The objective of this study is to characterize critical component structure-properties on a Dodge Neon for material response refinement in crashworthiness simulations. Crashworthiness simulations using full-scale finite element (FE) vehicle models are an important part of vehicle design. According to the National Highway Traffic Safety Administration (NHTSA), there were over six million vehicle crashes in the United States during 2004, claming lives of more than 40,000 people. Crashworthiness simulations on a detailed FE model of a 1996 Plymouth/Dodge Neon were conducted on the NHTSA for different impact crash scenarios. The top-ten energy-absorbing components of the vehicle were determined. Material was extracted from the as-built vehicle and microstructural analyses were conducted. Tension tests at different temperatures and strain rates were performed as well as microhardness tests. Different microstructural spatial clustering and mechanical properties were found for diverse vehicle components. A plasticity model based on microstructure was used to predict the material response of the front bumper.

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.].

In this work, the effectiveness of multi-objective design optimization using metamodeling techniques and an internal state variable (ISV) plasticity damage material model as a design tool is demonstrated. Multi-objective design optimization, metamodeling, and ISV plasticity damage material models are brought together to provide a design tool capable of meeting the stringent structural design requirements of today and of the future. The process of implementing this tool are laid out, and two case studies using multi-objective design optimization were carried out. The first was the optimization of a Chevrolet Equinox rear subframe. The optimized subframe was 12% lighter and met design requirements not achieved by the heavier initial design. The second case was the optimization of a Formula SAE front upright. The optimized upright meets all the design constraints and is 22% lighter.

One of the limiting factors in gas turbine design is the allowable metal temperatures and loads in critical components. Specially designed superalloys are used when the conditions are most severe. One of these superalloys is Inconel 718. To be able to design components for higher temperature and higher loads, an accurate understanding and computational model of the material is needed. In this thesis the deformation mechanisms of Inconel 718 have been investigated and a theoretical basis for modelling in a large deformation context has been established. Finally a viscoplastic nonlinear kinematic hardening material model with an Armstrong-Frederick backstress evolution law has been implemented as a first step in describing the constitutive behaviour of the material Inconel 718.

One of the limiting factors in gas turbine design is the allowable metal temperatures and loads in critical components. Specially designed superalloys are used when the conditions are most severe. One of these superalloys is Inconel 718. To be able to design components for higher temperature and higher loads, an accurate understanding and computational model of the material is needed. In this thesis the deformation mechanisms of Inconel 718 have been investigated and a theoretical basis for modelling in a large deformation context has been established. Finally a viscoplastic nonlinear kinematic hardening material model with an Armstrong-Frederick backstress evolution law has been implemented as a first step in describing the constitutive behaviour of the material Inconel 718.

In this project, two broad facets in the design of a methodology for performance optimization of indexable carbide inserts were examined. They were physical destructive testing and software simulation.For the physical testing, statistical research techniques were used for the design of the methodology. A five step method which began with Problem definition, through System identification, Statistical model formation, Data collection and Statistical analyses and results was indepthly elaborated upon. Set-up and execution of an experiment with a compression machine together with roadblocks and possible solution to curb road blocks to quality data collection were examined. 2k factorial design was illustrated and recommended for process improvement. Instances of first-order and second-order response surface analyses were encountered. In the case of curvature, test for curvature significance with center point analysis was recommended. Process optimization with method of steepest ascent and central composite design or process robustness studies of response surface analyses were also recommended.For the simulation test, AdvantEdge program was identified as the most used software for tool development. Challenges to the efficient application of this software were identified and possible solutions proposed. In conclusion, software simulation and physical testing were recommended to meet the objective of the project.

<p>One of the limiting factors in gas turbine design is the allowable metal temperatures and loads in critical components. Specially designed superalloys are used when the conditions are most severe. One of these superalloys is Inconel 718. To be able to design components for higher temperature and higher loads, an accurate understanding and computational model of the material is needed. In this thesis the deformation mechanisms of Inconel 718 have been investigated and a theoretical basis for modelling in a large deformation context has been established. Finally a viscoplastic nonlinear kinematic hardening material model with an Armstrong-Frederick backstress evolution law has been implemented as a first step in describing the constitutive behaviour of the material Inconel 718.</p>

Magnesium sheet alloys, such as wrought AZ31, have material properties that make them an attractive option for use in automotive and aircraft components. However, the low ductility of magnesium alloys at room temperature necessitates the use of high-temperature forming to manufacture complex components. Finite-element-method (FEM) simulations can assist in determining the optimum processing parameters for high-temperature forming, but only if an accurate material constitutive model is used. New material constitutive models describing the deformation behavior of AZ31 sheet at 450°C are proposed. These models account for both active deformation mechanisms at this temperature: grain-boundary-sliding creep and five-power dislocation-climb creep. Phenomena affecting these deformation mechanisms, such as material anisotropy and grain growth, are also investigated. This physics-based approach represents an improvement over previous material models, which require nonphysical parameters and can only predict forming for a limited range of conditions. Tensile tests are conducted to obtain data used in fitting constitutive models. New models are used in FEM simulations of both tensile tests and biaxial gas-pressure bulge tests. Simulation results are compared to experimental data for validation and determination of model accuracy. / text

Some metals, such as Ti-6Al-4V, have a high elongation to failure when strained at certain rates and temperatures. Superplastic forming is the utilisation of this property, and it can be used to form thin, geometrically complex components. Superplastic forming is a slow process, and this is one of the reasons why it is an expensive manufacturing process. Localised thinning occurs if the specimen is strained too quickly, and components with locally thin wall thickness fail prematurely. The goal of this study is to find a technique that can be used to minimise the forming time while limiting the minimum final thickness. The superplastic forming process is investigated with the finite element method. The finite element method requires a material model which describes the superplastic behaviour of the metal. Several material models are investigated in order to select a material model that can show localised thinning at higher strain rates. The material models are calibrated with stress-strain data, grain size-time data and strain rate sensitivity-strain data. The digitised data from literature is for Ti-6Al-4V with three different initial grain sizes strained at different strain rates at 927 C. The optimisation of the forming time is done with an approximate optimisation algorithm. This algorithm involves fitting a metamodel to simulated data, and using the metamodels to find the optimum instead of using the finite element model directly. One metamodel is fitted to the final forming time results, and another metamodel is fitted to the final minimum thickness results. A regressive radial basis function method is used to construct the metamodels. The interpolating radial basis function method proved to be unreliable at the design space boundaries due to non-smooth finite element results. The non-smooth results are due to the problem being path dependent. The final forming time of the superplastic forming of a rectangular box was successfully minimised while limiting the final minimum thickness. The metamodels predicted that allowing a 4% decrease in the minimum allowable thickness (1.0 mm to 0.96 mm) and a 1 mm gap between the sheet and the die corner the forming time is decreased by 28.84%. The finite element verification indicates that the final minimum thickness reduced by 3.8% and that the gap between the sheet and the die corner is less than 1 mm, resulting in the forming time being reduced by 28.81%. / Dissertation (MEng)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

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