Wire Strain Research Articles

Examination of factors affecting strain tolerance of multifilament MgB2 wires with Fe barrier

Abstract There are two fabrication processes, the wind and react method and the react and wind method, that are used to manufacture magnesium diboride (MgB2) magnets. The react and wind method is more desirable to simplify the coil fabrication process, but the understanding of the strain tolerance of the sintered MgB2 wire is insufficient. Hence, this study focused on determining the main factors that contribute to the strain tolerance of the MgB2 wire with Fe barrier. It is generally thought that irreversible strain of sintered MgB2 wire is mainly determined from the residual strain of MgB2 filament, which is caused by the difference in the coefficient of thermal expansion among MgB2 and metal sheaths. To estimate the residual strain of MgB2 wire, the effect of yielded material must be considered. We calculated the residual strain of each constituent material used in the ten filament MgB2 wire in which copper was yielded during the cooling process from sintering temperature to room temperature. The calculated residual strains of metal sheaths except copper were compared with yield strains, and whether they yield was confirmed. The estimated residual strain of the MgB2 filament was also compared with the experimentally obtained irreversible strain, and the difference in these strains suggests the strain tolerance of the MgB2 filament. By measuring the irreversible strains of the MgB2 with different sintering times but the same residual strain, it was confirmed that the effect of the mechanical strength of the MgB2 filament on the strain tolerance of the MgB2 wire is slight but certain.

Performance and behaviour of prebored and precast pile with floating pile tip based on A full-scale field static axial load test

This study investigates the load transfer mechanism of a Prebored and Precast pile (PP pile), constructed installed in accordance with the rules applicable to the Hyper-Straight pile method (HS pile), in clay soils. While the HS pile method, developed in Japan, typically results in high bearing capacity piles in various soil types, its performance in clay soils remains understudied. Our research focuses on a unique configuration where the pile tip “floats” within a soil–cement mixing (SCM) column near the bottom of the borehole, a condition that significantly influences the system’s performance.We conducted a full-scale axial static load test on a 500 mm diameter and 140 mm thickness straight shaft precast prestressed concrete spun pile. The pile was instrumented with vibrating wire strain gauges (VWSG) and displacement measuring devices (tell-tales), embedded 15 m deep in a 750 mm diameter SCM column (15.75 m long). The pile tip was positioned 75 cm above the bottom of the borehole, creating a floating condition within the SCM material. Both the pile and the surrounding SCM were instrumented to provide comprehensive data on the system’s behavior.The test involved two loading–unloading cycles. The 1st Cycle reached a maximum load of 3627 kN, resulting in a 75.52 mm pile head settlement. The 2nd Cycle achieved a maximum load of 4181 kN, leading to a 118.04 mm pile head settlement. In the 1st Cycle, we observed upward movement of the SCM material around the shaft after the pile skin friction reached its maximum capacity. Stress at the pile tip exceeded the unconfined compressive strength of the SCM material, indicating potential local shear failure.Contrary to expectations based on HS pile performance in other soil types, the ultimate bearing capacity of our pile was determined to be 2000 kN, comprising 545 kN from skin friction and 1455 kN from end bearing. This result aligns more closely with the behavior of conventional bored pile rather than the “hyper” capacity typically associated with HS pile. Consequently, we classify our pile as a “prebored and precast pile,” like systems used in China and Korea.Our study concludes that the strength of the SCM material and the pile tip location significantly influence the pile’s bearing capacity in clay soils. These findings highlight the critical impact of soil type on the performance of piles constructed using the HS method. The observed behavior suggests that current design methods for HS pile may overestimate capacity in clay conditions, emphasizing the importance of soil-specific analysis and testing.This research contributes to the understanding of PP pile behavior in clay soils, providing valuable insights for geotechnical engineers. It underscores the need for refined prediction models and design methods specific to these soil conditions, paving the way for more accurate and reliable foundation designs in regions with predominant clay soils.

P‐172: Study on The effect of Module Films on Metal Wire Strain During the Pad bending Process

Based on ABAQUS mechanical simulation software and the same bending radius, this paper simulated and an alyzed the strain change trends of metal wires on the different schemes for other key influencing films, such as BPL, PI and TPOC. On the basis of the simulation results, the conclusions are follows: PI thickness thinn ing or TPOC thickness increases can decrease the stra in of the metal wires at bending region. However, the change of BPL thickness has no significant effect.

Micro-resistance welding of NiTi shape memory alloy wire and MP35N wire

The micro-resistance welding between NiTi shape memory alloy and Co-35Ni-20Cr-10Mo alloy (MP35N) wires was investigated to gage the feasibility of their future applications. Welding current and electrode force significantly affected the joint breaking force. The highest joint breaking force (0.99 kgf) at the optimized welding parameter (0.51 kA, 7.500 kg) was accomplished by maximizing the solid-state bonded area and minimizing the heat-affected zone (HAZ). This highest joint breaking force was higher than that of the micro-resistance welded NiTi wire joint reported in previous studies. Furthermore, the cyclic tensile test revealed that the accumulated residual strain of NiTi wire was reduced after welding. This could be attributed to the reduction in the dislocation density through grain growth in the HAZ of NiTi wire during the welding process.

3D Printed MXene-Based Wire Strain Sensors with Enhanced Sensitivity and Anisotropy.

Stretchable strain sensors play a crucial role in intelligent wearable systems, serving as the interface between humans and environment by translating mechanical strains into electrical signals. Traditional fiber strain sensors with intrinsic uniform axial strain distribution face challenges in achieving high sensitivity and anisotropy. Moreover, existing micro/nano-structure designs often compromise stretchability and durability. To address these challenges, a novel approach of using 3D printing to fabricate MXene-based flexible sensors with tunable micro and macrostructures. Poly(tetrafluoroethylene) (PTFE) as a pore-inducing agent is added into 3D printable inksto achieve controllable microstructural modifications. In addition to microstructure tuning, 3D printing is employedfor macrostructural design modifications, guided by finite element modeling (FEM) simulations. As a result, the 3D printed sensors exhibit heightened sensitivity and anisotropy, making them suitable for tracking static and dynamic displacement changes. The proposed approach presents an efficient and economically viable solution for standardized large-scale production of advanced wire strain sensors.

Evaluation of Design Parameters (α and β) for Analysis and Design of Piles on Soft Clays

This paper presents the analyses of 12 prestressed concrete instrumented test piles (TPs) that were driven in different bridge construction projects of Louisiana as part of a load testing program. The 12 TPs were driven mainly in cohesive soils. Detailed soil characterizations including both laboratory and in situ tests were conducted to determine the different soil properties. The TPs were instrumented with vibrating wire strain gauges to be able to calculate the distribution of skin friction and end-bearing capacities separately. Static load tests and dynamic load tests were conducted on each TP after end of driving to calculate the ultimate load capacity. Fifty six soil layers exhibiting clayey soil behavior and sandy soil behavior dominated the remaining 15 soil layers. The total stress parameter (α) and the effective stress parameter (β) were back-calculated for each soil layer. The α values ranged from 0.22 to 1.80, and the β values ranged from 0.11 to 0.83. Regression analyses were performed on 42 soil layers (75% data) to develop an empirical model to predict α as a function of undrained shear strength. The remaining 25% of the data were used to verify the developed model, and good agreement was observed between the measured and predicted values.

Spatio-temporal autogenous shrinkage and cracking behavior of core concrete in full-scale CFST: Insights from the world's largest span arch bridge

A full-scale concrete-filled steel tube (CFST) examination was performed on the Tian'e Longtan Bridge, featuring a 600-meter span and 0.9-meter steel tube diameter, to assess internal autogenous shrinkage distribution. This study employed vibrating wire strain gauges and distributed optical fibers to measure the shrinkage and detect cracking in the core concrete. Analysis of the test results led to the formulation of models that describe the axial and radial shrinkage behavior over time and space. Increased optical fiber strain highlighted regions undergoing local plastic softening and cracking. This research facilitates the early prediction and precise identification of potential cracking areas in the core concrete through optical fiber monitoring.

P‐10.5: Study on The effect of Module Films on Metal Wire Strain During the Pad bending Process

P‐10.5: Study on The effect of Module Films on Metal Wire Strain During the Pad bending Process

Exploring key factors affecting the ultimate compression capacity of Unbonded Steel-mesh-reinforced Rubber Bearings

To address bearing-sliding damage in highway bridges during seismic events, the Unbonded Steel-mesh-reinforced Rubber Bearing (USRB) was developed. This novel bearing employs flexible, high-strength steel wire meshes as reinforcement, enhancing lateral deformation capacity and reducing bearing-sliding risk. Recent seismic specifications increased the bearings' vertical design load to 30 MPa, where existing bearings with flexible reinforcements (e.g., fiber-reinforced bearings) fail to meet this standard. Hence, for the first time, our study thoroughly investigated the ultimate compression capacity of USRBs and the key factors influencing the capacity. Through ultimate compression tests on full-scale prototypes, we demonstrated that USRBs can comply with heightened seismic requirements, with primary failure attributed to the tensile failure of the steel mesh reinforcement. These tests were complemented by 3D finite element modeling in ANSYS, employing the LINK180 elements for mesh reinforcement and defining the ultimate capacity as the point at which reinforcement stress reached tensile strength. This particular modeling approach, validated against experimental data, can accurately predict the ultimate compression capacity and the force-deformation response of USRBs. A comprehensive parametric analysis, using the validated modeling approach and an advanced statistical method LHS-PRCC, was conducted to identify the key factors influencing the compressive capacity, including bearing geometric parameters (i.e., bearing width, the second shape factor, and rubber layer thickness), steel-mesh configuration characteristics, and steel-mesh material properties. Our findings emphasize the significance of rubber layer thickness, steel mesh weight, and steel wire tensile strength and strain in influencing the USRBs' ultimate compression capacity. Based on these key factors, an empirical equation for the ultimate compression capacity of USRBs was established to guide the optimization design of USRBs. This study not only fills the gap in USRB's performance under extensive compression but also provides a foundation for future optimization of these bearings to enhance their performance in bridge engineering.

Realistic long-term stress levels in a deep segmented tunnel lining, from hereditary mechanics-informed evaluation of strain measurements

Realistic estimation of stresses in segmented tunnel linings is a challenge tackled herein by means of a hybrid, i.e. computational-experimental, approach. Thermistor-equipped vibrating wire strain gauges were installed (i) into concrete samples undergoing one year-long uniaxial creep tests under the environmental conditions of the tunnel site, and (ii) into the tubbings making up the tunnel lining of the Koralm tunnel. The data obtained from the creep tests allow for calibration and validation of an integro-differential thermo-viscoelastic model. The creep function combines a power-law for short-term creep with a logarithmic law for long-term creep. The corresponding relaxation function is determined by means of Laplace-Carson transformation, inversion, and back-transformation. This is the basis for translating the circumferential strain histories measured in the tubbings of Ring 2013 in Koralm tunnel KAT3 into circumferential and longitudinal stress evolutions. They are mainly due to mechanical ground-shell interactions. The corresponding degree of utilization increases during the first four months after ring installation, and remains virtually constant thereafter. Stress fluctuations due to seasonal temperature variations play only a minor role. With regards to a long-term prognosis, it is very interesting to note that the strain measurements recorded in the tubbings, when plotted as function of the logarithm of time, follow bi-linear trends. These trends can be extrapolated to 150 years, the targeted service life of newly built tunnels in Austria. Throughout this period, the viscoelasticity-based estimates of the stresses in the vicinity of the strain sensors stay temporally constant, at some 40% of the strength of concrete.

The development of unit shaft resistance along driven piles in subsiding soil

The influence of bitumen coating on the development of unit shaft resistance along driven steel and precast concrete piles resulting from subsiding surrounding soft soil (gyttja) induced by fill placement at terrain was investigated. All piles were instrumented with conventional discrete-point vibrating wire strain gauges and distributed fibre optic sensors to achieve high-resolution strain measurements. The magnitude of the mobilised unit shaft resistance along uncoated piles was observed to be primarily related to an increase in effective stress resulting from the dissipation of excess pore water pressures. The unit shaft resistance along bitumen-coated piles was found to be primarily related to the rate of relative movement between pile and soil, which highlights the effectiveness of bitumen coating in reducing shaft resistance.

Long-Term Shrinkage Measurements on Large-Scale Specimens Exposed to Real Environmental Conditions

This article presents an experimental testing campaign on large-scale concrete specimens with cross-sectional areas of up to 1 m2 and a specimen length of 3 m. The primary goal of the testing campaign was to study the shrinkage behaviour of large-scale specimens exposed to real environmental conditions. Large-scale prismatic concrete specimens were equipped with vibrating wire strain gauges to monitor the strain evolution inside the specimens. To analyse the shrinkage behaviour of the specimens, the thermal strain had to be deducted from the measured strain. To study the influence of seasonal environmental conditions, different specimen production dates (in summer and winter) were examined. The measured shrinkage strains of the large-scale specimens are compared with the results of shrinkage models developed by two engineering entities (fib (Fédération Internationale du Béton) and RILEM (International Union of Laboratories and Experts in Construction, Materials, Systems and Structures)). The comparison shows a poor agreement of the measurements with the models, even though the results from the model for small specimens tested in the laboratory under constant environmental condition agree well with the experimental results. This leads to the conclusion that the poor agreement between the measurements and the shrinkage models must be due to the seasonally changing environmental conditions. The comparison of the results from specimens with different production dates shows that different shrinkage behaviour occurs, especially in the first year of measurements.

Investigating Damage in Reinforced Concrete Members by Using Vibrating Wire Strain Gauge

Recently the use of vibrating wire strain gauges has increased to find out the damage in a reinforced concrete structure. The assembly and functioning of this acoustic strain gauge are presented. This gauge provides numerous benefits including its sensitivity to measure strain (up to 1micron) and its property of being easily attached on any concrete surface. The gauge apparatus can be made in a lab due to its low cost which gives it an edge over the conventional systems. The gauge was calibrated after considering the variations in temperature. The purpose of the experimentation was to set up a low-cost vibrating wire strain gauge, calibrate it and use it for static strain damage assessment of a reinforced concrete beam. The strain readings from the vibrating wire strain gauge were cross-checked using a Demec gauge. Discrete Fourier transforms moving window was utilised to analyse the vibration signals specifically the change in natural frequency with respect to time. The gauge setup provided a cheap and accurate way for measuring long-term static strain in reinforced concrete structures. The results are presented and reviewed.

High-temperature mechanical properties and failure modes of UHSS wire for cable-supported bridge

The frequency of fire accidents in cable-supported bridges is increasing, but the ultra-high strength steel (UHSS) wire for cable-supported bridges lacks a unified expression of the degradation law of its high-temperature mechanical properties. Therefore, for the emerging 1960 and 2060 MPa UHSS wires, a series of steady-state tests are carried out in this study. The stress-strain response, elastic modulus, yield strength, ultimate strength, ultimate strain, and failure strain of the UHSS wires in the temperature range of 20–900 °C are obtained, as well as the failure parameters such as elongation and shrinkage after rupture. Based on the test data, a calculation model suitable for the prediction of the degradation law of high-temperature mechanical indicators of 1670‐–2060 MPa UHSS wire is established. Experimental investigations show that the stress-strain development process of UHSS wire at elevated temperature can be described by a three-stage model. Due to differences in chemical composition and manufacturing process, there are significant differences in the degradation patterns of mechanical indicators of different steel materials at elevated temperatures. The failure mode of the steel wire is brittle failure when the temperature does not exceed 200 °C, but the failure mode changes from brittle failure to plastic failure when the temperature exceeds 200 °C. Compared with the existing experimental results, it is obvious that the high-temperature mechanical indicator degradation model of high-strength steel wires proposed in this study can be used as input data for computer models to evaluate the fire resistance of cable members of cable-supported bridges.

Pile Capacity Checking Tool based on Distributed Fibre Optic Sensing for Instrumented Pile Load Test

Pile load test instrumented using Distributed Optical Fibre Sensing (DOFS) offers a superior ability to assess pile capacity through continuous strain profiles as opposed to the discrete measurement method such as Vibrating Wire Strain gauges. Due to the vast amount of spatial data generated by the sensor, processing the raw data from DOFS is not always straightforward, often done manually with careful interpretation of various factors affecting the measurements. Experts are reconciling with different data processing algorithms to assess pile capacity (t-z curve) from the DOFS data and verify it, leading to a demand for standard practice. Currently, the verification is done by comparing the pile capacity assessed from DOFS data to the analysis from the commercially available numerical software. The software typically requires input parameters such as extensive soil data, structure geometry, and loading intensity. Some of these parameters are limited (due to bureaucracy or trade secrecy) for the pile load test contractor to verify the pile capacity computation. This paper presents a checking tool that has been developed to automate the processes including raw file parsing, initial processes (trimming, positioning, and averaging), and post processes (pile capacity computation and checking). The post processes utilised the simplified Finite Element Method (FEM) to perform the checking which only utilised the DOFS data. In this paper, an application of the developed tool to a DOFS instrumented pile load test in Kuala Lumpur is reported. This exercise provides the information that the tool can be helpful to verify the pile capacity computation from DOFS data with promising performance reliability at 95%.

Structural performance and on-site monitoring of steel-concrete composite bridge with link slab

The project case of Qiwu Bridge using link slab action between simply supported composite spans is introduced. The 60 m-span girder of Qiwu Bridge is the longest and heaviest among the composite girders erected by bridge-erecting machine in China. Qiwu Bridge consists of a series of 3 simply supported spans built with composite girders and connected at the pier supports by a link slab. This solution has both advantages of (1) smooth driving condition and enhancement of durability by removing expansion joints and (2) clear structural behavior as simply supported spans. A finite element model was established to simulate and predict the mechanical response of this semi-continuous solution. Numerical results showed that the removal of the shear connection around the link slab decreased the stress level but also caused a stress mutation. Qiwu Bridge was also monitored by vibrating wire strain gages to follow its actual structural response. From preliminary monitoring data and numerical results, it can be concluded that the proposed construction method and the static scheme is safe for the 60-span composite girder with a large safety margin. Further experimental results will be obtained during the service stage of the bridge to validate the in-service performance of the proposed steel-concrete composite bridge with link slab.

Effect of polyurethane coating on mechanical response of shape memory alloy wires

In micro-electro-mechanical systems, the risk of short circuit arises when shape memory alloy (SMA) wire actuators mistakenly come into contact with other metal parts. Coating the SMAs with insulating layer can solve this problem. However, unlike traditional conductive wires that experience minimal length changes with current, SMA wires undergo significant length variations during electrical execution. This can affect the bonding between the coating and the SMA wires, as well as the mechanical response of the actuators. Therefore, this study investigated the effect of an insulating coating on the mechanical response of SMA wires. The results show that a layer of polyurethane coating provides long-term insulation to the SMA wires. While this coating reduces the recoverable strain of SMA wires under passive heating, its effect on actuation strain under electrical heating is relatively minor. Additionally, the coating enables the SMA wire to work smoothly by relieving overshooting and vibration phenomena during execution, and helps the wire work in a wider current range than an uncoated wire. Moreover, the coating enhances the response speed of SMA wires during power-on but reduces the response speed during power-off, this influence weakens as driving currents increase. These distinct mechanical responses can be primarily attributed to the coating’s influence on heat transfer behavior of the SMA wires.

Study on method of controlling interaction between wires of Galfan spiral strands

This paper presents a method of controlling the interaction between the wires of Galfan spiral strands. Axial tensile tests were carried out on 1 × 7, 1 × 19, 1 × 37, and 1 × 61 strands. The material properties of the wire, the bearing capacity of the strand, and the surface strain of the outer wire were measured. The wear of the wire after loading was observed by cutting open the 1 × 7 strand and the 1 × 19 strand. The initial contact state between the wires was then determined by calculation and modelling. The contact state between the wires under load was analyzed by ABAQUS. Finally, the contact pressure caused by the interaction was investigated. The method of controlling the maximum contact pressure was developed. A formula for the complete elimination of the maximum contact pressure was also proposed.

Review of Wireless RFID Strain Sensing Technology in Structural Health Monitoring.

Strain-based condition evaluation has garnered as a crucial method for the structural health monitoring (SHM) of large-scale engineering structures. The use of traditional wired strain sensors becomes tedious and time-consuming due to their complex wiring operation, more workload, and instrumentation cost to collect sufficient data for condition state evaluation, especially for large-scale engineering structures. The advent of wireless and passive RFID technologies with high efficiency and inexpensive hardware equipment has brought a new era of next-generation intelligent strain monitoring systems for engineering structures. Thus, this study systematically summarizes the recent research progress of cutting-edge RFID strain sensing technologies. Firstly, this study introduces the importance of structural health monitoring and strain sensing. Then, RFID technology is demonstrated including RFID technology's basic working principle and system component composition. Further, the design and application of various kinds of RFID strain sensors in SHM are presented including passive RFID strain sensing technology, active RFID strain sensing technology, semi-passive RFID strain sensing technology, Ultra High-frequency RFID strain sensing technology, chipless RFID strain sensing technology, and wireless strain sensing based on multi-sensory RFID system, etc., expounding their advantages, disadvantages, and application status. To the authors' knowledge, the study initially provides a systematic comprehensive review of a suite of RFID strain sensing technology that has been developed in recent years within the context of structural health monitoring.

Analysis of the destruction processes of carbon fiber samples using acoustic emission and tensometry

With samples made of carbon fiber, static tests were carried out to failure. Defects were controlled using acoustic emission and tensometry. Four wire strain gauges were glued to each sample in the area of the hole, and four piezoelectric gauges were installed along its edges, forming the working zone of control. Registration of signals associated with the destruction of the composite material of the samples, and their location was carried out by the acoustic emission system. In the process of testing, the tensometric system recorded loads and deformations, at which the process of destruction of carbon plastics began. The types of destruction were determined during the analysis of micro-glyphs, which were made from location zones. The main informative parameters (amplitude, dominant frequency, MARSE, structural coefficient) of acoustic emission signals were associated with the type of failure of carbon fiber reinforced plastics.