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A B S T R A C T R I~ S U M I ~Fatigue tests were carried out on notched microconcrete beams subjected to three-point bending tests in a saturated atmosphere.The feature of the crack growth was studied by means of the replica technique associated with scanning electron microscopy, in conjunction with the measurement of the crack mouth opening displacement (CMOD). Two domains must be distinguished in which the fatigue can be considered, depending on the upper boundary of the cyclic load. Beyond a given threshold for the upper boundary of the cyclic load, the first cycle induces an actual crack at the tip of the artificial notch. Observations of fatigue crack propagation are presented in that case and compared with previous investigations in static tests. The influence of the load level on the crack growth rate is discussed. Des essais &fatigue ont dtd rdalise's sur des @rouvettes encoch&s de microbdton, en flexion trois points sous atmo

SUMMARYIn this paper, the problem of delay‐dependent robust L2 −L ∞  (energy to peak) control for a class of uncertain fuzzy descriptor systems with time‐varying delay is investigated. The parametric uncertainties are assumed to be of a linear fractional form involving all system matrices. First, a delay‐dependent criterion is given in terms of LMIs to guarantee that the fuzzy descriptor system is regular, impulse free, and stable. Based on this criterion, a state fuzzy feedback controller is designed to ensure that the closed‐loop system is regular, impulse free, and robustly stable with a prescribed L2 −L ∞  performance satisfied for all admissible parameter uncertainties. Numerical examples are given to show the effectiveness of the proposed approach. Copyright © 2011 John Wiley & Sons, Ltd.

The problem of sliding-mode control (SMC) with dissipativity for a class of time-delay Takagi-Sugeno fuzzy singular systems is investigated. The system is subject to uncertainties and input non-linearity. Based on an integral sliding surface, a delay-dependent criterion is developed in terms of linear matrix inequalities, which ensures the sliding mode dynamics to be robustly admissible and strictly (Q, S, R)-dissipative. Moreover, an SMC law is established such that the reachability of the specified sliding surface is guaranteed. Finally, the validity and applicability of the proposed approach are illuminated by two simulation examples.