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Journal of the Brazilian Society of Mechanical Sciences and Engineering
Print version ISSN 1678-5878
RITTO, T. G.; SOIZE, C. and SAMPAIO, Rubens. Stochastic dynamics of a drill-string with uncertain weight-on-hook. J. Braz. Soc. Mech. Sci. & Eng. [online]. 2010, vol.32, n.3, pp.250-258. ISSN 1678-5878. http://dx.doi.org/10.1590/S1678-58782010000300008.
A drill-string is a slender structure that turns and drills into the rock in search of oil. There are many sources of uncertainties in this complex dynamical system. However, this article is concerned only with uncertainties in the weight-on-hook, which is the supporting force exerted by the hook at the top. A probabilistic model is constructed for the random variable related to the weight-on-hook using the Maximum Entropy Principle, and the random response of the system is computed through Monte Carlo simulations. The idea is to understand how the performance of the system (which is measured by the rate of penetration) is affected by the uncertainties of the weight-on-hook. The continuous system analyzed is discretized by means of the Finite Element Method and a computer code is developed to do the simulations.
Keywords : random weight-on-hook; uncertainty modeling; stochastic dynamics; drill-string dynamics; reduced models.