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Classically, structural component fatigue design is based on testing and empirical models. First a series of average stress-life curves are generated from fatigue tests. Constant life diagrams are then developed accounting for mean stress effect, casting quality, surface finish, volume and other factors. Component design is then based on keeping the effective alternating stress below the diagram limit stress. While this procedure has worked well to design many components, it is based on extensive fatigue testing and empirical stress reduction factors. Thus, material and process improvements and computerization of the design process are difficult to incorporate into this test/empirical based design methodology. Fracture mechanics and damage tolerant design methodologies are used in aerospace for fatigue design. These methods predict well the fatigue life for surface scratches (rogue inspectable flaws) of about 0.25-1.27 mm in size.

Draw bead simulator tests were performed on various tool materials using aluminum alloys 2008-T4 and 6111-T4. The tool materials included hardened cast steel J435/0050A, D2 alloy, cast steel with ion nitride and PVD chromium nitride surface treatments, and cast steel with standard chromium and Wearalloy™ chromium coatings. Friction and galling behavior were monitored over an extended period of testing which allowed differentiation of the tool materials and alloys. Wearalloy™ and CrN tool coatings consistently demonstrated improved ability to prevent material transfer for both aluminum alloys, in spite of friction coefficients which were higher than the uncoated and ion nitrided tools. The ion nitrided surface exhibited the lowest friction coefficients of the surface treatments tested, but showed appreciably more wear. For a given lubricant and dilution ratio, alloy 2008-T4 exhibited an increased tendency for material transfer compared to alloy 6111-T4 for all tool materials tested.

Weight considerations and the need for corrosion resistance make aluminum fasteners attractive for new automotive design. This paper reviews design considerations in using aluminum fasteners. Newly developed high-strength fastener alloys complimented by lightweight and the well known attributes of aluminum give the designer wide latitude in using aluminum for standard and special purpose fasteners.

Two new aluminum alloys, 6009 and 6010, for auto body sheet are described and technical data are presented. The 6XXX-series alloys are ideal for body sheet in several respects, providing excellent corrosion resistance, improved spot weldability, and freedom from Luder's lines, together with favorable response to aging in many paint bake cycles. The result is a combination of excellent formability in the T4 temper and, after aging, higher strength than achievable in any other aluminum alloy system having other characteristics desired in body sheet. The latter translates to excellent dent resistance, superior even to that of steel. Furthermore, scrap loop problems are eliminated; compatible alloys 6009 and 6010 may be used together to obtain optimum strength and formability without any penalties in scrap utilization. Forming, aging, finishing, and joining data for these alloys are presented.

The use of polished aluminum fuselage skins has been a standard on U.S. commercial jet transport aircraft for decades. Increasingly stringent environmental regulations for paint stripping combined with fuel and maintenance savings allows consideration of flying polished non-painted aircraft. Boeing, McDonnell Douglas and Embraer currently manufacture commercial aircraft with polished alclad aluminum fuselages. Commercial airlines such as American Airlines, USAir, Eastern, Northwest and ASA fly non-painted fleets. These customers require the aircraft to be delivered with a polished appearance incorporating minimum fleet graphics. The manufacturing of polished aircraft requires unique production and handling procedures to fabricate all exterior panels with identical color match and reflectivity.