Analysis of the Influence of Bidirectional Journal Bending on the Lubrication Performance of Marine Stern Bearings

Abstract

Abstract. This study establishes a generalized Reynolds equation model that incorporates the bending deformation of the stern shaft journal under combined vertical and horizontal loads. The journal deflection was obtained via finite element analysis, and cubic polynomials were used to construct spatial attitude functions. These fitted expressions were then integrated into the lubrication model to assess the effects of shaft deformation on stern bearing performance. Results show that increasing vertical and horizontal loads lead to a reduction in minimum film thickness, a rise in maximum film pressure with greater unevenness, and a higher friction coefficient. The lubrication regime shifts from hydrodynamic to mixed lubrication, with increased local contact pressure and wear risk. Under equal-magnitude lateral loads, negative horizontal loading (right turning) offers better lubrication than positive loading (left turning), and slight right turning even outperforms straight sailing. The study provides a theoretical basis for analyzing and optimizing stern bearing lubrication performance under shaft deformation.