Plates Of Different Thicknesses Research Articles

A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests.

Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the 'wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, 'wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Ballistic Limit Thickness and Failure of Steel Targets with Different Strengths under EFP Impact

The protective performance of different armour steels and structural steels against the impact of an explosively formed projectile was investigated. For the tests the impact velocity of the EFP projectiles was kept constant at 1400 m/s. Machinely formed EFP simulants have been accelerated with a powder gun instead of using explosively formed and accelerated EFPs. First tests have been done with EFP simulants with a mass of about 140g, for later tests downscaled projectiles with a scaling factor of ½ have been used. To evaluate the protective performance of the different steels target plates of different thicknesses have been prepared. In the case of perforation the residual velocity of the projectile after perforation has been determined as a measure of the protective performance of the steel.First, a classical RHA armour steel with hardnesses of about 350 HBW has been tested. In the case of the EFP projectile impacting a RHA steel plate with a thickness in the ballistic limit range, the penetration and perforation process of this kind of projectile seems to consist of two parts: a ductile hole enlargement process of a deformable projectile in the first part and shear failure leading to plugging in the second, dominant part. The shear failure leading to the formation of a massive plug is governed by adiabatic shear banding, what was observed from metallographic analysis.To investigate the influence of the hardness and strength on the protective performance against the EFP, additionally some steels with higher and with lower hardness than the RHA steel were tested. For the steels of higher hardness, classical armour steels with hardnesses of 500 HBW and 600 HBW have been chosen, also as new armour steel grades with hardnesses of 440 HBW and 600 HBW with increased toughness for blast applications. For the steels with lower hardness, the structural steels S355J2+N, S690QL and S960QL have been chosen.It was found, that the mechanical properties of the steels do not influence their protective performance, at least if the residual velocity after perforation is taken as a measure for the protective performance. In the case where the plate thickness was sufficient to stop the projectile it seems, that the structural steels perform at least as good as RHA steel. The S690QL steel was able to stop the projectile at thicknesses lower than the RHA steel. This behavior was assigned to its lower sensitivity to the formation of adiabatic shear bands.

Mathematical model of temperature field distribution in thin plates during polishing with a free abrasive

The purpose of this paper is to estimate the dynamic characteristics of the heating process of thin plates during polishing with a free abrasive. A mathematical model of the temperature field distribution in space and time according to the plate thickness is based on Lagrange equation of the second kind in the thermodynamics of irreversible processes (variation principle Bio). The research results of thermo elasticity of thin plates (membranes) will allow to correct the modes of polishing with a free abrasive to receive the exact reflecting surfaces of satellites reflector, to increase temperature stability and the ability of radio signal reflection, satellite precision guidance. Calculations of temperature fields in thin plates of different thicknesses (membranes) is held in the Excel, a graphical characteristics of temperature fields in thin plates (membranes) show non-linearity of temperature distribution according to the thickness of thin plates (membranes).

Fatigue assessment on butt welded splices in plates of different thicknesses

Fatigue performance of butt welded splices in plates of different thicknesses (hereafter referred to as BWSPDT) was investigated in this paper. Fatigue tests were conducted on 26 specimens. Experimental S-N curve of 95% survival probability for BWSPDT was established based on 21 effective fatigue test data involving 7 stress levels. Both analytical and numerical fatigue crack propagation analysis were fulfilled. It was found that the numerical approach would provide a lower stress intensity factor (SIF) level than that obtained through the analytical approach, as the numerical approach can better reflect the relationship between the local crack development and the variation of the stress distribution of the whole structural details. The influences on fatigue life due to the variation of the size, shape and location of the initial crack were investigated. The calculation formula for the fatigue crack propagation life in terms of arbitrary initial crack between 0.075mm and 0.4mm was derived. For the fatigue crack propagation analysis for BWSPDT, a semi-circular crack with 0.075mm initial depth locating at the center of the specimen was recommended to be adopted as the initial crack input when no detailed inspection information on initial flaws available.

Effects of Connecting Plates on Cold-Formed Steel Wall Plate System

The paper presents experimental investigations on cold-formed steel (CFS) wall plate system. The behavior and the modes of failure of the system under uplift were studied. The parameters tested were the presence of gaps and the thickness of connecting plates. Results showed that samples with and without gaps at the supports experienced the same failure mode. Failure began with the yielding of connecting plates followed by the buckling of C-channel. Similar ultimate capacity was also obtained for samples with and without gaps. When connecting plates of different thicknesses were used to connect the wall-plate, different modes of failure were observed. Instead of yielding in the connecting plates, screw pull-out was observed in the connection before the C-channel buckled. Besides, it was observed that the ultimate capacity of the system was reduced when thicker connecting plates were used. It is not conservative to estimate the capacity of screwed connection according to the design standard and it is proposed that the capacity of the wall plate system is taken as the yield capacity of the connecting plates of the same material properties.

Pd/Uio-66/Ti Electrode for Electrocatalytic Debromination of Tetrabromobisphenol a

Metal organic frameworks (MOFs) have engendered great interest due to their high surface areas, tunable porous size, and functionalities. They are explored in a wide range of applications including absorption, gas storage or separation, catalysis, biomedicine and drug delivery. Presently, a large number of reports appraise the application of MOFs in the field of electrochemistry, from rechargeable batteries, supercapacitors to fuel cells. Among these various metal organic frameworks, UiO-66 as a type of highly stable zirconium-based MOF linking by 1,4-benzenedicarboxylate (BDC), has been extensively studied. It is reported that UiO-66 demonstrates high structural stability in water medium, thus, it shall be a feasible strategy to incorporate UiO-66 with other functional materials for the applications in aqueous medium, water treatment and water splitting for instance. Herein, palladium nanoparticles supported UiO-66 was fabricated on Ti plate electrode (Pd/UiO-66/Ti) in this study. White UiO-66, as a bridging layer with controlled size and thickness, was first deposited on Ti plate via an electrochemical film deposition method. UiO-66/Ti plates of different thickness were acquired by changing the ratio of electrochemical deposition solution. Pd/UiO-66/Ti was further made by dipping Pd2+ solution onto the UiO-66 surface and then reduced by impregnating in 0.1 % NaBH4 solution for two hours. The obtained dark Pd/UiO-66/Ti electrode was characterized by X-ray diffraction (XRD). And the electrochemical properties of the Pd/UiO-66/Ti cathode electrode were investigated through cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The results revealed that UiO-66 films with different thickness were successfully deposited on the Ti cathodes (UiO-66/Ti), Pd particles well dispersing on the surface of the UiO-66/Ti. The electro-catalytic performance was evaluated by electrocatalytic debromination of 5 mg/L tetrabromobisphenol A (TBBPA) in a 200 mL vessel, containing Pd/UiO-66/Ti as cathode, graphite as anode at a current of 6.67 mA/cm2. It was found that degradation rate of TBBPA was 80% within 60 min by Pd/ UiO-66/Ti cathode electrode. The excellent electro-catalytic performance could be ascribed to the adsorption of TBBPA on UiO-66 and the reaction with hydrogen at the palladium/UiO-66 interface. The results indicated that Pd/UiO-66/Ti should be a promising cathode for the application on electrochemical.

Experimental and theoretical analysis of the deformation of transversely isotropic plates under creep conditions

This paper describes the results of calculations and experiments on the torsion of plates made of isotropic and transversely isotropic VT-20 and 1163T alloys with low resistance to creep strain in the direction perpendicular to the median surface. The numerical simulation results for plates of different thicknesses related to the class of rigid and flexible plates are compared using the pure bending theory and the finite element method. It is found that the curvature values are smaller in the case of deformation of a plate made of anisotropic material into a sign-variable saddle surface than in the case of a plate of isotropic material. The calculation in the assumption of pure bending provides an upper bound of the curvature difference in the deformation of plates made of transversely isotropic and isotropic materials.

A Novel Method for Manufacturing Polymer/Metal Hybrid Structures

In this study, a method for manufacturing polymer/metal hybrid structure is presented in which traditional plastic injection machine was converted to plastic injection forming (PIF). In this method, deforming of the metal and adhering the metal to the polymer is done in one step. In the experimental study, a special mold within rectangular cavity was used during PIF process. Aluminum plates of different thicknesses were used as the metal parts of the structure. The injected polymers were pure polystyrene and elastomer-added polystyrene. The deformability of the Al plates was examined under different injection pressures. In order to provide adhesion between metal and polymer, an adhesive of elastomeric nature was applied on the metal plate prior to injection molding. Bending test was applied to determine the flexural strength and maximum deflection of the polymer/metal hybrid structures. The obtained results were satisfactorily acceptable in improving the method for designing and manufacturing polymer/metal hybrid structures in one step.

Verification of Methods Used for Fatigue Testing of Small Steel Specimens Taken from Existing Structures

This paper presents results of fatigue tests performed on standard specimens and minispecimens taken from two EN 1.4301 acid-resistant steel plates of different thickness. The tests were required for determination of the state of vibrating machines made from the same material. The results confirmed that the proposed testing method can be used for experimental tests.

Development of IN-RAFM steel and fabrication technologies for Indian TBM

India has indigenously developed its own Indian Reduced Activation Ferritic Martensitic Steel (IN-RAFM steel) which, it is proposed to use for fabrication of Indian TBM to be installed in ITER. With an objective of qualifying this material for use in ITER, extensive testing of this material to generate the necessary data required to offer this material for Particular Material Appraisal of ITER has been undertaken. Accordingly, data generation on creep, fatigue and physical properties of this steel is in progress. Physical properties like thermal diffusivity, heat capacity and thermal expansion coefficient for this steel at various temperatures have been measured and thermal conductivity estimated from the measured physical properties. Values obtained for these physical properties are comparable with those reported for other RAFM steels. Results of creep tests that are in progress also indicate that creep is comparable to that of other RAFM steels. Low cycle fatigue (LCF) behaviour of this steel has been studied in air with total strain control in the strain amplitude range of ±0.25–1% and temperatures range of 300–873K at a constant strain rate of 3×10−3s−1. Results confirm that fatigue life of IN-RAFM steel is at par with that of the European Union grade Eurofer 97 RAFM steel.During production of IN-RAFM steel plates of different thicknesses, it is observed that processing parameters have a major role in ensuring consistency in the property of the steel. Accordingly, processing map for this steel has been generated from compression tests conducted at various strain rates and temperature. Safe processing zone of temperature and strain rate has been identified from this map.During technology development for electron beam (EB) welding of IN-RAFM steel, it is found that ductile brittle transformation temperature (DBTT) for the weld metal is higher than that of the base metal and this is attributed to high W content in the steel and consequent formation of delta-ferrite in the weld metal. A welding procedure that produces weld metal with DBTT comparable to that of the base metal has been developed. IN-RAFM filler wires with matching composition to that of the base metal have been produced for TIG and NG-TIG (narrow gap-TIG) welds and the qualification of this consumable is in progress.For fabrication of TBM first wall, which is ‘C’ shaped plate with internal channels, hot isostatic pressing (HIP) of grooved plates which are pre-bent and assembled with ceramic core to produce channel is being adopted. Curved ceramic core and procedure to join this with straight core have already been developed and production of channel plate is in progress. Further, fabrication of three mock up ceramic breeder cassettes each using EB, laser and TIG welding techniques respectively has also been initiated. Fabrication of these mock ups is expected to help in finalizing the fabrication procedures for the actual breeder cassettes to be used in Indian TBM.Details of these developments in material, data generation and fabrication of mock ups of different components of TBM towards realization of the Indian TBM are being presented in this paper.

Measurement of circumferential Lamb waves using a line-focus poly(vinylidene fluoride) transducer and cross correlation waveform analysis

This paper presents a method for measuring circumferential Lamb waves propagating on a cylindrically curved thin plate. The measurement is carried out using a wideband and line-focused poly(vinylidene fluoride) transducer along with a defocusing waveform measurement method. After synthesizing the acquired waveforms, interference patterns can be obtained and a cross correlation method is developed to accurately extract the wave velocity as a function of wave frequency. Using three stainless steel thin plates of different thicknesses (100, 150, and 300 μm) and a radius of curvature of 10 mm, dispersion curves for several fundamental and higher order modes of circumferential Lamb waves are simultaneously determined. Theoretical dispersion curves are also calculated and compared with their experimental counterparts. Very good agreements are observed, which concludes the measurement accuracy of this measurement method.

Experimental and theoretical study of large deformation of rectangular plates subjected to water hammer shock loading

This paper presents experimental and analytical investigation of the dynamic inelastic response of rectangular metal plates subjected to liquid shock loading. A series of experimental results on fully clamped aluminum alloy and mild steel rectangular plates of different thickness and varying standoff distance of hammer is reported. The effect of varying both shock load and the plate material on the deflection is described. Also, an analytical procedure based on an upper bound solution is used to theoretically study the dynamic behavior of uniform impacted plates. In the present model, effects of strain rate and bending/membrane strain are assumed. The results of the analytical model and the experimental data have good agreement. So, this model can be useful for predicting deformation of rectangular plates under low impact loading.

A novel approach to evaluate the elastic impact of spheres on thin plates

A novel analytical approach to solve the otherwise mathematically strenuous Zener model for elastic sphere impacts on large, thin plates, has been presented to find a comfortable solution for the coefficient of restitution (CoR). The proposed analytical approach provides accurate results for the range of coefficients of restitution larger than 0.2 and gives a very good approximation of the Zener model. Furthermore, the Zener model has been numerical solved with high accuracy and has been used to evaluate the inelasticity parameter as well as the coefficient of restitution for different material combinations and ratios of sphere diameter to plate thickness. Both approaches have been used to evaluate the coefficient of restitution of elastic glass beads at impact with glass plates of different thicknesses using experimental free fall test measurements. A significant dependence of the coefficient of restitution of elastic spheres on the ratio of sphere diameter to plate thickness as well as on the impact velocity and on the inelasticity parameter has been observed respectively, which can be well described by the Zener model and the proposed analytical approach.

Effect of Specimen Thickness on Fatigue Limit in Carbon Composites

The fracture behavior and fatigue limit in notched specimens of C/C composites were investigated. Also, the effect of specimen thickness on fatigue limit was discussed. Two plates of different thicknesses of plates of C/C composites using fine-woven carbon fiber laminates with α=0°/90° direction were used for testing. α is the angle between the carbon fiber direction and specimen axis. The crack growth behavior and failure mechanism of specimens are derived from the shear damage in the fiber bundle and matrix. Slits of several sizes were cut on both sides of a test section and different geometries of the specimens were prepared. Specimens with slits and blunt-notches were used to compare the fatigue strength. The fatigue limit is related to the method of making the plate of carbon composites. Large sizes of voids are observed in the case of specimens of thinner thickness. The fatigue limit was related to the void fraction, and thinner specimens showed a lower fatigue limit.

Quench induced residual stress prediction in heat treatable 7xxx aluminium alloy thick plates using Gleeble interrupted quench tests

In this paper, a simple but realistic approach is presented to predict the as-quenched residual stress distribution in thick 7xxx aluminium alloy plates. Instead of modelling precipitation that occurs during quenching, a thermo-mechanical model is used whose parameters are identified using a limited number of tensile tests achieved after representative interrupted cooling paths in a Gleeble machine. The material behaviour law accounts for recovery at high temperature in a simple way and neglects the Bauschinger effect as suggested by a dedicated experiment. The results of this simple approach are compared to residual stress measurements in plates of different thicknesses for two different 7xxx alloys, AA7449 and AA7040.

A comparative study of fatigue behaviour of MAG and laser welded components using reliability analysis

Fatigue is one of the main causes of failure of structures and mechanical components, occurring due to the progressive weakening of their strength that reduces significantly their lifetime, when subjected to cyclic stresses over time. In welded components, the joints are the zones most susceptible to crack by fatigue.Therefore, the base of this study are the Metal Inert Gas/Metal Active Gas (MIG/MAG) and LASER welding manufacturing processes, focused in three main areas involved in an automotive metallic system under dynamic loads: Fatigue testing in order to prevent structural collapse; Heat Affected Zones (HAZ) characterization to evaluate the material properties modification originated by those different technologies; Reliability analysis in order to analyse the performance of the samples and to select the best connection in terms of product life cycle. For this purpose, samples representative of industrial automotive applications (long welds) have been selected to carry out this work. Two types of connected specimens were manufactured, consisting of two steel plates of different thicknesses, overlapping and welded by the MAG process (type A) or the Laser process (type B). Metallographic characterization was performed for both typologies, namely macrostructural and microstructural characterization of the weld joint, and respective HAZ. Mechanical properties were inferred by measuring and mapping microhardness variation on the neighbour of the weld joint. Fatigue tests were carried out for specimens type A and type B, using 15 samples of each type that were tested under 3 levels of stress amplitude. The samples manufactured by the Laser process show better fatigue behaviour when compared to the samples manufactured by MAG welding. The better weld joint solution is proposed in accordance with the reliability analysis of the obtained fatigue test results.

The Study of Large Plastic Deformation and Fracture of Plates by Blast of Explosives in the Tubes

Experimental studies and calculations of large plastic deformations and fracture of the aluminum alloy plates of different thickness by the shock waves of blasts of powerful explosives in tubes of different lengths and diameters were carried out. The deformations the plates were investigated with a single and consistent impact loading by shock waves. Parameters of shock waves and loads on the plates in the tubes were measured and method of their calculation was worked. The empirical dependences of the maximum residual deflections and increment area of the plates depending on the load pulse parameters and the plates were obtained. Dynamic strength of the aluminum alloy was defined.

Comparative Analysis of the Plastic and Out-of-plane Constraint Zones in Cracked Plates

In this work, the size and shape of the plastic and constraint zones are calculated along the crack front for cracked plates of different thicknesses. The extent of both zones has been compared in order to ascertain under which conditions it is appropriate to consider a pure elastic approach for the analysis of crack instability, such as that based on the first and second terms of Williams series expansion. For the sake of generality, the study is based on a dimensional analysis. The data have been obtained from 3D finite element results. For materials for which LEFM can be applied, it has been concluded that the constraint zone clearly engulfs the plastic zone (except near the free surfaces), even for thin plates whose thickness is less than the minimum plane strain thickness specified in current norms.

Monitoring of concrete structures by using the 14 MeV tagged neutron beams

The maintenance and repair of reinforced concrete structures, especially those submerged in the sea-water require effective inspection and monitoring techniques for assessing the state of corrosion in the reinforcement material. An underwater inspection system was developed which is able to monitor the corrosion of the reinforcement. The system is composed of a remotely operating vehicle (ROV) equipped with the sealed tube neutron generator (NG). By rotating the NG and by using the associated alpha particle technique it is possible to measure the concrete cover thickness together with the reinforcing bar diameter. The possibility of estimating the carbon and chloride contents in the concrete was investigated. Iron plates of different thickness, covered by 6 cm thick concrete block, were successfully detected and the thickness of the concrete cover was estimated. In addition, reinforcing bar of one and 3 cm in diameter were identified and measured. All measurements could be performed without cleaning the concrete surface from fouling material.

Stress intensity factor solutions for spot welds in square overlap parts of cross-tension specimens of different thicknesses and materials

Closed-form stress intensity factor solutions for spot welds in square overlap parts of cross-tension specimens are investigated in this paper. The opposite outer edges of the square overlap parts of cross-tension specimens are under combined opening and counter bending conditions. The closed-form analytical structural stress solutions for a rigid inclusion in a square plate under the combined opening and counter bending conditions are first reviewed. Then, the J integral and stress intensity factor solutions for spot welds between square plates of different thicknesses and materials under the combined opening and counter bending conditions are developed in terms of the closed-form structural stress solutions for a strip model. The results of three-dimensional finite element analyses for spot welds between square plates of different thicknesses and materials under the combined opening and counter bending conditions are then presented. The analytical stress intensity factor solutions at the critical locations for spot welds based on the structural stress solutions with the equivalent and fitting coefficients are compared with the computational results. The results indicate that the computational stress intensity factor solutions agree well with those based on the structural stress solutions with only the equivalent coefficients. Based on the closed-form structural stress solutions, complete sets of the normalized in-plane stress intensity factor solutions at the critical locations of spot welds in square overlap parts of cross-tension specimens as functions of the ratio of the plate width to the spot weld diameter are presented for combinations of steel, aluminum and magnesium sheets and combinations of aluminum and copper sheets for convenient engineering applications.