IPS - ESTS – DEM - Comunicações em congressos
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Browsing IPS - ESTS – DEM - Comunicações em congressos by Author "Baptista, Ricardo"
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- Automatic fatigue crack propagation calculation on welded high strength steelsPublication . Baptista, Ricardo
- Design optimization of cruciform specimens for biaxial fatigue loadingPublication . Baptista, Ricardo; Cláudio, Ricardo; Reis, L.; Guelho, I.; Freitas, M.; Madeira, J. F. A.In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS) method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests.
- Modelling of a prosthetic hand featuring individual grip on each one of the five fingersPublication . Rosa, Joana; Sousa, Joana; Baptista, RicardoThe aim of this work is to develop a prosthetic hand with individual grip functionality on each finger, reproducing the natural movement of the hand. After the preparation of sketches and creating a virtual model, the final model shows dimensions: 124,04 mm × 246,57 mm × 38 mm (palm-covered) and an estimated weight of 1 kg, with all components. Afterwards was executed the functioning simulation of the prosthetic hand, elaborated prehension experiments were made using a metal cylinder, a rubber ball and a wooden pencil, with the tool Motion Study from Solidworks. However in the tests with the pencil was difficult to reach equilibrium, tells us that the hand is not functional with width smaller objects, because they require a bigger finger precision. Was made the study of forces applied in links thinner in different prehensions using the Finite Element Method. This study concluded that the aluminum alloy 2024 T3 has enough resistance to the stresses incurred for the grasping. Finally, was made an estimate cost of production for a single working prototype prosthetic hand. The result was 1325€.