Electrical machines form part of our everyday life at home and in industry plants. Currently induction machines are the backbone of the industry machine installation as these are robust, reliable and have relatively high efficiency. However as the price of energy increases and stricter efficiency regulations are put into place there is a need for more efficient electrical machines. The majority of induction machines on Sasol's plants are between 2.2 kW and 22 kW. Of these, 95% machines are connected to pump loads and 2% to fan loads. Thus the majority of the machines operate at a constant speed. Rather than try to improve an induction machine, this project proposes the design for a more efficient LS PMSM that can also be used in the same applications as mentioned above. Although LS PMSMs aren’t a new concept, the demand and industry interest in this technology has increased in recent years. Since 2000 the number of research publications with regards to this machine has increased significantly. The goal of this project is to gain a better understanding of these machines by designing a prototype. The design entitles the stator and rotor. As Sasol provided the funding for the project it was decided to design a three phase, 7.5 kW 525V, four-pole machine. During the design phase several design techniques done by other researchers were incorporated into the prototypes. The design is done with the aid of two FEM software packages namely FEMM and ANSYS Maxwell® and verified against calculated values. The final prototype is tested and compared to the predicted values determined during the design. An industry available LS PMSM from Weg, the WQuattro is also used to compare the results of the prototype. The prototype machine’s no-load, full load and locked rotor behaviour is tested as well as the back-emf waveform. From the results gained the machine is validated. The machine did not perform as predicted and further investigation into the reason is needed. Due to the incorrect wiring of the stator and some other rotor manufacturing issues the prototype cannot be fully validated. However it was found that several of the designed values correlated to the measured values. Further investigation into the under performances as well as more relevant testing and practical manufacturing method is needed. / MIng (Electrical and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

<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.

<p>Denna studie hade som syfte att undersöka och analysera hur pedagoger arbetar med inlärningsstilar utifrån Dunn & Dunns modell. Data samlades in genom en kvalitativ undersökning i form av intervjuer med tre pedagoger, samt observationer i klassrumssituationer för att få kunskap om hur olika lärstilar fungerar i praktiken. Undersökningen visade att de observerade eleverna jobbade med alla sina sinnen i större eller mindre omfattning. Informanternas definition av inlärningsstilen var att individanpassa undervisningen, att ge eleverna möjlighet att testa sina multisensoriska sinnen, att undervisa från helheten till detaljerna, samt att skapa stimulans genom informell möblering. Informanterna jobbade i enlighet med sin egen definition av modellen, som däremot skiljde sig i förhållande till Dunn & Dunns teorier, genom att inte diagnostisera eleverna och att använda mindre andel av studiematerial. Inlärningsmodellen är ingen fulländad metod för undervisning, utan snarare ett verktyg att använda utifrån varje elevs individuella sätt att lära, i kombination med annan metodik, för att skapa motivation, självkänsla och arbetsglädje.</p>

Denna studie hade som syfte att undersöka och analysera hur pedagoger arbetar med inlärningsstilar utifrån Dunn &amp; Dunns modell. Data samlades in genom en kvalitativ undersökning i form av intervjuer med tre pedagoger, samt observationer i klassrumssituationer för att få kunskap om hur olika lärstilar fungerar i praktiken. Undersökningen visade att de observerade eleverna jobbade med alla sina sinnen i större eller mindre omfattning. Informanternas definition av inlärningsstilen var att individanpassa undervisningen, att ge eleverna möjlighet att testa sina multisensoriska sinnen, att undervisa från helheten till detaljerna, samt att skapa stimulans genom informell möblering. Informanterna jobbade i enlighet med sin egen definition av modellen, som däremot skiljde sig i förhållande till Dunn &amp; Dunns teorier, genom att inte diagnostisera eleverna och att använda mindre andel av studiematerial. Inlärningsmodellen är ingen fulländad metod för undervisning, utan snarare ett verktyg att använda utifrån varje elevs individuella sätt att lära, i kombination med annan metodik, för att skapa motivation, självkänsla och arbetsglädje.

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.

No description available.

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.

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.