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  • Engineering  (4)
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  • Engineering  (4)
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  • 1
    Online Resource
    Online Resource
    Damage characteristics of basalt fiber reinforced mortar under compression evaluated by acoustic emission
    Walter de Gruyter GmbH ; 2019
    In:  Materials Testing Vol. 61, No. 4 ( 2019-04-04), p. 381-388
    Details
    In: Materials Testing, Walter de Gruyter GmbH, Vol. 61, No. 4 ( 2019-04-04), p. 381-388
    Abstract: Basalt fiber is a new type of high quality reinforced material used in composite materials. The performance of cement-based materials can be improved by adding basalt fiber, but its damage mechanism is more complicated. Acoustic emission technique can monitor the internal damage of materials. In this paper, the influence of the basalt fiber on the compressive failure process of mortar and the effect of the basalt fiber volume fraction variation on the acoustic emission characteristics in the damage process were investigated. The characteristic parameters of the acoustic emission signals of basalt fiber reinforced mortar with 4 different volume fractions under axial load were analyzed. Through analysis of the acoustic emission cumulative hit number, the acoustic emission cumulative energy, the RA value, the AF value and the b value, it could be found that the acoustic emission parameters of different damage stages were different, and the failure mode of the specimen could be identified according to the acoustic emission parameters. Besides, the addition of basalt fiber improved the rigidity and the ductility of the specimen.
    Type of Medium: Online Resource
    ISSN: 2195-8572 , 0025-5300
    URL: Article
    DOI: 10.3139/120.111332
    RVK:
    ZG 1100
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2280363-4
    detail.hit.zdb_id: 206395-5
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Effect of different loading systems on acousto-ultrasonic characteristics of concrete under axial compression
    Walter de Gruyter GmbH ; 2019
    In:  Materials Testing Vol. 61, No. 6 ( 2019-06-01), p. 591-599
    Details
    In: Materials Testing, Walter de Gruyter GmbH, Vol. 61, No. 6 ( 2019-06-01), p. 591-599
    Abstract: In order to study the effects of different loading systems and stress history on the damage evolution of concrete, the acoustic emission characteristic parameters, the acoustic emission release rate, acousto-ultrasonic pulse wave velocity and the Rv value were compared and analyzed in the process of axial compression damage of concrete with different water cement ratios under step and intermittent loading. In this paper, the intermittent period led to a certain degree of “closure” in the internal microcracks of concrete, thus in the same HB to HD holding period, the acoustic emission release rate, mean value of acoustic emission characteristic parameters and mean acousto-ultrasonic pulse wave velocity under intermittent loading were all higher than that of step loading. The acousto-ultrasonic pulse wave velocity decreased with the increasing of the stress level and increased during the IA to ID intermittent period. Among them, with the decreasing of water cement ratio (from 0.6 to 0.4), the acoustic emission cumulative hits and the acoustic emission release rate increased, while the acousto-ultrasonic pulse wave velocity increased, and there were some differences in the acoustic emission release rate of the two loading systems at different water cement ratios. Furthermore, the R v value decreased with the decreasing of water cement ratio in the IA to IC intermittent period and in the ID intermittent period, the R v value increased with the decreasing of water cement ratio, thus the R v value could reflect the evolution law of concrete with different water cement ratios during the intermittent period. The obtained results show that the acoustic emission and acousto-ultrasonic characteristic parameters are not consistent under two different loading systems, so research in this paper can provide a theoretical basis for the damage identification and analysis of concrete structures under cyclic loading based on the acousto-ultrasonic technology in practical engineering.
    Type of Medium: Online Resource
    ISSN: 2195-8572 , 0025-5300
    URL: Article
    DOI: 10.3139/120.111360
    RVK:
    ZG 1100
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2280363-4
    detail.hit.zdb_id: 206395-5
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Strain rate effect on the acoustic emission characteristics of concrete under uniaxial tension
    Walter de Gruyter GmbH ; 2020
    In:  Materials Testing Vol. 62, No. 1 ( 2020-01-07), p. 5-11
    Details
    In: Materials Testing, Walter de Gruyter GmbH, Vol. 62, No. 1 ( 2020-01-07), p. 5-11
    Abstract: Concrete is an important engineering material whose tensile property plays an important role in structural safety. Thus, the effect of strain rate on crack evolution in concrete during tension cracking cannot be neglected. Within a strain rate range of 10 −6 to 10 −4 s −1 , an acoustic emission monitoring test for the whole process of concrete under uniaxial tension including the post-peak softening stage was conducted. Moreover, damage evolution, along with the cracking mechanism of concrete at various strain rates was discussed with respect to the effect of strain rate on acoustic emission. The results show that the acoustic emission activity of concrete is delayed due to an increase in strain rate. This indicates that the hysteresis of deformation and cracking can be observed in a uniaxial tension test of concrete. During the whole loading process, as the strain rate increased, the average level of the acoustic emission hit rate increased significantly, indicating that an increase in strain rate accelerates crack initiation and propagation in concrete. Average acoustic emission values, duration and energy also show an increasing trend, and the scatter distribution range between them and the acoustic emission amplitude changes significantly, a fact that can be used to identify the damage degree of concrete under different strain rates. A peak frequency and cd4 band wavelet energy spectrum coefficient tends to decrease, while the ca8 band wavelet energy spectrum coefficient increases. In other words, the proportion of low frequency acoustic emission signals increases, indicating that an increase in strain rate increases the proportion of macroscopic cracks in concrete. At various strain rates, the average level of acoustic emission characteristic parameters and the proportion of high frequency signals at the post-peak stage in concrete are higher than those at the pre-peak stage, indicating that the development of microcracks in concrete mainly concentrates during the post-peak softening stage.
    Type of Medium: Online Resource
    ISSN: 2195-8572 , 0025-5300
    URL: Article
    DOI: 10.3139/120.111445
    RVK:
    ZG 1100
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2280363-4
    detail.hit.zdb_id: 206395-5
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Acoustic emission fractal characteristics analysis of steel fiber reinforced concrete during uniaxial tensile damage
    Walter de Gruyter GmbH ; 2020
    In:  Materials Testing Vol. 62, No. 3 ( 2020-03-02), p. 329-336
    Details
    In: Materials Testing, Walter de Gruyter GmbH, Vol. 62, No. 3 ( 2020-03-02), p. 329-336
    Abstract: In order to study the influence of steel fiber on the damage characteristics of concrete under uniaxial tension, based on the improved G-P algorithm, the acoustic emission event rate correlation dimension (hereinafter referred to as correlation dimension) curves of steel fiber reinforced concrete under uniaxial tension failure before and after peak stress were obtained, and the evolution characteristics of the correlation dimension of concrete with different steel fiber contents analyzed. According to the correlation dimension, the R value, the F value and the variance (σ 2 ) were proposed to measure the effect of steel fiber on the micro-failure characteristics of concrete. The results show that before peak stress, the correlation dimension first increases and then decreases with an increase in the stress level; the mean correlation dimension increases with an increase in steel fiber; the addition of steel fiber reduces the R value by 36.13 % to 65.04 % compared with plain concrete, but has little effect on the F value. After peak stress, with a decrease in the stress level, the correlation dimension decreases with some fluctuation; and the variance of correlation dimension decreases with the increase of steel fiber; whereas the order degree of the system microstructure, measured by the correlation dimension, increases with an increase in steel fiber. These results can be used for structural health monitoring and the non-destructive testing of steel fiber reinforced concrete, which have an important value for enriching the early warning of fracture failure in steel fiber reinforced concrete based on acoustic emission technology.
    Type of Medium: Online Resource
    ISSN: 0025-5300 , 2195-8572
    URL: Article
    DOI: 10.3139/120.111474
    RVK:
    ZG 1100
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2280363-4
    detail.hit.zdb_id: 206395-5
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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