Growth behavior of microstructurally short cracks in the 6061 aluminum alloy with and without 22 Vol Pct SiC whiskers

Short crack growth behavior of the 6061 Al alloy with and without SiC whiskers was investigated. Fluctuations in the growth rate of short cracks converge with growth of the cracks and become substantially constant between 25 and 40 μm in the metal matrix composite (MMC) and 110 and 183 μm in the unreinforced alloy. This is attributed to the release of the short cracks from the microstructural effects,i.e., the interaction with reinforcement structure in the MMC and grain boundaries in the unreinforced alloy. Furthermore, there exists slowing down of short crack advance in the MMC, and this was explained from rapid development of crack closure obtained in this study.     

Characteristics of two-phase condensing flow by visualization using computed image processing

The mechanics of the condensing behavior of vapor bubbles in a subcooled bulk flow is complicated and influenced by both heat and mass transfer. To examine the characteristics of such thermal-nonequilibrium two-phase flow, experimental and analytical researches have been made. In the experiment, the movement of each vapor bubble in a flowing channel was recorded on video tapes and analyzed by an image processing system. As result, the distributions of void fraction along the test section were obtained. In the analysis, a simple analytical model was introduced to predict the distributions of void fraction and liquid subcooling temperature. By considering the rate of vapor condensation along the flow direction, the differential equation of energy balance between two phases was obtained. Integration of this equation yielded the void fraction and bulk liquid subcooling at any position. The condensation rate was estimated as a function of the local liquid subcooling, interfacial area and mass velocity. Finally, a close fit between calculated results and experimental data was obtained.     

Rate Effects on the Stress-Strain Behaviour of Eps Geofoam

The rate-dependency of the stress-strain behavior of EPS (Expanded Polystyrene) geofoam with densities of 19.3 and 28.0 kg/m³ was investigated by performing unconventional unconfined compression tests. A set of monotonic loading (ML) tests were performed at different constant values of vertical (axial) strain rate, ε_v. The ε_v value was stepwise changed many times and several sustained loading (SL) tests were performed during otherwise ML at a constant ε_v in other tests. A number of SL tests were performed during global unload and reload cycles to infer the stress-strain relation when ε_v=0. The elastic properties were evaluated by applying minute unload/reload cycles during otherwise ML. The rate-dependent stress-strain behaviour observed in these tests was described by an elasto-viscoplastic model (i.e., a non-linear three-component model), for which the vertical (axial) stress, σ_v, consists of inviscid and viscous components, σ_v^f and σ_v^v, while ε_v consists of elastic and irreversible components, ε_v^e and ε_v^ir. It is shown that the viscous property of EPS geofoam is of Isotach type in that, under the loading conditions where ε_v^ir is always positive, the current σ_v^v value is a unique function of instantaneous ε_v^ir and ε_v^ir, therefore the strength increases with ε_v. This viscous property was quantified based on the test results and incorporated into the model. The rate-dependent stress-strain behaviour, including the creep behaviour, observed in the experiment is simulated very well by the proposed model. In particular, the fact that the creep strain becomes significant when the sustained σ_v value becomes larger than the inviscid yield vertical stress is well simulated.     

Properties of cold-rolled high-strength steel sheets

For high-strength steel sheets, a new concept has become necessary,viz, the relation between strength and formability. When the relation between tensile strength and elongation is appraised for ranking in terms of the strengthening mechanism, it is found that the substitutional solid-solution hardening type is excellent and the precipitation hardening type is inferior. In batch annealing, the phosphorus-added aluminum-killed steel sheets are representative of the former type having excellent formability as indicated by a highr values despite their tensile strength of 450 N/mm². The titanium-added aluminum-killed steel sheets, which are representative of the latter type, have a tensile strength of 600 N/mm² and a relatively highr value. Continuous annealing of the highstrength steel sheets of the same chemical composition causes higher yield stresses and combinations of yield stress and elongation. Alternatively with continuous annealing the same level of strength can be achieved with smaller additions of alloying elements than with batch annealing. An additional advantage of continuous annealing is the uniformity of properties along the length of the coil. The rapid cooling possible after continuous annealing allows production of high strength steel sheets having excellent mechanical properties that are unobtainable in the batched annealed steels. For example, steel sheets of 0.4 pet Si and 1.4 pet Mn after continuous annealing, haven values and Erichsen values as higher than conventional low-carbon rimmed or capped steel sheets even while they have a tensile strengths of 550 N/mm².     

Dyeing Properties of Monoazo Dyes Derived from Aminonophthothiazole Derivatives

The preparation and dyeing properties of new monoazo dyes prepared from aminonophthothiazole derivatives using a tertiary amine as the coupling component. The fibres considered are: polyester, cellulose acetate, nylon 6 and acrylic.     

Intentional side etching to achieve low-noise GaAs f.e.t.

A very-low-noise 0.5 ?m-gate GaAs f.e.t. is realised by using intentional side etching of an Au/Ti double layer as the Schottky-gate metal. At 12 GHz, the minimum noise figure is 2.1 dB, with 7.6 dB associated gain at a bias of VD = 4 V, ID= 10 mA. Maximum stable gain is 14 dB at VD = 4 V, ID = 30 mA.     

Tool wear prediction and economics in machining stepped parts

For analysing economics of machining cylindrical stepped parts, tool life must be predicted. In this paper, tool life tests, to obtain tool life changing cutting speed before the tool reaches tool life criterion under a constant speed, are performed and the tool life is calculated. Using the results of the calculations machining economics of various forms of stepped parts for the constant spindle rpm method and the constant cutting speed method, are analysed.