Dynamic Disintegration of Explosively-Driven Metal Cylinder with Internal V-Grooves

Machining V-shaped grooves to the internal surface of cylindrical shells is one of the most common technologies of controlled fragmentation for improving warhead lethality against targets. The fracture strain of grooved shells is a significant concern in warhead design. However, there is as yet no reasonable theory for predicting the fracture strain of a specific grooved shell; existing approaches are only able to predict this physical regularity of non-grooved shells. In this paper, through theoretical analysis and numerical simulations, a new model was established to study the fracture strain of explosively driven cylindrical shells with internal longitudinal V-grooves. The model was built based on an energy conservation equation in which the energy consumed to create a new fracture surface in non-grooved shells was provided by the elastic deformation energy stored in shells. We modified the energy approach so that it can be applicable to grooved shells by adding the elastic energy liberated for crack penetration and reducing the required fracture energy. Cylinders with different groove geometric parameters were explosively expanded to the point of disintegration to verify the proposed model. Theoretical predictions of fracture strain showed good agreement with experimental results, indicating that the model is suitable for predicting the fracture strain of explosively driven metal cylinders with internal V-grooves. In addition, this study provides an insight into the mechanism whereby geometric defects promote fracturing.

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Thermal-EHD contacts lubricated with oil/refrigerant solutions: a new cavitation modeling approach based on refrigerant solubility

Journal of Tribology ◽

10.1115/1.4053542 ◽

2022 ◽

pp. 1-19

Author(s):

Fan Zhang ◽

Nicolas Fillot ◽

Rudolf Hauleitner ◽

Guillermo Morales Espejel

Keyword(s):

Thermal Effects ◽

Reynolds Equation ◽

Conservation Equation ◽

Point Contacts ◽

Energy Conservation Equation ◽

Cavitation Region ◽

Cavitation Intensity ◽

Thickness Prediction ◽

Generalized Reynolds Equation ◽

Good Agreement

Abstract A first cavitation modeling with thermal effects for oil/refrigerant solutions lubricated ElastoHydroDynamic (EHD) point contacts is reported in this work. The solubility of the oil/refrigerant system is introduced into the Generalized Reynolds equation coupled with the elasticity equation and the energy conservation equation. The numerical results show a very good agreement with the published experimental results concerning film thickness prediction. Moreover, the present model describes the cavitation region on a physical basis. A discussion with other cavitation models from the literature is proposed. It puts into light the necessity of taking into account the solubility of the refrigerant into oil for such problems. Compared to pure oil, oil/refrigerant solutions can potentially reduce the amount of liquid oil for the next contact due to its higher cavitation intensity.

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A Case Study on the Deformation of Metro Foundation Pit in Silt Stratum in North China

Shock and Vibration ◽

10.1155/2021/7454596 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Yonggang Zhang ◽

Yonghong Wang ◽

Yuanyuan Zhao

Keyword(s):

North China ◽

Deformation Energy ◽

Conservation Equation ◽

Lateral Movement ◽

Deep Foundation ◽

Foundation Pit ◽

Energy Conservation Equation ◽

Internal Support ◽

Controllable Factors ◽

Geological Conditions

Geological conditions of urban subway foundation pits are controllable factors in determining the deformation of pits. In this paper, the monitoring data and statistical data of a subway deep foundation pit in North China are presented and compared with those of Tianjin subway. The deformation characteristics of the proposed pit, open excavated with triple-layer steel supports, are introduced in detail. Based on the aforementioned information, the energy conservation equation of the mobilized strength design (MSD) method in which the compression deformation energy of internal support is considered is applied to predict the maximum lateral movement. The maximum lateral movement turns out to be 22.2 mm according to the improved MSD method, which is very close to the measured value.

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Prediction of average debris launch velocity from a reinforced concrete structure based on SDOF system

Advances in Structural Engineering ◽

10.1177/1369433220960277 ◽

2020 ◽

pp. 136943322096027

Author(s):

Seung-Hun Sung ◽

Hun Ji ◽

Surin Kim ◽

Jinwung Chong

Keyword(s):

Reinforced Concrete ◽

Comparative Study ◽

Conservation Equation ◽

Reinforced Concrete Structure ◽

Reinforcing Bars ◽

Sdof System ◽

Energy Conservation Equation ◽

Rc Structure ◽

Proposed Model ◽

Velocity Prediction

This study presents a physics-based model for debris launch velocity prediction of a reinforced concrete (RC) structure subjected to a blast load. The model is basically derived from energy conservation equation. Especially, a resistance-deflection relationship for the structural single degree of freedom (SDOF) system is newly considered to evaluate the energy consumed by the damage and fragmentation of the RC structure. By applying the resistance-deflection relationship, the proposed model can consider the interactions between reinforcing bars and concrete. Moreover, since the resistance-deflection curve is evaluated considering various structural properties as well as boundary conditions, the proposed model can be flexibly utilized compared to conventional approaches. In order to confirm the performance of the proposed model, a comparative study was carried out against benchmark experiments on closed concrete box structures under an internal blast. From the comparative study, it was shown that the debris launch velocities estimated from the proposed model had a good agreement with the test results compared with the other models.

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Analytical modeling of combustion of a single iron particle burning in the gaseous oxidizing medium

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406212452215 ◽

2012 ◽

Vol 227 (5) ◽

pp. 1006-1021 ◽

Cited By ~ 3

Author(s):

Mehdi Bidabadi ◽

Majid Mafi

Keyword(s):

Thermal Radiation ◽

Separation Of Variables ◽

Mass Conservation ◽

Iron Particle ◽

Conservation Equation ◽

Particle Combustion ◽

Energy Conservation Equation ◽

Proposed Model ◽

Combustion Processes ◽

Mass Conservation Equation

In the present study, a theoretical investigation is accomplished to model the combustion of a single iron particle by virtue of a novel thermophysical approach. It is assumed that a spherical iron particle falls freely in the gaseous medium and preheats and then burns heterogeneously on its external surface in this hot oxidizing environment and oxygen diffuses inward to the particle. A new physical parameter for thermal radiation is introduced. By solving the energy conservation equation for the iron particle, the temperature distribution of the iron particle during the preheating and combustion processes is calculated analytically. Also, by solving the oxygen mass conservation equation, the variation of oxygen concentration within the iron particle during the combustion stage is estimated. In the proposed model, the effect of thermal radiation and dynamic behavior of burning iron particle are considered. Because of high thermal conductivity and micro size of iron particle, the Biot number is negligibly small. The non-homogeneous partial differential equations of energy and mass species resulted from the modeling of combustion are solved by utilizing the method of separation of variables. The assumptions applied in the modeling are such that do not violate the actual combustion phenomenon. Also, the numerical solution of energy equation in the combustion stage is presented and compared with the obtained analytical solution. Also, the burnout time of iron particle is evaluated in this article. This investigation is one of the first performed efforts for analyzing and modeling of single iron particle combustion.

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On the Streamwise Development of Density Jumps

Journal of Fluids Engineering ◽

10.1115/1.4000794 ◽

2010 ◽

Vol 132 (2) ◽

Cited By ~ 1

Author(s):

A. Regev ◽

S. Hassid

Keyword(s):

Energy Conservation ◽

Software Package ◽

Momentum Conservation ◽

Conservation Equation ◽

Entrainment Ratio ◽

Layer Height ◽

Energy Conservation Equation ◽

Linear Expression ◽

Momentum Conservation Equation ◽

Good Agreement

The analysis of density jumps in two-layer channel flows of miscible fluids controlled by a downstream obstruction, in which one of the layers is infinitely deep and at rest, is extended to consider the dependence of its features on its streamwise dimension. The momentum conservation equation in the entrainment and roller regions, and the energy conservation equation after the jump are corrected to account for friction. The streamwise coordinate is related to the increase in the density layer height through a linear expression derived from CFD calculations. Three regimes are distinguished: (1) for short distances from the origin to the obstruction, only an entrainment region exists; (2) for medium distances, two regions can be distinguished, i.e., the entrainment region, and the roller region, in which no entrainment is assumed; and (3) for long distances, three regions can be distinguished—the entrainment, the roller, and the postjump regions, characterized by approximate energy conservation. It is shown that initially the dimensionless total entrainment ratio increases as the distance to the obstruction increases, until a roller region appears. A further increase in distance to the obstruction does not have a significant effect on the total entrainment, until the appearance of a postjump region, resulting in a gradual decrease in the total entrainment. These results are supported by numerical calculations using the FLUENT CFD software package, which are in good agreement with experimental results.

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Braking Indices of Pulsars Obtained in the Presence of an Effective Force

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194517600370 ◽

2017 ◽

Vol 45 ◽

pp. 1760037

Author(s):

Nadja S. Magalhães ◽

André S. Okada ◽

Carlos Frajuca

Keyword(s):

Energy Conservation ◽

Theoretical Calculation ◽

Open Problem ◽

Tangential Velocity ◽

Conservation Equation ◽

Magnetic Dipoles ◽

Effective Force ◽

Energy Conservation Equation ◽

Proposed Model ◽

Using Data

The theoretical calculation of braking indices of pulsars is still an open problem. In this work we present a study on this issue which adapts the model that assumes that pulsars are rotating magnetic dipoles by introducing a compensating component in the energy conservation equation of the system. Such component relates to an effective force that varies with the first power of the tangential velocity of the pulsar’s crust. We tested the proposed model using data available.

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An accurate model for free vibration of porous magneto-electro-thermo-elastic functionally graded cylindrical shells subjected to multi-field coupled loadings

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20986894 ◽

2021 ◽

pp. 1045389X2098689

Author(s):

Yiwen Ni ◽

Shengbo Zhu ◽

Jiabin Sun ◽

Zhenzhen Tong ◽

Zhenhuan Zhou ◽

...

Keyword(s):

Free Vibration ◽

Cylindrical Shells ◽

Functionally Graded ◽

Mode Shapes ◽

Comparison Study ◽

Accurate Model ◽

Various Boundary Conditions ◽

Proposed Model ◽

Good Agreement ◽

Analytical Frequency

An accurate model for vibration of a porous magneto-electro-thermo-elastic functionally graded (METE-FG) cylindrical shell made of barium titanate (BaTiO3) and cobalt diiron tetraoxide (CoFe2O4) with magneto-electro-thermal loadings is proposed within the framework of Hamiltonian system. Four types of porosity distribution profiles in the thickness direction are considered. By introducing a new total eigenvector, the higher-order governing differential equations are transformed into a set of lower-order equations. The exact solution for free vibration of METE-FG shells can be expanded in terms of specific symplectic eigenfunctions having seven possible explicit forms. Subsequently, analytical frequency equations and vibration mode shapes for METE-FG shells with various boundary conditions are derived simultaneously. A comparison study is presented to demonstrate the accuracy of the proposed model and very good agreement is observed. The effects of material properties and magneto-electro-thermal loadings on free vibration characteristics of METE-FG cylindrical shells are analyzed and discussed in detail.

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A Generalized Approach for Evaluating the Mechanical Properties of Polymer Nanocomposites Reinforced with Spherical Fillers

Nanomaterials ◽

10.3390/nano11040830 ◽

2021 ◽

Vol 11 (4) ◽

pp. 830

Author(s):

Julio Cesar Martinez-Garcia ◽

Alexandre Serraïma-Ferrer ◽

Aitor Lopeandía-Fernández ◽

Marco Lattuada ◽

Janak Sapkota ◽

...

Keyword(s):

Mechanical Properties ◽

Polymeric Nanocomposites ◽

Mechanical Reinforcement ◽

Future Studies ◽

Three Phase ◽

Theoretical Predictions ◽

Filler Network ◽

New Research ◽

Good Agreement ◽

Research Avenue

In this work, the effective mechanical reinforcement of polymeric nanocomposites containing spherical particle fillers is predicted based on a generalized analytical three-phase-series-parallel model, considering the concepts of percolation and the interfacial glassy region. While the concept of percolation is solely taken as a contribution of the filler-network, we herein show that the glassy interphase between filler and matrix, which is often in the nanometers range, is also to be considered while interpreting enhanced mechanical properties of particulate filled polymeric nanocomposites. To demonstrate the relevance of the proposed generalized equation, we have fitted several experimental results which show a good agreement with theoretical predictions. Thus, the approach presented here can be valuable to elucidate new possible conceptual routes for the creation of new materials with fundamental technological applications and can open a new research avenue for future studies.

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Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB

Energies ◽

10.3390/en14051286 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1286

Author(s):

Krzysztof Górecki ◽

Przemysław Ptak

Keyword(s):

Integrated Circuits ◽

Optical Model ◽

Printed Circuit Board ◽

Circuit Board ◽

Junction Temperature ◽

Optical Parameters ◽

Spice Simulation ◽

Light Emitting ◽

Proposed Model ◽

Good Agreement

This paper concerns the problem of modelling electrical, thermal and optical properties of multi-colour power light-emitting diodes (LEDs) situated on a common PCB (Printed Circuit Board). A new form of electro-thermo-optical model of such power LEDs is proposed in the form of a subcircuit for SPICE (Simulation Program with Integrated Circuits Emphasis). With the use of this model, the currents and voltages of the considered devices, their junction temperature and selected radiometric parameters can be calculated, taking into account self-heating phenomena in each LED and mutual thermal couplings between each pair of the considered devices. The form of the formulated model is described, and a manner of parameter estimation is also proposed. The correctness and usefulness of the proposed model are verified experimentally for six power LEDs emitting light of different colours and mounted on an experimental PCB prepared by the producer of the investigated devices. Verification was performed for the investigated diodes operating alone and together. Good agreement between the results of measurements and computations was obtained. It was also proved that the main thermal and optical parameters of the investigated LEDs depend on a dominant wavelength of the emitted light.

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Study of Influence of Width to Thickness Ratio in Sheet Metals on Bendability under Ambient and Superimposed Hydrostatic Pressure

Applied Mechanics ◽

10.3390/applmech2030030 ◽

2021 ◽

Vol 2 (3) ◽

pp. 542-558

Author(s):

Mohammadmehdi Shahzamanian ◽

David Lloyd ◽

Amir Partovi ◽

Peidong Wu

Keyword(s):

Hydrostatic Pressure ◽

Stress Ratio ◽

Fracture Strain ◽

Stress Triaxiality ◽

Volumetric Strain ◽

Thickness Ratio ◽

Sheet Metals ◽

The Finite Element Method ◽

Bending Strain ◽

Good Agreement

The effect of the width to thickness ratio on the bendability of sheet metal is investigated using the finite element method (FEM) employing the Gurson–Tvergaard–Needleman (GTN) model. Strain path changes in the sheet with change in the width/thickness ratio. It is shown that bendability and fracture strain increase significantly by decrease in the width/thickness ratio. The stress state is almost uniaxial when the stress ratio (α) is close to zero for narrow sheets. Stress ratio is nothing but the major stress to minor stress ratio. This delays the growth and coalescence of micro-voids as the volumetric strain and stress triaxiality (pressure/effective stress) decrease. On the other hand, ductility decreases with increase in α for wider sheets. Fracture bending strain is calculated and, as expected, it increases with decrease in the width/thickness ratio. Furthermore, a brief study is performed to understand the effect of superimposed hydrostatic pressure on fracture strain for various sheet metals with different width/thickness ratios. It is found that the superimposed hydrostatic pressure increases the ductility, and that the effect of the width/thickness ratio in metals on ductility is as significant as the effect of superimposed hydrostatic pressure. Numerical results are found to be in good agreement with experimental observations.

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