Wyniki wyszukiwania - Biblioteka Nauki

1

The selection of materials for the body deformation zones

100%

Evin E. , Kmec J.

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tom z. 3/99

47--53

EN

This paper presents a model application of Cause and Effect matrix operations support designers and manufacturing engineers in the preparation stage production of automobile components from sheet metal blanks that enables you to analyze the suitability of different types of materials in terms of safety, weight, emissions and costs. Deformation characteristics are analyzed for stress components deformation zones to move and bend. To verify the appropriateness of the proposed model were experimentally determined strength and deformation characteristics of deep-drawing steel DX 54 D, micro alloyed steel HSLA, high-strength multi-phase steels DP 600 and TRIP, anti-corrosive austenitic steels A304 2B and ferrite A 430 2B by tensile test and three-point bending. The analysis of the results obtained Cause and Effect matrix shows that for the front impact deformation zones are more suitable austenitic steels respectively. TWIP and for zones flanking the passenger compartment (cab) are preferable DP and TRIP steels.

PL

W artykule przedstawiono zastosowanie modelu "Przyczyna i Skutek", pozwalającego na operacje na macierzach, wspomagającego projektantów i inżynierów produkcji w fazie przygotowania produkcji komponentów samochodowych z metalowych półwyrobów (arkuszy blachy), który pozwala analizować przydatność różnych materiałów pod względem bezpieczeństwa, wagi, emisji i kosztów. Charakterystyki odkształcenia są analizowane w odniesieniu do stref zgniotu, gdzie elementy przemieszczają się i wyginają. Aby zweryfikować zasadność proponowanego modelu zostały określone doświadczalnie charakterystyki siły i odkształcenia, za pomocą testu rozciągania i zginania trzypunktowego: głęboko tłoczonej stali DX 54 D, stali mikrostopowych HSLA, wysoko-wytrzymałej stali wielofazowej DP 600 i TRIP, antykorozyjnych stali austenitycznych A304 2B i ferrytowych 430 2B. Analiza wyników uzyskanych z modelu macierzowego "Przyczyna i Skutek", pokazała, że dla przednich stref zgniotu lepsze są stale austenityczne, odpowiednio TWIP, a do stref otaczających kabinę pasażerską (cab) korzystniejsze są stale DP i TRIP.

2

Structural effects and real strain‑rate effects on compressive strength of sustainable concrete with crumb rubber in split Hopkinson pressure bar tests

100%

Feng W. , Chen B. , Tang Y. , Wei W. , He W. , Yang Y.

Archives of Civil and Mechanical Engineering

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2022

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tom Vol. 22, no. 3

art. no. e136

EN

The dynamic increase factor (DIF) of the concrete material strength, obtained using a split Hopkinson pressure bar (SHPB), includes structural effects that do not precisely reflect the real strain-rate effect of concrete. To further clarify the real strain-rate effects of rubberised concrete (RC), an experimental investigation regarding the dynamic compressive response of ordinary concrete (NC) and RC with three rubber contents (10%, 20%, and 30%) was performed in this study. Additionally, based on a dynamic constitutive model, i.e., the Karagozian and Case (K&C) concrete model, numerical SHPB tests were conducted using the LS-DYNA software. According to the experimental results, all parameters of the K&C model were discussed, and the damage factors were modified to satisfy the mechanical properties of RC. After validating the numerical model, it was observed that the experimental DIF included the inertial enhancement and the real DIF. Moreover, because rubber particles effectively reduce the density and improve the deformation capacity of concrete, the real strain-rate effect of RC was found to be more rate-sensitive than that of NC by analysing the radial stress distribution. In addition to lateral inertia, another external source, namely, the interface friction between the specimen and bars, which can produce lateral confinement, was further studied. It was found that interface friction significantly contributes to lateral confinement; however, as the strain rate increased, the impact generally decreased. Finally, the mechanism of the strain-rate effect of RC was clarified.

3

Experimental Investigation on the Compression Behaviours of 3D Angle‑interlock Woven Composites with Carbons Nanotube under High Strain Rates

84%

Ma P. , Jiang G. , Zhang F. , Chen Q. , Miao X. , Cong H.

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2015

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tom Vol. 23, no. 2 (110)

44--50

EN

The compressive properties of 3D angle-interlock woven/epoxy resin composites with various carbon nanotube (CNTs) contents were investigated under quasi-static and high strain rate loading to evaluate the compressive failure modes, which were influenced by various CNT contents and different strain rates. The results indicated that the stress strain curves were strain rate sensitive, and the compressive failure stress of composites with various CNT contents were increased with a change the strain rates and CNT contents. The compressive failure modes of 3D angle-interlock woven composites without CNT tended to be in shear deformation, delamination fibre breakage and matrix crack together, and the failure modes of 3D angle-interlock woven composites with high CNT contents presented delamination and shear deformation.

PL

Badano właściwości ściskające kompozytów 3D wzmacnianych tkaninami o skośnym splocie interlokowym modyfikowanych nanorurkami węglowymi. W celu wyznaczenia uszkodzeń powstałych na skutek ściskania, na które wpływa zawartość nanorurek i szybkości odkształcania, badania przeprowadzono pod obciążeniem quasi-statycznym i przy dużych szybkościach ściskania. Wyniki wykazały, że krzywe ściskania zależały od szybkości odkształcania i zawartości nanorurek. Uszkodzenia mają charakter rozwarstwienia i deformacji pod wpływem naprężeń ścinających.

4

Wpływ temperatury i szybkości odkształcania na charakterystyki wytrzymałościowe materiałów metalicznych

84%

Kyzioł L.

Zeszyty Naukowe Akademii Morskiej w Gdyni

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2017

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tom nr 100

109--119

PL

Przedstawiono różnicę pomiędzy odkształcaniem quasi-statycznym a dynamicznym materiałów metalicznych. Dla dużych szybkości odkształceń naprężenie (odkształcenie) w ciałach przemieszcza się z określonymi prędkościami jako fala. Odkształcanie dynamiczne związane jest z rozchodzeniem się fali, natomiast statyczne można rozpatrywać jako okresowe stany równowagi. Przy niedużych szybkościach odkształceń ciało pozostaje w warunkach izotermicznych, a dla dynamicznych procesów odkształcenia jest to proces adiabatyczny. Wprowadzono pojęcie naprężenia progowego ?^ (ang. mechanical threshold stress), które jest maksymalną wartością naprężenia dla danego rodzaju materiału metalicznego w temperaturze 0 K lub, ekwiwalentnie, przy nieskończenie dużej szybkości odkształcenia. Z obniżeniem temperatury następuje zmniejszenie się ruchliwości dyslokacji. Zjawisko to jest związane ze spadkiem zdolności poruszania się atomów w sieci w obniżonych wartościach temperatury, których ruchy drgające całkowicie ustają w temperaturze 0 K. Pojęcie naprężenia progowego zostało zobrazowane za pomocą przykładu obliczeniowego.

EN

The article presents the difference between the quasi-static and dynamic strain of metallic materials. At the high strain rate, stress (strain) in metallic materials moves with specified velocities as a wave. The dynamic deformation is related to the propagation of the wave while the static deformation can be seen as temporary states of equilibrium. At small speed deformations, the body remains in isothermal conditions, while the dynamic strain processes are the adiabatic processes. The concept of the mechanical threshold stress ?^ has been introduced, which is the maximum stress value for the particular type of metallic material for 0 K or, equivalently, infinitely high speed deformation. With the decrease of the temperature, there is a reduction of the dislocation mobility. This phenomenon is associated with a decrease in mobility of atoms in the network at reduced temperatures, which vibrating movement completely stops at 0 K. The concept of the mechanical threshold stress has been illustrated using the calculation example.

5

Wyznaczanie parametrów pełzania w konstytutywnym modelowaniu gruntów spoistych

84%

Olek B. S. , Woźniak H.

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tom Vol. 65, nr 10/2

873--882

EN

The paper presents methods of determining creep parameters based on uniaxial compression testing. Relevant analyses were carried out on the basis ofthe time resistance concept. Evaluation of the strain-time one-dimensional behaviour ofsoil is also described. The aim of this research was to put some light on methods of determination of creep parameters used in various constitutive creep models and to develop the reliable interpretation approach. In this work the values for creep parameters were defined with the help of oedometer tests on reconstituted clay samples from Chmielów.

6

Technological Development of a Yarn Grip System for High-Speed Tensile Testing of High-Performance Fibers

84%

Unger R. , Schegner P. , Nocke A. , Cherif C.

Autex Research Journal

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2019

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tom Vol. 19, no. 4

347--354

EN

Particularly in terms of carbon fiber (CF) rovings and further high performance fibers, it is a highly demanding task to clamp technical yarns with low elongations at break during high-speed tensile tests due to their sensitivity to shear stress. For fibers to be tested, a low elongation at break results in short testing times and requires high acceleration. In this paper, four different yarn grips that can be applied with various test machines will be introduced and compared to a wedge screw grip. By using most sensitive CF rovings, advantages and disadvantages of these gripping devices will be qualitatively evaluated by means of testing machines with test speeds of up to 20 m/s and strain rates of up to 200 s-1, respectively. Hence, the reproducibility and precision of test results were considerably enhanced by optimizing the geometry and mass of yarn grips. Moreover, theoretical approaches and calculations for the design of yarn grips suitable for test speeds of up to 100 m/s will be presented.

7

Erroneous GNSS Strain Rate Patterns and their Application to Investigate the Tectonic Credibility of GNSS Velocities

84%

Araszkiewicz A. , Figurski M. , Jarosiński M.

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2016

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tom Vol. 64, no. 5

1412--1429

EN

The paper concerns investigation of the credibility of tectonic interpretation of GNSS strain rates. The analysis was focused on stable regions, where the crustal deformations are small and the reliability of GNSS velocities is questionable. We are showing how the unreliable motion of stations affects calculated strains around them. We expressed distribution of local principal strains by a sinusoidal function and used them to investigate the significance of strain distortion. Then we used this method to investigate real motions of GNSS stations. As a test object we used Polish GNSS stations belonging to the ASG-EUPOS network. Station velocities were estimated on the basis of the 4.5 years of observations. The results let us identify stations that disturb the obtained local GNSS strain rate field. After verification and exclusion of some stations, the new GNSS strains show a much greater internal compatibility and also better fit to the directions of lithosphere stresses.

8

Contemporary overview of soil creep phenomenon

67%

Kaczmarek Ł. , Dobak P.

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tom Vol. 6, iss. 1

28--40

EN

Soil creep deformation refers to phenomena which take place in many areas and research in this field of science is rich and constantly developing. The article presents an analysis of the literature on soil creep phenomena. In light of the complexity of the issues involved and the wide variety of perspectives taken, this attempt at systematization seeks to provide a reliable review of current theories and practical approaches concerning creep deformation. The paper deals with subjects such as definition of creep, creep genesis, basic description of soil creep dynamics deformation, estimation of creep capabilities, various fields of creep occurrence, and an introduction to creep modeling. Furthermore, based on this analysis, a new direction for research is proposed.

9

Experimental and theoretical investigations of glass-fibre reinforced composite subjected to uniaxial compression for a wide spectrum of strain rates

67%

Pieczyska E. A. , Pęcherski R. B. , Gadaj S. P. , Nowacki W. K. , Nowak Z. , Matyjewski M. M.

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tom Vol. 58, nr 3

273-291

EN

Results of static and dynamic compression} tests for two types of glass fibre-reinforced polypropylene composites are presented. Stress-strain curves showing the influence of the strain rate on the composite mechanical properties have been obtained. A three-dimensional description of the material behavior during the deformation has been developed. The material constitutive parameters have been calculated. Specification of the parameters and description of the methods used for their identification have been worked out. The results are discussed in terms of the deformation processes and the material non-homogeneity.

10

Modele plastyczności Eyringa i Robertsona dotyczące tworzywa epoksydowego "EPY®"

67%

Urbaniak M.

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2008

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tom T. 53, nr 1

40-46

PL

Przedstawiono wyniki badania wpływu temperatury (23-100°C) i szybkości odkształcania przy ściskaniu (0,0208-20,8min-1) na charakterystyki mechaniczne i wartości wybranych wskaźników wytrzymałościowych dotwardzonego (80°C/2h) tworzywa epoksydowego "EPY®", stosowanego na podkładki fundamentowe maszyn. Sprawdzono możliwości wykorzystania teorii deformacji plastycznej Eyringa i Robertsona do prognozowania granicy plastyczności (...) tego tworzywa w zależności od temperatury i szybkości odkształcania. W tym celu porównano określone doświadczalnie i obliczone na podstawie tych teorii wartości ... w całym wspomnianym zakresie temperatury i szybkości odkształcania. Uzyskany dobry stopień zgodności świadczy o przydatności obu testowanych modeli teoretycznych do prognozowania rzeczywistej granicy plastyczności badanego tworzywa, co umożliwia przewidywanie jego zachowania się w różnych warunkach eksploatacji.

EN

The article presents the results of investigation of the effects of temperature (23-100°C) and compressive strain rate (0.0208-20.8min-1) on the mechanical characteristics of post-cured (at 80°C, 2h) EPY® epoxy material (applied for machine foundation chocks) and on the values of its selected strength parameters (Fig. 1-6). The possibilities of use of Eyring and Robertson plastic deformation theories to predict the yield stress (...) of this polymer, dependently on the temperature and strain rate were verified. So the agreement of ... values experimentally determined and calculated on the basis of the theories has been evaluated for the whole mentioned ranges of temperature and strain rate values (Fig. 7 and 8). The good agreement obtained indicates the usefulness of both theoretical models tested for prediction of true limiting yield stress of the polymeric material investigated. This makes possible to predict the material behavior in various service conditions.

11

Experimental study of compressive failure of concrete under static and dynamic loads

67%

Liu L. , An H. M.

Archives of Civil Engineering

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2020

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tom Vol. 66, nr 3

427--441

EN

The fracture and fragmentation of concrete under static and dynamic loads are studied. The uniaxial compressive strength test is employed to study the concrete behavior under static loads while the split Hopkinson pressure bar is used to study the dynamic behavior of the concrete under static loads. The theories for acquiring the stress, strain and strain rate of the concrete in the dynamic test by Hopkinson pressure bar has been introduced. The fracture patterns of the concrete in the uniaxial compressive test have been obtained and the static concrete compressive strengths have been calculated. The fracture patterns of the concrete in the uniaxial compressive test have been obtained and the static concrete compressive strengths have been calculated. The fracture and fragmentation of the specimen under dynamic loads have been acquired and the stress-strain curves of concrete under various impact loads are obtained. The stress-strain curve indicates a typical brittle material failure process which includes existing micro-fracture closure stage, linear-elastic stage, nonlinear-elastic stage, and post-failure stages. The influence of the loading rate for the compressive strength of the concrete has compared. Compared with the concrete under static loads, the dynamic loads can produce more fractures and fragments. The concrete strength is influenced by the strain rate and the strength increases almost linearly with the increase of the strain rate.