Issue 30

G. Zucca et alii, Frattura ed Integrità Strutturale, 30 (2014) 409-416; DOI: 10.3221/IGF-ESIS.30.49 410 This component function is the ailerons deflection. Being a primary importance actuator for the aircraft controllability, it is connected to both the hydraulic systems for safety reasons. The main parts of the DBA are the piston rod and the external case. Two bronze caps are placed at both ends, and they are fixed in position by means of two retainers. The DBA is hinged to the aircraft by a cylindrical support fixed at one end of the actuator case, named trunnion. The fracture surface was located at the actuator case end on the trunnion side, over the retainer (Fig. 1). This paper illustrates the failure analysis of the aforementioned actuator. Figure 1 : Rupture position. I NSTRUMENTS ptical examination was carried out using a Leica M 205 C microscope. Microfractographical evidences were acquired by a Gemini Ultra Plus Field Emission Scanning Electron Microscope (FESEM) equipped with an INCAx-Sight Oxford Instruments Xray energy dispersive spectroscopy (EDS) to perform a semi-quantitative microanalysis exam. Microstructural examination was made using a Leica CTR 6000 metallographic microscope, whereas a PANalytical Axios Max to perform X-ray Fluorescence Spectroscopy was used to determine the chemical composition of the forging. Hardness measurements were carried out with A200 Hardness Rockwell Tester Officine Galileo and Leica VMHT Auto. Metrologic measurements were performed using Konica Minolta RANGE 7 3D scanner. FEA was carried out by ANSYS 14.0 software program. R ESULTS Visual and Optical observation. he cap was found entangled inside the detached fracture surface and some force was needed to remove it (Fig. 2). However, no damages were produced in this operation. The two fracture surfaces showed the same features. The fracture started from the external surface, and propagated toward the internal one. The fracture surface was divided in two zones, named A and B (Fig. 3). Zone A was rough, dull, characterized by coarse grains and it was oriented at about 45° to the transversal section. Moreover, a plastic deformation, associated to the final phase of the failure, was O T