Contact Stress Design Parameters for Titanium Bearings

In response to NASA 2015 SBIR Topic H4.02, Air-Lock proposes to define the maximum allowable contact stress for Titanium bearings. The modulus of Titanium is lower than legacy spacesuit bearing materials (Stainless Steel). Due to this, Titanium bearings are more susceptible to deflection under man and plug load scenarios. Bearing deflection causes a limited number of balls to absorb the full load and results in higher, localized, contact stresses. Localized contact stress is believed to be the main contributor to the bearing race degradation observed during NASA's 2014 oxygen compatibility testing. In Phase 1, we will correlate analytical contact stress data with sample bearing test data. This correlation will characterize bearing wear and degradation relative to ball contact stress. Multiple test iterations will be performed to clearly identify the contact stress that degrades a titanium race. We will also determine if there are commercial surface treatments (coatings) that may enhance Titanium wear resistance. At the conclusion of Phase 1, we shall have identified the maximum allowable bearing contact stress. This data point will serve as a valuable design guideline for future bearing designs and should yield reduced certification and development costs.