Dynamic High‐temperature Testing of an Iridium Alloy in Compression at High‐strain Rates

Song, Bo; Nelson, Kevin Michael; Lipinski, Ronald J.; Bignell, John L.; Ulrich, George B; George, E.P.

doi:10.1111/str.12100

Cited by 18 publications

(9 citation statements)

References 22 publications

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“…Concerning the dynamic regime, not a single study of the dynamic response of pure iridium has been found in the literature apart from a few publications on stress-strain properties under dynamic and impact loading of DOP-26 (an iridium alloy containing 0.3 % of W to aid fabrication and approximately 40 ppm of Th to improve grain boundary cohesion at high temperatures), mainly motivated by the use of this material as cladding for radioisotope thermo-electric generator [15][16]. More recent publications have been found in the literature on the dynamic testing of DOP-26 alloy in tension [17][18] and compression [19] at different temperatures. In [18], an approach similar to those here proposed was applied to investigate the mechanical behaviour of the iridium alloy DOP-26 between 10 3 s -1 and 3×10 3 s -1 at high temperature (between 750 °C and 1030 °C).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Experimental results and strength model identification of pure iridium

Scapin

Peroni

Cabanilles

et al. 2017

International Journal of Impact Engineering

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  Mechanical characterization of pure iridium  Tension tests at different temperatures and strain-rates  Fracture surface analysis  Johnson-Cook model identification  Recrystallization temperature

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Section: Accepted Manuscriptmentioning

confidence: 99%

Experimental results and strength model identification of pure iridium

Scapin

Peroni

Cabanilles

et al. 2017

International Journal of Impact Engineering

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“…It may result in a significant error in the strain measurements of the specimen, particularly when specimen strain is small. In order to limit the punching effect, high stiffness and high strength platens are placed between the bars and the specimen [5]. However, the introduction of the platens may cause wave disturbances resulting from a wave impedance mismatch and imperfections of the contact surfaces (e.g.…”

Section: Introductionmentioning

confidence: 99%

Strain measuring accuracy with splitting-beam laser extensometer technique at split Hopkinson compression bar experiment

Panowicz¹,

Janiszewski²,

Traczyk³

2017

Bulletin of the Polish Academy of Sciences Technical Sciences

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Abstract. An accuracy problem of strain measurement at compression split Hopkinson compression bar experiments with a splitting-beam laser extensometer was considered. The splitting-beam laser extensometer technique was developed by Nie et al. to measure strain of a specimen during its tension under a high strain rate loading condition. This novel concept was an inspiration for the authors to develop own laser extensometer system, which allows for simultaneous and independent measurement of displacement of bar ends between which a compressed material specimen is placed. In order to assess a metrological property of this measuring system, a wide range of high strain rate experiments were performed, including tests with various sample materials (Al 5251, Cu OFE) with different rate of strain, and with the use of two bars material. A high accuracy of the developed laser extensometer was found in measurement of specimen strain, for which uncertainty is not greater than 0.1% and, for a typical specimen dimension, the maximum permissible error is 4.5 μm.Key words: SHPB test, strain rates, non-contact strain measurement, laser extensometer. The simplest approach is to use a high speed digital camera to photograph the specimen deformation [10,11]. The camera is focused on the entire gauge section and part of the nongauge section at both ends to achieve a sufficient image with the highest resolution possible. Due to motion analysis of the selected characteristic points, defining the strain gage length, a strain-time relationship can be determined. However, due to the limited frame rate and its corresponding resolution of a contemporary high speed camera, the obtained results did not provide sufficient data points to construct a full stress-strain curve [8]. Strain measuring accuracy with splitting-beam laserThe high-rate digital image correlation (DIC) is a further development of the above described techniques [12,13]. In this case, information about specimen deformation is given by motion analysis of a large number of points (speckle) spreading over the surface of the specimen gauge length [14,15]. A random speckle pattern is generated by a spraying black paint and a white base layer directly onto the surface of the specimen. Thus, DIC provides highly valuable information on dynamic full-field strain measurements in the specimen, however, the above-mentioned limitations resulting from the usage of a contemporary high speed camera and an extreme difficulty in acquiring a large quantity of high-resolution images at very high frame rates do not allow for constructing a precise stressstrain curve [8].Another strain measuring technique is the interferometric-strain-gauge method, which is one of the first diagnostic techniques applied to straightforward non-contact measurement of specimen strain in SHPB testing. Sharpe et al. [16] used this method for evaluation of strain uniformity in the compressed specimen by comparison of surface strain at the specimen midpoint to the average strain calculated from the conventional Kolsk...

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“…The split Hopkinson bar was largely applied to evaluate the strain rate sensitivity of materials at high strain rates; that is,̇∼< 5000 s −1 [1][2][3]. At very high strain rates (̇>∼ 5000 s −1 ), the direct-impact Hopkinson bar is now increasingly used [4,5].…”

Section: Introductionmentioning

confidence: 99%

A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10⁻⁵to 5 × 10⁴ s⁻¹

Othman¹

2015

Advances in Materials Science and Engineering

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In several industrial applications, metallic structures are facing impact loads. Therefore, there is an important need for developing constitutive equations which take into account the strain rate sensitivity of their mechanical properties. The Johnson-Cook equation was widely used to model the strain rate sensitivity of metals. However, it implies that the yield and flow stresses are linearly increasing in terms of the logarithm of strain rate. This is only true up to a threshold strain rate. In this work, a three-constant constitutive equation, assuming an apparent activation volume which decreases as the strain rate increases, is applied here for some metals. It is shown that this equation fits well the experimental yield and flow stresses for a very wide range of strain rates, including quasi-static, high, and very high strain rates (from 10−5to 5 × 104 s−1). This is the first time that a constitutive equation is showed to be able to fit the yield stress over a so large strain rate range while using only three material constants.

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Dynamic High‐temperature Testing of an Iridium Alloy in Compression at High‐strain Rates

Cited by 18 publications

References 22 publications

Experimental results and strength model identification of pure iridium

Experimental results and strength model identification of pure iridium

Strain measuring accuracy with splitting-beam laser extensometer technique at split Hopkinson compression bar experiment

A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10⁻⁵to 5 × 10⁴ s⁻¹

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Dynamic High‐temperature Testing of an Iridium Alloy in Compression at High‐strain Rates

Cited by 18 publications

References 22 publications

Experimental results and strength model identification of pure iridium

Experimental results and strength model identification of pure iridium

Strain measuring accuracy with splitting-beam laser extensometer technique at split Hopkinson compression bar experiment

A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10−5to 5 × 104 s−1

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A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10⁻⁵to 5 × 10⁴ s⁻¹