Metal Shell Research Articles

Application of physics-informed machine learning methods in buckling design of axially compressed cylindrical shells

A physics-informed artificial neural network (ANN) is developed for the buckling design of cylindrical shells under axial compression, and two strategies are applied to incorporate physical knowledge into the ANN model. One strategy is to introduce physics-informed features derived from the local reduced stiffness method (LRSM) as additional input features. The other strategy is to incorporate physical constraints based on elastic buckling theory into the loss function of ANN. The accuracy of the proposed model is verified using a buckling dataset of metal and non-metal cylindrical shells. Results demonstrate that the proposed physics-informed ANN model with four hidden layers achieves better predictive performance than pure data-driven random forest (RF), support vector machine (SVM) and ANN. Furthermore, the physics-informed model could predict moderately conservative buckling loads with a design factor of 1.25.

Dipole-dipole interactions in the presence of a topological insulator stratified sphere: dyadic Green’s function method

Dyadic Green’s functions (DGFs) are developed for calculating electric fields induced by multiple sources in the presence of a topological insulator (TI) stratified sphere within the framework of axion electrodynamics. Generalizing our previous work, these sources can be placed at arbitrary locations rather than be limited outside the TI stratified sphere. Utilizing these DGFs, we explore the topological magneto-electric (TME) effect of the dipole–dipole interaction in the presence of composite structures of an alternating metal-TI stratified sphere, causing some modifications of the energy transfer (ET) enhancement spectrum. Furthermore, for the multipolar resonances of the metal shells, we find the TME-induced red-shifts of each bonding and antibonding mode in the ET enhancement spectrum are independent on the locations and orientations of the two dipoles but only depend on the configuration of these composite structures. These phenomenological findings provide some useful guidance with experimenters to design realistic experiments for exploring possible unique TME signatures via the energy transfer between molecules near/in TI multicoated nanoparticles in the near-infrared region.

Effect of thin-wall copper on the mechanical properties of ultra-light 3D-printed polymeric sandwich panels

In this study, a portion of an ultra-light polymeric sandwich panel was produced by additive manufacturing with a dimension of 25 × 25 × 37 mm as a precursor. Then, the precursor was covered with a thin-walled copper through electroforming deposition as a portion of a copper sandwich panel. The weight of the polymeric sandwich panel increased from 2–4 g to 9–13 g for the copper sandwich panel during the electroforming process. Compressive strength and energy absorption density of the polymeric and the copper sandwich panels with open-cell cores measured for 4, 5 and 6 PPI. The results shown that the ultra-light polymeric and copper sandwich panels with 6 PPI have the best mechanical performance in terms of yield stress, energy absorption density and energy absorption efficiency. Moreover, the abovementioned characteristics are 0.09 MPa, 0.11 MJ . m − 3 and 80% for the polymeric sandwich panels, and 1.74 MPa, 0.98 MJ . m − 3 and 70% for the copper sandwich panels, respectively. Therefore, the addition of 9.01 g copper as a reinforcing around the core’s polymeric ligaments caused an increase in the yield stress for 20 times and in the energy absorption density for 9 times. Comparing to Ashby diagram, and previous studies, the sandwich panel portions of this study could develop the industry of sandwich panels by using the metallic shells as a reinforcement to ultralight polymeric sandwich structures.

Crack propagation and damage evolution of metallic cylindrical shells under internal explosive loading

This paper investigates the three-dimensional crack propagation and damage evolution process of metallic column shells under internal explosive loading. The calibration of four typical failure parameters for 40CrMnSiB steel was conducted through experiments and subsequently applied to simulations. The numerical simulation results employing the four failure criteria were compared with the differences and similarities observed in freeze-recovery tests and ultra-high-speed tests. This analysis addressed the critical issue of determining failure criteria for the fracture of a metal shell under internal explosive loads. Building upon this foundation, the damage parameter Dc, linked to the cumulative crack density, was defined based on the evolution characteristics of a substantial number of cracks. The relationship between the damage parameter and crack velocity over time was established, and the influence of the internal central pressure on the damage parameter and crack velocity was investigated. Variations in the fracture modes were found under different failure criteria, with the principal strain failure criterion proving to be the most effective for simulating 3D crack propagation in a pure shear fracture mode. Through statistical analysis of the shell penetration fracture radius data, it was determined that the fracture radius remained essentially constant during the crack evolution process and could be considered a constant. The propagation velocity of axial cracks ranged between 5300 m/s and 12600 m/s, surpassing the Rayleigh wave velocity of the shell material and decreasing linearly with time. The increase in shell damage exhibited an initial rapid phase, followed by deceleration, demonstrating accelerated damage during the propagation stage of the blast wave and decelerated damage after the arrival of the rarefaction wave. This study provides an effective approach for investigating crack propagation and damage evolution. The derived crack propagation and damage evolution law serves as a valuable reference for the development of crack velocity theory and the construction of shell damage evolution modes.

Dynamic response of clamped metallic thin-walled cylindrical shells under lateral shock loading

A combined experimental and numerical study was carried out to explore the dynamic response of Q235 thin-walled cylindrical shells under lateral shock loading. The machined Q235 specimens were clamped on both sides and subjected to centered lateral simulated shock loading via foam projectile impact tests, with their dynamic deformation evolution, mid-point deflections, and final deformation modes experimentally measured. The mid-point deflections of the impact side are all positive (the direction of deformation is the same as the impact direction) while those of the rear side all exhibit negative values (the direction of deformation is opposite to the impact direction). To further explore this phenomenon, the method of finite element (FE) was employed to simulate the foam projectile impact, with good agreement against experimental measurements achieved. Using the validated numerical model, the effects of impact velocity, length-to-diameter ratio, and thickness-to-diameter ratio on the dynamic response of the thin-walled cylindrical shell were further analyzed. The direction of both side deflections and deformation modes are significantly affected by the impact level and the shell geometries. For the rear side, within the given range of impact momentum and geometric parameters, the numerically predicted deflection varies from −1.775 mm to 2.45 mm. Thereupon, the coupling of indentation and bulge deformation patterns are indicated, and their corresponding contribution changes are considered the main mechanism for determining the final deformation of the thin-walled cylindrical shell's rear side.

Nonlocal effects in plasmon-emitter interactions

Abstract Nonlocal and quantum mechanical phenomena in noble metal nanostructures become increasingly crucial when the relevant length scales in hybrid nanostructures reach the few-nanometer regime. In practice, such mesoscopic effects at metal–dielectric interfaces can be described using exemplary surface-response functions (SRFs) embodied by the Feibelman d-parameters. Here we show that SRFs dramatically influence quantum electrodynamic phenomena – such as the Purcell enhancement and Lamb shift – for quantum light emitters close to a diverse range of noble metal nanostructures interfacing different homogeneous media. Dielectric environments with higher permittivities are shown to increase the magnitude of SRFs calculated within the specular-reflection model. In parallel, the role of SRFs is enhanced in noble metal nanostructures characterized by large surface-to-volume ratios, such as thin planar metallic films or shells of core–shell nanoparticles, for which the spill-in of electron wave functions enhances plasmon hybridization. By investigating emitter quantum dynamics close to such plasmonic architectures, we show that decreasing the width of the metal region, or increasing the permittivity of the interfacing dielectric, leads to a significant change in the Purcell enhancement, Lamb shift, and visible far-field spontaneous emission spectrum, as an immediate consequence of SRFs. We anticipate that fitting the theoretically modelled spectra to experiments could allow for experimental determination of the d-parameters.

Structural characteristics and mechanical properties of partially reacted and non-reacted Al–Fe66Cr10Nb5B19 metallic glass composites

The microstructure and mechanical properties of partially reacted and non-reacted Al–Fe66Cr10Nb5B19 metallic glass composites obtained by spark plasma sintering were comparatively analyzed. For the first time, the compositional features of core-shell particles formed upon the partial reaction of the Fe66Cr10Nb5B19 metallic glass with aluminum were examined using transmission electron microscopy combined with elemental mapping. The key finding is that iron of the alloy selectively dissolved in aluminum. The inner layer of the shell formed via diffusion of aluminum into the metallic glass. The introduction of the glassy reinforcement did not lead to such a dramatic ductility reduction as the formation of a complex “metallic glass core-thick intermetallic shell” reinforcement. In the non-reacted composite, the glassy reinforcement did not reveal its full potential in terms of the strengthening effect.

Implosion mechanisms of underwater ring-stiffened metallic cylindrical shells

Underwater cylindrical shells are prone to implosion due to the surrounding high hydrostatic pressure, and introducing ring-rib is a promising approach to reduce the risk. However, the influences of the ring-rib on the deformation mode and the fluid-structure interaction mechanism are still unclear. This paper investigates the dynamic response of ring-stiffened cylindrical shells during the implosion process. The finite element model is firstly established and the numerical simulation is verified by the existing experiment. Then, the numerical method is used to simulate the implosion of ring-stiffened cylindrical shells with various geometrical parameters. The fluid motion, induced pressure and deformation features are investigated and the relationship between them is clarified. Finally, pure and ring-stiffened cylindrical shell implosions are compared and parametric analyses are performed by varying the number and thickness of ring-ribs. Results show that ring-stiffened cylindrical shells with higher collapse resistance deform asymmetrically and the flow field response changes depending on the deformation mode. Introduction of ring-ribs can significantly increase the critical pressure and reduce the percentage of induced pressure. As the number and thickness of ribs increased, the critical and peak implosion pressures of the ring-stiffened cylindrical shells increased by 153% and 146%, respectively.

“Cup-in-Cup” for revision cup in total hip arthroplasty – An innovative technique

In a revision hip surgery with isolated poly-ethylene liner wear along with a stable acetabular shell involves difficult decision of revising the entire acetabular component or just the liner. However, unavailability of the similar poly liner in a high risk patient can be dealt with a novel technique of cup in cup by retaining the stable shell and cementing a polyethylene liner over it. A 77-year-old male came with complains of pain in the right hip and limp of 4 months duration after 17 years of a revision hip surgery. Poly-ethylene liner was found worn out intraoperative with both the metal shell and the stem very stable. Same company poly liner was not available. In order to prevent the extensive revision in a high surgical risk patient and to prevent the blood and the bone loss, a new Elite poly-ethylene cement cup was cemented over the old stable cementless metal shell. At 3 years short term follow up patient is able to walk pain free independently. The “cup-in-cup” technique with cemented PE cup into a retained well-fixed and well-positioned metal shell is a good technique in high surgical risk patients and gives promising result at short term follow up.

Rigorous Reliability Testing of an Encapsulated Thermal Pyrolytic Graphite (TPG) Heat Spreader for Passive Thermal Management Applications

Continued microelectronic miniaturization has resulted in higher power density, increasing the need for high performance thermal management. One possible solution for board-level thermal management is to fully encapsulate a high thermal conductivity material, such as Thermal Pyrolytic Graphite (TPG; ~1700 W/mK) in a metal (such as 6061 aluminum), producing an efficient passive heat spreader for thermal dissipation. The metal shell provides sufficient mechanical strength at a small detriment to the overall thermal conductivity. Reliability and consistent performance over time are critical for thermal management systems, especially in Defense and Aerospace applications. MIL-STD-883H provides test parameters for reliability involving exposure to mechanical shock (Method 2002.5), mechanical vibration (Method 2005.2), and thermal shock (Method 1011.9), with traditional evaluation criteria involving microelectronic device performance and/or a visual examination. For this work, the reliability of aluminum encapsulated TPG test coupons was evaluated with more demanding criteria: a visual examination, X-ray inspection, acoustic microscopy, and thermal conductivity performance testing, both before and after the previously discussed MIL-STD-883H exposures. The encapsulated coupons showed excellent robustness; the thermal conductivity properties remained constant with an average value around 965 W/mK, and the non-destructive imaging revealed excellent bond quality for the metal encapsulation, with no evidence of delamination. This more stringent evaluation criteria after MIL-STD-883H testing provides a better way to evaluate the reliability of passive thermal management systems. The study results also demonstrate the metal encapsulated TPG heat spreader as a superior thermal management solution with high performance and high reliability for demanding applications.

Spatial Localization of a Transformer Robot Based on Ultrasonic Signal Wavelet Decomposition and PHAT-β-γ Generalized Cross Correlation.

Because large oil-immersed transformers are enclosed by a metal shell, the on-site localization means it is difficult to achieve the accurate location of the patrol micro-robot inside a given transformer. To address this issue, a spatial ultrasonic localization method based on wavelet decomposition and PHAT-β-γ generalized cross correlation is proposed in this paper. The method is carried out with a five-element stereo ultrasonic array for the location of a transformer patrol robot. Firstly, the localization signal is decomposed into wavelet coefficients of different scales, which would realize the adaptive decomposition of the frequency of the localization signal from low frequencies to high frequencies. Then, the wavelet coefficients are denoised and reconstructed by using the semi-soft threshold function. Second, a modified phase transform-beta-gamma (PHAT-β-γ) method is used to calculate the exact time delay between different sensors by increasing the weights of the PHAT weighting function and introducing a correlation function. Finally, by using the proposed method, the accurate localization of the transformer patrol micro-robot is achieved with a five-element stereo ultrasonic array. The simulation and test results show that inside a transformer experimental oil tank (120 cm × 100 cm × 100 cm, L × W × H), the relative error of transformer patrol micro-robot spatial localization is within 4.1%, and the maximum localization error is less than 3 cm, which meets the requirement of engineering localization.

Fracture behavior and mechanism of highly fragmented steel cylindrical shell under explosive loading

An in-depth understanding of the fracture behavior and mechanism of metallic shells under internal explosive loading can help develop material designs for warheads and regulate the quantity and mass distribution of the fragments formed. This study investigated the fragmentation performance of a new high-carbon silicon-manganese (HCSiMn) steel cylindrical shell through fragment recovery experiments. Compared with the conventional 45Cr steel shell, the number of small mass fragments produced by the HCSiMn steel shell was significantly increased with a scale parameter of 0.57 g fitted by the Weibull distribution model. The fragmentation process of the HCSiMn shell exhibited more brittle tensile fracture characteristics, with the microcrack damage zone on the outer surface being the direct cause of its high fragmentation. On the one hand, the doping of alloy elements resulted in grain refinement by forming metallographic structure of tempered sorbite, so that microscopic intergranular fracture reduces the characteristic mass of the fragments; on the other hand, the distribution of alloy carbides can exert a "pinning" effect on the substrate grains, causing more initial cracks to form and propagate along the brittle carbides, further improving the shell fragmentation. Although the killing power radius for light armored vehicles was slightly reduced by about 6%, the dense killing radius of HCSiMn steel projectile against personnel can be significantly increased by about 26% based on theoretical assessment. These results provided an experimental basis for high fragmentation warhead design, and to some extent, revealed the correlation mechanism between metallographic structure and shell fragmentation.

Radial vibration analysis for piezoceramic shell-stacked spherical transducer with thick walls

With the development of ultrasonic transducers, spherical piezoelectric transducers have attracted tremendous attention in a variety of application fields due to their ability to resist higher pressures and produce omnidirectional radiation. However, the wall thickness of piezoceramic spherical shells is usually thin due to the limitations of polarization technology and operating voltage, leading to the limited vibration performance and power capacity of the spherical transducer. We present a piezoceramic shell-stacked spherical transducer (PSST) capable of addressing the problem of difficult excitation caused by the thick wall of the piezoceramic shell. The resulting device consists of a two-layered piezoceramic shell interposed between the inner and outer concentric spherical metal shells. By removing the equivalent mechanical transformers, a novel electromechanical equivalent circuit of the PSST is established to simplify the theoretical analysis of the designed PSST. The electromechanical characteristics of the resulting device are experimentally verified, and the measured results are in good agreement with the theoretical predictions and simulation results. Our design opens up possibilities for designing spherical transducers with high-vibration performance and may offer potential for a wide range of applications such as underwater detection and structural health monitoring.

Mechanical Response of Open‐Cell Metal Foams with Single‐ and Multilayer Shell during Uniaxial Compression Test

Metal foams are one of the unique materials that need more attention in terms of mechanical and microstructural characterizations. Herein, different kinds of metal foams such as Ni, Cu, and a novel type of multilayered metal foam with Ni–Cu and Cu–Ni coating layer orders are produced and characterized in terms of mechanical response and microstructure of these novel materials during a uniaxial compression test. These multilayered metallic foams have a strong mechanical adhesion at the interface due to the nature of electroforming process and the effect of solid‐solution area at these interfaces. Besides, multilayered metal foams are superior to Ni and Cu pure metal foams in terms of mechanical response; applying a multilayered metallic coat with 60 and 69 μm diameter for Ni and Cu improves the yield point of the Ni and Cu single‐layer metallic foams by 3 and 7 times, respectively. Moreover, in terms of energy absorption density, the multilayered metallic shell improves the energy absorption density by 3 and 5.5 times compared to Ni and Cu metal foams, respectively. This study shows that applying multi layered coatings to metal foams with Ni as the first layer has superior characteristics compared to single‐layer metal foams.

Impact of Earth Radiation Pressure Physical Analytical Model on Satellite Laser Ranging Orbit Determination

SLR (Satellite Laser Ranging) is a kind of important space geodesy technique for the establishment of a Terrestrial Reference Frame (TRF) and determination of EOP (Earth Orientation Parameters). It determines the origin and scale factor of TRF. The accuracy of future TRF is 1 mm. This requires improving the SLR data processing accuracy and importing higher accuracy SLR satellite data. The Earth Radiation Pressure (ERP) is an important perturbation force for SLR satellites. The traditional Earth radiation pressure model for SLR satellites is the simple Cannon Ball model. This paper establishes the Box-Wing physical Earth radiation pressure model for SLR satellites and takes Lageos-1 as an example to evaluate the physical analytical model. The Lageos-1 is divided into two blocks: metal shell and corner reflectors. The area and optical characteristics of each block are analyzed according to the requirements of three kinds of Earth albedo and emissivity models of point source, experience and grid models. The results show that after importing the physical analytical Earth radiation pressure model, the empirical force acceleration in the T direction is significantly reduced and the orbit overlap arc precision is about 3 mm smaller than that of the original model. The orbit prediction results show that the prediction accuracy of the new Earth radiation pressure model has generally improved significantly. The maximum improvement percentage of the physical analytical model is 12%, 16%, 28% and 25% respectively in the prediction arc length of 1 day, 3 days, 5 days and 7 days. The physical grid model performs the best with the increase of prediction arc length.

In Situ Copper Coating on Silicon Particles Enables Long Durable Anodes in Lithium-Ion Batteries.

Addressing the significant obstacles of volume expansion and inadequate electronic conductivity in silicon-based anode materials during lithiation is crucial for achieving a long durable life in lithium-ion batteries. Herein, a high-strength copper-based metal shell is coated in situ onto silicon materials through a chemical combination of copper citrate and Si-H bonds and subsequent heat treatment. The formed Cu and Cu3Si shell effectively mitigates the mechanical stress induced by volume expansion during lithiation, strengthens the connection with the copper substrate, and facilitates electron transfer and Li+ diffusion kinetics. Consequently, the composite exhibits a reversible specific capacity of 1359 mA h g-1 at 0.5 A g-1 and maintains a specific capacity of 837 mA h g-1 and an 83.5% capacity retention after 400 cycles at 1 A g-1, surpassing similar reports on electrochemical stability. This facile copper plating technique on silicon surfaces may be used to prepare high-performance silicon-based anodes or functional composites in other fields.

Buckling characteristics of carbon fiber composite/aluminium alloy combined cylindrical shells under external hydrostatic pressure

The buckling behaviour of combined shells fabricated from aluminium alloy and carbon fiber–reinforced polymer (CFRP) composites subjected to external hydrostatic pressure were investigated. Three sets of combined cylindrical shells with different combinations and one set of bare aluminium alloy cylindrical shells were designed and fabricated. The wall thickness of each cylindrical shell was measured. All the cylindrical shells were tested under external hydrostatic pressure, and the buckling load and final collapsed mode were recorded. Numerical models with real imperfections were established, linear and nonlinear analyses were performed to evaluate the buckling loads of cylindrical shells. The experimental and numerical results agreed favourably. On this basis, the effects of the thickness-diameter ratio, combination method and geometric imperfection on the buckling of combined cylinders were studied. This research can provide a reference for the design of combined shells made from CFRP and metal shell.

Thermally enhanced nanocomposite phase change material slurry for solar-thermal energy storage

This paper investigates the photothermal conversion performance of an innovative heat transfer fluid containing nano-encapsulated phase change material (PCM) with metallic shell materials in a solar thermal energy storage system. The influences of shell thickness, core size, shell material type, PCM mass and shell volume concentrations on the thermal performance of the heat storage medium are investigated and compared. The results show that the heat transfer rates of water-based Ag, Au, Cu and Al nanofluids are 6.89, 5.86, 7.05 and 6.99 W, respectively, while slurries formed by adding paraffin@Ag, Au, Cu and Al nano capsules to pure water enhance heat transfer by 6.18, 13.38, 10.8 and 11.33 %, respectively. The metallic nanoparticle-based shell materials further augment the temperature and energy storage gains by enhancing the solar radiation capture capability of the heat storage medium. Specifically, depending on the mass concentration of PCM, the storage capacity of paraffin@Cu slurry is augmented by up to 290 %. As the shell thickness of the Ag particles also decreases from 8 to 2 nm, it augments the slurry's storage ability for thermal energy by 7 %. The enhancement in the dimensions of the nano capsules, however, causes the surface area-to-volume ratio (SA:V) to reduce the photothermal conversion of the slurry by clustering. Therefore, the thermal energy storage behaviour of the Paraffin@Cu slurry is diminished by 5 % as the core size enhances from 10 to 40 nm. Further, the augmentation in the volume concentration of Al particles in the shell surprisingly reduces the thermal energy storage by 5 %. Finally, paraffin-based solid PCM is also experimentally tested for validation of the specific heat capacity model at various wind speeds and solar radiation.

Highly conductive riboflavin-based carbon quantum dot–embedded SiO2@MoS2 nanocomposite for enhancing bioelectricity generation through synergistic direct and indirect electron transport

A microbial fuel cell (MFC) is an advanced green battery that has limited application because of its low current density. In the present study, Shewanella oneidensis MR-1, which is an electricity-producing bacterium, was used in an electrochemical reactor as a bacterial model. Mesoporous spherical silica nanoparticles (NPs) loaded with riboflavin (RF) were prepared as the starting material, following which surface modification was conducted to expose the thiol group, which considerably increased the affinity of the NPs to MoS2 and resulted in the formation of a dense MoS2 shell on the surface after calcination. Moreover, the loaded RFs were successfully transformed into RF-based carbon quantum dots (CQDs), which resulted in a substantial increase in conductivity. The CQD-embedded SiO2@MoS2 NPs, which contained redox-active N-doped CQDs and had a metallic MoS2 shell, were able to receive electrons from exoelectrogenic bacteria (charging) and transfer electrons to an indium tin oxide electrode (discharging). Thus, these NPs could act as an electron nanoshuttle and a conductive medium in biofilms for enhancing systematic extracellular electron transport. A 10-fold increase in bioelectricity production than no NPs addition was achieved, which confirmed the applicability of the aforementioned NPs in advanced MFC applications. The NPs prepared in this study, which mimic biological electron shuttles (e.g., RF) in long-distance conduction, can usher in a new era in the development of advanced MFCs.

On the possibility of replacing forged blanks from 12X18H10T steel by casting into thin-walled metal shell molds with forced cooling

The possibility of replacing of forged blanks made of 12X18H10T steel with shaped castings obtained by casting into thin-walled metal shell molds with forced cooling is considered. Comparative tests of forged blanks made of 12Х18Н10Т steel and cast ones for strength, plastic properties and impact strength are carried out. Macrostructures, sulfur imprints, and distributions of non-metallic inclusions are studied. It is been established that cast billets are not inferior to forged ones in terms of a set of mechanical properties indicators. With a slight decrease in strength, cast workpieces are characterized by greater plastic properties and toughness. Keywords 12X18H10T and AISI 321 steels, alloy, structure, crystallization, casting, non-metallic inclusions, mechanical properties, metal shell shape