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In this paper, the influence of different fiber materials on the dynamic splitting mechanical properties of concrete was investigated. Brazil disc dynamic splitting tests were conducted on plain concrete, palm fiber-reinforced concrete, and steel fiber-reinforced concrete specimens using a split Hopkinson pressure bar (SHPB) test device with a 100 mm diameter and a V2512 high-speed digital camera. The Digital Image Correlation (DIC) technique was used to analyze the fracture process and crack propagation behavior of different fiber-reinforced concrete specimens and obtain their dynamic tensile properties and energy dissipation. The experimental results indicate that the addition of fibers can enhance the impact toughness of concrete, reduce the occurrence of failure at the loading end of specimens due to stress concentration, delay the time to failure of specimens, and effectively suppress the expansion of cracks. Steel fibers exhibit a better crack-inhibiting effect on concrete compared to palm fibers. The incident energy for the three types of concrete specimens is roughly the same under the same impact pressure. Compared with plain concrete, the energy absorption rate of palm fiber concrete is decreased, while that of steel fiber concrete is increased. Palm fiber-reinforced concrete and steel fiber-reinforced concrete have lower peak strains than plain concrete under the same loading duration. The addition of steel fibers significantly impedes the internal cracking process of concrete specimens, resulting in a relatively slow growth of damage variables.

In protective applications, polyurethane (PU) is a key material, yet the microstructural mechanisms governing its dynamic mechanical properties are not well understood. This study investigates the influence of hard segment content on the low strain rate compression and high strain rate impact properties of waterborne polyurethane (WPU) by modulating the NCO/OH ratio. Mechanical responses are characterized using a universal testing machine and a split Hopkinson pressure bar (SHPB) system. Additionally, the hydrogen bonding and microphase separation structure are analyzed using FTIR, DSC, DMA, and SAXS. These findings reveal that the glass transition temperatures (TgDSC and TgDMA) shift toward higher temperatures with increasing hard segment content, which is attributed to the intensified hydrogen bonding cross‐linked network, as corroborated by FTIR and SAXS analyses. The WPU demonstrates a pronounced strain rate sensitivity across a broad range of strain rates (10−4–104 s−1). Notably, the 45 wt.% hard segment WPU523 sample shows heightened sensitivity, attributed to complex hydrogen bonding heterogeneity and a higher Herman's orientation factor during loading, the key to WPU's dynamic mechanical response. This study explores how hard segment content (HS) modulates waterborne polyureathane's (WPU's) dynamic mechanical properties under low/high strain rates. Increasing HS enhances hydrogen bonding and microphase separation, with abundant hard domains acting as physical crosslinks. However, optimal HS content improves strain‐rate sensitivity, driven by HS‐regulated physical crosslinks balancing structural reinforcement and chain mobility, thereby promoting molecular chain alignment.

This paper presents an analytical prediction coupled with numerical simulations of a split Hopkinson pressure bar (SHPB) that could be used during further experiments to measure the dynamic compression strength of concrete. The current study combines experimental, modeling and numerical results, permitting an inverse method by which to validate measurements. An analytical prediction is conducted to determine the waves propagation present in SHPB using a one-dimensional theory and assuming a strain rate dependence of the material strength. This method can be used by designers of new SPHB experimental setups to predict compressive strength or strain rates reached during tests, or to check the consistencies of predicted results. Numerical simulation results obtained using LS-DYNA finite element software are also presented in this paper, and are used to compare the predictions with the analytical results. This work focuses on an SPHB setup that can accurately identify the strain rate sensitivities of concrete or brittle materials.

Honeycomb aluminum structures are used in energy-absorbing constructions in military, automotive, aerospace and space industries. Especially, the protection against explosives in military vehicles is very important. The paper deals with the study of selected aluminum honeycomb sandwich materials subjected to static and dynamic compressive loading. The used equipment includes: static strength machine, drop hammer and Split Hopkinson Pressure Bar (SHPB). The results show the influence of applied strain rate on the strength properties, especially Plateau stress, of the tested material. In each of the discussed cases, an increase in the value of plateau stresses in the entire strain range was noted with an increase in the strain rate, with an average of 10 to 19%. This increase is mostly visible in the final phase of structure destruction, and considering the geometrical parameters of the samples, the plateau stress increase was about 0.3 MPa between samples with the smallest and largest cell size for the SHPB test and about 0.15 MPa for the drop hammer test.

This study explored the dynamic behaviors and fracturing mechanisms of flawed granite under split‐Hopkinson pressure bar testing, focusing on factors like grain size and flaw dimensions. By means of digital image processing and the discrete element method, Particle Flow Code 2D (PFC2D) models were constructed based on real granite samples, effectively overcoming the limitations of prior studies that mainly relied on randomized parameters. The results illustrate that the crack distribution of granite is significantly influenced by grain size and flaw dimensions. Tension cracks predominate and mineral boundaries, such as between feldspar and quartz, become primary crack sites. Both flaw length and width critically affect the crack density, distribution, and dynamic strength of granite. Specifically, dynamic strength tends to decrease with the enlargement of flaws and increase with an increase in flaw angles up to 90°. This research examines granite's mechanical properties under split‐Hopkinson pressure bar testing, focusing on factors such as grain size and flaw dimensions. The study reveals that tension cracks are prevalent across grain sizes, with most intergrain cracks occurring between feldspar and quartz. Larger flaws in granite seem to act as stress‐relief channels, leading to reduced crack density. Highlights This research uses digital image processing and the discrete element method to accurately create granite models, capturing their authentic mineral content and spatial distributions. This study explores the mechanical properties and fracture mechanisms of granite subjected to dynamic loadings, highlighting critical factors including grain size, and the orientation and size of flaws. Analysis of correlation coefficients between various factors offers in‐depth insights into their individual and combined impact on the behaviors of granite under dynamic conditions.

The behavior of calcareous sand under repeated impact considerably differs from that of silica sand. Notably, calcareous sand is important in engineering projects in the South China Sea, such as pile driving. To understand the behavior of calcareous sand under multiple impacts, the improved split Hopkinson pressure bar (SHPB) system was selected for one-dimensional impact tests of silica and calcareous sand with particle sizes of 0.25–0.50 mm. The sand specimens were impacted 1, 3, 7 and 10 times. The test results reveal that the dynamic apparent stiffness of silica sand is approximately 6–8 times that of calcareous sand. The dynamic apparent modulus values of the two sands increase with an increase in the number of impacts, N. For calcareous sand, the compression index Cc decreases with an increase in N, and silica sand shows the opposite trend. The yield pressure pc of calcareous sand under impact loading is approximately 40% of that of silica sand. With an increase in N, the energy absorption capacity, energy dissipation rate and damage variables of the two sands exhibit a downward trend. In addition, the energy absorption efficiency of calcareous sand is better than that of silica sand. During the process of impact, a large number of sand particles will break, and particle breakage will change the particle size distribution (PSD), thereby significantly affecting the physical and mechanical properties of the corresponding soil. Based on the test results and fractal theory, an evolution model is established to characterize the PSD evolution in the breakage state for uniformly graded calcareous sand. Moreover, a Markov chain model is proposed to describe the PSD evolution of nonuniformly graded specimens. The predicted results of both models show agreement with the experimental values.

Tension failure of deep surrounding rock is a very common failure mode, which is closely related to the couple of static pre-stress and impact load. Thus, the dynamic tensile strength of pretension stressed Brazilian disc (BD) specimens subjected to the impact load was measured at the couple different pretension levels and loading rates with the modified split Hopkinson pressure bar (SHPB) system. Six groups of Linyi sandstone BD specimen were impacted with the loading rates from 400 to 1200 GPa/s under the pretension of 0, 0.48, 1.44, 2.39, 3.45 and 4.30 MPa. The test results reveal the dynamic tensile strength has a very significant linear positive correlation with the loading rate, wherein increases gradually with the loading rate increase, reflecting the obvious rate dependency. The dynamic tensile strength decreased significantly with pretension stress level increase at the same loading rate, showing an obvious dynamic tensile strength weakening effect. Besides, the mechanism of the dynamic tensile strength weakening effect is summarized, wherein the pretension stress level dominates and determines the dynamic tensile strength weakening level, and the impact load induces the appearance of the strength weakening effect.

In cold climate regions, rock engineering structures are subjected to repeated processes of freeze–thaw weathering and consequently the integrity of these structures will gradually deteriorate. The resulted reduction in rock strength makes the structures become increasingly more vulnerable to external loads, particularly to dynamic loads such as blasting or earthquakes, even when these loads are below the original designed capacity. In this work, the reductions in static and dynamic strengths of sandstones after they are treated with different number of freeze–thaw cycles were studied using conventional UCS experiments and impact tests with split Hopkinson pressure bar apparatus. Based on the experimental results, a decay model was used to describe the reduction of rock strength with the increasing number of freeze–thaw weathering cycles. For the prediction of the degradation of dynamic rock strength corresponding to freeze–thaw weathering, a model describing the dynamic increase factor for the dynamic rock strength corresponding to different strain rates and specimen sizes was proposed and its parameters are obtained by regression analysis of published experimental data. These two models were then combined into a unified model which can be used to describe the reduction in the dynamic strength of rocks when they are subjected to repeated freeze–thaw weathering processes. Though only tested on sandstones, the proposed unified model, with different parameters, is expected to be applicable to other types of rocks as long as the rocks undergo the same or similar damage mechanism when they are subjected to freeze–thaw weathering processes.

The effect of silica fume (SF) in concrete on mechanical properties and dynamic behaviors was experimentally studied by split Hopkinson pressure bar (SHPB) device with pulse shaping technique. Three series of concrete with 0, 12%, and 16% SF as a cement replacement by weight were produced firstly. Then the experimental procedure for dynamic tests of concrete specimens with SF under a high loading rate was presented. Considering the mechanical performance and behaviors of the concrete mixtures, those tests were conducted under five different impact velocities. The experimental results clearly show concrete with different levels of SF is a strain-rate sensitive material. The tensile strength under impact loading of the tested specimens was generally improved with the increasing content of SF levels in concrete. Additionally, the tensile strength under impact loading of the concrete enhances with the increase of the strain rates. Finally, failure modes, dynamic tensile strength, dynamic increase factor (DIF), and critical strain are discussed and analyzed. These investigations are useful to improve the understanding of the effect of SF in concrete and guide the design of concrete structures.

This study investigates the dynamic compressive behavior of three periodic lattice structures fabricated from Ti-6Al-4V titanium alloy, each with distinct topologies: simple cubic (SC), body-centered cubic (BCC), and face-centered cubic (FCC). Dynamic compression experiments were conducted using a Split Hopkinson Pressure Bar (SHPB) system, complemented by high-speed imaging to capture real-time deformation and failure mechanisms under impact loading. The influence of cell topology, relative density, and strain rate on dynamic mechanical properties, failure behavior, and stress wave propagation was systematically examined. Finite element modeling was performed, and the simulated results showed good agreement with experimental data. The findings reveal that the dynamic mechanical properties of the lattice structures are generally insensitive to strain rate variations, while failure behavior is predominantly governed by structural configuration. The SC structure exhibited strut buckling and instability-induced fracture, whereas the BCC and FCC structures displayed layer-by-layer crushing with lower strain rate sensitivity. Regarding stress wave propagation, all structures demonstrated significant attenuation capabilities, with the BCC structure achieving the greatest reduction in transmitted wave amplitude and energy. Across all configurations, wave reflection was identified as the primary energy dissipation mechanism. These results provide critical insights into the design of lattice structures for impact mitigation and energy absorption applications.