Dynamic mesoscale cracking modeling of energetic composite materials in Hopkinson bar test

2021 ◽  
pp. 114989
Author(s):  
Rui Liu ◽  
Peng-Wan Chen ◽  
Ge Kang ◽  
Shun-Peng Zhu ◽  
Andrea Carpinteri ◽  
...  
Keyword(s):  
Composite Materials ◽  
Hopkinson Bar ◽  
Bar Test

An optical method for direct measurements of strain in a torsional Hopkinson-bar apparatus

1975 ◽  
Vol 10 (3) ◽  
pp. 172-179 ◽  
Author(s):  
M G Stevenson ◽  
J D Campbell
Keyword(s):  
Torsion Test ◽  
Hopkinson Bar ◽  
Gauge Length ◽  
Wave Reflections ◽  
Multiple Wave ◽  
Torsional Waves ◽  
Direct Measurements ◽  
Angular Velocities ◽  
Bar Test

A method has been developed to measure the related rotation of the flanges of a thin-walled tubular specimen during a torsion test. The method, which is based on the Moiré-fringe technique, is capable of use at the high rates of strain encountered during a Hopkinson-bar test, as well as at low rates of strain. In the application described, the specimen gauge length is very short, but the method could be used for specimens of considerably longer gauge length. Direct calibration of the system is easily carried out at low angular velocities. The method can then be used to measure directly the specimen strain during a Hopkinson-bar test, and thus to check the value derived from measuremets of torsional waves in the elastic bars. Results of such comparisons are given, and it is found that the values given by the two method agree well, the differnce being attributable largely to inaccuracies in the torque measurement. The new method permits the determination of specimen deformation during the later stages of the test when multiple wave reflections render the wave analysis iaccurate. In particular, it has been found that the specimen may be subjected to reversed plastic straining, so that the total plastic strain connot be determined from the permenent deformation at the end of the test.

A New Approach to Determine Dynamic Strength Model Parameters under Taylor Impact Test

2012 ◽  
Vol 525-526 ◽  
pp. 377-380
Author(s):  
F. Xu ◽  
Wei Guo Guo ◽  
Q.J. Wang ◽  
Zhi Yin Zeng
Keyword(s):  
Impact Test ◽  
Dynamic Strength ◽  
Hopkinson Bar ◽  
Optimization Techniques ◽  
Model Parameters ◽  
Strength Model ◽  
New Approach ◽  
Taylor Impact ◽  
Bar Test ◽  
Taylor Impact Test

In this paper, to determine the dynamic strength model for steels, a new approach which does not rely on the Hopkinson bar test has been proposed. As the DH36 steel for example, using the results of Taylor impact test and the quasi-static compression test, the initial parameters of Johnson-Cook plastic strength model have been fitted out, then the initial strength parameters have been optimized using the optimization techniques of the sparse Taylor impact cylinder. It has been shown that the optimized results in numerical simulation are consistent with results of Taylor impact test, and the optimized Johnson-Cook model can also well describe flow stress curve fitted from the Hopkinson bar test.

scholarly journals Challenges related to testing of composite materials at high strain rates using the split Hopkinson bar technique

2018 ◽  
Vol 183 ◽  
pp. 02021 ◽  
Author(s):  
Ahmed Elmahdy ◽  
Patricia Verleysen
Keyword(s):  
Composite Materials ◽  
High Strain ◽  
Hopkinson Bar ◽  
Dynamic Strain ◽  
Strain Rates ◽  
High Strain Rates ◽  
Strain Fields ◽  
Split Hopkinson Bar ◽  
Gauge Section ◽  
Split Hopkinson

The design of sample geometries and the measurement of small strains are considered the main challenges when testing composite materials at high strain rates using the split Hopkinson bar technique. The aim of this paper is to assess two types of tensile sample geometries, namely dog-bone and straight strip, in order to study the tensile behaviour of basalt fibre reinforced composites at high strain rates using the split Hopkinson bar technique. 2D Digital image correlation technique was used to study the distribution of the strain fields within the gauge section at quasi-static and dynamic strain rates. Results showed that for the current experiments and the proposed clamping techniques, both sample geometries fulfilled the requirements of a valid split Hopkinson test, and achieved uniform strain fields within the gauge section. However, classical Hopkinson analysis tends to overestimate the actual strains in the gauge section for both geometries. It is, therefore, important to use a local deformation measurement when using these 2 geometries with the proposed clamping technique.

scholarly journals Dynamic Response of Deccan Trap Basalt under Hopkinson Bar Test

2017 ◽  
Vol 173 ◽  
pp. 647-654 ◽  
Author(s):  
Akx Malik ◽  
Tanusree Chakraborty ◽  
K.S. Rao ◽  
D. Kumar ◽  
P. Chandel ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Deccan Trap ◽  
Hopkinson Bar ◽  
Bar Test
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