Measurement of Specific Heat Capacity and Electrical Resistivity of Industrial Alloys Using Pulse Heating Techniques

The determination of the specific heat capacity and electrical resistivity of Inconel 718, Ti-6Al-4V, and CF8M stainless steel, from room temperature to near the melting temperatures of the alloys, is described. The method is based on rapid resistive self-heating of a solid cylindrical specimen by the passage of a short-duration electric current pulse through it while simultaneously measuring the pertinent experimental quantities (i.e., voltage drop, current, and specimen temperature). From room temperature to about 1300 K, the properties are measured using an intermediate-temperature pulse-heating system by supplying a constant current from a programmable power supply and measuring the temperature using a Pt-Pt:13% Rh thermocouple welded to the surface of the specimen. From 1350 K to near the melting temperatures of the alloys, the properties are measured using a millisecond-resolution high-temperature pulse-heating system by supplying the current from a set of batteries controlled by a fast-response switching system and measuring the temperature using a high-speed pyrometer in conjunction with an ellipsometer, which is used to measure the corresponding spectral emissivity. The present study extends the application of these techniques, previously applied only to pure metals, to industrial alloys.     

Talbot interferometer with circular gratings for the measurement of temperature in axisymmetric gaseous flames

A detailed study for measuring the temperature distribution in axisymmetric flames by using a Talbot interferometer with circular gratings is presented. We increased the sensitivity of the interferometer by optimizing the pitch of the grating and the Talbot plane. We compare the experimental results with the values that were measured with a thermocouple to an accuracy of ±0.2% of full scale ±4 digits. Good agreement is seen between the temperatures measured by use of a thermocouple and those measured by use of Talbot interferometry.     

Industrial on-line texture determination in rolled steel strips

In the manufacture of sheet metal, it is ofgreat importance that the quality should be homogeneous over the entire length of a strip. This can only be monitored using a continuous, on-line measuring method. A new X-ray transmission measuring technique has been developed for the nondestructive determination of texture-dependent technological data of rolled strip. It can be applied on-line for both hot and cold rolled metal strip, especially steel strip. The paper describes the measuring principle and gives information on the application for measuring ther _m -values and the earing-values of cold rolled steel strip. With the data from these values, the user can control the deep drawing characteristics of his strips. The extension of the basic measuring principle to a condition-free determination system will be demonstrated with its application for measuring texture dependent technological data of hot and cold rolled steel strip. Long term experience at Hoesch Stahl AG, typical results measured over the total strip length, integration in quality assurance systems, questions of maintenance, etc. will be discussed.     

Emissivity of condensed substances from their thermal radiation spectra

A technique for measuring the temperature and spectral emissivity of condensed substances is described. With this technique, measurements can be made in any spectral range, rather than only at short wavelengths, where the Wien approximation for the Planck formula holds. In particular, in the spectral range around the peak-emission wavelength, the highest signal-to-noise ratio can typically be attained, which raises the accuracy in temperature and emissivity determination. The proposed approach to processing the experimental emissivity curves offers the possibility of analyzing the effects of the major factors (signal-to-noise ratio, spectral range of measurements, type of the model function representing the spectral emissivity, and others) on the accuracy in temperature measurements. The potentialities of the technique are demonstrated by measuring the temperatures and emissivities of W, Re, and Ta strip lamps in the spectral range 0.9 to 2.1 Μm.     

Measurement of surface temperature and emissivity by a multitemperature method for Fourier-transform infrared spectrometers

Surface temperatures are estimated with high precision based on a multitemperature method for Fourier-transform spectrometers. The method is based on Planck's radiation law and a nonlinear least-squares fitting algorithm applied to two or more spectra at different sample temperatures and a single measurement at a known sample temperature, for example, at ambient temperature. The temperature of the sample surface can be measured rather easily at ambient temperature. The spectrum at ambient temperature is used to eliminate background effects from spectra as measured at other surface temperatures. The temperatures of the sample are found in a single calculation from the measured spectra independently of the response function of the instrument and the emissivity of the sample. The spectral emissivity of a sample can be measured if the instrument is calibrated against a blackbody source. Temperatures of blackbody sources are estimated with an uncertainty of 0.2-2 K. The method is demonstrated for measuring the spectral emissivity of a brass specimen and an oxidized nickel specimen.     

Normal Spectral Emissivity of Niobium (at 900 nm) by a Pulse-Heating Reflectometric Technique

The normal spectral emissivity of niobium strip specimens was measured using a new pulse-heating reflectometric technique. The hemispherical spectral reflectivity of the surface of a strip tangent to an integrating sphere is determined by a high-speed lock-in technique. At the same time, the radiance temperature of the strip is measured by high-speed pyrometry from approximately 1000K to the melting point. Details of the measurement method and of the related calibration techniques are reported. Results of the normal spectral emissivity of niobium at 900 nm from room temperature to its melting point are presented, discussing differences related to the heating rate and to surface conditions.     

Radiance Temperatures and Normal Spectral Emittances (in the Wavelength Range of 1500 to 5000 nm) of Tin, Zinc, Aluminum, and Silver at Their Melting Points by a Pulse-Heating Technique

The radiance temperatures at four wavelengths (in the range of 1500 to 5000 nm) of tin, zinc, aluminum, and silver at their respective melting points were measured by a pulse-heating technique using a high-speed fiber-coupled four-wavelength infrared pyrometer. The method is based on rapid resistive self-heating of a sample from room temperature to its melting point in less than 1 s while measuring the radiance emitted by it in four wavelength bands as a function of time. A plateau in the recorded radiance-versus-time traces indicates melting of the sample. The melting-point radiance temperatures for a given sample are determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal are, in turn, determined by averaging results for several samples. The normal spectral emittances at the melting transition of each metal are derived from the measured radiances at each wavelength and the published values of the thermodynamic (true) melting temperatures.     

Dielectric constant measurement technique for a dielectric strip using a rectangular waveguide

A dielectric constant measurement technique for dielectric strips is presented in this paper. In the measurement, the strip is placed parallel to the broad walls of a rectangular waveguide, and it is found that the measured reflection coefficient is insensitive to the position of the strip when it is placed around the middle of the waveguide cross section. The new sample placement scheme becomes very convenient, especially when a large number of strips have to be measured. To develop the forward scattering formulation, the reflection coefficient of the strip placed in the waveguide is evaluated using the method of moments. With this forward model, a genetic algorithm is developed to retrieve the dielectric constant of the strip from the measured reflection coefficient. The validity of the calculated reflection coefficient is verified by measuring a Teflon strip in a WR187 waveguide, and the dielectric constant of the Teflon is successfully retrieved from the measurement. For the measurement of many strips, a special sample holder is made to ensure insensitivity of the measured reflection coefficient to the position of the strip.     

Modelling of Microstructural Evolution and Prediction of Mechanical Properties of Plain Carbon Strip Steel in Hot Rolling Process

Based on hot rolling production line of strip steel, the off-line in-house software, termed as ROLLAN (Rolling Analysis), is developed. The code is mainly used to predict the evolution of temperature, rolling force, fraction and grain size of recrystallization, fraction and grain size of phase transformation and final mechanical properties. Almost all the processing parameters affecting microstructure and mechanical properties in the schedule from reheating to the coiling process are considered in detail. Self-learning coefficient is adopted to adjust the deviation between predicted and measured temperatures, such as roughing exit temperature (RT2), finishing exit temperature (FT7) and coiling temperature (CT). Due to the application of low-speed-threading, increasing-speed-rolling and decreasing-speed-delivery process during finishing rolling and different cooling condition, after coiling the thermal-mechanical history of different position, along strip longitudinal direction is different resulting in     

Energy and spatial response of silicon strip detectors to X-rays

This paper describes an experimental investigation of the energy and spatial response of silicon strip detectors used for X-ray measurements. The measurements of single strip amplitude distributions have been performed for a p⁺–n silicon strip detector irradiated with X-rays for different detector bias voltages and for two measurements geometries (with the detector irradiated from either the strip side or from the ohmic contact side). The measured amplitude distributions have been compared with those obtained from simulations using the developed simulation package. The spatial response of the detector has been measured by scanning an edge across the strips and measuring the corresponding strip count rate. The measured spatial response has been compared with that obtained from simulations.     

AN EXPERIMENTAL STUDY OF THE STRIP CASTING PROCESS OF ALUMINUM ALLOY BY THE TWIN ROLL METHOD

Experimental studies on the twin roll casting process in order to produce thin aluminum alloy strips are presented in this paper. A new twin roll caster was developed as an effective experimental tool. The caster is equipped with a complete casting system incorporating a control and measuring system using multiple sensors and various actuators. The data acquisition system of the caster can measure various process parameters including meniscus, casting speed, and temperature as well as roll gap and pressure. With this system, aluminum alloy thin strips were manufactured and the process parameters such as strip temperature, casting velocity, and pressing force of roll were investigated. Furthermore, the crystallizability, microstructure, and mechanical properties of the strip are evaluated by X-ray diffractometer, scanning electron microscope, and tensile test. The results revealed the ability of the twin roll caster to produce directly the thin strip of aluminum alloy with improved mechanical strength.     

Modeling of Temperature Conditions Between Temperature Artifact and Black Test Corner

The case study in this article is temperature condition modeling between a temperature artifact and a black test corner measuring instrument. The black test corner is an instrument which consists of two wooden walls and a floor, with build-in thermocouples fixed on the back side of the copper disks. The front of the disk is flush with the surface of the board. The black test corner is used for measuring how the temperature of a household appliance is influencing the surroundings in the real environment, e.g., in the kitchen, the living room, etc. The temperature artifact as presented in this article is a specially developed heating plate which is very stable and can be set to different temperatures. Technical standards for conformity assessment usually describe only what should be measured, in some cases also how accurate the measurement should be, but not what kind of measuring instrument should be used. Therefore, it sometimes happens that measurements are performed with improper equipment or in an improper way. For the same level of appliance conformance testing, laboratories shall use the same testing procedures and comparable measuring instruments. This article deals with the analysis of influencing parameters when measuring the temperature rise using the black test corner. Modeling of temperature conditions between a temperature artifact and a black test corner, using commercial modeling software, was performed to find out whether this modeling can be used for detailed evaluation of all possible influencing parameters of the mentioned testing procedure. A scheme and a list of influencing parameters that has to be modeled in the following research is prepared to arrange an optimal experiment.     

Effects of rolling and sintering temperature on peel strength of bonding interfaces for Ag/Cu bimetallic strips

Abstract

Cu/Ag bimetallic strips were prepared by roll bonding in the temperature range 293-873 K and sinter treating in the temperature range 523-1073 K. The interface peel strength was determined and the peeled surface morphology observed. High peel strength is obtained from the excellent metallurgical joint given by solute interdiffusion and matrix recrystallisation under sintering conditions 523-673 K for bimetallic strips rolled at ambient temperature. Sintering in the temperature range 873-1073 K results in reduced peel strength due to increased void formation at the interface, although some local contacts on the mated surface could melt and merge at 1073 K. Low peel strength due to poor metallurgical bonding is obtained if the bimetallic strips are roll bonded at temperatures lower than 623 K. The peel strength dramatically decreases due to the thick oxide layer present between the two strip surfaces when the bimetallic strips are roll bonded at excessively high temperatures.     

Densification and strength evolution in solid-state sintering Part I Experimental investigation

Prealloyed bronze (Cu-10Sn) powder and a mixed elemental steel (Fe-2Ni-0.9C) powder were evaluated for strength evolution during sintering. For the bronze powder, test samples were fabricated using a loose powder casting method, while the steel powder was formed by injection molding. In situ strength during sintering was measured using a bending fracture test. Primary focus was on measuring the effects of sintering temperature and time on in situ strength evolution. Sintering temperature had the most significant effect, but the strength underwent significant gains prior to densification. The results are explained by the competition among interparticler neck growth, densification, and thermal softening. Sinter strengthening is initially governed by interparticle bonding, followed by a contribution from densification at high temperatures. However, high temperatures also lead to significant strength degradation due to thermal softening. Densification is favored by the declining in situ strength associated with thermal softening at high temperatures.     

有限差分法和数值模拟在热轧带钢层流冷却中的应用

针对传统的热轧带钢层流冷却卷曲温度控制中数学模型的固有缺陷，分别采用了差分方程和有限元数值模拟的方法，建立带钢厚度方向上的温度场。结果表明：考虑带钢与介质的热交换的同时再考虑带钢内部的热传导是必要的，为定量地描述计算值与实测值之间的偏差提供了参考。     

Prediction of long-term viscoelastic behavior of amorphous resin based on the time-temperature superposition principle

This paper deals with the prediction of long-term viscoelastic behavior of amorphous resin at a temperature below the glass transition temperature T _g from measuring the short-term viscoelastic behavior at elevated temperatures based on the time-temperature superposition principle (TTSP) with vertical shift as well as horizontal shift. The long-term creep compliance as well as short-term and medium-term creep compliances were measured at elevated temperatures. The master curves of creep compliance can be constructed from measured data by shifting vertically as well as horizontally. The master curves of creep compliance constructed from measured data by short-term and medium-term creep tests agree well with those measured by long-term creep tests. Furthermore, the horizontal and vertical shift factors obtained from constructing the master curve are independent of the time period of creep tests. Therefore, the long-term viscoelastic behavior at a temperature below T _g can be predicted accurately from measuring the short-term viscoelastic behavior at elevated temperatures based on the TTSP with vertical shift as well as horizontal shift.     

Measurement of elastic modulus s(11)(D) of thin film ZnO by resonance method

The elastic modulus of thin film ZnO has been measured by attaching a Si-ZnO strip to a ceramic bimorph, deflecting the latter with an electric signal, and measuring the resonance frequencies of the Si-ZnO strip. The resonance frequencies of the Si-ZnO strip depend on the properties of both Si and ZnO. The properties of Si are known, and, thus, the elastic modulus of thin film ZnO can be calculated from the resonance frequency of the beam. The results we obtained are presented in this report     

A prototype kinetic inductance thermometer for X-ray calorimetry

We have measured the parameters of a prototype kinetic inductance thermometer for X-ray calorimetry which was fabricated at GSFC. This device consists of an aluminum meander strip and ground plane and operates at about 1.2 K. For thermal isolation, the device was suspended on Kevlar threads along with a heater and a germanium resistance thermometer. The meander strip was included in the tank circuit of a 10 MHz tunnel diode oscillator operating at about 1 K. The kinetic inductance was measured by monitoring the oscillator frequency. The temperature dependence of the kinetic inductance was found to be in reasonable agreement with the behavior predicted from the device parameters. Having characterized this proof-of-concept device, we intend to investigate the suitability of kinetic inductors operating at lower temperatures for X-ray calorimetry.     

Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye

A technique is described for the measurement of fluid temperatures in microfluidic systems based on temperature-dependent fluorescence. The technique is easy to implement with a standard fluorescence microscope and CCD camera. In addition, the method can be used to measure fluid temperatures with micrometer spatial resolution and millisecond time resolution. The efficacy of the method is demonstrated by measuring temperature distributions resulting from Joule heating in a variety of microfluidic circuits that are electrokinetically pumped. With the equipment used for these measurements, fluid temperatures ranging from room temperature to 90 degrees C were measured with a precision ranging from 0.03 to 3.5 degrees C-dependent on the amount of signal averaging done. The spatial and temporal resolutions achieved were 1 microm and 33 ms, respectively.     

Dimensional and ice content changes of hardened concrete at different freezing and thawing temperatures

Samples of concrete at different water-to-cement ratios and air contents subjected to freeze/thaw cycles with the lowest temperature at about ?80 °C are investigated. By adopting a novel technique, a scanning calorimeter is used to obtain data from which the ice contents at different freeze temperatures can be calculated. The length change caused by temperature and ice content changes during test is measured by a separate experiment using the same types of freeze–thaw cycles as in the calorimetric tests. In this way it was possible to compare the amount of formed ice at different temperatures and the corresponding measured length changes. The development of cracks in the material structure was indicated by an ultra-sonic technique by measuring on the samples before and after the freeze–thaw tests. Further the air void structure was investigated using a microscopic technique in which air ‘bubble’ size distributions and the so-called spacing factor, indicating the mean distance between air bubbles, were measured. By analyzing the experimental result, it is concluded that damages occur in the temperature range of about ?10 °C to ?55 °C, when the air content is lower than about 4% of the total volume. For a totally water-saturated concrete, damages always occur independently of the use of entrained air or low water-to-cement ratios. It is, further, concluded that the length changes of these samples correspond to the calculated ice contents at different temperatures in a linear fashion.