Redesigned rotor for a highly loaded, 1800 ft/sec tip speed compressor fan stage 1: Aerodynamic and mechanical design

A highly loaded, high tip-speed fan rotor was designed with multiple-circular-arc airfoil sections as a replacement for a marginally successful rotor which had precompression airfoil sections. The substitution of airfoil sections was the only aerodynamic change. Structural design of the redesigned rotor blade was guided by successful experience with the original blade. Calculated stress levels and stability parameters for the redesigned rotor are within limits demonstrated in tests of the original rotor

Influence of Different Material Models on the Result of Numerical High Speed Cutting Simulations

Extreme conditions for the workpiece and the tool can occur in high speed cutting processes. Temperatures above 1000 °C at very high strains over 3 and strain rates near 105 1/s are not unusual. In the first part of this paper an overview about the well known and new developed testing methods for these extreme conditions is given. For numerical simulations it is necessary to formulate closed material models which include strain, strain rate, and the temperature. In the second part some well known material models are presented and compared. Furthermore, advantages and disadvantages are named. The flow stress behaviour of two types of steel (1.1191, 1.2311) as a function of strain rate and temperature is presented. A Johnson-Cook and a Zerilli-Armstrong model is used for the comparative numerical simulations of an orthogonal cutting process. To indicate the process of chip segmentation, a damage model is often used. The influence of various damage models with different damage parameters and failure modes is shown. The calculated cutting forces and the shape of the chips are compared with results determined at a quickstop cutting device with integrated force measurement. Additionally, the calculated chip formation is compared with the measured shape by means of highspeed photography. The temperatures, forces, and chip shape for both used models are presented and the influence of different material models are evaluated and named

Linguistics

Contains research objectives and reports on three research projects.National Science Foundation (Grant GP-2495)National Institutes of Health (Grant MH-04737-04)National Aeronautics and Space Administration (Grant NsG-496)U. S. Air Force (Electronic Systems Division) under Contract AF19(628)-248

Linguistics

Contains reports on three research projects.National Science Foundation (Grant GP-2495)National Institutes of Health (Grant MH-04737-04)U. S. Air Force. Electronics Systems Division (Contract AFl9(628)-2487)National Aeronautics and Space Administration (Grant NsG-496

Cyclic behavior and microstructural stability of ultrafine-grained AA6060 under strain-controlled fatigue

AbstractThe strain-controlled fatigue behavior of AA6060, a precipitation hardening aluminum alloy, was investigated in ultrafinegrained (UFG) conditions after severe plastic deformation (SPD) by equal-channel angular pressing (ECAP). Two as-processed conditions, representing different stages of strain hardening and grain refinement as well as a ductility-optimized condition, achieved by a combined ECAP and aging treatment were considered. Low-voltage scanning transmission electron microscopy on samples stopped at characteristic stages of the fatigue process was applied to investigate the microstructural development. The as-processed as well as the optimized condition showed cyclic softening, which was found to be dependent on the amount of prestrain induced by ECAP processing. This is linked to dynamic recovery processes in the microstructure, indicated by a clearer distinction of grain boundaries and a reduction of dislocations in the grain interior. For all applied plastic strain amplitudes, ranging from Δεpl/2=1×10−3 to 5×10−3, the fatigue life of the ductility-optimized condition did not reach that of the severely work-hardened counterpart. For explaining this unexpected result, the differing (size-dependent) effectiveness of precipitates for the pinning of dislocations during cyclic loading was considered

Validation of Simple Shear Tests for Parameter Identification Considering the Evolution of Plastic Anisotropy

The evolution of plastic anisotropy plays a key role for an accurate computational springback prediction in complex, multistage forming processes. In many studies, the identification of material parameters is based on experimental results from shear testing because this technique allows for large plastic deformations without facing stability problems that occur, for instance, during uniaxial tensile testing. However, little is known about the   comparability of different shear test setups. In this study, we systematically compare two quite different and widelyused setups for the simple shear test, the Miyauchi setup and the Twente setup. In the shear tests performed on an AA6016 aluminum alloy sheet, we observed a good agreement for the flow stresses measured with the two different   setups. We then use the mechanical data for the identification of a phenomenological model of the evolution of plastic anisotropy, and we demonstrate the importance of consistent and reliable experimental data studying a model for combined isotropic-kinematic hardening

Linguistics

Contains research objectives and reports on two research projects.U. S. Air Force (Electronics Systems Division) under Contract AF 19(628)-2487Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E)National Science Foundation (Grant GK-835)National Institutes of Health (Grant 2 P01 MH-04737-06)National Aeronautics and Space Administration (Grant NsG-496

Realfast: Real-Time, Commensal Fast Transient Surveys with the Very Large Array

Radio interferometers have the ability to precisely localize and better characterize the properties of sources. This ability is having a powerful impact on the study of fast radio transients, where a few milliseconds of data is enough to pinpoint a source at cosmological distances. However, recording interferometric data at millisecond cadence produces a terabyte-per-hour data stream that strains networks, computing systems, and archives. This challenge mirrors that of other domains of science, where the science scope is limited by the computational architecture as much as the physical processes at play. Here, we present a solution to this problem in the context of radio transients: realfast, a commensal, fast transient search system at the Jansky Very Large Array. Realfast uses a novel architecture to distribute fast-sampled interferometric data to a 32-node, 64-GPU cluster for real-time imaging and transient detection. By detecting transients in situ, we can trigger the recording of data for those rare, brief instants when the event occurs and reduce the recorded data volume by a factor of 1000. This makes it possible to commensally search a data stream that would otherwise be impossible to record. This system will search for millisecond transients in more than 1000 hours of data per year, potentially localizing several Fast Radio Bursts, pulsars, and other sources of impulsive radio emission. We describe the science scope for realfast, the system design, expected outcomes, and ways real-time analysis can help in other fields of astrophysics.Comment: Accepted to ApJS Special Issue on Data; 11 pages, 4 figure