Change in resistance to micro-plastic deformation in Bi-Pb-Sb-Sr-Ca-Cu-O

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Effects of Constituent Concentration on Rheological Properties of Corn Oil-In-Water Emulsions

Rheological properties were studied with a tube viscometer. Emulsifying agents were soy lecithin and Tween 20. The volume concentration of dispersed phase, φ, ranged from 0.32-0.62. The emulsions behaved as pseudoplastic fluids. The flow behavior index, n, of the lecithin emulsions increased slightly with increasing φ and concentration of emulsifying agent, C_e. However, the n values of Tween 20 emulsions were nearly constant. Apparent viscosity of the emulsions increased with increase of φ and C_e. With φ constant the apparent viscosity was still strongly affected by C_e.     

Modified Ferromagnetic Chromium Dioxide

Several mixtures in the system Te-CrO₂ were prepared by the decomposition of anhydrous chromic acid, CrO₃, and telluric acid (H₆TeO₆) under high oxygen pressures; the physical and chemical properties were then studied. When Te was added, the grain size of CrO₂ decreased rapidly from 5 to 10 μ to 0.1 to 1.0 μ and the magnetic coercive force increased from 20 to 120 oersteds. The magnetic Curie temperature and the lattice constants of CrO₂ did not vary, however, with additions of Te up to 20 atomic %. X-ray analysis showed that the CrO₂ plus Te was not a solid solution but a mixture of CrO₂ and TeCr₂O₆ that was nonmagnetic.     

Fatigue strength of small-notched specimens under variable amplitude loading within the fatigue limit diagram

Although the fatigue limit diagram is defined in principle for constant stress amplitude, it is often considered that fatigue failure would not occur, even in varying loading, if applied stresses were kept within the fatigue limit diagram. However, it was shown in the case of small‐notched specimens that fatigue failure occurred in some special cases of variable amplitude loading, even when all stress amplitudes were kept within the fatigue limit diagram. The cause of this phenomenon was examined using two‐step stress and repeated two‐step stress patterns in which the first step stress was chosen to be equal to the fatigue limit with zero mean stress and a mean stress was superposed on the second step stress. A non‐propagating crack was formed by the first step stress. This crack functioned as a pre‐crack for the second step stress with high mean stress. Consequently, fatigue failure occurred even when all stress amplitudes were kept within the fatigue limit diagram. It was an unexpected fracture caused by the interference effect of a non‐propagating crack and a mean stress change.     

Non-propagating crack behaviour at giga-cycle fretting fatigue limit

Fretting fatigue fracture of industrial machines is sometimes experienced after a long period of operation. It has been a question whether the fatigue limit which means infinite life really exists in fretting fatigue or not. Fretting fatigue tests in ultra high cycle region up to 10⁹ cycles were performed. Test results showed that the S‐N curve had a knee point around 2 × 10⁷ cycles and a clear fatigue limit was observed in the giga‐cycle regime for partial slip conditions. An electropotential drop technique was applied to detect the crack growth behaviour under the contact pad. The real‐time measurement of crack depth during the fretting fatigue test at the fatigue limit showed that a crack initiated at an early stage and then ceased to grow after 2 × 10⁷ cycles and the crack became a non‐propagating crack. These results indicated that the fatigue limit exists in fretting fatigue and infinite endurance is achieved by the mechanism of forming a non‐propagating crack.     

Position Sensorless Control for IPMSM Based on Extended EMF and Voltage Injection Synchronized with Pulse‐Width Modulation Carrier

This paper presents a new position sensorless control system for an interior permanent magnet synchronous motor (IPMSM). The proposed method is based on the extended electromotive force (EMF) and voltage injection synchronized with a pulse‐width modulation carrier. The proposed method does not need to switch the estimation method by speed in order to estimate the magnetic pole position by extended EMF, even at low speeds. Further, the amplitude of the superimposing voltage is changed according to the extended EMF; the applied voltage is not saturated in the high‐load and high‐speed regions. The effectiveness of the proposed sensorless control system was verified experimentally.     

Effect of Adsorbent Diameter on the Performance of Adsorption Refrigeration

Adsorbents are important components in adsorption refrigeration. The diameter of an adsorbent can af-fect the heat and mass transfer of an adsorber. The effect of particle diameter on effective thermal conductivity was investigated. The heat transfer coefficient of the refrigerant and the void rate of the adsorbent layer can also affect the effective thermal conductivity of adsorbents. The performance of mass transfer in the adsorber is better when pressure drop decreases. Pressure drop decreases with increasing permeability. The permeability of the adsorbent layer can be improved with increasing adsorbent diameter. The effect of adsorbent diameter on refrigeration output power was experimentally studied. Output power initially increases and then decreases with increasing diameter under different cycle time conditions. Output power increases with decreasing cycle time under similar diameters.