bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Investigation of the 3-D Flow in Shell and Tube Heat Exchangers
Authors: Prithiviraj M. , Andrews M. J.
Published: July 2023

A three-dimensional computer program for simulation of the flow and heat transfer inside Shell and Tube Heat Exchangers has been developed. The simulation of shell and tube heat exchangers is based on a distributed resistance method that uses a modified two equation k-ε turbulence model along with non-equilibrium wall functions. Volume porosities and non-homogeneous surface permeabilities account for the obstructions due to the tubes and arbitrary arrangement of baffles. Sub-models are described for baffle-shell and baffle-tube leakage, shellside and tubeside heat transfer, with geometry generators for tubes, baffles, and nozzle inlets and outlets. The sub-models in HEATX use parameters that have not been altered from their published values.

Computed heat transfer and pressure drop are compared with experimental data from the Delaware project (Bell, 1963). Numerically computed pressure drops are also compared for different baffle cuts, and different number of baffles with the experiments of Halle et al. (1984) which were performed in an industrial sized heat exchanger at Argonne National Labs. Discussion of the results is given with particular reference to global and local properties such as pressure drop, temperature variation, and heat transfer coefficients. Good agreement is obtained between the experiments and HEATX computations for the shellside pressure drop and outlet temperatures for the shellside and tubeside streams.
An Experimental Study of Premixed Flame Impingement Heat Transfer
Authors: Mizuno K. , Mital R. , Viskanta R.
Published: July 2023

This paper reports results of an experimental study to determine the flame structure and heat transfer characteristics of a premixed methane-air flame impinging on a calorimeter. The flame structure is studied photographically and through temperature measurements. The convection and radiation heat transfer contributions of the flame are separated using a black and a highly reflecting water cooled calorimeter. The effects of nozzle-to-plate spacing, firing rate and equivalence ratio on the flame structure and average heat flux are reported. The axial temperature profiles are found to be a strong function of the gap between burner and calorimeter. The radial temperature profiles show a sharp decline near the burner edge. The photographs reveal that multiple jets, arranged in a circular configuration, exit between the cup-shaped ceramic burner and the calorimeter plate. The length of the flame increases with both the firing rate and the equivalence ratio. The heat flux is highest when the burner is closest to the calorimeter, except for the high firing rates when quenching occurs. Even though the heat flux increases, the heat transfer efficiency decreases with increasing firing rate. Heat flux is also found to increase as the flame becomes air rich in the range of parameters investigated.
Optimal Design of Constrained Plate Damping Layers Using Continuum Finite Elements
Authors: Lumsdaine Arnold , Scott Richard A.
Published: July 2023

The aim of this paper is to determine the optimal shape of a viscoelastic damping layer within a constrained layer plate that is undergoing harmonic excitation at its midpoint. The optimization objective is to minimize the peak displacement of the plate at the first resonant frequency. The material loss factor is monitored as well to determine the improvement in performance between an initial, uniform layer shape and the optimized shape. A fine mesh validation model is also created to verify the optimized shape. As manufacturing costs would be reduced for a uniform shape, the optimized shape is used as a guide to create a new, uniform damping layer, which is compared with the previous results. Several geometries and boundary conditions are examined. The ABAQUS finite element code is used to model the structures. Elasticity theory based continuum elements are used so that all stress effects are taken into account in the models. The optimization code uses a Sequential Quadratic Programming algorithm. Results show significant improvement in the loss factor for optimized shapes. For most models, the optimal shape tends towards being a thin, uniform damping layer, which indicates shearing effects dominate in producing the optimal shape. In one case, however, it appears that some normal stress effects also have some influence.
An Optimal Design Method to Control the Vibrations of Suspensions for Passenger Cars
Authors: Bouazara M. , Richard M. J.
Published: July 2023

In recent years, many studies treated the importance of suspension design. The problem is essentially one of a trade-off between many dynamic parameters. In this study, we consider many parameters such as an acceptable comfort level, suspensions deflection and good road handling behavior. It is well know that a soft suspension is inherently more capable of isolating the vehicle body from the effects of road disturbances compared with a firm suspension. However, the effects of accelerations, braking and cornering maneuvers are generally more severe with a softer suspension. Hence in this work, the response of a 2d vehicle equipped with passive, active or semi-active suspension to a road surface undulation interrelated with the vibrations of the human body is studied.
Estimation of Engine Performance Parameters via Time-Frequency Signal Processing of the Acoustic Emission Signal
Authors: Azzoni P. , Moro D. , Rizzoni G.
Published: July 2023

The aim of this paper is to estimate some engine performance parameters in anon intrusive way, processing the engine acoustic emissions signal by means of the application of joint time-frequency domain signal analysis method. The time-frequency analysis methodology represents a very interesting analysis approach with potential applicability to several specific engine diagnostics problems, such as knock detection, or detection of valve flutter in high performance engines. The paper begins with a brief presentation of time-frequency signal analysis; next the application problem is introduced; and finally experimental results are presented. The results of this study indicate that joint time-frequency signal analysis can be a powerful tool in the analysis of nonstationary signals, and can provide effective tools in the analysis of pass-by engine noise.
A Modeling Technique for Fuel Cell Stack Systems
Authors: Lee J. H. , Lalk T. R.
Published: July 2023

A technique for modeling a fuel cell stack is presented. The technique was specifically designed so that the models developed using it could be used to determine the fundamental thermal-physical behavior of a fuel cell stack for any operating and design configuration. Such models would be useful tools for investigating fuel cell power system parameters. The modeling technique can to be applied to any type of fuel cell stack for which performance data is available for a laboratory scale single cell. Use of the technique is demonstrated by generating sample results for a model of a Proton Exchange Membrane Fuel Cell (PEMFC) stack consisting of 125 cells each with an active area of 150 cm2. A PEMFC stack was chosen to demonstrate the technique because many researchers believe it is the type of fuel cell best suited for transportation applications.
Chatter Analysis of Machining Systems With Nonlinear Force Processes
Authors: Landers Robert G. , Ulsoy A. Galip
Published: July 2023

Regenerative chatter is a major limitation to the productivity and quality of machining operations owing to the poor surface finish, excessive tool wear, and reduced dimensional accuracy which are produced. Machining chatter analysis techniques examine the stability of the closed-loop model of the machining operation. This model is the combination of a force process model and a tool-workpiece structure model. Almost all chatter analysis techniques assume a linear force process although machining force processes inherently contain nonlinearities with respect to the cutting parameters (i.e., feed, depth-of-cut, and cutting speed). A novel machining chatter analysis approach is introduced for the stability analysis of machining systems with nonlinear force processes. The accuracy of this methodology is validated via comparisons to time domain simulations and experiments. The stability lobe diagrams (i.e., plots of the stable and unstable regions in the cutting parameter space) generated using linear and nonlinear force process models are compared and the machining force process nonlinearities are shown to significantly impact the resulting diagrams.
Closed-Loop Control of Sheet Metal Forming Using an Active Drawbead
Authors: Hao Shanlin , Klamecki Barney E. , Ramalingam Subbiah , Du Haiwei
Published: July 2023

The intent of this work was to develop the drawbead as an active element in the closed-loop control of sheet metal forming operations. An instrumented, computer controlled drawing press was built on which blank holddown force and drawbead penetration can be varied during drawing. Closed-loop strip drawing process control was demonstrated by in-process measurement of punch force and adjustment of drawbead penetration so as to follow a specified punch force trajectory. In addition, sensors and transducers were developed to measure local forces for process monitoring.
A Linear Observer Based Approach for Estimating Spindle Bearing Loads
Authors: Gibson Alex O. , Stein Jeffrey L.
Published: July 2023

Thermally induced bearing loads have long been recognized as a key factor limiting the performance of machine tool spindle systems. Previous researchers have developed a model based bearing load estimation system using a nonlinear heat transfer/thermal expansion model and nonlinear observer. While this system is capable of estimating the bearing loads, the difficulty of determining the parameters of the nonlinear model represent a significant barrier to transferring this technology to industry. This paper presents two linear design approaches, based upon disturbance rejection control (DRC) theory. The two approaches use an extended linear observer to estimate the nonlinear bearing friction torque heat input. This allows the division of the bearing load estimation problem into a linear temperature state estimation problem and a nonlinear bearing load calculation. The first approach calculates the bearing load by combining estimates of the bearing’s temperature states in a thermal expansion/bearing load calculation. The second approach uses the estimate of the nonlinear friction heat input to calculate the bearing load This approach allows a reduction in the temperature state model from third to first order, further reducing the model’s complexity. Time responses based upon experimental measurements are used to compare and contrast the above methods with the previously published nonlinear estimation approach. The bearing load estimate results demonstrate that DRC theory can be used to minimize the complexity of the bearing load estimation algorithm while maintaining the accuracy of the estimate.
Quantitative Experimental Analysis of Transparency and Stability in Haptic Interfaces
Authors: Lawrence Dale A. , Pao Lucy Y. , Salada Mark A. , Dougherty Anne M.
Published: July 2023

The notion of haptic transparency is used to quantify the fidelity with which virtual object properties are presented to, and perceived by, the human operator. Experimental results are presented quantifying the ability of humans to detect differences in mechanical impedances representing typical types of impedance corruption (loss of transparency) encountered in haptic interfaces due to stability-enhancing dynamic compensation. In particular, a poor connection is found between the stiffness of virtual walls and their perceptual “hardness”, prompting a new definition of hardness which is often dominated by the high frequency dynamics of the rendered impedance.
A New Mult-Finger Tactual Display
Authors: Tan Hong Z. , Rabinowitz William M.
Published: July 2023

A multi-finger positional display (the TACTUATOR) was developed to study communication through the kinesthetic and vibrotactile aspects of the tactual sensory system of the hand. The display consists of three independent single contact-point actuators interfaced (individually) with the fingerpads of the thumb, the index finger, and the middle finger. Each actuator utilizes a disk-drive head-positioning motor augmented with angular position feedback from a precision rotary variable differential transformer (RVDT). A floatingpoint DSP system provides real-time positional control using a digital PID controller. Stimuli from threshold to about 50 dB SL can be delivered throughout the frequency range from near DC to above 300 Hz, thereby encompassing the perceptual range from gross motion to vibration. Actuator frequency and step responses are well modeled as a second-order linear system. Distortion is low allowing delivery of arbitrary stimulus waveforms, e.g., 25 mm low-frequency motion with superimposed high-frequency vibration. System noise and inter-channel crosstalk are also small. As one example of behavioral performance verification, absolute thresholds measured with the stimulator are in general agreement with values in the literature. Overall, the TACTUATOR accurately follows its drive waveforms and is well suited for a variety of multi-finger tactual perceptual studies.
Performance Measurements for Robotic Actuators
Authors: Morrell John B. , Salisbury J. Kenneth
Published: July 2023

The first part of this paper present an argument on the importance of quantitative methods in robotic research. The remaining sections propose detailed performance metrics for actuator evaluation and example specifications. Several measurements which are new to actuator research are proposed: Impedance (“Backdrivability”), Force Dynamic Range and Force Fidelity. These specifications have emerged from research in robotics and haptics and address the need to obtain a more thorough understanding of machine performance.
Kinematic Design of a Three Degree of Freedom Parallel Hand Controller Mechanism
Authors: Adelstein Bernard D. , Ho Peter , Kazerooni H.
Published: July 2023

This paper presents the kinematic design of a 10 link “in-parallel” mechanism for use in a three degree of freedom force-reflecting haptic interface. The mechanism linkage couples three coplanar rotary electric motor shafts to the endpoint grasped by the human operator. The linkage permits all motor housings to be supported on a common base, thereby reducing the inertia and weight that the interface actuators and human operator must support and move. Furthermore, because only rigid links and rotary ball bearings are used, the linkage avoids the compliance, friction, and/or backlash associated with other types of transmission elements. The linkage workspace is bounded by the singular sphere of maximum reach and separated into two hemispheres by singularities in the plane of the motor shafts.
A Spatial Compliance Controller for Serial Manipulators
Authors: Fasse Ernest D.
Published: July 2023

The utility of robotic interactive control schemes such as stiffness control, admittance control and impedance control has been limited in part by the impedance selection problem. It is difficult to select appropriate impedance parameters to execute useful tasks. A spatial compliance controller is presented that simplifies compliance selection. The family of compliances is introduced with spatial transformation properties that simplify compliance parameter selection. A corresponding control law is derived assuming that the robot consists of a serial linkage of rigid links actuated by variable effort actuators. These results are a significant extension of previous results reported by Fasse (1995) and Fasse and Broenink (1995).
Transition Curves in the Quasiperiodic Mathieu Equation
Authors: Zounes Randolph S. , Rand Richard H.
Published: July 2023

In this work we investigate the following quasiperiodic Mathieu equation:x¨+(δ+ϵcos⁡t+ϵcos⁡ωt)x=0 We use numerical integration and Lyapunov exponents to determine transition curves bounding regions of stability in the δ–ω plane for fixed ϵ. In addition, we obtain approximate analytic expressions for these transition curves using two distinct methods: regular perturbations and harmonic balance. Comparison of the results of these methods with those of numerical integration shows that the perturbation method fails to converge in the neighborhood of resonant values of ω. The results obtained by harmonic balance do not display this undesirable feature.
System Dependent Stability of Direct Acting Relief Valves
Authors: Margolis Donald
Published: July 2023

Hydraulic pressure relief valves are known to become unstable at some operating conditions. A model is developed here that exposes instabilities in a fundamental way. It is shown that a valve can be unstable independent of the system to which it is attached. It is also shown that a stable valve can become unstable when it is placed in operation in some system. Some design relationships are developed that can help avoid potential problems during the system design process.
A Computational Tool for Failure Modes and Effects Analysis of Hydraulic Systems
Authors: Bull D. R. , Burrows C. R. , Edge K. A. , Hawkins P. G. , Woollons D. J.
Published: July 2023

Failure Modes and Effects Analysis is widely used in engineering for the assessment of reliability. With the current practice, the length of time involved in the analysis is prohibitive and therefore its full potential cannot be used in the design process. This paper proposes a computational tool, GNOME, which, when fully implemented, will provide a faster method. This paper will discuss its application to an FMEA of a simple hydrostatic transmission.
Review of Buckling Mode and Geometry Effects on Postbuckling Strength of Corrugated Containers
Authors: Urbanik Thomas J.
Published: July 2023

Various postbuckling models involving elastic versus inelastic buckling, linear versus nonlinear material characterization, and finite versus infinite length plate geometry were fit to historical data on compression strength of corrugated fiberboard box and tube specimens. The objectives were to determine if the buckling mode shape could be predicted and if inelastic buckling failure could be differentiated from elastic failure in the side panel and end panel components to account for specimen geometry and material property effects. The variation of a normalized panel strength with a panel slenderness was the criterion for discerning among alternative models. In some cases multiple solutions were feasible. Overall, a finite length plate theory, combined elastic-inelastic postbuckling model, and nonlinear material characterization with plate stiffness empirically corrected with respect to its aspect ratio consistently fit each data source.
Shakedown Load Bounds by Elastic Finite Element Analysis
Authors: Hamilton Robert , Boyle James T. , Shi Jinhua , Mackenzie Donald
Published: July 2023

A simple method for calculating lower and upper bound shakedown loads based on iterative elastic finite element analysis and the bounding theorems of classical plasticity is presented. Elastic and residual stress and strain fields, suitable for substitution into Melan’s lower bound theorem and Koiter’s upper bound theorem, are obtained by applying the elastic compensation method, in which the elastic modulus of each element in an iterative elastic finite element analysis is systematically modified according to calculated stress values from the previous iteration to form suitable residual stress fields. As a demonstration a sample plane stress problem — a biaxially loaded square plate with a central hole — is presented and the shakedown load bounds derived here for specific load cycles are compared with results available in the literature.
A Plane Strain Core Model for Crack Growth in Ductile Materials
Authors: Su X. M. , Sun C. T.
Published: July 2023

It is shown in the present paper that neither plane stress nor plane strain model can accurately simulate ductile fracture tests on ungrooved specimens. Three dimensional effects on the stress distribution at the crack tip must be considered. A moving plane strain core model is thus used in the simulation. For the moving plane strain core model, the deformation in a small region surrounding the crack tip is assumed to be in a state of plane strain and that of the rest of the specimen is in plane stress. With the plane strain core model, it is found that stresses at the crack tip remain constant during steady quasi-static crack growth for ungrooved specimens. For the specimens simulated, the stress at a critical distance from crack tip is independent of specimen size.
Mixed-Mode Crack-Tip Fields Under General Yielding Conditions and Implications to Low-Cycle Multiaxial Fatigue Theory
Authors: Wang Y. , Pan J.
Published: July 2023

The near-tip fields of small Case B cracks in power-law hardening materials are investigated under generalized plane-strain, mixed mode and general yielding conditions by finite element analyses. The results of the J integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trend of constant ΔJ contours on the Γ-plane is compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate.
Life Prediction for Composite Material Structures
Authors: Cassenti Brice N. , Koenig Herbert
Published: July 2023

Recently developed high performance composite materials, such as ceramic or metal matrix composites, exhibit a wide variety of mechanical and thermal effects. A simultaneous development has occurred in manufacturing, where two and three dimensional weaves are now common. These new manufacturing techniques have increased the complications already inherent in predicting the life of advanced composite material components. As a result a general life prediction model for composite material is being developed. A finite element analysis, using a nonlinear finite element code, forms the backbone of the system. A viscoplastic model, applicable to generally orthotropic materials, is included in the code. The finite element analysis simulates the loading history and response for at least one cycle, and possibly several cycles. These cycles do not need to be successive. The results of the finite element analysis are written to a post process file for use in the life model. The viscoplastic model includes parameters that can vary with environmental degradation. For example, SiC fibers may oxidize when present in air at high temperatures. The properties will then degrade with time. This degradation is included through the use of a chemical kinetics and diffusion model. Diffusion, in the case of SiC fibers, is primarily due to oxygen along the fiber matrix interface, but does occur through the fibers and the matrix. Hence the diffusion is orthotropic for a single layer of uniaxial material. The diffusion is modeled using a thermal finite element analysis. The chemical kinetics is included as a heat source. The results of the analysis are written to a post process file for use in the viscoplastic model and the life model. The life model can be either probabilistic or deterministic. The life probabilistic model is based on weakest link theory and includes time dependence. The probabilistic model can be run in a mode that is equivalent to existing damage models.
Review of Constitutive Modeling of Shape Memory Alloys
Authors: Jia Hongyu , Lalande Frederic , Rogers Craig A.
Published: July 2023

Shape memory alloys (SMAs) are increasingly used in many engineering fields, particularly in the smart or intelligent material area. The principal characteristic of shape memory alloys is their ability to memorize their original configuration after they have been deformed, by heating the alloys above the characteristic transition temperature. During this process, a large recoverable strain on the order of 8% can be obtained, making SMAs excellent actuators.

In order to fully utilize the SMAs potential, it is necessary to have a good understanding of their mechanical behavior under thermal and mechanical loading. For this reason, the constitutive modeling of SMA has been, and still is, the focus of many researchers. Several models based on various theories have been proposed thus far. Considering the various theories used, the proposed constitutive models can be classified to five categories: ferroelectrics models, internal variable models, plasticity models, hysteresis models, and non-isothermal models. A review of the SMA constitutive models is presented here.
Multi-Level Polysilicon Surface-Micromachining Technology: Applications and Issues
Authors: Sniegowski Jeffry J.
Published: July 2023

Polysilicon surface micromachining is a technology for manufacturing Micro-Electro-Mechanical Systems (MEMS) which has, as its basis, the manufacturing methods and tool sets used to manufacture the integrated electronic circuit. This paper describes a three-level mechanical-polysilicon surface-micromachining technology and includes a discussion of the advantages of this level of process complexity along with issues which affect device fabrication and performance. Historically, the primary obstacles to multi-level polysilicon fabrication were related to the severe wafer topography generated by the repetition of film depositions and etching. The introduction of Chemical Mechanical Polishing (CMP) to surface micromachining has largely removed these issues and opened significant avenues for device complexity. Several examples of three-level devices with the benefits of CMP are presented.

Of primary hindrance to the widespread use of polysilicon surface micromachining, and in particular microactuation mechanisms, are issues related to the device surfaces. The closing discussion examines the potential of several latter and post-fabrication processes to circumvent or to directly alleviate the surface problems.
Application of Freezing Rate Expressions and Gassing Power to Frozen Bread Dough
Authors: Bail Alain Le , Havet Michel , Pasco Maryvonne , Chourot Jean Marc
Published: July 2023

A literature review of the freezing point expressions shows the availability of various equations to estimate the freezing rate. The expression of the cooling rate during freezing is used to estimate the freezing rate. Cylinders of bread dough were frozen in a tunnel with three different freezing conditions. Gassing power of the yeasted dough (saccharomyces cerevisiae) after thawing were obtained with regards to the location. A finite difference scheme was used to model freezing of an infinite cylinder of bread dough and to calculate freezing rates. Experimental results pointed out that gassing power and thus the freezing rate were both location dependent. The influence of the beginning criterion and of the ending criterion for freezing are related to the freezing rate expressions. A modified expression of the freezing rate is proposed (weighted freezing rate) and is related to gassing power.
Simulating the Effects of a Large Blood Vessel on the Temperature Field Around a Surface Cryoprobe
Authors: Chayut Yehoshua , Shitzer Avraham
Published: July 2023

One of the current methods of treating malignant tissues is by localized freezing in situ. Large blood vessels traversing or situated proximal to the treated region, present a “thermal perturbation” to the developing temperature field. This may prevent certain areas of the tumor from being frozen. Alternatively, there is also the problem relating to the freezing of the blood vessel wall and the blood flowing in it.
Solid Freeform Fabrication: An Overview
Authors: Marcus Harris L. , Harrison Shay , Crocker James
Published: July 2023

Solid freeform fabrication (SFF) has become a prominent area of interest and research in the last 10 years. SFF produces parts directly through additive procedures, without any part-specific tooling. The deisgn for the part originates in a Computer Aided Design (CAD) file which is a three dimensional representation of the part that is sectioned into thin two dimensional layers from which the part is built. SFF vastly enhanced the prototype production process, and now looks to make advancesfor short run productions and tool and dies. This paper presents an overview of SFF, in terms of where it has been, what it is today, and where it will go in the future.
Analysis of Single Grit Cutting of Alumina
Authors: Lin I-Chung Joseph , Sathyanarayanan Guruswami , Plebani Louis J. , Buehler William L.
Published: July 2023

The effect of tool geometry on the material removal mechanisms associated with single grit cutting of alumina is presented. Experiments were conducted whereby conical diamond tips of different included angles were used to emulate the single grit cutting of an alumina workpiece. Analysis of resulting cutting force profiles and of the micrographs of the scratched grooves show that cutting tool geometry is one of the dominant factors affecting the material removal mechanisms. A fracture criterion formulating threshold load as a function of cutting tool included angle is shown to be in agreement with a model from fracture mechanics.
Plasma Enhanced Machining of Inconel 718
Authors: Shin Yung C. , Kim Jin-Nam
Published: July 2023

The experimental analysis of plasma enhanced machining (PEM) of Inconel 718 is presented in this paper. Surface temperatures due to plasma heating are systematically characterized through experimental investigation using infrared radiation thermometry and an empirical model is developed to predict the workpiece surface temperature in terms of various operating conditions. Benefits of PEM are also illustrated through a reduction of cutting forces and improved surface roughness over a wide range of cutting conditions. In addition, improvement of productivity in machining Inconel 718 with PEM is demonstrated.
Heat Partitioning and Temperatures in Grinding
Authors: Ju Y. , Farris T. N. , Chandrasekar S.
Published: July 2023

A theoretical analysis is presented of the energy partitioning and surface temperatures in grinding. The numerical results agree with the experimental results of Kohli et al. It is found that the presence of the fluid inside the grinding zone can reduce the heat flux into the workpiece and the workpiece temperature significantly. However, it is nearly impossible to keep the fluid active for the conventional grinding of steel with aluminum oxide. For the conventional grinding of steel with CBN, or the creep feed grinding of steel with aluminum oxide or CBN, it is possible to keep the fluid active and therefore to reduce thermal damage. To help understand the effects of grinding conditions, a simplified heat partition model is developed which is proved very accurate for down grinding and fairly accurate for up grinding. The effects of grinding conditions on the energy partition to the workpiece and the workpiece temperature are studied systematically.
On-Line Slab Temperature Calculation and Control
Authors: Staalman Dirk F. J. , Kusters Arend
Published: July 2023

This paper describes a modern control system for reheating furnaces in a hot strip mill. The system has been implemented in two pusher and two walking beam furnaces of Hoogovens Hot Strip Mill No.2, each with a capacity of 300 ton/h, and in the 280 ton/h walking beam furnace of the Tata Iron & Steel Company (Tisco), India.

The system consists of two main parts; the calculation model for reliable estimation of the slab temperatures and the controller part for reaching the desired slab temperatures. Except for the furnace control system itself, this paper describes a furnace simulator, based on multi variable system identification, that makes it possible to keep tuning of the new system on site to a minimum.

The calculation model proved to give good results; 95% of all slab temperatures are estimated within a range of +/− 20°C. With the knowledge of the actual slab temperatures at each position in the furnace and an individual heating curve for each slab, actual slab temperature control become possible. Zone temperature setpoints are generated by a controller with input deviations between the calculated and target slab temperatures in a control zone; This is the master loop. The fuel setpoints are generated in slave loop.

The performance of rougher temperature, but also of rundown and of skidmark have been improved remarkably, for both pusher and walking-beam furnaces.
Decoupling the Confounded Effect of Machine Error and Geometric Characteristics of Artifacts in Precision Measurement and Machine Calibration
Authors: Lee G. , Mou J. , Shen Y.
Published: July 2023

Inspection is commonly used to scrutinize the quality of manufactured products against established standards and specifications. However, the quality and reliability of many inspection processes are contaminated by various uncertainties. One of the prominent sources for measurement uncertainties is due to the imperfection of a measuring device and the confounded effect of its imperfection with geometric characteristics of a measured feature. To ensure the quality and reliability of any inspection process, measurement uncertainties need to be addressed for all data acquisition activities. A method is also needed to identify and decouple the effect of confounded uncertainties. If this can be done, then the collected data can be properly adjusted and a more meaningful analysis result can be drawn. In this paper, the issue of uncertainty identification for machine calibration and dimension measurement using artifacts with spherical feature is discussed. Analytical models are derived to first assess and then decouple the confounded effect of both types of uncertainties. Finally, case studies are used to illustrate the general application and the effectiveness of the derived models in assessing and decoupling the confounded effect, and thus, reducing the measurement uncertainties.
Reliability Assessment of BGA Interconnects With CADMP-II
Authors: McCluskey F. P. , Govind A. , Beaudet D.
Published: July 2023

Recently the plastic ball grid array (PBGA) has been gaining industry-wide acceptance in high pin count applications as a low-cost alternative to fine-pitch leaded packages such as the plastic quad flat pack (PQFP). The main factors leading to its use include low cost, high I/O density, a small footprint, and the potential for superior electrical and thermal performance with respect to PQFPs [Houghton 1993; Freyman and Pennisi, 1991]. However, concerns about interconnect reliability remain, particularly for systems to be joined with novel solders or conductive adhesives, which are being used increasingly both for environmental reasons and because of the need for higher temperature operating systems. Thus there exists a need to accurately evaluate design trade-offs arising due to these failures in order to increase reliability and drive design improvements.

A PC-based CAD tool for the assessment of the reliability of PBGA interconnects is presented. This tool facilitates the use of physics-of-failure methodology in design for reliability, virtual qualification and the selection of accelerated test conditions. The tool assesses candidate and existing package designs for reliability in many different environments using a database of fully validated physics-of-failure models. These models calculate times-to-failure for the fundamental mechanisms which cause failure of area array packages housing both bipolar and CMOS based systems. Particular focus is placed on the use of this tool for analyzing the reliability of area array solder joint interconnects, including those made with lead-free solders and conductive adhesives, and on conductive filament formation between the traces in a plastic ball grid array. The addition of the appropriate material properties for high temperature, fatigue resistant, lead-free solders to the materials database, the development of a package designer for PBGA designs, and the incorporation of failure mechanism models for flip chip solder fatigue, PBGA solder joint shear and tensile fatigue, and PBGA conductive filament formation will be discussed. The ability to use this tool to conduct assessments of the susceptibility of PBGAs to non-interconnect failure mechanisms is an added advantage as it permits a determination of the relative importance of interconnect failure as a failure mode.
Viscoelastic Analysis of IC Package Warpage
Authors: Yeung T. S. , Yuen M. M. F.
Published: July 2023

Package warpage was studied previously using thermoelastic finite element analysis. Epoxy Molding Compound (EMC) was assumed to be thermal-elastic with temperature dependent mechanical properties (usually assigned values above and below the glass transition temperature, Tg). The effect of thermal mismatch of components inside the package was examined without considering the time history of the curing process. To account for this, this study will examine the effect of viscoelastic properties of EMC with different degree-of-cure on package warpage during the encapsulation process.

In this study, warpage of a 160 leads Plastic Quad Flat Package (PQFP) was evaluated by employing a three-dimensional viscoelastic finite element model. Dynamic mechanical properties of the EMC for different degree-of-cure were measured in a Rheometrics RMS-800 analyzer at different temperatures: 160°C, 165°C, 170°C, 175°C, 180°C and 185°C to determine the viscoelastic shear modulus of G′ and G″. The test data were then used to formulate the Maxwell model for viscoelastic analysis using a commercial finite element package ABAQUS. The analysis examined the effect of degree-of-cure of EMC on warpage prediction. The predicted warpage values were compared with laboratory measurement using a Coordinate Measuring Machine (CMM).
A CFD Method With Cartesian Grids and Complex Geometries Defined by Cell Porosities
Authors: Willoughby Donald A. , Greiner Christopher M. , Carroll George W.
Published: July 2023

A CFD method for automotive cooling air flow applications based on structured cartesian grids and a cell based porosity approach to represent geometry is described. Steady Navier-Stokes equations with turbulence models are solved with a finite difference method using narrow-stencil upwind differencing. Fans and heat exchangers are represented by experimentally based models. The differencing scheme is a three dimensional implementation of a technique described in two dimensions by Sidlikover and Brandt[1]. The CFD code has been optimized and parallelized for RISC computers, vectorized parallel computers, and massively parallel computers. Geometry is represented by a series of triangular elements, but other representations could be used with the method. A completely automated preprocessor calculates porosities which represent intersections of the grid with the geometry. The porosities define an approximate surface representation of the actual geometry. Wall functions based on normal distances to surfaces and actual surface areas are used for wall boundary conditions.
Flow Analysis of a Diesel Engine Water Jacket Using Unstructured Tetrahedral Meshes
Authors: Birkett C. A. , Dhaubhadel M. N. , Daniel S. I. , Balachander R. S.
Published: July 2023

Computational Fluid Dynamics (CFD) has been hampered in the past by the amount of time required to generate accurate models for complicated geometries. Consequently, it has been difficult to incorporate CFD studies into the design process for complex components such as engine water jackets. This paper describes a methodology using unstructured tetrahedral meshes which largely overcomes this problem.

The cooling jacket for a 4-valve diesel engine cylinder head was analyzed. Because the model used tetrahedral elements to represent the complex geometry, it was possible to create an accurate model relatively quickly.

Flow and heat transfer coefficients were calculated for a maximum flow condition. Typical temperatures were assumed for boundary conditions at the walls.

The work showed the feasibility of calculating the detailed distribution of heat transfer coefficients and flow velocities inside engine cooling jackets. The process described proved to be fast and robust enough to be applied to such components in the design stage.
Evaluation of the Dynamic Subgrid-Scale Stress Model in Finite-Differenced Les: Effects of Grid Resolution and Inhomogeneous Test Filtering
Authors: Najjar Fady M. , Tafti Danesh K.
Published: July 2023

The dynamic subgrid-scale stress model (Germano et al., 1991) is used for the Large Eddy Simulations of the turbulent channel flow at Reτ = 1050. Finite difference approximations based on the Harlow-Welch scheme are used to discretize the governing flow equations. The test filter is based on a second-order trapezoidal rule. The effects of model predictions for different grid resolutions and the application of the test filter in the wall normal inhomogeneous direction are investigated. The grid resolution study showed that the dynamic model responds in a manner consistent with the physics. The results obtained are in good agreement with experiments as well as spectral LES (Piomelli, 1993) performed at the same Reynolds number. It is found that the application of the test filter in the inhomogeneous wall normal direction has a small effect on the dynamic constant and the turbulence statistics. In general the dynamic constant decreases making the model less dissipative.
Large Eddy Simulation of Isotropic Decaying Turbulence With Structured and Unstructured Grid Finite Volume Methods
Authors: Dailey Lyle D. , Simons Todd A. , Pletcher Richard H.
Published: July 2023

The performance of finite volume methods to obtain the large eddy simulation of homogeneous, isotropic, decaying turbulence in structured and unstructured grids has been studied. This simple flow was used for preliminary analysis of finite volume methods before application to more complex geometries. Both the Smagorinsky subgrid-scale model and the dynamic subgrid-scale model were evaluated.

The study has shown that both the structured and unstructured grid approaches work well with the Smagorinsky model. As expected, the structured grid scheme was slightly more accurate than the unstructured grid scheme. The dynamic model has also been shown to work well with the structured and unstructured grids.
Two- and Three-Dimensional Laminar Flows Between Disks Corotating in a Fixed Cylindrical Enclosure
Authors: Iglesias Immaculada , Humphrey Joseph A. C.
Published: July 2023

A numerical investigation is performed for the constant-property laminar flow of air in the space between a pair of disks clamped coaxially on a central hub and corotating in a stationary cylindrical enclosure. Both two- and three-dimensional flow conditions are examined in relation to the interdisk spacing, H, and the disk angular velocity, Ω. Two interdisk spacings are considered, corresponding to aspect ratios Γ = 0.186 and 0.279 [with Γ = H/(R2 + a – R1), where R2 is the disk radius, a is the disk rim-enclosure wall clearance, and R1 is the hub radius]. A range of rotational speeds encompassing the transition from axisymmetric two-dimensional steady flow to non-axisymmetric three-dimensional unsteady flow is considered for various values of the Reynolds number, Re (with Re = ΩR22/v, where v is the kinematic viscosity of air). Axisymmetric calculations are first performed for both aspect ratios in the range 3,858 ≤ Re ≤ 23,150. Fully three-dimensional calculations are then performed for the configuration with Γ = 0.186 and Re = 23,150, and for the configuration with Γ = 0.279 and Re = 7,715, 15,430, and 23,150. The axisymmetric calculations performed with Γ = 0.186 confirm many known features of the flow, including the transition from a steady flow to an oscillatory periodic regime. This occurs at about Re = 23,150 for a configuration with a/H = 0, and at about Re = 14,670 for one with a/H = 0.28 and a finite disk thickness (b/H = 0.2). Three-dimensional calculations performed for Γ = 0.186 with a/H = 0 and Re = 23,150 reveal a circumferentially periodic flow pattern with eight foci of intensified axial component of vorticity. The axisymmetric calculations performed with Γ = 0.279 yield a novel, non-unique steady solution for the velocity field that is asymmetric with respect to the interdisk midplane. No experimental verification of this finding exists to date, but similar situations are known to arise in the context of anomalous modes of the Taylor-Couette flow. Relaxing the axisymmetry constraint allows this flow to evolve to an oscillatory three-dimensional regime of increasing irregularity with increasing rotational speed. In this case, the number of foci of intensified axial vorticity varies with time, ranging from six at Re = 7,715 to between six and eight at Re = 23,150.
A Computational-Experimental Development of Vortex Generator Use for a Transitioning S-Diffuser
Authors: Wendt Bruce J. , Dudek Julianne C.
Published: July 2023

The development of an effective design strategy for surface-mounted vortex generator arrays in a subsonic diffuser is described in this report This strategy uses the strengths of both computational and experimental analyses to determine beneficial vortex generator locations and sizes. A parabolized Navier-Stokes solver, RNS3D, was used to establish proper placement of the vortex generators for reduction in circumferential total pressure distortion. Experimental measurements were used to determine proper vortex generator sizing to minimize total pressure recovery losses associated with vortex generator device drag. The best result achieved a 59% reduction in the distortion index DC60, with a 0.3% reduction in total pressure recovery.
Determination of Temperatures and Heat Fluxes on Surfaces of Multi-Domain Three-Dimensional Electronic Components
Authors: Martin Thomas J. , Dulikravich George S.
Published: July 2023

A new algorithm that uses the boundary element method (BEM) has been developed for determining steady thermal boundary conditions on surfaces of three-dimensional solids where such quantities are unknown. Given temperature and heat flux on surfaces where such data is readily available, the algorithm computes, non-iteratively, the temperature field within the entire object and any unknown thermal boundary conditions on the surfaces where thermal boundary values are unavailable. An inverse BEM computer program has been developed and was successfully tested on several simple geometries where the analytic solutions of the well-posed problem were known. Our non-iterative algorithm for inverse determination of unknown thermal boundary conditions is very fast and highly flexible in treating complex three-dimensional geometries including interior cavities, mixed thermal boundary conditions and multiple domains with different thermal properties. Besides surface input data, this algorithm accepts also temperatures and heat fluxes at isolated interior points as input data.
High Resolution Thermal Design Tools for Air-Cooled Electronics Components and Systems
Authors: Przekwas Andrzej J. , Athavale Mahesh M. , Ho Yin-H.
Published: July 2023

The packaging trends for the latter part of the 1990’s appear to suggest that advanced computing and military application multi-chip modules (MCMs) will generate tremendous heat loads. Advanced, accurate design tools will be needed to evaluate new cooling concepts entailing complex geometries and complex physics, and which are capable of solving large scale numerical problems. This paper presents a high resolution computational model for thermal design of high density electronic packages. Details of numerical model for strongly implicit conjugate heat transfer are discussed. A novel high accuracy numerical wall scheme has been presented to resolve near wall shear stresses and wall heat fluxes. Three electronics cooling problems have been selected to validate the computer code on complex geometry configurations. These configurations are: an SMT module with fully resolved leadframe, 256 pin heat sink and a 20 module MCM with 74 fin heat sink. Results of the computational study are compared with available experimental data. In all three cases very good agreement with experiment has been achieved.