ELASTIC EMBEDMENT SUPPORT: A NOVEL APPROACH TO THE PRELIMINARY DESIGN OF SHAFTS

Abstract

This study discusses the introduction of elastic embedment support in the preliminary design of shafts. The preliminary design of shafts idealizes the supports by considering them mobile articulated support, fixed articulated support, or embedded support. In several cases, these idealizations deviate from reality. While articulated supports produce internal forces, tensions, deflections, and gradients greater than real, embedded supports lead to internal forces, stresses, deflections, and deformation angles lower than real. These deviations in typical shaft design schemes have been corrected with safety factors. This study presents a novel elastic embedment support using a dimensionless stiffness coefficient to improve the preliminary shaft design and obtain more adequate results, with shaft dimensions more suitable for the acting loads. These results were assessed with the conventional analysis schemes for three bearing types for shaft lengths between 200 to 1000 mm. Contrasted to the conventional model articulating both shaft supports, the bending moment is significantly lower when considering the elastic embedment. The maximum bending moment from the conventional model is 65% higher than that obtained with the elastic embedment for single-row ball bearings, 58% higher for tapered roller bearings, and 40% higher for double-row ball bearings. Furthermore, the bending moment increases its significance with the shaft length. Thus, considering the bearing stiffness for the three rolling bearing types results in shaft support bending moments of 10 to 21% of the maximum bending moment obtained from the conventional model. These differences significantly impact the fatigue life estimation of the shaft because the deflection obtained from the conventional model is higher than that for the elastic embedded support, which impacts the fatigue life estimation of the shaft. Therefore, it is concluded that using the elastic embedment support in the preliminary shaft design, reduces the uncertainty in the results, leading to lower security coefficients. Keywords: Preliminary Shaft Design, Embedded Support, Articulated Support DOI： https://doi.org/10.35741/issn.0258-2724.58.1.47