Residual Stress Relaxation of Thin-walled Long Stringer Made of Aluminum Alloy 7050-T7451 under Transportation Vibration

Abstract

Thin-walled long stringer made of aluminum alloy 7050-T7451 is prone to deformation during transportation, so a research of residual stress relaxation was launched in this paper. The transport resonance stress of long stringer was analyzed based on the power spectral density of road transport acceleration. The residual stress relaxation experiment of aluminum alloy 7050-T7451 under different equivalent stress levels was designed and carried out. According to the amount of residual stress relaxation in the experiment, an analytical model was established with the equivalent stress level coefficient. The deflection range of long stringer was evaluated under different damping ratios. The results show that when the equivalent stress exceeds 0.8σ 0.2 , the residual stress relaxation of the thin-walled samples occurs. The residual stress relaxation increases linearly with the equivalent stress, which is logarithmically related to the loading cycle. The deformation caused by residual stress relaxation of the long stringer is proportional to the square of the length and the bending moment caused by stress rebalance, and inversely proportional to the moment of inertia of the structure. As the damping ratio decreases from 0.03 to 0.01, the total deflection of the long stringer increases from 0 to above 1.55 mm.

Surface roughness prediction of thin-walled parts impacted by radial depth of cut variations during peripheral milling process

“…To obtain the spatial solution of the ordinary differential equation ( 22), the mode shape (24) should be substituted into (22) that meets the boundary conditions ( 17) and (18), allowing the calculation of the mode shapes as in (25) and the natural frequency in (28) by the below expressions [20]:…”

“…At the same time, the rotational spindle speed is taken equal to N=1500 rpm with the determined tool revolution period equal to=0.01 s. In addition, the tangential and radial cutting and edge force coefficients are also given respectively [24]: K tc =1282.31N/mm 2 , K te =4.34 N/mm, K rc = 579.16 N/mm 2 , K re =5.38 N/mm for a given combination couple of cutting tool and workpiece material, tool geometry and so on. Moreover, the aluminum alloy's structural damping ratio is equal to =1.5% [25]. Afterward, the tool path positions are generated by fixing the distance between two consecutive tool positions equal to fz.…”