Penetration Regime Research Articles

Fluid Dynamics Studies on Bottom Liquid Detachment from a Rising Bubble Crossing a Liquid–Liquid Interface

The detachment regimes and corresponding detachment height of lower liquid from a coated bubble during the bubble passage through an immiscible liquid–liquid interface were studied. High-speed imaging techniques were used to visualize the lower liquid detachment from a rising bubble near the interface. Analysis of industrial slag samples by a scanning electron microscope (SEM) was also carried out. The results indicate that the detachment height of lower liquid from a rising bubble showed a distinct correlation to penetration regimes. Bubble size and a fluid’s physical properties exerted a significant influence on the detachment height of the lower liquid. The detachment height for medium bubbles (Weber number: 4~4.5; Bond number: 2.5~7.5) varied significantly with increasing bubble size, which contributes to the lower liquid entrainment in the upper phase due, significantly, to the higher detachment height and large entrainment volume. The maximum detachment height for large bubbles is limited to approximately 100 mm due to the early detachment with the liquid column at the interface though large bubbles transporting a larger volume of lower liquid into the upper phase.

Dynamic Drop Penetration of Horizontally Oriented Fiber Arrays.

In this experimental study, we combine drop impact into porous media and onto a single fiber to study drop impact into fiber arrays inspired by mammalian fur coats. In our 3D-printed arrays, we vary the packing density, fiber alignment, strand cross-section, and wettability. Drops impact fibers fixed at both ends, penetrating over short periods of time by momentum and laterally spreading throughout the array. Using image analysis, we measure penetration depth and wetted width into the array. Impact Weber number and intrinsic porosity define penetration, retraction, and rebound regimes. On average, at an impact Weber number of ≈80, staggered fibers reduce penetration by 24% in hydrophilic fibers and 34% in hydrophobic fibers, and the penetration reduction percentage is expected to increase with increasing Weber number. Our results indicate that as density grows toward the density of mammalian pelts, penetration will reach a maximum value independent of drop impact velocity, thereby providing an effective rain barrier. Hydrophilicity at the densities we test, 50-150 strands/cm2, aids fiber array resistance to dynamic penetration by impacting drops through the promotion of lateral drop spreading and inhibition of drop fragmentation. Conversely, hydrophobic fibers best resist low-speed wicking. The fraction of a drop that infiltrates hydrophilic and hydrophobic fibers is nearly identical for a fixed Weber number because lateral spreading restricts the penetration depth into hydrophilic fibers but does not restrict mass infiltration. Above a critical Weber number, the entire drop mass penetrates fiber arrays regardless of strand wettability.

Hydrodynamics of a bubble passing through a Kelvin cell in microchannel with shear-thinning fluid

Open cell solid foams (OCSF) show great potential for process intensification in heterogeneously catalyzed reactions due to their favorable properties regarding heat-mass transfer, pressure drop and specific surface area (SSA). As one of the most ideal OCSF structure, Kelvin cell (KC) exhibits a fundamental importance in fully understanding the complex flow and transport properties of these reactions, but the research involving gas-liquid two-phase flow is still missing. In this work, the hydrodynamics of a bubble through a representative elementary volume with KC model in minichannel with sodium carboxymethyl cellulose aqueous solution are investigated by coupled level-set and volume-of-fluid method. The regime of bubble penetration into KC is elucidated. The specific surface area and permeability of bubble are studied by systematically analyzing the influences of solution concentration, liquid velocity, KC's porosity and contact angle, as well as fluid type. Four penetration regimes of approaching stage, engraving stage, extruding stage, and deviating stage are identified, and a typical curve of SSA of bubble in terms of flow time is acquired accurately. It is found that the drastic changes in SSA and permeability are closely related to the engraving and extruding stages. The average SSA in two involved stages increases with solution concentration, decreases with KC's porosity. The maximum permeability corresponding to the transition point between two stages, decreases with solution concentration, increases slightly with KC's porosity. However, liquid flow velocity and KC's contact angle have no significant effect on both the average SSA and the maximum permeability. Compared with water, a small SSA tends to be obtained and the permeability climbs slowly but reaches a high peak in CMC solution.

Magnetic flux penetration in nanoscale wedge-shaped superconducting thin films

Thickness uniformity is regarded as an important parameter in designing thin film devices. However, some applications based on films with non-uniform thickness have recently emerged, such as gas sensors and optimized materials based on the gradual change of film composition. This work deals with superconducting Pb thin films with a thickness gradient prepared with the aid of a diffuse stencil mask. Atomic Force Microscopy and Energy-Dispersive X-ray Spectroscopy show variations ranging from 90~nm to 154~nm. Quantitative magneto-optical images reveal interesting features during both the abrupt and the smooth penetration regimes of magnetic flux, as well as the thickness-dependent critical current density ($J_c$). In addition, we observe a gradual superconducting transition as the upper critical field is progressively reached for certain thicknesses. Furthermore, the hysteresis observed for triggering flux avalanches when increasing and decreasing magnetic fields is also accounted for by the $J_c$ profile evolution along the thickness gradient. Numerical simulations based on the Thermomagnetic Model are in fair agreement with the experimental data. These findings demonstrate that wedge-shaped films are a viable approach to investigate, in a continuous fashion, thickness-dependent properties of a superconducting materials.

Nonlinear Dynamics of a Hysteresis Western Boundary Current Perturbed by a Mesoscale Eddy at a Gap with an Island

Abstract We study a hysteresis western boundary current (WBC) flowing across a gap impinged by a mesoscale eddy, with an island of variable meridional size in the gap, using a 1.5-layer ocean model. The hysteresis curves suggest the island with a larger size facilitates the WBC intrusion by shedding the eddy more easily. Both anticyclonic and cyclonic eddies are able to induce the critical WBC transition from penetration regime to leap regime, and vice versa. The vorticity balance analysis indicates increased (decreased) meridional advection that induces the critical WBC shifting from the eddy shedding (leaping) regime to the leaping (eddy shedding) regime. The meridional size of the island significantly affects the critical WBC transition in terms of the critical strength of the mesoscale eddy. The regime shift from penetration to leap is most sensitive to the eddy upstream of the WBC for small islands and most sensitive to the southern anticyclonic eddy and northern cyclonic eddy for moderate and large islands. It is least sensitive to the central cyclonic eddy for small islands and to the cyclonic eddy upstream of the WBC for moderate and large islands and to the northern anticyclonic eddy regardless of island size. The regime shift from leap to penetration is most sensitive to the cyclonic eddy upstream of the WBC and to the northern anticyclonic eddy. It is least sensitive to the anticyclonic eddy from the south, and the least sensitive location of the cyclonic eddy shifts northward from the gap center as the island size increases.

Experimental and Analytical Study on the Penetration Depth of Mortar Targets Subjected to Projectile Impact in the Hypervelocity Regime

A projectile may be deformed and eroded due to the high pressure generated by hypervelocity penetration, which makes it difficult to describe the penetration mechanism for protection engineering by existing theories at such high velocities. To analyze the penetration depth of concrete-like targets subjected to hypervelocity impact by kinetic energy weapons, experiments with ogive-nosed steel projectiles penetrating mortar targets are conducted, where the average uniaxial compressive strength of the mortar targets is 41.8[Formula: see text]MPa and the impact velocities range from 1[Formula: see text]225[Formula: see text]m/s to 2[Formula: see text]392[Formula: see text]m/s. The experimental results show that the crater diameter and crater depth have a linear relationship with the striking velocity. The depth of penetration (DOP) increases linearly first and then decreases sharply and increases slowly again. Three penetration regimes are observed in turn with increasing velocity, i.e. rigid projectile penetration, abrasive projectile penetration and semifluid projectile penetration. Furthermore, based on a study of the dynamic compression behavior and penetration resistance function of concrete, a hydroelastoplastic-frictional penetration model is established. The velocity range is divided into solid penetration, semifluid penetration and fluid penetration, which correspond to [Formula: see text], [Formula: see text] and [Formula: see text], respectively. Then, the rigid and abrasive projectile penetration models, which consider the projectile mass loss, are verified by the present test data. Finally, the semifluid projectile penetration model is evaluated with the existing test data. These results can provide support for research on the damage effect of hypervelocity kinetic energy weapons and the design of underground strategic protection engineering.

Passage of a rising bubble through a liquid‐liquid interface: A flow map for different regimes

AbstractThe passage of a rising air bubble through a stratified horizontal interface between two Newtonian liquids is studied numerically. A ternary phase‐field model has been utilized for capturing the interface between three immiscible fluids. According to the previous studies, the density, viscosity, and surface tension of the two liquids, in addition to the bubble diameter, are the effective parameters of bubble interaction with the interface. By changing these variables, three main flow patterns are identified in numerical simulations. Penetration flow regime is observed when the bubble enters the upper liquid alone and does not raise the lower liquid. Entrainment flow regime occurs when the bubble lifts some of the heavier liquid to the lighter liquid but still rises alone. If the bubble holds a film of the denser liquid when it rises in the upper liquid, envelopment flow regime takes place. A flow regime map is represented to distinguish the aforementioned flow patterns using Weber and Morton numbers and determine regime transition criteria based on these two dimensionless parameters. For Weber numbers lower than 30, or Morton numbers higher than 1.7 × 10−2, the penetration regime is observed. On the contrary, when the Weber number is higher than 65 and the Morton number is lower than 7 × 10−5, the envelopment regime occurs. The entrainment pattern happens between these ranges and two additional limiting relations of 320Mo0.18 < We < 1500Mo0.23.

Experimental study and visualization of impacting spherical hydrophobic particles on an air – Liquid interface: Newtonian and Boger liquid analysis

The impact of solid particles on gas-liquid interfaces has recently attracted considerable attention due to its numerous applications. In this study, the particle impacts on Newtonian and Non-Newtonian liquid surfaces were investigated. A viscoelastic fluid with constant viscosity was selected as a Non-Newtonian fluid to assess the elastic effect. The critical impact velocity, which is the maximum velocity that the particle would remain on the liquid surfaces, was evaluated. Also, the impact of 3–5 mm spherical hydrophobic particles on the surface of pure water and Boger fluid was experimentally studied. The particle impact onto the fluid interface was captured utilizing a high-speed camera with a rate of 4500 fps. A mathematical model was presented based on the energy balance for predicting the critical velocity. The sequential images of the hydrophobic sphere falling process were analyzed, and the floatation and penetration regimes were observed. The maximum penetration depth, rebound depth, rebound height, and the pinch-off depth were determined for different particle sizes. It was found that, at critical velocities, the particle penetration was associated with oscillatory motions. It was also shown that the increase in particle size would decrease the critical velocity. In addition, the particle velocity and the velocity of the three-phase contact line were analyzed at critical conditions. The mathematical model predictions were compared with the experiments, and good agreement was found.

Resistance of cement-based materials against high-velocity small caliber deformable projectile impact

This paper presents an experimental study on the resistance of cement-based materials across a wide range of compositions and material properties, against the impact of 8.0-mm-diameter, 7.8-g-mass, conical-nosed deformable ASSAB XW-42 steel and copper projectiles at velocities of approximately 400 m/s, in terms of the penetration depth. The cement-based materials investigated include cement pastes, mortars, concretes, engineered cementitious composites (ECCs), and ultra-high performance concretes (UHPCs) with compressive strengths from 37.9 to 229.4 MPa and elastic moduli from 18.7 to 108.8 GPa. For the range of relative characteristic properties between projectile and target considered, the relative effective hardness index (REH) is shown to provide a good characterization of the penetration depth as well as the projectile deformation including relative length change, diameter change, and mass loss. For the deformable penetration regime investigated, two sub-regimes are identified corresponding to a decreasing REH, i.e. regime I with projectile penetration mechanism and regime II with projectile deformation mechanism. It is also found that UHPCs exhibit better impact resistance against deformable projectiles than high performance concretes (HPCs) with granite coarse aggregate, whereas a reversed trend is observed when non-deformable projectiles are considered. The experimental results of this study provide insights into the quick estimation of penetration depth and guidance on the selection of protective materials for practical engineering applications.

Experimental and theoretical study on steel long-rod projectile penetration into concrete targets with elevated impact velocities

To have a better understanding of behaviors of projectiles and concrete targets during impacts at different velocities, experiments and analysis of medium carbon steel long-rod projectiles impact on concrete targets have been carried out in this paper. The impact mechanics of projectiles and concrete targets has been investigated for impact velocities in range of 500 m/s to 1700 m/s covering three penetration regimes. Based on the observation of the residual projectiles and penetration depths, a deforming model has been proposed to investigate the deformable process of projectiles. Furthermore, deforming penetration model was established based on a rigid penetration model and the projectile deformation parameters, which was validated by the experimental results. The applicability of existing eroding penetration models penetration into concrete were validated and discussed based on the experimental results. At last, the eroding penetration model was further justified and improved by taking the deforming penetration regime into consideration. Influence of projectile and target strength on penetration process were investigated based on the theoretical model. Results show that the crater diameter and depth are linearly proportional to the impact velocity, while the volume of the crater and the initial impact kinetic energy of the projectile have a linear relationship. The calculated diameters of residual projectiles and Depth of Penetration (DOP) with a board range of impact velocities are in good agreement with experimental results. It is noted that the strength of projectiles and concrete targets have significantly influences on DOPs and critical velocities.

Laser-based magnetic micro-inscription: Surface heating versus deep penetration regime

The technology of magnetic micro-inscription can be used for in-axis positioning measurements directly from a linear actuator which reduces the cost and size of the whole system. In this paper, two different regimes for laser-based magnetic micro-inscription were compared: a surface heating and a deep penetration heating. The first regime is the same as conductive heating and the second is similar to the process of keyhole welding. The experimental results show that both processes can be effectively stabilized by means of controlling the width and depth of the microstructure transformation cross-section, as they are able to compensate for external disturbances, such as higher roughness, and the gradual accumulation of heat. From numerical analysis it could be seen that the perfect inscription should have depth equal or more than 0.8 of period of inscription and width around 0.80 ± 0.05 of period which is not achievable with the surface heating regime, but only with the deep penetration regime. Results show that the deep penetration heating requires 5-times less laser energy which leads to lower heat accumulation and a more stable process, is unaffected by disturbances, such as higher roughness, and provides an almost 15% higher relative amplitude as measured by the reference magnetic sensor.

Thick plain concrete targets subjected to high speed penetration of 30CrMnSiNi2A steel projectiles: Tests and analyses

In this work, 2 sets of thick plain concrete target penetration tests are carried out with high strength steel alloy projectiles made of 30CrMnSiNi2A whereby the striking velocity ranges from 841 m/s to 1872 m/s. For test 1, 7 shots of ogival nose projectiles with 3.0 calibre radius head as well as 2 shots of double-ogival nose projectiles are comparatively conducted to study the effect of nose shape effect. We adopt 30-mm-diameter projectiles for test 2 to study the higher velocity penetration in concrete. Two penetration regimes including rigid projectile penetration and eroding projectile penetration are observed for this work which are divided by 1402 m/s striking velocity. The target impact surface damage indicates that the crater diameter maintains 0.804 m while the crater depth increases linearly with the striking velocity. Rigid penetration simulations for test 1 are then performed via the recently developed Lattice Discrete Particles Model (LDPM) which is featured with mesoscale constitutive laws governing the interaction between adjacent particles to account for cohesive fracture, strain hardening in compression and compaction due to pore collapse. The penetration numerical model is validated by matching the projectile deceleration curve of shot N1 and predicting the depth of penetration (DOP). By constant velocity penetration simulations, the target resistance R = 406 MPa (Forrestal et al. 2003) is achieved for concrete penetration test 1 scenario. Finally, the equivalent CRH value 3.8 is approximated for the double-ogival nose projectile in this study.

Sea-surface dimethylsulfide (DMS) concentration from satellite data at global and regional scales

Abstract. The marine biogenic gas dimethylsulfide (DMS) modulates climate by enhancing aerosol light scattering and seeding cloud formation. However, the lack of time- and space-resolved estimates of DMS concentration and emission hampers the assessment of its climatic effects. Here we present DMSSAT, a new remote sensing algorithm that relies on macroecological relationships between DMS, its phytoplanktonic precursor dimethylsulfoniopropionate (DMSPt) and plankton light exposure. In the first step, planktonic DMSPt is estimated from satellite-retrieved chlorophyll a and the light penetration regime as described in a previous study (Galí et al., 2015). In the second step, DMS is estimated as a function of DMSPt and photosynthetically available radiation (PAR) at the sea surface with an equation of the form: log10DMS=α+βlog10DMSPt+γPAR. The two-step DMSSAT algorithm is computationally light and can be optimized for global and regional scales. Validation at the global scale indicates that DMSSAT has better skill than previous algorithms and reproduces the main climatological features of DMS seasonality across contrasting biomes. The main shortcomings of the global-scale optimized algorithm are related to (i) regional biases in remotely sensed chlorophyll (which cause underestimation of DMS in the Southern Ocean) and (ii) the inability to reproduce high DMS ∕ DMSPt ratios in late summer and fall in specific regions (which suggests the need to account for additional DMS drivers). Our work also highlights the shortcomings of interpolated DMS climatologies, caused by sparse and biased in situ sampling. Time series derived from MODIS-Aqua in the subpolar North Atlantic between 2003 and 2016 show wide interannual variability in the magnitude and timing of the annual DMS peak(s), demonstrating the need to move beyond the classical climatological view. By providing synoptic time series of DMS emission, DMSSAT can leverage atmospheric chemistry and climate models and advance our understanding of plankton–aerosol–cloud interactions in the context of global change.

Optical and Chemical Monitoring during Foil Penetration Experiments to Study Intergranular Corrosion in AA2024

A modified version of the foil penetration technique based on an optical detection of the full penetrating intergranular defects through thin foils was applied to AA2024 samples of various thicknesses in contact with a dilute chloride solution. As the rear side of the foil was free during the experiments, it was straightforward to measure the pH of the electrolyte trapped inside the grain boundary network leaking through the emerging defects on the rear side of the foils. The penetration regime in the longitudinal direction was determined for various exposure and electrochemical conditions confirming the decrease of the propagation kinetics as function of the depth of the intergranular defects. pH measurements were used to support mass transport simulation inside a pore electrode mimicking the propagation of the anodic head of grain boundaries. After validation under potentiostatic conditions, the same modelling approach was applied under free corrosion conditions, to discuss the location of cathodic areas during immersion and droplet exposures.

Penetration of confined ceramics targets

We have investigated the penetration response of confined ceramic targets impacted by Tungsten long-rod projectiles in the so-called Lundberg test setup with the ceramic modelled using a mechanism-based constitutive model. The calculations accurately predict the three observed penetration regimes, viz. interface defeat, dwell followed by penetration and penetration with no/short dwell. More importantly, the calculations suggest that these regimes occur in both a ceramic target and a reference target where microcracking of the ceramic is artificially switched off. This is because penetration occurs by a spherical cavity expansion mechanism with the onset of continued penetration set by the attainment of either a critical size of a plastic or damage zone. The dwell time then correlates with the time required to establish this inelastic zone. The main influence of damage is to reduce the pressure required to setup this critical inelastic zone and thereby reduce the interface defeat velocity as well as increase the penetration rate for a given velocity above the interface defeat velocity. We further show that an increase in the downward force due to the backflow of the deforming impactor is not essential for a dwell regime to exist. The mechanism-based ceramic model includes three material length scales and we demonstrate that the penetration size effect reported in experiments is primarily associated with the length scale associated with rate dependent lattice plasticity and the critical size of the comminuted zone that is required to trigger granular flow. The material model is also used to probe the dependence of material properties such as strength and toughness on the penetration resistance. Two regimes of penetration, viz. a plasticity-dominated and a microcracking-dominated regime emerge from the calculations. These predictions suggest that increasing the strength rather than toughness of the Corbit-98 Alumina will have a greater beneficial influence on its penetration performance.

Wavelength Dependence of Light-Induced Cycloadditions.

The wavelength-dependent conversion of two rapid photoinduced ligation reactions, i.e., the light activation of o-methylbenzaldehydes, leading to the formation of reactive o-quinodimethanes (photoenols), and the photolysis of 2,5-diphenyltetrazoles, affording highly reactive nitrile imines, is probed via a monochromatic wavelength scan at constant photon count. The transient species are trapped by cycloaddition with N-ethylmaleimide, and the reactions are traced by high resolution mass spectrometry and nuclear magnetic resonance spectroscopy. The resulting action plots are assessed in the context of Beer-Lambert's law and provide combined with time-dependent density functional theory and multireference calculations an in-depth understanding of the underpinning mechanistic processes, including conical intersections. The π → π* transition of the carbonyl group of the o-methylbenzaldehyde correlates with a highly efficient conversion to the cycloadduct, showing no significant wavelength dependence, while conversion following the n → π* transition proceeds markedly less efficient at longer wavelengths. The influence of absorbance and reactivity has critical consequences for an effective reaction design: At high concentrations of o-methylbenzaldehydes (c = 8 mmol L-1), photoligations with N-ethylmaleimide (possible for λ ≤ 390 nm) are ideally performed at 330 nm, whereas at high light penetration regimes at lower concentrations (c = 0.3 mmol L-1), 315 nm irradiation leads to the highest conversion. Activation and trapping of 2,5-diphenyltetrazoles (possible for λ ≤ 322 nm) proceeds best at a wavelength shorter than 295 nm, irrespective of concentration.

Hemispherical nosed steel projectile high-speed penetration into aluminum target

Terminal ballistic performance of high-strength projectiles penetrating into metallic targets is mostly concerned by both weapon and armor designers. Most existing works are concentrated on the rigid-eroding penetration regime, and limited studies have addressed the rigid-deforming-eroding penetration regime. In this paper, nineteen shots of hemispherical nosed D6A steel projectiles penetration test on 5A06-H112 aluminum targets is conducted with a wide range of velocities (696m/s–1870m/s). The non-monotonic dependence of depth of penetration (DOP) on the impact velocity is observed, which successively corresponds to the three penetration stages, i.e., rigid projectile penetration, deforming projectile penetration without eroding and eroding projectile penetration. Then, for the non-monotonic rigid-deforming-eroding projectile penetration regime, the applicability of the existing six classical theoretical models for both rigid and eroding projectile penetrations is evaluated. Furthermore, the transition velocities (the upper limit of rigid penetration and the lower limit of eroding penetration) are discussed and an empirical judgement criterion for the occurrence of non-monotonic dependence is proposed. Finally, by conducting the dynamic compression test, quasi-static tension test under varying temperature, etc., the Johnson-Cook model parameters for the present target and projectile are calibrated and validated by numerically simulating the present test.

Universal weighted synthetic aperture focusing technique (W-SAFT) for scanning optoacoustic microscopy

Optoacoustic microscopy (OAM) is a hybrid imaging method that can achieve high spatial resolution at superficial depths through use of focused illumination; it can be adapted for imaging with ultrasonic resolution at much greater depths where the excitation light is diffuse. These two distinct modes of operation can be further combined to create a highly scalable technique that can image at multiple penetration scales by gradually exchanging microscopic optical resolution in superficial tissue layers with ultrasonic resolution at diffuse (macroscopic) depths. However, OAM commonly employs scanning acquisition geometries that impede the effective use of synthetic aperture focusing techniques due to varying illumination patterns and non-uniformity of the excitation light field. Here we present a universal framework for scanning optoacoustic microscopy that uses a weighted synthetic aperture focusing technique (W-SAFT) to create a uniform imaging sensitivity across microscopic, mesoscopic, and macroscopic penetration regimes. Robust performance of the new multi-scale reconstruction methodology is showcased with simulations and synthetic phantoms, and validated with experimental data acquired from a highly scattering juvenile zebrafish specimen. It is shown that consideration of the light fluence is vital for maintaining the optically dictated lateral resolution at ballistic depths while optimizing the resolution of out-of-focus ultrasonic data; additionally, the dynamic-range compression facilitates the visualization across the entire imaged volume. The newly introduced W-SAFT reconstruction framework is universally applicable to a wide palette of scanning-based optoacoustic imaging techniques employing non-uniform and/or varying illumination, such as acoustic resolution and hybrid focus microscopy, raster-scan optoacoustic mesoscopy, as well as tomographic approaches using scanning of focused array transducers.

Mechanism to remove oxide inclusions from molten aluminum by solid fluxes refining method

A novel flux charging method and a crucible quenching method were employed to study the mechanism of solid fluxes refining method regarding the removal of oxide inclusions (Al2O3) from molten aluminum. Electrochemical polishing method was adopted to prepare surfaces of the samples. Through experiments, the morphology of the residual solidified flux in the solidified samples as well as the wetting action of the molten flux during refining were observed for the first time. Three wetting regimes denoted by absorbing regime, engulfing regime and penetration regime correlating with the removal of oxide films (the most typical and common oxide inclusions in molten aluminum) were proposed in terms of different types and distributions of oxide films and different size ratios of the molten flux to oxide films. Particularly, from a thermodynamic point of view, for the first time, the penetration regime provided concrete evidence that the practical oxide inclusions can be wet by molten flux under ambient fluid of molten aluminum. A spreading model was proposed, according to which ingredients and size parameters of practical solid fluxes can be optimized.

Stability of tungsten projectiles penetrating adobe masonry – Combined experimental and numerical analysis

We investigate the penetration of tungsten-heavy-alloy projectiles into adobe targets. The analysis rests on two complementary parts. Firstly, experimental data comprising impact experiments with five different projectile variants against finite-thickness adobe targets is available. Although the data stems from earlier work, it is presented in full detail here for the first time. The general phenomenology is discussed mainly with respect to projectile failure and stability of the penetration in adobe. Secondly, a recently published hydrocode model for adobe under impact loading is applied without further modification for complementing the experimental results with additional time-resolved insight into the penetration mechanics. For the regime without projectile failure or significant plastic deformation, this hydrocode model is capable of reproducing the experimentally observed projectile-target interaction with good overall agreement between experiments and simulation. While the test data covers different penetration regimes from rigid-body motion to projectile failure, the numerical analysis is restricted to linear-elastic behavior of the impactors, in order to avoid any ambiguity due to the less established projectile material description. With the information from the hydrocode simulations, we are able to reveal the origin of the projectile-specific magnitude of instability in the penetration in adobe. The thereby achieved understanding of the motion of the differently shaped impactors within the formed cavity allows us to discuss possible explanations for the particular projectile failure observed in the experimental data.