http://www.dynalook.com daily 1 2012-03-08T14:07:29Z http://www.dynalook.com/international-conf-2002/Session_11-2.pdf The objective of this paper is to generate research information to enhance energy absorption characteristics in transportation infrastructures involved in vehicle crash accidents. A finite-element computer model, using the available LS-DYNA software, was developed to simulate crashes of a vehicle and a traffic light steel pole in frontal impact. The finite-element vehicle model was based on a 1991, 4-door, Ford Taurus. The steel pole was modeled using shell elements to capture the three-dimensional effect of the structure. Four configurations of steel pole supports were examined. The first support type was the typical steel base currently used over concrete foundation, with anchor bolts as specified by the Canadian Highway Bridge Design Code of 2000. The second support type was similar to the first one but with stressed springs between the nuts, over and under the steel base plate. In the third case, rubber-bearing pads were utilized between the base plate and the concrete foundation. In the fourth case, the steel pole was embedded into the soil with a certain embedding length (no concrete foundation is used). The structural response focused on energy absorption as well as the deformation of the steel pole. The fourth system of steel pole supports was proved to be strong enough to offer protection during minor impacts and under service loading, and to remain flexible enough to avoid influencing vehicle occupants, thus reducing fatalities and injuries resulting from the crash. No publisher admin 2009-03-26T12:37:46Z File http://www.dynalook.com/international-conf-2002/Session_11-1.pdf The G4(1S) strong post guardrail system is the most common guardrail system in the USA. Full- scale crash testing indicated that the vehicle rolled onto its impact side after exiting the guardrail system. This collision behavior of the roadside structure increases the occupant risk and is considered unsatisfactory for safety. Improvement of the G4(1S) guardrail system becomes an important issue concerned by the FHWA. The subject of this investigation is to understand the system behavior through parametric study and present a feasible approach for structural improvement. This paper provides a roadmap for simulation of highway safety structures. Some of the noteworthy observations are presented and discussed. The approach of reducing the embedment depth of post is investigated through both FE component simulation and full system crash simulation. This approach is recommended and is anticipated to be favorable for minimizing the risk of rollover of vehicles impacting the G4(1S) guardrail system. No publisher admin 2009-03-26T12:37:48Z File http://www.dynalook.com/international-conf-2002/Session_5-5.pdf Wear is a critical phenomenon affecting service life of products. Therefore, wear prediction is an important concern of study. In this study, sliding contact was modeled using LS-DYNA. FEMB was used to create the geometry of the model and the input file was manually modified as necessary. Studies were done to test, calibrate, and validate the model in LS-DYNA before simulation of the sliding wear by an asperity sliding over a plastically deforming and work hardening material surface. A flat half-space with dimensions of 30μm depth and 100μm width is subjected to sliding contact by a semicircular asperity of radius 10μm. The third dimension of the model was assumed to be infinite and therefore a plane strain condition was studied. Elastic indentations were performed to validate the finite element model. Elastic indentation results were compared to the predictions of the Hertz theory of elastic contact. With the help of mesh convergence study the best conditions to simulate sliding wear were determined. Mesh dimensions, hourglass control, contact algorithm, application of the normal load, and mass scaling were the main issues of the study. According to the Hertz theory, the maximum contact pressure and the maximum shear stress were calculated as 2684 and 805 MPa for the conditions studied. Numerical models predicted 10-15% higher values higher values for those stresses. However, normalized stress values show a very good agreement with the theoretical predictions. No publisher admin 2009-03-26T12:37:52Z File http://www.dynalook.com/international-conf-2002/Session_5-4.pdf Errant vehicles may pose a serious threat to neighboring traffic of pedestrians, bicyclists, and even to their drivers in a densely populated urban environment. Accident reconstructions have indicated that street curbs do not offer any meaningful protection against errant vehicles, which can easily traverse street curbs even at small velocity and shallow angles. The paper presents research results of a study, in which computational mechanics was utilized to predict vehicle trajectories upon traversing standard Florida DOT street curbs. Computational analysis was performed using LS- DYNA computer code and two public domain, finite element models of motor vehicles: Ford Festiva and Ford Taurus. The suspension systems of the original vehicle models were evaluated and additional suspension components were identified and developed. The finite element models of the required suspension systems were developed using geometry from the actual suspension parts, captured using a digitizing arm. Due to complex geometry of these parts, the MSC-PATRAN preprocessor was used to create data for LS-DYNA code. Shock absorbers were modeled using discrete spring and damper elements. Connections for the modified suspension systems were carefully designed to assure proper range of motion for the suspension models. Inertia properties of the actual vehicles were collected using tilt-table tests and were used for LS-DYNA vehicle models. A standard FDOT street curb model was developed using rigid wall option in LS-DYNA. Initial, computational mechanics analyses suggest that vehicles tend to retain larger amount of their kinetic energy after traversing street curbs. It is therefore dangerous to anticipate that performance of street curbs would be comparable with that demonstrated by guardrails. In order to validate the assumed discrete numerical models and the results of LS-DYNA analyses, full-scale experimental tests have been performed at Texas Transportation Institute. Two types of vehicles have been tested: Ford Festiva and Ford Taurus, both for two values of approach angle: 15 and 90 degrees, with impact velocity of 45 mph. Experimental results including accelerations, displacements and overall vehicles behavior were registered by high-speed video cameras and have been compared with numerical results and computer animations. Verification results indicated a good correlation between computational analysis and full-scale test data. The study also indicated a strong importance of properly modeled suspension and tires on resulting vehicle trajectories. The major goal of the research was to study the behavior of various vehicles (from small Ford Festiva to pickup truck Chevrolet C2500), for different approach angles, velocities and curb profiles. Experiences gained in preliminary numerical analyses and experimental tests allow studying a matrix of critical cases without time- consuming and costly additional experimental testing. No publisher admin 2009-03-26T12:37:56Z File http://www.dynalook.com/international-conf-2002/Session_5-3.pdf The steel bar breaking system is a component of sled test system for the automobile crashworthiness. The purpose of this study is to optimize the steel bar breaking system in order to extract the crash pulse close to the barrier test result. The design variables are the height, the thickness and the number of each array of the steel bar plates. The optimum design is obtained using DOE (design of experiments) and RSM (response surface method) in the LS-OPT. LS-INGRID is adapted to automate the optimization process because the dimensions of the steel bar plates could be changed in the design process. The optimum design values of the steel bar breaking system are determined to minimize the difference between the crash pulses of the test result and the simulation result. No publisher admin 2009-03-26T12:37:59Z File http://www.dynalook.com/international-conf-2002/Session_5-2.pdf Approximately every three years a 65,000 lb propane tractor-trailer crashes resulting in explosion that usually kills several people. The study presented in this paper first simulates the effects observed at one of these accident sites. This was simulated in LS-DYNA by building a full length model of the tanker trailer and also including the liquid in the tanker. The presence of the liquid in the model provide the initial effects of liquid on the tanker. The resulting model correlated very closely with the actual observation seen at the crash site. Then a variety of options where explored to determine how to improve the crash worthiness of the tanker for several crash scenario's. The result of this work illustrated that for less than $20,000 the velocity that would cause failure could be raised from 20 mph to over 55 mph through the use of energy absorbing materials. No publisher admin 2009-03-26T12:38:02Z File http://www.dynalook.com/international-conf-2002/Session_5-1.pdf A simulation of USGA’s test procedure for Rule 4-1e was optimized using 3 shape and 10 size design variables. The optimized solution increased the coefficient of restitution from 0.845 to 0.917 while maintaining stresses below 150 ksi and club head mass at 200 g. No publisher admin 2009-03-26T12:38:04Z File http://www.dynalook.com/international-conf-2002/Session_17-5.pdf The aim of this paper is to determine if Space Mapping technique using Surrogate Models in combination with the Response Surfaces Methodology (RSM) is useful in optimization of crashworthiness applications. In addition, the efficiency of optimization using Space Mapping will be compared to conventional structural optimization using the Response Surface Methodology (RSM). To determine the response surfaces, several evaluations must be performed and each simulation can be computationally demanding. Space Mapping technique uses surrogate models, i.e. less costly models, to determine these surfaces and their associated gradients with respect to the object and constraint functions. The original full model is used to correct the gradients from the surrogate model for the next iteration. Thus, the Space Mapping technique makes it possible to reduce the total computing time, needed to find the optimal solution. Two application problems are used to illustrate the algorithm. All examples are constrained optimization problems with one or two design variables. In all applications, the algorithm converged to the optimum solution. For the crashworthiness design problems the total computing time for convergence was reduced with 53% using Space Mapping compared to the conventional RSM. The conclusions are that optimization using Space Mapping and Surrogate Models can be used for optimization in crashworthiness design with maintained accuracy but with a significant reduction in computing time compared to traditional RSM. No publisher admin 2009-03-26T12:38:09Z File http://www.dynalook.com/international-conf-2002/Session_17-4.pdf Portable electronic devices have become smaller and lighter but they are also easily damaged during accidentally drop situation. Therefore, new electronic products are usually needed to pass requirements of shock and drop test before actually delivering to customers. FEM simulation provides engineers a useful and powerful approach to identify the potential weakness of products before the prototype is even made. The report will introduce the applications of the Ls-dyna in a virtual lab which simulates the experiment conditions of shock and drop tests in computers. It also shows Ls-dyna can be a very effective tool for engineers to improve the performance of their design in the shock and drop test. No publisher admin 2009-03-26T12:38:12Z File http://www.dynalook.com/international-conf-2002/Session_17-3.pdf The equations of motion for a two-lever pendulum are developed using Lagrange's equation. An assumed kinematic golf swing is used to generate generalized forces to drive the golf robot. These moments are used to generate a golf robot swing using LS-DYNA. The LS-DYNA model is flexible enough so that the model can be used as a virtual laboratory. No publisher admin 2009-03-26T12:38:16Z File http://www.dynalook.com/international-conf-2002/Session_17-2.pdf Component analysis of any complex system is frequently required to determine the true accuracy of a finite element model. Although a composite system may yield the “correct” final results, the system is not truly accurate unless individual components are performing correctly. The purpose of this paper is to describe the component testing and finite element modeling of a standard 5/16”-18 x 2” galvanized shoulder hook bolt used in cable barrier systems. These bolts hold the cable to the post of a cable barrier system. During a vehicle impact with the system, the cable loads many of the restraining hook bolts in different directions. Several of the hook bolts will reach their bending yield limits and “open up,” allowing the cable to disengage. This is designed behavior which allows the cable to capture the impacting vehicle. Successful modeling of these bolts is essential to have an accurate finite element model of a complete cable barrier system. No publisher admin 2009-03-26T12:38:23Z File http://www.dynalook.com/international-conf-2002/Session_17-1.pdf Irvin Aerospace Inc., has used the LS-DYNA Explicit Finite Element Analysis (FEA) tool for over five years for the analysis of static and dynamic fabric problems. The References provide many examples of this previous work. Our first application was the analysis of airbag landings for several spacecraft programs, including Reusable Launch Vehicles (RLV’s), various Unmanned Air Vehicles (UAV’s), Military Airdrop Systems, and planetary exploration systems. These are all covered in the references. This paper presents some current results along the lines of the above, and other recent developments. These include an air beam supported structure, which was evaluated for both snow and wind loads, and a fabric blanket system that was somewhat optimized by a combination of FEA analysis and testing. While these applications appear rather bland, the air beam structure is designed to house military fighter and rotary aircraft and must withstand significant snow and wind loads. The blanket system is used to constrain a target-missile that performs a unique ‘Air Launch’ mission, involving extracting the target from a cargo aircraft and allowing it to stabilize prior to release and ignition. No publisher admin 2009-03-26T12:38:26Z File http://www.dynalook.com/international-conf-2002/Session_10-4.pdf A new Eulerian-Lagrangian coupling algorithm and improved multi-material ALE-capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events, forging operations and penetration problems. This paper contains four example problems that illustrate the current features of the code. No publisher admin 2009-03-26T12:38:28Z File http://www.dynalook.com/international-conf-2002/Session_10-3.pdf Irvin Aerospace Inc. has used the LS-DYNA Explicit Finite Element Analysis (FEA) tool for over five years for that analysis of static and dynamic fabric problems. The references provide many examples of this previous work. Our first application was the analysis of airbag landings for several spacecraft programs, including Reusable Launch Vehicles (RLV’s), various Unmanned Air Vehicles (UAV’s), Military Airdrop Systems, and planetary exploration systems. These programs are thoroughly covered in the references, including comparisons between simulation and test. Our database of test to simulation comparisons and understanding model details where simulation does or does not apply continues to grow. Additional static and dynamic simulations include various pressurized fabric beams and fabric impact analysis; these are also covered in the references, including another paper presented at this conference. In the past year, Irvin has begun to explore the FSI capability within LS-DYNA through the explicit Navier-Stokes solver, the ALE solutions technique, and the various coupling options. This capability begins to provide Irvin with a capability, which in our industry is currently only available in Government Labs. The interaction of fluid systems and fabric is both the most basic of recovery system (parachute) problems, and perhaps the most difficult fluid structure interaction problem to solve. By beginning with simple problems, and continuously increasing the complexity, we have created early examples of where this simulation technology may lead. Along the way, we will include model size, solution time, and project to problems that will be solvable in the next two years. Additionally, we will report on required algorithmic enhancements and our suggestions on how to approach these. We will also present examples where we begin to apply the recently added Incompressible Navier-Stokes solver in LS-DYNA 960. Unfortunately, we will not report on comparisons to test data as, at the time of this writing, these are not available. No publisher admin 2009-03-26T12:38:31Z File http://www.dynalook.com/international-conf-2002/Session_10-2.pdf This paper discusses two new fluid solvers that will be included with releases of LS-DYNA after LS960. The first one is a new compressible solver based upon the Space-Time Conservation Element and Solution Element Method (or the CE/SE method for short), and the second one is an incompressible fluid FEM solver. No publisher admin 2009-03-26T12:38:35Z File