Sandwich structures have been widely used in marine applications due to their properties such as high weight/strength ratio. In contrast, the failure mechanism of these structures has a significant ...effect on the local and global dynamic responses. In the present study, sandwich panels with polymeric skins and PVC foam cores subjected to slamming impact are investigated experimentally and numerically. A high speed shock machine is used to keep approximately a constant velocity during the impact event. The dynamic resistance was analysed in terms of hydrodynamic loads, dynamic deformation and failure mechanisms for different impact velocities. On the other hand, the slamming model was implemented in Abaqus/Explicit software based on Coupled Eulerian Lagrangian model approach. In addition, different damage modes are incorporated in the numerical model, including the intralaminar, debonding in skin/core interface, and core shear to cover all possible damage modes throughout structures. Two failure criteria (Hashin criteria for the laminate composite and Christensen criteria for the core in sandwich structure) are defined and integrated into VUMAT sub-routine. In addition, the cohesive zone model is used to predict the debonding skin/core. A good agreement in both hydrodynamic loads and damage prediction were found between numerical and experimental results.
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•UHMWPE Tensylon is successfully thermaly spraying coated by 200 µm thick Alumina by using an intermediate Zn layer.•LASAT method has been successfully experienced to assess the ...coating adhesion at high strain rates.•The obtained hybridized structure reduces the rear face velocity under shock by more than half, very effective for impact resilience.
Composite materials are increasingly inescapable in engineered systems in various industrial fields, given their high strength to weight ratio for increasing autonomy, reducing energy consumption and enhancing mechanical strength of high added value products. However, their out-of-plane resistance could be improved by multimaterial assembly for structural hybridization. The purpose of this study is to explore the possibility of upgrading the shock resistance of UHMWPE Tensylon® by alumina coating. Thermal spraying was used for alumina deposition on UHMWPE and bond strength assessment of the obtained assembly was performed by Laser Adhesion Test (LASAT). During experiments, free surface velocities of specimens were recorded by the use of Photonic Doppler Velocimetry (PDV) allowing relevant observations complementary to optical observations. From the PDV analysis and cross section observations by microscopy, a diagnostic of the decohesion of the interface is proposed. The study shows the possibility of assembling alumina on UHMWPE to strengthen its shock resistance and makes now possible the improvement of the study of deposition process parameters thanks to LASAT evaluations.
Figure: Composite panels under slamming impact: panels and Servo-test machine.
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•Dynamic structural response of composite structures under slamming impact.•Experimental investigation ...on the slamming impact water of composite wedge.•Damage progressive in composites under slamming impact is presented.•Assessment to meet the specific requirements of marine vessels.
Generally, when marine vessels encounter the water surface on entry and subsequently re-enter the water at high speed, this can subject the bottom section of the vessels to high hydrodynamic loads, especially over very short durations. This phenomenon generates high hydrodynamic loads, which can cause a catastrophic failure in the structure. In contrast, the interaction between deformable structures and free water surface can be modified the fluid flow and changed the estimated hydrodynamic loads comparing with rigid body, due to appearance of hydroelastic effects. These effects are considered active challenge areas in structural ship design. This work presents an experimental study of the water impact for composite laminate wedge at different constant entry velocities. The aim of this study is to investigate the dynamic structural response of panels and predicts the hydrodynamic loads to meet the specific requirements of marine vessels. In order to better describe hydroelastic influence, two composite panels with different thicknesses namely 8 mm and 13 mm are subjected under constant impact velocities of 4, 6 and 8 m/s with the deadrise angle of 10°. The obtained experimental results were indicated that more flexible panels had a higher peak force and significant dynamic noise compared with higher stiffness panels. In addition, the maximum deformation occurred in the centre and close to the chine edge of the panel due to changes in local velocity and local deadrise angle. For this reason, special attention requires in both design phase and operation phase.
•Experimental study and the help of numerical methods the structural behavior and the effect of the flexibility of composite panels on hydrodynamic loads and the dynamic deformation response.•A high ...velocity shock machine was used to perform a constant velocity during water entry on composite panels.•The numerical model was implemented using Coupled Eulerian–Lagrangian (CEL) approach for modeling of a three dimensional slamming impact.•The numerical results give a good correlation with the executed experimental results in both hydrodynamic force and deformation response.•Results of this study can be assisting vessel designers to understand the influence of the elastic structural behavior on hydrodynamic loads.
The interaction between deformable structures and free water surfaces can modify the fluid flow and change the estimated hydrodynamic loads in relation to rigid bodies, due to the appearance of hydroelastic effects. The flexibility and damage failure modes in composite materials introduce additional complexity for predicting hydrodynamic loads when interactive with water. This is considered to be a key challenge when using these materials in marine applications. Therefore, particular attention should be paid to this fact in the design phase and over their period of use. The aim of this work is to study the structural behavior and the effect of the flexibility of composite panels on hydrodynamic loads and the dynamic deformation response experimentally and numerically. To study these effects, composite panels with two different rigidities were subjected to various impact velocities and investigated. It should be noted that all the panels tested at a10° deadrise angle. A high velocity shock machine was used to maintain constant velocity during water entry at impact velocities of 4 m/s, 6 m/s, 8 m/s and 10 m/s. The general analysis of experimental results indicated that compared to the higher stiffness panels, the more flexible panel has a higher peak force as velocity increases. This has been attributed to the change in local velocity and local deadrise angle along the water-panel interface. The numerical model was implemented based on the Coupled Eulerian–Lagrangian Model (CEL) built-in Abaqus/Explicit finite element software. The numerical results showed a good agreement compared with experimental data for both the hydrodynamic force and the deformation response. These quantitative structural-loading data can provide a clear guide for maritime ship design.
Figure: Water-entry problem: Experimental shock machine and numerical model. Display omitted
In the maritime environment slamming is a phenomenon known as short duration impact of water on a floating or sailing structure. Slamming loads are local and could induce very high local stresses. ...This paper reports a series of impact test results and investigate the slamming loads and pressures acting on a square based pyramid. In this study the slamming tests have been conducted at constant velocity impact with a hydraulic high speed shock machine. This specific experimental equipment avoids the deceleration of the structure observed usually during water entry with drop tests. Three velocities of the rigid pyramid have been used (10, 13 and 15ms−1). Time-histories of local pressures, accelerations and slamming loads were successfully measured. The relationship between the pressure magnitude and the impact velocity is obtained and the spatial distribution of pressures on pyramid sides is characterized. The impact velocity was found to have a negligible influence in predicting the maximum pressure coefficient.
The strong nuclear interaction is probed at short-distance and high-momenta using new measurements of the $^{12}$C$(e,e'p)$ and $^{12}$C$(e,e'pn)$ reactions, at high-$Q^2$ and $x_B>1$. The data span ...a missing-momentum range of 300-850 MeV/c and is predominantly sensitive to the dominant proton-neutron short-range correlated (SRC) pairs and complements previous $^{12}$C$(e,e'pp)$ measurements. The data are well reproduced by theoretical calculations using the Generalized Contact Formalism with both chiral and phenomenological nucleon-nucleon ($NN$) interaction models. This agreement, observed here for the first time, suggests that the measured high missing-momentum protons up to $850$ MeV/c belonged to SRC pairs. The measured $^{12}$C$(e,e'pn)$ / $^{12}$C$(e,e'p)$ ratio is consistent with a decrease in the fraction of proton-neutron SRC pairs with increasing missing-momentum. This confirms the transition from an isospin-dependent tensor $NN$ interaction at $\sim 400$ MeV/c to an isospin-independent scalar interaction at high-momentum around $\sim 800$ MeV/c.
The problem of the impact between a rigid body and a gas-liquid mixture is relevant to various engineering applications, including the design of breakwaters and LNG containers. In the present study, ...the particular problem of the impact of a rigid cone upon the surface of an aerated liquid is investigated. Numerical simulations of water entry of cones with different deadrise angles (7° and 15°) were performed using an explicit finite element method. The air-water mixture is modelled as a homogeneous fluid with a specific equation of state. In addition, experimental tests of the impact of a cone with a deadrise angle of 7° on the surface of bubbly water were performed. The air volume fraction was measured prior to the impact tests using optical probes, and the instantaneous impact force on the cone was measured using strain gauges. The results highlight a significant reduction of the impact load with the increase of the air volume fraction. Moreover, the numerical results show that this reduction is also dependent on the impact velocity. This phenomenon is found to be related to the nonlinearity of the equation of state of the air-water mixture.
Background: The electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four ...momentum transfer (Q2). Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed. Purpose: We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections in order to determine the TPE contribution to elastic electron-proton scattering and thereby resolve the proton electric form factor discrepancy. Methods: We produced a mixed simultaneous electron-positron beam in Jefferson Lab's Hall B by passing the 5.6 GeV primary electron beam through a radiator to produce a bremsstrahlung photon beam and then passing the photon beam through a convertor to produce electron/positron pairs. The mixed electron-positron (lepton) beam with useful energies from approximately 0.85 to 3.5 GeV then struck a 30-cm long liquid hydrogen (LH2) target located within the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered leptons and the recoiling protons we identified and reconstructed elastic scattering events and determined the incident lepton energy. A detailed description of the experiment is presented. Results: We present previously unpublished results for the quantity R2γ, the TPE correction to the elastic- scattering cross section, at Q2 ≈ 0:85 and 1.45 GeV2 over a large range of virtual photon polarization ε. Conclusions: Our results, along with recently published results from VEPP-3, demonstrate a non-zero contribution from TPE effects and are in excellent agreement with the calculations that include TPE effects and largely reconcile the form-factor discrepancy up to Q2 ≈ 2 GeV2. These data are consistent with an increase in R2γ with decreasing " at Q2 ≈ 0:85 and 1.45 GeV2. There are indications of a slight increase in R2γ with Q2.
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•Rosemary roots chemically activated by H3PO4 were used as activated carbon.•The activated carbon (ACRR) showed to be good adsorbent for Methyl Red.•The activated carbon (ACRR) is ...characterized by SEM, EDX, DRX, RAMAN, IR, and Zeta potential.•The theoretical study and experience design are used in this investigation•This study showed the perfect mechanism for Methyl Red.
Activated carbon is an internationally recognized adsorbent substance that removes contaminants from industrial discharges. In this study, we evaluate the capacity of Activated carbon produced by the chemical carbonization of Rosemary root, considered agricultural waste, by using phosphoric acid as an activator to adsorb Methyl Red (MR) from aqueous solutions. To identify the optimum conditions for the carbonization process, the effects of several factors on the removal of methyl red were examined. These parameters included carbonization time, temperature, phosphoric acid concentration, and contact time, with the help of experimental design. We found that 550 °C is the optimal temperature for carbonization of rosemary root, and the concentration of H3PO4 was discovered to be 5.5 mol/l. What about the times we determined for contact time and carbonization time, which were 30 min and 120 min, respectively. The resulting Activated Carbon of Rosemary Root (ACRR) material was then characterized using XRD, FTIR, Boehm titration, SEM/EDX, RAMAN, and Zeta potential. A batch system is used to perform our adsorption. In addition to pH effects, initial MR concentration, contact time, and masse effect were examined, and all the results were confirmed via experimental design using full factorial. In the present study, 15 mg of the adsorbent exhibited an adsorption capacity of 154.53 mg/g at pH 3.25 and a temperature of 328.15 k at a concentration of dye 50 mg/l. The adsorption results of methyl red onto ACRR powder showed that the adsorption process was best correlated with Freundlich isotherm and pseudo-second-order kinetic. According to the thermodynamic study, the system is exothermic. In order to understand the activated sites presented on MR and the mechanism of adsorption, density functional theory (DFT) using the B3LYP/6-311G base was used. Furthermore, the experimental results agree with the results of the computational model.
► This paper presents an original experimental approach of three-dimensional water impact at constant speed. ► The hydrodynamic force acting on axisymmetric rigid bodies striking a horizontal liquid ...surface at constant vertical speed is investigated using a hydraulic shock machine. ► The different aspects of the experimental device allowing to carry out impacts at high-speeds with small deviation of the velocity are initially detailed. ► Then, results of observations on several axisymmetric shapes are presented and discussed. ► Good agreements between theoretical model, numerical results and available experimental measurements have been obtained.
This paper presents an original experimental approach of three-dimensional water impact at constant speed. The hydrodynamic force acting on axisymmetric rigid bodies striking a horizontal liquid surface at constant vertical speed is investigated using a hydraulic shock machine. The different aspects of the experimental device allowing to carry out impacts at high-speeds with small deviation of the velocity are initially detailed. Then, results of observations on several axisymmetric shapes are presented and discussed.
Good agreements between theoretical model, numerical results and available experimental measurements have been obtained.
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