A family of higher-order single layer plate models meeting Cz0C^0_z -- requirements for arbitrary laminates

In the framework of displacement-based equivalent single layer (ESL) plate theories for laminates, this paper presents a generic and automatic method to extend a basis higher-order shear deformation theory (polynomial, trigonometric, hyperbolic, ...) to a multilayer $C^0_z$ higher-order shear deformation theory. The key idea is to enhance the description of the cross-sectional warping: the odd high-order $C^1_z$ function of the basis model is replaced by one odd and one even high-order function and including the characteristic zig-zag behaviour by means of piecewise linear functions. In order to account for arbitrary lamination schemes, four such piecewise continuous functions are considered. The coefficients of these four warping functions are determined in such a manner that the interlaminar continuity as well as the homogeneity conditions at the plate's top and bottom surfaces are {\em a priori} exactly verified by the transverse shear stress field. These $C_z^0$ ESL models all have the same number of DOF as the original basis HSDT. Numerical assessments are presented by referring to a strong-form Navier-type solution for laminates with arbitrary stacking sequences as well for a sandwich plate. In all practically relevant configurations for which laminated plate models are usually applied, the results obtained in terms of deflection, fundamental frequency and local stress response show that the proposed zig-zag models give better results than the basis models they are issued from

Requirements for artificial muscles to design robotic fingers

International audienceThis work is part of the ProMain project that concerns the modeling and the design of a soft robotic hand prosthesis, actuated by artificial muscles and controlled with surface Electromyography (EMG) signals. In a first stage, we designed a robotic finger based on the equivalent mechanical model of the human finger. The model takes into account three phalangeal joints, flexion and extension movements are studied. The robotic finger has three Degrees of Freedom (DoF). The finger is designed to be under-actuated and driven by tendons, i.e. only one servo motor actu-ates the whole finger, and the motor is coupled to the finger mechanism through two flexible wires. As the aim is to design a robotic hand prosthesis that uses artificial muscles, we propose and carry out two experiments to characterize the specifications of the actuator. The first experiment measures the pinch force of the human finger, and the second measures the achieved force using our robotic finger and five different servo motors. It allows us to enhance experimental results with the mathematical model of the finger, to identify the requirements of the artificial muscle

An efficient C1 finite element with continuity requirements for multilayered/sandwich shell structures

This paper deals with a new triangular finite element to analyze the behaviour of multilayered shells. This element is based on a refined kinematical model and uses both conforming finite element method and higher-order approximations. Including a nonlinear distribution with respect to the normal co-ordinate for the transverse shear stresses and continuity requirements between layers for both transverse shear stresses and displacements, this model does not require any shear correction factors. Moreover, it allows to satisfy the boundary conditions at the top and bottom surfaces of the shell. Various strain expressions available for shells are discussed. Although the program is able to calculate arbitrary shell shapes, present shell element performances are evaluated here in comparison with available analytical tests issued from literature. The present finite element shown very good responses on the classical shell test: pinched cylinder, pinched hemispherical shell, Scordelis–Lo roof. Finally, results in linear static, free vibrations and transient dynamic response for multilayered shells show the efficiency of this new shell finite element

New reference solutions and parametrics study for multilayered cylindrical shell

This work deals with the performances of a refined shell model for modelizing cylindrical multilayered deep or shallow, thin or thick shells. To this end, new 3D analytical solutions are built from the well known Ren cylindrical shell panel and stand for reference solutions. Next, a parametric study varying the shell geometry (radius of curvature, thickness, curve side length of the panel) and the number of layers is carried out numerically using a C1 finite element based on the present shell model. Numerical results are then compared to the new set of reference solutions established for laminates of 1, 2, 3 and 5 layers. Finally, use restrictions according to the shell geometry can be done. Moreover, indications about shell curvature can be obtained considering the ratio between radius and curve length

Analysis of laminated doubly-curved shells by alayerwise theory and radial basis functions collocation, accounting for through-the-thickness deformations

In this paper, the static and free vibration analysis of laminated shells is performed by radial basis functions collocation, according to a sinusoidal shear deformation theory (SSDT). The SSDT theory accounts for through-the-thickness deformation, by considering a sinusoidal evolution of all displacements with the thickness coordinate. The equations of motion and the boundary conditions are obtained by the Carrera's Unified Formulation, and further interpolated by collocation with radial basis functions

Making the link between critical appraisal, thinking and analysis

Nursing has become an all-graduate profession; as such, student nurses must develop their skills of critical analysis. The need to develop critical analytical thinking has been identified as the single most important skill in undergraduate education and reaching the academic requirements of level six study. In degree-level healthcare programmes, students are frequently asked to complete a structured critical appraisal of research. This paper examines how critical appraisal activities can be an opportunity for students to develop transferable critical thinking skills. Critical appraisal teaches objectivity, reflection, logic and discipline, which encourage students to think critically in both theory and practice.N/

Control of wrist movement in deafferented man: evidence for a mixed strategy of position and amplitude control

© 2017 The Author(s) There is a continuing debate about control of voluntary movement, with conflicted evidence about the balance between control of movement vectors (amplitude control) that implies knowledge of the starting position for accuracy, and equilibrium point or final position control, that is independent of the starting conditions. We tested wrist flexion and extension movements in a man with a chronic peripheral neuronopathy that deprived him of proprioceptive knowledge of his wrist angles. In a series of experiments, we demonstrate that he could scale the amplitude of his wrist movements in flexion/extension, even without visual feedback, and appeared to adopt a strategy of moving via a central wrist position when asked to reach target angles from unknown start locations. When examining the relationship between positional error at the start and end of each movement in long sequences of movements, we report that he appears to have three canonical positions that he can reach relatively successfully, in flexion, in extension and in the centre. These are consistent with end-point or position control. Other positions were reached with errors that suggest amplitude control. Recording wrist flexor and extensor EMG confirmed that the flexion and extension canonical positions were reached by strong flexor and extensor activity, without antagonist activity, and other positions were reached with graded muscle activation levels. The central canonical position does not appear to be reached by either maximal co-contraction or by complete relaxation, but may have been reached by matched low-level co-contraction

Radial Basis Functions collocation and a Unified Formulation for bending, vibration and buckling analysis of laminated plates, according to a variation of Murakami's zig-zag theory

In this paper, we propose to use the Murakami's zig-zag theory for the static and vibration analysis of laminated plates, by local collocation with radial basis functions in a finite differences framework. The equations of motion and the boundary conditions are obtained by the Carrera's Unified Formulation, and further interpolated by a local collocation with radial basis functions and finite differences. This paper considers the analysis of static deformations, free vibrations and buckling loads on laminated composite plates