Split Hopkinson Pressure Bar Tests Research Articles

Study of effect of loading rate on mechanical properties of SS316LN and evaluation of parameters of Johnson-Cook model using parametric FE analysis and experimental data

The objective of this work is to evaluate the parameters of strain rate dependent Johnson-Cook material model using a hybrid procedure which uses finite element analysis as well as experimental data. The large strain rate tests were conducted to using split Hopkinson pressure bar test setup, whereas the quasi-static test was carried out using conventional testing machines. Johnson-Cook material model has been used to simulate the plastic deformation behavior of material under the high strain loading. This model provides the flow stress of the material as a function of equivalent plastic strain, plastic strain rate and temperature. The parameters, i.e., A, B, n, C and m of the model have been determined using a hybrid procedure as mentioned earlier. One of the important issues in split Hopkinson pressure bar testing is the variation of strain rate during the duration of loading. Due to decrease in reflected strain magnitude, the strain rate continuously decreases (as strain rate is proportional to reflected strain signal) and it is a characteristic of the above test method. However, this creates problem in evaluation of parameters of Johnson-Cook material model using conventional procedure. In this work, a modified procedure has been developed in order to take into account of this variation in strain rate as function of applied strain. The results of the method has been validated with experimental data. The parameters have been evaluated only for room temperature data and the effect of temperature shall be studied in future.

Preparation of amphoteric polycarboxylate superplasticizer at low temperature and its application in cement-calcined kaolin blended system

As one of supplementary cementitious materials (SCMs), calcined kaolin (CK) has received increasing attention in the development of green and sustainable SCMs. When CK was applied into cement, the regular anionic polycarboxylate superplasticizer (PCE) is insufficient to disperse the cement-calcined kaolin blended system (CMT-CK system). Herein, a novel amphoteric polycarboxylate superplasticizer (VDA-1) was synthesized with hydroxybutyl vinyl polyoxyethylene ether (VPEG), acrylic acid (AA) and dimethyl diallyl ammonium chloride (DMDAAC) at low temperature (10 °C). Among a series of synthesized PCE samples, VDA-1 (nVPEG:nAA:nDMDAAC = 1:2.25:0.75) exhibits the best performance in the CMT-CK system. Results showed that the fluidity of the CMT-CK mixed slurry with VDA-1 increased by 127.9 % compared with pure CMT-CK slurry. Meanwhile, the mixed slurry with VDA-1 had good flow retention. The great fluidity of the mixed slurry with VDA-1 is attributed to that VDA-1 can be adsorbed on the surface of cement and calcined kaolin, which was demonstrated by total organic carbon (TOC) adsorption amount analysis. Besides, compared with pure CMT-CK system, the compressive and flexural strength of blended cement with VDA-1 was enhanced 2.26% and 10.60%, respectively. Split Hopkinson Pressure Bar (SHPB) test showed that the CMT-CK system containing VDA-1 exhibited large stress value before instability stage and the maximum absorption energy in the whole process.

Initial pore distribution characteristics and crack failure development of cemented tailings backfill under low impact amplitude

The stability of the cemented paste backfill is threatened by the dynamic disturbance during the excavation of the surrounding ore body. In this paper, the computerized tomography (CT) and Split Hopkinson Pressure Bar (SHPB) tests were conducted to explore the initial pore distribution characteristics of the cemented tailings backfill (CTB) and the development of the crack under low impact amplitude. SHPB tests were conducted with impact amplitudes of 34, 37, and 39 mV, respectively. Results show that the initial pores of CTB were steadily distributed with the height of CTB. The CTB contained many initial pores with similar pore size distribution characteristics, and the largest number of pores is between 0.1 and 0.3 mm. Most of the cracks in CTB after low impact amplitude develop and expand along the initial pores, and the damage of CTB mainly exists in shear cracks. A dependence has been established that the dynamic uniaxial compressive strength of the CTB increases, the total crack volume first increases and then decreases, and the number of cracks increases as the impact amplitude increases. The research results can provide a valuable reference for the dynamic performance of CTB under low impact amplitude and the design of mining backfill.

Study on the Dynamic Properties of Concrete under Freeze-Thaw Cycles and CT Fine View Damage

In order to study the dynamic mechanical properties of concrete under freeze-thaw cycles, uniaxial impact compression tests were conducted on concrete specimens with different number of freeze-thaw cycles (0, 25, 50, 75, and 100) using a 50 mm diameter split Hopkinson pressure bar (SHPB) test device at an impact air pressure of 0.4 MPa and combined with a CT scanning system to analyze the internal fissures of concrete specimens before and after freeze-thaw cycles. The results showed the following. (1) The concrete specimens were divided into linear elastic stage, plastic stage, and damage stage under the freeze-thaw cycle, and the macroscopic mechanical parameters of the specimens were weakened with the increase of the number of freeze-thaw cycles. (2) Freeze-thaw intensified the expansion and penetration of the internal fracture of the specimens, and the CT scan results showed that the internal fracture parameters of the concrete specimens were increased with the increase of the number of freeze-thaw cycles, and the structural characteristics of the internal fracture show gradually complex expansion and evolution characteristics. (3) The degree of damage was defined at the fine level, which increased with the number of freeze-thaw cycles, establishing an intrinsic link between the fine deterioration of concrete specimens and the loss of macroscopic parameters under freeze-thaw cycles. The results are of great significance to further elucidate the internal structural characteristics of concrete material damage under freeze-thaw conditions and to reveal the damage deterioration mechanism.

Static and dynamic tensile properties of ultra-high performance concrete (UHPC) reinforced with hybrid sisal fibers

Ultra-high performance concrete (UHPC) is widely applied in concrete structures against impact and explosive loads. To achieve a more eco-friendly and cost-effective UHPC material, mixed plant fibers instead of conventional steel fibers are considered in the present study. UHPC with single and hybrid long and short sisal fibers (12 mm long fibers and 6 mm short fibers) reinforcement (2% fiber content) were prepared and compared against UHPC with no fiber reinforcement. The quasi-static tensile and bending properties of these six types of UHPC specimens were investigated. A split Hopkinson pressure bar test has also been adopted to evaluate the dynamic tensile performance of UHPC specimens under five strain rates, the effect of strain rate has been investigated, and the failure process has been recorded with a high-speed camera. The experimental results showed that the UHPC containing 1% long sisal fibers (12 mm) and 1% short sisal fibers (6 mm) has optimum dynamic mechanical properties. Hybrid sisal fibers are more effective in strengthening UHPC specimens in dynamic tests than in static tests. A synergy effect is also introduced to further characterize the strengthening effect of hybrid sisal fibers. Finally, to more accurately predict the dynamic tensile strength of the specimens under various strain rates, an improved prediction model of the dynamic increase factor for tensile strength is proposed by combining the results of this experiment and previous experimental data.

Study of the Dynamic Failure Characteristics of Anisotropic Shales Under Impact Brazilian Splitting

The mechanical behaviors of shales with transversely isotropic characteristics under dynamic loading have great significance for structural instability in geotechnical engineering. To understand the effect of transverse isotropy on the deformability and tensile strength of shales subjected to dynamic loading, a group of impact Brazilian tests were carried out on shale specimens via a split Hopkinson pressure bar (SHPB) testing system. High-speed digital image correlation technology was applied to monitor the fracture process. The experimental results demonstrate that the failure strength has considerable anisotropy as the bedding angle of the embedded layers changes. Moreover, the tensile strength of shales with vertical bedding is usually higher than that of shales with parallel bedding. The observed failure mode is mainly the interaction between tensile and/or shear fractures, and with increasing loading rate, layer-activated fractures tend to occur. Furthermore, five typical failure patterns of transversely isotropic shales characterized by different mechanisms under dynamic Brazilian testing were found. The shales were sensitive to the strain rate when the deformation and fracture response under dynamic loading were assessed. In addition, the modified Nova‒Zaninetti criterion that considers the strain rate effect was proposed according to the Brazilian splitting data and dynamic coordinate system. The established criterion not only properly represents the law of dynamic strength but also provides a new understanding of the effect of strain rate on strength. It has proven to be effective for predicting the dynamic strength characteristics of shales.

Numerical Investigation of Tensile and Compressive Behavior of Mild Steel Subjected to High Strain Rate

Numerical simulations were conducted to validate computational and constitutive models for steel materials through dynamic material tests involving both tension and compression. These simulations involved the numerical modeling of the split Hopkinson pressure bar (SHPB) apparatus, with the appropriate loading applied directly in compression and indirectly in tension. To induce a tensile wave within the specimen, a shoulder, such as a coupler or collar, was interposed between the bars. The simulations were carried out using the LS-DYNA finite element code. In these numerical simulations of the SHPB tests, the MAT-15 Johnson–Cook material model was applied to represent mild steel. The resulting stress–strain relationships obtained under both compression and tension conditions were subsequently compared to corresponding experimental data. The primary objectives of these simulations were to determine the optimal placement of strain gauges on both the input and output bars of the tensile SHPB setup. Additionally, the simulations aimed to assess the influence of the gauge length-to-diameter ratio on the behavior of the mild steel specimen subjected to dynamic tension and compression. The results showed that the pulse produced due to the mechanical mismatch of the element at boundaries can be avoided using the length of the input bar smaller than the output bar. Further, the location of the strain gauge in the case of the output bar should be toward the output bar-shoulder interface, while in the case of the input bar, it should be considered at the center of the span of the bar.

Characterizing piezoelectric properties of PVDF film under extreme loadings

Polyvinylidene fluoride (PVDF) as a polymer has been proven to be an effective piezoelectric sensor with advantages of good flexibility, high mechanical strength, and high chemical resistance. Numerous studies have focused on the response of PVDF film at high strain rates, but few on low strain rate response, and the response of PVDF film at different strain rates is unknown. To address these limitations, we examine the piezoelectric properties of PVDF film at extreme high and low loading rates. We design quasi-static compression and dynamic split Hopkinson pressure bar (SHPB) test setups to examine the response of PVDF film. Quasi-static compression test results show that PVDF films have good repeatability and linearity. The charge shift phenomenon is observed at quasi-static loading conditions, and the charge shift rate is found to be related to the gain coefficient of charge amplifier. Next, SHPB tests are performed and results show that PVDF film can well capture the propagation of stress wave. Moreover, it is observed that the PVDF film under high loading rate has a higher failure strength in comparison to that of low loading rate. Finally, based on the measured points by quasi-static compression and SHPB tests, the piezoelectric coefficients of PVDF film under extreme low (on the scale of strain rate of 10−2 s−1) and extreme high (on the scale of strain rate 105 s−1) loading rates are found to be 30.79 pC/N and 27.72 pC/N, respectively. Note that, the strain rate difference is seven orders of magnitude, the piezoelectric coefficient difference is only 9.97%. We believe our findings can advance the design and application of PVDF films in practical engineering.

3D meso‐scale numerical model and dynamic mechanical behavior of reinforced concrete

AbstractBased on the modeling method of 3D meso‐scale finite element model of plain concrete, a 3D meso‐scale finite element model of reinforced concrete is established considering the interface transition zone between reinforcement frame and mortar, and the reliability of the established meso‐scale finite element model is verified by split Hopkinson pressure bar (SHPB) test results. The failure process of reinforced concrete specimens under typical impact velocity and the influence of interface effect on specimen strength are analyzed by numerical simulation. The research results show that the 3D meso‐scale model of reinforced concrete considers the meso‐scale structure of reinforced concrete more realistically, and can better reflect the damage change process inside the material in the dynamic loading process. The weak interface effect caused by reinforcement can lead to the slight weakening of the dynamic strength of the material, but at the same time the weak interface effect of the reinforcement is also the main reason why the residual form of reinforced concrete remains well aligned with the shape of the reinforcement frame after the failure.

Investigation of the dynamic behavior and fracturing mechanism of granite

In examining the dynamic behavior and fracturing mechanism of granite using numerical simulation methods, many studies assume a random distribution of minerals, which fails to accurately represent the actual distribution. The primary objects of this study are therefore to combine digital image processing (DIP) method with the discrete element method (DEM) to develop a more accurate granite model that matches the real mineral distribution of the granite specimen. The DEM is then used to simulate the Split Hopkinson Pressure Bar (SHPB) test, exploring how mineral properties like mineral content, grain shape, grain size, and loading conditions such as strain rate and confining pressure, affect the dynamic behavior and fracture pattern of granite. The results demonstrate that granite models, despite differing grain shapes and sizes, display similar dynamic strength (varying by 4.8%) when they have comparable mineral contents. Feldspar content significantly affects stress variations, while quartz and biotite have minor impact. Stronger minerals like quartz and feldspar show similar fracture patterns, whereas biotite leads to a larger damage area and denser fracture distribution. Loading conditions, such as strain rate and confining pressure, significantly influence the fracture behavior of granite specimens. Fracture propagation is primarily characterized by tension cracks, with shear cracks following, and their distribution varies based on mineral properties and loading conditions.

Study on the Numerical Relationship between Dynamic Compressive Strength and Crushing Energy Consumption in Dynamic Point Load Test under Different Corrosion Conditions

Compared with most dynamic tests, point load test is widely used in engineering practice because of its wide requirements for test conditions. In offshore mining engineering, the surrounding rock is affected by dynamic load impact and corrosion of various aqueous solutions for a long time. Therefore, it is of great significance to study the influence of hydrochemical corrosion on dynamic mechanical properties of rock to ensure the stability of surrounding rock. In this paper, a large number of dynamic point load and dynamic uniaxial compression tests were carried out on the granite mined from a large mine by using the Split Hopkinson pressure bar test device after the corrosion of pH values of 2, 5, and 7 solutions, respectively. Based on the energy theory, the crushing energy consumption in the test process is analyzed, and finally the fitting formula of the dynamic compressive strength and the crushing energy consumption in the dynamic point load test is obtained through fitting analysis. The results show that when the crushing energy consumption in the dynamic point load test is used to estimate the dynamic compressive strength, a certain crushing energy consumption (the final value of this test is 70 J in this paper) is more accurate, and it can estimate the dynamic compressive strength under various corrosion conditions under this crushing energy consumption. However, with the change of crushing energy consumption in the dynamic point load test, this transformation relationship is no longer accurate, and it is necessary to modify this transformation relationship with corrosion condition as the influencing factor. This conclusion can provide reference for obtaining the dynamic compressive strength of rocks under different corrosion conditions in engineering field in the future.

Dynamic mechanical properties and failure characteristics of layered composite rock containing a tunnel-shaped hole

To investigate the dynamic mechanical properties and failure characteristics of the surrounding rock mass in layered strata, composite specimens with a circular hole and a horseshoe-shaped hole were prepared using rock-like materials. Then, the split Hopkinson pressure bar (SHPB) test system and digital image correlation (DIC) technology were employed to conduct relevant experiments and analyses. The experimental results indicate that the influence of cross-sectional shape differences on the dynamic mechanical properties of composite specimens cannot be ignored. Compared to composite specimens with a circular hole, the composite specimens with a horseshoe-shaped hole have a more significant hindrance to wave propagation, and their dynamic compressive strength (DCS) and elastic deformation ability are also lower. In addition, the bedding inclination θ also has a significant impact on the dynamic mechanical properties. With increasing bedding inclination θ, the DCS of composite specimens shows a trend of increasing–decreasing-increasing. Moreover, the energy proportion was analyzed according to the experimental results. This study also investigated the failure characteristics of tunnels surrounding rock in layered strata. For composite specimens with a circular hole, four types of cracking and their distribution related to the dip angle of bedding planes were summarized. For composite specimens with a horseshoe-shaped hole, six types of cracking and their distribution versus the bedding inclination were summarized.

Influence of Specimen Diameter for Titanium Grade 1 on SHPB Tests and Its Verification Using FEM

The split Hopkinson pressure bar (SHPB) is a machine used for obtaining dynamic material properties at high strain rates of 102–104 s−1. In the SHPB test, the material properties obtained vary depending on the shape of the specimen. In other words, it is important to understand the behavior of the specimen when selecting the specimen dimensions. However, specific standards, such as the size of specimens and bars for the SHPB, have not yet been established. This study investigates the effect of changing the specimen diameter on strain and stress results. Comparison and verification with experimental results were performed using the LS-DYNA program. Specimens are cylindrical titanium grade 1. The specifications of bars and length (L) of the specimens were not changed. The results revealed that the reflected ratio increased, and the transmitted ratio decreased as the area of the specimen decreased. The ratios of these strains are affected by impedance (Z=ρAC). The area reduction of specimens under the same conditions made it possible to obtain dynamic properties at a higher strain rate. It was shown that the impedance relationship and strain rate can be altered by varying the diameter of the specimen without changing the dimensions or material of the bar itself.

Effects of polypropylene fibers and aggregate contents on the impact performance of coral aggregate concrete

The paper aims to study the effect of polypropylene (PP) fibers and aggregate contents on the impact compression mechanical performance of coral aggregate concrete (CASC). 5 PP fiber contents (0 kg/m3, 1 kg/m3, 2 kg/m3 3 kg/m3, 4 kg/m3), 3 natural gravel replacement ratios (0 %, 40 %,70 %), and 3 impact pressures (0.10 MPa, 0.12 MPa, 0.14 MPa) were designed for the split Hopkinson pressure bar (SHPB) test herein. The PP fiber contents and gravel replacement ratios effects on the impact compressive properties of CASC were assessed in term of the stress-strain curve, the strain rate effects and the toughness. The results showed that the dynamic compressive strength enhanced obviously with the increasing PP fiber contents and gravel replacement ratio, while the excessive fiber can degrade its properties instead. There exists the apparent strain rate effect of dynamic compressive strength and dynamic increase factor. The addition of PP fiber and the gravel can also improve the toughness of CASC and weaken the strain rate sensitivity. Eventually, the dynamic constitutive model based on ZWT constitutive model was established by considering the material damage, which can excellently forecast the dynamic stress-strain curve of CASC and the dynamic mechanical properties.

Parameter determination and verification of ZWT viscoelastic dynamic constitutive model of Al/Ep/W material considering strain rate effect

As a new type of energetic structural material, Al/Ep/W(Aluminum/epoxy/tungsten), whether as a fragment or projectile material, should comprehensively consider the impact energy release and structural strength, especially the structural strength is the premise to ensure the material integrity. The dynamic constitutive model of materials is the theoretical basis for describing the strength and dynamic behavior of materials. Therefore, it is great significance to determine the dynamic constitutive model parameters of Al/Ep/W materials considering strain rate effect, and to verify the reliability of the model. In this paper, Al/Ep/W material is prepared, and the stress/strain relationship curve of the material under high strain rate is obtained through Split Hopkinson Pressure Bar (SHPB) test. The ZWT viscoelastic constitutive model is selected based on the composition of the material and the distribution of the internal components, and the simplified ZWT constitutive model with damage under constant strain rate is derived, and the parameters of the constitutive model are fitted by the least square method. By using Kirchhoff stress and Green strain tensor theory, the incremental form of the constitutive model is derived, and the Abaqus user material subroutine is written and embedded in the finite element software. The accuracy of material VUMAT subroutine is verified by comparing the results of SHPB test and numerical simulation under high strain rate. Combined with the verified material model subroutine, the experiment and numerical simulation of Al/Ep/W cylindrical projectile impacting aluminum plate are conducted. The results show that the experimental and numerical simulation results are in good agreement. The proposed model can be used to evaluate the dynamic response characteristics of the new energetic material projectile to the lightweight aluminum armor protective structure.

Dynamic Behaviors of Fiber-Reinforced Cellular Concrete Fabricated with Millimeter-Sized Superabsorbent Polymer

A novel cellular concrete with millimeter-level pores fabricated with superabsorbent polymers and fiber is introduced. Porous structure with reinforcement of fiber are adopted to improve crack resistance and shock-absorbing ability. To investigate the dynamic mechanical performance of fiber-reinforced cellular concrete, quasistatic compression and split Hopkinson pressure bar tests with strain rate from 15 to 90 s−1 were conducted. Three different fiber volume fractions (0.2%, 0.6%, and 1%), and two types of fibers (polypropylene fiber and basalt fiber (BF)) were adopted. Along with two levels of porosities (20% and 60%), total of 12 mix designs of cellular concrete to three-level axial impacting. The research results show that the novel cellular concrete is sensitive to high strain rates, demonstrating increasing dynamic compressive strength, dynamic elastic modulus, dynamic increase factor (DIF), and peak toughness with the increase in strain rate. In addition to the inertia effect, the locally enhanced porous structure and fiber structure can change the stress field and crack path, along with the energy consumption of deformation and cracks in the pores. The amount of fiber, physicochemical property, distribution, and shape amplify or dampen through its thickening effect, interface reaction, and stress transmission. Recommended fiber types and dosages were proposed to improve strength, stiffness, and toughness. BF showed an enhanced performance in terms of strength, modulus, and sharp strain-rate effect. Rules of DIFs were also studied. Awareness of the dynamic properties provides a foundation for proper design of structural members and increases the use of cellular concrete.

Dynamic deformation behavior and constitutive model of a Zr–W alloy

In this paper, a Zr–5W alloy was fabricated via casting. In order to obtain the mechanical properties of the material, quasi-static compression tests at room temperature and split Hopkinson pressure bar tests at various temperatures were carried out. The x-ray diffraction result showed that the main components of the alloy were αZr and W2Zr, where αZr is the matrix and W2Zr is the reinforcement. The metallographic characterization results showed that there were two main forms of W2Zr in the material, namely, large particle boundary and small diffuse submicrometer precipitates. The reinforcements of both distributions have the effect of increasing the strength of the material, but the small submicrometer W2Zr precipitates would cause microcrack nucleation during the late plastic deformation stage, resulting in damage softening. In order to make theoretical calculations of the mechanical properties of materials, the Johnson–Cook (JC) constitutive model and Zerilli–Armstrong (ZAM) constitutive model of the material were obtained. It was found that the JC constitutive model had poor consistency in describing material properties. Although the consistency of the ZAM constitutive model was higher than that of the JC constitutive model, it still had obvious shortcomings. Combined with the deformation mechanism of the alloy, a modified constitutive relation was established by adding damage softening terms based on the hexagonal close-packed metal constitutive model inferred by the kinetics of heat-activated dislocations. The relative error results of all working conditions show that the correlation consistency of the improved constitutive model in this paper is significantly better than that of JC constitutive and ZAM constitutive.

Dynamic properties of steel fiber-reinforced potassium magnesium phosphate cement-based materials after high-temperature treatment

Potassium magnesium phosphate cement (MKPC) demonstrates remarkably high-temperature resistance and exhibits ceramic-like characteristics above 1000 °C. When micro steel fibers (MSF) are introduced, the resulting micro steel fiber-reinforced potassium magnesium phosphate cement-based (MSF-MKPC) material displays superior impact resistance even at high temperatures. Besides that, it is non-toxic and environmentally friendly. To investigate the impact resistance of MSF-MKPC at high temperatures, the split Hopkinson pressure bar test was conducted to analyze its dynamic mechanical properties under varying conditions, including MSF content, temperature, and strain rate. Mechanism analyses were carried out using scanning electron microscopy, mercury intrusion porosimetry, and X-ray diffraction testing. The experimental findings revealed the following key points: (1) MSF content has a more significant impact on enhancing the dynamic compressive strength of MSF-MKPC after high-temperature exposure compared to room temperature. Additionally, as the temperature increases, the residual dynamic compressive strength of MSF-MKPC initially decreases and then rises. (2) In contrast to room temperature conditions, the overall dynamic toughness index of MSF-MKPC shows an upward trend with increasing MSF content after high-temperature exposure. As the strain rate increases, the overall dynamic toughness index of MSF-MKPC also increases. (3) A dynamic impact constitutive regression equation is proposed for MSF-MKPC after high temperature, and the predicted results align well with the experimental findings. The analysis of the dynamic performance of MSF-MKPC after high temperatures can serve as a theoretical basis for the design of MSF-MKPC in future engineering applications, as well as for advancing the environmental sustainability and mechanical properties of fiber-reinforced cement-based composite materials.

Deformation failure mechanism and constitutive model of gradient aluminum foam under impact loading

The dynamic mechanical response and energy absorption characteristics of gradient aluminum foam under impact loading with strain rates of 150 s−1, 340 s−1, and 550 s−1 have been studied based on the Split Hopkinson Pressure Bar (SHPB) test in this paper. X-CT and numerical simulations were carried out to analyze the deformation of the micro-porous structure of gradient aluminum foam during impact compression. A constitutive model for gradient aluminum foam under impact load was further established. The results show that the mechanical properties of aluminum foam are positively correlated with the strain rate. The better energy absorption effect of gradient aluminum foams than the homogeneous aluminum foam under impact loading was confirmed. Negative gradient aluminum foam exhibited a 46.9 % higher specific energy absorption rate than homogeneous aluminum foam. The failure mode of homogeneous and positive gradient aluminum foam was observed to be 'from the proximal to the distal', whereas negative gradient aluminum foam exhibited a 'from the distal to the proximal' failure mode. The Sherwood-Frost model, considering the shape, density, and strain rate function correction, could accurately predict the impact stress–strain curve of gradient aluminum foam, which can be served as a reference for the optimal design of gradient aluminum foams.

Comparison of Measurement of Aluminium Alloy in High Strain Rate

Abstract This article describes the Split Hopkinson Pressure Bar test of aluminium alloy EN AW 7075-T6. This test is used for material testing at a high strain rate. Two approaches in measurement. In the first case was used one size of specimen and different initial pressure. In the second case was set one initial pressure and three different lengths of specimen. Based on measured data, constants of Johnson-Cook material model for FEM analysis were found.