Abstract:
A scaled-down nose wheel fork for a light aircraft was redesigned by applying topology optimization for manufacturing in Ti6Al4V(ELI) through laser powder bed fusion (LPBF). This scaled-down nose wheel fork was built together with the test specimens for tensile and fatigue testing in this study. The test specimens were quality checked, tested, and analyzed through standard procedures to obtain the porosity levels, tensile and fatigue properties, and fracture characteristics. The effect of the inherent surface roughness on the high-cycle fatigue properties of LPBF Ti6Al4V(ELI) test specimens was investigated. These test specimens were built to the standard geometry without subsequent machining in three orthogonal directions. They were tested under constant load in a tension–tension fatigue testing machine in accordance with the ASTM E 466 standard. The data was collected and complied with the ASTM F3001 – 14 standard for additive manufacturing (AM) Ti6Al4V(ELI) with laser powder bed fusion. The fatigue performance of the Ti6Al4V(ELI) specimens built to the standard geometry without subsequent machining was compared to that of machined test specimens. It was found that the inherent surface roughness of the specimens built to the standard geometry reduced their fatigue life by about half that of the machined specimens. A customized jig was designed and manufactured to simulate the operational conditions applicable to the scaled-down nose wheel fork. This jig allowed three critical load cases to be tested. The experimental results of the fatigue test specimens and the performance testing of the scaled-down nose wheel fork under static loading were used to evaluate the feasibility of LPBF for production of structural aircraft components, particularly the nose wheel fork. Based on the outcome of the study, it was concluded that it would be justifiable to build a fullscale prototype of the nose wheel fork for testing under operational conditions.
