Development and Implementation of an Anthropomorphic Underactuated Prosthesis with Adaptive Grip

This paper describes the design of a prosthetic hand for wrist amputations. The mechanism considers the use of three actuators: one each for the movement of the little finger, annular finger, and middle finger. The second actuator controls the index finger, and the third controls the thumb. The prototype is considered relevant as it is able to move the distal phalanx in all fingers; the little, annular, and middle fingers are able to adapt to the shape of the object being gripped (adaptive grip). The sequence of movements achieved with the thumb emulate the opposition/reposition and flexion/extension movements, commanded by a single actuator. The proposed design was built by additive manufacturing and effortlessly achieves a large number of grips. Additionally, the prosthesis could perform specific movements, such as holding a needle, although this grip demands higher precision in the control of the fingers. Due to the manufacturing method, the prosthesis weighs only 200 g, increasing to 450 g when the actuators are included, therefore weighing less than an average adult’s hand

DEM–FEA estimation of pores arrangement effect on the compressive Young’s modulus for Mg foams

This work reports the study of the effect of the pore arrangement on the compressive behavior of Mg foams with regular pore size and porosities ranging from 25% to 45%. Pore arrangements were modeled using Finite Element Analysis (FEA), with random and ordered models, and compared to the estimations obtained for a previous work. The coordinates of the random pore arrangements were firstly generated using Discrete Element Method (DEM), and used in a second stage for modeling the pores by FEA. Estimations were also compared to the experimental results for Mg foams obtained by means of powder metallurgy. Results show important drops in the Young’s moduli as the porosity increases for both, experimental results and FEA estimations. Estimations obtained using ordered pore arrangements presented significant differences when compared to the estimations acquired from models with random arrangements. The randomly arranged models represent more accurately the real topologies of the experimental metallic foams. The Young’s moduli estimated using these models were in excellent agreement with the experiments, whilst the estimations obtained using ordered models presented relative errors significantly higher. The importance of the use of more realistic FEA models for improving the predicting ability of this method was probed, for the study of the mechanical properties of metallic foams