DFR value testing and theoretical calculation on laser beam welded structures of fuselage panel

Abstract:

The aircraft fuselage panel is the key position of fatigue.To evaluate the fatigue performance of the laser beam welded (LBW) structures which are first applied in aircraft fuselage panel by Airbus Company instead of traditional riveted structure, two methods of experimental determination and statistical theoretical calculation were used.The fatigue tests, fracture analyses and detail fatigue rating (DFR) analyses were carried out on two groups of laser beam welded structures which were obtained by different post weld heat treatment (PWHT) processes(solid solution + aging treatment, and aging treatment) with the new type of aluminum lithium alloy 2060-T3, and the test DFR value was acquired as well as the theoretical DFR value.The analysis results show that the test DFR value of the solid solution + aging treatment is 118.0 MPa and the one of aging treatment is 113.7 MPa.The theoretical DFR values for them are 115.8 MPa (the relative error is 1.86%) and 112.2 MPa (the relative error is 1.32%), respectively.The source of cracks in the two structures is produced both at the weld toe.The crack propagates along the thickness of the plate and the crack propagation area is characterized by brittle cleavage river pattern.The difference is that final fracture region of the former is characterized by micropore aggregation fracture with many small dimples in the fracture, and the one of the latter is intergranular fracture with many grains in the fracture.The theoretical analysis can be used to restore the Weibull shape parameter, to verify the applicability of the theory of statistical analysis method, and to provide the reference for the DFR value of laser beam welded structures of fuselage panel.