Observations on differences between the energy determined using an instrumented striker and dial/encoder energy

Manahan, Michael P.; Stonesifer, R.B.; Siewert, Thomas A.; McCowan, Christopher N.; Vigliotti, D P.

doi:10.1016/s1566-1369(02)80025-5

Cited by 5 publications

(13 citation statements)

References 4 publications

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“…When plotting the difference between TK and mean{TO2-SI2/SI3} as a function of test date (Figure 9), a slightly increasing trend is observed. An investigation by Manahan et al [8], conducted in cooperation with NIST, offers a possible explanation to the systematically lower values yielded by the TK machine.…”

Section: Low-energy Specimensmentioning

confidence: 99%

“…Calculations performed on a simple two-mass, two-spring model of the striker/specimen assembly in [8] suggest that this difference in absorbed energy can be explained in terms of frequency shift in the applied force, caused by a stiffer design of the striker assembly in the TK machine. Indeed, this machine was found to be stiffer (less compliant) than TO2 or SI3 when the compliance of all the NIST Charpy machines was measured [9].…”

Section: Low-energy Specimensmentioning

confidence: 99%

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A Comparative Analysis of NIST Charpy Machines and Internal Reference Materials

Lucon¹,

Santoyo²

2016

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This report documents the results of a series of comparative analyses which were conducted on the Charpy machines located at NIST in Boulder, Colorado. The analyses were performed both on historical data, collected over a period of more than 20 years, and newly obtained test results from almost 300 instrumented and non-instrumented impact tests on verification specimens of low energy (13 J to 20 J), high energy (88 J to 136 J), and super-high energy (176 J to 244 J). The comparative analyses were completed for the purpose of understanding the limits of calibrating instrumented strikers for use in dynamic test through conventional static calibration procedures. Test results, obtained both in the past and within the current study, show that one of the so-called "master machines" (used to establish reference values for ASTM verification specimens) delivers consistently lower energy values than the other two master machines in the 15 J-20 J range. This is suspected to be due to its higher stiffness and hammer design (C-type), which increases its natural frequency of vibration and causes early fracture in a quasi-brittle (low-energy) test. The extremely large number of instrumented Charpy tests performed within this investigation (more than 200) allowed us to assess the reliability of the conventional static calibration procedure for our instrumented strikers, as compared to different approaches for the adjustment/correction of measured force values. Even though these approaches were found beneficial in improving the between-machine consistency, statistically significant differences remained nonetheless. It appears that, in order to reliably calibrate an instrumented striker, forces must be applied at loading rates that are equivalent to those encountered during actual tests (dynamic calibration of instrumented strikers). This should become a clear objective of the NIST Charpy program going forward.

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Section: Low-energy Specimensmentioning

confidence: 99%

Section: Low-energy Specimensmentioning

confidence: 99%

A Comparative Analysis of NIST Charpy Machines and Internal Reference Materials

Lucon¹,

Santoyo²

2016

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“…Length and bending stiffness exert the largest impact on the value of the strain energy of the pendulum arm. The publication [20] shows that a 20% increase in the pendulum stiffness results in a 9% increase in the registered energy of the impact-damaged samples. Therefore, it seems reasonable to claim that the standard beyond the dimensions of the specimens should impose these two characteristics of the test device: length and bending stiffness of the pendulum arm.…”

Section: Discussionmentioning

confidence: 99%

“…The investigated specimen was treated as a beam, supported on both sides, and loaded with a centrally focused force. The deflection of such a beam f is described as follows: (15) After the transformation taking into account the moment of inertia of the rectangular cross section, there is: (16) For the impact load model in question: (17) maximum stresses are the quotient of the bending moment and the flexural strength factor: (18) and the maximum deformation is described by the dependency: (19) In order to calculate the speeds of the deformation, it is necessary to divide them by the time after which there will be a deflection of the sample valued f: (20) where V is the speed of the pendulum.…”

Section: The Speed Of Deformation Of the Test Specimensmentioning

confidence: 99%

An Energy Analysis of Impact Strength Tests Using Pendulum Hammers

Godzimirski¹,

Komorek²,

Komorek³

2019

Adv. Sci. Technol. Res. J.

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An attempt to estimate the value of the deformation energy of a metal specimen and the research system during impact strength tests on pendulum hammers was made. In the experimental research it was found that the rectangular metal specimens of the same cross-sectional area exhibit different impact strength, depending on the direction of the load (bending stiffness) whereas the destruction work of such samples exposed to static bending is comparable. The article presents the results of the experimental research, completed with numerical calculations carried out to assess the value of the deformation energy during the impact tests. By performing numerical calculations, the authors estimated the deformation energies of specimens characterised by elastoplastic properties with reinforcement (bilinear) under destructive loads. The energy of the elastic deformation of the hammer arm was estimated analytically. On the basis of the research, it was found that in the impact strength test, a large part of the recorded energy is connected with the deformation of the test device, in particular, the pendulum which undergoes bending. Moreover, the recorded impact strength of the material is not proportional to its actual impact strength.

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“…A possible explanation of these findings was proposed in [16], based on previous work conducted by Manahan et al in cooperation with NIST [17]. Based on calculations performed on a simple two-mass, two-spring model of the striker/specimen assembly, it was suggested that the difference in absorbed energies can be explained in terms of frequency shift in the applied force, caused by the stiffer design of the striker assembly in the TK machine 10 .…”

Section: Influence Of Hammer Configuration (Machine Type) On Charpy Tmentioning

confidence: 97%

Charpy interlaboratory comparison between NIST and the Beijing Institute of Metrology (BIM)

Lucon¹,

Santoyo²

2019

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The Beijing Institute of Metrology (BIM, China) and NIST have participated in an interlaboratory comparison, in which reference Charpy specimens of three energy levels were tested. Each laboratory tested 75 specimens supplied by the other institute, 25 per energy level, at room temperature (21 °C ± 1 °C) and using an impact machine equipped with a 2 mm striker. The results obtained show good to excellent agreement between BIM and NIST, except at the low-energy level (20 J to 25 J), where NIST data obtained using a U-type machine were significantly higher than BIM data obtained using a C-type machine. Twentyfive additional low-energy BIM specimens, tested by NIST using a C-type machine, showed excellent consistency with BIM reference data and therefore confirmed that, for low-energy specimens, the configuration of the swinging hammer may affect test results, due to the different stiffness/compliance of the two machine types. A similar, but unexpected, trend was observed for the NIST super-high-energy specimens, and will need to be explained though further investigations. Key words2 mm striker; Charpy reference specimens; C-type hammer; interlaboratory comparison; U-type hammer.ii This publication is available free of charge from: https://doi.

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Observations on differences between the energy determined using an instrumented striker and dial/encoder energy

Cited by 5 publications

References 4 publications

A Comparative Analysis of NIST Charpy Machines and Internal Reference Materials

A Comparative Analysis of NIST Charpy Machines and Internal Reference Materials

An Energy Analysis of Impact Strength Tests Using Pendulum Hammers

Charpy interlaboratory comparison between NIST and the Beijing Institute of Metrology (BIM)

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