bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sinusoidal Torsional Buckling of Bars of Angle Section Under Bending Loads, as a Problem in Plate Theory
Authors: Plass H. J. 
Published: April 2021

Abstract
Timoshenko has applied plate theory to each leg of an angle-section bar to determine the critical compressive load needed to cause sinusoidal torsional buckling. In this paper his idea is used to calculate the critical bending load needed to cause sinusoidal torsional buckling of an angle bar. The bending is assumed to be applied so that the extreme fibers of the angle are in compression, the vertex in tension. Approximate results are first obtained by means of the Rayleigh-Ritz method. The approximate deflection functions from which the energy terms are computed are based upon certain infinite-series solutions. After having obtained approximate results, exact values are obtained, using the approximate values as a guide to limit the amount of calculation. The results of this calculation are shown in Fig. 5, where they are compared with those predicted by bar theory. Differences between the two theories become more noticeable as the bar becomes short compared to its flange width. It is found that the critical bending load becomes larger very rapidly as the ratio of length to width of the flanges decreases. Bar theory predicts no such increase. The reason for this difference is explained.
On the Inextensional Theory of Deformation of a Right Circular Cylindrical Shell
Authors: Hermes R. M. 
Published: April 2021

Abstract
The inextensional theory of bending of shells is considered. By the method of superposition the known solution is extended to include two cases which can easily be investigated experimentally. The experimental results are compared with the theoretical solution, indicating the degree of approximation involved in the use of the inextensional theory.
A General Method of Calculating the Mϵmax Diagram in Plastic Bending of Beams
Authors: Phillips Aris 
Published: April 2021

Abstract
In this paper we give a new method for finding the Mϵmax curve in the case of symmetrical pure bending of bars in plasticity. This method is both accurate and comparatively easy to use. At the end of the paper we show how it is possible to express any σ-ϵ curve as the sum of a number of elastic plastic-stress strain lines.
The Time Required for Constant-Volume Combustion
Authors: Campbell A. S. 
Published: April 2021

Abstract
By combining the results of an elementary thermodynamic analysis of the temperature distribution in the burned gases of a constant-volume bomb with an examination of the velocity relations at the flame front, it is possible to relate the “normal burning velocity” to the time rate of production of burned gases. Integration of this equation leads to an estimate of the time required for the combustion process.
Measurement of Recovery Factors and Friction Coefficients for Supersonic Flow of Air in a Tube: 1—Apparatus, Data, and Results Based on a Simple One-Dimensional Flow Model
Authors: Kaye J. , Keenan J. H. , Klingensmith K. K. , Ketchum G. M. , Toong T. Y. 
Published: April 2021

Abstract
For the past few years a program has been under way to obtain reliable data on the rate of heat transfer to air moving at supersonic speeds. The investigation was limited to air flowing at supersonic speeds in a round tube. The program was divided into two separate parts, the first for measurement of the adiabatic wall temperatures of a supersonic stream and the second for the heat-transfer rate. The first part of this program is described here. The details of three experimental test combinations used to measure the adiabatic wall temperature and local state of a supersonic stream of air are presented. The experimental data for forty runs, in the form of measured pressure and temperature distributions, are included. The range of diameter Reynolds number covered is from 0.15 × 105 to 5 × 105. The length Reynolds number extends to 120 × 105. The Mach number at the inlet to the round tube is about 2.6. The calculated quantities such as the local apparent friction coefficient, recovery factor, local Mach number, and so forth, are obtained from the simple one-dimensional flow model for which the properties of the stream are uniform at any cross section of the tube and boundary-layer effects are ignored. A subsequent paper deals with the calculation of these quantities when account is taken of the boundary-layer growth in the tube on the basis of a two-dimensional flow model.
The Theoretical Analysis of Metal-Forming Problems in Plane Strain
Authors: Lee E. H. 
Published: April 2021

Abstract
The plastic flow in plane strain of an ideally plastic material subjected to large strains is considered. Elastic strains are negligible and a rigid-plastic type of analysis is adopted. The equations to be satisfied are detailed, and they include stress and velocity equations in the plastic regions, as well as consideration of the stress field in the rigid regions to check the validity of small strains there. Complete solutions satisfying these conditions require the determination of the rigid-plastic boundaries to delineate the regions in which the various conditions must be satisfied. The fallacy of static determinacy of such problems in terms of the stress equations only is emphasized. The study of complete solutions indicates errors in solutions commonly accepted in the literature which are based on the stress equations only. Examples are discussed. The general occurrence of velocities in the boundary conditions of forming problems is pointed out, and the difficulty of setting such problems in terms of boundary stresses only is illustrated by examples.
Partially Plastic Thick-Walled Cylinder Theory
Authors: Steele M. C. 
Published: April 2021

Abstract
Previous theories for partially plastic thick-walled cylinders under internal pressure are reviewed. A quantitative comparison is given for (a) compressibility versus incompressibility of material, and (b) von Mises’ versus Tresca’s theory of failure. The former reveals that deflections at the outside and bore surfaces agree closely, although considerable percentage differences may be found in the axial stresses and strains. Large differences (except for the axial stress) are found in comparing the two theories of failure. Based on the comparison and available experimental evidence, a theory is presented in closed form to include the Hencky stress-strain relations, incompressibility, and Ludwik’s strain-hardening function.
Heat-Exchanger Tube-Sheet Design—2: Fixed Tube Sheets
Authors: Gardner K. A. 
Published: April 2021

Abstract
It is shown that “fixed” tube sheets may be designed in exactly the same manner as “floating” tube sheets with the same boundary restraint, provided that a fictitious uniform “equivalent design pressure” is used in the calculations instead of the actual hydrostatic pressure. This equivalent pressure is evaluated in terms of tube-side pressure, shell-side pressure, differential thermal expansion, and the condition of boundary restraint. The design factors for all tube sheets presented in an earlier paper are shown to be well represented by very simple expressions when the fundamental design parameter xa becomes large.
Lateral Vibrations as Related to Structural Stability
Authors: Lurie Harold 
Published: April 2021

Abstract
The apparently different physical problems of lateral vibration and elastic stability are limiting cases of a single phenomenon, the more general expression being the mode of vibration with end thrust. It is shown that the square of the frequency of lateral vibration is approximately linearly related to the end load. The linear relationship is exact if the mode of free vibrations is identical to the buckling mode. In all cases, the load corresponding to zero frequency is the critical buckling load. Experimental tests were conducted on elastically restrained columns in the form of rigid rectangular frames. It was found that the relationship between the square of the frequency and the load is practically linear, and that the extrapolated load corresponding to zero frequency coincides with the buckling load. Rigid-joint trusses also were tested. In some cases the relationship between the square of the frequency and the load deviates considerably from linearity, but the approximate buckling load can be predicted. In the case of thin flat plates, tests showed that the buckling load cannot be predicted from vibration tests in practice. It is indicated that this is probably because the linear plate equations are not valid owing to initial curvatures in the plate.
Bending Vibrations of a Pipe Line Containing Flowing Fluid
Authors: Housner G. W. 
Published: April 2021

Abstract
Both free vibrations and forced motions due to crosswinds may create important problems in the design of pipe lines supported above ground. An analytic investigation, based on simple beam theory, shows that the flow of fluid in such a pipe line has no beneficial effect upon the vibrations. The fluid velocity causes a dynamic coupling of the simple modes of vibration so that the normal modes of vibration are of complex shape with 90-deg out-of-phase components. The solution is presented for free vibrations and for steady-state forced vibrations, and it is shown that large amplitudes may be developed if the amount of damping is too small. It is shown that at low fluid velocities there is negligible effect upon the vibration of the pipe line, and at a certain high critical velocity the fluid flow causes a dynamic instability. The present analysis revises the conclusions which appeared in an earlier publication.
The Computation of Flexural–Torsional Buckling Loads
Authors: Michielsen H. F. 
Published: April 2021

Abstract
Solution by ordinary means of the cubic equation for the torsional buckling load, first derived by Kappus, often leads to insufficiently accurate results. A method is presented which avoids the loss of accuracy involved. The procedure is straightforward and no graphical means are involved. However, one formula is to be solved by trial and error.
Analysis of Elastic Two and Three-Section Short Columns
Authors: Tyler C. M. , Lee F. Z. 
Published: April 2021

Abstract
Short columns subjected to repeated loading or in which permanent deformation is not permissible should be designed on the basis of maximum fiber stress. This stress may vary considerably in apparently identical columns owing to small inaccuracies of shape and application of load. The effects of all probable deviations of both column and load can be represented by an “equivalent eccentricity of loading” or by an “equivalent curvature of the column” (1, 2). These equivalents are so chosen that calculated fiber stresses will equal the maximum probable stress encountered in the actual column. In the paper, analytical formulas in terms of equivalent eccentricity are developed for two and three-section short columns. These may be considered as extensions of the secant column formula (3) to more complicated shapes. Specific numerical examples of sectional short columns may be analyzed by a relaxation method (4). Sectional long columns have been treated by Thompson (5) and Radomski (6).
Optimum Single Propellers in Radially Varying, Incompressible Inflow
Authors: Lane Frank 
Published: April 2021

Abstract
The Betz process for minimizing the energy loss of single propellers is extended to the propeller operating in radially varying inflow, with a view toward the development of optimum stern propulsion for bodies of revolution. Assuming the usual lifting-line treatment of the propeller blades, an application of the isoperimetric problem in the calculus of variations is directed toward minimizing the energy loss while maintaining constant total thrust. Resulting expressions describe the optimum radial distribution of induced velocity in terms of an undetermined multiplier. The magnitude of the required total thrust, in turn, fixes the value of this multiplier, making the solution determinate. Inclusion of blade-profile drag at a later point in the development serves to determine an optimum propeller diameter for minimum over-all energy loss. The method gains in accuracy as the ratio of blade number to advance ratio increases, due to an approximation in the relation between the circulation and induced velocity.
Experiments on the Plastic Compression of a Block Between Rough Plates
Authors: Nye J. F. 
Published: April 2021

Abstract
Hill, Lee, and Tupper have recently published a theory for the plastic compression of a block between parallel plates. This paper describes experiments designed to check the theory as closely as possible. The theoretical predictions for the average pressure on the plates are very well verified by the experiments. The details of the strain distribution within the block and the positions of the elastic-plastic boundaries are closely compared with the theory.
The Plane-Stress Problem of Perforated Plates
Authors: Horvay G. 
Published: April 2021

Abstract
In an earlier paper it was indicated that perforated plates of triangular layout, with narrow ligaments, as they occur, for instance, in heat-exchanger tube sheets, can be treated in plane-stress calculations as solid sheets of suitable elastic moduli, provided that the stress distribution does not vary appreciably from hole to hole. This paper completes that study by providing suitable curves (Figs. 4, 8), from which deformations and stresses can be read off in terms of the values calculated for solid sheets, for mechanical, thermal, and gravitational loads.
Temperature Development in a Heated Contact With Application to Sliding Contacts
Authors: Holm Ragnar 
Published: April 2021

Abstract
The calculation of the development of the temperature in and around a heated contact is reduced to the use of some simple formulas for certain fundamental variables and to making readings from a diagram. Applications are made to a contact that is heated by the current and to circular or oval heat sources (for example, friction-heated sliding contact-surfaces) stationary or moving on the face of a semi-infinite body. The practicability of the method is due primarily to the fact that the numerical calculations, which are made before using the standard curves, are so simple that the chance of a numerical error is very small.
A Mathematical Analysis of the Relaxation Type of Vehicle Suspension
Authors: Gallagher Joseph , Volterra Enrico 
Published: April 2021

Abstract
The responses of the relaxation type of vehicle suspension to steady and transient disturbances are analyzed. The results are compared with the corresponding responses for the standard type of vehicle suspension. The relaxation suspension system shows a definite improvement over the standard suspension system in the response to transient disturbances, as the initial shocks following a sudden wheel movement are reduced greatly. In the particular case of critical adjustment of a relaxation suspension system the maximum amplitude of the transient vibration is approximately 30 per cent lower than that of the standard-type system at critical adjustment. The amplitude and phase-angle curves presented in the paper for the steady-state motion, together with the transient-state-response analysis, permit the design of a relaxation-type suspension system with known vibrational characteristics in both states.
Pressure Drops in the Pneumatic Conveyance of Solids
Authors: Pinkus Oscar 
Published: April 2021

Abstract
With the object of studying the characteristics of the horizontal flow of a mixture of solids and air a theoretical analysis of the flow pattern was attempted. Experiments were performed whose object was to determine the relationship between pressure loss, solids flow rate, and air velocity, and to obtain values for the frictional constants involved in the analysis. A justification for the developed equations was sought. It was found that the presence of the solid phase causes an appreciable pressure loss which is a linear function of both solid and gas flow rate. This justified the theoretical equations which predicted such a relationship. Experiments with two sizes of the same sand showed a higher pressure drop for the larger particles, other conditions being equal. These experiments, however, question the validity of applying the Fanning equation to a solid phase. The equation holds for a given solid but does not take into account variations in its size. The introduction of the dimensionless group d/D is proposed. On the basis of this investigation, it is concluded that the drag coefficient C is a function of the Reynolds number. The ratio of solids velocity to gas velocity is 0.5–0.6 for the small and 0.3 for the large sand. Following results of this work it would seem desirable to operate pneumatic systems at low gas velocities and high solid rates. Recommendations for further investigations are made.
Parameter Identification for Electrochemical Models of Lithium-Ion Batteries Using Sensitivity Analysis
Authors: Dangwal Chitra , Canova Marcello 
Published: April 2021

Abstract
Predicting the chemical and physical processes occurring in Lithium-ion cells with high-fidelity electrochemical models is today a critical requirement to accelerate the design and optimization of battery packs for automotive and aerospace applications. One of the common issues associated with electrochemical models is the complexity of parameter identification, particularly when relying only on experimental data obtained via non-invasive techniques. This paper presents a novel approach to improve the common methods of parameter calibration that consists of matching the predicted terminal voltage to test data via optimization methods. The study is conducted for an nickel-manganese-cobalt (NMC)-graphite cell, modeled using a reduced-order Extended Single Particle Model (ESPM). The proposed approach relies on using a large-scale particle swarm optimization (PSO), modified by including a term that accounts for the parameter sensitivity information, such that the rate of convergence and robustness of the algorithm to obtain a consistent solution in the presence of uncertainties in the initial conditions are significantly improved.
Ultrathin and Porous NiCo2O4 Nanosheet-Based Three-Dimensional Hierarchical Electrode Materials for High-Performance Asymmetric Supercapacitor
Authors: Ren Fuyong , Tong Zhixiang , Tan Shufen , Yao Junnan , Pei Lijun , Ji Yajun , Abulizi Abulikemu 
Published: April 2021

Abstract
It is well known that designing unique morphology and the structure of electrode materials is an effective strategy to achieve high-performance supercapacitors (SC). Herein, the ultrathin and porous NiCo2O4 nanosheet-based three-dimensional (3D) hierarchical electrode materials were synthesized via a simple and cost-effective solvothermal method and subsequent annealing process. Since the ultrathin and porous nanosheets could accelerate the transmission of ions and provide numerous active sites, the obtained NiCo2O4 nanosheet-based electrode exhibited great electrochemical performance with a high area capacity of 5.38 F/cm2 (2690 F/g1) at a current density of 10 mA/cm2 and good rate performance of 41% capacitance retention at 50 mA/cm2. Furthermore, the corresponding asymmetry supercapacitor was assembled by using the resulted NiCo2O4 nanosheets and active carbon as a positive electrode and a negative electrode, respectively. As expected, the corresponding supercapacitor delivered a superior energy density of 52.6 Wh/kg at a power density of 1.1 kW/kg and extraordinary capacitive retention of 80.9% after 3000 cycles at 20 mA/cm2. The high-energy storage performances suggested that the obtained ultrathin and porous NiCo2O4 nanosheet-based 3D hierarchical electrode materials could be a prospective candidate in the field of energy storage.
The Polytropic Approach in Modeling Compressible Flows Through Constant Cross-Section Pipes
Authors: Ferrari Alessandro , Vento Oscar , Zhang Tantan 
Published: April 2021

Abstract
A compressible flow with wall friction has been predicted in a constant cross section duct by means of a barotropic modeling approach, and new analytical formulas have been proposed that also allow any possible heat transfer to the walls to be taken into account. A comparison between the distributions of the steady-state flow properties, pertaining to the new formulas, and those of a classic Fanno analysis has been performed. In order to better understand the limits of the polytropic approach in nearly chocked flow applications, a numerical code, which adopts a variable polytropic coefficient along the duct, has been developed. The steady-state numerical distributions along the pipe, obtained for either a viscous adiabatic or an inviscid diabatic flow by means of this approach, coincide with those of the Fanno and Rayleigh models for Mach numbers up to 1. A constant polytropic exponent can be adopted for a Fanno flow that is far from choking conditions, while it cannot be adopted for the simulation of a Rayleigh flow, even when the flow is not close to choking conditions. Finally, under the assumption of diabatic flows with wall friction, the polytropic approach, with a constant polytropic exponent, is shown to be able to accurately approximate cases in which no local maximum is present for the temperature along the duct. The Mach number value at the location where the local maximum temperature possibly occurs has been obtained by means of a new analytical formula.
Hardened Edges Effects on Wear Characteristics of Cultivator Sweeps Using Circular Soil Bin Test
Authors: Tekeste Mehari Z. , Balvanz Loran R. , Al-Aani Firas , Boesenberg Adam , Hatfield Jerry L. 
Published: April 2021

Abstract
Tillage tools are subject to friction and low-stress abrasive wear processes with the potential deterioration of the desired soil quality, loss of mechanical weed efficacy, and downtime for replacing worn tools. Limited experimental methods exist to quantify investigate the effect of wear-resistant coatings on shape parameters of soil-engaging tools. ASTM standard sand/rubber wheel abrasion and pin-on-disk tests are not able to simulate wear characteristics of the complex shape of the tillage tools. Even though the tribology of tillage tools can be realistic from field tests, tillage wear tests under field conditions are expensive and often challenging to generate repeatable engineering data due to variable soil conditions in the field. A technique that simulated tillage wear of cultivator sweep in a circular soil bin filled with abrasive gravel medium and moisture condition was developed and applied to quantify the wear characteristics of cultivator sweeps with and without hardfaced edges. The hardfaced cultivator sweep had a cemented carbide chip applied to the bottom cutting edge and front tip sections of a standard cultivator sweep according to a proprietary CADEN Edge welding process. The CADEN Edge hardfaced sweeps showed improved wear performance 1.7 times and 3.5 times on mass and shape (sweep length and sweep wing cutting width) dimensions, respectively, compared with the un-hardened standard sweep. The results implied hardfaced cultivator sweep with cemented carbide chips provide potential in maintaining tillage productivity and the desired soil quality for seed-bed preparation.