Scaling aspects of quadrangular plates subjected to localised blast loads—experiments and predictions

A series of experimental results on clamped mild steel quadrangular plates of different thicknesses (1.6, 2.0, 3.0 and 4.0 mm) and varying length-to-width ratios (1.0–2.4) subjected to localised blast loads of varying sizes is reported. Disc shaped explosive charges of varying charge diameter-to-plate width ratios (0.2–0.37) and charge heights (1.8–14 mm) are centrally positioned on quadrangular plates to provide impulses resulting in mid-point deflections in the range from two plate thicknesses to central plate tearing. The effects of varying both the loading conditions and the plate geometries on the deformation are described. A modified dimensionless number is presented for the quadrangular plate response when subjected to localised circular blast loading. In addition, numerical predictions are carried out and compared with experiments for a limited selection of plate geometries.     

Simulation of the response of fibre–metal laminates to localised blast loading

The response of Fibre–Metal Laminates (FML) to localised blast loading is studied numerically in order to interpret the deformation mechanism due to highly localised pressure pulses causing permanent deformations and damage observed experimentally in FML panels comprising different numbers of aluminium alloy layers and different thickness blocks of GFPP material [Langdon GS, Lemanski SL, Nurick GN, Simmons MS, Cantwell WJ, Schleyer GK. Behaviour of fibre–metal laminates subjected to localised blast loading: part I – experimental observations and failure analysis. International Journal of Impact Engineering 2007;34:1202–22; Lemanski SL, Nurick GN, Langdon GS, Simmons MS, Cantwell WJ, Schleyer GK. Behaviour of fibre–metal laminates subjected to localised blast loading: part II – quantitative analysis. International Journal of Impact Engineering 2007;34:1223–45; Langdon GS, Nuric GN, Lemanski SL, Simmons MS, Cantwell WJ, Schleyer GK. Failure characterisation of blast-loaded fibre–metal laminate panels based on aluminium and glass-fibre reinforced polypropylene. Composite Science and Technology 2007;67:1385–405]. The influence of the loading and material parameters on the final deformation characteristics is examined. Particular attention is paid to the transient deformation process by using finite element and analytical models to analyse the panel behaviour. It is shown that the response of the FML panels is extremely sensitive to the spatial and temporal distribution variation of the pressure caused by the blast loading. The study reveals that the properties of GFPP in the through-thickness direction play an essential role in the velocity transfer, which influences considerably the failure and final deformed shape of the FML panel. Good agreement between the experimental and numerical results is observed. Comparisons between the responses of relatively thin FML panels, monolithic aluminium alloy plates of equivalent mass and a foam-core panel to localised blast are also presented and discussed.     

Effect of displacement current in magneto–electro-elastic plates subjected to dynamic loading

Dynamic response of moderately thick magneto?Celectro-elastic plate using magnetic vector potential in finite element formulation is presented in this paper. Dynamic loading generate time varying electric and magnetic fields in magneto?Celectro-elastic continuum. Displacement current is associated with the generation of magnetic field due to time varying electric field. The non-conservative electric field is represented using electric scalar potential and magnetic vector potentials. Studies are carried out for CCCC, CCFC, CFFC and FCFC boundary conditions of the plate excited with time-harmonic mechanical excitation, the frequency range being chosen based on the critical frequency of the plate analyzed. The magnetic flux density in longitudinal x-direction is not affected by the electric displacement current for all the boundary conditions. The longitudinal y-direction and transverse direction components of magnetic flux density are showing variations for FCFC boundary condition when displacement current is accounted. The effect of displacement current is significant when two opposite edges of the plate are clamped.     

Impact on HDPE and PVC plates – Experimental tests and numerical simulations

This paper presents first material tests on HDPE and PVC, and subsequently impact tests on plates made of the same materials. Finally, numerical simulations of the plate impact tests are compared with the experimental results. A rather comprehensive series of mechanical material tests were performed to disclose the behaviour of PVC and HDPE in tension and compression. Quasi-static tests were carried out at three rates in compression and two in tension. Digital image correlation, DIC, was used to measure the in-plane strains, revealing true stress–strain curves and allowing to analyze strain-rate sensitivity and isotropy of Poisson's ratio. In addition, dynamic compression tests were carried out in a split-Hopkinson pressure bar. Quasi-static and dynamic tests were also performed on clamped plates made of the same PVC and HDPE materials, using an optical technique to measure the full-field out-of-plane deformations. These tests, together with the material data, were used for comparative purposes of a finite element analysis. A reasonable agreement between experimental and numerical results was achieved.     

Investigation of pressure in pipe subjected to axial–symmetric pulse loading

The dynamic response of fluids in pipelines impacted by an external pulse loading with consideration of fluid–structural interaction effects was investigated. Two simple models to analyze the response of the fluid have been proposed. The simple models eliminate the need to solve the otherwise complicated fluid–structure interaction. The models predict the pressure magnitude and the pressure wave propagation through the pipeline. To verify the results from the simple models, finite element analyses with the ANSYS code considering fluid–structure interaction have been conducted. In the analyses, fluid–structure interaction effects have been considered by employing direct coupling elements. A comparison between the results from the simple models and the ANSYS analyses has been conducted. The simple models are shown to provide an easy way to estimate the pressure.     

The influence of paper type on the properties of structural paper – Polypropylene composites

In this work, different types of paper were used for producing cellulose reinforced polypropylene composites with MAPP as a coupling agent. The samples were prepared by a film stacking method of the polymer and paper layers, followed by hot pressing in order to fabricate structural composite laminates. Virgin copy, filter and newspaper were used as reinforcements for producing composites with varying paper content. The influence of paper type and content on the mechanical and physical properties of the laminates was investigated and discussed in detail. Remarkable results for tensile and bending test were obtained for copy and newspaper composites at a paper content of 30 and 40 vol.%, indicating a high potential for constructive and industrial applications of the laminates. Further characterization was carried out by Charpy impact test, water uptake study, TGA and light microscopic analysis. To summarize the characterization, structural paper reinforced composites with attractive properties were obtained.     

The influence of stress-controlled tensile fatigue loading on the stress–strain characteristics of AISI 1045 steel

This study analyses the influence of fatigue loading on the residual tensile properties of AISI 1045 steel. The fatigue tests were carried out under stress-controlled tensile loadings at a stress ratio equal to 0. The maximum applied stresses were within the range from 550 MPa to 790 MPa. An analysis of ratcheting strain and plastic strain amplitude evolution due to fatigue loading was performed on the experimental data. In the next stage of this study, the initial fatigue loadings were introduced. Two maximum stresses, 550 MPa and 750 MPa, and three cycle lengths, 25%, 50% and 75% of the total number of cycles required to fracture the material at a given stress, were used. The pre-fatigued specimens were subjected to tensile testing at strain rates from 10⁻⁴ to 10⁰ s⁻¹. A large number of fatigue cycles, equal to 75% of the fatigue life, induces material softening as well as a drop in elongation and a reduction of area. Pre-fatigue at maximum stress equal to 550 MPa results in the increase of the elastic limit and offset yield point as well. Both parameters reach almost constant value after number of cycles equal to 25 % of the fatigue life. The further increase in the number of cycles does not affect elastic limit and offset yield point in a clearly visible way. The increase of maximum stress of the initial fatigue loadings up to 750 MPa induces similar but stronger effect i.e. increase and stabilization of elastic limit and offset yield point values, however decrease of both parameters value is observed at large number of pre-fatigue cycles corresponding to 75% of the fatigue life.     

Environmental effect on fatigue life of glass–epoxy composite pipes subjected to impact loading

The main objective of this experimental study was to investigate the effects of seawater and impact loading on the fatigue life of glass–epoxy composite pipes under cyclic internal pressure. The pipes were produced by filament winding technique. Composite specimens were immersed in seawater for periods of 3, 6, and 9 months. After the impact tests are carried out at three different energy levels (5, 7.5, and 10 J), fatigue tests were conducted on the specimens. It is seen from results that fatigue life changes according to both impact energy and seawater immersion time. Fatigue life of non-impacted specimen is greater than the impacted one. Fatigue life increases in the impacted specimens up to 3 months and reaches generally maximum value. After that it decreases with increase in seawater immersion time. During the fatigue tests, fatigue damage types named perspiration, leakage, and eruption were observed.     

The influence of microcrack nucleation on dynamic crack growth––a numerical study

The study deals with the numerical investigation of microcrack nucleation in front of a fast running macrocrack. The computations are based on a time-domain boundary integral equation method. The influence of the microcracks on different parameters such as the stress intensity factor, energy release rate or crack speed are investigated. Results obtained from numerical simulations are discussed with respect to experimental findings.     

The influence of core properties on the perforation resistance of sandwich structures – An experimental study

The aim of this study is to investigate the perforation resistance of a range of foam-based sandwich structures. Nine foams, based on a crosslinked PVC, a linear PVC and PET, have been combined with thin glass fibre reinforced plastic skins to produce a range of lightweight sandwich structures, Initially, the mechanical properties of the different foams are characterised. Here, a new test geometry is used to evaluate the toughness characteristics and strengths of the foams under shear loading, a condition similar to that encountered during the impact perforation event.The influence of the plastic collapse stress of the foam in determining the failure thresholds of the front and rear composite skins is established. Here, an existing model has been used to successfully predict failure of the top surface composite skin in the sandwich structures. In addition, the force associated with perforating the lightweight core has been shown to be strongly dependent on the shear strength of the polymer foam. Finally, the perforation resistance of the sandwich structure has been shown to be closely linked to the Mode II work of fracture of the foam material. Here a unique relationship has been established between these two parameters, with all of the experimental points lying on one curve.     

The deformation and tearing of thin square plates subjected to impulsive loads—An experimental study

Experimental results for clamped mild steel square plates subjected to impulsive loads are reported. The strain rate-sensitive plates exhibit mode I (large ductile deformation), mode II (tensile-tearing and deformation) and mode III (transverse shear) failure modes. Three phases of mode II are identified as mode II¹ (partial tearing), mode IIa (complete tearing with increasing mid-point deformation), and mode IIb (complete tearing with decreasing mid-point deformation). For the cases where complete tearing occurs (modes II and III) the velocity of the square disc torn from the base plate is measured. An attempt to measure the speed of rotation of the disc is discussed. Threshold for the onset of failure modes II and III are given. Comparisons between the response of square and circular plates are discussed.     

Pentaerythritol crystallization – Influence of the process conditions on the granulometric properties of crystals

The quality of crystals depends on many factors that determine their granulometric properties. In order to obtain crystals of desired size distribution, proper selection of the operating conditions is of a great importance. Commonly, the unseeded cooling crystallization is controlled by selecting the appropriate cooling profile. The crystallization process can also be controlled by adding a certain number of seed crystals of a uniform size in the crystallizer at the saturation temperature. This paper investigates the influence of the process conditions (mixing intensity, cooling profile, batch time, saturation temperature and seeding) on the granulometric properties of pentaerythritol obtained by batch cooling crystallization. All investigated process conditions influence the crystal size distribution (seeded and unseeded experiments). On the other hand, the shape of crystals was the same for all experimental conditions. Optimal cooling profile, lower retention time, higher mixing rate, and smaller initial seed surface area improves the final crystal size distribution.     

The influence of antioxidants on the Spreadability of α-Tocopherol Gels

Abstract

This study is based on the elaboration of α-Tocopherol gels containing the antioxidants butylated hydroxitoluene and ascorbic acid for the purpose of subjecting them to a Theological study aimed at evaluating the influence of the components of the various preparations.     

On the resistance to penetration of stiffened plates,Part I – Experiments

The paper deals with hull damage in ships which are subjected to grounding actions. A ship is assumed to settle vertically on a rock. It is further assumed that contact actions are local and restricted to one plate section. The scenario is analyzed by conducting a series of panel indentation experiments. Various configurations of stiffened panels are loaded laterally by a cone shaped indenter until fracture occurs. The specimen dimensions represent a 1:3 scale of the dimensions found in medium sized tankers. Naturally, because damaged hull and cargo tanks may have severe environmental consequences, e.g. as exemplified by high profiled grounding accidents such as the Exxon Valdez grounding which lead to the discharge of nearly 240,000 barrels of oil, focus is on the plastic deformation and fracture resistance of the panel.     

The influence of neutron irradiation on the thermal conductivity of aluminum in the range 5–50 K

Measurements of thermal conductivity of 6N to 3N pure aluminum in the temperature range 5–50 K subjected to fast neutron irradiation, with exposures of 10¹³ and 10¹⁶ n · cm^–2, are reported. The thermal conductivity maximum was found to shift towards higher temperatures with an increase in the fast neutron irradiation exposure. At high temperatures, a departure from Wilson's theory was observed, which may be attributed to the existence of additional electron scattering mechanisms. An increase in both ideal and residual thermal resistivity components with an increase in the radiation exposure was noted.Nomenclature I ₅ (/t) Debye integral of the fifth order - –m slope of the straight line that crosses maximum thermal conductivity values - n exponent in ideal thermal resistivity component - T _m temperature corresponding to maximum thermal conductivity - W _e total electronic thermal resistivity - W _i ideal thermal resistivity - W ₀ residual thermal resistivity - ideal thermal resistivity coefficient in Eq. (4) - ideal thermal resistivity coefficient in Eq. (1) - constant related to the ideal part of thermal resistivity in Eq. (2) - () ideal thermal resistivity coefficient depending on irradiation exposure - () residual thermal resistivity coefficient depending on irradiation exposure - thermal conductivity - _m maximum thermal conductivity - Debye characteristic temperature - irradiation exposure     

The influence of carboxylate ions on the growth of β-FeOOH particles

Colloidal -FeOOH particles were produced by hydrolysis of FeCl₃ solutions doped with varied amounts of formate, lactate, oxalate, tartarate, pyromellitate and EDTA ions at 100 °C. The resulting particles were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric-differential thermal analysis, Fourier transform-infrared spectroscopy, elemental analysis, and the adsorption of nitrogen and water. With increasing concentration of added carboxylate ions, the mean modal size of the particles formed increased at low concentrations and decreased after passing the maximum. The crystallite sizes also revealed a maximum on adding EDTA, oxalate and lactate ions, while they monotonically decreased with the addition of other ions. Doping with tartarate and pyromellitate ions by more than 7 and 10 mol%, respectively, produced amorphous particles containing a large amount of these ions. The particles formed with 20 mol% tartarate ions adsorbed water selectively.