Split Hopkinson Bar Method Research Articles

Evaluation of impact characteristics of reduced alloy duplex stainless steel sheet

SUS821L1 has been effectively used on bridges and land rocks. However, it has been anticipated that these structures may experience impact loading from earthquakes and tsunamis. It is required to evaluate the mechanical properties of SUS821L1 by impact testing because impact loading yields different mechanical properties than static loading. In this study, a falling drop impact tester with the split-Hopkinson bar method is used to evaluate the impact parameters of SUS821L1. The impact tensile and the static tensile test have demonstrated that the maximum stress is 100MPa greater than the static tensile test and the maximum strain is 3% greater than the impact tensile test.

Identification and formulation of stress-strain relationship for pure nickel and Inconel 718 in a wide strain rate range （10<sup>−3</sup>/ss~10<sup>4</sup>/ss）

Cold spraying is a surface coating technique in which a powder material is impacted on a base material at high speed without melting to form a dense coating layer. However, the stress-strain relationship in the strain rate range of 5 × 103 to 2 × 104/ss , which is required for Cold spraying, has not yet been sufficiently obtained. In this study, stress-strain relationships of pure nickel and Inconel 718 as target materials in a wide range of strain rates from quasi-static strain rate (10−3/ss) to ultra-high strain rate up to 104/ss were investigated by means of a Split Hopkinson bar method and a high-speed material testing machine (TS2000 Saginomiya co. Ltd.). From the experimental results, the stress-strain relationships of pure nickel and Inconel 718 in the wide strain rate range were clarified and a strain rate sensitive constitutive model was formulated by referring the Tanimura-Mimura (2009) model.

On the effect of compaction velocity, size, and content of reinforcing particles on corrosion resistance of Mg–B4C composites

In this study, the effect of the compaction velocity as well as the size and volume fraction of the reinforcing particles on the corrosion properties of Mg–B4C composites were investigated. Micron/nano particles of boron carbide at different volume fractions (0, 5, and 10%) were added to the matrix (magnesium powder). Powder mixtures were milled in a planetary ball mill and compacted at 450 °C and different strain rates, using Split-Hopkinson bar (SHB), drop hammer, and Instron devices. Microstructural analysis and corrosion tests were carried out on the produced samples. The results indicated that the samples produced at higher compaction velocities had the lower corrosion rate mainly due to the lower porosity and higher relative density of the samples. For example, the measured corrosion rates for the magnesium samples reinforced with 5 vol% of micron B4C particles and compacted by the SHB method were 54 and 76% lower than the similar samples produced by the drop hammer and Instron device, respectively. It was also shown that decreasing the size and content of the reinforcing particles resulted in a reduction in the corrosion rate values. The recorded corrosion rate values for the samples reinforced with 5 and 10 vol% of B4C nanoparticles and compacted by the drop hammer device were 18.3 and 29.18 mm/year, respectively. These valuses were approximately 16 and 13% lower compared to the similar composites reinforced with micron-sized particles. The lowest corrosion rate (1.84 mm/year) was observed in the pure magnesium sample compacted by the SHB which was 29.42% lower than that of the magnesium sample reinforced with 10 vol% of micron-sized B4C.

An Experimental Investigation of the Behavior of Strain-Hardening Cement-Based Composites (SHCC) under Impact Compression and Shear Loading

The ductile behavior of strain-hardening cement-based composites (SHCC) under direct tensile load makes them promising solutions in applications where high energy dissipation is needed, such as in earthquakes, impacts by projectiles, or blasts. However, the superior tensile ductility of SHCC due to multiple cracking does not necessarily point to compressive and shear ductility. As an effort to characterize the behavior of SHCC under impact compressive and shear loading relevant to the aforementioned high-speed loading scenarios, the paper at hand studies the performance of a particular SHCC and its constituent, cement-based matrices using the split-Hopkinson bar method. For compression experiments, cylindrical specimens with a length-to-diameter ratio (l/d) of 1.6 were used. The selected length of the sample led to similar failure modes under quasi-static and impact loading conditions, necessary to a reliable comparison of the observed compressive strengths. The impact experiments were performed in a split-Hopkinson pressure bar (SHPB) at a strain rate that reached 110 s−1 at the moment of failure. For shear experiments, a special adapter was developed for a split-Hopkinson tension bar (SHTB). The adapter enabled impact shear experiments to be performed on planar specimens using the tensile wave generated in the SHTB. Results showed dynamic increase factors (DIF) of 2.3 and 2.0 for compressive and shear strength of SHCC, respectively. As compared to the non-reinforced constituent matrix, the absolute value of the compressive strength was lower for the SHCC. Contrarily, under shear loading, the SHCC demonstrated higher shear strength than the non-reinforced matrix.

Evaluation on Compressive Property of Polymer Material by Split Hopkinson Bar Method

Evaluation on Compressive Property of Polymer Material by Split Hopkinson Bar Method

Effect of strain rate on tensile properties of carbon steels by Split-Hopkinson Bar Method

Effect of strain rate on tensile properties of carbon steels by Split-Hopkinson Bar Method

Adapted Nakazima test to evaluate dynamic effect on strain distribution and dome height in balanced biaxial stretching condition

The knowledge of formability is important for the success of sheet metal forming processes. Notwithstanding they can involve relatively high speeds, higher than the quasi-static regime ones, few studies considering the strain rate effect on formability are available in literature. In the present paper, a study on the effect of strain rate on formability of AA6082 aluminum alloy, with a thickness of 1 mm, has been carried out. In order to evaluate the formability under dynamic loading conditions an experimental equipment, based on the Nakazima test, mounted on a direct tension-compression split Hopkinson bar (SHB), has been designed. The standard SHB method was also used to perform tensile to study the high strain rate behavior of AA6082 sheets. The results have been compared with the ones obtained in quasi-static conditions and engineering and true stress and strain data have been collected. A fast camera has been used to acquire images of the sheet samples during tests to obtain the true strain distribution. The study has been focused of the effect of high strain rates on sheet formability in balanced biaxial stretching condition.

Dynamic tension of aluminum alloy AMg-6 in a facility of Split Hopkinson Bar

The results are presented to create a facility for studying dynamic tension of structural materials by using the Split Hopkinson Bar Method (SHB method). The explosive method of loading and a cylindrical corner-rounding sample are used in a facility. A sample has threads at both end faces and it fastened in rods by the help of threads. The results of test experiments are presented in the facility for studying dynamic tension of the aluminum alloy AMg-6 at strain rates of 1160-1450 s-1. The diagrams of dynamic tension σ-ε were built. The data on peculiarities of deformation AMg-6 were gained.

Numerical Study on Impact Testing of Low-Strength Materials Using Flanged Split-Hopkinson Bar Method

In this study, we investigated the effect of flange part on stress wave propagation in the compression test of low strength material using flanged Split Hopkinson Bar method. Due to the flange with a larger radius than the input/output bar, a pair of reflected waves of compression and tension with apparently different shapes from the one-dimensional reflected wave depending on mechanical impedance mismatch was observed. Depending on the relationship between the elastic wave propagation speed in the input/output bar and the gauge position, the precursive reflected wave of compression corresponds to the rising time of the stress wave, and the tensile reflected wave propagated subsequently corresponds to the falling time. It was found that when the flange is used for impact compression test of low strength material, the effect of the flanges on the reflected wave becomes small. However, it was suggested that the transmitted wave may be affected in the impact compression test of low strength material.

Effects of Additives on Tensile Properties of Polyhydroxyalkanoate/Polycaprolactone Polymer Blends

Bioplastics have attracted attention over the years from a perspective of environmental protection. Recently, attention is focused on bioplastics derived from inedible objects. Polyhydroxyalkanoates (PHAs) are known as a microbial origin plastic and expected to deal effectively with the food security issue. In this study, in order to use PHA for industrial and machinery parts and products, polycaprolactone (PCL) was blended with a PHA-based pellet to improve ductility and tensile strength. The effects of additives on tensile strength and elongation at break, dynamic tensile tests of the polymer blends were examined using split Hopkinson bar (SHPB) method at high strain rates.

ボロン添加ステンレス鋼の破壊じん性に及ぼすひずみ速度の影響

Fracture toughness tests were performed for borated stainless steel in the present study. Fracture resistance curves were determined by the unloading elastic compliance method based on the ASTME1820 as well as an image processing technique. The latter was applied to investigate the effect of strain rate on the fracture toughness using split Hopkinson bar method.

Strain rate change tests with the Split Hopkinson Bar method

In this paper, methods to produce rapid strain rate changes for strain rate sensitivity measurements in Split Hopkinson Bar arrangements are presented and discussed. Two different cases are considered: a strain rate change test within the high strain rate region in compression, and a tension test incorporating a large strain rate jump directly from the low strain rate region to high strain rates. The former method is based on the loading wave amplitude manipulation, while the latter method is based on the incorporation of a low strain rate loading device into a Tensile Split Hopkinson Bar apparatus.

Improvement of dynamic tensile properties of Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) polymer alloys using a crosslinking agent and observation of fracture surfaces

Stress-strain curves of poly(lactic acid)/Poly(butylene adipate-co-terephthalate) polymer alloys (80/20, 70/30, 60/40, 50/50, 30/70) were measured using the tensile split Hopkinson bar method. The effects of mixing ratio and crosslinking agent addition on Young's modulus, maximum stress, elongation at break and dissipated work were examined. The crosslinking agent addition significantly increased elongation at break when the mixing ratio was 50/50 and 30/70. The results were compared with the results of Izod impact tests which measure the fracture toughness of materials. The tensile behavior of specimens during dynamic tensile tests was observed using a high speed video camera. The deformation of the gage area was major. The results of Young's modulus, maximum stress, and elongation at break were compared with the mixture laws of composite materials. The fracture mechanism of the specimens was discussed using observation of the fracture surfaces of the tensile test specimens. When the crosslinking agent was not used, it seemed that the fracture occurred along an interface between the PLA-rich region and the PBAT-rich region.

Split Bar Hopkinson with Springs Striker Bar Launcher

Research on the dynamic strength of various materials such as metallic materials, polymers, concrete has been done by many researchers. The Split Hopkinson Bar method is still used to produce a high strain rate. In this method, a striker bar is usually launched using pressurized gas. However, high security system is required to prevent leakage as the operating pressure is very high. Avoiding the use of high-pressure gas, in this study, a mechanical system of springs used to propel the Striker Bar. By varying the spring deflection of 1 cm to 8 cm, a linear Striker Bar velocity from 2.17 m/s until 19.45 m/s is obtained. Aluminum alloy Al-2024 has been tested with this tool and it is found that at the maximum Striker Bar velocity, strain rate on the material can be reach 1132 s-1, and dynamic compression yield strength increase 56% from quasi-static compression yield strength.

Interrupted Test of Advanced High Strength Steel with Tensile Split Hopkinson Bar Method

The phase fraction evolution in a material during quasi-static and dynamic tests can be studied by interrupting the test at predetermined elongation values. While it is straightforward to interrupt quasi-static tests at a predetermined level of elongation, this interruption presents difficulties at high strain rate conditions. In the present paper, an interruption mechanism has been developed to control the elongation of specimens at high strain rate using a modified split Hopkinson tensile bar. This interruption mechanism is based on the interaction between the test specimen and the external interruption device. The influence of the designed external device on the stress waves and also the ability of the system to support the interruption of the deformation process were considered in the numerical analysis and verified by the experimental results. Finally, the influences of strain and strain rates on the volume fraction evolution of the retained austenite in quenched & partitioned steel were reported.

Effect of preloading on the formation of adiabatic localized shear in copper

This paper presents the results of a study of the formation of localized shear in M1 copper of two types: as-received and after preloading by a quasi-entropic compression wave. The experiments were performed with hat-shaped samples using the split Hopkinson bar method. For both types of copper, dynamic compression diagrams were obtained at strain rates of 2100–2500 s−1. The copper structure was subjected to metallographic analysis, and the effect of preliminary shock deformation on the dynamic mechanical properties of the material was estimated. It is shown that preloaded higher-strength metals with a smaller degree of strain hardening are more prone to the formation of adiabatic shear bands.

20206 有孔CFRP積層板引張強度のひずみ速度依存性(OS3-5【高分子系複合材料の成形と力学的特性(5)】)

This study investigates strain-rate dependence of tensile strength of open hole composite specimen. The strain range dealt with in the presort study is from 10^<-13> to 10^2, which is very wide range. For the low strain rate, time-temperature superposition is applied. For the high strain rate, Split Hopkinson Bar method is employed. Failure mechanism is investigated by digital image correlation technique. The tensile strength decreases first with decrease in strain rate, but increases then with that when the strain rate is slow.

OS1907 スプリット・ホプキンソン棒法におけるキーテクノロジー : インピーダンス効果再考

Historical development of the SHPB method is briefly reviewed, and the concept of mechanical impedance is emphasized as a key technology. Various incident waves are shown for the constant strain rate, the strain rate change, the reverse deformation, and so on. It is also discussed the effect of mechanical impedance of loading bars on stress distribution of a specimen and ramped incident wave is a useful method to realize uniform stress distribution at high strain rate deformation..

Effect of Output Bar Supporting Methods on High Velocity Tensile Behavior for Steel Plate

In order to obtain precise and correct dynamic stress-strain behavior for steel plate, the split Hopkinson (Kolsky) bar method or the one bar method has been adopted as a testing method. In these two methods, a dynamic load transducer is the thin steel bar (s). On the input and output bars, typically two or four strain gages are adhered at the same distance from the end of the bars to detect elastic strains of the bars as dynamic load signal. The bars are usually mounted on simple supports, allowing a little axial elongation of the bars. Then, ball bearings or polytetrafluoroethylene parts are frequently installed between the bars and supports, because the friction between them will affect the quality of the dynamic load signal. On the other hand, only for the one bar method, it is reported that a relatively tight support, neighboring the loading end of the output bar, is effective to reduce an extraordinarily-high initial stress peak on dynamic stress-strain curve. In this paper, some trials have been carried out to find the optimum supporting condition for the output bar loading end in the one bar method. An assembly for a steel plate specimen is connected to an impact block. The other end of the assembly is an extension of the output bar. Usually, from the end of gage length of the specimen plate, there is no output bar support within approximately 650mm, for the present apparatus. This situation is designated as “no support”. At a location of 60mm from the end of the gage length, a simple output bar support is introduced additionally. This situation is called as “simple support”, because the output bar is left on the V-shaped top of the support. Additional upper supporting parts can be installed to the simple support condition. After the installation, a square hole is formed on the top of the support. The output bar touches four sides of the hole. This situation is called as “surrounding support”. In addition, specimen assembly types are also included in experimental conditions. Shapes of obtained stress-strain curves in each experimental condition are mutually compared. Also they are compared with that of a reference curve which has the quality of interchangeable with the curves obtained by the split Hopkison bar method. Two experimental conditions are recommended to detect acceptable stress-strain relationships for steel plate.

Testing Aluminum Alloy from Quasi-static to Dynamic Strain-rates with a Modified Split Hopkinson Bar Method

An aluminum alloy(1) was tested at quasi-static to dynamic strain-rates (from 10(-1) to 5 10(3) s(-1)), using a single measuring device, a modified Split Hopkinson Bar. A wave separation technique [Bussac et al., J Mech Phys Solids 50:321-350, 2002] based on the maximum likelihood method was applied to process the strain and velocity measurements recorded at various points on each bar. With this method, it is possible to compute the stress, strain, displacement and velocity at any point on the bar. Since the measurement time is unlimited, the maximum strain measured in a given specimen no longer decreases with the strain-rate, as occurs with the classical Split Hopkinson Bar method.