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International audience; L-stubs are commonly used to model the tensile parts of ring flange bolted connections. Contact between opposite flanges has a significant effect on the elastic and plastic behaviour of these tensile joints. In the present paper, the effects of contact between flange plates are modelled via a refined beam model which has been previously applied with success to represent the elastic behaviour of non-preloaded L-stubs and T-stubs. Taking into account the behaviour of the flange in the contact area and bolt bending, a model is developed to predict the plastic resistance of L-stub joints. Simplifications are proposed to facilitate the determination of the contact zone and the ultimate resistances corresponding to failure modes involving flange and bolt. The comparison between analytical results with 3D finite element elasto-plastic analyses and experimental tests indicates that the proposed model provides good capacity predictions. Effects of contact, and therefore of the prying force, are particularly important in the case of relatively thin flanges. © 2017

International audience; The condition based maintenance is an increasing challenge for flight control systems. In this paper, a methodology for the diagnosis of a roller screw in an electromechanical actuator is proposed. As this component is critical, its diagnosis is essential to use it on aircrafts. The methodology is based on the extraction of features by identifying a model of the actuator. First, a specific waveform, made of increasing steps of speed, is run on the actuator. Then, the measurements are processed to reduce the noise and the bias of the different sensors. In order to accelerate the identification, an equivalent point is calculated for each step of the waveform. Then, the identification is realized and the identified parameters are gathered in a feature vector. Finally, a model including backlash and deformation of the stem is used to validate the approach and to generate a set of data. The aging is simulated by making assumptions on the evolution of parameters. Classification is made by using k-Nearest Neighbors (kNN). Performances of the algorithm on this application are evaluated in terms of precision and robustness.

International audience; Faced with an increasingly fast-changing market, airplane manufacturers have to reduce the development time of their new programs whilst dealing with more and more complex composite structures. The European project Maaximus (More Affordable Aircraft Structure Lifecycle through eXtended, Integrated & Mature nUmerical Sizing) aims at providing methods and tools to enable the fast development and right-first-time validation of a highly optimized composite airframe. In this context, accurate models of fasteners are crucial to ensure correct structure modeling at a higher level. The present study focuses on the mechanical behavior of a threaded assembly subjected to an axial tensile load. After a review of the state-of-the-art in this domain, the first part of the paper shows what benefits can be expected from explicit simulation for large quasistatic models. Parallelization strategies for High-Performance Computing (HPC) are presented, bringing out the need for consistency between the parallelization strategy and the computation structure. These simulation techniques are then applied to the modeling of a tensile test of a fastener. The results of corresponding experiments for two fastener diameters are presented. A successful correlation between simulations and experiments is found, both qualitatively and quantitatively. This study shows the efficiency of a well-chosen resolution algorithm in a coherent HPC environment for solving large non-linear models.

INSPEC Accession Number: 10364160; International audience; This paper presents ABLE, an innovative exoskeleton for the upper limb currently under development at CEA-LIST Interactive Robotics Unit (Fig 1). Its distinctive high performance mechanical transmissions-screw and cable patented arrangement [9]-and its integrated architecture makes it the very first of its category. The first 4 axis model is described here but more complete models are already planned: a 7 axis model as well as portable versions. Its back-drivable, high efficiency, low inertia actuators provide a high capacity (around 40 N continuous effort at the hand) and allow hybrid force-position control without requiring any force sensor. Its first application is currently a research program in rehabilitation (BRAHMA project) and professional use is already in view. Assistance tasks for disabled persons (carrying a bottle) are also typical tasks to be performed by ABLE as well as intuitive telerobotics, haptic device for VR, and sport training, etc. Furthermore, its versatility and simple design allow industrial versions to become soon available. Fig 1. CEA-LIST 4 axis exoskeleton actuated by screw-and-cable actuators (SCS actuator) I. THE GENESIS OF ABLE-A SHORT STORY OF THE SCS ACTUATOR ABLE exoskeleton is directly related to electrical master-slave manipulator (EMSM) teleoperation technology in which our laboratory has played a historical role. Fig 2 shows a quick summary of well-known pioneering machines [8], [11], [12], [13], [14], [15], [16] illustrated with their mechanical solutions. Model E1Î circa 1954 (ANL/CRL) Joint transmission cable Motors (multiples) Spur gears Model E1Î circa 1954 (ANL/CRL) Joint transmission cable Motors (multiples) Spur gears Joint transmission cable Motors (multiples) Spur gears MA 23 circa 1974 (CEA/La Calhène) Motor Cabstan (positive) Block-and-tackle Joint transmission cable MA 23 circa 1974 (CEA/La Calhène) Motor Cabstan (positive) Block-and-tackle Joint transmission cable Motor Cabstan (positive) Block-and-tackle Joint transmission cable Hand Controller circa 1990 (JPL) Capstan (adherence) e Joint transmission cable Hand Controller circa 1990 (JPL) Capstan (adherence) e Joint transmission cable Capstan (adherence) Capstan (adherence) e e Joint transmission cable Fig 2. Landmarks in torque amplification for back-drivable electrical master-slave telemanipulator (EMSM) The first principle has been used by R. Goertz (ANL) in his E1-E4 and Model M. Motor torque is amplified using high-precision spur gears driving the joints either directly (translation joints) or, like the scheme shows, trough transmission cable (for remote rotation joints). The second is due to J. Vertut and is team (CEA) for the MA 23. Motor