Back Plate Thickness Research Articles

Study on ballistic impact performance of bionic fish scale protective armor

Composite bulletproof armor used in modern battlefield environments is mostly composed of ceramic/ultra-high molecular weight polyethylene (UHMWPE). In order to further improve its bulletproof performance, this study draws on the superposition of fish scales. The upper layer of the flexible protective armor consists of composite scale layers stacked on top of each other, and the lower layer consists of UHMWPE plates with grooved structures at the corresponding locations of the scales, where a single composite scale consists of an upper SiC ceramic layer and a lower UHMWPE layer. Finite element simulation is used to analyze the protective performance of the protective armor. The effects of back plate thickness, scale tilt angle, and impact location on the protection performance are investigated. The results show that the 8 mm thick back plate can effectively resist the impact of Type 53 7.62 mm armor-piercing incendiary ammunition, and the protective effect is best when the scale tilt angle is 30°. The maximum depression depth of the backplane is 12.4 mm, and the deformation of the backplane is reduced by 3 mm when the bullet hits the overlapping area of the scale compared with the central area of the target scale, accounting for 32.67% of the total deformation. The research work has guided the development of new bionic flexible protective armor.

Numerical study on the optimized thickness of layer configuration against the 7.62 APM2 projectile

This study aimed to select suitable materials and optimize the thickness of these materials so that they could prevent the perforation of 7.62-mm AP bullets at 830 m/s impact velocity. A numerical method is used to analyze the impact on layered configurations of Al2O3 and Al 7075-T651 to fulfill this aim. In order to optimize the thickness of the armor, normal impact and angular impact conditions were considered. Initially, a 20-mm Al2O3 front plate with a 20-mm Al 7075-T651 back plate is analyzed for layered configuration. Back plate thickness is reduced in steps to 10 mm such that no plastic deformation is observed on the rear side of the target. For further optimization of weight, the thickness of the Al2O3 plate is reduced to 18 mm. The weight of this configuration is 1.77 kg, and the areal density is 97.22 kg/m2. This configuration is analyzed for target orientations such as 80°, 70°, and 60°. In this analysis, the projectile deformed in a mushroom shape for 90° and 80° target orientations, while for 70° and 60° target orientations, the projectile experienced more damage on the shank part. The most effective configuration with the highest degree of ballistic performance is a layered combination of the 18-mm Al2O3 front plate and 10-mm Al 7075-T651 back plate at 70° target orientation.

Numerical Investigation on Protective Mechanism of Metal Cover Plate for Alumina Armor against Impact of Fragment by FE-Converting-SPH Method.

It is of extreme importance to develop a reliable numerical prediction technique to simulate the ballistic response of ceramic armor subjected to high-velocity impact (HVI) to economize the test cost and shorten the design period. In the present manuscript, a series of experiments on tungsten heavy alloy (WHA) fragment's penetration into 99.5% alumina (AD995) armors are systematically simulated by employing the FE-converting-SPH technique. The numerical results are compared with the experimental counterparts to find that the FE-converting-SPH method is fairly efficient in predicting the depth of penetration, the residual velocity, length and mass of fragment, and reproducing the crack forms of ceramic. The applicability and accuracy of the numerical model in terms of the algorithm, material model parameters and contact definitions are validated. Then, the relevant parameters of the calibrated numerical model are incorporated to explore the influence of cover-layer thickness on the armor performance. A few mechanisms regarding the cover plate have been identified to act on the armor performance, such as the alteration of fracture cone half-angle, proportion of energy absorbed by ceramic, mushrooming deformation of fragment, etc. The result of multi-mechanism superposition is that the best ballistic performance is endued with 1 mm cover-layer armor, which demonstrates a 24.6% improvement over the bi-layer armor with 4.96 g/cm2 area density, only at the cost of 15.7% increase in areal density, when back-plate thickness is held as 2 mm; for a constant area density of 4.96 g/cm2, a 1 mm cover-layer is also expected to be the best choice, with 10.7% improvement in armor performance.

An experimental and numerical study on the impact of various parameters in improving the heat transfer performance characteristics of a water based photovoltaic thermal system

The hybrid photovoltaic thermal system (PV/T) has been developed to harvest solar energy's electrical and thermal forms. However, effective heat evacuation from the backside of photovoltaic panels remains difficult, limiting their thermal and electrical performance. The current study presents a numerical and experimental examination of various parameters for improving a photovoltaic thermal system's heat transfer performance. The influence of flow parameters, tube diameters, and base plate thickness on the heat transfer, electrical, and overall performance characteristics of the water-based PV/T has been investigated. According to the current research, the water-based PV/T with a 16 mm tube diameter and a water flow rate of 1.02 L per minute has the highest average thermal, electrical, and overall efficiency of 44.5%, 14.8%, and 59.3%, respectively. The findings show that the photovoltaic thermal (PV/T) system's thermal and electrical efficiency increase when Reynolds numbers increase. The heat transfer rate of the PV/T system may increase by 15% with an increased Reynolds number. A maximum decrease in cell temperature is obtained by increasing the tube diameter and decreasing the backplate thickness of the photovoltaic thermal (PV/T) system. An increase in the tube diameters of the PV/T system results in a maximum reduction of 6 °C in cell temperature. The experiment and numerical findings were in better agreement in this study, with the highest relative error of 3.96%.

Backplate-reinforced structures for enhancing solder joint reliability of server CPU assembly under thermal cycling

ABSTRACT To meet the requirement of the high I/O and fine-pitch interconnects, the conventional insertion-mount socket for central processing unit (CPU) has been changed to surface-mount one with ball grid array. The solder ball joint reliability of the socket used in the CPU assembly becomes very important. In this study, the socket's solder joint reliability of the backplate-reinforced CPU assembly and its related mechanics under mechanical and thermal loadings are investigated experimentally using strain gauge and shadow moiré, and numerically by a finite element method (FEM). The validated FEM results have suggested that maximum stress of solder balls increases almost linearly with decreasing the backplate thickness under mechanical loading during the CPU assembly, but is insensitive to the backplate thickness under thermal loading during the thermal cycling. It is also found that the residual (bending) strain on the PCB proportional to the maximum von Mises stresses of solder joints (or balls) can be used as a key parameter to correlate with the solder joint failures or cracks during the thermal cycling. Overall, experimental and FEM results in this study reveal that solder joint reliability in the CPU assembly during thermal cycling can be improved by adopting the thicker reinforced backplate.

Research on ceramic fragmentation behavior of lightweight ceramic/metal composite armor during vertical penetration

In order to investigate the ceramic fragmentation behavior of light ceramic composite armors in the process of anti-penetration, ballistic impact tests of ceramic/metal composite armors with different back cover and ceramic thicknesses using a penetrating projectile of 12.7 mm in diameter was carried out. The target was installed in a recycling bin, and the recovery rate of ceramic fragments was above 95%. By observing the macroscopic failure characteristics of the recovered target ceramics, the relationship between different thickness combinations of the ceramics and the main failure characteristics was analyzed. And through the multi-stage screening and weighing of the ceramic fragments, the size distribution law of the ceramic fragments with different thickness combinations was analyzed. The results show that the fracture cone of the ceramic was the main failure characteristic of the ceramic panel, and the macroscopic cracks mainly include radial cracks, ring cracks and conical cracks. The ceramic cone can be subdivided into a crushing zone composed of small powdered ceramic fragments caused by high compressive stress and a broken zone composed of large ceramic fragments caused by stress waves. The size distribution of the ceramic fragments in the ceramic cone after impact satisfies the Rosin-Rammler distribution model. With the increase of the back plate thickness, the half conical angle of the ceramic cone increases, which leads to increases in the overall volume of the ceramic cone and the proportion of the broken zone. The resulting ceramic fragments are mainly large size fragments, and the overall broken size in the ceramic cone increases. When the ceramic thickness increases, the half conical angle and the number of radial cracks remain basically unchanged, the proportion of the crushing zone in the ceramic cone increases, and the overall crushing size decreases.

Analytical model for the prediction of solar cell temperature for a high-concentration photovoltaic system

This study presents a simple analytical model for the prediction of solar cell temperature for a high concentration photovoltaic system. The model is based on a heat transfer approach through the system's backplate. The results show that the solar cell temperature is governed by the incident light, material characteristics, ambient conditions, and cell size. The parameters that have a crucial impact on reducing the solar cell temperature were the backplate emissivity, wind velocity, backplate thickness, and backplate length. The backplate coating was found to be of paramount importance due to the considerable reduction of the solar cell temperature with emissivity. Higher wind speeds ventilated the HCPV system and helped lower the cell temperature through convective heat transfer. The thicker the backplate, the lower the cell temperature is due to thermal diffusion on the plate. But this finding prevailed only up to a certain thickness, after which its feasibility is neither maintained nor guaranteed. The study recommends using smaller cell sizes in harsh environments of ambient temperature higher than 40 °C to help manage the reduction of the cell temperature below a critical value of 80 °C.

Nanoporous microneedle arrays seamlessly connected to a drug reservoir for tunable transdermal delivery of memantine

Conventional transdermal drug patches have been on the market since 1997 but their applicability for drug delivery is limited: currently only nearly two dozen of molecules have been approved by the regulatory authorities for transdermal administration and have reached the market. The possibilities for drug delivery via the skin can be improved and expanded by using microneedle patch technologies. However, most microneedle patches focus on the delivery of low amounts of drugs that are generally very potent due to the small dimensions of the microneedle systems. In this study nanoporous microneedle arrays (npMNAs) were combined with a liquid drug reservoir. The parameters that influence the diffusion of memantine from the drug reservoir through the npMNAs in an acceptor solution were investigated. Based on these results a model was developed to predict the diffusion of low-molecular-weight drugs as a function of npMNA properties (i.e., backplate thickness and surface area) and reservoir properties (i.e., volume and drug concentration). This generated an in silico model to predict the release of low-molecular-weight drug from a drug reservoir through a microneedle array into receptor solution, showed a good correlation with the delivery of memantine in a preclinical minipig study. The drug release rates by the npMNAs can be tuned and allow for both zero and first order release kinetics. Summarizing, this work shows that the npMNA technology is a versatile drug delivery system. The npMNAs can be combined with a (seamlessly connected) external drug reservoir and this integrated drug delivery system can be used to deliver at least 9 mg of memantine over 72 h in a preclinical minipig study.

Study on transition from dwell/interface defeat to penetration of long-rod projectile impacting silicon carbide

Dwell/interface defeat phenomenon plays a pivotal rule in enhancing the protective ability of ceramic armor. In this study, the transition from dwell to penetration was studied experimentally and numerically, focusing on the dwell time, penetration and damage evolution in ceramic. A series of depth of penetration experiments were conducted of silicon carbide impacted by tungsten–iron–nickel (93%W–Fe–Ni) conical long-rod projectile (LRP) between 900 and 1400 m/s. The transition from interface defeat to extended dwell to penetration of ceramics was observed experimentally. Data analysis suggested that instead of a sharp transition velocity above which dwell phenomenon stopped, dwells with a phase of gradual decreasing time over a range of velocities were observed in experimental work. This observation was then studied by using numerical simulation software AUTODYN with two material models, Johnson–Cook for LRP and witness target, while Johnson–Holmquist for ceramic. The results of numerical simulation agreed well with the corresponding experimental data. Significant influences of nose shape of LRP, projectile material, ratio of each layer of target structure and thickness of back plate on transition from dwell to penetration were investigated numerically. It is shown that dwell/penetration transition predominantly depends on the damage accumulation in ceramic and the performance of back plate. In addition, mass erosion of LRP, rather than the decrease of velocity, functions vitally in affecting the transition when different projectile materials are taken into consideration.

Ballistic reliability study on SiC/UHMWPE composite armor against armor-piercing bullet

The ballistic reliability of composite armors is significantly affected by the random material properties. In this paper, the mosaic SiC ceramics/ultra high molecular weight polyethylene (UHMWPE) composite targets with bonding adhesives are tested near the limit ballistic penetration conditions. The uncertain material and adhesive properties led to complete penetration and partial penetration at bullet initial velocity of 776 m/s and 791 m/s, respectively, and a contrary tendency is also observed in the tests between the bulging deformation and the minimum target thickness of back plate. A state function of penetration for reliability evaluation is formulated based on a validated numerical model. Results from sensitivity analysis indicate that twelve uncertain material parameters are strongly sensitive to the penetration state. Then, the ballistic reliability under the test velocities is obtained by both Monte Carlo method and design point method. Finally, an optimization problem with a probability constraint is established in order to achieve a minimum deformation. The results show that the bulging deformation and the value of penetration state function vary with the adhesive strengths oppositely. Therefore, the adhesive strengths are designed to control the contradiction between the deformation and the minimum target thickness. It is significant to recognize the uncertain properties of composite armors and to improve the ballistic performance against armor-piercing bullet.

Simulation and sensitivity analysis of wear on the automotive brake pad

In this paper, an algorithm is proposed for finite element simulation of wear employing the Archard's wear equation. To evaluate the accuracy of a FE model, an experimental test is performed on a standard-sized pin, made of a known brake pad. Comparison of worn masses, obtained by experimental and numerical approaches shows good accuracy of the developed algorithm. As the next step, passenger car single-piston and double-piston brake pad wear cases are simulated using the proposed algorithm. The rotor/pad contact area and worn mass are compared between the two cases. It is shown that usage of a double-piston brake pad over a single-piston one, can improve brake performance. The Taguchi Method with an orthogonal array L9 is then applied to optimize the design parameters, meaning maximization of the ``contact area'' and minimization of the ``worn mass''. The ANOVA method is also used for evaluating the impact of each design parameter on desired outputs. It is shown that the contact area is most likely to be affected by back plate thickness, while the worn mass is more sensitive to the diameter of the piston, closer to the leading edge of the pad.

Influence of Geometry and Hardness of the Backing Plate on Ballistic Performance of Bi-Layer Ceramic Armor

The high hardness and strength of technical ceramics is exploited to design ballistic armors and their low toughness, brittleness is overcome by joining them with a metallic or long fiber reinforced composite backing plate. The thickness of backing plate (BP) on the ballistic performance SiC ceramic armor is studied through finite element simulations based on AUTODYN®. In this work, depth of penetration (DOP) from experimental measurements is compared with simulations using explicit software AUTODYN® for 3D modelling. The ballistic performance of three layer armor (cover plate (CP), ceramic tile and backing plate (BP)) under normal and oblique (NATO 60°) for long rod projectile (LRP) with a conical tip is investigated. The LRP and CP have been modelled using smooth particle hydrodynamic (SPH) particles and rest of the component is modelled using lagrangian processor. The Johnson-Cook and Johnson-Holmquist (JH-2) constitutive models are used for metal and ceramic materials, respectively. It is found that thicker BP enhances SiC armor via supporting longer period and prevent any premature failure at the rear surface of ceramic. It is also noticed that high hardness (low ductile) BP improves the ballistic performance of ceramic armor through offsetting tension of ceramic.

Stability Analysis and Improvement of Uncertain Disk Brake Systems With Random and Interval Parameters for Squeal Reduction

Stability analysis and improvement of disk brake systems for squeal reduction have been investigated by automotive manufacturers for decades. However, most of the researches have not considered uncertainties. For this case, a practical approach for analyzing and improving the stability of uncertain disk brake systems is proposed in this paper. In the proposed approach, a hybrid uncertain model with random and interval parameters is introduced to deal with the uncertainties existing in a disk brake system. The parameters of brake pressure, densities of component materials, and thickness of back plate are treated as random variables; whereas the parameters of frictional coefficient and Young's modulus of component materials are treated as interval variables. Attention is focused on stability analysis of the disk brake system for squeal reduction, and the stability is investigated via complex eigenvalue analysis (CEA). The dominant unstable mode is extracted by performing CEA based on a linear finite element (FE) model, and the negative damping ratio corresponding to the dominant unstable mode is selected as the indicator of system stability. To improve the efficiency of analysis, response surface methodology (RSM) is used to replace the time-consuming FE simulations. Based on RSM and CEA, the stability analysis model of the disk brake system is constructed, in which reliability analysis, hybrid uncertain analysis and sensitivity analysis are applied to deal with the uncertain problems. The analysis results of a numerical example demonstrate the effectiveness of the proposed approach, and show that the stability and robustness of the uncertain disk brake system can be improved effectively by increasing the stiffness of back plate.

Numerical analyses of sandwich panels with triangular core subjected to impact loading

Sandwich panels made of metal sheets with unfilled cellular cores are found to exhibit lower deflections compared to an equivalent monolithic plate of same metal and similar mass per unit density. The structures having such sandwich panels are suitable under impact loading due to low deflection. However, the process of localized impact on solid structures is quite complicated involving plastic deformation, high strain rates, temperature effect, material erosion, etc. Further, the sandwich panel having triangular corrugated core depends on various design parameters such as thickness of front plate, thickness of back plate, thickness of core, thickness of webs, and angle of web. The influences of these parameters on the structural performance are studied while designing a triangular corrugated core structure for improved ballistic limit for a given mass per unit area. In this research, a numerical analysis of impact of empty triangular corrugated core sandwich panels by ogive nose steel rod projectiles is carried out. Design parameters of the corrugated structure; namely web thickness, core thickness, web angle, front and back plate thickness are varied; and residual velocity of projectile is obtained for each case. Impact at webs resulted in higher projectile retardation and deflection than impact at the base of the prism. For base impacts, improvement in ballistic performance at minimum cost of structural weight can be achieved by increasing web angle or front or back plate thickness, while the same can be achieved for web impacts by increasing web thickness. Since web impacts experience higher penetration resistance than base impacts, designing the panel using optimum design parameters for web impacts is desirable.

Estudo da redução de espessura de suporte metálico em pastilhas de freio automotivo

Brake system is a critical component for vehicle safety and performance. One type of brake system widely used in passenger cars is disc brake system due to its compactness and efficient heat dissipation. In this system brake pads play a key function, distributing the hydraulic force by the uniform contact with the brake disk with no deformations. Brake pads are composed of a support metallic backplate, where friction material is adhered. This work presents a study to evaluate the minimum acceptable backplate thickness, considering passenger vehicles braking performance and requirements. The main parameters evaluated on this work were associated with braking torque and force and working temperature. These parameters were validated based on dynamometer tests under severe braking conditions together with tensile and micro hardness tests. Results showed that a reduction up to 1 mm in backplate thickness is possible, complying with all mechanical and thermal specifications required for braking systems

A combined approach of complex eigenvalue analysis and design of experiments (DOE) to study disc brake squeal

This paper proposes an approach to investigate the influencing factors of the brake pad on the disc brake squeal by integrating finite element simulations with statistical regression techniques. Complex eigenvalue analysis (CEA) has been widely used to predict unstable frequencies in brake systems models. The finite element model is correlated with experimental modal test. The ‘input-output’ relationship between the brake squeal and the brake pad geometry is constructed for possible prediction of the squeal using various geometrical configurations of the disc brake. Influences of the various factors namely; Young’s modulus of back plate, back plate thickness, chamfer, distance between two slots, slot width and angle of slot are investigated using design of experiments (DOE) technique. A mathematical prediction model has been developed based on the most influencing factors and the validation simulation experiments proved its adequacy. The predicted results show that brake squeal propensity can be reduced by increasing Young’s modulus of the back plate and modifying the shape of friction material by adding chamfer on both sides of friction material and by introducing slot configurations. The combined approach of modeling brake squeal using CEA and DOE is found to be statistically adequate through verification trials. This combined approach will be useful in the design stage of the disc brake. Keywords: Disc brake squeal, finite element analysis, experimental modal analysis, design of experiments

Reducing disc brake squeal through FEM approach and experimental design technique

This paper presents a novel approach to understand the influencing factors of the brake pad on the disc brake squeal by integrating finite element simulations with statistical regression techniques. The complex eigenvalue analysis has been widely used to predict unstable frequencies in brake system models and to provide design guidance. The 'input-output' relationships between the brake squeal and the brake pad geometry is constructed for possible prediction of the squeal using various geometrical configurations of the disc brake. Influences of the various factors, namely back plate Young's modulus, back plate thickness, chamfer, distance between two slots, slots width and angle of slots, are investigated using design of experiments technique. The proposed approach is aimed towards prediction of optimal pad design to reduce the damping ratio of the dominant unstable modes through the various factors of the brake pad geometrical construction. The damping ratio is analysed and a non-linear mathematical prediction model is developed based on the most influencing factors.

Hypervelocity impact into oblique ceramic/metal composite systems

A numerical study for the analysis of oblique ceramic/metal composite armour systems against L/D = 20 projectiles has been performed. The ballistic performance of the add-on lightweight armours was examined by determiningthe effect of areal density of the system on ballistic limit or depth of penetration (DOP). To do this, a series of three-dimensional numerical simulations has been conduced. The impact velocities considered are 2.2 and 2.6 km/s. The oblique angle of the plate is 60 degrees. Simulation results for ballistic limits appear to match fairly well with the test values. Although the previous data for the penetration of 7.62 AP projectile into relatively thin alumina/aluminium composite targets revealed an optimum value of the front plate to back plate thickness ratio in the region of 1.5, the current data for the impact of long rod into relatively thick composite targets are scattering. This is because the distinguishing features of thin composite armour systems against 7.62 AP and 40.7g steel projectiles are crack propagation, ceramic conoid formation and failure of backing plate, while these effects are less significant in thick targets, especially at high impact velocities.

Analysis of ceramic/metal armour systems

A combined numerical and experimental study for the analysis of ceramic/metal composite armour system against 40.7 g steel projectiles has been performed. The ballistic performance of the add-on lightweight armours was examined by varying the thickness of tiles, while maintaining equal areal density of the system. A numerical study using smoothed particle hydrodynamics scheme is promising since the major distinguishing features of composite armour systems such as, projectile erosion, crack propagation, ceramic conoid formation and failure of backing plate, are successfully captured. Simulation results for ballistic limits appear to match fairly well with the test values and reveal an optimum value of the front plate to back plate thickness ratio.

Characteristics of metal-plate/film detectors at therapy energies. I. Modulation transfer function.

Measurements of modulation transfer function (MTF) for front and back metal-plate/film portal detectors are reported for the Cobalt-60 and 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of Al, Cu, brass, or Pb with thicknesses varying from 0 to 4.81 mm. Secondary electrons produced within the front plate generate the main signal, but the MTF decreases with an increase in front plate thickness greater than the maximum range of electrons Rmax because of photon scatter in the front plate. Because the decrease of MTF with backplate thickness ceases for backplate thickness greater than Rmax, the MTF is influenced more by the backscatter electrons than the backscatter photons.