Springs of vibrating screens are prone to fatigue induced failure because they operate in a heavy duty environment, with abrasive dust and under heavy cyclic loads. If a spring breaks, the stiffness at supporting positions changes, and therefore the amplitude of motion and the static and dynamic angular inclination of deck motion also change. This change in the amplitude and in the inclination of motion produces a reduction in separation efficiency. Available models are useful to determine motion under nominal operating conditions when angular displacement is not significant. However in practice there is significant angular motion during startup, during shutdown, or under off-design operating conditions. In this article, a two-dimensional three-degree-of-freedom nonlinear model that considers significant angular motion and damping is developed. The proposed model allows the prediction of vibrating screen behavior when there is a reduction in spring stiffness. Making use of this model for an actual vibrating screen in operation in industry has permitted determining a limit for spring’s failure before separation efficiency is affected. This information is of practical value for operation and maintenance staff helping to determine whether or not it is necessary to change springs, and hence optimizing stoppage time.

Up to now, model updating methods based on forced responses and local matrix sensitivities use both experimental and analytical quantities (FRFs and model impedance matrices) all evaluated at the same frequency(ies). However, this approach does not consider that between a reference system (the experimental model) and a perturbed one (the initial finite elements model), it exists a shift along the frequency axis that can be estimated using the Frequency Domain Assurance Criterion. In this paper, a model updating method based on this observation is introduced. It can be interpreted as a generalisation of the existent techniques.

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