Front Face Research Articles

Experimental evaluation of the short and long fatigue crack growth rate of S355 structural steel offshore monopile weldments in air and synthetic seawater

Welded steel structures used in the offshore wind industry are exposed to harsh marine environments, which can result in corrosion-induced fatigue damage. Of particular concern is the heat affected zone (HAZ) of welded joints, a region known for its altered microstructure and mechanical properties, which can significantly influence the initiation and propagation of fatigue cracks. This study investigates the short and long fatigue crack growth rates, and the effect of seawater exposure, for the HAZ in S355 steel weldments. Single-edge notch bend (SENB) specimens are used, with a shallow notch in the HAZ. A series of specimens is immersed in synthetic seawater that is continuously circulated at a controlled temperature to assess the synergistic effects of corrosion and fatigue. The experimental method integrates a novel application of front face strain compliance for monitoring short cracks, alongside an extended back-face strain compliance approach for monitoring long crack propagation. It is concluded that the short fatigue crack growth rate of the HAZ is 2.7 to 3.5 times higher in seawater as compared to air. As the crack propagates and enters into the long crack regime, the ratio decreases to 2.2 times at the transition point of the two-stage crack growth curve and further decreases to 1.5 times when the notch advances towards fracture. The findings indicate that the fatigue crack growth rates documented in standards tend to be on the conservative side. This study significantly enriches the fatigue crack growth data available in literature, which will contribute to a more accurate lifetime assessment offshore wind turbine structures.

Deformation of vegetated channel bed under ice-covered flow conditions

A common feature of cold regions is the presence of ice cover on water surface. In the presence of vegetation in the channel bed which is normally leafless in winter, interaction between river ice and vegetated channel bed becomes very complex. In the present study, the impacts of ice cover and submerged leafless vegetation on channel bed deformation and flow resistance have been investigated based on 144 experiments conducted in a large-scale outdoor flume. The independent variables associated with the maximum scour depth around vegetation elements have been assessed and equations have been developed. Results indicate that the most important variable affecting the maximum scour depth around vegetation under ice-covered flow conditions is the ratio of the ice cover roughness to the bed roughness (ni/nb). However, under open channel flow conditions, the flow Froude number is the most important variable influencing the maximum scour depth. The methods based on the law of the wall provide reliable Manning's coefficient for both smooth and rough ice covers in the presence of submerged vegetation in the channel bed. As the vegetation density increases, the size of scour holes becomes smaller. With the increase in vegetation density, the median grain size of the armour layer in scour holes decreases correspondingly. When vegetation elements are placed in a staggered configuration, the median grain size of the armour layer in scour holes is less than that of squared configuration of vegetation elements. Regardless of the roughness of ice cover on water surface and the grain size of sediment in the bed, the maximum depth of scour holes always occurs at the upstream front face of each vegetation element. Under the rough ice-covered flow condition, the maximum depth of scour holes is more than that under the smooth ice-covered and open flow conditions.

Form generative approach for front face design of electric vehicle under female aesthetic preferences

Vehicles are the most representative product of both transportation and industry. Fueled by the growing popularity of energy-saving and environmentally friendly ideas and policies, new energy technologies and their supporting industries are experiencing constant development and refinement. As a result, electric vehicles (EVs) are steadily displacing traditional fuel-powered vehicles as the dominant force in the vehicle market. The experience economy is driving a significant shift in the direction of EV development, which is transitioning from improving functionality to optimizing the emotional connection consumers have with their vehicles. This means the form factor of the vehicle itself is becoming a key element in attracting consumers and influencing purchasing decisions. Over half of China's EV consumer market is comprised of females. However, many companies continue to develop products solely from a male perspective, missing out on a vast market opportunity. Therefore, incorporating design elements that cater to female aesthetic preferences into EVs can undoubtedly play a crucial role in unlocking this significant segment of the market. Based on this, the paper proposes a form generative design approach that specifically caters to the preferences of female consumers within the theoretical framework of Kansei engineering.The research process begins by obtaining Kansei imagery through the collection and analysis of big data. Subsequently, eye-tracking experiments are conducted to define the key design elements of the automobiles. Concurrently, appropriate aesthetic measurement indicator (AMI) system is established. Next, AMI values are computed for the sample set. This data is then leveraged to create a mapping relationship with the Kansei imagery, enabling the objective reflection of subjective aesthetic evaluations. Finally, an integrated Kansei evaluation equation serves as the fitness function within a generative approach that utilizes genetic algorithms and visual AI to produce form design solutions for electric vehicles. The evaluation confirms that the proposed design approach successfully generates a substantial number of high-quality creative solutions that align with female aesthetic preferences, while maintaining low cost and high efficiency.

Parametric analysis of the flow past a square cylinder in the interface of two different-velocity streams

We address the linear stability of the two-dimensional incompressible flow past a square cylinder immersed in the wake of an upstream splitter plate, which separates two streams of different velocities, UT (top) and UB (bottom), to three-dimensional perturbations. The analysis is done in the so-called wake transition regime, across which two-dimensional vortex shedding incorporates spanwise modulation. In addition to the top and bottom stream Reynolds numbers (ReT,B=DUT,B/ν, with D the square cylinder side and ν the kinematic viscosity of the fluid), a parametric analysis is conducted to gauge the effects of splitter plate length (S) and the gap between the trailing edge of the splitter plate and the front face of the cylinder (G) on the leading three-dimensionalizing instabilities. Modes akin to the A- and B-type instabilities that characterize the wake transition regime past circular and square cylinders in homogeneous incoming flow are observed only at very small values of the top-to-bottom Reynolds number ratio R=ReT/ReB, while a third mode, mode C, is ubiquitous beyond more than very mild values of R. Increasing S at constant small G has a stabilizing effect on mode C, whose onset is pushed to higher values of R. Only for long S is mode A observed. Fixing a short S and increasing G results instead in a destabilization of mode C, and mode B is favored over mode A.

Ballistic performance and energy transfer of ultrahigh molecular weight polyethylene laminate

Soldier protection is crucial in contemporary localized conflicts, However, the impact response mechanism of UHMWPE laminate as the insert plate of ballistic helmet and bulletproof vest is still unclear. This study utilized 3D-DIC technology to analyze the impact response of UHMWPE laminates subjected to a 9 mm lead-core pistol bullet at a velocity of 334.93 m/s. The damage mode and response characteristics of the back surface were revealed; an effective numerical calculation method was established and could reveal the energy conversion process. The bullet penetrated the front face with 1.01 mm, resulting in a cross-shaped failure feature due to fiber bundle compression and aggregation. The numerical model confirmed its accuracy by comparing the height, width, and inplane strain distribution within the inplane of the bulge with experimental results. It further investigated the interaction between the bullet and the laminate, and energy transformation. The bullet's kinetic energy decreased by 80.64 %, in which the laminate absorbs 30.84 % of the bullet's energy as internal energy and 35.06 % as kinetic energy, meanwhile the bullet's internal energy increases by 11.77 %. The results show the damage mode and energy transformation of laminate, which provides theoretical support for revealing the impact response mechanism and improving the protective energy absorption efficiency.

Fission counter array for pulse-mode measurements of high-flux and high-energy neutrons

This manuscript describes a neutron counting system based on cylindrical fission counters that can monitor neutron activity for high-energy neutron flux above 10 MeV under electrically noisy environments with intense gamma rays. Miniature fission counters with depleted uranium as sensitive material and modular electronics were built for digital signal processing and high-countrate operation. The counters are 9.5 mm in diameter and 71.1 mm in active length. The author presents the results of Monte Carlo simulations of the fission-counter response for selected neutron sources and energies based on ENDF7.1, JENDL-5, and TENDL-2021 nuclear data libraries from 1 meV to 200 MeV. For a white neutron beam (E‾ = 16.36 MeV) that irradiates the front face of a counter, the intrinsic efficiency is evaluated to be (2.24 ± 0.02) × 10−5 counts/n, while the efficiency of the counter in the array appears to increase by at most 6.7%.

Clinker High-Hollow Ceramic Stones: Prospects for Technology and Application

A substantiation is given for the prospects of using clinker large-format ceramic stones of increased hollowness with a water absorption of less than 3% in construction. It has been shown that due to the high strength of the ceramic material itself (more than 100–150 MPa), ceram-ic stones will have the necessary strength – more than 10–15 MPa in terms of compressive strength. Due to the increased void content with as many rows of voids as possible per 100 mm length of the ceramic stone and a smaller thickness of the internal walls, the stones will have reduced thermal conductivity. Due to the low porosity of clinker ceram-ics as a material and the use of appropriate masonry mortars, masonry made of clinker stones will be guaranteed not to be vapor permeable, which will significantly increase the service life of buildings. When us-ing certain technological techniques, namely the application of cham-fers, relief, engobes on the front faces, large-format high-hollow clinker stones can also play the role of facing products, which will significantly increase their consumer attractiveness. With an increase in the hollow-ness of stones, the costs of mass preparation, drying and firing of products are proportionally reduced, which significantly reduces their cost. It has been shown that the “ideal” raw material for producing clinker large-format ceramic stones can be stone-like clay raw materials – argillite-like clays, argillites, shales and their transitional varieties. When grinding them and preparing molding masses, due to the for-mation of a certain grain composition and the introduction of corrective microadditives, it is possible to obtain molding masses with optimal pre-firing technological properties and a clinker shard with water ab-sorption of up to 3% and a compressive strength of up to 200 using one raw material. MPa, bending strength up to 50 MPa.

An Experimental Investigation into Wind Effect on Tall Buildings with Pentagonal Cross Section

The effect of wind load is one of the very significant factors in building and structure design. An investigation has been carried out into the wind effect on a Pentagonal cross-section with an open circuit wind tunnel. The experiment was conducted at a constant flow velocity of 13.2 m/s and a Reynolds number of 4.22 x 104. The test was carried out on a single cylinder positioned facing across the flow direction at various angles of attack from 0° to 72° at a step of 9°. Each face of a pentagonal cylindrical model was divided into five tapping points and connected with inclined multi-manometers using copper capillary and plastic tubes to measure the surface static pressure on the cylinder surface. Pressure coefficients were calculated from the measured surface static pressure, which was then used to estimate the drag and lift coefficients. A significant drop of 0.52 in the drag coefficient values has been observed for the single pentagonal cylinder in comparison to that of the single square cylinder. The overall lift coefficient values of the single pentagonal cylinder are found to be lower than that of a single square cylinder except at 90. The fluctuation of the lift coefficient curve has a 90 phase shift than that of the square cylinder; however, the pattern of their variations has shown a similar trend except for the angle of attack of 00. The stagnation point was identified on the front face of the pentagonal cylinder. These findings will assist engineers and architects in designing much safer buildings.

Experimental study on the dam-break-induced surge impact on an inclined wall

The front faces of coastal structures are not always perpendicular to its foundation. To investigate the surge impact characteristics on an inclined wall, laboratory experiments about the dam-break-induced surge impact were conducted on downstream walls with four different inclination angles, i.e., −30°, −10°, 0°, and 10° (positive for forward inclination). Before the water tongue forms, surge water in front of the wall can be classified into the bottom solid water and the upper aerated water. Although the measured maximum water level is the largest in front of the vertical wall, it contains a large proportion of aerated water. In contrast, the −30° wall exhibits the largest proportion of solid water, which is associated with the force exerted on the wall. As the wall inclines forward, the impact pressure experiences an increase in its peak value and spatial extent, while a decrease in its duration. The maximum impact pressure and the maximum horizontal force induced by the initial impact increase from the backward to forward inclination, while the maximum horizontal force in the transition or quasi-static phase increases as the wall inclines. In addition, it is found that the calculation method for designing breaking wave loads on nonvertical walls underestimates the surge-induced maximum horizontal force. Regarding the potential sliding/overturning failure, the 10°/−30° wall presents the highest risk among the considered cases under the same incoming hydrodynamic conditions. These findings extend our understandings on the surge–structure interactions, being helpful for the safe design of relevant coastal structures.

Identification of the Thermal Activation Network in Human 15-Lipoxygenase-2: Divergence from Plant Orthologs and Its Relationship to Hydrogen Tunneling Activation Barriers.

The oxidation of polyunsaturated fatty acids by lipoxygenases (LOXs) is initiated by a C-H cleavage step in which the hydrogen atom is transferred quantum mechanically (i.e., via tunneling). In these reactions, protein thermal motions facilitate the conversion of ground-state enzyme-substrate complexes to tunneling-ready configurations and are thus important for transferring energy from the solvent to the active site for the activation of catalysis. In this report, we employed temperature-dependent hydrogen-deuterium exchange mass spectrometry (TDHDX-MS) to identify catalytically linked, thermally activated peptides in a representative animal LOX, human epithelial 15-LOX-2. TDHDX-MS of wild-type 15-LOX-2 was compared to two active site mutations that retain structural stability but have increased activation energies (Ea) of catalysis. The Ea value of one variant, V427L, is implicated to arise from suboptimal substrate positioning by increased active-site side chain rotamer dynamics, as determined by X-ray crystallography and ensemble refinement. The resolved thermal network from the comparative Eas of TDHDX-MS between wild-type and V426A is localized along the front face of the 15-LOX-2 catalytic domain. The network contains a clustering of isoleucine, leucine, and valine side chains within the helical peptides. This thermal network of 15-LOX-2 is different in location, area, and backbone structure compared to a model plant lipoxygenase from soybean that exhibits a low Ea value of catalysis compared to the human ortholog. The presented data provide insights into the divergence of thermally activated protein motions in plant and animal LOXs and their relationships to the enthalpic barriers for facilitating hydrogen tunneling.

Efficient design of composite honeycomb sandwich panels under blast loading

Hybrid composite honeycomb sandwich structures (HCHSS) were employed due to high specific strength and stiffness and higher impact resistance property required for the aerospace and defence fields. The numerical modelling of the efficient HCHSS was developed for the core, front and back face plate using the C3D8R elements to determine the realistic failure behaviour for the honeycomb sandwich structure. The ConWep blast simulation loading was applied for the HCHSS. Advanced composite materials were used for the blast analysis of the HCHSS (carbon/epoxy, graphite/epoxy, woven basalt fibres/polypropylene and woven Kevlar fibres/polypropylene). The damage initiation and damage propagation based progressive damage modelling was developed and implemented in the VUMAT code for composite materials to determine the actual failure behaviour of the HCHSS. The face sheets used in this model were of a stainless-steel alloy AL-6XN. The sandwich structure was subjected to blast loads of 1, 2 and 3 kg of TNT and their performance was compared w.r.t both front and back-face deflection. The effectiveness of sandwich panels was further examined by altering the thickness of the core. Fibre-metal laminates (FML) were used in place of the steel face sheets in the panel in order to minimise its mass, and a thorough analysis of the panel’s mass in relation to its peak deflection was carried out. Upon analysing the results, it was noted that the panel with the basalt fibre reinforced polymer (BFRP) core gave the best results compared to other composite materials. For a blast load of 3 kg TNT, the peak back face deflection (PBFD) of HCHSS with a BFRP core decreased by 10.64%, 7.61% and 4.75%, respectively, compared to panels with CFRP, GFRP, and KFRP cores. The peak deflection of the panel decreased as the BFRP core thickness increased. The energy absorption capacity of the panel also increased with increasing thickness. Additionally, it was found that panels with BFRP cores and KFRP-steel laminate face sheets provided the optimum balance of strong blast resistant performance and light weight. Compared to the metallic (steel) sandwich panel, the mass of the sandwich panel with KFRP-steel laminate face sheets and BFRP core was reduced by 33%, but at the same time, its PBFD increased by almost 50%.

Analysis of heat and mass transfer in a porous solar thermochemical reactor

Solar thermochemistry shows great potential as a viable solution for addressing the challenge of energy storage. The design of the reactor is still challenging the development and rapid upscaling of solar thermal conversion and storage processes. This study presents a novel reactor that capable of gas reheating and develops a comprehensive three-dimensional model that effectively couples the processes of heat transmission, gas flow and chemical reaction for the optimization of the reactor. It is demonstrated that the maximum thermal efficiency is 43.67% as the incident solar power is 3730 W, but it decreases as the temperature rises. The re-radiation loss at the reactor front face is found as a major factor affecting the reactor thermal efficiency. The result indicates that the thermal efficiency of the reactor is significantly improved as using the cutoff wavelength coating technology. As the cutoff wavelength is 1 μm, the average temperature of porous material increases from 1510.77 °C to 1634.87 °C at 60 min, and the reactor's thermal efficiency increases from 11.65% to 13.51%. This study provided comprehensive insights into heat and mass transfer in a porous solar thermochemical reactor.

A novel method for the efficiency calibration of in situ gamma spectrometry systems

The FEPE calibration of in situ gamma spectrometer is very complex and limits its widespread use. In this study, a novel method for the absolute FEPE calibration of in situ spectrometer is proposed. The proposed method is applied for the FEPE calibration of HPGe detector (GC-3020) intended to use for in situ measurements. The intrinsic FEPE of detector is determined by measuring standard radioactive point sources 152Eu,137Cs, 133Ba and 60Co at a distance of 25 cm from front face of the detector. The method is validated by Monte Carlo simulations in Geant4. The absolute FEPE values obtained through the proposed methodology are compared to those computed using MC simulations. A good agreement between them validates the proposed method, in the energy range of interest. The proposed method may be employed for the rapid calibration of in situ gamma spectrometry systems during nuclear emergency.

Toxicity of agrochemicals: Impact on environment and human health

Agrochemicals, while essential for increasing agricultural yields and pest control, have unintended consequences. They contaminate soil and water, disrupting ecosystems, reducing biodiversity, and threatening aquatic life. Furthermore, agrochemicals harm non-target organisms, disrupting ecological balance. On the human health front, farmworkers and pesticide applicators face acute poisoning risks, with symptoms ranging from discomfort to severe illness or death. Chronic health effects include links to cancer, neurological disorders, and reproductive problems, raising concerns about food safety and worker well-being. Addressing agrochemical toxicity requires a multifaceted approach. Governments must enforce strict regulations to minimize environmental contamination and ensure safe handling practices. The agricultural industry can adopt sustainable methods like integrated pest management (IPM) and organic farming to reduce reliance on agrochemicals. Innovations such as precision agriculture, biological pest control, nanotechnology, and artificial intelligence for early risk detection are essential. Collaboration among stakeholders is critical for a more sustainable and environmentally friendly agriculture sector, involving regulatory measures like maximum residue limits (MRLs) and sustainable practices like IPM and organic farming. In summary, this review highlights the urgent need to address agrochemical toxicity holistically, balancing agricultural productivity with environmental and health concerns to ensure a sustainable future for agriculture and the planet.

Generative artificial intelligence and building design: early photorealistic render visualization of façades using local identity-trained models

Abstract This paper elucidates an approach that utilizes generative artificial intelligence (AI) to develop alternative architectural design options based on local identity. The advancement of AI technologies has increasingly piqued the interest of the architecture, engineering, construction, and facility management industry. Notably, the topic of “visualization” has gained prominence as a means for enhancing communication related to a project, especially in the early phases of design. This study aims to enhance the ease of obtaining design images during initial phases of design by drawing from multiple texts and images. It develops an additional training model to generate various design alternatives that resonate with the identity of the locale through the application of generative AI to the façade design of buildings. The identity of a locality in cities and regions is the capacity for the cities and regions to be identified and recognized as a specific area. Among the various visual elements of urban and regional landscapes, the front face of buildings may play a significant role in people’s aesthetic perception and overall impression of the local environment. The research proposes an approach that transcends the conventional employment of three-dimensional modeling and rendering tools by readily deriving design alternatives that consider this local identity in commercial building remodeling. This approach allows for financial and temporal efficiency in the design communication phase of the initial architectural design process. The implementation and utilization of the proposed approach’s supplementary training model in this study proceeds as follows: (i) image data are collected from the target area using open-source street-view resources and preprocessed for conversion to a trainable format; (ii) textual data are prepared for pairing with preprocessed image data; (iii) additional training and outcome testing are performed using varied text prompts and images; and (iv) the ability to generate building façade images that reflect the identity of the collected locale by using the additional trained model is determined, as evidenced by the findings of the proposed application method study. This enables the generation of design alternatives that integrate regional styles and diverse design requirements for buildings. The training model implemented in this study can be leveraged through weight adjustments and prompt engineering to generate a greater number of design reference images, among other diverse approaches.

Laboratory studies of the soil erosion and alluvium processes in the area of bridge supports

The results of experimental studies of the process of bottom erosion during the construction of bridge supports under the protection of a sheet pile structure are presented. To protect the sheet piling box from the influence of ice floes during the period of ice drift, it is planned to install an ice-cutting protective device located upstream of the sheet piling box. In the process of conducting research, the principles of modeling the processes of river sediment transport taking into account the size of transported particles, non-erosive velocities and channel slopes are substantiated. Laboratory studies of the processes of forming erosion and alluvium are carried out for two cycles of parameters. At the same time, the influence of the ice-cutting device position relative to the sheet piling box on the amount of erosion and alluvium is studied. Experiments were carried out for various options of the ice cutter position relative to the sheet piling box; the ice cutter moved upstream along the axis of the tray with a step of 0.1 m (5 m for natural conditions). Based on measurements of bottom surface marks, two-dimensional erosion plans are constructed. For several options for the location of structures, the trajectories and directions of flow movement are determined by photographing the movement of surface floats, which makes it possible to create a grid of streamlines and determine the values of surface current velocities. An analysis of the velocity distribution over the surface and in the flow volume has shown that a horseshoe-shaped vortex is formed around the structure, with riffles and ridges appearing along its wings. A stagnation zone is established inside the “horseshoe”; in this zone the bottom remains relatively smooth. In the absence of an ice cutter, the main zones of soil erosion arise in the vicinity of the corners of the front face of the box, and alluviums form in the rear part of the structure. When installing an ice-cutting device in the shape of a triangle in front of the box, directed at an acute angle towards the oncoming flow, the erosion zones move to the vicinity of the corners lying at the base of the triangular ice cutter facing the box. The absolute values of erosion depth and alluvium height are reduced compared to the option without the ice cutter. When the ice cutter moves upstream relative to the box, a washout zone appears in the gap between the ice cutter and the box. The maximum values of erosion and alluvium occur in the absence of ice cutter and when placing the ice cutter at a distance of 200–300 mm from the box. The minimum values of erosion and alluvium are recorded when the ice cutter is placed close to the support box. With increasing flow rates and depths, the values of erosion and alluvium increase. Installing the ice-cutting device improves the hydraulic conditions of flow around the sheet piling box structure, which leads to a decrease in washout depths.

Reflection behaviour of SH0 from small defects in thin sheets, with application to EMAT inspection of titanium

ABSTRACT Defects can arise within the weld during the laser welding process of thin titanium sheets, and it is critical that these defects are detected. Shear horizontal (SH) waves offer good potential for defect detection, but require an understanding of how the ultrasonic waves interact with defects, in order to develop an optimised inspection setup, increasing the probability of defect detection. The geometry of a defect strongly affects the reflected signal magnitude, with finite element simulations showing that defect width and length determine the maximum SH0 wave reflection. Experiments confirm this behaviour. The defect width is shown to affect the reflection behaviour due to wave interference. Phase differences between the front face reflection and back face reflection cause a shift in the peak position. In addition, the experimental work presented in this paper also shows the potential for electromagnetic acoustic transducers to be used for the inspection of titanium components.

Field‐representative evaluation of PID‐polarization in TOPCon PV modules by accelerated stress testing

AbstractPotential‐induced degradation‐polarization (PID‐p) can reduce module power, but how to project the extent to which PID‐p may occur in field conditions considering the factors of system voltage, condensed moisture, temperature, and illumination has not been clarified. Using tunnel oxide passivated contact (TOPCon) modules, this work demonstrates a method to test full‐size crystalline silicon PV modules for PID‐p to provide field‐representative results. In initial screening tests with positive or negative 1000 V electrical bias applied at 60°C for 96 h using Al foil electrodes on the glass surfaces, the module type exhibited reversible PID‐p only on the front face when the cell circuit was in negative voltage potential. No PID was detected on the rear after testing in either polarity. We then evaluated the PID‐p sensitivity on the front side under different UV irradiances while maintaining the glass surface wet to estimate real‐world susceptibility to PID‐p. The magnitude of the observed behavior was fit using a previously developed charge transfer and depletion by light model. Whereas power loss with −1000 V applied to the cell circuit at 60°C for 96 h in the dark was about 30%, testing the module front under 0.051 W·m−2 nm−1 at 340 nm UVA irradiation using fluorescent tubes, the mean degradation was only 3%. When the modules were tested in the dark for PID‐p with in situ dark current–voltage (I‐V) characterization, the thermal activation energy for degradation was 0.71 eV; for recovery in the dark, it was 0.58 eV. Whereas recovery from the degraded state at 60°C in the dark without voltage bias was 5% absolute in 38 h, rapid recovery of about 5% absolute was observed with 1000 W·s/m2 exposure at 25°C using a flash tester.

Ballistic performance of monolithic rubber-ceramic composite armor

This work presents the research results regarding the ballistic response characteristics of monolithic ceramic armors. Two different configurations of armors are considered for investigation, aiming at identifying ways to increase the ballistic performance of Small Arms Protective Insert (SAPI). The first configuration consists of a monolithic ceramic tile (Al2O3) with a backing plate made of high-performance Kevlar-29 fiber reinforced composite; the second one has the same design as the first, but the monolithic ceramic tile is covered by a thin rubber layer. The impact behavior of the ceramic composite armors is analyzed numerically, using the finite element method. Some characteristic features, including the ballistic performance and the fracture conoid angle (for the ceramic tile) are discussed. The numerical models developed for the two armor configurations are validated by ballistic tests, where the projectile impact on the armors and the mechanical integrity of the armor systems after impact are observed. The results from simulations and experiments show that the Al2O3/Kevlar 29 composite armor is able to capture a 7.62 mm bullet with a striking velocity of 690 m/s and the rubber-ceramic composite armor is able to capture 5.56 × 45 mm bullet M855 (with an armor piercing tip) with an impact velocity of 894 m/s. It has been found that, when a rubber layer is placed on the front face of a ceramic composite armor, better ballistic performance is achieved. The experiments show that, when a rubber material is impacted by a projectile, its behavior at high velocities and high strain rates changes from elastic to brittle.

Comparative study of the influence of charge shapes on the distribution of blast pressure on a structural unit

Since limited research results are available in the area of blast wave interactions with structural surfaces, a comparative study is undertaken to ascertain the interaction effects of blast waves generated by exploding spherical and cylindrical charges on the surface of a concrete structural unit. The effective blast pressure experienced by a concrete unit is evaluated and its distribution across the front face is studied here for two distinct charge shapes, namely spherical and cylindrical. The finite element analysis is carried out for nine different scaled distances. Random forests algorithm was utilized to analyze the 450 observations to evaluate the results and build predictive models. The best models were selected based on standard performance indicators. For cylindrical charges, the aspect ratio was also factored in the analysis. The distribution of effective pressure indicates unique patterns for the two different charge shapes in the graphical comparison. The effective pressures caused by the cylindrical charge shape for the specific aspect ratios considered here are lower by 84 % on average compared to the effect caused by a spherical charge, which results from the distinct characteristics of blast waves generated by the explosion of cylindrical charges.