Direct Assessment of the Creep Strength of DS Cast Turbine Blades Using Miniature Creep Specimens

The present paper presents a novel approach which allows a direct assessment of the creep strength of thin walled DS turbine blades at temperatures up to 1100 °C using a grain morphology sensitive miniature creep specimen test technique. The work builds up on earlier investigations by DeMestral and co-workers ([i] B. DeMestral et al., Met. and Mat. Transactions A, 27A (1996) pp. 879–890 and [ii] B. DeMestral and G. Eggeler, Prakt. Metallogr., 29 (1992) pp. 174–191) on the influence of grain morphology on creep deformation and damage accumulation in superalloys with elongated macrograins. The paper reports the important features of this new procedure which include (i) the creep test technique (specimen geometry and grip design) and (ii) the removal of creep specimens from a DS CM 247 LC cast blade with respect to the morphology of the macrograins. The paper also reports creep results obtained with this new technique at temperature of 1030 °C and a tensile stress of 180 MPa and discusses the results on the basis of the associated microstructural creep deformation and damage mechanisms.     

Running intensity as determined by heart rate is the same in fast and slow runners in both the 10- and 21-km races

The aims of this study were to determine (1) whether running speed is directly proportional to heart rate (HR) during field testing and during 10- and 21-km races, and (2) whether running intensity, as estimated from HR measurements, differs in 10- and 21-km races and between slow and fast runners at those running distances. Male runners were divided into a fast (65-80 min for 21 km; n = 8) or slow (85-110 min for 21 km; n = 8) group. They then competed in 10- and 21-km races while wearing HR monitors. All subjects also ran in a field test in which HR was measured while they ran at predetermined speeds. The 10-km time was significantly less in the fast compared with the slow group (33:15 +/- 1:42 vs 40:07 +/- 3:01 min:s; mean +/- S.D.), as was 21-km time (74:19 +/- 4:30 vs 94:13 +/- 9:54 min:s) (P < 0.01). Despite the differences in running speed, the average running intensity (%HRmax) for the fast and slow groups in the 10-km race was 90 +/- 1 vs 89 +/- 3% and in the 21-km race 91 +/- 1 vs 89 +/- 2%, respectively. In addition, %HRmax was consistently lower in the field test at the comparative average running speeds sustained in the 10-km (P < 0.01) and 21-km (P < 0.001) races. Hence, factors in addition to work rate or running speed influence the HR response during competitive racing. This finding must be considered when running intensity for competitive events is prescribed on the basis of field testing performed under non-competitive conditions in fast and slow runners.     

The barium sulfate seeding process

The maximum brine temperatures in the final heaters of multistage flash evaporators, being limited by calcium sulfate scaling, in the case of acid decarbonized sea water, might be enhanced by seeding processes. Use of barium sulfate (barite) as seed has recently been proposed in a feasibility study and reported to have the advantage of recycling of a given amount of barite, and the special advantage of inherent diminution of the calcium concentration in the circulating brine. Using the MEWAK I closed loop system, experiments have shown that barite particles remain active as seed when the suspension system is alternatively heated and cooled several times. The “loading” and “unloading” velocity is satisfactory. Further experiments are concerned with the separation of barite from its suspension in sea water brine by hydrocyclones.     

Broadband emission and laser action of Cr3+doped zinc tungstate at 1 µm wavelength

We report on the spectroscopic properties of Cr : ZnWO4, which channels all the fluorescence into the broadband⁴T2-⁴A2transition at about 1 μm wavelength. Two different Cr³⁺centers with lifetimes of 0.5 and 5.4 μs at 300 K are analyzed. Both centers emit broad-band fluorescence with zero-phonon lines located at 834 and 877 nm wavelength. The effect of intrinsic and extrinsic charge compensation on the Cr³⁺centers is explained by a local and nonlocal compensation mechanism. With intrinsically compensated crystals we obtained CW laser action at 77 K and pulsed laser action at 300 K.     

On the performance of ENDF/B-VII.0 data for fast neutron fluence calculations

The newest release of the Evaluated Nuclear Data File, ENDF/B-VII.0, has recently become available, along with the announcement of its significant advances over previous versions. The older ENDF/B releases, however, have been assessed for numerous applications in the past and, as such, currently find wide application in the nuclear industry. An analysis of the influence of the recent upgrade in the data file is thus needed with respect to specific practical applications. The present technical note addresses the effects of modifications of the neutron cross-sections in the ENDF/B-VII.0 library, relative to the preceding ENDF/B-VI.8 release, on calculations of the fast neutron fluence accumulated in a PWR reactor pressure vessel, which is of direct relevance for the licensing and safe operation of nuclear power plants.     

The engineering background of the concept of isoelastic implants

The concept of the so-called isoelastic implant is re-evaluated in three different aspects, using old and basic principles of mechanical engineering. All three are different approaches to the nut and bolt model. The results of these calculations confirm the well-established engineering knowledge that all such essentially cylindrical interfaces necessarily result in a stress concentration in the area beginning (or ending) the load-transmitting interface closest to the point of load application if loaded axially, and that this concentration is more pronounced the more the situation of isoelasticity is approached. Some general conclusions as to the limits of the usefulness of the concept of isoelastic implants and some possible advantages of their applications are outlined in the discussion.