Hysteresis Tests Research Articles

Highly Stretchable Strain Sensor with a High and Broad Sensitivity Composed of Carbon Nanotube and Ecoflex Composite

Wearable strain sensors with high and broad sensitivity, high stretchability and excellent mechanical endurance will be widely useful in smart wearable electronics. In this work, we developed a stretchable strain sensor fabricated with a simple stencil printing technique. The stretchable strain sensor was fabricated using a multi-walled carbon nanotubes (MWCNTs)-Ecoflex composite paste on an Ecoflex substrate. In particular, using IPA solvent, CNT particles were uniformly dispersed in the Ecoflex binder. The effect of the amount of Ecoflex resin on the stretchability and sensitivity of the sensor were also investigated. It was found that as the amount of Ecoflex resin increased, the stretchability of the sensor increased. The fabricated stretchable strain sensor showed a maximum stretchability of 1,000% with a wide sensitivity range from 3 to 12,287. The hysteresis tests indicated that the hysteresis of the fabricated stretchable strain sensor was very small, the electrical resistances of the sensors quickly returned to original value after tests. The strain sensor showed excellent mechanical durability during cyclic repeated tensile tests of 400,000 cycles. The results of the cross-cut adhesion tests indicated that the adhesion strength between the sensor composite layer and Ecoflex substrate was excellent. We also demonstrated the potential application of the stretchable sensor in wearable electronics by bending tests on a human finger and wrist.

Role of interface/border traps on the threshold voltage instability of SiC power transistors

In this paper the role of interface/border defects on the threshold voltage drift (ΔVTH) of SiC power MOSFETs has been investigated by means of slow and fast positive bias temperature instability (PBTI), hysteresis and conductance tests. Results have shown an opposite temperature (T) dependency based on the level of the applied gate bias (VG) and on the adopted stress technique. With VG > 30 V and a slow-PBTI procedure, the creation of new oxide defects and/or the charge trapping in deep states occurs, showing a positive T-dependency. On the contrary, with a lower VG and a fast-PBTI test, the ΔVTH shows a negative T-dependency, associated to dominant role of pre-existing interface and/or border traps.

Exploiting a Simple Asymmetric Pleating Method to Realize a Textile Based Bending Actuator

This work presents the design, modeling and control of an asymmetrically pleated textile actuator (APTA). The presented actuator utilizes a simple inflatable beam which is constrained asymmetrically using a pleat that is fixed only to a single side. Due to the difference in length between the constrained side and the unconstrained side, a bend at the pleat is generated upon inflation. This method utilizes sewing and/or heat sealing to create bending, making it easy to manufacture compared to many soft actuators and further allows for the creation of complex 3D structures in conjunction with methods presented in literature due to the in-plane bending generated by the presented pleating method. The design, fabrication and modeling of the APTA are presented and the actuator characterization in the form of bending angle, quasi-static torque and hysteresis tests are performed. A maximum normalized output torque of 400 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{Nm/kPa.m}^{3}$</tex-math></inline-formula> was demonstrated by the presented APTA. An empirical model for the APTA using the collected data was derived to predict torque output throughout the actuator range of motion. A controller using the empirical model was designed to track desired torque profiles. Single and Multiple step response experiments were conducted to evaluate the efficacy of the controller for burst-like actuation which could have implications in physical assistance for biological systems and in shape forming deployable structures. Further, we present several potential applications to this actuator in the form of 3D inflatable structures, a continuum module segment, and a wearable elbow device.

Damping Properties of Large-Scale Overlap Joints Bonded with Epoxy Hybrid Resin or Polyurethanes: Experimental Characterisation and Analytical Description

Structures in various industries are exposed to dynamic loads. The dissipative properties of adhesively bonded joints can contribute to the damping of dynamically stressed structures. Dynamic hysteresis tests are carried out to determine the damping properties of adhesively bonded overlap joints by varying the geometry and test boundary conditions. The dimensions of the overlap joints are full-scale and thus relevant for steel construction. Based on the results of experimental investigations, a methodology is developed for the analytic determination of the damping properties of adhesively bonded overlap joints for various specimen geometries and stress boundary conditions. For this purpose, dimensional analysis is carried out using the Buckingham Pi Theorem. In summary, it can be stated that the loss factor of adhesively bonded overlap joints investigated within this study is in the range between 0.16 and 0.41. The damping properties can particularly be increased by increasing the adhesive layer thickness and reducing the overlap length. The functional relationships of all the test results shown can be determined by dimensional analysis. An analytical determination of the loss factor considering all identified influencing factors is enabled by derived regression functions with a high coefficient of determination.

Magnetic Behavior of a Laser Deposited Fe–Ni–Mo Alloy

Magnetic shielding in spacecraft is a mission‐critical issue that must be addressed in a timely and effective manner. The high permeability of Fe–Ni–Mo alloys, makes them excellent candidates for magnetic shielding. This article explores a new and innovative approach, enabled by additive manufacturing (AM), to design, build, and test geometrically complex magnetic shields. A Fe–79.7Ni–4.1Mo alloy is additively manufactured using blown powder laser‐directed energy deposition (DED). AM build conditions are explored in the production of magnetic test rings and magnetic shield prototypes. Magnetic hysteresis test data are obtained, allowing for the determination of magnetic permeability, saturation, and coercivity. Detailed microstructural characterization is carried out. Three different prototype shield designs are printed and magnetic shield attenuation data is obtained. The magnetic field attenuation (shield effectiveness) obtained for the AM components is comparable to wrought equivalents. The values reported here for the magnetic permeability are the highest, and that for the magnetic coercivity the lowest, for any blown powder DED‐printed material currently known. The magnetic behavior is discussed with regard to grain size and orientation, as well as grain boundary effects, with all of these attributes contributing to the ultimate performance.

Mechanical properties of curvature-consistent frictional pendulum bearings and isolation performance of spherical reticulated shells

With the increasing demand for isolated long-span spatial structures, the seismic performance of structures during rare earthquakes should be improved. In this study, we proposed a type of curvature-consistent frictional pendulum bearing (CC-FPB) that may induce notable seismic isolation effects in long-period and long-span spatial structures during rare earthquakes. Hysteresis tests were performed on the structure with the CC-FPB, and a refined numerical simulation method was established to analyse the isolation performance of the CC-FPB was established. The accuracy of the simulation method was verified by comparing the simulation results with experimental results. Based on the refined numerical simulation method, the CC-FPB was applied to a single-layer spherical reticulated shell structure, and the dynamic time history response of the structure was analysed. Furthermore, the seismic isolation effect was compared with that of the classical friction pendulum bearing (C-FPB). Parametric analysis was performed for structures with different roof qualities and input ground motions. We also analysed the seismic isolation effect and isolation influence mechanism of the structure with the CC-FPB. The results indicated that the CC-FPB had high isolation performance and energy dissipation capacity. Although the isolation performance had negligible influence on the loading frequency, the energy dissipation capacity and isolation performance increased with the increase in the loading frequency and loading displacement. The isolation efficiency of the isolation structure with the CC-FPB improved in comparison with that of the structure with the C-FPB. The isolation performance and energy dissipation capacity of the isolation structure increased with the increase in the seismic amplitude. The energy dissipation and damping capacity of the CC-FPB improved under high-frequency excitation.

Experimental Study on Seismic Behavior of a new fully precast rocking beam-column joint

A new fully precast replaceable energy dissipation rocking beam-column joint (RBCJ), formed by adopting the splice joint and connecting through energy-dissipating steel plates, was proposed via referring to the mortise-tenon work in Chinese ancient architectures, aiming to improve the repairable performance of reinforced concrete (RC) joints after strong earthquakes, reduce the residual deformation of the structure and realize the rapid recovery of building functions after earthquakes. Two one-half scale beam-column joints with different lap lengths were designed and fabricated. Unidirectional low-cycle reciprocating loading of the specimen by quasi-static test, the failure process, and the influence of lap length of the splice joint on the seismic performance of the specimen were studied, and the hysteresis tests was carried out on the repaired specimen again to study the repairable performance of the RBCJ. The research showed that the residual displacement of the specimen was small, and the plastic deformation was concentrated on the replaceable energy-dissipating parts. The concrete at the edge of the dapped-end part in the long-lap-RBCJ-connecting specimen was slightly cracked, and there was no serious damage in other areas of the prefabricated member. The short-lap specimen had better seismic performance than the long-lap one. After the loading drift of the short-lap specimen reached 1 /50, the repair work was completed by replacing energy-dissipating connecting steel plates, and the seismic performance of the repaired joint had not decreased significantly. To facilitate engineering application, the equations of yield load and ultimate load that joint can undergo were deduced according to thin plate theory, the relationship between ultimate bearing capacity and thickness of energy-dissipating steel plates was given, and local stress and failure mechanism of the splice joint were analyzed, and shear and pull-out checking calculations of bolts were carried out.

Asymmetric Bouc-Wen hysteresis modeling for MFC actuator via hybrid APSO-TRR identification algorithm

Macro fiber composite (MFC) is widely used in active vibration and deformation control. The intrinsic asymmetric hysteresis nonlinearity of MFC affects the control accuracy. In this paper, a modified Bouc-Wen (MBW) model based on the sigmoid function is proposed to describe the asymmetric hysteresis characteristics of MFC, and its parameters are identified by a hybrid algorithm composed of the trust-region reflection method and asynchronous particle swarm optimization. The accuracy of the proposed MBW model is verified though hysteresis tests of MFC under different drive frequencies. The results show that the MBW model can accurately model the asymmetrical hysteresis of the MFC actuator, the modeling error is reduced by 72% compared with the classic Bouc-Wen model. The proposed hybrid parameter identification method saves 95% of the time compared with the particle swarm optimization and asynchronous particle swarm optimization algorithms. • A modified Bouc-Wen (MBW) model is proposed to describe the asymmetric hysteresis characteristics of MFC actuators. • A hybrid algorithm (APSO - TRR) with global and local search ability is proposed for parameter identification. • Performance of proposed APSO - TRR is compared with classical PSO、APSO and TRR algorithms. • Accuracy of proposed asymmetric Bou–Wen model is compared with classical Bou–Wen model.

Property-Structure Relationship on the Mechanics of Carbon Nanotube Yarns

Carbon nanotube yarns (CNTYs) are twisted hierarchical fibers which exhibit a strong property-structure relationship. Understanding of the property-structure relationship of CNTYs will allow their use in structural and energy dissipation (damping) applications. For this reason, the morphology and structure of dry-spun CNTYs are characterized by means of Raman spectroscopy mapping, atomic force microscopy, and scanning electron microscopy and correlated to their quasi-static and dynamic mechanical properties. The continuous CNTYs present some degree of structural variability, which explains the variability measured in their dynamic mechanical response. Under tension, 42.3 μm diameter (0.71 porosity) CNTYs reach specific strengths of ~0.8 N/tex and ultimate strains ranging from 4% to 7%. Mechanical hysteresis tests under incremental cyclic strain show that the CNTYs exhibits high energy dissipation, which concur with dynamic mechanical analysis (DMA). DMA shows that CNTYs are unconventional materials with high specific stiffness (per unit weight) as well as a very high damping ratio. The damping ratio increases with temperature and reach ~0.6 at 60 °C. The mechanical response of the CNTYs under tension can be explained mainly from changes in the hierarchical structural conformation of the yarn, rather than from changes in the carbon nanotube bond distance or inherent material properties.

Study on hysteretic performance of welded T-joints circular tube on platform considering seawater corrosion

In this study, the macroscopic hysteretic mechanical behaviour of welded circular tube T-joints corroded by seawater was evaluated through hysteretic mechanical performance tests. Full immersion accelerated electrochemical corrosion tests with a proportioned seawater medium were conducted on steel specimens obtained from tube joints. The generalised degradation rule of the mechanical performance of the material with the development of corrosion was obtained via a monotonic tensile test of steel specimens. The hysteresis test of corroded joints revealed that corrosion and cyclic loading have degradation effects on joint strength, stiffness, bearing capacity, and energy dissipation. At a low number of cycles, the effect of corrosion is generally greater than that of cyclic loading. A hysteretic skeleton model that can determine the ultimate load of the corroded joint was established based on the load–displacement curve. Moreover, the hysteretic rules that describe the degradation characteristics of the loading and unloading stiffness were established. Finally, the hysteresis model of corrosion joints was proposed. The model was validated using experimental results, and we demonstrated that it can accurately reflect the effect of the degree of corrosion and loading process on the hysteretic characteristics of joints.

Mechanical compressive behavior of pomelo peel and multilayer polymeric film/foam systems

The study of natural cellular materials offers valuable insights into the superior properties and functions underlying their unique structure and benefits the design and fabrication of advanced biomimetic materials. In this study, we present a systematic investigation of the mechanical behavior of fresh and oven-dried pomelo peels. Density measurements revealed the gradient structure of the pomelo peel, which contributed to its mechanical properties. Step-by-step drying revealed two types of water in the peel. Both uniaxial compression and low-strain hysteresis tests were conducted, and the results showed that fresh pomelo peel exhibits soft elastomer-like behavior, while dried pomelo peel behaves more like conventional synthetic polymer foam. Compared to fresh pomelo peel, dried peel samples showed higher compressive modulus and energy loss in 6, 8 and 10% strain hysteresis tests. The rehydration process was studied using hysteresis tests at three different strains. In addition, multilayer gradient EO/EO and LDPE/LDPE film/foams with 16 alternating layers were produced using the microlayer coextrusion technique. The morphology and mechanical properties were examined and indicated great potential for biomimicking the structure and properties of pomelo peel.

Dynamic mechanical properties of magnetorheological polyurethane elastomers in comparison to existing antivibration rubbers

ABSTRACT This article primarily focused on dynamic mechanical analysis over a frequency range (0.1 to 140 Hz), temperature range (−100 to 50°C) and strain amplitude (0.1 to 5 percent). During hysteresis testing, the damping coefficient (Tanδ) and energy dissipation of isotropic and anisotropic magnetorheological elastomers with iron nanoparticles in a polyurethane rubber matrix to existing antivibration rubber were compared. Under tensile loading, energy dissipation was measured using universal testing. Different percentages of carbon black (CB) filler (30 phr, 50 phr and 70 phr) in a polyurethane matrix were selected for anti-vibration rubber comparison. During hysteresis testing, energy absorption has been found to be greater in CB Magnetorheological Elastomers(MREs) than in isotropic and anisotropic MREs, owing largely to the inclusion of CB in the formulation. CB additives were also tested on materials that were like anisotropic MREs. Relative comparative samples with the same percentage concentration of CB mixed with iron nanoparticles have greater damping characteristics and energy absorption. However, at the glass transition temperature (Tg), certain trends in energy absorption have shifted because segment flow motion of rubber chains has the greatest impact on energy absorption at glass transition temperature.

Static and Dynamic Mechanical Characterization of Polydimethylsiloxane (PDMS) under Uniaxial Tensile Loading

The present study is based on performing mechanical characterization of polydimethylsiloxane (PDMS) under tensile loading. PDMS samples are developed by mixing prepolymer and curing agent with 10:1 ratio. Mechanical characterization of the PDMS samples is carried out using static and dynamic mechanical testing methods. In particular, the material is characterized under monotonic loading, different strain rates, and force-controlled cyclic loading. The monotonic loading tests are performed at different grip tightening levels to optimize gripping that avoids slipping and reaches failure point. The strain rate dependency and cyclic loading tests are performed to study the viscoelastic behaviour of the material. Strain rate dependency tests are carried out at the strain rates of 6.7×10-3 s-1, 3.2×10-2 s-1, and 6.2×10-2 s-1. The hysteresis tests are performed at the force rates of 0.1 – 2 N/s. The obtained results show that fixing the testing specimen made of soft hyperviscoelastic material such as PDMS is challenging and can significantly affect its stress-strain behaviour and mechanical properties. A higher strain rate increases the stiffness of the material due to the viscoelastic nature of the material. Observing the stress-strain curves, with respect to the lowest strain rate case, the curve for 6.2×10-2 s-1 strain rate diverges at 40% strain compared to 3.2×10-2 s-1 strain rate curve that diverges at 80% strain. The material shows a nonlinear hysteresis behaviour and similar energy dissipation for the considered force-controlled cyclic loading cases.

Quasi-linear viscoelastic behavior of fresh porcine ureter.

To evaluate the viscoelastic properties of the fresh porcine ureter. Prove the QLV theory can sufficiently model the stress relaxation function of porcine ureters, and determine the QLV model constants which may provide insight into the synthesis of ureteral scaffolds with biomimetic viscoelastic properties in tissue engineering. Hysteresis tests were applied to study the differences in dissipated energy ratio for each different strain group. In stress relaxation tests, samples were sub-grouped and quickly ramping up to 5%, 20%, and 30% strain in each group and gradually relaxed to a corresponding level. Bringingtogether the quasi-linear viscoelasticity (QLV) theory and stress relaxation function to determine the eight constants of the ureteral tissue, and fitting the raw data with the model via MATLAB. The hysteresis response measurement results revealed that the porcine ureter was a highly dissipative material and there were differences between toe and linear region in stress-stain curve. The stress relaxation results revealed ureters responded with time-dependent decay of stress. The eight constants of the ureteral QLV model were determined for three different strain groups, and we proved that the QLV model can sufficiently adapt the experimental data of the ureter stress relaxation. This study investigated the time-dependent properties of the porcine ureter, and demonstrated the QLV theory could be used to evaluate the viscoelastic properties of the porcine ureteral tissue.

Synthesis, microstructure and ferroelectric properties of PbO-TiO2-B2O3 based glass ceramics

The following compositions were utilised to make these glasses: PbO (50-X) TiO2 (25 + X) and B2O3 (X = 0, 5, 10, and 12.5 mol percent) are the main components of this mixture. A two-stage heat treatment process was used to make glass-ceramics.. In the glass ceramics, tetragonal lead titanate and lead borate were found to be the main crystalline phases, according to XRD data (PbB2O4). P-E hysteresis tests confirmed the glass–ceramic samples' ferroelectricity. Remenant polarisation (Pr) and hysteresis loop saturation were greater in glass ceramic samples that were heated for an additional 10 h at 793 K.

Performance coordination design method applied to replaceable artificial controllable plastic hinge for precast concrete beam-column joints

This report proposes a novel performance coordination design method wherein the precast beam-column joint cooperates with an artificial controllable plastic hinge (ACPH). This approach introduces three deformation coordination coefficients to manage the bearing capacity, rotational stiffness, and deformability between the ACPH and the reinforced concrete components. Ultimately, structural deformation resulting from seismic action is mainly concentrated on the ACPH to prevent damage to the concrete components. The design process and philosophy were translated into formulas and compiled in this paper. The ACPH performance and design process efficacy were explored using a hysteresis test performed on a ½-scale specimen and simulated using the finite element models. The results indicated that the precast reinforced concrete structure containing an ACPH exhibited excellent deformability and ductility, while guaranteeing structural integrity.

Study on hysteresis and threaded fitting behavior of bolted joint with non-parallel bearing surface

Obtaining the static hysteresis behavior of bolted joint and identifying joint parameters are of great significance to design and formulate the assemble process for the bolted joint. In this study, the relationship between the hysteresis behavior and joint parameters of bolted joint is proposed by the bolt analytical model. Then, the tightening process and thread fitting mechanism of bolt under non - parallel bearing faces are analyzed. Next, the effects of non-parallel bearing surface and external load on the joint parameters are analyzed by parametric finite element method. Finally, the friction coefficient extraction and static hysteresis test experiment of the single bolt lap beam are carried out, which verified the theory and finite element model. The results show that establishing a single bolt lap beam with threads and introducing friction coefficient can more accurately predict the stiffness and damping of the bolted joint. The tightening of the non-parallel bearing face bolt generates an additional threaded contact friction pair, which causes a deviation of preload and affects the identification results of the joint parameters.

Seismic and axial compression performance of insulated concrete sandwich wall

A new type of composite insulated concrete sandwich (ICS) wall is proposed. The wall consists of a three-dimensional spatial steel wire mesh skeleton, insulating core material and inner and outer concrete layers, all of which form a synergistic composite wall panel to work as the main stress-bearing member in the construction of multistorey high-rise buildings. To analyse the mechanical properties of the wall body, its failure mode was investigated. The wall's hysteresis curve, strength, stiffness and deformation were all analysed through a low reversed cyclic load test on two specimens, followed by an evaluation of its seismic performance. The deformability, failure mode, strain and ultimate bearing capacity of the specimens under the action of axial compression were also studied through an axial compression test on three specimens. The hysteresis test indicated that, in comparison with an ordinary shear wall, the ICS wall, connected through effective construction measures, had superior overall working performance under the same reinforcement ratio and its ductility and energy-dissipating capacity were improved. The results of the axial compression test also confirmed that the ICS wall had excellent axial compressive resistance, bending and deformation resistance, and high stability.

Seismic behavior of a replaceable artificial controllable plastic hinge for precast concrete beam-column joint

To promote and effectively control precast structures' seismic performance, a novel bending-shear decoupled prefabricated beam-column joint with a replaceable Artificial Controllable Plastic Hinge (ACPH) was proposed in this paper. The ACPH was composed of two energy dissipation systems with energy-dissipation plates for bearing the bending moment and a connection system for bearing the shear force. To explore the seismic behavior of joint affected by ACPH, hysteresis tests of two beam-column joints with ACPH and one cast-in-situ beam-column joint were carried out. It found that the ACPH can significantly affect the failure mode compared with cast-in-situ specimen while offering excellent hysteresis behavior, sufficient ductility, and superior energy consumption capacity. Even if half of the energy-consuming system fails, the ACPH still maintains remarkable seismic performance except for reduced bearing capacity. Although only the location of the ACPH has been changed, the crack development, skeleton curve, and energy consumption performance have all undergone significant changes. The bearing capacity of the ACPH specimen was enhanced with the distance between ACPH and column surface increasing, while other seismic performances were affected at different levels. Besides, the calculation model and formula of yield bearing moment capacity for the ACPH were proposed.

Thixotropy of cellulose nanocrystal suspensions

The thixotropy of cellulose nanocrystal (CNC) water suspensions is intrinsically dependent on the hierarchical structure of the suspension. The diverse hierarchies that comprise individual CNC nanoparticles and mesophase liquid crystalline domains, chiral nematic and nematic structures, contribute selectively to the rheological material response. Here, we combine rheology with polarized light imaging (PLI) to elucidate the thixotropic behavior of CNCs suspended in water. The simultaneous monitoring of PLI and rheological tests enables the observation of mesogens and their orientation dynamics. Creep, dynamic time sweep, ramped hysteresis loop, and thixotropic recovery tests combined with PLI aim to differentiate the contribution of the different hierarchical levels of CNC suspensions to their thixotropy. The range of concentrations investigated comprised biphasic (4 and 5 wt. %) and liquid crystalline phase suspensions (6, 7, and 8 wt. %). The CNC suspensions exhibited complex thixotropy behavior, such as viscosity bifurcations in creep tests and overshoot in ramped hysteresis loop tests. The restructuring and destructuring appeared to correspond to different levels of their hierarchical structure, depending mainly on the phase, in agreement with previous studies. Restructuring was attributed to re-organizations of an individual CNC, e.g., in the isotropic fraction of biphasic suspensions and at the mesogen interfaces in liquid crystalline phase suspensions. However, by increasing liquid crystalline fraction in the biphasic concentrations, restructuring could also involve mesogens, as indicated in the creep tests. For flow conditions above the yield stress, as evidenced by the ramped hysteresis and thixotropy recovery tests, destructuring was dominated by orientation in the flow direction, a process that is readily observable in the form of PLI “Maltese-cross” patterns. Finally, we show that a simple thixotropy model, while unable to capture the finer details of the suspension’s thixotropic behavior, could be employed to predict general features thereof.