bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Properties of a Moving Thread Line
Authors: Moustafa M. A. , Salman F. K.
Published: November 2010

A mathematical model representing the transverse vibration of axially moving elastic strings is presented considering tension and mass variation. A suggested numerical scheme was successfully used to solve the nonlinear partial differential equations of motion. For axially nonmoving strings, the effect of initial amplitudes, and consequently the tension variation on the fundamental frequency is obtained. Also, the effect of the initial tension and the mass of the string per unit length on the fundamental frequency and their corresponding mathematical relations are presented. For axially moving strings, the effect of the axial velocity on the fundamental frequency as well as the tension distribution along the thread is given. Also the behavior of the string at velocities equal and greater than the wave speed is shown.
Some Aspects of Computer Numerical Control With Reference to Interpolation
Authors: Milner D. A.
Published: November 2010

In the production of a component by numerical control various stages require relatively different volumes of data, as is indicated in the paper. Three different types of interpolation are indicated and corresponding program sizes obtained. Finally the “way ahead” regarding interpolation is given and mention made of the other two vital functions, namely, the control of acceleration/deceleration and the closing of the position loop.
Vibration Damping Characteristics of Multilayered Beams With Constrained Viscoelastic Layers
Authors: Asnani N. T. , Nakra B. C.
Published: November 2010

Results are reported on damping effectiveness during flexural vibrations of multi-layered beams, with constrained viscoelastic layers. These are given for simply supported beams with number of layers up to 15, all viscoelastic layers being identical. The elastic layers are also taken to be similar to one another. The influence of number of layers and thickness ratio of viscoelastic to elastic layers, for constant size, constant weight and constant static stiffness criteria, has been studied. In order to obtain maximum value of loss factor or of displacement response effectiveness for multilayered beams, under specific requirements of static stiffness, weight and size, a suitable choice of number of layers and thickness ratio of viscoelastic to elastic layers, is found to be important.
Metal Flow in Two-Die Swaging
Authors: Ovens W. G. , Bartholomew E. L. , Biederman R. R.
Published: November 2010

A study of materials subjected to reductions in area by two-die swaging shows that non-uniform hardening occurs. The amount of cold work strengthening on the surface is the same as that for a similar reduction in area by cold rolling. The center hardness, however, is significantly greater. Cracks at the center of specimens are frequently observed. These effects are attributed to redundant working since successive blows strike new areas around the periphery but every blow affects the center.
Analysis of Flexible Rotor Whirl and Whip Using a Realistic Hydrodynamic Journal Bearing Model
Authors: Myrick S. T. , Rylander H. G.
Published: November 2010

An analytical method has been developed for the simulation of the transient and steady-state response of flexible rotors supported by realistic incompressible-film hydrodynamic journal bearings. The coupled nonlinear differential equations of rotor motion, formulated as an initial-value problem, are solved in conjunction with a “realistic” Reynolds equation solution which includes finite bearing length, wedge and squeeze films, fluid film cavitation, oil inlet geometry, and eccentricity and tilt (gyroscopics) of the journal. Presented in this paper are some of the results of a numerical and experimental study of rotor whirl using that analytical model. The response of a flexible rotor, for speeds up to the threshold of instability, is demonstrated as a function of disk unbalance and viscous damping. The validity of the analytical model is confirmed by comparison of experimental whirl data with numerical simulations of the response of the test rotor through the critical speed region to the onset of oil whip.
An Experimental Investigation of the Dynamic Behavior of the Spatial RSSR Crank and Rocker Mechanism With an Asymmetrical Coupler
Authors: Begg W. S. , Ellis J. R.
Published: November 2010

An experimental RSSR crank and rocker mechanism has been devised and manufactured to facilitate the dynamic investigation of the input and output torques present, the force components acting in the link members and at the joints of the machine under various loading conditions, for a number of different configurations. The behavior of the so-called redundant or passive degree of freedom is also investigated by means of a coupler (floating link) having its center of gravity offset from the center line of the spherical joints at its ends. Experimental observations are made for the constant torque and constant velocity input conditions, as obtained in a practical mechanism, for the various machine configurations and loading arrangements. An analytical model is developed using the classical Newton-Euler approach and an example of the correlation of the analytical and experimental results is given.
The Role of Fracture Mechanics in Design Technology
Authors: Sih G. C.
Published: November 2010

Fracture mechanics has in recent years become an independent discipline that deals with determining the conditions under which machine or structural elements attain uncontrollable failure by crack propagation. A knowledge of these conditions can assist the designer to safeguard structures against catastrophic fracture. In contrast to the conventional approach, which does not account for flaws initiated in the material by manufacturing procedures, overloads, or fatigue loadings, fracture mechanics [1] assumes that all materials contain cracks from which failure starts. This concept has been used successfully for high-strength/low-toughness materials design and for structures that exhibit brittle behavior. Obtained from laboratory specimens loaded symmetrically with respect to the crack plane is a critical stress intensity factor parameter K1c. It is a characteristic of the material commonly referred to as the fracture toughness value. When machine elements are subjected to combined loading, where symmetry does not exist, the direction of crack initiation is no longer known as an a priori. The condition of crack instability can then be predicted from the strain energy density factor S whose critical value, Sc, is related to K1c from uniaxial tension tests by the relation Sc = (1 − 2ν)K1c2/4 π μ, with ν being the Poisson’s ratio and μ the shear modulus of elasticity. Numerous numerical examples involving press fit, rotating disk, thermally stressed pipe, pressure vessel, etc., are presented to show how fracture mechanics can be used for estimating the load that a member can sustain without causing unstable fracture. The results are compared with those obtained from the conventional design approach whenever possible.
A Computer Simulation Model for Determining Fleet Size and Composition
Authors: Schultz G. C. , Enscore E. E.
Published: November 2010

A heterogeneous vehicle fleet is one that is composed of several types of vehicles. The number of each type of vehicle in the fleet is called the fleet’s composition. The problem of determining the best fleet size and composition for an in-house heterogeneous company fleet having a known demand was solved in this paper. A computer model was developed which tied a fleet simulation model to two different search algorithms. One of the search algorithms is a complete factorial nonsequential search and the other is a combination of a partial factorial nonsequential search and a heuristic sequential hill-climbing search. The objective of both searches is to select the fleet size and composition which provides the lowest total vehicle travel costs to the company. Several examples were used to demonstrate the use of the model.
Effects of Truck Design on Hunting Stability of Railway Vehicles
Authors: Hadden J. A. , Law E. H.
Published: November 2010

A general model of a dual-axle railway vehicle truck is derived. By suitable choices of primary suspension elements, this general model may be specialized to become (1) a roller-bearing freight truck, (2) a plain-bearing freight truck, (3) a roller-bearing truck with primary suspension elements, (4) a passenger truck, (5) a generic model of a freight truck with interconnected wheelsets, or (6) a rigid truck. The truck model is combined with a car body capable of lateral and roll displacements. The effects of the various design parameters on the critical speed for hunting are examined for each configuration.
Optimization of Cutting Conditions for Multi-Pass Operations Considering Probabilistic Nature in Machining Processes
Authors: Iwata K. , Murotsu Y. , Oba F.
Published: November 2010

This paper deals with the problem of optimizing the number of passes required together with the cutting speed, the feed, and the depth of cut at each pass for a given total depth of cut to be removed from a workpiece, considering both the probabilistic nature of the objective function and the constraints in the machining processes. Applying the concept of dynamic programming and stochastic programming, the problem is formulated in an analytically tractable form and a new algorithm is developed for determining the optimum value of the cutting speed, feed, depth of cut, and number of passes, simultaneously. For illustration, a typical example is solved to obtain the cost-minimizing cutting conditions in a turning operation, and the effect on the optimum cutting conditions of the various factors such as total depth of cut, uncertainty of the tool life, and constraints are discussed.
Cut-Forming: A New Method of Producing Wire
Authors: Hoshi T. , Shaw M. C.
Published: November 2010

A new method of making wire is discussed in which cutting and forming are combined into one process. A chip is first obtained by cutting a billet using a specially designed cutting tool. This chip immediately enters a circular die adjacent to the cutting edge of the tool and is forced past the orifice of the die by the cutting force. The chip leaving the orifice is in the form of a perfectly round wire.
Natural Resting Aspects of Parts for Automatic Handling
Authors: Boothroyd G. , Ho C.
Published: November 2010

A theoretical study is made of the orientations in which small parts will naturally feed in a vibratory-bowl feeder. The results are applied to regular prismatic part shapes and are tested experimentally. The results of the work are useful in the analysis of vibratory-bowl feeder orienting systems.
Investigation of Spiking in Electron Beam Welding Using Stationary Stochastic Models
Authors: Phadke M. S. , Joglekar A. M. , Wu S. M.
Published: November 2010

The spiking phenomenon in electron beam welding is characterized using the second-order continuous autoregressive model. The model parameters are then physically interpreted in terms of the random fluctuation in the beam power and the diffusion of heat energy in the plates being welded; and a mechanistic model is proposed for the spiking phenomenon. Finally, regression models are obtained to relate the spiking behavior to the accelerating voltage, the beam current, and the welding speed.
The Generalized Reduced Gradient Method: A Reliable Tool for Optimal Design
Authors: Gabriele G. A. , Ragsdell K. M.
Published: November 2010

This paper is a presentation of a method, called the Generalized Reduced Gradient Method, which has not received wide attention in the engineering design literature. Included is a theoretical development of the method, a description of the basic algorithm, and additional recommendations to produce an efficient code. A Fortran code employing this theory was written and tested on the Eason and Fenton [1] test problems, illustrating the method to be efficient and reliable.
Spherical Acrylic Plastic Hulls Under External Explosive Loading
Authors: Stachiw J. D.
Published: November 2010

NEMO-type acrylic spherical hulls have been subjected to underwater explosions in order to determine their resistance to hydrodynamic impulse loading. Six 15-in. OD and one 66-in. OD spheres have been subjected to explosions of sufficient magnitude to initiate fracture in the hull. The tests were conducted at simulated depths of 10, 100, 1000, and 2000 ft utilizing explosive charges of 1.1, 8.2, 14.6, 169.9, 387.8, and 688.6 grams. The tests have shown that an acrylic sphere will fracture in 0–50 ft depths range under dynamic peak pressures that are smaller in magnitude than static pressures required for general implosion of the sphere. At depth that is equal to 0.2 of static implosion pressure, the magnitude of dynamic peak pressures must be in excess of the static implosion pressure before fracture of the acrylic sphere is initiated. Fractures were generally initiated on the internal surface of the sphere at two locations: (a) at a point closest to the explosive and (b) at a point most remote from the explosive. The fractures were generally in the shape of a star.
Shape and Frequency Composition of Pulses From an Impact Pair
Authors: Herbert R. G. , McWhannell D. C.
Published: November 2010

With the need to improve the reliability and noise emissions from real mechanisms, an impact in the classical impact pair configuration is investigated considering the impact pulse level and its frequency composition as possible sources of high-frequency energy in articulated systems. The analog representation of the impact pair uses a nonlinear surface stiffness together with a nonlinear surface damping. Developments of the Dubowsky model carried out by Crossley are further extended to allow the surface damping coefficient, as a function of the coefficient of restitution, to be calculated assuming energy is dissipated throughout the impact for any series power law representation of the surface stiffness. The practical system used by Veluswami is simulated, and the results for Dubowsky, Crossley, and the direct solution are compared to Veluswami’s practical data.
On Wedge Indentation and Its Relationship With Incipient Plastic Deformation in Metal Cutting
Authors: Weinmann K. J.
Published: November 2010

This paper deals with plane strain indentation of annealed brass by both symmetric and half wedges, and the connection between wedge indentation and incipient chip formation by a positive rake angle tool. Indentation forces and wedge-plate contact lengths were measured, and plastic deformation underneath the indenters was studied by microhardness scanning and discussed. Half-wedge indentations at decreasing distances from the plate corner were shown to result in a transition from wedge indentation to chip formation.
Analysis of Transients in an Adaptive Control Servomechanism for Milling With Constant Force
Authors: Tlusty J. , Elbestawi M. A. A.
Published: November 2010

Characteristics of a reasonably well-adjusted NC servo are given as measured as well as modeled. A model of an A/C loop is added and investigated for stability and for a transient in meeting a sudden increase of depth of cut. Both the classical approach and a numerical simulation (state-space approach) are used. The important effect on stability is shown of a time delay between table velocity change and cutting force change, which is due to the interval between the action of individual cutter teeth. The beneficial effect of a rate feedback on stability is demonstrated.
A Sparsity-Oriented Approach to the Dynamic Analysis and Design of Mechanical Systems—Part 1
Authors: Orlandea N. , Chace M. A. , Calahan D. A.
Published: November 2010

The work described herein is an extension of sparse matrix and stiff integrated numerical algorithms used for the simulation of electrical circuits and three-dimensional mechanical dynamic systems. By applying these algorithms big sets of sparse linear equations can be solved efficiently, and the numerical instability associated with widely split eigenvalues can be avoided. The new numerical methods affect even the initial formulation for these problems. In this paper, the equations of motion and constraints (Part 1) and the force function of springs and dampers (Part 2) are set up, and the numerical solutions for static, transient, and linearized types of analysis as well as the modal optimization algorithms are implemented in the ADAMS (automatic dynamic analysis of mechanical systems) computer program for simulation of three-dimensional mechanical systems (Part 2). The paper concludes with two examples: computer simulation of the front suspension of a 1973 Chevrolet Malibu and computer simulation of the landing gear of a Boeing 747 airplane. The efficiency of simulation and comparison with experimental results are given in tabular form.
Summarization and Comparison of Freight Car Truck Load Data
Authors: Johnson M. R.
Published: November 2010

Methods of summarizing and presenting freight car truck load data obtained on service tests are described. Data from four separate test programs are presented in various formats. The data show considerable ranges in the load magnitudes and rates of occurrence from the various test environments. This type of information is essential for evaluating the fatigue, safety, and reliability properties of freight car truck components.
Bunker Design—Part 1: Bunker Outlet Design and Initial Measurements of Wall Pressures
Authors: Richards P. C.
Published: November 2010

Experiments have shown that the Jenike bunker outlet design method is accurate with respect to both the flow pattern (mass flow or funnel flow) and the minimum outlet required. Initial measurements of wall pressures in a 0.6-m-dia mass flow bunker were used to select a suitable measuring technique for use in larger scale equipment, which is also described.
A New Look at Subcritical Quenching (SCT) for Fatigue Strength Improvement
Authors: Neifert H. R.
Published: November 2010

A comprehensive summary of in-house information concerned with thermal prestressing of large forgings for fatigue strength improvement is presented. Seven commercial grades of carbon and alloy steel railway forgings with and without a subcritical quenching treatment (SCT) are compared. Conventional designs of full-size press-fitted assemblies and a filleted shaft were tested in rotating bending to evaluate the treatment. Fatigue strength improvement values ranging from 45 to over 130 percent have been established for breaking off in the wheel fit, depending upon the yield strength of the shaft material and the configuration at the press fit. Compressive residual stresses induced by the treatment were measured for most materials, and in some instances the loss of surface compression due to cyclic stressing was evaluated. An example of practical use of the information summarized is cited by a discussion of the application of SCT in the development of a tubular axle for transit car service. Information being presented in this paper updates published literature with current technology pertinent to the application of thermal prestressing to a variety of large forging materials. It provides a comprehensive reference background to substantiate and stimulate greater use of the treatment by others confronted with the design of fatigue resistant assemblies.
Linear Bending of an Orthotropic Rectangular Sandwich Plate
Authors: Willis T. , Pal M. K.
Published: November 2010

The work reported here is a simplified approximate analysis to take into account, the effects of allowing the supported edges of a rectangular plate to deflect, both in bending deflection, and in rotational (twisting) deflection and is for a plate with two opposite edges simply supported, the two remaining edges supported on elastic beams with finite flexural and torsional rigidity.
Bivariate Time Series Analysis of the Effective Force Variation and Friction Coefficient Distribution in Wood Grinding
Authors: DeVries W. R. , Dornfeld D. A. , Wu S. M.
Published: November 2010

A new technique for analyzing the normal and tangential grinding force is presented, which can be used to extract the dynamic characteristics of the grinder structure, the work material, and measurement transducers from experimentally measured forces. The technique involves developing bivariate time series models from the data which represent the dynamics imparted to the random force variation at the wood-stone interface. Removing the dynamics allows a simple model for the grinding force to be postulated, from which the statistical distribution of the resultant force and friction coefficient can be determined. Two sets of data from an experimental wood grinder are analyzed. Based on independent experiments, the frequencies in the measured normal and tangential forces can be related to factors other than the true grinding forces. The methodology developed is used to remove these dynamic effects and find the force and friction coefficient distributions. The mean value of the friction coefficient determined with this method appears to be more sensitive in detecting changes in friction for different grinding conditions.
Analytical Prediction of Three Dimensional Cutting Process—Part 3: Cutting Temperature and Crater Wear of Carbide Tool
Authors: Usui E. , Shirakashi T. , Kitagawa T.
Published: November 2010

Through the energy method proposed in the previous parts of this study, it is possible to predict chip formation and cutting force for a single point tool of arbitrary geometry. By using the predicted results together with an assumption made on the stress distribution on the tool face, the temperature distribution within chip and tool is obtained through a numerical analysis. A characteristic equation of crater wear of carbide tool is derived theoretically and verified experimentally. Computer simulation of crater wear development is then carried out by using the characteristic equation, and the predicted distributions of the stress and the temperature.
Concerning Analysis of Central Burst in Metal Forming
Authors: Lee E. H. , McMeeking R. M.
Published: November 2010

A criterion for the generation of internal cracks normal to and astride the central axis in a drawing or extrusion process has been based on the conditions requiring less driving force with such cracks than without. Application of the upper bound theorem of limit analysis to approximate these forces yields a criterion for central burst. However, use of the lower bound theorem indicates that the cracked work-piece will always deform with less force, so that such a criterion would always predict the occurrence of this forming defect. Energy required to initiate and extend the crack must be included for a correct analysis.
Analysis of the Flow-Type Manufacturing Systems Using the Cyclic Queuing Theory
Authors: Hitomi K. , Nakajima M. , Osaka Y.
Published: November 2010

A stochastic mathematical model was built and solved by using cyclic queuing theory for the multistage flow-type automated manufacturing system which is composed of several automated machine tools, movable pallets, transfer lines, and workpiece loading/unloading equipment, in an attempt to investigate the system’s behaviors such as production rate of a machine utilized in each stage, production rate of the system, mean number of waiting pallets at each stage, mean number of in-process inventories in each stage, and cycle time of a pallet. In case of limited space for in-process inventory at each stage, it was found that there exists the optimal number of pallets on the transfer line to maximize production rate. In addition, the computational procedures for analyzing the automated manufacturing system were developed and used to solve typical examples of the automated manufacturing system.
Determination of Fiber Cross-Sectional Circularity From Measurements Made in a Longitudinal View
Authors: Barker R. L. , Lyons D. W.
Published: November 2010

A procedure is described for obtaining information concerning the circularity of fiber cross-sections from measurements made in a longitudinal view of the fibers. A method is developed for viewing and measuring the projected diameter of fibers viewed longitudinally, and an analytical procedure is described for analyzing these measurements to determine the flatness or roundness of the fiber cross-sections. Experimentation conducted to test the reliability of these procedures is discussed as these methods are used to measure numerous different samples of fibers of known and varied cross-sectional shapes and sizes.
An Investigation of Regenerative Blowers and Pumps
Authors: Hollenberg J. W. , Potter J. H.
Published: November 2010

The regenerative turbomachine was investigated as a pressure-increasing device, using both air and water as working fluids. Three machines were involved, representing two geometries. A non-dimensional correlation was developed, relating pressure and flow to driving torque. This was confirmed by experiments, using data from widely separated investigations. This information was used to prepare a study of maximum efficiency as a function of specific speed. A single loss coefficient was found to be the governing parameter.
The Stress-State in the Shear Zone During Steady State Machining
Authors: The´ J. H. L. , Scrutton R. F.
Published: November 2010

In order to calculate the stress state at any point in the shear zone, a new method has been developed which incorporates the effects of strain—hardening, strain-rate and temperature. Previous attempts have employed a modified slip-line field technique. The method is based on an empirical formula derived from published experimental data over a period of fifteen years relating flow stress values with values of strain, strain-rate, and temperature. From an experimentally derived deformation pattern, the strain and strain-rate distributions may be determined assuming a simple shear deformation mode. By using the empirical flow stress formula, the stresses and temperatures in the plastic zone may be calculated easily. Theoretical predictions agree well with experimentally observed values. The method is applied to a parallel-sided zone.
Electrochemical Grinding of WC-Co Cemented Carbides
Authors: Levinger R. , Malkin S.
Published: November 2010

An investigation is reported on electrochemical grinding (ECG) of WC-Co cemented carbides, with particular consideration of their heterogeneity. An analysis of the electro-chemical removal process for these materials indicates that electrochemical dissolution into the cobalt phase occurs initially at a much faster rate than into the carbide phase. It is proposed that selective removal of the cobalt in this way weakens the composite material, thereby reducing the power requirements for mechanical material removal during ECG. Experimental results are presented which illustrate the interaction between the electrochemical and mechanical processes.
Deformation and Curvatures in Sheet-Metal in the Bulge Test
Authors: Shang H. M. , Hsu¨ T. C.
Published: November 2010

The displacements and strains of a circular specimen subjected to hydraulic pressure are studied and are compared with theoretical results predicted by previous investigators. By proposing a concept called prolateness, which gives an indication of the deviation of a local surface from a perfect sphere, it is found that the shape of the deformed bulge is not as simple as it has often been thought to be—the prolateness of a bulge is never constant at any deformation stage. Results also show that, between the beginning and the end of the forming process, there are the initial, stable and unstable regimes of deformation.
Nonlinear Thermoelastic Behavior of Structural Joints—Solution to a Missing Link for Prediction of Thermal Deformation of Machine Tools
Authors: Attia M. H. , Kops L.
Published: November 2010

The analysis of the process of heat transfer across the joints in machine tool structures reveals their non-linear thermoelastic behavior. Nonlinearity basically results from two distinctive causes. First, it is the material nonlinearity due to the fact, that the stiffness of the surface asperities takes a nonlinear, load-dependent form. The second cause is the nonlinearity resulting from the thermoelastic behavior of contacting elements, which experience a closed-loop interaction between the thermal field and the thermal deformation of structural elements in contact. This interaction affects the distribution of the contact pressure along the joint and causes a consequent redistribution of the thermal contact resistance. As a result, the final pattern of deformation depends on the final contact pressure distribution which is unknown in advance. The nonlinear thermoelastic behavior of the joint is inherent to the process of heat transfer across the interface. By considering this behavior of the joint, characterized by the time-dependent distribution of the thermal contact resistance along the interface, thermal deformation of the whole structure can be treated with thermally interacting structural elements taken into account. This was a missing link in predicting the thermal deformation. As a solution, a consecutive-iteration technique is proposed, which, with introduction of contact elements representing equivalent properties of the joint, allows us to portray the thermal deformation of the structure under transient and steady state conditions.
Effects of Thermal Loading on Fiber-Reinforced Composites With Constituents of Differing Thermal Expansivities
Authors: Hoffman C. A.
Published: November 2010

Estimates of the magnitudes of elastic stresses and elastic-plastic stresses and strains were made for tungsten fiber-reinforced 80Ni + 20Cr matrix composites; heating or cooling between 80 and 2000 deg F (26.5–1093.5 deg C) was assumed. The calculated elastic stresses exceeded representative or estimated strengths of constituents. For composites with less than 0.65 volume fraction of fiber, plastic flow was considered possible, and elastic-plastic solutions indicated that stresses would be reduced but with the concomitant occurrence of sufficiently large strain ranges, particularly in the matrix, to pose a possible thermal fatigue problem. Limited experimental studies on tungsten fiber-copper matrix composites heated and cooled a number of times between 80 deg F (26.5 deg C) and 1600 deg F (877 deg C) in a conventional furnace and then heated from 80 deg F (26.5 deg C) to 1652 deg F (900 deg C) in a hot stage microscope resulted in matrix microfracture for a 70 volume fraction fiber composite and substantial matrix strain for a 40 volume fraction fiber composite.
The Crawling Rail
Authors: Carter W. J. , Upthegrove W. R.
Published: November 2010

The beam on elastic foundation is employed as a mathematical model to develop an explanation for the crawling phenomena observed for the rails used to support the rotating beds of large rotary kilns.
State of Stress During Solidification With Varying Freezing Pressure and Temperature
Authors: Pedroso R. I. , Domoto G. A.
Published: November 2010

An analysis is presented to estimate the state of stress when solidification occurs with varying liquid pressure and freezing temperature. A model assuming the state of stress in the freezing front is presented. An equation expressing mass conservation at the freezing front is derived. The solid is described by a linear isotropic thermoelastic model. Numerical results are given for inward freezing with spherical symmetry and infinitely slow solidification rates. It is shown that stresses will remain in the solid after the liquid pressure is released and the external traction is made to vanish.
A Further Study of Residual Stresses in Circumferential Welds
Authors: Vaidyanathan S. , Weiss H. , Finnie I.
Published: November 2010

The residual stress distribution for a circumferential weld between cylinders was obtained in a prior publication for a full penetration, single pass weld with no variation of alloy content across the weld. In the present work the approach is extended to cover a wider variety of weld conditions. It is shown that the effects of multipass welds, partial penetration welds, and welds with filler metal differing greatly in properties from the base metal can approximately be taken into account. Experimental results are presented to support the proposed method of analysis.
A General Statistical Model for Random Fatigue
Authors: Wirsching P. H. , Haugen E. B.
Published: November 2010

A general statistical model for fatigue under stationary random gaussian stress is presented. This phenomenological model requires only a limited amount of data from fatigue tests in which specimens are subjected to stationary narrow band, gaussian stresses. A theoretical extension is made to predict fatigue under wide band stresses and arbitrary mean values. Statistical variability in material strength is included in the model. Moreover, the model has the property of adaptability in that it is easily modified to reflect new data as it becomes available. Furthermore, it is easily incorporated into probabilistic design procedures where reliability requirements are specified.
Elasto-Plastic Indentation of a Layered Medium
Authors: Kennedy F. E. , Ling F. F.
Published: November 2010

An analysis is performed, using the finite element method, of the indentation of a thin elasto-plastic layer resting on or attached to a substrate of a different material, which may also deform plastically. The indentation size, contact pressure, applied load, and amount of plastic deformation are found for the elasto-plastic case, and the results are compared with those found by an elastic analysis. It is found that plastic deformation, which occurs in all indentation tests, has a considerable effect on the results, and that the deformation in the indented layer is also affected by such variables as: the material properties of both layer and substrate, the thickness of the layer, and the condition of the interface between layer and substrate. The “piling-up” that has been observed experimentally in indentation tests is found to depend on the same variables and occurs especially when a thin layer is adhered to a more rigid substrate. The analysis is valid throughout the loading-unloading cycle.
Fatigue Crack Growth in SA508-CL2 Steel in a High Temperature, High Purity Water Environment
Authors: Gerber T. L. , Heald J. D. , Kiss E.
Published: November 2010

Fatigue crack growth tests were conducted with 1 in. (25.4 mm) plate specimens of SA508-CL2 steel in room temperature air, 550 deg F (288 deg C) air and in a 550 deg F (288 deg C), high purity, water environment. Zero-tension load controlled tests were run at cyclic frequencies as low as 0.037 CPM. Results show that growth rates in the simulated Boiling Water Reactor (BWR) water environment are 4 to 8 times faster than growth rates observed in 550 deg F (288 deg C) air and these rates are 8 to 15 times faster than the room temperature rate. In the BWR water environment, lowering the cyclic frequency from 0.37 CPM to 0.037 CPM caused only a slight increase in the fatigue crack growth rate. All growth rates measured in these tests were below the upper bound design curve presented in Section XI of the ASME Code.
Fatigue Crack Propagation in a 5456-H117 Aluminum Alloy in Air and Sea Water
Authors: Chu H. P.
Published: November 2010

Fatigue data on a 5456-H117 aluminum alloy have been obtained in air and sea water by fracture mechanics methods. It is found that the presence of sea water increases the crack growth rates and lowers the threshold stress intensity. The data for five stress ratios are correlated with two empirical equations. The effect of sea water on fatigue cracking is also examined by electron fractographs.
A Procedure for Verifying the Structural Integrity of an Existing Pressurized Wind Tunnel
Authors: Taylor J. T. , Lewis P. E. , Ramsey J. W.
Published: November 2010

This paper describes the application of material test, stress-fatigue-fracture mechanics analyses, nondestructive examinations and repairs to verify the structural integrity and the remaining cyclic life in a large pressurized wind tunnel (65,000 ft3) (1840 m3). The tunnel with pressures up to 135 psig (0.93 MPa) was constructed in 1940 and has been in service to the present date. The only record of a non-destructive examination conducted on the vessel prior to this evaluation was a hydrostatic test-pressure at 1 1/2 times the maximum working pressure. The material tests were performed on a sample of material (A-70 steel) cut from the tunnel shell. These tests included fracture toughness (R-curve, Kc) as determined from a compact tension specimen, crack growth rate (da/dn vs ΔK), Charpy V-notch, dynamic tear (from which the nil-ductility temperature was determined), and tensile and chemical tests. The results and applications are presented and discussed. Stress analyses include computer programs based on finite element and numerical integration techniques. Fatigue analyses incorporating a fatigue reduction or stress amplification factor to account for a small flaw existing in a weld are presented. Fracture mechanics analyses of the tunnel shell were performed for (1) the general membrane regions, (2) regions of high bending stress, and (3) areas at tunnel penetrations. The critical flaw sizes at each location are determined. The use of the “leak before break” criterion is discussed. The non-destructive examinations (radiograph, ultrasonic, sonic, and magnetic particle) to verify the assumptions of fatigue-fracture mechanics analyses and ASME Code applications are documented. Penetrations in the tunnel shell that were fatigue limited are shown “before” and “after” repair. The remaining cyclic life as obtained by the fatigue-fracture mechanics analyses and the operating envelope which resulted from these studies for metal temperature vs pressure was determined to be approximately 10 years.
Effects of Change of Phase on Temperature Distribution Due to a Moving Heat Source
Authors: Kang C. S. , Chang Y. P.
Published: November 2010

This paper presents a numerical method for the solution of problems of moving heat sources with change of phase and with any boundary condition. Calculated results of two specific cases are shown: one for a plane moving source in a rod and the other for a line source in a plate. It is found that for low heat input and/or low initial temperature, the change of phase does not affect significantly the temperature distribution in the medium, were it of solid only. However, the higher the heat input and/or the initial temperature, the larger is the effect of phase-change to the temperature field.
Analysis of Thermal Stresses and Metal Movement During Welding—Part I: Analytical Study
Authors: Muraki T. , Bryan J. J. , Masubuchi K.
Published: November 2010

This is the first part of a study of thermal stresses and metal movement during welding. This part discusses analysis of two-dimensional thermal stresses and metal movement during bead-on-plate and butt welding. A finite-element formulation has been derived, based on the variational principle. The formulation includes temperature dependence of material properties as well as the yield criterion.
Prediction of Temperature Distributions in Axisymmetric Compression and Torsion
Authors: Lahoti G. D. , Altan T.
Published: November 2010

Two numerical methods, one for axisymmetric compression and the other for axisymmetric torsion, have been developed to predict nonsteady-state temperature fields in these deformation processes. In compression, the upper-bound method has been used to determine the velocity field prior to temperature calculations. In both compression and torsion, the predicted temperatures agree well with experimental data obtained by other workers. The compression analysis has been also used for investigating (1) the effect of friction upon temperatures and (2) the effect of ram speed upon metal flow and temperatures. The results of these investigations indicate that the numerical approach predicts, within approximations, the trends observed in experimental studies.
The Effect of Strain-Rate Upon the Tensile Deformation of Materials
Authors: Davies R. G. , Magee C. L.
Published: November 2010

The tensile strength of seventeen engineering materials including steels, Al alloys, and fiber-reinforced plastics, has been determined at strain-rates from 10−3 to 103 sec−1. Variable effects on the stress-strain behavior were found in the different materials with the Al alloys showing minimal strain-rate sensitivity and the plastics highest. All results exhibit a logarithmic dependence of flow stress on strain-rate and thus the dynamic factors (ratio of dynamic to low rate or quasi-static strengths) are as dependent upon changes in quasi-static testing speed (∼1 in./min (0.42 mm/s) as they are to changes at high speed (50,000 in./min or 50 mph (22.35 m/s). No significant influence of strain-rate on elongation or reduction in area has been found for any of the materials. Steels, which comprise the majority of the presently investigated materials, exhibit a higher rate sensitivity for yielding than for higher strain deformation. It is shown that the flow stress results for these steels leads to an internally consistent scheme when (1) strength level and (2) strengthening mechanisms are properly accounted for.
Fractographic Analysis of Fatigue Failures
Authors: McIntyre D.
Published: November 2010

Although fractography is usually applied to basic research, it can also be used in studies of machine components which have failed in service or in testing. This paper discusses fractographic methods which can be used to obtain information about the stress state, environmental factors, initiating cause, and crack growth characteristics of fatigue failures. The macroscopic and microscopic fracture surface features of fatigue failures are illustrated with photomacrographs and scanning electron microscope (SEM) fractographs, and the use of SEM fractography in crack growth studies is described.
Creep-Rupture Properties, Resistance to Temper Embrittlement and to
Attack by Hydrogen of a 1.4 Percent Mn — 0.25 Percent Mo — 0.03 Percent Cb
Steel
Authors: Wada T. , Sponseller D. L.
Published: November 2010

A laboratory heat of an improved boiler steel containing 0.13 percent C, 1.36 percent Mn, 0.27 percent Mo, 0.03 percent Cb, and 0.010 percent N was prepared; creep-rupture properties, resistance to temper embrittlement and resistance to hydrogen attack were investigated. The rupture strength was much higher than that of carbon steel and columbium-treated carbon steel, but was somewhat lower than that of two European carbon-0.3 percent Mo boiler steels. Creep-rupture ductility was high. The experimental steel exhibited high toughness, especially in the normalized and stress-relieved condition. No temper embrittlement was induced by step-cooling normalized or normalized and stress-relieved material. Good resistance to hydrogen attack was revealed by tests in a hydrogen autoclave at a pressure of 1000 psi (6.9 N/mm2); the steel retained the original Charpy impact toughness after exposures up to 5000 hr at 900 deg F (480 deg C) and 500 hr at 1000 deg F (540 deg C). No blistering or fissuring were observed.
Strain-Hardening Characteristics of Ti-6Al-2Sn-4Zr-2Mo Alloy
Authors: Chakrabarti Amiya K. , Roberson James A. , Kerr William R.
Published: November 2010

The strain-hardening exponent (n) is considered to be numerically equal to the uniform plastic strain for materials which exhibit a power low true stress true strain relation. In Ti-6Al-2Sn-4Zr-2Mo alloy a considerable deviation between the uniform plastic strain and the strain hardening exponent has been observed irrespective of the variations in microstructures and grain size. The present investigation indicates that a power law true stress true strain relation of the type σ = Kεn may not be valid for this material.
Moisture Diffusion in Fiber Reinforced Plastics
Authors: McKague E. L. , Reynolds J. D. , Halkias J. E.
Published: November 2010

Fiber-reinforced epoxy laminates were exposed to several combinations of temperature and relative humidity. The purpose was to determine rates and extent of moisture absorption. Diffusion rates varied with temperature, and equilibrium moisture contents varied with relative humidity. Data analysis provided values for the material properties that determined diffusion behavior. A nonlinear diffusion model containing these values was shown to describe and predict absorption behavior for any combination of temperature and humidity. The model also describes desorption and correlates well with experimental data from changing humidity conditions.
Particle Erosion Measurements on Metals
Authors: Young J. P. , Ruff A. W.
Published: November 2010

A method being used to measure the erosive wear of metals at different temperatures and under controlled environmental conditions is described. A commercial apparatus has been modified that can be used for tests at 500°C and above and over a wide range of particle types, sizes, velocities, and concentrations. Test results from several iron and nickel base alloys are presented. Particular interest has been placed in the role of the oxide scale, in the particle velocity dependence and the impingement angle dependence of erosion rates, as well as the effect of varying particle concentration in the stream. Reproducibility among the tests of about 10 percent can be realized if care is exercised with regard to several important experimental parameters.
Erosion of 310 Stainless Steel at 975°C in Combustion Gas Atmospheres
Authors: Ives L. K.
Published: November 2010

Erosion tests were conducted on 310 stainless steel in combustion gas atmospheres at 975°C. SiC particles of 100 mesh (150 μm) size were employed over a velocity range of 15–70 m/s at a 90 deg (perpendicular) angle of impingement. A comparison is made with results obtained at 25°C in air using the same test equipment. Scanning electron microscopy examination of the eroded surfaces revealed important information concerning the nature of the erosion-corrosion process. A multiple component test specimen is described for application in comparing alloys under nearly identical test conditions.
Erosion of a Tube by Gas-Particle Flow
Authors: Sheldon G. L. , Maji J. , Crowe C. T.
Published: November 2010

A numerical model for particle-laden flow in a tube has been developed which predicts the erosive wear of the tube wall by the action of the impinging particles. Empirical relationships are used to correlate the particles’ momentum before and after impact with material properties. Erosion of a straight duct conveying a particle-laden stream was studied as experimental verification of the model. Specifically, an aluminum tube was eroded by much harder spherical particles and the resulting wear pattern compared with that predicted by the model. A close correlation was found. This is a first step in modeling more complex erosion effects in equipment in which two- and three-dimensional flows predominate.
Fracture Analysis of Adhesively Bonded Cracked Panels
Authors: Swift T.
Published: November 2010

An analysis procedure is presented for predicting crack tip stress intensity factors, adhesive stiffener stresses and strains, and the residual strength of adhesively bonded stiffened panels containing cracks equally spaced between stiffeners. The approach considers the cracked skin as a linear elastic fracture mechanics problem but accounts for the effects of plasticity on both adhesive and stiffener. The solution is based on displacement compatibility between the cracked sheet and the stiffener, accounting for shear distortion of the adhesive. Displacements in the cracked sheet are determined using the Westergaard complex stress function approach. The analysis was correlated with test using data from a cracked panel, simulating typical aircraft fuselage construction, previously tested during the Air Force Primary Adhesive Bonded Structures Technology (PABST) Program.