Search

The dynamic response description of materials in high-speed impact fields is of practical significance to structural design and practical engineering application. In this paper, an electromagnetic impact (EI) loading process was proposed to acquire dynamic stress-strain relationships of 2A10 aluminum alloys. A modified Johnson-Cook (J-C) material model was obtained by combining with Quasi-static experiments and verified by numerical simulations. Comparing the J-C model obtained by a Split Hopkinson pressure bar, the simulative results about maximum deformation displacements showed the modified J-C model was more in line with actual experimental results. The accuracy under the discharge energy of 4 and 5 kJ was improved by 50% and 11%, respectively. In addition, electromagnetic impact loading characteristics and microstructure evolution of materials were studied. The discharge current with an attenuated sine wave caused that electromagnetic impact forces demonstrated a bimodal trend. The maximum impact velocities reached up to 4.7 m/s and 6.7 m/s under the discharge energy of 4 and 5 kJ, respectively (the maximum strain rates are 655.0 and 932.3 s−1, respectively). The high-speed impact effect led to the emergence of adiabatic shear bands (ASBs) during deformation microstructure evolution. Due to higher impact speed, the deformation concentration degree was more remarkable under the energy of 5 kJ. [ABSTRACT FROM AUTHOR]

Fracture connectivity refers to the degree to which fractures within a rock mass are spatially arranged and interconnected. As a result, fracture connectivity can affect the pattern and magnitude of deformations, and induced brittle damage in response to external forces. Traditionally, fracture intensity has been a standard metric for characterising rock mass quality. This paper explains why fracture connectivity should be included in addition to fracture intensity as a characterisation parameter. Fracture intensity alone cannot capture the complex interactions and pathways that fractures create within the rock mass. On the other hand, fracture connectivity offers a more comprehensive view of how fractures propagate and interact, enabling a deeper understanding of stress transfer and deformation patterns. This paper reviews the Network Connectivity Index (NCI) and its applications in rock engineering design. It is discussed that NCI, considering both fracture intensity and fracture connectivity, serves as a more objective measurement to reduce the degree of subjectivity of many empirical methods. Furthermore, an extensive set of DFN models suggests that NCI correlates better with block sizes and can serve as a more representative parameter than P32\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${P}_{32}$$\end{document} for fragmentation assessment in cave mine design.Fracture connectivity can affect the pattern and magnitude of deformations and induce brittle damage in response to external forces.Fracture intensity has limitations in capturing the complex interactions and pathways that fractures create within the rock mass.Fracture connectivity offers additional information as to how fractures propagate and interact.The Network Connectivity Index (NCI) is a novel and objective measurement that can be easily extracted from discrete fracture network models.NCI correlates better with block sizes and can serve as a more representative parameter than P32 for fragmentation assessment in cave mine design.Fracture connectivity can affect the pattern and magnitude of deformations and induce brittle damage in response to external forces.Fracture intensity has limitations in capturing the complex interactions and pathways that fractures create within the rock mass.Fracture connectivity offers additional information as to how fractures propagate and interact.The Network Connectivity Index (NCI) is a novel and objective measurement that can be easily extracted from discrete fracture network models.NCI correlates better with block sizes and can serve as a more representative parameter than P32 for fragmentation assessment in cave mine design.Highlights: Fracture connectivity refers to the degree to which fractures within a rock mass are spatially arranged and interconnected. As a result, fracture connectivity can affect the pattern and magnitude of deformations, and induced brittle damage in response to external forces. Traditionally, fracture intensity has been a standard metric for characterising rock mass quality. This paper explains why fracture connectivity should be included in addition to fracture intensity as a characterisation parameter. Fracture intensity alone cannot capture the complex interactions and pathways that fractures create within the rock mass. On the other hand, fracture connectivity offers a more comprehensive view of how fractures propagate and interact, enabling a deeper understanding of stress transfer and deformation patterns. This paper reviews the Network Connectivity Index (NCI) and its applications in rock engineering design. It is discussed that NCI, considering both fracture intensity and fracture connectivity, serves as a more objective measurement to reduce the degree of subjectivity of many empirical methods. Furthermore, an extensive set of DFN models suggests that NCI correlates better with block sizes and can serve as a more representative parameter than P32\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${P}_{32}$$\end{document} for fragmentation assessment in cave mine design.Fracture connectivity can affect the pattern and magnitude of deformations and induce brittle damage in response to external forces.Fracture intensity has limitations in capturing the complex interactions and pathways that fractures create within the rock mass.Fracture connectivity offers additional information as to how fractures propagate and interact.The Network Connectivity Index (NCI) is a novel and objective measurement that can be easily extracted from discrete fracture network models.NCI correlates better with block sizes and can serve as a more representative parameter than P32 for fragmentation assessment in cave mine design.Fracture connectivity can affect the pattern and magnitude of deformations and induce brittle damage in response to external forces.Fracture intensity has limitations in capturing the complex interactions and pathways that fractures create within the rock mass.Fracture connectivity offers additional information as to how fractures propagate and interact.The Network Connectivity Index (NCI) is a novel and objective measurement that can be easily extracted from discrete fracture network models.NCI correlates better with block sizes and can serve as a more representative parameter than P32 for fragmentation assessment in cave mine design. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical behavior of ultra-high performance concrete-filled steel tubes (UHPCFST) subjected to repeated axial compression. A total of 34 specimens of UHPCFST were systematically designed, constructed, and evaluated experimentally. The design parameters encompassed steel tube wall thickness, UHPC type, specimen size (varying diameters while preserving a consistent diameter-to-thickness ratio), and loading scheme. The failure patterns, stress-strain relationships, axial load-bearing capacity, and stiffness were meticulously examined. Predominantly, shear failure and drum-shaped upsetting failure were identified as the primary failure mechanisms in the specimens. The axial load-bearing capacity was found to increase notably with the use of thicker steel tubes and higher-grade UHPC. Under repeated loading, a reduction in stiffness was noted, which was dependent on factors such as the steel content, tube diameter, and the volume of coarse aggregate of UHPC. Current predictive equations for the axial load-bearing capacity of CFST were assessed using the experimental results of UHPCFST and were determined to over-predict the axial load-bearing capacity of UHPCFST. Consequently, a refined equation is proposed to yield a more precise estimation of the axial load-bearing capacity for UHPCFST. Furthermore, an empirical model was developed to characterize the stress-strain behavior of UHPCFST under repeated axial compression, offering a tool for practical engineering design and analysis. • We tested UHPCFSTs under monotonic and repeated axial compression. • We proposed a compressive stiffness degradation formula. • We evaluated existing codes of practices. • We proposed an empirical load-strain model. [ABSTRACT FROM AUTHOR]