COMPUTATIONAL AND EXPERIMENTAL MECHANICS RESEARCH GROUP

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1 COMPUTATIONAL AND EXPERIMENTAL MECHANICS RESEARCH GROUP The University of Texas at El Paso PURPOSE The Computational and Experimental Mechanics Research Group at the University of Texas at El Paso (UTEP) was organized to create a diverse group of highly skilled and experienced individuals that can address significant engineering problems taking advantage of the group s extensive experience and resources. Group members possess a wide spectrum of experience including working in national laboratories, and academia. Disciplines encompassed include Mechanical Engineering, Engineering Mechanics, Materials Science, Program Management, Field Test, and Instrumentation. Each member has an earned doctorate and an average of 20 years of experience. Key to the group s capability is the availability of a wide array of computer programs (codes), a new supercomputer, testing laboratories, and a machine shop. The group also has a working relationship with other universities and the Energetic Materials Research and Testing Center at New Mexico Tech, Socorro, NM (EMRTC/NMT). The members of this group are committed to collaborative efforts where the group s capabilities may be applied to significant problems involving national defense and security and industrial research. Graduate research assistants are utilized in projects as needed. This brochure briefly describes capabilities for the group including qualifications and experience of individual group members, available computer codes that the group is currently using, and available experimental facilities. For further information, please contact Michael Huerta ( , mhuerta@utep.edu). 1

2 PERSONNEL The following table lists the group members. Resumes are available upon request. In addition to these individuals, Dr. John L. Meason, Director of the Energetic Materials Research and Testing Center at New Mexico Tech, will assist the group in planning and conducting field tests. Overview of Group s Qualifications: UTEP group has over 85years of combined experience Last Degree Applicable Experience Michael Huerta (Group Director) (915) mhuerta@utep.edu Cesar Carrasco Jack Chessa Lawrence E. Murr Stella A. Quinones Ph.D., Mechanical Engineering, The University of Texas at Austin, 1974 Ph.D. Materials Science and Engineering, The University of Texas at El Paso, 2000 Ph.D., Theoretical and Applied Mechanics, Northwestern University, 2002 Ph.D., Solid State Science, Pennsylvania State University, 1967 Ph.D. Materials Science and Engineering, The University of Texas at El Paso, 1996 Experienced running the CTH hydrocode as well as various explicit and implicit finite element codes. Over 25 years of experience in performing structural analyses. Extensive experience with shipping casks for radio-active materials. Experienced with finite element and hydrocodes including NASTRAN, MAGI, AUTODYN. Expert in hypervelocity impacts. Ten years of experience as researcher and developer of finite element, meshless and numerical methods, and as a structural analyst. Performed fundamental research in enriched finite element methods (X-FEM) for FSI, Multiscale methods, interface tracking and MD simulations. Over 36 years of experience in Materials Science and Metallurgy, Engineering Mechanics. Expert in shock wave and high-strain-rate phenomena, experienced with hydrocode analyses, over 600 publications Experienced in using the AUTODYN hydrocode, extensive work in analyzing and characterizing hypervelocity impacts 2

3 CODES Key to the group s capability is its wide experience with finite element and hydrocodes. The group routinely uses the following computer codes: CTH (Sandia National Laboratories hydrocode) MAGI (Los Alamos National Laboratories, smooth particle velocity hydrocode) AUTODYN ( Commercial Lagrangian and Eulerian hydrocode) LS-DYNA ( Commercial explicit finite element code) ABAQUS (Commercial finite element code) NASTRAN ( Finite element code with aeroelasticity package for flutter analysis) ALGOR (Commercial finite element, static, dynamic, non-linear, mechanical event simulations, heat transfer, and fluid flow) A large number of additional codes are available to the group and its members have the expertise to utilize them. The following is a brief description of the principal codes that the group is currently using. CTH The CTH system of codes was developed at Sandia National Laboratories. These codes are designed to treat a wide range of shock wave propagation and material motion problems in 1, 2, and 3 dimensions. Finite-difference analogs of the Lagrangian equations of momentum and energy conservation are employed with continuous rezoning to construct Eulerian differencing. CTH has a wide variety of models for diverse shock physics problems. Models are included for material strength, fracture, and high explosives. Sample problems where CTH can be utilized include hypervelocity impacts, penetration mechanics, and the analysis of shaped charges and their effects. MAGI MAGI is a Smoothed Particle Hydrodynamics (SPH) code based on recent developments in the field of Computational Fluid Dynamics (CFD). The original code was developed at Los Alamos National Labs. The technique utilized is based on a gridless Lagrangian approach, which is ideally suited to the analysis of high deformation dynamic events (hypervelocity impacts and explosions). The code has been parallelized and can be run on PC s and UNIX machines. MAGI is distributed with the source code which allows for the modification and implementation of new algorithms and material constitutive models. 3

4 AUTODYN AUTODYN is a fully integrated software program used for solving complex nonlinear dynamic problems in 2d and 3d. This software is user friendly and was developed by Century Dynamics. It uses finite element techniques along with Lagrange, Eulerian, Shell and Smooth Particle Hydrocode processors to model technical problems. AUTODYN is capable of simulating high strain rate, large strain and large deformation materials behavior associated with shock phenomenon. The program includes several material constitutive equations, failure models and a materials library. The program can handle coupled Eulerian and Lagrangian problems. Rezoning and erosion techniques can be used in order to improve modeling capabilities. LS-DYNA LS-DYNA is a full function finite element program which specializes in explicit transient nonlinear analysis. Its capabilities include over 100 material models as well as user defined constitutive laws, explicit and implicit time integration, fully coupled fluid, solid, and thermal analysis, Eulerian, Lagrangian, ALE finite element formulations as well as SPH and EFG meshless formulations, crack and failure analysis, underwater shock, with specialized features for automotive crash worthiness (seatbelt, airbags, pretensioners and hybrid III dummy models etc.), nine different contact/impact algorithms, adaptive remeshing, hourglass stabilization for SRI continuum and structural elements. ABAQUS ABAQUS is a powerful suite of programs based on the finite element method. It contains an extensive library of elements and material models including metals, rubber, polymers, composites, reinforced concrete, crushable and resilient foams, and geotechnical materials such as soils and rock. It contains two main analysis modules including implicit and explicit formulations. In addition to structural analysis ABAQUS can simulate problems in heat transfer, mass diffusion, acoustics, soil mechanics, and piezoelectric analysis. NASTRAN MSC Nastran is the world s most widely used FEA program for linear and nonlinear analyses of structural, fluid, thermal, and coupled systems. MSC Nastran is modular allowing the addition of sophisticated analyses capabilities like Spot Welding and Aeroelasticity on top of the basic linear static, normal modes, and buckling analyses. UTEP currently owns a license for MSC NASTRAN and PATRAN and the Aeroelasticity I and II modules. 4

5 ALGOR ALGOR is a commercially available system of codes that is in wide use by practicing engineers and used at UTEP for introducing students to the finite element method. The code s capabilities include static stress with linear and non-linear material models, mechanical event simulation, linear dynamic analysis, steady-state and transient heat transfer, steady and unsteady fluid flow analysis with turbulence, electrostatic analysis, and piping systems analysis. COMPUTER HARDWARE The group has distributed facilities that include a large number of PC s. In addition the group is acquiring a very fast parallel processing computer system. UTEP has through an IBM SUR grant acquired an IBM p690 massive parallel processor (MPP) computer. This is a 16 way 1.3 GHz +, $1,000,000, machine which has 32 GB of core memory and 2TB of disk storage. MPP versions of Autodyne and LS- DYNA optimized for this architecture are available. Members of the Computational Mechanics Group at UTEP have been identified as primary users of this machine. Also, the group has capabilities to develop and implement HPF, OpenMP and MPI programs on this machine. TEST FACILITIES UTEP has a complete machine shop, a CNC machining laboratory, and capabilities for performing static structural testing. We have the facilities for instrumenting hardware with strain-gages and other sensors and of acquiring data with a computerized data acquisition system. This equipment is located in the Mechanical Engineering department at UTEP. The Metallurgy and Materials Engineering Department at UTEP also has equipment and test facilities to support experimental work. This includes an ISO and a Phillips Scanning electron microscope, a Hitachi Transmission Electron Microscope, a Vickers Microhardness Tester and several Harness Testers, a Tensile/ Compression machine with strain-rate monitoring capabilities. Field tests will be conducted at EMRTC/NMT, Soccoro, NM. 5

6 SAMPLE ANALYSES The following is an example of an analysis performed with the CTH code. It utilized a High Explosive (HE) burn model as well as material models and equations of state for aluminum, copper, and air. Figure 2, below, illustrates three points in time in the analysis. Figures 2(a) and 2(b) are plots of material, on the right side, and pressure on the left side of the axisymmetric model. CTH has the capability of plotting a large number of parameters including material, pressure, stress, density, and temperature. Figure 2(a) illustrates a shaped charge model just prior to initiating the high explosive. Figure 2(b) is a plot at a point near the end of the HE burn phase. At this point the copper liner is beginning to implode and form a jet. Figure 2(c) illustrates the jet formed as it is moving at hypervelocity. Jet characteristics can be studied as well as the effects of jets impacting a target. Target damage in terms of cratering or penetration can then be assessed. (b) (a) (c) Figure 2. Plots from a CTH Analysis of a Shaped Charge Effects of hypervelocity impacts into layered targets can be analyzed with hydrocodes. Figure 3 illustrates the effect of a shaped charge impact into a 2-material layered target. (a) (b) (c) Figure 3. Shaped Charge Fired into Layered Materials 6

7 In this analysis the shaped charge was set off at a stand-off distance and fired into the target. Figure 3(a) illustrates a shaped charge being shot downward into the layered target. Figure 3(b) illustrates the jet at the point where it makes contact with the target. Figure 3(c) illustrates the perforation made by the shaped charge through the layered material. Material models are available for a large range of materials including metals, plastics, polymers, organic and inorganic materials, ceramics, and geological materials. Figure 4 illustrates an AUTODYNE simulation of a Tantalum (Ta) explosively formed penetrator (EFP). Figure 4. AUTODYN Analysis of an Explosively Formed Penetrator Part (a) of Figure 4 illustrates various stages of the simulation process along with the initial set-up. Part (b) illustrates an actual cross-section of the EFP, soft caught sample. This simulation was carried out using a Lagrangian grid for the liner, case and base, and a Eulerian grid to model the explosive. A Zerilli-Armstrong strength model was used for the Ta and a Composition B (RDX/60, TNT/40) was used for the explosive. Figure 5 illustrates results of a penetration problem accomplished using LS- DYNA. In this analysis a Ta rod was impacted at an angle against an ANSI C1020 steel plate. Both materials are governed by J2 plasticity laws with kinematic hardening. The 7

8 material failure is modeled by element eroding at a critical strain value (taken here as 0.8). The initial speed of the rod is 360 m/s. Figure 5 LS-DYNA Analysis of a Projectile Penetrating a Plate This figure illustrates three points in time during the penetration process. The following series of plots, Figure 6, illustrate penetration of a Tungsten cylindrical rod into five (5) layered steel plates at a velocity of 2km/s. The simulations were executed in MAGI for seven (7) different cylinder orientation angles with respect to the normal. The impact velocity vector is normal to the plates. 00 º 15 º 30 º 45 º 60 º 75 º 90 º Figure 6. MAGI Analysis of Tungsten Rods Penetrating Steel Plates at Different Orientations. The MAGI simulations were run with Johnson Cook and Mie-Gruneisen material constitutive models and without a fracture algorithm. RESUMES Resumes can be provided upon request. 8