Research On Fretting Damage Of Aviation Involute Spline Couplings

Involute spline couplings has so many advantages such as force uniform, large bearing capacityand better capability of centralization and orientation that it is widely used in aviation industry. Butbecause of poor working conditions and hollow thin-walled structure, it is prone to fretting damage.For these reasons, the research on fretting damage of aviation involute spline couplings is extremelyimportant.Firstly, based on finite element method, the nonlinear friction contact property of spline couplingswas analyzed, the contact stress and relative slip distributions of spline couplings were obtained, andthe influence of contact geometry parameters was considered. The changing of contact stress andrelative slip was obtained during the rotation of spline couplings with angular misalignment, and theeffects of torque and angular misalignment were discussed. The results show that the contact stressand relative slip distributions of spline couplings are uneven, and the value of the end is relativelylarger. Increasing the contact length cannot increase the carrying capacity. With the reduce of splinewall thickness, contact stress and relative slip of the end increase. Friction coefficient is negligible tocontact stress, but is inversely proportional to relative slip. In the rotating process of spline couplingswith angular misalignment, the contact stress and relative slip distributions of involute splinecouplings are cyclic variation. Angular misalignment causes uneven load of spline couplings, and themaximum contact stress and relative slip of most teeth rise obviously as the angular misalignmentincreasing. Angular misalignment and torque increase fretting wear of spline couplings, but frettingwear is more dependent on angular misalignment than torque.Secondly, a piecewise parabolic function of spline couplings axial modification was presented.Based on finite element method, the contact stress and relative slip distributions of modified splinecouplings were obtained, and the influence of modified position and modified quantity was got. Theresults show that the piecewise parabolic function meets the requirement of spline modification, and itcan effectively reduce concentrated phenomenon of contact stress and relative slip. Modified positionshould be the ends and latter half of external spline in the typical model. Modification quantity of theends should be a reasonable choice for the model, and modification quantity of the back is generallylarger than the front.Then, based on bearing characteristics of spline coupling, the relation of fracture position andpolar moment of inertia was analyzed. With two fretting damage parameters and bending stress,failure forms of spline couplings were studied. The results show that fracture position of spline couplings is related with polar moment of inertia, and spline shaft with smaller polar moment ofinertia is easy to fracture. Bending stress concentrates seriously in the root of bearing tooth surface,that may lead to fatigue damage. Fretting wear occurs at the ends of tooth and tooth surface near theborder of the vulnerable is easy to produce fretting fatigue crack propagation. With friction coefficientincreasing, fretting wear and fatigue failure of spline aggravate.Finally, in order to validate the theoretical analysis, fretting experiment of spline coupling wascarried out and the results prove that the theoretical analysis of this paper is correct. Through mixedprogramming of VB.NET and CATIA, the design and modeling software of spline coupling was got,and structure design, strength calculation and parameterized modeling of spline coupling wereachieved.