bluuebunny/crossref_metadata_2025 huggingface dataset:
Geometrical Adaptive Control in NC Turning Operation
Authors: Shiraishi M.
Published: July 2009

A geometrical adaptive control in an NC turning operation has been achieved by a newly developed noncontact measuring system which can continuously monitor the radius change of a workpiece in an on-line fashion. The emphasis of this system is placed on the continuous pursuits of a workpiece axis by double laser beams and the detection of the workpiece with curvatures. Satisfactory control results were obtained not only for the straight profiles but also for the curved profiles within the accuracy close to the tolerance limits of the NC machine used.
A Mechanistic Model for the Prediction of the Force System in Face Milling Operations
Authors: Fu H. J. , DeVor R. E. , Kapoor S. G.
Published: July 2009

A mechanistic force system model for the face milling process has been developed and implemented on the computer. The model predicts the force system in face milling over a range of cutting conditions, cutter geometries, workpiece, and process geometries including relative positions of cutter to workpiece, spindle tilt, and runout. Machining tests have been conducted for both fly cuting and multitooth cutting with polycrystalline diamond tools on plain surfaces. The 390 casting aluminum alloy has been used as the workpiece material. Force data from these tests were used to estimate the empirical constants of the mechanistic model and to verify its prediction capabilities. Data bases from flycutting tests have been used to predict forces under multitooth face milling and the results indicate good agreement with observed data from multitooth tests.
Vented Compression Molding
Authors: McCree J. O. , Erwin L.
Published: July 2009

A new process for molding low density particulates, vented compression molding, is presented. Vented compression molding is a modification of standard compression molding that uses a perforated surface as the molding surface. The mold cavity is filled with an excess of material, which is forced through the openings in the surface of the mold as the mold closes. The resulting frictional forces, which can be determined approximately by a Mohr-Coulomb yield criterion, generate the pressure that compacts the material. Thus the pressure in the mold is governed by the geometry of the openings and the mechanical properties of the particulate, and not by the displacement or the volume of the mold. This uncoupling of the pressure-displacement relationship allows uniform material distribution and compaction without requiring large-scale flow of the particulates.
Mechanical Property Enhancement of Semi-Crystalline Polymers by Solid State Rolling
Authors: Bigg D. M. , Smith E. G. , Epstein M. M. , Fiorentino R. J.
Published: July 2009

Calendering of molten thermoplastics is frequently used to produce sheet materials of uniform thickness. The mechanical and chemical properties of such sheets are those inherent to the basic isotropic material. If semicrystalline polymers are rolled into sheets at temperatures below their melting point, significant molecular orientation takes place. Mechanical property enhancement and improved chemical stability then accompany good thickness control in the oriented sheet. In a series of experiments with high-density polyethylene and polypropylene, tensile moduli and tensile strengths as high as 8.7 GPa and 300 MPa, respectively, have been obtained. Output speeds as high as 20 m/min are easily reached. Chemical and dimensional stability in hot polybutene oil has been demonstrated. Less than 2 percent change in weight, thickness, or length of samples has been observed after 5000 hr exposure in the oil at 100°C. The most critical factors in obtaining and controlling these properties are roll temperature and degree of thickness reduction obtained during rolling. Property control and reproducibility have been shown to be good.
Backward Extrusion of Internally Shaped Tubes From Round Billets
Authors: Yang D. Y. , Han C. H.
Published: July 2009

An analytical method is proposed for estimating the steady-state punch pressure for three-dimensional backward extrusion (or piercing) of complicated internally shaped tubes from circular billets. A kinematically admissible velocity field is derived to formulate an upper-bound solution using velocity transformation and mapping function. The configuration of deforming boundary surfaces are determined by minimizing the extrusion power with respect to some chosen parameters. Experiments are carried out with commercially pure aluminum billets for internally shaped tubes at various reductions of area by using different sizes of shaped punches, such as square and regular hexagons. It is shown that the theoretical predictions for extrusion load are in good agreement with the experimental values.
The Study of Distorted Grid Patterns for Flow-Through Conical Converging Dies by the Multi-triangular Velocity Field
Authors: Pan J. , Pachla W. , Rosenberry S. , Avitzur B.
Published: July 2009

A variety of velocity fields may be used to analyze the intermediate and final distorted grids for the so-called “flow-through” metal forming processes such as wire drawing, rolling, extrusion, etc. In this paper the triangular velocity field describes the flow of homogeneous, perfectly plastic Mises’ material through a conical converging die. The traditional triangular velocity field was treated and the solution extended. The shape of the distorted grids was uniquely determined by the minimization of the power (drawing or extrusion stresses) required to cause its distortion for a given set of independent process parameters, i.e., process geometry-reduction in area and semi-cone angle, and friction. Actual power (forming stress requirements) was estimated by the upper-bound technique. For the unitriangular velocity field, the power was minimized with respect to the shape of the workpiece (the shape of the triangle). For the multitriangular velocity field, the power was minimized with respect to the shape and the number of triangles. Further, the number of triangles was treated as a real number. Thus, the accurate lower upper-bound was found and the reasonable solution in predicting real distortion grid patterns was then obtained. The analysis determines the severity of the distortion as a function of process geometry and friction.
Tool Fracture Probability Under Steady State Cutting Conditions
Authors: Sampath W. S. , Lee Y. M. , Shaw M. C.
Published: July 2009

Tool fracture probability for 6 weight percent cobalt tungsten carbide tools turning AISI 4340 steel (HB = 235 kg/mm2) at 200 fpm was found to be small at the beginning of a cut or during steady state cutting at feeds up to 0.100 ipr (2.54 mm/rev). Steady state fracture probability was found to be high only when cutting with severe chatter at feeds of 0.100 ipr (2.54 mm/rev) or higher. Tool fracture probabilities were determined by finite element analysis for elastic tool stresses, an intensified maximum tensile stress fracture criterion associated with circular defects [9] and Weibull plot giving percent failed versus fracture stress in uniaxial compression.
Quantitative Expressions for Some Aspects of Surface Integrity of Electro Discharge Machined Components
Authors: Rajurkar K. P. , Pandit S. M.
Published: July 2009

An on-line adaptive control of the Electrical Discharge Machining (EDM) process needs proper quantitative relationships between output parameters and input variables of the process. This paper presents an attempt to develop mathematically simple expressions for the depth of cracks, the depth of damaged layer, and the depth of martensitic layer in terms of pulse duration and current. The transient temperature distribution developed by Data Dependent Systems analysis of the EDM process is used in obtaining thermal stress expressions. The hypothesis that the cracks are the consequence of thermal stresses exceeding the fracture level leads to the expression for the depth of occurrence of cracks. The estimation of the thickness of martensitic layer is based on the phase transformation temperature isothermal obtained from the temperature distribution. A simple expression for the depth of the damaged layer is also obtained using the experimental conclusions reported in the literature. Regression equations suitable for the on-line adaptive control of the EDM process are developed. The theoretical estimates are compared with the experimental measurements.
Inclined Moving Heat Source Model for Calculating Metal Cutting Temperatures
Authors: Dawson P. R. , Malkin S.
Published: July 2009

The analysis of an inclined plane heat source moving along the surface of a semi-infinite solid is presented. Material passing by the heat source is eliminated from the analysis to simulate its removal by an orthogonal cutting process. The solution, expressed in terms of dimensionless parameters, is obtained by solving the heat equation numerically with the finite element method for a wide range of cutting conditions. The solution is used to evaluate shear plane temperatures in orthogonal machining and grinding zone temperatures in conventional and creep feed grinding.
Buckling Loads and Natural Frequencies of Drill Bits and Fluted Cutters
Authors: Magrab E. B. , Gilsinn D. E.
Published: July 2009

The buckling loads, natural frequencies and mode shapes of twist-drill bits and certain fluted cutters under a variety of combinations of twist angle, cross-section geometry, and axial loading have been obtained. The drill bit is modelled as a twisted Euler beam under axial loading that is clamped at both ends. The governing system of differential equations is solved by the Galerkin procedure. Explicit forms for the basis functions used to generate the Galerkin coefficients are presented in general form in an appendix. They may be used for obtaining numerical results for that class of problems which use the Rayleigh-Ritz-Galerkin methods with beam-type functions as the basis functions. The representative set of modes obtained exhibit a complex out-of-plane twisting-type motion that suggests a possible explanation for the out-of-roundness of certain drilled holes.
New Electrostatic Spinning Concept for Cotton
Authors: Robert K. Q. , Baril A. , Reif R. B. , McCrady P. E.
Published: July 2009

A new compact design was developed for the electrostatic spinning of cotton yarns by use of the best technology derived from previous research conducted at the Southern Regional Research Center, New Orleans (USDA) and Battelle Columbus Laboratories. The new design consists of a miniature card-type fiber feed system, a rotating grounded tail electrode, a conical insulating chamber, and a high-voltage twisting electrode located at the apex of the conical chamber.
Space Station Environmental, Thermal Control and Life Support (ETCLS): “Meeting the Evolutionary Growth Challenge”
Authors: Brose H. F.
Published: July 2009

Renewed interest and planning for a Space Station, probably NASA’s next major space activity, poses a new challenge for ETCLS technology not previously emphasized. Over the past two decades, regenerative life support technology development for Space Station has been underway. This development effort was always aimed at regenerative (closed loop) life support for a full capability Space Station. The level of priority for manned space presence and current budgetary pressures dictate the need for a low cost profile program with an evolutionary growth Space Station. The initial capability may be a small station with a crew of 2 or 3. This station could grow in size and capability by the addition of modules to a station with a crew of 8 to 12 with the possibility of multiple stations in orbit. Depending upon the selected missions, the early station may be best served by an open or only partially closed loop ETCLS whereas the final station may need a completely closed loop ETCLS. The challenge would be to grow in-orbit the ETCLS system capability in a “no-throw-away” fashion in order to minimize annual and total program cost. This paper discusses a possible ETCLS system evolutionary growth scenario, the Space Station architecture variations influencing the ETCLS system design, and a technology preparedness plan for Space Station ETCLS.
Subsystem Impact on Space Station System Design
Authors: Cole E. G. , Nussberger A. A.
Published: July 2009

This article shows that space station evolutionary system designs are strongly influenced by subsystem technology. To understand this impact, the article describes an evolutionary space operations system and element interactions with mission user payloads. This description addresses what and who are involved, what are the accommodations, and when, where, and how space station facility users are accommodated. Other topics discussed include space-based orbit transfer vehicles (OTV’s), station electrical power levels, subsystem tradeoff issues and their technology development challenges, cost interactions with benefits, and payload accommodations (user-subsystem interfaces). A highlight of the discussion is the view presented of requirements for subsystem supporting technology developments.
Space Station Data Management: A System Evolving From Changing Requirements and a Dynamic Technology Base
Authors: Mosley W. C.
Published: July 2009

Certain aspects of the space station data system set it apart from any other spacecraft data system ever developed: serviceable and repairable to a degree never before possible; operational lifetime spans generations of technology; dynamically extendible to accommodate evolutionary growth; unprecedented levels of complexity will occur early in the life cycle; unprecedented levels of data storage and onboard processing capacity will be required early in the life cycle. These factors, as well as others that are known, top-level space station requirements, form the basis from which derived data management system requirements (again top-level) are assembled. From these requirements, the architectural properties that need emphasis in the architectural selection process are identified. Additionally, other issues that may influence the architecture are identified and an architectural baseline is established. From this base, an example of controlled growth helps to identify other technology issues, so that the architectural discussion ends with a summary of technology issues that result from the requirements and the need for tools and techniques to support controlled growth. The architecture discussion is followed by a discussion of generic technology areas as well as related technology areas and the challenges to initial space station development. Technology areas that offer promise of enhanced capabilities in the future are also identified. This paper is not a comprehensive assessment of data management system technology, nor is it advocating a particular approach. Its purpose is to illuminate design and technology areas for further discussion and formal investigation.
Attitude Stabilization and Control for a Manned Space Station
Authors: Stubberud A. R.
Published: July 2009

The present planning for the construction of a manned space station calls for modular construction in space over a period of several years with each module having different dynamic characteristics and attitude control requirements. Several of the modules will be best modeled as distributed (flexible) bodies. It is necessary that the attitude control system be capable of providing appropriate attitude control to a suitable accuracy for the individual modules at all times during the construction. This plus the extreme flexibility pose far more difficult problems to the attitude control designer than in previous spacecraft. In spite of this, the author believes that the design techniques for past spacecraft will be used as the starting point for the attitude control system of the space station. The new theories for flexible control systems will probably be used in computer simulations for preflight validation of the control system design. Substantial improvements in the attitude control will more than likely come from new mechanical designs for actuators, intersections between modules, and passive dampers.
Further Investigation of Multifacet Drills (MFD’s)—Mathematical Models, Methods of Grinding, and Computer Plotting
Authors: Chen L. H. , Wu S. M.
Published: July 2009

The geometric characteristics of nine representative Multifacet Drills (MFD’s) are summarized. Mathematical models of the various component surfaces are derived and analyzed using coordinate transformations. The mathematical models of the geometric elements are used to deduce appropriate grinding methods. Computer plots of MFD’s are also presented to check the mathematical models and to lay a foundation for future work on computer-aided design (CAD) of MFD’s.
On-Line Diagnostics of Rear Axle Transmission Errors
Authors: Milenkovic V. , Shmuter S. , Field N.
Published: July 2009

This paper describes a methodology suitable for implementation on the production floor, to perform measurement of gear-induced vibrations in assembled axle carriers outside of a vehicle. A dynamic approach to computerized axle testing is described which has resulted in a machine capable of testing more than 100 axle carriers per hour, while exhibiting 95–98 percent correlation with laboratory measurements. The high resolution of measured conjugate gear error of 1 part in 10,000 in terms of angular velocity variations is achieved. The following three major tasks are addressed in the course of the paper: development of an angular sensor; synthesis of a dynamic drive train; configuration of a data processing system. The dynamic concept of the drive train is chosen to measure the conjugate gear error in the most direct possible manner, as torsional oscillations; to ensure adequate transmissibility for both frequency ranges of interest, mesh and boom; and to provide immunity from extraneous inputs. A real-time signal processing technique is developed, employing a peripheral array processor. Along with a decision of acceptability the machine furnishes, whenever needed, a set of supporting indicators to provide for diagnosis of the faults. An efficient method of modeling a drive train for torsional oscillations, and a computer algorithm for rapid and noise-free conjugate gear order analysis, both of general nature, are also described.
Systems Technology and Operations
Authors: Kline R. , Nathan C. A.
Published: July 2009

The Space Station, as an integral part of the Space Transportation System, utilizes man in space to enhance system effectiveness and operations productivity. As a permanent facility, the Space Station must meet evolving requirements over its virtually unlimited life. The presence of man enables the expansion of capabilities and the orderly incorporation of advancing technologies. This paper addresses systems technology and operations requirements as driven by performance sensitivities relative to technology improvements. The implications of space station growth (both size and capability) and the need to “design in” the ability to accept growth is addressed. From these assessments, recommendations of the level of technology desired for incorporation into the initial station and in later growth phases are discussed.
Autonomy and Automation for Space Station Housekeeping and Maintenance Functions
Authors: Turner P. R.
Published: July 2009

The space station crew will be a critical resource for economical operation of science and commercial payloads. Core station housekeeping and maintenance functions should be provided in a manner that requires a minimum of crew interaction. This paper outlines a prospective functional architecture for allocation of autonomous and automated control of these functions and discusses implementation issues arising from safety of manned operations, integration test requirements, and evolution of future station capabilities.
Servicing Spacecraft From the Space Station
Authors: Fisher H. T. , Forsberg K. J.
Published: July 2009

This paper presents the currently envisioned role of the Space Station relative to servicing both at and distant from the Station. Once operational (1990+), the Station will substantially benefit from the experience gained via the Orbiter’s servicing role, i.e., during the next 5 to 6 years. It is anticipated that there will be a complimentary role for both the Orbiter and the Station for varying servicing functions. Focus of this paper will be on the Station servicing activities and on orbital mechanics, which play a pivotal cornerstone in the accomplishment of the servicing mission. Both the Teleoperator Retrieval System and Orbital Maneuvering System are key elements to servicing functions, e.g., spacecraft retrieval, capture, and/or on-site servicing. Servicing technology is available today and spacecraft are already being designed for that purpose. Accordingly, an extension of the Orbiter’s servicing capability to the Station will be a natural and evolutionary process well within the present state-of-the-art.
Modeling of Continuous Mixers in Polymer Processing
Authors: Arimond J. , Erwin L.
Published: July 2009

The numerical modeling of creeping flow and continuous mixing in polymer processing equipment is considered. The decoupling of axial and transverse flow problems is the main subject of analysis. The conditions under which and the procedures whereby a steady three-dimensional mixing problem can be modeled via numerical procedures in two dimensions are discussed. The flow through a Kenics Static Mixer is chosen as a sample problem. Symmetry is exploited by formulating the problem in a nonorthogonal helical coordinate system, and a splitting method is devised for the resulting finite-difference equations which solves the axial and transverse problems alternately until convergence is reached. Three criteria are postulated as necessary and sufficient conditions for such decoupling. Finally, a method is presented whereby the result of the flow analysis can be used to model mixing. Graphical representations of the progress of mixing with down-channel displacement in the Kenics are obtained, and its mechanism of mixing is discussed.
Planning for a Space Station
Authors: Nolan M. B. , Pritchard E. B.
Published: July 2009

The Space Shuttle, as the keystone of the United States Space Program, is providing routine and efficient access to and return from low Earth orbit. The next major space initiative must build on and complement these existing space systems while significantly enhancing the national capabilities for routine and efficient operations in space. Past and current studies indicate that a permanent research and operations base in low Earth orbit is the correct next step for NASA to pursue. The operations and research base, as currently perceived, is a combination of manned and unmanned facilities located in low Earth orbit and interconnected by teleoperated transportation stages. A Space Station thus provides new and unique operational and research opportunities that complement the capabilities of the Space Shuttle principally by removing the constraint of time from future mission planning. The current assessment of requirements in the areas of science and applications, commercial utilization, technology development, and national security are discussed. The paper concludes with a discussion of the future plans within the Space Station Program.
An Analytical Model of Cutting Dynamics. Part 2: Verification
Authors: Wu D. W. , Liu C. R.
Published: July 2009

The dynamic force model developed in the preceding paper [1] is further examined. The analysis shows a successful prediction of the forms of stability boundary over a wide range of cutting speed. It reveals that the cutting force acting on tool rake face controls the high-speed stability, while the ploughing force acting on tool nose region dominates the low-speed stability. A series of cutting tests were carried out to examine the validity of the model. The result shows a fairly good agreement between the theoretical prediction of stability limit and the experimental determination of critical width of cut when the cutting conditions are properly chosen to avoid the presence of built-up-edge on tool tip.
An Arbitrarily Inclined Triangular UBET Element and Its Application to Combined Forging
Authors: Yang D. Y. , Kim J. H. , Lim C. K.
Published: July 2009

A kinematically admissible velocity field is derived for a proposed arbitrarily inclined triangular UBET element. The method is applied to combined forging to show the flexibility of application. From the derived velocity fields upper-bound loads on the punch and deformed configurations are determined by optimizing some given parameters related with geometry and velocity field. Experiments on combined forging are carried out with annealed Al-2024 billets at room temperature for several punch shapes. The theoretical predictions both in the forming load and deformed configuration are in good agreement with the experimental results. It is shown that arbitrarily inclined triangular elements proposed in this work can effectively be used for the prediction of the forming load and deformation in combined forging and can be applied to other forming processes with flexibility.
Control of a Sequential Brakeforming Process
Authors: Hardt D. E. , Chen B.
Published: July 2009

The process of sequential three point bending (or “bumpforming”) is often used to produce smoothly varying simple curvature parts. The process involves bending and incrementing the bend line in sequence to produce the desired curvature profile along the arc length of the part. The actual shape produced represents the integration of small local shape changes, and the opportunity for error is great since knowledge of the bending properties of the material is required to accurately plan and execute the sequence. As a result, the manual process is slow and highly inaccurate. In this paper an in-process control method is presented that performs two functions: 1) sequence planning based upon an optimization between allowable variations about the desired shape and processing time; and 2) closed-loop control of the desired shape to insure accurate parts even when material properties or dimensions change.
Cutting Performance Comparison of Bonded and Brazed End Mills
Authors: Zhang L. S. , Sadek M. M. , Wale D. H.
Published: July 2009

In this paper the feasibility of fabricating spiral carbide tipped end mill adhesive using bonding technique has been investigated. Cutting tests were performed and cutting forces, vibrational motion, tool wear, and surface roughness were measured. The cutting performance of the bonded end mill has been assessed in relation to those of the brazed tool. This investigation shows that the performance of the bonded end mills is almost identical to that of the commercially available brazed ones in both cases of normal cutting conditions with and without coolant. The vibration characteristics show that the damping effect of the bond layer is insignificant due to dimensions and geometry of the bond line. Infrared prints demonstrate a pronounced heat isolation due to the low thermal conductivity of the adhesive, which can be improved by mixing metallic particles in the bonding material.
Sequential Estimation of Machinability Parameters for Adaptive Optimization of Machinability Data Base Systems
Authors: Balakrishnan P. , DeVries M. F.
Published: July 2009

Mathematical model type machinability data base systems require suitable model building procedures to estimate the model parameters. The estimation procedure should be capable of using subjective prior information about the models and must also be capable of adapting the model parameters to the particular machining environment for which the data are needed. In this paper, the sequential Maximum A Posteriori (MAP) estimation procedure is proposed as the mathematical tool for performing these functions. Mathematical details of this estimation procedure are presented. The advantages of this method over conventional regression analysis are discussed based on the analysis of an experimental tool life data set. Details regarding the selection of the various initial values needed for starting the sequential procedure are presented. The use of prior information about the models in order to improve the parameter estimates is investigated. The adaptive capability of the procedure is analyzed using simulated tool life data. The results of this analysis indicate that the proposed sequential estimation procedure is a valuable tool for estimating machinability parameters and for the adaptive optimization of machinability data base systems.
Using High-Speed Image Analysis to Estimate Trash in Cotton
Authors: Taylor R. A.
Published: July 2009

Two new scanning type cotton trashmeters are being developed to indicate the amount of trash and foreign matter in lint cotton. These instruments are primarily intended to replace the current visual method of grading cotton for market quality. They both perform a two dimensional surface scan using a black and white television camera. High-speed microprocessors provide an analysis of the TV signal at video scan rates. Only a fraction of a second of time is required to complete all scanning, signal processing, and data analysis for each cotton sample exposure. This article discusses some common problems in TV image analysis and how they relate to cotton scanning. Also discussed are instrument precision and design features and a method of calibrating each instrument.
A Design for Spinning Tension Control
Authors: Taylor R. A. , Brown R. S.
Published: July 2009

A new cap-spinning design is described. A unique feature enables the cap to be operated at different speeds from the bobbin to increase or decrease yarn tension as needed. The new spinner will operate as a modification on a conventional ring spinning frame. However, it eliminates the need for rings and travelers. Due to the spinners independent tension control, it can be operated at extremely high speeds without increasing the ends down rate. Yarn grade and tension comparisons with a ring spinning are reported.
Cutting Dynamics Identification by Dynamic Data System (DDS) Modeling Approach
Authors: Ahn T. Y. , Eman K. F. , Wu S. M.
Published: July 2009

The dynamics of the cutting process have been conventionally characterized in terms of the Dynamic Cutting Force Coefficients (DCFC) which represent its transfer characteristics at discrete frequencies. However, this approach fails to obtain the transfer function of the process in closed analytical form. Anticipating the stochastic nature of the cutting process and the double modulation principle, a two-input one-output multivariate system was postulated for the dynamic cutting process identification model. The Dynamic Data System (DDS) methodology was used to formulate and characterize the dynamic cutting process using Modified Autoregressive Moving Average Vector (MARMAV) models. Subsequently, transfer functions of the inner and outer modulation dynamics of the cutting processes were obtained from the identified models.
Automated Chatter Suppression by Tool Geometry Control
Authors: Liu C. R. , Liu T. M.
Published: July 2009

A new concept of controlling tool geometry for in-process chatter suppression is quantitatively evaluated. Experimentally derived relationships between machining stability and tool geometry, namely, rake angle, clearance angle, and side cutting angle are developed. The results indicate an order of magnitude increase in the production rate if the control method is properly used.
The Ledge Tool: A New Cutting Tool Insert
Authors: Komanduri R. , Lee M.
Published: July 2009

The salient features of a simple, wear-tolerant cemented carbide tool are described. Results are presented for high-speed machining (3 to 5 times the conventional speeds) of titanium alloys in turning and face milling. This tool, termed the ledge cutting tool, has a thin (0.015 to 0.050 in.) ledge which overhangs a small distance (0.015 to 0.060 in.) equal to the depth of cut desired. Such a design permits only a limited amount of flank wear (determined by the thickness of the ledge) but continues to perform for a long period of time as a result of wear-back of the ledge. Under optimum conditions, the wear-back occurs predominantly by microchipping. Because of geometric restrictions, the ledge tool is applicable only to straight cuts in turning, facing, and boring, and to face milling and some peripheral milling. Also, the maximum depth of cut is somewhat limited by the ledge configuration. In turning, cutting time on titanium alloys can be as long as ≈ 30 min. or more, and metal removal of ≈ 60 in.3 can be achieved on a single edge. Wear-back rates in face milling are about 2 to 3 times higher than in straight turning. The higher rates are attributed here to the interrupted nature of cutting in milling. Use of a grade of cemented carbide (e.g., C1 Grade) which is too tough or has too thick a ledge for a given application leads to excessive forces which can cause gross chipping of the ledge (rapid wear) and/or excessive deflection of the cutting tool with reduced depth of cut. Selection of a proper grade of carbide (e.g., Grades C2, C3, C4) for a given application results in uniform, low wear-back caused by microchipping. Because of the end cutting edge angle (though small, ≈ 1 deg) used, the ledge tool can generate a slight taper on very long parts; hence an N.C. tool offset may be necessary to compensate for wear-back. The ledge tool is found to give excellent finish (1 to 3 μm) in both turning and face milling. In general, conventional tooling with slight modifications can be used for ledge machining. The ledge tool can also be used for machining cast iron at very high speeds.
Analysis of Extrusion of Polygonal Sections Through Streamlined Dies
Authors: Gunasekera J. S. , Hoshino S.
Published: July 2009

A new upper-bound solution is developed for the extrusion of polygonal sections through shaped dies. The surface of the die is generated by an envelope of curved lines drawn from points on the perimeter at the entry section to corresponding points at the exit of the die. The present investigation is concerned with the analysis of streamlined dies (a subset of shaped dies), though the method is applicable to other curved dies such as parabolic, convex or concave shapes. It is concluded that the streamlined die is superior to the straightly converging dies from the aspect of reducing the extrusion load.
A Method for Generating Desired Contact Pressure Distributions in Experimental Interfacial Studies
Authors: Attia M. H. , Kops L.
Published: July 2009

Computer simulation of the thermal deformation behavior of machine tools requires a priori knowledge of the correlation between the contact pressure distribution and the thermal contact resistance distribution along the structural joint. To establish this correlation experimentally, a method for generating different distributions of contact pressure has been devised in the present work. The method provides also a basic tool toward the satisfaction of the requirements of simulative wear testing. In this paper, the effect of the relative flexural rigidity of two solids in contact on the shape of the distribution of contact pressure is presented as a means for generating desired contact pressure distributions. The theoretical background of the concept is discussed considering two limiting cases: a rigid body on an elastic semi-infinite mass, and an elastic layer on a rigid base. Through a photoelastic analysis, the geometric parameters of contacting bodies, which allow us to generate the desired distributions, have been defined. The results of the analysis were verified by a two-dimensional, plane-stress finite element model. The results indicated that a finite plate, whose dimensions are not less than threefold the contact length can simulate a two-dimensional rigid base or a semi-infinite elastic mass. A change in the height-to-contact length ratio of the contacting beam from 0.5 to 2.5, causes a significant change in its elastic response from a flexural to a rigid body.
A Theoretical Investigation for High-Speed Cold Forging of Short Metal Cylinders Between Two Large Elastic Tools
Authors: Benuzzi E. , Soavi F.
Published: July 2009

A theoretical solution is obtained for the pressure distribution at the die-material interface during a high-speed cold forging operation of a short metal cylinder workpiece, taking into account the elastic deformation of the tool considered as a half-space. The influence of the combined effects of axial and radial inertia forces, impact velocity, frictional conditions, plastic resistance of material, and radius to height ratio on pressure distribution and die surface deflection, are numerically evaluated. An illustrative example of dynamic compression with a gravity drop hammer is presented.
Control of Magnesium Loss During Laser Welding of Al-5083 Using a Plasma Suppression Technique
Authors: Blake A. , Mazumder J.
Published: July 2009

A major problem of autogeneous laser welding Al-5083 is the loss of magnesium by evaporation or plasma formation. This consequently results in welds of low tensile strength and unacceptable porosity. A method has been developed to control plasma formation during welding resulting in satisfactory welds with little or no magnesium loss and porosity. Plasma formation was controlled by manipulation of a main gas jet in a shielding arrangement during welding. Shielding gas pressure needed to suppress the plasma was within an order of magnitude of the theoretically estimated pressure required to sustain a vapor filled “keyhole.” The experiment was carried out using a 10 kW CW-CO2 laser. A two-level factorial experimental design correlated the effects of the independent laser processing variables with as-welded alloy chemistry. Alloy composition was characterized quantitatively using electron probe microanalysis techniques. Observations revealed that magnesium loss could be minimized to as low as 0.9 percent. Radiographic examination and tensile tests further demonstrated that low porosity welds with strengths at least as great as the parent material may be produced by controlling alloy composition via a specially designed inert gas shield.
Nondestructive Assessments of Residual Stresses in Railroad Wheel Rim by Acoustoelasticity
Authors: Fukuoka H. , Toda H. , Hirakawa K. , Sakamoto H. , Toya Y.
Published: July 2009

Residual stress in the rim of railroad solid wheel was measured nondestructively by an acoustoelasticity method which makes use of the birefringent effect. The acoustic anisotropy is a fractional velocity difference of two shear waves polarized perpendicularly in principal directions and is proportional to the principle stress difference. However, in order to get the residual stress nondestructively, the contribution of texture anisotropy has to be separated from the total acoustic anisotropy. The scatter of the texture anisotropy was investigated using seven wrought wheels, four of which were used for drag brake tests that were to change the residual stress level. The initial and after braked residual stress was analyzed by acoustoelasticity, and the results were compared with the conventional methods and FEM analysis. Conclusively, it is expected through this study that the residual stress averaged through thickness in the rim can be assessed nondestructively by using the average value of the texture anisotropy in the rim within 40 MPa of difference compared with the estimation by conventional destructive methods.
Principles of Dust Removal in Gin Machinery: Theoretical and Measured
Authors: Anthony W. S. , Columbus E. P.
Published: July 2009

Some textile mill workers develop byssinosis as a result of cotton dust. A wet extraction process can be used to remove most of the respirable dust but the quality of the yarn is lowered. Gin processes remove proportional quantities of respirable dust as a result of the pneumatic and mechanical forces that are applied to the dust particles. The effectiveness of each gin process in removing 15-micron diameter dust particles was evaluated experimentally and a lint cleaner was the only machine that effectively removed dust particles. Theoretical analyses of the effect of the gin processes on 15-micron diameter dust particles attached to the cotton fibers indicated that maximum pneumatic forces of 17.0 × 10−8 N were applied during the conveyance of seed cotton, and maximum mechanical forces of 28.7 × 10−5 N were applied during lint cleaning.
Stability Analysis of a Constant Force Adaptive Control System for Turning
Authors: Masory O. , Koren Y.
Published: July 2009

Adaptive Control Constrains (ACC) as applied to machine tool systems refers to the regulation of the cutting process characteristics such as spindle power, cutting force etc., by varying the only changeable process parameters which are feedrate and cutting speed. Even a simple ACC system, as in this case, in which the cutting force is regulated by changing the feedrate, is quite complex. Experiments with this simple system, implemented on a computerized numerical control (CNC) lathe, have shown that the CNC/ACC system can become unstable due to changes in depth-of-cut or spindle speed. This paper presents stability analysis of the above CNC/ACC system, thus making it possible to select appropriate gains which will maintain the system stable. Also, experimental results, which describe the stability region of such a system, will be provided.
A Dynamic Analysis of High-Speed Machining
Authors: Recht R. F.
Published: July 2009

The dynamics of chip formation during high-speed orthogonal machining (planing) is examined. Merchant’s vector diagram of the forces acting upon the continuous chip free body is expanded to include inertial force components. Expressions are developed for cutting force and pressure. Energy balances are used to show that Merchant’s classical equation relating shear angle φ to rake angle α and friction angle τ applies, independent of cutting speed. Apparent differences between experimental observations of shear angle φ and Merchant’s prediction are attributed to workpiece material anisotropies, tool wear, built-up edge, and inaccurate measurement of the friction coefficient at the tool–chip interface. It is shown that good experimental values of the shear angle and friction coefficient may be obtained by measuring cutting pressure, utilizing dynamic material properties data, and invoking Merchant’s relation to resolve the energy balance. Continuous and segmented chip formation are contrasted. Melting in the tool–chip interface is verified.
Analysis of Three-Dimensional Cutting Process Dynamics
Authors: Yang X. G. , Eman K. F. , Wu S. M.
Published: July 2009

A new experimental method for three-dimensional cutting analysis based on times series models and the Dynamic Data System methodology is introduced. Its theoretical formulation allows the treatment of both orthogonal and three-dimensional cutting without any additional complexity. Furthermore, it facilitates an easy explanation and proof of the independence of the inner and outer modulation effects and the use of a simple experimental setup. It is shown that the overall transfer matrix of the three-dimensional cutting process relating the force and relative displacement components can be identified in a single experiment. Based on the proposed theoretical models of the cutting process, suitable experimental procedures and methods were proposed and used in actual cutting. The obtained results confirmed the theoretical expectations.
Kinematic Synthesis of a Three-Axis Twist Drill Point Grinding Machine
Authors: Fugelso M. A.
Published: July 2009

Recently developed computer-controlled twist drill grinding machines have allowed the production of precisely defined points of widely different shapes. The design methodology used for these machines has yielded machines that have up to seven separate axes. This paper shows that in a machine where all the axes can move simultaneously only two rotations and one translation are required to grind drill points. The design methodology employed in this paper uses modern matrix kinematic methods. The kinematic equations developed are simple enough to be solved iteratively on a desktop computer. In addition, the requirement to preset the drill in the drill holder with a fixture is eliminated in this machine.
A Consideration on Deep-Drawability of Commercially Pure Aluminum Sheets
Authors: Kawai N. , Mori T. , Hayashi N. , Eguchi A. , Yasui Y.
Published: July 2009

Correlation between the deep-drawability of commercially pure aluminum sheets and the r value is investigated in detail. First, sheets with various r values are specially made for this study, and the conditions for making extra high r-value sheets are clarified. Then, it is found from the deep-drawability test that the limiting drawing ratio has a positive though weak correlation with r value. The reasons are considered both from the standpoints of drawing resistance and fracture strength and attributed to the variations of the r value during working. As a result, finding a strain path to enhance the r value is considered to be a future problem in the improvement of deep-drawability.
Contact Pressure Between an Annular Indenter and a Flat Surface
Authors: Kato T. , Kato S. , Yamaguchi K.
Published: July 2009

The pressure distributions on the contact surface between annular indenters of three different inner radii and flat surfaces were measured experimentally by using a newly developed method, in which the contact pressure was found by measuring the change in surface roughness. On the basis of the experimental results an empirical formula was proposed which represents the contact pressure distribution between an annular rigid indenter of any inner diameter and a flat elastic surface.
Unconventional Tee Forming on Metal Tubes
Authors: Moreira Filho L. A. , Al-Qureshi H. A.
Published: July 2009

An experimental machine using elastomer rod has been developed for the forming of tee-junction on metal tubes. This was achieved by applying loading-unloading cycles to the tube and the elastomer simultaneously. The success of the operation is governed by the so called “clearance height” which controls the relationship between the displaced volume of the elastomer and the reduced length of the tube. Present experiments have confirmed the validity of the empirical expression previously found. The upper-bound theory is found to be in good agreement with experimental results, for predicting the total forming load. The experiments were performed on materials with different work-hardening characteristics. In addition, the effects of other variables on the process are examined.
Overturning and Equilibrium Speeds and Speed Safety Margin—A Sensitivity Analysis
Authors: Kumar Sudhir , Prasanna Rao D. L.
Published: July 2009

Two critical speeds viz., the equilibrium speed and the overturning speed, are recognized to play an important role in defining operational and safety characteristics of railroads. An analysis of the sensitivity of the critical speeds to important operating parameters is presented. Two parameters called the ‘Speed Safety Margin’ and the ‘Speed Factor’ are defined to assist in evaluating the severity of a set of operating conditions. It is concluded that degree of curve has the most drastic effect on safety followed, in decreasing order of effect, by height of CG, superelevation, and track gage. Some comments are offered as a possible guide to safe and economical operation of railroads.
Wheel-Wear Compensation for Numerical Form Grinding
Authors: Giridharan T. , Dix R. C. , Nair S.
Published: July 2009

A new method for reducing the effect of grinding wheel wear on workpiece inaccuracy in numerically controlled form grinding of surfaces of revolution is proposed and analyzed. A mathematical model to describe wheel wear and contour production is developed for the grinding of a cyclindrical surface. The model results in a first-order hyperbolic differential equation for the radius of the wheel profile as a function of time and position. This equation is solved numerically using the method of characteristics. Closed-form solutions are also presented for a simplifed version of this equation. Pertinent results, such as reduction in the error in the workpiece radius, are presented to demonstrate the effectiveness of the proposed method.