Top PDF Behaviour of the peach under underwater shock wave loading

Behaviour of the peach under underwater shock wave loading

Behaviour of the peach under underwater shock wave loading

Shock wave is a pressure wave, which propagates in a medium, such as gas, liquid or solid, by chan- ging its physical state rapidly. The shock wave propa- gates in a medium faster than the acoustic velocity, so called “super sonic velocity”. Shock wave is a com- pression wave, and its pressure, temperature, and density behind the shock wave increases than that of the region ahead of it. In many cases, shock wave is accompanied with an expansion wave, so that it attenuates during the propagation, and fi nally the velocity becomes acoustic wave (Ando et al., 1999; Iyama, 2003).
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Machine-learning prediction of underwater shock loading on structures

Machine-learning prediction of underwater shock loading on structures

The problem, depicted schematically in Figure 1a, is analyzed. It shows a marine vessel partially immersed in water and an explosive device detonated at a point far away from it. A simple model for studying deformations of the marine vessel subjected to a shock wave produced by the detonation of the explosive device is shown in Figure 1b. For estimating the effects of the structural stiffness and its damping on the transmission and reflection of the incident wave, the problem is simplified considerably by modelling the structure as two infinite parallel rigid plates interconnected by a linear spring and a linear dashpot as shown in Figure 1. The incident wave and the wave reflected from the left plate travel in water, but the wave emanating from the right plate may propagate either into water or into air.
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Modelling of the behaviour of metal foams under shock compression

Modelling of the behaviour of metal foams under shock compression

The aim of the present work is to develop a continuum model able to describe the behaviour of cellular materials under shock loading. The proposed model is based on a micromechanical analysis and takes macroscopic and microscopic inertia into account. In the case of elastic-plastic cellular solids (made of a rate- independent base material), an analytical expression of the Hugoniot stress-strain curve was obtained. A method to determine the Hugoniot and the structure of shock waves in viscoplastic foams is also proposed.

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Performance of Pre-Stressed Sandwich Composites Subjected to Shock Wave Loading

Performance of Pre-Stressed Sandwich Composites Subjected to Shock Wave Loading

Abstract. The present paper experimentally studies the dynamic behaviour of pre- stressed sandwich composites under blast loading. The in-plane static compression loadings are implemented on the sandwich composites before they are subjected to the transverse shock wave loading. Three different pre-stress levels are chosen. 3-D real- time deformation data are captured by two high-speed photography systems: a back- view Digital Image Correlation (DIC) system and a side-view camera system. The results show that pre-stresses can induce local buckling in the front face-sheet of sandwich composites, consequently reduce the blast resistance of sandwich composites.
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Peridynamic modeling of composite laminates under explosive loading

Peridynamic modeling of composite laminates under explosive loading

The applicability of this approach is demonstrated by simulating the damage evolution in a 13-ply composite laminate under shock-type loading. The PD predictions are compared against an experimental study performed by LeBlanc [4]. A Conical Shock Tube (CST) was used to replicate underwater shock phenomena. The geometry and mechanical properties of the composite plate are the same as those reported by LeBlanc. The CST experimental setup is shown in Fig. 4. Shock wave propagates from the breech, at which the charge is located, and strikes the test plate. The test plate, shown in Fig 5, is clamped along the boundary region using bolts.
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Laser shock experiments to investigate and to model various aspects of the response of metals to shock loading

Laser shock experiments to investigate and to model various aspects of the response of metals to shock loading

Dynamic yielding of iron has been the subject of extensive studies for many years. A compression front splits into an elastic precursor followed by a slower plastic wave. The amplitude of the elastic precursor is reported to decrease with increasing propagation path length, and stress relaxation is observed before the plastic wave [4]. This highly rate-dependent behaviour has been attributed to the nucleation and motion of dislocations and deformation twinning [5]. Free surface velocity profiles measured in laser shock-loaded iron samples are plotted in Fig. 2, showing both elastic precursor decay and stress relaxation. Similar profiles have been recorded with piezoelectric transducers and reported in the past, together with micrographs of the recovered targets showing considerable twin formation [6]. The measured values of elastic particle velocities are much higher than those reported in thicker specimens under conventional shock loading [4, 5], which confirms the rate-dependency of the response. A constitutive model [5] has been adapted to simulate this behaviour, as fully detailed elsewhere [6]. It involves a volume fraction of twinned material ξ:
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Use of Genetic Algorithms for Optimal Design of Sandwich Panels Subjected to Underwater Shock Loading

Use of Genetic Algorithms for Optimal Design of Sandwich Panels Subjected to Underwater Shock Loading

Sandwich composite panels are increasingly used in the construction of marine vehicles because of their outstanding strength, stiffness and light weight properties. However, the use of composite panels comes with difficulties in the design process as a result of the large number of design variables involved, including composite material design, topologies and laminate schemes. Hence, this work deals with the presentation of an optimal design of laminated composite sandwich marine structures subjected to underwater explosion. The optimization process is performed using a genetic algorithm (GA), associated with the finite element method (FEM) for the structural analysis. In this optimization procedure, sandwich composite panel finite element model is built up, then the coupled acoustic–structural arithmetic from the widely used calculation program of the finite element “ABAQUS” is used to simulate and analyze the transient dynamic response of a sandwich composite panel that experiences loading by an acoustic pressure shock wave resulting from an underwater explosion “UNDEX”. This approach is well suited for enhancing the response of orthotropic and/or laminated composites which involve many design variables. In GA method, a new approach is considered to improve this evolutionary algorithm for laminated stacking sequence and material selection of face layer and cores. Simple crossover, modified ply mutation, and a new operator called “ply swap” are applied to achieve these goals. Keywords: optimization, genetic algorithm, finite element method, sandwich panel, underwater explosion, cavitation
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Machine-Learning Prediction of Underwater Shock Loading on Structures

Machine-Learning Prediction of Underwater Shock Loading on Structures

The architecture of the BPNN for parametric predictions of underwater explosion problems based on analytical and numerical results was proposed and validated in this study. Taylor’s analysis of the motion of a rigid plate has been extended, with one side exposed to water and the other to air, to the case of two rigid parallel plates interconnected by a spring and a dashpot. The system was immersed in water with an exponentially decaying plane wave striking the left plate at normal incidence. The motions of the two plates as a function of their masses, spring stiffnesses, and their damping coefficients, were computed. Assuming that the fluid cannot support any tensile pressure, the cavitation time, the dependence of the momentum transfer coefficient, and the cavitation time upon the fluid–structure parameter were quantified. For more complicated problems, we can further advance the machine-learning model using finite element method for training purposes. The machine-learning model can significantly reduce the computational resources required for three dimensional simulations of underwater explosions.
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Experimental studies on the deformation and rupture of thin metal plates subject to underwater shock wave loading

Experimental studies on the deformation and rupture of thin metal plates subject to underwater shock wave loading

However the level of understanding of the response of these structures at these high loading rates is not as established as that under static conditions. In this paper, A FSI apparatus was developed to generate an exponentially decaying pressure in lieu of explosive detonation by Xiang [11] in reference of Espinosa’s works [9]. Combined with this equivalent device, 3D DIC technology and high-speed photography, the dynamic response of air- backed copper circular plates with pre-notches subjected to underwater impulsive loading was recorded in real- time. Compared with the strain gauge results and DIC results, the accuracy and advantage of DIC technology was proven obviously. The final failure modes for specimens with different pre-notches are evaluated by recycling the specimens. Moreover, the effects of pre-notches on the failure modes of thin circular plate were discussed. This work will be useful to those involved in research into the response of structures to explosive loading, a subject that has become increasingly important with heightened public awareness of potential explosive threats to civilian safety.
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On the viscoelastic behaviour of beef meat under compression loading

On the viscoelastic behaviour of beef meat under compression loading

It is evident that the parameters of the rheologi- cal model are strongly dependent on the values of the force or stress, respectively. It means that the strain behaviour of the tested beef exhibits signifi- cant non – linear viscoelastic features. This behavi- our cannot be described only in terms of the Maxwell model mentioned above. In order to describe the ob- served stress – strain behaviour of the beef meat we have used an analogy in the similarity between stress – strain curves obtained in this work with those obta- ined for some polymeric foam (Zhang et al., 1997), rubber (Yang et al., 2000) and some other polymeric materials (Wang and Yang, 1992). The description of these results is given in terms of the visco – hypere- lastic constitutive equation. According to this theory which is well described e.g. by Yang and Shim (2004) the uniaxial stress consists of two parts. The first part
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BEHAVIOUR OF FERROCEMENT PANELS UNDER DROP WEIGHT LOADING

BEHAVIOUR OF FERROCEMENT PANELS UNDER DROP WEIGHT LOADING

resistance of fibre reinforced concrete, incorporated with steel fibres at various dosages. For this, a drop weight test was performed on the 28 days cured plain and fibre reinforced concrete samples as per the testing procedure. Crimped and hooked end steel fiber of length 50mm with an aspect ratio equal to 50 was added to concrete in different proportions i.e. 0%, 0.5%, 1.0%, 1.5% with water cement ratio of 0.42. From the test results, it was proved that the FRC was effective under the impact loads thus improving the impact resistance. Also, the reduction of strength under impact load in each specimen for every 3 blows was determined by ultrasonic pulse velocity test. The addition of steel fibers to concrete can significantly improves their compressive strength when compared with plain concrete. The impact energy at failure was increased by 80%, 160% and 260% in case of crimped steel fiber and it was increased by 100%, 200% and 280% in hooked end steel when compared plain concrete. Also the impact energy of concrete is increased in both the cases ie, hooked end FRC and crimped FRC when compared to PC and this increase in energy is slightly greater in case of hooked end fiber reinforced concrete when compared to crimped fiber reinforced concrete.
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Basic Characteristics of the Explosive Welding Technique Using Underwater Shock Wave and Its Possibilities

Basic Characteristics of the Explosive Welding Technique Using Underwater Shock Wave and Its Possibilities

side to the farthest end. The result is better explained with respect to the change in the underwater shock pressure, which decreases to the farthest end as a result of increasing the stand-off distance between the explosive pack and the plates to be welded, as explained earlier. Figure 7 shows the change in the vertical plate velocity with distance x, and the calculated result suggests that there is a decrease in Vp with increasing x. As shown in Fig. 6, the measured wavelength shows a deviation from the averaged line. It is considered that the result is attributable to the effect of the propagation of reflected waves.
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Research of dynamic properties of alloys of AMg6BM and AMg6M in shock-wave experiment on a gas gun

Research of dynamic properties of alloys of AMg6BM and AMg6M in shock-wave experiment on a gas gun

Experimental data were obtained in the form of profiles of free surface velocity W (t) for each type of samples of AMg6M and AMg6BM. Experimental data were processed and analyzed, the values of spall strength, dynamic yield limit, elastic limit and shear stress were determined. Threshold values of pressure were also determined, under which, spall destruction begins. For each material, dependences of spall strength on amplitude of loading pulse and deformation rate were built. Experimental profiles were used for determination of parameters of Johnson-Cook material model with Mie- Gruneisen.
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Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading in tantalum

Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading in tantalum

Abstract. Widespread research over the past five decades has provided a wealth of experimental data and insight concerning the shock hardening, damage evolution, and the spallation response of materials subjected to square-topped shock-wave loading profiles. However, fewer quantitative studies have been conducted on the e ff ect of direct, in-contact, high explosive (HE)- driven Taylor wave (unsupported shocks) loading on the shock hardening, damage evolution, or spallation response of materials. Systematic studies quantifying the e ff ect of sweeping-detonation wave loading are yet sparser. In this study, the shock hardening and spallation response of Ta is shown to be critically dependent on the peak shock stress and the shock obliquity during sweeping-detonation-wave shock loading. Sweeping-wave loading is observed to: a) yield a lower spall strength than previously documented for 1-D supported-shock-wave loading, b) exhibit increased shock hardening as a function of increasing obliquity, and c) lead to an increased incidence of deformation twin formation with increasing shock obliquity.
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Dynamic behaviour of composite sandwich beams and plates with debonds

Dynamic behaviour of composite sandwich beams and plates with debonds

A new generation composite sandwich made up of GFRP skins and high strength phenolic core material has been developed in Australia. Compared to the traditional sandwich panels, the new GFRP sandwich panel has a higher core density resulting in an improved structural behaviour (Awad et al. 2012a). The new panel composition comprises approximately 15 kg of polymer per square meter, and 65 % of this polymer is plant based, and it has a carbon foot print similar to timber making it environmentally sustainable, in addition to improved strength characteristics (Van- Erp 2010). Since a major percentage of the polymers used in the panel are plant- based, the atmospheric carbon absorbed by these plants during their growth becomes permanently locked into the panel during the manufacturing process, and, by recycling the panel at the end of its life this carbon will not be returned to the atmosphere, thus reducing the carbon footprint of the construction industry (Aravinthan 2008). Figure 1.2 illustrates the results of a study conducted to compare the energy consumption of the novel GFRP with four other common building material options (Aravinthan 2008). It is clear from Figure 1.2 that the novel GFRP uses significantly less energy than the traditional building materials.
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Dynamic Characterization of Microcantilevers with a Shock Wave Excitation Method under High Temperature

Dynamic Characterization of Microcantilevers with a Shock Wave Excitation Method under High Temperature

In this paper, the TCF of single crystal silicon microcantilevers was studied under high temperatures ranging from 299 K to 773 K. A dynamic testing system with a high-temperature loading unit was established. In the system, an impact base excitation device with shock wave was developed to excite the microstructures. A LDV was used to obtain the vibration response signals of microstructures. A silicon microcantilever with uniform rectangular crossing section and a T-shaped silicon microcantilever were fabricated. The TCFs of two microcantilevers were tested, and the results were discussed.
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Behaviour of Reinforced Concrete Conical Tanks under Hydrostatic Loading

Behaviour of Reinforced Concrete Conical Tanks under Hydrostatic Loading

Intensive studies on liquid containing conical tanks started after a catastrophic failure of a steel conical water tank in Belgium in 1978. One of these studies was initiated at Ghent University by Vandepitte et al. (1982). The research was mainly conducted experimentally. A large number of small-scale conical vessel models were constructed. The models had different dimensions and were made of different materials. The experiments were conducted by gradually increasing the height of water inside the models. The water height at which each model buckled was detected. The experimental results were employed to develop a set of equations that can be used to assess the stability of conical tanks. Later on, Bornscheuer et al. (1983) studied the elasto-plastic behaviour of conical vessels using a degenerated shell element. The results of their study showed that the buckling strength of the studied tanks is significantly reduced by the presence of axisymmetric imperfections.
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<p>The Effect of Extracorporeal Shock Wave Therapy in the Treatment of Patients with Trigger Finger</p>

<p>The Effect of Extracorporeal Shock Wave Therapy in the Treatment of Patients with Trigger Finger</p>

Thumb (33% in adults and 90% in children) followed by ring fi nger (27%) are the most commonly involved fi ngers. 2,3 Moreover, the right hand is more frequently involved compared to the left hand 4,5 and the dominant hand is more frequently involved compared to the non- dominant hand. 3 The age distribution of trigger fi nger is showing a pattern that includes children under the age of 6 years and adults over 40 years old, especially women aged between 50 and 60 years old. 4 The prevalence of trigger fi nger is higher in patients with rheumatoid arthritis 2 and diabetes (with a prevalence of 10% to 20%) 6,7 compared to the normal population (with a prevalence of 2% to 3%). 7 Additionally, patients with rheumatoid arthritis and dia- betes can experience trigger fi nger in multiple fi ngers. 2,7 Other conditions associated with the disease include carpal tunnel syndrome, osteoarthritis, de quervain ’ s tenosynovi- tis, and hypothyroidism. 8–11
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Behaviour of beam lap splices under seismic loading

Behaviour of beam lap splices under seismic loading

The splices of the deformed longitudinal beam bars in Specimen One resisted several cycles of increasing load, including two generating inelastic tensile strains, before they came apart [r]

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Behaviour of Steel Frame Structure under Dynamic Loading

Behaviour of Steel Frame Structure under Dynamic Loading

The 3D mathematical model of gable stay frame structure isgenerated in SAP2000 as shown in fig 3. The loads acting on the structure are defined and assigned to an individual members. The nonlinear time history analysis of an industrial steel frame is carried out under ground motions as mentioned in table 7.The plastic hinges are generated for column and beam member of a mathematical model as per ASCE 41-13.The ground motions are scaled as per spectral matching using time domine for peak ground acceleration of specific zone. The graph showing scaled pseudo spectral acceleration is shown in fig 4.
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