Friction effects on the load capacity of a column and a hydraulic cylinder

Over the last years, a better comprehension of hydraulic cylinder performance is observed to be a prime objective of many owing to demanding applications. By observing these hydraulic cylinder applications, we see currently proposed models and design criteria do not take into account real factors, and further there are misalignment and boundary conditions in the end supports, mechanism interaction, dust, clearance and imperfections. Since these boundary conditions can develop progressive moments, the ideal simple supported bi-articulated configuration of the actuator is no longer valid, and virtual clamped configuration appears with friction moments that substantially modify the buckling analysis. In a previous work, misalignment effects were studied and discussed. In the present work a study of the influence of friction moments when misalignment effects are deliberately left aside is carried out. In order to separate these two phenomena (friction and misalignment) boundary conditions in a column are analysed. From this analysis, a theoretical and experimental work has been carried out for columns and an actuator characterizing the critical factors that cause the collapse. The aim of this paper is to describe the behaviour of actuators under load capacity with experimental validation when friction moment is taken into account and becomes an unknown variable. Experimental and theoretical results point out the importance and influence of the friction effects in columns and hydraulic cylinders. Then, it is recommended that knowledge of the hydraulic cylinder application to predict its load capacity owing to that direct extrapolation of results from current theories and criterions could lead to incorrect estimations.     

High performance fully plastic actuator based on ionic-liquid-based bucky gel

In a previous paper, we reported the first dry actuator that can be fabricated simply by layer-by-layer casting, using ‘bucky gel’, a gelatinous room-temperature ionic-liquid containing single-walled carbon nanotubes (SWNTs). Our actuator has a bimorph configuration with a polymer-supported internal ionic-liquid electrolyte layer sandwiched by two polymer-supported bucky-gel electrode layers, which allows quick and long-lived operation in air at low applied voltages. In this paper, we propose a new two-step process using a ball-mill method for preparing the casting solution for the bucky-gel electrode in order to improve the performance of the actuator by developing the bucky-gel electrode layer with a high content of SWNTs which are well dispersed in the electrode layer. We measured the displacement and the blocking force of the new bucky-gel actuator fabricated by hot-pressing the prepared electrode and electrolyte layers and analyzed its experimental results by the tri-layer polymer actuator model which was developed by Alici et al. for conducting polymer actuators. We developed the low-voltage driven solid-state actuator that shows the maximum stress and the strain of 4.7 MPa and 1.9%, respectively, which are comparable with any other low-voltage driven solid-state electroactive polymer actuator technology to our knowledge. The advantage of our bucky-gel actuator is not only in its good performance but also in its easy process in fabrication. The present development provides an important step for electromechanical polymer actuator technologies.     

Smart sensors/actuators for biomedical applications: Review

This paper reflects on review of smart sensor activities for biomedical applications. The rise of biotechnology has provided innovative development of new therapies and detection methods for life threatening diseases. As a worldwide research focus, there is especially a strong interest in the use of microsystems in health care, particularly as smart implantable devices. Recent years have seen an increasing activity of hip and knee replacement and other type of implants, which are some of the most frequently performed surgical procedures in the world. Loosening of hip prosthesis is the dominant issue for many patients who undergo a hip arthroplasty. Artificial joints are subject to chronic infections associated with bacterial biofilms, which only can be eradicated by the traumatic removal of the implant followed by sustained intravenous antibiotic therapy. This review focuses on the clinical experience using all kinds of smart implants like orthopedic implants instrumented with strain gauges, retina implant system using image sensors. Technical design improvements will enhance function, quality of life, and longevity of total knee arthroplasty and all other kind of implants. Application of biocompatible nanomaterials in implantable biosensors for continuous monitoring of metabolites is an area of sustained scientific and technological interests.     

形状记忆合金线性驱动器的设计及位移特性分析

为克服传统带有偏置装置形状记忆合金驱动器结构复杂、响应速度慢的缺点,利用形状记忆合金(Shape memory alloy,SMA)的单程形状记忆效应,设计并制造一种不带偏置装置且可实现双程运动的线性驱动器,该驱动器由两根形状记忆合金丝、滑轮、部件、导轨、支座及固定螺钉组成。接着基于Brinson一维本构方程及转换方程,推导出两根SMA丝在不同条件下的应变表达式;提出将马氏体相变应力看作体力,分析温度变化与驱动器位移的关系及外载荷变化对驱动器最大位移的影响。对计算结果进行试验验证,结果表明,所设计驱动器可实现往复双程运动;随着SMA丝温度的升高所获得的位移呈非线性增大,当温度超过奥氏体转变结束温度Af,位移达到最大,而初始化过程获得的最大位移为正常运动的一半;增大载荷,驱动器的最大位移逐渐减小,当载荷达到51.0 N时,驱动器停止运动,即位移减小为零。     

Piezoelectric patch control using an integral equation approach

Closed-loop displacement feedback control for a beam using bonded piezoelectric patch sensors and actuators is considered. It is shown that there is an equivalence between the eigensolutions of the differential equation formulation of the problem and the eigensolutions of a certain integral equation. It is also shown that a pair of aligned oriented sensors and actuators generate an orthogonal set of eigenfunctions. The natural frequencies are found numerically for a cantilevered beam using the integral equation.     

Dielectric elastomer film with anisotropic actuation deformation on film plane

A new dielectric elastomer (DE) film, which was able to show anisotropic large plane deformation actuated by an external electric field, was designed and synthesized. Specifically, an asymmetric di-vinyl monomer cyclohex-3-enylmethyl acrylate (CEA) was incorporated into the middle block of poly(styrene-b-butyl acrylate-b-styrene) as potential crosslinking points. By widely used UV curing technique through a mask, the DE films could be locally hardened any area one selected. This could break the symmetry of the actuation deformation on the DE film plane, maximizing the deformation in a given direction while the actuation area strain remained unchanged. The actuation strain_y/strain_x reached 2.3, strain in x direction was 10.3% while in y direction was 23%, when the DE film of S(BA-ran-CEA)S with 2.5 mol % CEA incorporated was locally hardened in the form of soft and hard belt of 1 mm width alternatively along y direction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48795.     

能动薄镜面的有限元分析

介绍了我们采用有限元法对能动薄镜面进行计算分析的一些结果：（１）利用“Ａｌｇｏｒ Ｆｅａｓ”有限元软件系统建立了直径厚度比为６２．４：１薄镜面的有限元模型，并利用该模型进行了以下的工作；（２）计算了在重力作用下，不同驱动器支撑数量时薄镜自身的变形量；（３）计算了该镜面在不同的驱动器排布方式下拟合准Ｚｅｒｎｉｋｅ多项式几个低阶象差时薄镜面的应力分布情况和薄镜对不同象差的拟合误差，并从得到的计算数据中     

Electrochemical actuation properties of a novel solution-processable polythiophene

A solution-processable polythiophene, poly((E)-4,4″-didecoxy-3′-styryl[2,2′:5′,2′′]terthiophene) demonstrated large electrochemically induced strain up to 11.5%. Free-standing polymer films were characterised using four-point probe conductivity measurements, cyclic voltammetry and electrochemical actuation measurements. Conductivities of ∼6 × 10⁻⁵ S/cm (reduced state) or ∼1-2 S/cm (oxidised state) were measured. Well-defined polymer oxidation-reduction responses were observed in both the propylene carbonate and acetonitrile electrolytes, with electrochemical efficiency of >80% observed under ideal conditions. Results obtained suggested that the actuation strain approximately correlates with the size of the anion (i.e. TFSI > PF₆⁻ > ClO₄⁻) used in the electrolyte. The largest strain ∼11.5% was obtained in an electrolyte solution consisting of 0.1 M Li.TFSI in acetonitrile. The maximum strain attainable increased with an increase in the anodic potential applied and decreased with an increase in stimulation frequency or increasing mechanical load. Such functionalised polythiophene material has the combined advantage of solution processability and the ability to produce large strain.     

Electro-thermal behaviour of Al/SiC clamped-clamped beams

The electro-thermal behaviour of silicon carbide (SiC) clamped-clamped (bridge) resonators actuated by aluminium (Al) electrodes has been studied. The structures with a beam length of 150 μm, beam width of 60 μm and thickness of 2 μm have been fabricated and actuated electrothermally. The influence of two electrode configurations, slab and u-shaped, on the vibration magnitude at resonance has been compared. In addition, the effect of the electrode length on the vibration amplitude, maximum temperature and the temperature distribution in the beam has been investigated. The vibration amplitude is measured to be higher in the slab configuration compared to the one obtainable in the u-shaped layout and has been attributed to the fact that the slab layout induces a higher maximum and average temperature through the resonator hence enhancing the vibration amplitude of the beam. For both configurations examined, the electrode dimensions and location have been shown to play an important role in maximizing the vibration amplitude of the resonator.