bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Invasive Measurement of Counter-Current Flows in a Hemodialyzer Using Fourier-Velocity Magnetic Resonance Imaging
Authors: Hardy Peter A. , Poh Churn K. , Huang Zhongping , Liao Zhijie , Gao Dayong
Published: December 2021

The objectives of this paper are: (1) to show the usefulness of Fourier-velocity magnetic resonance imaging (MRI) technique in validating numerical models in the design of an optimal hemodialyzer, and (2) in characterizing non-invasively the spatial counter-current flow distribution in a hemodialyzer. The relative amount of flows at different velocity range for both the blood and dialysate compartments of a CT190G hemodialyzer (Baxter Healthcare Corporation, Deerfield, IL) was measured non-invasively using the Fourier-velocity MRI technique. This technique was first validated by imaging a flow phantom. The flow phantom consisted of two parallel-Plexiglas tubes with flows introduced counter-currently in each tube. In both cases, twenty-four images were acquired at thin cross sections corresponding to the flows at the mean velocities {−24, ..., −4, −2, 0,+2, +4, ..., +22} mm/s. These images were acquired at the mid-section of both the two-parallel-Plexiglas tube and the hemodialyzer. The empirical results were found to be comparable to numerical results computed from the Navier-Stokes equations. Images of the hemodialyzer demonstrated a wide spatial flow distribution both inside the blood and dialysate compartments. A segment of the hemodialyzer had reduced intra-fiber flow indicating a region of occlusion in the blood compartment. Flow at the dialysate compartment was greater at the periphery of the hollow-fiber bundle adjacent to the housing.
Modeling of Crack Growth in Thin Sheet Aluminum
Authors: Siegmund T. , Brocks W. , Heerens J. , Tempus G. , Zink W.
Published: December 2021

The present study reports on the application of a cohesive zone model to the analyses of crack growth in thin sheet specimen of a high strength aluminum alloy. In addition to the elastic-plastic material properties, the two parameters cohesive strength and cohesive energy describe material separation. For the sheet specimen under investigation the cohesive energy is determined via a numerical-experimental approach using tests on notched tensile specimens as well as a damage indicator. The cohesive energy is found to be close to the corresponding value of plane strain fracture toughness. The cohesive strength is approximately twice the yield strength. With these two additional material parameters being determined crack growth experiments in center crack panels are analyzed. Good agreement with experimental records is found. Finally the applicability of the model to study complex crack configurations as in multi-site damaged specimens is demonstrated.
Three-Dimensional Analyses of Single Rivet-Row Lap Joints — Part II: Elastic-Plastic Response
Authors: Iyer K. , Rubin C. A. , Hahn G. T.
Published: December 2021

Three-dimensional finite element analyses of an elastic-plastic, single rivet-row, aluminum lap joint are presented and compared with previous results for linear elastic models. The calculations treat non-countersunk aluminum and steel rivets, 3 different configurations of countersunk rivets as well as two values of the friction coefficient. The compliance of the connection, rivet tilt, the stresses in the panels, peak plastic strains and the contact pressures and slip amplitudes at the rivet-panel and panel-panel interfaces are evaluated. The transverse, axial, and shear stress distributions and the stress concentrations generated in four different rivets are derived from the linear elastic models and related to the rivet geometry. Laboratory measurements of the lap joint compliance and local out-of-plane displacements that support the reliability of the finite element analyses are presented.
Bolt Thread and Head Fillet Stress Concentration Factors
Authors: Lehnhoff Terry F. , Bunyard Bradley A.
Published: December 2021

Linear finite element analysis (fea) was performed to determine stress concentration factors for the threads and the bolt head fillet in a bolted connection. The fea models consisted of axisymmetric representations of a bolt and two circular steel plates each 20 mm in thickness. The bolts studied were 8, 12, 16, 20, and 24 mm diameter grade 10.9 metric bolts with the standard M thread profile. The threads were modeled at both the minimum and maximum allowable depths. The fillet between the bolt shank and bolt head connection was modeled at its minimum radius. Each bolt was loaded to its proof strength. A comparison is made to stress concentration factors typically used in bolted connection design. Stress concentration factors in the head fillet were 3.18, 3.23, 3.63, 3.58, and 3.90 for the 8, 12, 16, 20, and 24 mm bolts, respectively. Thread stress concentration factors were highest in the first engaged thread and decreased in each successive thread moving toward the end of the bolt. Stress concentration factors for the shallow thread models ranged from 1.17 to 4.33, 0.87 to 4.32, 0.83 to 4.67, 0.87 to 4.77, and 0.82 to 4.82 for the 8, 12, 16, 20, and 24 mm bolts, respectively. Likewise, stress concentration factors for the deep thread models ranged from 1.18 to 4.80, 0.88 to 4.80, 0.78 to 5.12, 0.83 to 5.17, and 0.82 to 5.22 for the 8, 12, 16, 20, and 24 mm bolts, respectively.
Comparison of Two Axisymmetric Finite Element Models of Threaded Connections
Authors: Hommel Mark
Published: December 2021

Predicting the fatigue life of threaded connections using finite element analysis generally requires a 2-D axisymmetric model capable of handling non-axisymmetric loading in order to simulate an applied bending moment. This is desirable from the standpoint of computer run time, as compared with the alternative approach, namely, developing a full 3-D model. Unfortunately, due to their esoteric nature, the 2-D axisymmetric elements with non-axisymmetric loading capability are not supported by the software vendors as well as the other elements, hence pre- and post-processing are more challenging. In addition, due to the Fourier representation of the non-axisymmetric load, computer run time and storage is increased significantly over that of a strictly 2-D axisymmetric model. In view of this, common practice has been to use instead the conventional axisymmetric model with an equivalent applied axial tensile stress equal to the mean bending stress through the wall thickness in order to simulate the bending moment and thereby avoid the necessity for non-axisymmetric loading. The question therefore arises as to how well the results from the strictly axisymmetric model agree with the results from the axisymmetric model with non-axisymmetric loading capability.

The purpose of this paper is to compare the results of the two models. A 5-1/2 F.H. threaded connection is modeled by means of a commercial finite element code. First, the axisymmetric model with non-axisymmetric loading capability is treated and results are obtained. Second, the axisymmetric model with applied equivalent tensile load is examined and its results are compared with the former model. It is found that the value of the primary variable of interest for quantification of fatigue life, namely, alternating stress, agrees between the two models within 4%. Thus, it is concluded that the simplified model provides a viable alternative for modeling fatigue life of threaded connections.
Analysis of Interfacial Fracture in Thin Films Subjected to Thermal Loading
Authors: Gosz M. , Okyar A. F.
Published: December 2021

We consider the problem of a three-dimensional interface crack between a film and a substrate to gain a better understanding of how the problem of peeling in film-substrate material systems subjected to thermal loading can be alleviated. We assume that the crack lies in the plane of the interface and is located at one of the free comers of the structure. The fracture parameters (mixed mode stress intensity factors, phase angles and the energy release rate) along the crack front are obtained using an interaction energy integral technique developed by Gosz et al. (1998) for analysis of three dimensional, bimaterial interface cracks. The technique is a very accurate domain integral method that is employed as a post-processing step after a finite element solution for the stress, strain, and displacement fields in the solid has been obtained. In the paper, we investigate the effect of film thickness on the fracture parameters and the results are discussed.
Detailed Stress Analysis of a Spherical Acrylic Submersible by 3-D Finite Element Modeling
Authors: Das Partha S.
Published: December 2021

Harbor Branch Oceanographic Institution (HBOI) designed, built and has operated two JOHNSON-SEA-LINK (JSL) manned submersibles for the past 25 years. The JSL submersibles each incorporate a 66–68 in. (1.6764–1.7272 m) OD, 4–5.25 in. (0.1016–0.13335 m) thick acrylic two-man sphere as a Pressure Vessel for Human Occupancy (PVHO). This type of spherical acrylic sphere or submersible was first introduced in around 1970 and is known as Naval Experimental Manned Observatory (NEMO) submersibles. As the demand increases for ocean exploration to 3000 ft. (914.4 m) depth to collect samples, to study the ocean surfaces, the problem of developing cracks at the interface of these manned acrylic submersibles following few hundred dives have become a common phenomena. This has drawn considerable attentions for reinvestigation of the spherical acrylic submersible in order to overcome this crack generation problem at the interface. Therefore, a new full-scale 3-D nonlinear FEA (Finite Element Analysis) model, similar to the spherical acrylic submersible that HBOI uses for ocean exploration, has been developed for the first time in order to simulate the structural behavior at the interface and throughout the sphere, for better understanding of the mechanical behavior. Variation of the stiffness between dissimilar materials at the interface, lower nylon gasket thickness, over designed aluminum hatch are seemed to be few of the causes for higher stresses within acrylic sphere at the nylon gasket/acrylic interface.

Following the basic understanding of the stresses and relative displacements at the interface and within different parts of the submersible, various models have been developed on the basis of different shapes and thickness of nylon gaskets, openings of the acrylic sphere, hatch geometry and its materials, specifically to study their effect on the overall performance of the acrylic submersible. Finally, the new model for acrylic submersible has been developed by redesigning the top aluminum hatch and hatch ring, the sphere openings at both top and bottom, as well as the nylon gasket inserts. Altogether this new design indicates a significant improvement over the existing spherical acrylic submersible by reducing the stresses at the top gasket/acrylic interface considerably. Redesigning of the bottom penetrator plate, at present, is underway. In this paper, results from numerical modeling only are reported in details. Correlation between experimental-numerical modeling results for the new model will be reported in the near future.
Mechanical Engineering Education for 1st Year Seminar Using Real Products
Authors: Sakamoto Haruo , Kusukawa Kazuhiro , Jorgensen Jens
Published: December 2021

An engineering education experience for a 1st year mechanical engineering seminar using real world products is described. The seminar contains product dissection, report writing, and oral presentations. The objectives are to observe the real engineering world and to provide engineering experience for 1st year students. The product dissection items consist of a hand drill, hand cleaners, coffee maker, single-use camera, hedge trimmer, electric drill, and sheet finishing sander, some of which were obtained from the US and Japanese markets. It provides a comparison of consumer requirements in the US and Japanese markets as well as some technical aspects. The seminar was 1997 and 1998 at the Kochi University of Technology, which was opened in April, 1997. The seminar seemed successful because 1st year students were able to experience a first look at real world technology, although some modification will be needed for future sessions.
A Role of the Resultant Cutting Force in Deep-Hole Drilling
Authors: Latinovic V. N. , Astakhov V. P. , Osman M. O. M.
Published: December 2021

This paper present results of the analysis of a tool static stability in deep-hole drilling. The analysis has been carried out to determine the optimal location of the drill guide pads relative to the drill’s cutters (based upon criteria of equal total pad reactions and equal stability indicators). It is demonstrated that the optimal location can be achieved under asymmetrical location of the supporting pads relative to the direction of the resultant cutting force in a plane perpendicular to the drill axis. By consideration of the drill static force system in the plane which contains the drill axis and the resultant cutting force vector, a new design criterion is proposed. The essence of this concept is to design the deep-hole drills with minimum rubbing and wear of the guide pads and provide for the tool self-piloting.
An Orthogonal Cutting Model Based on Finite Deformation Analysis: Part I — Model Development
Authors: Zheng Y. , Sutherland J. W.
Published: December 2021

Based on the finite deformation theory of continuum mechanics, the velocity, Eulerian strain, Eulerian strain rate, and deformation rate distributions along a family of assumed streamlines are analytically obtained for an orthogonal cutting operation. An iterative incremental method is used to predict the temperature on the shear plane. The total power in orthogonal cutting may be expressed in terms of three parameters, which are predicted by minimization of the total power. This model allows a general form for the material constitutive equation, which, in general, is a function of strain, strain rate, and temperature. The rotation effect of streamlines on the strain and strain rate calculations is automatically considered using the finite deformation theory of continuum mechanics. In Part I of this paper, the theoretical underpinning for the orthogonal cutting model is established. The verification of the model, including determination of the material constitutive equation using the Hopkinson bar technique, is presented in Part II of this paper.
Physical Constraints in the Control of Chip Breakability
Authors: Brailov Alexander Yu.
Published: December 2021

The aim of the paper is to propose and discuss a new criterion of chip breakability. The comparisons of the proposed and known criteria are made for different cutting feeds and speeds. It is demonstrated that, in contrary to the known criteria, the proposed criterion reflects the chip ability to be broken. On the basis of practical experimental data, the criteria values for different kinds of chips obtained during machining stainless steel X18H10T are calculated.
On the Development of a Tangential Clamped-On Chipbreaker for Difficult-to-Machine Materials
Authors: Airikyan Armen L.
Published: December 2021

Everyday practice of cutting process planning requires reliable chipbreacking and this is particularly true when machining difficult-ti-machine materials as austenitic stainless steels. The use of pressed-groove type of chipbreakers prove to provide a partly solution of the problem since their utilization unavoidably leads to increasing cutting force and chipping of the cutting edge. The use of clapped-on chipbreaker seems to solve these problems. However new design and application problem arise. This paper deals with the analysis of these problema and offers a methodology for it resolving. As a result, a new type of a clamped-on chipbreaker has been developed.
Generating and Modeling Subsurface Damage in Grinding γ-Ti-48Al
Authors: Nelson Luis , Razavi H. Ali , Kurfess Thomas , Danyluk Steven
Published: December 2021

This paper reports on an experimental investigation and modeling results for the grinding-induced subsurface damage in gamma titanium aluminide (γ-TiAl). Grinding was carried out at various depths of cut, wheel and workpiece speeds with a friable diamond grinding wheel. The type/pattern and extent of the subsurface damage was determined by a bonded interface technique using optical microscopy and a surface laser profiler. The results show that the damage beneath the ground surface can be measured from the depth of a rumpled region that is identified with plastic deformation or shear/slip-fault deformation, distortion and microcracks. It was also determined that the depth of grinding-induced subsurface damage in the nearly fully lamellar γ-Ti-48Al microstructure ranges from 150 μm to 400 μm. The severity and depth of the subsurface damage was found to increase with an increase in grinding speed ratio and depth of cut.
Process Specification Language (PSL): Results of the First Pilot Implementation
Authors: Schlenoff Craig , Ciocoiu Mihai , Libes Don , Gruninger Michael
Published: December 2021

In all types of communication, the ability to share information is often hindered because the meaning of information can be drastically affected by the context in which it is viewed and interpreted. This is especially true in manufacturing because of the growing complexity of manufacturing information and the increasing need to exchange this information among various software applications. Different manufacturing functions may use different terms to mean the exact same concept or use the exact same term to mean very different concepts. Often, the loosely defined natural language definitions associated with the terms contain so much ambiguity that they do not make the differences evident and/or do not provide enough information to resolve the differences.

A solution to this problem is the development of a taxonomy, or ontology, of manufacturing concepts and terms along with their respective formal and unambiguous definitions. This paper focuses on the Process Specification Language (PSL) effort at the National Institute of Standards and Technology whose goal is to identify, formally define, and structure the semantic concepts intrinsic to the capture and exchange of discrete manufacturing process information. Specifically, it describes the results of the first pilot implementation, where PSL was successfully used as an interlingua to exchange manufacturing process information between the IDEF3-based ProCAP1 process modeling tool and the C++ based ILOG Scheduler.
The RMS Characteristics of Acceleration and Force Signals Depending on Tool Wear in Stable Cutting
Authors: Chiou Richard Y. , Kwon Y. K. , Liang Steven Y.
Published: December 2021

An analysis of the RMS (Root Mean Square) characteristics of fluctuating force and acceleration signals for a cutting tool engaged in a turning operation in the presence of wear flat on the tool flank is presented in this research. The RMS of acceleration and force signals obtained from experiments in stable cutting is compared with theoretical machining models due to the tool wear effect. The RMS is a measure of the energy, at the tool tip-workpiece interface along the flank, to the random vibration of the cantilever portion of the tool holder. Increasing flank wear results in an increasing stability and decreasing RMS in the thrust direction, dependent upon flank wear-land width. The RMS force and acceleration signals in machining is calculated by frequency band RMS method at the first natural frequency of the cantilever portion of the tool holder in the frequency domain. By reference to experimental evidence, the theoretical predictions show generally good agreement with test results.
3D Shape-Generating Processes and the G-Buffer Modeling for CNC Machining
Authors: Chiou Chuang-Jang , Lee Yuan-Shin
Published: December 2021

In this paper, a new approach is presented to construct the G-buffer models by finding 3D shape-generating profiles of milling cutters. The G-buffer method is commonly used in 3-axis machining verification. In this paper, the analytic 3D shape-generating profiles are formulated to construct the swept envelope in 5-axis tool motion. The 5-axis machining G-buffer model is updated by the constructed swept envelope. The techniques presented in this paper can be used for 5-axis tool path generation and the machined surface error analysis.
The Effect of Workpiece Hardness and Cutting Speed on the Machinability of AISI H13 Hot Work Die Steel When Using PCBN Tooling
Authors: Ng Eu-Gene , Aspinwall David K.
Published: December 2021

When machining hardened steel (≥ 45 HRC) with polycrystalline cubic boron nitride (PCBN) tooling, the cutting speeds used produce high temperatures in the primary shear zone, which are sufficient to plasticise the workpiece. The paper initially reviews the effect of workpiece hardness and cutting speed on chip formation, workpiece surface integrity and cutting forces. Equations are detailed for determining the primary shear zone temperature, the proportion of heat conducted into the workpiece and the shear flow stress. Following on from this, experimental work is presented involving the orthogonal machining of AISI H13 hot work die steel with PCBN tooling. Tests were carried out over a range of cutting speeds with workpieces of different hardness, in order to provide cutting force, shear angle, chip morphology and primary shear zone thickness data.

The shear flow stress decreased with increasing cutting speed and/or workpiece hardness. With the AISI H13 heat treated to 49±1 HRC, the stress magnitude changed more significantly with cutting speed and the proportion of heat conducted away from the workpiece approached 99% at 200 m/min. Shear localised chips were produced with white unetched layers due to intense heat generation followed by rapid cooling.
A PC-Based Open Architecture Controller: Design, Implementation, and Operation
Authors: Marchetti Louis A. , Wright Paul K.
Published: December 2021

This paper reports the implementation of an open architecture controller on a 3-axis machining center. This new controller, called MOSAIC-PC, takes advantage of readily available, off the shelf components, and the flexibility and low cost of the personal computer. While commercial products have been used as the building blocks for MOSAIC-PC, the overall architecture is novel. Specifically, high level CAD curves and patches, such as NURBS, can be incorporated at the machine level and sensor based machining is integrated in real-time. A description of the hardware and software components is given and the ease of integrating third party components is described. Finally the functionality of MOSAIC-PC is demonstrated.
A Unified Model of a Proportional Valve
Authors: Eryilmaz Bora , Wilson Bruce H.
Published: December 2021

Developments in nonlinear control theory have made it possible to design controllers for systems having non-smooth nonlinearities in their dynamics. Hydraulic systems that use inexpensive proportional valves are examples of such systems, where non-smooth nonlinearities arise due to valve geometry and spool imperfections. Without a proper valve model, however, nonlinear analysis and control of these hydraulic systems is not possible. We have developed nonlinear equations for a generic proportional valve model and have used them to obtain simplified flow rate expressions under generally accepted assumptions. These equations related a set of geometric spool properties and physical model variables to the flow rate through the valve ports. The development focuses on obtaining a single set of flow rate equations for the cases of critical center, overlapped, and underlapped proportional valves. The proportional valve model equations are useful for system simulation and for nonlinear controller design.
Modeling and Control Design of a Powertrain Simulation Testbed for Earthmoving Vehicles
Authors: Prasetiawan Eko A. , Zhang Rong , Alleyne Andrew G. , Tsao Tsu-Chin
Published: December 2021

A nonlinear model of an Earthmoving Vehicle Powertrain Simulator is developed using both first principles as well as I/O data. The model is an interconnection of subsystem models, which consist of a prime mover, a variable-displacement pump, proportional flow valves, and fixed-displacement motor models. In addition, a typical drive or tractive load of an earthmoving vehicle is also presented and implemented in the system as one of the loads. Efforts have been directed to develop a simple model in order to cater to developing and testing powertrain controllers as well as studying the dynamic behavior of such systems. An initial control design approach utilizing the Linear Quadratic technique is also presented. The controller is aimed at regulating load speeds in presence of a step load disturbance. The simulation results of the compensated system response are presented.
A Study of the Impact of Knurling Parameters on Knurl Quality With the Design of Experiments Approach
Authors: Feng Chang-Xue (Jack) , Tran Chinh
Published: December 2021

A local company produces various types of connecting cables for a number of military and civilian customers. A key part of these cables is the knurled component to provide proper frictional force for easy assembly and maintenance. In the past, the company has usually faced a problem of inconsistent knurl quality. There has been no report in the literature about knurling process design. Vendors of knurling tools could only recommend the traditional try-and-error method. This research uses the design of experiments (or 2n-k fractional factorial design) approach to examine the impact of different knurling process parameters on the knurl quality. Our purpose is to determine the key factors and factor interactions that have significant effect on the knurl quality so that we could set the process parameters in such a way that the process is robust (or insensitive) to any uncontrollable factors. As a result, a robust knurl quality is achieved. A case study illustrates our approach.
Experiments and Modeling of a Mesoscale Laminar Plate Heat Exchanger
Authors: Hong Seung-Ho , Kenning Vanessa , Call Charles , Shekarriz Reza
Published: December 2021

In this paper, the results of an experimental and computational study on the development of a plate heat exchanger are presented and discussed. We have evaluated the characteristics of a miniature counterflow plate heat exchanger (PHE) using air as the working fluid. Because of the small characteristic channel dimension (Dh ≤ 1.9mm) and specific application of interest, the Reynolds number produced ranged between 20 < ReD < 1500, well within the laminar flow regime. The mass flow rates of the two hot and cold streams were maintained the same. Two different configurations were tested and modeled. The first configuration was the single-layer condition where one cold air stream was adjacent to another hot air stream in a counter-flow arrangement. The second configuration was the interleaved channel arrangement where the different layers alternate between cold and hot streams.

Experiments were performed on a series of heat exchangers made of aluminum and stainless steel. The channel dimensions were 1mm × 20mm × 75mm. Because the flow region consists of hydrodynamically developing and fully developed flow for the range of Reynolds numbers tested, the experimental results show higher pressure drop compared with the results of fully developed parallel-plate channel flow and this difference increases with increasing Reynolds number. The dependency of Nusselt number on Reynolds number in the periodic boundary condition was larger than the single-layer arrangement. Further, the periodic boundary condition generates higher effectiveness than the single-layer arrangement. It was found that when using aluminum plates instead of stainless steel, axial conduction results in nearly 35% reduction in the overall heat transfer coefficient between hot- and cold-side channels. Computational results, corroborated with experimental data, suggested the use of an interleaved channel geometry for obtaining an effectiveness of 90% or higher when operating within the low mass flow rate regime.
Microlamination for Microtechnology-Based Energy, Chemical, and Biological Systems
Authors: Paul Brian K. , Peterson Richard B.
Published: December 2021

Microlamination is a process for fabricating micro and meso scale systems having intricate arrays of components interconnected within a single block of metal, ceramic, or polymeric material. The process begins by surface machining, or through cutting, individual laminae with patterns containing the desired structure. The laminae are often shims of a base material having desirable mechanical and thermal properties important to the functioning of the final device. Once the patterns are cut, the shims are surface treated and stacked in a prearranged order. Bonding then takes place forming a single laminate. Some post processing of the final part can be performed to dissociate internal structures if needed. This paper describes work being accomplished at Oregon State University on the microlamination process. The paper emphasizes laser micromachining of metal and polymeric laminates. Laser techniques covered include pulsed Nd:YAG-based micromachining at the fundamental and higher harmonics. Also, examples of CO2 laser machining are presented. Process descriptions are provided and examples given of micro and mesoscale components needed for producing devices useful in the energy, chemical, and biological areas.
Available Energy: I. Gibbs Revisited; II. Gibbs Extended
Authors: Gaggioli Richard A. , Richardson David H. , Bowman Anthony J. , Paulus David M.
Published: December 2021

The concept of available energy, as defined by Gibbs (1873b) is revisited. He gave representations of available energy for two circumstances. The first was the available energy of a “body,” for the case when a body, alone, is in a nonequilibrium condition and therefore has energy available. In turn, he presented the available energy of “the body and medium,” for the energy which is available because a body is not in equilibrium with some arbitrarily specified medium. Gibbs’ representations were graphical. Since Gibbs, representations with formulas have been developed and are common, for the “available energy of body and medium.”

Gaggioli (1998a, b) has developed formulas which are more general, to represent “the available energy of the body (alone)” and to assign an exergy to subsystems of the body as a measure of each sub-system’s contribution to the available energy. In contrast to the available energy, exergy is an additive property, so that balance equations can be written. And the formulas are independent from any “medium,” which is important both theoretically and practically — because of its relevance to proper selection of “the dead state.” These issues are discussed and extended, after reviewing Gibbs development of available energy and additional concepts which he introduced, such as “available vacuum” and “capacity for entropy.”

It is argued that these “availabililty” and “capacity” concepts are all equivalent to one another. In turn, because of interconvertability, it is seen that available energy is something more fundamental than “maximum useful work.”

Furthermore, it is illustrated that available energy, equilibrium and stability, and thermostatic property relations are relative, to “constraints.”
Analysis of Thermal Efficiency in a Hydrogen Premixed Spark Ignition Engine
Authors: Shudo Toshio , Nakajima Yasuo , Futakuchi Takayuki
Published: December 2021

Hydrogen has higher flame velocity and smaller quenching distance than hydrocarbon fuels, and is supposed to have special characteristics in combustion process of internal combustion engines. In this research, contributors to thermal efficiency in a hydrogen premixed spark ignition engine were analyzed and compared with methane combustion. Results showed hydrogen combustion had higher cooling loss to combustion chamber wall, and thermal efficiency of hydrogen combustion was mainly dominated by both cooling loss to combustion chamber wall and degree of constant volume combustion.
On the Calculation of Efficiencies and Costs in Thermal Systems
Authors: Lazzaretto Andrea , Tsatsaronis George
Published: December 2021

This paper is an extension, generalization and simplification of a concept presented in two previous papers. A general method for defining and calculating exergetic efficiencies and exergy-related costs in thermal systems is presented.
Entropy Production as a Predictive Performance Measure: I — Turbomachinery
Authors: Paulus David M. , Gaggioli Richard A. , Dunbar William R.
Published: December 2021

It is proposed that consideration be given to an alternative, streamlined manner for mathematical modeling of the performance of energy conversion and transfer equipment. We make the case, here, by application to compressors. It is advocated that, instead of using an expression for efficiency as one of the governing equations, performance can be accounted for directly, with entropy production. It is shown that (1) the modeling is more straightforward, using fewer relations, and (2) that compressor performance (e.g. maps) can be represented equally well.
A Model of Crack Nucleation in Layered Electronic Assemblies Under Thermal Cycling
Authors: Chandra A. , Huang Y. , Jiang Z. Q. , Hu K. X.
Published: December 2021

A model for crack nucleation in layered electronic assemblies under thermal cycling is developed in this paper. The present model includes three scales: (i) at the microscale or the mechanism level, the damage mechanisms such as diffusive void growth or fatigue cracks, determine the damage growth rate; (2) at an intermediate mesoscale, the localized damage bands are modeled as variable stiffness springs connecting undamaged materials; and (iii) at the macroscale or the continuum level, the localized damage band growing in an otherwise undamaged material is modeled as an array of dislocations. The three scales are then combined together to incorporate damage mechanisms into continuum analysis. Traditional fracture mechanics provides a crack propagation model based on pre-existing cracks. The present work provides an approach for predicting crack nucleation. The proposed model is then utilized to investigate crack nucleations in three-layered electronic assemblies under thermal cycling. The damage is observed to accumulate rapidly in the weakest regions of the band. Estimates are obtained for critical time or critical number of cycles at which a macroscopic crack will nucleate in these assemblies under thermal cycling. This critical number of cycles is found to be insensitive to the size of the damage cluster, but decreases rapidly as the local excess damage increases.
Modeling of Thermal Expansion
Authors: Rooney Francis J. , Bechtel Stephen E.
Published: December 2021

In this paper we treat two types of thermomechanical constraints, temperature-deformation and entropy-deformation. It is shown that for the temperature-deformation constraint equilibrium states are unstable, in that certain perturbations of the equilibrium state grow exponentially. The entropy-deformation constraint, however, does not exhibit this instability. By considering the constrained materials as limits of unconstrained materials, it is shown that the instability is associated with the loss of convexity of the internal energy.
Short Apron Drop Tests in Support of Automotive Composites Consortium Focal Project I
Authors: Browne Alan L. , Johnson Nancy L.
Published: December 2021

This paper documents the short apron drop tests that were conducted in support of ACC Focal Project I. The objective of Focal Project I, which has been successfully completed, was to develop a composite front apron that demonstrated acceptable structural and energy management characteristics while using a manufacturable preform configuration. The purpose of the short apron drop tests described in this paper was to validate various composite apron fabric/reinforcement designs and crush initiation methods in terms of their ability to produce stable progressive crush at acceptable force levels in frontal axial impacts prior to full scale sled, cart, and barrier tests. Most of the design approaches evaluated in these short apron tests were selected on the basis of promising performance in crush tube tests, of both hourglass (apron lower rail) and square-to-rectangular (apron upper rail) cross-section crush tubes. The subject short apron drop tests allowed a full scale check of these concepts on the apron level prior to significantly more expensive and time consuming full scale sled and barrier testing. A total of 17 such drop tests were conducted during the several year duration of Focal Project I, testing in general being in more of an iterative mode where we kept trying to move closer to the desired goal. The fact that these tests proved to be an important contributor to the success of Focal Project I is based on two observations, first the fact that more than one test was necessary, meaning that the first design (and several subsequent iterations) didn’t result in the desired response and second that the final short apron test, which was an unqualified success, gave support for the final successful full scale barrier test.
Transition From a Frontal Impact to a Redirection Impact on a New Bullnose Guardrail System Design
Authors: Reid John D.
Published: December 2021

Bullnose guardrail systems are used to protect vehicles from hazards in the median of divided highways. The Midwest Roadside Safety Facility is currently designing and testing a new bullnose system that will meet relatively new Federal safety performance specifications. After developing a system that successfully handled frontal impacts, attention was then focused on the redirection impacts required of such systems. Similar to vehicle design for frontal and side impact, there are many differences in the modeling and simulation requirements between frontal and redirection impacts for bullnose systems. Several complicated modeling problems were solved that only became evident when contacts became unstable during the simulations. The problems were mainly related to modeling issues such as course mesh sizes, contact penalty factors, contact thicknesses, edge-to-edge penetrations not being addressed in the model, and unstable element formulations after significant hourglassing had been induced. The resulting model can now be used to help re-design the bullnose system to meet the redirection requirements of such systems.
An Investigation of Thermal Enhancement on Flip Chip Plastic BGA Packages Using CFD Tool
Authors: Lee Tien-Yu Tom
Published: December 2021

This paper demonstrates the advantage of applying Predictive Engineering in thermal assessment of a 279 I/Os, 6-layer, depopulated array flip chip PBGA package. Thermal simulation was conducted using a Computational Fluid Dynamics (CFD) tool to analyze the heat transfer and fluid flow in a free air environment. This study first described the modeling techniques on multilayer substrate, thermal vias, C5 ball, and PCB. For a flip chip package without any thermal enhancement, more than 90% of the total power was conducted from the front surface of the die through the solder ball interconnects to the substrate, then to the board. To enhance the thermal performance of the package, the heat transfer area from the backside of the die needs to increase dramatically. Several thermal enhancing techniques were examined. These methods included copper heat spreader with various thicknesses and with thermal pads, metallic lid, overmolded with and without heat spreader, and with heat sink. With an aluminum lid and a heat sink, it gave the best improvement; followed by a heat spreader with thermal pads. Both methods reduced thermal resistance by an average of 50%. Detailed analyses on heat flow projections are discussed.
Computation of Transient and Steady Turbulent Isothermal Flows With an Impinging Rectangular Jet
Authors: Tucker P. G. , Pan Z.
Published: December 2021

The computation of both transient and steady turbulent incompressible isothermal flows is studied. The flow is very complex, having streamline curvature, large vortex structures and stagnation resulting from an impinging rectangular jet. For transient computations, the standard k-ε model is adopted. For steady flows, the k-ε, high and low Reynolds number k-l and mixing length models are tried. Zonal approaches combining the above turbulence models are also investigated. None of the models are found to give satisfactory agreement with velocity measurements.
Predictive Techniques for Turbulent Oscillatory Flows
Authors: Tucker P. G.
Published: December 2021

The prediction of turbulent oscillatory flow at around transitional Reynolds numbers is considered for an idealized electronics system. To assess the accuracy of turbulence models, comparison is made with measurements. A stochastic procedure is used to recover instantaneous velocity time traces from predictions. This procedure enables more direct comparison with turbulence intensity measurements which have not been filtered to remove the oscillatory flow component. Normal wall distances, required in some turbulence models, are evaluated using a modified Poisson equation based technique. A range of zero, one and two equation turbulence models are tested, including zonal and a non-linear eddy viscosity models. The non-linear and zonal models showed potential for accuracy improvements.
Effect of Humidity on PEM Fuel Cell Performance: Part I — Experiments
Authors: Lee W. K. , Van Zee J. W. , Shimpalee S. , Dutta S.
Published: December 2021

It is well known that proper water management inside a polymer electrolyte membrane (PEM) fuel cell is essential for obtaining high performance. Insufficient water lowers the conductivity of the membrane and yields low currents at a fixed voltage whereas excess water leads to flooding of the electrode and low currents at a fixed voltage due to a decreased reaction area. Typically the internal hydration is adjusted by the inlet humidity of the feed streams however the optimum depends on the given membrane and electrode assembly. As a first step in predicting this optimum a priori, data are presented for a 10-cm2 test cell with serpentine flow channels. Currents were measured for various unsaturated inlet humidity conditions, at different cell voltages, and for various operating cell temperatures. Data on the closure of water balances are presented and used to quantify the humidity effects on the current. These experimental data provide a basis for the numerical simulations presented in part II of this paper.
Slug Flow Model for Infiltration Into Fractured Porous Media
Authors: Martinez M. J.
Published: December 2021

A model for transient infiltration into a periodically fractured porous layer is presented. The fracture is treated as a permeable-walled slot and the moisture distribution is in the form of a slug behind an advancing meniscus. The wicking of moisture from the fracture to the unsaturated porous matrix is a nonlinear diffusion process and is approximated by self-similar solutions. The resulting model is a nonlinear Volterra integral equation with a weakly singular kernel. Numerical analysis provides solutions over a wide range of the parameter space and reveals the asymptotic forms of the penetration of this slug in terms of dimensionless variables arising in the model. The numerical solutions corroborate asymptotic results given earlier by Nitao and Buscheck (1991), and by Martinez (1988). Some implications for the transport of liquid in fractured rock are discussed.
Local Furnace Data and Modeling Comparison for a 600MWe Coal-Fired Utility Boiler
Authors: Hwang Yuh-Long , Howell John R.
Published: December 2021

Reductions in Furnace Exit Gas Temperature (FEGT) by changing boiler operating variables and/or adding wall soot blowers and/or lowering burner elevations are investigated. Evaluation of these approaches requires experimental furnace testing and computational furnace modeling. The experimental facility is a Combustion Engineering corner-fired pulverized-coal boiler with a capacity of 606 MWe. Local gas temperature distributions, local radiative and total wall heat flux distributions, and stack NOx were measured during constant-load furnace tests under various combinations of burner configuration, burner tilt angles, excess-O2 setpoints and overfire airflow rate. These measurements are used for tuning and calibrating a furnace model based on the PCGC-3 code developed by Brigham Young University. The experimental data gathered in this work comprises a comprehensive set under controlled conditions on a very-large-scale coal-fired plant, and provides information for use in comparing the predictions of furnace-design codes.
The Influence of Oxygen Injection Configuration in the Performance of an Aluminum Melting Furnace
Authors: Nieckele Angela O. , Naccache Mônica F. , Gomes Marcos S. P. , Kobayashi William T.
Published: December 2021

In the present work, a numerical simulation of the 100% oxy-firing combustion process inside an industrial Aluminum Remelting Reverb Furnace is presented. A staged combustion oxy-fuel burner is being simulated. The natural gas and oxygen were injected toward the aluminum bath, which was considered as an isotherm wall at melt temperature. Two types of burners are compared. For the first case, the oxygen and natural gas jets at the burner exit are parallel to each other, while for the second burner, a divergent oxygen jet is employed. The furnace heat loss to the ambient is neglected since it is small in relation to the heat liberated by the combustion process.

The k-ε model of turbulence was selected to represent the turbulent flow field. The combustion process was determined based on the Arrhenius and Magnussen Laws, and the discrete transfer radiation model was employed to predict the radiation heat transfer. The numerical procedure was based on the Finite Volume Method.

This numerical model is utilized to determine the flame pattern, species concentration distribution, and the velocity field. The temperature distribution is very useful in the evaluation of the furnace performance. Further, critical regions associated with high temperature spots at the refractory surface were discovered. The effect of the divergent jet in the heat flux distribution at the aluminum bath is also investigated.
Effect of Thin Films on Radiative Transport in Chemical Vapor Deposition Systems
Authors: Mazumder Sandip , Kersch Alfred
Published: December 2021

The thermal behavior of a wafer during a Rapid Thermal Chemical Vapor Deposition (RTCVD) process depends on its spectral radiative properties, along with other factors. One of the major contributing factors is the thin film that is deposited on the wafer substrate. The presence of a thin film (of thickness anywhere above 0.1 nm) can drastically alter the radiative properties of the wafer surface, thereby leading to significantly different wafer temperatures. This article presents a model to simulate thin film effects in RTCVD processes. Radiative transfer is modeled using a Monte-Carlo ray-tracing technique. Radiative properties are calculated using fundamental Electromagnetic Wave Theory. Simulation results match remarkably well with experimental data, demonstrating the importance of thin film effects.
Nanosecond Laser Experiments of Microstructure Adhesion Reduction
Authors: Rogers James W. , Phinney Leslie M.
Published: December 2021

Due to the small size of structures in modern microdevices, surface forces can create undesirable adhesion between microstructures, which is referred to as stiction. Prior investigations have used ultrashort-pulse lasers to recover stiction-failed microcantilevers. The current experiments study the use of a 400 ns, 1064 nm, Nd:YAG laser to free polycrystalline silicon microcantilevers stuck to the underlying substrate. The results show that a Nd:YAG, 1064 nm laser is capable of recovering failed microstructures with yields exceeding those reported in earlier studies. Yields of 100 percent for cantilevers up to 1 mm in length were demonstrated for several laser operating conditions. The yields are strongly dependent on laser fluence and slightly dependent on exposure time, with a single-shot at 160 mJ/cm2 resulting in yields around 60 percent.