bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Doubly Regenerative Stability of a Grinder: The Mathematical Analysis of Chatter Growth
Authors: Thompson R. A.
Published: July 2009

The growth of doubly regenerative chatter in a typical plunge cylindrical grinder is analyzed. The work is based on the mathematical method developed in reference [1]. Throughout, the physics of double regeneration is explained: (a) the individual contribution to chatter of wheel and workpiece regeneration is illustrated; (b) the wear resistant Borazon* wheel, although slightly more chatter prone, is shown to have an advantage over alumina because it requires less frequent dressing; and (c) the best in-process measure of grinding stability is shown to be wheel and workpiece lobe precession. The paper is concluded by showing how the optimum wheel and workpiece speeds are chosen. Under optimum conditions part tolerance and machine noise limit the maximum allowable grinding time and wheel wear establishes the dressing schedule.
On Shear Instability in Machining a Nickel-Iron Base Superalloy
Authors: Komanduri R. , Schroeder T. A.
Published: July 2009

The deformation in chips produced in machining a nickel-iron base superalloy (Inconel 718), at various speeds up to 213.5 m/min [700 surface feet per minute (SFPM)] has been investigated. In addition to slip, considerable twinning in the chips is observed at all speeds. Up to a cutting speed of about 30.5 m/min (100 SFPM), the chips formed are essentially continuous and ribbon-like, although deformation in the chip is inhomogeneous. At cutting speeds above 61 m/min (200 SFPM), shear-localized chips form. The longitudinal midsections of the chips show gross inhomogeneous deformation with shear localization between any two segments, and relatively low deformation within any individual segment. With an increase in speed the extent of contact between segments decreases rapidly, until a speed is reached where the individual segments become completely detached. The speed at which this occurs for other difficult-to-machine materials, such as AISI 4340, was found in an earlier study, to depend upon the metallurgical condition of the material and its hardness. Based on this study, the mechanism of chip formation when machining Inconel 718 is very similar to that reported earlier for machining both titanium alloys and hardened AISI 4340 steels at higher speeds. While the hcp crystal structure of titanium alloys in addition to titanium’s poor thermal properties (kρc) is believed to be partly responsible for the intense shear localization in that material, results with Inconel 718 (fcc) and AISI 4340 steel (bcc) indicate that the effect of structure on shear localization is not yet well understood.
Whirling Vibration in Drilling. Part 1: Cause of Vibration and Role of Chisel Edge
Authors: Fujii H. , Marui E. , Ema S.
Published: July 2009

The whirling vibration of the drill in the beginning of the drilling operation is experimentally investigated. Special attention is paid to how vibration develops as the drill proceeds into the workpiece. Three types of drills with different web thicknesses are used, and the characteristics and cause of the vibration are discussed. Whirling vibration, which has an elliptical orbit, is a self-exited vibration accompanied by a phase lag with respect to the revolution of the workpiece. The vibration energy is provided by the regenerative effect at the major cutting edge, while the chisel edge acts to dampen the vibration.
Effect of Hardness on the Surface Integrity of AISI 4340 Steel
Authors: Matsumoto Y. , Barash M. M. , Liu C. R.
Published: July 2009

The effect of hardness on the residual stress in the machined surface of AISI 4340 steel was studied. Chips produced during the machining also were examined and the surface structure was investigated using optical microscope and scanning transmission microscope. Reflection electron diffraction study revealed the existence of austenite in the white layer of the machined surface together with untempered martensite. The residual stress near the machined surface or hardened steel is a compressive stress, and it changes to tensile stress as the hardness decreases. Chip segmentation was observed when steel with hardness of over Rc 50 was machined.
Tool Wear Monitoring Through the Dynamics of Stable Turning
Authors: Rao S. B.
Published: July 2009

This paper describes a microcomputer-based technique for monitoring the flank wear on a single-point tool engaged in a turning operation. The technique is based on the real-time computation of a Wear Index (WI). This WI is a measure of the resistance, at the tool tip-workpiece interface along the flank, to the forced oscillations of the cantilever portion of the tool holder, during machining. Increasing flank wear results in an increasing area of contact between tool tip and workpiece. This translates to an increasing WI, proportional to flank wear-land width and independent of other cutting process variables. This WI, which can be computed on-line as a ratio of the measured dynamic force amplitude to the vibration amplitude, at the first natural frequency of the cantilever portion of the toolholder, forms the basis of the microcomputer system described in this paper for tool wear monitoring.
Improving Contouring Accuracy of NC/CNC Systems With Additional Velocity Feed Forward Loop
Authors: Masory O.
Published: July 2009

One of the factors which affects the contouring accuracy of multi-axis NC/CNC contouring systems is axes mismatch which means that the time constants and the open-loop gains of the machine servo drives are not identical. In conventional NC/CNC system each axis is separately controlled by a closed-loop velocity controller. Therefore, a position-following error which is a function of the open-loop gain and the time constant, is generated. Since the values of these parameters are different for each axis, a contouring error is produced. By adding a velocity feed forward loop to this controller, the position-following error can be reduced, or even eliminated, and consequently the contouring error is reduced.
A Crack Detection Technique for Use With Brittle Materials
Authors: Sampath W. S. , Ramaraj T. C. , Shaw M. C.
Published: July 2009

Crack gages are sensors designed to monitor crack initiation and growth in engineering structures by alteration of electrical conductance. Present gages involve a thick (5 μm) metal foil on an even thicker polymer substrate and are not suitable for use on brittle materials where the crack opening is small. The new technique employs a very thin (300 Å) gold film sputtered on a nonconducting brittle specimen. The method also enables crack propagation velocity to be estimated.
Distortion in Thermal Field Around Inserted Thermocouples in Experimental Interfacial Studies
Authors: Attia M. H. , Kops L.
Published: July 2009

The disturbance in a two-dimensional steady temperature field due to the presence of a thermocouple void is investigated. The void is located at a distance from an isothermal surface in a direction perpendicular to the heat flow lines. Using the electrical analog method, a computer-aided scanning and measurement system was developed for this study. The following two effects are investigated: (a) the change in the temperature field with the change in the distance between the void and the isothermal boundary. This allows us to define the location of the quasi-null point, (b) the interaction between two adjacent voids located along the direction of the heat flow; an aspect which has not been studied before. The results of this study are presented in a dimensionless form in terms of the contour maps of the disturbed temperature field and the temperature difference field. Estimates of the temperature measurement errors due to the above effects are presented.
An Improved Method for Cutting Force and Surface Error Prediction in Flexible End Milling Systems
Authors: Sutherland J. W. , DeVor R. E.
Published: July 2009

As more emphasis is placed on quality and productivity in manufacturing, it becomes necessary to develop models that more accurately describe the performance of machining processes. An improved model for the prediction of the cutting force system and surface error in end milling has been developed and has been implemented on the computer. This enhanced model takes into account the effect of system deflections on the chip load, and solves for the chip load that balances the cutting forces and the resulting system deflections. Such a model allows for the evaluation of cuts in which deflections significantly effect the chip load. The flexible system model predictions of forces and surface error are compared against both measured and rigid system model-predicted values associated with the machining conditions for experiments performed on the 390 casting aluminum alloy. It is shown that the enhanced chip load model gives predictions of both cutting force signatures and surface error profiles that are significantly better than the rigid system chip load model developed previously. The fact that system deflections temper the effects of runout, and reduce both peak cutting force and maximum surface error is demonstrated and discussed.
Governing Equations of the Shear Angle Oscillation in Dynamic Orthogonal Cutting
Authors: Wu D. William
Published: July 2009

Chatter is a complex physical process in machining. One of the practical ways of modeling its transfer behavior is to derive the force functions theoretically from the substance of steady state cutting. This often requires a knowledge about the shear angle variation during the process. This paper presents a new method of modeling the angular oscillation in dynamic orthogonal cutting. The system governing equations were derived based on the work-hardening slip-line field theory in cutting mechanics by taking into account the changes of stress conditions on both the shear plane and the tool-chip interface. The result of a simulation study conducted for a wide range of cutting conditions has shown a very good agreement between the theoretical predictions and the existing experimental evidence.
Nonisothermal Axisymmetric Forging
Authors: Dadras P. , Burte P. R.
Published: July 2009

An approximate solution for nonisothermal upset forging is presented. A finite difference thermal analysis and an upper-bound deformation solution are used for this purpose. The thermal analysis is for a homogeneous state of strain, it ignores deformation heating, but accounts for all modes of heat flow during the transfer of the billet to the tooling and throughout the deformation. The upper-bound solution is based on admissible velocity field equations, the recorded temperature data from the thermal analysis, and constitutive equations for temperature, strain, and strain rate-dependence of flow stress. The size of the chilled zone is determined by minimization of total power for the deformation process. Theoretical predictions for load-displacement behavior and the size of the chilled zone are compared with the experimental results for 304 stainless and AISI 1042 steels.
The Upper Bound Approach to Plane Strain Problems Using Linear and Rotational Velocity Fields—Part II: Applications
Authors: Avitzur Betzalel , Pachla Waclaw
Published: July 2009

Following Part I which investigated an upper bound approach to plane strain deformation of a rigid, perfectly plastic material, this Part II considers the same approach as applied to actual forming operations. The processes of drawing and extrusion, of metal cutting and of rolling are analyzed, and explicit equations are developed to calculate the surfaces of velocity discontinuity (shear boundaries), velocity discontinuities, and the upper bound on power for these processes. Both the simple, unielement velocity fields as well as the more complex multielement fields are explored. The upper bound solution is shown to be a function of the independent (input) and pseudoindependent (assumed) process parameters as minimized by an optimization procedure. Rules concerning the assumption of pseudoindependent parameters are presented and the optimization procedure is discussed. Final conclusions lead the way for the application of upper bound analyses to such industrial processes as sheet and strip drawing, extrusion, forging, rolling, leveling, ironing and machining, and to the investigation of such flow failure modes as central bursting, piping and end splitting (alligatoring).
Analysis of Acoustic Emission Signal Generation During Martensitic Transformation
Authors: Kannatey-Asibu Elijah , Pingsha Dong
Published: July 2009

The formation of cold cracks during welding of high strength steels is almost always preceded by martensite formation. Real time detection of both the martensite and cracks formed is a basic necessity of automated welding systems. Acoustic emission has been found to be highly suited for this purpose. Unfortunately, most of the work done to date on AE generation during martensitic phase transformation has been qualitative in nature. This paper presents a quantitative analysis of AE signal generation during martensite formation, using an energy method. This formulation relates the chemical free energy change which is the driving force for the transformation to the RMS value which is a measure of the energy content of AE signals. The analysis shows that the RMS signal is dependent on carbon concentration, volume transformed, cooling rate, and temperature. This is consistent with previous experimental work.
Micromechanical Property Prediction for Flexible Matrix Composite Materials
Authors: Gupta B. P.
Published: July 2009

Several closed-form solutions exit to predict elastic constants of a composite material. Most of these methods give comparable results for epoxy matrix composites, but not for flexible matrix composites, where the matrix is much softer than the fiber. We have devised a method that uses energy values given by finite element analyses of composite models, subjected to various independent displacement conditions. Results for flexible matrix composites thus obtained are compared with those determined by some of the existing methods. Closed-form solutions are recommended for approximate prediction of the different elastic constants by this comparison.
Finite Element Limitations for Orthotropic, Laminated Beam Analysis
Authors: Zak A. R.
Published: July 2009

This paper discusses the limitations of the existing finite element beam models for the analysis of orthotropic laminate beam analysis. These limitations are illustrated by comparing the existing models with a finite element model which has recently been developed by the author. This new model overcomes some of the existing limitations and is applicable to thin, laminated beam cross sections which are either open or closed. A simple numerical example is given and discussed comparing the existing theories with the results from the new model. The main limitations of the existing finite element models fall into two categories. The first of these is the problem of accurately modeling stresses in laminated configurations, especially if the orthotropic properties vary from layer to layer. The second difficulty is to model accurately the interaction between various deformations such as, for example, shear and normal strains.
Mixed Finite Element Models for Laminated Composite Plates
Authors: Reddy J. N. , Sandidge D.
Published: July 2009

Mixed finite element models of the classical and shear deformation plate theories are described, and their relative advantages, disadvantages and limitations are discussed. Numerical results showing the accuracy of the mixed finite elements are presented. Two main advantages of mixed models are the relaxation of continuity requirements on the interpolation functions and the accurate determination of the stress resultants. The disadvantages of mixed formulations are the difficulty in establishing convergence, accuracy and stability of finite element approximations and the computational expense.
A Case Study of Cure Cycle Shrinkage Deformations
Authors: Stanton E. L. , Mack T. E.
Published: July 2009

A case study of curing deformations in square struts laminated from unidirectional prepreg is presented that uses laminate and three-dimensional finite element analyses to analyze critical shrinkage behavior. The manufacture of square graphite epoxy struts is complicated by twisting deformations during cooling from autoclave cure temperatures that are not predicted by laminate analyses. Three-dimensional finite element analyses are presented that correctly predict the twisting but not its amplitude which appears to be dependent on a geometric nonlinearity. The three-dimensional and laminate results both show large self equilibriating stresses in individual plies caused by local shrinkage and stiffness property differences. This is a key finding that identified the source of shape instability and confirmed design changes to minimize twisting deformations that were first determined experimentally.
Surface Roughness Measurement Using Scanning Electron Microscope with Digital Processing
Authors: Sato H. , O-hori M.
Published: July 2009

Surface roughness measurement by scanning electron microscope (SEM) is investigated. The investigation was made by a digital processing technique, which follows a study by the analog method. The intensity of the backscattered electron signal is in proportion to the inclination of the surface profile, so that the surface profile can be obtained by integrating the backscattered electron signal along the scanning. The digital method made it possible to address the scannings and to designate the starting points for the processing on the respective scannings. The integral was carried out by a minicomputer that was connected through optical fibers which made the system free from transmission noise. The indicated positions can be monitored on a CRT display by overlapping these on the backscattered electron image. A simple and reliable calibration method is proposed by putting a standard test piece of the surface roughness close to the specimen. This confirmed that the order of 1/1,000 μm was obtained as the resolution of this method, as far as the inclination can be detected. The two dimensional roughness obtained for the scanning can be illustrated by isometric view (or by the equicontour map); this was impossible using the analog method. The noise effect by low- and high-frequency components could be eliminated by subtraction or by averaging, so a more accurate profile could be obtained.
Analysis of Hydrostatic Bulging of Anisotropic Rectangular Diaphragms by the Rigid-Plastic Finite Element Method
Authors: Yang D. Y. , Kim Y. J.
Published: July 2009

A variational formulation is derived for the incremental analysis of the nonsteady large deformation of normal anisotropic sheet metal which exhibits a rigid-plastic work-hardening behavior. The associated finite element equations are formulated for the analysis of the hydrostatic bulging process of square and rectangular anisotropic metal diaphragms. The relation between bulging pressure and deformation is studied using the finite element analysis. Instability related with the bulging deformation is analyzed by using the instability criterion for sheet metal. The effect of anisotropy on deformation and instability is investigated and discussed. The theoretical results are shown to be in excellent agreement with the existing experimental results and to be very helpful for a better understanding of the process.
An Analysis of Three-Dimensional Upset Forging of Regular Polygonal Blocks by Using the Upper-Bound Method
Authors: Yang D. Y. , Kim J. H.
Published: July 2009

A simple kinematically admissible velocity field for three-dimensional deformation in upset forging of regular polygonal blocks is proposed which takes into account the sidewise spread as well as the bulging along thickness. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to three chosen parameters. Experiments are carried out with annealed commercially pure copper at room temperature for different thicknesses, billet shapes and lubrication conditions. The theoretical predictions both in the forging load and the deformed configuration are in good agreement with the experimental results. It is thus shown that the velocity field proposed in this work can be conveniently used for the prediction of the forging load and deformation in the upset forging of regular polygonal blocks.
Comparison of Grinding and Lapping of Ferrites and Metals
Authors: Chandrasekar S. , Shaw M. C. , Bhushan B.
Published: July 2009

Mechanical finishing of ferrite materials used in magnetic storage systems are found to have a shallow magnetically inactive layer due to residual elastic stress in the surface. The residual stresses in ground and lapped Ni-Zn surfaces are measured and compared with comparable values for steel. Whereas the residual stress in a diamond ground ferrite surface is of predominantly mechanical origin (compressive) that in a conventionally ground steel surface is predominantly of thermal origin (tensile). Methods of reducing the residual stress in a lapped ferrite surface are discussed.
Morphology of Ground and Lapped Surfaces of Ferrite and Metal
Authors: Chandrasekar S. , Shaw M. C. , Bhushan B.
Published: July 2009

Scanning electron microscope pictures of ground and lapped ferrite (sinfered magnetic ceramic) and steel surfaces and chips are studied and compared. These reveal considerably more plastic action associated with the formation of metal chips in fine grinding than for ferrite chips. Individual chips are an order of magnitude larger for metals than for ferrites. These results are consistent with the much greater specific grinding energy for metals than for ferrites. The depth of the plastically deformed layer beneath a ground surface revealed by etching corresponds closely with the depth of residual surface stress.
On Tool Materials for High Speed Machining
Authors: Kramer B. M.
Published: July 2009

The trend towards increased machining automation improves plant utilization by reducing the nonmachining component of the production cycle and places a premium on reducing machining time. Improved tooling systems allow increased production rate with existing plant and equipment and result in increased production at negligible additional cost. Whereas new tool materials have traditionally been developed empirically, the state of understanding of the mechanisms of tool wear has advanced considerably in recent years. Therefore, an attempt has been made to identify specific strategies for developing new tooling systems for high speed machining in the light of current knowledge.
Honing Conditions for Effective Use of Diamond and Cubic Boron Nitride Sticks
Authors: Ueda T. , Yamamoto A.
Published: July 2009

Based on the honing theory developed earlier [12], the nominal depth of cut a¯i, was found to express the severity of honing conditions when using diamond and CBN sticks. The critical nominal depth of cut a¯ic is the important factor in evaluating the cutting ability of sticks, the machinability of work materials, and optimum operational conditions. Good honing performance can be obtained in the case where a¯ic > a¯i.
An Investigation into the Relationship between Torque and Load in Ring Rolling
Authors: Yang D. Y. , Ryoo J. S.
Published: July 2009

In the ring-rolling process most of the required forming energy is transferred from the roll into the deforming region by the aid of friction between the roll surface and the ring. In this paper a concept of “equivalent” coefficient of friction (μeq) is proposed, which is the ratio of frictional force of the driven roll to pressing load of the pressure roll. Considering the ring geometry and the related kinematics, the relationship between equivalent coefficient of friction and process parameters is derived. The upper-bound torque is also found based on the geometrical simplifications, and the roll of μeq for the upper-bound solution is investigated. The effects of various process parameters on equivalent coefficient of friction in ring rolling are then discussed.
Mathematical Foundations for Manufacturing
Authors: Kim S. H. , Suh N. P.
Published: July 2009

For the field of manufacturing to become a science, it is necessary to develop general mathematical descriptions for the analysis and synthesis of manufacturing systems. Standard analytic models, as used extensively in the past, are ineffective for describing the general manufacturing situation due to their inability to deal with discontinuous and nonlinear phenomena. These limitations are transcended by algebraic models based on set structures. Set-theoretic and algebraic structures may be used to (1) express with precision a variety of important qualitative concepts such as hierarchies, (2) provide a uniform framework for more specialized theories such as automata theory and control theory, and (3) provide the groundwork for quantitative theories. By building on the results of other fields such as automata theory and computability theory, algebraic structures may be used as a general mathematical tool for studying the nature and limits of manufacturing systems. This paper shows how manufacturing systems may be modeled as automatons, and demonstrates the utility of this approach by discussing a number of theorems concerning the nature of manufacturing systems. In addition symbolic logic is used to formalize the Design Axioms, a set of generalized decision rules for design. The application of symbolic logic allows for the precise formulation of the Axioms and facilitates their interpretation in a logical programming language such as Prolog. Consequently, it is now possible to develop a consultive expert system for axiomatic design.
Acoustic Emission Sensing of Tool Wear in Face Milling
Authors: Diei E. N. , Dornfeld D. A.
Published: July 2009

Acoustic Emission (AE) signal analysis was applied to on-line sensing of tool wear in face milling. Cutting tests were conducted on a vertical milling machine. AE signals, feed and normal components of cutting force and flank wear were measured and compared. A signal processing scheme for intermittent cutting forces and AE signals, based on the concept of time domain averaging (TDA) is proposed. The results indicate that both AE and cutting forces have parameters that correlate closely with flank wear.
A Method for Analyzing Spread, Elongation and Bulge in Flat Rolling
Authors: Kennedy K. F.
Published: July 2009

A method for analyzing spread, elongation, and bulge in flat rolling is developed. The analysis is based on an upper-bound approach in which an iterative numerical procedure is used to minimize the energy dissipation rate for kinematically admissible velocity field solutions for the rolling problem. Once the velocity field and the final shape of the plastically deforming body are known, then elementary stress analysis techniques are used to determine the force related aspects of the rolling problem. It is assumed that the rolled material is rigid perfectly plastic, and only the purely mechanical aspects of the metal deformation problem in rolling are considered, assuming isothermal conditions. The analysis shows good agreement with spread, elongation, roll separating force, and roll torque measurements in the hot rolling of mild carbon steel. Discussion of the factors which lead to single-bulge or double-bulge deformation in flat rolling, and a suggested technique for estimating the interface friction conditions in rolling, the Flat Bar Test, are also included.
Real-Time Identification and Control of Springback in Sheet Metal Forming
Authors: Chandra A.
Published: July 2009

Sheet metal forming processes are prone to variations in material and process parameters. In an unmanned manufacturing cell, all the control functions must be automated and real-time measurement, identification, and control are necessary for satisfactory operation in the presence of these disturbances. A methodology is developed here for on-line identification of key material and process parameters in a combined stretch-bend situation. The springback predictions obtained from this scheme are verified, and an algorithm for on-line control of springback in plane strain stretch-bend operations is then discussed.
An Analysis of the Drill Wandering Motion
Authors: Lee S. J. , Eman K. F. , Wu S. M.
Published: July 2009

An analytical model has been developed to investigate the drill wandering motion quantitatively. It has been shown mathematically why the resulting distorted polygon-shaped hole always has an odd number of sides during drill entry, and how the profile of the hole gradually becomes round with increasing hole depth. Drilling processes were simulated using this mathematical model and the results compared with experimental evidence. Subsequently, an experimental analysis on the influence of point geometry on drill wandering has been presented.
Analysis of Strip Rolling by the Upper Bound Approach
Authors: Avitzur B. , Gordon W. , Talbert S.
Published: July 2009

The process of strip rolling is analyzed using the upper bound technique. Two triangular velocity fields, one with triangles in linear rigid body motion and the other with triangles in rotational rigid body motion, are developed. The total power is determined as a function of the four independent process parameters (relative thickness, reduction, friction and net front-back tension). The results of these two velocity fields are compared with the established solution from Avitzur’s velocity field of continuous deformation. Upon establishing the validity of the triangular velocity field as an approach to the strip rolling problem, recommendations are suggested on how this approach can be used to study the split end or alligatoring defect.
Analyses of Axisymmetric Sheet Forming Processes by Rigid-Viscoplastic Finite Element Method
Authors: Park J. J. , Oh S. I. , Altan T.
Published: July 2009

Two types of sheet forming processes are analyzed by rigid-viscoplastic FEM (Finite Element Method): axisymmetric punch stretching and hydrostatic bulge forming. The present formulations, based on the membrane theory and the Hill’s anisotropic flow rule, include the rate sensitivity which is a key factor in controlling the forming of superplastic materials. Normal anisotropy is taken into account and Coulomb friction is assumed at the interface between punch and sheet. Nonsteady-state deformation processes, investigated in this study, were quasi-statically and incrementally analyzed. An FEM code was developed, using two-node linear elements with two degrees of freedom at each node, and applied to solve four categories of problems: (1) A.K. steel punch stretching, (2) hydrostatic bulging of a rate-insensitive material, (3) hydrostatic bulging of rate-sensitive materials, and (4) hydrostatic bulging of a superplastic material (Ti-6-4). Strain distributions and shape changes predicted in the first two problems were compared with experiments and results of other analyses. The results of the third problem could not be compared with experiments; however, the results showed that the rate sensitivity affects the deformation as expected. The fourth problem is the main theme of this paper. To maintain the superplasticity in forming processes and to produce sound products, the control of the strain-rate is a key factor. A hydrostatic bulge forming process, which is often used for manufacturing structural aerospace parts, was analyzed and discussed. Further, an optimum pressure curve (pressure versus time), which maintains the desired strain-rate in the deformed material, was obtained and compared with the results of an analytical prediction, available in the literature.
Effects of Punch Cross-Section on Deep-Drawability of Square Shell of Aluminum Sheet
Authors: Kawai N. , Mori T. , Hayashi H. , Kondoh F.
Published: July 2009

Effects of product shape and a planar-anisotropy on a square shell drawability were studied, using commercially pure aluminum sheet. Two phenomena were mainly considered to affect a forming limit: (a) the prevention of crack initiation at the corner of a punch by adjacent straight punch profile regions, (b) the metal flow in the flange region from the corner to the straight side, the “Strain Relief Effect,” which serves to decrease the deformation at the corner.
A Dynamic State Model for On-Line Tool Wear Estimation in Turning
Authors: Danai K. , Ulsoy A. G.
Published: July 2009

This paper proposes a dynamic state model of tool wear. This model is developed for the design of an adaptive observer which is used for on-line tool wear sensing in turning based on force measurement. The model treats flank wear and crater wear as state variables, cutting force as the output, and feed as the input. Relationships from the manufacturing literature are used in constructing this nonlinear model. Simulation results are presented for the nonlinear model, and eigenanalysis and controllability and observability analyses are performed on a linear model obtained by linearizing the nonlinear model about an operating point along its trajectory. The simulation results show good agreement with results in the manufacturing literature. The eigenanalysis shows the linear model to be unstable, reflecting the continually increasing nature of the wear processes modeled; and the model is shown to be controllable by feed and observable by cutting force for the cutting conditions considered in the paper.
Gains Selection for a Variable Gain Adaptive Control System for Turning
Authors: Lin Shield Bao-Hsin , Masory Oren
Published: July 2009

The adaptive control constraint system described is a nonlinear, sampled data system designed to regulate the cutting force during turning operations. The controller keeps the system stable under wide variations in process parameters, limits the force overshoot, and provides fast transient response. The stability region of the nonlinear system was determined in order to define the boundaries of the gain space within which the optimal gains that minimize the ISE index of performance were selected. As a result, a data base for optimal gains as functions of process parameters was generated. Since in most cases the depth-of-cut changes in an unknown manner, the use of this data base is limited. To overcome this problem, an on-line adaption scheme of the gains was designed to achieve optimal response without the need for depth-of-cut measurements. With this control scheme, a series of simulations were performed that demonstrate excellent response under wide variations of process parameters.
Abrasive Grain Temperature at the Beginning of a Cut in Fine Grinding
Authors: Ramanath S. , Shaw M. C.
Published: July 2009

In any grinding operation heat flows periodically into the abrasive grains in the surface of the wheel during wheel-work contact and is extracted during the remaining portion of a single revolution of the wheel. If it can be assumed that all of the heat flowing inward is extracted outward during the cooling portion of a single wheel revolution, then the thermal partition coefficient R=heattowork/totalgrindingenergy may be readily estimated. This paper discusses conditions under which this assumption represents an acceptable approximation.
On-Line Estimation of Tool/Chip Interface Temperatures for a Turning Operation
Authors: Chow J. G. , Wright P. K.
Published: July 2009

This research has been concerned with the measurement of on-line temperature in a turning operation. The goal has been to develop a measurement sensor and algorithms that allow tool-chip interface temperatures to be estimated during machining. The measuring scheme relies on the signal from a standard thermocouple, located at the bottom of the tool insert, the response time of which has been observed to be on the order of one second. The important feature of the prediction scheme is that it can also estimate the interface temperatures for an interrupted cut and for the case when tool wear is present. The estimated interface temperatures have been compared with those obtained with a previously described metallographic technique [1] and a difference of 5–13 percent between these two results has been reported.
A Hierarchically Structured Knowledge-Based System for Welding Automation and Control
Authors: Thompson D. R. , Ray A. , Kumara S.
Published: July 2009

The paper presents the concept and prototype development of a hierarchically structured knowledge-based system (KBS) for coordinated control of a welding robot and a positioning table. The KBS is designed for continuous seam welding in an autonomous manufacturing environment. The structure of the KBS allows updating and installation of individual function and database modules such as those used for determining welding parameters and identifying constraints and parameters for robot and table controllers. The KBS is designed to plan the feasible table configurations and robot trajectories as well as to coordinate the movements of the robot and positioning table. The KBS has a modular structure which can accommodate multiple configurations of different types of robots and positioning tables within a flexible manufacturing cell. Initial testing has demonstrated the feasibility of integrated heuristic and algorithmic procedures for real-time applications. A fully implemented version of this KBS will enable a user to perform high quality welds in a relatively short period of time with (possibly) incomplete knowledge of the welding cell equipment. The KBS software is written in the C language and has been tested for real-time operations within a simulated welding cell environment.
High Accuracy Slit-Ray Position Measurement
Authors: Nomura Y. , Naruse H. , Morimitsu T.
Published: July 2009

The accuracy of slit-ray position measurement on an image plane of a TV camera is improved to the order of one-hundredth of pixel spacing by a regression analysis and an error analysis. Also, the effectiveness of the method is confirmed by means of shape measurement experiments.
Finite Element Modeling of Plane-Strain Strip Drawing With Interface Friction
Authors: Lu S. C-Y. , Wright P. K.
Published: July 2009

Numerical results of plane-strain strip drawing are presented emphasizing the interfacial friction conditions between workmaterial and drawing die. The results are based on a large-strain elasto-plastic finite element code with a special boundary condition capability to treat interface friction. Two different modeling approaches are developed. In the interface velocity model, finite element solutions are based on the velocity boundary conditions along the die-work interface measured through transparent sapphire dies. In the interface traction model, a technique called “General Linear Boundary Condition,” is developed to incorporate many different existing friction models. Predicted values of drawing force, die separating force, global friction, and residual stresses from both models are favorably compared with the corresponding experimental measurements.
Precision Crack-off of Brittle Materials
Authors: Chandrasekar S. , Shaw M. C.
Published: July 2009

A phenomenon called the “pinch-off effect” discovered by P. W. Bridgman about seventy five years ago that constituted a mode of failure in his high pressure equipment may be used to advantage to cleave brittle materials with potentially high precision, This paper discusses the nature of this phenomenon, how to estimate the required fluid pressure, requirements for successful use, and some possible applications.
Computer-assisted Prediction of Drill-failure Using In-process Measurements of Thrust Force
Authors: Thangaraj A. , Wright P. K.
Published: July 2009

A real time control system has been developed in the laboratory to monitor the performance of twist drills. Emphasis has been placed on the prediction of the incipient failure of the drill and retraction before significant damage has occurred. It has been found that the gradient of the drilling thrust force, calculated using a digital filter with the necessary frequency specifications, exhibits a sharp increase several seconds before any serious failure. Details of the filtering technique and results for several cutting conditions are presented.
Belt Forces With Grinding
Authors: Kim H. , Marshek K. M.
Published: July 2009

This paper investigates belt forces in abrasive belt grinding. The distribution of normal and tangential belt forces are determined analytically and experimentally for belt grinding with both a driving and a driven pulley contact wheel. The experimental results are compared with the analytical results.
The Mechanism of Chatter Vibration in a Spindle-Workpiece System: Part 3—Analytical Considerations
Authors: Marui E. , Kato S. , Hashimoto M. , Yamada T.
Published: July 2009

Chatter vibration occurring in the spindle-workpiece system of a lathe is treated theoretically, considering the phase lag of cutting force and chatter marks, the dynamic variation effects on cutting force of cutting velocity, and the rake angle during vibration. As a result, it is clarified that the chatter vibration is mainly induced by the phase lag of cutting force (primary chatter) and by the phase lag of chatter marks in successive cutting (regenerative chatter). The dynamic variations of the cutting velocity and rake angle make the spindle-workpiece system more unstable under vibration. The effect of cutting velocity variation is more remarkable than that of rake angle in both types of chatter. Chatter vibration can effectively be suppressed by enlarging the damping capacity of the system.
Estimating the Nonlint Content of Yarn With Television Images
Authors: Taylor R. A.
Published: July 2009

Video scanning type trashmeters have been developed to identify and integrate the amount of trash observed in cotton. They perform a surface scan of trash particles in lint samples compressed against an observation window. This study reports the use of video scanning measurements on yarn samples to estimate the quantity of visible trash remaining in yarn. Methods described can be used to rapidly grade yarn for visual quality and fabric defect potential.
An In-Process Flatness Error Measurement and Compensatory Control System
Authors: Park C. W. , Eman K. F. , Wu S. M.
Published: July 2009

The principles of a new in-process measurement and control system for flatness errors in machining have been introduced. The laser-based system consists of a stylus, a geometrical table measurement system, and a forecasting compensatory controller. Through the application of the proposed system to simulated and actual cutting data it has been shown that improvements of flatness on the order of 80 percent are feasible.
Monitoring Drilling Wear States by a Fuzzy Pattern Recognition Technique
Authors: Li P. G. , Wu S. M.
Published: July 2009

This paper introduces a new approach for on-line monitoring of drill wear states by using a fuzzy C-means algorithm. Experimental and simulation results have shown that drill wear conditions can be represented by four fuzzy grades. They are: “initial,” “small,” “normal,” and “severe.” The grade “severe” is proposed to be used as the prediction of tool replacement. This fuzzy technique is more adequate than conventional pattern recognition technqiues.
Plastic Anisotropy in Drawn Metal Tubes
Authors: Kyriakides S. , Yeh M. K.
Published: July 2009

A relatively simple experimental procedure for establishing the anisotropic yield characteristics of commercially available drawn metal tubes is described. Hill’s [4] extension of the Von Mises yield criterion to anisotropic yielding is used to describe the anisotropy present. Results from commercially available stainless steel are presented where the anisotropy is characterized by differences between the yield stresses in the circumferential and axial directions.
Chatter Vibration in Drilling
Authors: Ema S. , Fujii H. , Marui E.
Published: July 2009

Chatter vibration of long drills has been investigated using several drills with different overhang lengths and special drills with different pieces of additional mass. The frequency, amplitude, initiation boundary, and unstable range of chatter vibration were measured at various cutting parameters. The experimental results showed that the vibration is a regenerative chatter and its frequency is equal to the bending natural frequency of the drill when the drill point is supported in a machined hole. Based upon the experimental results, the stability of chatter vibration was discussed. It was clarified that unstable ranges appear only when the chatter frequency in one workpiece rotation is an odd number.
Tool Fracture at the End of a Cut—Part 1: Foot Formation
Authors: Ramaraj T. C. , Santhanam S. , Shaw M. C.
Published: July 2009

Refractory metal cutting tools exhibit an unusually high probability of edge chipping and gross fracture when suddenly unloaded after cutting a strong material at high speeds and feeds. After identifying three possible mechanisms of brittle fracture when a cutting tool exits a cut, that associated with so-called “foot” formation is discussed in detail. This involves a sudden shift from steady state chip formation by concentrated shear to gross fracture of the workpiece as the end of the cut is approached. The other possible mechanisms are discussed in a companion paper to follow.
On the Machinability of Powder Metallurgy Austenitic Stainless Steels
Authors: Agapiou J. S. , Halldin G. W. , DeVries M. F.
Published: July 2009

Powder Metallurgy (P/M) materials, especially those made of high strength steels, are often reported in the technical literature to have poor machinability when compared to their wrought or cast counterparts. In order to characterize the machinability of single phase P/M materials and to identify the influence of porosity on that behavior, the machinability of P/M 304L austenitic stainless steel was evaluated as a function of porosity, in the range of 64 to 90 percent of theoretical density. Machinability was defined in terms of the average drill point temperature. It was found that the drill temperature increased with porosity to a point. Further increases in porosity produced decreasing levels of average drill point temperature. The nonlinear machinability response was attributed to the offsetting contributions of the thermal conductivity, the work-hardening, and the bulk properties of the P/M material.
Dynamic Modeling for Control of the Milling Process
Authors: Lauderbaugh L. K. , Ulsoy A. G.
Published: July 2009

In the interest of maximizing the metal removal rate and preventing tool breakage in the milling process, it has been proposed that fixed gain feedback controllers, which manipulate the feed rate to maintain a constant cutting force, be implemented. These process controllers have resulted in substantial improvements in the metal removal rate; however, they may have very poor performance when the process parameters deviate from the design conditions. To address these performance problems, an empirical second order model of the force response for a milling system to feedrate changes is presented along with experimental results which show that the parameters of this model vary significantly with cutting conditions. These variations are shown to have significant effects on the performance of fixed-gain proportional plus integral action and linear model following controllers. This is demonstrated using machining tests as well as through digital simulations.