Properties of MR Transmission under Thermal Affect

CHARACTERIZATION OF RHEOLOGICAL PROPERTIES OF NOVEL MAGNETORHEOLOGICAL FLUIDS

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.

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 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 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.

Neurogenic bladder, a bladder dysfunction resulting from injury or disease affecting the central or peripheral nervous systems, significantly compromises patient quality of life and poses potentially life-threatening risks. Currently, no reliably effective clinical treatments are available. In this context, medicine-engineering integrated approaches aimed at developing artificial detrusor systems to facilitate voluntary voiding demonstrate unique value and advantages. However, existing artificial detrusor system designs face significant challenges, including structural complexity and suboptimal biomechanical compatibility. This study proposes a novel artificial detrusor system, inspired by the physiological mechanisms of human urine storage and voiding, driven by shape memory alloy (SMA) springs and powered via transcutaneous energy transfer (TET). The system employs the shape memory effect of SMA springs to mimic detrusor contraction and utilizes TET for non-contact energy transmission. The driving performance and feasibility of the system were evaluated using simulation experiments and animal studies. Results indicate that excitation voltage, SMA spring specifications, and energization duration significantly influence the voiding rate and temperature increment of the artificial detrusor. The animal-tested prototype effectively induced bladder voiding. This study presents a promising artificial detrusor system that combines SMA-driven actuation with TET to address neurogenic bladder dysfunction. This system features a simple structure and a feasible working principle, providing a basis for subsequent optimization of artificial detrusor designs and offering a new technical pathway for assistive solutions addressing neurogenic bladder dysfunction.

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.

The performance of magnetorheological (MR) brakes depends on the rheological and tribological properties of MR fluid. An additive-free MR fluid does not offer better braking performance, which limits the commercial application of MR brake. In view of these issues, MR fluids were prepared in this present work employing graphite flakes as an additive. The required rheological properties of these MR fluids were measured on the magneto rheometer, and their braking performances were measured as per braking standard IS13453 using a fabricated MR disk brake on a 2/3-wheeler brake inertia dynamometer. Due to the interaction of MR fluid with the rotor and housing surface, the MR gap (i.e., another performance parameter) varies. Therefore, the effect of the interaction of prepared MR fluids on the rotor surface properties of the MR disk brake was also investigated. The constituents of MR fluids generate roughness on the rotor and housing surface. As a result, a mathematical model for surface roughness was presented and verified with experimental results. Based on the study, it is found that 0.5% (w/w) of graphite flake is better than additive-free MR fluid.

A new modified model for the rheological properties of magnetorheological fluids based on different magnetic field

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.

Magnetorheological (MR) fluid devices are now applied in various applications. Although a lot of studies have been discussed in long-term implementation of MR devices, only few studies have concerned on MR fluid application in valve operation mode, such as at MR valve. The experiments were conducted on a dynamic test machine in a custom MR damper with meandering MR valve. The experiment test was applied at continuous-load in long term-operation with parameters of 20 mm length of stroke, 0.4 Hz of frequency, 0.5 A of applied current and 175,000 cycles. The rheological properties of MR fluid were characterized using rotational and oscillatory shear rheometer. The result showed that the rheological properties of MR fluid changed after applied in long-term operation. The changed of MR fluid also investigated through morphological characteristics using SEM and EDX.

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.