Damage Tolerance Analysis of Grinding Burn Cracks in High Strength Steels

Award Information
Agency: Department of Defense
Branch: Air Force
Contract: FA8222-19-C-0011
Agency Tracking Number: F172-001-0057
Amount: $749,700.00
Phase: Phase II
Program: SBIR
Solicitation Topic Code: AF172-001
Solicitation Number: 2017.2
Solicitation Year: 2017
Award Year: 2019
Award Start Date (Proposal Award Date): 2019-03-21
Award End Date (Contract End Date): 2021-03-21
Small Business Information
6669 Fyler Ave., St. Louis, MO, 63139
DUNS: 018571666
HUBZone Owned: N
Woman Owned: N
Socially and Economically Disadvantaged: N
Principal Investigator
 Dr. Thomas Mills
 (636) 399-7580
Business Contact
 Craig Brooks
Phone: (314) 644-6040
Email: cbrooks@apesolutions.com
Research Institution
Landing gear are often made from high strength steels, such as 300M , which are known to have excellent damage resistance when properly manufactured and maintained but to have lesser damage tolerance when compromised. For example, the grinding process, when done improperly, can heat the steel excessively and cause undesirable microstructural transformations, called grinding burns, which often contain cracks. These burned microstructures are extremely detrimental to fatigue and stress corrosion resistance.The USAF seeks methods to incorporate grinding burns into damage tolerance methods. The Phase I program recently completed by APES illustrated that grinding burns can be readily incorporated into the ASIP process. Methods for systematic, repeatable generation of grinding burns are presented in this proposal, and an analytical framework for transforming these burns into defect criteria is defined.Analytical and physical damage correlation of grinding burns is supported by a research program featuring destructive metallography, non-destructive testing, fatigue testing, failure analysis, stress intensity development and validation, and crack growth modeling. Mitigation strategies for grinding burns were also scoped using laser peening as the solution path.Potential benefits of the technology to warfighter can be recognized through increased safety, reduction in unscheduled or unnecessary maintenance, and increased aircraft readiness rates.

* Information listed above is at the time of submission. *

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