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Loosening of press - fitted pivots
Dobiáš, Jiří ; Höschl, Cyril
If a press-fitted clamped-free pivot is exposed to alternating loading at its free end while the forces act normal to its central axis, a gradual global displacement of the pivot in the axial direction may occur under some circumstances.
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On the solution of a natural vibration of cylindrical shells in interaction with flowing fluid
Zolotarev, Igor ; Pelletier, D.
The present paper is a contribution to the solution of a natural vibration of circular cylindrical shells in interaction with flowing inviscid fluid. The mathematical model of the studied system contains general boundary conditions of the shell for ends clamped elastically and allows to use the method of solution are based on the [1,2,4,5]. A new more accurately algorithm for calculation of the action of flowing fluid on the vibrating surface of the shell and frequency-modal properties of the studied system there are presented. Obtained results correspond to the earlier calculations of the natural frequencies and its variations on the flow velocities [4,5].
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Critical stress for crack propagation in concrete
Náhlík, Luboš ; Knésl, Zdeněk
Concrete is modelled as a two-phase material. Behaviour of a crack with its tip on the interface between two different materials - hardened cement paste (matrix) and aggregate (particle) - is studied. In contrast to cracks in homogeneous materials the stress singularity for a crack terminating at the interface is of the type r -lambda, where the value of the stress singularity exponent, lambda, is in the interval 0 < lambda < 1. Than classical fracture mechanics theory and criterion cannot be applied. In the paper a new stability criterion is used to estimate the critical stress for the intersection of coarse aggregate particles.
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