LS-DYNA3D is an easy to use yet sophisticated multi-physics analysis tool for highly nonlinear dynamic problems. It is a 3-D finite element analysis (FEA)-based code that uses an explicit time integration scheme (Central Difference Method). Explicit integration enables the solution at time (t+dt) to be based on equilibrium conditions at time (t) rather than (t+dt). This means there is no factorization of stiffness matrices at each time step, which greatly reduces both solution time and hard disk usage, and limits model sizes. Engineers involved with virtually any large deformation or contact/impact problem will appreciate LS-DYNA3D's robustness.
Model generation can be done totally within the Finite Element Model Builder (FEMB) preprocessor or in conjunction with imported IGES, DXF, or NASTRAN files. Interfacing is also available with ANSYS, I-DEAS PATRAN, etc. FEMB is CAD-like and allows the user to generate 3-D wireframes and surfaces, nodes, elements, and contacting interfaces. Models of up to 100,000 elements can be developed with FEMB. Necessary data such as material properties, element real constants, and boundary conditions can be fully assigned. FEMB provides selective control over the model by enabling the user to designate part names to any section or component. Features can be toggled on/off through part-name control or by material property, element sets, interfaces, etc.
Coupling of LS-DYNA3D's extensive element library with a host of interface types to more than 30 standard and advanced material models provides the user with a wide range of solutions. Once model generation is completed, the user saves the model in a database file and LS-DYNA3D input deck. Dialog boxes prompt the user to specify problem title, solution end time, type, and output interval times for writing time history data, restarts, etc. These boxes were structured with keyword abbreviations that I often found awkward, forcing me to refer to the on-line documentation outside of FEMB for explanation.
Proper selection of the time step size is critical for stability and accuracy of the integration scheme since the Central Difference Method is only conditionally stable. Dynamic programs without auto-time stepping controls require the user to perform a modal analysis to establish a suitable (dt). LS-DYNA3D eliminates this burden from the user. It automatically computes the critical time step based on the highest frequency of all elements within the model.
After the solution is obtained, the user returns to FEMB to begin post processing the results. FEMB's post processor is very simple to use and conveniently structured. It performs animation of deformed shapes in wireframe form, rendered form, and shaded surfaces with stress/strain contours. The user has total control over which time steps will be animated. He or she can also freeze the model at a specified time step for contouring the results, for example, at the initiation of contact between parts. Section cuts can be made to the model for a review of responses through the structure's thickness. Also, by importing time history results, the user can plot selected time-dependent responses such as velocities with impressive graphics support.
LS-DYNA3D is geared toward large deformation behavior involving nonlinear structural dynamics. It is impossible to discuss the full wealth of LS-DYNA3D's extensive element formulations, material models, and coupled physics capabilities here. Although a few quirks were discovered with LS-DYNA3D operating in Windows 95, I was impressed with its robustness, speed and performance of its solver, and ease of use. I recommend LS-DYNA3D to engineers faced with nonlinear structural problems in automotive, aircraft, transportation, research, and defense industries.
LS-DYNA3D is available for use with 486 or Pentium PCs, Unix workstations, supercomputers, and other platforms. Minimum requirements for a 486 or Pentium system: Windows 95 or NT, 16 Mbytes RAM, 500 Mbytes hard drive space, an NE 2000-compatible network card, and an SVGA display adapter with 800x600 resolution and 1 Mbyte RAM.
KBS2 Inc., 455 S. Frontage Rd., Suite 112, Burr Ridge, IL 60521; ph: (630) 850-7878; fax: (630) 850-9455;e-mail:[email protected]
Livermore Software Technology Corp., 2876 Waverly Way, Livermore, CA 94550; ph: (510) 449-2500; fax: (510) 373-0588; e-mail:[email protected]
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MSC NASTRAN -- The MacNeal Schwendler Corp., 815 Colorado Blvd., Los Angeles, CA 90041; ph. (213) 258-9111; fax: (213) 259-3838.