| Popis: |
To meet with stringent European and U.S. environmental legislation, the automotive industry has been actively researching methods of improving the fuel economy of their vehicles, in order to reduce harmful pollutant emissions. One of the most logical ways to achieve this is by reducing vehicle kerbside weight. This is increasingly difficult since customers are demanding more comfort and safety features in their vehicles, which add weight. Despite the customers' demands, significant advances in technology, e.g. state-of-the-art materials and component manufacturing techniques, have meant that vehicle weight can be reduced considerably. One significant area of lightweight technology, which has been researched in this Engineering Doctorate thesis, is that of laser welded tailored blanks (LWTB). A LWTB is produced by laser butt welding two or more materials together to form a single composite blank. The materials studied in this thesis were high strength steels, including newly developed ultra high strength steels, for application in structural body-in-white components. Although a wealth of LWTB research has been conducted since 1985, only now are their production and formability becoming fully understood. This thesis begins with an in-depth practical and FEA simulation study of simple small scale axi-symmetric tests, which were carried out on unwelded and laser welded blanks. The results from these tests were used to create LWTB design guidelines which culminated in the successful pressforming of a larger scale complex component utilising LWTBs comprising various steel combinations (dissimilar thicknesses and/or strengths). The huge potential of tailored welded blanks as a significant lightweighting technology is unquestionable. With rapidly increasing demand, and with many automotive manufacturers preferring to outsource their LWTB requirements, it is vital that welded blank producers should gain comprehensive knowledge of the processing and formability of LWTBs. This thesis provides design guidelines that can assist welded blank producers. |
