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RESEARCH PAPERS

J. Basic Eng. 1961;83(4):481-488. doi:10.1115/1.3662240.

An evaluation program was conducted on Type 316 stainless-steel sheet material to determine the effects of residual cold-work and welding on the room-temperature and elevated-temperature mechanical properties to 1800 deg F. Short-time tensile and tensile-creep elongations tests were run to determine the stresses required to produce elongations up to 10 per cent in 2 min. The effect of welds in tension was to lower the elongation with no loss in strength. The effect of cold-work on the annealed material was to increase appreciably the strength properties, thus allowing for higher design stresses. The results of a few tests indicate that Type 316 stainless steel retains some strength properties up to 2300 deg F. A definite stress-strain relationship exists in which the 0.2 per cent yield stress is very close to the tensile stress.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):489-498. doi:10.1115/1.3662243.

The tensile properties of AISI types 304 and 347 annealed stainless steels were investigated for the temperature range from 75 to 800 F. Several lots of materials were studied in each of several section sizes ranging from bar stock to extremely large forgings. A considerable variation in properties, particularly yield strength and elongation, were observed between different lots of a given type of steel of a given size category. These variations correlated with variations in the annealed hardness and are attributed to the use of different annealing treatments by the suppliers. At equivalent hardness levels the properties obtained from the various section sizes were comparable. Within any given lot or forging the properties were quite uniform for equivalent specimen orientations. The transverse ductility of the large forgings was considerably less than the longitudinal ductility. However, this relatively poor ductility did not lead to notch sensitivity or embrittlement problems.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):499-508. doi:10.1115/1.3662246.

The yielding and fracture characteristics of Zircaloy-2 as a function of stress state were investigated at room temperature through the medium of thin-walled cylindrical specimens under internal pressure and axial tension. Stress states from uniaxial longitudinal tension to uniaxial tangential tension were examined. Two tests at elevated temperature were performed at a single stress ratio. It was found that the fracture ductility lessened with increasing biaxiality. A minimum in ductility was found at balanced biaxial tension where the fracture ductility, as expressed by the effective strain, was 29 per cent. The yielding and plastic flow properties were found to be highly anisotropic. Two methods were used to express the plastic flow data: a graphical approach and a theoretical analysis based on a theory proposed by R. Hill, either one of which is suitable to express the flow properties of Zircaloy-2 under various states of combined stress.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):513-517. doi:10.1115/1.3662250.

A simple analytic theory for the effect of cell geometry on both the shear modulus and the density of sandwich panel core is presented. The core shear modulus in different directions is analyzed to include the effects of the angle α and the aspect ratio b/a of the cell. It is also found that the minimum cell weight of the sandwich core depends both on the cell angle α and the cell aspect ratio b/a. The theory compares fairly well with some available experiments. The cell geometry chosen is so general that the regular hexagonal and square cells of commercial sandwich cores are special cases.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):519-527. doi:10.1115/1.3662253.

The paper describes some experimental work designed to investigate the bursting of pipe and pressure vessels by gaseous detonation. The test specimens were 3.25-in-OD tubes, 12 in. long, and of 0.040 to 0.070-in. wall thickness. The specimens, cut from hot-rolled carbon-steel pipe, and also from drawn carbon-steel tubing, were tested at several temperatures, which were chosen to produce failures both above and below the brittle transition temperatures for the two materials. In addition, an austenitic stainless-steel specimen was tested under very severe conditions in several unsuccessful attempts to fragment it.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):529-534. doi:10.1115/1.3662256.

A general concept of the accumulation of damage is described. This concept is combined with a particular hypothesis for the accumulation of fatigue damage. Initial and failure conditions are established for use with the equation and the solution for constant stress amplitude is discussed. Simple algebraic expressions are developed in terms of the nominal stresses and cycles commonly associated with machine design and stress analysis. These expressions are compared with data from rotating bending tests of steel specimens and found to be in good agreement. Nondimensional co-ordinates are used to provide a composite plot of S-N data from a wide range of steels.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):541-544. doi:10.1115/1.3662260.

Effects of various methods of notch preparation on the notched slow bend fracture strengths of heat-treated alloy steel specimens were studied. The results indicate that several kinds of cracks result in about 35 per cent lower strength than a machined 0.005 in. root radius notch. The importance of testing sufficiently large size specimens to reveal this difference is shown.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):545-550. doi:10.1115/1.3662263.

A class of constant stress and constant stress ratio closures, σθ /σφ = K (1 < K < 2), was studied analytically. One type with the ratio K = 4/3 was investigated experimentally both elastically and in creep.

Topics: Creep , Stress , Shells
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):551-556. doi:10.1115/1.3662266.

The impact strength of hardened Type 410 stainless steel is known to be adversely affected when the steel is tempered between 750 and 1050 F. However, a desirable combination of other properties may be obtained by tempering within this range. An investigation was performed to determine the extent of improvement in impact strength that may result from certain variations in heat-treating procedures. The hardening operation was studied thoroughly, and a large number of commercial heats was included in the program to establish the consistency of results. It was found that the cooling rate through the martensite transformation range has a significant effect upon the impact properties after subsequent tempering. Rapid cooling such as that which occurs during oil quenching is detrimental, but air cooling of 0.4-in-diameter bar samples was sufficiently slow to bring about a marked improvement. This improvement was present for samples tempered at all temperatures through 1000 F with the greatest degree of improvement occurring for samples tempered in the range of 700 to 900 F. No improvement was observed for samples tempered at 1100 F and above. Martempering procedures are particularly suited for taking advantage of this phenomenon.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):557-564. doi:10.1115/1.3662267.

The influence of temperature and strain rate on the upper yield point of ingot iron was studied. Torsion tests were conducted using strain rates of 12.5/sec, 0.25/sec, and 0.0001/sec over the temperature range 77 to 525 deg K. The upper yield point showed a rapid increase as the temperature was lowered. An increase in the strain rate also caused an increase in the yield point. An apparent activation energy can be associated with the strain rate and temperature dependence of the yield point. This energy is influenced by stress level, and it appears from the present study that the relationship can be described by an equation of the form

ΔH = ΔHτ − ττb.
If this relationship is substituted for ΔH in a modification of the Boltzmann relation, the following result is obtained:
log γ̇γ̇1
   = M ΔHRT1τ − τ1τb
   1 − T1T τ − ττ − τ1b.
This equation describes the experimental data within ± 3000 psi. The results of this investigation compared with tensile test data from other investigators confirm that state of stress is an important factor in determining whether a material will behave in a ductile or brittle fashion.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):565-571. doi:10.1115/1.3662268.

A criterion for low-cycle fatigue is developed which supposes that the segment of strain hysteresis associated with work-hardening is a measure of damage. On the basis of this “damage” work criterion and assuming a linear work-hardening law, the well-known plastic strain-cyclic life equation, N1/2 Δεp = C is derived. The constant C in this equation is evaluated by setting the total damage energy absorbed in N cycles equal to the damage work of a static tensile test. This method of predicting the constant C is in much better agreement with room-temperature strain-cycling data than the previously suggested method of plotting the fracture ductility at 1/4 cycle.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):572-578. doi:10.1115/1.3662269.

A complete oil film solution of Reynolds equation is found that takes into account the presence of a point source. The solution gives integrated journal bearing characteristics in finite form. With the load in a vertical plane and the source at the top or bottom of the bearing, two simple universal relationships have emerged between the angle indicating the line of centers (α) and the eccentricity (b). With the source at the base of the bearing and −cos α = b, the plot of coefficient of friction versus the Sommerfeld variable goes through the origin and is essentially independent of bearing length to diameter ratio. Also, lubricant end flow becomes vanishingly small as the Sommerfeld variable approaches zero. With the source at the top of the bearing a friction axis intercept can be obtained depending upon a source parameter, q . With cos α ≈ b/2, a rapid rise in the co-efficient of friction can also be simulated by properly varying the source parameter. Also, lubricant end flow increases monotonically as the Sommerfeld variable approaches zero.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):579-586. doi:10.1115/1.3662270.

A general method is derived for the solution of the Reynolds equation including the effects of tangential and normal velocities. It is applied to the solution of a full journal bearing under a fluctuating load with no journal rotation. The characteristics of a finite journal bearing under a cyclic sinusoidal load are shown in curve form.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):589-593. doi:10.1115/1.3662273.

Reynolds equation for the pressure in a full finite journal bearing which is nonhomogeneous has been reduced to a homogeneous equation. By separating the variables the problem is reduced to an eigenvalue problem. The orthogonal functions expansion method is used to determine the eigenvalues and eigenfunctions. First four eigenvalues are calculated. Design charts are prepared for the eccentricity ratios of 0.2, 0.4, 0.6, 0.8 and length to diameter ratios of 0.5, 1.0, 1.5, and 2.0.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):595-602. doi:10.1115/1.3662276.

An externally pressurized gas journal bearing which achieves its load carrying capability by utilizing flow throttling dams parallel to the direction of rotation is discussed in this paper. Test procedures and equipment used to develop this bearing concept are described. A theoretical method of determining pressure distribution and load carrying capacity for the bearing is presented and correlated with experimental data for non-rotating shafts. Experiments showing the behavior of the bearing under shaft whirl conditions are described and illustrated. Suggested ranges of the design parameters are indicated. The paper also points out advantages accruing from the design simplicity as well as the static and dynamic stability of this bearing concept.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):603-610. doi:10.1115/1.3662277.

The rolling-contact fatigue properties of crystallized glass ceramic balls together with AISI M-1, AISI M-50, Halmo, and WB-49 alloy steel balls tempered to various hardness levels were determined in the NASA spin rig and in the five-ball fatigue tester. A continuous increase in fatigue life and load capacity for each steel was observed with increased ball hardness. These results correlate with resistance to plastic deformation as measured with spherical specimens in rolling contact but do not correlate with elastic limit and yield strength measured for bar specimens. These bar specimens showed optimum values at intermediate hardness levels. Extremely low scatter in fatigue life for the ceramic balls indicate that the degree of structural homogeneity may be an important factor in life scatter of bearing materials.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):613-618. doi:10.1115/1.3662280.

The paper presents a construction of a simplified model approximating the actual observed flow pattern. The resulting expressions for frictional pressure drop are found to agree fairly well with the author’s data for steam and water and the data for air and water of other investigators. The similarity with a portion of the Chenoweth-Martin correlation appears to present a logical explanation for the applicability of that correlation to slug flow.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):619-630. doi:10.1115/1.3662281.

The assumption of a homogeneous fluid in thermodynamic equilibrium has frequently been made in describing the behavior of a vapor-liquid mixture flowing in constant area pipes. Although this flow model is acceptable for a range of conditions, its extensive use has been prohibited by the large amount of computational labor involved. In the present paper the equations of this flow model are reviewed, several conventional but unnecessary restrictions are removed, and computed results are presented on working charts suitable for practical purposes. Critical flow rates and the amount of subcooling necessary to avoid flashing in the pipe were given special attention.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):632-636. doi:10.1115/1.3662284.

It is shown that a relatively simple analysis predicts the functional variation of temperature and pressure in a vortex chamber with radius and inlet velocity. The predicted variation is in good agreement with experimental observations. By assuming that the flow at the outside of the chamber occupies some effective flow area, which is essentially independent of flow rate, the inlet velocity may be expressed in terms of the chamber dimensions and the fluid properties at entrance. The effective flow area assumption is verified experimentally for two chamber exit configurations using air.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):637-647. doi:10.1115/1.3662285.

In previous reports, theory [1, 2] and experiments [3–7] were discussed on profiles that promised to possess desirable characteristics when incorporated into cascades of given arrangement. These previous studies concerned profiles destined for use in decelerating cascades. The present report is the first of a series on accelerating cascade profiles.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):648-656. doi:10.1115/1.3662286.

A perfect fluid theory, which neglects the effect of gravity, and which assumes that the pressure inside a cavitation bubble remains constant during the collapse process, is given for the case of a nonhemispherical, but axially symmetric cavity which collapses in contact with a solid boundary. The theory suggests the possibility that such a cavity may deform to the extent that its wall strikes the solid boundary before minimum cavity volume is reached. High-speed motion pictures of cavities generated by spark methods are used to test the theory experimentally. Agreement between theory and experiment is good for the range of experimental cavities considered, and the phenomenon of the cavity wall striking the solid boundary does indeed occur. Studies of damage by cavities of this type on soft aluminum samples reveals that pressures caused by the cavity wall striking the bounda y are higher than those resulting from a compression of gases inside the cavity, and are responsible for the damage.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):657-661. doi:10.1115/1.3662287.

In the turbulent flow of a fluid along a corner, secondary flows occur which have a marked influence on the velocity distributions in planes normal to the mean flow direction. All published explanations of the cause of these secondary flows deal with the turbulent structure of the flow. In this paper, measurements of isotach patterns and directional turbulence intensities in the corner of a rectangular channel with zero pressure gradient and a range of free-stream turbulence intensity of 0.8 to 2.3 per cent are reported. (An isotach is a constant velocity line in a plane normal to the mean flow direction.) Within the range of variables investigated, the following conclusions are drawn: (a) Isotach patterns are essentially independent of free-stream turbulence intensity; (b) at any point the ratio of turbulence components in orthogonal directions in a plane normal to the mean flow direction is a maximum for directions tangent and normal to the isotach at that point; (c) the ratio w′ /v′ , where w′ and v′ are turbulence components, respectively, tangent and normal to the isotach at any point, is always greater than unity; and (d) in the vicinity of the bisector of the corner angle the ratio w′ /v′ increases with increasing isotach curvature.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):663-670. doi:10.1115/1.3662291.

Previous studies of shock reflection from open-ended duct configurations indicate that a steady discharge is not instantaneously formed and that the effects of this lag may occasionally be important. A theory is available which satisfactorily describes the lag effects in subcritical flow, but its validity for supercritical flow has not previously been verified. Shock-tube experiments are therefore carried out to study the lag effects in supercritical flow from a sharp-edged orifice. The incident shock wave either modifies an initial supercritical discharge, or establishes such a discharge with the gas initially being at rest. Schlieren photographs show a violent transition of the flow downstream of the orifice that lasts several milliseconds. Pressure records taken inside the duct indicate a small, but distinct, pressure rise that also lasts for several milliseconds following the passage of the reflected shock wave. It is shown that this apparent agreement of the transition times is accidental. A method is described to evaluate the effect of boundary-layer growth on the pressure behind the reflected shock wave, and the results indicate that the entire observed pressure rise is accounted for by this effect. Consequently, flow adjustment in the orifice may be considered as instantaneous for all practical purposes.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):671-678. doi:10.1115/1.3662292.

Vortex-induced vibrations of thin flat plates are studied as a function of trailing edge geometry. In an effort to extend the analysis to a more comprehensive treatment than that provided by the common vortex model, the vibrations are considered as hydroelastic phenomena. An equation of motion is formulated. From a qualitative analysis of this nonlinear equation some expected features of its solution are set forth. A detailed experimental determination is made of the amplitude spectra of various thin plates mounted at zero mean angle of incidence in the test section of a water tunnel and suspended by a torsion spring through their leading edge. The effects of trailing edge geometry and elastic properties of plate support are explored. Data analysis gives interesting confirmation of the formulated equation of motion. The vibration is shown to become self-excited and the degree of two dimensionality of the wake is deduced to be determinative in regard to the severity of the vibration.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):679-682. doi:10.1115/1.3662293.

This paper examines the mechanics of surges in air vents and advances methods for calculating their magnitude. Particular attention is paid to the magnitude of the backsurge which can occur an the air vent behind an intake gate.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):685-696. doi:10.1115/1.3662299.

This paper presents complete pump characteristics of specific speeds 1800, 7600, and 13,500 (gpm units) in the ν – hP (flow ratio-head ratio) co-ordinate system. The method of developing these complete pump characteristics from test data is described. The three complete pump characteristics are compared, and the effects of specific speed on hydraulic transients caused by power failure or pump shutoff is presented.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):700-707. doi:10.1115/1.3662303.

An investigation of the phase-plane solution curves of the nonlinear differential equation describing the motion of the water level in a simple surge tank operating in conjunction with a turbine governed for constant hydraulic power acceptance. The phase-plane solution picture is developed by determining the form of the solution of the equation near each of its singularities. The picture enables prediction and interpretation of instability and drainage phenomena.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):709-718. doi:10.1115/1.3662306.

Presented below is a method of calculating the off-design performance of multistage axial compressor characteristics that differs in concept from previous methods. A set of resulting calculations has certain general properties; namely, that it is independent of absolute stage work and flow coefficient, number of stages, and annulus geometry. The set depends only on a stage characteristic “shape” which is normalized so that the work and pressure coefficient is unity when the flow coefficient is unity. One set of tabulated results can be applied to many different designs. Two comparisons with experiment are presented below and the agreement is fairly good. An added benefit derived from this kind of general approach is that one gains physical understanding of the various regions of compressor operation. In this regard the concepts of “axial equilibrium” and “match point” have been developed which in the present context are defined in a precise, quantitative manner.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1961;83(4):719-723. doi:10.1115/1.3662307.

Extra losses from partial admission operation of a gas turbine occur both in the nozzle flow arc and away from it. The latter have been related to the theory of fluid flow over a rotating disk expressing a dimensionless moment coefficient as a function of Reynolds number. By direct measurements of drag torque, the moment coefficient has been determined over a range of Reynolds number from 2.0 × 104 to 4.5 × 106 for several aspect ratios, axial and radial shroud clearances, and solidities. Losses increase with increasing aspect ratio. Small increases from minimum practical clearance have little effect, but blade pumping losses become severe at radial and axial clearances of the order of half the disk radius. Typical changes in solidity have only small effects on losses.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

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Commentary by Dr. Valentin Fuster

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