A Simplified Design for a Split-Hopkinson Tension Bar with Long Pulse Duration

Ganzenmüller, Georg; Blaum, E.; Mohrmann, D.; Langhof, T.; Plappert, David; Paul, Hanna; Hiermaier, Stefan

doi:10.1016/j.proeng.2017.08.087

Cited by 13 publications

(11 citation statements)

References 8 publications

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“…We are aware of the difficulties associated with the determination of dynamic moduli, nevertheless, this value compares favorably to the quasi-static Young's modulus of E QS = 2.46 ± 0.01 GPa, assuming viscoelastic effects as also reported in [10]. The upper yield strain is resolved very well and the observed value agrees with the viscoplastic relationships reported in [2,10].…”

Section: Experimental Validationsupporting

confidence: 73%

“…To assess the suitability of the new constant acoustic impedance clamping device, the stress-strain behavior of Polycarbonate at elevated rates of strain is investigated. We employ the SHTB setup described in [2], which uses aluminum bars of 16 mm diameter and a striker of 3000 mm length. This setup features a long pulse duration of 1.2 ms which makes it well suited to test materials such as PC with a very large strain to failure.…”

Section: Experimental Validationmentioning

confidence: 99%

“…The analogue of the universal testing machine's crosshead speed is the striker velocity, which is limited by the strength of the striker and the strength of the bar material. In practice, maximum pulse durations on the order of 1 ms and striker velocities up to 40 m/s are currently possible [2][3][4]. From these numbers, the achievable strain rates can be calculated for a given test specimen geometry.…”

Section: Introductionmentioning

confidence: 99%

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A Constant Acoustic Impedance Mount for Sheet-Type Specimens in the Tensile Split-Hopkinson Bar

2018

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This paper addresses a problem well-known amongst practitioners of the Split-Hopkinson Tension Bar method: attaching a flat test specimen made from sheet material to the cylindrical input-and output bars. To date, slotting the bar ends and gluing the specimens into these ends with high-strength adhesives is the gold standard. However, this approach is not universally applicable because some materials are difficult to bond, and the adhesion surface is limited by the bar diameter, meaning that only small width specimens can be tested. In contrast, the hitherto published mechanical clamping mechanisms typically introduce excessive additional mass into the Split-Hopkinson system which detrimentally affects wave propagation and thus causes errors in the stress-strain signals. We circumvent this problem by designing a mechanical clamping device which has the same acoustic impedance as the bar material and is suitable to securely attach specimens with a width larger than the bar diameter. The benefits of our new clamping device are demonstrated by reporting tensile stress-strain data for Polycarbonate at high strain rates. The data is free from unwanted oscillations and enables accurate determination of dynamic strength and stiffness.

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Section: Experimental Validationsupporting

confidence: 73%

Section: Experimental Validationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Constant Acoustic Impedance Mount for Sheet-Type Specimens in the Tensile Split-Hopkinson Bar

2018

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“…While the original inception of the SHB was based on the compression mode, 2 tension-mode instruments 33–41 were developed thereafter. A tensile SHB is capable of measuring stress–strain curves at a strain rate of approximately 400–2000 s −1 .…”

Section: Introductionmentioning

confidence: 99%

“…39 While a compressive stress pulse is generated by impacting the striker onto the incident bar, the generation of a tensile pulse in the incident bar is not a simple task. Thus far, a number of techniques have been developed to generate tensile pulses, which include several methods using (1) a hollow cylinder striker and transfer flange and, 33–41 (2) indirectly loaded hollow tube, 42–45 (3) by-pass collar, 46 (4) stored tension energy, 47 and (5) specially designed specimens such as hat-shaped 48 and M-shaped 49 specimens. Among these methods, the method using a hollow cylinder striker and transfer flange is probably the most employed.…”

Section: Introductionmentioning

confidence: 99%

Design guidelines for the striker and transfer flange of a split Hopkinson tension bar and the origin of spurious waves

Shin

Lee

Kim

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part C:

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Characteristics of the stress pulse generated by impact of a hollow striker on the flange of a split Hopkinson tension bar are investigated via an explicit finite element analysis. Design guidelines are extracted for the hollow striker and flange from the viewpoint of eliminating spurious waves located between the incident and reflected pulses. According to design guidelines, it is desirable to have a striker cross-sectional area the same as that of the flange. It is also desirable to make the cross-sectional area of the striker (flange) the same as that of the bar. As for the flange length, it is recommended to be comparable to the diameter of the bar. The magnitude and duration of the primary stress pulse are consistent with the results of a one-dimensional analysis even when spurious waves are present; meanwhile, overly long spurious waves should be avoided to eliminate their superposition with the reflected pulse. Spurious waves appear when general impedance of the striker is higher than the bar. The origin of spurious waves is a series of step-wise residual pulses generated by multiple cycles of striker impact that make the striker keep compressing the flange after the first cycle of impact. Step-wise residual pulses appear in two forms (continuous waves and discrete waves) in spurious waves due to the secondary impacts during the entrance process of step-wise residual pulses to the flange. The consequences of spurious waves in the use of split Hopkinson tension bars are discussed.

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