Abstract:The proposed paper discusses the design and characterization of a soft minia ture Magneto-Rheological (MR) shock absorber. In particular, the final application con sidered for the insertion of the designed devices is a controllable variable stiffness sole for patients with foot neuropathy. Such application imposes particularly challenging con straints in terms of miniaturization (cross-sectional area #1.5 cm 2 , height # 25 mm) and high sustainable loads (normal loads up to 60 N and shear stresses at the foot/device interface up to 80 kPa) while ensuring moderate to low level of power consumption. Initial design considerations are done to introduce and justify the chosen novel configu ration of soft shock absorber embedding a MR valve as the core control element. Suc cessively, the dimensioning of two different MR valves typologies is discussed. In par ticular, for each configuration two design scenarios are evaluated and consequently two sets of valves satisfying different specifications are manufactured. The obtained proto types result in miniature modules (external diam. # 15 mm, overall height # 30 mm) with low power consumption (from a minimum of 63 mW to a max. of 110 mW) and able to sustain a load up to 65 N. Finally, experimental sessions are performed to test the behaviour of the realized shock absorbers and results are presented.

Magneto-Rheological Fluids (MRFs) are smart materials whose physical properties can be controlled by an exciting magnetic field. MRFs are described as Bingham plastics with variable magnetic field dependent yield stress. Thanks to their particular features, MRFs have been largely employed to realize controllable power dissipating devices and, among them, regulable valves without moving parts. The most commonly configuration used for MRF based valves consists on fluid flow through an annular duct. The conception of such valves implies to deal with different physics. In particular, the magnetic circuit is usually designed and verified by mean of FE (Finite Element) analysis, while the duct geometry is usually dimensioned using an approximated formula based on fluid flow between parallel plates.In the presented work, a complete and detailed derivation of the analytical model is discussed in order to describe the flow of MRFs through an annulus using an approximate parallel plate geometry. Successively, the Bingham-Papanastasiou regularization is chosen as the mean to accurately describe the continuous non-linear yield stress and shear dependent viscosity of a commercially available MRF and it is then implemented into a FE software. This step allows to built a complete multiphysics problem for the design of MRFs based devices.Results obtained from the analytical model and FE analysis are then compared and the different steps in the proposed approaches are validated.

An innovative design of a Large Angle Flexure Pivot (LAFP) is described. It combines the advantages of flexure mechanisms while surpassing one of their few flaws, small displacement strokes. The LAFP design exceeds these angular limitations to reach a deflection of 180° (±90°). The centre shifts laterally by less than ±35 μm throughout the full rotation range. The LAFP is meant to be mounted in pairs, coaxially and with the payload between them. The intended application of the LAFP is to angularly guide an optical component in a space environment for future science missions operating in a cryogenic environment. A dedicated performance test bench was developed and manufactured to test the pivot characteristics notably the lateral shift using Eddy current sensors. The test bench incorporates a representative dummy payload for mass and inertia. Extensive FEM analysis has been performed to validate the design at component level and further analysis with the pivots mounted with a representative payload on a test bench for random vibration, shock and thermal cycling environment. The second test bench for the vibration and shock tests has been manufactured incorporating a simplified launch locking device. The performance tests have confirmed a lateral shift of less than ±35 μm over an angular range of ±90°. The pivots have been successfully tested and survived vibration loads for high level sine at 24 g and random vibration at 12 grms in all three directions.

Cohesiveness is one of the most important characteristics of grain to obtain high-quality pasta. It is strictly linked to the rheological properties of dough, in which gluten network confines starch, avoiding the end product to become gluey after boiling. The present rheological study was performed using a Chopin alveograph, that is a non-conventional mechanical equipment suitable to monitor very low biaxial strains. This work aims at evaluating the reliability and reproducibility of the UNI 10453 rheological standard method. A mathematical model is also proposed to investigate the dependence either of the alveographic indexes or the strain energy on grain composition in wheat grain blends.

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