This study presents the first continuous, uninterrupted in-situ characterization of void evolution in an Al-Sc-Mg alloy (Scalmalloy) during tensile tests spanning quasi-static to dynamic loading ( 10^-3 to 30 s ^-1 ). High-speed X-ray phase contrast imaging at a synchrotron source, combined with custom image-processing and meshless strain computation, enables real-time tracking of individual voids without test interruption. The results reveal a strong dependence of void evolution on both stress triaxiality and strain rate. Higher stress triaxiality in notched specimens accelerates void growth and coalescence, causing fracture at longitudinal strains, compared to unnotched specimens. This is consistent with the Rice-Tracey criterion and the Gurson-Tvergaard-Needleman framework. At low strain rates, void growth is linear in strain in a single regime. At high strain rates, a two-stage bi-linear response emerges: an initial slow nucleation phase followed by abrupt coalescence, attributed to suppression of dynamic strain aging at high loading rates. Preliminary GTN-compatible damage parameters; the critical void fraction at coalescence onset, the void fraction at final rupture, and the strain-controlled nucleation rate, are extracted from the measured void fraction slopes, providing a first quantitative basis for model calibration. A key limitation of the approach is its 2D projection nature, which precludes through-thickness void reconstruction; full 3D microstructural characterization remains a direction for future work.
The impact of a bird strike has become one of the major concerns in the aviation sector, as it can cause material degradation to aerospace structures. Collisions between airborne animals and aerospace surfaces frequently occur during take-off or landing, or at low altitudes. Bird strike impacts can also occur at high altitudes, from 6000 to 9000 m. The main objective of this paper is to correlate quasi-static indentation (QSI) results with low-velocity impact (LVI) results. Unlike previous studies that mainly focused on conventional fibre metal laminates and global force–displacement correlations, this study investigates the relationship between the damage evolution of QSI and LVI responses in compression-moulded Al/CFRP laminates and validates the observed failure mechanisms through finite element analysis. The performance of the fibre-metal laminate is evaluated using quasi-static indentation and low-velocity impact tests. This hybrid laminate is fabricated using a compression moulding technique. The one-sided aluminium sheet metal has been roughened with a metal-sanding method to improve bonding between the fibre and the metal layer. In the QSI and LVI tests, the specimens were tested in the range of 1–100 mm/min and 2.70–4.50 m/s, respectively. The failure behaviour of the fibre-metal laminate is predicted using numerical analysis. The numerical analysis results showed good agreement with the experimental observations, indicating that QSI can provide a useful qualitative assessment of LVI behaviour for the investigated Al/CFRP laminate configuration. The peak force was recorded from QSI data at 100 mm/min (4.44 kN) and from LVI data at 4.50 m/s (4.30 kN). When the speed and crosshead speed increased, the force also increased. The continued loading resulted in matrix cracking, delamination, penetration, and perforation. An improvement to fibre metal laminate is proposed by considering the correlation between QSI and LVI tests. In conclusion, thermoset-based composite materials would be useful in lightweight aerospace structures subjected to impact loading.
This study presents an experimental comparison of the ballistic response of hybrid SECURE 500 steel–AA5083-H116 aluminium armour incorporating circular, diamond-shaped and slot-shaped perforation patterns. A 38.1 mm thick AA5083-H116 plate was tested both monolithically and as a backing plate behind 8 mm thick perforated steel plates positioned at a fixed standoff distance of 110 mm. Three 7.62 × 51 mm armour-piercing projectiles were fired at each configuration at measured velocities of 860–920 m/s. Shot-wise velocity measurements, high-speed imaging, crater-depth measurements and post-impact observations were used to examine the associated projectile-defeat mechanisms. The monolithic aluminium plate underwent complete perforation in all three tests, whereas no complete perforation occurred in any of the nine tests conducted on the hybrid configurations. Circular perforations promoted controlled core damage, local bending and partial deflection, producing the lowest and most closely grouped crater depths, with a mean of 3.33 ± 0.40 mm. Diamond-shaped perforations produced the strongest observed tendency towards extensive projectile-core fragmentation, together with the highest mean crater depth and widest measured crater-depth spread, at 6.03 ± 2.44 mm. Slot-shaped perforations primarily induced projectile yaw, trajectory deviation and partial core breakup, resulting in an intermediate mean crater depth of 4.23 ± 1.17 mm. The slot configuration also had the lowest total areal density of 140.83 kg/m2, compared with 152.60 and 150.97 kg/m2 for the circular and diamond configurations, respectively. The corresponding mass-effectiveness factors relative to rolled homogeneous armour were 0.891, 0.901 and 0.966. The results indicate that the investigated perforation architectures produced different trade-offs among system mass, residual backing damage, measured crater-depth spread and residual projectile condition under the present test conditions.
To explore the behavior of Barium sulfide (BaS) under dynamic pressure, commercially available barium sulfide was purchased and investigated. The samples were subjected to different series of shock waves, such as 100, 200, and 300 shock waves at 0.59 MPa transient pressure and 520 K temperature with a 1.5 Mach number. XRD, RAMAN, and SEM were performed before and after shock-loaded conditions. XRD was used to analyze the crystallinity of BaS, and confirmed the formation of a cubic structure with space group Fm-3 m; its crystallite size was calculated. The Raman spectra revealed the vibrational modes of the control and shock-loaded BaS. Using SEM, the morphology of BaS was studied; an irregular morphology was found, and the particle size was calculated. Shock wave impact also cause changes in crystallite size, morphology, and particle size. XRD and Raman confirmed the formation of a partially mixed-phase transition of BaS and BaS3 for 300 shock pulses. Compared to the pure BaS phase, this mixed phase structure provides superior material performance due to the synergistic effects of BaS and BaS3. It improves aerospace applications, such as spacecraft coatings and fuel tank sealants, offering superior thermal protection, durability, and leak prevention. This cost-effective method, optimizes material properties, making it a promising candidate for advanced aerospace materials. This article describes how shock waves cause the partial mixed phase to occur.
Off-Hugoniot states are critical for exploring new pressure-temperature regimes and investigating material response beyond the principal Hugoniot. We report reproducible methods for the reliable generation and observation of off-Hugoniot pressure states up to 4.9 Mbar in tantalum using a two-stage gas gun with layered impactors. This work provides detailed methods for the preparation of multi-layer impactors using low-impedance polymer front layers that are designed to prevent delamination at impact velocities up to 7.4 km/s, enabling robust multi-shock loading. Using simultaneous multi-probe Photonic Doppler Velocimetry (PDV) measurements and a statistical averaging procedure, we obtain high precision interface velocity histories and quantify the uniform region of the drive. Combined with one- and two-dimensional hydrodynamic simulations, these data are used to assess lateral release, validate the one-dimensional loading in the central region of the target, and determine the equation-of-state-predicted pressure–temperature paths for each experiment. We compare these loading paths to those produced by graded density impactors and laser or magnetic ramp platforms and show that multi-shock gas-gun loading can access similar multimegabar, relatively low-temperature states using a simple and accessible driver. This work establishes layered impactors on a gas gun as a practical platform for future high-pressure studies of strength, phase transitions, and other off-Hugoniot phenomena.
The effects of cold rolling on the shock response of silver have been investigated. Although rolling significantly increases the one-dimensional yield strength (Hugoniot Elastic Limit; HEL), the spall strength is effectively unaffected by pre-shock material state. In contrast, similar experiments on copper showed an increase in both HEL and spall strength when comparing annealed to rolled material. We have also observed a Bauschinger effect in both variants of silver and the cold rolled copper. In hot forged (low dislocation density) silver, we believe that as some of the shock induced deformation is accommodated via twinning, these will act as barriers to dislocation motion, creating a large back stress that aids dislocation motion on stress reversal during the release phase, effectively reducing the yield stress. In the case of cold rolled silver and copper, the initial high pre-shock dislocation density will also act as an effective barrier to dislocation motion with similar results. In contrast, the higher stacking fault energy in copper allows greater ease in the ability of dislocations to overcome obstacles and hence the Bauschinger effect in annealed copper is reduced to the point where a clear distinction between elastic and plastic release can be observed.
Depth of penetration (DOP) is a key indicator of the penetration performance of the earth penetration weapon (EPW). The nose shape of EPW is the main factor which affects the target resistance and the penetration performance. This study introduces a novel asymmetric grooved-nose projectile designed to enhance penetration capability. Considering the combined loading of radial compression and tangential shear during the penetration of asymmetric grooved-nose projectile into concrete targets, an extended quasi-static cylindrical cavity expansion model is proposed, which incorporates the effect of shear stress on penetration resistance. Based on the geometric characterization of the asymmetric grooved-nose projectile and the solutions of the extended cylindrical cavity expansion model, an analytical model was derived to calculate the ultimate DOP and characterize the passive rotation effect of the projectile. Comparative penetration tests were conducted on semi-infinite concrete targets using the asymmetric grooved-nose projectile and the traditional ogive-nose projectile, with impact velocity ranging from 500 m/s to 800 m/s. The DOP and passive rotation effect of the asymmetric grooved-nose projectile were analyzed, and a comparison was made between the predictions of the analytical model and the experimental results. The results show that the theoretical analysis is in good agreement with the experimental data. Passive rotation effect of the asymmetrically grooved-nose projectile is observed both in the experiments and the theoretical model based on localized interaction models (LIMs). The asymmetrically grooved-nose projectile exhibits excellent penetration performance, and its passive rotation effect reduces the penetration resistance.
Understanding the high-strain-rate (HSR) behavior of granular materials at the particle scale is critical for enhancing predictive models in geotechnical, defense, and materials engineering applications. This study presents a comprehensive experimental analysis of the dynamic compressive response of ASTM2030 single-crystalline silica sand particles subjected to one-dimensional (1D) unconfined compression using a mini-Kolsky bar system. Twenty-four individual grains were tested across five distinct high-strain rate (HSR) loading rates (1 m/s, 2.25 m/s, 3 m/s, 5 m/s, and 14.5 m/s). The initial crystallographic orientations of sand grains were determined using Laue X-ray diffraction, and their morphologies were characterized via 3D high-resolution X-ray computed tomography (micro-CT) images. Post-loading microstructural investigations demonstrated that the compressive strength is highly influenced by both strain rate and internal composition, particularly the presence of high atomic number (Z) inclusions. Experimental results demonstrated a strong linear relationship between the loading rate and the peak fracture force. Grains tested along the crystallographic c-axis exhibited up to twice the fracture strength of rotated grains, while those contained fewer voids and a higher content of high-Z inclusions exhibited a higher resistance to failure. These findings underline the significance of microstructural characteristics in driving dynamic particle failure and provide a much-needed dataset for calibrating particle-scale discrete element models (DEM) that account for fracture processes and incorporate particle morphology and crystal structure. The results have extensive applications to enhance the design and performance of granular systems subjected to dynamic loading conditions.
The effects of long term, high pressure salt water exposure on the dynamic behavior of additively manufactured polymers has been investigated through an experimental study. Specifically, the compressive and flexural properties at moderate and high-rate loading before and after salt water exposure are quantified. Three additively manufactured polymers were investigated with the Material Extrusion and Vat Photopolymerization methods utilized in specimen printing. The Material Extrusion process was utilized for the generation of Markforged Nylon and Onyx specimens while Vat Photopolymerization was employed for Formlabs ClearV5 resin specimens. Specimens were exposed to 3.5
High-velocity microparticle impacts involving ductile metals underpin destructive events and solid-state deposition processes, such as cold spray. Simulating these dynamic events enables detailed evaluation of complex, rapidly evolving phenomena such as adiabatic shear instability. However, the rapid upturn in dynamic flow strength at extreme strain rates (> 106 /s) associated with high-velocity impacts is often neglected, and validation exercises are scarce. This study presents meshfree simulations of microparticle impacts involving oxygen-free high-conductivity copper (Cu) and commercially pure aluminum (Al), using an axisymmetric smoothed particle hydrodynamics (SPH) approach coupled with a modified Johnson–Cook constitutive model with Cowper-Symonds rate sensitivity. The simulations were validated against recently published experimental data involving low-velocity particle rebound, critical profile dimensions, the onset of material jetting, deposition, and hydrodynamic penetration. Matched Al-Al and Cu–Cu, and mismatched Al/Cu particle-substrate pairs were considered, with particle diameters between 10 and 30 μm and impact velocities between 50 and 1300 m/s. The coefficients of restitution for low-velocity impacts and the critical velocity for bonding were predicted with average errors of 20.6
Carrying out the constitutive model research of melt-cast explosives is helpful to evaluate the safety of explosives, optimize the performance design, guide the material research, and improve the accuracy of engineering design. This study focuses on the development and calibration of the Visco-SCRAM (Viscoelastic Statistical Crack Mechanics) model specifically tailored for dynamic compression tests of a DNP (3,4-dinitropyrazole)-based melt-cast explosive. The Visco-SCRAM model, which combines viscoelastic effects with statistical crack mechanics, is particularly suited for capturing the complex mechanical behavior of melt-cast explosives under dynamic loading conditions. In this study, dynamic compression tests were conducted on DNP-based melt-cast explosive specimens using the Split Hopkinson Pressure Bar (SHPB) setup. The experimental data were then used to calibrate the parameters of the Visco-SCRAM model, including the viscoelastic parameters and the crack parameters. The calibrated model was validated through numerical simulations, demonstrating its ability to accurately predict the stress–strain behavior of the explosive under various strain rates and confining pressures.
This study employed a split Hopkinson pressure bar system to conduct dynamic compression tests on recycled aggregate concrete (RAC) specimens featuring diverse replacement ratios of recycled coarse aggregate, and scanning electron microscopy was employed to characterize the micro-morphology of the resulting fragments. Based on quantitative characterization of the old mortar content, a new three-dimensional mesoscale model for RAC was developed using self-written Python code. Unlike previous models that assume complete encapsulation of aggregates by old mortar, the proposed model incorporates six distinct material phases and accounts for the random spatial distribution, coverage, and thickness of adhered old mortar. Experimental results revealed that RAC exhibits higher strain-rate sensitivity and larger fragment sizes than natural aggregate concrete (NAC). The simulation results indicated that failure is primarily caused by tensile damage. Although the overall damage extent in RAC is comparable to NAC’s, damage localization is significantly more pronounced within weak interfacial phases. The old mortar content predominantly modulates the elastic modulus and crack width development in RAC, while its coverage plays a crucial role in determining compressive strength and crack density evolution.
We conducted a series of plate impact experiments to examine the efficacy of < 111>-oriented gadolinium gallium garnet (GGG) single crystals as high-impedance optical window for Photonic Doppler velocimetry (PDV) under shock and double-shock loading. At 123 GPa, shocked GGG remains fully transparent to 1550 nm light for at least 250 ns without any signal degradation. Above 135 GPa, PDV data measured through GGG exhibit a gradual loss of fringe contrast following shock entrance, which eventually leads to transparency loss. The duration for which shocked GGG remains transparent decreases with increasing pressure, and at 148 GPa, it becomes opaque within 20–30 ns. This limits the use of GGG as an interferometry window between 110–140 GPa under single shock loading. Within this pressure range, the refractive index of GGG increases linearly with density: n = 1.552 + 0.054ρ. In contrast to single shock loading, where GGG becomes opaque rapidly above 140 GPa, double-shocked GGG remains optically transparent for over 100 ns when it is first shocked to 123 GPa and then reshocked to significantly higher pressures (215–233 GPa). Our findings raise the exciting possibility of GGG being used as a high-impedance optical window in multi-shock and shock-ramp loading experiments.
The mechanical response of Viton-A is investigated across a wide range of dynamic strain rates (685 s ^-1 - 8200 s ^-1 ) with a Kolsky Bar, aka Split-Hopkinson Pressure Bar (SHPB), testing and visco-elastic model fitting. A bi-linear stress–strain response is observed at each strain rate, with secondary moduli values that increase with strain rate, ranging from 21 MPa to 35 MPa. A visco-elastic model, that utilizes Boltzmann’s superposition integral, is used to simulate the stress–strain response for Viton-A across the same range of strain rates that were experimentally tested. Overall, good agreement is seen between the visco-elastic model and the experimental tests. The model is able to capture the change in modulus observed experimentally at each strain rate, and the model predictions fall within two standard deviations of stress at every 0.5
This paper reports a thorough experimental examination of the anisotropic and rate-dependent constitutive properties of synthetic α-quartz single crystals. The constitutive response was analyzed using uniformly sized 1 mm3 synthetic silica cubes across three primary crystallographic orientations: (2 1 1 0) for the a-axis, (0 1 1 0) for the m-face, and (0 0 0 1) for the c-axis. The cubes were subjected to unconfined quasi-static compression, high strain-rate (HSR) loading ( 1700-4100 s^-1 ) using a mini-Kolsky bar, and nano-indentation to evaluate both macroscopic and microscale elastic characteristics. Results from all testing methods consistently demonstrated a significant elastic anisotropy: the a-axis had the highest stiffness and fracture resistance, followed by the c-axis: however the m-face exhibited the lowest stiffness and strength. Nano-indentation corroborated these findings, demonstrating a scale-invariant directional dependency of strength properties. A distinct sensitivity to loading rate was noted, with Young’s modulus exhibiting a linear increase with strain rate across all orientations. The most pronounced rate dependence was observed along the a-axis, indicating fundamental microstructural stiffening mechanisms. The results highlight the significance of crystallographic orientation and loading rate in influencing the strength performance of quartz-rich materials. The results reported in this paper have substantial ramifications for modeling and engineering applications in geomechanics, microelectromechanical systems (MEMS), and the manufacturing of brittle crystalline materials.
Multiphase equations of state (EoS) must remain numerically robust during simulations of dynamic loading when large variations of density and internal energy can occur. In the liquid regime, removing van der Waals loops via a Maxwell construction captures the liquid gas transition and prohibits negative pressures (liquid-boiling), while leaving the loops in place allows tension (liquid-tension) and enables approximate spall-like behaviour in the absence of a cavitation model. This paper documents the pragmatic approximations introduced for robustness in a SESAME-style tabular multiphase EoS: namely, extended, bridging, and buffer zones; a monotonic energy-temperature constraint along isochores; and a mass-weighted sound-speed for use with artificial viscosity. Comparisons of the two liquid treatments in 1D hydrocodes are made against (i) shock-vapourisation experiments in lead, and (ii) the tin shallow-bubble-collapse (SBC) experiment. Across shock-vapourisation cases, both liquid treatments reproduce the witness-plate velocity history with only minor differences, although the liquid-boiling option occasionally yields a more ramp-like rise representative of certain lead shots. In the SBC experiment, the computed temperatures with liquid-boiling agree closely with the measurements, whereas liquid-tension under-predicts the temperature rise. The results support using liquid-boiling where temperature predictions inside cavitated zones matter, while documenting the approximations and safeguards that make such EoS practical for production hydrocodes.
Accurate and efficient prediction of concrete anti-penetration behavior enables rapid safety assessments of protective structures. Concrete penetration involves complex multi-physical coupling (material dynamics, stress wave propagation, strain rate effects), while scarce test data and noise interference limit empirical formulas and phenomenological models. Numerical simulations also suffer from low efficiency. Thus, developing a model that can rapidly and precisely forecast the depth of concrete penetration is crucial. This paper proposes Back Propagation Neural Network (BP) combining Genetic Algorithm (GA) and Adaptive Boosting Algorithm (AdaBoost). First, a bias-based outlier detection method is used to screen the outliers in the sample data. The GA is used to optimize the weights and thresholds of the BP. The optimized GA-BP serves as a weak learner. Multiple weak learners are then combined using the AdaBoost to create a strong learner model. Secondly, the prediction effects of BP model, GA-BP model and GA-BP-AdaBoost model are compared on the same dataset, the results show that the coefficients of determination of the three are 0.79, 0.81, and 0.9, respectively, which proves that the GA-BP-AdaBoost model significantly improves the prediction accuracy and has obvious advantages compared with traditional methods. Finally, penetration tests were performed using a 20 mm ballistic gun with sub-caliber techniques, firing tungsten alloy projectiles at speeds from 168 to 266 m/s. The test data were input into the model for verification. The results showed that the predicted values were close to the experimental values, which indicated that the model has good practical value.
An innovative experimental scheme is proposed to separate the coupled effects of adiabatic heating and strain rate on Strain-Induced Martensitic Transformation (SIMT) in FA-grade ultra-high-strength steel (UHSS) at high strain rates. This method combines strain-controlled tests (non-isothermal) and strain increment tests (quasi-isothermal). Conventional split Hopkinson tensile bar (SHTB) devices face difficulties in performing strain increment/controlled tests at high strain rates due to interference from multiple impulse loadings. A novel SHTB device, incorporating a dual-momentum capture bar and sleeve structure, enables reliable single-pulse dynamic loading in both test modes. Quantitative analysis was conducted to compare the relative influences of adiabatic heating and strain rate on martensite suppression, supplemented by microscopic characterization. The results indicate that the martensitic phase transformation volume fraction increases with strain but decreases with increasing strain rate in both test modes. Adiabatic heating was identified as the dominant factor suppressing SIMT (accounting for 44.6
This study presents experimental and numerical investigations of the structural behavior of reinforced concrete (RC) slabs exposed to blast loading at three different scaled distances: 0.83 m/kg1/3, 0.42 m/kg1/3, and 0.21 m/kg1/3. Two blast loading techniques, Load Blast Enhanced (LBE) and Structured Arbitrary Lagrangian-Eulerian (SALE), implemented in LS-DYNA, were evaluated by comparing numerical blast pressures and accelerations with test data from the largest scaled distance test. For the rest of the cases, the numerical models were compared with the failure mechanism and with the size of the damage produced in the tests. The SALE model, combined with the concrete material models Karagozian Case (K C) and Continuous Surface Cap Model (CSCM), effectively captured the dynamic behavior of RC slabs, including failure mechanisms. The study also examined three different explosive shapes (cube, cylinder, and bag) aimed at resolving uncertainties in the explosive geometry used in the experiments. Numerical simulations at intermediate and small scaled distances demonstrated that the cubic and bag-shaped explosives, particularly when used in conjunction with the K C model, accurately reproduced the damage patterns observed in the RC slabs during close-in explosions. These findings highlight SALE coupled with K C/CSCM as the most robust and reliable modeling strategy for blast analysis of RC structure.
When using numerical simulation to study the destruction of concrete under the action of projectile penetration, the Holmquist-Johnson-Cook (HJC) constitutive model is one of the most commonly used in concrete, and the reliability of its parameters is a crucial factor affecting the accuracy of numerical simulation results. This paper first prepared C100 grade ultra-high-strength concrete (UHSC) and characterized its fundamental mechanical properties. Based on these properties, the parameters of the yield surface equation, damage equation, and state equation in the corresponding HJC constitutive model for concrete were accordingly updated, resulting in a set of HJC constitutive model parameters applicable to UHSC. Second, using the LS-DYNA software, a numerical model of a reinforced UHSC military protective slab (RUHSCS) was constructed to investigate its mechanical responses under the projectile penetration. The simulated depth of penetration (DOP) using the updated parameters showed excellent agreement with experimental data, validating the model’s reliability. Subsequently, a parametric study on rebar configuration revealed that reducing rebar grid spacing is the most effective measure in decreasing DOP, followed by reducing layer spacing and increasing rebar diameter. Furthermore, it was demonstrated that for a given volumetric rebar ratio, employing smaller-diameter rebar with denser grid and layer spacing constitutes the most efficient reinforcement strategy for enhancing the ballistic anti-penetration of RUHSCS.
