A gravity-driven split Hopkinson tension bar for investigating quasi-ductile and strain-hardening cement-based composites under tensile impact loading

2020 ◽  
Vol 105 ◽  
pp. 103430 ◽  
Author(s):  
Ali A. Heravi ◽  
Iurie Curosu ◽  
Viktor Mechtcherine
Keyword(s):  
Strain Hardening ◽  
Impact Loading ◽  
Tensile Impact ◽  
Split Hopkinson ◽  
Gravity Driven ◽  
Split Hopkinson Tension Bar

scholarly journals An Investigation of The Behavior of Strain-Hardening Cement-Based Composites (SHCC) Obtained in a Split Hopkinson Tension Bar and the Influence of Structural Inertia

2020 ◽  
Author(s):  
Ali A. Heravi ◽  
Joško Ožbolt ◽  
Viktor Mechtcherine
Keyword(s):  
Impact Loading ◽  
High Speed ◽  
Image Correlation ◽  
Analytical Models ◽  
Rate Dependent ◽  
Dependent Behavior ◽  
Structural Inertia ◽  
Split Hopkinson ◽  
Fiber Matrix ◽  
Split Hopkinson Tension Bar

The performance of a normal-strength SHCC under impact loading was studied using the results obtained from a split Hopkinson tension bar (SHTB). The focus of the investigation is to explain the mechanisms behind the peculiar rate-dependent behavior of SHCC under tensile loading. With the help of frames obtained by high-speed cameras and the subsequent Digital Image Correlation (DIC) analysis, the stress-strain relation of the SHCC obtained in SHTB was analyzed. The investigation of the composite’s behavior was supported by constituent-level experiments on the non-reinforced matrix of the SHCC and on the fiber-matrix bond. In the case of the constituent matrix, the well-known apparent increase in the tensile strength of the cement-based matrix and its influence on the behavior of SHCC was studied. For this purpose, experiments on the SHCC specimens with different geometries were performed in the SHTB. The results obtained from these experiments and those obtained by DIC show that commonly used analytical models, in which the specimen is assumed elastic, cannot capture the effects of structural inertia on the results. Thus, an alternative novel method based on the results of DIC has been used to explain and quantify the contribution of structural inertia. The rate-dependent behavior of the fiber-matrix bond was studied by performing high-speed single fiber pullout tests in a miniaturized split Hopkinson tension bar. This novel experimental technique enabled explanation of the rate-dependent bridging action of the fibers in SHCC. Based on the results, the enhanced behavior of SHCC under impact loading is explained.

Effect of Material Composition on Impact Energy Absorbing Capability of Composite Laminates

2016 ◽  
Vol 715 ◽  
pp. 147-152
Author(s):  
Ryota Haruna ◽  
Takayuki Kusaka ◽  
Ryota Tanegashima ◽  
Junpei Takahashi
Keyword(s):  
Impact Loading ◽  
Composite Laminates ◽  
Fiber Type ◽  
Material Composition ◽  
Control Technique ◽  
Dynamic Stress Field ◽  
Split Hopkinson ◽  
Split Hopkinson Pressure Bars ◽  
Crushing Behavior ◽  
Energy Absorbing

A novel experimental method was proposed for characterizing the energy absorbing capability of composite materials during the progressive crushing process under impact loading. A split Hopkinson pressure bars system was employed to carry out the progressive crushing tests under impact loading. The stress wave control technique was used to avoid the inhomogeneity of dynamic stress field in the specimen. The progressive crushing behavior was successfully achieved by using a coupon specimen and anti-buckling fixtures. With increasing strain rate, the absorbed energy during the crushing process slightly decreased, whereas the volume of the damaged part clearly increased regardless of material type. Consequently, the energy absorbing capability decreased with increasing loading rate. The effects of material composition, such as fiber type, matrix type and fabric pattern, on energy absorbing capability were also investigated by using the proposed method.

scholarly journals Development of a True-Biaxial Split Hopkinson Pressure Bar Device and Its Application

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7298
Author(s):  
Shumeng Pang ◽  
Weijun Tao ◽  
Yingjing Liang ◽  
Shi Huan ◽  
Yijie Liu ◽  
...  
Keyword(s):  
Stress Wave ◽  
Impact Loading ◽  
Split Hopkinson Pressure Bar ◽  
Axial Stress ◽  
Dynamic Mechanical Properties ◽  
Stress Waves ◽  
Hopkinson Pressure Bar ◽  
Dynamic Mechanical ◽  
Split Hopkinson ◽  
Pressure Bar

Although highly desirable, the experimental technology of the dynamic mechanical properties of materials under multiaxial impact loading is rarely explored. In this study, a true-biaxial split Hopkinson pressure bar device is developed to achieve the biaxial synchronous impact loading of a specimen. A symmetrical wedge-shaped, dual-wave bar is designed to decompose a single stress wave into two independent and symmetric stress waves that eventually form an orthogonal system and load the specimen synchronously. Furthermore, a combination of ground gaskets and lubricant is employed to eliminate the shear stress wave and separate the coupling of the shear and axial stress waves propagating in bars. Some confirmatory and applied tests are carried out, and the results show not only the feasibility of this modified device but also the dynamic mechanical characteristics of specimens under biaxial impact loading. This novel technique is readily implementable and also has good application potential in material mechanics testing.

scholarly journals Stress Transfer Mechanism of Flange in Split Hopkinson Tension Bar

2020 ◽  
Vol 10 (21) ◽  
pp. 7601
Author(s):  
Hyunho Shin ◽  
Sanghoon Kim ◽  
Jong-Bong Kim
Keyword(s):  
Stress Transfer ◽  
Transfer Mechanism ◽  
Explicit Finite Element ◽  
Impact Theory ◽  
Quantitative Basis ◽  
Split Hopkinson ◽  
One Step ◽  
The One ◽  
The Impact ◽  
Split Hopkinson Tension Bar

To reveal the stress transfer mechanism of the flange in a split Hopkinson tension bar, explicit finite element analyses of the impact of the hollow striker on the flange were performed across a range of flange lengths. The tensile stress profiles monitored at the strain gauge position of the incident bar are interpreted on a qualitative basis using three types of stress waves: bar (B) waves, flange (F) waves, and a series of reverberation (Rn) waves. When the flange length (Lf) is long (i.e., Lf > Ls, where Ls is the striker length), the B wave and first reverberation wave (R1) are fully separated in the time axis. When the flange length is intermediate (~Db < Lf < Ls, where Db is the bar diameter), the B and F waves are partially superposed; the F wave is delayed, then followed by a series of Rn waves after the superposition period. When the flange length is short (Lf < ~Db), the B and F waves are practically fully superposed and form a pseudo-one-step pulse, indicating the necessity of a short flange length to achieve a neat tensile pulse. The magnitudes and periods of the monitored pulses are consistent with the analysis results using the one-dimensional impact theory, including a recently formulated equation for impact-induced stress when the areas of the striker and bar are different, equations for the reflection/transmission ratios of a stress wave, and an equation for pulse duration time. This observation verifies the flange length-dependent stress transfer mechanism on a quantitative basis.

Tensile behavior of strain-hardening geopolymer composites (SHGC) under impact loading

2020 ◽  
Vol 113 ◽  
pp. 103703 ◽  
Author(s):  
Ana Carolina Constâncio Trindade ◽  
Ali A. Heravi ◽  
Iurie Curosu ◽  
Marco Liebscher ◽  
Flávio de Andrade Silva ◽  
...  
Keyword(s):  
Strain Hardening ◽  
Impact Loading ◽  
Tensile Behavior ◽  
Geopolymer Composites

Micromechanics Analysis of the Tensile Behavior of Twaron Fiber Tows at Various Strain Rates

2011 ◽  
Vol 181-182 ◽  
pp. 749-753
Author(s):  
Lv Tao Zhu ◽  
Bao Zhong Sun
Keyword(s):  
Mechanical Properties ◽  
Fracture Surface ◽  
Strain Rate ◽  
Failure Strain ◽  
Tensile Behavior ◽  
Failure Stress ◽  
Strain Rates ◽  
Split Hopkinson ◽  
Electronic Microscope ◽  
Split Hopkinson Tension Bar

In this study, tensile experiments of Twaron fiber tows under different strain rates (quasi-static:0.001s-1, dynamic: 800s-1~2400s-1) were carried out with MTS 810.23 materials tester and split Hopkinson tension bar (SHTB) respectively. The results showed that the mechanical properties of the Twaron fiber tows were sensitive to strain rate: the stiffness and failure stress of the fiber tows increased distinctly as the strain rate increased, while the failure strain decreased. From scanning electronic microscope (SEM) photographs of the fracture surface, it is indicated that the Twaron fiber tows failed in a more tough mode and the axial split will become more severe as the strain rate increases.

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

2020 ◽  
Author(s):  
Ali A. Heravi ◽  
Oliver Mosig ◽  
Ahmed Tawfik ◽  
Manfred Curbach ◽  
Viktor Mechtcherine
Keyword(s):  
Shear Strength ◽  
Strain Hardening ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Tensile Load ◽  
High Energy ◽  
Shear Loading ◽  
Impact Compression ◽  
Split Hopkinson ◽  
The Impact

The ductile behavior of strain hardening cement-based composites (SHCC) under direct tensile load makes them promising solutions for applications where high energy dissipation is needed, such as earthquake, impact by a projectile, or blast. However, the superior tensile ductility of SHCC due to multiple cracking does not necessarily entail compressive and shear ductility. As an effort to characterize the behavior of SHCC under impact compressive and shear loading, relevant to the mentioned high-speed loading scenarios, the paper at hand studies the performance of a 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 the quasi-static and impact loading conditions, which was necessary for a reliable comparison of the obtained 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 performing impact shear experiments on planar specimens using the tensile wave generated in the SHTB. Results showed a dynamic increase factor (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 yielded the higher shear strength than the non-reinforced matrix.

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