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 Minimum Required Distance of Strain Gauge from Specimen for Measuring Transmitted Signal in Split Hopkinson Pressure Bar Test

2020 ◽  
Vol 308 ◽  
pp. 04005 ◽  
Author(s):  
Daesung Kim ◽  
Hyunho Shin
Keyword(s):  
Strain Gauge ◽  
Split Hopkinson Pressure Bar ◽  
Hopkinson Pressure Bar ◽  
Element Analysis ◽  
Design Modification ◽  
Explicit Finite Element ◽  
Specimen Diameter ◽  
Explicit Finite Element Analysis ◽  
Split Hopkinson ◽  
Pressure Bar

The minimum required distance of the strain gauge on the transmitted bar of the split Hopkinson bar has been determined from the position of a metallic specimen via an explicit finite element analysis. The minimum required distance was determined when the strain-time profiles at r = 0, 0.5Ro and 1.0Ro, were coincident (r is the radial position and Ro is the radius of the bar.). The determined minimum required distance, f(x), is presented as a function of the relative specimen diameter to that of the bar (x = D/D0): j(x) = - 0.9385.x3 + 0.6624.x2 - 0.7459.x + 1.4478 (0.1 ≤ x ≤ 0.9). This result demonstrates the Saint-Venant's principle of rapid dissipation of localized stress in transient loading. The result will be useful for the design/modification of the pseudo-one-dimensional impact instruments that utilise a stress pulse transmitted through the specimen. The result will also allow one to avoid unnecessarily remote strain gage position from the specimen.

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.

Confinement device to assess dynamic crushability of wood material

2017 ◽  
Vol 232 (8) ◽  
pp. 1418-1432 ◽  
Author(s):  
J Wouts ◽  
G Haugou ◽  
M Oudjene ◽  
H Naceur ◽  
D Coutellier
Keyword(s):  
Finite Element ◽  
Split Hopkinson Pressure Bar ◽  
Large Diameter ◽  
Hybrid Approach ◽  
Hopkinson Pressure Bar ◽  
Wood Material ◽  
Element Analysis ◽  
Multiaxial Stress State ◽  
Split Hopkinson ◽  
Pressure Bar

Cellular materials such as wood are widely and advantageously used as shock absorbers in various transport applications. The design and manufacturing of structures made of these materials require the knowledge of their dynamic compressive properties at various strain rates and stress states. Therefore, it is challenging to conduct dynamic multiaxial stress state experiments and especially on split-Hopkinson pressure bar apparatus where stress hardening increases as a function of velocity. This paper presents the so-called verification and validation methodology for confining solutions dedicated to impact on viscoelastic split-Hopkinson pressure bar system with large diameter bars. The method is a hybrid approach combining finite element analysis and an original experimental validation. Based on finite element results, particular attention is given to the mass, the material and the geometry to minimize the confining device influence on the propagation of elastic waves and thus on the material response of the tested specimens. It is essential to avoid spurious reflected waves at the new interfaces of the system in order to ensure the validity of the experimentation. The numerically predicted solutions are experimentally validated and preliminary results in the context of dynamic loadings using wood material are presented.

Wave Propagation in the Split Hopkinson Pressure Bar

1983 ◽  
Vol 105 (1) ◽  
pp. 61-66 ◽  
Author(s):  
P. S. Follansbee ◽  
C. Frantz
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Split Hopkinson Pressure Bar ◽  
Strain Curve ◽  
Leading Edge ◽  
Elastic Wave Propagation ◽  
Mathematical Treatment ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar

Elastic wave propagation in the split Hopkinson pressure bar (SHPB) is discussed with an emphasis on the origin and nature of the oscillations that often trail the leading edge of the pressure wave. We show that in the conditions of the SHPB test the pressure bars vibrate in the fundamental mode and that elastic wave propagation can be fully described mathematically. Excellent agreement is found between experimental results and predictions of the mathematical treatment. This suggests that dispersion effects in the pressure bars can be removed from the strain gage records, which reduces the magnitude of the oscillations in the resulting stress strain curve.

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.

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.

scholarly journals Dynamic Behavior of Aluminum Alloy Aw 5005 Undergoing Interfacial Friction and Specimen Configuration in Split Hopkinson Pressure Bar System at High Strain Rates and Temperatures

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4614 ◽  
Author(s):  
Amine Bendarma ◽  
Tomasz Jankowiak ◽  
Alexis Rusinek ◽  
Tomasz Lodygowski ◽  
Bin Jia ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Element Analysis ◽  
Wide Range ◽  
Temperature Experiment ◽  
Split Hopkinson ◽  
Pressure Bar

In this paper, experimental and numerical results of an aluminum alloy’s mechanical behavior are discussed. Over a wide range of strain rates (10−4 s−1 ≤ έ ≤ 103 s−1) the influence of the loading impact, velocity and temperature on the dynamic response of the material was analyzed. The interface friction effect on the material’s dynamic response is examined using a split Hopkinson pressure bar (SHPB) in a high temperature experiment using finite element analysis (FEA). The effect of different friction conditions between the specimen and the transmitted/incident bars in the SHPB system was examined using cylinder bulk specimens and cylinder plates defined with four-layer configurations. The results of these tests alongside the presented numerical simulations allow a better understanding of the phenomenon and reduces (minimizes) errors during compression tests at high and low strain rates with temperatures ranging from 21 to 300 °C.

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