47 research outputs found
Estimation of mixed-mode stress intensity factors using digital image correlation and an interaction integral
Computer-assisted cartography using topographic properties: precision and accuracy of local soil maps in central Mexico
On some nonlinear inverse problems in elasticity
In this paper, we make a review of some inverse problems in elasticity, in statics and dynamics, in acoustics, thermoelasticity and viscoelasticity. Crack inverse problems have been solved in closed form, by considering a nonlinear variational equation provided by the reciprocity gap functional. This equation involves the unknown geometry of the crack and the boundary data. It results from the symmetry lost between current fields and adjoint fields which is related to their support. The nonlinear equation is solved step by step by considering linear inverse problems. The normal to the crack plane, then the crack plane and finally the geometry of the crack, defined by the support of the crack displacement discontinuity, are determined explicitly. We also consider the problem of a volumetric defect viewed as the perturbation of a material constant in elastic solids which satisfies the nonlinear Calderonâs equation. The nonlinear problem reduces to two successive ones: a source inverse problem and a Volterra integral equation of the first kind. The first problem provides information on the inclusion geometry. The second one provides the magnitude of the perturbation. The geometry of the defect in the nonlinear case is obtained in closed form and compared to the linearized Calderonâs solution. Both geometries, in linearized and nonlinear cases, are found to be the same
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Steerable percussion air drilling system
In the Steerable Percussion Air Drilling System (SPADS), air percussion is used to drill directionally in hard formations. Compared to mud or air powered PDM motors, SPADS offers directional drilling at high penetration rate, reduced mud costs, negligible formation damage, and immediate indication of hole productivity. Field tests turned up problems ranging from tool design to operation procedures; remedies were developed. There is an optimum WOB (weight on bit) at which torque is reasonably low. The hammer was tested at three different line pressures (200, 300, 350 psig) at optimum WOB in granite, limestone, and sandstone