PSI - Issue 24

Filippo Cianetti et al. / Procedia Structural Integrity 24 (2019) 526–540 Author name / Structural Integrity Procedia 00 (2019) 000–000

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(a)

Fig. 2: Process Flow Chart

The discussion will follow a thematic division, first of all dealing with the dynamic problem, passing through the experimental validation of the model and the load spectra, up to the stresses, then the proper aspects of fatigue that will be addressed in the frequency domain.

2. Dynamic Representation and Experimental Validation

This section describes the steps that represent the core of the work, according to an approach, dear to the authors Braccesi et al. (2005, 2008, 2018b); Cianetti et al. (2019); Zucca et al. (2018), in which a proper and e ffi cient use of finite elements (FEM), coupled with simple calculation tools, allows the component to be represented in a streamlined and e ff ective manner as a dynamic system.

2.1. Wohler Curve and Material Model

The frame is an assembly of two parts (Fig. 4 (a)), CNC machined from solid billet of two di ff erent aluminum alloys: 6061 T6 for the green part, and 7075 T6 for the gray one (Fig. 4 (a)). In Tab. 1 the mechanical characteristics of interest are reported, from which starting from the ultimate tensile stress, ( S ut ) through the (1) and the (2) have been estimated the stress value at 10 3 and at 5 · 10 8 cycles, respectively the low cycle fatigue limit and the endurance limit conventionally used for aluminum alloys Budynas and Nisbett (2006); Collins and Smith (2010). S 10 3 = 0 . 7 S ut (1) S e = S 5 10 8 = 0 . 3 S ut (2) The curves shown in Fig. 3 are the results of equation: S f = aN b (3)