bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Indentation Test to Determine the Proteoglycan Content of Articular Cartilage
Authors: Lu Xin , Sun Daniel D. , Guo X. Edward , Chen Hui , Lai W. Michael , Mow Van C.
Published: June 2008

The indentation experiment has been widely used to determine mechanical properties of articular cartilage [e.g., 1–3]. This method does not disrupt the fibrous network of the tissue nor does it require removing the tissue from the underlying bone. The biphasic indentation theory has been successfully used to determine the effect of interstitial fluid flow and pressurization (load support) on the creep and stress-relaxation behaviors of articular cartilage, and to determine its apparent mechanical properties (i.e., the elastic moduli of the extracellular solid matrix and its permeability) [1, 3]. However, due to its proteoglycan content, articular cartilage is a charged tissue with a high fixed charge density (FCD) [4]. Proteoglycan and collagen contents, water, etc, vary with age or with orthteoarthritis [4, 5]. The FCD plays important physicochemical roles in load support and mechano-electrochemial behaviors of the tissue and also regulates chondrocyte biosynthetic activities [4–7]. It is therefore important to develop an effective technique to determine not only the mechanical properties but also the electrochemical property (e.g., FCD) of the tissue, simultaneously and at the same location. The purpose of the current study is to determine, for the first time, both the mechanical properties and FCD of the extracellular matrix using an indentation test.
Viscoelastic Properties of Human MCL in the Transverse Direction
Authors: Bonifasi-Lista Carlos , Lake Spencer P. , Small Michael S. , Weiss Jeffrey A.
Published: June 2008

Ligament viscoelasticity is an important determinant of tissue response to rapid loading and potential for injury, and may also play a role in tissue nutrition via fluid movement during loading/unloading. Because ligaments are anisotropic multiphase structures, it is likely that their viscoelastic response is direction-dependent. Previous efforts to describe ligament viscoelasticity have either reported experimental data without theoretical interpretation (e.g., [1]), or assumed a particular form for the viscoelastic response a priori [2–4]. Small sinusoidal perturbations about an equilibrium strain value allow application of linear viscoelasticity theory for determination of storage modulus (dynamic stiffness) and loss modulus (phase, or damping) as a function of frequency and equilibrium strain level. With these data, one can assess the appropriateness of different viscoelastic and/or poroelastic models to describe time- and rate-dependent constitutive behavior.
Segmental Cervical Spine Kinematics Due to Posteroanterior Impact Acceleration
Authors: Stemper Brian D. , Yoganandan Narayan , Pintar Frank A.
Published: June 2008

An experimental investigation was performed to determine the segmental cervical spine kinematics in rear impact acceleration. Segmental motions were analyzed at the time of maximum S-curve for 10 isolated head-neck specimens (5 male, 5 female). Females experienced greater segmental angles at each level of the spine for all input velocities. Statistically significant gender differences were obtained for levels C2-C3, C5-C6, and C6-C7. Motions were statistically dependent upon input velocity for C4 to C7 segments. Results of this study provide a biomechanical basis for the differing rates of reported whiplash injuries between males and females.
Vertical Impulse Analysis of Seat Belt Buckles
Authors: Clarke Richard , Sances Anthony
Published: June 2008

Review of various buckle testing studies is given. More than 100 different standard production end release seat belt buckles have been tested and repeatability and validation studies have been done. The buckle stalks were modified to accommodate the vertical acceleration test fixture. Some buckles opened with vertical accelerations as low as 91 g’s while others did not release at levels as high as 489 g’s.
Analysis of Structural Deformation in Vehicular Drop Studies
Authors: Herbst Brian , Meyer Steve , Forrest Steve , Syson Steve , Sances Anthony , Kumaresan Srirangam
Published: June 2008

Various tests are used to evaluate the roof strength of production vehicles. Dynamic rollover tests have been conducted as part of FMVSS 208 and static evaluation using FMVSS 216. The National Highway Transportation Safety Administration (NHTSA) is investigating methods to upgrade FMVSS 216 roof crush resistance to reduce injuries and fatalities in passenger cars, pickup trucks, vans, and multipurpose passenger vehicles from roof intrusion in rollover crashes (1). Roof crush intrusion is estimated to occur and potentially contribute to about 26 percent of serious or fatal injuries. Motor vehicle rollovers have been a concern for more that 30 years because they carry a very high risk of occupant death or risk compared to other types of crashes (2).
Finite Element Model of a Cell Incorporating Cell Membrane, Cytoskeletal Structure and Intracellular Fluid Pressure
Authors: Venkatesan Vidyashankar , Mukherjee Nilay
Published: June 2008

Compressive loading is intrinsic to certain tissues in our body like articular cartilage and bone (1). In situ experiments in cartilage suggest that chondrocytes can undergo significant deformation due to compressive loading on the tissue (2). In situ and isolated cell experiments have concluded that cells are quite resilient to compressive loading, aspiration etc. and exhibit a moduli in the range of 0.6 to 2 kPa (3). However, few studies have attempted to understand the compressive behavior of cells in terms of its structural components. The structural components of a cell consist of a membrane and a dense network of at least three elements (actin, microtubules and intermediate filaments). Using finite element analysis techniques we wanted to explore the role of these structural components in determining the ability of the cell to withstand compression.
Enzymatic Digestion Technique Influences Regulatory Volume Decrease of Isolated Bovine Chondrocytes
Authors: Hulme Paul , Chi Simon , Young Dominic , Matyas John , Duncan Neil A.
Published: June 2008

Cell volume regulation has been observed in almost all cell types examined to date. When cells are exposed to hypotonic solutions a quick increase in volume is followed by a more gradual return, termed regulatory volume decrease (RVD). The mechanism associated with RVD depends upon cell type and species, but in bovine chondrocytes the non-selective osmolyte channels are mainly responsible [1]. In a chondrocyte, volume control is critical for the maintenance of metabolism, and biosynthesis. Volume fluctuations can be due to changes in hydrostatic pressure, fluid flows, deformation, and extracellular matrix (ECM) hydration. Alterations in hydration can occur during static loading of articular cartilage or during the early stages of osteoarthritis [1], which have been correlated with changes in cellular metabolism. The swelling behaviour of chondrocytes, and the mechanism by which they sense and respond to changes in their physico-chemical environment, are not well understood [1]. To investigate the effects of osmotic environment on chondrocyte behaviour it is often beneficial to isolate cells from the ECM, which can be achieved by a variety of techniques. To investigate the effect of isolation technique on the swelling behaviour of bovine chondrocytes, two enzymatic digestion techniques were chosen for this study.
Noise Sources and Transmission in Piping Systems
Authors: Hambric Stephen A. , Hwang Yun Fan , Chyczewski Thomas S.
Published: June 2008

An overview of the vibro-acoustic behavior of fluid-filled piping systems is given, summarizing noise sources, how piping structures and fluids accept energy from noise sources, and how the energy is then transmitted and exchanged by wavetypes throughout the piping. Discrete and broad-band frequency noise sources from active components, such as pumps, and passive components, such as valves and flow over piping, are described, and scale on flow velocities and operating speeds. The turbulence in the fluid flow contributes to piping system noise and vibration. The turbulence in the core flow impinges on both active and passive devices, causing discrete and broad-band noise sources. Turbulence near pipe walls excites structural piping modes. Techniques for quantifying the turbulence and its effects are described. An overview of the mechanisms of acoustic and vibrational energy propagation in piping walls and fluids is given, along with a discussion of various tools used to model the propagation, such as finite element (FE) and boundary element (BE) analysis, transfer matrix (TM) analysis, and statistical energy analysis (SEA). FE and BE models may be used to model high levels of complexity in both structural-acoustic systems and noise sources, but require large model sizes at high frequencies. TM and SEA models sacrifice modeling generality, but can represent high frequency behavior at low computational cost. Finally, means of mitigating acoustic and vibration energy transmission, such as narrow-band acoustic attenuation devices (quarter wavelength silencers and Quincke tubes), broad-band acoustic attenuation devices (mufflers and acoustic filters), and broad-band structural vibration attenuation devices (isolators and rubber piping), are outlined.
Structural-Acoustic Wave Transmission and Reflection in a Hose-Pipe System
Authors: Hwang Y. F.
Published: June 2008

An analysis of sound and vibratory transmission and reflection losses in a fluid filled planar piping system which consists of straight pipe segments, flexible hose, elbows and/or U-joints is discussed in this paper. The transfer matrix approach is used for the analysis. The wave propagation constants for various types of waves calculated from the transfer matrix method were verified with an exact elasticity theory. Although calculation of the transmission losses for a hose-pipe system has been widely discussed in the literature, the reflection characteristics of a hose-pipe system, however, have not received proper attention. In this paper, we calculate the reflection, absorption, and transmission coefficients of a piping system simultaneously. The numerical example shows that very large pressure and bending wave transmission losses that occur in a hose-pipe system are not only caused by attenuation and dissipation but also by the reflection from the system.
Statistical Energy Analysis of Fluid-Filled Piping Vibrations and Acoustics
Authors: Manning Jerome E.
Published: June 2008

The flow of vibratory energy in turbo-machinery piping systems can contribute significantly to the noise emission. Fluctuating pressures and mechanical vibrations of pumps and valves generate coupled vibration and acoustic waves that propagate throughout the system and radiate noise to the surrounding acoustic space. Statistical energy analysis provides a method to analyze the energy transmitted by these waves and to develop noise and vibration mitigation designs. The development of SEA models requires that special consideration be given to piping elbows and tees, where the coupling between structural vibrations and fluid acoustic waves may be high. This paper reviews the development of piping system prediction models and their limitations. A mobility-based approach is described to improve predictions at mid-frequencies where both statistical energy and finite element procedures often fail to provide accurate predictions.
Effects of Equipment Loading on the Vibrations of Edge-Stiffened Plates and Associated Modeling Issues
Authors: Campbell Robert L. , Hambric Stephen A.
Published: June 2008

Predicting structural radiated noise is a process that involves several steps, often including the development of a finite element (FE) model to provide structural response predictions. Limitations of these FE models often govern the success of overall noise predictions. The purpose of the present investigation is to identify the effects of real world attachments on edge-stiffened plates and identify advanced modeling methods to facilitate vibroacoustic analyses of such complex structures. A combination of experimental and numerical methods is used in the evaluation. The results show the effects of adding attachments to the edge-stiffened plate in terms of mode shape mass loading, creation of new mode shapes, modifications to original mode shapes, and variations in damping levels. A finite element model of the edge-stiffened plate with simplified attachments has been developed and is used in conjunction with experimental data to aid in the developments. The investigation presented here represents a necessary first step toward implementing an advanced modeling technique.
Vibration Analysis of Steam Generators and Heat Exchangers: An Overview — Part II: Vibration, Response, Fretting-Wear, Guidelines
Authors: Pettigrew Michel J. , Taylor Colette E.
Published: June 2008

Design guidelines were developed to prevent tube failures due to excessive flow-induced vibration in shell-and-tube heat exchangers. An overview of vibration analysis procedures and recommended design guidelines is presented in this paper. This paper pertains to liquid, gas and two-phase heat exchangers such as nuclear steam generators, reboilers, coolers, service water heat exchangers, condensers, and moisture-separator-reheaters. Part 2 of this paper covers forced vibration excitation mechanisms, vibration response prediction, resulting damage assessment, and acceptance criteria.
The Flow-Induced Vibration of Cylinders in a Cross Flow
Authors: Takano W. , Tozawa K. , Yokoi M. , Nakai M. , Sakamoto I.
Published: June 2008

Flow-induced vibrations occur in general heat exchangers and nuclear reactors. They cause the tube failures through fretting wear or fatigue. Fluid elastic instability may lead to vibration amplitudes large enough to cause tube-to-tube clashing and in such cases will lead to relatively rapid failures. Therefore mechanisms of elastic vibration induced by cross flow are significant problems for large vibration amplitudes. The aims of this study are to analyze the vibration of cylinders at various flow velocities and to get the fundamental data of design for the prevention of accidents in heat exchanger. In this study, the experimental apparatus was built so that cylinder tip motions could be measured at various flow velocities. The experiments were conducted in different cylinder arrays. The cylinder vibration was induced in normal direction to flow by an alternate vortex. Moreover, once the flow velocity was increased to a certain value, the cylinder oscillation amplitude increased rapidly with flow and had a maximum. When five cylinders were arranged in a row normal to flow, the wandering of energy was generated between the two cylinders. For three cylinders arranged in tandem, two cylinders in upstream and downstream positions mutually vibrated out of phase. For many cylinders, the entropy had the maximum at a specific flow velocity and oscillating behavior of cylinders became chaotic state which could not predict its behavior.
Analytical and Experimental Flow-Induced Vibration Analysis of a Shell and Tube Cooling Water Heat Exchanger
Authors: Ghiselli Alberto F. Marti´n , Kulichevsky Rau´l M. , Sacchi Mauricio A. , Pastorini Alberto J. , Belinco Ce´sar G.
Published: June 2008

A flow-induced vibration problem evaluation of a shell and tube cooling water heat exchanger equipment installed in a power plant is presented in this paper. The problem produced loss of thickness in many tubes of the bundle, by impact or fretting wear, and the need to plug these tubes to avoid leakage. These vibrations could had been produced by changes in the equipment operational conditions or by a wrong evaluation during the design stage. An analytical and experimental evaluation was made to predict tubes dynamical response and to identify the excitation mechanisms. The original design modification adopted to solve the problem is presented and evaluated.
MEMS in the Consumer Disposable Products Industry
Authors: Sherman F. , Gartstein V.
Published: June 2008

The consumer products industry is a good example of broad usage of disposable products. Consumer disposable products, in general, have two key unique characteristics that are very important drivers for new product inventions: low cost and large volume scalability. These two properties have always limited the penetration of MEMS technology into the consumer disposable product industry. Even though MEMS is traditionally spoken of as a low cost high volume technology, this holds true for industries outside the one described within here. The reality surrounding traditional silicon MEMS technology is that the cost structures is at best two orders of magnitude above acceptable levels and the infrastructure available to make the needed volumes is non existent. For these two reasons, plastic microfabrication and scalable design principles adaptation offers a viable solution for MEMS technology within the context of disposable consumer products. Using our low cost, large volume scalable plastic microneedle technology as an example, it was demonstrated that a successful transition from silicon to plastic microfabrication was achieved while maintaining excellent structural functionality for the purpose of glucose sensing from interstitial fluid (ISF).
Parallel Iterative Methods for the Helmholtz Equation With Exact Nonreflecting Boundaries
Authors: Ianculescu Cristian , Thompson Lonny L.
Published: June 2008

Parallel iterative methods for fast solution of large-scale acoustic radiation and scattering problems are developed using exact Dirichlet-to-Neumann (DtN), nonreflecting boundaries. A separable elliptic nonreflecting boundary is used to efficiently model unbounded regions surrounding elongated structures. We exploit the special structure of the non-local DtN map as a low-rank update of the system matrix to efficiently compute the matrix-by-vector products found in Krylov subspace based iterative methods. For the complex non-hermitian matrices resulting from the Helmholtz equation, we use a distributed-memory parallel BICG-STAB iterative method in conjunction with a parallel Jacobi preconditioner. Domain decomposition with interface minimization was performed to ensure optimal interprocessor communication. For the architectures tested, and using the MPICH version of MPI, we show that when implemented as a low-rank update, the non-local character of the DtN map does not signicantly decrease the scale up and parallel eciency versus a purely approximate local boundary condition.
Local Complexity and Global Nonlinear Modes in Large Arrays of Fluid-Elastic Oscillators
Authors: Kuroda Masaharu , Moon Francis C.
Published: June 2008

Transition from local complexity to global spatio-temporal dynamics in a two dimensional array of fluid-elastic oscillators is examined experimentally with an apparatus comprising 90–1000 cantilevered rods in a wind tunnel. Wave-like behavior is observed which may be related to soliton solutions in nonlinear arrays of nonlinear oscillators. The 90 to 1000 steel and polycarbonate rods have gap ratios ranging from 1.0 to 2.5. As the Reynolds number (based on rod diameter) increases from 200 to 900, a pattern with characteristics of spatio-temporal chaos emerges in global behavior of the elastic-rod array. There are local and global patterns. Local patterns comprise transient rest, linear motion, and elliptical motion. In 90-rod experiments, a cluster-pattern entropy measure based on these three patterns is introduced as a quantitative measure of local complexity. No significant dynamics appear below a threshold wind velocity. Video images reveal that, at first, each rod moves individually; then clusters consisting of several rods emerge. Finally, global wave-like motion occurs at higher flow velocities. Spatial patterns in rod-density distribution appear as more rods impact with their nearest neighbors. Furthermore, these collective nonlinear motions of rods are observed and categorized into several global modes. Using accelerometer data, the rod impact rate versus flow velocity shows a power-law scaling relation. This phenomenon may have application to plant-wind dynamics and damage as well as heat exchangers in energy systems. This experiment may also be a two dimensional analog of impact dynamics of granular materials in a flow.
A Carbon Fiber Based Sensor for Measurement of Serotonin From Platelets
Authors: Frilot Clifton F. , Patton Stephen R. , Jones Steven A.
Published: June 2008

The fluid dynamic environment within an artery is an important contributor to haemostasis. Fluid mechanics can alter the biochemical environment through convection and diffusion of reactive substances. It can bring the platelets close to the wall through convection and enhanced diffusion, cause platelet activation through hemodynamic shear stresses, and alter the substrate for platelet adhesion through shear effects on endothelial cells. Shear produces long-term effects on endothelial cells, such as morphological changes in the cells and adaptation of the size of the artery. It can also affect endothelial cells in the short term by increasing calcium release or release of nitric oxide.
Upgrading of Tubular Heat Exchangers by the Helical Spacer Method and Evaluation
Authors: Eisinger F. L. , Sullivan R. E.
Published: June 2008

The tubular heat exchangers described exhibited a sensitivity to flow-induced tube vibration at about 50% of their design shell-side flow. Following a detailed theoretical analysis, the heat exchangers were modified by the helical spacer method providing additional tube supports in-between the existing support plates and in the U-bend. This modification aimed at allowing the heat exchangers to operate safely and reliably at full load, including a 25% overload. Post modification sound and vibration testing was performed which confirmed the adequacy of the modification. The test results showed however, that at the overload condition, an unusual acoustic wave inside the shell was developing. It was determined that this wave would not be harmful to the safe operation of the heat exchangers. The paper will discuss the findings in more detail.
Mechanical Properties Characterization of Abdominal Aortic Aneurysm Tissue Using Biaxial Testing
Authors: Marra Steven P. , Kennedy Francis E. , Fillinger Mark F.
Published: June 2008

An abdominal aortic aneurysm (AAA) is an abnormal, localized enlargement of the aorta. If untreated, a AAA will continue to enlarge in size and eventually rupture. Currently, AAA diameter is used as the principal indicator of impending rupture. However, this method it is not totally reliable. In an effort to improve the estimation of rupture risk, some researchers are currently studying the mechanical wall stresses of AAAs using patient-specific medical imaging techniques and finite element modeling [1,2]. The accuracy of these models depends significantly on the constitutive law used to describe the mechanical properties of the AAA tissue. To date, only isotropic constitutive laws have been used in these models.
Ex Vivo Measurement of Mouse Pulmonary Artery Biomechanics
Authors: Chesler Naomi C. , Thompson-Figueroa John A. , Millburne Kenneth M.
Published: June 2008

Primary pulmonary hypertension (PPH) is a rapidly progressing and often fatal disease that induces substantial pulmonary vascular remodeling [1]. Although a genetic factor has been identified in familial and sporadic cases of pulmonary hypertension [2], the etiology of the disease for most victims remains unknown.
Experimental Investigation of Acoustic Modes in Baffled Heat Exchangers
Authors: Goyder H. G. D. , Hameed A.
Published: June 2008

The standard method for preventing a heat exchanger from generating a loud noise is to insert acoustic baffles which subdivide the vessel. It had previously been thought that such baffles would increase the acoustic natural frequency and thus prevent a resonance condition involving interactions between the sound field and wake oscillations behind tubes. Theoretical and experimental investigations, described in this paper, show that the effect of introducing an acoustic baffle into a shell is to decrease the acoustic natural frequency. This effect is not helpful and may result in resonant conditions being more common. However, an additional effect of an acoustic baffle is to change the direction of the acoustic waves and thus prevent good spatial correlation between wake oscillations and the sound field. It is this latter effect which makes acoustic baffles effective. Hence, spatial correlation should be made the basis of any design method.
Microcantilever Arrays for Multiplexed Biomolecular Analysis
Authors: Yue Min , Dedrick Daniel E. , Lin Henry , Satyanarayana Srinath , Majumdar Arunava
Published: June 2008

An accurate, efficient, and quantitative method for detection of multiple biomolecules, such as DNA and proteins, would benefit many bio-medical applications. These applications include diagnostics of complex diseases such as cancer, drug discovery, and development of fundamental scientific knowledge regarding signaling pathways. We have developed a chip-level microcantilever array designed for high-throughput biomolecular analysis. In particular, biological reactions on one surface of a microcantilever beam change its surface tension due to intermolecular energetic and entropic interactions. These interactions generate sufficient torque to deflect the cantilever beam. Integration of microfluid cells on the chip allows for individual functionalization of each cantilever. Each cantilever is designed to respond uniquely to a specific target analyte allowing for simultaneous and quantitative analysis of multiple bio-molecules. Experiments testing the physical response of the microarray describe the repeatability of the cantilevers while providing information regarding the limits on the detection time for reaction-induced deflections to dominate over random drift of the cantilevers. Statistical analysis shows that the cantilevers exhibit thermomechanical sensitivity within ±7% variation. The maximum observed trend of the long-term drift is about 2.1nm/min, which suggests reactions should be completed within 10 minutes, for a reliable bioassay.
Force Response of Single Living Cells Due to Localized Deformation (Invited Talk)
Authors: Saif T. , Sager C. , Coyer S.
Published: June 2008

We present a method for measuring the mechanical response of a single cell in-situ when local deformation is applied at an adhesion site(s) by a functionalized MEMS (Micro Electro Mechanical Systems) force sensor with pN – nN force resolution, and with force and displacement ranges of 100s of nNs and μms. The force sensor is a micro mechanical cantilever beam made of single crystal silicon (SCS), coated by a thin layer of Fibronectin, an extra cellular matrix (ECM) protein, to activate cell adhesion. The end of the beam is brought in contact with a cell to form the adhesion site(s). The cantilever is then moved away from the cell to locally deform it. The force on the cell is measured from the deformation of the cantilever until the adhesion sites fails. We demonstrate the method by deforming several endothelial and fibroblast cells. Force response of the fibroblast cell shows linear behavior.
Transport Enhancement in Tunable Laser Cavity Sensor
Authors: Sigurdson M. , Meinhart C. , Wang D. , Liu X. , Feng J. J. , Krishnamoorthy S. , Makhijani V. B.
Published: June 2008

Dielectrophoresis and Electrothermal Flow are two physical processes investigated for enhancing transport of antigen to a region of immobilized conjugate antibodies on an immunosensor surface. Computational fluid dynamics (CFD) modeling is employed to understand these phenomena in detail to aid in the design optimization of the device.
Impact Work-Rate and Wear of a Loosely Supported Beam Subject to Harmonic Excitation
Authors: Knudsen Jakob , Massih Ali R.
Published: June 2008

Impact work-rate of a weakly damped beam with elastic two-sided amplitude constraints subject to harmonic excitation is calculated. Impact work-rate is the rate of energy dissipation to the impacting surfaces. The beam is clamped at one end and constrained by unilateral contact sites near the other end. This system was an object of a vibro-impact experiment which was analyzed in our earlier paper (Knudsen and Massih 2000). Detailed nonlinear dynamic behavior of this system is evaluated in our companion paper (Knudsen and Massih 2002b). Computations show that the work-rate for asymmetric orbits is signifi-cantly higher than for symmetric orbits at or near the same frequency. For the vibro-impacting beam, under conditions that exhibit a stable attractor, calculation of work-rate allows us to predict the “lifetime” of the contacting beam due to fretting-wear damage by extending the stable branch and using the local gap between contacting surfaces as a control parameter. That is, upon computation of the impact work-rate, the fretting-wear process time is calculated through back-substitution of the work-rate and gap-width in a given wear law.
Vibration and Work-Rate Measurements of Steam-Generator U-Tubes in Air-Water Cross-Flow
Authors: Janzen Victor P. , Hagberg Erik G. , Patrick James N. F. , Pettigrew Michel J. , Taylor Colette E. , Whan Tim G.
Published: June 2008

In nuclear power plant steam generators, the vibration response of tubes in two-phase cross-flow is a general concern that in some cases has become a very real long-term wear problem. This paper summarizes the results of the most recent U-bend vibration-response tests in a program designed to address this issue. The tests involved a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to two-phase air-water cross-flow over the mid-span region of the U-bend. Tube vibration properties and tube-to-support interaction in the form of work-rates were measured over a wide range of flow velocities for homogeneous void fractions from zero to 90%, with three different tube-to-support clearances. The measured vibration properties and work-rates could be characterized by the relative influence of the two most important flow-induced excitation mechanisms at work, fluidelastic instability and random-turbulence excitation. As in previous similar tests, strong effects of fluidelastic instability were observed at zero and 25% void fraction for pitch velocities greater than approximately 0.5 m/s, whereas random turbulence dominated the tube vibration and work-rate response at higher void fractions. In both cases, a link between vibration properties and the effect of the flat-bar supports could be established by comparing the vibration crossing frequency, extracted from time-domain vibration signals, to the participation of the lowest few vibration modes and to the measured work-rate. This approach may be useful when fluidelastic instability, random turbulence and loose supports all combine to result in high work-rates. Such a combination of factors is thought to be responsible for excessive U-tube fretting-wear in certain types of operating steam generators.
Productivity of Parallel-Serial Manufacturing Lines With and Without Crossover
Authors: Freiheit Theodor , Shpitalni Moshe , Hu S. Jack
Published: June 2008

The productivity of a manufacturing system is greatly influenced by the configuration of the manufacturing system. However, the number of system configurations possible for a set of manufacturing operations can be very large, causing difficulty in the efficiency of general methods to calculate the productivity. Therefore the focus of this paper will be limited to configurations that are characteristic of automotive machining transfer lines. The traditional automotive line is serial and parallel operations are generally not used except where a balanced line cannot be achieved. Yet productivity gains can be made from parallel lines. Traditional lines also use buffers between operations to isolate the impact of a machine failure on the productivity of the system. However, a buffer does not isolate the failure to complete a product from failure in the last operation. When production machinery is of high reliability, and reduced work-in-process inventory costs are important, the examination of machining lines that do not rely on buffers becomes important. This paper examines the productivity improvements that can be obtained by bufferless parallel-serial lines, i.e. multiple machining lines in parallel, both with and without crossover between the operations. It will be shown that significant improvements to productivity can be obtained by placing operations in parallel, and that there is a synergistic improvement to productivity from having crossover between the operations.
An Excitation Spectrum Criteria for the Vibration-Induced Fatigue of Small Bore Pipes
Authors: Moussou Pierre
Published: June 2008

The purpose of the study is to determine an easy-to-use criterion to evaluate the risk of vibration induced fatigue of small bore pipes. The failure mechanism considered is the resonant amplification of a stationary broadband excitation of the main pipe by natural modes of the small bore pipe, leading to bending stresses above the fatigue limit of the steel. Based on the Euler beam theory, a simple model is built up for the natural mode shapes of the small bore pipe close to its root. It is shown that the velocity spectrum at the root of the small bore pipe is equal to the RMS value of the bending stress multiplied by a function of the natural frequency, the damping coefficient, the speed of elastic waves in the steel, the Young modulus and a non-dimensional factor weakly depending on the geometry of the small bore pipe. A maximum velocity spectrum can then be deduced, assuming that a small bore pipe vibrates mainly on its natural mode shapes. The maximum excitation spectrum is defined for each frequency ƒ as the one which would generate a maximum bending stress equal to the endurance limit of the steel, would the small bore pipe have a natural frequency equal to ƒ. Using envelope values of the dimensional factor, the stress intensification factor, the peak factor and the endurance limit of the steel, one obtains the following maximum velocity spectrum for the stainless steel: v<6mm/s/sqrt(ƒ) and the following maximum velocity spectrum for the ferritic steel: v<2.7mm/s/sqrt(ƒ) The velocity spectrum criterion appears less penalizing than the 12 mm/s criterion and more conservative than the strict enforcement of the ANSI-OM3 standard. Comparisons with former studies show that the velocity spectrum criterion leads to the correct fatigue diagnosis.
Module Selection Methodology for Designing Reconfigurable Machining Systems
Authors: Chen Li , Xi Fengfeng , Macwan Ashish
Published: June 2008

This paper presents a systematic, feature-based selection methodology to select the minimum yet sufficient set of modules (DP’s) to satisfy a given set of machinable features (FR’s) in order to construct a reconfigurable machining system capable of producing a part family. Two cases of selection are considered: selecting DP’s for single FR’s, and for multiple FR’s. The second case considers two selection scenarios: selecting separate DP’s to individually satisfy the FR’s, and selecting a single DP to simultaneously satisfy all the FR’s. These selection cases and scenarios are necessitated by our previous work done on developing a method for module identification. Each step of the methodology is presented in detail, and then subsequently illustrated by being applied to a case study. The case study deals with the design of the overall layout of a reconfigurable machining system required to machine a given family of die molds.
Capacity Management in Reconfigurable Manufacturing Systems With Stochastic Market Demand
Authors: Asl Farshid Maghami , Ulsoy A. Galip
Published: June 2008

An optimal solution, based on Markov Decision Theory, is presented for the capacity management problem in Reconfigurable Manufacturing Systems with stochastic market demand with a time delay between the time capacity change is ordered and the time it is delivered. The optimal policy in this paper is presented as optimal boundaries representing the optimal capacity expansion and reduction levels. The effects of change in the cost function parameters and the delay time on the optimal boundaries are presented for a capacity management scenario. The major differences between this research and the ones in inventory control lie in two folds. One is the fact that unlike inventory, capacity levels can be reduced according to the market demand. The other one is the novel approach presented in this paper to solve the delay problem which unlike the inventory control does not account for the cumulative unmet demand as a decision factor.
Manufacturing Practices in Dynamic Markets: Reconfigurability to Enable a Service-Based Manufacturing Capacity Supply
Authors: Urbani Alessandro , Molinari-Tosatti Lorenzo , Pasek Zbigniew J.
Published: June 2008

Many markets today are characterized by a fast pace of change, coupled with high, internationally enlarged competition based on differentiation and customer-oriented production. In such scenario, Mass Customization is going to be a relevant paradigm for tomorrow. The manufacturing paradigms introduced so far are not sufficient to cope with such manufacturing challenges. This paper proposes possible evolution of the manufacturing capacity supply that may help to improve response to the market requirements, emphasizing the needs that drive such a trend. The supply of a manufacturing service is pointed out as the desirable solution when compared with other possible scenarios. Reconfigurability is viewed as the main enabler to set up a manufacturing capacity supply that puts into practice the idea of service providing.
Compliant Mesoscale Grinding of 3-Dimensional Free Form Shapes in Silicon Wafers
Authors: Jiang B. , Shannon M. A. , Philpott M. L.
Published: June 2008

This paper presents a new approach to create three-dimensional free form shapes in silicon wafers by compliant grinding. Instead of requiring high rigidity in traditional ultra-precision grinding systems, the proposed compliant grinding method requires relatively low rigidity. It achieves the required surface roughness, form accuracy and surface integrity by utilizing grinding force feedback and adaptive control. Compliant grinding mitigates microfractures, chipping, and defect formation in the silicon substrate, so that both electronic and mechanical properties of the Si are not degraded. A prototype silicon die grinder has been built and initial rough grinding results are promising.
Remote Sensing and Geospatial Technologies Application for Developing Options to Relocate CSX Railroad From Mississippi Gulf Coast Townships
Authors: O’Hara Charles G. , King Roger L. , Cartwright John , King Jason
Published: June 2008

An environmental assessment will be conducted to study the impacts of relocating segments of the CSX railroad out of significant population growth areas along the environmentally sensitive Mississippi Gulf Coast. The environmental assessment project, which is to be jointly managed by the Mississippi DOT and FHWA, will make broad use of remote sensing and geospatial technologies. The project has been awarded and will be supported by the technical and research resources of the National Consortium on Remote Sensing in Transportation (www.ncrst.org). The National Consortia on Remote Sensing in Transportation (NCRST) comprises four university research consortia sponsored by the US DOT. The consortia conducts research to improve our understanding about how remote sensing and geospatial technologies can provide planners, managers, engineers, and analysts with information resources that can be used to improve multimodal transportation planning, design, operation, and maintenance efforts. Consortia activities also are focused on conducting technical outreach with transportation agencies and organizations to demonstrate how remote sensing and geospatial technologies can be effectively implemented and to improve understanding of where additional research, outreach, and training activities are most needed. The environmental assessment component of the consortia works with new sources of high resolution data to provide improved information for evaluating options, assessing environmental conditions, screening sensitive areas, optimizing potential alignments, and conducting preliminary planning and design. Research activities have shown that if appropriate remote sensing data are collected early in the project life cycle the benefits of the data include: • Enhancing transportation planning; • Improving early design processes; • Improving the ability to develop and provide informational materials for public access; and • Better communication and demonstration of benefits of planned transportation service improvements.
Critical Infrastructure Protection Using Image Intelligence From Space-Based Aerial Sensors
Authors: Morain Stanley A.
Published: June 2008

America’s transportation systems are predicated on economic, social, and political stability. After the epiphany of September 11, and subsequent national alerts, however, all sectors of transportation, not just in the USA, but around the world have become keenly aware of the vulnerabilities inherent in such systems; and of the cascading consequences that can arise from attacks at critical nodes in any one or more of the transportation sectors. Critical infrastructure protection can be enhanced significantly through better and more routine use of intelligence extracted from real time, time sequential, and archival images obtained by aerial and satellite sensors. Since we cannot, and probably never would, re-engineer current transportation infrastructures to harden them against random attacks, planners can use image-derived intelligence to redesign their information and decision support systems to detect, prepare, prevent, protect, and respond to incidents. In many instances technology already exists to begin these redesigns, but before 9/11 there was little incentive to invest in the effort. Measures that were once difficult to justify as protection against acts of nature are now justifiable as protection against deliberate acts of aggression. These measures, once learned and implemented, will be applicable to both natural and deliberate incidents.
Target Setting for Vehicle Side Impact Using a Statistical Approach
Authors: Deb Anindya , Saha Nripen K.
Published: June 2008

Designing a vehicle for superior side impact performance is an important consideration in automotive product development. The challenges involved in this design are many as side impact is a relatively short duration event and interaction between the crash test dummy and vehicle side structure including side airbag (if present) is involved, and engagement of the moving deformable barrier with the stiffer underbody of a car may not always take place (unlike in the case of frontal NCAP test in which the front rails will necessarily play a major role in energy-absorption). The safety engineer nevertheless has to set targets for relevant side crash-related variables in the initial phase of design when very limited information on vehicle structure is available. As shown in the present study, linear regression-based relationships can be utilized for setting quantitative targets for structural response and packaging-related variables for side impact safety design of a new vehicle.
Random Excitation of a Structure Interacting With Liquid Sloshing Dynamics
Authors: Ikeda Takashi , Ibrahim Raouf A.
Published: June 2008

The nonlinear random interaction of an elastic structure with liquid sloshing dynamics in a cylindrical tank is investigated in the neighborhood of 1:2 internal resonance. Such internal resonance takes place when the natural frequency of the elastic structure is close to twice the natural frequency of the antisymmetric sloshing mode (1,1). The excitation is generated from the response of a linear shaping filter subjected to a Gaussian white noise. The analytical model involves three sloshing modes; (1,1), (0,1) and (2,1). The system response statistics and stability boundaries are numerically estimated using Monte Carlo simulation. The influence of the excitation center frequency, its bandwidth, and the liquid level on the system responses is studied. It is found that there is an irregular energy exchange between the structure and the liquid free surface motion when the center frequency is close to the structure natural frequency. Depending on the excitation power spectral density, the liquid free surface experiences zero motion, uncertain motion (intermittency), partially developed motion, and fully developed random motion. The structure response probability density function is almost Gaussian, while the liquid elevation deviates from normality. The unstable region, where the liquid motion occurs, becomes wider as the excitation intensity increases or as the bandwidth decreases. As the liquid depth decreases, the region of nonlinear interaction shrinks which is associated with a shift of the peak of the structure mean square response toward the left side of the frequency axis.
Modeling Approaches to Hypersonic Aeroelasticity
Authors: Thuruthimattam B. J. , Friedmann P. P. , McNamara J. J. , Powell K. G.
Published: June 2008

The hypersonic aeroelastic problem of a double wedge airfoil typical cross-section is studied using three different unsteady aerodynamic loads: (1) third order piston theory, (2) Euler solution, and (3) unsteady Navier-Stokes aerodynamics. Computational aeroelastic response results are obtained, and compared with piston theory solutions for a variety of flight conditions. Aeroelastic behavior is studied for 7 < M < 15 at an altitude of 70,000 feet. A parametric study of offsets and wedge angles is conducted. Piston theory and Euler solutions are fairly close below the flutter boundary, and differences increase with increase in Mach number, close to the flutter boundary. Differences between viscous and inviscid aeroelastic behavior can be substantial. The results presented serve as a partial validation of the CFL3D code for the hypersonic flight regime.
Dynamic Behavior of Monolithic and Composite Materials by Split Hopkinson Pressure Bar Testing
Authors: Costanzi Marco , Sayal Gautam , Newaz Golam
Published: June 2008

A Split Hopkinson Pressure Bar (SHPB), an experimental apparatus for testing of solid materials at high strain rates, was in-house designed and realized by the Mechanical Engineering Dept. of WSU: it can test different types of materials and provide their dynamic mechanical properties (e.g. Young’s modulus, hardening or plasticization coefficients, yield strength). This SHPB works at strain rate levels between 1000 and 3000 s-1 and impact speeds between 6 and 9 m/s. The specimen is simply a 6 mm dia. 3 mm long cylinder. The apparatus and its software were benchmarked by means of tests on Aluminum and Titanium, whose mechanical properties are well known, and later successfully applied to non-metallic materials like Nylon, Epoxy, Carbon fiber and glass fiber reinforced composites.