Wire Temperature Research Articles

A Study on the Effect of Bond Wires Lift-Off on IGBT Thermal Resistance Measurement

Bond wire lift-off will cause an increase of remaining wires’ power dissipation, which usually is ignored for healthy modules. However, only partial wires’ power dissipation transfers through thermal path from junction to case, which will lead to overestimate the whole power dissipation from collector to emitter pole and underestimate the calculated thermal resistance using the proportion of temperature difference to power dissipation. A FEM model is established to show the change of heat flow after bond wires were removed, the temperature of bond wires increases, and the measured thermal resistance decrease after bond wires lift-off. It is validated by experimental results using open package Insulated Gate Bipolar Transistor (IGBT) modules under different current conditions. This conclusion might be helpful to indicate the bond wires lift-off and solder fatigue by comparing the change of measured thermal resistance. Using the Kelvin setup to measure thermal resistance will cause misjudgment of failure mode due to the ignoring of wires’ power dissipation. This paper proposed that the lift-off of bond wires will lead to underestimating the thermal resistance measurement, which will overestimate the lifetime of IGBT module and misjudge its state of health.

Machine learning based effective linear regression model for TSV layer assignment in 3DIC

On the integration of 3D IC design, thermal management issues play a significant role. So, it is required to implement an effective approaches and solutions for integrating 3DIC. The TSV causes problems with the distinct coefficients of thermal expansion that induces mismatch strains and stresses. The major drawback of 3DIC is the thermal management issues which increases the power consumption through the current crowding, perhaps the temperature upraised by the slacked layers due to its heat generation. Several research has not been undergone in 3DIC utilizing machine learning approaches which is highly complicated. This paper firstly proposes an efficient ML model to achieve better reduction in wire length and temperature. An efficient linear regression model is preferred here in order to achieve significant performances in TSV layer assignment. The linear regression utilized gradient based approach where the error is predicted at every instance through tracing gradient cost function. An optimized TSV layer assignment is achieved with this flexible ELRM. The performance analysis of data shows that the proposed ELRM based TSV assignment achieved better wire length and temperature. The ISPD98 Circuit Benchmark Suite is utilized for result evaluation and it achieves improved TSV layer assignment through reducing wire length and temperature.

Experimental study on vibration control using shape memory alloy based vibration absorber

The main purpose of this study is to analyze the dynamic performance of Adaptive tuned vibration absorber (ATVA). For analysis, a baseline model consists of a base excited single degree of freedom system coupled with an ATVA mode prepared. Shape memory alloy (SMA) which has a variable frequency with respect to temperature, is used for adaptive tuning after its material characterization. Tests are performed to determine the peak Transmissibility by varying the temperature of SMA wire i.e. stiffness. The results showed that the peak Transmissibility of ATVA is nearly 46% lower than low temperature. Results further showed that increase in stiffness reduces the vibration levels at higher temperature, also the frequency span increases.

Characterization and Behavior Study of Nitinol Shape Memory Alloy Wire for Effective and Efficient Use in Soft Robotics as an Actuator

Soft Robotics is an emerging field due to high degree of freedom, their soft and delicate interaction, almost no vibration during operations etc. are some among many reasons, why scientists and researchers got attracted towards this field. Nitinol is commonly used in soft robotics and easily available Shape Memory Alloy (SMA) actuator. In present investigation, the authors attempted to understand the characteristics and behaviour of Nitinol SMA Actuator wire with change in various parameters such as length, diameter, current, and temperature. Moreover, it is investigated, how resistance, power consumption, force developed, hysteresis, and displacement changing takes place with current passing through the wire and corresponding temperature developed. Various experiments are performed and based on the results and findings related to the selection of wires for specific requirement have been discussed and suggestions were made for the use of the SMA actuator efficiently and effectively.

Simplified Calibration Method for Constant-Temperature Hot-Wire Anemometry

This study proposes a unique approach to convert a voltage signal obtained from a hot-wire anemometry to flow velocity data by making a slight modification to existing temperature-correction methods. The approach was a simplified calibration method for the constant-temperature mode of hot-wire anemometry without knowing exact wire temperature. The necessary data are the freestream temperature and a set of known velocity data which gives reference velocities in addition to the hot-wire signal. The proposed method was applied to various boundary layer velocity profiles with large temperature variations while the wire temperature was unknown. The target flow velocity was ranged between 20 and 80 m/s. By using a best-fit approach between the velocities in the boundary layer obtained by hot-wire anemometry and by the pitot-tube measurement, which provides reference data, the unknown wire temperature was sought. Results showed that the proposed simplified calibration approach was applicable to a velocity range between 20 and 80 m/s and with temperature variations up to 15 °C with an uncertainty level of 2.6% at most for the current datasets.

A comprehensive numerical model for kerf width prediction in hot wire cutting of expanded polystyrene

Improving accuracy in cutting of expanded polystyrene (EPS) foam using hot wire depends on understanding and controlling the kerf width, which in turn depends on temperature distribution in the foam during cutting. We present here a comprehensive temperature-validated numerical thermal model that incorporates important factors such as convective heat transfer between the wire and molten/ablated foam and the surroundings, thermal coupling between the wire and EPS, temperature dependent EPS foam and wire properties and the latent heat of melting and ablation of EPS, to predict the three-dimensional temperature distributions in the EPS foam in the region immediately around the hot wire and across the entire width of the EPS foam being cut. Based on isothermal temperature contour at the melting point of the foam, kerf width is predicted and compared with experimental measurements. Average kerf width and kerf width variation across the width of the work are seen to be predicted reasonably by the model. The barrelling of the cut profile due to the variation of wire temperature along its length is also quantified and compared with experiments. Selectively switching off various model parameters such as temperature dependent EPS and wire properties and the thermal coupling between wire and EPS shows significant contributions of these factors towards the error in kerf width predictions. Convective heat losses are found to be important when the width of EPS being cut is less such as in thin sheets. As confirmed by experimental data, kerf width is higher near the work edges and stays constant within the bulk region of the work. The model developed comprehensively captures the thermal effects and thus can be used to improve precision while cutting EPS shapes.

Differences in temperature measurement by commercial room temperature sensors: Effects of room cooling system, loads, sensor type and position

Thermostats control the heating, ventilation and air-conditioning (HVAC) system of a building based on the temperature they measure. Integration with communication network technologies allows wireless sensors to be used as the temperature sensing component of an HVAC system, increasing the flexibility in the selection and positioning of sensors. This study compared the temperature measuring performance of nine wireless and two conventional wired temperature sensors against reference air and globe temperature sensors in a climate chamber with a two-person office setup. The influence of sensor position, room cooling system (all-air or radiant with ventilation) and cooling load (33, 61 W/m2) was studied.Sensors placed at the same position had a measurement difference of up to 1.8 K, and assumptions about the type of temperature a sensor measures (air or globe) had the largest impact on the deviation from the reference temperatures. As opposed to common assumptions, conventional wired temperature sensors measured closer to globe temperature sensors and could be a possible indicator for the operative temperature. When the load settings were high, measurements in radiant system cases had smaller deviations from the reference sensors compared with all-air systems, due to the chilled surface compensating for the radiation from the loads.

Temperature of metal wires for nanosecond and microsecond electrical explosions in vacuum

Experiments show an inverse correlation between temperature and heating time for the electrical explosion of thin metal wires in vacuum. Faster heating of the wire results in higher energy release in a short time, while slow heating lasts longer but releases less energy before breakdown. Breakdown is a natural barrier to the direct release of Joule energy and an increase in the metal temperature to an abnormally high value. An increase in the current rate from 0.07 to 170 A/ns leads to a decrease in the heating time from 5 μs to 5 ns and an increase in the wire temperature from 450 K to 4000 K before the voltage breakdown. This inverse correlation between the heating time and the temperature of the wire in a vacuum can be explained by the inertia of evaporation of the hydrocarbon impurity from the surface of the hot metal.

Thermal analysis and numerical simulation of Pulley-Belt driven type NiTiNOL heat engine

The NiTiNOL heat engine, belongs to the unique category of a non-conventional type of mechanically-driven engine, where the work done by an engine depends on the phase transformation that is taking place within the material by absorbing heat. The present investigation is about the experimental and numerical analysis of a NiTiNOL heat engine, where the experimental part includes the temperature monitoring of both the Ni-Ti wire and the working fluid using non-contact type and contact type sensors, respectively. But, the numerical part includes the thermal simulation of the entire physical system using ANSYS-FLUENT 15.0 Software Package. The objective of this study is to correlate the variation in temperature of Ni-Ti wire with the performance (cycle efficiency) of the NiTiNOL heat engine. It was found that the temperature-dependent material property that is affected by the martensite volume fraction (ζ) during the phase transformation (M → A), plays an important role in controlling the cycle efficiency of the heat engine. The measured values of Ni-Ti wire temperature, at specified locations using a non-contact type thermal sensor, are found to be well supported with the numerical simulation results. The time taken to reach the steady state temperature of the Ni-Ti wire during the working cycle of the engine was found to be varying in nature due to the initial temperature of the working fluid. The cycle efficiency of the engine has increased from 27% to 31%, and the thermal efficiency of the engine decreased from 70% to 50% with the time elapsed.

Finite differential hot-wire method for localized heat transfer characterization at microscale

In this work, we develop a finite differential hot-wire method to uncover the localized heat dissipation physics along microwires. The localized convection effect can be decoupled at the finite differential element with a spatial resolution of 10 microns. The heat convection coefficient is characterized from 314 W m−2 K to 1116 W m−2 K along different positions of microwires with different diameters, which decreases from wire ends to its middle point. The slope of temperature gradient at wire surface versus temperature is determined from 20150 m−1 to 8640 m−1, which can be used to calculate the boundary layer thickness around microwires.

Transient thermal analysis in nanofluid suspensions

An analytic approach is utilized to investigate the heat transfer mechanism in nanofluids containing spherical nanoelements. The transient thermal conduction process in a cylindrical geometry is assessed according to the Dual-Phase-Lag (DuPhlag) model and then compared with the classic Fourier solution. For the first several seconds, the wire temperature values calculated by the two models as well as their corresponding slopes are different; the curves merge at longer times depending on the nanofluid properties. At the initial stages, the realistic temperature magnitude of the suspension is also smaller than the Fourier solution, since in reality, the transient heat transfer rate is comparatively smaller owing to the certain time lags in the heat flux/temperature gradient relationship. The key parameters that govern in the initial stages of the heat transport inside the domain are the thermophysical properties of the components of a nanofluid, their relative velocity, the size/shape and concentration of the nanoparticles, and the system geometry. Two typical parameters, the conductivity and heat flux indexes, are also introduced to evaluate the deviation of the Fourier theory from the DuPhlag model. The conductivity index has a minimum value at the initial stages, and then, it is beginning to recover. A fluctuating distribution of the heat flux index is observed at the beginning of the process which is smoothed out after a lapse of time. A decrease in the nanoparticle diameter and/or an increase in the concentration may result in accelerating the transient response of the medium to the input thermal excitation.

Ignition and combustion behavior of zirconium-based pyrotechnic igniters and pyrotechnic delays under aging

Pyrotechnic materials often necessitate high reliability and stability to be utilized in energetic devices. However, prolonged storage of these materials degrades their performance in many ways and results in failure of these devices. Only a few studies have focussed on their burning characteristics, and reported limited understanding on the effect of aging on this behavior of such materials. In this study, ignition and combustion behavior of pyrotechnic materials based on zirconium (Zr) as fuel and potassium perchlorate (KClO4) or iron(III) oxide (Fe2O3) as oxidant are investigated, for various aging conditions. Pristine samples are compared with samples subjected to aging under 91 °C (thermally aged) and seasonal changes (naturally aged). The ignition delay time as a function of maximum wire temperature is obtained through high-speed combustion photography for these samples. Surface features and oxide content are analyzed using scanning electron microscopy and x-ray photoelectron spectroscopy techniques. Results indicate that ignition delay time increases significantly with aging period for both pyrotechnic igniter and pyrotechnic delay samples. However, this time reduces as the maximum wire temperature is increased for all samples. Naturally aged samples exhibit longer ignition delay times and higher metal oxide content when compared to thermally aged ones. Both pre-oxidation of metallic fuel and prior thermal decomposition of oxidizer play an important role in causing this behavior with aged samples.

An experimental investigation on time response characteristics of SMA wire actuators under electric heating for engineering design

Shape memory alloys (SMAs) are proved to have high energy-to-volume ratio and large displacement. However, they have the defect of longer recovery time. In practice, designing SMA wire actuators is a very complex and exhausted thing because of extensive and various needs. In this study, a special setup was designed, which can test many characteristics of a SMA wire heated by electric current, including temperature, deformation, response time, recovery time, wind speed (for cooling), and load. Besides, an empirical model of the wires temperature was presented for avoiding overheating the wires. By fitting experiment data, unknown parameters in this model are determined. Next, main design parameters are investigated on how they exert effects on the characteristics of the SMA wires, including wire radius, convection type, load, and voltage. At last, the time response characteristics were also analyzed. Through this study, one can make clear how each design parameter plays its part in SMA wire actuators.

Assessment of climatic factors influence on the time to reach maximum wire temperature of overhead power lines

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Effects of the Size of Charged Nanoparticles on the Crystallinity of SiC Films Prepared by Hot Wire Chemical Vapor Deposition

Non-classical crystallization suggests that crystals can grow with nanoparticles as a building block. In this case, the crystallization behavior depends on the size and charge of the nanoparticles. If charged nanoparticles (CNPs) are small enough, they become liquid-like and tend to undergo epitaxial recrystallization. Here, the size effect of SiC CNPs on film crystallinity was studied in the hot-wire chemical vapor deposition process. To do this, SiC nanoparticles were captured under different processing conditions—in this case, wire temperature, precursor concentration and the filament bias. Increasing the temperature of tungsten wires and decreasing the ratio of (SiH4 + CH4)/H2 reduced the size of the SiC nanoparticles. When the nanoparticles were small enough, an epitaxial SiC film approximately 100-nm-thick was grown, whereas larger nanoparticles produced polycrystalline SiC films. These results suggest that the size of the CNPs is an important process variable when growing films by means of non-classical crystallization.

Acceptability Evaluation of a Developed Thermal Infrared Device for Fire Risk Management

A novel thermal infrared device was developed to measure wire temperature in application to fire risk management. Findings show that the device is as effective as the conventional thermocouple thermometer. The technology adoption of the device was also assessed using the unified theory of acceptance and use of technology (UTAUT) model. From the assessment, it was found out that user age has a negative effect on the UTAUT constructs on performance expectancy (PE), the effort expectancy (EE), and facilitating condition (FC). Moreover, the user gender was found to have an adverse effect on PE. Furthermore, the construct which has the highest positive effect on the user behavioral intention (BI) is social influence (SI) with a value of 0.552. All the factors have values greater than or equal to 0.7 thresholds for Cronbach's alpha, 0.5 for composite reliability, and 0.5 for average variances.

Influence of different storage temperatures on the mechanical properties of NiTi, Cu-NiTi and SS orthodontic archwires: An in vitro study

Due to their exceptional temperature sensitivity, the mechanical properties of Nickel-titanium and Copper Nickel-titanium wires may be influenced by their storage temperature. This in turn may have clinical implications and may also affect the outcomes. This study analyzed the influence of storage temperatures on the mechanical properties of orthodontic wires in a laboratory setting. Stainless steel (SS), Nickel-Titanium (NiTi), and three variants of Copper-NiTi (Cu-NiTi 27°C, 35°C and 40°C), 0.017×0.025 inches in size were analysed using a three-point bending test in a pre-heated chamber at 36°C. The orthodontic wires were stored for twenty-four hours before the mechanical testing at four different temperatures (5°, 22°, 36° and 60°C). The obtained results showed that the mechanical forces exerted by 27°C Copper-NiTi exhibit the most stable behaviour after having been stored at different temperatures, whereas 35°C Copper-NiTi showed the highest variability. As to be expected, Stainless steel shows no changes in its bending mechanical properties. Furthermore, the results of this investigation reflect the importance of controlling the storage temperature of orthodontic NiTi and Copper-NiTi wires tested in a research environment in order to avoid unexpected bias.

Study on combustion stability of a miniature reciprocating piston internal combustion engine

The combustion of a micro-piston internal combustion engine with platinum wire glow ignition is diagnosed. The results show that the combustion starting point of the micro piston internal combustion engine varies greatly, and the combustion duration is various and long. The coefficient of variation of pmax is as high as 28.5%, the combustion stability is poor. Therefore, it is suggested to improve the thermal environment in the cylinder to improve the combustion stability. One method is to increase the temperature in the cylinder to reduce the duration and the cyclic variation of combustion. The other method is to increase the temperature of the platinum wire to improve the stability of the starting point of combustion and to reduce the cyclic variation of combustion. The test results show that with the increase in the cylinder body temperature, the distribution of combustion starting point is more concentrated, and the coefficient of variation of pmax decreases by about 38.6%. The stability of combustion increases. So the combustion stability can be improved by appropriately increasing the temperature of cylinder body. With the increase temperature of the platinum wire, the ignition and combustion will be facilitated and the combustion stability will be improved. At the same time, the movement of the gas near the platinum wire will be accelerated, which gives rise to affect the flame-kernel development and flame propagation. The ignition points will become scattered, which increases the instability of combustion.

On mechanical properties of NiTi SMA wires prestrained by cold rolling

This study investigates mechanical properties and recovery stress of NiTi shape memory alloy (SMA) wires prestrained by different degrees of cold rolling. Using differential scanning calorimetry (DSC), the phase transformation temperature in cold rolled wires are compared with as received one. Monotonic and hysteretic tensile tests are conducted to determine the stress-strain curves of each cold rolled wire. Thickness recovery ratio, recovery and residual stress of constrained wires are measured during temperature variations. It is found that cold rolling can reduce detwinning process in tensile behavior and finally eliminate it with more cold work. Moreover, the optimal degree of cold rolling is obtained in terms of maximum induced recovery stress, safety of storage and minimum morphological changes and costs. Based on the experimental data, the degree of cold rolling can be categorized into three ranges of slight, moderate and extensive.

Experimental study on thermal and fire behaviors of energized PE-insulated wires under overload currents

The electric fires are highly likely caused by the combustible wire insulation material ignited by a short circuiting or overload current in residential and commercial buildings, nuclear power plants, etc. It is important to know fire behaviors of the insulation materials over energized wires under overload currents, so fire behaviors are investigated experimentally over high-current energized polyethylene (PE)-insulated copper wires A and B with different sizes (dc/do = 0.9 mm/3.0 mm and 1.3 mm/4.2 mm for wires A and B, respectively, where dc and do denote the core and outer diameter of wire, respectively). The results show that the flame height rises firstly and then remains steady with the increasing current under low current, which is similar with the previous research, while the flame height drops sharply when the current is extremely high over 40 A. The flame width also drops with current under high-current condition. In addition, the surface temperature of wire, measured by infrared thermography, agrees well with the predicted balance temperature of wire under low current, but deviates from the balance temperature under high currents. Correspondingly, the measured flame spread rate agrees well with the prediction model based on the thermal balance temperature at low currents, while shows an obvious deviation under large currents. The flame spread rate grows approximately with the square of the current, but tends to increase slowly and even remains steady under high current. Moreover, the effects of wire size on flame spread are also investigated. The flame of wire with large diameter is wider, but its flame spread rate is lower and rises slower with current. The results of this work provide important information about fire behaviors over energized wires under overload currents and may guide the design of future electric fire safety.