Strain Memory Effect Research Articles

Benchmark solution for multilayer magneto-electro-elastic plates adhesively bonded by viscoelastic interlayer

An analytical solution is developed for a simply supported multilayer magneto-electro-elastic plate, which is adhesively bonded by viscoelastic interlayer and subjected to transverse loading. The three-dimensional equations of magneto-electro-elasticity are used to describe the mechanical behavior in each layer of the plate, while the mechanical property of the viscoelastic interlayer is simulated by the standard linear solid model with strain memory effect. The imperfect electric conditions between adjacent layers are considered. Making use of the Fourier series expansion as well as the state-space method, a linear equation system to the solution of the problem considered is derived. By means of the Laplace transformation, the undetermined coefficients contained in the equation system are obtained analytically. The present solution can be used as the benchmark to assess the other numerical solutions. The comparison study shows a trend that the finite element solution converges to the proposed theoretical results as the mesh density increases; in contrast to the theoretical solution, the finite element solution is, however, time-consuming, in terms of mesh division and calculation. In this study, the effects of the time; interlayer thickness; and interlayer electric coefficient on the mechanical, electric, and magnetic fields are also investigated.

Tristate ferroelectric memory and strain memory in Bi1/2Na1/2TiO3-based relaxor ferroelectrics

Tristate ferroelectric memory and strain memory of Bi1/2Na1/2TiO3 (BNT)-based relaxor ferroelectrics are proposed. These memory effects can be realized in BNT-based materials with double-like P-E hysteresis loops and obvious non-zero remanent polarization. An underlying triple-well free-energy landscape, in which the relaxor state serves as an intermediate stable state between two ferroelectric remanent states, is thought to be responsible for such a ferroelectric behavior and provides the basis for the tristate ferroelectric memory effect. Besides, the strain memory effect utilizes the inherent strain difference between relaxor and ferroelectric states. Experimental verifications on Bi1/2(Na0.8K0.2)1/2(Ti0.955Fe0.030Nb0.015)O3 ceramics show that the tristate ferroelectric memory and the strain memory can be operated as proposed, and the programmability and the retention ability of both effects are fairly good. The present study provides a facile approach to the multistate ferroelectric memory and shape memory piezoelectric actuator applications.

Enhanced electric field induced strain in (1-x)((Bi0.5Na0.5)TiO3-Ba(Ti, Zr)O3)-xSrTiO3 ceramics

In this paper, we investigated electric field induced strain (EFIS) and corresponding electric properties of the ternary ceramic system (1-x) (0.93(Bi0.5Na0.5)TiO3 − 0.07Ba(Ti0.945Zr0.055)O3)-xSrTiO3 ((1-x)(BNT-BZT)-xST). The result of unipolar strain-electric field (S-E) measurement reveals a large EFIS of 0.4% at a driving electric field of 5 kV/mm is obtained in the component x = 0.2. The corresponding large signal d33* reaches up to 800 pm/V, which is superior to most reported BNT-based ceramics. This large EFIS only occurs in a narrow area where dominated nonergodic relaxor state (NR) just converts into ergodic relaxor state (ER). As ST content increases, the measurements of the electric properties suggest a deepening ergodic degree at room temperature (RT). The ferroelectric-to-relaxor transition temperature TF-R can be modulated in a wide temperature range by the modification of ST. Since TF-R reflects the coexisting limit of NR and ER, this effect is helpful to accomplish large EFIS at a certain temperature. Due to internal bias field existed in the samples, bipolar S-E loops exhibit asymmetry to form strain memory effect, which may offer another direction for memory device design. In view of such a low driving electric field required for the large EFIS production, (1-x)(BNT-BZT)-xST ceramics become a promising candidate for application in electromechanical devices.

Large field-induced strain, giant strain memory effect, and high thermal stability energy storage in (Pb,La)(Zr,Sn,Ti)O3 antiferroelectric single crystal

(Pb,La)(Zr,Sn,Ti)O3 (PLZST) tetragonal antiferroeletric single crystals have been grown by conventional flux method. Phase structure, domain evolution, electric field-induced strain and energy storage properties of the as-grown PLZST crystals with [100] crystallographic orientation have been investigated systematically. A large electric field-induced strain up to 0.76% at 110 °C and a giant memory strain of 0.51% at 100 °C have been realized in the PLZST crystals. This field-induced strain has a nonlinear relationship with the square polarization, which simultaneously stems from the quadratic and higher order electrostrictions. Furthermore, a good thermal stability of energy storage performance with the recoverable energy variation less than 5% in a wide temperature window (105 °C) has been achieved. The combination of high strain and good thermal stability of energy storage wound make the PLZST crystals one of the most important candidates for high temperature electromechanical coupling and high reliability energy-storage devices.

A Facile and General Approach to Recoverable High-Strain Multishape Shape Memory Polymers.

Fabricating a single polymer network with no need to design complex structures to achieve an ideal combination of tunable high-strain multiple-shape memory effects and highly recoverable shape memory property is a great challenge for the real applications of advanced shape memory devices. Here, a facile and general approach to recoverable high-strain multishape shape memory polymers is presented via a random copolymerization of acrylate monomers and a chain-extended multiblock copolymer crosslinker. As-prepared shape memory networks show a large width at the half-peak height of the glass transition, far wider than current classical multishape shape memory polymers. A combination of tunable high-strain multishape memory effect and as high as 1000% recoverable strain in a single chemical-crosslinking network can be obtained. To the best of our knowledge, this is the first thermosetting material with a combination of highly recoverable strain and tunable high-strain multiple-shape memory effects.

Enhanced and stable strain memory in Mn‐doped Pb(Mn1/3Sb2/3)O3–Pb(Zr,Ti)O3 ceramics realized by sesquipolar loading

AbstractThe negative electric field, field cycling and frequency dependence of strain memory effect in poled and aged Mn‐doped Pb(Mn1/3Sb2/3)O3–Pb(Zr,Ti)O3 (PMS–PZT) piezoceramics under sesquipolar loading were investigated. The strain memory effect of Mn‐doped PMS–PZT is especially sensitive to the applied negative electric field. Maximum strain memory of 0.32% is achieved when the negative electric field is around negative coercive field of ~2.1 kV/mm, which can be ascribed to the partially depoled state with randomized domains. And this strain memory shows very good cycling stability, varying less than 5% up to 104 cycles, while almost 40% degradation is found under bipolar signal. In addition, due to the stabilized defect dipoles, the strain memory exhibits stable characteristic over a broad frequency range from 0.01 Hz to 20 Hz. The results may shed new insights into designing the novel strain memory actuators where stable strain state could be realized after the removal of electric field.

Large strain and strain memory effect in bismuth ferrite lead-free ceramics

An electric-field-induced strain in ferroelectric materials has extensive applications in actuators and sensors.

Defect-dipole alignment and strain memory effect in poled Li doped (Bi0.5Na0.4K0.1)0.98Ce0.02TiO3 ceramics

Asymmetric ferroelectric hysteresis (P–E) loops and strain hysteresis (S–E) curves are detected in poled-aged Li doped (Bi0.5Na0.4K0.1)0.98Ce0.02TiO3 ceramics at room temperature. Temperature dependence of electrical and structural analysis is used to study the stability of electrically induced long-range ferroelectric order. Interestingly, this asymmetric characteristic can sustain at 80 °C ≤ T ≤ 90 °C, where the ferroelectric and non-ergodic relaxor phase coexist. Our results suggest that the preferentially reoriented defect dipoles have the pinning effect on temperature- and electric field- induced phase transition between long-range ferroelectric and relaxor.

A constitutive model for uniaxial/multiaxial ratcheting behavior of a duplex stainless steel

In the framework of rate-independent plasticity theory, a constitutive model capable of simulating the uniaxial strain cycling and the uniaxial/multiaxial ratcheting responses of a super duplex stainless steel (S32750) which has cyclic hardening characteristics under strain-controlled cyclic loading is derived. In the developed constitutive model, the steady cyclic flow was reflected by the nonlinear evolution of the proposed kinematic hardening rule based on the Chaboche model and the Burlet and Cailletaud model; the cyclic hardening was modeled by the evolution of isotropic hardening; the strain memory effect was also considered through the asymptotic value of the isotropic hardening variable. Verification of the proposed constitutive model was achieved by simulating the uniaxial/multiaxial strain- and stress-controlled cyclic loading tests and comparing the predicted results with the experimental measurements.

Influence of Silver nanoparticles addition on the phase transformation, mechanical properties and corrosion behaviour of Cu–Al–Ni shape memory alloys

Incorporation of silver nanoparticles into Cu-based shape memory alloys is recommended to enhance their phase transformation behaviour. However, this incorporation can affect their transformation temperatures, mechanical, microstructural and corrosion characteristics. Four different phase reactions β, α, NiAl and γ2 were detected on a derivative curve during the solidification by-computer-aided cooling curve thermal analysis. The highest fraction solid (82%) was calculated for the parent phase (β) based on the Newtonian baseline method. The microstructural changes and mechanical properties were investigated using field emission scanning electron microscopy, X-ray diffraction tensile test and shape memory effect test. It was found that the addition of Ag can control the phase morphology and orientations along with the formation of the Ag-rich precipitates, and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect are improved. Remarkably, the shape recovery ratio reached approximately 80% of the original shape. The corrosion behaviour of the Cu–Al–Ni shape memory alloy were investigated using electrochemical tests in NaCl solution and their results showed that the corrosion potential (Ecorr) of Cu–Al–Ni SMA is shifted towards the nobler direction from −307.4 to −277.1m VSCE with the addition of 0.25wt.% Ag.

Influence of addition of carbon nanotubes on structure–properties of Cu–Al–Ni shape memory alloys

The influence of the addition of 0·2 wt-% carbon nanotubes on the microstructure and mechanical properties of Cu based shape memory alloy with a composition of Cu–11·5 wt-%Al–4·5 wt-%Ni were investigated using optical microscopy, X-ray diffraction, scanning electron microscopy and a universal testing machine. The experimental results show that the carbon nanotubes’ (CNTs’) addition has an effective influence on the martensite–austenite transformation temperatures, type, behaviour and morphology. Furthermore, the addition of CNTs can control the grain size and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect can be enhanced. Remarkably, the shape recovery ratio reached ∼68% of the original shape; this can be attributed to the precipitation and formation of the CNTs into the microstructure, effectively on the grain boundaries, which can help to reduce/relief the concentration of internal stress.

A theoretical investigation into the orientation of buckling direction of the reinforcing fibers in EMC laminate

Due to its high packaging strain and shape memory effect, elastic memory composite (EMC) has considerable potential application in future deployable space structures. Buckling of the reinforcing fibers is the primary deformation mechanism of such a new class of functional materials to realize a higher folding strain than that of conventional fiber reinforced composites. In this paper, the orientation of buckling direction of the reinforcing fibers in EMC laminate will be theoretically analyzed to better understand such deformation mechanism. The results reveal that the bucking protruding from the edge produces the lower energy needed for EMC laminate.

Wood as a natural smart material

The dominant feature of artificial smart materials is the “shape memory” effect. This phenomenon is based on frozen strains (FS). They were detected in wood fastened specimens during drying in the early 1960s. The integral law of wood deforming under loading and moisture content and/or temperature changes was subsequently formulated. This law takes into account the forming of FS. It was applied for the calculation of wood drying stresses. Stress memory and strain memory effects for wood were discovered. Wood has the ability to recollect the type of loading (tension or compression) which it had undergone. The difference between the free and restrained shrinkage is named “frozen shrinkage” (FSh). In calculations of drying stresses, it is more justified to use the FSh concept than “mechano-sorptive creep” (MSC). The MSC phenomenon is observed at cyclical change of moisture content in loaded wood. “Hygrofatigue” that reduces wood stiffness plays the main role in this process.

Superelastic behavior and microstructure of Ti19Nb9Zr1Mo (at%) alloy

This letter reports a new strain glass, Ti–19Nb–9Zr–1Mo, exhibiting a combination of good superelasticity of ∼3.1% strain after unloading from ∼3.5% strain and complete shape memory effect at room temperature. An effect of doping point defect with Mo suppresses the formation of long range strain order's martensites. This doping effect leads to the formation of nanodomains with α″ martensites in microstructure. The superelasticity relates to a random distributed point defect which opposes to the formation of favorable single variant in the alloy.

Large stable strain memory effect in poled Mn-doped Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics

Large strain memory effect was confirmed in the poled and aged Mn-doped 0.05Pb(Mn1/3Sb2/3)O3-0.50PbZrO3-0.45PbTiO3 ceramics due to the presence of asymmetric strain hysteresis curve with two stable strain states at zero electric field. This strain memory is two times larger than that of the unipolar strain output. Moreover, the large strain memory effect is quite stable at high electric field or down to 0.01 Hz and shows good stability even after 20 000 fatigue cycles. These results indicate that strain memory piezoelectric actuator, which could keep its output strain without any operating fields, may be fabricated using this kind of material.

The strain and thermal induced tunable charging phenomenon in low power flexible memory arrays with a gold nanoparticle monolayer

The strain and temperature dependent memory effect of organic memory transistors on plastic substrates has been investigated under ambient conditions. The gold (Au) nanoparticle monolayer was prepared and embedded in an atomic layer deposited aluminum oxide (Al(2)O(3)) as the charge trapping layer. The devices exhibited low operation voltage, reliable memory characteristics and long data retention time. Experimental analysis of the programming and erasing behavior at various bending states showed the relationship between strain and charging capacity. Thermal-induced effects on these memory devices have also been analyzed. The mobility shows ~200% rise and the memory window increases from 1.48 V to 1.8 V when the temperature rises from 20 °C to 80 °C due to thermally activated transport. The retention capability of the devices decreases with the increased working temperature. Our findings provide a better understanding of flexible organic memory transistors under various operating temperatures and validate their applications in various areas such as temperature sensors, temperature memory or advanced electronic circuits. Furthermore, the low temperature processing procedures of the key elements (Au nanoparticle monolayer and Al(2)O(3) dielectric layer) could be potentially integrated with large area flexible electronics.

Intermartensitic Transformation in Ni54.8Mn23.2Ga21.7 Ferromagnetic Shape Memory Alloy Nano Powder

The Ni-Mn-Ga Ferromagnetic shape memory alloys are becoming an important element of sensor and actuator materials due to their large magnetic-field-induced strain and shape memory effect in recent years. The martensitic transformation temperature of the Heusler alloy system has been intensively studied. The Ni54.8Mn23.2Ga21.7 irregular agglomerated nanoparticles were prepared by ball milling method, and characterized by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy techniques. These particles reveal a disordered non modulated face centered tetragonal structure. For the first time, nanopowder has been found to undergo a sequence of temperature-induced intermartensitic transformation in addition to the martensitic transformation on cooling. It is believed that relaxation of internal stresses is the main issue in this case. The resistivity of the material has been measured on cooling from 450 K to 300 K. It is observed that the resistivity is maximum in the nano crystalline state and it decreases substantially with decrease of the temperature. Both amorphous and nanocrystalline material coexisted in the ball-milled sample, such a nanomagnetic structure is considered to be ideal for soft nanomagnetic material.

Cyclic behaviour and plastic strain memory effect of 55NiCrMoV7 steel under low cycle fatigue

Cyclic plastic behaviour of tempered martensitic tool steel 55NiCrMoV7 with four different initial hardness levels was studied under tensile-compress low cycle fatigue (LCF) in the temperature range from room temperature up to 873 K. Cyclic behavior tests and strain memory effect tests were performed in symmetrical tensile-compression strain loading with a triangular waveform. The results show that steel represents cyclic softening behaviour. The cyclic stress response generally shows an initial exponential softening for the first few cycles, followed by a gradual softening without saturation. Cyclic stress response depends on strain rate. The steel represents cyclic viscoplasticity. The steel shows the plastic strain memory effects at each test temperature, the cyclic stress and cumulated plastic strain depends on the history of cyclic loading. If strain amplitude increases after a previous linear softening is achieved, a new rapid non-linear cyclic softening appears. In the opposite, if strain amplitude decreases from higher one to lower, softening remains linear, and moreover σ-p curve goes along the previous way at the previous same strain loading level. It was discussed that the influences of initial hardness, fatigue temperature, strain rate and cyclic strain amplitude on cyclic plasticity of the steel.

Field-induced Strain Memory with Non-180?ª Domain-reorientation Control

Using non-180◦ domain-reorientation control, we propose the strain memory effect in ferroelectric ceramics. Electric fields with asymmetric amplitudes were applied to soft-type lead zirconate titanate (PZT) ceramics, and the strain hysteresis and the polarization loop were measured. The butterfly curve became asymmetric under an electric field with a particular asymmetric amplitude. The asymmetric butterfly curve had two stable strain states at zero electric field. Thus, the strain memory effect was realized as the difference between the two stable strain states. An XRD analysis was carried out to verify the contribution of the non-180◦ domain reorientation to the strain memory effect. The non-180◦ domain reorientation was determined as the intensity ratio of the (002) to the (200) peak. The strain memory determined from macroscopic strain measurements had a linear relationship to the non-180◦ domain volume fraction. This result indicated the origin of the strain memory to be the non-180◦ domain reorientation.

Macro versus micro-scale constitutive models in simulating proportional and nonproportional cyclic and ratcheting responses of stainless steel 304

A recent study by Hassan et al. [Hassan, T., Taleb, L., Krishna, S., 2008. Influences of nonproportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plasticity, 24, 1863–1889.] demonstrated that some of the nonproportional ratcheting responses under stress-controlled loading histories cannot be simulated reasonably by two recent cyclic plasticity models. Two major drawbacks of the models identified were: (i) the stainless steel 304 demonstrated cyclic hardening under strain-controlled loading whereas cyclic softening under stress-controlled loading, which depends on the strain-range and which the existing models cannot describe; (ii) the change in biaxial ratcheting responses due to the change in the degree of nonproportionality were not simulated well by the models. Motivated by these findings, two modified cyclic plasticity models are evaluated in predicting a broad set of cyclic and ratcheting response of stainless steel 304. The experimental responses used in evaluating the modified models included both proportional (uniaxial) and nonproportional (biaxial) loading responses from Hassan and Kyriakides [Hassan, T., Kyriakides, S., 1994a. Ratcheting of cyclically hardening and softening materials. Part I: uniaxial behavior. Int. J. Plasticity, 10, 149–184; Hassan, T., Kyriakides, S., 1994b. Ratcheting of cyclically hardening and softening materials. Part II: multiaxial behavior. Int. J. Plasticity, 10, 185–212.] and Hassan et al. [Hassan, T., Taleb, L., Krishna, S., 2008. Influences of nonproportional loading paths on ratcheting responses and simulations by two recent cyclic plasticity models. Int. J. Plasticity, 24, 1863–1889.] The first model studied is a macro-scale, phenomenological, constitutive model originally proposed by Chaboche et al. [Chaboche, J.L., Dang-Van, K., Cordier, G., 1979. Modelization of the strain memory effect on the cyclic hardening of 316 stainless steel. In: Proceedings of the Fifth International Conference on SMiRT, Div. L, Berlin, Germany, L11/3.]. This model was systematically modified for incorporating strain-range dependent cyclic hardening–softening, and proportional and nonproportional loading memory parameters. The second model evaluated is a polycrystalline model originally proposed by Cailletaud [Cailletaud, G., 1992. A micromechanical approach to inelastic behavior of metals. Int. J. Plasticity, 8, 55–73.] based on crystalline slip mechanisms. These two models are scrutinized against simulating hysteresis loop shape, cyclic hardening–softening, cross-effect, cyclic relaxation, subsequent cyclic softening and finally a broad set of ratcheting responses under uniaxial and biaxial loading histories. The modeling features which improved simulations for these responses are elaborated in the paper. In addition, a novel technique for simulating both the monotonic and cyclic responses with one set of model parameters is developed and validated.