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1
Harrigan, John J., Bright Ahonsi, Elisavet Palamidi e Steve R. Reid. "Experimental and numerical investigations on the use of polymer Hopkinson pressure bars". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, n. 2023 (28 agosto 2014): 20130201. http://dx.doi.org/10.1098/rsta.2013.0201.
Testo completoAbstract (sommario):
Split Hopkinson pressure bar (SHPB) testing has traditionally been carried out using metal bars. For testing low stiffness materials such as rubbers or low strength materials such as low density cellular solids considered primarily herein, there are many advantages to replacing the metal bars with polymer bars. An investigation of a number of aspects associated with the accuracy of SHPB testing of these materials is reported. Test data are used to provide qualitative comparisons of accuracy using different bar materials and wave-separation techniques. Sample results from SHPB tests are provided for balsa, Rohacell foam and hydroxyl-terminated polybutadiene. The techniques used are verified by finite-element (FE) analysis. Experimentally, the material properties of the bars are determined from impact tests in the form of a complex elastic modulus without curve fitting to a rheological model. For the simulations, a rheological model is used to define the bar properties by curve fitting to the experimentally derived properties. Wave propagation in a polymer bar owing to axial impact of a steel bearing ball is simulated. The results indicate that the strain histories can be used to determine accurately the viscoelastic properties of polymer bars. An FE model of the full viscoelastic SHPB set-up is then used to simulate tests on hyperelastic materials.
2
Pham, Thanh Nam, Hyo Seong Choi e Jong Bong Kim. "A Numerical Investigation into the Tensile Split Hopkinson Pressure Bars Test for Sheet Metals". Applied Mechanics and Materials 421 (settembre 2013): 464–67. http://dx.doi.org/10.4028/www.scientific.net/amm.421.464.
Testo completoAbstract (sommario):
Determination of theflow stress of materials at high strain rate is very important in automotive and military areas.The compressive flow stress at high strain rate can be obtained relativelyexactly by SHPB(Split Hopkinson Pressure Bars) tests. However, it is difficult to determinethe flow stressexactlyin the tensile state by using the SHPB tests. The difficulty in the tensile SHPB tests is how to fix a specimen on two bars. So, the design of a specimen and holders is needed to obtain more accurate measurement of the flow stress. In this study, the accuracy of the tensile SHPB tests results was numerically investigated. Finite element analyses of the tensile SHPB were carried out for various cases of fixing bolt location and bolting force. From the analysis results, a design guide for the fixing structure was obtained and the causes of error were investigated.
3
Quinn, R. M., L. H. Zhang, M. J. Cox, D. Townsend, T. Cartwright, G. Aldrich-Smith, P. A. Hooper e J. P. Dear. "Development and Validation of a Hopkinson Bar for Hazardous Materials". Experimental Mechanics 60, n. 9 (18 agosto 2020): 1275–88. http://dx.doi.org/10.1007/s11340-020-00638-w.
Testo completoAbstract (sommario):
Abstract Background There are a variety of approaches that can be employed for Hopkinson bar compression testing and there is no standard procedure. Objectives A Split-Hopkinson pressure bar (SHPB) testing technique is presented which has been specifically developed for the characterisation of hazardous materials such as radioactive metals. This new SHPB technique is validated and a comparison is made with results obtained at another laboratory. Methods Compression SHPB tests are performed on identical copper specimens using the new SHPB procedures at Imperial College London and confirmatory measurements are performed using the well-established configuration at the University of Oxford. The experiments are performed at a temperature of 20 ∘C and 200 ∘C. Imperial heat the specimens externally before being inserted into the test position (ex-situ heating) and Oxford heat the specimens whilst in contact with the pressure bars (in-situ heating). For the ex-situ case, specimen temperature homogeneity is investigated both experimentally and by simulation. Results Stress-strain curves were generally consistent at both laboratories but sometimes discrepancies fell outside of the inherent measurement uncertainty range of the equipment, with differences mainly attributed to friction, loading pulse shapes and pulse alignment techniques. Small metallic specimens are found to be thermally homogenous even during contact with the pressure bars. Conclusion A newly developed Hopkinson bar for hazardous materials is shown to be effective for characterising metals under both ambient and elevated temperature conditions.
4
Kariem, Muhammad Agus, John H. Beynon e Dong Ruan. "Numerical Simulation of Double Specimens in Split Hopkinson Pressure Bar Testing". Materials Science Forum 654-656 (giugno 2010): 2483–86. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2483.
Testo completoAbstract (sommario):
The split Hopkinson pressure bar (SHPB) is the most commonly used technique to characterize the dynamic behaviour of materials at very high strain rates. However, a classic single specimen test only generates a single stress-strain curve at the average strain rate of the test. This paper proposes three arrangements on the use of double specimens in SHPB compression testing. All waves propagating along the bars have been used to analyse the dynamic behaviour of the specimens. To simulate the test and predict its dynamic performance, an axisymmetric finite element analysis using LS-DYNA was conducted for the experiment using 13 mm bar diameter. The validity of the simulations was checked with experimental data from normal SHPB testing. Based on the simulations, the modified techniques are achievable and at least two stress-strain curves of materials can be extracted without violating the requirement of a valid SHPB test.
5
Baranowski, Pawel, Roman Gieleta, Jerzy Malachowski, Krzysztof Damaziak e Lukasz Mazurkiewicz. "SPLIT HOPKINSON PRESSURE BAR IMPULSE EXPERIMENTAL MEASUREMENT WITH NUMERICAL VALIDATION". Metrology and Measurement Systems 21, n. 1 (1 marzo 2014): 47–58. http://dx.doi.org/10.2478/mms-2014-0005.
Testo completoAbstract (sommario):
Abstract Materials and their development process are highly dependent on proper experimental testing under wide range of loading within which high-strain rate conditions play a very significant role. For such dynamic loading Split Hopkinson Pressure Bar (SHPB) is widely used for investigating the dynamic behavior of various materials. The presented paper is focused on the SHPB impulse measurement process using experimental and numerical methods. One of the main problems occurring during tests are oscillations recorded by the strain gauges which adversely affect results. Thus, it is desired to obtain the peak shape in the incident bar of SHPB as “smooth” as possible without any distortions. Such impulse characteristics can be achieved using several shaping techniques, e.g. by placing a special shaper between two bars, which in fact was performed by the authors experimentally and subsequently was validated using computational methods.
6
Nie, Hailiang, Weifeng Ma, Junjie Ren, Ke Wang, Jun Cao, Wei Dang, Tian Yao e Kang Wang. "Size Effect in the Split Hopkinson Pressure Bar Experiment". Journal of Physics: Conference Series 2160, n. 1 (1 gennaio 2022): 012065. http://dx.doi.org/10.1088/1742-6596/2160/1/012065.
Testo completoAbstract (sommario):
Abstract For many structures, their service environment is very strict, and the requirements for the impact resistance of materials are very high. Therefore, the dynamic testing method has important scientific significance and application value for practical engineering. Split Hopkinson pressure bar (SHPB) is one of the most common experimental methods for obtaining dynamic mechanical properties of materials. However, there is no uniform standard for the size of the bars and specimens used in the test. Theoretically, the size has little influence on the experimental results, but it has not been proved by experiments. This paper mainly studies the influence of device/specimen sizes of split Hopkinson pressure bar through experiments, it is demonstrated that the sizes of bars and specimen have little effect on experimental results.
7
Adorna, Marcel, Jan Falta, Tomáš Fíla e Petr Zlámal. "PREPROCESSING OF HOPKINSON BAR EXPERIMENT DATA: FILTER ANALYSIS". Acta Polytechnica CTU Proceedings 18 (23 ottobre 2018): 77. http://dx.doi.org/10.14311/app.2018.18.0077.
Testo completoAbstract (sommario):
This work presents a data preprocessing procedure for signal acquired during high strain-rate loading using a custom Split Hopkinson Pressure Bar (SHPB). Before the evaluation of the experimental data, preprocessing of the measured signals including application of suitable digital or analog filter needs to be performed. Our department mainly focuses on measurements performed on advanced materials (e.g. materials with predefined structures or hybrid foams). For such measurements, it is essential to perform data preprocessing and apply suitable filter, to be able to appropriately determine deformation pulses on the measuring bars. This paper focuses foremost on spectral analysis of the measured signals, and design of optimal method of data filtering. Data from several different SHPB experiments were processed and results of different filtering methods are shown in this paper. Parameters of the best performing filter were optimized and shown to be universal for wide range of SHPB measurements.
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Zhang, Xing, Bao Cheng Li, Zhi Min Zhang e Zhi Wen Wang. "Investigation on Deformation in ZK60 at High Strain Rate". Materials Science Forum 488-489 (luglio 2005): 527–30. http://dx.doi.org/10.4028/www.scientific.net/msf.488-489.527.
Testo completoAbstract (sommario):
Split Hopkinson Pressure Bars (SHPB) was applied to investigate shock resistance of magnesium alloy. The deformation behaviour was reported of ZK60 magnesium alloy at high strain rate, and the relationship was established between the dynamic properties and the impact velocity. Results indicate: with impact velocity improvement, much twinned crystal and fine grain can be obtianed, this made dynamic properties enhancement of ZK60 alloy.
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Zhao, Peng Duo, Yu Wang, Jian Ye Du, Lei Zhang, Zhi Peng Du e Fang Yun Lu. "Using Split Hopkinson Pressure Bars to Perform Large Strain Compression Tests on Neoprene at Intermediate and High Strain Rates". Advanced Materials Research 631-632 (gennaio 2013): 458–62. http://dx.doi.org/10.4028/www.scientific.net/amr.631-632.458.
Testo completoAbstract (sommario):
The strain rate sensitivity of neoprene is characterized using a modified split Hopkinson pressure bar (SHPB) system at intermediate (50 s-1, 100 s-1) and high (500 s-1, 1000 s-1) strain rates. We used two quartz piezoelectric force transducers that were sandwiched between the specimen and experimental bars respectively to directly measure the weak wave signals. A laser gap gage was employed to monitor the deformation of the sample directly. Three kinds of neoprene rubbers (Shore hardness: SHA60, SHA65, and SHA70) were tested using the modified split Hopkinson pressure bar. Experimental results show that the modified apparatus is effective and reliable for determining the compressive stress-strain responses of neoprene at intermediate and high strain rates.
10
Lee, Sang Hyun, Brian Tuazon e Hyung Seop Shin. "Construction of Data Acquisition/Processing System for Precise Measurement in Split Hopkinson Pressure Bar Test". Applied Mechanics and Materials 566 (giugno 2014): 554–59. http://dx.doi.org/10.4028/www.scientific.net/amm.566.554.
Testo completoAbstract (sommario):
The Split Hopkinson Pressure Bar (SHPB) testing technique has been used to derive the constitutive equations of engineering materials at high strain rate using the reflected and transmitted waves measured from the input and output bars. In this case, a precise measurement of the reflected and transmitted waves is important to determine a reliable stress-strain relation. In this study, to achieve the precise measurement of the reflected and transmitted waves in the SHPB experiment, a data acquisition scheme utilizing the LabVIEW software and a post processing program have been constructed. With the constructed system, an accurate data acquisition without a digital storage oscilloscope and a convenient post processing of the signals obtained through the SHPB test for identifying the mechanical properties have been possible. Therefore, a fast and simple generation of the strain rate - time curve and the nominal stress - nominal strain curve has been implemented by just selecting the specified regions on the reflected and transmitted wave profiles acquired. Also, the process to set the appropriate test configuration in the SHPB test for various kinds of materials has become easy with the constructed system.
11
SHU, DONG WEI, CHUN QI LUO e GUO XING LU. "NUMERICAL SIMULATIONS OF THE INFLUENCE OF STRIKER BAR LENGTH ON SHPB MEASUREMENTS". International Journal of Modern Physics B 22, n. 31n32 (30 dicembre 2008): 5813–18. http://dx.doi.org/10.1142/s0217979208051212.
Testo completoAbstract (sommario):
Split Hopkinson Pressure Bar (SHPB) has become a frequently used technique for measuring uni-axial compressive stress-strain relationship of various engineering materials under high strain rates. The pulse shape generated in the incident bar is sensitive to the length of the striker bar. In this paper, a finite element simulation of a Split Hopkinson Pressure Bar is performed to estimate the effect of varying length of striker bar on the stress-strain relationship of a material. A series of striker bars with different lengths, from 200mm to 350mm, are employed to obtain the stress-strain response of AL6061-T6 in both simulation and experiment. A comparison is made between the experimental and the computed stress-strain curves. Finally the influence of variation of striker bar length on the sample's stress-strain response is presented.
12
Peng, Kang, Ke Gao, Jian Liu, Yujiao Liu, Zhenyu Zhang, Xiang Fan, Xuyan Yin, Yongliang Zhang e Gun Huang. "Experimental and Numerical Evaluation of Rock Dynamic Test with Split-Hopkinson Pressure Bar". Advances in Materials Science and Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/2048591.
Testo completoAbstract (sommario):
Feasibility of rock dynamic properties by split-Hopkinson pressure bar (SHPB) was experimentally and numerically evaluated with ANSYS/LS-DYNA. The effects of different diameters, different loading rates, and different propagation distances on wave dispersion of input bars in SHPB with rectangle and half-sine wave loadings were analyzed. The results show that the dispersion effect on the diameter of input bar, loading rate, and propagation distance under half-sine waveform loading is ignorable compared with the rectangle wave loading. Moreover, the degrees of stress uniformity under rectangle and half-sine input wave loadings are compared in SHPB tests, and the time required for stress uniformity is calculated under different above-mentioned loadings. It is confirmed that the stress uniformity can be realized more easily using the half-sine pulse loading compared to the rectangle pulse loading, and this has significant advantages in the dynamic test of rock-like materials. Finally, the Holmquist-Johnson-Concrete constitutive model is introduced to simulate the failure mechanism and failure and fragmentation characteristics of rock under different strain rates. And the numerical results agree with that obtained from the experiment, which confirms the effectiveness of the model and the method.
13
Butt, Hafiz Sana Ullah, e Pu Xue. "Wave Dispersion and Attenuation in Viscoelastic Split Hopkinson Pressure Bar". Key Engineering Materials 535-536 (gennaio 2013): 547–50. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.547.
Testo completoAbstract (sommario):
The Split Hopkinson Pressure Bar (SHPB) is most commonly used facility to obtain material properties at high strain rates. Testing of soft materials using this method requires that bars made of low impedance material should be used, in order to improve signal-to-noise ratio of transmitted stress. However, utilization of such bars poses some difficulties in data processing as the wave dispersion and attenuation becomes noticeable due to their viscoelastic nature. Wave propagation coefficients of a viscoelastic pressure bar are evaluated using incident and reflected strain waves generated through impact of two different length striker bars. Two approaches are proposed for propagation coefficient measurement in this study, namely direct and waves-overlap. Using two approaches, it is found that the calculated attenuation coefficients are same, while the wave numbers are different. The difference in wave number in the case of two approaches is due to the difference in calculated phase change of incident and reflected waves, which is found as integer multiple of 2Π. Moreover, propagation coefficients calculated through different striker impacts are found different. The propagation coefficient found through long striker impact, when used for propagation response prediction of waves generated by short striker impact, resulted in high oscillations in predicted waves.
14
Lee, Ouk Sub, Yong Hwan Han e Dong Hyeok Kim. "Influence of Temperature and Heat-Aged Condition on the Deformation Behavior of Rubber Material Using SHPB Technique with a Pulse Shaper". Key Engineering Materials 353-358 (settembre 2007): 619–26. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.619.
Testo completoAbstract (sommario):
The Split Hopkinson Pressure Bar (SHPB) technique with some special experimental apparatus can be used to obtain the dynamic material behavior under high strain rate loading conditions. An experimental technique that modifies the conventional SHPB has been developed for measuring the compressive stress strain responses of materials with low mechanical impedance and low compressive strengths such as rubber. This paper uses PEEK (Poly-ether-ether-ketone plastic) bars to achieve a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rise time of the incident pulse to ensure stress equilibrium and homogeneous deformation of the rubber specimen. It is confirmed that the modified technique is useful to record the dynamic deformation behavior of rubbers under various conditions such as high strain rate with various temperature effect. Furthermore, the dynamic deformation behaviors of heat-aged rubber material under compressive high strain rate are evaluated using the modified SHPB technique.
15
Zuanetti, Bryan, Kyle J. Ramos, Carl M. Cady, Chris S. Meredith, Daniel T. Casem, Adam Golder e Cynthia A. Bolme. "Miniature Beryllium Split-Hopkinson Pressure Bars for Extending the Range of Achievable Strain-Rates". Metals 12, n. 11 (28 ottobre 2022): 1834. http://dx.doi.org/10.3390/met12111834.
Testo completoAbstract (sommario):
Conventional Split Hopkinson Pressure Bars (SHPB) or “Kolsky” bars are often used for determining the high-rate compressive yield and failure strength of materials. However, for experiments generating very high strain-rates (>103/s) miniaturization of the setup is often required for minimizing the effects of elastic wave dispersion in order to enable the inference of decreasingly short loading events from the data. Miniature aluminum and steel bars are often sufficient for meeting these requirements. However, for high enough strain-rates, miniaturization of steel or aluminum Kolsky bars may require prohibitively small diameter bars and test specimens that could become inappropriate for inferring representative properties of materials with large grain size relative to the test specimen size. The use of a beryllium Kolsky bar setup is expected to enable high rates to be accessible with larger diameter bars/specimen combinations due to the inherent physical properties of beryllium, which are expected to minimize the effects of elastic wave dispersion. For this reason, a series of beryllium Kolsky bars have been developed, and, in this paper, the dispersion characteristics of these bars are measured and compare the data with those of similarly sized 7075-T6 aluminum and C350 maraging steel. The results, which agree well with the theory, show no appreciable frequency dependence of the elastic wavespeed in the data from the beryllium bars, demonstrating its advantage over aluminum and steel in application to Kolsky bars.
16
Church, Philip, Rory Cornish, Ian Cullis, Peter Gould e Ian Lewtas. "Using the split Hopkinson pressure bar to validate material models". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, n. 2023 (28 agosto 2014): 20130294. http://dx.doi.org/10.1098/rsta.2013.0294.
Testo completoAbstract (sommario):
This paper gives a discussion of the use of the split-Hopkinson bar with particular reference to the requirements of materials modelling at QinetiQ. This is to deploy validated material models for numerical simulations that are physically based and have as little characterization overhead as possible. In order to have confidence that the models have a wide range of applicability, this means, at most, characterizing the models at low rate and then validating them at high rate. The split Hopkinson pressure bar (SHPB) is ideal for this purpose. It is also a very useful tool for analysing material behaviour under non-shock wave loading. This means understanding the output of the test and developing techniques for reliable comparison of simulations with SHPB data. For materials other than metals comparison with an output stress v strain curve is not sufficient as the assumptions built into the classical analysis are generally violated. The method described in this paper compares the simulations with as much validation data as can be derived from deployed instrumentation including the raw strain gauge data on the input and output bars, which avoids any assumptions about stress equilibrium. One has to take into account Pochhammer–Chree oscillations and their effect on the specimen and recognize that this is itself also a valuable validation test of the material model.
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Zhang, Dan, Zhiwu Zhu e Zhijie Liu. "Dynamic Mechanical Behavior and Numerical Simulation of Frozen Soil under Impact Loading". Shock and Vibration 2016 (2016): 1–16. http://dx.doi.org/10.1155/2016/3049097.
Testo completoAbstract (sommario):
Split Hopkinson pressure bars (SHBP) were used to perform impact experiments on frozen soil under various impact velocities and temperatures to analyze the effect of these parameters on the mechanical behavior of the soil. Based on the Holmquist-Johnson-Cook constitutive model, the dynamic mechanical properties under impact loading were analyzed. The SHPB experiments of frozen soil were also simulated using the finite element analysis software LS-DYNA, and the simulation results were similar to the experimental results. The temperature effect, strain rate effect, and the destruction process of the frozen soil as well as the propagation process of stress waves in the incident bar, transmission bar, and frozen soil specimen were investigated. This work provides a good theoretical basis and technical support for frozen soil engineering applications.
18
Lu, Fang Yun, Xiao Feng Wang, Rong Chen, Xiang Yu Li, Duo Zhang, Yu Liang Lin, Chao Yang Zhou e Shi Yong Wu. "Comparison Investigation of Tensile Fracture Properties of Al Alloy at Different Dynamic Loadings". Key Engineering Materials 535-536 (gennaio 2013): 156–59. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.156.
Testo completoAbstract (sommario):
Spall Strength, uniaxial tensile strength and fracture toughness, are three typical parameters describing the fracture properties of materials subjected to different loadings. Actually, these three macroscopically parameters are connected to the tensile fracture (Model I) properties, and many papers have been trying to find the intrinsic connection between each other. In this work, ZL205A aluminum is conducted by varies experiments: the spallation test loaded by a light gas gun, the dynamic uniaxial tensile test using the Split Hopkinson Tensile Bars (SHTB), and the dynamic fracture toughness obtained with a three point bending specimen loaded by Split Hopkinson Pressure Bars (SHPB). The three parameters are compared with the view of energy. The results show that the cavity expansion model is successfully used to set up a connection between spallation strength and dynamic uniaxial tensile strength of this material, while the energy release rate or the surface energy can give a good prediction of dynamic tensile strength and fracture toughness.
19
Corallo, Luca, e Patricia Verleysen. "The split Hopkinson bar bulge setup: a novel dynamic biaxial test method". EPJ Web of Conferences 250 (2021): 01019. http://dx.doi.org/10.1051/epjconf/202125001019.
Testo completoAbstract (sommario):
In sheet metal forming, very often, large plastic deformations are imposed to a thin plate. An accurate description of the material’s elastoplastic response is therefore of paramount importance to perform finite element (FE) simulations of an actual forming operation. Reliable stressstrain data till significantly larger strains compared to tensile tests can be identified by means of bulge test. In this work, a dynamic hydraulic bulge test is proposed. The novel split Hopkinson bar bulge setup, combines features of classical split Hopkinson pressure bar (SHPB) and hydraulic bulge tests. The special configuration of the Hopkinson bars leaves the sample surface fully accessible. As such, high-speed optical measurements can be performed on the sample surface allowing the application of, for instance, digital image correlation (DIC) for full-field displacement strain mapping. The potential of the facility is explored by performing experiments on 0.8mm thick Al2024-T3 sheet.
20
Tarfaoui, Mostapha. "Dynamic Composite Materials Characterisation with Hopkinson Bars: Design and Development of New Dynamic Compression Systems". Journal of Composites Science 7, n. 1 (11 gennaio 2023): 33. http://dx.doi.org/10.3390/jcs7010033.
Testo completoAbstract (sommario):
The split Hopkinson pressure bars (SHPB) system is the most commonly employed machine to study the dynamic characteristics of different materials under high strain rates. In this research, a numerical investigation is carried out to study different bar shapes such as square, hexagonal, and triangular cross-sections and to compare them with the standard cylindrical bars. The 3D finite element model developed for circular cross-sectional shapes was first validated with the experimental results and then compared with the other proposed shapes. In most scientific research, cylindrical cross-section bars with a square cross-section specimen are traditionally used as they have several advantages, such as in situ imaging of the side surfaces of the specimen during stress wave propagation. Moreover, the flat surfaces of the proposed shapes counter the problem of debonding strain gauges, especially at high impact pressures. Comparison of the results showed an excellent confirmation of the sample dynamic behaviour and different geometric shapes of the bar geometries, which validates the choice of the appropriate system.
21
McArthur, Jennifer, Christopher Salisbury, Duane Cronin, Michael Worswick e Kevin Williams. "High Strain Rate Characterization of Shock Absorbing Materials for Landmine Protection Concepts". Shock and Vibration 10, n. 3 (2003): 179–86. http://dx.doi.org/10.1155/2003/961910.
Testo completoAbstract (sommario):
Numerical modelling of footwear to protect against anti-personnel landmines requires dynamic material properties in the appropriate strain rate regime to accurately simulate material response. Several materials (foamed metals, honeycombs and polymers) are used in existing protective boots, however published data at high strain rates is limited.Dynamic testing of several materials was performed using Split Hopkinson Pressure Bars (SHPB) of various sizes and materials. The data obtained from these tests has been incorporated into material models to predict the initial stress wave propagation through the materials. Recommendations for the numerical modeling of these materials have also been included.
22
Bendarma, Amine, Tomasz Jankowiak, Alexis Rusinek, Tomasz Lodygowski, Bin Jia, María Henar Miguélez e Maciej Klosak. "Dynamic Behavior of Aluminum Alloy Aw 5005 Undergoing Interfacial Friction and Specimen Configuration in Split Hopkinson Pressure Bar System at High Strain Rates and Temperatures". Materials 13, n. 20 (16 ottobre 2020): 4614. http://dx.doi.org/10.3390/ma13204614.
Testo completoAbstract (sommario):
In this paper, experimental and numerical results of an aluminum alloy’s mechanical behavior are discussed. Over a wide range of strain rates (10−4 s−1 ≤ έ ≤ 103 s−1) the influence of the loading impact, velocity and temperature on the dynamic response of the material was analyzed. The interface friction effect on the material’s dynamic response is examined using a split Hopkinson pressure bar (SHPB) in a high temperature experiment using finite element analysis (FEA). The effect of different friction conditions between the specimen and the transmitted/incident bars in the SHPB system was examined using cylinder bulk specimens and cylinder plates defined with four-layer configurations. The results of these tests alongside the presented numerical simulations allow a better understanding of the phenomenon and reduces (minimizes) errors during compression tests at high and low strain rates with temperatures ranging from 21 to 300 °C.
23
Demiral, Murat, Anish Roy e Vadim V. Silberschmidt. "Dynamic Behavior of Advanced Ti Alloy under Impact Loading: Experimental and Numerical Analysis". Applied Mechanics and Materials 70 (agosto 2011): 207–12. http://dx.doi.org/10.4028/www.scientific.net/amm.70.207.
Testo completoAbstract (sommario):
Industrial applications of Ti-based alloys, especially in aerospace, marine and offshore industries, have grown significantly over the years primarily due to their high strength, light weight as well as good fatigue and corrosion-resistance properties. A combination of experimental and numerical studies is necessary to predict a material behavior of such alloys under high strain-rate conditions characterized also by a high level of strains accompanied by high temperatures. A Split Hopkinson Pressure Bar (SHPB) technique is a commonly used experimental method to characterize a dynamic stress-strain response of materials at high strain rates. In a SHPB test, the striker bar is shot against the free end of the incident stress bar, which on impact generates a stress pulse propagating in the incident bar towards the specimen sandwiched between the incident and transmitted bars. An experimental study and a numerical analysis based on a three-dimensional finite element model of the SHPB experiment are performed in this study to assess various features of the underlying mechanics of deformation processes of the alloy tested at high-strain and -strain-rate regimes.
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Zhao, Zhangyong, Yanyu Qiu e Mingyang Wang. "Effects of Strain Rate and Initial Density on the Dynamic Mechanical Behaviour of Dry Calcareous Sand". Shock and Vibration 2019 (22 luglio 2019): 1–10. http://dx.doi.org/10.1155/2019/3526727.
Testo completoAbstract (sommario):
The dynamic compressive behaviour of dry calcareous sand under rigid confinement was characterised using a split-Hopkinson pressure bar (SHPB). Sand samples were confined inside a sleeve of hardened stainless steel and capped by a pair of aluminium cylindrical rods. This assembly was subjected to repeated dynamic compaction to attain precise bulk mass densities. It was then sandwiched between the incident and transmission bars of SHPB for dynamic compression testing. Sand specimens of three initial mass densities, namely, 1.26 g/cm3, 1.35 g/cm3, and 1.42 g/cm3, were loaded by incident pulses applying a stress of 35 MPa, 71 MPa, and 143 MPa, respectively. Experimental results show that in the strain rate range of 335 s−1 to 1253 s−1, the dynamic mechanical behaviours of dry calcareous sands exhibited no significant strain rate effect. The Lundborg model and the Murnaghan model could be used to describe the deviatoric and volumetric behaviours of calcareous sand with different initial densities, respectively.
25
Hou, B., S. B. Tan, R. Xiao e Han Zhao. "Impact Combined Shear-Compression Testing of Honeycombs Using a Rotatable Hopkinson Bar". Key Engineering Materials 725 (dicembre 2016): 168–73. http://dx.doi.org/10.4028/www.scientific.net/kem.725.168.
Testo completoAbstract (sommario):
This paper presents a new method based on the split Hopkinson pressure bar (SHPB) to perform impact combined shear-compression test for cellular materials. For this purpose, a bevelled end is cemented to the input bar and the output bar are rotatable to be parallel to the inclined plane of the bevelled end. The system uses the friction between the specimen and the pressure bars to apply the combined shear compression loading on the honeycomb specimen. Such a testing method is validated by the simulation of the whole loading system (split bar + specimen) using ABAQUS code. It shows that this combined shear-compression test provides a quite accurate measurement. Tests on the 5052 aluminium honeycombs are performed. The shear stress-strain behaviour and the compressive behaviour are separated. The experiment result confirms previous testing results and reveals that the shear component will weaken the compressive strength of the honeycomb at high strain rate.
26
Fíla, Tomáš, Petr Zlámal, Jan Falta, Tomáš Doktor, Petr Koudelka, Daniel Kytýř, Marcel Adorna et al. "Testing of Auxetic Materials Using Hopkinson Bar and Digital Image Correlation". EPJ Web of Conferences 183 (2018): 02045. http://dx.doi.org/10.1051/epjconf/201818302045.
Testo completoAbstract (sommario):
In this paper, a split Hopkinson pressure bar (SHPB) was used for impact loading of an auxetic lattice (structure with negative Poisson’s ratio) at a given strain-rate. High strength aluminum and polymethyl methacrylate bars instrumented with foil strain-gauges were used for compression of an additively manufactured missing-rib auxetic lattice. All experiments were observed using a high-speed camera with frame-rate set to approx. 135.000 fps. High-speed images were synchronized with the strain-gauge records. Dynamic equilibrium in the specimen was analyzed and optimized pulse-shaping was introduced in the selected experiments. Longitudinal and lateral in-plane displacements and strains were evaluated using digital image correlation (DIC) technique. DIC results were compared with results obtained from strain-gauges and were found to be in good agreement. Using DIC, it was possible to analyze in-plane strain distribution in the specimens and to evaluate strain dependent Poisson’s ratio of the auxetic structure.
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Hou, Bing, Meng Zhao, Pei Yang e Yu Long Li. "Capture of Shear Crack Propagation in Metallic Glass by High-Speed Camera and In Situ SEM". Key Engineering Materials 626 (agosto 2014): 162–70. http://dx.doi.org/10.4028/www.scientific.net/kem.626.162.
Testo completoAbstract (sommario):
The dynamic double-notched experiments by using Split Hopkinson Pressure Bars (SHPB) and high-speed camera were performed on bulk metallic glass. In the double-notched experiment, shear crack propagating process was captured with the high temporal resolution of high-speed camera and the crack front propagating velocity was estimated to be 1137m/s. the shear strain/shear stress curve of BMG under dynamic loading was also obtained. Static in-situ SEM tensile experiments were included to study the multiple shear bands propagating behavior on a glassy ribbon. It was found that shear bands propagates progressively in an intermittent and discontinuous manner, and the choice of which shear bands to propagate and which ones to keep still among multiple shear bands is quite stochastic. This is explained qualitatively from the view point of energy.
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Kii, Nobuhiko, Takeshi Iwamoto, Alexis Rusinek e Tomasz Jankowiak. "A Study on Reduction of Friction in Impact Compressive Test Based on the Split Hopkinson Pressure Bar Method by Using a Hollow Specimen". Applied Mechanics and Materials 566 (giugno 2014): 548–53. http://dx.doi.org/10.4028/www.scientific.net/amm.566.548.
Testo completoAbstract (sommario):
The split Hopkinson pressure bar (SHPB) technique is widely-used to describe the impact compressive behavior of different materials including metals. During the impact test, the specimen deforms in a wide range of impact strain rate from 102 to 104 s-1. It is a reason why the method is studied for many years even though the structure of the apparatus based on the SHPB is simple. Actually, the cylindrical specimens are widely used for a compressive test and it is clearly seen that stress measured by the test includes the increment of stress (an error) derived by friction effect between a specimen and pressure bars. Therefore, it is important that the measured stress should indicate similar value as the proper stress of the material by reducing friction effect during not only quasi-static but also the impact test. Various attempts to reduce a friction effect in past have been conducted. A method to reduce friction effect is in general a use of lubricants. However, it is ineffective because it can be considered that this method contributes to an attenuation of the stress wave for obtaining the stress-strain curve under impact loading. Thus, rise time of waves obtained by the experiment becomes longer compared with a case not to use lubricants. Recently, a study can be found using a ring specimen, however, the determined thickness of the specimen is quite thin and it can be considered that a buckling effect cannot be vanished. In this study, a use of hollow specimen is suggested to solve the problem related to reduce the friction effect by decreasing a contact area between a specimen and pressure bars instead of a cylindrical specimen. The compressive experiments at various strain rates are conducted by using a hollow specimen.
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Adorna, Marcel, Petr Zlámal, Tomáš Fíla, Jan Falta, Markus Felten, Michael Fries e Anne Jung. "TESTING OF HYBRID NICKEL-POLYURETHANE FOAMS AT HIGH STRAIN-RATES USING HOPKINSON BAR AND DIGITAL IMAGE CORRELATION". Acta Polytechnica CTU Proceedings 18 (23 ottobre 2018): 72. http://dx.doi.org/10.14311/app.2018.18.0072.
Testo completoAbstract (sommario):
In this paper Split Hopkinson pressure bar (SHPB) was used for dynamic testing of nickel coated polyurethane hybrid foams. The foams were manufactured by electrodeposition of a nickel coating on the standard open-cell polyurethane foam. High strength aluminium alloy bars instrumented with foil strain-gauges were used for dynamic loading of the specimens. Experiments were observed using a high-speed camera with frame-rate set to approx. 100-150 kfps. Precise synchronisation of the high-speed camera and the strain-gauge record was achieved using a through-beam photoelectric sensor. Dynamic equilibrium in the specimen was achieved in all measurements. Digital image correlation technique (DIC) was used to evaluate in-plane displacements and deformations of the samples. Specimens of two different dimensions were tested to investigate the collapse of the foam structure under high-speed loading at the specific strain-rate and strain.
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Chen, Lu, Lan Qiao, Jianming Yang e Qingwen Li. "Laboratory Investigation of Energy Propagation and Scattering Characteristics in Cylindrical Rock Specimens". Advances in Civil Engineering 2018 (24 settembre 2018): 1–7. http://dx.doi.org/10.1155/2018/2052781.
Testo completoAbstract (sommario):
Deep mining involves complex geological environments. Moreover, along with strong disturbance, rockbursts and other severe dynamic hazards can occur frequently. Energy theory is widely regarded as the most appropriate method for understanding the mechanism of deep dynamic problems. When modeling dynamic disasters, energy theory includes the energy storage, energy accumulation, and energy transfer. To study the energy transfer characteristics in rock, a series of split-Hopkinson pressure bar (SHPB) impact tests were conducted with long granite specimens (400 mm in length and 50 mm in diameter) and modified incidence bars (having the same cross-sectional area but different shapes). The test results indicate that the impact energy decays exponentially with an energy attenuation coefficient of −0.42. For the scattering characteristics of energy in the rock, the scattering distance is found to be approximately three times the specimen diameter, which is very similar to Saint-Venant’s principle in elastic mechanics.
31
Xie, Beixin, Peidong Xu, Liqun Tang, Yongrou Zhang, Kejia Xu, Hong Zhang, Zejia Liu, Licheng Zhou, Yiping Liu e Zhenyu Jiang. "Dynamic Mechanical Properties of Polyvinyl Alcohol Hydrogels Measured by Double-Striker Electromagnetic Driving SHPB System". International Journal of Applied Mechanics 11, n. 02 (marzo 2019): 1950018. http://dx.doi.org/10.1142/s1758825119500182.
Testo completoAbstract (sommario):
As an ultra-soft material (elastic modulus in magnitude of kPa), polyvinyl alcohol (PVA) hydrogels have the potential to substitute articular cartilage, but the measurement of the dynamic stress–strain relations of ultra-soft materials is still challenging. In this paper, a double-striker electromagnetic driving split-Hopkinson pressure bar (SHPB) system was developed, in which all the bars were made of polycarbonate, and the polycarbonate striker was pushed by a metal striker driven electromagnetically to ensure the precise control of impact velocity. With the new SHPB system, well design of the size of hydrogel specimen and rational processing of the signal data, the stress–strain relations of hydrogels with varied PVA contents at different strain rates were measured successfully. Experimental results indicate that PVA hydrogels are a positive strain rate sensitive material with different strain-rate effects at low and high strain rates. Finally, based on the latest quasi-static constitution of the PVA hydrogel, a rate-dependent constitutive equation was recommended, which may well depict the mechanical behaviors of hydrogels with different fiber contents at varied strain rates. It also derives that the contributions of strain rate and fiber content on the mechanical behaviors of the hydrogel are relatively independent.
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Doktor, Tomáš, Tomáš Fíla, Petr Zlámal, Daniel Kytýř e Ondřej Jiroušek. "HIGH STRAIN-RATE COMPRESSIVE TESTING OF FILLING MATERIALS FOR INTER-PENETRATING PHASE COMPOSITES". Acta Polytechnica CTU Proceedings 25 (6 dicembre 2019): 21–24. http://dx.doi.org/10.14311/app.2019.25.0021.
Testo completoAbstract (sommario):
In this study behavior of the selected types of filling material for the inter-penetrating phase composites was tested in compressive loading mode at low and high strain-rates. Three types of the filling material were tested, (i) ordnance gelatin, (ii) low expansion polyurethane foam, and (iii) polyurethane putty. To evaluate their impact energy absorption bulk samples of the selected materials were tested in compression loading mode at strain-rates 1000 s−1 to 4000 s−1. The high strain-rate compressive loading was provided by Split Hopkinson Pressure Bar (SHPB) which was equipped with PMMA bars to enable testing of cellular materials with low mechanical impedance. Based on the comparative measurement response to compression at both low and high strain-rates was analysed. The results show a significant strain-rate sensitivity of the ordnance gelatin and of the polyurethane putty, while strain-rate effect in the polyurethane foam was not observed.
33
Pei, Pei, Zhongcai Pei e Zhiyong Tang. "Numerical and Theoretical Analysis of the Inertia Effects and Interfacial Friction in SHPB Test Systems". Materials 13, n. 21 (28 ottobre 2020): 4809. http://dx.doi.org/10.3390/ma13214809.
Testo completoAbstract (sommario):
The dynamic properties of materials should be analyzed for the material selection and safety design of robots used in the army and other protective structural applications. Split Hopkinson pressure bars (SHPB) is a widely used system for measuring the dynamic behavior of materials between 102 and 104 s−1 strain rates. In order to obtain accurate dynamic parameters of materials, the influences of friction and inertia should be considered in the SHPB tests. In this study, the effects of the friction conditions, specimen shape, and specimen configuration on the SHPB results are numerically investigated for rate-independent material, rate-dependent elastic-plastic material, and rate-dependent visco-elastic material. High-strength steel DP500 and polymethylmethacrylate are the representative materials for the latter two materials. The rate-independent material used the same elastic modulus and hardening modulus as the rate-dependent visco-elastic material but without strain rate effects for comparison. The impact velocities were 3 and 10 m/s. The results show that friction and inertia can produce a significant increase in the flow stress, and their effects are affected by impact velocities. Rate-dependent visco-elasticity material specimen is the most sensitive material to friction and inertia effects among these three materials (rate-independent material, rate-dependent elastic-plastic material, and rate-dependent visco-elastic material). A theoretical analysis based on the conservation of energy is conducted to quantitatively analyze the relationship between the stress measured in the specimen and friction as well as inertia effects. Furthermore, the methods to reduce the influence of friction and inertia effects on the experimental results are further analyzed.
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Gavrus, Adinel, Florina Bucur, Adrian Rotariu e Sorin Cănănău. "Analysis of Metallic Materials Behavior during Severe Loadings Using a FE Modeling of the SHPB Test Based on a Numerical Calibration of Elastic Strains with Respect to the Raw Measurements and on the Inverse Analysis Principle". Key Engineering Materials 554-557 (giugno 2013): 1133–46. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.1133.
Testo completoAbstract (sommario):
The complex loading paths of non-conventional or rapid forging processes, especially as regards the important gradients of the plastic strain and strain rate characterizing the material deformation, require a reliable knowledge of the rheological constitutive equations. Some recent studies propose adequate phenomenological formulations taking into account the corresponding local physical mechanisms and the sensitivity of the true stress with respect to all mechanical variables. At the same time important scientific efforts have been focused in order to identify correctly all the constitutive law parameters, using adequate mechanical tests and robust numerical tools based generally on the inverse analysis principle. It is known that this new method requires building of a rigorous and adequate experimental space, using data obtained from loading conditions close to the industrial forming process. Then to explore high variations of plastic strain and strain rate, one of the most suitable tests are based on high speed hydraulically press and on the Split Hopkinson Pressure Bars test (SHPB). Consequently this paper propose to improve the experimental data accuracy obtained from the SHPB device by using finite element simulations of the entire high speed mechanical experiment together with the description of the inverse analysis strategy applied in order to analyze the thermo-mechanical constitutive behavior of metallic materials behavior and to identify the corresponding rheological parameters. The first part of this study will be dedicated to a short description of the experimental SHPB test analysis and to the analysis of the measurement data which can be used to describe the real mechanical loadings of the specimen. A new experimental calibration method of the acquisition signals, based on the finite element modeling of the elastic bars deformation during an impact without specimen, will be detailed. Using ABAQUS and CAST3M software, this method is validated from the comparison of the elastic strains variation obtained by the numerical simulations. In a second part will be detailed the inverse analysis strategy together with a real application concerning the rheological behavior of an aluminum alloy using a “dumbbell” specimen during a high speed upsetting test starting from a proposed constitutive relationship. Finally, special “cap” geometries of the material sample will be analyzed during a SHPB compression test in order to understand the feasibility of the proposed method to expand the material constitutive behavior identification to severe loadings. It is then shown the capacity to describe deformation path close to the rapid manufacturing processes and high speed machining.
35
Hong, S. N., H. B. Li e L. F. Rong. "Experimental Study on Stress Wave Propagation Crossing the Jointed Specimen with Different JRCs". Shock and Vibration 2021 (3 novembre 2021): 1–12. http://dx.doi.org/10.1155/2021/3096253.
Testo completoAbstract (sommario):
Most of the rock masses in the outer crust of the Earth are discontinuous. They are divided by joints, faults, fractures, etc. And those discontinuities, generally referred to as joints, greatly affect the property of the rock masses. The paper experimentally investigates the stress wave propagation crossing the jointed specimens. The tests were conducted on the split Hopkinson pressure bar (SHPB). The test specimens consist of two parts cast by cement mortar. Both parts have an irregular surface, and they were designed to match each other completely. The surfaces where two parts meet make an artificial joint. The surfaces of the joints were scanned by a three-dimensional scanner to obtain its actual topography and then to calculate the roughness of the surface, i.e., the joint roughness coefficient (JRC). A set of jointed specimens with JRC ranging from 0 to 20 were made and used in dynamic compression experiments. During the tests, signals were captured by strain gauges stuck on the incident and transmitted bars of the SHPB apparatus. The incident, reflected, and transmitted waves across the jointed specimens were obtained from the test records. We found out that more stress wave would transmit through the jointed specimen with larger JRC. Besides, collected data were processed to get the dynamic stress-strain relation of jointed specimens and the stress-closure curves of the joints. The results show that the joint increases the deformation of the specimen, and the stiffness of the jointed specimen would increase slightly when the joint is rougher.
36
Miao, Chun-He, Liang-Zhu Yuan, Jian-Hua Lu, Peng-Fei Wang e Song-Lin Xu. "Deformation evolution and diffusion characteristics of PMMA under impact loading". Acta Physica Sinica 71, n. 21 (2022): 216201. http://dx.doi.org/10.7498/aps.71.20220740.
Testo completoAbstract (sommario):
Dynamic compression experiments on cubic polymethyl methacrylate (PMMA) specimens and two kinds of trapezoid PMMA specimens are carried by changing the transmission bars into steel bar and aluminum bar on the experimental device of split Hopkinson pressure bar (SHPB). The compression processes of PMMA specimens are recorded by high-speed photography, and the breakage processes of PMMA specimens are analyzed based on the force displacement curves and high-speed images. The evolutions of deformation and diffusion resistances of PMMA specimens under impact loading are discussed. The results show that the failure of the sample is caused mainly by the partial failure front at the contact end, and then the failure front propagates to the inside of the sample, s leading the sample to break. The failure front of cubic sample is generated preferentially at the transmission end under low speed impact and at the incident end under the higher speed impact. After changing the shape of the specimen and the material of the transmission bar, the relaxation phenomenon is prominent, and the failure front occurs only at the incident end. The compressive deformation of the trapezoid sample before breakage is non-uniform, and the stress and strain in the sample gradually decrease with the increase of the cross section, and show a linear diffusion distribution. The strain distribution and shear activation diffusion equation are used to obtain the generalized diffusion resistance distribution of the failure front. The generalized diffusion resistance increases first in front of the failure front and decreases after the failure front, and the amplitude of the generalized diffusion resistance is related to the release of local strain energy.
37
Ren, Kerong, Rong Chen, Yuliang Lin, Shun Li, Xianfeng Zhang e Jun Dong. "Probing the Impact Energy Release Behavior of Al/Ni-Based Reactive Metals with Experimental and Numerical Methods". Metals 9, n. 5 (28 aprile 2019): 499. http://dx.doi.org/10.3390/met9050499.
Testo completoAbstract (sommario):
Reactive metals (RMs) are a new class of material that can withstand mechanical loads and chemically react to release large amounts of heat under strong impact loading. They are gradually becoming widely used in defense and military fields, including for high-efficiency warheads and reactive armor. For the numerical simulation method considering the combined mechanical-thermo-chemical process for the impact energy release behavior of the RMs, the Al/Ni-based RMs were investigated in this work by combining experiments, theoretical calculations and a numerical simulation. Three kinds of Al/Ni-based RMs (Al-Ni, Al-Ni-CuO and Al-Ni-MoO3), were prepared using the hot-pressing forming process. Firstly, the compressive behavior and the parameters of the Johnson-Cook constitutive model were obtained using a mechanical testing machine and split Hopkinson pressure bars (SHPB). Secondly, the parameters of the equation of state (EOS) under the medium and low pressure conditions of the Al/Ni-based RMs, which were was seen as porous mixtures with high theoretical material density percentages (TMD%), were calculated based on the cold-energy superposition theory and the Wu-Jing method. Third, the impact energy release behaviors of the three RMs were studied with direct ballistic tests. The shock temperatures at different impact velocities were calculated based on the existing shock-induced chemical reaction thermo-chemical model while considering the chemical reaction efficiency, the relationship between the shock temperature and the extent of the chemical reaction was established, and the parameters of the relevant chemical kinetic equations were fitted. Finally, the user’s subroutines defining the material model were implemented to update the stresses in the solids elements in LS-DYNA. The model was based on the Johnson-Cook constitutive model with consideration of the mechanical-thermo-chemical coupling effect, which was verified by the experimental results. The results show that the constitutive model developed in this work can describe the impact energy release behavior of the Al/Ni-based RMs.
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Zhang, Zhi Gang, Meng Shen Li, Xiao Long Wang, Xiao Lei Zhong e Qing Li. "Ø100mm SHPB Equipment and its Application". Applied Mechanics and Materials 99-100 (settembre 2011): 891–95. http://dx.doi.org/10.4028/www.scientific.net/amm.99-100.891.
Testo completoAbstract (sommario):
Hopkinson Pressure Bar (HPB) is one of the main sets to study material dynamic mechanic properties. Large diameter HPB is mainly used for nonhomogeneous materials. In this paper the properties of Split Hopkinson Pressure Bar (SHPB) of Ø100mm are introduced, including its structure and performance index. The main problems of large diameter SHPB are analyzed. The further development and application of SHPB are also explored.
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Ganorkar, Kavita, Ketan Arora, Lekhani Gaur, M. D. Goel e Tanusree Chakraborty. "Dynamic Characterization of Concrete using Split Hopkinson Pressure Bar". Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, n. 1 (19 dicembre 2022): 1217–21. http://dx.doi.org/10.38208/acp.v1.643.
Testo completoAbstract (sommario):
Concrete exhibits brittle behaviour and is weak under tensile and flexural loading. The response of concrete to dynamic loading is of interest in a variety of civilian and military applications. Understanding the response of concrete to impact or explosive loading is important for effective protection of defence and civil structures. The split Hopkinson pressure bar (SHPB) technique has been used widely to measure the dynamic strength enhancement of materials at high strain rates. Although, SHPB technique has been verified for metallic materials, but validity and accuracy of SHPB results for non-metallic, e.g. concrete materials have not been thoroughly studied so far. The present study examines the application of SHPB to determine the dynamic strength of concrete under compressive loading. The aim of this study is to understand the strain rate effect on the ultimate uniaxial compressive strength of concrete in SHPB tests for two different grades of concrete. The behaviour of concrete at strain rates of the order of 200 - 600 per second and pressures up to 0.38 MPa are studied experimentally. The strength of concrete is found to be increased with the increase in strain rates. Further, it is observed that due to the composite microstructure of concrete, deformation and stresses are non-uniform in the concrete specimens.
40
Kariem, Muhammad A., Dong Ruan e John H. Beynon. "Numerical Study of Round-Robin Tests on the Split Hopkinson Pressure Bar Technique". Key Engineering Materials 535-536 (gennaio 2013): 518–21. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.518.
Testo completoAbstract (sommario):
It is known that the split Hopkinson pressure bar (SHPB) technique has not been standardised yet. The standardised SHPB technique is necessary in order to provide guidelines for determining the intrinsic material properties. This paper examines whether consistent results can be achieved from various sets of SHPBs. Finite element analysis has been conducted using ANSYS/LS-DYNA. Numerical simulation of the round-robin tests was conducted to study the consistency of results for OFHC copper, which were obtained from three sets of apparatus, namely: 12.7 mm diameter SHPB made from the AISI 4140 steel, 13 mm diameter SHPB made from the high strength steel (HSS) and 14.5 mm diameter SHPB made from maraging steel 350 (AISI 18Ni). The current study shows that consistent flow stresses (within an acceptable error of 2.5%) were obtained from those three sets of SHPBs, which indicates the possibility of SHPB standardisation in the future.
41
Jin, Hong Bin. "Numerical Simulation the Stress Uniformity in Split Hopkinson Pressure Bar Testing". Advanced Materials Research 634-638 (gennaio 2013): 2861–64. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.2861.
Testo completoAbstract (sommario):
The assumption of uniform stress in a test specimen is fundamental to SHPB test technique. In the present paper, a numerical simulation of wave propagation in SHPB is performed to validate the assumption. A one-dimensional model based on CSPM is firstly developed. Then the wave propagations in SHPB with various area ratios of bar/specimen are simulated. The results show that the condition of stress uniformity is not satisfied, especially at the beginning of wave propagation. For the large area specimen, the stress tends to be uniform. While for the small area specimen, the non-uniformity of stress is more apparent.
42
Afdhal, Afdhal, Leonardo Gunawan e Tatacipta Dirgantara. "Experimental Work for Bar Straightness Effect Evaluation of Split Hopkinson Pressure Bar". Journal of Engineering and Technological Sciences 53, n. 6 (31 dicembre 2021): 210613. http://dx.doi.org/10.5614/j.eng.technol.sci.2021.53.6.13.
Testo completoAbstract (sommario):
Bar straightness is one of several factors that can affect the quality of the strain wave signal in a Split Hopkinson Pressure Bar (SHPB). Recently, it was found that the bar components of the SHPB at the Lightweight Structures Laboratory displayed a deviation in straightness because of manufacturing limitations. An evaluation was needed to determine whether the strain wave signals produced from this SHPB are acceptable or not. A numerical model was developed to investigate this effect. In this paper, experimental work was performed to evaluate the quality of the signal in the SHPB and to validate the numerical model. Good agreement between the experimental results and the numerical results was obtained for the strain rates and stress-strain relationship for mild steel ST37 and aluminum 6061 specimen materials. The recommended bar straightness tolerance is proposed as 0.36 mm per 100 mm.
43
Lei, Jin Tao, Ming Hua Zhang e Jian Kang Chen. "Electro-Conductive Property of Polymeric Composite under Impact Loading Using a Modified SHPB". Advanced Materials Research 291-294 (luglio 2011): 1243–46. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1243.
Testo completoAbstract (sommario):
In order to detect the variation of electro-conductive property of polymeric composite under impact loading, a modified split Hopkinson pressure bar (M-SHPB) is suggested. Such M-SHPB is constructed by designing a new test electrocircuit, and connecting it to the specimen and oscillograph. On the other hand, a copper foil cover is designed and placed on the whole SHPB equipment for avoiding interference of electromagnetic wave existing in the testing environment. By means of M-SHPB, the relation between the resistance and dynamic strain is effectively detected.
44
Chen, Jiangping, Weijun Tao, Shi Huan e Chong Xu. "Data processing of wave propagation in viscoelastic split Hopkinson pressure bar". AIP Advances 12, n. 4 (1 aprile 2022): 045210. http://dx.doi.org/10.1063/5.0083888.
Testo completoAbstract (sommario):
In this study, the polymethyl methacrylate (PMMA) bar was taken as an example to study the data processing of the viscoelastic Split Hopkinson pressure bar (SHPB) during shock wave propagation. First, SHPB tests of the PMMA bar were conducted, and the strain data measured at the position of the strain gauges on the viscoelastic PMMA bar were processed by using the improved Lagrange analysis method (LAM) to obtain the full-field strain, particle velocity, and stress data. Then, the Zhu–Wang–Tang dynamic viscoelastic constitutive model was adopted, and the parameters were calibrated to determine the dynamic constitutive equation of the PMMA bar. By combining the characteristics method and the dynamic constitutive equation, numerical simulation was conducted to obtain the physical quantity data at each point on the PMMA bar, so as to realize the closed-loop test. By comparing the data obtained by the improved LAM with the data obtained by the characteristics method, it was found that the improved LAM can improve the calculation accuracy at the later loading stage and was more consistent with the actual situation, and the validity of data processing and the applicability of the dynamic constitutive equation at the early loading stage were verified as well. The improved LAM can be extended to the propagation calculation of the attenuation wave in SHPB tests of soft materials or low density materials.
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Mauko, Anja, Branko Nečemer e Zoran Ren. "INVERSE COMPUTATIONAL DETERMINATION OF JOHNSON-COOK PARAMETERS USING THE SHPB TEST APPARATUS". Acta Polytechnica CTU Proceedings 25 (6 dicembre 2019): 64–67. http://dx.doi.org/10.14311/app.2019.25.0064.
Testo completoAbstract (sommario):
The paper describes determination of the material parameters of the Johnson-Cook constitutive model of steel S235 JR sample material by applying the inverse computational methodology using the digital twin model of the SHPB. A quasi-static tensile testing of bulk material was conducted first to determine the base material parameters. This was followed by dynamic impact testing at two different strain rates using the SHPB. A digital twin computational model was built next in the LS-Dyna explicit finite element system to carry out the necessary computer simulations of the SHPB test. The inverse determination of strain hardening material parameter of Johnson-Cook model was done by using the Nelder-Mead simplex optimisation by comparing the measured and computed stress to time signals on incident and transmission bars. The obtained Johnson-Cook material parameters much better describe the sample material behaviour at very high strain-rates in computational simulations, if compared to the parameters derived by the classic, one-dimensional wave propagation Hopkinson procedure.
46
Fadillah, Hafiz, Sigit Puji Santosa, Leonardo Gunawan, Akbar Afdhal e Agus Purwanto. "Dynamic High Strain Rate Characterization of Lithium-Ion Nickel–Cobalt–Aluminum (NCA) Battery Using Split Hopkinson Tensile/Pressure Bar Methodology". Energies 13, n. 19 (26 settembre 2020): 5061. http://dx.doi.org/10.3390/en13195061.
Testo completoAbstract (sommario):
The dynamic behavior of the lithium-ion battery is evaluated by simulating the full battery system and each corresponding component, including the jellyroll and thin-foil electrodes. The thin-foil electrodes were evaluated using a novel design of split Hopkinson tensile bar (SHTB), while the jellyroll was evaluated using the split Hopkinson pressure bar (SHPB). A new stacking method was employed to strengthen the stress wave signal of the thin-foil electrodes in the SHTB simulation. The characteristic of the stress–strain curve should remain the same regardless of the amount of stacking. The jellyroll dynamic properties were characterized by using the SHPB method. The jellyroll was modeled with Fu-Chang foam and modified crushable foam and compared with experimental results at the loading speeds of 20 and 30 m/s. The dynamic behavior compared very well when it was modeled with Fu-Chang foam. These studies show that the dynamic characterization of Li-ion battery components can be evaluated using tensile loading of stacked layers of thin foil aluminum and copper with SHTB methodology as well as the compressive loading of jellyroll using SHPB methodology. Finally, the dynamic performance of the full system battery can be simulated by using the dynamic properties of each component, which were evaluated using the SHTB and SHPB methodologies.
47
Jia, Bin, Zheng Liang Li, Lu Cheng e Hua Chuan Yao. "Experimental Study on Dynamic Mechanical Behaviour of Concrete with High Temperature". Advanced Materials Research 194-196 (febbraio 2011): 1109–13. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.1109.
Testo completoAbstract (sommario):
An experimental system of high-temperature split Hopkinson pressure bar (SHPB) was developed by combination of the split Hopkinson pressure bar (SHPB) and microwave heating system, then tests of concrete whose temperature changed from room temperature to 650°С and impact velocity from 5m/s to 12m/s were completed. Based on the test results, the dynamic strength of concrete increases with increasing impact velocity whether with high temperature or room temperature, meanwhile the dynamic strength of concrete with high temperature has the strain rate effect, but the effect keeps decreasing with temperature increasing, even at temperature above 500°С , compressive strength will not have strain rate sensitive effect any longer when strain rate surpasses a certain value. In the meantime, the strain rate hardening effect is coupled with high temperature weakening effect, but the latter has greater influence.
48
Lee, Ouk Sub, Jong Won Lee e Sung Hyun Kim. "Dynamic Deformation Behavior of Rubber (NR/NBR) under High Strain Rate Compressive Loading". Key Engineering Materials 297-300 (novembre 2005): 172–77. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.172.
Testo completoAbstract (sommario):
This paper presents a modified Split Hopkinson Pressure Bar (SHPB) technique to obtain compressive stress-strain data for rubber materials. An experimental technique that modifies the conventional SHPB has been developed for measuring the dynamic compressive stress-strain responses of rubber materials with low mechanical impedance and low compressive strengths. This paper introduces an all-polymeric pressure bar set-up which achieves a closer impedance match between the pressure bar and the specimen materials. In addition, a pulse shaper is utilized to lengthen the rising time of the incident wave which helps the stress equilibrium and homogeneous deformation of rubber materials. It is found that the modified technique can determine the dynamic deformation behavior of NR and NBR rubber more accurately than those from the conventional SHPB technique.
49
Zuo, Li Sheng, Xing Quan Zhang, Liu San Chen, Jian Ping She, Huan Li e Wei Chen. "Simulation of Laser Shock Wave Propagation and Dispersion in SHPB". Advanced Materials Research 681 (aprile 2013): 105–9. http://dx.doi.org/10.4028/www.scientific.net/amr.681.105.
Testo completoAbstract (sommario):
Laser shock wave oscillation caused by lateral inertia effects of Hopkinson bar in large-diameter SHPB apparatus, and the geometry dispersion effect, particularly, the rise time of the stress wave in different diameters and lengths of Hopkinson bar were investigated. The three-dimensional model of member bar is established by the finite element analysis software ABAQUS, and the different shapes pressure pulses including rectangular, triangular and Gaussian pulses induced by laser shock have been loaded on the end face of the bar, respectively. Results indicate that the triangle pressure pulse and Gaussian pressure pulse show less dispersion effect than rectangle stress pulse on wave shape, and Gaussian stress pulse can keep the morphology better and reduce the dispersion effect more effectively than triangle stress pulse in the propagation process. In addition, as the bar diameter increases and the distance of the propagating stress wave raises, wave oscillation enhances significantly in the bar, the same as the rise time of stress wave increases gradually and the maximum stress also has a certain degree of attenuation, which have influence on laser shock processing or forming.
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Gong, J. C., L. E. Malvern e D. A. Jenkins. "Dispersion Investigation in the Split Hopkinson Pressure Bar". Journal of Engineering Materials and Technology 112, n. 3 (1 luglio 1990): 309–14. http://dx.doi.org/10.1115/1.2903329.
Testo completoAbstract (sommario):
Dispersion of an elastic wave propagating in a 76.2-mm-diameter (3 in.) Split Hopkinson Pressure Bar system was investigated with two consecutive pulses recorded in the transmitter bar. Assuming that the dispersive high frequency oscillatory components riding on the top of the main pulse originate from the first mode vibration, the dispersion was corrected by using the Fast Fourier Transform (FFT) and Fourier series expansion numerical schemes. The good agreement validates the assumption that only the first mode was significant. The dispersion correction technique was employed in a test of a concrete specimen having the same diameter as that of the SHPB. Better agreement of the two specimen-bar interface stresses versus time and fewer oscillations in the stress-strain curve demonstrated advantages of the application of dispersion corrections.