Design and validation of a high wear-resistance composite spline with a sacrificial elastic ring

Splines that are used in aeronautic applications often suffer contact stress concentration and sliding due to inevitable misalignment, resulting in severe fretting wear. This work proposes a composite spline consisting of a metal circular-arc external spline, an elastic spline ring, and a metal involute internal spline along with two engagement spline pairs, namely one circular-arc spline pair, and one involute spline pair. The concept of the proposed composite spline is to minimize fretting wear of the baseline metal spline and transfer the inevitable wear to the sacrificial spline ring. The inner circular-arc spline pair is interference fitted, while the outer involute spline pair is clearance fitted. A deformable and self-lubricating material, such as PEEK, is desirable for a spline ring. The design methods for the spline ring and circular-arc spline pair are developed. The high wear-resistance ability of the composite spline is validated using contact stress analysis using finite element models and wear-resistance experiments under rotating conditions with constant torques.