Modeling, Prototyping, and Testing of Helical Shape Memory Compression Springs With Hollow Cross Section

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Igor Spinella ◽  
Eugenio Dragoni ◽  
Francesco Stortiero
Keyword(s):  
Shape Memory ◽  
Cross Section ◽  
Helical Spring ◽  
Lower Mass ◽  
Hollow Section ◽  
Sma Actuators ◽  
Helical Springs ◽  
Compression Springs ◽  
Sma Helical Spring ◽  
Mechanical Actuation

Shape memory alloys (SMAs) are used in many applications as actuators. The main drawbacks that limit the use of the SMAs in the field of mechanical actuation are the low mechanical bandwidth (up to a few Hertzs) and the unsatisfactory stroke (several millimeters). This paper contributes to enhancing the performances of SMA actuators by proposing a new SMA helical spring with a hollow section. The hollow spring is modeled, then it is constructed, and finally it is tested in compression to compare its performances with those of a spring with a solid cross section of equal stiffness and strength. Emptied of the inefficient material from its center, the hollow spring features a lower mass (37% less) and an extremely lower cooling time (four times less) than its solid counterpart. These results demonstrate that helical springs with a hollow construction can be successfully exploited to build SMA actuators for higher operating frequencies and improved strokes.

Modelling, Prototype Construction and Testing of Helical Shape Memory Springs With Hollow Cross-Section

2009 ◽  
Author(s):  
Igor Spinella ◽  
Eugenio Dragoni ◽  
Francesco Stortiero
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Cross Section ◽  
Helical Spring ◽  
Lower Mass ◽  
Hollow Section ◽  
Sma Actuators ◽  
Helical Springs ◽  
High Bandwidth ◽  
Sma Helical Spring

Shape memory alloys (SMAs) are used in many applications as actuators. The main drawbacks that limit the use of the SMAs in the field of micro-actuation are the low bandwidth and the unsatisfactory stroke. This paper contributes to enhancing the performances of SMA actuators by proposing a new SMA helical spring with hollow section. The hollow spring is modelled, then it is constructed and finally it is tested, comparing its performances with those of a spring with solid cross-section of equal stiffness and strength. Emptied of the inefficient material from its centre, the hollow spring features a lower mass (37% less) and an extremely lower cooling time (four times less). These results demonstrate that helical springs with hollow construction can be successfully exploited to realize SMA actuators with high bandwidth and stroke.

Helical Springs of Hollow Circular Cross Section

1959 ◽  
Vol 81 (1) ◽  
pp. 30-35
Author(s):  
C. W. Bert
Keyword(s):  
Experimental Investigation ◽  
Elasticity Theory ◽  
Cross Section ◽  
Circular Cross Section ◽  
Shear Stresses ◽  
Helical Spring ◽  
Circular Section ◽  
Helical Springs ◽  
Elastic Shear ◽  
Theory Solution

A theoretical and experimental investigation of elastic shear stresses and deflection in an axially loaded helical spring having a hollow circular section is reported in this paper. Two analyses are presented: An approximation of the stresses by strength-of-materials theory and a more accurate elasticity-theory solution for stresses and deflection. The results are compared with strain and deflection measurements on an actual tubular spring.

scholarly journals Behaviour of NiTi SMA Helical Springs under Different Temperatures and Deflections

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
R. Santhanam ◽  
Y. Krishna ◽  
M. S. Sivakumar
Keyword(s):  
Shape Memory ◽  
Smart Materials ◽  
Shape Recovery ◽  
Scanning Calorimetry ◽  
Helical Springs ◽  
Heating And Cooling ◽  
Niti Sma ◽  
Different Temperatures ◽  
Sma Spring ◽  
Sma Helical Spring

Shape memory alloys (SMAs) are one of the most widely used smart materials in many applications because of their shape memory effect property. In this work, the behaviour of NiTi SMA helical spring was evaluated through isothermal force-displacement experiment (IFDE) and shape recovery force experiment (SRFE). The transformation temperatures of SMA spring were determined by differential scanning calorimetry (DSC) test. In situ heating of SMA spring by direct electric current was used instead of conventional furnace heating. The continuous measurement of temperature of SMA spring during heating and cooling was ensured with attaching the thermocouple by heat shrinkable sleeve. From IFDE, the force-deflection behaviour under different constant temperatures and from SRFE and the force-temperature behaviour under different constant deflections are obtained. The results of IFDE show that the force increases and the residual displacement decreases with an increase in the temperature, and the stiffness of the spring at austenite state is greater than that at martensitic state. The results of SRFE show that the shape recovery force increases more or less linearly with an increase in the initial deflection for the same temperature range. But the shape recovery forces are not similar during heating and cooling stages. This paper presents the experimental setup, experimental procedures, and the observed behaviour of SMA helical springs under different temperatures and deflections.

scholarly journals Stability of Physically-Loaded Helical Springs used in Smart Fork Lift

2019 ◽  
Vol 9 (2) ◽  
pp. 3839-3845
Keyword(s):  
Heat Treatment ◽  
Spring Steel ◽  
Original Form ◽  
Helical Spring ◽  
Storage Devices ◽  
Helical Springs ◽  
Conical Shape ◽  
Steel Material ◽  
Compression Springs ◽  
Mechanical Devices

In the following section, the behavior of helical compression springs is considered in smart fork lift (established in previous work). We have used commonly used cylindrical and conical shape helical spring as storage devices in which stability defined in term of load-gains, deflections and evaluation of spring-rates. Springs’ rates of both springs were compared on a common platform. Initially both springs (helical-conical) was prepared from the coiled wires. These prepared springs also known as coil springs which regain its original form and position when distorted by the loaded in smart fork-lift apparatus. These coils springs here developed by the applying the heat treatment and quenching processes on the galvanized spring steel material by using the threaded shape fixtures. This prescribed work focused on effect of physically-loaded gains by cylindrical and conical shaped helical spring in smart fork lift. Here, springs worked as mechanical devices to bear the lifting load which differed here greatly in strength and in size depending on changing its parameters. Both the cylindrical and conical shape was made of helically coiled wires with constant clearance between the active coils and able to absorbed external counteracting loads applied against each other in their axis. One direction deformation in axially format was considered.

Structural fatigue and fracture of shape memory alloy actuators: Current status and perspectives

2021 ◽  
pp. 1045389X2110572
Author(s):  
Md Mehedi Hasan ◽  
Theocharis Baxevanis
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Current Status ◽  
Structural Fatigue ◽  
Sma Actuators ◽  
Empirical Relations ◽  
Fatigue And Fracture ◽  
And Performance ◽  
Commercial Applications ◽  
Crack Growth Rates

Shape Memory Alloy (SMA)-actuators are efficient, simple, and robust alternatives to conventional actuators when a small volume and/or large force and stroke are required. The analysis of their failure response is critical for their design in order to achieve optimum functionality and performance. Here, (i) the existing knowledge base on the fatigue and overload fracture response of SMAs under actuation loading is reviewed regarding the failure micromechanisms, empirical relations for actuation fatigue life prediction, experimental measurements of fracture toughness and fatigue crack growth rates, and numerical investigations of toughness properties and (ii) future developments required to expand the acquired knowledge, enhance the current understanding, and ultimately enable commercial applications of SMA-actuators are discussed.

Analytical and Numerical Modelling of Shape Memory Alloy Negator Springs for Long-Stroke Constant-Force Actuators

2012 ◽  
Author(s):  
Andrea Spaggiari ◽  
Eugenio Dragoni
Keyword(s):  
Shape Memory ◽  
Mechanical Behaviour ◽  
Volume Ratio ◽  
Constant Force ◽  
Helical Springs ◽  
Finite Element Software ◽  
Spiral Spring ◽  
High Area ◽  
Flat Shape ◽  
Long Stroke

This paper explores the merits of shape memory Negator springs as powering elements for solid state actuators. A Negator spring is a spiral spring made of strip of metal wound on the flat with an inherent curvature such that, in repose, each coil wraps tightly on its inner neighbour. The unique characteristic of Negator springs is the nearly-constant force needed to unwind the strip for very large, theoretically infinite deflections. Moreover the flat shape, having a high area over volume ratio, grants improved bandwidth compared to any solution with solid wires or helical springs. The SMA material is modelled as elastic in austenitic range while an exponential continuum law is used to describe the martensitic behaviour. The mathematical model of the mechanical behaviour of SMA Negator springs is provided and their performances as active elements in constant-force, long-stroke actuators are assessed. The SMA Negator spring is also simulated in a commercial finite element software, ABAQUS, and its mechanical behaviour is estimated through FE analyses. The analytical and the numerical prediction are in good agreement, both in martensitic and in austenitic range.

A Multi-Purpose Method for SMA Actuator Development

2013 ◽  
Author(s):  
Sven Langbein ◽  
Alexander Czechowicz
Keyword(s):  
Standardized Testing ◽  
Shape Memory ◽  
Smart Materials ◽  
Research Work ◽  
Simulation Tools ◽  
Sma Actuators ◽  
Shape Memory Actuators ◽  
Computer Aided ◽  
Sma Actuator ◽  
Actual Shape

Shape memory alloys (SMA) are thermally activated smart materials. Due to their ability to change into a previously imprinted actual shape through the means of thermal activation, they are suitable as actuators for mechatronical systems. Despite of the advantages shape memory alloy actuators provide, these elements are only seldom integrated by engineers into mechatronical systems. Reasons are the complex characteristics, especially at different boundary conditions and the missing simulation- and design tools. Also the lack of knowledge and empirical data are a reason why development projects with shape memory actuators often lead to failures. Therefore, a need of developing methods, standardized testing of empirical properties and computer aided simulation tools is motivated. While computer-aided approaches have been discussed in further papers, as well as standardization potentials of SMA actuators, this paper focuses on a developing method for SMA actuators. The main part of the publication presents the logical steps which have to be passed, in order to develop an SMA actuator, considering several options like mechanical, thermal, and electrical options. As a result of the research work, the paper proves this method by one example in the field of SMA-valve technology.

Surging in Helical Valve Springs

1933 ◽  
Vol 37 (271) ◽  
pp. 641-654
Author(s):  
J. Dick
Keyword(s):  
Internal Combustion Engine ◽  
High Speed ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Helical Spring ◽  
Dynamic Effects ◽  
Helical Springs ◽  
Air Resistance ◽  
Speed Of Propagation

The high-speed internal combustion engine presents many problems arising from dynamic effects. Amongst these is the phenomenon known as “ surging ” in the helical springs used for the operation of the valves.If a helical spring is held at both ends, any disturbance in the spring passes up and down as a wave, being reflected at each end in turn. This to and fro movement continues until it is damped out by friction and air resistance. With most springs the speed of propagation of the disturbance is considerable and only a confused flutter of the coils is apparent to an observer. A disturbance of this type is caused by any movement of the end of the spring. The more abrupt the movement of the end, the more pronounced will the disturbance be. An instance of the type of movement producing a pronounced surge is that due to impact between the tappet and the valve when the valve commences to open.

scholarly journals Localized electrodeposition micro additive manufacturing of pure copper microstructures

2021 ◽  
Author(s):  
Wanfei Ren ◽  
Jinkai Xu ◽  
Zhongxu Lian ◽  
Xiaoqing Sun ◽  
Zheming Xu ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Electrochemical Deposition ◽  
Closed Loop ◽  
Pure Copper ◽  
Closed Loop Control ◽  
Helical Spring ◽  
Loop Control ◽  
Helical Springs ◽  
Atomic Force ◽  
Microscopic Morphology

Abstract The fabrication of pure copper microstructures with submicron resolution has found a host of applications such as 5G communications and highly sensitive detection. The tiny and complex features of these structures can enhance device performance during high-frequency operation. However, the easy manufacturing of microstructures is still a challenge. In this paper, we present localized electrochemical deposition micro additive manufacturing (LECD-μAM), combining localized electrochemical deposition (LECD) and closed-loop control of atomic force servo technology, which can print helical springs and hollow tubes very effectively. We further demonstrate an overall model based on pulsed microfluidics from a hollow cantilever LECD process and the closed-loop control of an atomic force servo. The printing state of the micro-helical springs could be assessed by simultaneously detecting the Z-axis displacement and the deflection of the atomic force probe (AFP) cantilever. The results showed that it took 361 s to print a helical spring with a wire length of 320.11 μm at a deposition rate of 0.887 μm/s, which could be changed on the fly by simply tuning the extrusion pressure and the applied voltage. Moreover, the in situ nanoindenter was used to measure the compressive mechanical properties of the helical spring. The shear modulus of the helical spring material was about 60.8 GPa, much higher than that of bulk copper (~44.2 GPa). Additionally, the microscopic morphology and chemical composition of the spring were characterized. These results delineated a new way of fabricating terahertz transmitter components and micro-helical antennas with LECD-μAM technology.

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