Penetration Hole Research Articles

Research on combined damage characteristics of underwater armor-piercing and explosion based on supercavitating projectile

Recent studies of supercavitating projectiles primarily focus on the formation and evolution of the cavity, as well as its underwater ballistic characteristics, while neglecting the terminal damage effects. Little attention has been given to exploring the combined damage effects of armor-piercing-explosion supercavitating projectiles (APESP). Therefore, this study comparatively analyzes the response processes and failure modes of an underwater aluminum alloy cylindrical shell target under the action of three different types of loads: armor piercing, explosion, and combined armor-piercing and explosion. This study investigates the underwater combined damage mechanisms of the APESP, clarifies each damage phase under the combined effect, discusses the advantages of damage resulting from the combined armor-piercing and explosion effect based on the target responses and damage modes, and explores the reasons for dissipation of explosion energy. The results show that: the APESP combines localized point damage characteristics of armor piercing with overall surface damage features of underwater explosion. Depending on load stages and target responses, the target response process under the action of the APESP can be divided into the hydrodynamic ram phase, penetration phase, shock wave phase, stable vibration phase, and bubble pulsation phase. The entire physical system can be abstracted as a low-frequency series spring system (equivalent to bubble pulsation frequency) with high-frequency external energy input, based on the energy relationship of the medium and the structure. The concept of the 'blower effect' is proposed based on target behavior during the stable vibration phase. Following the application of different loads, the plastic deformation of the target in a stable state is ranked as: underwater explosion > combined armor-piercing and explosion > underwater armor piercing. Supercavity, shell casing and penetration hole will cause the dissipation of explosion energy.

Characteristics of Penetration Strength and Fracture Features under Nonuniform Stress Field around Borehole Surrounding Rock.

In the process of mining coal energy, the excavation of roadways and drilling causes the formation of a nonuniform stress field around the penetration holes, which will lead to a significant concentration of stress around the penetration hole. It even leads to the destruction of the surrounding rock of the penetration hole, affecting the integrity of the surrounding rock of the penetration hole. It has an effect on the strength of the rock obtained by the borehole penetration methods. Based on Abaqus software, the numerical model of borehole penetration was constructed by embedding cohesion elements between solid elements. After analyzing the simulation results obtained under different stress boundaries and penetration directions, the following findings are obtained. (1) Using the occurrence of cracks in the borehole surrounding rock as the criterion, the rock is categorized into either an elastic stress state or a plastic stress state after applying different stress boundary conditions. (2) When the borehole surrounding rock is in the elastic (plastic) stress state, the penetration strength increases (decreases) with the increase of lateral pressure coefficient. (3) In the elastic stress state, borehole surrounding rock's fracture area and crack penetration depth increase (decrease) with the increase of lateral pressure coefficient when the penetration direction is parallel (perpendicular) to the maximum principal stress. In the plastic stress state, the fracture area increases, while crack penetration depth decreases with higher lateral pressure coefficient.

An improved multi-frequency eddy current array sensor for detecting micro-defects of welding seam in metal plates

This study proposes an improved multi-frequency eddy current array sensor for the accurate detection of micro-defects (under-welding, over-welding, partial welding breakage, and minute penetration holes) of welding seam in metal plates. The primary goal is to further reduce the external and internal noise of the induced coil by optimizing the composition structure of the eddy current probe, thereby improving its sensitivity and signal-to-noise ratio in micro-defect detection. In response to the issue of external noise, this research introduces a gradient differential coil model, which can compensate for initial errors based on a geometrically balanced structure. By establishing a 3D simulation model and a physical mechanical structure, the suppression effect of this structure on excitation magnetic field and external environmental interference is verified. Furthermore, for the internal noise, a mathematical model of the direct stranded litz wire is established. Theoretical calculations and experimental validation confirm that the litz wire exhibits lower eddy current loss and higher Q value compared to traditional copper conductors, thus mitigating internal noise and improving signal-to-noise ratio. On this basis, the excitation mode of the eddy current coil probe array is set to a multi-frequency excitation method based on a center frequency, greatly reducing the electromagnetic interference between channels. Experimental results demonstrate that the improved eddy current sensor can effectively recognize as low as Φ1 mm weld penetration defect at a lift-off value of 0.5 mm, achieving a remarkably high signal-to-noise ratio of approximately 17.7 dB.

The relationship of the male's proctodeal gland size to sperm-egg interaction and the duration of fertility in Japanese quail

In avian species, male fertility significantly impacts reproductive success. This study investigates the relationship between proctodeal gland size in male Japanese quails and sperm function, as well as female fertility duration. Six hundred adult Japanese quails were selected and housed in individual cages. Males (n = 300) were divided into 6 groups (50/group) based on the size of their proctodeal glands. Females (n = 300) were randomly assigned to corresponding groups. After acclimatization, sperm kinematics and the frequency and weight of foam discharge were evaluated. Males were paired with females for 24 h, and eggs were collected for 20 d postcopulation. Eggs were incubated to assess fertility duration. Fresh eggs (n = 20/group/d) were used to assess sperm penetration into the perivitelline membrane on the 2nd, 9th, and 16th d postinsemination. Plasma testosterone levels and the testes' relative weight were determined. The results indicated a significant increase (p < 0.0001) in sperm concentration, total and progressive motility, and nearly all sperm kinematic parameters such as VSL, VCL, VAP, LIN, WOB, and STR values as the size of the proctodeal gland increased. Quails copulated with males having a small and average proctodeal gland area (<400 mm2) laid fertile eggs for a shorter period and had significantly fewer sperm penetration holes than those mated with males having a larger proctodeal gland area (>400 mm2). The proctodeal gland size was positively correlated with testicular weight, plasma testosterone concentrations, and sperm kinetic variables. The results indicate that the size of the proctodeal gland in males can be used to predict sperm function and the duration of fertility in Japanese quail.

An investigation on the jet formation and penetration characteristics of the CuCoCrFeNi high-entropy alloy liner

This study performs a series of mechanical tests, quasi-static and dynamic, on CuCoCrFeNi high-entropy alloys (HEAs) using an experimental setup to explore the performance of Cu-based HEAs in shaped charges. It derives the parameters for the Johnson–Cook constitutive model through fitting. A static penetration test is conducted with a small cone angle and a thin-walled liner. The outcomes are then compared to simulation data generated by AUTODYN software. They indicated that the CuCoCrFeNi HEA liner can produce a shaped-charge jet that achieves both penetration and reaming effects when driven by explosives. In a C45 steel target, the diameter of the penetration hole is 46.43% of the charge diameter. The experimental findings align closely with the simulations, indicating discrepancies of less than 12.13% in the diameters of the penetration holes and ∼2.56% in penetration depths. Hence, the numerical simulation approach and its parameters can be utilized to investigate the penetration characteristics of Cu-based HEA jets, providing a groundwork for future optimization of HEA-shaped charge designs.

Failure analysis of leaking firefighting pipeline used in nuclear power plant: Corrosion development process and key influence factors

A penetrating hole has been found in the inner wall of the firefighting pipeline (A106 steel) used for 20 years in a nuclear power plant of China, and the pipeline is filled with almost stagnant tap water before failure. The failed pipeline is taken from a vertically placed water outlet pipeline. The corrosion process and key influence factors of the failed firefighting pipeline were studied using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that there exist two typical corrosion characteristics on the inner wall of the failed pipeline besides leakage hole, that is, corrosion nodulation and corrosion bulge. The corrosion nodulation, mainly consisting of a mixture of calcium and iron oxides, is the initiation position of perforation corrosion, and the iron-oxidizing bacteria (IOB) play a key role in the formation of corrosion nodulation. Then the sulfate-reducing bacteria (SRB) is involved in the propagation of corrosion nodulation when the dissolved oxygen concentration is low. The corrosion nodulation gradually become loose and form large bulge with extended service time. The corrosion pits under the corrosion bulge also develop gradually. Eventually, the inner wall of the pipeline is thinned and perforated.

Dynamic Response Characteristics of Composite Concrete Structures Subjected to Reactive Jet Impact

Composite concrete structures, commonly found in urban infrastructures, such as highways and runways, are pivotal research object in the protection field. To study the dynamic response of composite concrete structures subjected to reactive jet penetration coupled with an explosive effect, a full-scale damage experiment of composite structures under the action of 150 mm caliber shaped charges was performed, to derive the dynamic damage modes of different concrete thicknesses under the combined kinetic and chemical energy damage effects. The results indicated that under aluminum jet penetration, concrete layers exhibited minor funnel craters and penetration holes. However, concrete layers displayed a variety of damage modes, including central penetration holes, funnel craters, bulges, and radial/circumferential cracks when subjected to the PTFE/Al jet. The area of the funnel crater expanded as the thickness of the concrete increased, while the height of the bulge and the number of radial cracks decreased. The diameter of penetration holes increased by 76.9% and the area of funnel crater increased by 578% in comparison to Al jet penetration damage. A modified-RHT concrete model that reflected concrete tensile failure was established, utilizing AUTODYN. Segmented numerical simulations of damage behavior were performed using the FEM-SPH algorithm and a restart approach combined with reactive jet characteristics. The spatial distribution characteristic of the reactive jet and the relationship between kinetic penetration and explosion-enhanced damage were obtained by the simulation, which showed good concordance with the experimental results. This study provides important reference data and a theoretical basis for the design of composite concrete structures to resist penetration and explosion.

Dermal tissue penetration of in-plane silicon microneedles evaluated in skin-simulating hydrogel, rat skin and porcine skin

Recently, microneedle-based sensors have been introduced as novel strategy for in situ monitoring of biomarkers in the skin. Here, in-plane silicon microneedles with different dimensions and shapes are fabricated and their ability to penetrate skin is evaluated. Arrays with flat, triangular, hypodermic, lancet and pencil-shaped microneedles, with lengths of 500–1000 μm, widths of 200–400 μm and thickness of 180–500 μm are considered. Fracture force is higher than 20 N for all microneedle arrays (MNA) confirming a high mechanical stability of the microneedles. Penetration force in skin-simulating hydrogels, excised rat abdominal skin and porcine ear skin is at least five times lower than the fracture force for all MNA designs. The lowest force for skin penetration is required for triangular microneedles with a low width and thickness. Skin tissue staining and histological analysis of rat abdominal skin and porcine ear skin confirm successful penetration of the epidermis for all MNA designs. However, the penetration depth is between 100 and 300 μm, which is considerably lower than the microneedle length. Tissue damage estimated by visual analysis of the penetration hole is smallest for triangular microneedles. Penetration ability and tissue damage are compared to the skin prick test (SPT) needle applied in allergy testing.

An injectable, robust double network adhesive hydrogel for efficient, real-time hemostatic sealing

Despite significant progress in bioadhesive hydrogels, achieving injectable adhesives with robust mechanical strength, strong wet-tissue adhesion and anti-postoperative tissue adhesion is challenging. Herein, an injectable double network adhesive hydrogel (DNAH) consisting of catechol-branched polyacrylamide network formed by radical polymerization and chitosan-oxidized hyaluronic acid covalent network produced by Schiff base condensation is reported. Benefiting from the catechol groups, chemically crosslinked network, a tough dissipative matrix, as well as dynamic oxidation of catechol to quinone, DNAH exhibits high mechanical strength, robust wet-adhesiveness, and postoperative anti-adhesion after injection. Combining the above ideal features with their good injectability and shape-adaptability to complex wound contours, DNAH can coagulate instantaneously in situ and firmly glue to the tissue surface to seal the wounds in rat models of cardiac penetration holes and portal vein injuries, achieving efficient hemostasis. Overall, DNAH developed in this work is demonstrated to be a promising candidate for rapid hemostasis in clinic.

Numerical simulation of reactive composite jet penetrating concrete target

In order to allow more reactive material to enter the penetration hole when the initiation delay time of reactive material arrives, a double-layered liner structure with inner and outer liners of unequal height is designed. The outer liner is polytetrafluoroethylene/aluminum (PTFE/AL) reactive material, and the inner liner is metal material. The AUTODYN software were used to study the effects of height ratio α of the inner and outer liners and inner liner material on the reactive composite jet forming and penetrating C35 concrete target. The results show that when α varies, the composite liner forms a reactive composite jet composed of different materials at the head. When α is 4/5, the composite jet can both cause a large penetration depth on the target plate and allow more reactive material to enter the penetration hole. When the material of inner liner is titanium, almost all the reactive material follows the metal precursor penetrator into the penetration hole, which can significantly exert the combined damage effect of penetration and demolition.

Study on jet formation and penetration performance of shaped charge with untypical double-cone titanium liner

Based on the platform of AUTODYN-2D code, the shaped charge with untypical double-cone titanium liner penetrating concrete targets are investigated. The influence of the titanium liner thickness and the height ratio of top cone on the jet tip-velocity and jet characteristics are analyzed. The titanium liner thickness, the height ratio of top cone, and the standoff affecting on the penetration performance of the concrete targets are also conducted. The numerical simulations indicated that, with increasing the titanium liner thickness, the jet tip-velocity gradually decreased, and the penetration depth of the concrete targets first increased and then decreased. When the height ratio of top cone was 0.5, the shaped charge with untypical double-cone titanium liner can combine the advantage of the small cone-angle liner and the large cone-angle liner, which will ensure the sufficient penetration depth and hole diameter. Furthermore, the shaped charge with untypical double-cone titanium liner can penetrate the concrete with a thickness of 1000mm at the standoff within a region between 2.0 CD and 2.5 CD.

Explosion resistance performance of reinforced concrete box girder coated with polyurea: Model test and numerical simulation

To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder, two segmental girder specimens were made at a scale of 1:3, numbered as G (without polyurea coating) and PCG (with polyurea coating). The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests. The reliability of the numerical simulation using LS-DYNA software was verified by the test results. The effects of different scaled distances, reinforcement ratios, concrete strengths, coating thicknesses and ranges of polyurea were studied. The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder. The top plate of middle chamber in specimen G forms an elliptical penetrating hole, while that in specimen PCG only shows a very slight local dent. The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%, respectively, compared with those of specimen G. For the TNT explosion with small equivalent, the polyurea coating has a more significant protective effect on reducing the size of fracture. With the increase of TNT equivalent, the protective effect of polyurea on reducing girder displacement becomes more significant. The optimal reinforcement ratio, concrete strength, thickness and range of polyurea coating were also drawn.

Damage Monitoring of Braided Composites Using CNT Yarn Sensor Based on Artificial Fish Swarm Algorithm.

This study aims to enable intelligent structural health monitoring of internal damage in aerospace structural components, providing a crucial means of assuring safety and reliability in the aerospace field. To address the limitations and assumptions of traditional monitoring methods, carbon nanotube (CNT) yarn sensors are used as key elements. These sensors are woven with carbon fiber yarns using a three-dimensional six-way braiding process and cured with resin composites. To optimize the sensor configuration, an artificial fish swarm algorithm (AFSA) is introduced, simulating the foraging behavior of fish to determine the best position and number of CNT yarn sensors. Experimental simulations are conducted on 3D braided composites of varying sizes, including penetration hole damage, line damage, and folded wire-mounted damage, to analyze the changes in the resistance data of carbon nanosensors within the damaged material. The results demonstrate that the optimized configuration of CNT yarn sensors based on AFSA is suitable for damage monitoring in 3D woven composites. The experimental positioning errors range from 0.224 to 0.510 mm, with all error values being less than 1 mm, thus achieving minimum sensor coverage for a maximum area. This result not only effectively reduces the cost of the monitoring system, but also improves the accuracy and reliability of the monitoring process.

Rapid positioning test method for cylindrical structure penetration based on machine learning

Focusing on the requirements of rapid damage location test for multi-layer steel plates penetration of cylindrical structure in the complex and harsh environment, this paper studies the propagation characteristics of high-speed impact stress waves in steel plates. Also, the measurement effects of impact stress in the near zone of penetration hole are compared with different sensors, so as to select appropriate PZT sensors to measure the velocity of impact stress wave in the actual steel plates. Then the array layout scheme is designed, and the corresponding damage location algorithm is determined. Finally, the deep learning algorithm is used to improve the accuracy and efficiency of damage location.

Anatomic Risks with Overpenetration of the Volar Locking Plates' Proximal Holes.

Background Volar locking plate fixation (VLP) is commonly used to treat distal radius fractures (DRF). Risk of dorsal compartment injury with distal screw hole fixation has been studied; however, the risk with proximal screw hole fixation is not well studied. Purpose The goal of this study was to investigate the risk of dorsal structure injury from the screw holes proximal to the two distal rows. Methods Nine cadaveric forearms were used. After volar distal radius exposure, a long VLP was applied. Kirschner wires were placed through the most proximal holes into the dorsal compartments. The extensor structures penetrated were noted and tagged with hemoclips. The distance from the dorsal cortex to the structures was measured. Results The abductor pollicis longus (APL) and extensor pollicis brevis (EPB) muscle bodies were only penetrated; no tendons were penetrated. Proportion of muscle penetration increased with the more proximal screw holes. EPB was more likely to be penetrated distally and APL proximally; both were injured at holes 2 and 3. The extensors were 2 mm from the dorsal cortex of the radius on average; this did not decrease with compression of the forearm. Conclusions This is the first study to examine the anatomic risk of extensor structure injury with VLP proximal screw hole penetration. No extensor tendons were penetrated by these proximal screw holes; first dorsal compartment muscle bellies may be irritated with overpenetration. Our findings suggest that proximal VLP screws do not need to be downsized if they are not over 2 mm prominent.

Simulation and Experimental Study on Jetting Projectile Charge Penetrating Multi-Layer Spaced Targets with Large Spacing

To study the ability of shaped charges to penetrate typical ship targets, two shaped charges with the same diameter of 200 mm but different configurations are designed to generate two forms of jetting projectile charge (JPC). Based on the protective structure of typical ship targets, static penetration tests are performed using the two types of a shaped charge with copper liner and 10-layer spaced targets with a total span of 16 m which is made in 921A steel. Numerical simulations under the same working conditions are also carried out. It is found that the simulation results of the penetration depth and the number of layers of target perforated by the JPC are much greater than the experimental results. In fact, the JPC breaks up when moving to a certain distance, and the JPC segments after breakup have a transverse drift velocity, causing the segment to deviate from the original penetrating channel. The influence of drift velocity after JPC fracture cannot be considered in numerical simulation, resulting in significant differences between numerical simulation and experimental results. Thus, this paper proposed a segment-based numerical simulation method and analyzed the penetration process of JPC fragments after JPC fracture. Combined with experimental results, the radial motion after JPC fracture and the final distribution of penetration holes can be well revealed. It is found that the penetration depth and the number of layers of target perforated by the JPC depend on the tip velocity of each segment and the jet length.

Numerical Simulations of Reactive Material Double-Layered Liner Shaped Charge Penetrating Steel Target

The jet formation and penetration behaviors of shaped charge with a reactive material double-layered liner (RM-DLL) are presented in this paper based on the AUTODYN-2D code. Numerical results show that the wall thickness ratio of the RM-liner to the metal liner has a significant influence on the formation and penetration characteristics of composite jet. As the wall thickness ratio increases, the tip velocity of composite jet, the pressure on the RM-liner, and the temperature of RM-elements decrease. The effect of the wall thickness ratio on the penetration performance of RM-DLL shaped charges against steel targets significantly depends on the RM-initiation delay time (τ). The penetration depth (PD) of the composite jet with titanium liner into the steel target is limited. In the case of the RM-tungsten liner, the RM-mass following into the penetration crater is very small. In the case of the RM-copper liner, the penetration capability of composite jet is well matched with the mass of follow-thru RMs. Compared with the PD, the standoff has a more significant impact on the RM-mass entering the penetration hole.

Evaluation of Projectile Penetration Position on Perforated Plate on Ballistic Resistance of Composite Sandwich Panels

This paper evaluates the performance of perforated plates in composite sandwich panel under high-velocity impact. The ballistic resistance of composite sandwich panels made of steel plate on the outer layer and the rubber on the middle layer was evaluated using experimental and numerical methods. The front plate is modified with 3 mm diameter of holes, and the distance between the holes is 10 mm. Experimental testing was carried out by firing a 9 mm full metal jacket projectile at a distance of 5 m and an angle of attack of 90° on the target. Experimental results and numerical simulations show that the position of the projectile penetration at the side of the hole in the composite panel stops the projectile velocity faster at 1.1619 x 10−4 s with a maximum energy absorption of 532.9 J than at center of hole and middle of four holes. The failure of the side of the hole penetration position is the asymmetrical deformation of the back plate due to changes in the penetration position of the projectile with the initial trajectory, fractural projectile core and brass jacket projectile erosion. The projectile penetrates the front plate due to plastic deformation, and rubber in the middle layer is pushed and perforated in the projectile direction, causing the back plate to form a bulge.

Study on Perforation Behavior of PTFE/Al Reactive Material Composite Jet Impacting Steel Target

To study the penetration and cratering effect of reactive material composite jets, a series of experiments are carried out for the shaped charge (SC) with different composite liners damaging steel targets. The inner layer of composite liners is metal and the outer one is a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material. Copper (Cu), titanium (Ti) and Al inner liners are used in this paper. The reactive material liner is composed of 73.5 wt.% PTFE and 26.5 wt.% Al powder through mass-matched ratios. Reactive material composite liners are prepared through machining, cold pressing and a sintering process. The SC mainly consists of a case, a composite liner, high-energy explosive and an initiator. The steel target is steel 45#, with a thickness of 66 mm. A standoff of 1.0 CD (charge diameter) is selected to conduct the penetration experiments. The experimental results show that when the inner layer of the composite liner is composed of Ti and Al, the hole diameters on the steel target formed by the reactive material composite jet are significantly larger than that of the inner Cu liner. By introducing the initiation delay time (τ) and detonation-like reaction model of PTFE/Al reactive materials, an integrated numerical simulation algorithm of the penetration and detonation-like effects of reactive material composite jets is realized. Numerical simulations demonstrate that the initial penetration holes on the steel targets are enlarged under the detonation-like effects of PTFE/Al reactive materials, and the simulated perforation sizes are in good agreement with the experimental results.

Study on Penetration Behavior of the Reactive Material Composite Jet against Concrete

To improve the damage performance of the shaped charge when damaging the concrete target, a new structure of shaped charge with reactive material composite liner was proposed. The behavior of reactive material composite liner-shaped charge penetrating the concrete target was researched by numerical simulation in the finite element simulation platform Autodyn-2D. The effects of the ratio of liner diameter and the ratio of the liner thickness of the inner liner to the composite liner on the penetration depth, hole diameter, and the following behavior of reactive materials were obtained. Numerical simulations show that, with increasing the liner diameter ratio and the liner thickness ratio, the penetration depth and hole diameter of the composite jet into concrete first increase and then gradually decrease. However, the increase of the liner diameter ratio and thickness ratio also means a decrease in the reactive materials’ total mass, which will significantly affect the following reactive materials into the penetration hole. Simulated results further show that it is better to find out that the liner diameter ratio is 0.7 and the liner thickness ratio is 0.2~0.4. The penetration depth and hole diameter of the composite jet into the concrete match well with the quality of the following reactive materials.