Strain rate dependence of anisotropic compression behavior in porous iron with unidirectional pores

The strain rate dependence of anisotropic compression behavior in porous iron with cylindrical pores oriented in one direction was investigated. Through high strain rate (˜103 s−1) compression tests along the orientation direction of pores using the split Hopkinson pressure bar method, it was shown that the stress–strain curve exhibits a unique plateau-stress region where deformation proceeds with almost no stress increase. The appearance of the plateau-stress region is related to the buckling deformation of the iron matrix and provides superior energy absorption. However, for the middle (˜10−1 s−1) and low strain rates (˜10−4 s−1), compression along the same direction produces no such plateau region. In fact, in contrast to compression in the parallel direction, compression perpendicular to the orientation direction of pores produces no plateau-stress regions in any of the three strain rates.

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Strain-Rate Dependence of Vacancy Cluster Size in Hydrogen-Charged Martensitic Steel AISI410 under Tensile Deformation

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.373.171 ◽

2017 ◽

Vol 373 ◽

pp. 171-175 ◽

Cited By ~ 2

Author(s):

Kazuki Sugita ◽

Yasumasa Mutou ◽

Yasuharu Shirai

Keyword(s):

Strain Rate ◽

Positron Lifetime ◽

Tensile Deformation ◽

Martensitic Steel ◽

Vacancy Cluster ◽

Rate Dependence ◽

Strain Rate Dependence ◽

Strain Rates ◽

Vacancy Clusters ◽

Positron Lifetime Spectroscopy

The strain-rate dependence of vacancy cluster sizes in hydrogen-charged martensitic steel AISI410 under tensile deformation was investigated using positron lifetime spectroscopy. The vacancy-cluster sizes in hydrogen-charged samples tended to increase with decreasing strain rates during the tensile deformations. The vacancy-cluster sizes significantly correlated to the tensile elongations to fracture. It was revealed that the presence of large-sized vacancy-clusters can cause the degradation of mechanical properties and followed by brittle fracture.

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The mechanical characteristics of a porcine spinal cord under static loading in vitro

Inżynieria Powierzchni ◽

10.5604/01.3001.0012.2277 ◽

2018 ◽

Vol 23 (2) ◽

pp. 43-51

Author(s):

Robert Pasławski ◽

Monika Jacyna ◽

Krzysztof Jacyna ◽

Adrian Janiszewski ◽

Romuald Będziński

Keyword(s):

Spinal Cord ◽

Stress Relaxation ◽

Strain Rate ◽

Mechanical Characteristics ◽

Young Modulus ◽

Rate Dependence ◽

Least Square ◽

Strain Rate Dependence ◽

Strain Rates

Background – In spite of a number of researchers, it is well known that mechanical behaviour of a spinal cord under loading has not yet been studied extensively enough. Methods - Specimens were loaded at various strain rates: 0.02/s and 0.002/s to 5% and 10% strain. After reaching defined strain value, samples were left at a constant strain for stress relaxation. Findings – The demonstrated tensile testing stress-strain response is a highly non-linear curve corresponding to low stiffness. In the toe region stress increases exponentially with the applied strain. The highest calculated stress value for 10% strain was 0,014 MPa (strain rate 0,02/s) and 0,008 MPa (strain rate 0,002/s). Linear approximation of the stress by the least square method allowed to derive Young modulus of the value: 39,68 kPa at strain rate 0,02/s and 31,07 kPa at strain rate 0,002/s. R squared value for both regressions was above 0,99 and confirmed a good quality of approximation. A and β coefficients were 1,5MPa and 31,3 at 0,02/s strain rates and 1,3MPa and 25,3 at 0,002/s strain rates correspondingly. Relative stress relaxation increased from 20% to 37% after 60 s. Absolute stress relaxation was from 0,4kPa to 2,4kPa, at 0,002/s strain rate by 5% maximum strain and 0,02/s strain rate by 10% respectively. Interpretation - Mechanical characteristics demonstrated a visible strain-rate dependence as stiffness was significantly increasing with an increase of strain rate. Mechanical characteristics demonstrated a visible strain-rate dependence as stiffness was significantly increasing with an increase of strain rate.

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236 Strain Rate Dependence of Flow Stress of A2017-T4 at Very High Strain Rates

Proceedings of the 1992 Annual Meeting of JSME/MMD ◽

10.1299/jsmezairiki.2005.0_159 ◽

2005 ◽

Vol 2005 (0) ◽

pp. 159-160

Author(s):

Kiyotaka SAKINO ◽

Masahiro HORITA

Keyword(s):

Flow Stress ◽

Strain Rate ◽

High Strain ◽

Rate Dependence ◽

Strain Rate Dependence ◽

Strain Rates ◽

High Strain Rates ◽

Very High

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Dynamic Compression Behavior of Lotus-Type Porous Iron

Materials Science Forum ◽

10.4028/www.scientific.net/msf.658.193 ◽

2010 ◽

Vol 658 ◽

pp. 193-196

Author(s):

Masakazu Tane ◽

Tae Kawashima ◽

Keitaro Horikawa ◽

Hidetoshi Kobayashi ◽

Hideo Nakajima

Keyword(s):

Split Hopkinson Pressure Bar ◽

Dynamic Compression ◽

Testing Machine ◽

Porous Iron ◽

Compression Tests ◽

Hopkinson Pressure Bar ◽

Static Compression ◽

Plateau Stress ◽

Stress Region ◽

Quasi Static Compression

Dynamic and quasi-static compression tests were conducted on lotus-type porous iron with porosity of about 50% using the split Hopkinson pressure bar method and universal testing machine, respectively.　In the dynamic compression parallel to the pore direction, a plateau stress region appears where deformation proceeds at nearly constant stress, while the plateau stress region does not appear in the quasi-static compression. The plateau stress region is probably caused by the buckling deformation of matrix iron which occurs only in the dynamic compression. In contrast, the compression perpendicular to the orientation direction of pores exhibits no plateau-stress regions in the both dynamic and quasi-static compression.

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