A Novel Artificial Detrusor System and Preliminary Experimental Study.

Though the conventional pyrotechnic fastener mechanisms are widely used in spacecraft for their reliable releasable-fastening function, they still have several unavoidable problems: physical shock, high maintenance cost, to name a few. This paper introduces a new type of smart releasable mechanism based on a Shape Memory Alloy (SMA) spring and its corresponding heating apparatus. To obtain the high heating efficiency and increase the response speed, the SMA spring is transitionally fit with the heating apparatus shell instead of directly heating by electric current. As soon as the heating apparatus begins to work, the SMA spring will provide an un-locking force to release the fastening device within the standard time, which also realizes the similar releasable-fastening function comparing with the conventional pyrotechnic fastener mechanisms. In order to ensure the reliability of space products, the heating apparatus is composed of two identical ceramic heating elements which can be controlled independently or synchronously. Finally, the experimental results clearly show that, under the satellite power supply at the constant value of 28 V, the SMA spring can reach the desired 30 N unlocking force within 93 s and 51 s by single or dual heating elements, respectively. The maximal output force can even be increased as large as 40 N under the limited volume of the releasable mechanism.

A transmission method of magnetorheological(MR) fluid in disc type driven by shape memory alloy (SMA) spring with the thermal effect was proposed. The torque changed at difference temperatures. Based on the thermal effect of SMA, the expression for displacement of SMA spring was established and the rheological properties of MR fluids under the magnetic fields was described by Herschel-Bulkley model. The shear flow of MR fluid between two discs was analyzed by the momentum equation and the expressions of flow velocity and torque were obtained. The experimental results show the displacement of SMA spring and the transmit torque of MR Fluid are directly proportional to the temperature and the applied magnetic field, respectively. The transmit torque of MR Fluid can be continuously controlled by the SMA spring in difference temperatures. Keywords-thermal affect; SMA spring; MR fluid; transmission property

This paper presents a gripper actuated by a pair of differential shape memory alloy (SMA) springs with the tactile feedback controller of the polyvinylidene fluoride (PVDF) films. The SMA actuator is heated by the electric current and cooled by the fans, and a proportional-integral (PI) controller is proposed to control the output position of the gripper. In order to handle soft, deformable or slippery objects very well, the PVDF sensor is added to the finger of the gripper to perform the tactile feedback when it grasps the objects. The hardware system is established including data acquisition and signal processing parts, the control system is programmed. Experiments of grasping a soft object are carried out, and the gentle grasp ability of the gripper is also tested. Experiments results show that the SMA gripper with the PVDF tactile sensor could grasp a soft object through controlling tactile forces.

This paper designs a new composite transmission device for improving the transmission torque by squeezing magnetorheological fluid (MRF) with an electrothermal shape memory alloy (SMA) spring. Based on the finite element method, a numerical analysis of the magnetic circuit and magnetic field distribution of the magnetorheological (MR) transmission is presented, as well as a theoretical derivation and calculation of the squeezing force output by the electrothermal SMA spring and the transfer torque of the variable thickness MR transmission. In addition, the output characteristics of the electrothermal SMA spring at different temperatures are analyzed, as are the torque characteristics of the variable thickness MR transmission. The research shows that the electrothermal SMA springs exhibit a highly non-linear squeezing force output during the temperature rise, and the increase in current affects the martensite phase transition quality, and thus the phase transition temperature. The squeezing force generated by the springs increases significantly when the temperature is within the martensitic phase transformation interval, with a maximum squeezing force of 318.43 N when the SMA temperature reaches 100 °C. The proposed variable thickness MR transmission can increase the maximum torque by 4.88 times under SMA spring squeezing force, and its maximum transmitted torque is increased from 15.08 to 73.56 N·m. By squeezing the MRF with an electrothermal SMA spring, the torque of the variable thickness MR transmission can be increased quickly and effectively.

This study details the design and construction of an Analog Water Heater Chamber (AWHC) specifically tailored for tensile testing of Shape Memory Alloy (SMA) rods and springs. The AWHC is designed to simulate various temperature conditions, enabling precise control over the thermo-mechanical behavior of SMA specimens. Energy conversion from the electrical to heat form is achieved using an electrical heating element of 1000 watts. This heat is transferred to the SMA spring/wire using convection using a water medium, and phase transformation occurs. The chamber's unique design allows for real-time monitoring of deformation and recovery processes under controlled temperature and loading conditions. Different test results for both the SMA rod and SMA spring at various loading rates and constant temperature, and continuous loading rate and different temperatures showed a good thermo-mechanical coupling result The AWHC's performance was validated through tensile testing of SMA rods and springs, demonstrating its efficacy in evaluating the mechanical properties and phase transformation temperatures of these materials. The results show excellent correlation with theoretical predictions, confirming the AWHC's suitability for characterizing SMA behavior under diverse thermal and mechanical conditions. This research contributes to the development of efficient testing protocols for SMA components, paving the way for their enhanced integration into various engineering applications, thus the aim of which AWHC is designed for is achieved.

Simultaneous measurements for the interlink of electro-thermo-mechano-electro characteristics in shape memory springs

Buckling enhancement of epoxy columns using embedded shape memory alloy spring actuators

Shape memory alloys (SMAs) have several unique characteristics, including their Young's modulus-temperature relations, shape memory effects, and damping characteristics. The Young's modulus of the high-temperature austenite of SMAs is about three to four times as large as that of low-temperature martensite. Therefore, a spring made of shape memory alloy can change its spring constant by a factor of three to four. Since a shape memory alloy spring can vary its spring constant, provide recovery stress (shape memory effect), or be designed with a high damping capacity, it may be useful in adaptive vibration control. Some vibration control concepts utilizing the unique characteristics of SMAs will be presented in this paper. Shape memory alloy springs have been used as actuators in many applications although their use in the vibration control area is very recent. Since shape memory alloys differ from conventional alloy materials in many ways, the traditional design approach for springs is not completely suitable for designing SMA springs. Some design approaches based upon linear theory have been proposed for shape memory alloy springs. A more accurate design method for SMA springs based on a new nonlinear thermomechanical constitutive relation of SMA is also presented in this paper.

This paper presents an extension of the existing phase kinetics model of shape memory alloy (SMA) wire on a SMA spring actuator. The phenomenological modeling of an SMA spring under two different bias conditions – SMA spring with (A) normal spring (B) SMA wire along with the computing algorithm is addressed. The results of Case A are found in close agreement with the published literature. Whereas, the results of Case B are reported for the first time and outperform the results of Case A in terms of equal deflection, more controllability, and degrees of freedom as compared with Case A.

The use of Shape Memory Alloy (SMA) materials for actuation represents a technological opportunity for the development of innovative applications. The issue of using the SMA actuators is an enticing solution that has attracted the interest of specialists in recent years, due to their numerous advantages (i.e. reliability, compactness and flexibility, reduced cost, linear or angular movement etc.). In addition, their unmatched energy density, easy integration into various structures and the simplicity in terms of design, have all motivated the authors to develop a barrier structure model, actuated by three SMA helical springs. The actuator used in this structure works as a linear actuator, contracting with great strength and speed, thus exerting the necessary force to lift the barrier arm in the SMA springs heat-activated, austenitic state. The first part of this paper provides a description of the accomplished model and of its functioning principle. The second part of the study presented in this paper focuses on the authors' investigation on how the performances of the actuator inserted in the barrier structure—namely the actuator's heating time, cooling time, actuation time and stroke—are affected by the SMA spring activating direct current values. The tests were conducted while keeping the geometrical parameters of SMA springs and the weight of the barrier arm constant.

A soft actuator module (SAM) actuated by shape memory alloy (SMA) springs was proposed in this paper. The SAM can realize a three-dimensional bending movement. Taking the SAM as module unit, a four-joint soft manipulator was modularly assembled. Based on the characteristics of SMA resistance, a self — feedback control system was established, and the parametric analysis of the SAM was carried out. Furthermore, a multi-model locomotive control system of the soft manipulator was built to grasp objects by curling its arm, which proves the flexibility in spatial motion of the soft manipulator.

Shape memory alloys (SMA) are smart materials with a dual function as a sensor as well as an actuator that can generate cyclic contraction and extension when exposed to an increasing and decreasing temperature. In this work, the potential of SMA in the form of spring as an actuator that activates a warning system for detecting high temperatures in vehicle engine is investigated. The working principle of SMA spring is it activates thermomechanically to generate linear reciprocating motion as a result of the contraction (heated) and extension (cooled). This unique feature is employed in the design of a new type of smart automatic switch that regulates and controls the temperature of the vehicle engine instead of using conventional sensors such as thermocouple. The smart automatic switch has two poles positive and negative, where the positive pole represents the SMA spring, which is completely immersed in the water of the engine. While the negative pole is the operating shaft that collects all the parts of the smart switch and is installed on the engine body. A lab scale experiment was conducted to analyse the displacements and results shown that contraction of 20 mm can be produced from the SMA spring due to pulling force when the temperature of the engine increases from 50 ℃ to 80 ℃ and the recovery of the SMA spring to the original position can be obtained by the pushing force 0.5 N from a bias spring when the temperature decreased. From this experiment, a design of the smart switch is that can be utilized the shape memory function is presented. The simplified design proposed demonstrates the shape memory alloy as having good potential in automotive applications such as this as it low cost, space saving, silent operation, and simple in design aspect.

Shape Memory Alloy (SMA) can be used as actuators in different robotic systems. Small size and weight of SMA springs make them appropriate for micro robotic devices such as surgery grippers. In this paper, a novel gripper actuated by SMA springs is designed and fabricated. Both closing and opening of the gripper's jaws is produced by a SMA spring which is actuates by applying voltage. A Fan is also considered in the gripper's design for increasing the low rate of operating frequency of SMA springs.

To unlock the lock of futuristic developments, nowadays shape memory alloys (SMAs) are acting as key by outnumbering the existing smart materials in view of new design competence, innovative techniques, enhanced technologies, and meeting the dire need according to the demand of ongoing scientific and industrial progress. Undoubtedly, it can be worthy to associate SMAs with the term polymorphism, as they possess unique capability to encapsulate multitudinous inherent characteristics under their name. Shape memory effect, superelasticity, and damping are there to name a few among many others, as prime indicators. The exhibition of these characteristics of SMAs is due to the transformation that takes place between austenite phase and martensite phase which is achieved either by temperature or stress variation. The fascinating characteristics they possess enable them to attract researchers and designers toward their potential applications in diverse domain as smart and multi-functional materials. The present work focuses on the review of research works accomplished in the recent 5 years pertaining to modeling and applications of shape memory alloys in distinct domains. Under the topic of modeling, a look into the research carried out on a variety of SMA structures—like functionally graded SMAs, SMA springs, porous SMAs, novel SMA actuators—is presented. In addition to this, the work carried out to represent SMAs with large strains and large rotations and to model polycrystalline SMAs is also covered. This is supplemented by application-oriented domains, each of which disseminates the attributes of SMAs that are self-sufficient to express what factors make SMAs more prominent. It is believed that the foregoing works comprehensively detailed in this review article will certainly lay a solid platform for the future investigations that are going to take place in time to come.

A research study was undertaken to measure the transmissibility of nickel-titanium (Ni-Ti) shape memory alloy (SMA) springs and to compare the results to corresponding data on steel and IN-CONEL springs. It was motivated by interest in an effective metal alternative to rubber-based machinery isolation mounts, with possible active control features. Ni-Ti was used due to its well-known properties of shape memory and high intrinsic damping. Acceleration transmissibility was measured on a spring-mass system. Due to the distributed mass in the spring coils, standing waves occurred at high frequencies. However, due to the high intrinsic damping in Ni-Ti, the standing wave resonance peaks were as much as 20 dB lower than corresponding peaks in steel and 1NCONEL springs. Thus, the capability of Ni-Ti springs for high frequency acoustic isolation is significantly better than that of steel or INCONEL. Also, it is judged that the Ni-Ti material could be used in a variety of other isolation mount designs with a high likelihood for further improvement in passive isolation properties. In addition, it may be possible to use the shape memory effect (SME) in active control concepts.