scholarly journals Effects of annealing and specimen geometry on dynamic compression of a Zr-based bulk metallic glass

2007 ◽  
Vol 22 (2) ◽  
pp. 389-401 ◽  
Author(s):  
George Sunny ◽  
John Lewandowski ◽  
Vikas Prakash
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Split Hopkinson Pressure Bar ◽  
Peak Stress ◽  
Specimen Geometry ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Split Hopkinson ◽  
Pressure Bar

High strain-rate compression experiments were performed with a split-Hopkinson pressure bar (SHPB) at 500–4000/s on cylindrical samples of a Zr-based bulk metallic glass (LM-1) in both the fully amorphous and annealed conditions. The effects of changes to the specimen geometry (i.e., L/D ratio) and the material heat treatment [i.e., annealing versus amorphous (as-received)], on the peak stress, strain-to-failure, and failure behavior were determined with the aid of an in situ video obtained by using a high-speed digital camera in conjunction with the split-Hopkinson pressure bar (SHPB). Examination of the in situ video recordings and light optical microscopy showed that the failed samples revealed preferential failure initiating at the sample ends due to stress concentration at the sample-insert interface. A new insert design was developed using transient, elastic-plastic finite-element simulations to reduce the effects of these stress concentrations. SHPB testing, combined with in situ video, subsequently revealed that this new experimental configuration promoted failure within the gage length and away from the sample ends in the samples tested. Significant effects of specimen geometry, insert design, and annealing on the apparent values of the peak stress, strain-to-failure, and fracture behavior were exhibited.

An improved method for compressive stress-strain measurements at very high strain rates

1992 ◽  
Vol 438 (1902) ◽  
pp. 153-170 ◽  
Keyword(s):  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Pure Copper ◽  
High Strength ◽  
Tungsten Alloy ◽  
High Speed Photography ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Split Hopkinson ◽  
Pressure Bar

This paper describes a modification of the split Hopkinson pressure bar, to allow compression testing of high strength metals at a strain rate of up to about 10 5 s –1 . All dimensions are minimized to reduce effects of dispersion and inertia, with specimens of the order of 1 mm diameter. Strain is calculated from the stress record and calibrated with high-speed photography. Particular attention has been paid to the accuracy of the technique, and errors arising from nonlinearity in the instrumentation, dispersion, frictional restraint and inertia have all been quantitatively assessed. Stress–strain results are presented of Ti 6A14V alloy, a high strength tungsten alloy, and pure copper.

Dynamic Compression Test of CFRP Laminates Using SHPB Technique

2014 ◽  
Vol 566 ◽  
pp. 122-127
Author(s):  
Takayuki Kusaka ◽  
Takanori Kono ◽  
Yasutoshi Nomura ◽  
Hiroki Wakabayashi
Keyword(s):  
Compressive Strength ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Failure Process ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Cfrp Laminates ◽  
Split Hopkinson ◽  
Pressure Bar

A novel experimental method was proposed for characterizing the compressive properties of composite materials under impact loading. Split Hopkinson pressure bar system was employed to carry out the dynamic compression tests. The dynamic stress-strain relations could be precisely estimated by the proposed method, where the ramped input, generated by the plastic deformation of a zinc buffer, was effective to reduce the oscillation of the stress field in the specimen. The longitudinal strain of gage area could be estimated from the nominal deformation of gage area, and consequently the failure process could be grasped in detail from the stress-strain relation. The dynamic compressive strength of the material was slightly higher than the static compressive strength. In addition, the validity of the proposed method was confirmed by the computational and experimental results.

Measurement of Mechanical Properties of St 37 Material at High Strain Rates Using a Split Hopkinson Pressure Bar

2014 ◽  
Vol 660 ◽  
pp. 562-566 ◽  
Author(s):  
Akbar Afdhal ◽  
Leonardo Gunawan ◽  
Sigit P. Santosa ◽  
Ichsan Setya Putra ◽  
Hoon Huh
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Test Specimen ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Split Hopkinson ◽  
Pressure Bar

The dynamic mechanical properties of a material are important keys to investigate the impact characteristic of a structure such as a crash box. For some materials, the stress-strain relationships at high strain rate loadings are different than that at the static condition. These mechanical properties depend on the strain rate of the loadings, and hence an appropriate testing technique is required to measure them. To measure the mechanical properties of a material at high strain rates, ranging from 500 s-1 to 10000 s-1, a Split Hopkinson Pressure Bar is commonly used. In the measurements, strain pulses are generated in the bars system, and pulses being reflected and transmitted by a test specimen in the bar system are measured. The stress-strain curves as the material properties of the test specimen are obtained by processing the measured reflected and transmitted pulses. This paper presents the measurements of the mechanical properties of St 37 mild steel at several strain rates using a Split Hopkinson Pressure Bar. The stress-strain curves obtained in the measurement were curve fitted using the Power Law. The results show that the strength of St 37 material increases as the strain rate increases.

Experiment on Mechanical Behavior of Reinforced Concrete Subjected to Impact Loading

2012 ◽  
Vol 450-451 ◽  
pp. 523-526 ◽  
Author(s):  
Hai Feng Liu ◽  
Wei Wu Yang ◽  
Jian Guo Ning
Keyword(s):  
Reinforced Concrete ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Peak Stress ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Rate Dependent ◽  
Split Hopkinson ◽  
Reinforced Steel ◽  
Pressure Bar

The dynamic compression tests of reinforced concrete with different reinforcement ratios are carried out by split Hopkinson pressure bar (SHPB). Reinforced steel bar is placed along longitudinal and transverse direction. Experimental results show that reinforced concrete is non-linear and rate-dependent. With the enhancement of strain rate, the peak stress of reinforced concrete increases correspondingly

Dynamic Mechanical Properties of Float Glass

2013 ◽  
Vol 631-632 ◽  
pp. 383-387
Author(s):  
Lei Li ◽  
Jian Hua Liu ◽  
Yao Feng Ji
Keyword(s):  
Mechanical Properties ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Mechanical Properties ◽  
Float Glass ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Dynamic Mechanical ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Nonlinear Elastic

In order to study dynamic mechanical properties of float glass under blast and ballistic/fragmentation impacts, the curves of stress- strain are obtained in higher ranges by using the modified Split Hopkinson Pressure Bar (SHPB) techniques. Experimental results indicate that float glass is nonlinear elastic-brittle materials, and its dynamic curves of stress-strain are nonlinear and can be divided into three stages: elastic, nonlinear strengthening and stress drop. The dynamic Young’s modulus and the dynamic compressive strength of float glass increase with the increasing of strain rate. Finally, an explanation was given according to principle of energy equilibrium of Griffith.

Quasi-Static and Dynamic Confined Compressive Behavior of Glass Beads by In-Situ X-Ray Micro-Computed Tomography

2020 ◽  
Author(s):  
Runyu Zhang ◽  
Huiluo Chen ◽  
Sadeq Malakooti ◽  
Simon Oman ◽  
Bing Wang ◽  
...  
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Glass Beads ◽  
Hopkinson Pressure Bar ◽  
Micro Computed Tomography ◽  
Volumetric Images ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading

Abstract Granular materials are one of the most important materials in several industries such as civil engineering, agriculture, and energy production. They are a collection of distinct macroscopic particles. Although these materials appear very simple to be described, they exhibit highly different mechanical behavior under quasi-static and dynamic loading conditions. Traditionally, glass beads have been considered as a benchmark granular material for the fundamental understanding of the mechanics of granular materials under complex mechanical loadings. In this study, we intend to characterize the compressive behavior of glass beads under confinement using in-situ X-ray micro-computed tomography at low (quasi-static) and high strain (dynamic) rates. At high strain rates, samples with similar bulk densities to the quasi-static samples are compressed using a long split Hopkinson pressure bar and later imaged with the tomography system to acquire their volumetric images. In the case of low strain rates, a similar sample is compressed, and subsequently, its volumetric images are captured at the same strain level as the dynamically compressed samples using the long split Hopkinson pressure bar. The volumetric images for each case are then analyzed to determine three-dimensional morphologies and to investigate and compare the damage and crushing characteristics of the glass beads at quasi-static and dynamic loading conditions.

Numerical Simulation of Double Specimens in Split Hopkinson Pressure Bar Testing

2010 ◽  
Vol 654-656 ◽  
pp. 2483-2486
Author(s):  
Muhammad Agus Kariem ◽  
John H. Beynon ◽  
Dong Ruan
Keyword(s):  
Dynamic Behaviour ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Performance ◽  
Strain Curve ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Element Analysis ◽  
Specimen Test ◽  
Split Hopkinson ◽  
Pressure Bar

The split Hopkinson pressure bar (SHPB) is the most commonly used technique to characterize the dynamic behaviour of materials at very high strain rates. However, a classic single specimen test only generates a single stress-strain curve at the average strain rate of the test. This paper proposes three arrangements on the use of double specimens in SHPB compression testing. All waves propagating along the bars have been used to analyse the dynamic behaviour of the specimens. To simulate the test and predict its dynamic performance, an axisymmetric finite element analysis using LS-DYNA was conducted for the experiment using 13 mm bar diameter. The validity of the simulations was checked with experimental data from normal SHPB testing. Based on the simulations, the modified techniques are achievable and at least two stress-strain curves of materials can be extracted without violating the requirement of a valid SHPB test.

scholarly journals The dynamic compressive behavior of beryllium bearing bulk metallic glasses

1996 ◽  
Vol 11 (2) ◽  
pp. 503-511 ◽  
Author(s):  
H. A. Bruck ◽  
A. J. Rosakis ◽  
W. L. Johnson
Keyword(s):  
Metallic Glass ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Testing ◽  
Adiabatic Heating ◽  
Nominal Composition ◽  
Hopkinson Pressure Bar ◽  
Thermal Detector ◽  
Split Hopkinson ◽  
Pressure Bar

In 1993, a new beryllium bearing bulk metallic glass with the nominal composition Zr41.25Ti13.75Cu12.5Ni10Be22.5 was discovered at Caltech. This metallic glass can be cast as cylindrical rods as large as 16 mm in diameter, which permitted specimens to be fabricated with geometries suitable for dynamic testing. For the first time, the dynamic compressive yield behavior of a metallic glass was characterized at strain rates of 102 to 104/s by using the split Hopkinson pressure bar. A high-speed infrared thermal detector was also used to determine if adiabatic heating occurred during dynamic deformation of the metallic glass. From these tests it appears that the yield stress of the metallic glass is insensitive to strain rate and no adiabatic heating occurs before yielding.

scholarly journals Testing of Weakly Weathered Granites of Different Porosities Using a Split Hopkinson Pressure Bar Technique

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Lei Yan ◽  
Liansheng Liu ◽  
Shenghui Zhang ◽  
Depei Lan ◽  
Jiangchao Liu
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Peak Stress ◽  
Stress Waves ◽  
Porous Rocks ◽  
Average Strain ◽  
Hopkinson Pressure Bar ◽  
Average Strain Rate ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Damage Impact

Nuclear magnetic resonance (NMR) and damage impact testing, using a split Hopkinson pressure bar (SHPB) technique, were conducted on weakly weathered granites of different porosities. Based on this, this study determined and analysed the pore structure and distribution, propagation characteristics of stress waves, changes in initial tangent modulus, and energy dissipation in weakly weathered granites of different porosities. The research demonstrated that the nature of the internal porosity of weakly weathered granites changed with total porosity. Pore structure significantly influenced the amplitude of reflected waves and distortion of transmitted waves. Under constant-damage impact loads, the initial tangent modulus decreased with increasing porosity, whereas the stress-strain curves, after reaching the peak stress, had similar shapes. Peak stress and average strain rate showed a strong power-law correlation with porosity, and peak stress decreased in a power-law correlation with the increase of average strain rate. In other words, the difference in average strain resulted from different porosities when the incident energy was same, and the average strain was negatively correlated with porosity. Under damaging impact, the energy absorbed per unit volume decreased with increasing porosity. The research results reveal dynamic characteristics of natural porous rocks under damage impacts, which provide a reference for studying damage effects of porous rocks under the effects of stress waves.

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