Nonlinear active vibration control of variable-thickness smart sandwich panel under impact loads

Fractal characteristics of fragmentation and evolution law of dissipated energy in early-age concrete–surrounding rock composite under impact loading

Relaxation-time approach for modelling complex coupled rate–temperature effects of metallic materials under impact loads

Dynamic response of muscle tissue under waterjet impact based on a visco-hyperelastic constitutive model considering large deformation failure.

Concrete seawall panels were tested under impact loading, and the effect of concrete compressive strength (50, 60, and 75 MPa) and reinforcement ratios of glass fiber-reinforced polymer (GFRP) bars (0.33%, 0.50%, and 0.83%) was investigated. The experimental analysis included the comparison of crack, force, deflection, acceleration, GFRP bar strains, and energy absorption behavior. Moreover, an analytical study was conducted to compare the experimental results to the predicted analytical results. The experimental data showed enhanced force and maximum deflection behavior of seawall panels with a higher reinforcement ratio, whereas concrete compressive strength adversely affected the impact behavior of panels because of brittleness becoming dominant, especially after 60 MPa. The strain and energy absorption of GFRP bars was maximum for the panel with 200 mm bar spacing and 60 MPa concrete compressive strength, whereas the maximum post-cracking energy absorption in concrete was the highest for the panel with 200 mm bar spacing and 50 MPa concrete compressive strength. The SDOF equation reliably estimated the impact behavior of the panels with a compressive strength of 60 MPa or lower and a bar spacing of not less than 200 mm, in the case of the panels with a reinforcement ratio of 0.50% or less. The results demonstrate the maximum design configuration of GFRP bars in seawall structures under a 2 m impact. • Influence of concrete compressive strength and reinforcement ratios on the impact response is studied. • Failure behaviour, deflection, force, acceleration, strain, and energy absorption are investigated. • Analytical verification (SDOF) and comparison with experimental results are conducted. • Optimal design configuration of GFRP-reinforced seawalls under 2 m impact is presented.

Loading rate during weight acceptance: Differential contributions of the knee and contralateral ankle with aging.

Investigating impact loading induced capacity degradation in Li-NMC batteries and developing predictive models for control strategies

Dynamic behavior and energy dissipation mechanisms of coral aggregate concrete under high strain rate impact loading

Porosity evolution and damage mechanism of fractured rock under drop hammer impact load

Repetitive impact loading strengthens commercial-purity titanium without losing ductility and strain-hardening capacity

To investigate the improvement effect of PVA fibers on the dynamic mechanical properties of concrete in water conservancy dams under dry-wet cycles and impact loads, C40 plain concrete and PVA fiber concrete were selected as the research objects. 0 to 120 dry-wet cycle tests and SHPB dynamic compression tests under different air pressures of 0.2 to 0.5 MPa were carried out. The evolution laws of damage degree, stress-strain curves, peak stress, toughness, energy dissipation and fracture fragmentation morphology of the specimens were systematically analyzed to reveal the strengthening and toughening mechanism of PVA fibers.The results show that the increase in the number of dry-wet cycles and the increase in impact pressure significantly affect the mechanical properties of concrete. The damage degree of both types of concrete increases with the increase in the number of cycles, and the peak stress and toughness continuously decrease.Under the same conditions, the damage degree of PVA fiber concrete is significantly lower than that of plain concrete. Its peak stress, toughness and dissipation energy are all higher than those of plain concrete, and the rate of performance degradation is slower.As the number of dry-wet cycles increases, the internal cracks in the plain concrete rapidly expand and penetrate, showing obvious brittle disintegration characteristics. Meanwhile, the PVA fibers form a three-dimensional network structure in the matrix. Through bridging crack resistance, stress dispersion and energy absorption and toughening effects, they inhibit crack initiation and propagation, delay damage accumulation, and transform the failure mode from brittle fracture to ductile progressive failure.Research has confirmed that PVA fibers can effectively enhance the dry-wet cycle resistance, dynamic bearing capacity and impact toughness of hydraulic concrete, significantly improving its durability and structural safety in complex service environments. This provides experimental basis and theoretical support for the application of high-performance fiber concrete in water conservancy projects.

Hybrid III lumbar spinal column injury risk curves from vertical impact.

When reinforced concrete (RC) slabs are subject to low velocity impacts (LVI), they will experience highly non-linear behaviors based upon the combined effects of flexural deformations; tensile membrane actions; punching shears; and local crushing as well as the evolving nature of damage in these structures. Most analytical models have been developed under restrictive simplifications; lack complete partitioning of energies; and depend heavily upon computationally intensive finite element simulations. An analytical-energy-based approach is presented to predict the non-linear dynamic behavior of RC slabs subjected to both LVIs and equivalent blast loads. The proposed model integrates an improved two degree-of-freedom (2-DoF) dynamic interaction system with an explicit multi-mechanism energy partitioning procedure which can be used to quantify all of the major forms of energy consumption including flexural; membrane; shear; crushing; damping and damage. The analytical framework has incorporated strain rate enhancement through use of dynamic increase factors (DIFs); punching shear capacity through application of the critical shear crack theory (CSCT); and geometrically non-linear membrane behavior via Xie's formulation for large deflection membrane behavior. A wide-ranging parametric analysis was performed to examine the effect of impact energy; slab thickness; reinforcement ratio; boundary conditions and advanced materials systems such as normal strength concrete (NSC); ultra high-performance concrete (UHPC); and ultra high-performance fibre reinforced concrete (UHPFRC). Results indicated that an increase in the magnitude of impact energy from 1 to 6kJ resulted in an approximate 301% increase in slab displacement. Furthermore, an increase in the slab thickness from 60 to 125mm resulted in a reduction of approximately 68% in slab displacement. It was also found that when compared with RC slabs made with NSC, those made with UHPFRC had displacements decreased by approximately 61% and reduced damage dissipation energy by approximately 69% due to higher levels of crack bridging and membrane resistance. Lastly, it was determined that twisted and hooked end fibres had the greatest energy absorbing capability and provided the longest delay to punching shear failure. Validation studies were conducted against existing experimental data and comparative non-linear ABAQUS CDP simulations indicating prediction error margins generally less than ± 5-10% and good correlation in terms of slab displacement response; crack development; and failure progression. The validation studies also showed that the method could be easily adapted for equivalent blast load analyses using impulse equivalency principles thus enabling a rapid predictive tool for designing RC slab systems resistant to either low velocity impact or blast loads.

ABSTRACT To address wellbore blockage and mechanical sticking caused by sulfur deposition in high-sulfur gas wells, a variable-diameter high-frequency vibration sulfur-removal tool was developed. This study focuses on the structural characteristics and performance evaluation of its self-excited oscillation module. A fluid simulation model based on the LBM-LES approach was established to investigate the effects of cavity length L and outlet diameter d2 on axial impact load and vibration frequency. The results indicate that increasing L enhances the impact load while reducing the dominant frequency, with L = 110 mm providing the best overall performance. The outlet diameter markedly affects impact loading, and d2 = 24 mm achieves higher impact amplitude with lower pressure loss. Scaled laboratory experiments were conducted to validate the numerical findings, showing discrepancies of less than approximately 20% in amplitude and 27% in dominant frequency. The validated results demonstrate that the proposed oscillation module can generate stable high-frequency axial impact, providing theoretical support for structural optimization and field application of high-frequency sulfur-removal tools.

Computational head models are essential tools for predicting the risk of mild traumatic brain injury (mTBI). However, computational models vary in the level of anatomical details, most notably the cortical folds. This study aims to determine the effect of modeling cortical folds on mTBI risk assessment. We compared gyrencephalic (with cortical folds) and lissencephalic (without cortical folds) finite element (FE) head models of 18 subjects aged 9-18 years, subjected to a rotational head acceleration of 10 krad/s (10 ms duration) about each principal head axis. We analyzed the effect of cortical folds on different tissue-level mTBI injury metrics, including maximum principal strain (MPS95), maximum principal strain rate (MPSR95), and cumulative strain damage measure (CSDM15). The inclusion of cortical folds consistently yielded higher injury metrics across all individuals and rotational directions, with a bias (mean ± std. dev. relative to maximum lissencephalic values) of in MPS95, in MPSR95, and in CSDM15. Differences in the spatial strain distribution were also found between the models, with the DICE similarity coefficient ranging between and for the peak MPS and CSDM15, respectively. Increases in peak injury metrics (up to 50%) were found for brain regions such as the corpus callosum, cerebellum, and brain stem. This study finds that the inclusion of cortical folds significantly alters the pattern of deformation in the brain and results in a prediction of higher mTBI risk.

A finite element model of a single-storey cold-formed thin-walled steel house frame structure was established using ABAQUS software to analyze the effects of different impact locations and impact angles on the dynamic response of the structure under a single impact load. Also, to establish a continuous impact model of single-storey cold-formed thin-walled section steel house skeleton structure at different locations and analyze the effect of two impact objects on the dynamic response of house skeleton structure under different impact time intervals. Combined with the basic theory of impact dynamics, the principle of the energy method was to determine the impact dynamic response analysis method of low-storey cold-formed thin-walled section steel housing skeleton structure under the impact-prone position, and put forward two measures to improve the impact resistance of cold-formed thin-walled section steel housing skeleton structure. The results show that: the lower node of the side column, the lower node of the middle of the wall and the lower middle point of the side column are the dangerous impact points of the housing skeleton structure; an impact angle of 90° (whether horizontal or vertical) represents the most critical scenario for the structure; the two impact objects acting at the same moment have the greatest degree of damage to the housing skeleton structure; after the side column is increased from double-limb to three-limb C-section steel collocation form, the impact resistance of the dangerous impact point of the side column is significantly improved, and the displacement is reduced by 37%; the addition of diagonal bracing at the side column of the impacted wall skeleton. The plastic strain energy of other members in the skeleton structure of the house is significantly reduced, and the displacement along the impact force direction is reduced by 18%.

ABSTRACT Running on unpaved trails is commonly perceived to reduce impact loading and injury risk, yet biomechanical evidence remains limited across age groups. We investigated the effects of paved versus unpaved surfaces on running biomechanics and surface-related injury risk perceptions in Master and young adult runners. Sixty participants (30 Master, 30 young adult) completed 5 km runs on both surfaces while wearing triaxial tibial accelerometers. We compared average cadence, peak resultant and axial tibial acceleration (TA), and cumulative resultant and axial TA using ANCOVA, controlling for running speed. Peak resultant TA was higher on unpaved than paved surfaces (p = .014), whereas cadence, peak axial TA, and cumulative axial and resultant TA did not differ between surfaces (p > .05). Master runners exhibited higher cadence and lower peak resultant TA than young adults (p < .05), while cumulative resultant TA did not differ by age (p > .05). Nearly half the participants (48.3%) perceived that running on unpaved trails reduces injury risk. Overall, unpaved trails produced higher peak TA without changing cumulative TA. Age-group differences in cadence were accompanied by lower peak resultant TA for Master runners, suggesting an age-related shift towards reduced per-step impact magnitude.

Face-centred cubic high-entropy alloys offer remarkable strain hardening and damage tolerance, yet moderate strength limits their performance under dynamic loading. While nanostructures can greatly improve strength, they are thermally unstable. Here we design a thermally stable three-dimensional-heterostructured (FeCoNi)86Al7Ti7 alloy. The hierarchical heterostructure, consisting of bimodal core-shell architecture, uniformly distributed nanoprecipitates and nanosized oxide particles (in the shell), remains stable up to 1,000 °C. The heterostructured alloy achieves high impact toughness, exhibiting 2.2-GPa yield strength and 1,100-MJ m-3 energy absorption density at a strain rate of 5 × 103 s-1. The massive martensitic transformation accommodates strain under impact loading, forms nano-martensite networks that strengthen the material, and sustains plasticity. Strain partitioning between core and shell provides potent back-stress hardening, while profuse interfaces facilitate martensite nucleation. The synergy of heterogeneous deformation, precipitation strengthening and thermally stabilized nanostructures establishes a robust design pathway for alloys with high strength and impact toughness across extreme conditions.

AlxCr30Fe30Ni20Ti(20-x) (x = 10, 12, 14 at%) high-entropy alloys with varying Al and Ti contents were prepared to investigate the effects of the element composition on the phase structure, mechanical properties, and fracture morphology of the alloy. Quasi-static compression and dynamic impact tests were performed to examine the mechanical properties and fracture behaviors of the alloy under different strain rates. The results showed that all three alloys had dual-phase FCC/BCC structures. Among them, the Al10Cr30Fe30Ni20Ti10 alloy exhibited the highest yield strength under both quasi-static and dynamic conditions. However, the Al12Cr30Fe30Ni20Ti8 and Al14Cr30Fe30Ni20Ti6 alloys showed better ductility. The fracture morphology observations revealed that all the alloys developed a fish-scale-like ductile dimple structure after quasi-static compression fracture. In contrast, under dynamic impact loading, the alloys formed tearing-type ductile dimples and cleavage planes, indicating a significant reduction in ductility at higher strain rates.

Conventional settlement monitoring techniques are inadequate for seawall construction environments due to severe physical impacts, the absence of terrestrial communication networks, and highly dynamic disturbances. This research proposes a multi-source fusion settlement monitoring system designed specifically for the construction phase to overcome these constraints. An integrated inclinometer–magnetoresistive sensing unit is the central component of this system. The unit achieves physical isolation from the severe impact loads of rock backfilling, guarantees protection in high-salinity and high-humidity environments, and accommodates the large deformations typical of soft foundations by utilizing a structural design that includes a rigid channel steel sheath, anti-corrosion sealing, and flexible joints. In terms of computation, a cascaded attitude fusion framework is developed that combines a Multiplicative Extended Kalman Filter (MEKF) with Quaternion Estimator (QUEST) initialization. High-precision displacement inversion via quaternion rotation is made possible by the introduction of an adaptive mechanism based on the Mahalanobis distance that precisely detects and suppresses transient acceleration disturbances induced by construction machinery and waves. Additionally, data transmission issues in remote offshore areas are resolved by combining solar power and BeiDou short-message communication technologies. This adaptive technique minimizes attitude estimate errors in dynamic situations by approximately 84.56%, as demonstrated by experimental and field validation. The system was deployed as a 165 m array comprising 49 sensing units and monitored continuously for 458 days, achieving a normalized RMSE of 9.44–11.02% compared to reference settlement tubes and capturing a maximum settlement of 1.7 m in the core high-fill section. These results confirm the system’s high monitoring accuracy and resilience in harsh construction conditions.