Wire Stress Research Articles

Modeling of multi-strand wire ropes subjected to axial tension and torsion loads

A new model characterizing the response of a multi-strand wire rope subjected to axial tension and axial torque is presented in this paper. Apart from most of previous approaches which deal with a straight wire strand, the present model fully considers the double-helix structure in multi-strand configuration. To be further, a new method to compute local deformation parameters (two curvatures and a twist defined by Love, 1944) of each wire is introduced. The proposed model well predicts the global stiffness of the rope. It is found that different friction states between adjacent wires can lead to quite a different distribution of local bending and torsion deformation of double-helix wire. The variations of stresses in double-helix wires along the rope axis are analyzed and the results show that torsion stress of a double-helix wire can be neglected when the rope is subjected to axial tension (axial torsion is restrained). The present model provides a new way to estimate the local deformation and stresses at the wire level, which sheds new insight into the understanding of the fatigue and failure behavior of the wire rope.

Frequency analysis of sandwich plate with active SMA hybrid composite face-sheets and temperature dependent flexible core

In this research, a new finite element model is presented for frequency analysis of a sandwich plate with composite face sheets embedded with pre-strained SMA wires under thermal condition. Mechanical properties of a flexible core are considered temperature dependent. The mixed LW/ESL models in the framework of Carrera’s Unified Formulation are employed in this study in order to increase the accuracy of the results with low computational cost. In this regard, the nonlinear strains are used for obtaining the thermal effects and also the effect of recovery stresses in the SMA wires. The constitutive equation proposed by Brinson is used for modeling the recovery stresses in the SMA wires. In this research, the total stiffness of the structure is categorized to essential and acquired stiffness types and results are more discussed. Results show that as the temperature increases, the natural frequencies of the classic sandwich plate decreases due to the degradation of the core’s properties, while, by using the active SMA wires, the stiffness of the sandwich plate can be improved and therefore has a positive effect on the natural frequencies of the sandwich plate.

Investigation on local and global behaviors of pseudoelastic shape memory alloy wires in simple tensile test considering stress concentration of grippers

To investigate the local phenomena of nucleation and propagation in the simple tensile test of shape memory alloys, the existing models consider geometrical imperfections in the specimen to indirectly take the effects of grippers’ stress concentration into account. In this article, the grippers are directly modeled in studying shape memory alloy wires in simple tensile test. A finite element model is created in ABAQUS to determine the distributions of cross-sectional area and stress in a shape memory alloy wire when tightening the grippers. Then, using this stress distribution as the pre-stress, tension of the specimen is studied by employing a coupled thermomechanical model to obtain distributions of the stress, strain, martensite volume fraction, and temperature at any strain rate. The results indicate that the nucleation and propagation of transformation fronts are observed using this method of directly considering the pre-stress and initial area distribution due to fastening the grippers. It is also shown that the local and the nominal strains are not the same during nucleation and propagation of phase fronts. A simple tensile test is conducted on an NiTi wire, and a good agreement is seen between the experimental and the numerical stress–strain responses and local–nominal strain diagrams.

Effects of Strain Aging in NiTi SMA Wire for Dampers

The thermo-mechanical properties of Shape Memory Alloys (SMA) as smart materials suggest their application as actuators, but also as dampers, thanks to the high damping properties during the hysteresis of the thermo-elastic martensitic transformation. Damping in civil engineering is needed to minimize earthquake effects on buildings, and also to limit the damage produced by wind or traffic induced oscillations in stayed cables in bridges. In this work, we explore the consequences of strain aging the material at moderate temperatures (100°C). A quasi-static stress and temperature aging of NiTi SMA wires of 2.46mm diameter was done at 373K. The experimental measurements establish a monotonic effect related to the introduced strain. Aging under larger strains modifies the hysteretic shape and induces an increase in the maximal stress on the transformation from 600MPa to 800-1000MPa. Aging at 373K under 7-8% strain, the effect was up to 200MPa in three months and near 400MPa in eight months. The modified stress-strain curves suggest potential application as dampers under larger summer-winter temperature changes, i.e., from 233 to 323K.

Effect of confining pressure due to external jacket of steel plate or shape memory alloy wire on bond behavior between concrete and steel reinforcing bars.

For external jackets of reinforced concrete columns, shape memory alloy (SMA) wires are easy to install, and they provide active and passive confining pressure; steel plates, on the other hand, only provide passive confining pressure, and their installation on concrete is not convenient because of the requirement of a special device. To investigate how SMA wires distinctly impact bond behavior compared with steel plates, this study conducted push-out bond tests of steel reinforcing bars embedded in concrete confined by SMA wires or steel plates. For this purpose, concrete cylinders were prepared with dimensions of 100 mm x 200 mm, and D-22 reinforcing bars were embedded at the center of the concrete cylinders. External jackets of 1.0 mm and 1.5 mm thickness steel plates were used to wrap the concrete cylinders. Additionally, NiTiNb SMA wire with a diameter of 1.0 mm was wound around the concrete cylinders. Slip of the reinforcing bars due to pushing force was measured by using a displacement transducer, while the circumferential deformation of specimens was obtained by using an extensometer. The circumferential deformation was used to calculate the circumferential strains of the specimens. This study assessed the radial confining pressure due to the external jackets on the reinforcing bars at bond strength from bond stress-slip curves and bond stress-circumferential strain curves. Then, the effects of the radial confining pressure on the bond behavior of concrete are investigated, and an equation is suggested to estimate bond strength using the radial confining pressure. Finally, this study focused on how active confining pressure due to recovery stress of the SMA wires influences bond behavior.

Strata behaviour during depillaring in Blasting Gallery panel by field instrumentation and numerical study

Selection of a suitable mining method for economical and safe underground extraction of a thick coal seam is an extremely delicate process and brings a number of geo-technical parameters into consideration. Charbonnage de France (CdF) proposed Blasting Gallery (BG) for the extraction of virgin thick seams as well as developed pillars in thick seams in a single lift. The method was very successful resulting in 85 % of extraction with high productivity. But this method experienced strata control problems during final extraction at East Katras Colliery in Jharia Coalfield, Coal India Ltd., and also at GDK No. 8 Incline, Singareni Collieries Company Ltd. In this paper, the role of different parameters influencing development of mining-induced vertical stress, and maximum roof deformation in a BG 1/12 panel (GDK No. 8 Incline, SCCL) during depillaring in specific geo-mining conditions was visualized through numerical simulation models using ANSYS software. In this study, extensive field monitoring is carried out using modern instruments such as vibrating wire stress gauges, extensometers, load cells, and telescopic convergence rods to understand the strata behaviour during depillaring in the BG panel. Salient findings of field instrumentation data analysis such as mining-induced vertical stress development over the pillars, load over the support, bed separation at different horizons, and convergence of roof in rooms with face advance are presented in this paper. The results of induced stress, deformation, and factor of safety of pillar obtained by the finite element method (FEM) analysis are validated with the results of field instrumentation data analysis.

Stress Forming of Fine Metal Wire Based on Ultrasonic Vibration

The assembling process of the flex lead of an accelerometer can bring in internal stress, which causes drift error and affects the precision of the accelerometer. The paper introduces a method using ultrasonic vibration to reduce the internal stress, discusses the theory of ultrasonic stress relief on fine wires, shows ultrasonic stress relief experimental apparatus which uses an optimized ultrasonic tool head to inflict ultrasonic vibration to fine wires. By introducing the displacements of the fine wire ends into ANSYS, changes of the internal stress of the fine wire can be obtained. The experiment studies the performance of ultrasonic vibration to fine wire internal stress and deals with the relationship between infliction time and results. The experiment results confirmed that by selecting the suitable experiment parameters, ultrasonic vibration is an effective way to internal stress relief, the internal stress decline as infliction time increase then stays.

Free vibration response of a multilayer smart hybrid composite plate with embedded SMA wires

In this paper, free vibration response of a hybrid composite plate was studied. Effects of some geometrical, physical and material parameters on response of the composite plates embedded with shape memory alloy (SMA) wires were investigated, which have not been reported in the literature thus far. Some of these parameters included important factors affecting free vibration response of the smart hybrid composite plates. The SMA wires were embedded within the layers of the composite laminate. First-order shear deformation theory (FSDT) was utilized to obtain the governing equations of hybrid composite plates. Transverse shear and rotary inertia effects of the plate were taken into consideration. For simply-supported boundary conditions, systematic closed form solutions were obtained by Navier's technique. It was established that dynamic behavior of the smart hybrid composite plate depended on various parameters such as volume fraction, temperature dependent recovery stress and tensile pre-strain of SMA wires and aspect ratio of the laminated hybrid plate.

Fabrication and characterization of a dual-joint smart inhaler nozzle actuated by embedded SMA wires

Shape memory alloy (SMA) wires offer a novel solution for many embedded actuator and sensor applications. Small SMA wires in particular can be heated with a relatively low electric current, cool rapidly, and serve as a sensor thanks to a measurable resistance change. However, the challenges of fabrication with SMA actuator wires as well as their hysteretic nature have prevented them from finding mainstream application. This work focuses on the process used to control the fabrication of an SMA-actuated adaptive nozzle for the previously presented Smart Inhaler application. The elements of nozzle design that facilitate fabrication are summarized and an assembly setup and procedure is presented for controlling the stress and strain in the SMA wires while they are attached to the nozzle structure via temperature-resistant adhesives. Finally, the performance of the nozzle is characterized by measuring the changes in nozzle deflection and SMA wire strain and resistance in response to a controlled Joule heating power input. Results show controlling pre-stress in the wires during assembly can lead to reproducible behavior, an input heating power serves to control nozzle deflection, and a measured resistance can provide a useful sensor of SMA wire strain and nozzle joint deflection.

Recovery stress of shape memory alloy wires induced by hydration heat of concrete in reinforced concrete beams

The goal of this study is to investigate the prestressing effect of shape memory alloy bars in reinforced concrete beams; bars are prestressed by external force or recovery stress due to shape memory effect. The shape memory alloy bars are heated by hydration heat of concrete during curing to induce the shape memory effect. To achieve this goal, this study conducts bending tests of concrete beams reinforced by shape memory alloy bars as well as those reinforced by steel bars. The beams with shape memory alloy bars with recovery stress show the same or slightly larger flexural strength than those with shape memory alloy bars prestressed with external force. Thus, this study indicates that the recovery stress of shape memory alloy bars plays the same role as the prestressing force, and that the shape memory effect can be induced by hydration heat of concrete instead of heating by electronic resistance.

Pretension-Dependent Residual Stress of Alumina Fiber-Reinforced Composite Wire

The relationship between pretension and residual stress of an aluminum wire reinforced with 45 vol pct continuous Nextel™ 610 alumina fibers is investigated. It is shown that as pretension stress increases, the matrix residual stress decreases. A transition in matrix residual stress from tension to compression occurs at a pretension stress of about 80 MPa. The initial rapidly decreased residual stress caused by pretension at relatively low pretension stresses is a result of matrix elastic compressive deformation; while the later gradually decreased residual stress at higher pretension stresses comes from matrix plastic compressive deformation. As the matrix yield stress and hardening exponent increase, the decrease in matrix residual stress with pretension stress is more rapid and the absolute value of matrix residual stress increases. An analytical model suitable for fiber-reinforced metal matrix composites (MMCs) with strong interfacial bonding is developed to describe the relationship between pretension and matrix residual stress and is shown to be in good agreement with the experimental and finite-element calculated results. The pretension-dependent matrix residual stress phenomenon suggests that the mechanical properties of fiber-reinforced MMCs associated with matrix residual stress may be effectively improved by applying tensile loads.

Stress dependent electrical resistivity of orthodontic wire from the shape memory alloy NiTi

The aim of this study was to compare and evaluate the stress induced martensitic phase under different loading conditions in orthodontic wire from the Shape Memory Alloy Nickel–Titanium (NiTi). For this purpose we investigated the phase transformation from austenite to martensitic due to the different loading conditions by measuring the electrical resistance which could show the type of deformation which occurs at the beginning of phase transformations. In this framework we developed two special devices for measurements of electrical resistance in different types of load and their combination on the orthodontic wire. These results were compared with the analytically calculated stresses in the orthodontic wire. It was shown that they caused complex or multi-axial stress state phase transformation rather than other more simple load such as uniaxial loading. Finally, the article presents the deformation which occurs at the change of phase that is nearly connected to the useful superelasticity effect of the Shape Memory Alloy NiTi.

Nonlinear Finite Element Analysis of FQQB

The mechanical properties of the whole wall and the wall with openings under vertical loads are analyzed by nonlinearity finite element method (NFEM). The results show that the stress of steel wire has a direct relationship with the load form. The inclined plug wire mainly carries the stress caused by load differences between the two sides of concrete, it makes both sides of concrete work together better. As the diameter of the inclined plug wire increased, the effects on the FQQB mechanical properties become greater, wire mesh stress on both sides decrease, and the vertical displacement of FQQB decrease. Cracks appear above the openings of FQQB which has been cut holes. Steel wire tends to be tension stress concentrated, and there are obvious stress concentration belts on both sides of the opening. However, the size of the opening has little effects on the ultimate bearing capacity of wall panel.

Field application of elasto-magnetic stress sensors for monitoring of cable tension force in cable-stayed bridges

Recently, a novel stress sensor, which utilizes the elasto-magnetic (EM) effect of ferromagnetic materials, has been developed to measure stress in steel cables and wires. In this study, the effectiveness of this EM based stress sensors for monitoring of the cable tension force of a real scale cable-stayed bridge was investigated. Two EM stress sensors were installed on two selected multi-strand cables in Hwa-Myung Bridge, Busan, South Korea. Conventional lift-off test was conducted to obtain reference cable tension forces of two test cables. The reference forces were used to calibrate and validate cable tension force measurements from the EM sensors. Tension force variations of two test cables during the second tensioning work on Hwa-Myung Bridge were monitored using the EM sensors. Numerical simulations were conducted to compare and verify the monitoring results. Based on the results, the effectiveness of EM sensors for accurate field monitoring of the cable tension force of cable-stayed bridge is discussed.

Experiment Research on Square Columns Reinforced by High Strength Wire Mesh Mortar

To investigate the influence of wire mesh type, wrapped way and stress of column on the behavior of RC square columns, the experiment including an unreinforced column and 7 strengthened columns with the high strength wire mesh mortar were tested. The results were shown that the strength and axial deformation of columns reinforced by high strength wire mesh mortar were enhanced. Finally, the calculation formula for ultimate bearing capacity of the reinforced columns was given based on the test results, which agreed with the tested results well.

Effect of Annealing on the Transformation Behavior and Mechanical Properties of Two Nanostructured Ti-50.8at.%Ni Thin Wires Produced by Different Methods

A Ti-50.8at.%Ni wire produced using a co-drawing method and a commercial Ti-50.8at.%Ni wire were annealed between 450°C and 700°C. Grains with diameter less than 100nm were revealed by TEM for both wires before annealing treatment. However, the microstructural heterogeneity of the co-drawn wire is more obvious than that of the commercial wire. The transformation behavior and mechanical properties of both wires were found to be sensitive to the annealing temperature. Multi-stage martensitic transformation was observed in the co-drawn wire, compared with the one-stage A↔M transformation in the commercial wire after annealing at 600°C for 30min. Moreover, the ultimate tensile stress and plateau stress of the commercial wire were found to be higher than that of the co-drawn wire under the same annealing conditions. The differences of total elongation, plateau strain and pseudoelastic recoverable strain between the commercial wire and the co-drawn wire were also observed. The differences of the transformation behavior and mechanical properties between the commercial wire and the co-drawn wire are attributed to the microstructural difference between these two wires.

Mechanical Properties of Controlled Memory and Superelastic Nickel-Titanium Wires Used in the Manufacture of Rotary Endodontic Instruments

IntroductionThe aim of this study was to investigate the structure and mechanical properties of newly developed controlled memory (CM) nickel-titanium wires used in the manufacture of rotary endodontic instruments. MethodsThe composition and the phase transformation behavior of both types of wires were examined by x-ray energy dispersive spectroscopy and differential scanning calorimetry, respectively. Conventional superelastic (SE) nickel-titanium wire was used as a control. The mechanical properties of the wires at selected temperatures (room temperature, 37°C, and 60°C) were evaluated with tensile, cyclic tensile, and cantilever bending tests by using an Instron 3365 universal testing machine. The data of austenitic transformation finishing temperature (Af) were analyzed statistically by using 1-way analysis of variance test at a significance level of P < .05. ResultsThe raw CM wires contained a nickel content of 50.7% ± 0.5% and possessed a relatively higher Af than SE wires (P < .05). The critical plateau stress and ultimate tensile strength of the CM wires were lower than they were for the SE wires, but the maximum strain before fracture of the CM wires (58.4% ± 7.5% to 84.7% ± 6.8%) was more than 3 times higher than it was for SE wires (16.7% ± 3.8% to 27.5% ± 5.4%). The maximum strain of the CM wires with a diameter of 1.22 mm tested at room temperature (23°C ± 2°C) was up to 84% ± 6.4%. CM wires were not SE at either room temperature or 37°C; however, they exhibited superelasticity when heated to 60°C. ConclusionsThe raw CM wires exhibited different phase transformation behavior and mechanical properties when compared with SE wires, attributing to the special heat treatment history of CM wires. This study suggested greater flexibility of endodontic instruments manufactured with CM wires than similar instruments made of conventional SE wires.

Effect of annealing on martensite stabilization due to deformation via cooling under stress in cold-worked NiTi thin wire

Most practical applications of NiTi shape memory alloys involve self-motivated shape recovery of the alloys associated with the reverse transformation. An increase of the reverse transformation temperature (martensite stabilization) implies a retardation, or complete avoidance, of the shape recovery, thus failure of the function. Therefore, understanding the mechanism of martensite stabilization in NiTi alloy is extremely important and still needs in-depth studies for its successful use. In the present paper the influence of annealing on martensite stabilization due to deformation via cooling under constant tensile stresses in cold-worked NiTi thin wires has been investigated. The annealed samples exhibit different degrees of martensite stabilization. The stabilization effect was much smaller in 550°C and 650°C annealed samples than that in 350°C and 450°C annealed ones. It increases with increasing annealing temperature up to 450°C and decreases when annealed above 450°C. The result implies that other mechanisms are involved apart from plastic deformation under such deformation mode.

Enhancing GMI properties of melt-extracted Co-based amorphous wires by twin-zone Joule annealing

The influence of twin-zone Joule annealing (TJA) on the microstructure and magnetic properties of melt-extracted Co68.2Fe4.3B15Si12.5 amorphous microwires has been investigated. Experimental results indicated that twin-zone Joule annealing treatment improved the GMI property of as-cast wires to a greater extent comparing with Joule annealing (JA) and conventional vacuum annealing (CVA) techniques. At 15MHz, e.g., the maximum GMI ratio [ΔZ/Z0]max of a TJA wire increases to 104.29%, which is more than 5 times of 20.49% for the as-cast wire, nearly two times of 56.47% for the JA wire, while the CVA wire has a decreased GMI ratio; the field response sensitivity of the TJA wire increased to 171.62%/Oe from 80.32%/Oe for the as-cast wire, exceeding the values of 140.76%/Oe for the JA wire and of 39.17%/Oe for the CVA wire. The stress or structural relaxation in TJA wire increases circumferential permeability, and magnetic moment achieves a critical state of excitation for overcoming eddy-current damping or “nail-sticked” action in rotational magnetization process at relatively high frequency. From the microstructural point of view, the role of regularly arranged atomic micro-regions (RAAM) and of medium range order region (MROR) determines the efficiency of various annealing techniques. Conclusively, TJA is established as an efficient annealing technique to enhance the GMI effect of wires, which can subsequently be used for detecting weak magnetic field at relatively wider working range (±2.0Oe).

Modeling and experimental characterization of the stress, strain, and resistance of shape memory alloy actuator wires with controlled power input

Recently, a novel power controller has been presented that simultaneously controls electric power input and measures resistance of a commercially available Flexinol shape memory alloy wire. This work exploits the new power controller by plotting shape memory alloy stress, strain, and resistance versus Joule heating power instead of input voltage or current. Heating power is directly related to shape memory alloy temperature, whereas standard constant voltage or constant current inputs cause more or less heating as the resistance of the wire changes due to phase transformation. A simple experimental setup consisting of a 50-µm-diameter Flexinol wire mounted in series with the tip of a compliant cantilever beam is used to systematically study the shape memory alloy behavior. Actuator performance is reported for a range of prestress values and actuation frequencies. All the experimental data are compared with simulated behavior that is derived from a free energy–based numerical model for shape memory alloy material. Additionally, a new resistance model based on the simulated wire temperature and phase fractions is introduced and compared to experimental data. Exploiting a multifunctional power controller and an improved understanding of the resistance change during phase transformation will help enable the use of shape memory alloy wires in simultaneous sensing and actuating applications.