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The effective use of existing Finite Element Codes in the direct simulation of hypervelocity impacts by projectiles is limited by the dependence of the size of localized failure regions on the mesh size and alignment. This gives rise to a... more
The effective use of existing Finite Element Codes in the direct simulation of hypervelocity impacts by projectiles is limited by the dependence of the size of localized failure regions on the mesh size and alignment. This gives rise to a non-physical description of the penetration and perforation processes. A micromechanical constitutive model that couples the anisotropic thermo-viscodamage mechanism with the thermo-hypoelasto-viscoplastic deformation will be presented as a remedy to this situation. Explicit and implicit microstructural length scale measures, which preserve the well-posed nature of the differential equations, are introduced through the use of the viscosity and gradient localization limiters. Simple and robust numerical algorithms for the integration of the constitutive equations will be also presented. The proposed unified integration algorithms are extensions of the classical rate-independent return mapping algorithms to the rate-dependent problems. A simple and direct computational algorithm is also used for implementing the gradient-dependent equations. This algorithm can be implemented in the existing finite element codes without numerous modifications as compared to the current numerical approaches for integrating gradient-dependent models. Model capabilities are preliminarily illustrated for the dynamic localization of inelastic flow in adiabatic shear bands and the perforation of Weldox 460E steel plates with various thicknesses by a deformable blunt projectile at various high impact speeds.
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A series of computational models and simulations were conducted for determining the dynamic responses of a solid metal projectile impacting a target under a prescribed high strain rate loading scenario in three-dimensional space. The... more
A series of computational models and simulations were conducted for determining the dynamic responses of a solid metal projectile impacting a target under a prescribed high strain rate loading scenario in three-dimensional space. The focus of this study was placed on two different modeling techniques within finite element analysis available in the Abaqus software suite. The first analysis technique relied heavily on more traditional Lagrangian analysis methods utilizing a fixed mesh, while still taking advantage of the finite difference integration present under the explicit analysis approach. A symmetry reduced model using the Lagrangian coordinate system was also developed for comparison in physical and computational performance. The second analysis technique relied on a mixed model that still made use of some Lagrangian modeling, but included smoothed particle hydrodynamics techniques as well, which are mesh free. The inclusion of the smoothed particle hydrodynamics was intended ...
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To insert individual citation into a bibliography in a word-processor, you can open the article, select your preferred citation style and drag-and-drop it into the document. ... CONSIDERATION OF THE STRENGTH AND STRUCTURAL CHARACTERISTICS... more
To insert individual citation into a bibliography in a word-processor, you can open the article, select your preferred citation style and drag-and-drop it into the document. ... CONSIDERATION OF THE STRENGTH AND STRUCTURAL CHARACTERISTICS OF FILAMENTARY ...
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A constitutive equation for strain rate dependent behavior of viscoplastic materials under different temperature is presented and implemented in a finite element code. A state variable constitutive equation to calculate the state variable... more
A constitutive equation for strain rate dependent behavior of viscoplastic materials under different temperature is presented and implemented in a finite element code. A state variable constitutive equation to calculate the state variable histories from the stress and strain histories is presented. The effect of temperature is included in the constitutive equations. Based on the presented equations, the constitutive model is modified and implemented in the three-dimensional explicit finite element simulation code LS-DYNA to simulate the mechanical response of viscoplastic material. Since this model is implemented in the explicit finite element method it can be used for structural components under impact. Examples of tensile response of Rene 95 and Weldox 460 E steel material are presented in this study. The experimental data are compared with the predicted results calculated from the constitutive model. Good agreement is achieved between them.
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This study develops a general consistent and systematic framework for the analysis of heterogeneous media that assesses a strong coupling between rate-dependent plasticity and anisotropic rate-dependent damage for dynamic problems within... more
This study develops a general consistent and systematic framework for the analysis of heterogeneous media that assesses a strong coupling between rate-dependent plasticity and anisotropic rate-dependent damage for dynamic problems within the framework of thermodynamic laws and gradient theories. The gradient theory of rate-independent plasticity and rate-independent damage that incorporates macroscale interstate variables and their higher-order gradients is generalized here
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ABSTRACT
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... and/or external pressure loads on the bonding surfaces (eg internal pressures of tires), interlaminar normal stresses and strain energy can be very high [eg see Noor et al. ... i)dA A _ -fA fb~}T [m]f dA, A where... more
... and/or external pressure loads on the bonding surfaces (eg internal pressures of tires), interlaminar normal stresses and strain energy can be very high [eg see Noor et al. ... i)dA A _ -fA fb~}T [m]f dA, A where p"I is the undeformed mass density of the ith layer, f = fu, T3i,YaTi i,YsTm ...
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... J. Turvey (GJT) should co-author a book on the buckling of laminated composite plates. ... with the passage of six whole years, the research literature on laminated composite plate buckling ... Carbon, glass, aramid and other... more
... J. Turvey (GJT) should co-author a book on the buckling of laminated composite plates. ... with the passage of six whole years, the research literature on laminated composite plate buckling ... Carbon, glass, aramid and other fibre-reinforced plastics materials are now laminated into ...
Page 1. COMPUTATIONAL AERODYNAMIC ANALYSIS OF THE FLOW FIELD ABOUT A HYPERVELOCITY TEST SLED THESIS Andrew J. Lofthouse, Captain, USAF AFIT/GAE/ENY/02-07 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY ...
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The Earthquake Engineering Online Archive - (Nisee e-library). Asymmetric structures and seismic codes : ductility demand. Benbenishti, Avitzur; Rutenberg, Avigdor. no. 305, Haifa, Israel : Technion, Israel Institute of Technology,... more
The Earthquake Engineering Online Archive - (Nisee e-library). Asymmetric structures and seismic codes : ductility demand. Benbenishti, Avitzur; Rutenberg, Avigdor. no. 305, Haifa, Israel : Technion, Israel Institute of Technology, Faculty of Civil Engineering, Faculty publication ;, 1991, 16 (555.5 B46 1991). Paper copy available only at this time. Please contact the NISEE library for further assistance. ...
This paper attempts to trace the movement of a sled along a track at speeds up to Mach 4.5. The sled is supported with slippers that are loosely connected to the rail in such a way that sliding is allowed relative to the stationary rail,... more
This paper attempts to trace the movement of a sled along a track at speeds up to Mach 4.5. The sled is supported with slippers that are loosely connected to the rail in such a way that sliding is allowed relative to the stationary rail, but the aerodynamic forces acting on the vehicle create bouncing effects within its movement. The model developed makes use of a finite-difference analysis of sliding and bouncing with a one-dimensional differential equation that includes possible melting. The results from this approach are incorporated into a two-dimensional finite-element model that treats the solution incrementally in time within a quasi-steady-state fashion. The results display temperature as a function of conduction and convection including the boundary-layer and Couette conditions along the lower surface. The aerodynamics and boundary layer along the leading edge and top surface are also included. The finite difference is integrated into a finite-element analysis to evaluate sliding, bouncing, and aerodynamic effects on a slipper as it traverses a rail at high velocity. The importance of the research is to determine the temperature profile that can be incorporated into a mechanical evaluation as related to material wear. Nomenclature C p = specific heat, J∕kg · K H = slipper flange thickness, 14.7 mm h = heat transfer coefficient, W∕m 2 · K k = thermal conductivity, W∕m · K L = slipper length, 203.2 mm M = Mach number Nu = Nusslet number Pr = Prandtl number q 0 0 = heat flux, W∕m 2 Re = Reynolds number T aw = adiabatic wall temperature, K T e = temperature at edge of boundary layer, K T r = reference temperature, K T s = surface temperature, K T T = total temperature, K T ∞ = free flow temperature, K u c = Couette velocity, m∕s u 1 = air speed in front of shock, m∕s u 2 = air speed behind shock, m∕s α = partition function γ = ratio of specific heats μ = viscosity, kg∕m · s μ d = dynamic viscosity, kg∕m · s ρ = density, kg∕m 3