bluuebunny/crossref_metadata_2025 huggingface dataset:
Darryl E. Metzger Memorial Session Paper: Experimental Heat Transfer and Friction in Channels Roughened With Angled, V-Shaped, and Discrete Ribs on Two Opposite Walls
Authors: Taslim M. E. , Li T. , Kercher D. M.
Published: March 2013

Experimental investigations have shown that the enhancement in heat transfer coefficients for air flow in a channel roughened with angled ribs is on the average higher than that roughened with 90 deg ribs of the same geometry. Secondary flows generated by the angled ribs are believed to be responsible for these higher heat transfer coefficients. These secondary flows also create a spanwise variation in heat transfer coefficient on the roughened wall with high levels of heat transfer coefficient at one end of the rib and low levels at the other end. In an effort basically to double the area of high heat transfer coefficients, the angled rib is broken at the center to form a V-shaped rib, and tests are conducted to investigate the resulting heat transfer coefficients and friction factors. Three different square rib geometries, corresponding to blockage ratios of 0.083, 0.125, and 0.167, with a fixed pitch-to-height ratio of 10, mounted on two opposite walls of a square channel in a staggered configuration, are tested in a stationary channel for 5000 < Re < 30,000. Heat transfer coefficients, friction factors, and thermal performances are compared with those of 90 deg, 45 deg, and discrete angled ribs. The V-shaped ribs are tested for both pointing upstream and downstream of the main flow. Test results show that: (a) 90 deg ribs represent the lowest thermal performance, based on the same pumping power, and is essentially the same for the 2:1 change in blockage ratio, (b) low-blockage-ratio (e/Dh = 0.083) V-shaped ribs pointing downstream produced the highest heat transfer enhancement and friction factors. Among all other geometries with blockage ratios of 0.125 and 0.167, 45 deg ribs showed the highest heat transfer enhancements with friction factors less than those of V-shaped ribs, (c) thermal performance of 45 deg ribs and the lowest blockage discrete ribs are among the highest of the geometries tested in this investigation, and (d) discrete angled ribs, although inferior to 45 deg and V-shaped ribs, produce much higher heat transfer coefficients and lower friction factors compared to 90 deg ribs.
An Experimental Investigation of Stator Induced Unsteadiness on Centrifugal Impeller Outflow
Authors: Ubaldi M. , Zunino P. , Barigozzi G. , Cattanei A.
Published: March 2013

Detailed flow measurements were taken in a centrifugal turbomachine model to investigate the aerodynamic influence of the vaned diffuser on the impeller flow. The model consists of an unshrouded centrifugal impeller with backswept blades and a rotatable vaned diffuser, which enables a continuous variation of the vaned diffuser location with respect to the measuring points. Phase-locked ensemble-averaged velocity components have been measured with hot-wire probes at the impeller outlet for 30 different relative positions of the probe with respect to the diffuser vanes. The data also include the distribution of the ensemble-averaged static pressure at the impeller front end, taken by means of miniature fast response pressure transducers flush-mounted at the impeller stationary casing. By circumferentially averaging the results obtained for the different circumferential probe locations, the periodically perturbed impeller flow has been split into a relative steady flow and a stator-generated unsteadiness. The results for the different probe positions have also been correlated in time to obtain instantaneous flow field images in the relative frame, which provide information on the various aspects of the diffuser vane upstream influence on the relative flow leaving the impeller.
Experimental and Computational Results From the NASA Lewis Low-Speed Centrifugal Impeller at Design and Part-Flow Conditions
Authors: Chriss R. M. , Hathaway M. D. , Wood J. R.
Published: March 2013

The NASA Lewis Low-Speed Centrifugal Compressor (LSCC) has been investigated with laser anemometry and computational analysis at two flow conditions: the design condition as well as a lower mass flow condition. Previously reported experimental and computational results at the design condition are in the literature (Hathaway et al., 1993). In that paper extensive analysis showed that inducer blade boundary layers are centrifuged outward and entrained into the tip clearance flow and hence contribute significantly to the throughflow wake. In this report results are presented for a lower mass flow condition along with further results from the design case. The data set contained herein consists of three-dimensional laser velocimeter results upstream, inside, and downstream of the impeller. In many locations data have been obtained in the blade and endwall boundary layers. The data are presented in the form of throughflow velocity contours as well as secondary flow vectors. The results reported herein illustrate the effects of flow rate on the development of the through flow momentum wake as well as on the secondary flow. The computational results presented confirm the ability of modern computational tools to model the complex flow in a subsonic centrifugal compressor accurately. However, the blade tip shape and tip clearance must be known in order to properly simulate the flow physics. In addition, the ability to predict changes in the throughflow wake, which is largely fed by the tip clearance flow, as the impeller is throttled should give designers much better confidence in using computational tools to improve impeller performance.
Structures and Dynamics Committee Best Paper of 1996 Award: Inlet Distortion Generated Forced Response of a Low-Aspect-Ratio Transonic Fan
Authors: Manwaring S. R. , Rabe D. C. , Lorence C. B. , Wadia A. R.
Published: March 2013

This paper describes a portion of an experimental and computational program (ADLARF), which incorporates, for the first time, measurements of all aspects of the forced response of an airfoil row, i.e., the flow defect, the unsteady pressure loadings, and the vibratory response. The purpose of this portion was to extend the knowledge of the unsteady aerodynamics associated with a low-aspect-ratio transonic fan where the flow defects were generated by inlet distortions. Measurements of screen distortion patterns were obtained with total pressure rakes and casing static pressures. The unsteady pressure loadings on the blade were determined from high response pressure transducers. The resulting blade vibrations were measured with strain gages. The steady flow was analyzed using a three-dimensional Navier–Stokes solver while the unsteady flow was determined with a quasi-three-dimensional linearized Euler solver. Experimental results showed that the distortions had strong vortical, moderate entropic, and weak acoustic parts. The three-dimensional Navier–Stokes analyses showed that the steady flow is predominantly two-dimensional, with radially outward flow existing only in the blade surface boundary layers downstream of shocks and in the aft part of the suction surface. At near resonance conditions, the strain gage data showed blade-to-blade motion variations and thus, linearized unsteady Euler solutions showed poorer agreement with the unsteady loading data than comparisons at off-resonance speeds. Data analysis showed that entropic waves generated unsteady loadings comparable to vortical waves in the blade regions where shocks existed.
Rotordynamic Forces Due to Turbine Tip Leakage: Part I—Blade Scale Effects
Authors: Song S. J. , Martinez-Sanchez M.
Published: March 2013

An experimental and theoretical investigation has been conducted on rotordynamic forces due to nonaxisymmetric turbine tip leakage effects. This paper presents an actuator disk model that describes the flow response to a finite clearance at the rotor tip. The model simplifies the flow field by assuming that the radially uniform flow splits into two streams as it goes through the rotor. The stream associated with the tip clearance, or the underturned stream, induces radially uniform unloading of the rest of the flow, called the bladed stream. Thus, a shear layer forms between the two streams. The fraction of each stream and the strength of shear layer between the two are found as functions of the turbine loading and flow parameters without resorting to empirical correlations. The results show that this model’s efficiency predictions compare favorably with the experimental data and predictions from various correlations. A companion paper builds on this analysis to yield a model of the three-dimensional disturbances around an offset turbine and to predict the subsequent cross forces.
Analysis of Instability Inception in High-Speed Multistage Axial-Flow Compressors
Authors: Hendricks G. J. , Sabnis J. S. , Feulner M. R.
Published: March 2013

A nonlinear, two-dimensional, compressible dynamic model has been developed to study rotating stall/surge inception and development in high-speed, multistage, axial flow compressors. The flow dynamics are represented by the unsteady Euler equations, solved in each interblade row gap and inlet and exit ducts as two-dimensional domains, and in each blade passage as a one-dimensional domain. The resulting equations are solved on a computational grid. The boundary conditions between domains are represented by ideal turning coupled with empirical loss and deviation correlations. Results are presented comparing model simulations to instability inception data of an eleven stage, high-pressure-ratio compressor operating at both part and full power, and the results analyzed in the context of a linear modal analysis.
The Simulation of Turbomachinery Blade Rows in Asymmetric Flow Using Actuator Disks
Authors: Joo W. G. , Hynes T. P.
Published: March 2013

This paper describes the development of actuator disk models to simulate the asymmetric flow through high-speed low hub-to-tip ratio blade rows. The actuator disks represent boundaries between regions of the flow in which the flow field is solved by numerical computation. The appropriate boundary conditions and their numerical implementation are described, and particular attention is paid to the problem of simulating the effect of blade row blockage near choking conditions. Guidelines on choice of axial position of the disk are reported. In addition, semi-actuator disk models are briefly described and the limitations in the application of the model to supersonic flow are discussed.
Rotating Stall Control of an Axial Flow Compressor Using Pulsed Air Injection
Authors: D’Andrea R. , Behnken R. L. , Murray R. M.
Published: March 2013

This paper presents the use of pulsed air injection to control rotating stall in a low-speed, axial flow compressor. In the first part of the paper, the injection of air is modeled as an unsteady shift of the compressor characteristic, and incorporated into a low dimensional model of the compressor. By observing the change in the bifurcation behavior of this model subject to nonlinear feedback, the viability of various air injection orientations is established. An orientation consistent with this analysis is then used for feedback control. By measuring the unsteady pressures near the rotor face, a control algorithm determines the magnitude and phase of the first mode of rotating stall and controls the injection of air in the front of the rotor face. Experimental results show that this technique eliminates the hysteresis loop normally associated with rotating stall. A parametric study is used to determine the optimal control parameters for suppression of stall. The resulting control strategy is also shown to suppress surge when a plenum is present. Using a high-fidelity model, the main features of the experimental results are duplicated via simulations.
Parallelism Improvement of Ground Silicon Wafers
Authors: Matsui S. , Horiuchi T.
Published: March 2013

This paper discusses substituting grinding for lapping in machining processes of silicon wafers. To attain this goal, the rotating wafer grinding method, in which a rotating wafer is ground by continuous infeed of a cup wheel, is investigated. The parallelism of a silicon wafer ground by this method is within 2 μm for a 5 in. (125 mm) wafer.
Computer Aided Design of a Mold Cavity With Proper Rigging System for Casting Processes: Part 2
Authors: Park Jong Cheon , Lee Kunwoo
Published: March 2013

An interactive computer program to design a mold cavity with the proper rigging system has been developed. In addition to the pattern and the risers generated as described in Part 1 of this work, the various components of the gating system are generated in complete three-dimensional models by a rational approach. Then they are laid interactively by the user, and united together with the pattern and the risers to result in the three-dimensional model of the mold assembly. Finally, the vents and the mold box are constructed following the user’s interactive specification and then the mold cavity is completed in a three-dimensional geometric model by subtracting the mold assembly and the vents from the mold box. The three-dimensional model of a mold cavity is useful for many related applications such as the solidification simulation for mold evaluation and the NC tool path generation for mold production.
Experimental Investigations into Traveling Wire Electrochemical Spark Machining (TW-ECSM) of Composites
Authors: Jain V. K. , Sreenivasa Rao P. , Choudhary S. K. , Rajurkar K. P.
Published: March 2013

Fiber reinforced composites, though relatively new, have already become important engineering materials. So far the main emphasis of research has been on the development of materials, but nowadays more attention is being paid to the industrial manufacture of products made of composites. Conventional machining methods and some unconventional machining methods like laser beam machining (LBM) and water jet machining (WJM) cannot be effectively applied for machining of composites due to the resulting problems of air borne dust, tool wear, and thermal damage. Recently electrochemical spark machining (ECSM) has been applied for the cutting and drilling of holes in composites. The success achieved in the application of ECSM for cutting of composites has stimulated interest in exploring the prospects of use of traveling wire electrochemical spark machining (TW-ECSM) process for cutting of composites. An apparatus for TW-ECSM is designed and fabricated in the laboratory. The results about the feasibility of the process and its performance during machining of composites are presented in this paper. Experiments are carried out on glass-epoxy and kevlar-epoxy composites, using sodium hydroxide (NaOH) as electrolyte. The wire and the workpiece were kept in physical contact with each other by the use of a gravity feed mechanism. The effects of voltage and concentration of the electrolyte on material removal rate, average diametral overcut, tool wear rate, and wire erosion ratio are reported. The theoretical analysis of the mechanism of the process identifies the thermo-mechanical phenomena as the main source of material removal in ECSM.
Effect of Process Variables on Die-Billet Temperature History in a Slow Speed Hot Coining Type Process
Authors: Shamasundar S. , Marathe A. G. , Biswas S. K.
Published: March 2013

A computer code is developed as a part of an ongoing project on computer aided process modelling of forging operation, to simulate heat transfer in a die-billet system. The code developed on a stage-by-stage technique is based on an Alternating Direction Implicit scheme. The experimentally validated code is used to study the effect of process specifics such as preheat die temperature, machine ascent time, rate of deformation, and dwell time on the thermal characteristics in a batch coining operation where deformation is restricted to surface level only.
Active Contact Stresses at Epitrochoid Generated Rotor-Stator Set of Fixed Axis or Equivalent System ‘ROPIMA’ Type Hydrostatic Units
Authors: Maiti R.
Published: March 2013

The development of the turning moments and their patterns in various models of epitrochoid generated “ROPIMA” type hydrostatic units with “fixed axis” or “equivalent system” rotors has been studied. Analysis of the contact stresses and the generation of the gaps at the active contacts and their possible reductions are the major aims of this work. The deflection and the stresses have been estimated using Hertz’s contact stress theory with the help of a proposed dimensionless analytical technique.
The Effect of Noise on Grinding Cycles
Authors: Fedoseev Oleg B.
Published: March 2013

This paper presents a new analysis for grinding cycle simulation based upon the Fokker-Planck equation. This approach is able to describe both the deterministic behavior and the random noise for infeed controlled grinding cycles. Non-zero residual elastic deflection of the system is demonstrated for long spark-out times in the presence of noise due to random cutting force variations and feed velocity fluctuations.
A Laboratory Investigation of Threshold Stress in Wheel/Rail Interaction for Heavy Axle Loads
Authors: Singh S. P. , Kumar S.
Published: March 2013

This study is a continuation of earlier investigations to determine acceptable upper bound of contact stresses (threshold stress) for new wheel and rail under heavy axle load conditions. Using sharply increased wear rate (as initial maximum contact stress increases) under free rolling conditions as an indicator of threshold stress, laboratory investigations of wheel-rail rolling contact wear, simulating the 125-ton car wheel load, were conducted. Tangent track conditions with clean and dry surfaces were tested on two facilities; one of one-quarter scale and the other of one-fifteenth scale wheel-rail simulation. The earlier experiments conducted in the IIT Railroad Engineering Laboratory to investigate threshold stress used a varying load with the same wheel-rail profiles, the present study used constant load with varying wheel-rail profiles to determine whether the above increase in wear rate phenomenon will still be observed. While the results of the small (1/15th) scale facility were not considered quantitatively conclusive because of small size, qualitatively they indicated the presence of threshold stress phenomenon. The results of the one-quarter scale test facility very clearly confirmed that there is indeed a threshold stress above which the rolling contact wear rates increased sharply. The value of this stress, found to be approximately the same as reported in the earlier study, was nearly 200 ksi (for standard carbon steel rail). From the earlier and the present investigations of threshold stress, it is clearly concluded that the increased wear rates are primarily due to the increased initial contact stresses and 200 ksi is the value of threshold stress for standard carbon steel rail. Initial wheel-rail contact stresses for new wheel-rail should not be allowed to exceed this value to reduce damage to rail for heavy axle loads. It is recommended that new wheel-rail profiles should be developed to achieve stresses at or below this threshold stress level. Benefits of improved rail life with this approach are also discussed.
On the Generation of Coordinated Motion of Five-Axis CNC/CMM Machines
Authors: Chou Jui-Jen , Yang D. C. H.
Published: March 2013

This paper presents an analytical study on the command generation for five-axis CNC machining or CMM measurement. In the integration of CAD and CAM, it is necessary to relate machine tool kinematics and control in a CAM process to the geometrical data in a CAD model. The data stored in a CAD model is usually static in nature and represented by unitless parameters. Yet, in machine tool motion and control, the data should be transformed into a time dependent domain. In this paper, a general theory on the conversion from desired paths to motion trajectory is analytically derived. The geometrical properties of a desired path, including position, tangent, and curvature are related to the kinematics of coordinated motion including feedrate, acceleration and jerk. As a result, the motion commands used as control references to track arbitrary space curves for five-axis computer-controlled machines can be generated in a rather straight-forward as well as systematic way.
Turning Process Identification Through Force Transients
Authors: Nair R. , Danai K. , Malkin S.
Published: March 2013

A method is presented for identifying the chip formation, plowing, and sliding forces in turning from force transients. For this purpose, a simple model is used which separates the cutting force into a sharp tool chip formation component and a residual component associated with both rubbing between the wear land and the workpiece and plowing at the cutting edge. Variations of the cross-sectional area of the cut during a transient are used to tune the model and estimate its parameters.
Monitoring Milling Processes Through AE and Tool/Part Geometry
Authors: Sturges R. H.
Published: March 2013

This paper discusses an approach to monitoring cutting tool/part interactions in milling processes using processed acoustic emission (AE) signals and the combined geometric aspects of the tool and the part. The expected events marking interactions of the tool edge with respect to the part during a cut are computed from a priori knowledge of tool and part geometry. Each event period is characterized by its timing and expected AE spectrogram. During cutting, AE signals are periodically converted to spectrograms to determine the peak signal frequency band. This band then defines a bandpass filter through which AE signals pass in real time, reporting the levels and event times of the actual process. Comparison of expected and actual event times and levels forms the basis for a continuous on-line tool/part interaction monitor which detects workholder failure and certain tool failure conditions.
Friction Behavior in the Cup Ironing Process of Aluminum Sheets
Authors: Kawai N. , Dohda K. , Saito M. , Hayashi N. , Wang Z.
Published: March 2013

The object of this paper is to clarity the surface flattening mechanism in the cup ironing process based on the lubricating mechanism. A new experimental apparatus for the ironing process was made and experiments on ironing were carried out with aluminum cups using various lubricants and reductions in thickness. The experiments revealed that on the die surface the friction coefficient becomes minimum under the appropriate conditions of viscosity of lubricant and reduction in thickness. It was also confirmed that the cup surface is best flattened under conditions where the minimum friction coefficient appears.
An Analysis of Void Deformation Caused by Power Law Creep and Diffusion Enhanced by Mechanical Stress in HIP Process
Authors: Lee Y. S. , Kim K. T.
Published: March 2013

A dominant deformation mechanism in an isostatic pressure sintering process of a powder compact is known as power law creep. The deformation of a pore was predicted from the existing stress analysis based on power law creep assuming a hollow sphere and a hollow cylinder. The deformation at high temperature (T> 0.4 Tm) involves both power law creep and diffusion enhanced by mechanical stress. The analysis performed by previous investigators included only the deformation caused by power law creep. The analysis in this paper is considering for both the deformation caused by power law creep and diffusion in the final stage of the HIP process for a hollow sphere and hollow cylinder models. The contribution of the diffusion mechanism to the total densification is investigated. The experimental results published for CoO are compared with the analytical result for power law creep only and for power law creep and diffusion. The results show that the effect of diffusion on the total densification is insignificant for densities of the order of 80 percent of theoretical at low applied pressure, and for a small vacancy diffusion coefficient (Dv). However, the contribution of diffusion is increased in the high densification region (ρ>0.95), with high applied stress and high Dv. It is concluded that the diffusion mechanism enhances the densification and its rate in the final stage of HIP process.
Design Analysis of a Twin Head Horizontal Hydraulic Press
Authors: Singh U. P. , Miller P. P.
Published: March 2013

Because of economical reasons, use of the single or multi-head hydraulic press is finding popularity in recent times in assembly work for automotive parts in particular. As this type of press offers opportunity for large parts to be assembled with ease, their design and performance poses complexity and challenge to press designers in regard to the high precision required by assembly work. This paper deals with the design analysis of a twin head horizontal press using the finite element method. The three-dimensional finite element model, developed for the press, gives quantitative results useful to press designers. Some suggestions are made to improve the stiffness and torsional rigidity of the press.
Aspects of Process Model for Automatic Control of Edge-Deburring with Filamentary Brush
Authors: Cariapa V. , Stango R. J. , Chen L. , Hermann R.
Published: March 2013

In this paper, process models are reported for a dynamic system consisting of a polymer/mineral abrasive filamentary brush during an orthogonal deburring operation. Dynamic process models are generated by employing both a viscoelastic representation and Dynamic Data Systems approach for predicting brush response under random penetration depth operating conditions. A process model for material removal is obtained by the use of a multiple regression method in conjunction with experimental results for burr material removal under various brushing conditions. Time constants for both the viscoelastic dynamic system and material removal characteristics of brushes are reported and discussed. An examination of system transfer functions indicates that the system is stable. In addition, generally good agreement is obtained when comparison is made between the process model for burr removal and actual measurement of machined burrs.
A Study of Quenching: Experiment and Modelling
Authors: Aksel B. , Arthur W. R. , Mukherjee S.
Published: March 2013

This paper describes the design, execution, mathematical modelling, and simulation of a simple, yet very useful quenching experiment—the asymmetric one-sided quenching of a beam. This experiment yields valuable information regarding the mechanical variables at the end of a quenching process, without the need for measurement of residual stresses in the quenched object. The final (residual) curvature of the beam is strongly sensitive to the inelastic deformation behavior of the material of the quenched object. This problem—experiment and simulation—is recommended as a benchmark problem for future research in this subject area.
Design of Cellular Manufacturing Systems
Authors: Irani S. A. , Cohen P. H. , Cavalier T. M.
Published: March 2013

This paper describes a method for layout design of a Cellular Manufacturing System (CMS) that would allow simultaneously, the grouping of machines unique to a part family into cells and those shared by several cells to be located together in functional sections. Using an illustrative example, this integration of the flexibility of a functional layout, the reduced handling gained from cell formation and allowance of limited intercell flows among adjacent cells is described. Thereby, the traditional strategy of simultaneous formation of part families and distribution of machines into independent cells which creates machine distribution and unbalanced utilization problems is avoided. This is justified by an analysis of the complex interactions between the critical subproblems in cell formation—machine grouping, part family formation, distribution and utilization of shared machines, intracell layout, intercell (or shop) layout and material handling. This approach represents a new direction in cell formation where, by allowing the handling function to limit the extent of machine duplication between adjacent cells, a new graph theoretic structure for simultaneous machine grouping and layout design was developed and validated.
The Effect of Weld Gas Flow Rate on Al-Li Weldability
Authors: Martinez L. F. , McClure J. C. , Nunes A. C.
Published: March 2013

Adequate shield and plasma gas flow rate during plasma arc welding are crucial factors in achieving high quality welds. Too low a shield gas flow rate lets atmosphere enter into the arc and too high a rate wastes weld gas and may cause turbulence and entrain atmosphere. Sufficient plasma gas flow is required for keyhole welding and, as shown in this paper, can reduce hydrogen contamination in the weld. In-situ optical spectroscopy used to detect oxygen and hydrogen in the welding arc during variable polarity plasma arc (VPPA) welding of aluminum 2090 revealed that there is an easily detected critical shield gas flow rate needed to exclude atmosphere and that this critical rate can be used to automatically control gas flow rates during welding.
Rattling Loose of Thread Connected Steels in Percussive Rock Drilling
Authors: Fu C. C.
Published: March 2013

A common practice to uncouple drill steels in percussive rock drilling is by rattling. Rattling is primarily a continuation of a drilling process without the rotation of the drill steels. By examining the forces which exist at the contacting threads between two drill steels and a coupling, it is shown that normal thread loads in tightly coupled steels and coupling systems always produce a loosening torque. The loosening torque is opposed by circumferential friction torques developed at the thread interface and at the drill steels’ interface. Using a theory developed by Goodier for loosening of threaded fasteners by vibration, it is shown how tensile forces generated by rattling can overcome the friction torques to provide a mechanism for uncoupling the drill steels. A sequence of events during rattling loose of multiple steels is postulated, and conditions which facilitate the loosening process are discussed. Repeated pushing and pulling tests of manually torqued-up steels and couplings in a tensile testing machine for four commonly used steels confirms that tensile forces generated during rattling are indeed responsible for rattling loose. Complete loosening was achieved for all four steels tested under various combinations of an initial tightening torque and the cyclic tensile load, and the total number of load cycles required for a complete loosening were determined. Test results also show that loosening due to compressive forces generated during rattling should be very small. The dependence of rattling loose on the helix angle and the static thread efficiency of the thread form is discussed.
Thermal Design and Experimental Analysis of Laser and Electron Beam Hardening
Authors: Festa R. , Nenci F. , Manca O. , Naso V.
Published: March 2013

Dimensionless correlations for an easy prediction of the hardened depth in electron and laser beam heating treatments are derived from two analytical thermal models. Electron beam heat treating is carried out on 9Cr-2Mo and C40 steels. Effects of the translation speed and the spot dimensions were taken into account. The fairly good agreement between analytical and experimental data suggests that the proposed correlations can be used in applications.
Advanced Interpolation Techniques for N.C. Machines
Authors: Bedi S. , Ali I. , Quan N.
Published: March 2013

This paper describes two methods for curve and surface interpolation. The layout of the machine and the implementation of these methods on an N.C. machine are discussed. The requirement for additional computational power to implement these interpolation methods is addressed by a network of computers called transputers. The interface between the controller and the network is described. This network also provides the ability to do interference checking in real time using the subdivision technique. The advantage of this implementation is that it enhances the ability of the conventional controller and avoids problems such as communication errors, jerky motion, gouging, and closed architecture. The method used to determine the accuracy of the interpolator is described and some results are given. Curved surfaces described as a series of B-spline curves can be machined using the curve interpolator, whereas a B-spline surface can be machined with the surface interpolator. Sample surfaces are machined to show the ability of the controller in both the curve interpolation and surface interpolation modes.
Measurement and Control of a Straightening Process for Seamless Pipes
Authors: Katoh T. , Urata E.
Published: March 2013

This paper deals with an automatic curing process for out-of-straightness of terminal ends of seamless pipes. The developed curing process is composed of a measuring stage and a controlling stage. In the measuring stage, the out-of-straightness pattern of each pipe is measured automatically, then reference pressure points and press strokes are determined to minimize the sum of squares of deflection angles. In the controlling stage, elastic springback of the pipe is predicted by an observer using the calculated press stroke, on-line measured values of reactive force, and deflection of the pipe. Through a series of experiments, the validity of the proposed process was verified.
Damping Capacity of Turning Tools, Part 2: Mechanism Initiating the Damping Capacity
Authors: Hashimoto M. , Marui E. , Kato S.
Published: March 2013

This paper examines the mechanism initiating the damping capacity of a turning tool. The turning tool is considered as a beam on an elastic foundation. Parameters of the model are estimated from the experimental result of the free damped vibration frequency. Next, the magnitude of damping energy is calculated from the friction resistance and the relative slip between the tool shank and the tool post (elastic foundation) during vibration in both tangential and normal directions. The calculated result of damping energy agrees well with the experimental result of the damping capacity qualitatively, for various clamping loads and various surface topographies. This result indicates that the damping capacity of the turning tool system is mainly caused by the relative slip at the tool shank.
Spherical and Circular Blending of Functional
Surfaces
Authors: Pegna J. , Wilde D. J.
Published: March 2013

A method is presented for designing smooth blending between structural surfaces when only local alterations of the original surfaces are allowed. A simple kinematic analogy to the blending process is to represent the blending surface as the envelope of a sphere, possibly of variable radius, moving while in contact with the original surfaces. This scheme is then generalized to blending surfaces which can be represented by sweeping a (possibly variable) arc of circle. By design, this method guarantees continuity of the unit surface normal and of the normal radius of curvature along the common boundary with the blending surface, called the linkage curve.
CTOD Testing of HAZ and Analysis of Pop-In Behavior
Authors: Koc¸ak M. , Chen L. , Terlinde G. , Gnirss G. , Schwalbe K.-H.
Published: March 2013

HAZ CTOD tests were carried out on nonmatching bead on plate SAW weldments at room temperature. The effects of the notch position and weld metal matching on the HAZ toughness were studied by taking weld metals with three strength levels (austenitic, ferritic and martensitic weld metals). The notches were located parallel (L-type) and perpendicular (T-type) to the straight fusion line and across the beveled fusion line (cross-bond type). The results indicate the T-type CTOD specimens may be used for screening the most brittle zone of the HAZ and may to a certain extent ease the experimental difficulties of the HAZ CTOD testing. The CTOD crack initiation (pop-in) values are controlled by the microstructure of the crack tip zone and the strength of the adjacent material. The recently proposed pop-in assessment procedure was used for the evaluation of the pop-ins and results were discussed in terms of the measurements of the load drop, crack extension and the CTODjump values.
System Identification of Remotely Operated Vehicle
Dynamics
Authors: Goheen K. R. , Jefferys E. R.
Published: March 2013

Models for Remotely Operated Underwater Vehicles (ROVs) are difficult to derive because their dynamics are strongly coupled, highly nonlinear and vary according to the vehicle’s operating configuration. In addition, conventional modeling techniques require the use of expensive, specialized testing equipment. An alternative procedure using System Identification (SI) to process data gathered during simple free-running trials can generate fast, inexpensive and accurate ROV models. Three SI algorithms, Least Squares (LS), Extended Least Squares (ELS) and the Recursive Prediction Error Method (RPEM), are tested on simulated ROV data and compared for accuracy and economy. The vehicle studied in this paper, the UMEL Seapup, can be represented accurately by a linear model at the low speeds where accurate maneuvering control is most important and gain scheduling can be used to switch models at higher speeds.
On the Effect of Roughness on Cylinders
Authors: Sarpkaya T.
Published: March 2013

The purpose of this paper is to examine the differences and/or similarities in some of the existing data on the effect of roughness on cylinders in sinusoidally oscillating planar flow, to reflect upon the fluid-mechanical and/or facility-dependent causes of the differences, and to make some recommendations regarding the design and execution of future database as well as concept-base experiments.
A Model-Based Approach to 3-D Imaging and Mapping Underwater
Authors: Stewart W. K.
Published: March 2013

An approach to multidimensional representation of underwater environments is presented with results of applications of 3-D sonar mapping. A nondeterministic model incorporates information from multiple knowledge sources and creates a framework for real-time processing. Probabilistic methods account for nonideal sensors; spatial decomposition and numerical techniques treat amorphous underwater features and facilitate an incremental approach. An emphasis on representational and modeling issues is maintained with examples drawn from computer simulations and field data from profiling and imaging sonars.
Storage Tanks Under Earthquake Loading
Authors: Rammerstorfer Franz G. , Scharf Knut , Fisher Franz D.
Published: March 2013

This is a state-of-the-art review of various treatments of earthquake loaded liquid filled shells by the methods of earthquake engineering, fluid dynamics, structural and soil dynamics, as well as the theory of stability and computational mechanics. Different types of tanks and different possibilities of tank failure will be discussed. We will emphasize cylindrical above-ground liquid storage tanks with a vertical axis. But many of the treatments are also valid for other tank configurations. For the calculation of the dynamically activated pressure due to an earthquake a fluid-structure-soil interaction problem must be solved. The review will describe the methods, proposed by different authors, to solve this interaction problem. To study the dynamic behavior of liquid storage tanks, one must distinguish between anchored and unanchored tanks. In the case of an anchored tank, the tank bottom edge is fixed to the foundation. If the tank is unanchored, partial lifting of the tank’s bottom may occur, and a strongly nonlinear problem has to be solved. We will compare the various analytical and numerical models applicable to this problem, in combination with experimental data. An essential aim of this review is to give a summary of methods applicable as tools for an earthquake resistant design, which can be used by an engineer engaged in the construction of liquid storage tanks.
On the Dynamics of Cracked Rotors: A Literature Survey
Authors: Wauer Jo¨rg
Published: March 2013

Propagating fatigue cracks can have detrimental effects on the reliability of rotating machinery. An early crack warning can considerably extend the durability of these very expensive machines, increasing their reliability at the same time. Vibration monitoring as a means of detecting crack initiation has been receiving much interest. A detailed study of the vibrational behavior of cracked rotating shafts, therefore, is an important problem for engineers working in the area of the dynamics of machines. This article presents a review of the field of the dynamics of cracked rotors, including the modeling of the cracked part of the structure and finding different detection procedures to diagnose fracture damage. The material should be helpful to scientists and researchers working in this area or planning to work in it in the future. Since the study of nonrotating, cracked structural elements obviously is relevant to the cracked rotor problem, the review can also be a basis for discussing the dynamics of cracked beams and columns.
Assessment of Computational Models for Multilayered Composite Shells
Authors: Noor Ahmed K. , Burton W. Scott
Published: March 2013

A review is made of the different approaches used for modeling multilayered composite shells. Discussion focuses on different approaches for developing two-dimensional shear deformation theories; classification of two-dimensional theories based on introducing plausible displacement, strain and/or stress assumptions in the thickness direction; first-order shear deformation theories based on linear displacement assumptions in the thickness coordinate; and efficient computational strategies for anisotropic composite shells. Extensive numerical results are presented showing the effects of variation in the lamination and geometric parameters of simply supported composite cylinders on the accuracy of the static and vibrational responses predicted by eight different modeling approaches (based on two-dimensional shear deformation theories). The standard of comparison is taken to be the exact three-dimensional elasticity solutions. The quantities compared include both the gross response characteristics (eg, vibration frequencies and strain energy components); and detailed, through-the-thickness distributions of displacements, stresses, and strain energy densities. Some of the future directions for research on the modeling of multilayered composite shells are outlined.
Some Experiments on the Steady State Characteristics of a Cylindrical Fluid-Film Bearing Considering Thermal Effects
Authors: Tonnesen J. , Hansen P. K.
Published: March 2013

The paper presents the results of systematic experiments conducted on a 100mm diameter cylindrical bearing having a L/D = 0.55 and a C/R = 1.5 × 10−3. Joint measurements are taken of the steady state position, the pressure distribution, and the journal and bearing wall temperatures as a function of speed, load, viscosity, and oil inlet geometry. The journal has built-in transducers for measuring displacement, pressure and temperature. The speed is varied from 6.7 to 133.3 Hz, the load from zero to 9000 N, the viscosity from 4 to 28 mPa•s and the oil inlet geometry is 2-holes or 2 axial grooves. Correlation with theoretical predictions is presented.
Minimum Load Requirements for the Prevention of Skidding in High Speed Thrust Loaded Ball Bearings
Authors: Boness R. J.
Published: March 2013

This paper describes the development of an empirical equation used to determine the minimum thrust load that is required to prevent gross ball and cage skidding in high speed angular contact bearings. Based on extensive computer results the equation is shown to give excellent agreement with existing experimental evidence.
Contact Stresses Between Elastic Cylinders: A Comprehensive Theoretical and Experimental Approach
Authors: Hartnett M. J. , Kannel J. W.
Published: March 2013

The purpose of the paper has been to present a comparison of theoretical predictions and experimental data for contact stresses between two bodies lubricated in contact. The theoretical analysis is based on a three-dimensional linear elastic solution to the problem and combines Boussinesq force-displacement relationships for a half-space with a modified flexibility method. The experimental approach involves the direct measurement of contact pressures between profiled rollers using a thin-film pressure transducer. Pressure measurements and predictions were made for three roller designs under various conditions of loads and misalignments. The agreement between theory and experiments is very good.
On the Traction Behavior of Several Lubricants
Authors: Gupta P. K. , Flamand L. , Berthe D. , Godet M.
Published: March 2013

A number of lubricants in the well known classes denoted by MIL-L-23699 and MIL-L-7808 specifications and a traction fluid are investigated for their traction behavior in rolling sliding contacts. The experimental traction data are reduced to simple rheological models and the appropriate coefficients are computed. The reduced models are presented in a form which is readily adaptable to the rolling bearing performance simulation computer programs.
Structural and Compositional Characterization of RF Sputter-Deposited Ni-Cr + Cr2O3 Films
Authors: Bhushan Bharat
Published: March 2013

An RF-sputtered chrome oxide coating with metallic binders was developed. The chrome oxide coating has high-temperature capabilities and is wear resistant, and has some self-lubricating properties. A nichrome metallic binder was added in the coating to improve its ductility without significant loss in the hardness. The sputtering parameters were optimized to obtain a smooth coating with the maximum adherence. The coatings were applied using bias-sputter and sputter-deposit modes on the heat treated and annealed foil substrates. The coating applied on annealed foils using the sputter-deposit mode was smooth and had the best adherence. Metallurgical examinations showed that the coating was Ni-Cr + Cr2O3. The coating as applied was amorphous and it crystallized during substrate heat treatment.
Thermoelastic and Dynamic Phenomena in Seals
Authors: Wu Yih-Tsuen , Burton R. A.
Published: March 2013

An analysis of a seal model is made where the rotating element has both fixed tilt and two-lobe waviness. The stator is assumed to be gimbal mounted and to have inertial mass. Hydrodynamic lubrication is assumed, following the short bearing or narrow seal model. Conditions are examined where the stator precesses in synchronism with the rotor rotation. Particular interest is given to operating conditions where such behavior appears to degenerate. The objective of this study is to explain a coupled, inertial/thermoelastic phenomenon observed in experiments performed by Banerjee.
An Experimental Evaluation of the Hamrock and Dowson Minimum Film Thickness Equation for Fully Flooded EHD Point Contacts
Authors: Koye K. A. , Winer W. O.
Published: March 2013

Fifty-seven measurements of the minimum lubricant film thickness separating the elastohydrodynamically lubricated point contact of a steel crowned roller and a flat sapphire disk were made by an optical interferometry technique. The data collected were used to evaluate the Hamrock and Dowson minimum EHD film thickness model over a practical range of contact ellipticity ratio where the major axis of the contact ellipse is aligned both parallel and perpendicular to the direction of motion. A statistical analysis of the measured film thickness data showed that the experimental data averaged 30 percent greater film thickness than the Hamrock and Dowson model predicts.