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The underbody of a vehicle system, either military or civil, is typically made of a relatively thin metallic plate, thus vulnerable to mine blast attacks. To improve the blast resistance, a multitude of protective structures have been proposed as attachments to the thin plate. In the present study, a novel ultralight all-metallic sandwich panel with three-dimensional (3D) tube cellular cores mounted to the vehicle underbody was envisioned as such a protective system. A metallic substrate (mimicking vehicle bottom) was placed above the proposed sandwich panel to construct a sandwich-substrate combinative structure. A series of sandwich panels having 3D tube cellular cores were fabricated via argon protected welding and laser welding. Mechanical responses of the combinative structure subjected to the denotation of 6 kg TNT explosives shallow-buried in dry sand were experimentally measured. Full numerical simulations with the method of finite elements (FE) were subsequently carried out to explore the physical mechanisms underlying the observed dynamic performance and quantify the effects of key geometrical parameters and connection conditions of the protective system. The performance of the proposed sandwich panel under shallow-buried explosives was also compared with competing sandwich constructions having equal mass. Finally, a preliminary optimal design of the 3D tube cellular core was carried out.

TiB2/TiN/WC gradient ceramic tool materials are designed to solve the problem of high brittleness and low toughness of non-gradient ceramic tool materials. The finite element method is used to establish gradient symmetric distribution models with different numbers of layers and thickness ratios and analyze their residual stress distribution. The corresponding gradient ceramic tool materials are prepared by vacuum hot pressing sintering method, the mechanical properties being tested and microstructure observed. The results show that the number of layers, layer thickness ratios and thermal expansion coefficient of each gradient layer affect the distribution of residual stress in different aspects. With the increase of the number of layers or layer thickness ratio, the material surface residual compressive stress increases gradually. The flexural strength and fracture toughness of the tool material with 7 layers and thickness ratio of 1 are 974.8 MPa and 8.5 MPa·m1/2 respectively, and the Vickers hardness of the tool surface is 19.68 GPa, which are 27.68%, 44.07% and 12.26% higher than those of the non-gradient ceramic tool materials. The fracture mode of the surface layer of tool material changes from intergranular fracture to synergistic effect of intergranular fracture and transgranular fracture. The increase of residual compressive stress is the main strengthening and toughening mechanism.

Free vibration of ultralight all-metallic (Ti-6Al-4V alloy) sandwich beams with corrugated channel cores was investigated by experiments and finite element (FE) simulations. The natural frequencies and mode shapes were measured and compared with simulations from both three-dimensional model (3D model) and two-dimensional equivalent model (2D model). Predictions of the 2D model agreed well with results obtained from the 3D model and experiments. It was found that for sandwich beams, the topological change from corrugated core to corrugated channel core eliminates the anisotropy of the structural stiffness and suppresses the local modes of vibration. The effect of geometrical parameters on the first natural frequency was also explored. In addition, preliminary assessment of the influence induced by varying the core topology was carried out. The first natural frequency of sandwich beams with corrugated channel cores having an inclination angle θ > 45° is higher than those of sandwich beams constructed with competing core topologies, including tetrahedral, Kagome and pyramidal trusses and hexagonal honeycombs.

Metallic circular tube with external uniform grooves has excellent behaviors on axial crashworthiness during axial compression because it can generate stable responses. In the present research, three novel energy absorbers are proposed based on uniform grooved tube (UGT), namely, depth gradient grooved tube (D-GGT), thickness gradient grooved tube (T-GGT) and coupling gradient grooved tube (C-GGT). A theoretical model considering both the depth and thickness gradients and an efficient numerical model based on axisymmetric assumption are put forward. Meanwhile, some quasi-static compression experiments are performed to validate the theoretical and numerical models. The results conclude that the deformation of gradient grooved tubes (GGTs) under axial buckling can be classified into two modes, namely, random asymptotic buckling (RAB) and sequential asymptotic buckling (SAB). Compared with UGT, the D-GGT has a slight improvement on the axial energy performance even though the sum of depth of thin-walled sections is constant; for T-GGT, a force-displacement curve with upward trend and an obvious improvement of energy absorption are observed; specially, the energy absorption characteristics of D-GGT and T-GGT will occur simultaneously when C-GGT is subjected to axial loading.

Novel ultralight sandwich panels, which are comprised of corrugated channel cores and are faced with two identical solid sheets, subjected to generalized bending are optimally designed for minimum mass. A combined analytical and numerical (finite element) investigation is carried out. Relevant failure mechanisms such as face yielding, face buckling, core yielding and core buckling are identified, the load for each failure mode derived, and the corresponding failure mechanism maps constructed. The analytically predicted failure loads and failure modes are validated against direct finite element simulations, with good agreement achieved. The optimized corrugated channel core is compared with competing topologies for sandwich construction including corrugations, honeycombs and lattice trusses, and the superiority of the proposed structure is demonstrated. Corrugated-channel-core sandwich panels hold great potential for multifunctional applications, i.e., simultaneous load bearing and active cooling.

Ultralight all-metallic sandwich cylindrical shells with corrugated cores are designed and fabricated using a method involving tamping and shape correction. Quasi-static axial compressive behaviors of the sandwich shells are investigated using a combined experimental, theoretical and numerical approach. Based on the analytical model and numerical approach, systematic parametric study is carried out to explore the effects of key geometrical parameters on the failure load and energy absorption capacity. Minimum weight design as a function of the failure load is subsequently carried out for the proposed sandwich shell. As an attempt for further performance enhancement, the foam-filled corrugated-core sandwich cylindrical shell is proposed and a preliminary experimental study is carried out. The superiority of sandwich shells over monolithic shells in terms of initial failure load and energy absorption is clearly demonstrated, potentially important for applications demanding simultaneous ultra-lightweight, load-bearing and energy absorption. Keywords: Sandwich cylindrical shell, Corrugated core, Axial compression, Minimum weight design

A refined four-unknown quasi-3D zigzag beam theory is developed to model the free vibration and buckling behaviors of multilayered composite beams subjected to axial mechanical loading (e.g., distributed load and terminal force) and uniform temperature variation. Types of the composite beams considered include laminated composite beams, sandwich beams with composite face sheets, and fiber metal laminates. The proposed theory accounts for not only thickness stretching but also interlaminar continuity of transverse shear stresses and displacements. Associated eigenvalue problems for various boundary conditions are derived using the Ritz method. Accuracy and effectiveness of the theoretical predictions are verified by comparison with existing results and present finite element simulations. The theory is employed to quantify the effects of axial distributed load/terminal force and temperature variation on free vibration and buckling for different boundary conditions, geometric parameters and material properties. The present theory could produce sufficiently accurate predictions of natural frequencies and buckling capacities of multilayered beams at a very low computational cost.

Fe3O4 nanoparticle-infiltrated chromatography paper is prepared using a low-cost blending method. Upon characterizing the basic material properties of the Fe3O4/paper nanocomposite, beam-, accordion- and star-shaped actuators are constructed using the nanocomposite and the corresponding actuation performance is investigated experimentally. The beam-shaped actuator exhibits a reversible flexural deformation due to low magnetic hysteresis loop of the Fe3O4/paper nanocomposite, maintaining a stable response after 100 cycles. The accordion-shaped actuator can reach a maximum strain of 100% while the star-shaped actuator can capture a spitball twice heavier than itself.

Dual-level stress plateaus (i.e., relatively short peak stress plateaus, followed by prolonged crushing stress plateaus) in metallic hexagonal honeycombs subjected to out-of-plane impact loading are characterized using a combined numerical and analytical study, with the influence of the strain-rate sensitivity of the honeycomb parent material accounted for. The predictions are validated against existing experimental measurements, and good agreement is achieved. It is demonstrated that honeycombs exhibit dual-level stress plateaus when bucklewaves are initiated and propagate in cell walls, followed by buckling and progressive folding of the cell walls. The abrupt stress drop from peak to crushing plateau in the compressive stress versus strain curve can be explained in a way similar to the quasi-static buckling of a clamped plate. The duration of the peak stress plateau is more evident for strain-rate insensitive honeycombs.

Ultralight sandwich constructions with corrugated channel cores (i.e., periodic fluid-through wavy passages) are envisioned to possess multifunctional attributes: simultaneous load-carrying and heat dissipation via active cooling. Titanium alloy (Ti-6Al-4V) corrugated-channel-cored sandwich panels (3CSPs) with thin face sheets and core webs were fabricated via the technique of selective laser melting (SLM) for enhanced shear resistance relative to other fabrication processes such as vacuum brazing. Four-point bending responses of as-fabricated 3CSP specimens, including bending resistance and initial collapse modes, were experimentally measured. The bending characteristics of the 3CSP structure were further explored using a combined approach of analytical modeling and numerical simulation based on the method of finite elements (FE). Both the analytical and numerical predictions were validated against experimental measurements. Collapse mechanism maps of the 3CSP structure were subsequently constructed using the analytical model, with four collapse modes considered (face-sheet yielding, face-sheet buckling, core yielding, and core buckling), which were used to evaluate how its structural geometry affects its collapse initiation mode.

Degradation of the prothioconazole by three strains of microorganisms isolated from activated sludge obtained from a pesticide factory was assessed, and an ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QqTOF-MS) method for the determination of prothioconazole and its metabolites was established. The optimal conditions for the degradation of prothioconazole were determined by single factor optimization experiments. A degradation rate of 93.32% is achieved when the prothioconazole is co-cultured with the strain W313 at a cultivation time of 60 h, a cultivation temperature of 30 °C, a pH of 6.33, a prothioconazole concentration of 50 mg L−1, a microorganism volume of 10%, and a dextrose volume of 4%. The three effective microorganism strains were identified by morphological and molecular biology to be Candida tropicalis, Enterobacter cloacae, and Pseudomonas aeruginosa. UPLC-QqTOF-MS analysis allowed the identification of 62 different prothioconazole degradation products produced by the strain cultures, with prothioconazole-desthio, prothioconazole-dechloropropyl, and oxidizing prothioconazole being the main products. In addition, degradation products from different strains and conditions were compared. The results of scatter plot (S-Plot) analysis indicated that C9H7NO, C10H17N7, and C12H13ClN2O were only detected in the products incubated with Enterobacter cloacae. Thus, this study demonstrates that Enterobacter cloacae and Pseudomonas aeruginosa possesses high potential for bioremediation of prothioconazole-contaminated environments.

The security of cloud infrastructure is an important issue. Many solutions have been proposed to protect the integrity of cloud infrastructure through integrating Trusted Computing hardware. However, these existing solutions suffer from high complexity, repetition and latency. In this paper, we propose a blockchain based cloud service dependency attestation framework–CloudCoT (Cloud Chain-of-Trust). With CloudCoT which combines trusted computing and blockchain technology, cloud users are able to automatically extract the valid dependency of their applications deployed on cloud. And they can attest the valid dependency with low latency through its measurement mechanism and verification mechanism. In addition to the decentralized features, we can see that CloudCoT has higher efficiency while maintaining strong safety in experimental evaluation.

This article proposes a modified sequential multilateration method for measuring three-dimensional coordinates. The measuring system consists of a single laser tracker and four relay targets whose relative positions have been pre-calibrated by the multilateration method. The laser tracker is fixed on three prescribed positions successively, and these positions can be calibrated by using the distances between the laser tracker and the four relay targets based on the multilateration principle. Subsequently, the three-dimensional coordinates of each under-test point can be determined by the three laser trackers’ positions based on the trilateration principle. This method is more flexible than previous multilateration methods for three-dimensional coordinate collection, especially if the measurement space is partially covered by other objects. The mathematical model of this method is established. Based on the Monte Carlo method, a series of computer simulations are performed to optimize the system arrangement by investigating the performances of the measuring system with different system arrangement, and an optimal system arrangement is finally obtained. Practical measurement is also conducted to demonstrate the validity of the proposed method by comparing with a reference coordinate measuring machine.

In this paper, noise removing of the well test data is considered. We use the Legendre expansion to approximate well test data and a truncated strategy has been employed to reduce noise. The parameter of the truncation will be chosen by a discrepancy principle and a corresponding convergence result has been obtained. The theoretical analysis shows that a well numerical approximation can be obtained by the new method. Moreover, we can directly obtain the stable numerical derivatives of the pressure data in this method. Finally, we give some numerical tests to show the effectiveness of the method.

A novel sandwich core topology – corrugated channels (periodic fluid-through wavy passages) – was proposed for simultaneous load-bearing and active cooling applications. Relative to a sandwich panel with parallel plate channels, the sandwich with corrugated channel core exhibits not only significantly enhanced convective heat transfer rate but also superior mechanical performance. To explore the underlying deformation and failure mechanisms, corrugated-channel-cored sandwich panels (3CSPs) with low relative densities (

The ballistic performance of ultra-high molecular weight polyethylene (UHMWPE) laminated plates and UHMWPE encapsulated aluminum structures were numerically characterized. Full three-dimensional continuum model for each type of target was built, and the UHMWPE was simulated using a sub-laminate approach with a composite material model. Simulation results were compared with existing experimental measurements, with good agreement achieved both on final deformation morphology and ballistic data. Underlying penetration mechanisms of laminated plate were then explored, and the effect of interface strength was quantified. The ballistic improvement of UHMWPE encapsulated aluminum structures was mainly attributed to the stretching of lateral swathing laminates. However, the benefit of encapsulation decreased as the initial impact velocity or lateral dimensions of encapsulated structure were increased. These findings are helpful for designing lightweight UHMWPE composite structures with superior ballistic resistance.

All-metallic sandwich panels with lattice truss cores are typically ultralight, stiff and strong, yet poor in passive vibration damping. Novel laser-welded corrugated-core (LASCOR) sandwich panels with polyurea-metal laminates (PML) as face sheets were proposed and fabricated, and their vibration and damping characteristics were systematically investigated, both experimentally and numerically. Frequency/time response curves, natural frequencies, vibration mode shapes and damping loss factors were measured and compared with LASCOR sandwich panels without embedded polyurea layers. A combined finite element-modal strain energy (FE-MSE) method was proposed to predict the vibration damping performance and explore the underlying enhancement mechanisms, with the frequency-dependent damping behaviors of polyurea considered. Good agreement was achieved between numerical simulations and experimental measurements. The PML face sheets enabled remarkable damping enhancement, due mainly to viscoelastic energy dissipation of the polyurea layers. The capacity of the sandwich panel in passive vibration suppression could be further improved by tailoring the polyurea layer thickness and the distribution of polyurea layers.

How sand filling affects the dynamic response of metallic corrugated sandwich beams under shock loading was characterized, both experimentally and numerically, with shock loading simulated by high-speed impact of aluminum foam projectiles at beam mid-span. To facilitate evaluating the effects of sand filling, both empty and sand-filled corrugated core sandwich beams were assessed and compared for shock resistance. Representative deformation processes, deformation and failure modes, and beam deflections were experimentally obtained and analyzed. Sand-filled sandwich beams exhibited much higher shock resistance than the empty ones. Numerical simulations were subsequently conducted using a coupled discrete particle/finite element approach that takes into account the coupling interaction between the sand grains and corrugation members. The simulations predicted reasonably well the primary features (permanent mid-span deflections and deformation modes) of both the empty and sand-filled sandwich beams observed experimentally. The validated numerical model was employed to evaluate how the properties of the filling sand and other granular filling materials, e.g., density, stiffness, friction and damping, affect the shock resistance of sandwich beams. The results indicated that the shock resistance was sensitive to, firstly, the density and stiffness of sand and, secondly, the friction between sand particles. In contrast, the damping between sand particles had little effect.

A novel composite projectile is put forward to simulate combined blast and single fragment impact loading, which is comprised of a cylindrical aluminum foam projectile embedded with a fragment simulation projectile (FSP). Comparison between cased explosive and composite projectile in terms of the generated combined loading shows that the composite projectile technique is theoretical feasible. Experimental tests for normal impact of the composite projectile on clamped plates are carried out. Results show that the proposed composite projectile can induce both blast-induced deflection and fragment-induced perforation on the clamped plate. The arrival time interval between blast and fragment has significant influence on the extent of induced damage on the plate and the residual FSP velocity. Numerical simulations with the method of finite elements are carried out to provide further insight into the interaction between the composite projectile and clamped plate, and to explain observations and measurements in experiments. The present study reveals a new synergetic effect of combined blast and single fragment impact loading on clamped plate: arrival time interval between blast and impact loading affects significantly the residual velocity of the FSP.