bluuebunny/crossref_metadata_2025 huggingface dataset:
Solutions for the Combined Motion of Finite Length Squeeze Film
Dampers Around the Bearing Center
Authors: Zhang J. X. , Roberts J. B.
Published: February 2008

Analytical expressions for the hydrodynamic forces, and four related dynamic coefficients, are presented for finite length squeeze film dampers (SFDs) executing combined radial and tangential motion around the bearing center, with small amplitude. Previous analyses by Mulcahy (1980) and San Andres and Vance (1987) are shown to be particular cases of the present treatment. The influence of combined motion on the coefficients is found to differ, in several respects, from that which can be deduced from results for one dimensional radial motion and circular centred orbital motion. The effects of combined motion on the mean flow velocity and the wall stress are also studied. The study provides further insight into the validity of bulk flow assumptions, often used when dealing with lubrication problems where fluid inertia effects are significant.
A Numerical Analysis of the Nonsteady EHL Process in High-Speed
Rotating Engine Cam/Tappet Pairs
Authors: Xuesong Mei , Youbai Xie
Published: February 2008

In this paper, by accounting for the effect of dynamic behavior in valve train mechanisms on the surface contact load of a cam/tappet pair, a full numerical solution of nonsteady EHL for a high-speed diesel engine cam/tappet pair is obtained by a fast solution scheme. The shape of the lubricant film and the characteristics of pressure distribution on cam/tappet pair surfaces are further studied. The lubrication process of a cam/tappet pair at the opening and closing sides and in the most dangerous zone in normal working conditions is also analyzed. This analysis provides the theoretical basis which best approximates practical working conditions for designing cam profiles and establishing reasonable running-in condition.
Scuffing as Evaluated From the Viewpoint of Surface Roughness and
Friction Energy
Authors: Horng Jeng Haur , Lin Jen Fin , Li Ke Yang
Published: February 2008

The surface scuffing occurring in line-contact lubrication is related to the roller’s roughness pattern and asperity height. For surfaces with same contact asperity height, the magnitudes of friction power (Pf = fWVs) relevant to various roughness patterns are found to have the same sequence as the critical local temperatures. Instead of using the nominal contact area, the real contact area (At) is used to obtain the true friction power intensity (Ptfi = Pf/At). A new scuffing failure model (Ptfi · σ−0.317 = C, where σ denote rms roughness) shows that the scuffing resistance of surfaces with transverse roughness pattern is higher than that of surfaces with longitudinal and oblique patterns. For certain roughness patterns, a high root mean square roughness height a is always associated with the high Ptfi value just before scuffing.
Crack Path Prediction Under Fretting Fatigue—A Theoretical and Experimental Approach
Authors: Lamacq V. , Dubourg M. C. , Vincent L.
Published: February 2008

In this paper, the direction of crack growth under fretting fatigue loading is studied through an experimental and theoretical approach. The experimental work enabled the fretting conditions to be known and the site of initiation and crack trajectory to be viewed; theoretical work permitted a prediction of those processes. Fretting wear and fretting fatigue loadings induce non-proportional mixed mode loading at the tip of the cracks initiated within the contact zone. The classical criteria predicting the direction of crack growth cannot account for the non-proportional loading. Tests were carried out to study the cracking phenomena under cumulative effects of contact and external loadings, i.e., fretting fatigue loading. The fretting contact between the two contacting bodies is modeled to evaluate the operating contact loading conditions. The response of the cracked body is determined in terms of stress intensity factors using the continuous distribution of dislocations theory coupled with a unilateral contact analysis with friction. The angle of crack extension is then predicted, at different stages of crack life, according to a new approach. The correlation of the predicted angle of crack extension with the experimental observation enables the conclusion that, under fretting fatigue loading, cracks propagate by a mode I process.
On the Possibility of Chemo-Mechanical Action in Magnetic Float Polishing of Silicon Nitride
Authors: Komanduri R. , Umehara N. , Raghunandan M.
Published: February 2008

Chromium oxide abrasive has been reported in the literature to provide efficient chemo-mechanical polishing action for silicon nitride ceramic. Since aluminum oxide and chromium oxide abrasives are nearly of the same hardness, magnetic float polishing tests were conducted on silicon nitride balls with these two abrasives to investigate mechanical versus chemo-mechanical aspects of polishing. Tests results show higher removal rates and smoother surface texture (with fewer pits) with chromium oxide abrasive compared to aluminum oxide abrasive. Formation of pits due to brittle fracture seems to be the more predominant mode of material removal with aluminum oxide abrasive than with chromium oxide abrasive. While there may be some mechanical action (abrasion) with chromium oxide abrasive initially, subsequent removal is believed to be due to chemo-mechanical action. This could be due to degeneration of the chromium oxide abrasive (both mechanical and chemical) during polishing. Various hypotheses for the material removal mechanism (both mechanical and chemo-mechanical) were considered. Based on that, the higher removal rates and smoother surface texture on the silicon nitride balls with chromium oxide abrasive in semifinish polishing is interpreted here as possibly due to chemo-mechanical action. Higher chemical stability of aluminum oxide abrasive (compared to chromium oxide abrasive) and the known role of chromium oxide as a catalyst for the oxidation of silicon nitride are some of the reasons attributed for this action.
Modeling of Surface Modified Layers in the Presence of Surface Irregularities
Authors: Gupta Vikas , Hahn George T. , Bastias Pedro , Rubin Carol A.
Published: February 2008

Finite element calculations that examine the effects of surface modification on the deformation produced by pure rolling contact are presented. The model simulates the repeated, two-dimensional (line) contact of a cylinder that is rolling over a semi-infinite half space. The half space is treated as an elastic-linear-kinematic-hardening-plastic (ELKP) material with the cyclic flow properties of a hardened, HRC-62, bearing steel. Two different cases are examined: (i) a smooth half space is studied using a one-body model, and (ii) a half space with a 100 μm wide and 7 μm deep surface asperity is studied using a two-body model. In both cases, calculations are performed for a homogeneous body and a body with a shallow, surface modified layer. The surface modified layer is alternately: (a) stiffer, (b) harder, (c) softer, and (d) harder and stiffer as compared to the substrate. Consistent with the earlier studies of surface modification (Bhargava, 1987), the present findings indicate that the benefits of the mechanical property modifications are confined to the altered layer itself. This may explain the improvement in performance realized by relatively thin modified layers (≈5 μm).
Investigations in Abrasive Water Jet Erosion Based on Wear Particle Analysis
Authors: Momber A. W. , Kwak H. , Kovacevic R.
Published: February 2008

In the study, gray cast iron specimens are cut by abrasive water jets with pressures between p = 140 MPa and p = 345 MPa. Wear particles collected during cutting are analyzed based on average grain size and grain size distribution. The average diameter of the removed wear particles was found to be between D = 60 μm and D = 70 μm and drops with rising pump pressure. A semi-empirical model is developed to describe this relation. The grain distribution of the wear particles can be characterized by a Rosin-Rammler-Sperling (RRSB)-distribution. The surface area of the removed wear particle samples increases with an increase in the pump pressure. The progress drops at higher pressure levels indicating accelerated efficiency losses if the pump pressure exceeds a certain value. An efficiency parameter, Φ, is defined which relates the jet kinetic energy to the creation of the wear particles, and a method for its estimation is developed. It was found that the efficiency parameter exhibits a maximum value at a pressure level of about three times the material threshold pressure. The average efficiency parameter is estimated to φ = 0.02.
A Model of Slider/Disk Interface Wear for Proximity Recording
Authors: Li Yufeng , Menon Aric
Published: February 2008

Slider/disk interface wear is inevitable for ultra-low flying hard disk drives and is the central issue for proximity recording. While disk wear has been addressed in the literature, slider wear has been largely considered to be trivial and is ignored. However, with the improvement of disk overcoat and introduction of diamond-like-carbon overcoat on slider air bearing surface, the surface hardnesses of the slider and disk are approaching each other and, therefore, the slider surface wear becomes significant or, in some conditions, even dominant. In this study, a theoretical model is developed for semi-steady-state slider/disk interface evolution of proximity recording which takes account of both the disk and slider wear. It includes the effects of the air bearing characteristics, pitch stiffness, material properties, and surface topography of both the slider and disk. Numerical results are illustrated for typical proximity recording interface, where the evolutions of the slider, disk, contact force, and pitch angle are evaluated for various air bearing stiffnesses, material properties, and surface topographies. This model is intended to provide some fundamental understanding of the slider/disk interface evolution during proximity recording process.
Capillary and Viscoelastic Effects on Elastohydrodynamic Lubrication in Roller Nips
Authors: Carvalho M. S. , Scriven L. E.
Published: February 2008

A viscocapillary model of liquid movement and film-splitting in deformable nips between an elatomer-covered roll and a hard roll is presented here. This “soft” elastohydrodynamic regime is described by Reynolds’ equation of lubrication flow and a simple set of spring-and-dashpot elements for the viscoelastic behavior of elastomeric roll covers. Capillary effects around the film-split are accounted for with an augmented Young-Laplace equation from film-flow theory. Effects of the liquid’s surface tension (via capillary number) and the elastomeric cover’s relaxation time (via Deborah number) are predicted and compared with available experiments. Application to the flows through the multiple roller nips of printing press systems is discussed.
Axial Load Capacity of Water-Lubricated Hydrostatic Conical Bearings With Spiral Grooves (On the Case of Rigid Surface Bearings)
Authors: Yoshimoto S. , Anno Y. , Tamura M. , Kakiuchi Y. , Kimura K.
Published: February 2008

This paper describes the static characteristics of water-lubricated hydrostatic conical bearings with spiral grooves. Hydrostatic conical bearings treated here have been designed for high speed spindles and are intended to apply to spindles for drilling small holes of printed circuit-boards. Pressurized water is first fed to the inside of the rotating shaft and supplied to spiral grooves on the shaft surface through feeding holes. Therefore, water pressure is greatly increased at outlets of feeding holes due to the centrifugal force by shaft rotation. Furthermore, water pressure is also increased by the viscous pump effect of spiral grooves. Water pressures in the bearings under concentric condition are numerically obtained by using the finite element method and calculated results are compared with experimental ones. It is consequently found that this water-lubricated hydrostatic conical bearings with spiral grooves are very suitable for precision high speed spindles.
Experimental Study on the Effect of a Circumferential Feeding Groove on the Dynamic Force Response of a Sealed Squeeze Film Damper
Authors: Arauz G. L. , San Andres Luis
Published: February 2008

The influence of a circumferential feeding groove on the dynamic force response of a sealed squeeze film damper is determined experimentally. The damper is sealed by means of a serrated piston ring located at the discharge end of the damper. Damper configurations with two different groove depths and journal orbit radii were tested at increasing whirl frequencies. Large levels of dynamic pressure were measured at the circumferential groove, and relatively large tangential (damping) forces are produced at the groove which contribute considerably to the damping characteristics of the test damper. Radial forces were also determined at the feeding groove and at the film land for uncavitated flow conditions.
A Nonlinear Model for Structural Vibrations in Rolling Element Bearings: Part I—Derivation of Governing Equations
Authors: Datta J. , Farhang K.
Published: February 2008

This paper, the first of two companion papers, presents a model for investigating structural vibrations in rolling element bearings. The analytical formulation accounts for tangential and radial motions of the rolling elements, as well as the cage, the inner and the outer races. The contacts between the rolling elements and races are treated as nonlinear springs whose stiffnesses are obtained by application of the equation for Hertzian elastic contact deformation. The derivation of the equations of motion is facilitated by assuming that only rolling contact exists between the races and rolling elements. Application of Lagrange’s equations leads to a system of nonlinear ordinary differential equations governing the motion of the bearing system. These equations are then solved using the Runge-Kutta integration technique. Using the formulation in the second part—“A Nonlinear Model for Structural Vibrations in Rolling Element Bearings: Part II—Simulation and Results,” a number of effects on bearing structural vibrations are studied. This work is unique from previous studies in that the model simulates vibration from intrinsic properties and constituent elements of the bearing, and takes into account every contact region within the bearing, representing it by a nonlinear spring.
Analytical and Numerical Modeling of Engagement of Rough, Permeable, Grooved Wet Clutches
Authors: Berger E. J. , Sadeghi F. , Krousgrill C. M.
Published: February 2008

A simple mathematical model for the engagement of rough, permeable, grooved wet clutches has been developed and used to determine the effect of various input parameters (applied load, grooved area, and friction material permeability) on engagement. The model includes the effects of surface roughness according to Patir and Cheng (1978), friction material permeability according to Natsumeda and Miyoshi (1994) and Beavars and Joseph (1967), and grooving in the friction material according to a new approximation. The approach reduces the system of Reynolds and force balance equations to a single, first-order differential equation in film thickness and time. A line searching algorithm, exploiting the low computational cost of function evaluations for the new model, is used to find the set of input parameter combinations yielding the same engagement characteristics. This set of design points is presented as an engagement isosurface in the parameter space (Fapp, Φˆ, Ared). The isosurface implicitly gives information about engagement time, and it shows regions in which the desired engagement characteristics cannot be achieved. The input parameters are classified as those affecting the transient portion of engagement and those affecting the steady-state portion.
FFT Thermoelastic Solutions for Moving Heat Sources
Authors: Ju Y. , Farris T. N.
Published: February 2008

An analytical frequency domain solution is obtained using the spatial Fourier transform for thermal and thermoelastic fields due to an arbitrary heat source or thermal distribution moving at constant speed over the surface of an insulated, traction free elastic half space. Conversions between the space and frequency domains for the input and output are performed efficiently and robustly using FFT techniques. The method is validated by comparison to the analytical result for the moving line heat source in which it is shown that numerical evaluation of the analytical solution is problematic for large speeds or distances from the heat source. The utility of the method is illustrated on the constant patch moving heat source and discretely distributed multiple heat sources known as the “hot spot” problem. It is shown, through several examples, that the effect of hot spots on surface displacement and tangential stress is small. Finally, this conclusion is generalized by quantifying the frequency domain solution for the moving heat source problem as a low pass filter.
On the Stability of Gas Lubricated Triboelements Using the Step Jump Method
Authors: Miller B. , Green I.
Published: February 2008

The step jump method was developed approximately three decades ago to help determine the stability of gas lubricated triboelements. In the approach, the force contribution from the gas layer is characterized by its step response, which is the transient force response resulting from pressure diffusion in the gas film after a step increase in film thickness. The procedure is broadened by implementing Duhamel’s theorem to yield the system characteristic equation. Since its inception in the literature, the step response has been approximated in the equations of motion using a series of Laguerre polynomials, which allows for a closed form analysis. This paper will prove that using Laguerre polynomials can violate the second law of thermodynamics, and a test case will show that stability results predicted by this approach can be inaccurate. It will be proven that a mathematical correlation exists between the dynamic behavior of the gas film and the dynamic behavior of a linear viscoelastic medium. This correlation is advantageous since much of the viscoelastic theory can be applied to the dynamic analysis of gas lubricated triboelements.
Sliding Wear of Titanium
Authors: Kailas S. V. , Biswas S. K.
Published: February 2008

Titanium pins were slid against flat surfaces of alumina disks under dry condition and a normal load of 50N at sliding speeds varying from 0.1 to 4 ms−1. Estimated strain rate and temperature distribution in the subsurface when superposed on a microstructure evolution map in temperature-strain rate space give the microstructural response of the material to different sliding velocities at different subsurface depths. The map was obtained by conducting uniaxial compression tests. The experimentally observed variation in wear rate with sliding velocity was found to have a qualitative correspondence with the predicted variation of microstructure in the near surface region.
Active Control of Multi-Mode Rotor-Bearing Systems Using HSFDs
Authors: Hathout J. P. , El-Shafei A. , Youssef R.
Published: February 2008

This paper summarizes the modeling and control of hybrid squeeze film dampers (HSFDs) for active control of vibration of rotors exhibiting multiple modes. In a recent paper (El-Shafei and Hathout, 1994), it was shown that the automatically controlled HSFD based on feedback on rotor speed can be a very efficient device for active control of rotor vibration. It was shown that this closed-loop, on-off control strategy results in a much improved behavior of the rotor system. The previous investigation was performed on a Jeffcott rotor model. The model was simple and fluid inertia effects were not taken into consideration. In this paper, major strides were made in both the modeling of the rotor and the HSFD. Modal analysis was implemented in the dynamic analysis of the squeeze film damper supported rotor in a novel and unique manner of performing modal analysis on nonlinear rotor systems. This allowed the modeling of any number of modes using modal analysis and hence to verify the capability of the HSFD to control multiple modes. Also, fluid inertia forces were considered in our model for the HSFD due to their direct influence in changing the behavior of the damper (El-Shafei and Crandall, 1991). A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. Finally, based on the feedback on speed, the closed-loop behavior was studied from both steady-state and transient points of view and showed an overall enhanced behavior for the rotor system.
Transient Analysis of Gas-Lubricated Journal Bearing Systems by Differential Quadrature
Authors: Bert C. W. , Malik M.
Published: February 2008

This paper is an extension of an earlier work in which the present authors demonstrated the application of the differential quadrature method (DQM) to the steady-state analysis of incompressible and compressible lubrication problems. In the present work, the DQM is applied to the transient-state analysis of compressible lubrication problems. For this purpose, the analysis of gas-lubricated plain journal bearings under the conditions of nonuniform journal rotation is considered. The computed results from the solutions of the reference problem included in the paper provide a comparison of the convergence characteristics and computational efficiency of the differential quadrature and finite element methods.
Prediction of Ductile Fracture in Cold Forging of Aluminum Alloy
Authors: Kim Hong-Seok , Im Yong-Taek , Geiger Manfred
Published: February 2008

In this paper, the limitation and applicability of the ductile fracture criteria based on a work hypothesis and Cockcroft and Latham were investigated. For this purpose, experimental and numerical investigations for simple upsetting were conducted for aluminum alloys Al1100-O, Al2024-T3, Al6061-T4, and Al7075-T4. As a result, the fracture mode of each alloy was observed. The study was extended for pin-shape cold forging of Al1100-O and Al6061-T4 to compare the likeliness of fracturing according to two criteria. Based on experimental data of simple upsetting, the damage factors for the same two criteria were calculated by adopting rigid-viscoplastic finite element analysis. With this approach, the prediction of surface cracking was attempted by comparing the calculated limiting damage factors between simple upsetting and pin-shape forging. It was observed in simple upsetting that Cockcroft and Latham’s criterion gave a more reasonable prediction for crack initiation site than work hypothesis, but the limiting damage factors differ depending on the process. In spite of the differences, however, Cockcroft and Latham’s criterion might be useful in designing upsetting-like cold forging processes in which the influence of the induced circumferential tensile stress on failure is dominant.
An Engineering Model for Laser-Induced Sintering of Polymer Powders
Authors: Kandis M. , Buckley C. W. , Bergman T. L.
Published: February 2008

Laser-induced sintering of powders has become prevalent in a number of Solid Freeform Fabrication technologies such as Selective Laser Sintering (SLS), which is used to produce nearly solid parts from initially-porous powder via laser irradiation. In this paper, a model is presented which can be used to predict the shape and general features of consolidated heat affected zones produced by laser-induced, non-isothermal sintering of polymer powder. Comparisons between experimental results and predictions are made, and the model is used to investigate the influence of various thermal processing parameters on the sintering operation. The model is then extended to simulate the manufacture of a simple multiple layer part which is produced in a manner similar to SLS.
Energy Partition in Conventional Surface Grinding
Authors: Kato T. , Fujii H.
Published: February 2008

In order to estimate the energy partition to the workpiece in surface grinding, the temperatures at various depths from the ground surface of the workpiece were measured using the PVD (physical vapor deposition) film method developed by the authors. In this method a thin film deposited on the workpiece is used as a thermal sensor. The energy partition for various grinding wheels was estimated with the maximum temperature rise at the surface obtained by extrapolating the temperatures measured at various depths. It was found that the partition changes significantly from 0.3 to 0.8, depending on the combination of the workpiece material and the wheel material in conventional dry surface grinding.
Prediction of Shear Angle in Oblique Cutting with Maximum Shear Stress and Minimum Energy Principles
Authors: Shamoto E. , Altıntas Y.
Published: February 2008

A new shear angle prediction theory is proposed for oblique cutting operations. Oblique cutting mechanics are described by two components of shear angle, two angles defining direction of resultant cutting force, and chip flow angle. The five unknown parameters describe the geometry of chip deformation, velocities and forces in oblique cutting. When combined with the material dependent shear stress and average chip—rake face friction coefficient, cutting forces in three Cartesian directions can be predicted. In this paper, the mechanics of oblique cutting are described by five expressions. Three of the expressions are derived from the kinematics of oblique cutting, and the remaining two are derived either by applying Maximum Shear Stress or Minimum Energy Principle on the process. Unlike the previous solutions, the proposed methods do not require any intuitive or empirical assumptions, but use only the material properties, tool geometry and the physical laws of deformation. The oblique cutting parameters and forces predicted by the proposed models agree well with the empirical and experimental results reported in the classical cutting literature. The proposed models are experimentally verified in predicting forces in helical end milling which has oblique cutting mechanics.
Mechanistic Force Models for Chip Control Tools
Authors: Zhu R. , Kapoor S. G. , DeVor R. E. , Athavale S. M.
Published: February 2008

A mechanistic modeling approach to predicting machining forces for grooved tools is developed. The models are based solely on the grooved tool geometry and the specific normal cutting energy and friction energy for flat tools. Special grooved tools (M2 grade HSS) were designed and fabricated and orthogonal cutting tests were performed to validate the model. The workpiece material used was Al 6061-T6. The force predictions from the model are found in good agreement with the measured forces. The effects of groove design parameters on the cutting forces are also determined.
Scan Welding: Thermal Modeling and Control of Material Processing
Authors: Korizis G. , Doumanidis C.
Published: February 2008

This article provides a thermal analysis of scan welding, as a redesign of classical joining methods, employing computer technology to ensure the composite morphologic, material and mechanical integrity of the joint. This is obtained by real-time control of the welding temperature field by a proper dynamic heat input distribution on the weld surface. This distribution is implemented in scan welding by a single torch, sweeping the joint surface by a controlled reciprocating motion, and power adjusted by feedback of infrared temperature measurements in-process. An off-line numerical simulation of the thermal field in scan welding is established, as well as a linearized multivariable model with real-time parameter identification. An adaptive thermal control scheme is thus implemented and validated both computationally and experimentally on a robotic Gas-Tungsten Arc Welding setup. The resulting productivity and quality features of scan welding are comparatively analyzed in terms of material structure and properties of the joint.
Interval Model Based Robust Control of Weld Joint Penetration
Authors: Zhang Y. M. , Li L.
Published: February 2008

Weld penetration sensing and control with a weld-face sensor are among the most relevant research issues in automated welding. Previous studies showed that the geometry of the weld pool contains accurate, instantaneous information about the weld penetration. In this study, the weld pool is measured in real-time to provide the feedback of the weld penetration, and the welding current is selected as the control variable. Analyses reveal that the influence of mandatory variations in welding conditions on the process dynamics can be described by an interval model that has bounded parameter intervals. A robust control algorithm with guaranteed closed-loop stability is used to overcome the interval uncertainty in the process dynamics. Dynamic experiments are performed using different welding conditions and varied welding parameters. From the experimental data the bounded parameter intervals are identified for the model of the process being controlled. Closed-loop control experiments are done under different perturbations. Experimentation shows that the variations encountered in practical welding can be overcome by the developed control system. In addition to penetration control, this work provides an example for developing robust manufacturing process control systems based on objective quantitative descriptions of the process uncertainty.
Workspace Synthesis for Flexible Fixturing of Stampings
Authors: Lee Jinkoo , Hu S. Jack , Ward Allen C.
Published: February 2008

Fixtures are used to position and hold parts for a series of assembly operations. In automotive body assembly, these fixtures conventionally have been dedicated, therefore they must be replaced whenever there are model changes in an auto body assembly plant. In recent years, however, the automotive industry has been changing from high volume to small-to-medium volume production per model with an increasing number of models because customer tastes are diversifying. To cope with this change, auto companies need to be capable of producing a variety of models in small-to-medium volume, and they rely on flexible assembly lines and flexible fixtures. These flexible fixtures use robots as programmable fixture elements so that they can be reprogrammed for different stamped sheet metal parts. When designing flexible fixtures, fixture designers need to be concerned with fixture workspaces for a set of different stampings. However, existing fixture design methods address the fixturing of one stamping only. This paper presents a system that fixture designers can use to synthesize flexible fixture workspaces for a set of different stampings. Based on circular workspaces for flexible fixture robots, this system finds optimal workspace sizes and centers on a fixture base plate with a graphical display for visual checking. This system is simple to use and produces results quickly.
Modelling, Identification and Control of Thermal Deformation of Machine Tool Structures, Part 5: Experimental Verification
Authors: Fraser S. , Attia M. H. , Osman M. O. M.
Published: February 2008

Machining accuracy is more often governed by thermal deformation of the machine tool structure than by static stiffness and dynamic rigidity. Since thermally induced errors cannot completely be eliminated at the design stage, the use of control and compensation systems is an inevitable course of action. Existing control systems are based on two different approaches; the use of empirical compensation function, and on-line execution of numerical simulation models. To overcome the limitations of these methods, a new control system has recently been proposed by the authors. This system, which is based on the concept of generalized modelling, incorporates a realtime inverse heat conduction problem IHCP solver to estimate the transient thermal load applied to the structure. With this information, the relative thermal deformation between the tool and the workpiece is estimated and used as a feedback control signal. In previous parts of this series, computer simulation test cases were carried out to examine the dynamic response, accuracy and stability of the system. In the present study, the performance of various components of the control system, specifically, the IHCP solver, the thermal deformation estimator, and the feedback controller are verified experimentally using a three-component structure. The results showed that the derived generalized thermoelastic transfer functions and algorithms are indeed quite accurate in predicting and controlling the transient thermoelastic response behaviour of a predominantly linear structure. The results showed that the a IHCP solver is inherently stable even when the temperature measurements are contaminated with random errors. The excellent computational efficiency of the integrated system is shown to be well suited for real-time control applications involving multi-dimensional structures, achieving a control cycle of less than 0.5 second. The experimental results showed that in real structures higher modes can be present, and therefore, a fourth order deformation model should be used to improve the prediction accuracy. The proposed PID control system, with feedforward branches, was capable of reducing thermal deformations of the order of 200 μm to levels below ±8 μm. These results also demonstrated the effectiveness of artificial heat sources as a control actuation mechanism, in spite of their inherent limitations, namely, thermal inertia, coupledness, and unidirectionality.
The Identification of Radial Runout in Milling Operations
Authors: Seethaler R. J. , Yellowley I.
Published: February 2008

The authors discuss a novel approach to estimation of individual tooth runout in milling. The approach is based upon a simplified linear force model and leads to good results at high values of immersion. Two variants of the approach for estimating runout are presented. The first method utilizes torque while the second considers in plane force components as indicators of runout. Simulations are used to verify the equations that were derived for relating runout to in plane forces and to allow the assessment of the influence of the spacing of the discrete force samples on accuracy. Experimental evidence validates the approach for a wide range of immersion values. Experiments also show that the approach is able to identify edge breakage in the presence of significant initial runout.
An Improved Algorithm for Cross-Coupling Control of Multi-Axis Machine Tools
Authors: Lo Chih-Ching
Published: February 2008

This paper presents an improved algorithm for cross-coupling controlled systems. In contrast to the existing algorithms, which must be re-formulated for different types of curves and may be inconvenient to implement, the proposed algorithm is adequate for general nonparametric and parametric curves. In addition, the proposed algorithm requires less computational time but achieves the same performance as compared with the existng ones.
The Role of Flank Face Interference in Improving the Accuracy of Dynamic Force Predictions in Peripheral Milling
Authors: Ranganath S. , Narayanan K. , Sutherland J. W.
Published: February 2008

An enhanced model for the dynamic behavior of the peripheral milling process is described. The model predicts the cutting forces and cutter deflections by including the effects of the flank face interference mechanism in addition to the chip removal effects. The interference mechanism is accounted for by considering the flank interference forces to be proportional to the interference volume. The volume of interference is estimated numerically. The total force acting on the tool is a combination of the forces due to the cutting action and forces due to the interference. Experiments performed on 6061-T6 Aluminum validate the simulation results.
Stability Analysis in Face Milling Operations, Part 1: Theory of Stability Lobe Prediction
Authors: Jensen S. A. , Shin Y. C.
Published: February 2008

This paper involves development of an algorithm to predict stability lobes in face milling operation. The modeling is based on frequency domain analysis and is an extension of Budak and Altintas to a three dimensional case. It considers the effects of insert and cutter geometry, cutting conditions, process nonlinearity, entry and exit angles and the fully dimensional structural dynamics of both the machine tool and workpiece, including axial dynamics which are often neglected by many researchers. In addition, the predictive capability of stability lobes by the presented models is compared with those results obtained by time domain simulations.
Development of a Magnetostrictive Torque Sensor for Milling Process Monitoring
Authors: Ohzeki Hiro , Mashine Akihiro , Aoyama Hideki , Inasaki Ichiro
Published: February 2008

This paper deals with a sensor system based on the magnetostrictive effect which is installed in a tool holder for sensing cutting torque in order to monitor the milling process. Changes in the magnetic permeability of ferromagnetic alloy layers formed onto a rotating shaft due to torque are detected by coils as changes in impedance without contacting the rotating shaft. By mounting the magnetostrictive sensor on a tool holder, it has become possible to detect cutting torque as close to the cutting point as possible. The accuracy of the proposed sensor system is confirmed through static and dynamic evaluation tests. In order to investigate the relationship between tool failure and cutting torque, cutting tests were performed. As the results, the possibility of estimating flank wear and tool fracture from cutting torque detected by the proposed sensor system is recognized.
A Grinding Power Model for Selection of Dressing and Grinding Conditions
Authors: Chen Xun , Rowe W. Brian , Allanson D. R. , Mills B.
Published: February 2008

The grinding power is often used as a parameter for monitoring the grinding process. The power may also be used to monitor the effects of dressing. Empirical models are required to guide the selection of the dressing and grinding conditions. In this paper, the effects of dressing conditions and grinding conditions on grinding force and grinding power are reviewed. The effects of grinding conditions and dressing conditions on grinding force and grinding power are related to the shape of the idealized chip thickness. It is found that the grinding force and grinding power can be related to the dressing operation by considering the effective density of the cutting edges on the wheel surface. The semi-empirical model developed in this paper can be used to predict the variation of the grinding power during the wheel redress life cycle. Therefore the model can be used to guide the selection of dressing and grinding conditions. The potential use of the model for adaptive control of the grinding process is also described.
Iso-phote Based Tool-path Generation for Machining Free-form Surfaces
Authors: Han Zhonglin , Yang Daniel C. H.
Published: February 2008

This paper presents a novel approach for generating efficient tool paths in machining free-form surfaces. Concept of iso-phote is used to facilitate tool-path generation. An iso-phote is defined as a region on a surface where the normal vector does not differ by more than a prescribed angle from a fixed reference vector. The boundary curves of the iso-phote, called iso-inclination curves, are numerically generated and are served as the initial master tool paths. These iso-inclination curves are then projected to a 2D plane which is perpendicular to the fixed reference vector. 2D curve offsetting of the projected iso-inclination curve is then performed. The resulted 2D offset curves are projected back to 3D surface to form final tool paths. The resulted tool paths can guarantee the satisfaction of machining tolerance requirements. A comparison study of this iso-phote based machining with the conventional iso-parametric machining and the iso-planar machining shows favorite result for the new approach.
Diamondlike Carbon-Coated Dies for Deep Drawing of Aluminum Sheets
Authors: Murakawa M. , Koga N. , Takeuchi S.
Published: February 2008

Soft and hard diamondlike carbon die coatings were used to deep draw aluminum sheets with a very light and environment-friendly water-soluble oil lubricant and even without a lubricant. The water-soluble oil lubricant with poor lubrication ability caused premature rupture of the aluminum blank when drawn with a noncoated steel die, whereas a die coated with soft diamondlike carbon (WC/C) had a lifetime of over 7000 drawing operations. A cost-effective die could be made of a die steel body on which a sintered tungsten carbide alloy overlayer was deposited by high-velocity thermal spraying and further coated with a hard diamondlike carbon (DLC), which gave a life of up to 6000 operations even without a lubricant. Tool life was almost equal to that for a solid sintered carbide alloy die coated with DLC.
Springback Analysis and Control in Small Radius Air Bending
Authors: Elkins K. L. , Sturges R. H.
Published: February 2008

A critical factor for quality small lot sheet metal production is the control of flange angles. For small radius pressbrake bending operations, i.e., punch radius less than sheet thickness, control of angle requires extensive setup time, making small batch runs inefficient. This paper demonstrates the use of relatively simple measurements of material properties to provide the information necessary to estimate and control springback with accuracy approaching 1/4 degree. The control method combines the generality of a modelbased approach with accurate on-line loaded angle measurement. An analytic bending model is developed which provides insights into the material and geometric variables that affect springback. Estimates are made of the relative sensitivity of springback to changes in these variables. In addition, a set of variable ratios are determined which are linearly related to springback and thus serve as the input data for a linear regression model of springback based on experimental results.
Sheet Metal Bending: Generating Shared Setups
Authors: Gupta S. K. , Bourne D. A.
Published: February 2008

Contemporary process planners for sheet metal bending solve the process planning problem for individual parts. Quite often, many different parts can be produced on shared setups. However, plans generated by current process planning systems fail to exploit this commonality between setups and try to generate optimal setups for individual parts. In this paper, we present an algorithm for multi-part setup planning for sheet metal bending. This algorithm takes a set of parts and operation sequences for these parts, and tries to find a shared setup plan that can work for every part in the set. Setup changes constitute a major portion of the production time in batch production environments. Therefore, multi-part setup planning techniques can be used to significantly cut down the total number of setups and increase the overall through-put.
Mixed-Integer Programming Model for Fixture Layout Optimization
Authors: Sayeed Q. A. , De Meter E. C.
Published: February 2008

Workpiece deformation during machining is a significant source of machined feature geometric error. This paper presents a linear, mixed integer programming model for determining the optimal locations of locator buttons, supports, and their opposing clamps for minimizing the affect of static workpiece deformation on machined feature geometric error. This model operates on discretized candidate regions as opposed to continuous candidate regions. In addition it utilizes a condensed FEA model of the workpiece in order to minimize model size and computation expense. This model has two advantages over existing nonlinear programming (NLP) formulations. The first is its ability to solve problems in which fixture elements can be placed over multiple regions. The second is that a global optimal solution to this model can be obtained using commercially available software.
Locator and Sensor Placement for Automated Coordinate Checking Fixtures
Authors: Wang Yu (Michael) , Nagarkar Sanjeev R.
Published: February 2008

This article proposes a systematic method for the optimal design of sensor locations for an automated Coordinate Checking Fixture (CCF). The fixture can be employed for making at-machine assessments of the dimensional accuracy of manufactured components. Coordinate measurements obtained by the sensors built into the fixture can be utilized in estimating geometric parameters of a manufactured part. Two important issues that arise in the design of a CCF are the optimal number of sensors to be used and the best locations for each sensor. The proposed method uses statistical analyses of the Fisher information matrix and the prediction matrix to obtain an optimal set of sensors from an initial candidate set. Sensors are placed at locations that maximize the determinant of the Fisher information matrix for best parameter estimation, while the sensor of the least contribution to the measurement objective is iteratively eliminated. With the benefit of physical insight, the design procedure results in a balanced decision for the optimal placement of sensors. The developed method also addresses the problem of selection of part locators for part localization in the CCF. Examples are provided for illustration of the developed procedure for automotive space frame extrusion parts.
A Total Cost Comparison of Alternative Tolerancing Formulae
Authors: Graves S. B.
Published: February 2008

An important part of many engineering design projects is to specify the amount of variability permitted in critical characteristics of materials, components, and assembly. Different formulae have been suggested for relating input and output specifications. This article reviews the four basic tolerancing formulae that have appeared in the literature and shows that each solves a slightly different problem. In particular, optimal tolerances are based on costs and the probability distributions of input characteristics. Examples of alternative cost-distribution models are provided that support the use of each of the four basic formulae as well as a solution not related to any of these formulae. This establishes that optimal tolerancing is influenced by issues not explicitly considered in the traditional debate over worst-case vs. statistical tolerancing. The approach here differs from previous optimal tolerancing studies in two respects. First, earlier work optimized the allocation of tolerances to components to achieve a given assembly tolerance, while we seek global optima. Second, earlier studies advocated an author’s favorite model, while we explore the relative domains of applicability of alternative formulae.
An Entropy-Based Index Evaluation Scheme for Multiple Sensor Fusion in Classification Process
Authors: Chen Y. , Orady E.
Published: February 2008

Sensor fusion aims to identify useful information to facilitate decision-making using data from multiple sensors. Signals from each sensor are usually processed, through feature extraction, into different indices by which knowledge can be better represented. However, cautions should be placed in decision-making when multiple indices are used, since each index may carry different information or different aspects of the knowledge for the process/system under study. To this end, a practical scheme for index evaluation based on entropy and information gain is presented. This procedure is useful when index ranking is needed in designing a classifier for a complex system or process. Both regional entropy and class entropy are introduced based on a set of training data. Application of this scheme is illustrated by using a data set for a tapping process.