4].

19

Modelling of dynamic crack experiment by the boundary element method

Fedeliński P.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

1999

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z. 10

77-82

EN

The compact compression specimen positioned between two faces of the split Hopkinson bar and subjected to dynamic loading is analyzed. The motion of the specimen is modelled using the time domain formulation of the boundary element method. Two types of the displacement boundary conditions are considered. The velocities of the bar-specimen interfaces and dynamic stress intensity factors determined experimentally and numerically are compared.

PL

W pracy przedstawiono analizę zwartej próbki umieszczonej między powierzchniami podzielonego pręta Hopkinsona obciążonego dynamicznie. Ruch próbki modelowano metody rozwiązań w dziedzinie czasu i metodą, elementów brzegowych. Rozpatrzono dwa przypadki warunków brzegowych. Porównano prędkości powierzchni styku prętów z próbką i dynamiczne współczynniki intensywności naprężeń wyznaczone doświadczalnie i numerycznie.