0


RESEARCH PAPERS

J. Eng. Ind. 1974;96(3):705-712. doi:10.1115/1.3438426.

The input-output displacement equation is expressed as a degree eight polynomial in the half-tangent of the output angular displacement. A procedure for determining uniquely all the linkage variables verifies the closures and in addition explains the physical significance of the closures of equivalent five-link R5 spherical mechanisms. The equation can be used to generate input-output functions of spatial five-link RCCRR and RCRCR mechanisms. The results are illustrated by numerical examples.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):713-717. doi:10.1115/1.3438427.

The input-output displacement equation is expressed as a degree eight polynomial in the half-tangent of the output angular displacement. The equation can be used to generate input-output functions of spatial five-link RCRCR and RCRRC mechanisms. The results are illustrated by numerical examples.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):718-721. doi:10.1115/1.3438428.

The input-output displacement equation is expressed as a degree eight polynomial in the half-tangent of the output angular displacement. The equation can be used to generate the input-output function for the spatial five-link RRCCR mechanism. The results are illustrated by numerical examples.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):722-728. doi:10.1115/1.3438429.

Underwater plate vibration and its associated noise are of interest for the analysis of ship structures, propeller blades, and other areas of underwater acoustics. In order to analyze the relationship between a plate vibrating underwater and the acoustic pressure in the near-field, optical interferometric holography, using a blue-green laser beam, was used to determine surface displacement for the vibrating plate, which was excited through a fluid-coupled system. Acoustic measurements of the same source were made in a water tower concurrently with the holography and later at a precision acoustic testing facility. This method permits prediction of underwater plate modal frequencies and shapes with high accuracy.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):729-734. doi:10.1115/1.3438430.

Pipelines were installed aboveground at the U. S. Bureau of Mines, Morgantown (W. Va.) Energy Research Center, to develop and evaluate different types of systems—vacuum or pressurized, horizontal or vertical—and to obtain information for the design and operation of a practical system. A previous publication [1] gave references on conveyance of lump-size solids, presented one of many concepts of pneumatic transportation of coal underground, and described the experimental system and its safety features. This paper presents the results of experiments in the vacuum horizontal transport of up to 2 1/2-in. coal through 2-, 4-, 6-, and 8-in. dia pipelines. Minimum air rates required to move the coal in full suspension and pressure losses resulting therefrom were related to coal and pipe variables in the form of empirical equations that were used in predicting minimum power requirements.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):735-740. doi:10.1115/1.3438431.

In this paper a general survey of material handling by vibrating equipment is presented with a discussion on applications and basic design considerations. Attention is given to the need of designing vibrating equipment properly in order not to produce unacceptable environmental pollution in the form of noise and structural vibrations. It is also shown in this paper that the stiffness method of structural analysis may be applied effectively in the design and analysis of vibrating conveyors to give accurately the motion and the forces along a vibrating conveyor. The effect of the vibrating material is considered in the analysis as mass effect and equivalent frictional factors. Experiments conducted for the determination of these factors are reported. Also, a computer program outline for the analysis of vibrating conveyors under load is presented and numerical examples are given to illustrate the method.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):741-746. doi:10.1115/1.3438432.

The three types of reaction devices used for mass flow measurement of solid materials are described and compared as to function. These, as a class, are compared with weighing type devices. The incorporation of mass flow reaction devices into instrument system loops is considered with recommendations and suggestions for handling, flow control, proportioning solid to solid, solid to liquid, totalizing and batching.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):747-751. doi:10.1115/1.3438433.

A major construction program, including a computerized automatic control system, was initiated to improve the ore handling and ship docking facilities at Sparrows Point. Although the basic concept for the handling of ore has not changed, many innovations have been implemented.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):752-760. doi:10.1115/1.3438434.
Abstract
Topics: Machinery , Wheels
Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):761-764. doi:10.1115/1.3438435.

Problems of undesirable vibrations in an ore unloading structure are described. Earlier unsuccessful attempts to eliminate vibrations by changing allegedly exciting frequencies mechanically and by increasing natural frequencies structurally are cited. Scientific evaluations of granular material flow patterns in the bin are presented, which identify possible causes of and methods to alleviate the vibrations. Finally, the corrective measures in flow control taken to eliminate vibrations are illustrated.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):766-772. doi:10.1115/1.3438438.

Recent increases in bulk material tonnage being transported throughout the world are requiring the planning of many new ship and barge unloading installations, as well as the renovation and updating of a number of existing facilities. For many years, the clamshell unloader has been the heart of the typical unloading facility, and in spite of new unloading techniques, it will continue to play a major role in years to come. Since today’s high performance, high capacity unloader can represent an investment of several million dollars, it is important that the operation of this machine be well understood and appreciated by all those involved. The purpose of this presentation is to discuss the various types of reeving systems that are available, their major advantages and limitations, and the features that are essential to any system to insure smooth and trouble free operation.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):773-777. doi:10.1115/1.3438439.

There is an accelerating trend toward application of modern static control and drive technology to cranes and heavy material handling systems, and the backbone of these systems are the thrysitor and the static regulator with its many printed circuit cards and small electronic components. This article reviews these elements with respect to performance while subjected to typical crane operating conditions, including shock, vibration, dirt, low line voltage, etc. Design features and special packaging considerations for crane installations are discussed, as well as alternate design approaches.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):778-784. doi:10.1115/1.3438440.

User demands for higher performance from today’s clamshell unloaders have led to a critical examination of the operator himself. In order to reduce dependency on this unpredictable individual, it becomes desirable to automate the unloading cycle as much as possible to achieve maximum efficiency. This paper discusses some of the computer simulation which has been done to determine an automated cycle, and the electrical controls involved in implementing the automation.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):785-787. doi:10.1115/1.3438441.

A dimensionless ratio is proposed relating isenthalpic and isentropic changes in real gases. The new parameter meets the requirements for a property, and is shown to depend only upon the equation of state. Some possible applications are indicated.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):788-794. doi:10.1115/1.3438442.

Methods based on fundamental thermodynamic principles and the notion of statistical probability have been used to estimate the point of instability and the lower critical Reynolds number for a round pipe and an infinite channel. It is also shown that order of magnitude estimates of the ratio of the average shear stresses for each regime allow one to draw definite conclusions about the lower and the upper critical Reynolds number in a variety of geometries.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):795-800. doi:10.1115/1.3438443.

A similarity parameter suitable for use in both analog and digital analyses of time-dependent inlet pressure distortion data has been developed. This parameter, when used in conjunction with the recently developed Method D distortion methodology, facilitates prediction of full scale instantaneous pressure distortion levels from scale model inlet dynamic data. The similarity parameter was developed by relating the inlet size to the data frequency bandwidth by simple acoustic wave theory. This parameter is shown not only to collapse data from different scale sizes of the same inlet but also to produce similar ratios of dynamic to steady-state distortion levels for inlets of different types and sizes operating at or near engine matched conditions. When operating supercritical the increase in dynamic distortion relative to steady-state distortion is seen to be consistent for the various sizes of inlets at constant values of the similarity parameter. Along with the development of the inlet dynamic distortion similarity parameter, this paper treats the subject of analog filtering and digital averaging of the time-dependent pressure data prior to computation of the Method D parameters. Under certain conditions analog filtering and digital averaging are shown to be equivalent. Furthermore, by use of the similarity parameter, consistent selection of either analog filter bandwidth or digital average time can be made for comparison of trends in inlet dynamic distortion between inlets of different types and sizes.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):801-806. doi:10.1115/1.3438444.

This paper presents an approach that predicts the resonant frequency of a high-performance dc servomotor. The correlation between this approach and experimentally determined resonant frequencies is good. The design of the armature, the coupling shafts, and the annular couplers is discussed with regard to maximizing the resonant frequency of the motor.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):807-810. doi:10.1115/1.3438445.

Two methods of reducing the idle emissions of gas turbine engines have been investigated. The methods were (1) fuel zoning, whereby a portion of the fuel nozzles were shut down and all of the fuel passed through the remaining nozzles and (2) larger than normal compressor overboard bleed. Both methods operate on the fact that a combustor’s efficiency increases as the fuel/air ratio is increased from idle to full power conditions. Fuel zoning increases the local fuel/air ratio making those portions of the combustor which are operating more efficient. This method has been shown to reduce the idle emission of total hydrocarbon by 5 to 1 in a double annular combustor sized for a large augmented turbofan engine. Operating with a larger than normal compressor overboard bleed allows increasing fuel/air ratio without increasing idle thrust. By using this method in a P&WA™ JT3C-7 engine a reduction of 2 to 1 in the emission of total hydrocarbon was demonstrated.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):811-819. doi:10.1115/1.3438446.

The problem of predicting installed propulsion system performance for a specific configuration from isolated inlet, nozzle and airframe data, and from data for similar configurations is discussed. The degree to which element performance may be isolated from measurements made on an integrated propulsion system will be discussed. An approach to evaluation of external performance of inlets and nozzles is presented. The design of parametric tests and some correlations for afterbody pressure drag from such tests are described. Improvement of data quality from model tests with sophisticated simulation of propulsive flows by pretest studies and in-test quality control are proposed.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):820-826. doi:10.1115/1.3438447.

Airframe/propulsion system interactions can strongly affect the stability and control of supersonic cruise aircraft. These interactions generate forces and moments similar in magnitude to those produced by the aerodynamic controls, and can cause significant changes in vehicle damping and static stability. This in turn can lead to large aircraft excursions or high pilot workload, or both. For optimum integration of an airframe and its jet propulsion system, these phenomena may have to be taken into account.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):827-832. doi:10.1115/1.3438448.

The temperature and membrane stress distributions in an elastic square plate with an insulated central elliptic hole are investigated. The temperature varies along coordinates within the plane. The temperature distribution is determined as the solution of the steady state heat conduction equation, then the membrane stresses due to the temperature are analyzed. For both steps, the free edge conditions around the insulated elliptic hole as well as the boundary conditions at the fully restrained outer edges of the plate are satisfied at selected points by the method of least square point matching. The formulation is valid for any arbitrary orientation of the major axis of the elliptic hole. The numerical results for temperature distribution and membrane stresses are presented for two orientations and compared with the corresponding results for a circular hole.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):833-838. doi:10.1115/1.3438449.

An experimental program was carried out to determine the effect of aspect ratio on cantilever plate deflections under point loadings. These results were compared to deflection information obtained using the theoretical technique outlined by Szmelter, Sulikowski and Lipinski [1]. The theory and experiment gave good agreement over the range of aspect ratio studied. A series of curves giving the maximum deflection of a cantilever plate as a function of aspect ratio and load position are presented. These curves show the transition of plate deflections from the cantilever beam case to the infinitely wide cantilever plate case.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):839-844. doi:10.1115/1.3438450.

Spring materials are purchased under specifications which impose limits on the tensile strength but do not control the crucial properties, i.e., resistance to plastic flow and stiffness. Present techniques for characterizing spring material are discussed in detail. A novel test is described which is quick, inexpensive, and reliable and holds promise for both research and quality control applications. The test is based on a dynamic determination of energy dissipation in a sample stressed in bending or torsion, the usual modes of deformation for most springs. Stiffness and permissible deformations are determined directly and the elastic modulus and yield strength can be calculated easily. The results obtained in this way compare favorably with those determined by tensile testing. An example is given which illustrates the operation of the test and the calculation of results. Since the entire test from sample preparation to calculation of results requires about five minutes, and since the apparatus should be relatively inexpensive, the test ought to find application in many areas where testing is not practical at the present time.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):845-852. doi:10.1115/1.3438451.

The free lateral bending vibrations of an “infinitely” long or simply-supported thin-walled circular cross-section beams having elastic-viscoelastic-elastic layers are investigated to determine the natural frequencies and associated composite loss factors. The analysis considers the inner and outer beams to behave as elastic beams in which the mass and mass-moment of inertia are both considered along with the interaction of the two elastic beams through the viscoelastic material. The results indicate that there are two natural frequencies. The lower one associated with the two elastic beams moving together so that little damping is obtained in this mode of vibration; the higher mode in which the two elastic beams vibrate in opposite directions so that there is an amount of damping comparable to the material loss factor of the viscoelastic material. A simplified model analysis is performed which is used to corroborate the trends obtained in the computer solutions of the more rigorous analysis. A series of curves are obtained for equal thickness elastic layers which can be used to obtain natural frequencies and composite loss-factors for a realistic range of geometrical and physical properties of a laminated circular cross-section simply supported beam.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):853-857. doi:10.1115/1.3438452.

An approximate relation between the reliability of a design and the classical deterministic factor of safety, used in the design, is presented. An expression of the reliability as function of the mean value and coefficient of variation of the probability density distribution of the factor of safety, is derived. Further, the relation between the deterministic factor of safety and the statistical values of the probabilistic factor of safety, is discussed. Finally an expression for the reliability as a function of the deterministic factor of safety and the parameters determining the stress and strength distributions, is obtained. This function relationship is expressed in a design nomogram relating all the parameters involved.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):858-862. doi:10.1115/1.3438453.

Equations are developed which predict the maximum hydrostatic pressures and the corresponding bulge heights of circular safety diaphragms comprising two thin disks of dissimilar materials. Diagrams which are based on the equations facilitate the selection of materials, and dimensions and general design.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):863-869. doi:10.1115/1.3438454.

This work describes the conduction of heat in a braking disk. It also gives a base for an optimum design of braking disks. The optimum theory is based on temperature as the limiting factor.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):870-876. doi:10.1115/1.3438455.

This paper presents a general solution for a thin ring under a self-equilibrating loading system comprising any combination of radial, tangential, and moment loads. The formulations are applicable to concentrated loads as well as to distributed load functions. Closed-form solutions are obtained for each case for engineering applications. Comparisons with recent published results for some special cases are demonstrated in some of the sample problems.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):877-885. doi:10.1115/1.3438456.

In a previous report [2] the author presents a new theory for V-belt drives. In that work special attention is directed to the motion of the belt. Stress variation in the cord of the belt is treated in another report (3). In the present report the earlier theory is extended and the main interest here is how the power loss is influenced by different belt and drive properties. The contribution to the power loss can be divided into two main parts viz: losses due to external friction (sliding between belt and pulley) and internal friction (sliding between molecules-hysteresis). The former losses are treated theoretically and the latter experimentally. A further separation is also made and power losses due to external friction arising when the belt enters and leaves the pulley are specially treated. Different types of contribution to the power loss are calculated by Gervas and Pronin (4) and in another paper (5) Gervas measures the internal friction losses caused by the bending (flexure) of the belt. However, the experimental method used didn’t separate the losses due to external and internal friction. In a chapter on optimum tensioning of a belt drive, different types of losses are combined and the efficiency reaches a maximum for a certain combination of transmitted power and pretension.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):886-892. doi:10.1115/1.3438457.

A method is presented for formulating and solving the Newton-Euler equations of motion of a system of interconnected rigid bodies. The digital simulation may involve numerical integration of the kinematic equations as well as the dynamic equations. The reaction forces and torques resulting from rigid constraints imposed at the connecting joints are also determined. The derivation of kinematic expressions for first and higher derivatives is demonstrated based on direct differentiation of the rotation matrix in the spirit of the classical vector approach. A representative problem in spatial mechanism analysis is solved and illustrated with numerical results.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):893-900. doi:10.1115/1.3438458.

The paper describes a new continuous extrusion forming process, for metals, which is particularly applicable in the wire, section, and tube manufacturing fields. The principle of the process is based on the mechanical friction which exists between a billet and its container in conventional extrusion. If the container is rectangular in cross section and three sides are formed as a groove in a rotating wheel, with the fourth side forming a stationary shoe fitting against the outside of the wheel, then rotation of the wheel will carry the billet along with it. If a stop with die orifice is sized to fit the groove and is fixed to the shoe, then as the billet is forced against the die, extrusion can occur. The development of the process from a laboratory bench top model for lead wire, to a powered experimental machine capable of continuously extruding aluminium wire through ratios of 40:1 is described in the paper. The possibilities for future development are discussed and some guide is given to the possible size and capacities of projected machines.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):901-911. doi:10.1115/1.3438459.

Void behavior has a pronounced effect on the properties and soundness of most materials, and is strongly influenced by the magnitude of hydrostatic pressure during plastic deformation. Using the upper bound theorem approach with a model of idealized geometry to simulate a void-material composite, an analytical criterion for the minimum effective pressure necessary to initiate a permanent void volume change is developed. This pressure is called critical pressure, and its absolute value is the same whether for compression and void closure or tension and void opening. A deviation parameter is also defined, and it indicates that voids of a given geometry will start to open faster under tension than they will start to close under compression of the same magnitude. To compare the aforementioned analytical predictions with real material behavior, copper split billets with artificially introduced voids of predetermined geometries were deformed under different magnitudes of hydrostatic pressure: the process of wire drawing for low pressure deformation, and the fluid environment of hydrostatic extrusion for higher pressure deformation. Those characteristics found to lead to significant void volume change are: (a) high void volume fraction, (b) large relative void size, and (c) voids of unity or greater aspect ratio. Experimental data compared well with the analytical curves; thus, the analytical expressions should be useful in explaining and predicting the behavior of voids in some real materials.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):912-916. doi:10.1115/1.3438460.

The effect of the tooling-workpiece interface condition on the metal flow in extrusions is shown to be of critical importance in the achievement of sound product. For 2:1 reduction ratio extrusions, the central burst defect is shown to occur when low fractional restraint interfaces are employed. Sound internal product is shown to occur when high frictional restraint interfaces are employed. In metal alloy powder compaction-extrusion processes, a low density core is shown to be associated with compaction at low extrusion ratios employing low frictional restraint interfaces. The experimental results are discussed in terms of recent theoretical analyses of metalworking processes which are based on the effect of the interface friction influencing the volume of the plastic deformation zone and the subsequent strain rate fields.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):917-922. doi:10.1115/1.3438461.

Employing a transformation technique, an analysis is made of the properties of the solution of the differential equations resulting from the analysis of the elastic behavior of an eccentrically loaded thin strut. The thin strut is made to experience large deflections and the end supports are simultaneously pinned and restrained by torsional bar springs. The paper is divided into two parts. Part 1 deals primarily with the properties of the solution of the equations; and Part 2 deals with the practical engineering aspect where, employing Part 1, realistic values and ranges of parameters are assigned. The resulting design curves and tables, useful to the design engineer, are presented.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):923-930. doi:10.1115/1.3438462.

Employing the method developed in Part 1, the practical engineering design aspects are treated for the selected problem of an eccentrically loaded thin strut. The strut is made to experience large elastic deflections, and the end supports are simultaneously pinned and restrained by torsion bar springs. Realistic values, ranges, and combinations of physical parameters are assigned and design curves, data, and tables are presented. The paper is so written that the engineer may use Part 2 independent of study of Part 1 if he so desires to bypass the mathematical and property study of the solution of the defining equations.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):931-935. doi:10.1115/1.3438463.

An analytical solution is developed for the tapered arbor spring slip clutch by introducing approximations that do not appreciably affect the accuracy of the important clutch quantities. In addition, the influence of the coefficient of friction on the output torque, the axial force on the spring coil, and the radial contact forces alongthe tapered arbor are shown.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):936-939. doi:10.1115/1.3438464.

Hypotheses are presented here for improving bulk solids flowability. They are directed toward a quantitative design goal for gas-solids flow systems. An effort is made to relate gas control in gas-solids flow systems to the Jenike design method. Cohesion and friction in slumped beds are frequent barriers to flow. Gas or liquid moving through bulk solids interstices can reduce interparticle cohesion. Changes in interstitial fluid pressure can modify friction angles and so change channel flow factors and bulk solid flow functions. Mass flow can be achieved in gas-solids flow systems using comparatively large hopper half apex angles.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):940-945. doi:10.1115/1.3438465.

The effectiveness of a three-element dynamic absorber and of dual dynamic absorbers in reducing the transmissibility across a simple spring-mass system at resonance has been investigated and shown to be considerably greater than that of the conventional dynamic absorber. From the complete information provided, much in graphical form, it is possible to design and to estimate the performance of both the three-element and the dual dynamic absorbers for a wide range of absorber masses. Utilizing design parameters that have been determined and specified here for the first time, it is shown 1) that the three-element absorber can be more effective than a conventional absorber of twice its mass, and 2) that by use of dual absorbers, it is possible to obtain a significant trough in transmissibility while avoiding the two resonant peaks of large magnitude that are normally introduced at neighboring frequencies. The three-element absorber requires no increase, and the dual absorbers require only a modest increase in mass beyond that of the conventional dynamic absorber.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):946-953. doi:10.1115/1.3438466.

The vertical penetration of sedimentary materials is of importance for many scientific and engineering purposes, including soil sampling and pile driving. One approach to this problem is to achieve orbital motion of a probe in a horizontal plane, thereby displacing the soil radially, with excitation produced by a rotating unbalance. The probe thus reacts with the soil, resulting in radial and tangential forces. The former produce hole enlargement, and the latter are in the nature of frictional drag related to orbital motion. The analysis indicates that such a system is bistable, with radial probe amplitudes dependent upon whirl frequency, soil friction, soil compressive resistance, probe mass, and exciter unbalance. Such a device exhibits several desirable operational characteristics, tending to enlarge the hole at increased radial resistance, and to decrease amplitude at reduced resistance, thus being somewhat self-regulating. A prototype has been built and tested experimentally; however, this paper is primarily a study of the steady-state vibratory behavior of a whirl-excited probe, with basic design equations presented.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):954-959. doi:10.1115/1.3438467.

This paper discusses the reduction in the applied drawbar force required to penetrate soil with vibrating plows. Harmonically forced linear and orbital motions of a plow blade are investigated. A rigid blade, vibrating with constant amplitude and a two-parameter soil model is used to represent the system. The assumption that the soil force opposes the instantaneous blade velocity vector is sufficient to describe the soil-blade interaction. Bounding solutions, which relate applied drawbar force to average plowing speed and other system parameters, are obtained as simple equations. These equations put into perspective the relative merits of each of these vibratory motions.

Topics: Force , Motion , Blades , Equations , Soil
Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):960-968. doi:10.1115/1.3438468.

The problem of nonsynchronous whirl induced by internal friction is shown to be important when rotating machinery is designed for operation at supercritical speeds. Mathematical methods are used to determine the stability speed threshold of nonsyncronous whirl instability for an unbalanced flexible rotor on a rigid foundation. This threshold of instability is shown to be the same as the threshold for balanced rotors established by previous investigations. The location of the external damping (foundation or rotor) is shown to be important in determining stability when the foundation is made very rigid. The effect of shaft stiffness orthotropy on nonsynchronous whirl induced by internal friction is also investigated. Results from the stability analyses are verified by numerical solution of the differential equations. It is concluded that rotors can be safely operated up to speeds about eighty percent above the significant critical speed if the external damping is larger than the internal friction, and that shaft stiffness orthotropy has an insignificant effect on friction-induced whirl.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):969-975. doi:10.1115/1.3438469.

Porcelain enamels are thin, inorganic, glassy coatings, extensively used to protect metal surfaces exposed to the corrosive and erosive effects of hot gases. They are known to increase the fatigue life and vibratory damping of the coated member in some cases but the amount of improvement and the governing parameters are not known. Three pieces of equipment for measuring the damping and complex moduli of porcelain enamel coatings as a function of temperature, strain level and state of stress have been developed as part of a program now underway to determine these properties. All three are designed to cover the temperature range from room temperature to 2000 deg F. The first is an adaptation of the low frequency torsional pendulum equipment useful from about 1 to 20 Hz. The second uses a flat beam in bending to cover the frequency range from 10 Hz to 200 Hz and the third uses a hollow torsional specimen to cover the range from 150 Hz to 600 Hz. This paper describes the design details, advantages and disadvantages and error analysis of each of the three pieces of equipment.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):976-982. doi:10.1115/1.3438470.

This paper investigates squeeze film bearings supporting a centrally preloaded rigid rotor mounted in antifriction bearings. Assuming the short bearing approximation and isothermal, incompressible lubrication, design data are presented for such a system over a wide range of operating conditions. Design considerations include the possibility of undesirable operation modes, the maximum unbalance for which the squeeze film support is superior to the rigid mount, the transmissibility at design speed and the forces transmitted during start-up. It is shown that unbalance force attenuations by factors of three or more are a practical possibility with a consequent increase in antifriction bearing life. A numerical example is included.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):983-987. doi:10.1115/1.3438471.

Analysis of the Gyroscopic Vibration Absorber (GVA) is made with a view to improve its effectiveness as a linear synchronous absorber. Theoretical consideration reveals that much of the nonlinearity of the governing equations of motion of the structure-absorber system involves terms containing an absorber parameter IE . The experimental development of a GVA for which this parameter is made to vanish by appropriate proportionment of certain absorber moments of inertia is shown to be feasible. Laboratory tests examining the nulling potential of this experimental GVA show that linear synchronization of the antiresonant frequency to the speed of the GVA rotor can be obtained for a wider range of excitation frequencies than when the absorber parameter is not equal to zero. Comparison of the experimental results with analytical predictions is also favorable.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):988-993. doi:10.1115/1.3438472.

An analysis is made of the axisymmetric elastic and plastic stresses and deformations in thick-wall cylindrical shells subjected to internal dynamic pressures. The study utilizes a direct numerical approach called the discontinuous-step analysis. This analysis is based on the direct use of the boundary conditions and the applicable physical laws to propagate dynamic changes in the cylinder by finite steps. Reflection of stress waves from both inner and outer boundaries is automatically generated. The validity of the method is checked by comparison of numerical results in the elastic range with published results for thick-wall cylinders. Comparison is made with experimentally measured strains from the high-pressure section of a hypervelocity launcher. This analysis assumes that the work hardening of the material is independent of the strain rate and is constant for a large variation of plastic strain. Stress-strain relationships are derived for the condition of plane strain in the cylinder which is held to be representative of the actual conditions in the launcher high-pressure section. The digital computer program developed from this study predicts the distribution of dynamic stress and strain throughout the cylinder, the internal radial growth, the distribution of particle displacement, the distribution of yield stress in an autofrettaged cylinder, and the residual stress.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):994-999. doi:10.1115/1.3438473.

The normal mode method is used to determine the steady state response of a simply supported, uniform thin cylindrical shell to a radical harmonic force with hysteretic damping included in the analysis. Numerical results are given for the variation with excitation frequency of the radial component of amplitude at different points along the shell for three levels of damping. The response at the resonances, corresponding to the first few modes of each shell, and their convergence, as the number of modes included in the solution is increased, are considered in detail. Novozhilov’s thin shell theory is used in the analysis, but the effects upon resonant response of using other shell theories are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1000-1005. doi:10.1115/1.3438398.

A detailed dynamic analysis is made of a heavily damped foundation structure designed for the multidirectional isolation of machinery vibrations. The principal components of the structure are damped sandwich beams and complex-shaped rubber blocks. In order to study the complete structure, each component was analyzed for its mechanical impedance data. Where possible, these were obtained theoretically, but in some cases it was necessary to resort to experimental measurement. The individual components were then connected together using the dynamic stiffness coupling technique in order to predict the vibration characteristics of the complete structure. The accuracy of the final results testifies to the feasibility of combining measured and theoretical data in this way in order to analyze a complex mechanical structure.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1006-1009. doi:10.1115/1.3438399.

A general and direct method for the analysis of branched systems is presented, in which transfer matrices are used in Holzer-type solutions. The method is shown here for torsional vibrations, but should be applicable to other branched systems. As presented here, this method is much different than the usual procedure found in the literature. Unlike other methods, no matrix inversions (or equivalent operations) are required to account for branches at a junction. A single determinant giving natural frequencies is arrived at irrespective of the number of branches and junctions. Thus the method is straightforward, compact, and economical for computer solutions.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1010-1014. doi:10.1115/1.3438400.

The vibration of a single-story frame with bilinear hysteresis supporting a rotating machine is analyzed. The excitation force caused by the rotating unbalanced mass of the machine has a frequency dependent amplitude. The bilinear hysteresis of the resisting force of the frame to the motion is derived from the bilinear moment-curvature relationship of the frame columns. Solving the equation of motion of the system by the method of slowly varying parameters, the system exhibits unbounded resonance when the product of the machine unbalanced mass and its eccentricity exceeds a critical value. For the purpose of design and analysis of this type of structures, the displacement amplitude is plotted against arguments of the frequency for various values of two parameters involved.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1015-1021. doi:10.1115/1.3438401.

The purpose of this paper is to investigate thermally induced vibration of a rectangular plate with one edge fixed and other three edges simply supported. The plate was subjected to a sinusoidal heat input, which varied with respect to time, on one face while the other face of the plate was insulated. An approximate solution to the governing differential equation of motion of the plate was assumed in the form of a double trigonometric series which satisfied all the boundary conditions. Galerkin’s method was then used to obtain the deflection curve for the plate and corresponding stresses at various points in the plate. Certain interesting phenomena indicate the possibility of predicting early fatigue failure. Results are presented in graph forms and discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1022-1027. doi:10.1115/1.3438402.

The orthogonality condition for vibrating three-dimensional framed structures has been directly applied to solve initial value problems. In solving the dynamic response problems due to force and displacement excitations by using the mode expansion method it is necessary to use the same orthogonality condition.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1028-1035. doi:10.1115/1.3438403.

Calculation of the total potential energy of a system is performed in the case of thin rotating plates. The structure is divided into plane triangular elements with three nodes and eighteen degrees of freedom. The mass and stiffness matrices in which the rotation effects have been introduced are derived using area coordinates. First, the initial stresses due to the rotation are calculated; next, frequencies and modes are determined by a simultaneous iterative technique. The method is then applied to an existing compressor blade. The correlation with experimental results is good for the first ten frequencies and the first five modes. A calculation process for machine designers based on the methods introduced by Petricone-Sisto and Rawtani-Dokainish and the finite element method is then presented.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1036-1040. doi:10.1115/1.3438404.

This paper considers the flexural vibrations of free thin circular cylinders. A frequency equation is derived using free-free characteristic beam functions to represent the variation of mid-surface shell displacement components, u, v and w, with respect to the axial direction. Timoshenko strain-displacement relations for thin cylinders are used to determine elastic vibratory strain energy. Energy methods are applied to obtain the frequency equation and associated amplitude ratios for each of its roots. This energy solution is checked experimentally using a vibration exciter and numerically using the SABOR IV finite element program. With minor modification, the frequency equation conforms to the one obtained in a similar way by Arnold and Warburton for cylinders with clamped ends and simply supported ends. Thus the proposed form of frequency equation, by accommodating a greater variety of boundary conditions, simplifies the task of determining cylinder vibration characteristics.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1041-1047. doi:10.1115/1.3438405.

An energy rate balance is employed to develop the incremental equations of motion for a shock loaded, inelastically constrained rigid-body structural system. Lagrangian multipliers provide the coupling mechanism necessary to reduce the overall system of equations to a set of modified rigid-body equations which include the nonlinear geometric and structural material effects. Kinematic material hardening and a modified yield criteria are used. Examples illustrate the technique and are compared with experimental results.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1048-1053. doi:10.1115/1.3438406.

The finite element method has been extensively applied to the solution of static and dynamic problems. Some work has been done in finite element wave propagation but matrix techniques typically employed require vast amounts of computer main memory and peripheral storage devices. In this work, a method is presented which utilizes the sparse nature of the coefficient matrix. The method enables problem execution in a smaller main memory space than standard techniques. A comparison is made on memory requirements and run times for both standard methods utilizing conventional assembly techniques, some sparse matrix techniques and the proposed scheme.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1054-1059. doi:10.1115/1.3438407.

Prediction of the vibration properties of turbomachine blades and disks is an essential part of turbine design. However, the complexity of modern machines and the necessity to analyze the complete assembly of disk, blades, and shroud combine to make this a lengthy task. This paper describes an investigation aimed at improving the efficiency of such prediction techniques. The assembly is analyzed by studying each component individually and then combining these together with a receptance coupling technique by matching forces and displacements at each connection point. A study is made to establish which of the 6 coordinate directions at each junction need to be included in this process. The results of this study clearly demonstrate the necessity for including certain coordinates while others may be omitted with little loss of accuracy.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1060-1064. doi:10.1115/1.3438408.

In the present paper a series of experimental results obtained by several authors on the phenomena of the vortex street behind a vibrating cylinder are analysed. From this we can establish a flow model for the relationship between the vortex shedding, the cylinder movement, the vortex lift and the variation in the position of the separation point. This relationship reveals that a close synchronization of the vortex shedding and the lift generated by it will arise when the flow velocity enters the lock-in region. Furthermore, the flow model will enable us to predict the narrowing of the vortex street shed by a vibrating cylinder for certain Reynolds number ranges. The theory can thus qualitatively explain the corresponding phenomena observed by Koopmann, Griffin and Votaw.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1065-1071. doi:10.1115/1.3438409.

The phenomenon on the tubes in a tube row, which vibrate alternately along the row in the transverse and stream-wise directions, will be explained by a vortex model. This model consists of the symmetrical vortex pair trains behind the stream-wisely vibrating tubes, and the Karman vortex streets behind the transversely vibrating tubes. It will be shown in the paper that the coupling between these two groups of vortex systems can excite the tube arrays to perform this fluidelastic vibration. A criterion for the onset of this orbital movement will be given with the expression ξ = R/Sxt . This criterion predicts a strong fluidelastic vibration for tubes with low transverse tube spacings and low natural flexible frequencies in a high speed flow. The theory leading to this criterion is based on the phenomenon of the variation in the position of the separation point for the free shear layer during the cylinder vibration. A switching of the jet for maintaining the fluidelastic vibration is then a result of this variation.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1072-1075. doi:10.1115/1.3438410.

The damping criterion previously proposed by Chen 1964/1968 is evaluated with respect to a series of existing units using various fuels. The critical value of this criterion, which was given by Chen as 600 for the ideal case with uniform velocity distribution, has been found to be about 2000 for the tube bank heat exchangers in boiler units. The reason for this difference appears to lie in the degree of uniformity of the velocity distribution over the streaming section. Since the velocity distribution in the boiler units cannot be uniform at all, the vortex streets formed in the tube bank will disturb each other. A large damping will thus arise. The damping criterion can thus be employed to design a sonic vibration-free tube bank through proper consideration of tube spacings, Reynolds number, and Strouhal number.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1076-1081. doi:10.1115/1.3438411.

Although common problems with well established solutions are met in all rotor systems embodying hydrodynamic bearings, a number of factors peculiar to centrifugal pumps radically affect their vibrations response. Close internal clearances retaining pressure act as powerful hybrid bearings. In high performance pumps with vaned diffusers, large hydraulic forces are exerted on the rotor at part-load: these forces depend qualitatively and quantitatively on the ratio of flow to optimum flow. A calculation method taking all relevant factors into account is described. Some typical forced whirling response and stability results for a multistage rotor system are given. The application of calculations to remedial action in a service problem is described.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1085-1088. doi:10.1115/1.3438414.

An experimental investigation into the effect of hydrostatic pressure on corrosion-fatigue at a frequency of 20,000 cycles per sec is reported for a number of materials currently considered for use in the ocean environment. The high-frequency fatigue technique used for this study is based on the principle of producing longitudinal vibrations in a properly designed fatigue specimen at its resonant frequency. This, in turn, produces maximum uniaxial alternating strains at the specimen nodal point. The fatigue specimens are tested in a uniquely designed pressure chamber containing synthetic seawater under constant temperature. The investigation shows that the corrosion-fatigue life of some of the materials tested is significantly reduced when they are subjected to a hydrostatic pressure of 2000 psi as compared to that experienced at atmospheric pressure. It appears that the mechanism of the influence of hydrostatic pressure is primarily chemical in nature. This is evidenced by scanning electron microphotographs of specimens fatigued under hydrostatic pressure which reveal that the fracture surface is rougher and contains multiple crack zones, greater substructure secondary cracking, deeper rivering arrays, and innumerable crack branching. These features are not prevalent in specimens tested at atmospheric pressure.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1089-1096. doi:10.1115/1.3438415.

The paper describes the design, hardware, testing, and performance of a breadboard semi-closed cycle power system proposed for undersea operations by the Naval Undersea Center. The work was performed to prove the feasibility of the system. The system includes a commercially available spark-ignition engine, which operates on natural gas, oxygen, and recirculated exhaust gas, and a specially designed liquid oxygen/excess exhaust gas converter. The converter utilizes heat from dry, precooled exhaust gas to vaporize liquid oxygen and provide oxygen for the engine. While providing heat for liquid oxygen vaporization, the exhaust gas becomes frozen. The well-insulated converter is designed with ample storage capacity for both liquid oxygen and solidified exhaust. Nonoptimized hardware provided reliable airbreathing and nonairbreathing operation. Tests indicate that the approach is feasible for undersea applications.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

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

TECHNICAL BRIEFS

J. Eng. Ind. 1974;96(3):1097-1099. doi:10.1115/1.3438416.

In this work, the stresses in stiffened thick tubes are calculated. The results obtained from the proposed theory are compared with experimental values of stresses measured at the outer surface of steel tubes.

Topics: Pressure , Stress , Steel
Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1974;96(3):1099-1100. doi:10.1115/1.3438417.

This paper presents a generalization of a commonly used stress relaxation relationship. The generalization applies to tension or compression members which have constant elongations and which obey the Bσn creep law.

Commentary by Dr. Valentin Fuster

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In