Characterization of a Laser Extensometer for Split Hopkinson Pressure bar Experiments

Joyce, Bryan; Dennis, Mark R.; Dodson, Jacob; Wolfson, Janet

doi:10.1007/s11340-017-0302-2

Cited by 4 publications

(4 citation statements)

References 25 publications

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“…The extensometer is installed in the experiment to obtain the more accurate compression displacement (Figure 2). 16 The compression characteristics of UCFREP at strain rates of 0.001 s À1 , 0.01 s À1 and 0.1 s À1 can be obtained by changing the speed v of MTS's pressure head, and the preloading of 0.1 KN should be set up before the experiment. The head speed v is derived from the formula (1) by engineering strain rate _ e. According to formula (2), the engineering stress r and engineering strain e can be obtained by the force-displacement curve, and then transformed it into true stress r T and strain e T via the relation (3).…”

Section: Experimental Process and Principlementioning

confidence: 99%

Research on compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP)

Zhao

Zhou

Changxing

et al. 2020

Journal of Composite Materials

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To research the axial compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP), the compression experiments at different strain rates were carried out by using the MTS universal electronic testing machine and the equipment of split Hopkinson pressure bar (SHPB). Furthermore, the finite element analysis (FEA) was also used to study the compression properties of UCFREP with different conditions. The true stress-strain curves in quasi-static and dynamic compression were obtained, and the relationship between yield limit and strain rate was coupled. The microstructure of the failure area was observed by scanning electron microscope (SEM). A formula for predicting compression strength of combined buckling under the quasi-static condition was presented. The application range of Chang-Chang failure criterion was discussed by FEA, and the compression failure of UCFREP with different fiber directions was predicted. The results show that UCFREP has the obvious strain rate effect, the mechanical properties at dynamic compression are nonlinear. Shear is the main compression failure mode, which includes the shear cracking of matrix between fibers and the shear buckling of fiber. The direction of the fiber is the main factor that causes the shear cracking, such as the shear cracking shows the feature of 45° when the direction of the fiber is 45°. As a conclusion, increasing the shear strength of matrix and fiber will be a way to increase the compression strength of UCFREP. This paper could be used as a reference to develop the new constitutive model, especially considering the nonlinear effect.

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Section: Experimental Process and Principlementioning

confidence: 99%

Research on compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP)

Zhao

Zhou

Changxing

et al. 2020

Journal of Composite Materials

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“…This grid method requires a regular grid pattern on the sample surface with a high-resolution high-speed camera and associated image processing technique [39]. In addition to the full-field measurement methods mentioned above, laser-based strain measurement techniques have been widely published in the literature [33,34,[40][41][42][43][44][45]. Zhu et al [40,41] designed a high-speed laser extensometer, based on laser interferometry, to measure the tensile strain history at moderate strain rates up to 24 s −1 rather than higher strain rates.…”

Section: Improved Experimental and Diagnostic Techniques For Dynamic ...mentioning

confidence: 99%

“…Li and Ramesh [42] developed an optical-based direct non-contact extensometer technique for radial deformation measurement, and obtained similar results measured by the on-specimen strain gages. Guzman et al [33] adopted a single channel laser extensometer system to capture the large tensile strain at high strain rate, while Joyce et al [44] used the single channel laser extensometer to measure the compressive strain of silicone samples and obtained accurate axial strain at different strain rates. They also pointed out that the measurement accuracy was deteriorated by the large radial expansion of the soft material at high axial strains.…”

Section: Improved Experimental and Diagnostic Techniques For Dynamic ...mentioning

confidence: 99%

Improved experimental and diagnostic techniques for dynamic tensile stress–strain measurement with a Kolsky tension bar

Qiu¹,

Loeffler²,

Nie

et al. 2018

Meas. Sci. Technol.

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Kolsky tension bar experiments were improved for dynamic tensile stress-strain measurements with higher fidelity and minimal uncertainties. The difficulties associated with specimen gripping, relatively short gage section, and geometric discontinuity at the bar ends all compromise the accuracy of the traditional strain measurement method in a Kolsky tension bar experiment. In this study, an improved three-channel splitting-beam laser extensometer technique was developed to directly and independently track the displacement of the incident and transmission bar interfaces. By adopting a dual-channel configuration on the incident bar side, the resolution and measurement range of this laser extensometer were coordinated between the two channels to provide highly precise measurement at both small and large strains under high strain-rate loading condition. On the transmission bar side an amplified channel, similar to that used on the incident bar side, was adopted to measure the transmission bar displacement with high resolution. With this novel design, a maximum resolution of approximately 500 nm can be obtained for the bar displacement measurement, which corresponds to a strain of 0.0079% for a specimen with 6.35 mm gage length. To further improve the accuracy, a pair of lock nuts were used to tighten the tensile specimen to the bars in an effort not only to prevent the specimen from potential pre-torsional deformation and damage during installation, but also to provide better thread engagement between the specimen and the bar ends. As a demonstration of this technique, dynamic tensile stress-strain response of a 304L stainless steel was characterized with high resolution in both elastic and plastic deformations.

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“…The results showed that this measurement method was in good agreement with the strain gauge curves. 10,11 Fu et al 12 installed two shutters at the end of the bars to measure the velocity directly between the faces using a micro-displacement fiber interference system for each reflector. Using this method, both stress and strain of the sample were calculated with acceptable accuracy.…”

Section: Introductionmentioning

confidence: 99%

Determination of dynamic material properties using laser measurement technique in split Hopkinson pressure bar

Mirshafiee

Ashrafi

Mousavi

2023

The Journal of Strain Analysis for Engineering Design

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The split Hopkinson pressure bar (SHPB) is a commonly used technique to measure the stress-strain of materials at high strain rate. Using the strain records in the input and output bars, the average stress-strain and strain rate in the sample can be calculated by SHPB formulas based on the one-dimensional wave propagation theory. The accuracy of a SHPB test is based on this assumption. In this paper, first a laser measuring system is designed, implemented, and calibrated in order to obtain the dynamic properties of different materials using split Hopkinson pressure bar test. In this method which is a non-contact one, the displacements of bar/sample interfaces are measured directly using a laser extensometer technique, by using the provided equations, in addition to the strain, the stress of the tested sample can be calculated. Moreover, the operation of the method is evaluated using numerical simulation. Aluminum 7075 and copper C10200 samples were studied to evaluate the implemented measurement method. The comparison with other measurement methods shows good agreement of numerical and experimental results. Moreover, since the one-dimensional wave propagation is not used directly in this method, we show the proposed method can be used even with shorter pressure bars which can reduce the cost of manufacturing and maintenance of the SHPB apparatus.

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Characterization of a Laser Extensometer for Split Hopkinson Pressure bar Experiments

Cited by 4 publications

References 25 publications

Research on compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP)

Research on compression properties of unidirectional carbon fiber reinforced epoxy resin composite (UCFREP)

Improved experimental and diagnostic techniques for dynamic tensile stress–strain measurement with a Kolsky tension bar

Determination of dynamic material properties using laser measurement technique in split Hopkinson pressure bar

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