Thermocouple Wire Research Articles

Effect of Dentin Bonding Agent on Intrapulpal Temperature during Fabrication of Provisional Restorations by a Direct Method: An In Vitro Study

To determine the effect of three different provisional restorative materials (PRMs) and application of dentin bonding agent (DBA) on intrapulpal temperature rise during fabrication of provisional crowns using a direct method. Three PRMs-polymethyl methacrylate resin (PMMA), bis-acrylic resin, and dimethyl methacrylate resin (DMMA)-were used in the study. Dentin bonding agent (Single Bond 2, 3M ESPE, Germany) was applied in a single layer or double layer as an insulating material. A total of 45 molars were prepared for complete coverage restoration with chamfer finish line and 1.5 mm axial and 2 mm occlusal reduction. After application of a single or double layer of DBA, provisional materials were polymerized according to the manufacturer's instructions. The temperature increase inside the pulp chamber was measured with a T-type thermocouple wire. The readings were averaged for each group to determine the mean value of temperature rise. Statistical analysis was performed with analysis of variance (ANOVA) followed by post hoc Tukey test (a = 0.05). The temperature rise varied according to the provisional restoration material used (PMMA > DMMA > bis-acrylic resin) (p < 0.001) and the single or double layer of DBA (p < 0.001). Polymethyl methacrylate resin produced a higher intrapulpal temperature. Application of a double layer of DBA resulted in a significantly lower intrapulpal temperature.

A Comparison of Thermal Changes among Four Different Interproximal Reduction Systems in Orthodontics

Interproximal enamel stripping is routinely used in orthodontics, different methods were utilized by clinicians to reduce the width of teeth but no previous study addressed the factors affecting the thermal safety of such systems on the dental pulp. The present study was conducted to measure thermal changes among four different interproximal reduction (IPR) systems in orthodontics. A total of 130 extracted human premolar teeth were used in this study. Teeth were distributed into three experimental groups each having three subgroups and one control group. Thus, a total of 10 subgroups were created of 13 teeth each. Stripping procedures were performed using four diamond tools (burs, discs, saw, and manual strip) with different speed setup, with and without a coolant for the higher speed setup for each tool. A K-type thermocouple wire was positioned in the center of the pulp chamber and was connected to a data logger during the application of stripping procedures. Data were analyzed by the Krushkal-Wallis test using the SPSS PC+ version 21.0 statistical software. There was a highly statistically significant difference in the mean ranks of temperature values among the four groups with different speed levels. Among the 10 subgroups, the higher change in temperature registered was in the bur and disc groups when operated with the highest recommended speed without a coolant. The change in temperature was statistically significantly higher than the temperature values of other groups (p < 0.001). All recorded temperatures were below the critical temperature (5.5 °C) registered. Based on the results of this study, IPR is a safe procedure on the dental pulp for the teeth with a medium dentin thickness with or without a coolant.

Steel-CF/PA 6 hybrids manufactured by a laser tape placement process: Effect of first-ply placement rate on lap shear strength for garnet blasted substrates

Abstract This paper investigates the manufacture of selectively reinforced metal/composite hybrids in a laser-assisted automated tape placement process. Unidirectional carbon fibre/PA 6 composite tapes were applied to 1.9 mm hot rolled steel substrates. The bonding of the first ply to the substrate is critical to the success of the metal-composite hybrid. This work investigates the effect of increasing the first-ply placement rate for speeds of 25 mm/s, 50 mm/s and 100 mm/s. The steel substrates were pre-treated by garnet blasting and then coating with a 60 μm layer of PA 6. The garnet blasted surface texture was quantified using white light interferometry. The thermal history for bonding of the first ply was measured with fine wire thermocouples. The interfacial bond strength of the hybrid laminates was assessed by ASTM D 3165 lap shear tests. The lap shear strength increased to the highest value of 22.4 MPa at 50 mm/s. Analysis of the fracture surfaces and thermal history suggest that the lower strengths at 25 mm/s and 100 mm/s are due to lower adhesion of the PA 6 coating to the metal substrate, most probably due to lower levels of crystallization.

Miniature Uncooled and Unchopped Fiber Optic Infrared Thermometer for Application to Cutting Tool Temperature Measurement.

A new infrared thermometer, sensitive to wavelengths between 3 μm and 3.5 μm, has been developed. It is based on an Indium Arsenide Antimony (InAsSb) photodiode, a transimpedance amplifier, and a sapphire fiber optic cable. The thermometer used an uncooled photodiode sensor and received infrared radiation that did not undergo any form of optical chopping, thereby, minimizing the physical size of the device and affording its attachment to a milling machine tool holder. The thermometer is intended for applications requiring that the electronics are located remotely from high-temperature conditions incurred during machining but also affording the potential for use in other harsh conditions. Other example applications include: processes involving chemical reactions and abrasion or fluids that would otherwise present problems for invasive contact sensors to achieve reliable and accurate measurements. The prototype thermometer was capable of measuring temperatures between 200 °C and 1000 °C with sapphire fiber optic cable coupling to high temperature conditions. Future versions of the device will afford temperature measurements on a milling machine cutting tool and could substitute for the standard method of embedding thermocouple wires into the cutting tool inserts. Similarly, other objects within harsh conditions could be measured using these techniques and accelerate developments of the thermometer to suit particular applications.

Real-time imaging-guided microbubble mediated high intensity focused ultrasound heating in an ex-vivo machine-perfused pig liver

High intensity focused ultrasound (HIFU) is used clinically for the ablation of prostate and liver tumors. More recently, HIFU has been used in the brain for locally controlled thermal treatment of nonessential tremors. However, the thermal lesion location is restricted to a small area in the tissue due to geometric and boundary limitations (avoiding skin and bone burns). Bubble-enhanced heating (BEH) allows for the use of lower power and can generate spatially controlled thermal lesions in regions not currently accessible with conventional HIFU. We have studied BEH in vitro and in a machine perfused pig liver (MPL). The MPL presents a versatile platform for perfusion and BEH studies because it is clinically relevant and allows for delivery of microbubbles under ultrasound imaging. We first applied conventional HIFU and BEH in vitro, in an enclosure with acoustic windows contaiing glycerin and microbubbles while monitoring the temperature with a fine wire thermocouple. A focused 1 MHz transducer and various clinically approved microbubbles were used. Then we applied BEH on the MPL by introducing microbubbles under image guidance. With this initial study, we have observed that BEH has resulted in 5-10x energy reduction for the formation of a reference lesion in vitro, and 3-6x in the MPL.

Influence of Cr-Content on the thermoelectric and mechanical properties of NiCr thin film thermocouples synthesized on thermally sprayed Al2O3

Ni/Ni-Cr thin film thermocouples were deposited by means of DC magnetron sputtering for the application in plastic extrusion dies. In order to ensure the application of the thermocouples on complex surfaces, a thermally sprayed Al2O3 layer was used between the substrate and the thin films for thermal insulation and electrical isolation. The study includes the deposition, characterization, calibration, and validation of thin film thermocouples. The influence of the composition (10 at.-%, 20 at.-% and 30 at.-% Cr) was analyzed concerning mechanical and electrical properties. It was found out that the electrical resistance increases with the temperature and the Cr-content due to a decreasing crystallite size. By means of a scratch-tester and nanoindentation, a higher scratch load and hardness were observed for larger Cr-contents on the thermally sprayed Al2O3 coating. Despite the composition, the influence of the size as well as the thickness of the thermocouples were analyzed regarding the Seebeck coefficient. Independent from the size and Cr-content, all thermocouples feature a comparable Seebeck coefficient of about 40 μV/K. This high coefficient is similar to that of wire thermocouples, showing a low number of defects in the thin films. The ceramic coating features a thermal insulation of about 20 °C at 200 °C, allowing a more accurate measurement of the ambient medium.

A study on the measurement and prediction of LED junction temperature

In this study, an innovative method for the measurement of the LED junction temperature is proposed. In the proposed technique, the temperature values at the LED chip surface, at the solder joint, and at a substrate point in the vicinity of the LED are measured, and the results are compared with the junction temperature measured by transient thermal measurements method. The aforementioned three temperature values are precisely measured via an IR thermometry and thin wire thermocouple. For the demonstration of the feasibility of the IR thermometry to the LED chip surface, the spectral distribution of the LED emission is analyzed using a spectroradiometer. The results show that there is negligible IR irradiation at the LED, suggesting no IR-induced interference is expected for the surface temperature estimation. In order to validate the experimentally obtained temperature distribution, an FEM-based numerical study is also performed. The experimental and numerical results are shown to agree well to each other within 15%. Based on the results, an empirical equations that correlate the junction temperature and the temperature at the solder joint, substrate, and surface of LED are developed. In addition, we show that analyzation of the structure function containing thermal resistance data of LED package obtained from the transient thermal measurement can yield a good interpretation in regard to the thermal resistance of the LED itself. The proposed methodology can act as a good guideline for the thermal management of the LED-related products.

Study of melting and crystallization of Cu – P alloy using a universal vacuum viscometer and thermal analysis

Methods of differential thermal analysis (DTA) and measurement of the melt viscosity are widely used in studying the properties of alloys at high temperatures. We have made an attempt to combine those two complementary methods of research. In contrast to the single-stranded Shvidkovskii viscometer, a bifilar suspension on two thermocouple wires is used in the proposed construction of the installation. The system based on the bifilar suspension provides using thermocouple in contact with the crucible with a sample, thus ensuring measurements of the crucible temperature like the measuring cell in DTA. The adjusting thermocouple located near the coil of a bifilar heater is used as a reference thermocouple. Since thermal analysis requires linear heating at a constant rate, and the viscosity is usually measured in a steady-state (steady-state) regime with long exposures at each measurement temperature, a series of dynamic viscosity determinations with a heating rate of 1, 2, 3 and 5 °C/min is carried out, the heating rates of 1 and 2 °C/min being approximately equal to the average heating rate under steady-state conditions. It is shown that when measuring in a dynamic mode at a heating rate up to 3 °C/min, the viscosity curves coincide with the measurement data in a steady-state mode, and the results of the thermal analysis (experimental setup) are consistent with the data of DTA (STA 409 setup). Results of measuring the logarithmic decrement of vibrations for Cu – 7.3% P alloy and data of thermal analysis are presented. Data of thermal analysis obtained on our experimental setup coincide completely with the DTA results obtained on a STA 409 unit. A model experiment carried out to explain the delay of growth of the logarithmic damping decrement at the beginning of melting and sharp decrease at the beginning of crystallization indicates to the effect of blocking free flow of the liquid melt component by the solid skeleton having a higher melting point.

Devolatilization of millimeter-sized biomass particles at high temperatures and heating rates. Part 1: Experimental methods and results

In the framework of a general research on biomass combustion, this paper presents and discusses the experimental techniques developed to analyze the heating, drying and devolatilization of biomass particles of few millimeters, a size range scarcely studied in the past. Individual particles were suspended in a stream of hot gases generated by a Flat Flame Burner, with controlled temperature and composition. The evolution of their morphology was monitored by time-lapse photography; additionally, an estimate of the instantaneous volatile release rate was derived from the picture series based on the size of the volatile shell flame. The temperature inside the particles (3–15 mm in diameter) was measured with pairs of fine wire thermocouples located at the particle's center and near its surface. The systematic error associated to this technique (deviations up to 300 K in relation to the actual particle temperature), due to the intense heat transfer along the metal wires, was evaluated experimentally and modeled; the agreement found in the comparison allowed for establishing a procedure to correct those signals and thus adequately evaluate the thermal gradients within the particles. A subsequent comparison of the experimental results (evolution of size, shape, internal temperature and temperature gradients, volatile release rate in a variety of conditions) with simulations performed with models which alternatively consider or neglect internal gradients is presented in a separate paper [21].

The compatibility between thermocouple wires and sheath alloy for small diameter mineral-insulated metal-sheathed (MIMS) thermocouples in long-term aging

In this paper, the influence of long-term aging on the electromotive force (EMF) drift of small diameter mineral-insulated metal-sheathed thermocouples has been investigated on the two typical commercial thermocouple alloys for the nuclear reactor application. The results show that the stability of the de2-316L thermocouples is superior to that of de1 thermocouples. The drift is attributed to inhomogeneous oxidation, especially the KN thermoelement. The alloying elements diffuse towards the surface of thermocouple wire causing inhomogeneous composition even in the un-oxidized area. However, a premature failure is shown in the de2-Inconel thermocouples. This is because of the precipitation of Cr and Fe elements, which reduces the concentration of Cr and Fe in the Ni matrix. Fe generates a larger distortion of the crystal lattice and increases the instability of the solid solution. The deep understanding of the compatibility between the thermocouple alloys and sheath alloys is of crucial important in terms of the manufactures of thermocouple sensors and the safety operation systems in the nuclear reactor.

Direct Measurement of the Electrocaloric Temperature Change in Multilayer Ceramic Components using Resistance‐Welded Thermocouple Wires

AbstractA method for direct measurement of the adiabatic temperature change inside the active region of multilayer ceramic (MLC) components without detailed knowledge on geometry and properties of inactive regions in the MLC is reported. Thin thermocouple wires serve as the temperature sensor with sufficiently small response time with regard to the relaxation time into the inactive regions. They are mounted on top of the MLC by resistance welding. The accuracy of the method is estimated using finite element analyses of the measuring setup. Experiments are used to validate the numerical analyses as well as the proposed measuring method. In its current implementation the method reaches an accuracy of almost 90 %, which can be improved to approximately 97 %. Therefore, neither fitting nor correction is required.

Ex Vivo Assessment of Multiple Parameters in High Intensity Focused Ultrasound.

High Intensity Focused Ultrasound (HIFU) is a very promising technology for a non-invasive treatment of several pathologies, especially in oncology. However, optimizing the stimulation parameters for better tuning the induced lethal effects (thermal and/or mechanical) in the targeted area is not trivial and it has not been achieved yet. The aim of this study is to present the results of a combined analysis of temperature, acoustic cavitation and lesion geometry induced in ex vivo tissues during HIFU procedures by varying power, sonication time and duty cycle. Temperature rise was analyzed using a thin wire thermocouple embedded in the sonicated tissue; stable and inertial cavitation were measured using a passive cavitation detector (PCD), and lesion volume was assessed using both ultrasound imaging and optical visualization. The obtained results may represent an important guideline for clinical treatments, providing useful nformation for better tuning HIFU operational parameters to induce a desired type of ablation (i.e. thermal, mechanical or a combination of both).

Experimental Validation of a Boundary Layer Convective Heat Flux Measurement Technique

If a steady thermal boundary layer is sufficiently thick, wall heat fluxes and associated convective heat transfer coefficients can be directly calculated from measured temperature distributions taken within it using a traversing thermocouple probe. The boundary layer can be laminar, turbulent, or transitional and on a surface of arbitrary surface temperature distribution and geometry. Herein, this technique is presented and validated in a steady, turbulent, two-dimensional boundary layer on a flat, uniform-heat-flux wall. Care is taken to properly account for radiation from the wall and conduction within the thermocouple wire. In the same setting, heat flux measurements are made for verification purposes using an energy balance on a segment of the test wall carefully designed to minimize and include radiation and conduction effects. Heat flux values measured by the boundary layer measurement technique and by the energy balance measurement agree to within 4.4% and the difference between the two lie completely within their respective measurement uncertainties of 5.74% and 0.6%.

Exprimental study on the evaporation characteristics of the kerosene gel droplet

The purpose of this study is to investigate the evaporation characteristics of a single kerosene gel droplet experimentally. An isolated kerosene gel droplet with an initial diameter of ∼2 mm is suspended at the welding point of a thermocouple wire, and is suddenly exposed to an elevated temperature (in the range of 100–500 °C) at atmospheric pressure (0.1 Mpa) under normal gravity. The droplet changing process is observed and recorded by a high-speed image formation system. The results indicated that the evaporation process of a single gel droplet can be divided into three stages: the stage of the evaporation of kerosene; the stage of the gellant layer formation; the stage of the swell of the gellant layer and microexplosion taking place. Several unique phenomena, such as bubble nucleation, gellant layer formation, disruption of gellant layer, and slight explosion of the initial droplet were observed. Then the dn2/d02–tn/d02 curve was acquired by processing the images, which indicated that the evaporation rate of kerosene gel resembled the evaporation rate of pure kerosene droplet at a relative low temperature. However, microexplosion would occur when the environment temperature exceeds the boiling point of kerosene.

Investigation on transient temperature of a reciprocating compressor based on a two-thermocouple probe

Measuring transient pressure and temperature simultaneously inside a compressor can lead to a thorough characterization of the thermodynamic process in the compressor. However, the rapid changes in airflow temperature make it difficult to measure these conditions precisely, partly due to large thermal inertia of common thermometers such as thermistors and thermocouples. Measurement of rapid temperature changes requires thermometers that have a time constant of a few microseconds or less. Therefore, in this study, two fine wire thermocouples 18 and 35 μm in diameter, respectively, were prepared in advance. A two-thermocouple probe consisting of these two fine wire thermocouples was then used to measure the transient temperature of airflow in the working chamber of a reciprocating compressor. The temperatures detected by the two-thermocouple probe were used to reconstruct the true temperatures. Mean and fluctuating time constants were both evaluated and used to compensate for the raw temperatures. The estimated mean time constants of the two thermocouples were 9.98 and 29.97 ms at 420 rpm, respectively. The maximum difference between the two reconstructed temperatures was 9.7 °C, with an average value of 2.4 °C. Cycle-by-cycle variations of the transient temperatures were also measured.

An analysis of the specific heat loss at the tip of severely notched stainless steel specimens to correlate the fatigue strength

The specific heat loss per cycle (Q parameter) was used in previous works to synthesise more than one hundred experimental fatigue test results generated from plain and bluntly notched specimens made of AISI 304L stainless steel. It was shown that Q can be estimated at a point of a specimen or a component starting from the cooling gradient measured immediately after the fatigue test has been stopped. Since the cooling gradient was measured by means of thermocouple wires attached to the specimen’s surface by means of a 1.5-to 2-mm glue dot diameter, notches with tip radii greater than 3mm were tested, because the glue dot diameter would have been too large to capture the specific heat loss at the tip of sharper notches. In this paper, the cooling gradient has been measured by means of an infrared camera, equipped with proper lens and an extender ring to achieve a 20μm/pixel spatial resolution; therefore the investigation could be extended for the first time to notch tip radii lower than 3mm. Fully reversed axial fatigue tests have been carried out on 4-mm-thick, hot-rolled AISI 304L stainless steel specimens. As a result, the new fatigue data have been found to collapse inside the existing heat energy-based scatter band previously calibrated on blunter notches. The heat energy distribution close to the notch tip has also been investigated.

Low-cost standalone multi-sensor thermometer for long time measurements

We present a portable device for long-time recording of the temperature at multiple measuring points. Thermocouple wires are utilized as the sensors attached to the objects. To minimize the production cost, the measured voltage signals are relayed via a multiplexer to a set of amplifiers and finally to a single microcontroller. The observed temperature and the corresponding date and time, obtained from a real-time clock circuit, are recorded in a memory card for further analysis. The device is powered by a rechargeable battery and placed in a rainproof container, thus it can operate under outdoor conditions. A demonstration of the device usage in a mandarin orange cultivation field of the Royal project, located in the northern Thailand, is illustrated.

The effect of light-cured nanofilled composite resin shades on their under-surface temperature

The objective of this study was to observe the effect of shades of light-cured nanofilled composite resins on their under-surface temperature. Resin composites specimens of shades bright, medium, and dark shade were obtained from a cylindrical mold. While polymerizing using a curing unit, the under-surface temperature was determined at the bottom of the specimens using a thermocouple wire 20 sec after the start. Results showed that the under-surface temperature of the darker shade specimens were relatively higher that those of the brighter shades with significant diffferences between the resin composites of different shades. To conlude, the under-surface temperature of the light-cured nanofilled resin composites raised from the brighter to the darker shades.

The research on improving the anti-oxidation of tungsten rhenium alloy wires

The research compared the stability of EMF (Electromotive Force) though the same electrode testing method. Oxidation, morphology and composition of Tungsten Rhenium alloy thermocouple wire was characterized by Zeiss scanning electron microscope (EV018)and XPS (X-ray Photoelectron Spectroscopy). The results showed that a small amount of rare earth elements droping tungsten rhenium alloy Wire can keep stable at a longer period of time in high temperature oxidation environment. Through the analysis of the SEM (Scanning Electric Microscopy) and XPS (X-ray Photoelectron Spectroscopy), the oxide film dopping rare earth is much denser, as well as lower valence oxide content. In a word, the rare earth droping in the tungsten rhenium alloy wire stabilize the EMF with specific films.

Development of Technology of Nicrosil and Nisil Thermocouple Materials Using Extrusion of Metal Powders

Nicrosil-nisil (NiCrSi-NiSi) thermocouples (Type N) have a high thermal EMF stability, radiation resistance, resistance to oxidation of the thermocouple wires and can be used as a universal means of measuring temperatures up to 1300 °C. However, when the traditional metallurgical method is used for the production of rod and wire materials of nicrosil and nisil from ingots of metals, it is difficult to ensure the homogeneity of the ingots and materials of the thermocouple. It is known that powder metallurgy methods can provide a greater homogeneity of the material compared to casting technology. The aim of this work was to study the possibility of using powder technology for the fabrication of rods of nicrosil and nisil thermocouple materials by extrusion and sintering of powders of source metals. Reduction in size and mixing of the raw powder components in a planetary ball mill was investigated. The regularities of pressing the prepared mixtures and microstructure of materials sintered from them were determined. Samples of nicrosil and nisil thermocouple materials in the form of cylindrical rods with a diameter of about 5 mm and a length of 200 mm with an uniform microstructure were also fabricated by extrusion of prepared mixtures followed by sintering. Experimentally determined specific differential thermal EMF of the thermocouple made from the sintered rods coincided with the theoretical value.