Numerical Simulation on Ceramic/Metal Armours Impacted by Deformable Projectile

Numerical simulation for the dynamic response of ceramic/metal armours impacted by deformable projectile is carried out with LS-DYNA3D.The simulated penetration processes are shown. The mushrooming of the projectile is displayed. A distinct conoid shaped zone of fragmented ceramic is observed. A significant bending of the backing plate is revealed. Simulation results match fairly well with the experimental values and the theoretical analysis results. The accuracy of the numerical simulation is validated.

Direct Comparison between Tensile Strength and Flexural Strength of Ceramic/Metal Brazing Joint

A design of the sandwich joint,steel/ ceramic/steel,was made for direct comparison be- tween tensile and flexural strength of ceramic/metal joint.The flexural strength is about twice as high as the tensile strength for the same joint.The results also showed that the flexural test is more excellent than tensile test for joint with a high interracial bond strength.

ANALYTICAL MODEL OF CERAMIC/METAL ARMOR IMPACTED BY DEFORMABLE PROJECTILE

A new analytical model was established to describe the complex behavior of ceramic/metal armor under impact of deformable projectile by assuming some hypotheses. Three aspects were taken into account： the mushrooming deformation of the projectile, the fragment of ceramic tile and the formation and change of ceramic conoid and the deformation of the metal backup plate. Solving the set of equations, all the variables were obtained for the different impact velocities： the extent and particle velocity in rigid zone; the extent, cross-section area and particle velocity in plastic zone; the velocity and depth of penetration of projectile to the target; the reduction in volume and compressive strength of the fractured ceramic conoid; the displacement and movement velocity of the effective zone of backup plate. Agreement observed among analytical result, numerical simulation and experimental result confirms the validity of the model, suggesting the model developed can be a useful tool for ceramic/metal armor design.

A Ballistic Limit Analytical Model of Tungsten Ball Perforating Ceramic/Aluminum Composite Target

From the experimental data on ceramic/aluminum composite target, the mechanism of tungsten ball impacting a ceramic/aluminum composite target has been studied. By analyzing the transition of energy in the process of impact, a simple ballistic limit analytical model of tungsten ball impacting a ceramic/aluminum composite target has been proposed; and the result taken from this model is consistent with that of the experiment.

Microstructure and properties of the joints of ZrO2 ceramic/ stainless steel brazed in vacuum with AgCuTi active filler metal

The ZrO2 ceranfic was successfully jointed to stainless steel by vacuum brazing with active filler metal. The AgCuTi active filler metal was used and the joining was performed at a temperature of 850 ℃ for 10 rain. The microstructures of the joints were characterized by metallographic microscopy, scanning electron microscopy （SEM）, and energy dispersive spectroscopy （EDS）. Metallographic microscopy analysis shows that the morphology of the cross section was a sandwich structure and the TiO is observed in the surface of ZrO2/ stainless steel. The diffusion and enrichment of the elements are the key roles in the brazing of ZrO2 ceramic and stainless steel. The formation of TiCu compounds inhibited the further diffusion of titanium into stainless steel or the ZrO2 ceramic to form TiO compound. In the experimental conditions, the average tensile strength is 80MPa for the joint of ZrO2 ceramic / AgCuTi/ stainless steel systems. A complete joint is formed between the ZrO2 ceramic and stainless steel with the leakage rate at the degree of 10 ^-12 Pa · m^3/s.

Numerical Simulations of Tungsten Alloy Rods Penetration into Alumina Ceramic/Armor Steel Composite Target

The Johnson-Holmquist constitutive ceramic model is re-implemented into the LS_ DYNA3D program to simulate the penetration of long rod projectile into ceramic/armor steel composite targets. The damage evolution, fracture propagation, and spall damage in the ceramic/armor targets is represented during the simulation procedure and the accuracy of the penetration depth comparing between the simulating and experimental results is reliable with an error less than 8 %. The relationship between the mass efficiency factor, differential factor and ceramic tiles thickness is given out for the penetration results with/without a cover plate.

Experimental study on the penetration effect of ceramics composite projectile on ceramic/A3 steel compound targets

In order to improve the penetration of projectiles into ceramic composite armors,the nose of 30 mm standard projectile was replaced by a toughened ceramic nose,and the performance of ceramic-nose projectiles penetrating into ceramic/A3 steel composite targets has been experimentally researched.According to impact dynamics theory,,the performances of 30 mm ceramic-nose projectile and 30 mm standard projectile penetrating into the ceramic/A3 steel composite targets were analyzed and compared using DOP method,especially focusing on the effects made by different nose structures and materials.The aperture and depth of perforation of projectile into the armor plates as well as the residual mass of bullet core under the same conditions were comparatively analyzed.A numerical simulation was built and computed by ANSYS/LS-DYNA.Based on the simulated results,the penetration performance was further analyzed in terms of the residual mass of bullet core.The results show that the ceramic nose has a great effect on the protection of bullet core.

Preparation of defect free ceramic/Ti composite membranes by surface modification and in situ oxidation

Al2O3 ceramic powder was applied to modify the large pores defects on the surface of the porous metal Ti support,in situ oxidation method was a convenient method to prepare defect free ceramic/Ti composite membranes on this basis.In situ oxidation conditions experimental results show that the best condition for preparing the TiO2-Al2O3/Ti composite membrane is under 800°C for 2 h,and the microstructure and pore sizes of the TiO2-Al2O3/Ti composite membranes are affected obviously.The thickness and composition of the TiO2/Ti composite membranes are determined by SEM and XRD completely.The pore size distribution of the composite membrane is measured by bubble pressure method,the most probable aperture is about 3.12μm,while the average pore size of defect free TiO2-Al2O3/Ti is about 3.23μm.After ultrasonic treatment,the slight weight change of membranes reveals no observable change,which indicates that TiO2-Al2O3/Ti composite membranes maintain a good stability.

Identification and evolution of interfacial structure of SiO2 glass ceramic/Ti-6AI-4V alloy joint bonded with AgCu/Ni interlayer

AgCu/Ni composite interlayer was utilized to join SiO2 glass ceramic （74. 52% SiO2-23. 40% Al2 03 -2. 08 % K2 O, wt. % ） and Ti-6Al-4V alloy by eutectic reaction. Interface structures of the joints were identified by means of TEM analysis. This joining method contains three characteristic processes, which are the melting of AgCu eutectic alloy, eutectic reaction between interlayer and Ti-6Al-4V base material and active reaction of element Ti to SiO2 glass ceramic. It is different from traditional active brazing because active element Ti totally dissolves from Ti-6Al-4 V and reacts with SiO2 glass ceramic. SiO2 glass ceramic can be joined suecessfuUy to Ti-6Al-4 V alloy by this novel bonding method and the joint exhibits high shear strength, up to 110 MPa.

FEM simulation on residual stress distribution during diffusion bonding between Ti （ C, N） metallic ceramic/interlayer/40Cr steel

Based on ANSYS FEM software, the distribution of residual stress in the diffusion bonding joints between Ti（ C,N） metallic ceramic/interlayer/4OCr steel was calculated and experimentally ver^ed. The results showed that the trend on the distribution of residual stress field in the joints was not changed with the use of interlayer. The maximum residual stress was always located in metallic ceramic with area ranging from 1 mm to 4 mm to the interlayer. The maximum residual stress in the joints was also affected by diffusion temperature. The satellite pulse current during the initial stage on diffusion bonding can promote the formation of liquid film at the interface, by which diffusion temperature and loading pressure can be greatly decreased. The crack initiation was easily produced at the corner of Ti （ C, N） metallic ceramic close to the interlayer. If a higher residual stress produced in the joints, the crack was propagated into the whole ceramic.

Processing and mechanical properties of network ceramic/steel composites by pressureless infiltration

A new style Ni-containing alumina ceramic foam based continuous three-dimensional interconnected skeleton was prepared by impregnating a polymeric sponge with aqueous ceramic slurry.Subsequently,alumina ceramic foam/steel metal matrix composites(MMCs) were prepared successfully by sand mold casting technique.The microstructure and mechanical properties of MMCs were investigated by SEM,EDS and compressive test.The results show that the depth of infiltration is about 40 μm to the bonding interface of ceramic/steel and the fracture strength σmax and plastic strain limit εp of composite are 520 MPa and 11.2%,respectively.The fretting wear mechanism of MMCs is mainly performed at the oxidative wear mode with lower load/friction frequency and the predominant oxidation wear together with slight adhesive wear and abrasive wear multiple mode with higher load/ friction frequency.Moreover,the infiltration bonding and continuous three-dimensional interconnected ceramic skeleton play a vital role in the stability of the bonding interface and excellent mechanical properties.

NUMERICAL SIMULATION OF IMPACT RESPONSE OF COMPOSED CERAMIC/COMPOSITE ARMOUR

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Influence of Boundary Conditions on Ceramic/Metal Plates under Ballistic Loads

Ceramic/metal plate is one of the most widely used light weight armors, especially to protect armor piercing (AP) bullet. Experimental investigation of projectile penetration mechanism into the ceramic/metal plate requires costly sensitive equipment to capture impact phenomenon that completes within microseconds. Alternatively, the impact mechanism can be efficiently investigated using numerical simulations. Among recent investigations on the protective capability of this ceramic/metal plates, few only discussed the influence of the boundary effects on the ballistic protection. This study thus aims to examine the effect of boundary conditions by changing shapes of the plate, border constraints and bounded materials in numerical simulation. Material models of the ceramic and the backing metal plate made of aluminium 2017-T6 are selected. The 7.62 AP projectile’s core was modeled by a solid cylinder. The initial projectile velocity was 940 m/s. The plates are represented by either a square or a hexagonal tile. The edges of the plates were fixed or enclosed by a soft epoxy. To investigate the effect of backing plate, a small gap was introduced between some of the ceramic and aluminum interfaces. The results showed that the hexagonal tiles reduce the deformation of the backing plate. The plates bounded by the epoxy exhibit inferior performances compared to the fixed plates. Finally, the small gap between the ceramic and the aluminum interfaces significantly increases the time to stop the projectile.

Grindability Evaluation of Ultrasonic Assisted Grinding of Silicon Nitride Ceramic Using Minimum Quantity Lubrication Based SiO_(2)Nanofluid

Minimum quantity Lubrication(MQL)is a sustainable lubrication system that is famous in many machining systems.It involve the spray of an infinitesimal amount of mist-like lubricants during machining processes.The MQL system is affirmed to exhibit an excellent machining performance,and it is highly economical.The nanofluids are understood to exhibit excellent lubricity and heat evacuation capability,compared to pure oil-based MQL system.Studies have shown that the surface quality and amount of energy expended in the grinding operations can be reduced considerably due to the positive effect of these nanofluids.This work presents an experimental study on the tribological performance of SiO_(2)nanofluid during grinding of Si_(3)N_(4)ceramic.The effect different grinding modes and lubrication systems during the grinding operation was also analyzed.Different concentrations of the SiO_(2)nanofluid was manufactured using canola,corn and sunflower oils.The quantitative evaluation of the grinding process was done based on the amount of grinding forces,specific grinding energy,frictional coefficient,and surface integrity.It was found that the canola oil exhibits optimal lubrication performance compared to corn oil,sunflower oil,and traditional lubrication systems.Additionally,the introduction of ultrasonic vibrations with the SiO_(2)nanofluid in MQL system was found to reduce the specific grinding energy,normal grinding forces,tangential grinding forces,and surface roughness by 65%,57%,65%,and 18%respectively.Finally,regression analysis was used to obtain an optimum parameter combinations.The observations from this work will aid the smooth transition towards ecofriendly and sustainable machining of engineering ceramics.

Advances and challenges in direct additive manufacturing of dense ceramic oxides

Ceramic oxides,renowned for their exceptional combination of mechanical,thermal,and chemical properties,are indispensable in numerous crucial applications across diverse engineering fields.However,conventional manufacturing methods frequently grapple with limitations,such as challenges in shaping intricate geometries,extended processing durations,elevated porosity,and substantial shrinkage deformations.Direct additive manufacturing(dAM)technology stands out as a state-of-the-art solution for ceramic oxides production.It facilitates the one-step fabrication of high-performance,intricately designed components characterized by dense structures.Importantly,dAM eliminates the necessity for post-heat treatments,streamlining the manufacturing process and enhancing overall efficiency.This study undertakes a comprehensive review of recent developments in dAM for ceramic oxides,with a specific emphasis on the laser powder bed fusion and laser directed energy deposition techniques.A thorough investigation is conducted into the shaping quality,microstructure,and properties of diverse ceramic oxides produced through dAM.Critical examination is given to key aspects including feedstock preparation,laser-material coupling,formation and control of defects,in-situ monitoring and simulation.This paper concludes by outlining future trends and potential breakthrough directions,taking into account current gaps in this rapidly evolving field.

Rational Design of Ruddlesden-Popper Perovskite Ferrites as Air Electrode for Highly Active and Durable Reversible Protonic Ceramic Cells

Reversible protonic ceramic cells(RePCCs)hold promise for efficient energy storage,but their practicality is hindered by a lack of high-performance air electrode materials.Ruddlesden-Popper perovskite Sr_(3)Fe_(2)O_(7−δ)(SF)exhibits superior proton uptake and rapid ionic conduction,boosting activity.However,excessive proton uptake during RePCC operation degrades SF’s crystal structure,impacting durability.This study introduces a novel A/B-sites co-substitution strategy for modifying air electrodes,incorporating Sr-deficiency and Nb-substitution to create Sr_(2.8)Fe_(1.8)Nb_(0.2)O_(7−δ)(D-SFN).Nb stabilizes SF’s crystal,curbing excessive phase formation,and Sr-deficiency boosts oxygen vacancy concentration,optimizing oxygen transport.The D-SFN electrode demonstrates outstanding activity and durability,achieving a peak power density of 596 mW cm^(−2)in fuel cell mode and a current density of−1.19 A cm^(−2)in electrolysis mode at 1.3 V,650℃,with excellent cycling durability.This approach holds the potential for advancing robust and efficient air electrodes in RePCCs for renewable energy storage.

New Strategy for Boosting Cathodic Performance of Protonic Ceramic Fuel Cells Through Incorporating a Superior Hydronation Second Phase

For protonic ceramic fuel cells,it is key to develop material with high intrinsic activity for oxygen activation and bulk proton conductivity enabling water formation at entire electrode surface.However,a higher water content which benefitting for the increasing proton conductivity will not only dilute the oxygen in the gas,but also suppress the O_(2)adsorption on the electrode surface.Herein,a new electrode design concept is proposed,that may overcome this dilemma.By introducing a second phase with high-hydrating capability into a conventional cobalt-free perovskite to form a unique nanocomposite electrode,high proton conductivity/concentration can be reached at low water content in atmosphere.In addition,the hydronation creates additional fast proton transport channel along the two-phase interface.As a result,high protonic conductivity is reached,leading to a new breakthrough in performance for proton ceramic fuel cells and electrolysis cells devices among available air electrodes.

Porous high-entropy rare-earth phosphate(REPO_(4),RE=La,Sm,Eu,Ce,Pr and Gd)ceramics with excellent thermal insulation performance via pore structure tailoring

Thermal insulation materials play an increasingly important role in protecting mechanical parts functioning at high temperatures.In this study,a new porous high-entropy(La_(1/6)Ce_(1/6)Pr_(1/6)Sm_(1/6)Eu_(1/6)Gd_(1/6))PO_(4)(HE(6RE_(1/6))PO_(4))ceramics was prepared by combining the high-entropy method with the pore-forming agent method and the effect of different starch contents(0–60vol%)on this ceramic properties was systematically investigated.The results show that the porous HE(6RE_(1/6))PO_(4)ceramics with 60vol%starch exhibit the lowest thermal conductivity of 0.061 W·m^(-1)·K^(-1)at room temperature and good pore structure stability with a linear shrinkage of approximately1.67%.Moreover,the effect of large regular spherical pores(>10μm)on its thermal insulation performance was discussed,and an optimal thermal conductivity prediction model was screened.The superior properties of the prepared porous HE(6RE_(1/6))PO_(4)ceramics allow them to be promising insulation materials in the future.

High-strength,multifunctional and 3D printable mullite-based porous ceramics with a controllable shell-pore structure

The quest for lightweight and functional materials poses stringent requirements on mechanical performance of porous materials.However,the contradiction between high strength and elevated porosity of porous materials severely limits their application scenarios in emerging fields.Herein,high-strength multifunctional mullite-based porous ceramic monoliths were fabricated utilizing waste fly ash hollow microspheres(FAHMs)by the protein gelling technique.Owing to their unique shell-pore structure inspired by shell-protected biomaterials,the monoliths with porosity of 54.69%–70.02% exhibited a high compressive strength(32.3–42.9 MPa)which was 2–5 times that of mullite-based porous ceramics with similar density reported elsewhere.Moreover,their pore structure and properties could be tuned by regulation of the particle size and content of the FAHMs,and the resultant monoliths demonstrated superior integrated performances for multifunctional applications,such as broadband sound insulation,efficient thermal insulation,and high-temperature fire resistance(>1300℃).On this basis,mullite-based porous ceramic lattices(porosity 68.28%–84.79%)with a hierarchical porous structure were successfully assembled by direct ink writing(DIW),which exhibited significantly higher compressive strength(3.02–10.77 MPa)than most other ceramic lattices with comparable densities.This unique shell-pore structure can be extended to other porous materials,and our strategy paves a new way for cost-effective,scalable and green production of multifunctional materials with well-defined microstructure.

Structural and Luminescent Properties of Mg_(0.25-x)Al_(2.57)O_(3.79)N_(0.21):xMn^(2+)Green-Emitting Transparent Ceramic Phosphor

A series of spinel-type Mg_(0.25-x)Al_(2.57)O_(3.79)N_(0.21):xMn^(2+)(MgAlON:xMn^(2+))phosphors were synthesized by the solid-state reaction route.The transparent ceramic phosphors were fabricated by pressureless sintering followed by hot-isostatic pressing(HIP).The crystal structure,luminescence and mechanical properties of the samples were systematically investigated.The transparent ceramic phosphors with tetrahedrally coordinated Mn^(2+)show strong green emission centered around 515 nm under blue light excitation.As the Mn^(2+)concentration increases,the crystal lattice expands slightly,resulting in a variation of crystal field and a slight red-shift of green emission peak.Six weak absorption peaks in the transmittance spectra originate from the spin-forbidden ^(4)T_(1)(^(4)G)→^(6)A_(1) transition of Mn^(2+).The decay time was found to decrease from 5.66 to 5.16 ms with the Mn^(2+)concentration.The present study contributes to the systematic understanding of crystal structure and properties of MgAlON:xMn^(2+)green-emitting transparent ceramic phosphor which has a potential application in high-power light-emitting diodes.