Annular Pulse Shaping Technique for Large-Diameter Kolsky Bar Experiments on Concrete

Martin, Brad; Heard, William F.; Slawson, Thomas R.; Nie, Xu; Basu, Prodyot K.

doi:10.1007/s11340-014-9899-6

Cited by 45 publications

(12 citation statements)

References 39 publications

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“…Chen et al [19] have used a pulse shaper to filter out high frequency noise generated during impact and maintaining force equilibrium across a sample. Moreover, Heard et al [20] have designed a novel annular pulse shaper, which produces stress equilibrium and constant strain rate in a chosen concrete test material. Chen et al [21] have employed a pulse-shaping technique by sticking a pulse shaper on the impact end of the incident bar to prevent a sudden hit by the striker bar and ensure a nearly constant strain rate condition in a concrete specimen.…”

Section: Introductionmentioning

confidence: 99%

Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

Zhu

Niu

et al. 2017

Shock and Vibration

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During the Split-Hopkinson pressure bar (SHPB) tests driven by pendulum hammer, employing a proper special shape striker is an effective way to obtain dynamic stress equilibrium condition and to get constant strain rate of the rock specimen. To find the proper special shape striker, a striker with a cambered surface was introduced and eight geometrically different hammers were designed to analyze the effect of hammer geometry on the waveform of excited incident stress waves. Based on experiments and simulations, parameter effects, including the cambered hammer curvature radius and hammer diameter, length, and impact velocity, on the incident wave shape were examined. These parametric studies provided guidelines for achieving constant strain rates in rock specimens during SHPB tests. The use of different diameter hammers was noted for shaping stress-time curves to follow the stress-strain behavior of green sandstone. Finally, to examine the applicability of using hammer geometry for shaping incident waves to achieve constant strain rate, SHPB tests on green sandstone specimens were conducted. The results demonstrated that a constant strain rate (100 s −1 ) lasting for 70 s was achieved with the 8# hammer (3.7 kg; curvature radius, diameter, and length of 100, 70, and 126.3 mm, resp.). In addition, dynamic experiments on green sandstone were carried out under various strain rates and the results showed that the initial tangential modulus was almost unaffected by strain rate. The strain at peak stress tended to increase with rising strain rate and the dynamic strength of green sandstone showed an apparent rate dependency.

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Section: Introductionmentioning

confidence: 99%

Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

Zhu

Niu

et al. 2017

Shock and Vibration

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“…The profile of the incident bar can be controlled by the pulse shaper material and dimensions. A new pulse shaping technique for large-diameter SHPB using annual copper disk was recently developed and validated under uniaxial loading conditions [12]. In the present study a thin disk of lead (approx.…”

Section: Dynamic Tests Experimental Method: Split Hopkinson Pressure Barmentioning

confidence: 95%

Experimental Investigation of the Confined Behavior of Dry and Wet High-Strength Concrete: Quasi Static Versus Dynamic Loading

Piotrowska

Forquin

2015

J. dynamic behavior mater.

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This paper presents an experimental investigation of the behavior of high-strength concrete (f c28 = 80 MPa) under very high pressure and quasi-static and dynamic loadings. Concrete specimen is inserted in an elastic, high-strength steel ring and subjected to an axial compression. In order to evaluate the confining pressure acting on concrete the ring is instrumented with multiple hoop strain gauges glued on its outer lateral surface. Dry and wet specimens are tested in both static and dynamic loadings in order to assess the influence of the free water content and the strain rate. Dynamic test are performed with a large diameter (80 mm) split Hopkinson pressure bar facility, adapted to test samples of large size (required for testing concrete material) at high stress levels. A strong effect of the free water content and the strain rate is observed in both deviatoric and volumetric behaviors of high-strength concrete. Both, the shear strength and volumetric stiffness increase with the increase of loading rate. One the other hand, free water has a beneficial effect on the volumetric stiffness and a strong negative influence on the deviatoric strength of high-strength concrete. The behavior of highstrength concrete was also compared to that of an ordinary concrete (f c28 = 30 MPa), tested in a similar experimental campaign. In both static and dynamic conditions, dry specimens of the two concretes reach approximately the same deviatoric stress level. However, when the specimens are saturated with free water, high-strength concrete exhibits a deviatoric strength much greater than ordinary concrete.

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“…Constant strain rates were produced with pulse shaping by placing circular annealed copper disks between the striker and incident bars (see Figure 1). 48,49 The loading conditions and pulse shaper diameter and thickness for all 120 tests are summarized in Table I. During testing, incident and transmission bar strain gauge data and pickup coil voltages from the sample (N ¼ 2 turns) were collected.…”

Section: Methodsmentioning

confidence: 99%

High strain-rate magnetoelasticity in Galfenol

Domann

Loeffler

Martin

et al. 2015

Journal of Applied Physics

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This paper presents the experimental measurements of a highly magnetoelastic material (Galfenol) under impact loading. A Split-Hopkinson Pressure Bar was used to generate compressive stress up to 275 MPa at strain rates of either 20/s or 33/s while measuring the stress-strain response and change in magnetic flux density due to magnetoelastic coupling. The average Young's modulus (44.85 GPa) was invariant to strain rate, with instantaneous stiffness ranging from 25 to 55 GPa. A lumped parameters model simulated the measured pickup coil voltages in response to an applied stress pulse. Fitting the model to the experimental data provided the average piezomagnetic coefficient and relative permeability as functions of field strength. The model suggests magnetoelastic coupling is primarily insensitive to strain rates as high as 33/s. Additionally, the lumped parameters model was used to investigate magnetoelastic transducers as potential pulsed power sources. Results show that Galfenol can generate large quantities of instantaneous power (80 MW=m 3 ), comparable to explosively driven ferromagnetic pulse generators (500 MW=m 3 ). However, this process is much more efficient and can be cyclically carried out in the linear elastic range of the material, in stark contrast with explosively driven pulsed power generators. V C 2015 AIP Publishing LLC. [http://dx.

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Annular Pulse Shaping Technique for Large-Diameter Kolsky Bar Experiments on Concrete

Cited by 45 publications

References 39 publications

Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

Experimental Investigation of the Confined Behavior of Dry and Wet High-Strength Concrete: Quasi Static Versus Dynamic Loading

High strain-rate magnetoelasticity in Galfenol

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