Large Deformation Conditions Research Articles

Performing Magnetic Boundary Modulation to Broaden the Operational Wind Speed Range of a Piezoelectric Cantilever-Type Wind Energy Harvester

Small piezoelectric wind-induced vibration energy harvesting systems have been widely studied to provide long-term sustainable green energy for a large number of wireless sensor network nodes. Piezoelectric materials are commonly utilized as transducers because of their ability to produce high output power density and their simple structure, but they are prone to material fracture under large deformation conditions. This paper proposes a magnetic boundary modulated stepped beam wind energy harvesting system. On the one hand, the design incorporates a composite stepped beam with both high- and low-stiffness components, allowing for efficient vibration and electrical energy output at low wind speeds. On the other hand, a magnetic boundary constraint mechanism is constructed to prevent the piezoelectric sheet from breaking due to excessive deformation. Experiments have confirmed that the effective operational wind speed range of the harvester with magnetic boundary constraints is doubled compared to that of the harvester without magnetic boundary constraints. Furthermore, by adjusting the magnetic pole spacing of the boundary, the harvesting system can generate sufficiently high output power under high-wind-speed conditions without damaging the piezoelectric sheet.

Mechanical Properties of Iron Tailing Sand Grout Sleeve Joints and Force Analysis.

In this paper, the mechanical properties and internal stress condition of the reinforcing bar sleeve connectors with ferro-tailed mineral sand cementitious grout as filler material were analyzed as research objects. Firstly, an experimental study was carried out on the reinforcing bar sleeve connectors of iron tailing sand grout with a 40% substitution rate of mechanism sand to analyze the mechanical properties of different grout types, age, and reinforcement diameters under unidirectional tensile, high stress, and large deformation of repeated tensile and compressive stresses. Next, five groups of sleeve joints with different anchorage lengths were set up for unidirectional tensile tests. The results show that, with the decrease of the diameter of the reinforcement, the grip force and bond strength of the iron tailing sand grout on the internal reinforcement gradually increase. Under conditions of large deformation and high stress due to repeated tensile loading, the residual deformation and total elongation of iron tailing sand grout sleeve joints are satisfactory. Additionally, the restraining anchorage effect of iron tailing sand grout in the end section is small. The utilization rate and integrity of iron tailing sand grout in the initial anchorage section are better.

Design, preparation and properties of biomedical Ti-Nb quaternary alloys with high strength and low modulus: insights from first-principles calculations

In this paper, we designed and developed biomedical β-type Ti-Nb quaternary alloy materials with high strength and low modulus. Building upon the d-electron alloy design method and the valence electron concentration e/a method, we use a Python program and thermodynamic theoretical parameters to determine a Ti-Nb quaternary alloy with the characteristics of a single-phase solid solution. Subsequently, we engage in theoretical and experimental investigations on the low modulus alloys identified through first-principles calculations. The results show that both Ti7Nb6Zr1Al2 and Ti11Nb2Ta2Al1 maintain a single β phase before and after cold rolling, which is related to the strong electronic density of states of s and p orbitals at low energy levels in the crystal structure of the two alloys. Ti11Nb2Ta2Al1 has a strong charge distribution on the (001) crystal plane, which causes a large amount of internal stress under large deformation conditions to promote grain crushing and weaken the intensity of the (001)[1-10] texture in the ODF diagram of 2 = 45°. The cold-rolled Ti11Nb2Ta2Al1 exhibits better corrosion resistance and biocompatibility than the cold-rolled Ti7Nb6Zr1Al2, and the good biocompatibility is related to the strong covalent bond between Al and Ta that inhibits the diffusion of Al ions. 90% cold-rolled Ti11Nb2Ta2Al1 stands out as an exceptionally promising orthopedic implant material due to its high elastic allowable strain (ReH/E), good corrosion resistance and biocompatibility.

Fatigue Analysis of BRB Weld under Low Period and Large Deformation based on DIC Technology

This paper conducts an in-depth study on the fatigue performance of buckling-restrained braces (BRBs) under low-cycle large deformation conditions. As a device that utilizes the hysteretic energy dissipation of metal yielding, BRBs have been widely used in the design of new structures and the seismic strengthening of existing structures. Its remarkable advantages include stable performance, convenient fabrication, low cost, and excellent hysteretic performance. Applying DIC technology to the fatigue analysis of BRB welds under low-cycle large deformation can achieve full-field measurement of deformation and stress at the weld, providing strong technical support for in-depth study on the fatigue performance of BRB welds.

StrainNet-LD: Large Displacement digital image correlation based on deep learning and displacement-field decomposition

First, a displacement-field decomposition strategy is proposed that effectively enhances the accuracy of digital image correlation (DIC) algorithms under large displacement or deformation conditions. The implementation methodologies of displacement-field decomposition under both Lagrangian and Eulerian descriptions are derived and presented. Second, displacement-field decomposition is applied to speckle image correlation algorithms based on deep learning, resolving the contradiction between registration capability of large displacement and the accuracy. A CUDA-accelerated and residual learning-based strain fitting algorithm is proposed for high-precision and real-time strain computation. This method is named “StrainNet for Large Displacement” (StrainNet-LD). StrainNet-LD achieves a calculation speed of 768 × 768 × 6 fps (768 × 768 × 3 fps with strain calculated simultaneously) on GPU with displacement MAE < 0.05 pixels and strain MAE < 0.002ε. Finally, rubber tensile tests, 3D motion measurement of composite shells, and morphology reconstruction experiments of speckle-free composite repair structures are conducted to validate the algorithm's robustness and efficiency. Some vital discussions of displacement-field decomposition are given in the Appendixes. The code and dataset are available at https://github.com/GW-Wang-thu/StrainNet-LD.

Research on the mechanical model of anchorage resistance in deeply filled jointed rock masses

The calculation model of anchorage resistance is the core issue in the study of anchorage theory in jointed rock masses. Due to the complex geological environment of deep rock masses, the anchorage mechanism of soft rock filled in joints is even more complicated and has not yet been clearly defined. Based on the theory of structural mechanics, considering the restraining stress in the plastic extrusion deformation zone of the bolt as a rectangular distribution pattern is more in line with the interaction state between the bolt and the surrounding medium when the rod is at its limit load. Taking into account the influence of the joint filling part, the value of restraining stress is revised to include a formula expression that factors in the strength of the filling material(σcj) and the degree of filling(Δ).Develop a mechanical model of anchorage resistance for filled joint soft rock considering large deformation conditions due to turning angles. Further, conduct shear tests on anchored filled joint rock bodies under various σcj−Δ combination patterns with constant normal stiffness (CNS) boundary conditions to validate and analyze the model. The research results indicate that under the influence of deep rock mass mechanical boundaries, the ratio of the shear deformation section length to the bolt diameter differs from existing research results, with specimens l/D under different σcj−Δ combinations typically ranging between 0.7 and 1.5 times.The displacement of the bolt at turning angle θ increases with the increase of Δ and decreases with the decrease of σcj, where Δ is the main factor affecting the degree of tensile-bending deformation of the bolt. As Δ increases, the calculated contribution rates of bolt shear resistance under three different σcj conditions increase from 9.8% to 34.8%, 40.3%, and 39.4%, respectively. This indicates that an increase in Δ can reduce the increment of normal stress, further decrease the overall stress and compressive deformation zone’s normal constraint stress in the rock mass, leading to a gradual increase in the degree of tensile-bending deformation of the bolt and an increase in resistance contribution.For the specimens with three different values of σcj, the ratio of shear force to axial force providing resistance on the joint surface decreased from a maximum of 2.83 to 0.72, 1.04, and 2.01, respectively. This indicates that when σcj is relatively large, tensile-bending deformation is more likely to occur, mobilizing the axial force of the bolt to provide the main resistance. Further systematic analysis was conducted on the length of the shear deformation section of the bolt and the distribution characteristics of the anchor resistance under condition β=30°∼90°. The reasonableness of the model was verified through the comparison of model calculation results with experimental data. Finally, a series of recommendations were proposed for preventing failure of the anchored system in filled jointed rock masses in actual engineering projects.

Fabrication and Characterization of Electrically Conductive 3D Printable TPU/MWCNT Filaments for Strain Sensing in Large Deformation Conditions (Adv. Sensor Res. 6/2024)

Fabrication and Characterization of Electrically Conductive 3D Printable TPU/MWCNT Filaments for Strain Sensing in Large Deformation Conditions (Adv. Sensor Res. 6/2024)

Fabrication and Characterization of Electrically Conductive 3D Printable TPU/MWCNT Filaments for Strain Sensing in Large Deformation Conditions

AbstractThis study investigates the development of thermoplastic polyurethane (TPU) filaments incorporating multi‐walled carbon nanotubes (MWCNT) to enhance strain‐sensing capabilities. Various MWCNT reinforcement ratios are used to produce customized feedstock for fused filament fabrication (FFF) 3D printing. Mechanical properties and the piezoresistive response of samples printed with these multifunctional filaments are concurrently evaluated. Surface morphology and microstructural observations reveal that higher MWCNT weight percentages increase filament surface roughness and rigidity. The microstructural modifications directly influence the tensile strength and strain energy of the printed samples. The study identifies an apparent percolation threshold within the 10–12 wt.% MWCNT range, indicating the formation of a conductive network. At this threshold, higher gauge factors are achieved at lower strains. A newly introduced Electro‐Mechanical Sensitivity Ratio (ESR) parameter enables the classification of composite behaviors into two distinct zones, offering the ability to tailor self‐sensing structures with on‐demand properties. Finally, flexible structures with proven application in soft robotics and shape morphing are fabricated and tested at different loading conditions to demonstrate the potential applicability of the custom filaments produced. The results highlight a pronounced piezoresistive response and superior load‐bearing performance in the examined structures.

Deciphering non-elastic deformation in amorphous alloy: Simultaneous aging-induced ordering and rejuvenation-induced disordering

The mechanical and physical properties of amorphous alloys depend on their time, temperature, and stress history. Due to their out-of-thermodynamic-equilibrium nature, describing the nonelastic deformation while considering the evolution of the structural state poses a significant challenge. We address this challenge by incorporating a parameter for structural state changes into a conventional deformation theory. This allows us to account for aging-induced ordering and deformation-induced disordering in the description of the mechanical deformation. In the apparent elastic regime (small strain), aging dominates while disorder caused by deformation can be disregarded. In this context, we have also made modifications to the widely used stretched exponential function, incorporating in-situ aging during deformation. This modification successfully describes the stress relaxation behavior under small deformation conditions and provides insights into parameter evolution in this process. Under large deformation conditions, both aging and deformation induced rejuvenation effects on the structural state must be considered simultaneously. By analyzing the evolution of defect concentration during this process, we describe relevant experimental results within the framework of the free volume theory, effectively separating the contributions of aging and rejuvenation to the structural state during the deformation process.

A Dynamical Model for the Control of a Guyed Tensegrity Beam Under Large Displacements

Abstract Most studies regarding models of tensegrity systems miss the possibility of large static deformations or provide elaborate and lengthy solutions to determine the system dynamics. Contrarily, this work presents a straightforward methodology to find the dynamic characteristics of a guyed tensegrity beam structure, allowing the application of vibration control strategies in conditions of large deformations. The methodology is based on a low-order, adaptive, nonlinear finite element model with pre-stressed components. The method is applied to numerical and experimental models of a class 2 tensegrity structure with a high length-to-width aspect ratio. Image processing and accelerometer data are combined to extract the experimental natural frequencies of the structure, which are compared to numerical results. Prony’s method is applied to estimate damping, and a numerical control strategy is employed using the dynamical model of the structure.

Accurate rotation identification of flexural structures using long-gauge fiber optical sensors

The rotation of beam and column components is a key parameter in structural health monitoring (SHM), which providing analysis of bending deformation, evaluation of structural stability, and overall structural performance. Conventional sensors directly measuring rotation are typically designed assuming linear behavior. It becomes challenging to achieve precise and rapid measurements of small deformations while accurately measuring significant large deformations. This study obtained experimental and analytical studies to identify the rotation response of flexural structures using long-gauge fiber optical sensor array. Rotation is determined through two mechanisms: the plane section assumption, utilizing strain distributions on the compression and tension sides, and the sectional fiber model (SFM)-based neutral axis identification. In order to discuss the applicability of these two mechanisms from elastic to plastic state, four identification methods are proposed: Method 1 uses strain distribution on the concrete surface to identify rotation, Method 2 uses strain on steel bars, and Methods 3 and 4 use SFM-based neutral axis identification with strain measured on the compression side concrete surface and tension side steel reinforcements, respectively. Laboratory tests of beams and columns as well as field tests were shown. First, a comparison of the rotation identification accuracy among the four methods was conducted using a reinforced concrete (RC) beam test in the elastic state. Results showed good agreement between the rotations identified by all four methods and those directly measured by the tilt meter. And then, the accuracy of rotation identification in crack state and inelastic state was discussed by using a RC column test. The results indicate that, following the occurrence of cracks in concrete surface, neither Method 1 nor Method 2 can accurately identify the rotation. This is attributed to the fact that cracks disrupt the correspondence between the strain on the tension side and the compression side. Meanwhile, Methods 3 and 4 maintain a good rotational identification accuracy even after cracks happened. Moreover, when the steel reinforcement undergoes yielding and the concrete column enters the inelastic state, the rotation results identified by Methods 3 and 4 still match with the directly measured rotations. This underscores the effectiveness of the SFM-based rotational identification under large deformation conditions. Furthermore, experimental results indicate that with the increase in deformations, slip occurred in the sensing units near the column base in the sensor array on the tension side. This shows that the sensing units installed on the steel reinforcement (Method 4) are more suitable for calculating rotations during the large deformation state compared to the sensing units positioned on the concrete surface (Method 3). At last, two case studies involving the monitoring of an actual bridge grid and a bridge column were investigated to assess the effectiveness of dynamic rotation identifications. The performance evaluation results for various rotation angle measurement sensors demonstrate that long-gauge fiber optical sensors can be used for rotation identification, ensuring the stability of dynamic rotation identification.

An improved DIC method for full-field strain measurement in tensile tests on aluminium alloys under hot stamping conditions

Digital image correlation (DIC) outperforms other strain measurement technologies due to its versatility, accuracy, non-contact nature, and capability to capture full-field strains. However, for aluminium alloys like AA6082 under high-temperature and large-deformation conditions, the shiny effects observed in the gauge area degrade the quality of the captured deformation images, leading to failures in the DIC analyses. In this study, the source of the shiny effects was investigated by analysing the evolution of AA6082 specimen surfaces painted with speckle patterns during hot stamping deformation. It was found that the shiny effects were attributed to the exposure of the reflective base material due to paint peeling and cracking. To overcome these problems, the DIC method was improved by developing a novel procedure for generating more effective speckle patterns and utilising a cross-polarisation optical system (XPOL) to mitigate the shiny effects. The improved DIC method was applied to AA6082 in both uniaxial and biaxial tensile tests under diverse hot stamping conditions, along with applications to boron steel for comparison. These improvements significantly reduced the shiny effects and increased the time over which full-field strains can be measured for AA6082, reaching over 96% (up from 75%) of the fracture time in the uniaxial tests and even 100% in the biaxial tests. The improved DIC method enables the full-field strain measurement for aluminium alloys under hot stamping conditions, allowing for the accurate determination of their thermomechanical properties.

Large‐Scale Synthesis of Flexible Cermet Interdigital Electrodes with Stable Ceramic‐Metal Contact for Fire‐Resistant Pressure Tactile Sensors

AbstractCermet has broad applications in electronics, but achieving stable ceramic‐metal contact has always been a challenge, particularly at hot temperature and large deformation conditions, due to the significant differences in thermal expansion coefficient and stiffness of ceramics and metals. Here, stress matching and strong interphase bonding at the heterogenous ceramic‐metal contact are realized by using flexible ceramics, leading to stable applications in flexible fire‐resistant pressure tactile sensors. Cu/Au nanolayers are deposited first onto the toughened flexible SiO2 nanofibers with a chemical plating method to form sensitive interdigital electrode sensors, then use an in situ thermal reaction strategy to form conformal and interlocked Au3Cu and CuSiO3 interphases, which enhance the mechanical thermal stability of the ceramic‐metal contact. With deep learning technique, the as‐fabricated intelligent pressure tactile gloves can accurately recognize the human body parts in low‐visible burning environments and show a long‐term stability over 1000 cycles with a high sensitivity of 112.18 kPa−1, which is important for developing intelligent firefighting.

Stretchable flexible fiber supercapacitors for wearable integrated devices

PANI-TPU films were prepared by electrostatic spinning and in situ polymerization, and a fiber supercapacitor that maintains stable performance under large tensile deformation conditions can be realized by twisting.

Coaxial Electrohydrodynamic Printing of Microscale Core-Shell Conductive Features for Integrated Fabrication of Flexible Transparent Electronics.

Reliable insulation of microscale conductive features is required to fabricate functional multilayer circuits or flexible electronics for providing specific physical/chemical/electrical protection. However, the existing strategies commonly rely on manual assembling processes or multiple microfabrication processes, which is time-consuming and a great challenge for the fabrication of flexible transparent electronics with microscale features and ultrathin thickness. Here, we present a novel coaxial electrohydrodynamic (CEHD) printing strategy for the one-step fabrication of microscale flexible electronics with conductive materials at the core and insulating material at the outer layer. A finite element analysis (FEA) method is established to simulate the CEHD printing process. The extrusion sequence of the conductive and insulating materials during the CEHD printing process shows little effect on the morphology of the core-shell filaments, which can be achieved on different flexible substrates with a minimum conductive line width of 32 ± 3.2 μm, a total thickness of 53.6 ± 4.8 μm, and a conductivity of 0.23 × 107 S/m. The thin insulating layer can provide the inner conductive filament enough protection in 3D, which endows the resultant microscale core-shell electronics with good electrical stability when working in different chemical solvent solutions or under large deformation conditions. Moreover, the presented CEHD printing strategy offers a unique capability to sequentially fabricate an insulating layer, core-shell conductive pattern, and exposed electrodes by simply controlling the material extrusion sequence. The resultant large-area transparent electronics with two-layer core-shell patterns exhibit a high transmittance of 98% and excellent electrothermal performance. The CEHD-printed flexible microelectrode array is successfully used to record the electrical signals of beating mouse hearts. It can also be used to fabricate large-area flexible capacitive sensors to accurately measure the periodical pressure force. We envision that the present CEHD printing strategy can provide a promising tool to fabricate complex three-dimensional electronics with microscale resolution, high flexibility, and multiple functionalities.

Experimental study on the mechanical properties of longitudinal joints of shield tunnels under large deformation conditions

Known to be the weakest part of the shield tunnel lining rings, the longitudinal joints render the lining rings prone to large deformation and related diverse defects under nonuniform pressure loading, thereby seriously compromising the safety, serviceability and durability of the tunnel structure. In light of the paucity of studies regarding the performance of joints under large deformation, this paper presents a series of experiments examining the damage mechanism of longitudinal joints under large deformation and investigating the effects of the bolt strength, initial joint configuration, and loading level on the mechanical properties of longitudinal joints. Moreover, a finite element model was developed for the joint, capable of simulating large deformation and bolt yielding. Results show that the specimen’s failure is characterized by concrete cracking and spalling at the compression side of the joint, and/or the thread stripping or fracture failure of the bolts. Besides, an increase in bolt strength can increase the bending capacity of the joint. The discontinuous joint configuration determines the compression height of the joint section cannot be continuously changed, which results in an abrupt change in structural stiffness and a four-stage change in bolt strain. Changes in the loading level not only affect the joint’s bending capacity to some extent, but also alter how cracks develop near the joint. Furthermore, the relationship between the joint opening angle and the segmental rotation angle proves the rigid body deformation characteristics of the segment before the bolts yielded. With the segmental rotation angle increased, the maximum joint opening width and mid-span deflection increased linearly, but the compression height decreased meantime. In addition, the relationship between the bolt strain and the segmental rotation angle exhibited a two-stage linearity after the bolt began to be stressed.

Microstructural and mechanical evolution of ZnAlAg superplastic alloy under large deformation conditions

Microstructural and mechanical evolution of ZnAlAg superplastic alloy under large deformation conditions

Research on the breakage and fractal characteristics of calcareous sand

Calcareous sand is widely used in coastal engineering and island construction, which has the characteristic of easy crushing. A series of ring shear and one-dimensional compression creep tests were carried out for the crushing evolution under the influence of large deformation and time length effects. The mechanical characteristics and deformation properties of the single-graded specimens were analyzed, focusing on the crushing characteristics, and fractal properties under the action of different shear displacements, stress levels, initial gradations and creeping motion effects. The results show that the fractal dimension is positively correlated with crushing, the increase of shear displacement, stress level, and initial mean particle size has a facilitating effect on crushing. Under large deformation conditions, this promoting effect gradually tends to slow down, and the characteristic of limit fractal exists. The creep behavior reflects the continuous deformation characteristics of calcareous sand, and the specimen as a whole is still in the stage of crushing development, and the effect of time duration on the fractal is limited.

Wireless, Smart Hemostasis Device with All-Soft Sensing System for Quantitative and Real-Time Pressure Evaluation.

The properly applied pressure between the skin and hemostasis devices is an essential parameter for preventing bleeding and postoperative complications after a transradial procedure. However, this parameter is usually controlled based on the subjective judgment of doctors, which might cause insufficient hemostatic effect or thrombosis. Here this study develops a compact and wireless sensing system for continuously monitoring the pressure applied on the radial artery and wrist skin in clinical practice. A liquid metal (LM)-based all-soft pressure sensor is fabricated to enable conformal attachment between the device and skin even under large deformation conditions. The linear sensitivity of 0.007kPa-1 among the wide pressure range of 0-100kPa is achieved and the real-time detection data can be wirelessly transmitted to mobile clients as a reference pressure value. With these devices, detailed pressure data can be collected, analyzed, and stored for medical assistance as well as to improve surgery quality.

Development of PSS-bolt with high load and large deformation capacities

As mining migrates to deep levels, engineering disasters such as excessive deformation, rockburst and massive roof collapse occur frequently. It is important to develop rockbolts that have high load and large deformation capacities, which translates into high energy-absorption capacity, for ground support. This paper presents a piston self-swelling bolt (abbreviated as PSS-bolt) that utilizes steel stretching and frictional sliding to maximize the bolt’s energy absorption capacity. The structure design and working mechanism of the PSS-bolt are introduced. The influence of rod strength, piston length and tube shape on the load–displacement curves of the PSS-bolt was investigated. Laboratory and field static pull-out tests were carried out to optimize the piston length of the PSS-bolt. The test results show that when the piston length is 1350 mm, the load varies between 180 and 210 kN, the displacement can reach 500 mm, and the energy absorption capacity is 95 kJ. In addition, the bolt can reach 71.4% and 100% of its ultimate strength 12 h and 24 h after installation, respectively. The PSS-bolt presented in this paper has high force and large deformation capacities, which can provide a large energy capacity for ground support in high stress and large deformation conditions.