Search Results (268)

This study addresses the need for flexible and high-toughness materials for transmission tower pile foundations subjected to typhoons and earthquakes by investigating the static and dynamic mechanical behavior of rubberized concrete prepared using vibratory mixing. The objectives are to assess how vibratory mixing influences strength evolution, failure modes, strain rate sensitivity, and energy absorption of rubberized concrete compared with conventional mixing at 0%, 20%, and 30% rubber contents. Quasi-static compression tests and Split Hopkinson Pressure Bar (SHPB) dynamic compression tests were conducted to quantify these effects. The results show that vibratory mixing significantly improves the paste–aggregate–rubber interfacial structure. It increases the compressive strength by 8.4–30% compared with conventional mixing and reduces the strength loss at the 30% rubber content from 51.12% to 38.98%. Under high-speed impact loading, vibratory mixed rubber concrete exhibits higher peak strength, stronger energy absorption capacity, and a more stable strain rate response. The mixture with 20% rubber content shows the best comprehensive performance and is suitable for impact-resistant design of transmission tower foundations. Future research should extend this work by considering different rubber particle sizes and vibratory mixing frequencies to identify optimal combinations, and by incorporating quantitative fragment size distribution analysis under impact loading to further clarify the fracture mechanisms and enhance the application of rubberized concrete. Full article

To address the impact-induced damage to concrete pile foundations of transmission structures caused by nearby blasting vibrations, this study investigates the dynamic splitting tensile behavior of an environmentally friendly lightweight rubberized concrete—Rubber-Toughened Ceramsite Concrete (RTCC)—under impact loading. Quasi-static tests show that the static splitting tensile strength increases first and then decreases with increasing rubber content, reaching a maximum value of 2.01 MPa at a 20% replacement ratio. Drop-weight impact tests indicate that RTCC20 exhibits the highest peak impact force (42.48 kN) and maximum absorbed energy (43.23 J) within the medium strain-rate range. Split Hopkinson Pressure Bar (SHPB) tests further demonstrate that RTCC20 shows the highest strain-rate sensitivity. Overall, RTCC with 20% rubber content provides the best comprehensive performance, achieving a favorable balance between strength and toughness across the entire strain-rate range. These findings offer experimental support for applying RTCC to blast-vibration-resistant transmission structure foundations. Full article

This study presents a comparative investigation of the dynamic compression behaviors of steel fiber-reinforced cementitious composites (SFRCC) and steel fiber-reinforced concrete (SFRC) under elevated temperatures up to 800 °C, utilizing a split Hopkinson pressure bar (SHPB). The experimental results demonstrate that SFRCC exhibits enhanced overall performance at high temperatures, maintaining a progressive failure mode and approximately 40% residual strength even at 800 °C, while SFRC experiences rapid deterioration beyond 600 °C. In the low-to-medium temperature range of 200–400 °C, SFRCC shows significantly higher dynamic peak stress and toughness compared to SFRC. However, in the high-temperature range of 600–800 °C, the superior thermal stability of the aggregate–matrix system in SFRC results in better performance in these metrics. The findings provide insights into the damage evolution mechanisms of fiber-reinforced cement-based materials under coupled thermal and dynamic loads, offering a critical theoretical foundation for material selection in engineering structures exposed to extreme thermal environments. Full article

As a widely used structural material in construction, the energy dissipation characteristics of concrete under dynamic impact are crucial for evaluating a structure’s impact resistance and safety performance. However, conventional methods for evaluating energy dissipation characteristics fail to adequately account for the multi-parameter coupling effects during dynamic impact processes. Herein, the dynamic behavior of C15, C20, C30, and C40 concrete specimens was investigated using a split Hopkinson pressure bar (SHPB) apparatus. The dynamic response and energy dissipation mechanisms under impact loading were analyzed. The correlation between energy dissipation density and multiple parameters—including initial loading conditions, peak strain, dynamic compressive strength, and strain rate—was examined. Based on this analysis, a performance index P_i, grounded in energy dissipation density, was proposed for evaluating dynamic energy dissipation. The results show that under dynamic impact loading, concrete specimens of different grades basically show brittle damage mode and obvious strain-rate strengthening effect. Specifically, the dynamic compressive strength of C15-3 is 22.10 MPa, representing an increase of approximately 47.3%, while that of C40-3 is 46 MPa, showing an increase of approximately 15%. The energy transfer in concrete specimens is influenced by initial loading conditions, concrete material properties, and damage modes, among other factors. All of these parameters exhibit a strong correlation with the energy dissipation density. The comprehensive multi-parameter performance index P_i for dynamic energy dissipation yields superior evaluation results compared to using energy dissipation density alone. The research results provide an innovative reference for structural safety protection. Full article

This study investigates the development of adiabatic shear bands (ASBs) in AISI 1045 carbon steel under high-strain-rate uniaxial compression, emphasizing the conditions governing their onset and growth. Split Hopkinson pressure bar (SHPB) experiments were carried out at strain rates of 1000, 2000 and 4000 s⁻¹ with controlled displacement/strain interruption to capture gradual ASB formation throughout the process. Stress–strain data were analyzed alongside optical microscopy to determine the critical strain for ASB initiation, document ASB morphology, dimensions and type, and connect ASB formulating stages to material macroscopic mechanical behavior. The observations clarify how deformation evolves from homogenous plastic flow to localized shear instability as the strain and strain rate increase, linking mechanical response to microstructural features. Integrating these results, the effects of strain rate and strain progress on ASB formation and evolution characteristics are investigated. These findings enhance our understanding of shear localization phenomena under dynamic loading and provide a basis for predicting failure modes in structural applications. Full article

To investigate the mechanical behavior and energy evolution characteristics of various rock materials under impact loading, dynamic impact tests were conducted on five representative rock types using a split Hopkinson pressure bar (SHPB) apparatus, combined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The dynamic mechanical response, energy characteristics, mineral composition, and associated microstructural features of these typical rocks were systematically analyzed. The results show that basalt exhibits the highest peak strength, followed by blue sandstone and granite; all three display typical brittle failure characteristics, whereas red sandstone and green sandstone demonstrate greater ductility and plastic deformation capacity. By introducing the energy-time density index, the energy-time density of the rocks ranks from strongest to weakest as follows: green sandstone, red sandstone, granite, blue sandstone, and basalt. An innovative dynamic strength–energy-time density mapping model was established to elucidate the clustering and distinguishing characteristics of these rock materials. Assay results and mesoscopic images confirm the relationship between mineral composition and the fine structure of rock fragmentation mechanisms, highlighting that the critical transition from intergranular to transgranular fracture is the key mechanism governing impact pulverization. Furthermore, fractal analysis reveals that higher fractal dimensions are associated with more complex microcrack structures and may correlate with the corresponding energy dissipation intensity. These findings provide profound insight into the failure mechanisms of rocks under dynamic loading, offering significant theoretical value and engineering application prospects, particularly in fields such as mining excavation and rock mass stability assessment. Full article

Polypropylene (PP) fibers, known for their high fracture strength, low density, and cost-effectiveness, can significantly enhance the impact resistance of concrete, making the material suitable for specialized engineering applications. This study combined Split Hopkinson Pressure Bar (SHPB) tests with a three-dimensional mesoscale numerical model to investigate the dynamic compressive behavior of PP fiber-reinforced concrete (PFRC). The model, developed using MATLAB, explicitly represented polyhedral aggregates, mortar, the interfacial transition zone (ITZ), and PP fibers. Numerical simulations of impact compression were then performed using LS-DYNA and validated against experimental results. The simulated results exhibit close agreement with the experimental data in terms of peak stress, peak strain, and failure characteristics. The incorporation of 0.1% polypropylene fibers significantly enhanced the dynamic compressive strength of the specimen by 24.45%, with a mere 2.10% deviation from the experimental measurement. When the impact velocity was increased to 8 m/s and 10 m/s, the peak stress showed increases of 6.14% and 22.62%, respectively, while the peak strain increased by 11.72% and 23.32%. Damage analysis revealed that the aggregates experienced minimal failure, with cracks primarily initiating from the mortar and the ITZ. The polypropylene fibers improved the dynamic mechanical performance by dissipating energy through both fiber fracture and pull-out mechanisms. Furthermore, as the impact velocity increased, the fibers absorbed more energy, leading to a progressive increase in their own damage. Full article

Coupled high temperature and dynamic loading often leads to the complicated degradation of performance in industrial kilns, enclosures, or other concrete structures, which constitutes a serious hazard to the safety of concrete structure. To bridge this research gap, this study investigates not only the mechanical response but also the damage mechanisms of normal concrete (NC), basalt fiber-reinforced concrete (BFRC), and steel fiber-reinforced concrete (SFRC) under the coupled effects of high temperature and dynamic loading. Test specimens were conditioned for ambient conditions, 200 °C, 400 °C, and 600 °C, and underwent quasi-static and dynamic splitting tensile tests using the Split Hopkinson Pressure Bar (SHPB) with strain rates varying between 24 and 91 s⁻¹. Significantly, the high-temperature-induced degradation of all types of concrete is remarkably suppressed by fibers, especially steel fibers. The best thermal degradability resistance was displayed by the SFRC with the highest remaining residual dynamic strength, peak strain, and energy dissipation, especially in the most severe (600 °C, 0.15 MPa) circumstances among these three types of materials. All materials revealed a clear strain rate strengthening effect. An empirical model, integrating the coupling effect of strain rate, temperature, and fiber type in DIF, was also developed, yielding better prediction capability than those already available. This reveals that the comprehensive performance of SFRC can meet structure requests, so it is suitable for applications involving steel fiber in environments characterized by high temperature and high strain rates. Full article

Building structures are inherently susceptible to damage from extreme dynamic loads, while conventional concrete exhibits inadequate tensile resistance. While hybrid fibers systems can surpass the limitations of single-fiber reinforcement through their synergistic action, their internal damage mechanisms under impact loading remain inadequately understood. This study investigates the dynamic splitting behavior of hybrid fibers-reinforced cementitious composites combining polyvinyl alcohol (PVA) with either steel (SF) or polyethylene (PE) fibers, using Split Hopkinson Pressure Bar (SHPB) tests at strain rates of 5–31 s⁻¹, along with industrial CT scanning for meso-scale damage analysis. Results indicate that the SF–PVA hybrid improved strength by up to 15.6% compared to mono-PVA, while the PE–PVA hybrid achieved an 11.1% increase. All hybrid systems exhibited improved energy dissipation (which rose 25–45% with strain rate) and displayed secondary stress peaks. Quantitative CT analysis revealed distinct damage patterns: the mono-PVA specimen developed extensive damage networks (porosity: 7.20%; crack ratio: 4.48%), the SF-PVA hybrid system displayed the lowest damage indices (porosity: 3.29%; crack ratio: 1.76%), whereas the PE-PVA hybrid system exhibited the most significant dispersed damage pattern (crack-to-pore ratio: 39.32%). The hybrid systems function via distinct mechanisms: SF–PVA offers multi-scale reinforcement and superior damage suppression, whereas PE–PVA enables sequential energy dissipation, effectively dispersing concentrated damage. These insights support tailored fiber hybridization for impact-resistant structural design. Full article

Traditional concrete suffers from high energy consumption during production and low flexural strength, making it prone to flexural failure under impact loading. To address these issues, an eco-friendly non-autoclaved rubber concrete (NARC) was developed. The dynamic flexural performance of NARC was systematically investigated using a 100 mm diameter split Hopkinson pressure bar (SHPB) apparatus, with variations in rubber content (0%, 5%, 10%, 15%, and 20%). The results demonstrate an inverse correlation between dynamic flexural strength and rubber content. A replacement level exceeding 10% resulted in strengths inadequate for practical applications. At a 5% rubber content, the strain rate sensitivity was the most pronounced, where both dynamic strength and mid-span displacement exhibited a significant positive correlation with increasing strain rate. This enhanced performance is attributed to the high strength and dense microstructure of NARC, which facilitates more effective aggregate fracture under high-energy, short-duration impacts, thereby improving its dynamic load resistance. These findings provide valuable insights for promoting the practical and environmentally friendly production of rubber concrete. Full article

The assessment of the dynamic mechanical performance of fiber-reinforced composites has gained importance in specific high-tech applications like aerospace and automobiles. However, three dimensional (3D) auxetic reinforcements offering viable performance have remained unexplored. Hence, this study investigates the energy absorption capabilities and high strain impact behaviors of 3D woven fabric-reinforced composites. Three different types of 3D woven reinforcements i.e., warp interlock (Wp), weft interlock (Wt), and bidirectional interlock (Bi) were developed from jute yarn, and their corresponding composites were fabricated using polycarbonate (PC) and polyvinyl butyral (PVB). Out-of-plane auxeticity was measured for reinforcements while composites were analyzed under dynamic tests. Wp exhibited the highest auxeticity with a value of −1.29, Bi showed the least auxeticity with a value of −0.31, while Wt entailed an intermediate value of −0.46 owing to variable interlacement patterns. The dynamic mechanical analysis (DMA) results revealed that composite samples developed with PC resin showed a higher storage modulus with the least tan delta values less than 0.2, while PVB-based samples exhibited higher loss modulus with tan delta values of 0.6. Split Hopkinson pressure bar (SHPB) results showed that, under 2 and 4 bar pressure tests, PVB-based composites exhibited the highest maximum load while PC-based composites exhibited the least. Warp interlock-based composites with higher auxeticity showed better energy absorption when compared with the bidirectional interlock reinforcement based (with lower auxeticity) composites that exhibited lower peak load and energy dissipation. Full article

The impact mechanical properties of coral aggregate seawater concrete (CASC) are crucial for its application in island construction. This study examines how the dynamic compressive mechanical properties of CASC degrade in a marine setting. Laboratory tests were conducted to simulate the corrosion of CASC under three different immersion scenarios: full immersion (FI), semi-immersion (SI), and salt spray (SS). Dynamic compressive mechanical property tests were performed using a split Hopkinson pressure bar (SHPB). The study analyzed the effects of immersion condition and duration on key dynamic properties, including strength, elasticity, dynamic increase factor (DIF, defined as the ratio of dynamic strength to static strength), and energy dissipation. The experimental stress–strain data were fitted using the Guo model. Results show that the dynamic strength and energy dissipation in FI and SI conditions first increased, peaking at 30 days of corrosion, before decreasing. The DIF of CASC was linearly related to the strain rate and was largest in the SS zone, followed by the SI zone, and smallest in the FI zone. The experimental stress–strain data were well fitted by the Guo model, validating its effectiveness and offering insights into CASC use in island-reef engineering. Full article

Cyclic dynamic loading significantly influences the dynamic mechanical properties of cemented tailings backfill (CTB). This study investigates the dynamic mechanical properties and mesoscopic characteristics of CTB under cyclic dynamic loading. Using a Split Hopkinson Pressure Bar (SHPB) system, impact tests were conducted on CTB specimens subjected to varying numbers of cyclic impacts. The dynamic peak compressive strength (DPCS), elastic modulus, energy evolution, and failure modes were analyzed. Additionally, computed tomography (CT) scanning and 3D reconstruction techniques were employed to examine the internal pore and crack distribution. Results indicate that cyclic impacts lead to a gradual reduction in DPCS and energy absorption capacity, while the elastic modulus shows strain-rate dependency. Mesostructural analysis reveals that cyclic loading promotes the initiation and propagation of microcracks. This study establishes a correlation between mesoscopic damage evolution and macroscopic mechanical degradation, providing insights into the durability and stability of CTB under repeated blasting disturbances in mining environments. Full article

This study investigates the impact of expanding and reducing deformation ratios on the performance of L360 straight-seam welded pipes formed by the JCO process for offshore oil and gas transportation. The Split Hopkinson Pressure Bar (SHPB) experimental technique was used to examine the stress/strain relationships, yield strength, and compressive strength of the pipe materials subjected to high strain rates. The results indicated that the impact performance of the pipes significantly improves with both expansion and reduction processes, demonstrating an enhancement effect of deformation. The impact of yield strength and compressive strength increases with higher expansion ratios, reaching maximum values of 1009 MPa and 847 MPa, respectively, at an expansion ratio of 1.2%. At a reduction ratio of 0.8%, the impact yield strength increased by 64% and the compressive strength by 14%. These findings not only provide theoretical support for optimizing the expansion and reduction processes and their associated equipment but also have direct and significant practical implications for enhancing the performance and safety of offshore oil and gas transmission pipelines, thereby contributing to the advancement of the field. Full article

Temperature and strain rate play a crucial role in determining the mechanical properties of metals. These critical parameters are typically assessed using the split Hopkinson pressure bar (SHPB) test. However, previous studies have seldom considered the coupled influence of temperature and strain rate on dynamic mechanical behavior, thereby reducing the accuracy of constitutive models. To accurately characterize the dynamic mechanical behavior of 34CrNi3MoA low-alloy steel, a new constitutive model combining temperature and strain rate was developed. Firstly, SHPB experiments under varying temperatures and strain rates were designed to obtain actual stress–strain curves. The results indicate that the mechanical properties of 34CrNi3MoA low-alloy steel are significantly influenced by both temperature and strain rate. True stress has a significant temperature-softening effect within the temperature range of 25 °C to 600 °C, while the flow stress in the yield stage increases with rising strain rate. Secondly, a novel constitutive model was established by integrating a correction function. The model comprises three components: a strain rate-strengthening function influenced by temperature, a temperature-softening function influenced by strain rate, and a strain-hardening correction function accounting for the coupling of temperature and strain rate. Comparing the mean relative error, the new model significantly improves accuracy compared to the original Johnson–Cook (J-C) model. Full article