http://www.dynalook.com daily 1 2009-03-06T17:29:14Z http://www.dynalook.com/european-conf-2005/Leblanc.pdf Modeling structures response to blast loads interests more and more people concerned about industrial accidents and/or terrorism. Today, two approaches are available: one can either use an ALE model (*ALE) with a lagrangian-eulerian coupling (*CONSTRAINED_LAGRANGE_IN_SOLID) or a pure lagrangian approach where an analytical loading of the structure replaces the computation of the propagation. The lagrangian approach allows the use of a much smaller model since only the structure is modeled. This kind of approach, based on the empirical model described in the TM5-855 US army handbook (CONWEP), is currently available in LS-DYNA (*LOAD_BLAST). However, it is limited to the treatment of the explosions of hemispherical charges on the ground or spherical charges in the air without ground interaction. In many cases, the interaction of the shockwave with the ground induces blast reinforcement. CRIL TECHNOLOGY, in order to get more precise blast load evaluation with a pure lagrangian approach, has developed a new user-loading model (evolution from *LOAD_BLAST) to take into account new abacuses for TNT and for reflecting coefficients, ground effects and Mach stem. Major evolutions are based on empirical models described in the TM5-1300 US army handbook. This new user-loading, in many cases leads to more precise and more conservative load while retaining a reasonable model size as the method is purely lagrangian. No publisher admin 2009-03-23T21:29:03Z File http://www.dynalook.com/european-conf-2005/Haufe.pdf No publisher admin 2009-03-23T21:30:38Z File http://www.dynalook.com/european-conf-2005/McCallum.pdf During the past several years, research within BAE SYSTEMS has concentrated on developing a capability for simulating Hydrodynamic Ram (HRAM). In this paper we demonstrate how the ALE technique in LS-DYNA can be used to simulate the principal stages of HRAM with liquid aeration. LS-DYNA is used to simulate the impact of a small steel sphere at 2km/s into a water-filled container manufactured from 3.2 mm thick aluminium alloy L165. The simulation results are compared with laboratory experiments from a two-stage gas-gun facility showing close agreement with peak pressure and impulse values. In additional simulations, aeration is modelled using an effective equation of state, which describes the compressibility of the water (on a macro-scale) inside the container. The simulation results show that aeration can be used to alleviate the shock wave that forms ahead of the projectile in order to reduce damage on the surrounding structure. No publisher admin 2009-03-23T21:30:02Z File http://www.dynalook.com/european-conf-2005/Mascheroni.pdf Birdstrike is a menace for flight safety likely to have tragic consequences. In view of that, the efforts provided to design high-efficiency bird-proof structures are fully justified. In this work the impact of a standard 4-lb bird onto a nacelle made of composite material required for the certification of the component has been investigated using LS-Dyna 970. Initially, the dynamic behaviour of the composite material used in the manufacturing of the external skin panels of the intake was achieved by referring to specific experimental tests. It was observed, in fact, that the dynamic behaviour of the composite material has a deep influence on the failure mechanism of the structure. Subsequently, the numerical model worked out for the composite material was used to numerically reproduce a bird impact certification test. A SPH model of the bird validated in previous research was used. A good numerical-experimental correlation between experimental data and numerical results was obtained. No publisher admin 2009-03-23T21:29:17Z File http://www.dynalook.com/european-conf-2005/Feng.pdf A failure criterion, for polymers and soft biological materials subjected to very large deformation, is presented in this paper. The criterion is written in terms of the strain invariants in finite elasticity. Experimental tests for determining the failure criterion of a material and some numerical results from LS-DYNA are shown. No publisher admin 2009-03-23T17:21:34Z File http://www.dynalook.com/european-conf-2005/copy_of_Haufe.pdf Reliable prediction of the behaviour of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behaviour properly are still not available in commercial finite element codes. First, we give an overview of material laws for thermoplastics and show how the behaviour can be characterized and approximated by using visco-elasticity and metal plasticity, respectively. Experimental work is presented to point out important phenomena like necking, strain rate dependency, unloading behaviour and damage. A constitutive model including the experimental findings is derived. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, need to be taken into account. With the present formulation, standard verification tests can be simulated successfully. Also, an elastic damage model is used to approximate the unloading behaviour of thermoplastics adequately. No publisher admin 2009-03-23T17:21:31Z File http://www.dynalook.com/european-conf-2005/Hilding.pdf This paper presents experience from using a recently developed material model for austenitic stainless steels with TRIP-effect for simulation of sheet metal forming. Results from two different forming operations are presented. In materials with TRIP-effect, a phase transformation from austenite to martensite occurs during forming that significantly affects the hardening behavior. The effect is sensitive to the amount of straining as well as the temperature. For materials that have a strong TRIP-effect new forming techniques are possible that can lead to very light and strong components. The material model for austenitic stainless steel sheet exhibiting the TRIP-effect has been implemented in LS-DYNA. No publisher admin 2009-03-23T17:22:39Z File http://www.dynalook.com/european-conf-2005/Tung.pdf Frontal collision tests indicate that the energy absorbing components playing the main role of providing protection for the occupants during the crashing processing. The frontal rails are the main components to absorb energy during collision. The position of the spot welding, beads, the cross section and thickness of the frontal rails are significantly facts that affect the energy absorption during impact. This paper is concentrated on improving the energy absorbing efficiency of the vehicle’s front rails during impact and giving better existing space of the passenger compartment after collision by using LS-DYNA. Utilize the improved model to enhance the exiting vehicles and compare the results to the frontal impact test. No publisher admin 2009-03-24T10:29:01Z File http://www.dynalook.com/european-conf-2005/copy_of_Xue.pdf In this paper, the authors present a crashworthiness assessment of a conventionally designed railway passenger vehicle and suggest modifications for its improvement. The analytical approach consisted of two stages. Firstly, the crashworthiness of the coach was assessed by simulating a collision between the coach and a rigid wall. Then, after analysing the structural weaknesses, the design of the coach was modified and simulated again in the same scenario. It was found that bending or jack-knifing is a main form of failure in conventionally designed rail vehicle structures and components. The coach design, as modified by the authors, overcomes the original weaknesses and shows the desired progressive collapse behaviour in simulation. The conclusions have general relevance and suggest the need for a rethink of some aspects of rail vehicle design. No publisher admin 2009-03-24T10:28:47Z File http://www.dynalook.com/european-conf-2005/Shabrov.pdf Crash-test simulations of the car models by LS-DYNA code are carried out on the HPC 16 CPU AMD64 Opteron processors Cluster. Simulations are based on the large 3D finite element car models that contain more then one million DOF. Architecture and benchmark of the HPC 16 CPU AMD64 Cluster were tested by engineering applications with commercial engineering codes LS- DYNA instead of synthetic benchmark. For this purposes several tasks were taken from www.topcrunch.org. The tasks named “3 Vehicle Collision” and “Neon”. Benchmark tests have shown pretty good results for such type of industrial problems and confirmed that Opteron processor on AMD platform is preferable to Itanium processor on Intel platform. LS-DYNA code was used for crash analysis of real modern cars produced by AVTOVAZ in Russia. HyperMesh software was used to create finite element mesh and for a pre- processor for LS-DYNA solver. To visualize simulations as 3D virtual reality objects crash analysis results obtained on HPC Cluster were imported on 3D Virtual reality system named WorkBench. WorkBench 3D virtual reality system contains soft screen, two multimedia projectors, computer with dual heads graphics adapter and tracking system Flock of Birds. COVISE software was used for visualization of CAD models of the cars and crash analysis results as 3D virtual reality objects. No publisher admin 2009-03-23T17:12:40Z File http://www.dynalook.com/european-conf-2005/Boetticher.pdf This paper presents LS-DYNA 970.5434a transient simulations for the fluid- structure interaction (FSI) in a prototype biomedical duct. Standard and element free Galerkin (EFG) elements are compared for the nearly incompressible membrane out of *MAT_SOFT_TISSUE, which is a composite reinforced hyperelastic material. The coupling of a multi-fluid arbitrary Lagrangian Eulerian (ALE) solid domain to an EFG solid domain is possible and its LS-DYNA implementation keeps developing. The paper describes particularities of this coupling. The EFG simulation for nearly incompressible materials necessitates a non-default support of 1.4x1.4x1.4 or even higher for accurate results. The EFG simulation demands higher computation times than the standard formulation with reduced integration and type 6 hourglass control. An example is shown, in which the high ratio of the elastic moduli chosen for the fibers and the bulk of the soft tissue material generates a severe hourglass problem that only the EFG method can cope with. The standard formulation, however, is remarkably robust and it proves difficult generating an extreme situation where only EFG works and the solver run would abort otherwise. So the potential of the EFG method lies in the accurate prediction without introducing non-physical energy in the system for hourglass stabilization, in situations, where selective reduced or full integration show a too stiff behavior and reduced integration has a hourglass problem. Although LS-DYNA 5434a is already much faster than 5434, a more computational efficient implementation of EFG for solid elements is required. Therefore, the features of the LS-DYNA 971 beta version, which address this lack of performance, are assessed as well. The paper features an abstracted input deck. No publisher admin 2009-03-24T10:29:26Z File http://www.dynalook.com/european-conf-2005/Mccallum.pdf This paper describes the results of simulations to assess the influence of bird shape during bird-strike. In the first part of this paper, simulations are presented which compare the results of a traditional bird shape model (hemispherical ended cylinder) impacting a square flat panel using the ALE and SPH techniques. In each case the bird is modelled with a mass of 8 lb and has physical dimensions (torso) representative of a Canadian goose. The simulation results show close agreement with one another for stagnation pressure and displacement of the panel. Biometric data obtained from the IBRG (International Bird-Strike Research Group) is then used to construct a more detailed bird model of a Canadian goose that includes multi-material parts. The model is simulated using SPH and compared to the results of the hemispherical ended cylinder. The simulation results obtained using this new bird model indicates that a target may become pre-stressed from the initial impact of the head and neck, prior to the impact of the torso. This may have an important consequence for damage initiation and failure of the target. No publisher admin 2009-03-23T17:06:05Z File http://www.dynalook.com/european-conf-2005/Tokura.pdf Understanding the wave-dissipating mechanism of seashore structures is important to design effective seashore protection system against high waves. From the engineering point of view, wave dissipation with seashore structures is considered as a kind of fluid-structure interaction (FSI) problem. Recently constructing a submerged structure "flexible mound" is increasing for some advantages. The flexible mound is made of rubbery material and is deformable. Authors tried to apply the ALE (Arbitrary Lagrangian Eulerian) capability in an explicit finite element program LS-DYNA to this problem and compared the behavior of conventional "rigid mound" (breakwater) and flexible mound. Through this preliminary study authors showed that the FSI analysis using LS-DYNA could widely be used to design shore structures. No publisher admin 2009-03-23T17:06:40Z File http://www.dynalook.com/european-conf-2005/Deguemp.pdf Whether end-users need to access local or remote systems, to use a batch system or to run jobs interactively, they will always raise the same questions: “Which system can I run my job on?” and “How do I get data to the machine where my job will execute?” Users should only need to know what applications they want to run and where the inputs for these applications are located. To answer these needs, Fujitsu markets a middleware product called SynfiniWay which hides all issues related to CPU location, and allows execution of complex applications via workflows. The conclusion of this paper is that the SynfiniWay middleware can solve LS- DYNA iterative problems: the search for an optimal mesh size or successive LS- DYNA calculations with modified initial conditions. SynfiniWay provides an infrastructure to execute these studies automatically and transparently on remote computers (grid computing). No publisher admin 2009-03-24T10:33:10Z File http://www.dynalook.com/european-conf-2005/Clifford.pdf No publisher admin 2009-03-23T17:08:49Z File