Ti6Al4V metal cutting chip formation experiments and modelling over a wide range of cutting speeds

Measured forces, chip geometry and tool temperatures from machining a mill annealed Ti6Al4V at cutting speeds mainly from 1 to 100 m/min, but in some cases down to 0.1 m/min, are reported, as well as mechanical testing of the material. Finite element simulations with inputs the measured flow stress, and subsequently a small high temperature strain hardening recovery correction, and a failure model calibrated from the cutting tests at speeds from 1 to 10 m/min, give satisfactory agreement with the higher speed tests once surface strain hardening and damage from the previous pass of the tool are taken into account. This paper’s originality is firstly to show that more complicated flow stress models involving large strain softening are not needed provided shear failure is included; and secondly its failure model: this proposes a non-zero failed shear stress depending on local pressure and temperature. The simulations provide relations between tool mechanical and thermal loading and cutting conditions to aid process improvement

IKO: A Five Actuated DoF Upper Limb Exoskeleton Oriented to Workplace Assistance

IKerlan’s Orthosis (IKO) is an upper limb exoskeleton oriented to increasing human force during routine activity at the workplace. Therefore, it can be considered as a force-amplification device conceived to work in collaboration with the human arm and implementing biomimetic principles. The aim of the proposed design is to find the best compromise between maximum reachable workspace and minimum moving mass, which are the key factors for obtaining an ergonomic, wearable exoskeleton. It consists of five actuated degree of freedom (DoF) to move the human arm and three non-actuated DoF between the back and shoulder to allow relative displacement of the sterno-clavicular joint. Conventional electrical motors are used for most of the DoF and pneumatic muscles for one of them (forearm rotation). Power transmission is based on Bowden cables. This paper presents the IKO design, the mechanical structure of a first prototype and the redesign process from an aesthetic point of view. Controller set-up and control strategies are also shown, together with dynamic performance from experimental results