For many applications, direct measurement of forces in mechanical systems is difficult or even impossible, and indirect measurement involving inverse analysis must be adopted. One such application of major industrial relevance is the accurate measurement of contact forces acting on rolling bodies. In this paper, a newly proposed strategy for load identification is applied to an example problem of a rolling disc. Based on strain gauge measurements, the contact force is estimated using finite element analysis. A virtual calibration procedure is introduced in order to reduce the dependency of the results on the spatial discretization. In particular, the sensitivity of the results with respect to finite element discretization, sensor placement and noise is discussed. Numerical results based on synthetic data illustrate the behavior and accuracy of the proposed strategy.
The wheel–rail contact force is an essential parameter in many aspects in railway mechanics, for instance, in rolling contact fatigue analysis. Since the wheel–rail contact force cannot be measured directly, instrumented wheelsets have been developed to collect the radial strains at certain positions on the wheel web. In this paper, an inverse method to estimate the wheel–rail contact force history based on strain measurements is discussed. In the proposed method, the contact force is determined by minimizing the least-squares discrepancy between measured radial strains and corresponding computed strains from a three-dimensional finite-element model of the wheel. The inverse method is compared with the existing method based on direct extraction of the contact force from combinations of measured strains using Wheatstone bridges. Using synthetic data, it is found that the proposed inverse method is insensitive to the eigenmodes of the wheel, as opposed to the existing method. In addition, noise reduction by using Tikhonov regularization and by choosing proper sampling rates are discussed.
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