scholarly journals Strain measuring accuracy with splitting-beam laser extensometer technique at split Hopkinson compression bar experiment

2017 ◽  
Vol 65 (2) ◽  
pp. 163-169 ◽  
Author(s):  
R. Panowicz ◽  
J. Janiszewski ◽  
M. Traczyk
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Measuring System ◽  
Beam Laser ◽  
Typical Specimen ◽  
Material Specimen ◽  
Wide Range ◽  
Split Hopkinson ◽  
Novel Concept

Abstract An accuracy problem of strain measurement at compression split Hopkinson compression bar experiments with a splitting-beam laser extensometer was considered. The splitting-beam laser extensometer technique was developed by Nie et al. to measure strain of a specimen during its tension under a high strain rate loading condition. This novel concept was an inspiration for the authors to develop own laser extensometer system, which allows for simultaneous and independent measurement of displacement of bar ends between which a compressed material specimen is placed. In order to assess a metrological property of this measuring system, a wide range of high strain rate experiments were performed, including tests with various sample materials (Al 5251, Cu OFE) with different rate of strain, and with the use of two bars material. A high accuracy of the developed laser extensometer was found in measurement of specimen strain, for which uncertainty is not greater than 0.1% and, for a typical specimen dimension, the maximum permissible error is 4.5 μm.

Evaluation of Bodner-Partom Model Parameters at High Strain Rate

1986 ◽  
Vol 108 (1) ◽  
pp. 75-80 ◽  
Author(s):  
A. M. Rajendran ◽  
S. J. Bless ◽  
D. S. Dawicke
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Material Behavior ◽  
Model Parameters ◽  
Plate Impact ◽  
Plane Plate ◽  
Wide Range ◽  
Split Hopkinson ◽  
Stress States

The objective of this paper is to model the high strain rate material behavior of metals using Bodner-Partom visco-plastic constitutive model. A unique algorithm has been developed to evaluate the model parameters from the split Hopkinson Bar and plane plate impact tests data. The model parameters were successfully determined for the 6061-T6 aluminum, 1020 steel, and HY 100 steel. Using the evaluated model parameters, the test data obtained from an unusually wide range of stress states for these three metals were successfully modeled.

The use of the split Hopkinson pressure bar techniques in high strain rate materials testing

1997 ◽  
Vol 211 (4) ◽  
pp. 273-292 ◽  
Author(s):  
M M Al-Mousawi ◽  
S R Reid ◽  
W F Deans
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Measuring System ◽  
Materials Testing ◽  
Hopkinson Pressure Bar ◽  
Simple Method ◽  
Split Hopkinson ◽  
Pressure Bar

The use of the split Hopkinson pressure bar (SHPB) techniques for materials testing under a high rate of loading is described, including various modifications of the original compression testing set-up for tension testing, torsion testing and dynamic fracture testing. Details of measurement techniques and instrumentation are included together with the calibration of the air gun and strain wave measuring system. The SHPB techniques provide a relatively cheap and simple method for high strain rate materials testing with an acceptable level of accuracy when sufficient care is taken for the proper lubrication of the interfaces and the correct length—radius ratio of the specimen is chosen. The limitations of the method are discussed and possible improvements using FFT (fast Fourier transform) techniques to take into account dispersion effects are considered.

Tensile Ductility of Ultra-Fine Grained Copper at High Strain Rate

2010 ◽  
Vol 160-162 ◽  
pp. 260-266 ◽  
Author(s):  
Tao Suo ◽  
Kui Xie ◽  
Yu Long Li ◽  
Feng Zhao ◽  
Qiong Deng
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Testing Machine ◽  
Coarse Grained ◽  
Dislocation Dynamic ◽  
Pressing Method ◽  
Fine Grained ◽  
Angular Pressing ◽  
Split Hopkinson

In this paper, ultra-fine grained copper fabricated by equal channel angular pressing method and annealed coarse grained copper were tensioned under both quasi-static and dynamic loading conditions using an electronic universal testing machine and the split Hopkinson tension bar respectively. The rapture surface of specimen was also observed via a Scanning Electron Microscope (SEM). The experimental results show that the ductility of polycrystalline copper decreases remarkably due to the grain refinement. However, with the increase of applied strain rate, ductility of the UFG-Cu is enhanced. The fracture morphologies also give the evidence of enhanced ductility of UFG-Cu at high strain rate. It is believed the enhanced ductility of UFG materials at high strain rate can be attributed to the restrained dislocation dynamic recovery.

High Strain Rate Response of Rocks Under Dynamic Loading Using Split Hopkinson Pressure Bar

2017 ◽  
Vol 36 (1) ◽  
pp. 531-549 ◽  
Author(s):  
Sunita Mishra ◽  
Hemant Meena ◽  
Vedant Parashar ◽  
Anuradha Khetwal ◽  
Tanusree Chakraborty ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Dynamic Loading ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar

High Strain-Rate Compressive Behavior and Constitutive Modeling of Selected Polymers Using Modified Ramberg-Osgood Equation

2014 ◽  
Vol 566 ◽  
pp. 80-85
Author(s):  
Kenji Nakai ◽  
Takashi Yokoyama
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Compressive Stress ◽  
Constitutive Modeling ◽  
High Strain ◽  
Strain Rates ◽  
Stress Strain ◽  
Strain Behavior ◽  
Least Squares Fit ◽  
Wide Range

The present paper is concerned with constitutive modeling of the compressive stress-strain behavior of selected polymers at strain rates from 10-3 to 103/s using a modified Ramberg-Osgood equation. High strain-rate compressive stress-strain curves up to strains of nearly 0.08 for four different commercially available extruded polymers were determined on the standard split Hopkinson pressure bar (SHPB). The low and intermediate strain-rate compressive stress-strain relations were measured in an Instron testing machine. Six parameters in the modified Ramberg-Osgood equation were determined by fitting to the experimental stress-strain data using a least-squares fit. It was shown that the monotonic compressive stress-strain behavior over a wide range of strain rates can successfully be described by the modified Ramberg-Osgood constitutive model. The limitations of the model were discussed.

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