Comparison of 1D and 3D Spring Models for Valvetrain Dynamics

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Comparison of 1D and 3D Spring Models for Valvetrain Dynamics

Ballard, Helen / Plail, Jonathan / Grinac, Petr

In this paper, a mathematical model for simulating the 3D dynamic response of a valve spring is described. The 3D model employs a ‘geometrically exact’ 3D beam connected between each mass of the discretised mass-elastic system. Shear deformations within the beam are also considered, which makes it a Timoshenko type finite element.Results from the 3D model are compared with results from a more conventional 1D model. To validate the results further, some results are compared with real test data that was gathered during a technical consulting project. In this project, a prototype valvetrain that was originally giving acceptable durability began to wear the spring seats when a new batch of springs were procured and tested. 1D and 3D simulation results were used to help understand the cause of the failure and to make recommendations to resolve the issue.Results showed that the 3D model was able to predict the spring seat loads with greater precision than the 1D spring could. The measured and predicted force traces generally agreeing. However, the magnitude of critical coil clash (impact) loads are consistently under-predicted. This may be due to inaccuracies in the load cell calibration or another missing phenomenon within the mathematical model.