| Popis: |
Automobile manufacturers are attempting to reduce the weight of their vehicles in order to meet strict fuel economy legislation. To achieve this goal, a combination of different materials such as steel, aluminum and carbon fiber composites are being used in the body of the vehicle. The ability to join different materials is an area of focus for automobile manufacturers. Multiridged fasteners are a viable option for multi-material joining. Commercial systems such as the RIVTAC® are being used in the industry. However, there is plenty of scope to develop new ridged nails, which could potentially be better than the RIVTAC®. The goal of this thesis was to propose, prototype and test novel ridged nail designs which can be used for multi-material joining.The proposed designs were classified based on the nail geometry into three groups: end modified nails, enhanced ridge engagement nails and 2-part and hollow nails. Each nail group contains a number of nail designs. The design philosophy of the end modified nails is to create a safer flat-end fastener whilst not compromising on strength characteristics. The enhanced ridge engagement nails is an attempt to increase the amount of sheet material that fills the ridges of the nail. The 2-part and hollow nails are aimed at improving joint strength by increasing the second moment of inertia of the nail and using a large diameter fastener to improve retention strength. To analyze these nails, joints are created in aluminum 6061-T6 are tested in two loading conditions: shear and cross-tension, based on the Japanese Industrial Standards. A baseline strength comparison between the proposed designs and the RIVTAC® was performed to assess the performance of the designs. From the results, good performance was observed in some designs of the end modified nail group. These were only 5% weaker than a RIVTAC®. For the enhanced depth engagement nails, good performance was observed. However, to gain a concrete conclusion, it was deemed that further testing was required. In the 2-part and hollow nail design group, the 2-part nail could not be fabricated due to manufacturing limitations and only the hollow nails were fabricated and tested. From the results, hollow nails were found to be weaker than a RIVTAC® by 12-15% and are not recommended for usage. |
