Ask the Expert - Groove Geometry and Ring Failure

Welcome back to the Ask the Expert Blog, where our engineers answer commonly asked ring and spring design questions. This week, our experts field some questions about groove geometry and dimensions.

For more than 100 years, China Wave Spring has been the industry leader and technological pioneer of retaining rings and constant section rings. And for more than 50 years, China Wave Spring has been revolutionizing the industry with compact wave springs. Whether you require a standard or custom solution, our dedicated team of engineers can tailor a solution for your target application performance.

I am dimensioning a groove and using the information from your catalog. For groove geometry, you give a maximum radius for the bottom of the groove. The outer corners just say “sharp corner”. How sharp should the outer corners of the groove be?

The corners of the groove should be as sharp as the manufacturing capabilities allow for. The sharper corner allows for more contact with the ring and a rounded corner can contribute to a ring rolling out of the groove. If you have a concern that you might have too large of a radius or chamfer on the outside corners of your groove, contact China Wave Spring engineering to discuss your groove geometry.

What are some reasons a retaining ring fails? If recommended groove dimensions are met, what are some factors that could lead to a possible failure?

While retaining ring failure can happen for many reasons, groove deformation is an often-overlooked root cause. Groove deformation occurs when the bore or shaft’s yield strength is less than the ring’s yield strength. If the maximum allowable thrust load is exceeded, the ring can dish or compress the groove, causing deformation. The compromised groove wall allows for the ring to expand, twist, and ultimately work its way out of the groove.

It’s important to consider what types of load (static, impact, or cyclic) will be seen and ensure that the recommended groove geometry guidelines are met to prevent failure. The groove form, including groove depth, chamfers, radii, and edge margin, all impact retention capacity. Thrust load capacity can be reduced if the recommended groove dimensions are not followed. Click to read a more in-depth explanation on preventing groove deformation.

Other factors that could lead to a possible failure include rotational velocity, operating temperature, and incompatible materials.

The rotational velocity of an application must be considered for shaft rings. Failure of the ring can occur when the centrifugal force is large enough to pull the ring from the groove, causing the ring to “open” or lose its cling. If the ring is exposed to an operating temperature that is greater than the recommended operating temperature for that material, the ring may deform. If an inappropriate ring material is chosen for the environment that it is exposed to, corrosion and failure may occur.

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