Unbuckling of superelastic shape memory alloy columns

2018 ◽  
Vol 29 (7) ◽  
pp. 1360-1378 ◽  
Author(s):  
Ryan T Watkins ◽  
John A Shaw
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Compressive Load ◽  
Bending Moment ◽  
Load Level ◽  
Stiff Material ◽  
The Stability ◽  
The Right ◽  
Novel Applications ◽  
Feasible Space

Our recent buckling experiments on superelastic shape memory alloy columns (initially straight rods and tubes) discovered that during axial shortening, certain specimens bent (buckled) at a critical compressive load and then, surprisingly, straightened (unbuckled) at a larger compressive load. This “buckling–unbuckling” phenomenon, defined here as the deviation from and then return to a straight configuration during monotonic loading, is not only an intriguing phenomenon (contrary to the post-buckling behavior of conventional materials) but also presents the possibility for novel applications. This work aims to provide a clearer understanding of when and why unbuckling occurs, presenting the experimental observations of this phenomenon and the stability analysis of a modified Shanley column model that captures the unbuckling behavior. Unbuckling behavior is shown to be a consequence of a secondary branch that deviates from the principal path at a low-load level (critical buckling load), but reattaches to the principal path at a higher load level (unbuckling load). The analysis shows that unbuckling behavior can only occur for certain combinations of column geometries and nonlinear (stiff–soft–stiff) material laws, that is, relatively stout columns with the right sequence of softening/stiffening to create the necessary restorative bending moment to reset the column to a straight configuration. The feasible space is defined by closed-form bounds on geometric and material parameters, along with a sensitivity analysis of these parameters on the amplitude of unbuckling.

Effect of deformation on the stability of stress-induced martensite in nanocrystalline NiTi shape memory alloy

2014 ◽  
Vol 131 ◽  
pp. 233-235 ◽  
Author(s):  
Xiaobin Shi ◽  
Mengying Yu ◽  
Fangmin Guo ◽  
Zhenyang Liu ◽  
Daqiang Jiang ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Shape Memory Alloy ◽  
The Stability

Smart Crash Management by Switching the Crash Behavior of Fiber-Reinforced Plastic (FRP) Energy Absorbers With Shape Memory Alloy (SMA) Wires

2013 ◽  
Author(s):  
Moritz Hübler ◽  
Sebastian Nissle ◽  
Martin Gurka ◽  
Sebastian Schmeer ◽  
Ulf Paul Breuer
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Essential Element ◽  
Load Level ◽  
Switching Behavior ◽  
Fiber Reinforced ◽  
Reinforced Plastics ◽  
Reinforced Plastic ◽  
Energy Absorbers ◽  
Energy Absorbing

In this paper two innovative concepts for adjustable energy absorbing elements are presented. These absorbers can serve as an essential element in a smart crash management system e.g. for automotive applications. The adaptability is based on the basic idea of adjusting the stiffness of the absorber in relation to the actual load level in a crash event. Therefore the whole length of the absorber element can be used for energy dissipation. The adjustable absorbers are made from fiber reinforced plastics and shape memory alloy wires as actuating elements. Two possibilities for the basic design of the absorber elements are shown, the performance of the actuating SMA elements is characterized in detail and the switching behavior of the whole elements, between a stiff “on” state and a flexible “off” state, is measured.

Theoretical analysis on the adaptive vibration attenuation of a fixed-fixed beam realized by a piezo-shape memory alloy ferrule

2019 ◽  
Vol 30 (14) ◽  
pp. 2079-2090 ◽  
Author(s):  
Longfei Wang ◽  
Ying Wu ◽  
Zishun Liu
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Self Regulation ◽  
Nonlinear Dynamic Response ◽  
Adaptive Property ◽  
Proposed Model ◽  
Vibration Attenuation ◽  
The Stability ◽  
System Characteristics ◽  
Fixed Beam

In this article, the vibration attenuation of a fixed-fixed beam with a piezo-shape memory alloy ferrule is theoretically investigated. First, a dynamic model of the beam with a piezo-shape memory alloy ferrule is established, and the nonlinear dynamic response of the model is numerically analysed. The results show that the stability of the beam structure can be improved adaptively through self-regulation of the stiffness of the piezo-shape memory alloy ferrule undergoing external excitations. The effects of some internal system characteristics, such as the ferrule dimensions as well as the initial ferrule temperatures and boundary conditions, on the vibration attenuation of the beam are discussed. The stability of the proposed model under different external factors, including damping and external excitations, is also investigated. Compared with an aluminium ferrule, the present ferrule is better at the suppressing vibrations of the beam, and its adaptive property avoids the structural resonances for bigger ferrule sizes, making it more intelligent, efficient and convenient.

scholarly journals Failure Envelopes of Composite Bucket Foundation for Offshore Wind Turbines under Combined Loading with considering Different Scour Depths

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yuanxu Jing ◽  
Yuan Wang ◽  
Jingqi Huang ◽  
Wei Wang ◽  
Lunbo Luo
Keyword(s):  
Wind Turbines ◽  
Bending Moment ◽  
Offshore Wind ◽  
Combined Loading ◽  
Failure Envelope ◽  
Bucket Foundation ◽  
Offshore Wind Turbines ◽  
Failure Envelopes ◽  
The Stability ◽  
The Right

The composite bucket foundation of offshore wind turbines is subjected to a variety of loads in the marine environment, such as horizontal load H, vertical load V , bending moment M, and torque T. In addition, due to the characteristics of its connection section, the water flow around the foundation will produce scour pits of various degrees, reducing the depth of the bucket foundation, which has a nonnegligible impact on the overall stability of the bucket foundation. In this paper, the failure envelope characteristics of different combinations of loads on bucket foundations, including V -H-T, V -M-T, conventional V -H-M, and noncoplanar V -H-M, are numerically investigated with considering different scour depths. The numerical results indicate that the V -H-T, V -M-T, conventional V -H-M, and noncongruent V -H-M failure envelopes gradually shrink inwards with increasing scour depth, and the stability of the composite bucket foundation decreases; the conventional V -H-M failure envelope shows an asymmetry of convexity to the right, and the noncongruent V -H-M failure envelope shows an asymmetry of outward convexity to the left and right. The corresponding mathematical expressions for the failure envelope are obtained through the normalized fitting process, which can be used to evaluate the stability of the bucket foundation based on the relative relationship between the failure envelope and the actual load conditions, which can provide practical guidance for engineering design.

Influence of the Manufacturing Process on Hot Extruded Shape Memory Alloy Metal Matrix Composites

2018 ◽  
Author(s):  
C. Dahnke ◽  
A. E. Tekkaya
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Thermal Activation ◽  
Matrix Material ◽  
Bending Moment ◽  
Matrix Composites ◽  
Activation Temperature ◽  
Alloy Metal

Continuous composite extrusion offers the possibility for manufacturing shape memory alloy metal matrix composites (SMA-MMC) with an actuator function. Due to an eccentric position of the SMA wires as well as the transformation stress caused by the suppressed shape memory effect, a bending moment can be generated during thermal activation. In this paper it is examined how the amount of necessary prestrain as well as the activation temperature influences the generated curvature of the specimens. The investigated actuator concept requires a sufficient bonding between matrix material and SMA wire to transfer the occurring stresses. For this reason, it is furthermore investigated how the process steps of stretching and subsequent thermal activation affect the quality of the bonding zone. Conventional NiTi wires (SM495) with a diameter of 1.5 mm are embedded in an aluminum AA6060 matrix for experimental investigation.

scholarly journals Operational Space Control of a Lightweight Robotic Arm Actuated by Shape Memory Alloy (SMA) Wires

2016 ◽  
Author(s):  
Serket Quintanar-Guzmán ◽  
Somasundar Kannan ◽  
Miguel A. Olivares-Mendez ◽  
Holger Voos
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Closed Loop ◽  
Loop System ◽  
Robotic Arm ◽  
Control Law ◽  
Closed Loop System ◽  
End Effector ◽  
Position Regulation ◽  
The Stability

This paper presents the design and control of a two link lightweight robotic arm using a couple of antagonistic Shape Memory Alloy (SMA) wires as actuators. A nonlinear robust control law for accurate positioning of the end effector of the two-link SMA based robotic arm is developed to handle the hysteresis behavior present in the system. The model presented consists of two subsystems: firstly the SMA wires model and secondly the dynamics of the robotic arm itself. The control objective is to position the robotic arm’s end effector in a given operational plane position. For this regulation problem a sliding mode control law is applied to the hysteretic system. Finally a Lyapunov analysis is applied to the closed-loop system demonstrating the stability of the system under given conditions. The simulation results demonstrate the accurate and fast response of the control law for position regulation. In addition, the stability of the closed-loop system can be corroborated.

Stochastic recruitment control of shape memory alloy cellular actuators based on multi-state Markov chain model

2021 ◽  
pp. 1045389X2110026
Author(s):  
Chen Zhang ◽  
Jianjiang Cui
Keyword(s):  
Markov Chain ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Markov Chain Model ◽  
Open Loop ◽  
Chain Model ◽  
Control Laws ◽  
Loop Control ◽  
Stochastic Recruitment ◽  
The Stability

A new broadcast stochastic recruitment approach to the control of shape memory alloy (SMA) cellular actuators is proposed. The control design is based on a Markov chain model of multi-state cells, which is able to better characterize the inherent hysteresis of SMA in phase transition. The closed-loop and open-loop control laws are derived from random Lyapunov stability analysis and the stability conditions are analyzed. Simulation experiments demonstrate the effectiveness of the proposed method.

Research on stability and nonlinear vibration of shape memory alloy hybrid laminated composite panel under aerodynamic and thermal loads

2016 ◽  
Vol 27 (20) ◽  
pp. 2851-2861 ◽  
Author(s):  
Zhenhua Zhang ◽  
Piao Sheng
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Nonlinear Vibration ◽  
Laminated Composite ◽  
Composite Panel ◽  
Dynamic Equations ◽  
Stable Region ◽  
Thermal Loads ◽  
Aerodynamic Pressure ◽  
The Stability

The stability and nonlinear vibration of a NiTi shape memory alloy hybrid laminated composite panel under aerodynamic and thermal loads are investigated. The partial differential dynamic equations of the shape memory alloy hybrid laminated composite panel are derived based on the large deformation theory, the first-order piston theory of aerodynamic pressure and a simple constitutive model of shape memory alloy. Then, the general expressions of multimode discrete equations of the shape memory alloy hybrid laminated composite panel are obtained for the first time using Galerkin method. The stability of the shape memory alloy hybrid laminated composite panel is analyzed first based on the Routh–Hurwitz criteria, and the results show that the temperature and aerodynamic pressure parameter plane can be divided into a flat and stable region, a flutter region, and a buckling region, and the flat and stable region can be greatly enlarged as the shape memory alloy volume fraction increases. Meanwhile, numerical results of the dynamic equations show that the shape memory alloy hybrid laminated composite panel can produce various dynamic motions, and the bifurcation characteristics of the responses with temperature obtained by numerical method coincide well with the stability boundaries determined by analytical method.

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