scholarly journals Experimental and numerical investigations on the use of polymer Hopkinson pressure bars

2014 ◽  
Vol 372 (2023) ◽  
pp. 20130201 ◽  
Author(s):  
John J. Harrigan ◽  
Bright Ahonsi ◽  
Elisavet Palamidi ◽  
Steve R. Reid
Keyword(s):  
Curve Fitting ◽  
Rheological Model ◽  
Split Hopkinson Pressure Bar ◽  
Fe Model ◽  
Hopkinson Pressure Bar ◽  
Hyperelastic Materials ◽  
Wave Separation ◽  
Derived Properties ◽  
Set Up ◽  
Pressure Bar

Split Hopkinson pressure bar (SHPB) testing has traditionally been carried out using metal bars. For testing low stiffness materials such as rubbers or low strength materials such as low density cellular solids considered primarily herein, there are many advantages to replacing the metal bars with polymer bars. An investigation of a number of aspects associated with the accuracy of SHPB testing of these materials is reported. Test data are used to provide qualitative comparisons of accuracy using different bar materials and wave-separation techniques. Sample results from SHPB tests are provided for balsa, Rohacell foam and hydroxyl-terminated polybutadiene. The techniques used are verified by finite-element (FE) analysis. Experimentally, the material properties of the bars are determined from impact tests in the form of a complex elastic modulus without curve fitting to a rheological model. For the simulations, a rheological model is used to define the bar properties by curve fitting to the experimentally derived properties. Wave propagation in a polymer bar owing to axial impact of a steel bearing ball is simulated. The results indicate that the strain histories can be used to determine accurately the viscoelastic properties of polymer bars. An FE model of the full viscoelastic SHPB set-up is then used to simulate tests on hyperelastic materials.

Features of Meso-Deformation and Failure of Aluminum Foam under Impact

2012 ◽  
Vol 602-604 ◽  
pp. 2235-2240
Author(s):  
Bao Yang ◽  
Li Qun Tang ◽  
Yi Ping Liu ◽  
Ze Jia Liu ◽  
Zhen Yu Jiang
Keyword(s):  
High Speed ◽  
Aluminum Foam ◽  
Split Hopkinson Pressure Bar ◽  
Digital Camera ◽  
Fe Model ◽  
Hopkinson Pressure Bar ◽  
Camera System ◽  
Deformation And Failure ◽  
Split Hopkinson ◽  
Pressure Bar

Deformation and failure of meso-structures take great effect on the loading and energy absorption of aluminum foam under impact. We designed a split Hopkinson pressure bar (SHPB)-high speed digital camera system to monitor the meso-deformation and failure features, and measure the nonuniformity of deformation of aluminum foam under impact. The meso-deformation and failure of aluminum foam were observed successfully by the system, and it showed that there does exist remarkable nonuniform deformation along the specimen. In order to expand the experimental results, the specimen of aluminum foam with meso-structures is modeled by 3D Voronoi technique. The numerical results show that the FE model can simulate the experiment well, and shows that nonuniformity of deformation appears in aluminum foam specimen significantly. The analysis indicates that the assumption of uniform deformation of specimen in SHPB cannot be strictly satisfied for the material of aluminum foam.

Analysis of the Impact of the Frequency Range of the Tensometer Bridge and Projectile Geometry on the Results of Measurements by the Split Hopkinson Pressure Bar Method

2013 ◽  
Vol 20 (4) ◽  
pp. 555-564 ◽  
Author(s):  
Wojciech Moćko
Keyword(s):  
Test Bench ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Spectral Width ◽  
Hopkinson Pressure Bar ◽  
Computing Environment ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact ◽  
Bench Model

Abstract The paper presents the results of the analysis of the striker shape impact on the shape of the mechanical elastic wave generated in the Hopkinson bar. The influence of the tensometer amplifier bandwidth on the stress-strain characteristics obtained in this method was analyzed too. For the purposes of analyzing under the computing environment ABAQUS / Explicit the test bench model was created, and then the analysis of the process of dynamic deformation of the specimen with specific mechanical parameters was carried out. Based on those tests, it was found that the geometry of the end of the striker has an effect on the form of the loading wave and the spectral width of the signal of that wave. Reduction of the striker end diameter reduces unwanted oscillations, however, adversely affects the time of strain rate stabilization. It was determined for the assumed test bench configuration that a tensometric measurement system with a bandwidth equal to 50 kHz is sufficient

scholarly journals Effect of High Strain Rate on Adiabatic Shearing of α+β Dual-Phase Ti Alloy

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2044
Author(s):  
Fang Hao ◽  
Yuxuan Du ◽  
Peixuan Li ◽  
Youchuan Mao ◽  
Deye Lin ◽  
...  
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Damage Tolerance ◽  
Shear Bands ◽  
Dual Phase ◽  
Ti Alloy ◽  
Hopkinson Pressure Bar ◽  
Β Phase ◽  
Schmid Factor ◽  
Pressure Bar

In the present work, the localized features of adiabatic shear bands (ASBs) of our recently designed damage tolerance α+β dual-phase Ti alloy are investigated by the integration of electron backscattering diffraction and experimental and theoretical Schmid factor analysis. At the strain rate of 1.8 × 104 s−1 induced by a split Hopkinson pressure bar, the shear stress reaches a maximum of 1951 MPa with the shear strain of 1.27. It is found that the α+β dual-phase colony structures mediate the extensive plastic deformations along α/β phase boundaries, contributing to the formations of ASBs, microvoids, and cracks, and resulting in stable and unstable softening behaviors. Moreover, the dynamic recrystallization yields the dispersion of a great amount of fine α grains along the shearing paths and in the ASBs, promoting the softening and shear localization. On the contrary, low-angle grain boundaries present good resistance to the formation of cracks and the thermal softening, while the non-basal slipping dramatically contributes to the strain hardening, supporting the promising approaches to fabricate the advanced damage tolerance dual-phase Ti alloy.

Tension and Compression Behavior of Pre-Stressed Steel Strands at High Strain Rate

2011 ◽  
Vol 82 ◽  
pp. 154-159 ◽  
Author(s):  
Anatoly M. Bragov ◽  
Ezio Cadoni ◽  
Alexandr Yu. Konstantinov ◽  
Andrey K. Lomunov
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Gauge Length ◽  
Hopkinson Pressure Bar ◽  
Dog Bone ◽  
Tension And Compression ◽  
Set Up

In this paper is described the mechanical characterization at high strain rate of the high strength steel usually adopted for strands. The experimental set-up used for high strain rates testing: in tension and compression was the Split Hopkinson Pressure Bar installed in the Laboratory of Dynamic Investigation of Materials in Nizhny Novgorod. The high strain rate data in tension was obtained with dog-bone shaped specimens of 3mm in diameter and 5mm of gauge length. The specimens were screwed between incident and transmitter bars. The specimens used in compression was a cylinder of 3mm in diameter and 5mm in length. The enhancement of the mechanical properties is quite limited compared the usual reinforcing steels.

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