Gear noise evaluation through multibody TE-based simulations

The possibility of estimating noise radiating from a gearbox is essential to achieve valid design solutions in shorter timeframes and to limit the testing phase, especially in those industrial fields, such as automotive, helicopter and wind turbine industry, with a strong demand for gear noise reduction. This paper presents a methodology for the calculation of gear bearing forces, useful for the acoustic analysis of gearboxes and applicable to spur as well as helical parallel gear systems. The methodology is based on the implementation of a procedure for the computation of the dynamic transmission error (DTE) in a multibody environment. The DTE is obtained from the static transmission error (STE), i.e. the static relative displacement between meshing teeth, which is variable along the mesh cycle. The adopted multibody technique enables to overcome the principal drawbacks of FEM, achieving good computational efficiencies, and of analytical models, avoiding to lump the system in one or few degrees of freedom. These goals are reached by means of a user-defined force element, acting as teeth meshing force, which stems from the integration of the multibody software, LMS Virtual.Lab Motion, with an external program specialized in gear meshing analysis. The multibody software captures the system dynamics and includes the nonlinear effects such as gear backlash, bearing clearances and stiffness; the specialized software enables to consider tooth microgeometry, assembly errors, global and contact tooth stiffness and also shaft deflections. The new feature introduced by the proposed technique is the ability to take into account the instantaneous torque with good computational efficiency.