Temperature Rise Of Specimen Research Articles

Effect of joule heating in electrochemical measurement of hydrogen transport

It is shown that Joule heating during electrochemical charging at high current densities can produce substantial heating of the specimen and results in an increase in measured anodic current. Localized electrolyte heating and specimen temperature rise is a function of cell geometry and electrolyte circulation. The anodic current increase due to heating depends on the anodic current before charging and the palladium coating used. The steady state corrosion current depends on the strain rate and the method of deposition of the palladium coating on the anodic side. Finally, the present work demonstrates clearly that the increase in anodic current observed immediately after electrochemical charging during plastic deformation in nickel is due to Joule heating of the specimen and not dislocation transport of hydrogen.

Fatigue of polymers

The general nature of fracture in polymers, when subject to alternating loads as distinct from static or steadily increasing loads, is reviewed; and the molecular mechanisms and micromechanics aspects of the fatigue fracture process are discussed. Some attention is given to thermal fatigue, where fracture results primarily from a large specimen temperature rise due to hysteresis heating. However, primary emphasis is devoted to mechanical fatigue, in which fracture is a result of initiation and propagation of a crack, as a result of the periodic nature of the applied load.

Transverse 1/f noise in InSb thin films and the signal-to-noise ratio of related Hall elements

Transverse 1/f noise in approximately 2-μm-thick InSb thin films is investigated experimentally at room temperature. Linear dependence of noise voltage on dc bias current is shown quantitatively. The noise intensity is inversely proportional to the number of conduction electrons in the bulk. The temperature rise of specimens due to Joule heating does not affect the noise intensity coefficient. The coefficient differs from sample to sample, which is reduced by the heat treatment of specimens, but is independent of the doped impurity concentration. As a result, the signal-to-noise ratio of related Hall elements is formulated for the first time for audio magnetic heads applications. The signal-to-noise ratio is nearly 80 dB for a 10-G magnetic field in the audio frequency range.

Radiation damage due to knock-on processes on carbon foils cooled to liquid helium temperature

Radiation damage on a holey carbon foil was investigated in an electron microscope with a superconducting lens system, where the temperature of the specimen and its environment initially was 4 K. Due to an electron dose of 2 X 10(4) As/cm2 the diameter of a hole increased 5 nm. Rough calculations show that this increase can be ascribed to knock-on processes. Estimates of the rise in specimen temperature during the irradiation are given.

Abrasive wear of engineering materials by mineral and industrial wastes

Abrasive wear damage in eight engineering materials was evaluated through a statistically designed experiment in a laboratory model hard rubber disk wear testing machine. Mineral and industrial wastes were used as abrasives incorporated in different media and at two concentrations. Wear rate, coefficient of friction and specimen temperature rise were correlated with material, abrasive, medium and abrasive concentration. The abrasive particle size and shape and worn specimen surface characteristics were analyzed by scanning electron microscopy. Alumina, followed by silica sand and iron ore, is the most aggressive mineral in increasing wear rate. The least abrasive mineral is limestone, with red mud as a close second. Quantitatively, silica sand wears all materials 100 times faster than limestone. Similarly, fly ash and iron ore wear all materials 2.2 and 4.2 times faster, respectively, than coke breeze. Tool steel wears the least, with chromium plated steel wearing 2.5 times faster than tool steel. Mild steel wears 2.5 times faster than cast iron with maraging steel falling between them. The different media have no effect on wear rate. The 50% concentration of abrasive increased wear rate by a factor of 5 over 10% concentration. Mild steel generates twice the coefficient of friction μ over tool steel and 25% more over cast iron. Silica sand increases μ by 61% over coke breeze. Water generates a 67% increase in μ over high viscosity oil. Acidic water increases μ by 7% over neutral water but produces a 50% less temperature rise. Bronze increases μ by 17% and temperature by 38% over cast iron.

Plane Bending Fatigue of Thermoplastic Materials

Owing to the thermal and viscoelastic natures, the mechanical properties of thermoplastics closely depend on the various factors such as testing temperature, test speed and so on. In fatigue under repeated stresses, the materials are more sensitive to such factors and sometimes show the considerable temperature rise which generally causes the reduction of fatigue strength.Two kinds of thermoplastic materials were prepared, namely Polymethylmethacrylate (PMMA) sheet of 4mm in thickness and Polycarbonate (PC) sheet of 3mm in thickness. Their glass transition temperatures are 120°C and 150°C respectively, and the elastic modulus of PMMA is 1.5 times larger than that of PC.They were fatigued in plane bending with the test speed of 1800rpm to obtain the dependencies of their fatigue strengths on the testing temperature and pause periods during fatigue test and to examine the relations between the fatigue behavior and the temperature rise of specimen itself, deflection change during fatigue test and fracture surface.At high stress levels PMMA failed in cyclic thermal softening by extraordinary temperature rise resulting from the internal damping, but at low levels it fractured by fatigue crack propagation. As for PC, the temperature rise was relatively so small that all the failures took place by fatigue crack propagation over the wide range of stress levels. Moreover, the fatigue behavior of PMMA was strongly affected by the test conditions, especially thermal conditions. The fatigue life decreased as the testing temperature rised but it was prolonged by the pause during fatigue. On the other hand, the fatigue behavior of PC was not so much influenced by the above conditions as PMMA. These differencies in fatigue behavior correspond to that in temperature dependency of mechanical properties of these materials.

ひずみ時効処理された炭素鋼の疲労挙動について

The push-pull fatigue behavior of a carbon steel S45C was studied by using the annealed, prestrained and strain-aged specimens. The prestrain was 5% or 10%. The aging treatment after straining was done by heating the specimens at 100°C, 250°C or 300°C. Under these conditions, S-N curves, the temperature rise of specimens during cyclic stressing and the repeated plastic strain range were discussed. As a result, it was found that the fatigue strength of the strain-aged specimen increased by about 34% at maximum in comparison with the annealed, and that the temperature rise corresponded with the increase of the repeated plastic strain range. In addition, the sum of the repeated plastic strain range of the strain-aged specimen was smaller than that of the prestrained or the annealed.

Thermal detection of paramagnetic resonance

Abstract

Electron beam damage: Applications to bubble devices

The interaction between bubble domains and areas of deliberately introduced material damage is described. The damaged regions, of controlled extent and precise location, were introduced by exposing the material to a beam of electrons typically 8 micrometers in diameter. Using either samarium-terbium orthoferrite or epitaxial garnet, no domain interaction was apparent until the beam energy density was sufficient to cause visible surface damage to the specimen. In the latter case, the interaction between the damaged region and the domain wall was found to be of a repulsive nature, in contrast to the usual attractive interaction with naturally occurring defects. By producing continuous damage extending around the outline of a rectangle a large number of domains were constrained within the rectangle. Their symmetrical spacing from the lines of damage confirmed the repulsive nature of the interaction. The specimen temperature rise during exposure is calculated and possible mechanisms for the domain behavior considered. Some practical device applications using the damage technique are described. For instance, the motion of bubbles might be constrained to specific propagation channels, or the interaction used to perform logic functions.

Temperature rise of specimen due to electron irradiation

A rise in specimen temperature due to electron irradiation was directly measured by using a microthermocouple composed of evaporated gold and palladium films. The temperature rise with an increase in electron current density was explained referring to the thermal conduction and thermal radiation effects. The experimental results obtained by varying irradiated areas and film thicknesses were compared with Leisegang's theory. The thermal conductivity and thermal emissivity values for metallic films as well as the energy loss value that contributes to the temperature rise were estimated.

The Method of Measuring Modulus Change Continuously during Fatigue Test of Plastics

In this report a new method of explaining the fatigue of plastics in terms of the change of their properties is proposed. The fatigue testing machine used here is ASTM (D 671-63 T, Method B) type, constant amplitude of force, cantilever flexural fatigue, and is equipped with differential transformer displacement meter and the moment bar with strain gage. According to the dynamic rheological theory, |E*|=σ0/ε0=KP0/d0 where |E*|: absolute value of complex dynamic Young's modulus, σ0·ε0·P0·d0: peak value of stress·strain·load·deflection respectively, K: size parameter of specimen, and K was derived as follows. In the case of rectangular specimen K=4L3/bh3 and ASTM type triangular specimen K≈3L2/tan θ h3 where L·b·h·θ: distance between both grips·width·thickness·inclination angle of side line, of specimen respectively. When K, P0 are given, the change of |E*| can be observed during the fatigue test by measuring d0 continuously with dynamic displacement meter.The results of experiment show that the change of d0 and the temperature rise of specimen are characteristic of the materials, though the calculation of |E*| has sometimes been disturbed by the rise and growth of crack in the specimen. It is concluded that this method is applicable to the study of the fatigue of polymeric materials.

Iron Losses in Elliptically Rotating Fields

Power frequency losses in silicon iron alloys due to an elliptically rotating magnetic field have been measured by a calorimetric technique and predicted approximately using a simple model. Previously reported experiments for measuring these losses fail to approach saturation and have doubtful field unformities. A thin disk-shaped specimen is placed in the elliptically rotating field of a set of two phase air-cored rectangular Helmholtz-type coils. The 60-cps rotational loss is calculated from the initial rate of specimen temperature rise sensed by a copper-Constantan thermocouple attached to the disk. The thermocouple output is amplified and recorded with an accuracy of 10−3°C. The field coil system produces fields uniform to 2% in a 1.0-in.-diam. region and of strengths up to 250 oe, which is sufficient to approach saturation in 0.005-in. thick by 0.875-in.-diam disks. The losses have been measured for grain oriented and single-crystal materials with all materials showing a decrease in loss for an increase in flux density for large, nearly circular fields. The losses for elliptical magnetization may be approximated with a simple model composed of a mixture of lossless domain rotation, eddy current loss, and alternating hysteresis loss proportional to an alternating flux. This model is intended only for the calculation of rotational hysteresis losses and not to explain the origin of these losses. The calculated and experimental losses agree for all amplitudes and eccentricities of magnetization to within 40% for rotation in the (100) plane with the worst discrepancy for circularly rotating magnetization.

Fatigue Tests of Thin Walled Tubular Specimens at Elevated Temperatures

Torsional fatigue tests on 0.16%C carbon steel are made at room temperature, 350°C and 500°C. The strengths of thin walled tubular specimens where the stresses are considered to be distributed uniformly over the cross section are compared with those of solid specimens to study the effect of stress gradient on the fatigue strength. On the nominal stress basis, higher strengths are obtained in solid specimens at elevated temperatures as well as at room temperature. On the true stress basis, no difference of strength is found at room temperature. While the solid specimens are rather stronger than the tubular specimens at elevated temperatures. These results may be explained by the gradient of true stress which is smaller at room temperature than at elevated temperatures. The temperature rise of specimens during tests and the shapes of failure are also discussed.

Some Studies on Fatigue of Large Steel Specimens : Part 1, Construction of Testing Machine and Results of Fatigue Test on Smooth Surface Specimens

ie authors have newly designed and manufactured a large rotating bending fatigue testing machine (cantilever type, max. bending moment 7 t-m, standard size of specimen 125φ mm) intending to investigate the fatigue strength of marine propellar shaft. In this paper the construction of the testing machine is outlined and test results of 125φmm smooth surface specimens made of 0.2 carbon forged steel and size effect referring to 10φ mm specimens are described. The following facts have been revealed by these results. (1). The size effect on fatigue limit of acid open-hearth steel is 8.5%, while that of electric furnace steel 18%. (2). It should be noted that the fracture of electric furnace steel is shown by some pits in the vicinity of the center. These pits may be caused by some faults in material, but seem to have no effect on the fatigue strength. (3). Propagating speed of fatigue crack under constant bending load may be presumed 1.0∼1.5μ/c at the initial stage of crack, and about 10μ/c at the stage, where the rupture is nearing. (4). Remarkable temperature rise of specimen is noted only when the working stress exceeds 90% of fatigue limit. Temperature rises to a maximum steady value after 2 or 3 hours, and keeps almost constant till final fracture.

Experimental Studies on Temperature Rise of Specimens during Fatigue Test

Tests were carried out to measure temperature rise of specimens together with damping constant due to the internal friction of materials, during the fatigue test. Temperature rise is a function of the magnitude of cyclic stresses, and a relationship between temperature rise and life of the specimen is found. Damping constant c is influenced by temperature of specimens, and has no relation to the magnitude and the cycle number of stresses after considerable repetitions. When plotted c under fatigue tests and damping constant measured by torsion pendulum against temperature, the curves thus obtained have shapes similar to each other, having the same temperature for extreme point. And the fatigue strength vs. temperature has an inverse shape of the former. Further, scatters of fatigue lives are found to be influenced by the differences of damping constant, that is, temperature rise of specimens.