The use of the Hopkinson bar to validate constitutive relations at high rates of strain

Noble, Jessica; Goldthorpe, B.D.; Church, P.; Harding, J.E.

doi:10.1016/s0022-5096(97)00090-2

Cited by 49 publications

(14 citation statements)

References 6 publications

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“…Following the presentation of the temperature distribution in eq (8), it seems convenient to discuss the steady-state temperature distribution separately from the transient temperature response. It is shown below that the analysis of the steady-state temperature distribution leads to some general and important conclusions.…”

Section: (3) Thermal Analysismentioning

confidence: 99%

Infrared temperature sensing of mechanically loaded specimens: Thermal analysis

Rabin

Rittel²

2000

Experimental Mechanics

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ABSTRACT--Infrared temperature-sensing techniques have the major advantages of virtually no interference of the sensor with the sensed phenomenon and fast inherent response. On the other hand, infrared temperature sensing, as a superficial measurement technique, does not indicate the specimen's core temperatures, and hence a complementary thermal analysis is required. A thermal analysis of surface temperature measurements of a mechanically loaded cylindrical specimen is presented. The specimen is modeled as an infinite cylinder, suddenly exposed to a uniformly distributed volumetric heat source. This heat source results from the conversion of mechanical energy into thermal energy. A closedform solution is obtained and numerical examples are given for metallic and polymeric specimens. The current analysis provides the upper boundaries for temperature differences between the core and the surface temperatures when compared with the actual problem of a finite specimen. It is shown that surface temperature measurement is a good indication of the core temperature for metallic specimens but may lead to some poor results in the case of polymeric specimens. It is found that the transient thermal response of the infinite cylinder to sudden heating behaves like a first-order process. In the case of cyclic loading, the typical time scale of loading is found to be at least two orders of magnitude shorter than the typical time scale of heat transfer. Hence, the specimen is affected by the average power of heat generation, and not by the instantaneous effect of heating within a single loading cycle.

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Section: (3) Thermal Analysismentioning

confidence: 99%

Infrared temperature sensing of mechanically loaded specimens: Thermal analysis

Rabin

Rittel²

2000

Experimental Mechanics

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“…In a lot of works the attention was focused on Zerilli-Armstrong model, but also more physically-based and micromechanical models were identified, usually by using data interpolation techniques. Differently from analytical approaches, the inverse procedure, as that it is proposed here, can be applied for the strength model calibration also in case of necking/instability up to fracture [17][18][19][20]: a Finite Element (FE) based approach allows to take into account the effect of the geometry changes during the necking phase. The stress versus strain curve after necking starts cannot be derived using nominal relation starting from engineering data: the stress state is no longer uniform and uniaxial as a consequence of the increased triaxiality which implies the logarithmic stress differs from the Von Mises stress.…”

Section: Introductionmentioning

confidence: 99%

Investigation and Mechanical Modelling of Pure Molybdenum at High Strain-Rate and Temperature

Scapin

Peroni

Carra

2016

J. dynamic behavior mater.

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This work shows the results obtained from the investigation of the mechanical behavior of two batches of pure molybdenum specimens (C99.97 % Mo, Mo1 supplied by Plansee and Mo2 supplied by AT&M) under static and dynamic loading conditions at different temperatures, both under tensile and compressive loading conditions. Due to its properties molybdenum has applications in several fields including nuclear. At this moment, it is a good candidate for structural material application for Beam Intercepting Devices of the Large Hadron Collider at CERN, Geneva. The experimental tests in tensile loading condition were performed on small dog-bone specimens. A series of tests at room temperature and a range of strainrates was performed in order to obtain information about the strain-rate sensitivity of the material. A series of tests at different temperatures in both static and high dynamic loading conditions was performed in order to obtain information about the thermal softening of the material. The dynamic tests were performed using the Hopkinson Bar technique, and the heating of the specimen was performed using an induction coil system. The experimental tests in compression were carried out on cylindrical specimens at room temperature and a range of strain-rates. The experimental data were analyzed via a numerical inverse method based on Finite Element numerical simulations.This approach allows to obtain the effective stress versus strain curves, which cannot be derived by using standard relations since instability and necking were present. Moreover, it also allows the non-uniform distribution of strain-rate and temperature inside the specimen to be accounted for. The results obtained from compression tests confirm the data obtained in tension in terms of strainhardening and strain-rate sensitivity, even if the material exhibits a tension-compression asymmetry of the behavior. The analysis of the hardening, temperature and strain-rate sensitivities reveals that a unique standard visco-plastic model could not be defined to reproduce the material strength behavior under different loading conditions, especially over wide range of variation of the variables of interest.Keywords Refractory metal Á High temperature Á High strain-rate Á Hopkinson bar Á Tensile and compression Á Nuclear applications Á Instability Á FE-based numerical inverse approach

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“…In particular, dog-bone shaped specimens accumulate strain outside the gauge length, and calculations of true stress must account for necking in the specimen [3]. For this reason, authors have adopted high speed photography as a means to obtain more widely applicable data [4,5].…”

Section: Introductonmentioning

confidence: 99%