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RESEARCH PAPERS

J. Basic Eng. 1968;90(3):319-324. doi:10.1115/1.3605098.

Thermal ratcheting is the cyclic growth of a structure that is subjected to successive cycles of heating and cooling. The mechanism of thermal ratcheting in a simple two-element assembly is investigated. The conditions required for nonratcheting captive thermal cycling and for ratcheting cyclic growth are defined and a method is developed for computing the magnitude of the plastic strains and the cyclic growth.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):325-331. doi:10.1115/1.3605099.

The laminar velocity field between a rotating disk and a stationary disk of the same diameter was investigated by means of a pulsed dye technique without throughflow and in the presence of radial inflow. A stability limit for steady laminar flow was experimentally determined as a function of disk Reynolds number, ReD = R2 ωD /ν, and the ratio of gap width to disk radius, z0 /R, for the no throughflow case and for a throughflow rate of 0.31 cfm. The basic steady-state data were obtained as a series of paired photographs, a top view and a side elevation, of a dye stream pulsed at a known rate. Data was obtained for ReD = R2 ωD /ν from 4.45 × 103 to 1 × 104 , z0 /R from 0.0476 to 0.0952, and Kν = RωD /Vra from 1.70 to ∞.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):333-341. doi:10.1115/1.3605102.

The transient nature of the flow through square-edge orifices during discharge from a cylinder and the accompanying expansion of the air have been examined in systematic experiments based on dimensional considerations. It has been found that the expansion of the air in the cylinder is not adiabatic. The effects due to heat transfer to the air, to orifice geometry, and to fluid dynamical quantities on the flow through an orifice have been examined separately. The results obtained under transient conditions are compared with steady flows for which the upstream conditions are similar.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):343-354. doi:10.1115/1.3605105.

To spin polymers or glass into continuous fibers, molten material is forced through a nozzle into air forming a free liquid jet. The jet is cooled as it proceeds through the air and the cold fiber is collected on a rotating drum. The drum maintains tension on the jet causing it to attenuate as it cools. The behavior of a variable viscosity jet of glass was studied analytically and experimentally. In the analysis, it was assumed that the velocity and temperature distributions within the jet were one dimensional. Predictions of the jet shape, the temperature distribution and the tension in the jet as a function of the material properties and the process variables were obtained. Measurements of the jet shape and the tension distribution in the jet were made for various values of the flow rate, the collecting drum speed, and the nozzle temperature. The analytical predictions were found to be in error in the region of the jet within three to four nozzle diameters of the nozzle exit; below this point the theoretical and experimental results were in good agreement.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):355-366. doi:10.1115/1.3605106.

On the basis of presently known erosion theories, an analogy is made between jet impact and cavitation erosion, and confirmed by experiments. As a consequence of this analogy, data on jet impact experiments are used to explain some peculiar aspects of cavitation damage.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):368-372. doi:10.1115/1.3605109.

An analytical model is developed to describe gas-jet driven two-phase vortex flow. Utilizing experimental data, the model is used to calculate the velocity distributions of the two phases within an air-water vortex. The computed velocities are in very good agreement with independent measurements and with trends predicted from other investigations of single-phase vortex flow.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):373-377. doi:10.1115/1.3605110.

The coupled oscillations of a liquid partially filled container having an elastic bottom or elastic walls have been studied. Two different tank configurations, a rectangular and a circular container both with flat bottoms are considered. For the cases where the flexibility of the container walls of a rectangular tank are taken into account, the lowest frequency of the system occurs when the tank is completely filled. The frequency increases as the depth of the liquid decreases. The corresponding natural frequencies for a rectangular tank having one flexible wall only are slightly higher. The effect of flexibility of the bottom of a rectangular tank shows a reduction of natural frequencies of the system. The frequency increases as the depth of the liquid increases and gradually approaches to the value corresponding to that of the rigid container. The more flexible the bottom, the lower the frequency will be. For a circular cylindrical container the frequency increases with increasing wall thickness and exhibits lower values for larger liquid heights.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):378-386. doi:10.1115/1.3605111.
Abstract
Topics: Force , Cylinders
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):387-394. doi:10.1115/1.3605112.

A Method is developed for the exact calculation of the two-dimensional potential flow about two bodies, either or both of which are lifting, in nonlinear-unsteady flight. No restrictions are placed on either the body shapes or their motions. Pressures, forces, moments, and vortex-wake shapes are determined by applying a surface singularity method step by step in time. Calculated results for a variety of flow situations are presented.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):395-399. doi:10.1115/1.3605113.

The development of a pulsating velocity field in a rigid, circular tube was experimentally investigated. The wall pressure and the radial variation of the axial velocity were measured at several axial locations. The measured inlet velocities were compared with the fully developed velocities. The experimental results show that, for the range of parameters investigated, the developing pulsating flow can be considered to be simply a superposition of a developing mean flow and a fully developed oscillating flow. These results are in agreement with a previous approximate analytical solution by Atabek and Chang.

Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):400-402. doi:10.1115/1.3605114.
Abstract
Topics: Pressure , Shock waves
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):403-408. doi:10.1115/1.3605115.

During fabrication, the cold forming of structural components may reduce the yield strength of a component if it is loaded in a direction opposite to that of the cold forming. This reduction in yield strength, referred to as the Bauschinger effect, is influenced by the state-of-stress under which the cold forming is performed, by the criterion used to determine the yield strength, and by the use of post-forming stress relief. To establish the importance and magnitude of these effects, specimens from 2 1/2 -in-thick plates of HY-80 steel, cold-formed by plane strain bending, were tested along with specimens that were cold-formed by plane-stress axial straining. For material tested in a direction opposite to that of cold forming, the Bauschinger effect was observed both in tension and compression, whereas for material tested at 90 deg to the direction of cold forming in plane strain, both the tensile and compressive yield strengths increased and no Bauschinger effect was observed. Because of the difference in restraint, the Bauschinger effect was greater for plane-stress axial deformation than for plane-strain bending deformation. The Bauschinger effect was greater when the yield strength was determined at small offsets and was essentially eliminated at an offset greater than 0.5 percent. In addition, the Bauschinger effect was greatest for small amounts of cold deformation and was progressively decreased by strain hardening at large amounts of cold deformation. The reduction in secant modulus and in yield strength (Bauschinger effect) in cold-formed material was essentially eliminated by stress-relief treatment at 1025 deg. F. The results indicate the importance of knowing the cold-forming state-of-stress, the criterion used in determining yield strength, and the effects of stress relief when assessing the effects of cold deformation on mechanical properties.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):412. doi:10.1115/1.3605125.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. Basic Eng. 1968;90(3):412-413. doi:10.1115/1.3605126.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

ERRATA

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Basic Eng. 1968;90(3):431-433. doi:10.1115/1.3605156.
Abstract
Topics: Turbulence , Pipes
Commentary by Dr. Valentin Fuster

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