Measuring and modeling of low temperature Hopkinson tests

Berkovic, L.; Chabotier, A.; Coghe, F.; Rabet, L.

doi:10.1016/j.proeng.2011.04.275

Cited by 6 publications

(3 citation statements)

References 2 publications

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“…The temperature of the compressive samples could not be measured directly in the process. Instead, a cooling curve was created with a reference sample, as described in [23]. A hole with a diameter of 1.5 mm and a depth of 3 mm was drilled into the surface of the sample.…”

Section: Methodsmentioning

confidence: 99%

High Strain Rate and Stress-State-Dependent Martensite Transformation in AISI 304 at Low Temperatures

Fricke

Gerstein

Kotzbauer

et al. 2022

Metals

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Deformation-induced martensitic transformation as the basis of a hardening process is dependent, among others, on the stress state. In applications such as cryogenic cutting, where a hardened martensitic subsurface can be produced in metastable austenitic steels, different stress states exist. Furthermore, cutting typically occurs at high strain rates greater than 103s−1. In order to gain a deeper insight into the behavior of a metastable austenitic steel (AISI 304) upon cryogenic cutting, the influence of high strain rates under different loading conditions was analyzed. It was observed that higher strain rates lead to a decrease in the α′-martensite content if exposed to tensile loads due to generated adiabatic heat. Furthermore, a lath-like α′-martensite was induced. Under shear stress, no suppression of α′-martensite formation by higher strain rates was found. A lath α′-martensite was formed, too. In the specimens that were subjected exclusively to compressive loading, almost no α′-martensite was present. The martensitic surface generated by cutting experiments showed deformation lines in which α′-martensite was formed in a wave-like shape. As for the shear specimens, more α′-martensite was formed with increasing strain rate, i.e., force. Additionally, magnetic etching proved to be an effective method to verify the transformation of ferromagnetic α′-martensite.

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Section: Methodsmentioning

confidence: 99%

High Strain Rate and Stress-State-Dependent Martensite Transformation in AISI 304 at Low Temperatures

Fricke

Gerstein

Kotzbauer

et al. 2022

Metals

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“…For these heat transfer models, the radiation is assumed negligible compared to the conductive heat transfer into the bars [9]. Two models were used: a finite element method (ANSYS R ) and a numerical heat transfer model [9,12]. Several tests were done at temperatures between −196…”

Section: The Split Hopkinson Pressure Bar (Shpb)mentioning

confidence: 99%

Constitutive equations of a ballistic steel alloy as a function of temperature

Berkovic

Chabotier

Coghe

et al. 2012

EPJ Web of Conferences

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Abstract. In the present work, dynamic tests have been performed on a new ballistic steel alloy by means of split Hopkinson pressure bars (SHPB). The impact behavior was investigated for strain rates ranging from 1000 to 2500 s −1 , and temperatures in the range from −196 to 300• C. A robotized sample device was developed for transferring the sample from the heating or cooling device to the position between the bars. Simulations of the temperature evolution and its distribution in the specimen were performed using the finite element method. Measurements with thermocouples added inside the sample were carried out in order to validate the FEM simulations. The results show that a thermal gradient is present inside the sample; the average temperature loss during the manipulation of the sample is evaluated. In a last stage, optimal material constants for different constitutive models (Johnson-Cook, Zerilli-Amstrong, Cowper-Symonds) has been computed by fitting, in a least square sense, the numerical and experimental stress-strain curves. They have been implemented in a hydrocode for validation using a simple impact problem: an adapted projectile geometry with a truncated nose (.50 calibre fragment simulating projectiles) was fired directly against an armor plate. The parameters of the selected strength and failure models were determined. There is a good correspondence between the experimental and computed results. Nevertheless, an improved failure model is necessary to get satisfactory computed residual projectile velocities.

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“…To study the dynamic mechanical properties of materials, experimental studies, constitutive model, and numerical simulations have been developed under various loading conditions. Electronic testing machines and the split-Hopkinson bar (SHPB) system have been used to investigate mechanical behavior under tension, compression, or other loading conditions [15][16][17]. Constitutive models including the physical model [18] and phenomenological model [19] have been developed to describe the flow stress and mechanical behavior of materials under various loading conditions.…”

Section: Introductionmentioning

confidence: 99%

Strain Rate‐Dependent Constitutive and Low Stress Triaxiality Fracture Behavior Investigation of 6005 Al Alloy

Peng

Chen

Peng

et al. 2018

Advances in Materials Science and Engineering

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In order to study the dynamic and fracture behavior of 6005 aluminum alloy at different strain rates and stress states, various tests (tensile tests at different strain rates and tensile shearing tests at five stress states) are conducted by Mechanical Testing and Simulation (MTS) and split-Hopkinson tension bar (SHTB). Numerical simulations based on the finite element method (FEM) are performed with ABAQUS/Standard to obtain the actual stress triaxialities and equivalent plastic strain to fracture. The results of tensile tests for 6005 Al show obvious rate dependence on strain rates. The results obtained from simulations indicate the feature of nonmonotonicity between the strain to fracture and stress triaxiality. The equivalent plastic strain reduces to a minimum value and then increases in the stress triaxiality range from 0.04 to 0.30. A simplified Johnson-Cook (JC) constitutive model is proposed to depict the relationship between the flow stress and strain rate. What is more, the strain-rate factor is modified using a quadratic polynomial regression model, in which it is considered to vary with the strain and strain rates. A fracture criterion is also proposed in a low stress triaxiality range from 0.04 to 0.369. Error analysis for the modified JC model indicates that the model exhibits higher accuracy than the original one in predicting the flow stress at different strain rates. The fractography analysis indicates that the material has a typical ductile fracture mechanism including the shear fracture under pure shear and the dimple fracture under uniaxial tensile.

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Measuring and modeling of low temperature Hopkinson tests

Cited by 6 publications

References 2 publications

High Strain Rate and Stress-State-Dependent Martensite Transformation in AISI 304 at Low Temperatures

High Strain Rate and Stress-State-Dependent Martensite Transformation in AISI 304 at Low Temperatures

Constitutive equations of a ballistic steel alloy as a function of temperature

Strain Rate‐Dependent Constitutive and Low Stress Triaxiality Fracture Behavior Investigation of 6005 Al Alloy

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