Rigid finite element model of a cracked rotor

Quasi-static numerical study of the breathing mechanism of an elliptical crack in an unbalanced rotating shaft

“…The unbalance has been taken into account considering an eccentric mass m, located at a radial distance e from the center of the shaft, at the same longitudinal position of the crack, and with an angular position, , with respect to the crack. This practice has been carried out by other authors (i. e. Bachschmid et al 2008or Kulesza et al 2012 although in the first case the eccentric mass and crack are located in separate positions along the shaft. For that, the eccentric mass has been placed on the disc situated at different angles (angle of eccentricity ) measured from the position of the crack as shown in Figure 3b).…”

“…A very common unbalance of shafts is due to the presence of eccentric masses: Sekhar and Prabhu (1998), Darpe et al (2004), Patel and Darpe (2008), Qingkai et al (2010), Gyekenyesi et al (2010), Cheng et al (2011) and Kulesza and Sawicki (2012). The unbalance, as mentioned before, modifies the dynamic behavior of the rotating shafts and may hide the presence of the cracks or, on the other hand, can increase their effects.…”

“…The transition between both situations produces partial opening or closing of the crack when the static deflection dominates the performance of the rotating shaft. The partial opening/closing of the crack has been studied, numerically or analytically, by different authors: Jun et al (1992), Dimarogonas and Papadopoulos (1983), Darpe et al (2004), Papadopoulos (2004), Patel and Darpe (2008), Bachschmid et al (2008), Al-Shudeifat and Butcher (2011) or more recently by Morais et al (2012), always considering an aligned and balanced shaft, although recent works pointed out in the direction of considering the breathing of crack in unbalanced shafts, see for example the works of Patel et al (2011), Kulesza and Sawicki (2012), Rubio et al (2012) and Munoz et al (2012). The opening and closing of the crack is very much influenced by the values taken by the Stress Intensity Factor (SIF) at the crack front as the shaft rotates.…”

Review of Recent Advances in the Application of the Wavelet Transform to Diagnose Cracked Rotors

“…Usually these models are based on information extracted from directly measured signals, signal models, and process models, as demonstrated by in [4][5][6]. Vibration methods are based on detecting variations in the response, which are then assigned to a crack.…”

Cracks Detection Using Active Modal Damping and Piezoelectric Components

“…Cracks can be modelled using several approaches [14], for example reduction in element stiffness or pinned joint at crack location [19,26]. Rigid finite element method can be used to model cracks with a set of spring-damping elements of variable stiffness as shown by Kulesza and Sawicki [20]. The approach can be first linear if the crack is supposed to be opened [12] and second non linear if the crack breathing is taken into account [2,9,24].…”