Finite element analysis with explicit time integration is widely used in commercial crash solvers to accurately simulate transient structural problems involving large-deformation and nonlinearity. Technological advances in computer software and hardware have expanded the boundaries of computational expense, allowing designers to analyse increasingly complex structures on desktop computers. This dissertation is a review of the use of finite element analysis for crash simulation, the principles of crashworthy design and a practical application of these methods and principles in the development of a concept energy absorber for a sailplane. Explicit nonlinear finite element analysis was used to do crash simulations of the glass, carbon and aramid fibre cockpit during the development of concept absorbers. The SOL700 solution sequence in MSC Nastran, which invokes the LS-Dyna solver for structural solution, was used. Single finite elements with Hughes-Liu shell formulation were loaded to failure in pure tension and compression and validated against material properties. Further, a simple composite crash box in a mass drop experiment was simulated and compared to experimental results. FEA was used for various crash simulations of the JS1 sailplane cockpit to determine its crashworthiness. Then, variants of a concept energy absorber with cellular aluminium sandwich construction were simulated. Two more variants constructed only of fibre-laminate materials were modelled for comparison. Energy absorption and specific energy absorption were analysed over the first 515 mm of crushing. Simulation results indicate that the existing JS1 cockpit is able to absorb energy through progressive crushing of the frontal structure without collapse of the main cockpit volume. Simulated energy absorption over the first 515 mm was improved from 2232 J for the existing structure, to 9 363 J by the addition of an energy absorber. Specific energy absorption during the simulation was increased from 1063 J/kg to 2035 J/kg. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

Finite element analysis with explicit time integration is widely used in commercial crash solvers to accurately simulate transient structural problems involving large-deformation and nonlinearity. Technological advances in computer software and hardware have expanded the boundaries of computational expense, allowing designers to analyse increasingly complex structures on desktop computers. This dissertation is a review of the use of finite element analysis for crash simulation, the principles of crashworthy design and a practical application of these methods and principles in the development of a concept energy absorber for a sailplane. Explicit nonlinear finite element analysis was used to do crash simulations of the glass, carbon and aramid fibre cockpit during the development of concept absorbers. The SOL700 solution sequence in MSC Nastran, which invokes the LS-Dyna solver for structural solution, was used. Single finite elements with Hughes-Liu shell formulation were loaded to failure in pure tension and compression and validated against material properties. Further, a simple composite crash box in a mass drop experiment was simulated and compared to experimental results. FEA was used for various crash simulations of the JS1 sailplane cockpit to determine its crashworthiness. Then, variants of a concept energy absorber with cellular aluminium sandwich construction were simulated. Two more variants constructed only of fibre-laminate materials were modelled for comparison. Energy absorption and specific energy absorption were analysed over the first 515 mm of crushing. Simulation results indicate that the existing JS1 cockpit is able to absorb energy through progressive crushing of the frontal structure without collapse of the main cockpit volume. Simulated energy absorption over the first 515 mm was improved from 2232 J for the existing structure, to 9 363 J by the addition of an energy absorber. Specific energy absorption during the simulation was increased from 1063 J/kg to 2035 J/kg. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

A finite element model of fibre metal laminate (FML) fuselage was developed in order to evaluate its impact response under survivable crash event. To create a reliable crash finite element (FE) model of FML fuselage, a ‘building block approach’ is adapted. It involves a series of validation and verification tasks in order to establish reliable material and damage models, verified impact model with structural instability and large displacement and verified individual fuselage structure under crash event. This novel development methodology successfully produced an FE model to simulate crash of both aluminium alloy and FML fuselage under survivable crash event using ABAQUS/Explicit. On the other hand, this allows the author to have privilege to evaluate crashworthiness of fuselage that implements FML fuselage skin for the whole fuselage section for the first time in aircraft research field and industry. The FE models consist of a two station fuselage section with one meter longitudinal length which is based on commercial Boeing 737 aircraft. For FML fuselage, the classical aluminium alloy skin was replaced by GLARE grade 5-2/1. The impact response of both fuselages was compared to each other and the results were discussed in terms of energy dissipation, crushing distance, failure modes, failure mechanisms and acceleration response at floor-level. Overall, it was observed that FML fuselage responded similarly to aluminium alloy fuselage with some minor differences which conclusively gives great confidence to aircraft designer to use FML as fuselage skin for the whole fuselage section. In terms of crushing distance, FML fuselage skin contributed to the failure mechanisms of the fuselage section that lead to higher crushing distance than in aluminium alloy fuselage. The existence of various failure modes within FML caused slight differences from the aluminium fuselage in terms of deformation process and energy dissipation. These complex failure modes could potentially be manipulated to produce future aircraft structure with better crashworthiness performance.

No description available.

Passive safety systems like airbags have significantly improved road safety. These occupant safety systems help in reducing the severity of injuries, and save lives in the event of a road accident. The airbag systems must be configured correctly to minimize the impact of collision and protect the occupants. To configure the airbag, test crashes are performed and data is recorded. This data is simulated to find out appropriate parameters for the airbag deployment. The airbag simulation results are stored into databases. Airbag application tools are used to handle the data stored in databases. The airbag simulation results must be extracted efficiently and required computations needs to be performed. This data is then stored to reports. RSDBnext is an airbag application tool, it stands for Result Database next generation. This tool is used for extraction of data from the database. The RSDBnext tool should be adapted to generate Standard Customer Reports. These reports are to be generated based on customer requirements. The existing methodology to generate Standard Customer Reports used Excel macros, which took a lot of time to generate the reports. This method was complex and unstable. Hence, a new methodology was proposed without using macros. In the proposed method, an XML file and XSLT StyleSheet were used to generate the report in Excel using C# with Visual Studio. This approach reduces report generation time, and overcomes the drawbacks of the previous approach. From the results, this methodology to generate reports is faster, easier, and more reliable.

Pedal misapplication (PM) is an error in which a driver unintentionally presses the wrong pedal. When drivers mistake the accelerator pedal for the brake pedal, the vehicle experiences a sudden unintended acceleration, and the consequences can be severe. A brief history of PM is covered, and several novel studies of PM are described. The goals of these studies were as follows: 1. Identify and analyze multiple samples of PM crashes from a variety of data sources using both established and novel methods to gain new insight into the characteristics and frequency of PM crashes. 2. Use the confirmed, real-world PM crash data to develop a custom vehicle dynamics simulation and evaluate the overall potential safety benefit of a theoretical PM advanced driver assistance system. Using an established keyword search identification method and two unique crash datasets, a PM crash frequency of approximately 0.2% of all crashes was found. These PM crashes were typically rear-end or road departure crashes in moderate- to low-speed commercial or residential areas. Female drivers and elderly drivers were more often involved in these PM crashes, which generally featured slightly lower injury severities and often involved inattention or fatigue. Anecdotally, PM crash narratives contained repeated evidence of unexpected events, driver inexperience, distraction, shoe-malfunction, extreme stress, and medical conditions/emergencies. A novel PM crash identification algorithm was developed to detect PMs from time-series pre-crash data. This algorithm was applied to a sample of crashes with event data recorder data available, and a frequency of 4.3% of eligible crashes were found to have exhibited PM behavior, suggesting that PM crashes may be more prevalent than previously thought. While the data from these crashes suggested that a PM occurred, this dataset lacked sufficient data regarding driver intention, which is necessary to confirm each crash as PMs. The characteristics of these PM-like crashes were analyzed and found to be largely similar to those of previous samples, with notable exceptions for higher proportions of male drivers, higher travel speeds, and higher maximum injury severities. More robust data from a naturalistic driving study (NDS) was acquired, and the novel algorithm was applied to all of the sample’s eligible crashes. Because the NDS data contained more data elements such as driver-facing video, crashes that exhibited PM behavior were individually inspected to confirm PM. This produced a PM crash frequency of 1.1%. The characteristics of these confirmed PM crashes were investigated, but a small sample size limits the generalizability of the results. Lastly, crash data from confirmed, real-world PM crashes was used to inform a custom vehicle dynamics model into which a theoretical PM advanced driver assistance system was simulated. The effect of the accelerator suppression system on crash avoidance and mitigation was evaluated to assess its potential safety benefit, which was found to be highly dependent on system threshold values and largely underwhelming in the absence of supplemental braking. The results indicated that a system that detected PM, suppressed acceleration, and applied braking could provide a substantially higher safety benefit. / M.S. / Pedal misapplication (PM) occurs when a driver presses the wrong pedal. When drivers mistake the accelerator pedal for the brake pedal, the vehicle experiences a sudden unintended acceleration, and the consequences can be severe. A history of the controversial subject of PM is covered, and several novel studies of PM are described. In these studies, PM crashes are identified among documented real-world crashes. This is done in three phases: (1) using narratives written by law-enforcement officers or crash investigators, (2) using event data recorders, or “black boxes,” that store vehicle data prior to crashes, and (3) using naturalistic driving study data, including video recordings of subjects during daily driving. These data are analyzed to develop the understanding of how often PM crashes occur and what factors are common among them. It is discovered that the frequency of PM crashes may be an order of magnitude greater than previously estimated. In the final study, real-world PM crash data is used to virtually reconstruct PM crashes and apply an advanced driver assistance system designed to detect PM, suppress the accelerator input, and reduce the severity of the crash or prevent it altogether. By simulating a wide range of system variations, we develop a sense of the feasibility of such a system’s implementation and overall safety benefit.

Plus d'un million de personnes meurent dans des accidents sur les routes du monde et beaucoup de millions sont gravement blessés chaque année. Selon les études, ‘Run-Off-Road accidents (ROR)’, c'est-à-dire que le véhicule a au moins une collision avec des équipements routiers, représentent environ 10% des accidents routières, mais 45% de tous les accidents mortels sont des ROR. Les dispositifs de retenue des véhicules (DDR) sont les infrastructures installées sur la route pour fournir un niveau de confinement du véhicule ‘hors de contrôle’. La barrière de sécurité routière est un DDR continu installé à côté ou sur la réserve centrale d'une route pour empêcher les véhicules errants de s'écraser sur les obstacles routiers et de les conserver en toute sécurité. Les résultats statistique montrent que l'existence des barrières peut réduire les morts jusqu'à un facteur de 4 par rapport aux collisions contre d'autres obstacles routiers. Les performances de sauvetage d'un DDR dépendent de la conception de l'appareil. Des normes telles que EN1317 ont normalisé les conditions des essais de chocs sous lesquelles une conception de DDR doit être testée et ont défini les critères pour l'évaluation des performances d'une conception. En fait, un DDR ne puisse pas vraiment être optimisé: il existe des critères multiples pour l'évaluation de la performance d'un DDR et tous les critères ne peuvent pas être optimisés en même temps; les conditions de travail d’un DDR, c'est-à-dire les conditions d'impact d’un DDR avec un véhicule errant, sont nombreuses; les facteurs incertains du DDR peuvent dégrader les performances d'une conception. La thèse vise à définir une approche qui peut servir : l'analyse de sensibilité (AS) et la conception robuste du DDR ; enrichissement des normes existantes dans la conception du DDR. Le cas d'une barrière de sécurité routière est spécifié dans l'étude : une barrière a été testée expérimentalement, le programme Ls-Dyna est utilisé pour la simulation de choc de l'appareil ; en tenant compte des propriétés du modèle de choc, les efficacités de différentes méthodes de l’AS ont été étudiées ; les influences des facteurs critiques dont les incertitudes contribuent le plus à l'instabilité de la barrière ont été quantifiées avec les approches d’AS sélectionnées ; compte tenu des incertitudes des facteurs critiques, l’optimisation robuste de multi-objectif de la barrière est réalisée ; des simulations d'impact de la barrière optimisée ont été effectuées sous des conditions d'impact différentes pour évaluer ses performances dans les véritables accidents. Les approches présentées dans l'article peuvent être utiles pour la conception d'autres DDR ou plus largement d'autres systèmes d'ingénierie complexes. On peut espérer que l'analyse de robustesse et l'analyse de la généralisation (c'est-à-dire l'évaluation de la performance du DDR sous différentes conditions d'impact) du DDR pourraient enrichir les normes de la conception des DDR / More than 1 million people die in crashes on the world’s roads and many millions are seriously injured each year. According to the studies: Run-Off-Road accidents (ROR), i.e. the vehicle run-off the road into the roadside and has at least one collision with either roadside equipment or the roadside itself, “represent about 10% of the total road accidents, while 45% of all fatal accidents are ROR”. Vehicle Restraint Systems (VRS) are the infrastructures installed on the road to provide a level of containment for an errant vehicle. Safety barrier is “continuous VRS installed alongside, or on the central reserve, of a road to prevent errant vehicles from crashing on roadside obstacles, and to retain them safely”. Statistic results show that “the existence of protective barriers on road can reduce fatalities up to a factor of 4 when compared to collisions against other road obstacles.” The life-saving performances of a VRS depend on the design of the device. Standards such as EN1317 normalized the impact conditions under which a design of VRS must be tested by crash tests, and defined the criteria for performance evaluation of a design. While a VRS cannot really be optimized: Multi-criteria exist for performance evaluation of a VRS and all the criteria cannot be optimized in the same time; the impact conditions of the VRS with the errant vehicle are numerous; uncertain factors of the VRS may degrade the performances of a design. The thesis aims to define an approach that can serve: sensitivity analysis (SA) and robust design of the VRS; Enrichment for the existing standards in the design of VRS. The case of a safety barrier is specified in the study: a safety barrier has been test experimentally, the program Ls-Dyna was used for crash simulation of the device; considering properties of the crash model, efficiencies of different SA methods were studied and influences of the critical factors whose uncertainties contribute the most to the instability of the barrier were quantified with the selected SA approaches; considering the uncertainties of the critical factors, Multi-Objective robust optimization of the tested barrier were realized; under different impact conditions, crash simulations of the optimized barrier were carried out to evaluate its performances in the real crash accidents. The approaches presented in the article can be useful for the design of other VRS or more broadly, other complex engineering systems. Hopefully, the robustness analysis and generalization analysis (i.e. performance evaluation of the VRS under different impact conditions) of the safety barrier could enrich the standards for the design of VRS

No description available.

In this thesis, a new modeling methodology applicable to adhesively bonded joints for crash simulations is presented. Using this approach, adhesive joints can be modeled without using minute solid elements thus reducing the size of the model. Moreover, coarse mesh can be used for substrates in the overlap region of a joint. Both of these improvements together yield significant reduction in simulation run times in crash analysis when compared to solid element representation of adhesive. The modeling can also capture effects of strain rate for a given ambient temperature. In order to develop the efficient modeling procedure mentioned above, experimental, analytical and numerical studies have been carried out. Mechanical behaviors of adhesively bonded joints are studied with the help of double lap shear (DLS) coupon tests conducted at different extension rates and temperatures. The joint specimens are made from dual-phase (DP) steel coupons bonded with epoxy resin. Tests are also carried out to ascertain the behaviors of these component materials at different extension rates and temperatures. A new semi-analytical solution procedure is developed considering material nonlinearity to predict mechanical behaviors of adhesively bonded DLS joints. The joint behaviors using the semi-analytical approach are predicted separately using the Von Mises and exponent Drucker-Prager yield criteria. The predicted force versus extension curves using semi-analytical solution are compared with test results. It is also hypothesized here that, the semi-analytical solution procedure can be used as a base to develop efficient modeling procedures of adhesively bonded joints in FEA. In finite element analysis, both adhesive and substrates are modeled as elastic-plastic materials. It is shown that the shell-solid model of the DLS joint, in which substrates are modeled using shell elements and adhesive is modeled using solid elements, can accurately predict the mechanical behavior of the joint. Both exponent Drucker-Prager and Von Mises material models in ABAQUS are used to calculate force versus extension curves. Numerical and experimental forces versus extension curves are compared. A new methodology for efficient modeling of adhesively bonded joints in LS-DYNA using equivalent material properties in the joint overlap region is proposed. Various models using this methodology are assessed by comparing their results with shell-solid model and test results. Finally, it is also shown that strain rate effects can be included in the efficient modeling approach.