THE DEVELOPMENT OF A CALCULATION METHOD FOR THE FATIGUE STRENGTH OF LUGS AND A STUDY OF TEST RESULTS FOR LUGS OF ALUMINIUM

Abstract This report treats single, symmetric, longitudinally loaded lugs, fitted with a non-interference pin. A calculation method for fatigue strength, which takes the shape and size of the lug into consideration, has been devised. With varying parameter values, substituted into assumed relations which are partly verified empirically, test results are reduced to refer to a ‘reference lug‘ of a defined shape and size. The method is presented, its background is related and it is applied to approximately 900 lugs, for which test results were available. These lugs represent two main groups of aluminium alloys, Al-Cu-Mg and Al-Zn-Mg-Cu, which are divided into 8 subgroups. About 400 of the lugs represent aluminium alloy of the 2024 type. This number allowed, to some extent, a statistical analysis of the test results. The size effect has been investigated in a special test series with lugs of aluminium 7079-T6 (Saab 3624). The pin diameters were 5, 10, 20, and 40 mm. Results from this test series have also been studied with respect to the scatter in fatigue strength.