Shape Memory Alloy Devices Research Articles

Separation and Release Devices for Aeronautical and Astronautical Systems: A Review

AbstractThis review presents an in-depth examination of the advancements, current state, and future trends of separation and release devices in aeronautical and astronautical systems, focusing on their classification into one-point and linear devices as well as the move from pyrotechnic to nonexplosive methods. For one-point separation devices, this review discusses the evolution from traditional explosive bolts, which use high explosives to operate, to nonexplosive actuators such as shape memory alloy devices that offer resettable, low-shock options. It also highlights devices that rely on pyrotechnic initiators without using high explosives as key developments for reducing shock and increasing safety. In the section on linear separation devices, the review examines flexible linear shaped charges and mild-detonating fuses, which are crucial for precise separations such as stage and fairing detachments. Introducing expanding tubes as a new method to avoid the usual debris and damage from pyrotechnics is a big improvement. In addition, the use of clamp-band joint systems for satellite separation, secured by either pyrotechnic bolts or nonexplosive dual-initiator devices, is a common approach. The recent focus on developing pneumatic linear separation devices marks a shift toward systems that can be reused and reduce shock without explosives. Moreover, the emergence of nonexplosive satellite separation systems represents a shift toward safer and more adaptable deployment technologies. These fully mechanical actuation methods facilitate shock-free separations, which are crucial for the integrity of sensitive payloads. This review suggests that continuous innovation in nonexplosive separation technology will significantly change mission planning and system design in the aeronautics and astronautics fields.

Effect of axial preloads on torsional behavior of superelastic shape memory alloy tubes – experimental investigation and simulation/predictions of intricate inner loops

Shape memory alloy (SMA) devices (utilizing wires/rods, springs or tubes) engage unique superelastic/pseudoelastic (SE) phenomenon for large stroke recovery, energy dissipation and damping applications. In particular, SMA components in torsion are also generally subjected to some pre-tension loads and hence understanding their combined effects on the torsional response is vital. In this work, some intricate internal loop and outer loop responses (large twists > 1500°) of SMA tubes under different twisting-untwisting scenarios are investigated to understand the effects of static pre-load on torsional responses. Key SMA hysteretic features like sink point memory (SPM) and return point memory (RPM) have not been well understood under torsion (with and without axial loads) have been investigated here. Further, a modified two variant thermodynamic Preisach modeling approach is proposed to simulate responses of twisted tubes with varying extents of twist and different axial loads. The central principle here is the use of a Gibbs Potential framework to separate the dissipative and thermoelastic parts of the SE responses using well established thermodynamic principles and then utilizing a non-ideal switching type disjunctive Preisach model to fit the nonlinear hysteretic dissipative section of the SE response. By using the outer loop response for model calibration, other complex loading unloading scenarios leading to intricate internal loops and effects of axial loads on these can be predicted. It is also shown that addition of a single interior loop detail for model calibration significantly enhances prediction of other more intricate internal loops. This approach dramatically simplifies the experimental data needed for the simulation of SMA components even under complex loading.

Seismic risk-based optimization of tension-only shape-memory alloy device for steel moment-resisting frames

This study introduces the seismic risk-based design of SMA devices for steel moment-resisting frame buildings. The investigation begins with the numerical representation of the device which includes SMA wires exhibiting super-elastic stress–strain response, along with steel components. The model is then compared against an actual test result. Accordingly, several four-story steel-frame buildings are numerically characterized, all designed to withstand similar seismic loads. This includes a control frame building (Bare-SMF), a frame building with SMA devices using a traditional design approach (SMA-D), and a frame with buckling restrained braces (BRB-D) for comparison. As the traditional design method relies on the first modal shape and static loads, the pushover analysis results for all structures possessed similar amount of strength and deformation capacity. However, the nonlinear time history analysis revealed inconsistencies in the responses of the retrofitted buildings (SMA-D and BRB-D) when compared to Bare-SMF. To address this issue, a seismic risk-based design approach that combines nonlinear time history analysis on a steel moment-resisting frame and the particle swarm optimization algorithm is employed. By using this approach, the SMA brace quantities were determined such that the cost of SMA devices can be minimized while the life-cycle probability of collapse and demolition is smaller than that of Bare-SMF. As a result of the risk-based design approach, three brace quantities are determined according to a decision maker’s attitude against the seismic risk. As a result, the cost of SMA devices could be reduced by more than 40% while maintaining a significant reduction in the life-cycle probability of collapse and demolition.

Experimental, mathematical model, and simulation of a dual-system self-centering energy dissipative brace equipped with SMA and variable friction device

The application of shape memory alloy (SMA) in seismic-resistant devices has received extensive attention due to its unique superelastic and shape memory effect. The poor energy dissipative capacity, insufficient reliability, and small bearing capacity are the main challenges that hinder the application of the developed SMA braces and dampers. The new system of self-centering energy dissipative (SCED) brace was proposed, fabricated, and tested, and the numerical model was defined and verified. The dates manifest that the load-displacement curve of the new dual-system SCED brace displays a typical flag shape. The new dual-system SCED brace exhibits the desirable energy dissipative ability and self-centering capacity and the theoretical and FE model established in this research can preferably express the hysteretic performance. The FE parametric analysis shows that the SMA screw preload has a small effect on the hysteretic curve of the new system brace, but it plays a decisive role in the shape of the hysteretic curve under small deformation. Furthermore, the bearing capacity and stiffness of the dual-system SCED brace can be adjusted by designing key parameters. The research shows that the new dual-system SCED device compensates for the shortcomings of the existing SMA braces and dampers, and it is a very promising and recommended self-centering energy dissipative device to use the wedge block system as the main energy dissipative system and SMA system as the main self-centering system.

Efficiency of shape memory alloy seismic restrainers for several conditions of bridge joints

Movement joints are needed in bridges to accommodate longitudinal expansion and contraction. Enough joint width needs to be available to accommodate not only longitudinal expansion but also expected movements of joints during earthquakes. This may result in excessive joint openings. Devices that can dissipate energy have been suggested to reduce joint displacements. Shape memory alloy (SMA) is one of these energy dissipation devices, which is well known for its ability to return to its natural shape after being deformed. Several cases of bridges and different conditions of seismic events are modeled and tested using developed software programs in MATLAB to show the efficiency of using SMA inside bridge joint openings. These models include the case of two adjacent frames with SMA inside them (2–frames), the case of multi–frames with constant hysteretic SMAs between every two of them (N–frames), the case of multi–frames with constant hysteretic SMAs taking the delay of seismic forces between frames into consideration (delay), and the case of variable masses of bridge frames. Also, parametric studies are performed to show the impacts of all parameters of bridge frames and SMA retrofit devices on seismically joint openings. The results show that the superelastic SMA device plays a huge role in controlling bridge opening and enables limiting the joint width of all models during earthquakes with different values reaching 60% in some cases depending on bridge frame properties, ground motion characteristics, and the hysteretic properties of SMA devices.

Active Disturbance Rejection Controller for a Flexible Walking Bioinspired Inchworm Mobile Robot Actuated With Shape Memory Alloy Devices

This study presents the development of a hybrid active disturbance rejection control (H-ADRC) implementing a homogeneous extended state observer (ESO) to solve the trajectory tracking problem of an inchworm bioinspired flexible robotic device (IBFRD) with partially unknown dynamics. The proposed controller is implemented on a self-designed IBFRD instrumented with shape memory alloys (SMAs) operating as actuators in each joint of the robotic mobile device. The set of SMAs constitutes an agonist–antagonist mechanism together with regular springs that counteract the SMA displacement. The characteristic two-anchor crawling of an inchworm is modeled as a hybrid system and exerted by a bistable pneumatic circuit that switches suction cups at the terminal links of the IBFRD to exert the inchworm walking. The corresponding reference trajectories emulate an inchworm in a regular gait cycle. Experimental results compare the H-ADRC with a proportional derivative and a proportional–integral–derivative (PID) controller. The obtained results show that the proposed H-ADRC enforces a reduced tracking error than the other controllers used for validation.

A collagen membrane for periosteal expansion osteogenesis using a timed-release system in rabbit calvaria

BackgroundThe purpose of this study was to evaluate the effects of resorbable membranes, combined with a shape memory alloy (SMA) mesh device, on bone formation using a timed-release system for periosteal expansion osteogenesis (TIME-PEO).Materials and methodsTwelve Japanese white rabbits were used in this study. An SMA device was inserted under the forehead periosteum, pushed and bent for attachment to the bone surface, and then fixed using resorbable thread. The rabbits were divided into four groups: C1 (5 weeks postoperatively without membrane), C2 (8 weeks postoperatively without membrane), E1 (5 weeks postoperatively with membrane), and E2 (8 weeks postoperatively with membrane). The rabbits were killed 5 or 8 weeks after the operation and the newly formed bone was assessed histologically and radiographically.ResultsSMA devices, concealed under soft tissue until the time of euthanasia, did not cause active inflammation. The mean activation height, from the original bone surface to the midpoint of the mesh, was 3.1 ± 0.6 mm. Newly formed bone was observed, and most of the subperiosteal space underneath the device was occupied by fibrous tissue. Immature bone was present at the outer surface of the original skull bone in all groups. On histomorphometric analysis, there was no significant difference in the volume of the new bone between C1 and E1 (p = 0.885), and C2 and E2 (p = 0.545).ConclusionsPEO using an SMA mesh device, which is based on guided bone regeneration (in atrophic alveolar bone), shows promise as an alternative for bone augmentation, irrespective of whether a resorbable membrane is used.

Critical Frequency of Self-Heating in a Superelastic Ni-Ti Belleville Spring: Experimental Characterization and Numerical Simulation.

The mechanical loading frequency affects the functional properties of shape memory alloys (SMA). Thus, it is crucial to study its effect for the successful use of these materials in dynamic applications. Based on the superelastic cyclic behavior, this work presents an experimental methodology for the determination of the critical frequency of the self-heating of a NiTi Belleville conical spring. For this, cyclic compressive tests were carried out using a universal testing machine with loading frequencies ranging from 0.5 Hz to 10 Hz. The temperature variation during the cyclic tests was monitored using a micro thermocouple glued to the NiTi Belleville spring. Numerical simulations of the spring under quasi-static loadings were performed to assist the analysis. From the experimental methodology applied to the Belleville spring, a self-heating frequency of 1.7 Hz was identified. The self-heating is caused by the latent heat accumulation generated by successive cycles of stress-induced phase transformation in the material. At 2.0 Hz, an increase of 1.2 °C in the average temperature of the SMA device was verified between 1st and 128th superelastic cycles. At 10 Hz, the average temperature increase reached 7.9 °C and caused a 10% increase in the stiffness and 25% decrease in the viscous damping factor. Finally, predicted results of the force as a function of the loading frequency were obtained.

Phenomenological hysteretic model for superelastic NiTi shape memory alloys accounting for functional degradation

AbstractThis study presents a simple hysteretic model to reproduce the stress–strain relationship of superelastic NiTi shape memory alloys (SMAs). The proposed model explicitly includes the functional degradation of SMAs, which has been ignored in earthquake engineering applications. This effect causes a reduction in the transformation stress and accumulation of residual strain. Because SMA devices are mainly used for seismic retrofit and account for a small portion of the structural system, their numerical model should not increase the computational time needed to perform nonlinear dynamic analyses. Computational efficiency can be achieved by representing their stress–strain response in a phenomenological way. Additionally, practitioners who may not have a professional background in materials science can easily manipulate the proposed model for the appropriate reproduction of model parameters such as transformation stress and residual strain. The ability to properly reproduce the experimental stress–strain response is validated for the test results of 65 NiTi SMA specimens. The amount of forward and reverse transformation stress degradation and the amount of residual strain accumulation per cycle, which are observed in the experimental results, are captured with reasonable accuracy in the proposed model. Additionally, the response of SMA braces in a four‐story steel moment frame is modeled using the proposed model to examine the residual story drift of the SMA braced frame under a set of ground motions. At higher intensity levels, the functional degradation of SMA braces increased the residual story drift up to 60% in comparison to the SMA‐braced model without functional degradation.

Controlling martensitic transformation characteristics in defect-free NiTi shape memory alloys fabricated using laser powder bed fusion and a process optimization framework

Laser Powder Bed Fusion (L-PBF) was utilized to fabricate fully dense, near-equiatomic (Ni50.1Ti49.9) and Ni-rich NiTi (Ni50.8Ti49.2) shape memory alloy (SMA) parts which exhibited tensile ductility up to 16%, shape memory strain of 6%, and tensile superelasticity up to 4%. Annealing heat treatments marginally improved the superelasticity of the as-fabricated Ni-rich NiTi parts due to the formation of a small volume fraction of Ni4Ti3 precipitates. The selection of optimum processing parameters that yielded fully dense parts was guided by a process optimization framework based on a computationally inexpensive analytical model used to predict the melt pool dimensions. The framework also included single-track experiments to validate the model predictions and a criterion for the maximum allowable hatch spacing to prevent the formation of lack of fusion porosity. This framework allowed for constructing L-PBF processing maps for the present NiTi SMAs and revealed that fully dense parts could be printed over a wide range of process parameters. By controlling the L-PBF process parameters, in particular laser power, laser scan speed, and volumetric energy density, in the processing space that result in fully dense parts, it was demonstrated systematically that the composition of the printed parts could be precisely changed by controlling the evaporation of Ni. The flexibility of parameter selection to print defect-free NiTi SMAs and composition control by preferential evaporation of Ni opens the possibility to print functional NiTi SMA parts or devices without post-processing.

Architected material analogs for shape memory alloys

Architected material analogs for shape memory alloys

Shaking table test of a frame structure retrofitted by externally-hung rocking wall with SMA and disc spring self-centering devices

An innovative externally-hung rocking wall (ERW) with shape memory alloy (SMA) and disc spring self-centering devices for retrofitting existing structures was proposed in this paper. By arranging steel corbels on the columns of an existing structure, the rocking walls were connected to the corbel using H-shaped connectors. Two types of self-centering devices, using disc spring and SMA separately, were installed between rocking wall and foundation to prevent collision damage, and can provide self-centering capability for the structure. The seismic performance characteristic of the ERW structure was studied via a shaking table test. For comparison, an unretrofit control (UC) structure was also tested. The UC structure was severely damaged and nearly collapsed after PGA = 1.2 g test cases: some steel bars at the bottom of the beam were fractured, and concrete at the beam end and column foot were crushed. For the ERW structure, the damage was significantly reduced after PGA = 1.5 g test cases: there were some cracks appeared in the structure, and concrete at the column foot were slightly crushed. However, no obvious damage was observed in the self-centering devices. The maximum story drift and residual deformation of the ERW structure are reduced 86.7% and 91.2%, respectively, relative to the UC structure.

Multifunctional Coating with Both Thermal Insulation and Antibacterial Properties Applied to Nickel-Titanium Alloy.

BackgroundWith excellent shape memory and superelastic properties, shape memory alloy (SMA) is an ideal actuator, and it can form smart structure for different applications in medical field. However, SMA devices cause apparent thermal damage to the surrounding tissues when it works in vivo, making the application of smart structure that is composed of SMA actuator in vivo is greatly limited.MethodsIn this paper, coating (APA) with PLA as the main body to limit the heat conduction, a multifunctional Ag nanoparticles (AgNPs)/polylactic acid (PLA)/Al2O3 was synthesized. The Al2O3 layer was formed by micro-arc oxidation (MAO) and AgNPs were synthesized by silver nitrate and ethylene glycol. Scanning electron microscopy, transmission electron microscope, and Fourier transform infrared spectra were applied to analyze the morphology and characterization of APA coating. The antimicrobial activity, thermal insulation activity, and biocompatibility of APA coating were furtherly explored and verified through animal experiments and immunohistochemistry.ResultsWith different particle sizes and concentrations of AgNPs, APA multi-functional films were successfully prepared. The Al2O3 layer was closely combined with SMA and formed a porous surface, so the PLA and AgNPs layers can firmly adhere to SMA, thus reducing the release of nickel ions in SMA. AgNPs gave APA coating excellent antibacterial activity and effectively inhibited the growth of Staphylococcus aureus. In addition, coupled with the low thermal conductivity of PLA and Al2O3, AgNPs were tightly anchored on the surface of PLA, which has high infrared reflectivity, making the APA coating obtain good thermal insulation performance.ConclusionWe have successfully prepared the APA coating and obtained the optimum amount of AgNPs, which makes it have good thermal insulation performance, good antibacterial activity and good biocompatibility, which provides a new prospect for the application of SMA.

Performance of Bridges Isolated with Sliding-Lead Rubber Bearings Subjected to Near-Fault Earthquakes

This paper investigates the seismic performance of bridges installed with a sliding-lead rubber bearing (LRB) isolation system subjected to near-fault earthquakes. A three-span continuous bridge isolated with sliding-LRB system is used as an example. Nonlinear time history analyses are conducted to investigate the sensitivity effects of isolation period, friction coefficient and sliding displacement limit on the bridge responses. The responses of the sliding-LRB system are compared with those of the conventional LRB system. The results show that the base forces of the piers can be reduced by employing proper friction coefficients. However, the residual displacement of the sliding-LRB system may be larger compared with that of the conventional LRB system. To overcome this disadvantage, an improved solution to reduce the residual displacement is proposed with its effectiveness investigated. It was also demonstrated that the residual displacement and peak displacement can be effectively reduced by employing the shape memory alloy devices in the sliding-LRB system without significantly increasing the base forces.

State-of-the-art: shape memory alloys for monumental consolidation and base isolation

This paper is a state of the art of the experience gathered by the author on the use of shape memory alloys (SMAs) in civil engineering. Since 2005, efforts have been focused on the invention of a new concept of base isolation and the retrofitting of monuments. First, an innovative system consisting of several SMA bars of particular geometry was proposed. Its numerical model was built, realised and experimentally tested. It was concluded that for cyclic loading, a large amount of energy was dissipated. Then and following conclusions drawn from laboratory tests, SMA wires were inserted practically and numerically on a number of monuments: the aqueduct of Larnaca (Cyprus), the minaret of Ajloun (Jordan) and the minaret of Mansourah (Algeria). The monuments were reinforced with different SMA devices distributed over different positions. The proposed technique was proved as significant via the improvement seen in the dynamic response of monuments.

Application of NiTi in Assistive and Rehabilitation Devices: A Review.

Shape memory alloys (SMAs) have found widespread applications as biomedical devices. Biocompatibility, corrosion resistance, and ductility make these alloys attractive for medical devices such as stents and filters. For these implants, the superelastic property is the primary function of SMAs. Additionally, these alloys, such as NiTi as the prime example, can be used for actuation. Several modes of actuation such as displacement control, force control, and compliance control have been used as harnesses with SMA devices. These two unique properties have opened another application in the form of neurosurgery and robot-assisted surgery devices, as well as controlled assistive and rehabilitation devices. This paper reviews the state of the art of application of SMAs in the latter category where control is applied to harness innovative medical devices. To this end, two major subsets of these devices: prosthesis and orthosis which take the advantage of SMAs in assistive and rehabilitation devices are studied. These devices are further categorized to hand prosthetics, elbow, knee and ankle orthotics. In most of these designs, SMA wires act as artificial muscles to mimic the motion of limbs in the target joints. The evolution of each category is explained, and the specific results of them are reported. The paper also reviews the SMA applications for neurological and neuromuscular rehabilitation. To this end, different categories of rehabilitation devices as a passive and aided exercise for the ankle, knee, and elbow are highlighted. The SMA actuator in these devices can be EMG-controlled to improved patient outcome. In addition to providing a comprehensive overview of the biomedical devices, this paper identifies several possible future directions of SMA related research in the area of assistive and rehabilitation devices.

Dynamic behavior of a seven century historical monument reinforced by shape memory alloy wires

This work resumes a research that proposes the use of the technique based on the dissipation energy of the shape memory alloy (SMA) ties. It focuses principally on the assessment of the effectiveness of the use of these smart materials on displacements, accelerations and the stresses of the minaret of the great mosque of Ajloun in Jordan. The 3-D finite element model of the minaret is performed by the ANSYS software. First of all, the proposed model is calibrated and validated according to the experimental results gathered from ambient vibration testing results. Then, a nonlinear transient analysis is considered, when the El-Centro earthquake is used as the input signal. Different simulating cases concerning the location, number and type of SMA devices are proposed in order to see their influence on the seismic response of the minaret. Hence, the results confirm the effectiveness of the proposed SMA device.

Finite element simulation of thermomechanical training on functional stability of shape memory alloy wave spring actuator

Pre-service thermomechanical training is of great significance to achieve functional stability for shape memory alloy device. This article presents a finite element simulation of the training behavior of a shape memory alloy wave spring actuator using a thermomechanically coupled and finite-strain shape memory alloy model (Wang et al., 2017a). The model is implemented into ABAQUS/Explicit by means of a user-defined material subroutine VUMAT. The introduction of a finite-Hencky-strain return-mapping integration scheme substantially improves the numerical efficiency and stability. Model predictions are validated against the experimental data. The good agreement between both demonstrates the capabilities of the model of well describing the training behavior of shape memory alloy when subjected to large cyclic thermomechanical loading. Simulation results illustrate several primary thermomechanical characteristics during training process, such as the expansion of the phase transformation zone, the accumulation of the residual deformation, and the concentration of the internal stress. The present finite element approach provides a powerful tool in design and optimization of shape memory alloy wave spring actuator, especially to improve the geometric precision and to enhance the two-way shape memory effect.

A Multi-mechanism Model Describing Reorientation and Reorientation-Induced Plasticity of NiTi Shape Memory Alloy

The recovery force or recovery strain is an important indicator of NiTi-based shape memory alloy devices. However, the restoring force or recoverable strain is partially restrained due to an interaction between reorientation and reorientation-induced plasticity. Therefore, a macroscopic multi-mechanism constitutive model was constructed to describe the degeneration of shape memory effect based on the phase diagram. The residual strain after cooling consists of reorientation strain and reorientation-induced plastic strain. An internal variable, i.e., the detwinned stress, and its evolution equation were introduced into the transformation kinetics equation to describe the nonlinear hardening characteristics induced by the combined reorientation and detwinning mechanisms during mechanical loading. Finally, the proposed model was numerically implemented to simulate the experiments of shape memory effect at different peak strains. Comparisons between the experimental and simulated results show that the proposed model can reasonably describe the degeneration of shape memory effect.

Uniaxial, pure bending, and column buckling experiments on superelastic NiTi rods and tubes

Many existing shape memory alloy (SMA) devices consist of slender beams and frames. To better understand SMA beam behavior, we experimentally examined the isothermal, room temperature response of superelastic NiTi rods and tubes, of similar outer diameters, subjected to four different modes of loading. Pure tension, pure compression, and pure bending experiments were first performed to establish and compare the baseline uniaxial and bending behaviors of rods and tubes. Column buckling experiments were then performed on rod and tube columns of several slenderness ratios to investigate their mechanical responses, phase transformation kinetics under combined uniaxial and bending deformation, and the interaction between material and structural instabilities. In all experiments, stereo digital image correlation measured local displacement fields in order to capture phenomena such as strain localization and propagating phase boundaries.Superelastic mechanical behavior and the nature of stress-induced phase transformation were found to be strongly affected by specimen geometry and the deformation mode. Under uniaxial tension, both the rod and tube had well-defined loading and unloading plateaus in their superelastic responses, during which stress-induced phase transformation propagated along the length of the specimen in the form of a high/low strain front. Due to the dependence of strain localization on kinematic compatibility, the high/low strain front morphologies differed between the rod and tube: for the rod, the high/low strain front consisted of a diffuse “neck”, while the high/low strain front in the tube consisted of distinct, criss-crossing “fingers.” During uniaxial compression, both cross-sectional forms exhibited higher transformation stresses and smaller transformation strains than uniaxial tension, highlighting the now well-known tension-compression asymmetry of SMAs. Additionally, phase transformation localization and propagation were absent under compressive loading. During pure bending, the moment-curvature response of both forms exhibited plateaus and strain localization during forward and reverse transformations. Rod specimens developed localized, high-curvature regions that propagated along the specimen axis and caused shear strain near the high/low curvature interface; whereas, the tube specimens exhibited finger/wedge-like high strain regions over the tensile side of the tube which caused nonlinear strain profiles through the thickness of the specimen that did not propagate. It was therefore found that classical beam theory assumptions did not hold in the presence of phase transformation localization (although, the assumptions did hold on average for the tube). During column buckling, the structures were loaded into the post-buckling regime yet recovered nearly-straight forms upon unloading. Strain localization was observed only for high aspect ratio (slender) tubes, but the mechanical responses were similar to that of rods of the same slenderness ratio. Also, an interesting “unbuckling” phenomenon was discovered in certain low aspect ratio (stout) columns, where late post-buckling straightening was observed despite continuous monotonic loading. Thus, these behaviors are some of the challenging phenomena which must be captured when developing SMA constitutive models and executing structural simulations.