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RESEARCH PAPERS

J. Eng. Ind. 1962;84(1):1-7. doi:10.1115/1.3667427.

Now that a number of techniques exist which permit the fabrication of circuits with a theoretical packing density of 1 million or more circuits per cubic foot, thermal design is an essential initial consideration. In most cases the drive toward microminiaturization is based on the need for a large number of circuits in a small weight and volume. If present circuit designs are taken as the basis for microminiaturization, it can be shown that with most materials being considered the temperature will rapidly rise to the point where circuits will become inoperative. This paper outlines some of the basic considerations in terms of heat conductivity of materials, maximum safe working temperatures, and circuit power levels as dictated by current devices. A method is described whereby a proposed design configuration can be computer-analyzed in terms of isothermal lines and maximum hot spot temperatures and decisions made on that basis as to which type of cooling is most appropriate.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):8-14. doi:10.1115/1.3667449.

Hydraulic servomechanisms are sometimes used to drive a load member which is predominantly inertia. The usual overriding requirements for output disturbance discrimination and high power efficiency dictate a simple closed center, flow type, servo valve, and a positive displacement actuator. The resulting transfer function relating output velocity to servo valve input current invariably includes an underdamped quadratic lag due to fluid compliance. In simple hydraulic servo systems, the corner frequency of this quadratic lag represents the absolute limit to system bandwidth. Pressure feedback systems have been devised to damp the fluid resonance so effectively that bandwidth extension beyond the quadratic corner frequency is entirely feasible. Unfortunately, such a scheme destroys the natural output disturbance discrimination inherent in the closed center hydraulic systems. A hybrid method of compensation is proposed whereby pressure feedback occurs only in the region of the resonant frequency, effectively preserving the natural output disturbance discrimination characteristics at the lower frequencies. The pressure drop across positive displacement type hydraulic actuators is a good measure of acceleration. Therefore, the technique involves feeding back this load differential pressure, sensed by electromechanical transducers, through a simple RC high pass (derivative) filter. The effectiveness of the damping is determined by the filter time constant and loop gain. Experimental results verify linear predictions of the possibility of extending the closed loop bandwidth beyond the uncompensated resonant frequency.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):15-20. doi:10.1115/1.3667399.

A method of measurement of the four-pole parameters of a system as a function of frequency is presented. This procedure consists of no-load dynamic measurements followed by measurements under a known load. From the foregoing measurements, the four-pole parameters of a system are derived. Application is made to an electrodynamic motion exciter with graphical presentation of the parameters with respect to amplitude, phase angle, real, and imaginary parts.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):21-34. doi:10.1115/1.3667429.

This paper deals with the application of the method of four-pole parameters to torsional vibrations. Results are developed from fundamental principles. The four-pole parameters for the basic rotational elements are derived. These include shafts (both lumped and distributed-parameter cases), disks, dampers, and gears. The equations which must be obeyed, when these elements are connected, are presented. The application to construction of equivalent electrical circuits is given and in particular a method for constructing the equivalent circuit of distributed-parameter systems is put forth. The torsional analogs of Thevenin’s and Norton’s theorems are given for rotational sources. The fundamentals mentioned above are then applied to the following problems: (a) The effect of substituting one four-pole for another in a torsional system. (b) The effect of opening a four-pole system and inserting a new four-pole between the separated four-poles. (c) Calculation of all the torques and angular velocities in a tandem system. (d) Calculation of natural frequencies of undamped four-pole systems.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):35-41. doi:10.1115/1.3667430.

Thermal stresses in cylinders, perfectly insulated on the outside and subjected to internal heat generation due to γ-ray radiation, are considered. Numerical values for the governing stress are presented up to q = 7 and η = 100. The asymptotic values are indicated, which permits the treatment of any problem of practical interest. Three simplified solutions, containing only elementary functions, are evaluated. These approximations are found to be surprisingly accurate, at least one of them being of sufficient engineering accuracy over the entire range of variables.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):42-47. doi:10.1115/1.3667432.

Studies were undertaken to determine a practical method of reducing the ozone content of cabin intake air typical of high-altitude, high-speed aircraft. To make use of the aircraft ram air temperature rise, catalytic filters were investigated for purposes of ozone destruction. The effective temperature range and life of the more promising catalytic materials were investigated. A brief study of ozone adsorptive materials at lower temperatures is included.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):49-52. doi:10.1115/1.3667436.

Land and crater wear data, obtained when machining SAE 1045 hot-rolled steel with Kennametal type KM carbide-tipped tools and with air, flood, and mist as cutting media, are presented. The volume of workpiece material which has to be removed to attain an average land width of 0.030 in. and a maximum crater depth of 0.010 in. is plotted versus the cutting speed. From these results the conditions of cutting speed and medium at which either land or crater wear governs tool life are established, as well as the cutting medium which permits the removal of the greatest volume of workpiece material at a given cutting speed.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):53-62. doi:10.1115/1.3667438.

Orthogonal cutting tests with artificial flank-wear lands were performed on steel SAE 1112 as-received (cold-drawn), steel SAE 4135 as-received (cold-drawn), aluminum alloy 6061-T6 (extruded), and alpha-brass as cold-drawn. Forces, workpiece temperature, average tool temperatures, and other pertinent data were taken. Each test was of short duration (approximately 10 revolutions of the workpiece or less) and the tools were reconditioned between each test run. The results show that, for steel SAE 1112, steel SAE 4135, and aluminum alloy 6061-T6, sublayer flow appears to take place when the flank wear-land clearance angle is set to a negative angle of magnitude −1 deg and the land is approximately 0.010 to 0.020 in. long. The condition for sublayer flow is predictable based on the state of plastic deformation and the stress-strain properties, at temperature and at appropriate strain rates for these materials.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):63-70. doi:10.1115/1.3667440.

The orthogonal metal-cutting process was reanalyzed and the several existing theories are discussed. Alternate methods of presentation of the theories were derived in terms of energy ratios and are shown graphically in the paper.

Topics: Metal cutting
Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):71-79. doi:10.1115/1.3667441.

The orthogonal metal-cutting process has been studied. It was found that the Ernst and Merchant solution, through the application of the limit-load theorems, appears to be a limiting solution for all cutting conditions. A new angle relationship has been developed from energy considerations and it was found that the new parameters, effectiveness η and machinability factor ξ, permit a better understanding of the machining process. It was found further that machining forces and power can now be predicted when the effectiveness η, the constant dynamic shear strength τ of the work material, and the chip ratio r or the friction angle β are known.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):81-88. doi:10.1115/1.3667446.

Plastic deformation in commercially pure lead strips during torque-free rolling was investigated. The experimentally determined slip-line field was compared with the theoretical solution of a similar problem and was found to be different, having a plastic-rigid boundary with inflection points at the entrance section. It was observed that plastic deformation occurred well ahead of the initial contact point between the strip boundaries and the roll surfaces.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):89-98. doi:10.1115/1.3667448.

Tools which provide controlled contact on the tool face are used to study the action of free machining steels. The mean normal stress on the tool face σc is found to increase with increased undeformed chip thickness (t = feed) or with a reduction in the controlled length of tool face contact. An increase in σc in turn is found to promote the stability of the built-up edge to higher speeds. The high-speed finish produced with a cut-away tool is thus found to be inferior to that produced with a conventional tool. Manganese sulfide is found to have a similar effect on surface finish, but lead tends to improve the finish obtained at a high cutting speed. The cut-away tool provides improved low-speed finish in all cases as does the addition of either manganese sulfide or lead to the steel. Manganese sulfide is found to become more effective with increased undeformed chip thickness t, while lead behaves in the opposite manner. This observation along with several others is in agreement with the idea that manganese sulfide is a poor solid “lubricant,” while lead is an effective solid lubricant. An optimum chip-tool contact length appears to exist at which the tool life will be a maximum at any combination of cutting speed and feed. From this it follows that an optimum combination of sulfur or lead content, degree of cold work, cooling capacity of cutting fluid, or extent of tool-face limitation exists, since all of these quantities influence the resultant length of contact between chip and tool.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):103-111. doi:10.1115/1.3667380.

A graphical method for the investigation of regenerative machine tool chatter is presented. The method is based on the harmonic response locus of the machine tool structure and allows the determination of the stable and unstable cutting speed ranges. The chip thickness variation effect as well as the penetration rate effect are taken into consideration. The method is illustrated by a number of examples relating to drilling or spot facing chatter arising on a radial drilling machine. The effects of mode interaction and of the penetration rate on the stability and on the variation of the chatter frequency are discussed. A critical assessment of the method is presented, in comparison with other methods available.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):113-126. doi:10.1115/1.3667383.

A new method for evaluating the hardness of grinding wheels has been developed. It involves crushing small amounts of abrasive from the surface of a grinding wheel while in rolling contact with a hard steel wheel. Measured reaction forces provide a sensitive indication of significant variations in the hardness as well as other important properties of bonded abrasives. A laboratory analysis of the method demonstrates that the hardness values incorporate the same elastic constants which have been shown to be important in actual grinding. The analysis shows also that it is feasible to establish a universally applicable industrial standard for grinding wheel hardness. The method is valuable also as a research tool and may be expected to aid in producing more uniform abrasive products and to yield information which will help improve practices in the manufacturing plant.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):129-132. doi:10.1115/1.3667387.

A photoelastic study was made of the superposition of stress raising notches. Recent investigations [1, 2] have indicated that where one stress raising notch is placed in the region of maximum influence of a second notch the resulting stress concentration factor may be determined by taking the product of the concentration factors for the individual notches. Test results presented gave general although not precise agreement with this method of combination. The tests of reference [1] were performed on specific materials for static and repeated loads, and hence combine the effects of stress concentration with the sensitivity of the particular material. The tests of reference [2] run on a brittle material indicate the same general agreement. Normal practice for applying stress concentration factors separates the two effects, i.e., the actual concentration of stress and the sensitivity of the material to such concentration. It was believed that photoelasticity might yield a better verification of the method for combining superposed stresses as photoelastic methods have shown close agreement with theoretical factors of stress concentration. Results of the present investigation indicate that the product gives the combined concentration factor with the same degree of accuracy to which the individual factors are known. A mathematical analysis was made to determine the stresses across the section.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):135-143. doi:10.1115/1.3667392.

A general method is presented for generating controlled rectilinear motion to any desired accuracy. The required motion is expressed in terms of a Fourier series whose coefficients are shown to be related to the governing dimensions of a plane mechanism. The mechanism may be designed to generate enough terms of the Fourier series to satisfy any desired accuracy. The technique is then used for a particular problem to illustrate its application and the method by which the error of approximation may be evaluated.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):144-148. doi:10.1115/1.3667394.

Expressions are derived for the bond stresses induced by a radially symmetric temperature distribution in spherical propellant grains bonded to spherical casings. Equations for the evaluation of radial and tangential stresses in the propellant and its casing have also been derived. Both solid and hollow propellant grains have been investigated. Design considerations have been developed to enable the designer to minimize the bond stress. A comparison between the hollow and solid spherical propellant assembly shows that the hollow sphere has a lower bond stress than the solid sphere, assuming all other factors are the same.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):149-155. doi:10.1115/1.3667396.

Expressions are derived which relate the maximum stresses encountered in simply supported beams and rectangular plates and in clamped circular plates vibrating at resonance to modal displacements and modal loadings. Computation of modal loadings from time-wise harmonic or random pressures is discussed. It is shown that the resonant maximum stress may be reasonably approximated by a simple formula suitable for conservative design calculations for all types of beams and plates.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):156-159. doi:10.1115/1.3667397.

The nature of the curves which can be generated by points on mechanisms is described in two theorems.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):161-164. doi:10.1115/1.3667402.

Some basic properties which govern the design of constant diameter cams and open cams with flat faced translating followers will be developed. It will be shown that the radius of cam curvature is the governing criterion and its proper use makes design of constant diameter cams for any desired dynamic characteristic possible.

Topics: Cams , Design
Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):165-178. doi:10.1115/1.3667408.

A complete thermodynamic analysis of closed, reversible, regenerative gas cycles is developed which among other refinements takes into account heat-transfer limitations, regenerator inefficiency, and flow losses. This results in a set of equations for the cyclic variations of temperatures, pressures, and flow rates in different parts of the system. A heat balance is set up for the integrated heat transfer and mechanical energy conversions per cycle and an accurate figure for the efficiency of prime movers or the Coefficient of Performance of heat pumps or refrigerators is derived from this. Special computational techniques simulating a differential analyzer on an IBM 704 electronic computer are described and the results of a typical practical case are given in graphs and figures.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):180-188. doi:10.1115/1.3667414.

The design of an apparatus for determination of Joule-Thomson coefficients is presented. An axial flow porous plug is utilized and the downstream flow is so arranged that one concentric flow path serves as a heat shield for the other. This guard-ring principle, together with virtual elimination of radiation and convection heat transfer, reduces the heat leakage that has been associated with previous axial-flow designs. A prototype was constructed and tested with gaseous nitrogen. The Joule-Thomson coefficients obtained agree, in the range 2-20 atmosphere and 50-150 C, within one per cent with published values.

Commentary by Dr. Valentin Fuster
J. Eng. Ind. 1962;84(1):191-195. doi:10.1115/1.3667420.

This paper presents a simplified method of tension calculations in belt conveyers, suggesting the same approach regardless of whether belts are straight or curvilinear. A Key Diagram is introduced for the quick identification of critical tensions for all basic conditions. It is common practice to use an analytical method for the calculation of tensions and horsepower of more complicated belt conveyers, especially curvilinear belt conveyers. The big advantage of this method is that it permits the establishment of tension values for the design of concave and convex curves and also for the design of drive and take-up when not located at conveyer ends. However, the so-called analytical method has a distinct disadvantage in practical engineering—it is tedious and time-consuming. The purpose of this paper is to present a faster way to find all belt tensions necessary for the proper design or selection of conveyer components.

Topics: Belts , Design , Tension , Horsepower
Commentary by Dr. Valentin Fuster

DISCUSSIONS

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

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