bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation and Ejection of EDM Debris
Authors: Rajurkar K. P. , Pandit S. M.
Published: July 2009

This paper presents a theoretical and experimental investigation into the debris formation and ejection mechanism. An expression for the size of a debris particle is derived using the drop formation energy and the kinetic energy of the ejected debris particle. The velocity of the ejected particle is obtained from expressions derived on the basis of the analysis of hydrodynamic propagation of shock waves generated due to electrical breakdown in dielectric. The debris particles were collected by machining AISI 1020 steel under various operating conditions. The projected areas were measured by a microscope following the standard procedure of particle size measurement. The particle size has been found to be log normally distributed. The experimental values of debris size compare well with the theoretical estimation indicating the validity of the proposed analysis.
A Theoretical Examination of Switching Functions for Solid Modeling Data Structures
Authors: Shpitalni M.
Published: July 2009

The role of geometrical modeling is of increasing importance in the field of CAD/CAM. In the present paper a new concept is presented for geometric modeling of the data structure using volumetric representation via switching functions in a Gray coded space (3-D Karnaugh map). The data structure consists of a single generic cuboid primitive which may vary in size and aspect ratios. This provides for more generalized and flexible object representation than uniform spatial occupancy enumeration. The combination of a single primitive, Gray coded space, and representation via switching functions yields a very efficient data structure oriented toward set operations which can be carried out via a simple assembler program or a parallel logic processor. As objects are represented by a nonhierarchial list of fixed format terms, uniform algorithms can be used to perform given tasks regardless of object shape, dimensions, or complexity.
Analysis of a Test Method of Sheet Metal Formability Using the Finite-Element Method
Authors: Toh C. H. , Shiau Y. C. , Kobayashi Shiro
Published: July 2009

The rigid-plastic finite element method was used to study the formability of sheet materials. In the finite element simulations, sheet material was assumed to be rigid plastic and to follow Hill’s anisotropic yield criterion and its associated flow rules. The work hardening effect and Coulomb friction were incorporated into the analysis. Hasek’s test, hemispherical punch stretching of the circular blank with circular cutoff, was analyzed in detail by simulation. The computed solutions were obtained using different blank geometries and coefficients of friction between the tool-sheet interface. Strain paths of critical elements were plotted in major and minor surface strain space. Experiments were also carried out using AISI 304 stainless steel sheets, and the results were compared with predictions for load-displacement curves and thickness strain distributions. Further, an attempt was made to construct a forming limit curve based on the detailed analysis of the test by computation.
Influence of Car Tonnage and Wheel Adhesion on Rail and Wheel Wear: A Laboratory Study
Authors: Kumar S. , Krishnamoorthy P. K. , Prasanna Rao D. L.
Published: July 2009

This study presents the results and analysis of a laboratory investigation, of rail and wheel wear under clean and dry tangent track conditions, utilizing the IIT-GMEMD quarter scale simulation facility. Important factors influencing rail degradation are discussed followed by five different load/lubrication classifications of contacts. Influence of two important parameters, viz. wheel load (N) and adhesion coefficient of the tractive wheels (μ), on rail and wheel wear has been studied under conditions of Hertzian simulation. Seven separate experiments were conducted to measure wear of rail and nontractive freight car wheels. These were followed by six additional wear tests, simulating a typical U.S. locomotive, to investigate the effect of adhesion coefficients. The wear rates for tonnages* exceeding 65–70 t car increase at a much higher rate than those for tonnages below 65 t. Nonlinear relationship showing wear rate proportional to N5.4 and a bilinear relation have been developed. Considerations of contact plasticity show that the stress corresponding to 68-t freight load is a threshold stress which when exceeded leads to continual plasticity of new rails thus preventing shakedown. The influence of adhesion coefficient is also quite nonlinear, the wear rates being much higher for μ > 0.3. Photomicrographs of the surfaces of the wheel and rail at the end of the tests showed mild wear for μ ≤ 0.25 and severe wear for μ ≥ 0.35 indicating a transition of wear mechanism from mild to severe slightly above μ = 0.25. Wear rate is found to be approximately proportional to the square of the adhesion coefficient. A bilinear relation of wear rate versus μ, which is more accurate, is also given. It was observed that the effect of adhesion is more severe than the effect of tonnage alone. However, the tonnage effect is of serious consequence regarding plastic shakedown of the rails. A formulation of wear rate as a combined function of tonnage and adhesion coefficient is given. The urgent need for a solution of this problem is pointed out.
A Generalized Finite Element Analysis of Sheet Metal Forming With an Elastic-Viscoplastic Material Model
Authors: Chandra A.
Published: July 2009

A finite element analysis for elastic-viscoplastic problems in the presence of large strains is presented in this paper. The formulation is capable of using any of a class of combined creep-plasticity constitutive models with state variables for the description of material behavior. The specific problem considered is plane strain sheet metal forming using the constitutive model originally proposed by Hart. Numerical results are presented for sample problems and the effects of variations in several process parameters, such as velocity, friction at punch, and die interfaces, are investigated. The present report includes membrane, bending, and shear effects as well as the coupling among them and no a priori assumption is made about the strain distribution across the thickness. Thus, it unifies the earlier approaches used in sheet metal forming analysis and helps in gaining crucial insights into the process of sheet metal forming. It can also be extended to other large strain design and manufacturing problems.
Measuring Tool-Chip Interface Temperatures
Authors: Kottenstette J. P.
Published: July 2009

A two-color pyrometer was developed for monitoring the surface temperature of metal chips formed during high-speed machining processes. Optical access to the tool-chip interface was obtained by cementing a plastic light pipe into a 1/16-in. (1.6-mm) hole milled through the carbide tool insert. The light pipe serves to transmit radiation falling on the rake face of the insert to radiation detectors located elsewhere. Radiation captured by the light pipe is passed through a lens-beam splitter combination and imaged on two identical photodiode detectors. The diodes have integral operational amplifiers to achieve high detectivity and low-noise operation. Each photodiode is masked by an interference type narrow-band filter having spectral bandpass frequencies chosen to match the point where the emittance of several metals is constant for all temperatures. Thus, the temperature of the chip stream monitored by the diodes is a function of the intensity measured for each spectral band at the same instant in time. The functional relationship between true temperature and the ratio of signal amplitudes (the calibration curve) was established for pyrometer over the interval 1000–1750 K using standard laboratory methods.
Buffer Size Planning Versus Transfer Line Efficiency
Authors: Villa A. , Fassino B. , Rossetto S.
Published: July 2009

The paper deals with the main design problem for series production systems, namely the choice of efficiency-optimal values of interstage buffer capacities. It is shown that the design tool must be an accurate dynamic model, able to describe both work station reliability and the couplings among stations (i.e., blocking and starving situations) due to finite storage spaces. By use of this model, the buffer size planning problem can be solved by developing a sensitivity analysis of the model operation modes with respect to buffer capacity values. According to this approach, an analysis of the transfer line efficiency reduction, due to either nonoptimal capacity values or station reliability variations, is also performed.
Geometric Representation of Translational Swept Volumes and its Applications
Authors: Leu M. C. , Park S. H. , Wang K. K.
Published: July 2009

This paper presents a method for representing the geometries of translational swept volumes of three-dimensional objects which can be constructed by the union of three types of primitive objects: blocks, cylinders, and spheres. The representation method involves three major steps. First, the swept volume of each primitive object is modeled by a boundary representation. Second, based on ray-casting and scan-rendering methods, the boundary representation is converted into a ray in–out classification, which represents the rays entering and exiting from the primitive swept volume. Third, the ray in–out classifications for various primitive swept volumes are combined to represent the swept volume of an object constructed from the primitive objects. Examples are given to illustrate how swept-volume representations can be useful in the context of off-line NC and robot program verifications.
Analysis of Core Fracture in Drawing of Bimetal Rods and Wires
Authors: Avitzur B. , Wu R. , Talbert S. , Chou Y. T.
Published: July 2009

A criterion for the prevention of core fracture during drawing of bimetal wire is proposed. In order to account for the contrary effect of friction between codrawing and coextrusion on the occurrence of core fracture, a model is considered which assumes a deformation geometry slightly different from that used in the development of the criterion for core fracture during coextrusion [1]. Comparison between the two criteria for codrawing and coextrusion is presented. The effects of independent process parameters on the incidence of core fracture are summarized and discussed.
Whirling Vibration in Drilling. Part 2: Influence of Drill Geometries, Particularly of the Drill Flank, on the Initiation of Vibration
Authors: Fujii H. , Marui E. , Ema S.
Published: July 2009

The development of whirling vibration is observed by using drills with various web thicknesses, point angles, relief angles, and various helix angles in order to investigate the effect of drill geometry on the initiation of vibration. It becomes clear that the flank surface of the major cutting edge can dampen the vibration. This, plus the fact that the chisel edge exerts a restraining effect (Part 1), makes it clear that the initiation boundary of the whirling vibration can be specified by two parameters, the chisel edge length and the flank surface configuration, which can be represented by a flank collision index introduced.
Criterion for the Prevention of Sleeve Fracture During Extrusion of Bimetal Rods
Authors: Avitzur B. , Wu R. , Talbert S. , Chou Y. T.
Published: July 2009

In conjunction with the previous analysis on core fracture [1, 2], a criterion for prevention of sleeve fracture in extrusion of bimetal rods is developed. The sleeve fracture is likewise affected by a set of independent process parameters, namely the reduction in area, die angle, friction, interfacial bonding, relative size, and relative strength of the sleeve. It is shown that the usage of the present criterion for sleeve fracture and the criterion previously described for core fracture can provide an effective path to a successful extrusion operation for bimetal rods and wires.
Optimal Continuous Path Planning for Seven-Degrees-of-Freedom Robots
Authors: Benhabib B. , Goldenberg A. A. , Fenton R. G.
Published: July 2009

The paper addresses the problem of end effector trajectory planning and control of seven degrees of freedom (DOF) kinematically redundant robots. An off-line optimal continuous path planning method is developed for on-line control at joint level. The specified end effector path is approximated by a set of location nodes selected on the desired path. The motion control of the robot is provided by cubic polynomial interpolation at joint level. The proposed approach to trajectory planning of kinematically redundant robots consists of obtaining an optimal set of nodes which guarantees minimum deviation from the desired Cartesian path. The redundant DOF of the robot is used as a constrained variable in the optimization search. The method is illustrated in an example.
Time Series Control Charts for Correlated and Contaminated Data
Authors: Notohardjono B. D. , Ermer D. S.
Published: July 2009

This paper discusses the development of control charts for correlated and contaminated data. For illustration the charts were applied to a set of maximum principal-stress data at two locations on a blast furnace shell. The Dynamic Data System (DDS) approach was used to model the correlated data which contained several types of discrepancies. After the standard DDS models were found, control charts for the averages and variances of the model residuals were constructed for two data sets. For more effective analysis, two methods for calculating the control limits for both charts are given. With this approach, dynamic process change, such as an increase in the production rate or the wearing out of the sacrificial lining, can be detected and separated from data with collection errors from instrument malfunctions. Furthermore, the tap hole opening timing is identified from the DDS model parameters, to help verify the time series model.
A Search Algorithm for the Bicriterion Group Technology Machine Loading and Product Mix Problem
Authors: Leong G. Keong
Published: July 2009

The bicriterion machine loading and product mix problem in a Group Technology (GT) setting is the key to improving production output and cost and involves the primary objective of maximizing output and secondary objective of minimizing production cost. This paper proposes a search algorithm for solving the bicriterion GT problem that provides better results than Hitomi and Ham’s algorithm [6]. The proposed algorithm allows only complete lots of parts to be selected for production.
A Remote Temperature Sensing Technique for Estimating the Cutting Interface Temperature Distribution
Authors: Yen David Wei , Wright Paul K.
Published: July 2009

Cutting temperature is a major factor in controlling tool wear rate. Thus, sensing and control of cutting temperature is important in achieving a desired tool performance. This paper is concerned with estimating the cutting interface temperature distribution based on remote temperature measurements. This class of problems of estimating unknown boundary conditions from known interior quantities is called the inverse problem. The inverse problem of a square insert under steady state conditions is considered in this paper. The temperature distribution in a square insert is best described in Ellipsoidal Coordinates. The mapping functional in the one-dimensional case is solved analytically. The mapping functionals in general three-dimensional cases are solved numerically using the semianalytical finite element method. The mapping functional in a three-dimensional case is represented by a transformation matrix which maps one vector representing the cutting interface temperature distribution to another vector representing the remote temperatures. The transformation matrix is then used to solve the inverse problem of estimating the interface temperature distribution with redundant remote measurements. Measurement errors and transformation matrix errors are imposed in simulation studies. The sensitivity of inverse solutions to these errors is discussed.
Analysis of Central Bursting Defects in Plane Strain Drawing and Extrusion
Authors: Avitzur B. , Choi J. C.
Published: July 2009

Based on the upper-bound theorem in limit analysis, the central bursting defect in plane strain drawing and extrusion is analyzed by comparing the proportional flow with the central bursting flow for the metal with voids at the center. A criterion for the unique conditions that promote this defect has been derived. The metal with voids may flow in the identical manner to that of solid strip with no voids to form a sound flow, deterring central bursting. A solid strip, on the other hand, or a material with voids, may flow in a manner so as to produce central bursting defects. A major conclusion of the study is that, for a range of combinations of inclined angle of the die, reduction, and friction, central bursting is expected whether or not the material originally had any voids. On the other hand, central bursting can be prevented even if the original rod contains small-size voids.
A Stochastic Model for Fatigue Crack Growth Rate Data
Authors: Ortiz K. , Kiremidjian A. S.
Published: July 2009

This paper summarizes a new approach to the probabilistic modeling of fatigue crack growth. The material’s resistance to fatigue crack growth is modeled as a stochastic process, which varies randomly along the crack path. Model parameters are determined through time analysis of fatigue crack growth rate data. Predictions of the statistics of crack growth are excellent, especially for small cracks.
Advanced Reliability Methods for Structural Evaluation
Authors: Wirsching P. H. , Wu Y.-T.
Published: July 2009

Approximate solutions to the general structural reliability problem, i.e., computing probabilities of complicated functions of random variables, can be obtained efficiently by the fast probability integration (FPI) methods of Rackwitz-Fiessler and Wu. Relative to Monte Carlo, FPI methods have been found by the authors to require only about 1/10 of the computer time for probability levels of about 10−3. For lower probabilities, the differences are more dramatic. FPI can also be employed in situations, e.g., finite element analyses when the relationship between variables is defined only by a numerical algorithm. Unfortunately, FPI requires an explicit function. A strategy is presented herein in which a computer routine is run repeatedly k times with selected perturbed values of the variables to obtain k solutions for a response variable Y. An approximating polynomial is fit to the k “data” sets. FPI methods are then employed for this explicit form. Examples are presented of the FPI method applied to an explicit form and applied to a problem in which a polynomial approximation is made for the response variable of interest.
Suppression of Machine Tool Chatter Using a Viscoelastic Dynamic Damper
Authors: Kim K. J. , Ha J. Y.
Published: July 2009

Optimization procedures to install a viscoelastic dynamic damper into a single degree of freedom primary system is briefly reviewed. Excitation methods are shown to identify elastic modulus and loss factor of a viscoelastic material at given prestrain, which are needed in the optimum design of the damper. An optimum-designed damper is attached on the toolpost of a lathe and its excellent chatter-suppressing effects are observed under six cutting conditions in terms of integrated power of the accelerations around the chatter frequency. Because one of the resonance frequencies responsible for the chatter varies depending upon the location of the carriage on the sliding surface, the prestrain of the viscoelastic element, which is initially optimum-tuned and damped at a location of the carriage, is readjusted for optimum tuning at the other locations. The effects of the readjustment are discussed in terms of the reduction of structural compliances and magnitudes of chatter vibrations.
A Consideration of Surface Roughness Measurement by Optical Method
Authors: Shiraishi M.
Published: July 2009

A modified reflection theory based on Beckmann and Spizzichino is described which evaluates the surface roughness in connection with Rmax roughness value. Computer simulations due to this theory are relatively in good agreement with the experiments. Further, the simulation results suggest that the reflection characteristics can be freely changed to some extent by varying the incidence and acceptance angles of light. Also, the proposed measuring system is easily applicable to the real-time detection of turned surfaces without affecting its working accuracy.
A New Tolerance Analysis Method for Designers and Manufacturers
Authors: Greenwood W. H. , Chase K. W.
Published: July 2009

Even when all manufactured parts for an assembly are produced within limits, these parts still may not assemble properly if the assembly tolerance analysis was inadequately performed. Naturally occurring shifts in a process can produce biased distributions which can result in increased assembly problems and a greater number of rejects than anticipated. The most common methods of analysis of assembly tolerance buildup are worst case and root sum squares. The limitations of each of these methods are discussed and a simple new method is proposed which accounts for expected bias. This new method includes both worst case and root sum squares as extreme cases.
Finite-Element Analysis of Flexible Fixturing System
Authors: Lee J. D. , Haynes L. S.
Published: July 2009

A computer software has been developed for the analysis and design of fixtures. This software can lead the designer to the optimal design of the fixturing system which minimizes the total work done on the workpiece, the fixturing force, the deformation index, or the maximum effective stress. The workpiece is modeled as a linear isotropic elastic solid. The machining forces are simulated by specifying applied forces acting on part of the surface of the workpiece. The fixturing system consists of a number of fixture elements, each in contact with the workpiece with specified location and area of contact. At the interface of contact, Coulomb’s law of friction is employed. The boundary conditions at the interface of contact are treated exactly. This computer software system is composed of a finite-element program and a computer graphic program which displays the undeformed and deformed workpiece with hidden lines removed. Three sample problems have been solved and the numerical results are presented in this paper.
A New Formulation of Generalized Velocity Field for Axisymmetric Forward Extrusion Through Arbitrarily Curved Dies
Authors: Yang D. Y. , Han C. H.
Published: July 2009

A new analytic method is proposd for estimating the extrusion pressure, the final effective strain of the extruded billet, and the grid distortion patterns in axisymmetric forward extrusion through arbitrarily curved dies. A generalized kinematically admissible velocity field is derived to formulate an upper-bound solution. The corresponding upper-bound extrusion pressure is then obtained by optimizing the process parameters. The effects of area reduction, frictional condition, die length, and the die profile are discussed in relation to the extrusion pressure, the distorted grid pattern, and distribution of the final effective strain on the cross-section of the extruded billet. In the computation a biquadratic polynomial is chosen for the die profile. The work-hardening effect is incorporated in the formulation. Experiments are carried out for AISI 4140 steel billets at room temperature. The theoretical predictions both in the extrusion load and deformed configuration are in excellent agreement with the experimental results and the results computed by the finite element method.
Contact Rigidity at Tool Shank of Turning Tools
Authors: Marui E. , Ema S. , Kato S.
Published: July 2009

This paper presents an experimental investigation of the contact rigidity between a turning tool shank and tool post. The contact rigidity is influenced by the flexural rigidity of tool shank, contact area in the tool shank and the Vickers hardness number of the shank material. The effects of these parameters on the contact rigidity are estimated by simple empirical expressions.
Selection of Grinding Wheels for the Snagging of Steels and Cast Iron
Authors: Matsuo T. , Nakasako K.
Published: July 2009

The selection of proper grinding wheels in snagging is an important problem with relation to the automation of this grinding process. In this study, a snagging test under constant load has been made on SUJ 2 bearing steel, 304 stainless steel, and FCD 45 cast iron, using a specially made grinding machine of 40KW. The grinding wheels used were regular alumina, sintered white alumina, 25 percent zirconia-alumina, and silicon carbide resinoid wheels, where wheel diameter is 455 mm. Wheel speed was 67 m/s and work’s traverse speed was 60 mm/s. A 1.0 m long plate workpiece of constant width was used to keep pressure constant during grinding. This experiment allowed the metal removal rate, the wheel wear rate, G-ratio and grinding force to be determined. Thus the effect of wheel type and wheel grade on grinding performance was evident and the selection of the proper wheel has been discussed.
The Stability of Spinning Balloon and Balloon Collapse
Authors: Zhang S.
Published: July 2009

This paper presents the criterion of the existence of a balloon. We find that there exists a limiting value (T0/mR2ω2)c which can predict the critical conditions under which a balloon can be built. Furthermore, we also concluded that the criterion to ascertain the existence of a balloon, formed at conventional ring-spinning frame, can be expressed in a more compact form: (M/m)<(M/m)c. All our results are founded on the rigorous wide amplitude balloon theory. The stability of an actual spinning balloon is also discussed. Both the stable and unstable configurations of a balloon formed under identical mechanical parameters are presented numerically and graphically.
Influence of the Abrasive on Fatigue in Precision Grinding
Authors: To¨nshoff H. K. , Hetz F.
Published: July 2009

The surface residual stresses produced by grinding may have a strong influence on the life of highly stressed components. Different abrasives such as aluminum oxide (Al2O3) and cubic boron nitride (CBN) may lead to very different results. While CBN produces compressive residual stresses in nearly all combinations of machining parameters, the use of Al2O3 normally leads to tensile residual stresses. Fatigue tests carried out in alternating bending showed a remarkable increase in fatigue strength for CBN ground specimens compared with Al2O3 ground ones.
Dynamic Modeling and Analysis of the Boring Machining System
Authors: Zhang G. M. , Kapoor S. G.
Published: July 2009

A system of model formulated in the state variable space is proposed to describe the dynamic characteristics of the boring machining system. Particular attention is paid to the effect of the tangential vibration on the system performance. Modal analysis in the eigenvector space is employed to derive the analytical form of the system response. Experiments are carried out under spiral cutting conditions and the critical cutting stiffness predicted by the proposed model is compared with corresponding measured values, showing good agreements.
A Methodology for Integrated Quality Systems
Authors: Dessouky M. I. , Kapoor S. G. , DeVor R. E.
Published: July 2009

This paper proposes a methodology for the design of a system for planning and controlling the quality of products and processes. The system considers the relationships of quality-related parameters along the stages of a product life cycle. Parameters include material properties, process parameters, product quality characteristics, and product performance in use. The methodology is based on modeling the transformation taking place at every stage and on the design of quality control windows which perform all the functions of a control cycle. Several applications of the methodology are described.
Predicting the Effects of Cold Working on the Machining Characteristics of Low Carbon Steels
Authors: Kopalinsky E. M. , Oxley P. L. B.
Published: July 2009

Experiments show that the cold working of low carbon steel work materials can improve their machinability by reducing cutting forces and improving surface finish and tool life. The somewhat paradoxical result of reducing cutting forces by cold working a material so that its hardness is increased is explained in this paper by using a machining theory which takes account of the flow stress properties of the work material and can thus allow for the effects of cold working.
Determination of Inner and Outer Modulation Dynamics in Orthogonal Cutting
Authors: Ahn T. Y. , Eman K. F. , Wu S. M.
Published: July 2009

Many efforts have been devoted in the past to the identification of the dynamic behavior of the cutting process. Nevertheless, there have been no consistent results due to the inherent complexity of the cutting process, and the methodological and experimental errors involved. Among the problems to be solved, the experimental realization of the double modulation is the most difficult one. Present approaches use elaborate instrumentation and assume the delayed inner modulation for the outer modulation. This assumption may not hold under all circumstances and it will be modified in this paper. The present method approaches the cutting process as a one-input one-output process consisting of the inner modulation and dynamic cutting force component. The application of bivariate time series models give the transfer function of the inner modulation dynamics. The outer modulation dynamics’ effect on the cutting process is subsequently determined from the disturbance noise dynamics. The theoretical background for the proposed approach along with a new modeling strategy has been introduced in detail. The experimental verification of the theoretical postulates and the identification of the cutting process dynamics were carried out using actual data collected from an orthogonal turning process of a tubular workpiece. External white noise excitation was used and the experimental setup was designed to minimize the errors caused by inertia and disturbances. Although the proposed method requires prior knowledge of the machine tool structure, it requires a comparatively simple experimental procedure and minimizes the possible errors associated with the signal processing task.
Turning With Abrasive-Waterjets—A First Investigation
Authors: Hashish M.
Published: July 2009

Quantitative and qualitative results of a novel turning technique that employs abrasive-waterjets as cutting tools are presented. These jets are formed by mixing abrasive particles with a high-velocity (up to 600 m/s) waterjet in a specially designed mixing nozzle. Samples of magnesium boron carbide metal matrix composite, aluminum and glass were turned with the abrasive-waterjet tool. The effects of different parameters on the turning results are discussed. In general, the results illustrate the great potential of this technique to produce near-net-shape parts at fast material removal rates. Efforts for further research and optimization are discussed.
In-Process Control of Cylindricity in Boring Operations
Authors: Kim K. , Eman K. F. , Wu S. M.
Published: July 2009

This paper presents a new on-line control scheme utilizing the Forecasting Compensatory Control (FCC) method for improving cylindricity in boring operations. The proposed control method was implemented through the development of a laser-based in-process cylindricity measurement, a digital microcomputer, and a piezoelectric actuator system. Through on-line cutting experiments, the improvement in cylindricity accuracy was found to be in excess of 60 percent.
Theoretical Analysis of Grinding Chatter
Authors: El-Wardani T. , Sadek M. M. , Younis M. A.
Published: July 2009

A mathematical model is proposed for the prediction of the grinding process chatter. It considers the machine structure as a multidegree of freedom system and takes into account various parameters affecting the process stability such as the workpiece and grinding wheel regeneration, wheel loading and its elastic characteristics. This model is based on a nonlinear relationship with the time factor which is introduced by the loading effect. Three-dimensional stability charts were predicted for the simultaneous variation of both the grinding wheel wear and loading. These stability charts relate the grinding wheel and workpiece speeds to the instantaneous limiting width of grinding. The validity of this mathematical model has been assessed with the aid of a series of chatter tests which were carried out in specially designed experiments. These tests show good quantitative and qualitative correlation between the theoretical results and those experimentally obtained. It has been found that the level of stability decreases with time, indicating the possibility of chatter occurring at a stable width of cut.
Further Development of Sheet Metal Forming Analysis Method
Authors: Majlessi S. A. , Lee D.
Published: July 2009

The finite element analysis procedure used to model the sheet metal forming process is further developed by incorporating a refined numerical procedure and an improved metal-tool friction analysis method. The shell-type model is capable of closely approximating the strain distribution of prescribed axisymmetric parts. Further refinements on the numerical procedure have resulted in the marked decrease of the time required to reach a convergence of solutions. At the same time, frictional conditions at the metal-die and metal-punch interfaces have been closely characterized by applying equilibrium conditions in an iterative manner. Effects of these improved procedures have been examined in detail by making a systematic sensitivity analysis and by comparing the analytical results against experimental data. Based on these results, a critical assessment of the simplified analysis method is made.
On the Efficiency of NC Tool Path Planning for Face Milling Operations
Authors: Wang H. , Chang H. , Wysk R. A. , Chandawarkar A.
Published: July 2009

Face milling operations are important for producing flat machined surfaces. Existing methodologies to generate NC tool path for face milling are employed everyday by manufacturing industries without considering the impact of tool path selection. A systematic study has been conducted in order to identify those critical control parameters affecting length of cut in face milling operations. Basic polygons, from triangles to heptagons, were planned using both window frame and stair case milling procedures. For each polygon, each vertex was introduced as a possible starting point for a single run in the window frame milling. The cutting orientation was further examined for stair case milling by enumerating the tool sweep angle from 0 to 180 (and 180 to 0 as well) degrees from each vertex. The results are analyzed and important conclusions are drawn noting the efficiency of the cutting process.
Reynolds Number Effects on Regenerative Pump Performance
Authors: Hollenberg J. W.
Published: July 2009

Reynolds number effects on the performance of a conventional design regenerative pump were investigated, using glycerine-water mixtures, between an impeller tip speed Reynolds number, RT, of 5.0×103 (all glycerine) and 1.6×106 (all water). Results show that the maximum efficiency, nm, can be expressed in terms of an output to loss ratio, nm/1−nm, which varies as RT0.203 for 2.0×104 < RT < 1.6×106 and as RT1.156 for RT < 2.0×104. These results are consistent with efficiency behavior reported in similar investigations on other types of turbomachines. Further, the design point flow coefficient increased over the range of Reynolds number investigated, while the design point head coefficient exhibited a maximum within this range. In addition, marked departure from scaling behavior occurred in the lower Reynolds number range. Finally, the correlation among torque coefficient, head coefficient, and flow coefficient previously established by the author was further verified and followed scaling behavior for the higher Reynolds number range.
Computer Models for the Mechanics of Three-Dimensional Cutting Processes—Part II: Results for Oblique End Turning and Drilling
Authors: Stephenson D. A. , Wu S. M.
Published: July 2009

Using the method described in Part I, numerical models for predicting chip form and the principal components of power consumption are developed for oblique end turning and drilling. Applying the method involves mainly specifying appropriate sets of independent variables for minimization calculations. Results predicted using the rigid-viscoplastic material model are compared with measurements from unlubricated tests on steel and aluminum alloy samples. The agreement between predicted and measured results for turning is generally good, particularly for chip thickness values, chip-tool contact lengths, and the qualitative effect of varying the depth of cut. The agreement is not as good for drilling; in drilling the main cutting edge torque contribution and qualitative effects of varying the spindle speed and feed rate are accurately predicted, but the average chip thickness is consistently underestimated while chip radii of curl are overestimated. The lack of agreement for the last two outputs appears to be due to constraint from the hole drill flute surf aces which would limit maximum radii of curl.
Process Models for Anticipatory Control of Turning Operations
Authors: Klamecki B. E.
Published: July 2009

A process model of the metal cutting process using a minimum energy input concept was formulated. The model relates the geometry of the workpiece to cutting force. Experiments in which cutting force was measured for various workpiece geometries verify the applicability of the concept and the usefulness of the model developed. Accurate process models not only allow for more precise control, but also present the opportunity for anticipatory control.
Theoretical Aspects of a Laser Machine Tool
Authors: Chryssolouris G. , Bredt J. , Kordas S. , Wilson E.
Published: July 2009

In order to overcome the limitations of traditional laser machining, a new concept of laser machining using two intersecting beams is proposed. The optimization of this process requires an understanding of the phenomena involved in so-called laser “blind” cutting, as the new process and the machine performing this process are based on the production of “blind” kerfs which, by intersecting, remove a desired volume of material. This paper is a first attempt to establish a theoretical model for laser “blind” cutting, taking an energy balance approach to the problem and predicting the depth of kerfs that can be produced in a given material with a given laser power. Experimental results achieved with several ceramic materials are compared with the proposed model. Furthermore, certain issues related to the dimensional accuracy of the new process are also addressed.
Evaluation of an Apparatus for Electrochemical Arc Wire-Machining
Authors: El-Hofy H. , McGeough J. A.
Published: July 2009

Electrochemical Arc Machining (ECAM) combines electrochemical dissolution and electro discharge in order to achieve metal removal rates, that can be about five and fifty times greater than those of electrochemical (ECM) and electrodischarge (EDM) machining, respectively. Since ECAM has already been successfully applied to hole-drilling, for this paper the prospects for wire-machining by this process have been explored. An apparatus for wire-ECAM is described, and the results of tests performed to assess the feasibility of the technique are presented. To that end, the effects of mode of electrolyte flushing, wire erosion and machining speed on metal removal rate and accuracy are discussed.
Pressbrake Bending in the Punch-Sheet Contact Region—Part 1: Modeling Nonuniformities
Authors: Pourboghrat F. , Stelson K. A.
Published: July 2009

A simple model of pressbrake bending in the punch-sheet contact region is presented. The pressure and shear stress at the punch-sheet interface cause the stress distribution in the sheet to change as a function of angle. In Part 1 of this paper, a model to predict nonuniformities as a function of the geometry and the frictional conditions is presented. In Part 2, the model will be used to predict the formation of a gap between the sheet and the punch. Elastic and rigid-plastic material models of the sheet are considered, and are shown to produce remarkably similar results.
Tool Failure Monitoring in Turning by Pattern Recognition Analysis of AE Signals
Authors: Emel E. , Kannatey-Asibu E.
Published: July 2009

Sensing of both gradual and catastrophic tool failure is a key aspect in producing high quality parts on fully automated machine tool systems. Acoustic emission provides a means of sensing tool failure, since it is generated from the processes that cause tool failure (e.g., tool wear, tool fracture). A linear discriminant function-based technique for detection of tool wear, tool fracture, or chip disturbance events is developed using the spectra of signals generated by these sources. In addition, a methodology for determining the feature dimensionality, the selection of best features, and the minimum training sample size is presented. The concepts of classification error minimization and manufacturing cost minimization have been applied to design classifiers using a hierarchical decision strategy to improve the performance of tool failure sensing. Results of an application indicate an 84 to 94 percent reliability for detecting tool failure of any type.
On the Permissible Fluid-Pressure Path in Hydroforming Deep Drawing Processes—Analysis of Failures and Experiments
Authors: Yossifon S. , Tirosh J.
Published: July 2009

The geometrical and material constraints which limit the quality of hydroforming products in regard to failure by wrinkling (buckling) and/or rupture (tensile instability) are investigated in a unified framework. The analysis is based on limit theorems of plasticity (with a power-law hardening and Mises-Hill normal anisotropy) and resulted in distinct bounds for the permissible operating fluid pressure path. The parameteric study which follows includes a wide range of physical variables, some of which (not considered hitherto) show substantial effects on anticipated failure. Experiments with copper, aluminum, steel, and stainless steel agree very well with the supposition that premature failure (up to certain situations) is avoidable if the fluid pressure path is restricted to travel only within the suggested bounds.
Workpiece Movement in Centerless Grinding and Its Influence on Quality of the Ground Part
Authors: Subramanya Udupa N. G. , Shunmugam M. S. , Radhakrishnan V.
Published: July 2009

The grinding action and the rounding mechanism are highly complex in centerless grinding. The process geometry and the dynamic stability of the workpiece are critical factors affecting the quality of the ground parts. The workpiece, because of floating condition, has an inherent tendency to become unstable during grinding. This is particularly true in the case of hollow workpieces like bearing races, bushes, cylinder liners, etc. In this paper, an attempt has been made to investigate the dynamic instability of the workpiece and to identify its effects on the quality of ground parts in infeed grinding. The details of the experimental investigations carried out to measure the horizontal and vertical movements of the workpiece directly on the machine are included. Some measures to minimize the vertical movement of the workpiece and to improve the quality of the ground part are also discussed.
Round Bar Heating With Swirl Burners
Authors: Sato K. , Biffin M. , MacGregor S. A. , Syred N.
Published: July 2009

A method of heating round steel bars using a swirl burner or swirl burner furnace combination is described. This technique is suitable for surface hardening or processing of long steel bars. The uniform heating around the steel bar, coupled with the high heat transfer rate of the swirling flow, allows a relatively small swirl burner to be used. Experimental results are presented from small-scale prototype trials with a 200 kW burner and 25 mm diameter mild steel bars.
Automated Group Technology Part Coding From a Three-Dimensional CAD Database
Authors: Henderson M. R. , Musti S.
Published: July 2009

A system of software, named CODER, has been written which can analyze the solid model of a part and generate a group technology part code through the identification of form features. The CODER algorithm is bottom-up in nature, first searching for small form-features and then constructing macro-features from the small elements. The program has been implemented using logic programming techniques and consists of facts, describing the part, which must be searched to satisfy rules defining the form-features. The rules and facts are written in Prolog. The facts are generated automatically in Prolog from the ROMULUS2 solid modeler. Rules can define form-features specific to a particular coding scheme and, therefore, form a code-specific knowledge base. The significance of this research is seen when applied to the many designs which have been generated on wire frame CAD systems in the past and, which, if converted to solid models, could be automatically coded for variant process planning, design retrieval and other applications germane to part coding. The algorithm is written in a combination of Prolog, Lisp and S.I™3.
Manufacture of High Precision Spur Gears With End Milling Cutters
Authors: Papaioannou S. G.
Published: July 2009

A new method is proposed for cutting large module spur gears on NC milling machines, using end milling cutters. End milling eliminates undercutting and leads to a significant reduction of tooling costs. The method relies on the motion of a simple geometry tool rather than the shape of an expensive form tool to generate the gear profile. The tool center path is defined and computed for the standard 20 deg full-depth system. Tool steps are generated by a highly precise interpolation algorithm. The practical aspects of the method are also investigated to establish its feasibility. The computation of the maximum tool size shows that sufficient tool rigidity can be secured for gear modules greater than or equal to 10 mm. The Lewis equation is used to investigate the beam strength of the resulting tooth profile and generate data for the design process. Gears made by end milling are shown to be comparable in strength to those produced by shaping or hobbing.
Assessment of Deep-Drawability of Mild Steel Sheets in Consideration of r-Value Change During Processing
Authors: Kawai N. , Hayashi N. , Matsui S.
Published: July 2009

In the previous study, it was found that the plastic anisotropy of commercially pure aluminum sheets changed during the deep-drawing process, and that this change influenced markedly the deep-drawability. In the present study we discuss the deep-drawability of mild steel sheets with a crystal structure different from aluminum. The following have been confirmed: (1) The limiting drawing ratio correlates positively and nonlinearly with average r value (r¯ value). (2) Fracture strength correlates positively with r¯ value as in the theory, but the relation between them is nonlinear. Maximum drawing load remains almost constant irrespective of r¯ value against the theory. These relations can be connected with the result of (1). (3) The relations in (2) can be explained by the r¯ value measured from sheets prestrained in equibiaxial tension and pure shear, which resemble the strain paths of fracture site at punch profile and flange, respectively. (4) The results of (2) and (3) are quite different from those of commercially pure aluminum sheets.