Section 4 Automotive Design and Manufacturing,Chapter 12 Automotive Manufacturing 12.1 Vehicle architecture design and manufacturing 12.2 Injection Moulding 12.3 Joining For Lightweight Vehicles,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,New Words,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,New Words,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,New Words,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,With the increasing trend toward lightweight vehicles, the body materials for automobiles are changing from mostly low carbon steels to a mix of materials that includes both low carbon steels and high strength steels, light non-ferrous alloys, such as aluminum and magnesium alloys, and fiber reinforced polymers. The acceptance of these materials will depend not only on their structural performance and manufacturability, but also on the joining methods that can be used to assemble them in a rapid, robust and reliable manner. The structural performance of a joint depends on the joining method, joint geometry and joint quality. The joining method often depends on the materials being joined, but under mass production conditions it must also be quick, less dependent on fit and dimensional variations of the parts being joined and as defect free as possible.,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,Joining is an important consideration in the design of an automobile, since joints are usually the weakest areas in the structure and they are often the failure initiation locations in service. Joining becomes even more important as the body material changes from a single material to a mix of materials, since the compatibility between different materials in terms of their mutual joinability, surface characteristics, corrosion, assembly stresses, etc. may pose many technical challenges and needs to be considered in the design process and selection of materials. Since high strength steels and aluminum alloys are emerging as the principal material options for body construction in the near future, the joining methods that are most applicable for these two types of materials are considered. These joining methods can be divided into four categories:,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,These joining methods can be divided into four categories: (i) liquid phase welding or fusion welding, (ii) solid phase welding, (iii) mechanical joining and (iv) adhesive bonding. There are several different techniques available under each of these categories (Table 12-1).,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,Table 12-1 Various joining methods used with sheet metals in the automotive industry,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,For example, liquid phase welding or fusion welding includes resistance spot welding (Figure 12-4), arc welding and laser welding. The two most common methods of arc welding are gas metal arc welding (GMAW) (Figure 12-5) and gas tungsten arc welding (GTAW) (Figure 12-6); but there are many other forms of arc welding methods that are used either in special cases or in limited applications. Solid phase welding, which is accomplished without melting the materials, includes friction stir welding and a few other emerging technologies, such as magnetic pulse welding and ultrasonic welding. Mechanical joining includes the conventional mechanical fastening methods using bolts and nuts, but also the newer techniques, such as self-piercing riveting and clinching.,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,Adhesive bonding is also an established method of joining, but a combination of adhesive joining and welding or riveting is relatively new and is finding wider application, especially in space frame designs. Liquid phase welding is performed by locally heating the materials to be joined to their liquid phases, applying pressure to create fusion bonding between them and allowing the fusion bonded liquid phase to cool under pressure to form the joining. The principal liquid phase welding processes used in the automotive industry are resistance spot welding and arc welding. Resistance spot welding is the principal jointing method used for low carbon steel body construction.,Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,Figure 12-4 resistance spot welding (RSW) process,Chapter 11 Automotive Design 12.3 Joining For Lightweight Vehicles,Figure 12-5 Gas metal arc welding (GMAW) process,Chapter 11 Automotive Design 12.3 Joining For Lightweight Vehicles,Figure 12-6 Tungsten gas arc welding (GTAW),Chapter 12 Automotive Manufacturing 12.3 Joining For Lightweight Vehicles,In solid phase welding, two sheets of the same material or different materials are joined by creating metallurgical bon