Constantan Wire Research Articles

3次元温度数値解析による研削エネルギー分配率の検討(第1報)

In order to determine the energy flowing rate into a workpiece in surface grinding, the temperature in workpiece was measured by the thermocouple insertion method, in which the fine constantan wire was inserted and welded in the small hole, and the temperature around the hole was numerically analyzed using 3-dimensional heat transfer equation by control volume method. Through the analysis the effects of temperature measuring methods, such as size of fine hole and existence of constantan wire, on the measured temperature were discussed in detail. The temperature around the bottom of the hole, measured point, becomes 2 or 3 times higher than that without hole, especially at near the ground surface. The energy flowing rate into workpiece was estimated using the results by 3-dimensional temperature analysis and the measured temperature with the thermocouple insertion method. The estimated ratio is 30-40% of the total grinding energy and the rate is about a half one which is obtained based on 2-dimensional analysis.

Temperature errors using multi-sensor thermocouple probes with a common constantan wire.

During the evaluation of thermal conduction errors in multi-sensor thermocouple probes in use for hyperthermia, an unexpected large temperature error occurred. When one of the sensors passed the temperature gradient between the hot and cold water bath a temperature offset occurred in the sensors further towards the tip of the probe. This effect caused by the temperature gradient over the thermocouple junction has been described earlier by Bach Anderson et al. (1984) and Dickinson (1985). However, their conclusion was that clinically this effect was of little importance because of the minor gradients in clinic, provided that the soldering/welding length of the junctions is small.

Embedded-strain-sensor development for composite smart structures

The winding or layup procedure for fiber-reinforced composites lends itself to convenient installation of embedded sensors during fabrication. These permanently installed and protected sensors could be used during the service lifetime of the structure to monitor real-time conditions and determine when loading or vibration is excessive, and when damage has occurred. Such ‘smart or intelligent’ structures could be used to provide continuous ‘health monitoring’ of the structure as well as provide input for active vibration control. In the present study, two sizes of constantan wire (0.15-mm and 0.025-mm diameter) with a very thin but tough polyimide insulation were embedded in graphite-epoxy bars and tubes. The 25-mm by 2.5-mm by approximately 300-mm long bars were fabricated from hand-laid-up panels and subjected to static four-point bending and cantilever bending. The tubes (42-mm diameter by 1.25-m long) were subjected to static cantilever bending. Output from the constantan wire was monitored with conventional strain-gage indicators. Results indicate accurate tensile and compressive measurements of the integrated strain along the length of the constantan wire when compared with beam formulas and surface mounted strain gages. The constantan strain wire shows promise as an embedded sensor for ‘smart structures’.

Vibration Measurement in Composite Members Using Embedded Constantan Wire

Constantan wire has been effectively and accurately used to measure strain and vibration in structures for several decades. This paper investigates the use of constan tan wire as an embedded sensor. The attractiveness of embedding sensors has led to much investigation in this area.

Modified thermal diffusion flow probe for the continuous monitoring of cortical blood flow

A small thermal diffusion flow probe has been developed to monitor the dynamic changes in cerebral blood flow in small animals. Constantan wire was used as a heat source to make a miniature probe. The pair of thermocouples used to detect the heat gradient between two gold plates was elongated to avoid heat conduction between them, and this improvement allowed us to make quantitative measurements. After several basic experiments, local cerebral blood flow was measured simultaneously, using both the modified thermal probe and the hydrogen clearance method in four rabbits. A close relationship was obtained between the local cerebral blood flow values measured by hydrogen clearance (F, ml/100g/min) and the reciprocal of the thermocouple voltage (1/V;1/mV). The regression line was F = 29111(1/V - 1/226), (r = 0.92, P less than 0.001). We suggest that the modified thermal probe is a reliable and quantitative means of measuring flow. In addition, another probe modified for clinical use was evaluated. Continuous monitoring of local cerebral blood flow in postoperative patients was performed, and some illustrative cases are described.

Modified Thermal Diffusion Flow Probe for the Continuous Monitoring of Cortical Blood Flow

Abstract A small thermal diffusion flow probe has been developed to monitor the dynamic changes in cerebral blood flow in small animals. Constantan wire was used as a heat source to make a miniature probe. The pair of thermocouples used to detect the heat gradient between two gold plates was elongated to avoid heat conduction between them, and this improvement allowed us to make quantitative measurements. After several basic experiments, local cerebral blood flow was measured simultaneously, using both the modified thermal probe and the hydrogen clearance method in four rabbits. A close relationship was obtained between the local cerebral blood flow values measured by hydrogen clearance (F, ml/100g/min) and the reciprocal of the thermocouple voltage (1/V;1/mV). The regression line was F = 29111(1/V- 1/226), (r = 0.92, P<0.001). We suggest that the modified thermal probe is a reliable and quantitative means of measuring flow. In addition, another probe modified for clinical use was evaluated. Continuous monitoring of local cerebral blood flow in postoperative patients was performed, and some illustrative cases are described.

Development of measurement techniques to determine the temperature rise caused by diagnostic ultrasound equipment in a tissue-mimicking test object.

An experimental test facility has been developed for determining the heating caused by diagnostic ultrasound. This incorporates fine-wire thermocouples embedded in a tissue-mimicking gel, along with a mechanical positioning system to align the transducer with the test object. To study experimental errors, information on the beam profile and the temperature rise as a function of time has been obtained for a variety of thermocouples. The viscous heating artifact is caused by the relative motion of the gel and the thermocouple, and this effect can be greater than the true temperature rise, particularly in highly focused fields, where the beam radius may be on the order of 0.5 mm. Conduction of heat away from the thermocouple junction is also important, and has been studied experimentally and theoretically for a range of thermocouple types. Improved methods of correcting for these sources of error have been developed and the corrected results are shown to agree with theory, for the best thermocouples used (50-μm-diam. manganin and constantan wires). When both sources of error are large (greater than about 50%), the correction methods are inadequate and errors on the order of 100% can occur. The system has been used to measure temperature rises on the order of 1 °C in the field of a diagnostic scanner.

Thermal diffusivity measurements by �ngstr�m's method in a fluid environment

Angstrom's method has been used for measuring the thermal diffusivity, a, and the radial heat loss coefficients of a thin constantan wire, both in a vacuum and with the wire immersed in air and in four different liquids, and using temperature wave periods of 1 to 1000 s. The presence of a surrounding fluid medium causes errors of up to 90% in the measured values of a. It is shown that both the experimental errors and the radial heat loss coefficients can be accurately calculated using simple models, both at high and at low frequencies, and that a previously developed two-frequency model can be used to obtain accurate data for a even under these conditions, provided the frequency is high enough. We also present a new variety of Angstrom's model, valid only at very low frequencies and with purely convective heat loss.

A New Thermal Diffusion Flow Probe for Continuous Monitoring of Cerebral Blood Flow in Small Animals

The Peltier stack, which allows quantitative measurement of cerebral blood flow (CBF) by means of thermal diffusion, has a probe too large for use in small animals. However, it is difficult to measure CBF by a thermal diffusion method involving the use of a constantan heating wire, because of heat conduction between the two gold plates. The authors developed a new thermal diffusion flow probe, using a constantan wire as a heat source rather than the Peltier stack. With the new probe, separation of the gold plates and attachment of a pair of long thermocouples minimize heat conduction between the two plates. Moreover, the probe itself is considerably smaller than that of the Peltier stack. The new probe was inserted to the subdural space of rabbits and the voltage (V; mV) was measured with an amplifier by the circuit of constant current method. CBF (F; ml/100 g/min) was measured simultaneously by the hydrogen clearance method in the adjacent cortex. A regression equation of F = 29, 111 (1/V-1/226) was obtained between 35 pairs of F and V (r = 0.92, p less than 0.001), which verified that CBF can be accurately measured with the new probe.

短波長放射のある室内における空気温度測定方法に関する実験的研究

There are two ways conceived to measure indoor air temperatures under shortwave radiant environments ; one is the positive measurement and the other is passive measurement. Possibilities and limitations of the two methods under the wind velocity range between doldrums and less than 1.0 meter per second were sought for, by varying shortwave radiant intensity. The positive measurement method used a 100-microne in-diameter thermocouple made of copper and constantan wires as sensor device, which was contained in a transparent vinyl tube of 3.8 milimeters in outer circumference. A double aluminum radiant shielding pipe (outer circumference 4.0 milimeters, thickness 0.1 milimeter) is installed on the top of the tube, where the sensor is located. This method is designed to forcefully absorb air around the sensor through the tube. Other devices were applied in order to reduce air volume to be absorbed at the time of measurement. The passive measurement method, on the other hand, used thermo-couples of 25, 50, 100 and 200 microns in diameter, where surface coating which was believed to have least radiant absorptivity was applied. This method heavily depends on excellence of the convective heat exchange due to slight air currents existing indoors.

A multicouple probe for temperature gradient measurements in biological materials.

An easy-to-make, sensitive, thin, flexible, multisensor probe for in vivo tissue temperature profile measurement is described. It is essentially a multijunction thermocouple (i.e., a multicouple) of type-T composition. Enamel-insulated copper wires (38 gauge) were soldered 5 mm apart to one common uninsulated constantan wire (36 gauge) and introduced into a polyethylene tube sealed at one end. The total outside diameter of the multicouple probe is less than 1 mm, and the maximum number of junctions using the specified wire sizes is approximately 16. This design permits the instantaneous measurement of a tissue temperature profile at 5-mm intervals over a distance of approximately 8 cm. An extensive calibration for the thermal conductivity effect (k effect) along the multicouple wires by means of a limb model is presented. The results show that the temperature readings of the individual junctions are significantly affected by the k effect when a thermal gradient exists along the multicouple, as is usually the case during tissue temperature measurements. However, calibration of the multicouple for the k effect yields a measurement accuracy of +/- 0.1 degree C under a wide range of gradients. This probe can be implanted in tissues to measure thermal gradients under different physiological conditions.

銅の超精密ダイヤモンド切削における切削温度の解析

The cutting temperature in the ultra-high precision diamond fly cutting of copper is discussed based on the experimental data. The cutting temperature and the temperature rise in the workpiece are measured with the thermocouple of copper and constantan wire. The temperature distributions in the workpiece are also analysed by employing the finite difference method and the calculated results are compared with the experimental results. The following results are obtained. (1) The cutting temperature reaches to 200°C or more during the diamond cutting. (2) The temperature rise in the workpiece is in the range of 0.1-2°C under the cutting conditions tested. The workpiece temperature increases with increases in the cutting speed, the feed rate and the depth of cut. (3) The temperature distributions in the workpiece calculated are in good agreement with those measured.

A thermocouple system for continuous thermometry in radiofrequency hyperthermia.

When treating cancer with hyperthermia, the most widely-used method of temperature monitoring is by thermocouples implanted in the tissue. However, since thermocouples are metallic they can interact with the applied electromagnetic field, giving rise to large errors in the indicated temperatures (Gammampila et al, 1981; Hahn, 1982). Our investigations show that when using capacitive coupling to apply RF power to the patient, the temperature errors can be reduced to an acceptably low level by suitable encapsulation of the thermocouple wires and in-line filtering. Thermocouples were constructed by twisting together the ends of copper and constantan wires 50 μm in diameter and securing with soft solder. Probes were formed by inserting the “hot” junctions into lengths of nylon tubing (1 mm diameter, 0.18 mm wall thickness), Araldite resin being injected into the end of each probe to envelop and anchor the junction.

Residual Stress in the Interfacial Bond Zone of Curing Adhesives by a Sensitive Strain Measurement Technique

Abstract Highly sensitive electrical resistance measurements are used as the basis for development of a technique to measure simultaneously the residual stresses developed in the interfacial bond and the bulk regions of a curing, initially liquid adhesive. Constantan wires of 0.025 mm diameter are immersed in the adhesive, and the resistance during cure is tracked on a six-digit ohmmeter. Stress values are calculated from the gage factor and the modulus of elasticity of the wire. The technique is applied to an Epoxylite 810—aluminum system. Significant differences in residual stress between the interfacial and the bulk zone in the cured adhesive are demonstrated.

Analysis and calibration of a foil heat flux sensor for convective measurements

The sensitivity of a Gardon-type sensor for convective heat flux measurements has been estimated analytically assuming uniform heat transfer coefficient over the foil surface. The linear range is characterised by a constant sensitivity factor of 0.25, and is attained, irrespective of sensor dimensions or environment, so long as the Biot number is less than 0.16. Calibration experiments have been performed on a heated aluminium sphere using four sensors of radius to thickness ratio 13.3 to 33.2 with foil thicknesses 0.05 and 0.075 mm. The sensor, essentially a constantan foil mounted on a copper tube, works as a differential thermocouple. Addition of a constantan wire to the copper base further enables measurement of local temperature.

An Improved Thermocouple Hygrometer for In‐situ Measurements of Soil Water Potential

AbstractA new dewpoint hygrometer for in‐situ measurements of soil water potential was designed and its performance evaluated. A porous silver membrane serves as the hydraulic connection between the soil and the measuring cavity which encloses a four‐terminal thermojunction made by cross welding chromel and constantan wires 0.001 in. (0.00254 cm) in diameter. The membranes were screwed to the copper body of the hygrometer and such configuration minimized the temperature difference between the vapor source and the reference junctions. When a thermal gradient was imposed on a hygrometer placed horizontally in a soil column, the maximum voltage offset observed was 0.05µV, but the soil water potential values as indicated by the hygrometer readings remained constant at −0.56MPa.This new device has a fast response for water flow with a time constant of approximately 5 min, and the time constant for salt diffusion in and out of the membranes is about 8 min. The results of soil water potential measurements under corn (Zea mays) plant hybrid United 108 grown in a growth chamber environment have shown that this new device is capable of following the changes in soil water potential very well. The difference in water potential observed between leaf and soil after the plant had been left several hours in the dark appeared to be related to uneven moisture distribution in the pot, and the plant was responding to the average soil water potential.

Design of a strain-gauge bridge to operate without an amplifier

The low-power output signal obtained from a wire strain-gauge is, as a rule, amplified. When making industrial tests in the damp and dusty atmosphere of underground mines, when testing farm machinery, and when using measuring transducers in metallurgical shops the adjustment and servicing of amplifiers involves considerable inconvenience and difficulty. Under these conditions it is convenient to work without an amplifier for the output signal by utilizing the so-called "high-power" strain-gauge transducers. The tensoresistors for them are specially made out of Constantan wire. The design of transducers with such tensoresistors is presented in [i].

Dwell times of thin exploding wires

Equations describing the dependence of the dwell times on the applied voltage of thin exploding wires whose restrikes are initiated at the exterior or the interior of the exploded wire are derived, using the energy equation for the ionized gas surrounding the wire and the Paschen law for the sparking potential, respectively. A comparison of the computed and the experimentally obtained dependences of dwell times on the applied voltage was made for thin constantan and tungsten wires.

Instabilities of electrically exploded wires

The experimental results summarized in this paper, which have been obtained with thin tungsten, copper, and constantan wires, give further evidence that electromagnetic macroinstabilities may develop near the melting point of thin wires which are heated by the sudden release of electrical energy and lead to their disintegration. At low-energy-input rates, screw-type instabilities develop in all the wire materials used. On the other hand, at high-energy-input rates, the copper and constantan wires show striations after the explosion, while tungsten wires are not striated but are split into tiny fibers which emerge along the whole wire. At the beginning the restrike channel of copper and constanstan wires has an helicoidal form. Annealed wires show the same results. Helical channels were not observed in tungsten wires. By twisting the copper and constantan wires in the opposite direction to the channel helix, it was possible to change the direction of the helix. Thus, the helical shape of the channel may be an effect produced by the twisting of the wire in mounting it betwen the electrodes. The possibility that the helicoidal shape of the channel is due to some other effect is also discussed.

Dwell times of exploding tungsten wires in air

The paper deals mainly with the voltage dependence of the dwell times of 130-mm-long tungsten wires with diameters of 0.05, 0.10, 0.15, and 0.20 mm. The results of the measurements reported show that tungsten wires have dwell times of only the short type, that the restrikes are always initiated at the exterior of the wires, and that during the dwell times tungsten wires have higher conductivity than copper or constantan wires. At low voltages the dwell times increase with increasing wire diameter. However, above 10 kV the dwell times within the range of experimental error are equal for all the diameters examined. A comparison with the results obtained from exploding copper wires with the same diameter shows that at low voltages the short dwell times of the copper wires are shorter than those of the tungsten wires and that at higher voltages the dwell times of the tungsten wires become much shorter than those of the copper wires, decreasing monotonically with increasing voltage. The special features of the exploding wires during the dwell times and the restrike phase are illustrated by films made by a rotating-mirror streak camera, a camera with a Kerr-cell shutter, and an image-converter camera.