Crater Diameter Research Articles

The penetration crater characteristics of thick steel plate impacted by tungsten alloy projectiles

Abstract The mild steel target plates impacted vertically by tungsten spherical projectiles with different initial velocities and projectile diameters were studied by ballistic experiments and numerical simulation. The macroscopic properties of the penetration crater were analyzed by the depth, diameter, and overall shape of the crater. The results show that crater diameter and depth increase as initial velocity or projectile diameter increases. With the increase in velocity, the deformation and erosion of tungsten projectiles significantly increased. Specific kinetic energy is used to normalize the velocity and size of the projectile, the expression of crater depth and diameter varying with specific kinetic energy is given, which accuracy R2 is 0.8. Based on THOR theory and experimental data, the accurate calculation model of penetration depth versus projectile mass, initial velocity, and the area of the contact was obtained, with an accuracy of R2 of 0.97.

Research and simulation study on the penetration behavior of Φ 30 mm armor-piercing bullets penetrating armored steel

Abstract To study the penetration behavior and ballistic characteristics of a Φ30mm tungsten alloy armor-piercing projectile penetrating homogeneous armor steel, penetration tests were conducted, and the penetration process was numerically simulated using LS-DYNA. The experimental results show that the presence of the conical section of the Φ30mm armor-piercing projectile forms a “saddle” shaped crater feature. The simulation results indicate that the penetration efficiency of the projectile and the incident velocity exhibit a quadratic function relationship. In the velocity range of 800-1200m/s, the kinetic energy consumed by the projectile for the same penetration depth is essentially the same, i.e., the lateral crater diameter is consistent at different speeds. Additionally, during the penetration process, the penetration depth as a function of time under different speeds also shows a quadratic relationship.

Influence of structural parameters of layered interception compound reactive liner on combined penetrating and implosion effects

Abstract In response to the bottleneck problem that the penetration depth of traditional fluoropyr-based reactive material(RMS) shaped charge is seriously insufficient, a Layered Interception Compound Reactive Liner (LICRL) shaped charge structure is proposed. Based on the MPM numerical simulation method, the influence of structural parameters such as the height ratio ϕ and thickness ratio η of the inner and outer liners on the jet formation and its penetration behavior is investigated. The results indicate that the variation in ϕ primarily affects the head shape of jet formation. When ϕ = 2/3, a composite jet comprising a precursor copper jet and a trailing reactive jet is formed, which causes a “Penetrating While Explosion” damage effect on steel targets. The variation in η mainly influences the shaping morphology of the copper jet. When η > 2/3, the damage power of the composite liner is weakened, this is attributed to the poorer shaping morphology of the coaxial copper jet under higher liner thickness ratios and premature fracture of the copper jet due to reactive material response. Compared to traditional single reactive jets, the layered interception compound reactive liner (LICRL) forms jets that penetrate steel targets to a greater depth, and significantly increase the crater diameter compared to single-metal jets.

Asymmetrical distribution of 1–20 km craters on the Moon

Previous studies have provided evidence for the synchronous rotation induced cratering asymmetry on lunar surface through numerical simulations and statistical analysis of a limited number of fresh craters. In this study, we reevaluated cratering asymmetry in lunar highland from (70°W, 60°N) to (70°E, 60°S) region using a new crater catalogue with diameters (D) ranging from 1 to 20 km. By utilizing a depth-to-diameter (d/D) ratio constraint to exclude the interference of degraded and secondary craters, we observed significant asymmetry in craters with d/D > 0.15. Moreover, leveraging the characteristic that larger diameter craters (D > 7 km) are less susceptible to degradation, we observed a more pronounced asymmetry with increasing diameter. Particularly, impact craters with larger D and d/D ratios (D > 7 km, d/D > 0.15) displayed an asymmetrical longitudinal distribution, aligning with predictions from the theoretical model. In the diameter range of 10 km–20km, for craters with d/D > 0.15, we observed that new crater influx occurring after 4.0 Ga years ago contributed little to this particular crater population. Therefore, we suggest that the cratering asymmetry was already present before 4.0 Ga. Due to the non-uniform ejecta from the Orientale Basin onto the highland regions, a significant number of smaller impact craters (1–5 km) have degraded or disappeared in the leading region, thereby diminishing the manifestation of the cratering asymmetry. The pronounced asymmetry exhibited in our statistical results might suggest the existence of a significant population of low-velocity impactors in early impact period (>4Ga) around the cis-lunar space.

Low-velocity penetration behavior of ice by steel projectile

In this study, the penetration of a steel projectile into a semi-infinite ice target is investigated through experiment and numerical simulation. Five tests with initial impact velocity varying from 42.5 to 110 m/s are conducted. The penetrating behavior of the projectile and the dynamic response of the ice target are captured by a high-speed camera. The experimental results show that the impact velocity has great impact on the dynamic behavior and failure mode of the ice target. Under a low-speed impact, the ice target forms a crater at the impact surface. However, a penetration tunnel is formed under a high-speed impact. The crater diameter and penetration depth increase almost linearly with increasing the impact velocity. Furthermore, the numerical simulation for the tests is carried out using the continuum discontinuum element method (CDEM). The simulated penetration depth history of the projectile and the failure characteristics of the ice target agree with the experimental results, validating the numerical simulation model. It indicates that the ice crater angle keeps almost the same during a penetration. In addition, the maximum deceleration of the projectile and the maximum von Mises stress of the ice elements increase with increasing the impact velocity. These results provide the failure behavior and numerical simulation method for ice penetration, improving the understanding of dynamic fracturing mechanism of ice in engineering applications.

Mercury’s Meteorite Mysteries: A Directional Statistical Guide to Mercury’s North Pole, Hidden Hazards and Roadmap to Safe Landing Havens Based on Solar Elevation, Ice Stability, Temperature

Studying meteoroid impact patterns on planetary surfaces is critical for understanding surface dynamics and selecting safe landing sites. Mercury, one of the least explored rocky planets, presents unique challenges due to its extreme temperatures and the angular nature of its surface data. Traditional linear statistical methods are often inadequate for analyzing such directional data. This study introduces a novel approach using directional data analysis techniques to interpret the cyclical nature of meteoroid impact locations on Mercury. We employed Watson’s test, Bayesian Information Criterion scores, and a mixture of von Mises–Fisher distributions to model the distribution of impact craters and solar elevations on Mercury’s surface. Our findings indicate that while location parameters adhere to the von Mises distribution, solar elevations do not exhibit directional distribution characteristics. Additionally, by filtering datasets based on temperature thresholds and crater diameters, we pinpointed areas with a high probability of providing suitable landing surfaces. These insights enhance our understanding of the surface conditions on Mercury and provide valuable groundwork for future exploration missions.

Statistical Methods for Interpreting Spatial and Temporal Heterogeneity of Martian Tropical Water Ice Informed by Properties of Crater Ejecta Types

AbstractThe martian tropical water ice spatial and temporal distribution was characterized using impact crater ejecta type, location, size, and age in one of two epochs, Ga and Ga, using statistical models designed for spatial and temporal correlation structures. The indicator thought to identify the presence of ice is craters with layered ejecta, while the indicator thought to identify no ice is craters with radial ejecta. These indicators imply the location (longitude and latitude) and, potentially, depth (crater diameter as a proxy) of ice, and when the ice was present. The spatial and temporal distribution of layered ejecta versus radial ejecta may inform on the geography and evolution of ice. A statistical spatial point analysis was conducted on a 54‐sample data set (craters with diameters 2.77–10.00 km) for an equatorial region ( to S, and E to W. The analysis shows the spatial and temporal distribution of tropical ice in the study region is most likely random.

MARS CHRONOLOGY DERIVED FROM CRATERS HETEROGENEITY AT GALE CRATER

Craters sample into diachronic surfaces and different depths on Mars and other planetary surfaces. These surfaces are affected by cosmonuclide radiation that offers one of the most reliable age anchors to date. Craters also accumulate, evolve and display an universal characteristic that can be measured at any scale, regardless of the geologic unit they sample, in the form of the heterogeneity parameter (Capitan, 2021). Here we use an age equation, which is based on the measurements of craters diameter, depths and area they occupy, to derive the ages of deposits that are sampled by medium-scale craters (meters to few hundred meters in diameter). We show that units sampled by the deepest craters near MSL exploration area are formed during the early stages of Gale crater formation before 2870 Ma. In contrast, units sampled by shallower craters were formed during the stages that correspond to the time of sediment recycling and lithification periods, near 2129 Ma to present. Given the heterogeneity of initial formation conditions of craters of diverse diameters and their different depths of sampling, our proposed synchronous ages with ground-truth ages has the potential to redefine the paradigm of using the impact crater morphometry as a tool to date the planetary surfaces.

Experimental study on the damage characteristics of steel fiber reinforced concrete slabs attacked by chloride ion under contact explosion

In order to study the damage characteristics of steel fiber reinforced concrete slabs attacked by chloride ion under explosive loading, contact explosion tests were performed for nine pieces of 500 mm × 500 mm × 60 mm slabs. These slabs were divided into three groups based on corrosion time of seawater (uncorroded, corrosion for 10 days, corrosion for 20 days) to achieve different degrees of chloride ion erosion effect. The dynamic response of the steel fiber reinforced concrete slab under contact blast loading were compared and analyzed, and the effects of explosives quality and degree of corrosion were explored. Besides, the propagation characteristics of the stress wave in the slab and the typical damage mode were also studied. The results show that the damage degree of steel fiber reinforced concrete slab has a non-linear increase with the increase of seawater corrosion. Slabs suffer different damage patterns such as cratering and spalling for different qualities of explosives. In addition, based on the experimental results, an empirical formula for predicting the diameter of the blast crater was established.

Discrete element model of low-velocity projectile penetration and impact crater on granular bed

The present study investigates the low-velocity impacts of a spherical projectile into a bed of spherical particles using Discrete Element Method (DEM) simulations and laboratory experiments. The findings reveal intricate forces and energy transformations, indicating the phenomena leading to projectile impact, penetration, cessation, and crater formation. The DEM result indicates that the penetration stopping time of the projectile is not influenced by impact velocity. Further, simulations show that projectile penetration depth correlates with 1/2.7 power of total impact height, while crater diameter and depth scale with 1/4.32 power of nondimensional impact energy. The shape of the resulting crater appears independent of impact velocity and the maximum diameter of the fluidized region varies with the 1/2.68 power of impact velocity. Experimental validation confirms the accuracy of predicted penetration depths and crater diameters, enhancing confidence in DEM simulations. These findings extend scaling laws and reveal the influence of larger particles on low-velocity impact dynamics, addressing unexplored aspects of granular cratering.

Correlating 300 million years of catastrophes

It is frequently proposed that large bolide impacts and voluminous volcanic eruptions may be responsible for environmental catastrophes. In the conventional approach, the potential causes and consequences are matched using an age-versus-age plot, with preferential ages selected for comparison. This approach inevitably results in a one-to-one correlation, which may be misleading. To address this issue, a novel statistical metric, named conformity, has been proposed which accounts for the possibility of age coincidence resulting from random processes (i.e. bad luck coincidence). The available and updated geochronological datasets of bolide impacts, large igneous provinces, CO2-concentration peaks in the atmosphere, mass extinctions, ocean anoxic events, and climatic optima and thermal highs were subjected to a comparison in terms of their concordance. The most significant discovery is the correlation between the ages of mass extinctions and those of giant bolide impacts (crater diameter >40 km), as well as volcanism of continental large igneous provinces and CO2-concentration peaks in the atmosphere. The severity of mass extinctions appears to be dependent upon the number of simultaneously occurring causes. The most pronounced Late Maastrichtian (∼66 Ma) and Changhsingian (∼252 Ma) mass extinctions were likely caused by a combination of factors, including the simultaneous occurrence of volcanism of continental large igneous provinces, giant bolide impact and CO2-concentration rise in the atmosphere. Conversely, the ages of large igneous provinces, bolide impacts and CO2-concentration peaks are not correlated, indicating that these three causes were not interdependent.

Penetration test and numerical simulation of scaled earth penetrator for coral aggregate seawater concrete cylindrical target

In order to study the mechanical properties of coral aggregate seawater concrete (CASC) subjected to the penetration of scaled earth penetrator, firstly, the penetration depth and damage of CASC and ordinary sand-gravel concrete under the same conditions were compared by experimental research, and the influence of concrete strength and projectile velocity on penetration performance was analyzed. Then, the three-dimensional mesoscopic model is used to simulate the test conditions, and the failure process and failure mechanism are analyzed. The results show that under the same penetration conditions, as the strength of CASC increases, the crater diameter becomes larger, which is consistent with the conclusion of ordinary concrete (OPC). During the penetration process, the CASC and the mortar are destroyed as a whole. At the same time, as the penetration speed of the projectile increases, the width of the crack on the surface of the target increases. When the projectile velocity is low, the anti-penetration performance of CASC with the same strength is not as good as that of OPC with the same strength. For the target with a thickness of 25 cm, the penetration depth of the concrete target with the same strength will increase with the increase of the velocity of the projectile. When the velocity of the projectile is constant, the penetration depth of CASC will decrease with the increase of the strength. The numerical simulation results obtained by using the K & C mesoscopic model are in good agreement with the experimental results, indicating that the model and its model parameters have high reliability in the analysis of CASC penetration mechanical properties.

Process simulation and optimization of process parameters of single-pulse femtosecond laser processing Invar 36 alloy

Invar 36 alloy has an extremely low coefficient of thermal expansion and is suitable for preparing a fine metal mask (FMM) for the evaporation of silicon-based organic light emitting display microdisplays. The higher the resolution and the greater the number of pixels, the finer and more delicate the holes required. Femtosecond laser processing technology is an effective technical means for processing Invar 36 alloy FMM due to its characteristics of extremely short pulse width, extremely high pulse energy density, smaller heat-affected zone, and more regular machining edges. The femtosecond laser processing parameters directly affect temperature distribution and then affect the manufacturing quality and efficiency of Invar 36 alloy FMM. At present, femtosecond laser processing of Invar 36 alloy FMM is still in the exploration stage, and the processing mechanism and technology are not clear. In this paper, a simulation model of single-pulse femtosecond laser processing Invar 36 alloy is established based on the two-temperature equation. By comparing the ablation morphology of the simulation output with the experimental measurement results, the validity of the simulation model is verified and the processing mechanism is preliminarily explored. Based on the simulation model, the effects of femtosecond laser energy density, pulse duration, and spot diameter on the electron temperature field, lattice temperature field, and ablation morphology of the craters are explored. The process window of laser processing parameters is determined. A full-factor test is conducted. Take the minimum length of the heat-affected zone, the maximum depth of the ablation crater, and the minimum diameter of the ablation crater as three optimization objectives and obtain Pareto optimal solutions based on genetic algorithm. The optimization of single-pulse femtosecond laser drilling Invar 36 alloy is realized.

The LCROSS Impact Crater as Seen by ShadowCam and Mini‐RF: Size, Context, and Excavation of Copernican Volatiles

AbstractThe Lunar CRater Observations and Sensing Satellite (LCROSS) impacted a Centaur rocket stage into a permanently shadowed region (PSR) in Cabeus crater, excavating water ice and other volatiles. We used the Miniature Radio Frequency (Mini‐RF) instrument on the Lunar Reconnaissance Orbiter and the ShadowCam instrument on the Korean Pathfinder Lunar Orbiter to detect the probable 22‐m diameter crater that resulted from the LCROSS impact. The crater formed superposed upon a dense small crater population along a crater ray from a larger pre‐existing crater. From its geologic context, the ice and regolith excavated by LCROSS were likely modified within the last 0.1–0.5 Gyr. An upper limit for the excavated volatiles is ~0.9 Gyr, as the location was not a PSR prior to that time. A young age for the LCROSS‐detected volatiles supports the idea that they were mostly emplaced by an exogenic mechanism, such as from comets or the solar wind.

Rapid Impact Crater Relaxation Caused by an Insulating Methane Clathrate Crust on Titan

Titan’s impact craters are hundreds of meters shallower than expected, compared to similar-sized craters on Ganymede. Only 90 crater candidates have been identified, the majority of which have low certainty of an impact origin. Many processes have been suggested to shallow, modify, and remove Titan’s craters, including fluvial erosion by liquid from rainfall, aeolian sand infill, and topographic relaxation induced by insulating sand infill. Here we propose an additional mechanism: topographic relaxation due to an insulating methane clathrate crustal layer in Titan’s upper ice shell. We use finite element modeling to test whether a clathrate crust 5, 10, 15, or 20 km thick could warm the ice shell and relax craters to their currently observed depths or remove them completely. We model the viscoelastic evolution of crater diameters 120, 100, 85, and 40 km, with two initial depths based on depth−diameter trends of Ganymede’s craters. We find that all clathrate crustal thicknesses result in rapid topographic relaxation, despite Titan’s cold surface temperature. The 5 km thick clathrate crust can reproduce nearly all of the observed shallow depths, many in under 1000 yr. A 10 km thick crust can reproduce the observed depths of the larger craters over geologic timescales. If relaxation is the primary cause of the shallow craters, then the clathrate thickness is likely 5–10 km thick. Topographic relaxation alone cannot remove craters; crater rims and flexural moats remain. To completely remove craters and reproduce the observed biased crater distribution, multiple modification processes must act together.

A performance-based ballistic design framework for RC panels and a probabilistic model for crater quantification

Ballistic design is crucial for widely utilised concrete structures in today’s unpredictable world. In the past, extensive experimental and numerical studies have investigated concrete panels, resulting in design guidelines and empirical formulations for local damage parameters. However, with the advent of performance-based design, notably in seismic design, the ballistic design of concrete structures lacks a comprehensive design philosophy. Additionally, deterministic empirical formulations for local damage parameters, particularly in the case of reinforced concrete (RC) panels’ crater formation, necessitate a probabilistic treatment. Consequently, this paper addresses the need for a well-defined ballistic design philosophy for concrete structures and introduces a probabilistic approach for crater quantification. Firstly, a novel multi-level and multi-parameter performance-based design framework for RC panels is proposed, centred on damage states, namely depth of penetration and crater area. This framework establishes an innovative design philosophy featuring four damage levels for each state. Secondly, using dimensionless explanatory functions, a Bayesian inference model is developed to estimate the crater diameter in RC panels under hard projectile impact, accounting for the associated uncertainties. LS-Dyna is used for numerical modelling of RC panels and rigid projectiles. The numerical models are validated with the experimental data and are utilised to develop the probabilistic model. This study reveals the profound influence of projectile and concrete properties in addition to the incidence angle of the projectile on crater formation. The developed probabilistic model is validated with experimental results demonstrating its reliability and accuracy. Consequently, a reliable design formula for estimating crater diameter for RC panels under hard projectile impact is proposed in addition to the novel ballistic design framework.

Numerical simulation of high-power density CO2 laser ablation of HgCdTe

A two-dimensional coupled model of phase transition, heat transfer and vaporization ablation of laser-irradiated HgCdTe materials has been developed for the first time using finite element analysis to simulate the behavior and characteristics of melting, phase transition and ablation of HgCdTe materials irradiated by a CO₂ laser with a wavelength of 10.6 µm at different laser powers. The results demonstrate that an increase in power density results in an exponential decrease in the time required for HgCdTe to reach the melting and gasification temperatures. The corresponding temperature points can be reached in the order of nanoseconds. During the heating phase, the increase in temperature results in a gradual enlargement of the melt pool in the ablation crater, with the minimum thickness of the melt pool occurring in the central region of the ablation. However, the diameter of the ablation crater tends to stabilize after the spot size is reached. An increase in power density results in a reduction in the size of the molten pool at the center of the ablation crater, while the size of the molten pool at the edges remains relatively constant. Once the laser irradiation ceases, the melt pool near the ablation crater’s center is initially dissipated because of heat generated by the material’s gasification process. In contrast, the melt pool at the periphery persists until the final stages of dissolution. The simulation results demonstrate that at a power density of 2.6 MW/cm2, the ablation crater depth is approximately 12 μm, which is enough to penetrate the HgCdTe layer of the detector. These results provide a foundation for further research on the damage mechanisms of HgCdTe detectors.

Case study of a cluster of simple and complex monogenetic volcanoes in the north‐east part of the Michoacan–Guanajuato Volcanic Field, Central Mexico: Nomenclature implications

With the advent of new terminologies to categorize and characterize the simple and complex monogenetic volcanoes, also came the semantic issues, which caused a predicament for the usage of terms like simple, complex, polycyclic, polymagmatic, complex monogenetic volcanoes with polygenetic inheritance. To analyse and validate this nomenclature, we studied an overlapping volcanic structure located south of the present‐day town of Irapuato, Central Mexico, that appears to be a monogenetic complex at first sight. Field observations, tephra stratigraphy, petrography and geochemistry of the tephra deposits confirms that the structure is in fact a cluster of three simple (San Joaquin tuff ring and two scoria mounds) and one complex, polycyclic, polymagmatic (La Sanabria‐San Roque tuff ring) monogenetic volcanoes formed by independent events, governed by distinct conduits and magma bodies of different origin (subduction‐related, OIB and E‐MORB origin) and separated by different tephra sequences of dissimilar components and depositional characteristics. We estimate the magma volumes (using the juvenile content and their vesicularity percentage) to be at 0.40–1.31 × 108, 0.25 × 108 and 0.42–0.90 × 108 m3 for San Joaquin, La Sanabria and San Roque, reckoning an eruption duration of 77 and 48 and 81 days, respectively (considering an average eruption rate of 6 m3/s from the well‐documented shallow crater (<30 m), Ukinrek maars in Alaska) occurring within the age range of 40–70 k years (crater diameter and depth ratio). This study not only aided to validate the above‐mentioned terms for monogenetic volcanoes, but also reconsider a few of them and avoid confusion with the polygenetic counterparts.

Analysis of a large buried impact crater and vertical mineral composition at the Chang'E-4 landing site by multi-source remote sensing data

Exploring the concealed subsurface structures and materials beneath the lunar surface can reveal significant insights into geological history. This study offers a comprehensive analysis of the stratigraphic interpretation and subsurface material composition at the Chang'E-4 landing site, integrating both in-situ and orbital radar with multispectral datasets. We report the identification of a subsurface structure, which resembles a buried impact crater (∼420 m in diameter) under the Yutu-2 rover's path. This crater could degrade over a period of 0.42 to 0.53 Ga, with an initial diameter of 293 to 323 m and an initial depth of 45.9 to 51.4 m. Surface material above the buried crater, evaluated by the in-situ visible and near-infrared imaging spectrometer (VNIS) detector, shows a higher abundance of clinopyroxene compared to surrounding areas, where a near-equal mix of clinopyroxene and orthopyroxene is observed. Assessment of crater diameters in proximity to the Chang'E-4 landing site, along with the mineral compositions at their epicenters, reveals a decrease in the abundance of clinopyroxene and plagioclase with depth. Conversely, the quantities of orthopyroxene and olivine increase, implying that orthopyroxene-rich Finsen ejecta significantly influenced the Chang'E-4 landing site's geological composition. Two potential stratigraphic boundary depths are identified at 13.5 and 22 m, based on pronounced variations in mineral abundance, offering fresh insights into subsurface delineation beyond radar data. Considering the VNIS and vertical mineral composition, we propose the buried crater's formation resulted from Finsen crater's ejecta. Also, we identify eight potential historical impacts by comparing subsurface relief variations with mineral composition ratios between clinopyroxene and orthopyroxene. The integration of subsurface structure, along with surface and subsurface mineral composition, enables a more robust stratigraphic interpretation, facilitates shallow material source analysis, and allows for historical impact tracing.

Study on the damage characteristics of single-crystal silicon ablated by 355 nm UV picosecond laser

Abstract The experimental investigation on picosecond laser ablation of single-crystal silicon is presented in this paper. An ultraviolet (UV) picosecond laser with a wavelength of 355 nm and a pulse width of 10 ps was employed to create single-pulse ablation craters on the surface of single-crystal silicon. The influence of laser power variation on the morphology of single-pulse ablation was analyzed. The diameter of the ablation craters was measured and statistically analyzed. Based on the results, the picosecond laser spot diameter was calculated to be 7.65 μm, and the ablation threshold of single-crystal silicon in this experiment was determined to be 0.212 J/cm2.