Coalescence Type Research Articles

Simple predictions from ALCOR c for rehadronization of charmed quark matter

We study the production of charmed hadrons with the help of ALCOR c , the algebraic coalescence model for rehadronization of charmed quark matter. Mesonic ratios are introduced as factors connecting various anti-baryon to baryon ratios. The resulting simple relations could serve as tests of quark matter formation and coalescence type rehadronization in heavy ion collisions.

Parametric Trends in the Flutter of Advanced Turboprops

The parametric trends in the aeroelastic behavior of an advanced turboprop were experimentally investigated using a subvelocity-scaled testing procedure. A 2-ft-dia subvelocity-scaled model was constructed and its flutter behavior was favorably correlated to that of a full-velocity-scaled UnDucted Fan™ model for which aflutter point had been documented. With the validity of the subvelocity-scaled procedure established, the inherent versatility was exploited through the construction and flutter testing of models which allowed for the parametric variation of sweep, mass distribution, and solidity. The correlation between an analytic model developed and the experiment is favorable for variation in mass distribution and sweep. As is typical of moderate mass ratio wings and blades, the flutter was found to be of a coalescence type, the onset of which is determined by a critical relative velocity with a slight dependence on loading and cascade effects.

Fatigue fracture of reaction injection molded (RIM) nylon composites

AbstractThis study was undertaken to determine how milled glass fibers affect the fatigue resistance of reaction injection molded (RIM) nylon 6. Specifically the effects of glass content, fiber length, orientation, and surface treatment were investigated. The fatigue crack growth rates for unfilled and glass‐filled samples were observed to follow the well‐known Paris equation in terms of dependence on cyclic stress intensity factor. For the unfilled nylon a line shaped zone was observed in advance of the crack tip. Fractography results suggest that the zone was the projection of the actual crack tip profile through the thickness of the sample rather than a distinct plastic or deformation zone. The fatigue fracture surface exhibited a patchy type structure with features 50–150 μm in size, suggesting a void coalescence type of mechanism as has been reported for injection molded nylons. A diffuse damage zone, several millimeters in size, was observed at the crack tip for the glass‐filled RIM nylon 6. The zone was observed to pulsate with the applied oscillating load. The growth of the damage zone volume with increasing crack length (and thus increasing stress intensity factor range) followed the Paris law, as did the crack growth rate data. The damage mechanism is attributed to void formation and microcracking at the fiber–matrix interface. The results of this study show that, for milled glass‐reinforced RIM nylon 6, the crack growth rates were much more rapid than observed for injection‐molded nylon 6 containing chopped glass fibers. This difference is attributed to the greatly reduced glass fiber lengths for the milled glasses.

インプラント試験とＲＲＣおよびＪＩＳ‐ｙ試験の比較

Comparison between Implant test, RRC and side-slotted JIS-y (Tekken) tests has been performed using the authors' new cracking parameter PHA which was introduced previously based on JIS-y test data.New formulae for predicting critical rupture stresses in 8-7 mm D Implant test have been developed by multiple regression analysis of 102 test data on HT50 to HT80 low-alloy high strength steels of low carbon contents of 0.04 to 0.18%. The formulae proved to be more accurate than conventional formulae thus far proposed.The 8-7 Implant critical rupture stresses of the tested HT50 to HT80 steels were compared with the critical crack initiation stresses in RRC and JIS-y tests predicted by PHA analysis. Equivalence of critical stress values between 8-7 Implant and RRC or side-slotted, JIS-y tests has been found to exist only in a limited stress range of 340 to 540 N/mm2, provided the test steel, electrode hydrogen content, and the cooling time are kept the same, respectively, in both the tests. In the higher stress range exceeding 540 N/mm2 in HT50 steels, the 8-7, Implant critical stress condition which leads to microvoid coalescence type fracture, does never seem to be realized in RRC and JIS-y tests.The estimated relationship between critical preheating temperature and Pcm obtained via Implant test seems to be practically identical to that via RRC or side-slotted JIS-y test, only in the case of critical stress level of approximately 451 N/mm2. Taking the critical stress to be equivalent to the yield stress of base metal seems to be reasonable only in the case of the said stress level and practical welded joint of mild restraint.

Mechanical properties of Fe-Cr-Co ductile permanent magnet alloys

The structure and mechanical properties of ternary Fe-Cr-Co magnet alloys containing 9 to 11 wt pct cobalt have been investigated. Fine scale spinodal decomposition of the iron rich bcc α-phase into (α + α2) structure increased the alloy strength and reduced the ductility. The degree of changes in the mechanical properties depended on the cobalt content and the final aging temperature and time which primarily determines the compositional amplitude. As a result of decomposition, the dislocation movement by slip became more difficult, and the mode of deformation changed from predominantly slip to predominantly twinning. The embrittlement during aging and the fracture behavior of these alloys go through two stages: i) from microvoid nucleation and coalescence type ductile fracture to quasi-cleavage type transgranular fracture (ductile-brittle transition) and ii) from transgranular to intergranular fracture. The cause of the transgranular fracture is attributed to the raised ductile-brittle transition temperature resulting from the increased strength and the tendency for deformation twinning which are likely to make the relief of local stress concentration more difficult. The cause of the intergranular fracture is ascribed to the formation of more or less continuous grain boundary precipitate that forms upon further decomposition at lower temperatures (below ∼540‡C). Both types of embrittlement were found to be reversible upon heat treatment at higher temperatures, either within the (α1 +α2) range or above the miscibility gap.

QUANTIFICATION OF NAVY OILS IN DETERGENT LADEN WATERS

ABSTRACT Accurate measurement of the concentration of oil in effluent discharged from ships is necessary so that water pollution regulations are not violated. Detergents used to clean machinery and deck surfaces aboard Navy ships often end up in bilge water and pass through gravitational and coalescence type oil/water separators. These detergents interfere in the solvent extraction and infrared (IR) spectrometry measurement technique for quantifying oil in water. They will absorb the IR energy at the wavelength used in quantifying oil; therefore, a method which can remove such interference, yet accurately measure the concentration of oil in water, is needed. A technique of eluting the solvent extract through silica gel removed most of this interference. Aqueous samples containing Navy oils and a non-ionic detergent in concentrations up to 1000 milligrams per liter were used to evaluate this technique. The solvent extract of these aqueous samples was filtered through silica gel and the IR absorbance of the effluent at 2,930 reciprocal centimeters was measured. The results demonstrated that this technique can yield the true concentration of oil in detergent laden water as long as the ratio of the concentration of detergent to oil is less than 10 to one. This technique can also be applied to quantify oil in water that does not contain detergent.

Flutter of Coaxial Cylindrical Shells in an Incompressible Axisymmetric Flow

The coalescence type of flutter of a long rotating cylindrical shell with its outer surface exposed to a general in vise id, incompressible, fully developed (axially), axisymmetric flow with vanishing radial velocity component is considered. The flow is governed by perturbation theory. The cylinder response is described by classical shell equations. Analytical solutions are obtained for the special cases of flows with uniform axial velocity, but the tangential velocity is: 1) represented by a coaxial, potential vortex, or 2) varying linearly with radius. Numerical solutions are presented for more general flows. The flutter speed and flutter frequency are compared with available experimental data.