Numerical simulations of stiffened multi-arch double-layered panels subjected to blast loading

Blast-resistant structures are traditionally designed and fabricated with solid materials of heavy weight to resist blast loadings. This not only increases the material and construction costs, but also undermines the operational performance of protective structures. To overcome these problems, new designs with either new structural forms or new materials are demanded against blast loads. A multi-arch double-layered panel has been proposed as a new structural form in a previous study [1]. Its performance has been numerically demonstrated better than other forms of double-layered panels in resisting blast loads. In this study, to further improve the effectiveness of the multi-arch double-layered panel in resisting blast loads, responses of a five-arch double-layered panel with rectangular stiffeners to detonations are investigated by using finite element code Ls-Dyna. The numerical results show that the stiffened panel outperforms the unstiffened panel of the same weight in terms of the blast-resistant capacity and energy absorption capacity. Parametric studies are conducted to investigate the effects of various stiffener configurations, boundary conditions, stiffener dimension, strain rate sensitivity and blast intensity on the dynamic response to blast loadings. The central point displacements, internal energy absorptions, boundary reaction forces and plastic strains are compared and the optimal configurations of blast-resistant panel are determined. It demonstrates that the strategic arrangement of stiffeners with appropriate boundary conditions can maximize the reduction of dynamic response of the panels to blast loadings. The stiffened multi-arch dotuble-layered panels have great application potentials in the blast-resistant panel design

A material model driver for DYNA3D

This report describes a material model driver which has recently been implemented in the DYNA3D code. The material model driver allows plotting of the constitutive response predicted by a material model under a given load path. This capability is particularly useful when fitting complex material models to experimental data. The plotting capability of the material model driver facilitates comparison of the simulated material stress-strain behavior with actual material test results. 1 ref., 6 figs., 4 tabs

User's manual for DYNA2D: an explicit two-dimensional hydrodynamic finite-element code with interactive rezoning

This revised report provides an updated user's manual for DYNA2D, an explicit two-dimensional axisymmetric and plane strain finite element code for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. A contact-impact algorithm permits gaps and sliding along material interfaces. By a specialization of this algorithm, such interfaces can be rigidly tied to admit variable zoning without the need of transition regions. Spatial discretization is achieved by the use of 4-node solid elements, and the equations-of motion are integrated by the central difference method. An interactive rezoner eliminates the need to terminate the calculation when the mesh becomes too distorted. Rather, the mesh can be rezoned and the calculation continued. The command structure for the rezoner is described and illustrated by an example

Synthesis of hydrocode and finite element technology for large deformation Lagrangian computation

Large deformation engineering analysis at Lawrence Livermore Laboratory has benefited from a synthesis of computational technology from the finite difference hydrocodes of the scientific weapons community and the structural finite element methodology of engineering. Two- and three-dimensional explicit and implicit Lagrangian continuum codes have been developed exploiting the strengths of each. The explicit methodology primarily exploits the primitive constant stress (or one point integration) brick element. Similarity and differences with the integral finite difference method are discussed. Choice of stress and finite strain measures, and selection of hour glass viscosity are also considered. The implicit codes also employ a Cauchy formulation, with Newton iteration and a symmetric tangent matrix. A library of finite strain material routines includes hypoelastic/plastic, hyperelastic, viscoelastic, as well as hydrodynamic behavior. Arbitrary finite element topology and a general slide-line treatment significantly extends Lagrangian hydrocode application. Computational experience spans weapons and non-weapons applications

DYNA3D, INGRID, and TAURUS: an integrated, interactive software system for crashworthiness engineering

Crashworthiness engineering has always been a high priority at Lawrence Livermore National Laboratory because of its role in the safe transport of radioactive material for the nuclear power industry and military. As a result, the authors have developed an integrated, interactive set of finite element programs for crashworthiness analysis. The heart of the system is DYNA3D, an explicit, fully vectorized, large deformation structural dynamics code. DYNA3D has the following four capabilities that are critical for the efficient and accurate analysis of crashes: (1) fully nonlinear solid, shell, and beam elements for representing a structure, (2) a broad range of constitutive models for representing the materials, (3) sophisticated contact algorithms for the impact interactions, and (4) a rigid body capability to represent the bodies away from the impact zones at a greatly reduced cost without sacrificing any accuracy in the momentum calculations. To generate the large and complex data files for DYNA3D, INGRID, a general purpose mesh generator, is used. It runs on everything from IBM PCs to CRAYS, and can generate 1000 nodes/minute on a PC. With its efficient hidden line algorithms and many options for specifying geometry, INGRID also doubles as a geometric modeller. TAURUS, an interactive post processor, is used to display DYNA3D output. In addition to the standard monochrome hidden line display, time history plotting, and contouring, TAURUS generates interactive color displays on 8 color video screens by plotting color bands superimposed on the mesh which indicate the value of the state variables. For higher quality color output, graphic output files may be sent to the DICOMED film recorders. We have found that color is every bit as important as hidden line removal in aiding the analyst in understanding his results. In this paper the basic methodologies of the programs are presented along with several crashworthiness calculations