bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Models for Prediction of Springback in Flanging
Authors: Song Nan , Qian Dong , Cao Jian , Liu Wing Kam , Viswanathan Vikram , Li Shaofan
Published: November 2021

A study on the prediction of springback angle is presented, with focus on the straight flanging operation. The objective is to evaluate the reliability of different ways of prediction. An experiment of straight flanging operation is conducted. Major prediction approaches such as analytical model, numerical simulation using Finite Element Method (FEM) and Meshfree Method are discussed. A set of sample problems is computed and comparisons are made with the experiment. The numerical analysis shows that the prediction from the 3D meshfree contact code matches well with the data from FEM 2d solid model. A material property described by the kinematic hardening law gives a better prediction of springback than the isotropic hardening law.
Two Dimensional Plane Strain Modeling of Tube Hydroforming
Authors: Kridli G. T. , Bao L. , Mallick P. K.
Published: November 2021

The tube hydroforming process has been used in industry for several years to produce components such as exhaust manifolds. Recent advances in forming machines and machine control systems have allowed for the introduction and the implementation of the process to produce several automotive components, which were originally produced by the stamping process. Components such as side rails, engine cradles, space frames, and several others can be economically produced by tube hydroforming. The process involves forming a straight or a pre-bent tube into a die cavity using internal hydraulic pressure, which may be coupled with controlled axial feeding of the tube. One of the remaining challenges facing product and process engineers in designing hydroformed parts is the lack of an extensive knowledge base of the process. This includes a full understanding of the process mechanics and the effects of the material properties on the quality of the hydroformed product.

This paper reports on the results of two dimensional plane strain finite element models of the tube hydroforming process, which were conducted using the commercial finite element code ABAQUS/Standard. The objective of the study is to examine the effects of material properties, die geometry, and frictional characteristics on the selection of the hydroforming process parameters. The paper discusses the effects of the strain-hardening exponent, friction coefficient at the die-workpiece interface, initial tube wall thickness, and die corner radii on the thickness distribution of the hydroformed tube.
Corner Fill Modeling of Tube Hydroforming
Authors: Chen J. Y. , Xia Z. C. , Tang S. C.
Published: November 2021

Hydroforming process provides important advantages for automotive structural components over conventional stamp-and-weld parts, but it also brings unique challenges in process design. This paper attempts to obtain fundamental understanding of the process through corner fill modeling. A round tube is pressurized to expand into a square box with tight radius in the numerical experiment. Several parameters are identified and investigated during the process, namely, the internal pressure, end feed, and the lubricant. Their effects on the deformation profiles are presented, and their importance in process design is discussed. The established design guidelines from the study can be a valuable tool for hydroforming process engineers and part designers.
Generation of Cyclic Stress-Strain Curves for Sheet Metals
Authors: Zhao K. M. , Lee J. K.
Published: November 2021

The main objective of this paper is to generate cyclic stress-strain curves for sheet metals so that the springback can be simulated accurately. Material parameters are identified by an inverse method within a selected constitutive model that represents the hardening behavior of materials subjected to a cyclic loading.

Three-point bending tests are conducted on sheet steels (mild steel and high strength steel). Punch stroke, punch load, bending strain and bending angle are measured directly during the tests. Bending moments are then computed from these measured data. Bending moments are also calculated based on a constitutive model. Normal anisotropy and nonlinear isotropic/kinematic hardening are considered. Material parameters are identified by minimizing the normalized error between two bending moments. Micro genetic algorithm is used in the optimization procedure. Stress-strain curves are generated with the material parameters found in this way, which can be used with other plastic models.
Spatial Free Plastic Forming of Slender Parts: Machine Design, Forming Limits, and Application
Authors: Thalmair M. , Lippmann H. , Reigl M.
Published: November 2021

Free plastic forming of a slender part means that an initially straight bar, clamped at its both ends, is bent and twisted by an appropriate motion of the end supports only. Emphasis is attached on the computer controlled, precise forming of work-pieces with prescribed shape. In this paper the design of an appropriate forming machine at the laboratory scale will be presented. Moreover the forming limits, due to re-plastification of already completed sections of the part, will be illustrated geometrically using one or two “cylinders of admissibility”. Finally the method will be demonstrated by means of actually formed parts.
Stress-Based Forming Limits in Sheet Metal Forming
Authors: Stoughton Thomas B.
Published: November 2021

A strain-based forming limit criterion is widely used throughout the sheet metal forming industry to gauge the stability of the deformed material with respect to the development of a localized neck prior to fracture. This criterion is strictly valid only when the strain path is linear throughout the deformation process. There is significant data that shows a strong and complex dependence of the limit criterion on the strain path. Unfortunately, the strain path is never linear in secondary forming and hydro-forming processes. Furthermore, the path is often found to be non-linear in localized critical areas in the first draw die. Therefore, the conventional practice of using a path-independent strain-based forming limit criterion often leads to erroneous assessments of forming severity. Recently it has been reported that a stress-based forming limit criterion appears to exhibit no strain-path dependencies. Subsequently, it has been suggested that this effect is not real, but is due to the saturation of the stress-strain relation. This paper will review and compare the strain-based and stress-based forming limit criteria, looking at a number of factors that are involved in the definition of the stress-based forming limit, including the role of the stress-strain relation.
Wrinkling Limit in Tube Bending
Authors: Wang Xi , Cao Jian
Published: November 2021

Thin-walled tube bending has found many of its applications in the automobile and aerospace industries. This paper presents an energy approach to provide the minimum bending radius, which does not yield wrinkling in the bending process, as a function of tube and tooling geometry and material properties. A doubly-curved sheet model is established following the deformation theory. This approach provides a predictive tool in designing/optimizing the tooling parameters in the tube bending.
FEM-Assisted Fuzzy Adaptive Blank Holder Control Approach for Sheet Stamping Process
Authors: Koyama Hiroshi , Manabe Ken-ichi , Yoshihara Shoichiro
Published: November 2021

To apply the database-oriented process control design concept to intelligent stamping processes of various shape products, the extension of the concept was required. The application of FEM simulation for production of the “ideal curve”, which plays an important role in the system, was proposed. The fuzzy adaptive controlled variable blank holder force (BHF) circular-cup deep-drawing system with the new ideal curve was developed. Through the implementation of the system for cup height improvement, the availability of the concept is confirmed. As a result, the potential application of the concept to the stamping processes of various shapes is suggested. In addition, using the experimental results, the influence of the BHF history on the thickness reduction behavior is investigated. An algorithm for cup wall thickness uniformity based on the BHF historical effects is proposed and the feasibility of the algorithm is verified.
Model of Biomass Concentration in Membrane Filtration Recycling Systems Subject to Single Substrate-Limited Growth Kinetics
Authors: Skerlos Steven J. , Rajagopalan N. , DeVor Richard E. , Kapoor Shiv G. , Sanford Robert A.
Published: November 2021

Membrane filtration has the ability to limit microbiological growth in metalworking fluids (MWFs). To appropriately design and size a membrane filtration system for this application, the rate of microbial removal must be assessed relative to microbial population (biomass) growth. This research utilizes the Monod Equation describing biomass growth limited by a single substrate to evaluate if biomass levels can be maintained below a prescribed level in a perfectly mixed MWF system. The model for predicting biomass in the MWF system is obtained by numerical solution of a system of coupled nonlinear differential equations. The model solution permits membrane filtration design and sizing decisions based on microbial growth data specific to MWF chemistries, microbial species, and manufacturing facilities. It is revealed that the ratio of the filtration rate to the MWF volume must exceed the maximum specific growth rate of microorganisms to control biomass concentrations in the system under arbitrary initial substrate and contamination levels. The control of microbial growth in the system also requires that appropriate cleaning intervals be selected for the membrane filtration process tank. The microbial rejection coefficient, which is characteristic to a given membrane, has a dominant impact on the required cleaning interval.
Cutting Fluid Mist Formation in Turning via Atomization: Part 2—Experimental Validation
Authors: Yue Y. , Gunter K. L. , Michalek D. J. , Sutherland J. W.
Published: November 2021

In Part 1 of this paper, models were developed to describe the formation mechanisms and dynamic behavior of cutting fluid mist. This part of the paper focuses on experimentally investigating mist formation during the turning process, and then simulating the dynamic behavior of the mist droplets, including the distribution and the mass concentration. Simulation results are compared to experimental measurements to validate the theoretical models presented in Part 1. It is seen that the model predictions adequately characterize the observed experimental behavior.
Prediction of Tool and Chip Temperature in Continuous Metal Cutting and Milling
Authors: Lazoglu Ismail , Altintas Yusuf
Published: November 2021

A finite difference method is presented to predict tool and chip temperature fields in continuous machining and time varying milling processes. Continuous machining operations like orthogonal cutting are studied by modeling the heat transfer between the tool and chip at the contact zone. The shear energy created in the primary zone, the friction energy produced at the rake face - chip contact zone and the heat balance between the moving chip and stationary tool are considered. The temperature distribution is solved using finite difference method. Later, the model is extended to milling where the cutting is interrupted and the chip thickness varies with time. The time varying chip is digitized into small elements with differential cutter rotation angles. The temperature field in each differential element is modeled as a first order dynamic system, whose time constant is identified based on the thermal properties of the tool and work material, and the initial temperature at the previous chip segment. The transient temperature variation is evaluated by recursively solving the first order heat transfer problem at successive chip elements. The proposed model combines the steady-state temperature prediction in continuous machining with transient temperature evaluation in interrupted cutting operations where the chip and the process change in a discontinuous manner. The mathematical models and simulation results are in satisfactory agreement with experimental temperature measurements reported in the literature.
Numerical Analysis of Cutting With Chamfered and Worn Edge Tools
Authors: Movahhedy Mohammad-R. , Altintas Yusuf , Gadala Mohamed S.
Published: November 2021

In high-speed machining of hard materials, tools with chamfered edges and tool materials resistant to diffusion wear are commonly used. In this paper, the influence of cutting edge geometry on the chip removal process is studied through numerical simulation of cutting with sharp, chamfered or blunt edges and with carbide or CBN tools. The analysis is based on the use of arbitrary Lagrangian-Eulerian (ALE) finite element method, which makes it possible to analyze the cutting action without having to resort to node separation methods or remeshing. Simulations include cutting with tools of different chamfer angles at a range of cutting speeds and the numerical results are compared with experimental data obtained under similar cutting conditions. The study shows that a region of dead material zone is formed under the chamfer and acts as the effective cutting edge of the tool (in accordance with experimental observations). As a result, the chip formation process is not significantly affected by the presence of the chamfer. However, the forces, the thrust force in particular, are considerably increased. The effect of cutting speed on the process is also studied and is shown to produce a significant increase in maximum temperature on the rake face.
Stability Analysis of Interrupted Cutting With Finite Time in the Cut
Authors: Bayly Philip V. , Halley Jeremiah E. , Davies Matthew A. , Pratt Jon R.
Published: November 2021

The stability of interrupted cutting is examined for the case in which the tool is in contact with the work piece for a small, but finite, fraction of the tooth-passing period. A model of a single degree-of-freedom tool excited by intermittent, regenerative cutting forces is analyzed. The equations are transformed into a discrete model by use of the exact analytical solution when the tool is free of the work piece, and by an approximate analytical solution (the method of weighted residuals) when the tool is in the cut. Stable combinations of spindle speed and axial depth of cut are found. These results confirm and refine predictions of additional stability regions made by Davies et al. (1999a, 2000) based on the approximation of infinitesimal time in the cut.
Single-Molecule Biomechanics: DNA and Protein Deformation
Authors: Bao Gang
Published: November 2021

With the advent of molecular biology and biophysics during the past decade, single-molecule biomechanics has emerged as a new field. Different techniques have been used to study the mechanical properties of DNA and protein molecules; various models have been developed to quantify the deformation of biomolecules under force. Here we review some of these advances, explore the connection between mechanics and biochemistry, and discuss the concepts, issues and challenges in developing molecular biomechanics.
A Growth Mixture Theory for Cartilage
Authors: Klisch Stephen M. , Sah Robert L. , Hoger Anne
Published: November 2021

In this paper we present a model of growth for cartilaginous tissues in which there exists a saturated solid matrix composed of multiple constituents that may grow and remodel independently of each other. Klisch and Hoger recently developed a general theory of volumetric growth for a mixture of ν−1 growing elastic materials and an inviscid fluid, which included a treatment of two special types of internal constraints that are relevant to cartilage. Here, that theory is specialized to construct a cartilage growth model. This theory allows the constituents of the solid matrix to grow independently of each other, and can model the evolution of the constituent pre-stresses and the tissue’s mechanical properties during developmental growth and degeneration. A simple example is presented which illustrates these features of the theory.
Real-Time Detection and Explicit Finite Element Simulation of Delamination in Composite Laminates Under Impact Loading
Authors: Minnaar K. , Zhou M.
Published: November 2021

A new experimental technique is developed to determine the onset and evolution of delamination in fiber-reinforced composites under impact loading. The configuration uses a split-Hopkinson bar for low-velocity impact loading and two Polytec laser vibrometer systems for real-time monitoring of the initiation and progression of delamination. The experiment allows the histories of load, displacement, and velocity of impacted specimens to be recorded and analyzed. The recorded profiles are used to characterize the damage initiation and evolution in the laminate. Numerical simulations are conducted using a cohesive finite element method. The method employs a cohesive zone model to simulate matrix cracking and interlaminar delamination and a transversely isotropic, elastic model to characterize the bulk behavior of each ply. The simulations provide time-resolved characterization of damage during the impact loading. The damage modes predicted by the numerical simulations agree well with experimental observations.
Dynamic Characterization of Multi-Functional Sandwich Composites
Authors: Vaidya Uday K. , Nelson Scott P. , Mathew Biju , Rodgers Renee M. , Hosur Mahesh V.
Published: November 2021

This paper deals with an innovative integrated hollow (space) E-glass/epoxy core sandwich composite construction that possesses several multi-functional benefits in addition to the providing light-weight and bending stiffness advantages. In comparison to traditional foam and honeycomb cores, the integrated space core provides a means to route wires/rods, embed electronic assemblies, and store fuel and fire-retardant foam, among other conceivable benefits. In the current work the low velocity impact (LVI) response of innovative integrated sandwich core composites was investigated. Three thickness of integrated and functionality-embedded E-glass/epoxy sandwich cores were considered in this study — including 6mm, 9mm and 17 mm. The low-velocity impact results indicated that the hollow and functionality embedded integrated core suffered a localized damage state limited to a system of core members in the vicinity of the impact. Stacking of the core was an effective way of improving functionality and limiting the LVI damage in the sandwich plate. The functionality-embedded cores provided enhanced LVI resistance due to energy additional energy absorption mechanisms. The high strain rate (HSR) impact behavior of these sandwich constructions is also studied using a Split Hopkinson Pressure Bar (SHPB) at strain rates ranging from 163 to 653 per second. The damage initiation, progression and failure mechanisms under low velocity and high strain rate impact are investigated through optical and scanning electron microscopy.
Feed Forward Plus Feedback Control of an Indexing Valve Plate Pump
Authors: Zhang X. , Nair S. S. , Manring N. D.
Published: November 2021

A feed forward plus feedback pressure control strategy is proposed for an indexing variable displacement pump design. Insights into the dynamics are developed to determine performance characteristics and limitations, prior to control development, and a methodology is proposed to estimate some of the parameters on-line. Theoretical as well as implementation insights for the control problem are also developed.
Two-Way Solenoid Valves in Low-Pressure Water Hydraulics
Authors: Linjama Matti O. , Tammisto Jyrki O. , Koskinen Kari T. , Vilenius Matti J.
Published: November 2021

The paper tests experimentally the suitability of inexpensive directly operated two-way solenoid valves for water hydraulic applications in the pressure range from 10 to 40 bars. Seven valves are tested and tested matters include the steady-state and dynamic characteristics as well as durability. Results show small delays and the durability of about ten million openings. The weak point of the valves is a small flow capacity but otherwise the valves are well suited for low-pressure water hydraulic applications. This is demonstrated by using them in a simple on/off position control of a water hydraulic cylinder.
An Open Framework for Enabling Lifelong Learning of Fluid Power Systems Design via the Internet
Authors: Richards Thomas G. , Hughes Edmund J. , Tilley Derek G.
Published: November 2021

Fluid Power systems design is a skilful and complex task requiring significant practical experience and heuristic knowledge gained over many years. With few formal Fluid Power design courses being taught in further and higher education, both academia and industry are seeking new methods of delivering this specialist knowledge. The Internet opens up low-cost, low-risk training opportunities for companies, particularly Small-to-Medium Enterprises, which may not be able to afford to send their staff on residential courses, and also for employees seeking career development within the context of lifelong learning. This paper describes the early stages of a project to develop an open, domain-independent, Java-based framework for the delivery of multimedia training. This framework forms part of an overall Performance Support System for trainees and professionals involved in Fluid Power systems design. Also described is a formative evaluation of the framework.
Coupled Deformations of Elastic Curves and Surfaces
Authors: Steigmann David
Published: November 2021

Theories of perfectly flexible elastic curves and surfaces are frequently used to describe diverse phenomena ranging from bioelasticity and fluid capillarity to rubber elasticity and the mechanics of structural networks. It is our aim here to present a treatment of the coupled response of such continua accounting for three-dimensional interactions in the presence of finite deformations and strains. A more expansive discussion of the subject of the present paper may be found in [1].
Existence and Uniqueness Results for Nonlinear Differential Equation Arising in Non-Newtonian Fluid Flow
Authors: Vajravelu K. , Cannon J. R. , Rollins D.
Published: November 2021

Solution for a nonlinear second order differential equation, arising in a viscoelastic fluid flow at a rotating cylinder, is obtained. Furthermore, using the Shauder theory and the perturbation technique existence, uniqueness and analyticity results are established. Moreover, the exact analytical solutions (in integral form) are compared with the corresponding numerical ones.
Failure of Impact Damaged Foam Core Sandwich Beams
Authors: Hallström Stefan , Shipsha Andrey , Zenkert Dan
Published: November 2021

The scope of this paper is to investigate the structural integrity of sandwich beams subjected to various load cases after local impact. The studied impact damages can be characterised as core indentation and face/core interface damage while the faces are virtually unaffected by the impact. At subsequent loading different types of post impact failure occur, depending on the size of the impact damages and the applied load.

Sandwich beams are impacted using two different impact energies and the resulting damage is inspected and measured. The measurements are used to characterise the damage and as input for analytical and finite element models in order to predict post impact failure in various load cases. The impact damages are modelled as face/core interface cracks but the approach is found to be too rough to achieve full agreement with experiments. It is concluded that the damaged face/core interface is not entirely separated but some bridging remains between the surfaces.
Static and Dynamic Buckling of Sandwich Columns
Authors: Simitses G. J. , Shen L.
Published: November 2021

The paper deals with the theoretical prediction of buckling loads for sandwich columns with metallic and laminated facings and foam core. The loading is a uniform axial compression, applied statically (very slowly) and suddenly with constant magnitude and infinite duration (step loading). The effect of length and boundary conditions is assessed and results are presented for the following cases for a cantilever column, a simply supported column and a clamped column for lengths of 80 inches and 240 inches. Several fiber materials are used in the laminated facings. The static critical loads are computed from three different sources and the dynamic critical loads are obtained by employing the computer code DYNA3D. For the dynamic case, the Budiansky-Roth criterion is applied.
A Lagrangian Particle Dynamics Model With an Implicit Four-Way Coupling Scheme
Authors: Smirnov Andrei , Celik Ismail
Published: November 2021

An implicit particle interaction mechanism is proposed, which can be applied to the problems of colliding particle jets and particle tracking in turbulent and unsteady flows. The mechanism is based on the idea of virtual particle-grid interactions and provides a linear dependence of the execution time on the number of particles. The scheme was used in conjunction with the random flow-generation procedure to simulate several cases of particle motion with different interaction mechanisms.
Proposed Use of the One-Dimensional Two-Fluid Model With Momentum Flux Parameters
Authors: Song Jin Ho , Kim H. D.
Published: November 2021

The dynamic character of a system of the governing differential equations for the one-dimensional two-fluid model, where the appropriate momentum flux parameters are employed to consider the velocity and void fraction distribution in a flow channel, is analyzed. In response to a perturbation in the form of a traveling wave, a linear stability analysis is performed for the governing differential equations. The analytical expression for the growth factor as a function of wave number, void fraction, drag coefficient, and relative velocity is derived. It provides the necessary and sufficient conditions for the stability of the one-dimensional two-fluid model in terms of momentum flux parameters. It is analytically shown that the one-dimensional two-fluid model is mathematically well posed by use of appropriate momentum flux parameters, while the conventional two-fluid model makes the system unconditionally unstable. It is suggested that the velocity and void distributions should be properly accounted for in the one-dimensional two-fluid model by use of momentum flux parameters.
Characterization of Cryogenic Spray Nozzles With Application to Skin Cooling
Authors: Aguilar Guillermo , Majaron Boris , Verkruysse Wim , Nelson J. Stuart , Lavernia Enrique J.
Published: November 2021

Cryogenic sprays are used for cooling of human skin during laser treatments of hypervascular lesions, such as Port Wine Stain birthmarks. In this work, six straight-tube nozzles, including two commercial nozzles, are characterized by obtaining photographs of cryogenic spray shapes, as well as measurements of the average droplet diameter, velocity and temperature. An evaporation model is used to predict the evolutions of average droplet diameter and temperature. The results show two distinct spray patterns—jet-like sprays for wide nozzle diameters, and cone-like sprays for narrow nozzle diameters. The wide nozzles show significantly larger droplet diameters, larger velocities and higher temperatures, as all these variables are measured as a function of distance from the nozzle. These results complement and support previously reported results, where it was shown that wide nozzles are capable of producing larger heat transfer coefficients than those obtained with narrow nozzles.
Investigation of an Open Refrigeration Cabinet Using Computational Simulations With Supporting Experiments
Authors: George B. N. , Buttsworth D. R.
Published: November 2021

Computational Fluid Dynamics simulations of a self-contained open refrigeration display cabinet have been performed. Experimental measurements of the cabinet operation including the refrigeration parameters and air flow conditions have been obtained. It is found that neither laminar nor turbulent simulations provide entirely satisfactory descriptions of the cabinet operation. The laminar simulation under estimates the sensible heat load on the cabinet by about 75%, and in the turbulent simulation, the sensible heat load is over estimated by approximately 50%. Similarly, the actual temperature profile within the air curtain is not accurately simulated by either the laminar or turbulent calculation, but roughly falls in between the laminar and turbulent estimates. It appears the simulation of open refrigeration display cabinets would benefit from improvements in the modelling of the low Reynolds number turbulent conditions.
Numerical Predictions and Experimental Measurements of the Near-Field of a Large Turbulent Helium Plume
Authors: DesJardin Paul E. , Tieszen Sheldon R. , O’Hern Timothy J. , Gerhart Andrew L.
Published: November 2021

Measurements of a large, 1 m in diameter, turbulent buoyant helium plume are taken and compared to results from numerical simulation. The experiments are carried out in Sandia’s FLAME (Fire Laboratory for Accreditation of Model by Experimentation) facility and consist of a low velocity (0.351 m/s) helium plume emitting upwards into ambient air with low velocity co-flow air supplied radially to minimize the effects of the test chamber walls. The measurement approach consists of measurements of time-resolved instantaneous velocity using Particle Image Velocimetry (PIV). The numerical simulations are based on the use of the Large Eddy Simulation (LES).

Results from this study show excellent agreement between the LES and experimental data for puffing frequency and mean and RMS streamwise velocity for downstream locations of X/Dp > 0.5. For locations very near the base of the plume (i.e. X/Dp < 0.5) the LES over-predicts the streamwise mean and RMS velocity and under-predicts the mean and RMS cross-stream velocities. In addition, the prediction of velocities near the base of the plume exhibit a strong sensitivity to grid resolution. This sensitivity suggests the need for modification of the current dynamic Smagorinsky and gradient diffusion turbulence models to account for the effects of subgrid scale buoyancy.
Single-Wave Peristalsis
Authors: Tadjfar M. , Yamaguchi T. , Himeno R.
Published: November 2021

Single-wave peristalsis propagating on the wall of a cylindrical tube is simulated. The unsteady, three-dimensional, incompressible Navier-Stokes equations are solved numerically. The flow is computed with moving boundaries and moving grid. A second-order in time and third-order upwind finite volume method for solving time-accurate incompressible flows utilizing pseudo-compressibility technique is used. In this study, the flow of an axisymmetric “tear-drop” shaped, single, peristaltic wave is analyzed. The effect of transient state on the flow is limited. The three-dimensional effects are also limited to the transient state. The lubrication theory application to the single wave flow may not be appropriate due to its inability to adjust the pressure nonlinearly.
Parallel Solver for Blood Flow in Human Vascular System
Authors: Tadjfar M. , Yamaguchi T. , Himeno R.
Published: November 2021

In order to simulate blood flow in human vascular system, the unsteady, three-dimensional, incompressible Navier-Stokes equations are solved numerically. The solver is capable of dealing with moving boundaries and moving grids. A second-order in time and third-order upwind finite volume method for solving time-accurate incompressible flows utilizing pseudo-compressibility technique is used. For parallel execution, the flow domain is partitioned. Communication between the subdomains of the flow on Riken’s VPP/700E supercomputer is implemented using MPI message-passing library. The code is capable of running on both shared and/or distributed memory architectures.
Analytical Full-Recursive Sensitivity Analysis for Multibody Dynamic Systems
Authors: Anderson Kurt S. , Hsu Yuhung
Published: November 2021

Computing of first-order sensitivity information is crucial for many gradient-base optimization strategies where the algorithms employed plays a key role on determining the computational efficiency of an optimization process. This paper presents an algorithm which is able to determine the state derivatives in a fully recursive manner so to significantly reduce the cost of determining analytic first-order sensitivity information for large scale tree-type dynamic systems. Qualitative and quantitative validation on the operational requirement of the present method are made through analytical means and empirical studies.
Heat Treatment Process and Parameter Design in Manufacturing
Authors: Grandhi Ramana V. , Li Zhichao
Published: November 2021

The heat treatment operation which is carried out post manufacturing is optimized. Simulation of the carburizing and quenching processes with parameter optimization are combined to attain the desired surface hardness with controlled distortion of final products. Parameters of interest for optimization include, the carbon content of gas, carburizing dwell time, material temperature before quenching, quenchant temperature and the heat transfer coefficient. The response surface method is used to obtain closed-form models of the objective (surface hardness) and the two constraints (hardness variance and physical distortion) in terms of the design variables. A finite element simulation tool is used to predict the material response (volume fraction of different phases, temperature and stress/strain) during the carburizing and quenching processes. This paper summarizes the methodology that is used to optimize the carburizing and quenching processes of an axisymmetric disk.
Real Asymmetric Matrix Eigenvalue Analysis for Dynamic Instability Problems
Authors: Lee Heewook , Kikuchi Noboru
Published: November 2021

Complex eigenvalue analysis is widely used when the dynamic instability of the structure is in doubt due to friction forces, aerodynamic forces, control systems, or other effects. MSC/NASTRAN upper Hessenberg method and MATLAB eigenvalue solver produce fictitious nonzero real parts for real asymmetric matrix eigenvalue problems. For dynamic instability problems, since nonzero real parts of complex eigenvalues determine the unstable eigenvalues, the accuracy of real parts becomes crucial. The appropriate double shift QR or the QZ algorithms are applied to eliminate fictitious nonzero real parts and produce only authentic complex eigenvalues for real asymmetric matrix eigenvalue problems. Numerical examples are solved using the double shift QR and the QZ algorithms, and the results are compared with the results of MSC/NASTRAN upper Hessenberg method and MATLAB solvers.
Simulation of Respiratory System for Identifying Airway Occlusion
Authors: Al-Jumaily A. M. , Mithraratne P.
Published: November 2021

A theoretical model is developed to study the dynamic response of the respiratory system using Weibel symmetric model based on the acoustic wave approach. Both rigid and compliant walls with rigid and compliant termination are investigated separately. For each case the response (normalised input impedance against prorogation frequency) is examined for occlusion at each generation from alveolar sacs up to the distal end of the trachea systematically.
Path Design of Large Flexible Material Handing
Authors: Lin Kuo-Chi , Wu Annie S. , Qu Zhihua , Joshi Tanmoy
Published: November 2021

When moving a partially constrained large and flexible material, vibration is always a concern, especially if the material is brittle. This paper suggests an approach that uses a genetic algorithm (GA) to search for the optimal path for moving a flexible structure within a given time constraint. A simple cantilever beam with a moving foundation is used as the implementation example. The results show that a GA can provide a set of “good” solutions within a small number of generations of evolution. This approach can be very efficient if the mathematical optimum is not absolutely necessary.
Thermal and Thermomechanical Phenomena During Ultrafast Laser Interaction With Tissue
Authors: Wang Xinwei , Xu Xianfan , Xu Lisa X.
Published: November 2021

Ultrafast (or ultrashort) pulsed laser ablation of biological tissue has drawn much attention due to the minimal collateral damage caused by laser irradiation. Many clinical applications of ultrafast laser ablation have been proposed, including ophthalmology, dentistry, and neurosurgery (Kim et al., 1998). During ultrafast laser interaction with biological tissues, which are dielectric materials, multiphonon absorption occurs which enhances the absorption of the laser beam in tissue. The tissue can then be heated rapidly to a high temperature, causing evaporation and tissue removal.
Measurement and Modeling of Latent Heat Release During Freezing of Aqueous Solutions in a Small Container
Authors: Devireddy Ramachandra V. , Bischof John C. , Leo Perry H. , Lowengrub John S.
Published: November 2021

The latent heat of fusion, ΔHf of a cryobiological medium (a solute laden aqueous solution) is a crucial parameter in the cryopreservation process. The latent heat has often been approximated by that of pure water (∼ 335 mJ/mg). However, recent calorimetric (DSC - Pyris 1) measurements suggest that the actual magnitude of latent heat of fusion during freezing of solute laden aqueous systems is far less. Fourteen different pre-nucleated solute laden aqueous systems (NaCl-H2O, Phosphate Buffered Saline or PBS, serum free RPMI, cell culture medium, glycerol and Anti Freeze Protein solutions) were found to have significantly lower ΔHf than that of pure water (Devireddy and Bischof, 1998). In the present study additional calorimetric experiments are performed at 1, 5 and 20 °C/min in five representative cryobiological media (isotonic or 1× NaCl-H2O, 10× NaCl-H2O, 1× PBS, 5× PBS and 10× PBS) to determine the kinetics of ice crystallization. The temperature (T) and time (t) dependence of the latent heat release is measured. The experimental data shows that at a fixed temperature, the fraction of heat released at higher cooling rates (5 and 20 °C/min) is lower than at 1 °C/min for all the solutions studied. We then sought a simple model that could predict the experimentally measured behavior and examined the full set of heat and mass transport equations during the freezing process in a DSC sample pan. The model neglects the interaction between the growing ice crystals and is most appropriate during the early stages of the freezing process. An examination of the coefficients in the heat and mass transport equations shows that heat transport occurs much more rapidly than solute transport. Hence, the full model reduces to one in which the temperature profile is constant in space while the solute concentration profile obeys the full time and space dependent diffusion equation. The model reveals the important physical parameters controlling the mass transport at the freezing interface and further elucidates the experimental results, i.e. the temperature and time dependence of the latent heat release.
Hyperthermia Induced 3D Temperature Distribution in a Human Sarcoma With Tumor Perfusion Reconstructed Using Fractal Interpolation Functions
Authors: Craciunescu Oana I. , Das Shiva K. , McCauley Robert L. , Samulski Thaddeus V.
Published: November 2021

Essential to the success of optimized thermal treatment during hyperthermia is accurate modeling. Advection of energy due to blood perfusion significantly perturbs the temperature and without accurate estimates of the magnitude of the local tissue blood perfusion it is unlikely that accurate estimates of the temperature distribution can be made. It is shown here that the blood mass flow rate per unit volume of tissue in the Pennes’ bio-heat equation can be modeled using a relative perfusion index (RPI) determined with dynamic-enhanced magnetic resonance imaging (DE-MRI). The existing technology limits the DE-MRI perfusion data to be acquired in a limited number of slices. Consequently, the tumor perfusion data is interpolated using fractal interpolation functions (FIFs), as it has been shown that the RPI data is fractal, and that fractal interpolation is superior to linear interpolation when a 3D fractal-like scaling exists. For illustration, a patient treated with hyperthermia at Duke University Medical Center for a high-grade leg tissue sarcoma is modeled. For control, the resultant temperatures are compared to non-invasively measured temperatures using the MR thermometry technique. Strong correlation is found between the DE-MRI perfusion images, the MR chemical shift images during heating, and the numerical simulation of the temperature field, emphasizing the relation between the DE-MRI measured values and advective heat loss in tissue. The fractal interpolation of DE-MRI data to obtain the 3D perfusion gives a more accurate temperature distribution compared to linear interpolation. For even a better temperature reconstruction, further models need to include large vessels.
Investigation of Corneal/Scleral Burning During Cataract Surgery
Authors: Bhowmick Sankha , Pedersen John , Bischof John C.
Published: November 2021

The use of ultrasound (US) probes in the emulsification and removal of cataracts has the side effect of corneal and scleral burning. In order to quantify the effects of burning on these tissues, experiments were conducted using bovine corneas to determine the activation energy (E) and frequency factor (A) from an Arrhenius damage model. Bovine corneas were heated on a constant temperature copper stage set at the desired temperature (ranging between 40–70°C). The damage criterion set was the loss of transparency of the tissue and the time required to reach the opacity was used to construct an Arrhenius injury model. Results yielded an activation energy of 98.56 kJ/mole and a frequency factor of 2.9×1013s−1. After determining the parameters for the Arrhenius damage integral, a numerical model was developed to simulate the damage based on variations of the temperature at the ultrasound probe tip with time. Results indicate that as much as 39% of the cornea (in area) can be damaged irreversibly (Ω>1) for temperatures reaching 65°C for a time period of 3 minutes. An intermittent procedure which does not allow temperatures to reach beyond 60°C for more than a minute was found to be optimal for treatment purposes. These results show that the sensitivity of the corneal tissue during US heating can be quantitatively measured and predicted. It is therefore important to optimize the treatment procedure to minimize thermal injury during the procedure.
Development of a Cooling Garment With Encapsulated PCM
Authors: Colvin David P. , Colvin Virginia S. , Bryant Yvonne G. , Hayes Linda G. , Spieker Michael A.
Published: November 2021

Under SBIR (Small Business Innovation Research) programs from the U.S. Marine Corps, investigators at Triangle Research and Development Corporation (TRDC) have conducted research toward the development of a unique passive cooling garment to provide significant microclimate cooling to Marines dressed in NBC (Nuclear/Biological/Chemical) protective clothing. The patented PECS (Protective Environmental Control System) garment utilizes 3–4 mm diameter macroencapsulated phase change material (macroPCM) particles distributed throughout a lightweight and highly breathable vest garment to provide 1–3 hours of cooling in high heat stress environments. With polymer walls encapsulating the paraffin PCM, the macroPCMs provide a wearable, packed bed heat exchanger that is flexible, highly breathable, and undergoes its solid/liquid phase change from 25–28°C, where its high latent heat storage can reach 60 calories/gram. This cooling range is at elevated and more comfortable temperatures than gel media used in other passive microclimate garments, which store their cold near 0°C and can cause shivering and discomfort. Although other microclimate garments require refrigeration or freezers to thermally recharge the cooling media, the passive 5-lb PECS cooling garment can be thermally recharged in the field at room temperatures (15–20°C) without refrigeration. Although earlier publications described the principles for such a cooling garment, this publication is the first to describe the garment’s construction, development and testing. Extensive laboratory testing has included Marine volunteers on a treadmill in a heated environmental chamber while dressed in Level IV MOPP and Level A protective clothing and a gas mask. PECS has also been used by costumed characters at Walt Disney World to provide extended cooling within an extended heat stress environment. Besides military uses, passive macroPCM garments should find other applications; including: protective clothing for firefighters, industrial workers, costumed characters and persons with heat stress disabilities.
Cryo, Hyper or Both? Investigating Combination Cryo/Hyperthermia in the Dorsal Skin Flap Chamber
Authors: Hoffmann Nathan E. , Chao Bo H. , Bischof John C.
Published: November 2021

Combination therapies have been investigated as a mean to increase efficacy of disease treatment. For example, combinations such as radiation and chemotherapy, surgery and chemotherapy, and two different chemotherapies have become standard treatment for most cancers. Current theories suggest that vascular-mediated injury is an important mechanism of cryosurgical (reviewed in Gage and Baust (1998)) and hyperthermic destruction (Badylak et al., 1985; Dudar and Jain, 1984) in the treatment of solid tumors. These techniques appear complementary. Freezing creates vascular damage and promotes stasis within the vessels (Rabb et al., 1974), whereas hyperthermia creates cell and vascular destruction more effectively with a compromised vasculature (Shakil et al., 1999). Thus, in this study, we investigated the effect of combining these therapies on the vascular and tissue injury from the two therapies. We chose the dorsal skin flap chamber (DSFC) implanted in the Copenhagen rat as the cryosurgical model for this study. This in vivo freezing model allowed us to monitor thermal history and investigate both vascular and tissue injury in response to the combination therapy.
Thermal Cycling Guidelines for Automotive, Computer, Portable, and Implantable Medical Device Applications
Authors: Raghunathan Rajiv , Pucha Raghuram V. , Sitaraman Suresh K.
Published: November 2021

The objective of this work is to develop qualification guidelines for Flip-Chip on Board (FCOB) and Flip Chip Chip-Scale Packages (FCCSP) used in implantable medical devices, automotive applications, computer applications and portables, taking into consideration the thermal history associated with the field conditions. The accumulated equivalent inelastic strain per cycle and the maximum strain energy density have been used as damage parameters to correlate solder fatigue damage during field use and thermal cycling. The component assembly process mechanics, the time and temperature-dependent material behavior, and the critical geometric features of the assembly have been taken into consideration for developing the comprehensive virtual qualification methodology.
Effect of Moisture on Durability of Flip-Chip-on-Board (FCOB) Interconnects
Authors: Okura J. H. , Dasgupta A. , Caers J. F. J. M.
Published: November 2021

The effect of constant temperature and humidity environments on the durability of interconnects in underfilled Flip-Chip-on-Board (FCOB) assemblies is investigated in this study. Polymeric underfills, used to enhance thermomechanical durability of the interconnects, are found to create new failure modes due to hygromechanical swelling. Based on experimental observations, the failure mechanism is hypothesized to be cracking of intermetallics, which have weakened due to thermal aging. Pseudo 3-D finite element analyses are conducted to quantify the moisture absorption and diffusion through the polymeric underfill, and the resulting hygromechanical viscoplastic stress history. The simulations are combined with accelerated aging tests to assess in-service durability in hot, humid environments. Model predictions are compared with results of accelerated life tests available in the literature.