Papers by Keyword: Strain Rate Sensitivity (SRS)

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Authors: Kenji Matsuki, Hiroshi Kawakami, M. Tokizawa, Yukitaka Murakami, S. Murakami
Authors: Pascal Forquin
Abstract: Shear fracture (mode II) may be observed in concrete structures when subjected to confined or impact loading. Among the different techniques developed to investigate the shear strength of geomaterials, figures the Punch-Through Shear test (PTS test). It consists of a short cylinder with two cylindrical notches made on the lower and upper surfaces. Shear fracture is produced in the ligament due to the displacement of the central zone beside the peripheral zone. An experimental setup has been developed in LEM3 laboratory to measure the shear strength of concrete under quasi-static and dynamic loading. A high-speed hydraulic press allowed reaching strain-rates up to few per second. Steel and aluminium alloy confining rings have been used to induce a confining pressure in the fractured zone. Furthermore, radial notches have been performed in the specimen in order to deduce the radial stress at the ligament surface from the contact pressure between the confining ring and the outer surface of the specimen. The experimental results have been used to discuss the influence of free water and strain-rate on the shear behaviour of concrete.
Authors: Fan Zhang, Cheng Wen Tan, Hong Nian Cai
Abstract: Supersaturated Mg-Gd-Y alloy followed by aging at 225 °C with different times were subjected to quais-static and dynamic strain rates to determine the influence of precipitate phase β′ on the strain rate sensitivity of magnesium alloy. Strain rate sensitivity (SRS) decreases with the increase of the size of β′. SRS decreases from initial condition to peak-aged condition due to the β′ increases the athermal component of flow stress. On the other hand, the influence of precipitate interfaces on dislocation generation and storage mechanisms may be responsible for the decrease of SRS from peak-aged to over-aged condition.
Authors: Magnus Johansson, Magnus Hörnqvist, Birger Karlsson
Abstract: In the present study the influence of strain rate and temperature on the behaviour of two commercial aluminium alloys, 6063-T6 and 7030-T6, was investigated. Both alloys are high strength precipitation hardened alloys that are expected to have low strain rate and temperature sensitivity. Tensile tests were performed at room temperature at strain rates ranging from 10-4 to 102 s-1, and at -40°C and +60°C at strain rates of 10-4 and 10-1 s-1, due to equipment limitations. Both alloys showed low but positive strain rate sensitivity at all temperatures. Also the temperature sensitivity was low, showing negative values in all cases. The dependence of the flow stress on temperature was more pronounced than the strain rate dependence. The area reduction at fracture was higher in 6063 than 7030, although the uniform elongation was larger in 7030. 6063 showed almost no strain rate dependence of the ductility and a limited reduction with increased temperature. 7030 showed markedly increasing area reduction with increasing temperature and decreasing values with increasing strain rate. The energy absorption was higher in 7030 by a factor of approximately three.
Authors: Olaf Engler, Jürgen Hirsch, Kai F. Karhausen, Günter Gottstein
Authors: Johannes Mueller, Karsten Durst, Dorothea Amberger, Matthias Göken
Abstract: The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.
Authors: Trevor B. Abbott, Mark Easton, William Song
Authors: Nilamber K. Singh, Ezio Cadoni, Maloy K. Singha, Narinder K. Gupta
Abstract: The purpose of the present paper is to investigate the mechanical properties of multi phase 800 high yield strength (MP800HY) steel under compressive loading at different strain rates (-4700s-1 to-0.001s-1). Specimens of MP800HY steel are tested on universal testing machine to study their stress-strain behavior under quasi-static (-0.001s-1) condition. Then, the specimens are tested under split Hopkinson pressure bar (SHPB) to study the strain rate sensitivity of the material under different rates of compressive loading (-4700s-1, -4300 1/s, -3800 1/s, -2900s-1 and-1600s-1). The effect of pulse shaper in SHPB experiments has been studied. Thereafter, the applicability of the existing Johnson-Cook material model to represent the flow stress of MP800HY is examined.
Authors: Feng Gao, Hiroshi Nishikawa, Tadashi Takemoto
Abstract: The lead-free casting solders Sn-3.5Ag-xCo (x = 0, 0.1, 0.5 and 1.0 mass%, respectively) were subjected to isothermal aging at 150°C for 0, 1008 and 2016 h, respectively. The nanoindentation methodology was employed herein to assess the mechanical properties. In particular, the strain rate sensitivity index value was derived from the creep deformation at the dwell time of the target constant load using Mayo-Nix theory. Basically, there is no remarkable tendency of the variation of Young’s modulus after aging, while to some extent, the hardness of the alloys drops. The strain rate sensitivity index value continues to decrease with the prolonged aging time. The solder grain growth and the coarsening of the intermetallics namely, Ag3Sn and CoSn2, are responsible for the mechanical evolution of the alloys. The 1.0% (mass%) Co additive improved the hardness of the solder alloy, and caused the decrease of the strain rate sensitivity value.
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