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1

Study on uniaxial impact compression characteristics of basalt fiber cement soil

Cao Hai, Zhang Xiangyang

Archives of Civil Engineering

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2022

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Vol. 68, nr 1

667--678

EN

In order to study the dynamic mechanical properties of cement soil, uniaxial impact compression tests with different strain rates of cement soil with no fiber and with 0.2% basalt fiber were carried out by using a 50 mm steel split Hopkinson pressure bar device. The test results show that the impact compressive strength, dynamic increase factor and peak strain increase with the increase of strain rate under the same basalt fiber content, showing obvious strain rate effect. The dynamic stress-strain curve of basalt fiber cement soil underwent elastic deformation stage, plastic deformation stage and failure stage. With the increase of strain rate, the degree of fracture of cement soil samples gradually increases, which shows that the number of fragments increases, the size decreases and tends to be uniform. After adding basalt fiber in cement soil, the crack can be delayed, the degree of fracture is smaller than that without fiber and the plasticity of the samples is enhanced. It shows that basalt fiber can improve the impact compressive strength of cement soil.

2

Structural effects and real strain‑rate effects on compressive strength of sustainable concrete with crumb rubber in split Hopkinson pressure bar tests

Feng Wanhui, Chen Baiyu, Tang Yunchao, Wei Wenbo, He Weiming, Yang Yongmin

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e136

EN

The dynamic increase factor (DIF) of the concrete material strength, obtained using a split Hopkinson pressure bar (SHPB), includes structural effects that do not precisely reflect the real strain-rate effect of concrete. To further clarify the real strain-rate effects of rubberised concrete (RC), an experimental investigation regarding the dynamic compressive response of ordinary concrete (NC) and RC with three rubber contents (10%, 20%, and 30%) was performed in this study. Additionally, based on a dynamic constitutive model, i.e., the Karagozian and Case (K&C) concrete model, numerical SHPB tests were conducted using the LS-DYNA software. According to the experimental results, all parameters of the K&C model were discussed, and the damage factors were modified to satisfy the mechanical properties of RC. After validating the numerical model, it was observed that the experimental DIF included the inertial enhancement and the real DIF. Moreover, because rubber particles effectively reduce the density and improve the deformation capacity of concrete, the real strain-rate effect of RC was found to be more rate-sensitive than that of NC by analysing the radial stress distribution. In addition to lateral inertia, another external source, namely, the interface friction between the specimen and bars, which can produce lateral confinement, was further studied. It was found that interface friction significantly contributes to lateral confinement; however, as the strain rate increased, the impact generally decreased. Finally, the mechanism of the strain-rate effect of RC was clarified.

3

Dynamic mechanical characteristics of filling layer self-compacting concrete under impact loading

Li Ning, Long Guangcheng, Fu Qiang, Song Hao, Ma Cong, Ma Kunlin, Xie Youjun, Li He

Archives of Civil and Mechanical Engineering

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2019

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Vol. 19, no. 3

851--861

EN

Filling layer self-compacting concrete (FLSCC) is a key construction material in China Rail Track System (CRTS) III slab ballastless track and its resistance to impact loading is of great importance to the service security of high-speed train. In this paper, the dynamic mechani-cal characteristics of FLSCC under impact loading were investigated with a split Hopkinson pressure bar (SHPB) at strain rates ranging from 101 s_1 to 102 s_1. Results show that the compressive strength, peak strain, elastic modulus and toughness ratio of FLSCC all increase with strain rate. The increase factors of compressive strength (DIFc) and strain (DIFe) of FLSCC increase linearly with decimal logarithm of strain rate. The elastic modulus (Ed) and toughness ratio (TR) increase linearly with strain rate. Self-compacting concrete (SCC) shows greater strain rate effect than normal concrete (NC). However, FLSCC presents lower strain rate effect but better toughness performance than normal SCC. The incorporation of large content of SP and VMA provides FLSCC with higher porosity, which makes it possess excellent dynamic mechanical performance.

4

Dynamic compressive mechanical behaviour and modelling of basalt–polypropylene fibre-reinforced concrete

Fu Q., Niu D., Zhang J., Huang D., Wang Y., Hong M., Zhang L.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

914--927

EN

Dynamic compressive behaviour of basalt–polypropylene fibre-reinforced concrete (BPFRC) was experimentally investigated using a 75-mm-diameter split-Hopkinson pressure bar. The results showed that the addition of basalt fibre (BF) and polypropylene fibre (PF) is effective at improving the impact-resistance behaviour of concrete. The dynamic compressive strength, critical strain, and energy absorption capacity of BPFRC increased with increasing strain rate. At strain rates of 20–140 s−1, the addition of BF and PF significantly increased the dynamic compressive strength, critical strain, and energy absorption capacity of concrete. The dynamic increase factor of BPFRC increased linearly with the decimal logarithm of strain rate. The hybrid addition of BF and PF significantly improved the strain rate effect of the dynamic compressive strength. The strengthening and toughening mechanisms of BF and PF are discussed in detail. The proposed dynamic damage constitutive model can be used to accurately describe the dynamic stress–strain relationship of BPFRC.

5

Blast loading on aluminum foam microstructure

Miedzińska D., Panowicz R.

Journal of KONES

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2010

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Vol. 17, No. 3

287-292

EN

One of the possible options as a material for protective layers is aluminum foams which become also very popular due to their lightweight and excellent plastic energy absorbing properties. Such characteristics have been appreciated by the automotive industry with continued research to further understand foam properties. Compressed foaming materials exhibit extensive plastic response, while the initial elastic region is limited in tension by a tensile brittle-failure stress. Aluminum foams have become also an attractive material as blast protective layers due to their desirable compressive properties. With different material engineering techniques (as, for example double-layer foam cladding) they can be customized to achieve the most desirable properties. Energy absorption capacity of foams microstructures under blast load was analytically confirmed based on a rigid-perfectly plastic-locking foam model Initial research indicates that energy absorbed by the cladding is much larger than that under quasi-static conditions due to strain rate effect. In this paper a numerical model of a closed cell aluminum foam idealistic microstructure was presented. The quasi static compression tests were carried out with the use of LS Dyna computer code. Then the sample was numerically loaded with the blast wavefrom detonation of explosives and its behavior was analyzed. The results ofboth analyses were compared.