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RESEARCH PAPERS

J. Basic Eng. 1966;88(3):555-565. doi:10.1115/1.3645902.

After prolonged cyclic stressing in rolling contact, AISI 52100 bearing steel parts develop extensive regions of microstructural alteration, designated as white etching areas. These are oriented in predictable directions relative to the rolling track. Lenticular carbides are always associated with these areas. Evidence is presented indicating that the boundaries of lenticular carbides constitute planes of weakness which may be preferred planes of fatigue cracking. In the transmission electron microscope the martensitic structure appears gradually transformed into a cell like structure by the action of cyclic stress. The size of crystallites is greatly reduced in this process. The density of microstructural change is found increased with cycling and is distributed in depth along a curve resembling that of the calculated maximum unidirectional shear stress with little or no visible change in the region of maximum orthogonal (alternating) shear stress.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):568-571. doi:10.1115/1.3645907.

The white-etching structural alteration occurring around nonmetallic inclusions in cyclically stressed bearing steels has been studied by transmission-electron microscopy. In order to use this method, thin foils have been prepared with an edge running through the alteration. It has been found that the alteration is due to the formation of 0.05 to 0.1-micron cells in ferrite. The cell formation is similar to that seen in fatigued iron except for the small cell size of the deformed steel. Evidence is also given that deformation causes breakup of the carbides produced on the tempering of steel prior to deformation.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):573-580. doi:10.1115/1.3645912.

Contact fatigue, brinnelling, and erosion are reported, for a stationary ball-on-flat contact, subjected to oscillatory normal load. Damage was least in the absence of lubricant, and greatest with a diester lubricant. Low-viscosity mineral oil was less severe in its effects than was a high-viscosity mineral oil. In those cases where damage was least, it could be attributed to a process of fatigue spalling. In those cases where it was severe, other processes such as fretting could be postulated, but fatigue still appeared to be the favored cause.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):583-586. doi:10.1115/1.3645916.

The general method for correlating the fatigue pitting life of simple rolling elements with the life of bearings is discussed. A “correlation equation” is presented which permits the pitting fatigue life of full scale bearings to be estimated from minimal rolling contact rig data. Three M-50 (MV-1) bearings are analyzed using this equation. In all three cases the life is predicted within a factor of two.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):589-598. doi:10.1115/1.3645920.

The stability of fully developed Poiseuille flow pulsating under a harmonically and a nonharmonically varying pressure gradient was studied experimentally. The characteristics of turbulent plugs were determined for both steady and pulsating flow by means of pressure transducers. It was found that (a) for oscillating, stable Poiseuille flow, the phase angles determined experimentally agree well with those determined theoretically; (b) for the same mean pressure gradient, pulsating flow is more stable than the corresponding steady Poiseuille flow; (c) in pulsating flow, the presence of one or more inflection points is necessary but not sufficient for instability; and (d) the curves of the critical Reynolds number versus the relative amplitude of the periodic component of the cross-sectional mean velocity reach their maximum when at least one inflection ring continues to exist a time period 53 percent of the period of oscillation.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):599-623. doi:10.1115/1.3645921.

The volume of lubrication literature continued to expand, reflecting the increased experimental and theoretical attention being given this discipline; this year’s Digest reviews more than five times the number of papers covered in the first Digest (for 1949).

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):624-635. doi:10.1115/1.3645922.

Fatigue life of tapered roller bearings and other elements subject to cyclic contact stress reflects the fatigue strength of the selected material under given environmental conditions. The various modes of contact-fatigue failure have been classified according to their appearance and the factors which promote their initiation and propagation. Illustrations of the various failure modes include rig test specimens and bearings representing normal catalog-rated life under laboratory and application environments. Evidence is presented for the propagation of contact fatigue from surface and subsurface origins.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):637-648. doi:10.1115/1.3645925.

The “wall stall” in compressor cascades has been observed by many research workers. There is a region of high loss in the corner bounded by the end wall and the suction surface of a blade. It is the separation of the flow in this region which is largely responsible for the increase in the axial velocity across the midspan section of the blades when there is no end-wall suction. It is important to differentiate between this wall stall and the two-dimensional stall of the blading. The work on wall stall described in the paper was carried out at the University of Cambridge and the University of Liverpool in the period 1955-1962.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):649-657. doi:10.1115/1.3645926.

Bubbles collapsing in water in a cavitating venturi are photographically observed. The large pressure gradient in the venturi causes the bubbles to collapse by flattening in the direction of flow. In many cases a torus is formed, implying the existence of a central jet which, as has been suggested by other investigators, may well be the primary damaging mechanism in cavitating flows. The effect of adjacent bubbles upon each other is visually observed. Numerous bubble rebounds, even in relatively degassed water, are noted. A comparison of observed collapse rates with incompressible theory for a spherical bubble indicates that the slowing down of collapse herein observed at small bubble radii probably results primarily from the asymmetry of the collapse and perhaps also from metastable compression of vapor within the bubble.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):658-666. doi:10.1115/1.3645929.

An experimental investigation of hydrostatic extrusion through conical dies using commercially pure lead billets was carried out with two different hydrostatic pressure systems; namely, a ram-type extrusion system (with a forced predetermined extrusion rate), and an injection pump (constant-pressure) system. Pressure characteristics, flow patterns, and the cavity, piping, and dead-zone effects were investigated. Experimental pressure results for both types of pressure systems agreed well with analytical predictions. Furthermore, dead-zone, cavity, and piping effects were found to be dependent upon the semicone angle and the amount of area reduction of the billet.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):669-672. doi:10.1115/1.3645932.

Specimens of 1.25 Cr–0.5 Mo steel which had been exposed for prolonged times at 1000 F under ASME Boiler and Pressure Vessel Code allowable stresses were rupture tested in order to evaluate the influence of service on subsequent elevated-temperature properties. Specimens were tested as-removed from service and after reheat-treatment. The prolonged service drastically reduced short-time rupture properties but did not have any significant influence on the expected long-time rupture strength. Reheat-treatment restored the short-time strength to a high level.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):675-681. doi:10.1115/1.3645937.

The effect of section size on the room-temperature notch strength of H-11 steel, 2014-T6 and 7075-T6 aluminum alloys, and Plexiglas was investigated in three different series of notched cylindrical tensile specimens and notched rectangular bend specimens. The three test series permit the separation of the influences of the geometrical parameters, which determine the stress field near the base of the notch, on the notch strength as the size of the specimen increases. The notch strength decreases with increasing size for all series investigated. The decrease in strength is most pronounced for the sharp machine-notched and fatigue-cracked specimens but it is also observed, to a much smaller degree, in the other series of notched specimens for all materials. An analysis of the results of this study indicates that the loss in strength with increasing section size is due to at least two factors: An increase in stress concentration factor and an increase in critically stressed volume with increasing size. With a superposition of stress concentration and volumetric effects, a loss in strength with increasing size greater than that predicted by existing fracture concepts for a brittle material may be anticipated and was actually observed for sharply notched H-11 steel specimens. Insight into the size effect and experimental scatter observed in notched specimens of real materials is gained from a consideration of the behavior of a model of an inhomogeneous material in the presence of external notches. The constant-fracture stress concept applied to this model yields a size-effect prediction on notch strength and an expression for experimental scatter in terms of the interflow spacing and the notch root radius.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Basic Eng. 1966;88(3):682-683. doi:10.1115/1.3645938.
Abstract
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):684-685. doi:10.1115/1.3645939.
Abstract
Topics: Pressure
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):685-687. doi:10.1115/1.3645940.
Abstract
Topics: Jets , Sprays , Superheating
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):687-688. doi:10.1115/1.3645941.
Abstract
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1966;88(3):688-690. doi:10.1115/1.3645942.

The motion of a wake as it passes through a blade row that moves relative to the wake generator is considered. Viscosity is neglected, and it is shown that the wake is modified by a chopping process that disperses it and also by uneven energy addition. Some hot-wire anemometer traces taken downstream of a rotor in a research compressor demonstrate the wake-chopping phenomenon.

Commentary by Dr. Valentin Fuster

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