Wire Specimens Research Articles

A stochastic modeling method for three-dimensional corrosion pits of bridge cable wires and its application

ABSTRACT Cables have usually served as critical and vulnerable structural components in long span cable-supported bridges. Cable inspections revealed that corrosion, fatigue or coupled corrosion-fatigue were the ones of the main failure mechanisms. This paper proposed a stochastic modelling method for three-dimensional (3-D) corrosion pits of high-strength bridge wires, which can be applied to rapid fatigue life evaluation according to mass loss caused by surface corrosion pits of bridge wires nondestructively. High-strength steel wire specimens dismantled from the cable-stayed bridge served for 15 years were scanned to obtain the original surface corrosion data. The spatial position coordinate of corrosion pits were considered as random variable and can be well fitted by uniform distribution. While the number of corrosion pits can be fitted with generalized extreme value (GEV) distribution. The uniform corrosion depth du, which can be equivalent to mass loss rate, was calculated as the input corrosion parameter for 3-D corrosion pit modelling. The maximum pitting depth dmax for the steel wire was found to be associated with du. The geometric parameters for individual corrosion pits were recognized as pit depth d, depth-to-width ratio d/b, and aspect ratio b/a, which were fitted with different probability distributions. What follows is 3-D spatial corrosion pits simulation based on the individual corrosion parameter that were sampled and combined from the corresponding probabilistic distributions. Hereafter, fatigue life evaluation of corroded wires was conducted based on equivalent surface defect method and compared with the experimental results, verifying the effectiveness of the proposed modelling approaches.

Optimizing ageing conditions for commercial NiTi archwires: Insights from thermal phase transformation and tensile deformation analysis

Superelastic nickel-titanium (NiTi) archwires are now commonly used as the standard archwire during the orthodontic alignment and levelling stage. They are preferred due to their ability to apply minimal force on teeth while allowing for a wide range of tooth movements. During orthodontic treatment, the orthodontist assesses the dimension and shape of the NiTi archwire to determine the amount and direction of force required to align misaligned teeth. The main contribution of this study is the parametric analysis and establishment of a set of optimal ageing temperatures and duration for the investigation of functionally graded nickel-titanium archwire using differential scanning calorimetry (DSC) and tensile deformation testing. The mechanical and thermal phase transformation behavior after ageing at six temperatures for duration of 15 minutes have been investigated using tensile deformation test and differential scanning calorimetry (DSC) test in this paper. Experimental results reveal that in thermal analysis as the ageing temperatures increase from 400 °C to 490 °C, the austenite finish temperature rises to a value between 9.53 °C and 35.48 °C, and subsequently decreases to 520 °C. The archwire specimen aged for temperature of 490 °C exhibited the austenite finish temperature of around 35.48 °C, and it is highest among the aged wire specimens closest to oral temperature. In tensile deformation, the ideal ageing temperature for orthodontic applications was determined to be 490 °C for 15 minutes, resulting in relatively low plateau slope 13.73 GPa with high superelatic ratio 12.04, and maximum plateau strain of 7 %.

Fatigue and fracture of small cracks in superelastic Nitinol

The present study develops a hybrid total life and damage-tolerant fatigue methodology for the determination of a small crack growth threshold in Nitinol. Axial tension–tension/Mode I fatigue testing was performed on superelastic Nitinol wire specimens with starter cracks milled into the specimens using focused ion beam (FIB). Fatigue testing was performed in displacement control at various strain amplitudes, typical for Nitinol fatigue characterization given its superelastic behavior. The simplistic geometry of the test specimen and axial loading conditions also allowed for the calculation of stress amplitude and initial stress intensity factor range. A logistic regression analysis was used to determine strain/stress-based fatigue limits. The small crack growth threshold for superelastic Nitinol was obtained for the first time from physically small cracks with sizes comparable to native inclusions. Lastly, a fractographic analysis was performed to examine crack initiation and propagation from the FIB-milled starter cracks and to identify relevant fractographic features. While the proposed methodology is centered around the use case of Nitinol medical devices, it could be adapted for other materials and applications where small crack initiation and propagation play an important role in fatigue lifetime prediction.

Comparative Evaluation of Antibacterial and Anti-Adherent Properties between Titanium Oxide, Silver Dioxide-Coated, and Conventional Orthodontic Wires Against Streptococcus Sanguis Causing Gingivitis

ABSTRACT Objective: To compare the antibacterial and anti-adherent properties of conventional stainless steel (SS) orthodontic wires and surface-modified silver dioxide-coated and titanium oxide-coated SS orthodontic wires against Streptococcus sanguis causing gingivitis Materials and Methods: The study used 60 orthodontic SS wire specimens, organized into six groups of ten each. The control group had uncoated wires, and the experimental group featured wires coated with silver dioxide and titanium oxide. Surface modification was done using DC sputtering, and microbiological tests assessed the antibacterial and anti-adherent properties of the AgO2- and TiO2-coated wires. Results: This study demonstrated the antibacterial effect against S. sanguis in orthodontic wires coated with the photocatalytic AgO2 and TiO2 compared to the uncoated wires. Also, this study demonstrated an anti-adherent effect in the AgO2- and TiO2-coated orthodontic wires. Moreover, the bacterial accumulation on orthodontic wires coated with AgO2 and TiO2 was lower compared to that on the uncoated wires Conclusion: During orthodontic treatment, the formation of dental plaque can be prevented by coating the surface of stainless-steel orthodontic wires with photocatalytic AgO2 and TiO2. Compared to silver dioxide, the titanium oxide-coated SS orthodontic wires showed better antibacterial and anti-adherent properties.

A Physics-Based Hybrid Dynamical Model of Hysteresis in Polycrystalline Shape Memory Alloy Wire Transducers

Shape memory alloys (SMAs) are a class of smart materials that exhibit a macroscopic contraction of up to 5% when heated via an electric current. This effect can be exploited for the development of novel unconventional actuators. Despite having many features such as compactness, lightweight, and high energy density, commercial SMA wires are characterized by a highly nonlinear behavior, which manifests itself as a load-, temperature-, and rate-dependent hysteresis exhibiting a complex shape and minor loops. Accurate modeling and compensation of such hysteresis are fundamental for the development of high-performance SMA applications. In this work, we propose a new dynamical model to describe the complex hysteresis of polycrystalline SMA wires. The approach is based on a reformulation of the Müller–Achenbach–Seelecke model for uniaxial SMA wires within a hybrid dynamical framework. In this way, we can significantly reduce the numerical complexity and computation time without losing accuracy and physical interpretability. After describing the model, an extensive experimental validation campaign is carried out on a 75- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m diameter SMA wire specimen. The new hybrid model will pave the development of hybrid controllers and observers for SMA actuators.

Role of crack offset and loading condition on fracture behavior of wire specimen

Accurate stress intensity factor (SIF) solutions for cylindrical specimens with varied wire aspect ratios, crack aspect ratio, relative crack depth and crack offset are required to evaluate the fracture toughness of high strength yet brittle rods, cables, fibres and wire specimens. The mode I geometric factor (GF) solutions of various crack configurations in a cylindrical fracture specimen in tension have been determined using linear elastic fracture mechanics in earlier studies. In the present study, finite element analysis (FEA) was used to compute these as a function crack offset and wire aspect ratios for two different boundary conditions-constrained and unconstrained. In constrained loading condition, the GF was seen to decrease significantly with crack offset for wires at lower aspect ratio in all the 3 crack curvatures – concave, straight and convex. GF stabilized as the wire aspect ratio was increased beyond 40. In unconstrained loading the GF values were independent of the wire aspect ratio and crack offset for the 3 crack curvatures.

0.8 mm Ni–Ti shape memory alloy wires: Post-training behavior and application in a cold-formed steel structure

This study explores the post-training performance, mechanical training strategy, and potential seismic application of shape memory alloy (SMA) wires. A part of SMA wire specimens were trained by different training protocols, and subsequently all the untrained and trained SMA wire specimens were tested at room temperature under various cyclic loading protocols. It is observed that the incremental cyclic training could lead to a higher post-yield stiffness during the post-training stage at a certain expense of residual strain and forward transformation stress, and the post-training hysteretic behavior will be stable and predictable within the historical training strain amplitude. The influence of training on mechanical performance of SMA wires under near-fault loading was revealed and evaluated. Following the test program, a cold-formed steel (CFS) joint model employing SMA wires is proposed and analyzed to demonstrate the feasibility and efficiency of trained SMA wires for optimizing seismic performance. The finite element (FE) analysis results indicates that the self-centering CFS joint can effectively optimize the original pinched hysteretic response, including mitigating residual displacement, and improving the peak strength, initial stiffness and energy-dissipate capacity.

Evaluation of the Effects of Povidone Iodine and Hydrogen Peroxide Mouthwashes on Orthodontic Archwires: An In Vitro Study.

To evaluate the effects of two preprocedural mouthrinses, hydrogen peroxide (H2O2) and povidone iodine (PI) on the surface characteristics and mechanical properties of nickel-titanium (NiTi) and stainless steel (SS) orthodontic archwires. Five wire specimens were used, each (0.016" NiTi, 0.016" SS wires, 0.016 × 0.022" NiTi and 0.016 × 0.022" SS wires) specimen was cut into 30 mm lengths and immersed in 9% of artificial saliva and 91% of two preprocedural mouthrinse solutions: 1.5% hydrogen peroxide mouthwash, 0.2% povidone-iodine mouthwash, and distilled water (control group) for 90 minutes and incubated at 37°C. The wire specimens were then subjected to a three-point bending test for mechanical testing and viewed under a scanning electron microscope (SEM) to evaluate their surface characteristics. The collected data were analyzed using one-way analysis of variance (ANOVA) and Bonferroni post hoc test. The results showed a significant increase in the flexural modulus (E) of Nitinol wires in povidone-iodine gargle (p < 0.05) and a significant increase in the E of stainless steel wires in hydrogen peroxide mouthwash (p < 0.05). Analysis using SEM showed varying qualitative surface changes in the form of corrosion, voids, and ridges on the wires after exposure to both the mouthwashes. Though there were significant changes in the flexural modulus of archwires for both the mouthwashes, hydrogen peroxide did not show a significant difference in the E of wires at most of the deflection intervals when compared with the other two solutions, hence, could be used in orthodontic patients as an effective preprocedural mouthrinse. Preprocedural mouthrinses can cause surface irregularities on the wires which in turn lead to an increase in friction at the bracket-wire interface, thereby disrupting effective tooth movement and extending the orthodontic treatment time.

Study on subsurface microcrack damage depth of diamond wire as-sawn sapphire crystal wafers

Sapphire crystals are widely used as window materials for infrared emitting devices, high intensity lasers, optical elements and microelectronic substrates due to the excellent material properties. The subsurface microcrack damage produced by diamond wire saw when cutting sapphire crystal is an important indicator of the cutting quality. In this paper, diamond wire sawing experiments were conducted within the industrial production processing parameters to investigate the as-sawn sapphire crystal wafers subsurface microcrack damage depth (SSD), and a numerical calculation model was established to predict the SSD based on the analysis of the scratching stress field of single abrasive. The effects of the saw wire speed and specimen feed speed, saw wire parameters on SSD were predicted. The results show that, within the parameters studied in this paper, the material was removed in brittle mode, increasing the saw wire speed (from 1000 m/min to 1600 m/min) and reducing the specimen feed speed (from 0.5 mm/min to 0.05 mm/min) can reduce the sapphire as-sawn wafers SSD, reduce the size of brittle tear-shape edge breakage, the number and size of brittle pits on the as-sawn wafer surface are reduced and the surface morphology consistency is improved. Increasing the abrasive density and reducing the abrasive size can reduce the SSD. The study results provide a reference for the reasonable matching of sawing process parameters and saw wire parameters in industry.

Abstract P2-14-01: MOLECULAR FLUORESCENCE-GUIDED SURGERY USING BEVA800 FOR THE ASSESSMENT OF TUMOR MARGINS DURING BREAST CONSERVING SURGERY OF PATIENTS WITH PRIMARY BREAST CANCER (MARGIN-II)

Abstract Introduction: The goal of breast conserving surgery (BCS) for early breast cancer (EBC) is to remove the tumor in toto and preserving as much of the normal breast tissue as possible. In 20-50% of cases a re-excision is necessary because of involved margins. Repeat surgeries are not only a burden to patients physically but also psychologically and can delay recommended adjuvant therapies. Accurate determination of tumor margins during surgery is therefore a critical need. Breast cancer tissue produces significantly higher amounts of VEGF-A than healthy tissue. VEGF-A stimulates tumor angiogenesis and is therefore a target for molecular imaging techniques. The fluorescence imaging agent bevacizumab-IRDye800CW (Beva800) is a conjugate of bevacizumab and IRDye800CW and binds specifically to VEGF-A. Beva800 provides a potentially efficacious approach to imaging specimen and cavity margins during BCS. We are presenting a phase II study that combined Beva800 with the SurgVision Explorer Air camera for intraoperative margin assessment during BCS for EBC. Methods: MARGIN II is a multicenter open-label single arm prospective clinical trial aimed at evaluating Beva800 for assessment of tumor margins in women with EBC scheduled for BCS. The study was a within-patient comparison of positive tumor margin rates using BCS standard of care margin assessment compared to intraoperative assessment with 4.5 mg Beva800 and fluorescence imaging with the SurgVision Explorer Air camera. All patients received an i.-v. bolus injection of 4.5 mg of Beva800 three days before surgery. The fluorescent signal was visualized during surgery using NIR fluorescence imaging (700–1000 nm). Standard of care margin assessment was defined as visual inspection, palpation and, in cases of pre-operative wire marking, specimen sonography or mammography. Beva800 efficacy was determined as the number of patients in which a pathology-confirmed positive margin was identified by fluorescence-guided surgery using Beva800 but not by standard of care BCS. Results: 49 patients were included in 5 centers. 4 training cases were only included in the safety analysis, 45 patients were evaluable for the efficacy analysis. 8 patients (17.8%) had involved margins after standard of care BCS, 4 of which were detected by molecular fluorescence intraoperatively resulting in the reduction of patients with positive margins by 50% (95% CI: 15.7%, 84.3%). 4 patients (8.9%; 95% CI: 2.5%, 21.1%) needed a re-excision because of involved margins. In 27 patients (60.0%) the additional molecular fluorescence guided cavity shaving did not change the resection status from positive to negative (false positive). Adverse events were reported by 16 of 49 patients (32.7%), but only 3 (6.1%) were related to Beva800 (syncope, hot flush, hypertensive crisis). One patient experienced a treatment related SAE (hypertensive crisis). No anti-Beva800 antibodies were detected. Conclusion: In our analysis the rate of necessary second operations was reduced by 50% using Beva800 and the SurgVision Explorer Air camera. The safety analysis confirmed the positive safety profile of Beva800 found in previous studies. Molecular fluorescence-guided surgery may have the potential to change the practice of breast conserving surgery by reducing unnecessary re-excisions. Future studies will have to address the high false positive rates. Citation Format: Hans-Christian Kolberg, Carmen Röhm, Angrit Stachs, Florian Schütz, Jens-Uwe Blohmer, Sarah Wetzig, Steffi Hartmann, Jörg Heil, Markus Hahn. MOLECULAR FLUORESCENCE-GUIDED SURGERY USING BEVA800 FOR THE ASSESSMENT OF TUMOR MARGINS DURING BREAST CONSERVING SURGERY OF PATIENTS WITH PRIMARY BREAST CANCER (MARGIN-II) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-14-01.

Corrosion and tensile behavior of intercritically heat-treated and cathodically polarized prestressing steel wires

The effect of the intercritical heat treatments producing various martensite volume fractions on the corrosion and tensile behavior of the cathodically polarized prestressing steel wires has been investigated. Potentiodynamic polarization and constant extension rate technique (CERT) tests are conducted to clarify these effects and to determine the mode of failure of the prestressing steel wires since the presence of the martensite in the prestressing steel wire microstructure results in the failure and breakage during the corrosion and cold drawing. The electrochemical data measurements reveal that the intercritically heat-treated and cathodically polarized prestressing steel wires containing higher volume fractions of martensite exhibit the lowest corrosion potentials and current densities which indicate higher corrosion rates. A significant decrease in the tensile strength and ductility by the accelerated corrosion tests is observed in the intercritically heat-treated and cathodically polarized prestressing steel wire specimens containing higher martensite volume fractions. The fracture surfaces of the intercritically and cathodically prestressed steel wire specimens containing higher fractions of martensite of 68% exhibit a mixed mode of failure, i.e., quasi-cleavage and microvoid coalescence after potentiodynamic polarization. Moreover, the brittleness due to the residual stresses induced by the formation of martensite and the generation of the galvanic corrosion cell between the martensite and pearlite is noted to be increased with increasing the amount of martensite in the prestressed steel wire specimens.

Inadvertent side effects of fixed lingual retainers : An in vitro study.

To better understand the side effects of fixed lingual retainers by means of an in vitro study in atwo-tooth model determining the three-dimensional (3D) force-moment components acting at adjacent teeth combined with different composite-wire interfaces. Triple-stranded round retainer wires were embedded in cured disks of flowable composite. At one side the composite-wire interface was untreated and checked to be absolutely fix. At the other side the composite-wire interface was configured as either an isolated compound with (1)petroleum jelly coating, or an adhered compound with (2)no manipulation, (3)ethanol degreasing or (4)ethanol degreasing and rectangular bending of the wire ends. The 3D force-moment components were registered, while the intertooth distance was increased in steps of 0.01 mm leading to increasing tension of the wire. Measurements were repeated after artificially aging the specimens. Retainer wire specimens with adhered compound (2, 3, 4) showed negative vestibulo-oral moments ranging maximally each between -0.3 and -0.9 Nmm in opposite direction to positive moments of 1.9 Nmm for specimens with isolated compound1. Significant tipping moments occurred in the group with isolated compound at lower forces than in those groups with adhered compound. Similar effects were observed after artificial aging. Side effects emerge under specific circumstances: an altered adhesive compound combined with the presence of oral forces. Compounds with lost adhesion at the composite-wire interface showed rotational moments in the direction of the wire windings even during low tensile forces similar to those that may occur in clinical settings. Opposite rotational moments leading to unwinding of the wire may occur in cases with adhered compounds at higher tensile forces. Utilization of round triple-stranded retainer wires without bent ends are of higher risk to induce inadvertent side effects.

Improvement of superelasticity conditions in Cu-based shape memory alloys for seismic control applications

Shape memory alloys (SMAs) are smart materials with self-centering characteristics that can be used to reduce the earthquake damage to structures. In this paper, the optimal thermal treatment to obtain the ideal mechanical properties of a CuAlBe SMA wires for seismic protection applications is discussed. For this purpose, the uniaxial cyclic and monotonic stress-strain response of a 1.4 mm-diameter wire subjected to heat treatments applied for different durations is evaluated. Wire specimens are tested in multiple environments at several strain amplitudes and loading protocols. The variation of mechanical properties over time is also addressed. Test results show that a minimum treatment time of 25 min at 750 °C (∼200 μm) is necessary for obtaining superelasticity at all ambient temperatures tested. Also, as the heat treatment time increases, the residual strain, functional fatigue, strength, energy dissipation and hysteresis degradation decrease, but the superelasticity limit and low cycle fatigue life are increased. However, a 35 min treatment (∼400 μm) causes the loops to become unstable at high temperatures and the training process is not efficient. The best conditions for seismic protection purposes are achieved with a 30 min treatment (∼300 μm), due to its maximum recoverable strain of 6.5 %, 3.6 % equivalent viscous damping, negligible residual strain and stable hysteresis under all temperatures evaluated and over time. A low-cycle fatigue model based on the Coffin - Manson relationship is also proposed.

Assessment of impact of fluoride on mechanical properties of NiTi and Cu NiTi orthodontic archwires

Background: The current study was carried out to assess the impact on the mechanical properties of orthodontic wires such as the NiTi and CuNiTi wires by fluoride available in various prophylactic products. Materials &amp; methods: 80 wire specimens were selected and were divided into two study groups with 20 specimens in each group as follows”: Group A: 0.019 x 0.025 inch NiTi archwires (NT3, American Orthodontics,USA), Group B: 0.019 x 0.025 inch CuNiTi archwires (Tritanium, American Orthodontics,USA). Following fluoride agent was taken as standard for the present study: Phos-Flur gel (Colgate oral pharmaceuticals, New York, USA). From the straight part of the archwire enrolled in the present study, wire specimens of dimensions 0.40 X 0.60 X 20 mm were cut. Control group: 40 specimens consisting of 20 specimens from each wire type; Solution used was deionized water, and Study group: 40 specimens consisting of 20 specimens from each wire group, placed in the Phos-Flur gel. Random selection of the wires was done followed by testing under universal force testing machine. Results: Among the study groups subjects, mean loading force among group A and group B specimens was 596.1 MPa and 368.4 MPa respectively.

Assessment of Impact of Fluoride on Mechanical Properties of NiTi and CuNiTi Orthodontic Archwires: An In Vitro Study

The current study was carried out to assess the impact on the mechanical properties of orthodontic wires such as the nickel-titanium (NiTi) and copper-nickel-titanium (CuNiTi) wires by fluoride available in various prophylactic products. Fifty-six wire specimens were randomly divided into two groups-control group in which deionized water was used as a medium and study group in which Phos-Flur gel was used. Both study group and control group were divided into two subgroups-NiTi wire group: 0.019 × 0.025 inch NiTi archwires (14 specimens) and CuNiTi wire group: 0.019 × 0.025 inch CuNiTi archwires (14 specimens). Testing of all the wires was done under a universal force testing machine. Mean loading force among NiTi wire group and CuNiTi wire group specimens with deionized water as a medium was 682.6 and 397.4 MPa, respectively, while the mean loading force among NiTi wire group and CuNiTi wire group specimens with Phos-Flur gel as a medium was 596.1 and 368.4 MPa, respectively. While comparing between study group and control group among NiTi wires, significant results were obtained. Also, while comparing between study group and control group among CuNiTi wires, significant results were obtained. Following exposure to fluoride agents, NiTi wires and CuNiTi wires are significantly associated with reduced mechanical properties. Although fluoride acts as a vital adjunct in maintaining oral hygiene, particularly among patients undergoing fixed orthodontic treatment, its influence on the mechanical properties of the wires is an area to be explored further; thereby, its use is to be monitored.

Assesment of electrochemical machining-induced pitting geometry on fatigue performance of flexible pipes’ tensile armor wires

In the extraction and production of oil and gas in sea environments, multiple components and systems are used, among them, flexible dynamic pipes, responsible for the transport of fluids. Because they are exposed to mechanical stress and corrosive conditions, it is important to assess the fatigue performance of the flexible pipe's components when there are signs of corrosion on their surfaces. Especially, the steel wires that bear the mechanical load during a riser's operation, are often vulnerable components to failure derived from the combination of corrosion and oscillating loads. The present work has the objective to assess the effects of corrosion pits, characterized by their dimensions, quantities and location, in the fatigue life of flexible pipes' tension wires. To make possible the correlation of the pits' parameters with their fatigue performance, the electrical discharge machining process was used, allowing a greater control of pits' development when compared to natural corrosion. The Taguchi method was employed to reduce the total amount of parameter combinations to be tested and to ascertain the effects of each parameter in the fatigue performance. Some pits obtained by electrical discharge machining didn't have the determined dimensions, especially the narrower and deeper pits. Fatigue tests were conducted in tensile armor wire specimens to assess the number of cycles to failure at pre-defined load levels. The fatigue testing results of electrical discharge machining corroded specimens suggest a more significant effect of the pits' diameter in reducing the fatigue performance, when compared to the controlled parameters of depth, quantity, location and aspect ratio. The maximum cycles reduction was around 73%, for wider pits, located in the planar face of the specimen, and the minimum reduction, around 40%, for narrower pits, located at the edge of the specimen.

EFFECTS OF FLUORIDE PROPHYLACTIC AGENTS ON THE MECHANICAL PROPERTIES OF ORTHODONTIC ARCH WIRES- AN INVITRO STUDY

Background And Objectives: There are the rising demand for esthetic orthodontic appliances and wires such as braided and co-axial wires. The effect of prophylactic agents on these relatively newly introduced arch wires are scarcely reported. Hence this study was undertaken to assess the effects of prophylactic uoride agents (1.Acidulated uoride agent (Phos-ur gel), 2. Neutral uoride agent (Prevident 5000)on the mechanical properties of non-coated Nickel-Titanium orthodontic wires and compare it with coated esthetic Ni-Ti wires and braided Ni-Ti wire. Materials And Methods: Total of 270 specimens of rectangular orthodontic nickel titanium arch wires were selected for this study and divided into three groups. All the three groups of wires (30 each) were immersed in 5 ml of articial saliva in plastic vials for 2 months (control). No uoride agents were used in sub-group a. Sub-group b and sub-group c samples were subjected to application of Phos-ur gel and Prevident 5000 respectively, one minute daily for 2 months. All the wires were tested for mechanical properties. Results: The results of the study showed that the mechanical properties of all the three groups of wires were affected by both acidulated uoride agent (Phos-ur gel) and neutral uoride agent (Prevident 5000). Conclusion: The study results proved that uoride prophylactic agents (mouthwash or gels) reduce the arch wire properties during orthodontic treatment.

Mechanical behavior and recoverable properties of CFRP shape memory alloy composite under different prestrains

This paper explored a prestressed CFRP/SMA composite system, which can be applied to add prestress to the civil structural members. The composite system was composed of carbon fiber reinforced polymer (CFRP) sheets and the embedded shape memory alloy (SMA) wires. The prestress in CFRP sheets was formed by the recovery of SMA wires. Four groups of fully composite (Type I) specimens were fabricated to bear a unidirectional static load to investigate their tensile mechanical properties. Three groups of partial composite (Type II) specimens and five groups of SMA wire specimens were used to study their recoverability. The static test results showed that two main failure modes of the Type I specimens were observed, and the strength of the material was affected by the structural form of the composite. The recovery test results showed that the SMA wire could generate different levels of recovery stress under various amounts of prestrain, and the maximum recovery stress can reach 394.2 MPa for the SMA wire with 6% prestrain by heating it to 131℃. More importantly, the recovery stress can be introduced into the CFRP sheets. In addition, an analytical model for predicting the stress–strain relationship and material strength of the fully composite was proposed, and an improved segmented recovery stress–temperature model of the SMA wire under constraint conditions was also put forward. The results indicated that the calculated values are in good agreement with the experimental values, and the proposed model can effectively predict the mechanical and recoverable properties of the composites.

The effect of oxygen on the CO2 corrosion of tensile wires in simulated annulus environments of flexible pipes

AbstractThe effect of oxygen on the CO2 corrosion of carbon steel wires in simulated annulus environments of flexible pipes was investigated. Wire specimens were exposed to modified artificial seawater solutions with and without dissolved oxygen. Dissolved corrosion products (Fe2+ and bicarbonate/carbonate) were added to the test solution to simulate corrosion in the annulus environment. Linear polarisation resistance technique was used to monitor the corrosion rates of specimens. The morphology of corrosion scales was investigated by scanning electron microscopy (SEM), and the crystalline phases were determined by X‐ray diffraction. Surface analysis of corroded specimens was carried out by means of SEM and optical profilometry. Different corrosion morphologies were observed, influenced by the different corrosion scales formed throughout the sequence of environmental conditions imposed on the material.

High-Temperature Deformation Characteristics of Cu&lt;sub&gt;3&lt;/sub&gt;Sn Evaluated by the Tests Using Composite Copper Wire Specimen.

In recent years, the propulsive movement of electrification of automobiles and airplanes is accelerating to realize a decarbonized society. Along with this movement, lightening of electric mobility is also required to reduce electricity consumption. The power modules used in electric mobility control high voltage and great current and are subjected to high temperature. Since most of the power modules employ Si semiconductor chips which can’t work in such a high-temperature range, cooling systems must be installed to prevent their failure. Therefore, next-generation power semiconductor chips using SiC or GaN, which can work properly in a high-temperature environment of over 200 ℃, are expected to be mounted in power modules to lighten them by eliminating cooling system. Cu3Sn intermetallic bonding technique which can form joints having a high melting point has attracted attention to achieve the mounting of the chips. To put the technique into practical use, the high-temperature deformation characteristics of Cu3Sn must be clarified. We previously proposed a materials testing method using a composite copper wire (CCW) specimen having a Cu3Sn layer to estimate the tensile characteristics of Cu3Sn. In this study, we conducted tensile tests, tension-strain maintenance tests, and cyclic tension-compression loading tests using the CCW specimen to evaluate the deformation characteristics of Cu3Sn in the temperature range between room temperature and 200 ℃.