http://www.dynalook.com daily 1 2009-03-06T17:29:14Z http://www.dynalook.com/european-conf-2003/structural-design-review-of-lcd-tv-module-by.pdf Display performance of LCD is going to be continuously high definition, high brightness, wide viewing angle. On the other hand, outline dimensions are demanded to be slimer and lighter. As the result of above demand, the space of each part becomes gradually narrow and tight. Therefore, the importance of design to prevent weakness for impact is embossed greatly. LCD products have to be subjected to various impact test for consumer's using environments. During the design, toolcorrection or modification caused by damage or large deformation of weak part give rise to time consumption and cost-up. For development of LCD-TV module, these problems become more important because of its large size and heavy weight. To improve these problems, we performed impact analysis of 40 inch LCD-TV module using LS-DYNA and applied the results to the development. In this analysis, we found out the weak regions and obtained improved reliability after design modification. Impact analysis using LS-DYNA is going to be applied in the all of LCD product developments hereafter, and development period reduction and reliability improvement are highly expected. No publisher mike 2010-04-06T12:21:41Z File http://www.dynalook.com/european-conf-2003/numerical-modelling-of-impacts-on-ski-safety-nets.pdf Safety nets are used to protect skiers during downhill competitions. However, although these nets are now able to retain skiers in almost all cases, the deceleration during such impacts can cause severe harm to skiers including hyperflexion injury or vertebra compaction. Experience showed that the behaviour of the nets is highly dependant on: • the material of which they are made of • the boundary conditions (installation and fastening). The aim of this study was : • to analyse the net constitutive material under dynamic loadings to determine its characteristics. • to analyse well defined impacts to be able to simulate them numerically • to improve the net behaviour during real impacts • to provide some recommendations concerning the geometry of the complete system. This study continues Fayçal Ben Yahia's work which was presented in Paris in June 2001. The whole study was performed under the funding of the French company Dalloz Montagnes and with the technical collaboration of the International Skiing Federation (FIS). As a first step, we used the tests on the net thread to model it in static and dynamic conditions. Then we compared the results from impact tests on small safety systems and simulations with LS-DYNA which led to the validation of the whole model. Finally, simulations of impacts on real size nets were used to study the influence of the boundary configuration on the net behaviour. The model developed during this study makes it possible to optimise the geometry of the whole system in order to increase skier protection. No publisher mike 2010-04-06T12:21:40Z File http://www.dynalook.com/european-conf-2003/optimization-of-a-cockpit-structure-according-to.pdf For a prototype of the new LANDROVER cockpit, developed by Siemens VDO Automotive, the design of the co-driver airbag area had to be optimized with the help of simulation in order to fulfill the guidelines of ECE-R 21. Furthermore a more limited inhouse-target had to be reached. The actual state of the prototype was illustrated by simulation and the influence of different measures on the crash behavior was examined. Among other things the following modifications were accomplished: • Changing the stiffness of the instrument panel by specific design of the rib structure • Reducing the stiffness of the airbag box and its connections • Partial absorption of the impact energy using foam depositors between instrument panel and airbag unit The influence of different strategic ways to optimize the crash behavior, in respect of head impact will be shown on a simplified cockpit model. Finally, a comparison of the simulation and the testing of the new RANGE ROVER cockpit will be given. No publisher mike optimization 2010-04-06T12:21:41Z File http://www.dynalook.com/european-conf-2003/numerical-simulation-of-a-flight-recorder2019s.pdf Development of a durable flight recorder’s protective case is a very difficult engineering problem. To save information, the case must be strong enough to withstand intensive accidental thermal and mechanical loading in aircraft crash. So the case must meets strong requirements. One of the toughest of these demands is that any flight recorder’s case must be strong enough to withstand a penetration resistance test - an impact of pin at any angle at a speed of 7.7 m/s. This paper presents the results of a series of 3D numerical simulations of penetration resistance test of a flight recorder’s protective case. The simulations performed with LS-DYNA. The computer simulations showed the most severe direction of pin impact to the case. No publisher mike 2010-04-06T12:21:42Z File http://www.dynalook.com/european-conf-2003/examples-manual-for-user-loading-option.pdf The aim of this study is to understand how the *USER_LOADING option works and to give some examples of its use. This option uses the subroutine loadud, its usage will be described step by step and it is illustrated with four examples : • Plate loaded with time dependant pressure, • Plate loaded with displacement dependant pressure, • Randers-Pehrson & Bannister Tests, • Plate loaded by an explosion of 5kg of TNT. Some of those examples use loadings that can be also applied through LS-DYNA existing options, thus the results obtained with the user loading option could be compared and validated. No publisher mike 2010-04-06T12:21:41Z File http://www.dynalook.com/european-conf-2003/improved-numerical-investigations-of-a-projectile.pdf Past perceptions to the processes of the penetration mechanisms of projectiles acting on textile structures [1] are often based on continuum models [2] or simplified models [3] and admit only limited conclusions concerning the real behavior of protective clothing made from several layers of fabric. Only a few investigations are known up to now with models based on single yarns as a major component for discretization [4]. Thus, for the prediction of the protective effect of several layers of high-strength fibers in a textile, a structural approach is chosen by a separate modelling of each fiber by a shell or continuum based element. The single modelled fibers interact over a contact formulation with the adjacent fibers in the same way the fibers in the different layers do. This allows to model the in-plane motion and deformation of each fiber separately, as well as the failure of fibers thereby avoiding artificial localization effects to a great extent. With the so-called explicit finite element code LS-DYNA [8] different possibilities of the discretization of the fiber bundles are investigated. Also the description of the fiber material by available material models is varied modifying the load deformation relation and the damage evolution. The goals of the current project [10] are first to achieve a geometrically consistent model of the layered structure and second to better understand the phenomenological process of the impact of ballistic projectiles on such textiles. Finally, the particular effect of different layer setups can be studied. INTRODUCTION Up-to-date bullet proof vests are consisting of several layers of fabrics made of high performance fibers like Kevlar® (Du Pont), Twaron® (Tijin) and Zylon® (Toyobo). These vests have a specific weight up to 2000 g/m². Many so called “trial-and-error” tests have to be performed to improve the weight of this vests. So far, only few attempts are known to predict the behavior of new constructions, like new fiber materials or different fiber materials for different layers, by way of exploring the mechanical phenomena. Numerical simulations by a finite element program could be a useful tool to detect this phenomena and they would allow the developers to optimize their products. To perform a numerical simulation, some research into fiber and fabric geometry and their possibilities to approximate them through finite elements is necessary. Also, the material behavior of the fibers exposed by high velocity loading must be measured to choose a suitable material model. The objective of this paper is the description of the fabric geometry, the discretization by shell and solid elements and first investigations of the model behavior in the analysis. Weave geometry and fiber properties Fabric and fiber geometry Following the approach to discretize the weave through a collection of single yarns, the shape of the cross section and the curve through the center of gravity of the cross sections must be acquired. To get this information of an unloaded weave, two specimen of a Kevlar® weave were embedded in epoxy resin. One of them was roG – I - 08 No publisher mike 2010-04-06T12:21:42Z File http://www.dynalook.com/european-conf-2003/simulation-of-full-scale-seismic-resistant.pdf This paper focuses on the finite element simulation of two full-scale tests of high performance, seismic-resistant structural frames using the LS-DYNA 960 implicit solver. The frame was physically tested as part of the design validation for the new Stanley Hall building on the University of California Berkeley Campus. The pseudo static non-linear analyses, showed excellent correlation with the measured test data. Two sequential tests were performed on the same frame but with different brace configurations, hence residual stresses and strains, and the process of brace replacement were important. This work illustrates the convenience of implicit LS-DYNA for structural applications – transferring this technology to the built environment. It also provides confidence in and verification of the software. The construction industry tends to shun non-linear analyses, deeming them too complicated; however it is ideal and indeed, essential for seismic applications. This simulation provides an alternative approach to full-scale testing for the future evaluation of this type of structure. It also provides the opportunity for the development of new and improved structural details as well as the retrofit assessment for existing structures. No publisher mike 2009-03-25T22:11:25Z File http://www.dynalook.com/european-conf-2003/stabilized-dsg-elements-2013-a-new-paradigm-in.pdf The Discrete Shear Gap Method, initially proposed for the elimination of transverse shear locking in plate and shell finite elements is extended to a more general concept, applicable to other locking problems, typically causing severe trouble in structural analysis, especially in the case of thin-walled structures. The outstanding feature of the proposed formulation is the fact that one unique method is used to avoid various different kinds of locking phenomena. It is applicable to beam plate and shell elements, but also to two-dimensional and three-dimensional solid elements. The fact that approximation quality is often subject to strong sensitivity to mesh distortion can be alleviated with the help of stabilization methods. No publisher mike 2009-03-25T22:11:19Z File http://www.dynalook.com/european-conf-2003/under-the-hood-of-implicit-ls-dyna.pdf No publisher mike 2009-03-25T22:12:22Z File http://www.dynalook.com/european-conf-2003/heat-transfer-in-ls-dyna.pdf LS-Dyna can solve steady state and transient heat transfer problems on 2dimensional parts, cylindrical symmetric parts (axisymmetric), and 3-dimensional parts. Heat transfer can be coupled with other features in LS-DYNA to provide modeling capabilities for thermal-stress and thermal-fluid coupling. This paper presents several examples using LS-DYNA for modeling manufacturing processes (e.g., upseting, extrusion, welding, casting). No publisher mike 2009-03-25T22:12:24Z File http://www.dynalook.com/european-conf-2003/ls-dyna-beam-elements-default-and-user-defined.pdf LS-DYNA provides several beam element formulations, see the keyword description for *Section_Beam in the User’s Manual. Several of these beam element formulations support user supplied integration of the cross section, via the *Integration_Beam keyword. While most LS-DYNA users are familiar with the similar through-the-thickness integration algorithm for shell elements, which is made trivial by the rectangular cross section geometry assumed for shell elements, the numerical integration of even simple beam element cross sections requires more effort, and as will be demonstrated, more planning. In this article, a detailed explanation of the beam element cross section integration algorithm is presented. Simple suggestions for calculating, and checking, user provided integration rules are illustrated through several examples. The examples also provide suggestions for improving the LS-DYNA Standard Cross Section Types, available via the ICST parameter of the *Integration_Beam keyword. No publisher mike 2009-03-25T22:11:22Z File http://www.dynalook.com/european-conf-2003/fluid-structure-interaction-in-ls-dyna-industrial.pdf Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation. It is a method where the material flows through a mesh that is completely fixed in space and where each element is allowed to contain a mixture of different materials. The method completely avoids element distortions and it can, through a Eulerian-Lagrangian coupling algorithm, be combined with a Lagrangian description of motion for parts of the model, see [3] and [4] The Eulerian formulation is not free from numerical problems. There are dissipation and dispersion problems associated with the flux of mass between elements. In addition, many elements might be needed for the Eulerian mesh to enclose the whole space where the material will be located during the simulated event. This is where the multi-material Arbitrary Lagrangian-Eulerian (ALE) formulation has its advantages. By translating, rotating and deforming the multi-material mesh in a controlled way, the mass flux between elements can be minimized and the mesh size can be kept smaller than in an Eulerian model. No publisher mike 2009-03-25T22:13:36Z File http://www.dynalook.com/european-conf-2003/jet-engine-fan-blade-containment-using-two.pdf In the rare event of a fan blade separation, the fan blade must not penetrate the case of a commercial jet engine. Due to this requirement the fan case is the heaviest single component of a jet engine. With a goal of reducing that weight, a simulation of a fan blade containment system was tested at the NASA GRC Ballistic Impact Lab and analyzed using LS-DYNA. A fan blade simulating projectile was shot at two alternate geometric containment case configurations. The first configuration was a flat plate which represents a standard case configuration. The second configuration had a surface curved outward from the projectile. The curved surfaced forces the blade to deform plastically, dissipating energy before the full impact of the blade is received by the plate. The curved case was thus able to tolerate a higher velocity of impact before failure. The LS-DYNA analytical model was correlated to the tests and a weight savings assessment was performed. No publisher mike 2009-03-25T22:18:06Z File http://www.dynalook.com/european-conf-2003/the-use-of-ls-dyna-fluid-structure-interaction-to.pdf No publisher mike 2009-03-25T22:16:00Z File http://www.dynalook.com/european-conf-2003/crashworthiness-optimization-in-ls-opt-case.pdf This crashworthiness optimization study compares the use of three metamodeling techniques while using a sequential random search method as a control procedure. The three methods applied are (i) the original Successive Linear Response Surface Method, (ii) the Neural Network method and (iii) the Kriging method. It is shown that, although NN and Kriging seem to require a larger number of initial points, the three metamodeling methods have comparable efficiency. The random search method is surprisingly efficient in some instances, but by nature much less predictable. No publisher mike optimization ls-opt meta model 2009-03-25T21:56:33Z File