Metallurgical failure analysis of AA 7050 main landing gear brake reducer for reusable launch vehicle. (March 2023)

• Record Type: Journal Article
• Authors: Jalaja, K.; Manwatkar, Sushant K.; Gupta, Rohit Kumar; Narayana Murty, S.V.S.
• Is Part Of: Engineering failure analysis. Volume 145(2023)
• Publication Date: 2023-03
• Subjects: Brake reducer -- Landing gear -- Failure analysis; System failures (Engineering) -- Periodicals; Fracture mechanics -- Periodicals; Reliability (Engineering) -- Periodicals; Pannes -- Périodiques; Rupture, Mécanique de la -- Périodiques; Fiabilité -- Périodiques; Fracture mechanics; Reliability (Engineering); System failures (Engineering); Periodicals; Electronic journals; 620.112
• DOI: 10.1016/j.engfailanal.2022.107042
• Languages: English
• ISSNs: 1350-6307

Abstract

Highlights: Brake reducer failed upon hand torquing. Metallurgical analysis was conducted to address the failure cause. Brake reducer material is made up of aluminium alloy 7050-T7451. The failure was in the short transverse (ST) direction. Proper directional control is recommended. Abstract: Braking systems are the most significant structural part of the main landing gear for reusable launch vehicles, and brake reducers play an important role. One of the hexagonal break reducers failed upon torquing during the assembly of the main landing gear. The brake reducer material is made up of aluminium alloy 7050 in T7451condition. As a part of the investigation, failed brake reducer along with another untested and three torque-tested brake reducers were characterized and analyzed. Fractographic analysis of the failed samples revealed dimple features indicative of overload failure. The failure was on a longitudinal plane indicating the stresses acted in the short transverse (ST) direction. Mechanical test data revealed that the ductility of the material in the ST direction is lower (4.7% versus 13.4% in the L direction). Based on the detailed metallurgical investigation, failure was attributed to ductile overload in the ST direction as it is the weakest direction where the grain orientation was perpendicular when compared to other successful torque-tested brake reducers.