Back Plate Research Articles

The anti-explosion performance of ceramic/high-strength steel composite protective structures

Ceramic composite structures are important in developing lightweight protection applications. Designers primarily design for armor-piercing threats. However, it is difficult to avoid the threat of high explosives or improvised explosive devices on the battlefield. In this work, three ceramic composite structures with different type and thickness of the ceramic panel were assessed by explosion test and finite element modelling to study their damage and failure characteristics. The ceramic composite structures exhibit good wave weakening ability. The type of ceramic does not change the anti-explosion performance of the composite structure when the surface density is similar, but the two kinds of ceramics show different damage and fracture mechanisms. Specifically, intergranular fracture mainly occurs in the alumina ceramic, whereas transgranular fracture mainly occurs in the SiC ceramic. In all cases, the back plate made of high strength steel undergoes plastic deformation and the ceramic panel is fragmented in response to the explosive impact, and the size of ceramic fragments increases from the center to the boundary of the ceramic panel.

Plate structure optimization and performance study of a new continuous flow electrocoagulation reactor

Electrocoagulation (EC) process is an environmentally friendly and effective water treatment method. A folded plate EC reactor has been developed to remove pollutants such as azo dyes and COD from wastewater. There is a dead zone in the corner position of this electrocoagulation reactor, so this study aims to improve this problem and strengthen the EC mass transfer process in the reactor. A circular perforation treatment at the corner of the folded plate electrode is proposed to promote the exchange between the dead zone and the active zone and enhance the mixing strength. Taking methyl orange as the target pollutant, the effects of perforation diameter, perforation spacing and plate arrangement were considered, and these parameters were optimized by Box-Behnken model. The results show that the removal efficiency of 92.16% is obtained when the perforation diameter is 4 mm, the perforation spacing is 20 mm and the plate arrangement is 0.5 L height difference between the front and back plates. In addition, the RTD curve shows that the dead zone of the perforated electrode is lower, the dimensionless variance is larger, and the mixing effect is better. The cost was reduced by perforation design and optimization of operating parameters, and the COD removal efficiency of 16.8% and the decolorization efficiency of 17.4% were increased in pharmaceutical wastewater.

An efficient underwater absorber using pentamode metamaterials for broadband frequency

To further design and develop broadband and efficient underwater sound absorption structure, we propose a hybrid acoustic structure composed of a rubber matrix layer, cylindrical cavity, pentamode metamaterial (PM) layer, impedance matching layer, and steel backing plate. Thanks to the special properties of the PMs, the hybrid acoustic structure obtains excellent broadband sound absorption performance (SAP) in the frequency range of 500–10000 Hz than that of the traditional cavity acoustic structure. To this end, we study the design principle of PM structure and its metal–water characteristics and analyze the sound absorption mechanism at the working frequency. In addition, the research shows that the material and geometric parameters of the structure have a significant impact on the SAP. By the optimization of structural material parameters, the average absorption coefficient at 500–10000 Hz can further increase to above 0.781. Finally, we also demonstrate that the structure still has good SAP under a wide range of oblique incidence angles. The research in this paper opens up bright perspectives for the design of underwater anechoic coatings for multifunctional applications.

Open-Circuit Fault Detection in a Single Conductor Transmission Line Using TM0 Mode Launcher

A novel surface wave (SW) launcher design for power line fault detection is presented in this paper. The launcher is capable of converting TE10 to TM0 mode and exciting SW signal at 5.5 GHz frequency with high efficiency, on a single conductor line. The average attenuation of 2 dB/m and front to back ratio of 19 dB are observed and verified by simulation and experiments. Effect of bend, nearby obstacles, and extra wire connection on SW propagation is also investigated by experiments, and corresponding S-parameter results are presented. The optimization of launcher design with dielectric window and conical back plate is also demonstrated. The proposed launcher is compact and lightweight and can be easily installed without damaging the conductor line. Close structure makes it capable of withstanding outdoor environmental conditions. Using this launcher, microwave signal can be efficiently transmitted and received over existing conductor lines such as live power lines, pipes, and HVAC ducts, and it can be used in applications such as power line communication, fault detection, and permittivity measurement.

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

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

Methods to Increase the Protective Effectiveness of Add-on Armour made of Perforated Ultra-High-Strength Nanobainitic Steel Plates

The mechanical properties of industrially produced perforated steel plates are obtained by hardening and low-temperature tempering to produce a martensitic microstructure. Another morphological type of steel microstructure that allows for ultra-high strength and, at the same time, a level of ductility that qualifies it for use in armour is nanobainite. Research into nanobainitic steels has led to the development of plates manufacturing technology at a level that can be implemented in industrial production, and has confirmed the high potential of this material for use as additional armour in the form of perforated plates. This paper reports the results of research aimed at developing a technology for the production of perforated armour plates made of nanobainitic steel, with properties competitive with currently available perforated steel plates on the world market with the highest protective effectiveness under conditions of multi-hit firing tests with small and medium calibre ammunition. The tests were performed on 300 260 mm plates, with the nominal thicknesses of 8 mm, 6 mm and 4 mm, produced from industrially melted nanobainitic steel NANOS-BA. The protective effectiveness of nanobainitic perforated plates in a system with a solid armour steel backing plate of 500 HBW hardness was tested by multi-hit firing, according to the procedures set out in the STANAG 4569 and AEP-55 vol. 1 specifications (adapted to the format of tested plates), against selected projectile types assigned to protection levels 2 and 3. Based on the analysis of the results of the firing tests and the macroscopic and microscopic examinations of the perforated plates before and after firing, the optimum perforation method was selected and the most favourable geometrical and dimensional arrangements of the perforations were determined for different plate thicknesses.

Single and double-layered kirigami corrugated sandwich panels against impact loads

The influences of geometric configurations on the impact resistance performances for single and double-layered kirigami corrugated (KC) sandwich panels are investigated in this study. By folding a portion of the cell wall of a conventional corrugated unit, a kirigami corrugate unit is formed with significantly improved resistance, which is then used to form single and double-layered sandwich panels. The numerical model is first constructed and validated against the pendulum impact test results of the KC panel. To evaluate the effect of the geometric configurations on their impact resistance performance, four factors are considered, including the number and location of the fold-ins of the single-layered KC panel, the stacking and layer orientation of the double-layered KC panels. In total, 38 configurations of the panels are numerically studied, and their impact performances including energy absorption, peak and residual back plate deflection, and impact force–displacement curves are evaluated and compared. Up to 84% reduction in the residual back plate deflection is observed for single-layered KC panel compared to the conventional corrugated panel. Superior impact resistance is demonstrated for single-layered KC panels with more fold-ins, especially near the impacting area. It is also found that the stacking configuration and layer orientation are not directly linked to the impact resistance performance of double-layered KC panels. However, enhanced impact resistance could be achieved by arranging the stacking and orientation of the two core layers to provide better supports to the top cores. This work provides general design guidelines for the proposed single and double-layered KC panels.

Influence of brush seal hysteresis effect on the nonlinear characteristics of rotor system

The hysteresis effect of brush seal is a key factor affecting the sealing performance of the rotor system, so it is particularly important to study the nonlinear behaviors of the rotor-bearing-brush seal system under the hysteresis effect. First, the entire circle of bristle pack is classified according to the position angle and contact condition of single bristle, and the rotor support force, the interaction force between the bristles, the air pressure and the friction of back plate are considered. It is proposed to use the loss rate to calculate the uniform load of the back plate, according to the linear beam theory, the bending force model of bristle under different rotor eccentricity is established. Second, the hysteresis angle is proposed to represent the degree of hysteresis effect of the whole circle of bristle pack, and the seal force model under hysteresis effect is established. Third, considering the interaction of seal force and oil-film force, the dynamic model of Jeffcott rotor-bearing-brush seal system is established. The influence of hysteresis effect on the dynamic characteristics of rotor system is studied by using bifurcation diagram, axis orbit, Poincaré map, spectrum diagram and time history. It is found that the hysteresis effect has different degrees of influence on the nonlinear dynamic characteristics of the rotor system in different rotational velocity intervals. In addition, the influence of seal interference on the motion state of rotor system cannot be ignored.

Ballistic performance of integral body armor with closed-cell aluminum foam: A numerical study

This numerical study is dedicated to investigating the ballistic performance of three-component integral body armor comprising ceramic façade, layers of ultra-high molecular weight polyethylene fiber-based composite (Dyneema) and closed-cell aluminum foam against NIJ-Type IV armor-piercing bullets. A numerical model of integral armor with a ceramic façade and a fiber-reinforced composite backing plate was developed in IMPETUS Afea Solver and verified against experimental data. The verified model was used to design a "baseline configuration" of two-component integral armor that can stop the NIJ-Type IV projectiles. Three-component armor configurations were obtained by introducing layer(s) of closed-cell aluminum foam into the laminate. Laminates with different stacking sequences of composite and porous layers and different foam relative densities were studied and compared with the baseline two-component configuration. The study presents new insights into the mechanics of perforation of integral armor with closed-cell foam and provides design recommendations for such armor systems.

A framework to measure readiness and barriers for the implementation of Industry 4.0: A case approach

Large businesses perceive the vital usefulness of Industry 4.0. They recognize how beneficial its implementation is to reinforce business competitiveness and to conserve, or even better, to increase their market share. Hence, top business management has embraced the challenge of the time: to evaluate the current level of digitization with the objective of proceeding to a full digitization phase in the future. With this concern, this paper proposes a framework to assist industries in promoting Industry 4.0 through two phases. In the initial phase, the case company’s level of readiness is evaluated, and in the second phase, the barriers that exist within the implementation of Industry 4.0 (based on the company’s readiness, obtained from the previous phase) are analyzed. Both phases have been carried out at a Danish case industry which is a third-tier supplier of anti-noise shims and back plates for manufacturers of disc brake linings. In the first phase, the assessment of readiness for Industry 4.0 demonstrates that the case industry is not fully ready; instead, they reside in the position of Industry 3.5 (in the middle of 3.0 and 4.0 revolutions). The limiting barriers to change for Industry 4.0 implementation are identified during the systematic literature review and analyzed using the DEMATEL method based on the industrial decision-makers’ responses in the second phase. Moreover, the analysis demonstrates the most influential barrier category is the policy & organization category. The barrier “leadership” is considered the greater influencer of all since it responds in some way to almost all 21 barriers. Thus, leadership is the most significant barrier a company must overcome to adopt the Industry 4.0 concept. In addition, firms are challenged by the organizational changes that the adoption of Industry 4.0 will bring, and the tool of organizational change management will be handy.

Temperature Calculation, Test and Structure Improvement of Magnetic Coupling under High Slip

The temperature effect caused by high slip has an important influence on the operation performance and reliability of magnetic coupling. Taking the self-developed single disk asynchronous magnetic coupling as the research object, the heat loss equation of the magnetic coupling is established. Based on the three-dimensional transient magnetic field simulation model of the magnetic coupling, the eddy current loss, torque, and eddy current distribution law of the magnetic coupling are obtained through simulation. The space flow field and structure temperature field distribution of the magnetic coupling are analyzed by using the fluid-thermal coupling simulation method, and the heat dissipation coefficient and temperature distribution law of the structure surfaces such as copper disk, the back lining yoke iron disk, and the aluminum disk are obtained. The test platform was built to test the torque and temperature of the magnetic coupling. The results show that the error between the test and simulation is 4.8% in the torque aspect, and the maximum error between the test and simulation is only 8.1% in the temperature aspect of each component, which further verifies the effectiveness of the simulation method. On this basis, three heat dissipation improvement schemes are proposed, including installing heat dissipation blocks, setting semicircular grooves on the back lining yoke iron disk, and a hybrid design. The results show that the degree of improvement for each scheme is in the following order: hybrid design, setting semicircular grooves on the back lining yoke iron disk, and installing heat dissipation blocks. Under the hybrid design, the temperature of the back lining yoke iron plate and a copper plate of the magnetic coupling is reduced by about 8.5 °C compared with the original model, and the effect is ideal. The research results can provide an optimization reference for high-speed magnetic coupling and the temperature effect caused by an overload-locked rotor.

Steven Test Modeling

The Steven test was introduced for studying low velocity impact initiation of explosives. The original diagnostics of the Steven test were blast gauges at a distance of about 3m. Trying to use these diagnostics to characterize the response of the explosive after its ignition, we realized that they’re not informative enough. We therefore replaced the blast gauges by velocity gauges, looking at the free surface of the back plate of the test sample. Our explosive is similar to LX07, and we performed several tests with impact velocities from 30m/s to 122m/s. The velocity histories we obtained from the gauges show the following: 1) there is a rather long delay between impact and ignition (or gauge response), 50µs for the highest impact velocity and around 250 µs for the 36m/s impact; 2) there’s no ignition at the impact velocity of 30m/s; 3) the gauge velocity histories rise gradually to a maximum and then continue with elastic oscillations. We model the response of the explosive assuming that it reacts through shear initiation. The projectile impact causes shear flow in the explosive, which leads to strain localization and formation of shear bands. The shear bands heat up and reach ignition temperature and deflagration waves expand out of them, similar to deflagration waves out of hot spots for shock initiation. Shear initiated reaction rate is rather slow as: 1) shear bands are surfaces (and not spots); and 2) the average distance between shear bands is of the order of 1mm, and not 0.1mm (as for hot spots). Also, shear-initiated reaction rate depends on pressure and not on reactant temperature (as for hot spot initiation). Here we use our PDSR (= Pressure Dependent Shear Reaction) model to reproduce our Steven test data. We get good agreement with delay times and amplitudes of the velocity gauge outputs.  

A compact high performance micro-electro-mechanical systems microphone

This paper reports on the development of a MEMS capacitive microphone design with 72 dBA signal-to-noise-ratio (SNR) in a compact 3.4 × 2.3 × 0.7 mm3package. The design incorporates a circular diaphragm disc suspended on one end of the cantilever beam. The diaphragm, under the bias conditions, is supported using peripheral and center protrusions extended from the back plate. The design optimization is targeted to achieve high sensitivity and low damping noise to achieve maximum SNR possible in the mentioned footprint. Finite element modeling (FEM) combined with the lumped element circuit modeling have been implemented to realize the microphone performance. The results have been validated against the measurement with very good correlation of sensitivity, noise and total harmonic distortion (THD). With the sensitivity of −35 dBV (ref. 1 V/Pa at 1 kHz) and acoustic overload point of 134 dBSPL, this is one of the highest performing MEMS analog microphone reported today. Therefore, it is very well suited for audio applications such as mobile phones, true wireless stereo (TWS) earphones, hearing aids and automotive, which demand miniaturized size, low cost and high performance.

Analysis of Friction Stirs Welding Using the PROMETHEE Method

In friction stir welding (FSW) near the tool Thermo-mechanical condition of the piece at work the aim of the present work is to simulate Using general purpose software for this A fully coupled three-dimensional solid mechanical model has been created. ABAQUS/Arbitrary Lagrange- Eulerian (ALE) formulation re-meshing and large Enables transparency with distortions. Of FSW One of the least understood aspects of in friction stir welding (FSW) near the tool. For different welding speeds, forces and equipment Temperatures are recorded accurately in standard welding are done. Conditions. Numerical the simulations implemented are arbitrary Based on the Lograngian Eulerian (ALE) formula have the key aspect of the numerical approach is the palette and contact and friction between the tool accurate calculations of surface area. Accurate calculation of surface area. PROMETHEE is a priority for assessment enrichment Ranking system and its interactive help Descriptive complementary geometric analysis known as Promethee methods. In this The PROMETHEE method is the best solution from the analysis the shorter the distance and the longer the negative-ideal solution Determines the solution with the distance, but of these distances the comparison was not considered significant. Alternative: Conductivity, Thermal capacity, Density, Effusively, Emissivity. Evaluation Preference: Work piece, FSW Tool, Backing plate, strength, and conductivity. As a result FSW tool is very low As a result passive tool is very low got first rank for strength. The value of the dataset for Friction stir welding in PROMETHEE method shows that it results in strength is and top ranking.

Numerical investigation of novel geometric solutions for erosion problem of standard elbows in gas-solid flow using CFD-DEM

As erosion by solid particles is a serious concern in the pipeline industry, especially in pneumatic transport pipelines, this study has investigated novel numerical geometric solutions to solve this problem using the computational fluid dynamics (CFD). The studied geometries included square section elbow (with a replaceable backing plate), T-plug, double T-plug, T-plug with axillary air and standard elbow with vane, ribbed-elbow (circular and square section) with different configurations, and elbow with air injection with different conditions. Results of the sensitivity analyses used to study the effects of the changes in the particle shape/size/velocity, mass loading, erosion model and turbulence model on erosion rate revealed that long-radius ribbed-elbow (circular and square section, θ = 30°), long-radius elbow with vane, long-radius elbow with square section, double T-plug and elbow with air injection (with Vinjection = 0.6Vmain and tilt angle = 45°) are good choices.

Inter-Stage Pressure Drop of Multi-Stage Brush Seal With Differentiated Structure

Abstract Uneven pressure drops among stages of multistage brush seal (MBS) leads to early failure of single-stage seal units, which directly affects service life of the seal used in aeroengines, gas turbines, and steam turbines. In this paper, influence factors of interstage pressure drop were studied to analyze formation mechanism of the uneven pressure drops. Moreover, an MBS with differentiated structure was presented, and its interstage pressure drops were further investigated. The results showed that the MBS with several same single-stage seal units had uneven pressure drops among stages under high inlet/outlet pressure ratios. In view of remarkably increasing velocity and decreasing pressure in downstream region of bristle pack near rotor surface during flow of airflow, adjustments of structural parameters (i.e., increasing height of backing plate to rotor surface Hb, increasing seal clearance Hg, and decreasing axial width of bristle pack B) could improve the uneven pressure drops among different stages due to increasing outlet air flow area of the stage. The closer pressure drop proportions of different stages to ideal average value indicated increase of Hb had a more effective effect to balance the pressure drops among different stages compared to increase of Hg and decrease of B. An MBS with differentiated structure, in which both Hb and Hg of all the single-stage seal units were increased progressively and B was decreased step by step, showed a good performance to obtain even interstage pressure drops.

Corrosion and Mechanical Aspects of Friction Stir Welded AA6061 Joints: Effects of Different Backing Plates

Corrosion and Mechanical Aspects of Friction Stir Welded AA6061 Joints: Effects of Different Backing Plates

Optimal design of electromagnetic metamaterial electronic device sensor with specific performance based on multivariate big data fusion

As the basic unit structure of electromagnetic metamaterial, the structure size of open resonant ring directly determines the constitutive parameters of SRR (dielectric constant ε and permeability μ). In order to improve the energy exchange efficiency of the electromagnetic acoustic transducer, the coil backplane of the electromagnetic ultrasonic shear wave sensor was optimized. First, the influence of the thickness of the coil backplane on the ultrasonic signal is studied by the experimental method, and then, the magnetic field distribution of the coil backplane is simulated by the finite element simulation software. Finally, the SNR and lift distance of the shear wave sensor before and after the coil backplane optimization are compared by experiments. In this article, a multi-hypothesis data fusion method in distributed detection system is proposed, which extends the multi-sensor data fusion rules to more general cases. The results show that the optimum thickness of the coil back plate in the electromagnetic ultrasonic transverse wave sensor is 1.5–2.0 mm. Using iron powder with the same length and width as the working area of the coil as the coil backplane can significantly increase the magnetic field strength in the working area of the sensor. Compared with the coil backplane made of non-magnetic materials, the optimized backplane can increase the signal-to-noise ratio of the sensor by about one time and the lift-off distance by about 1 mm.

Ductile fracture of 2024 aluminum under unequal biaxial in-plane tension and out-of-plane compression

The ductile fracture of 2024 aluminum loaded under unequal in-plane biaxial tension and out-of-plane compression is investigated. This stress state is induced in materials during ballistic impacts. A novel experimental design is presented which utilizes an elliptical shaped punch to induce unequal amounts of tension along the in-plane axes of a thin specimen plate. An annealed copper backing plate placed behind the specimen induces out-of-plane compression. Fracture is observed directly with Digital Image Correlation during continuous loading of unbacked specimens. Interrupted testing and acoustic emissions are used to determine the instant of fracture in tests where a backing plate is used. Numerical simulations are performed using an assumed plasticity model, and the model is validated by matching the simulated force-displacement response and strain with the experiments. The equivalent plastic fracture strain is determined for various stress states that correspond to averaged triaxiality values ranging from 0.14 to 0.61 and averaged Lode parameter values ranging from −0.72 to −0.29.

Transient dynamic response of brick masonry walls under low velocity repeated impact load

An experimental and numerical investigation have been carried out on the clay brick masonry walls against repeated impact load in order to estimate the transient dynamic response. The experiments were carried out on 110 mm thick masonry walls against 60 kg mass impactor with hemisphere nose shape with the velocity of 1.98 m/s. In the first phase, the experiment on the wall of 1.2 × 1.2 m (height (h) x breadth (b)) was conducted considering the bed (W1) and head (W2) joint of walls parallel to the boundary in order to verify the conservative design of the joint interface. It was observed that the W2 found resistance up to 3 hits whereas W1 offered resistance up to 11 hits and it was concluded that the W2 found to be sensitive. In the second phase, the aspect ratio of sensitive wall W2 was varied by reducing the breadth from 1.2 to 0.25 m, corresponding aspect ratio (h/b), 1.33 – 4.8 (W3-W6) whereas, the height of the wall remains constant, i.e. 1.2 m. It was observed that the aspect ratio was found to have marginal effect on the peak force however it changes the failure pattern significantly. In the third phase, the influence of mortar strength has been studied and it was observed that the mortar strength does not impart any stiffness into the wall. As a fourth phase, the response of W2, W3 and W4 walls was studied under repeated loading and the resistance offered up to 2, 3 and 2 hits by W2, W3 and W4 walls, respectively. Further, numerical simulations on W1, W2, W3 and W4 walls were carried out using ABAQUS and the Drucker Prager model and traction separation law were used to simulate the brick and interface joints, respectively. The results thus predicted were compared with the experimental results and found in good agreement however, a maximum deviation of 14% on the prediction of peak force. Further, the sensitive parameters were identified which are sensitive to the qualitative numerical results. It was concluded that the parameters such as cohesion, fracture energy, friction and penalty stiffness found to affect the numerical results significantly. Further, wall W2 with externally bonded engineered cementitious composite (ECC) layers has been studied in order to estimate the resistance of wall with backing plate. It was concluded that the ECC backing plate was found to enhance the response of masonry wall in terms of contact force, damage and failure pattern, significantly.