Papers by Author: Ciro Santus

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Authors: Emilio Valentini, Alessio Benincasa, Ciro Santus
Abstract: This paper shows a large validation activity of the strain gage Hole Drilling Method. The residual stress measurements can not be validated easily, unless with Round Robin activity and/or comparison with other residual stress measurements such as X-ray diffraction. An accurate validation procedure is reported in the present paper, using abending test rig. The bending stress experimentally simulated a residual stress (known with uncertainty lower than 1%) that was considered as the reference stress distribution. The results showed very accurate measurement in terms of relaxed strain distributions, that were compared with the prediction obtained with the Influence Function technique. The differences were in the order of 0.5 microepsilon as standard deviation on a large number of tests. The bending stress prediction was consequently very accurate and the stress differences were as small as 1 MPa showing the accuracy potentiality of the method.
Authors: M. Beghini, Ciro Santus, Emilio Valentini, A. Benincasa
Abstract: The Hole Drilling Method introduces a hole in a (residual) stressed volume of material, typically a metal, then a stress concentration follows. A portion of the volume near the hole can experience a stress concentration and then plasticity. The relaxed strains measured by the rosette strain gage grids are then affected by this plasticity volume especially when the residual stress is quite large with respect to the material yield stress. This is the so called Hole Drilling Plasticity Effect. The authors recently proposed a numerical procedure to correct this perturbation effect and retrieve more accurate residual stress components values. An experimental validation of this correction procedure is reported in the paper.
Authors: Ciro Santus, L. Bertini, M. Beghini
Abstract: The present paper proposes a new test rig to perform fretting fatigue tests on a shrinkfitted shaft assembly. A shrink-fitted shaft is put under rotating bending by means of an eccentric offset at one end. The shaft is driven near to its first resonance condition to significantly reduce the required force to produce bending. Test parameters are the imposed bending stress amplitude, and the hub radial pressure obtained through conical fitting. The proposed apparatus allows for changing bending stress amplitude and hub pressure to generate fretting fatigue tests at different conditions. In particular, the role of slip amplitude in fretting fatigue can be investigated. At the present stage the proposed apparatus is under construction at the Mechanical Department of the University of Pisa.
Authors: Michele Barsanti, M. Beghini, Ciro Santus, Alessio Benincasa, Lorenzo Bertelli
Abstract: The ring-core method allows the determination of residual stresses at high depth from the surface. The numerical calculation integral method, commonly used for the hole-drilling, can also be applied to the ring-core. The integral method coefficients were obtained for several depth steps after axial-symmetric FE simulations with harmonic load. These coefficients were then validated with a 3D finite element model. Finally, an application was reported, showing the performance of the Tikhonov regularization on experimental data.
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