High Strain Rates (high + strain_rate)

Distribution by Scientific Domains


Selected Abstracts


Hochdynamische Materialeigenschaften von Ultrahochleistungsbeton (UHPC)

BETON- UND STAHLBETONBAU, Issue 11 2009
Markus Nöldgen Dipl.-Ing.
Baustoffe; Versuche; Dynamische Einwirkungen Abstract Der vorliegende Bericht liefert einen Beitrag zur Werkstoffbeschreibung von Ultrahochleistungsbetonen unter hochdynamischer Belastung. Grundlage für die Ermittlung der Werkstoffeigenschaften ist eine Hopkinson-Bar Versuchsreihe, die Werte für die dynamische Zugfestigkeit, den dynamischen E-Modul und die dynamische Bruchenergie unter Dehnraten von 102 · s,1 liefert. Ein Vergleich mit den Ergebnissen dieser Parameter für Normalbeton und hochfesten Betonen ermöglicht eine Einordnung des Ultrahochleistungsbetons in etablierte Ansätze und Berechnungsvorschriften und liefert einen Bewertungsansatz für die maßgebenden mechanischen Vorgänge. Unter Einbeziehung der Bruchenergie und der Spannungs-Rissöffnungs-Beziehung für UHPC in das RHT-Betonmodell werden Hydrocode Simulationen durchgeführt, die den Versuch am Hopkinson-Bar adäquat abbilden können. Material Properties of Ultra High Performance Concrete (UHPC) at High Strain Rates The presented paper is a contribution to the material description of Ultra High Performance Concrete (UHPC) under high-speed dynamical loading conditions. Based on a series of Hopkinson-Bar experiments dynamical material parameters such as the Tensile Strength, Young's Modulus and Fracture Energy are derived at high strain rates of 102 · s,1. A comparison with the results of these parameters for normal and high strength concrete leads to a qualitative and quantitative evaluation of UHPC at high strain rates. With the extension of the established RHT material model for UHPC by the material's Fracture Energy and Stress-Crack-Opening-Relation the Hopkinson-Bar experiments are simulated appropriately. [source]


Comparison of mechanical properties of PP/SEBS blends at intermediate and high strain rates with SiO2 nanoparticles vs.

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
CaCO3 fillers
Abstract The present article focuses on the effect of two types of inorganic fillers (SiO2 and CaCO3) on the mechanical properties of PP/SEBS blend. The nominal particle diameters of SiO2 and CaCO3 are 7 nm and 1 ,m, respectively. The studied blend ratios were PP/SEBS/SiO2 (CaCO3) = 75/22/3 and 73/21/6 vol %. The morphology of polymer blends was observed and the distributions of the SEBS, SiO2, and CaCO3 particles were analyzed by transmission electron microscopy (TEM). Tensile tests were conducted at nominal strain rates from 3 × 10,1 to 102 s,1. The apparent elastic modulus has the local strain-rate dependency caused by SiO2 nanoparticles around SEBS particles in the blend of PP/SEBS/SiO2. The yield stress has weak dependency of morphology. The absorbed strain energy has strong dependency of the location of SiO2 nanoparticle or CaCO3 fillers and SEBS particle in the morphology. It is considered that such morphology, in which inorganic nanoparticles are located around SEBS particles, can prevent the brittle fracture while the increased local strain rate can enhance the apparent elastic modulus of the blend at the high strain rate. On the basis of the results of this study, the location and size of inorganic nanoparticles are the most important parameters to increase the elastic modulus without decreasing the material ductility of the blend at both low and high strain rates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Shear properties of epoxy under high strain rate loading

POLYMER ENGINEERING & SCIENCE, Issue 4 2010
Niranjan K. Naik
Shear properties of epoxy LY 556 under high strain rate loading are presented. Torsional Split Hopkinson Bar apparatus was used for the studies in the shear strain rate range of 385,880 per sec. Experimental details, specimen configuration and development, data acquisition, and processing are presented. Shear strength, shear modulus, and ultimate shear strain are presented as a function of shear strain rate. For comparison, studies are presented at quasi-static loading. It is observed that the shear strength at high strain rate is enhanced up to 45% compared with that at quasi-static loading in the range of parameters considered. Further, it is observed that, in the range of parameters considered, the change in shear properties with the change in shear strain rate is not significant. Comparison of torque versus time behavior derived from signals obtained from strain gauges mounted on incident bar and transmitter bar is also presented. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers [source]


Comparison of experimental and numerical results on metallic plates subjected to explosions

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009
ukasz Pyrzowski
A comparative study of dynamic response including damage and rupture processes of thin metallic plates subjected to shock-wave impulses , explosions is presented. The results of the finite element numerical analysis are related to experiments. Due to high strain rate during explosions the elasto-viscoplastic Chaboche's constitutive law including damage effects has been applied. For the assumed model proper material parameters identification has been done. In the dynamic, geometrically non-linear analysis the MSC.Marc system has been used. A good correlation between numerical and experimental results has been observed. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


The Role of Dynamic Material Properties in the Performance of Ceramic Armor

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2004
James Lankford Jr.
The penetration of ceramic armor by a kinetic energy penetrator is complex, involving a continual process of material damage, micro-crack nucleation, growth and coalescence, and multiaxial failure, all under conditions of high loading rate and inertial confinement. It will be shown that at sufficiently high stress, which usually requires either high loading rates or confinement (these conditions are known to prevail in the region just beneath a penetrator dwelling at the surface of an armor), plastic deformation occurs in ceramics. This deformation appears to limit the strength of most ceramics, since micro-cracks are subsequently nucleated at the sites of the deformation defects and these immediately begin to coalesce into fragments. The constraint/rate-limited flow of these fragments is the physical event that permits the penetration of ceramic armor. This paper considers the implications for modeling armor penetration of laboratory experiments involving both intact and fragmented ceramics tested under compressive loading at high strain rates and under confining pressure. [source]


Comparison of mechanical properties of PP/SEBS blends at intermediate and high strain rates with SiO2 nanoparticles vs.

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
CaCO3 fillers
Abstract The present article focuses on the effect of two types of inorganic fillers (SiO2 and CaCO3) on the mechanical properties of PP/SEBS blend. The nominal particle diameters of SiO2 and CaCO3 are 7 nm and 1 ,m, respectively. The studied blend ratios were PP/SEBS/SiO2 (CaCO3) = 75/22/3 and 73/21/6 vol %. The morphology of polymer blends was observed and the distributions of the SEBS, SiO2, and CaCO3 particles were analyzed by transmission electron microscopy (TEM). Tensile tests were conducted at nominal strain rates from 3 × 10,1 to 102 s,1. The apparent elastic modulus has the local strain-rate dependency caused by SiO2 nanoparticles around SEBS particles in the blend of PP/SEBS/SiO2. The yield stress has weak dependency of morphology. The absorbed strain energy has strong dependency of the location of SiO2 nanoparticle or CaCO3 fillers and SEBS particle in the morphology. It is considered that such morphology, in which inorganic nanoparticles are located around SEBS particles, can prevent the brittle fracture while the increased local strain rate can enhance the apparent elastic modulus of the blend at the high strain rate. On the basis of the results of this study, the location and size of inorganic nanoparticles are the most important parameters to increase the elastic modulus without decreasing the material ductility of the blend at both low and high strain rates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Influence of side-chain structures on the viscoelasticity and elongation viscosity of polyethylene melts

POLYMER ENGINEERING & SCIENCE, Issue 11 2002
Gwo-Geng Lin
Metallocene-catalyzed, low-density and linear low-density polyethylenes with similar melt indexes were used to investigate how side-chain structures influence the elongation viscosity and viscoelastic properties. The viscoelastic properties were determined with a rotation rheometer, while the elongation viscosities were acquired by using isothermal fiber spinning. The Phan-Thien-Tanner (PTT) model was also used to understand how the side-chain structure affects the elongation behavior. Experimental results demonstrate that the log G, vs. log G, plot can qualitatively describe the effects of the side chain branch on the rheological properties of polyethylene melts. According to the results determined by the PTT model, low-density polyethylene (LDPE) has low elongation viscosities at high strain rates. This low elongation viscosity can be attributed to the fact that LDPE has high shear thinning behavior. The long-chain branching tends to increase entanglements, thereby enhancing the storage modulus, elongation viscosity and shear-thinning behaviors. Uniform side-chain distribution lowers the entanglements, which results in a low storage modulus, elongation viscosity and shear-thinning behavior. [source]


A fluid mechanical model for granular flow in silos

PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005
Caroline Leppert
Granular materials may display both solid and fluid like behaviour. For low densities and high strain rates as in avalanches or during the discharge of silos the behaviour is mainly governed by interparticle collisions. On the other hand, frictional contacts characterise the solid state which is represented within the framework of plasticity theory. A fluid like constitutive model describes granular materials when subjected to large deformations and high strain rates. It bases upon a modified viscoplastic model that is valid for both yielded and unyielded regions. The central idea is the distinction between fluid and solid regions by means of comparing actual shear stress and Coulomb yield stress. The application to the simultion of the discharge of silos shows the feasibility of the chosen method. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Verhalten von hochduktilem Beton unter Impaktbelastung

BETON- UND STAHLBETONBAU, Issue 7 2010
Oliver Millon Dipl.-Ing.
Baustoffe; Versuche; Dynamische Einwirkungen/Erdbeben Abstract In diesem Aufsatz wird das Materialverhalten von Hochduktilem Beton (engl.: Strain Hardening Cementitious Composite , SHCC) bei Impaktbelastung beschrieben. Dazu werden Ergebnisse aus hochdynamischen Spallations-Experimenten an einem Hopkinson- Bar mit Dehnraten > 140 1/s den Resultaten aus quasi-statischen, zentrischen Zugversuchen mit Dehnraten von 0,001 1/s gegenübergestellt. Die Auswirkungen hoher Dehnraten auf das Materialverhalten erfolgt anhand eines Vergleiches der zentrischen Zugfestigkeit, des E-Moduls sowie der Bruchenergie. Die experimentellen Ergebnisse werden zudem mit den Kennwerten anderer Betone in Beziehung gesetzt. Unterschiede im Materialverhalten werden auf Grundlage von Phänomenen der Rissbildung und des Faserauszuges erklärt. Mechanical Behaviour of SHCC under Impact This paper describes the material behaviour of Strain Hardening Cementitious Composite (SHCC) at high strain rates. The results of high dynamic spall experiments using a Hopkinson Bar at strain rates > 140/sec were arrayed against the results of quasistatic, centric tensile tests at strain rates of 0,001/sec. This comparison is based on the parameters of tensile strength, elastic modulus, and fracture energy of the specimens. In addition, the experimental results of SHCC are related to the characteristic values of other concrete types. Differences in material behaviour are explained by the phenomena of crack formation and fibre pullout force. [source]


Hochdynamische Materialeigenschaften von Ultrahochleistungsbeton (UHPC)

BETON- UND STAHLBETONBAU, Issue 11 2009
Markus Nöldgen Dipl.-Ing.
Baustoffe; Versuche; Dynamische Einwirkungen Abstract Der vorliegende Bericht liefert einen Beitrag zur Werkstoffbeschreibung von Ultrahochleistungsbetonen unter hochdynamischer Belastung. Grundlage für die Ermittlung der Werkstoffeigenschaften ist eine Hopkinson-Bar Versuchsreihe, die Werte für die dynamische Zugfestigkeit, den dynamischen E-Modul und die dynamische Bruchenergie unter Dehnraten von 102 · s,1 liefert. Ein Vergleich mit den Ergebnissen dieser Parameter für Normalbeton und hochfesten Betonen ermöglicht eine Einordnung des Ultrahochleistungsbetons in etablierte Ansätze und Berechnungsvorschriften und liefert einen Bewertungsansatz für die maßgebenden mechanischen Vorgänge. Unter Einbeziehung der Bruchenergie und der Spannungs-Rissöffnungs-Beziehung für UHPC in das RHT-Betonmodell werden Hydrocode Simulationen durchgeführt, die den Versuch am Hopkinson-Bar adäquat abbilden können. Material Properties of Ultra High Performance Concrete (UHPC) at High Strain Rates The presented paper is a contribution to the material description of Ultra High Performance Concrete (UHPC) under high-speed dynamical loading conditions. Based on a series of Hopkinson-Bar experiments dynamical material parameters such as the Tensile Strength, Young's Modulus and Fracture Energy are derived at high strain rates of 102 · s,1. A comparison with the results of these parameters for normal and high strength concrete leads to a qualitative and quantitative evaluation of UHPC at high strain rates. With the extension of the established RHT material model for UHPC by the material's Fracture Energy and Stress-Crack-Opening-Relation the Hopkinson-Bar experiments are simulated appropriately. [source]