Fracture studies of Ultra-High Performance Concrete using dynamic Brazilian tests

Khosravani, Mohammad Reza; Silani, Mohammad; Weinberg, Kerstin

doi:10.1016/j.tafmec.2017.10.001

Cited by 89 publications

(32 citation statements)

References 30 publications

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“…when the dynamic loads between the UHPC specimen and the incident bar (P 1 ) and that between the UHPC specimen and transmission bar (P 2 ) become equal, the specimen is in equilibrium. On the tests, both bars and the specimen are equipped with the strain gauges [7]. The disc UHPC specimen between the bars and also the strain history are shown in Figs.…”

Section: Methodsmentioning

confidence: 99%

Investigations on dynamic fracture of ultra‐high performance concrete by Brazilian tests

Khosravani

Weinberg

2017

Proc Appl Math and Mech

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In the last years significant advances in energy-absorption capabilities of concrete and concrete-like materials have been made and a new generation of concrete has been introduced. A greatly improved microstructure compared to traditional concrete, leads to Ultra-high performance concrete (UHPC) which shows improved material properties and better mechanical properties. Despite of many potential applications, specific technical information about this material is still limited. This research presents a linear elastic fracture mechanic based model which is used to study fracture behavior and some mechanical fracture parameters of UHPC material. On the series of the experiments, all the specimens are tested by Split Hopkinson Pressure Bar (SHPB) experiments. The dynamic elastic modulus of UHPC material is determined by cylindrical UHPC specimens. Brazilian disc specimens are impacted by the SHPB and the dynamic tensile strength of the specimens is calculated. Data acquisition system recorded the strain history during the experiment by the help of strain gauges which are mounted on the incident and transmission bars and on the specimens. The achieved results proved that the Brazilian test is a powerful and efficient method to study dynamic fracture properties of UHPC material.

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Section: Methodsmentioning

confidence: 99%

Investigations on dynamic fracture of ultra‐high performance concrete by Brazilian tests

Khosravani

Weinberg

2017

Proc Appl Math and Mech

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“…The Hopkinson bars are employed to determine the limit loads of brittle and ductile materials at high strain rates. In this paper, we focus mainly on the experimental procedures; more details about the specimen material are published in Khosravani et al,; other investigations are still ongoing work. In the following text, we first outline the theoretical basis of the SHB experiments in section 2.…”

Section: Introductionmentioning

confidence: 94%

“…We exploit this anisotropy here and perform dynamic Brazilian experiments to determine the UHPC's tensile resistance. The experiments presented here are part of the results outlined in Khosravani et al…”

Section: Brazilian Tests On Ultra‐high Performance Concretementioning

confidence: 99%

“…In the dynamic regime, the analytical shape correction factor appears to overcompensate the geometrical effect. This has been confirmed by a simulation of our experiment using the extended finite element method (XFEM) where the critical stress for crack growth is reached at about the same loading state for both, circular and flat end specimens . Summarizing these observations, the UHPC has a tensile strength of about 19 MPa.…”

Section: Brazilian Tests On Ultra‐high Performance Concretementioning

confidence: 99%

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Hopkinson bar experiments as a method to determine impact properties of brittle and ductile materials

Weinberg

Khosravani

Thimm³

et al. 2018

GAMM-Mitteilungen

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Split Hopkinson bar experiments are fundamental test arrangements to determine elastic, plastic, and fracture properties of materials under high strain rates. A specimen is considered to be in a well‐defined state of uniaxial stress, and depending on the specific device, limit loads or high strains can be achieved through purely elastic loading in the bars where there are no shock waves present. Variations of the conventional Hopkinson bar procedure allow determining of the dynamic fracture toughness of brittle materials. Here, the results of dynamic Brazilian tests on ultra‐high performance concrete are compared with the results of spallation experiments that simultaneously allow for the determination of the specific fracture energy. Similar experiments are performed for water ice. In addition, the strain rate dependence of the plastic hardening of a medium carbon steel is investigated. The yield stress is determined at strain rates up to 1300s−1.

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“…When the SHPB device is used for the test, the loading method and forced deformation of the specimen during loading are as shown in Figure 2 [31]. …”

Section: Dynamic Brazilian Disc Testmentioning

confidence: 99%

Enhancement Mechanism of the Dynamic Strength of Concrete Based on the Energy Principle

et al. 2018

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This paper analyzes the relationship between the rates of change of elastic strain energy, the strength during the concrete failure process, and proposes that the increased dynamic strength of concrete was caused by the hysteresis effect of energy release—according to the basic principle of energy conversion. Dynamic Brazilian disc tests were carried out on concrete specimens, with diameter of 100 mm, by using the split Hopkinson pressure bar. Test results were obtained through using a gas gun, with an impact pressure of 0.15 MPa, 0.20 MPa and 0.25 MPa, respectively. The dynamic failure process of concrete is then reproduced by numerical calculation methods. Finally, the energy characteristics during the concrete failure process at different strain rates are studied, and the enhancement mechanism of the dynamic strength of concrete is verified. The results showed that the dynamic tensile strength of concrete increased by 9.79% when the strain rate increased by 61% from 60.25 s−1; and when the strain rate increased by 92.8% from 60.25 s−1, the dynamic tensile strength of the concrete rose by 46.28%. The rates of change of both input energy and dissipated energy meet at the peak stress of the material. The increases in rates of change for the two kinds of energy were not synchronized, so excess input energy could be stored as concrete strength increased. As a result, the extra energy stored after peak stress led to a higher degree of concrete fragmentation and greater kinetic energy of the fragment. These results offer research directions for improving the dynamic strength of concrete.

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Fracture studies of Ultra-High Performance Concrete using dynamic Brazilian tests

Cited by 89 publications

References 30 publications

Investigations on dynamic fracture of ultra‐high performance concrete by Brazilian tests

Investigations on dynamic fracture of ultra‐high performance concrete by Brazilian tests

Hopkinson bar experiments as a method to determine impact properties of brittle and ductile materials

Enhancement Mechanism of the Dynamic Strength of Concrete Based on the Energy Principle

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