Machinability study of aircraft series aluminium alloys 7075-T6 and 7050-T7451

The aluminium alloy 7050-T7451 is generally considered as the principal choice in aeronautical applications demanding adequate strength, stress corrosion cracking resistance, and toughness. Surprisingly, despite extensive research works on machining and machinability of aluminium alloys, including aluminium alloy 7075-T6, limited information was found on machining and machinability evaluation of 7050-T7451, which belongs to a similar family as 7075-T6. To remedy the lack of knowledge determined, dry ball-end milling operations were performed with coated end milling tools on both materials. Experimental characterization and cutting force measurements were performed to measure/evaluate the cutting forces, burr formation morphology, insert performance (wear/breakage), and surface quality attributes. According to experimental studies, 7050-T7451 was found more machinable than 7075-T6. Less burr formation and better surface quality were observed on 7075-T6. Machining attributes are influenced by different experimental factors. However, other machinability attributes, including residual stress, vibration modes, as well as particle emission, must be studied under various lubrication modes and machining operations in subsequent studies. This also recalls further studies on simultaneous multiple response optimization.

Study on the Influence of Anisotropy on Cutting Performance of Aviation Aluminium Alloy 7050-T7451

Based on the hypocycloid theory, a highspeed orthogonal cutting simulation model was established. The cutting parameters (cutting speed, feed rate) and plane forming angle of the workpiece of aeronautical aluminium alloy 7050-T7451 pre-stretched rolled sheet were simulated and validated. The mapping relationship between cutting parameters, anisotropy and cutting performance was analyzed. The results show that the degree of anisotropy and the difficulty of material cutting are proportional to the forming angle, and the anisotropy decreases with the increase of cutting speed and the decrease of feed speed. Finally, the optimal cutting process range of aluminum alloy 7050-T7451 was obtained, which provides data support for highspeed cutting of anisotropic materials.

A crack growth–based individual aircraft monitoring method utilising a damage metric

The need and benefits of individual aircraft fatigue monitoring are now well established. There are broadly two fatigue damage methods employed for this purpose, namely, crack growth and stress (or strain)-life. The crack growth methods tend to provide a relative comparison between an aircraft’s usage and a baseline usage, while the strain-life methods provide a measure of the amount of fatigue life consumed against that (generally) demonstrated through a fatigue test. In this article, a new crack growth–based tracking method is described that also includes a measure of the certified fatigue life consumed. The damage model is compared against the results of an extensive coupon fatigue test programme for aluminium alloy 7050-T7451.