Official Answer
Answer
In aluminum (e.g., 6061-T6), the yield strength $S_y \approx 35-40$ ksi is much lower than the steel ring. Under thrust, the spiral ring acts as a circular 'knife,' and the high contact pressure leads to 'groove wall yielding.' The groove wall deforms into a ramp, allowing the ring to expand and 'pop out.' This is often misidentified as ring failure. The solution is to increase the groove depth $G$, which increases the shear area $A = D \pi G$, or to use a 'load-spreading' washer. Engineers should use the formula $P_{all} = \frac{D \pi G S_y}{2}$ to ensure the aluminum housing can support the required axial load.
