Engineering structures in transportation industries like automobile, rail road cars and marine vessels demands reduction in weight, efficient joining technique and economical way of manufacturing. To meet stringent fuel economy standards, automakers must dramatically reduce vehicle weight. As a result, engineers are using more and more aluminum for body panels, engine components and structural parts. Aluminum use in vehicles is expected to double by 2025, as automakers roll out a wide variety of lighter weight models. Aluminum is corrosion-resistant and offers an excellent blend of strength and low mass that can help improve fuel economy. Vehicles made with aluminum components can also accelerate faster and brake quicker than their heavier counterparts. Traditionally, aluminum vehicles have been assembled with structural adhesives and rivets. Because higher production volumes hinder adhesive use, automakers have relied on self-piercing rivets to join aluminum body parts. However, rivets add cost, and riveting guns have a limited range of joint configurations. And, while this approach can be used to join lowerstrength steels with aluminum, it isn’t suitable for joining aluminum to ultra-high-strength steel. Automakers and part suppliers are focusing on new ways to join aluminium with tools and technology other than traditional resistance spot welding, which is prone to variability. Now, the automotive industry is keen to use thinner sheets, in order to build lighter vehicles and reduce production costs. More and more car manufacturers choose a hybrid design, where a combination of different materials such as steel and aluminium are joined. With classic welding methods, joining of dissimilar materials has not been possible. With friction stir welding, on the other hand, high quality dissimilar joints can be obtained. The welding temperature is kept below the melting point, which means that the alloy properties are not destroyed and strong joints are achieved.