Indiana University-Purdue University Indianapolis (IUPUI) / The use of carbon-fiber reinforced composite materials is not novel in the field of motorsports industry. Their use in collapsible structures for crashworthiness is however not fully understood and predicted. Due to the complex failure mechanisms occurring within the material, the energy absorbing capacity cannot be easily pre dicted. The need to understand their contributions in crashworthy structures is thus of great importance. Furthermore, failure of carbon-fiber composites is highly depen dent on the geometry of structure. Problems arise in both experimental and numerical modelling of these structures. Although many explicit FEA codes exist, they often include experimental parameters that need to be calibrated through either coupon tests or actual crash tests. As composite structures become more commonly used in automotive industry, it is necessary to set some guidelines to successfully model and simulate composite crashworthy structures. The numerical modelling was done in LS-DYNA Enhanced composite damage MAT54. The material properties were configured using experimental coupon tests. The tests were conducted on square composite tubes. The Specific Energy Absorption (SEA) of the tubes were calculated through several coupons. As SEA is a function of geometry, it was necessary to conduct tests with similar geometry as seen in nosecone. MAT54 was chosen to simulate both crush and crash simulations due to its capability to simulate element level crushing. Furthermore, various modifications within the material model, improve its accuracy to determine composite failure. The research utilizes the characterization of material inputs in MAT54 by con ducting quasi-static compression tests on simpler but similar geometry. By utilizing inputs, a zonal optimization was conducted on the nosecone geometry. The number of layers, layer orientations and ply thicknesses were varied to vary the energy absorbed per zone. The deceleration of the vehicle can thus be controlled, and the weight of the structure could be reduced.

Computer simulations are widely used in the truck industry in order to provide assistance in the product development. Bolt joints are common in trucks. A bolt fracture usually has a great influence on how a truck structure will behave in a crash. Therefore, when simulating truck crashes it is important to be able to predict when bolt fracture occurs. A material model for 10.9 bolts has been calibrated and validated by using the finite element software LS-DYNA. The material model consists of a failure strain surface, which depends on the triaxiality, Lode parameter and the element size. In this thesis, the calibrated material model is referred to as the bolt model. A good agreement to predict the force at fracture in bolts between simulation model results and physical test results has been obtained. Still, further validation is needed to evaluate the bolt model completely.

Formula One race cars have to pass rigorous safety tests before they are allowed on track. This type of testing has been in place for years but the requirements for testing are continually increasing in order to reduce the amount of risk to the drivers’ safety during a race. The number of structures that need to be made and tested can quickly make this process an expensive one. Additionally, it is necessary to pass the mandated tests within a reasonable amount of time so as not to have an impact on the development on the rest of the car. There is a desire to reduce the number of structures needed for testing through finite element analysis (FEA), and as such, to reduce the time needed to pass the safety tests. FEA of laminated composites can be complex and is a balance between accuracy and the time it takes to find a solution. The current project looks into increasing understanding of the requirements for material characterisation, experimental impact testing, and explicit simulation of a carbon fibre fabric pre-impregnated with epoxy resin. Mercedes-Benz Grand Prix (MGP) Formula One Team has provided a pre-preg material for evaluation. Material experiments were performed per the American Society for Materials and Testing (ASTM) in order to find the tensile modulus, tensile strength, Poisson’s ratio, compressive strength, shear modulus, and shear strength of the material. Nine tubes were manufactured at MGP and tested in the drop tower at the Cranfield Impact Centre (CIC) ... [cont.].

The design of new forming tools get more problemtic as the geometries get more complicated and the materials less formable. The idea with this project is to evaluate if an implementation of a simulation software in the designing process, to simulate the forming process before actually building the tools, could help Duroc Tooling avoid expensive mistakes. To evaluate this, the commercial FEM simulation software LS-DYNA was used in a complicated project, where the design of the forming tools for forming a girder was considered. The main objective was to avoid cracking and severe wrinkling which may result in the forming process. With help of simulations a stable forming process which did not yield cracks or severe wrinkling, was eventually found. The girder was almost impossible to form without cracking, but the breakthrough came when we tried to simulate a preforming step which solved the problem. Without a simulation software this would never have been tested since it would be to risky and expensive to try an idea which could turn out to be of no use. The simulations also showed that the springback - shape deformation occuring after pressing - was large and hard to predict without simulations. Therefore, the tools were also finally springback compensated. We concluded that simulations are very effective to quickly test new ideas which may be necessary when designing the tools for forming complicated parts. Simulation also provided detailed quantitative information about the expected cracks, wrinkles, and weaknesses of the resulting pieces. Even though there is cost associated with simulations, it is obvious from this project that a simulation software is a must if Duroc Tooling wants to be a leading company in sheet metal forming tools, and stand ready for the higher demands on the products in the future.

This thesis presents a computational study to examine lateral impact behavior of pressurized pipelines and to determine influence of internal pressure on the impact behaviors of pipelines. More than 300 numerical simulations were carried out on mild steel pipe models with different internal pressure levels and were struck at the mid-span and at the one quarter span positions. The computational results for the first time systematically revealed the effects of internal pressure, impact position, and outside diameter on the lateral impact behavior of the pipeline models. It inspects effects of important parameters such as the outside diameter and internal pressure. Quartic polynomial functions are applied to formulate the maximum crushing force (F), permanent displacement (W), and absorbed energy (E) of the pressurized pipelines during the impact problem. Response surfaces are plotted based on the generated quartic polynomial functions and the quality (accuracy) of those functions are verified through several techniques.

Die Blechumformungsimulation hat sich in den letzten 25 Jahren stark weiterentwickelt. Die Simulation des gesamten Tiefziehprozesses einschließlich Beschneiden, Bördeln und Rückfedern ist bei den meisten Automobilherstellern und Werkzeugbaubetrieben ein Standardverfahren. Die Verwendung von LS-DYNA, einem der genauesten Löser für die Blechumformung, erfordert noch einiges an Expertenwissen, was die Verwendung für Methodenplaner in ihrer täglichen Arbeit erschwert. Aus diesem Grund hat Ansys eine spezielle Software für die Simulation der Blechumformung entwickelt: „Ansys Forming“. Ansys Forming ist eine benutzerfreundliche GUI zum Aufbau und zur Auswertung einer Blechumformungssimulation ohne Expertenkenntnisse von LS-DYNA.

Sheet metal forming simulation has greatly evolved over the last 25 years. Simulation of the entire deep drawing process including trimming, flanging and springback is a standard procedure at most automotive OEMs and tool shops. Using LS-DYNA, one of the most accurate solvers for sheet metal forming, still needs some expert knowledge, which makes it difficult to use for method engineers in their day-to-day work. Therefore, Ansys has been developing a dedicated application for sheet metal forming simulation, “Ansys Forming”.

<div>The use of carbon-fiber reinforced composite materials is not novel in the field of motorsports industry. Their use in collapsible structures for crashworthiness is however not fully understood and predicted. Due to the complex failure mechanisms occurring within the material, the energy absorbing capacity cannot be easily predicted. The need to understand their contributions in crashworthy structures is thus of great importance. Furthermore, failure of carbon-fiber composites is highly dependent on the geometry of structure. Problems arise in both experimental and numerical modelling of these structures. Although many explicit FEA codes exist, they often include experimental parameters that need to be calibrated through either coupon tests or actual crash tests. As composite structures become more commonly used in automotive industry, it is necessary to set some guidelines to successfully model and simulate composite crashworthy structures. </div><div><br></div><div>The numerical modelling was done in LS-DYNA Enhanced composite damage MAT54. The material properties were configured using experimental coupon tests. The tests were conducted on square composite tubes. The Specific Energy Absorption (SEA) of the tubes were calculated through several coupons. As SEA is a function of geometry, it was necessary to conduct tests with similar geometry as seen in nosecone. MAT54 was chosen to simulate both crush and crash simulations due to its capability to simulate element level crushing. Furthermore, various modifications within the material model, improve its accuracy to determine composite failure. </div><div><br></div><div>The research utilizes the characterization of material inputs in MAT54 by conducting quasi-static compression tests on simpler but similar geometry. By utilizing inputs, a zonal optimization was conducted on the nosecone geometry. The number of layers, layer orientations and ply thicknesses were varied to vary the energy absorbed per zone. The deceleration of the vehicle can thus be controlled, and the weight of the structure could be reduced.</div>

Roadside safety hardware has traditionally been approved on the basis of full-scale crash tests. In recent years, nonlinear dynamic Finite Element (FE) programs like LS-DYNA, PAM-Crash or ABAQUS Explicit have been widely used in evaluating new or improved design of roadside hardware. Although a powerful tool, numerical models must be properly verified and validated in order to provide reliable results. Typically, the verification and validation (V&V) process involves a visual comparison of two curves and is based on a purely subjective judgment. This research investigated the use of comparison metrics, which are mathematical measures that quantify the level of agreement between two curves, for comparing simulation and experimental outcomes in an objective manner. A computer program was developed in Matlab® to automatically evaluate most of the comparison metrics available in literature. The software can be used to preprocess and compare either single or multiple channels, guiding the user through friendly graphical interfaces. Acceptance criteria suitable to represent the typical scatter of experimental tests in roadside safety were determined by comparing ten essentially identical full-scale vehicle crash tests. The robustness and reliability of the implemented method were tested by comparing the qualitative score of the computed metrics for a set of velocity waveforms with the corresponding subjective judgment of experts. Moreover, the implemented method was applied to two real validation cases involving a numerical model in roadside safety and a model in biomechanics respectively. Eventually, the program showed to be an effective tool to be used for assessing the similarities and differences between two curves and, hence, for assisting engineers and analysts in performing verification and validation activities objectively.

This work develops a methodology for full engine FEA simulation of the fan blade off containment test for a jet engine using LS-Dyna. The fan blade off containment test is a safety requirement involving the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact or rotating unbalance. The novel feature of the LS-Dyna simulation is the extensive full engine geometry as well as the widespread use of nonlinearities (mainly plasticity and friction) to absorb the large kinetic energies of the engine rotors. The methodology is simple to use, runs quickly and is being recognized by industry as a contender for widespread implementation. Future applications look promising enough that the methodology warrants further development and refinement.