Lifetime Of Wires Research Articles

Test Rig for Investigating the Functional and Structural Fatigue of Shape Memory Alloy Wires Based on Different Activation Profiles.

This work presents a test rig developed for testing the lifetime of electrically and cyclically activated shape memory alloy wires. This test rig is developed to provide information on the functional and structural fatigue of the wires. Therefore, electrical activation on the test rig can be carried out using different activation profiles, because it is of great research interest to determine whether those profiles have a significant influence on the wire's lifetime and functional behavior. The test rig monitors the process parameters such as stroke, current, voltage, and force. After presenting the electrical and mechanical design of the test rig, this publication evaluates an initial series of tests to demonstrate its functionality. Three different activation profiles are run in parallel on four identical test rig setups and are then evaluated. The functionality of the test rig is verified by a detailed evaluation of the process data on the one hand, and by comparing the results with existing literature on the other. The functionality of the test rig can thus be verified. At the same time, the strong influence of the different activation profiles on both the lifetime and the functional properties of the shape memory alloy wires becomes clear.

Lifetime of Liquid Metal Wires for Stretchable Devices

AbstractAs stretchable devices become well established for applications in soft robotics and wearable devices, the compliant conductors that make these applications possible must also be reliable and survive for the entire device lifetime. Liquid metals such as Galinstan are a potential solution as non‐toxic, stretchable, and low‐resistance conductors. Rigorous investigations of liquid metal lifetimes, however, are limited. This work presents the median lifetime of liquid metal‐filled silicone tubes under current density on the order of 1 kAcm−2, which is necessary for applications such as electromagnetic actuators. In these conductors, the median lifetime increases by a factor of over 4700 as current decreases from 2 to 1 kAcm−2. By cooling the sample, median failure time increases from 112 s to 9.4 h, which suggests straightforward solutions to maximize liquid metal wire lifetime by increasing thermal conductivity or by duty cycling the applied current.

Lifetime Estimation of Enameled Wires Under Accelerated Thermal Aging Using Curve Fitting Methods

Estimating the lifetime of enameled wires using the conventional/standard test method requires a significant amount of time that can endure up to thousands of testing hours, which could considerably delay the time-to-market of a new product. This paper presents a new approach that estimates the insulation lifetime of enameled wire, employed in electrical machines, using curve fitting models whose computation is rapid and accurate. Three curve fit models are adopted to predict the insulation resistance of double-coated enameled magnet wire samples, with respect to their aging time. The samples' mean time-to-failure is estimated, and performance of the models is apprised through a comparison against the conventional `standard method' of lifetime estimation of the enameled wires. The best prediction accuracy is achieved by a logarithmic curve fit approach, which gives an error of 0.95% and 1.62% when its thermal index is compared with the conventional method and manufacturer claim respectively. The proposed approach provides a time-saving of 67% (83 days) when its computation time is compared with respect to the `standard method' of lifetime estimation.

Corrosion fatigue and electrochemical behaviour of steel wires used in bridge cables

AbstractIn‐service bridge wires often fail prior to the design life subjected to alternating stresses and environmental erosion. In this paper, a novel corrosion fatigue test device, integrating fatigue testing machine and electrochemical accelerated corrosion assemblies, was developed to characterize the corrosion fatigue and electrochemical behaviour of the wires. Using the developed device, corrosion fatigue tests of corroded bridge wires under different corrosion and loading conditions were conducted. Electrochemical characteristics, corrosion fatigue behaviour, failure mechanism, and so forth were investigated according to electrochemical measurements, fracture morphologies and the lifetime of wires. Results evidence the synchronization of corrosion and fatigue and show the accelerated corrosion due to static and fatigue stresses. Additionally, cracking and fracture induced by multiple crack initiation was dominant in corrosion fatigue of corroded wires, and the coexistence of multiple corrosion pits decreased the lifetime significantly.

Stress-Based Model for Lifetime Estimation of Bond Wire Contacts Using Power Cycling Tests and Finite-Element Modeling

In this paper, a lifetime model for bond wire contacts of insulated gate bipolar transistors (IGBT) power modules is reported. This model is based on power cycling tests obtained under accelerated conditions, and a finite-element model taking into account the electrical, thermal, and mechanical coupling. It allows us to estimate the bond wire lifetime for a large scale of junction temperature swing amplitudes (ΔT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> ) and stress durations (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ). To build it, a numerical design of experiment was performed in both high and low stress values (ΔT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> ). Then, a strain-life curve has been constructed where the average strain values on a defined volume around the contact areas between top-metallization and the most exposed bond wires to fatigue and liftoff have been used. As a result, it has been shown that the total strain is linearly dependent with ΔT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</sub> and power law dependent with t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> . The combination of the strain-life relation and the strain dependency with stress parameters leads to the lifetime relationship. The obtained lifetime model has been satisfactorily validated with some additional experimental points obtained from literature and with a large range of values for t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> . This methodology can be easily replicated to other structures and is quite generic.

On hydrogen-induced damage in cold-drawn lean-duplex wires

Abstract Wire manufactures have recently started to produce a less-expensive class of high-strength wires referred to as lean-duplex. They are more attractive to the construction industry, which seeks alternatives to eutectoid prestressing steel and are able to enhance structural durability at a reasonable cost. Their suitability for prestressing is still poorly addressed in terms of sensitivity to hydrogen embrittlement, the root cause of stress corrosion damage. Hence, this paper assesses the resistance to hydrogen-induced stress corrosion (H-SCC) of one of this new generation of wires. In order to determine such resistance, two types of tensile tests were carried out with wires in the as-received condition and fatigue precracked, in air and in an aqueous solution of 20% ammonium thiocyanate (FIP solution) at 50 °C. The former was used to set out the collapse time under constant load in FIP solution and the latter (that is to say, the slow strain rate test) to observe and assess the failure mode in inert and aggressive environments. This provided additional insights from the damage mechanisms that govern the failure of the wires. Lastly, the damage tolerance of the tested lean-duplex wires was analyzed in the as-received condition and embrittled by hydrogen. Comparisons with similar data corresponding to cold-drawn eutectoid and high-alloyed duplex stainless steels wires were made. Although the lifetime of lean-duplex wires is limited (contrary to that of high-alloyed duplex wires), it exceeds that of eutectoid wires, currently used for prestressing purposes, by more than 10 times.

Fatigue life time modelling of Cu and Au fine wires

In this study, the influence of microstructure on the cyclic behaviour and lifetime of Cu and Au wires with diameters of 25μm in the low and high cycle fatigue regimes was investigated. Low cycle fatigue (LCF) tests were conducted with a load ratio of 0.1 and a strain rate of ~2e-4. An ultrasonic resonance fatigue testing system working at 20 kHz was used to obtain lifetime curves under symmetrical loading conditions up to very high cycle regime (VHCF). In order to obtain a total fatigue life model covering the low to high cycle regime of the thin wires by considering the effects of mean stress, a four parameter lifetime model is proposed. The effect of testing frequency on high cycle fatigue data of Cu is discussed based on analysis of strain rate dependency of the tensile properties with the help of the material model proposed by Johnson and Cook.

A study of the electric-field intensity of conductors of a 500-kV air line

Electrostatic-field intensities have been obtained by mathematical simulations of the electric field of AS conductors of a 500-kV air line (AL) and numerical analysis based on the finite-element method using the Ansoft Maxwell software. The irregularity of the wire surface of an air line and the inhomogeneities of surface of the last cable layer have been taken into account in the study. The latter lead to a local increase in the field intensity, which, in turn, results in a loss of useful power. Phase splitting is used to decrease the electric- field intensity on air lines. Furthermore, the intensity on the individual wire decreases and, as a result, loss of power is reduced with respect to the corona discharge and line inductive reactance. Thus, to decrease loss of power of wires and to prolong the lifetime of wires, it is necessary to determine correctly the cross section of wires and kind of phase splitting. A 2D mathematical model of the AL electrostatic field has been developed that takes into account the inhomogeneity of the shape of the wire surface. The analytical solution of the initial problem has been considered, and the numerical and analytical results for a cylindrical wire surface have been compared. The fields for four cases of an AS conductor with different versions of splitting have been studied. The curves of field intensities near a conductor surface as a function of the cross section and number of wires in the AL phase have been plotted.

Slicing parameters optimizing and experiments based on constant wire wear loss model in multi-wire saw

Multi-wire saw becomes the dominant method in slicing the hard brittle material into wafers. In this process, saw wire is the critical consumable and the dominant component of the wafer’s slicing cost. However, unreasonable process parameters lead to the fact that the saw wire was not fully used. This enormously increases the wire cost. For this reason, the constant wire wear loss model is presented by taking the free abrasive wire sawing as an example. This model takes the various cutting conditions into account and ensures the whole wire wear loss to reach the preset reasonable value. Firstly, a hypothesis that there is a mapping relation between the wire wear loss and the wire slicing area during the wire lifetime is built. According to this hypothesis, the wire allowed wear loss can be transformed into wire allowed slicing area. Secondly, the calculation method is deduced based on the model. The function relation is obtained between the wire feedback ratio and the actual slicing conditions under the constraint condition of the preset wire wear allowed loss. This rational feedback ratio of wire is obtained based on the actual process parameters. Thirdly, experiments are carried out. The results indicate that the relation between wire wear loss and wire slicing area is linear under the condition of the experiments and the wire consumption is reduced obviously. Meanwhile, wafers’ quality meets the requirements. This method can effectively save saw wire cost, referring to slicing other hard brittle materials by multi-wire saw.

Prediction of Bond Wire Fatigue of IGBTs in a PV Inverter under a Long-Term Operation

Bond wire fatigue is one of the dominant failure mechanisms in insulated-gate bipolar transistor (IGBT) modules under cyclic stresses. However, there are still major challenges ahead to achieve a realistic bond wire lifetime prediction in field operation. This paper proposes a Monte Carlo based analysis method to predict the lifetime consumption of bond wires of IGBT modules in a photovoltaic (PV) inverter. The variations in IGBT parameters (e.g., on-state collector-emitter voltage), lifetime models, and environmental and operational stresses are taken into account in the lifetime prediction. The distribution of the annual lifetime consumption is estimated based on a long-term annual stress profile of solar irradiance and ambient temperature. The proposed method enables a more realistic lifetime prediction with a specified confidence level compared to the state-of-the-art approaches. A study case of IGBT modules in a 10-kW three-phase PV inverter is given to demonstrate the procedure of the method. The obtained results of the lifetime distribution can be used to justify the selection of IGBTs for the PV inverter applications and the corresponding risk of unreliability.

Strategy for silicon based hot-wire chemical vapor deposition without wire silicide formation

Silicide formation of wires during hot-wire chemical vapor deposition (HWCVD) of silicon based coatings is a key challenge which has to be overcome before HWCVD can be transferred successfully into industry. Silicide formation of tungsten wires is not occurring at temperatures of approximately 1900°C and above when maintaining a silane partial pressure below approximately 1Pa. Proceeding silicide formation at the cold ends where the wires are electrically contacted was completely prevented by continuously moving the cold ends of the wires into the hot deposition zone, resulting in a retransformation of the tungsten phase. Thus the maintenance period of a HWCVD manufacturing tool can be freed from wire lifetime.

Thermomechanical Ageing of Copper-Clad Aluminum Wires Submitted to Creep Test Conditions

Creep tests were performed on copper-clad aluminum wires at 423 K and different stresses to cover potential operating load ranges in automotive industry. The lifetime of the wires is strongly dependent on the existence of an initial heat treatment and on the applied stress. It can be correlated with the formation of the three intermetallics Al2Cu, AlCu and Al4Cu9 identified by TEM diffraction. All results are discussed to understand mechanisms that could lead to the embrittlement of copper-clad aluminum wires by creep.

Time variation of partial discharge activity leading to breakdown of magnet wire under repetitive surge voltage application

This paper discusses partial discharge (PD) propagation, degradation and lifetime characteristics of magnet wires for inverter-fed motor under surge voltage application. Experimental results showed the time variation of PD activity, i.e. intermittent PD, successive PD, critical PD and breakdown (BD), under repetitive surge voltage application with a fixed peak value. Critical PD was a drastic change of PD activity and was identified as the partial BD of magnet wires. Since the final BD was confirmed to be always induced at the critical PD location, the critical PD was regarded as an important indicator to determine the lifetime of magnet wires. The experimental results also clarified that the lifetime of magnet wires could be determined by the total number of PD generation from its inception to breakdown. PD activity was interpreted by the time transition of PD generation frequency, and its mechanisms were discussed.

Refueling: Preventing Wire Degradation due to Electromigration

Electromigration is a major source of wire and via failure. Refueling undoes EM for bidirectional wires and power/ground grids-some of a chip's most vulnerable wires. Refueling exploits EM's self-healing effect by balancing the amount of current flowing in both directions of a wire. It can significantly extend a wire's lifetime while reducing the chip area devoted to wires.

Origins of enhanced proton transport in the Y7F mutant of human carbonic anhydrase II.

Human carbonic anhydrase II (HCA II), among the fastest enzymes known, catalyzes the reversible hydration of CO 2 to HCO 3 (-). The rate-limiting step of this reaction is believed to be the formation of an intramolecular water wire and transfer of a proton across the active site cavity from a zinc-bound solvent to a proton shuttling residue (His64). X-ray crystallographic studies have shown this intramolecular water wire to be directly stabilized through hydrogen bonds via a small well-defined set of amino acids, namely, Tyr7, Asn62, Asn67, Thr199, and Thr200. Furthermore, X-ray crystallographic and kinetic studies have shown that the mutation of tyrosine 7 to phenylalanine, Y7F HCA II, has the effect of increasing the proton transfer rate by 7-fold in the dehydration direction of the enzyme reaction compared to wild-type (WT). This increase in the proton transfer rate is postulated to be linked to the formation of a more directional, less branched, water wire. To evaluate this proposal, molecular dynamics simulations have been employed to study water wire formation in both the WT and Y7F HCA II mutant. These studies reveal that the Y7F mutant enhances the probability of forming small water wires and significantly extends the water wire lifetime, which may account for the elevated proton transfer seen in the Y7F mutant. Correlation analysis of the enzyme and intramolecular water wire indicates that the Y7F mutant significantly alters the interaction of the active site waters with the enzyme while occupancy data of the water oxygens reveals that the Y7F mutant stabilizes the intramolecular water wire in a manner that maximizes smaller water wire formation. This increase in the number of smaller water wires is likely to elevate the catalytic turnover of an already very efficient enzyme.

Improved Electromigration Lifetime for Copper Interconnects using Tantalum Implant

ABSTRACTIn this study, a novel method is explored for improving the electromigration lifetime of Cu wires, using Ta implantation into Cu. For high implant doses (2E15 cm−2), the electromigration lifetime is improved by over 5X using this method. An increase in lifetime is achieved, even for an average surface concentration of Ta on the order of 0.1 atm%. We propose that the improvement in electromigration lifetime is due to the reduction of defects at the SiN/Cu interface due to the presence of Ta. The line-to-line leakage at high voltages (&gt; 5V) increases with the Ta implant, with higher leakage at higher Ta concentrations, so the Ta dose must be limited to avoid excessive leakage.

The effects of a hydrogen environment on the lifetime of small-diameter drift chamber anode wires

Possible deterioration of anode sense wires used in a hydrogen-filled neutron detector is investigated. Wires were loaded with free weights and put into a wire detector environment. Stainless steel, tungsten, and platinum wires did not break after exposure to charge equivalent to many wire lifetimes. Furthermore, exposure to hydrogen gas caused no noticeable surface degradation or change in wire yield strength.

PVC Wire Coatings: Part II Characterizations and Performance Predictions

Theoretical background derived by the authors (1) covering the ageing processes in plasticized PVC is used to characterize the ageing processes in PVC wire coatings. The structural changes during ageing and the state of insulation at its break-down are determined. These experimental data are used to formulate a mathematical description of the ageing process in these systems and to predict the life-time of such wires in use.