bluuebunny/crossref_metadata_2025 huggingface dataset:
Predisposing factors to phlebitis in patients with peripheral intravenous catheters: A descriptive study
Authors: Uslusoy Esin , Mete Samiye
Published: April 2008

Purpose: The purpose of this study was to investigate the predisposing factors in the development of phlebitis in peripheral intravenous (IV) catheterization sites in patients treated with a variety of IV infusion solutions and drugs.

Data sources: Systematic observation of 568 IV sites inserted for fluid infusion and drug administration in 355 patients in the Department of General Surgery of a University Hospital in Turkey. A data collection tool was based on standards established by the Infusion Nurses Society. Patients’ infusion sites were monitored every 24 h during treatment and for 48 h after discontinuation of the IV.

Conclusions: In contrast to the usual findings in the literature, the authors found that infusion through an infusion pump and insertion of catheters in the veins around the elbow increased the risk of phlebitis. Also, the number of times infusions were started led to an increased rate of phlebitis. However, conflicting results were obtained about the relation between phlebitis, gender, and catheter size.

Implications for practice: Phlebitis causes sepsis, pain, additional diagnostic investigations, and treatments, and may lead to increased duration of hospitalization, patient’s stress level, and financial burden, as well as increasing staff workload. Advanced practice nurses need to be aware of the factors that increase the likelihood of phlebitis and take appropriate measures to prevent it.
Mindfulness‐based stress reduction: A literature review and clinician’s guide
Authors: Praissman Sharon
Published: April 2008

Purpose: To provide nurse practitioners (NPs) with clinical research about Mindfulness‐Based Stress Reduction (MBSR) and demonstrate its usefulness for reducing stress in a variety of populations.

Data Sources: A literature review was conducted using the following databases: EBSCO, Cinahl, Pschyline, and Medline. English language articles published between 2000 and 2006 in peer‐reviewed journals were reviewed. Search terms “mindfulness,”“meditation,” and “stress” were used. Additional information was obtained through select, reputable Internet sites.

Conclusions: MBSR is an effective treatment for reducing stress and anxiety that accompanies daily life and chronic illness. MBSR is also therapeutic for healthcare providers, enhancing their interactions with patients. No negative side effects from MBSR have been documented.

Implications for practice: MBSR is a safe, effective, integrative approach for reducing stress. Patients and healthcare providers experiencing stress or stress‐related symptoms benefit from MBSR programs. NPs can safely and effectively use this intervention in a variety of patient populations.
Changing Nutrition Standards in Schools: The Emerging Impact on School Revenue
Authors: Wharton Christopher M. , Long Michael , Schwartz Marlene B.
Published: April 2008

Background:  Although great focus has been placed on nutritional and other consequences of changes in food‐related policies within schools, few reports exist describing the impact of such changes on school revenue. This review provides an overview of the few revenue‐related studies published recently, as well as information from a sampling of state reports on the subject.

Methods:  A systematic review of the literature was conducted. Four peer‐reviewed papers and 3 state‐based reports were identified that assessed the impact on revenues of either targeted policy changes or overarching, district‐wide changes in food‐related policies.

Results:  Thus far, few data exist to substantiate the concern that changes in nutrition standards in schools lead to a loss in total revenue. An interesting phenomenon of increased participation in the National School Lunch Program was noted in a number of reports and might play a role in buffering financial losses.

Conclusions:  A renewed focus on school policies related to health provides the opportunity for researchers to investigate how nutrition‐related policy change can affect, if at all, food service and overall school revenues.
The processes for releasing a zoo‐bred Sumatran orang‐utan Pongo abelii at Bukit Tigapuluh National Park, Jambi, Sumatra
Authors: COCKS L. , BULLO K.
Published: April 2008

Perth Zoo released a sub‐adult ♀ Sumatran orang‐utan Pongo abelii in November 2006 into the protected Bukit Tigapuluh National Park in Jambi, Sumatra, where the Sumatran Orang‐utan Conservation Programme (SOCP) is trying to re‐establish an orang‐utan population. This was the first release of a captive‐born orang‐utan into the wild. Temara is being closely tracked and monitored by Perth Zoo and SOCP staff. The aim is that she will be followed for at least 2 years. This paper describes: the pre‐release preparation, the release process, the benefits of the programme, the monitoring process and the post‐release results.
Conservation of threatened amphibians in Valle del Cauca, Colombia: a cooperative project between Cali Zoological Foundation, Colombia, and Zoo Zürich, Switzerland
Authors: FURRER S. C. , CORREDOR G.
Published: April 2008

Amphibians are facing a massive crisis: one‐third of the world's amphibians are threatened with extinction. The International Union of Conservation of Nature and Natural Resources – The World Conservation Union has urged that ‘All Critically and Extinct in the Wild taxa should be subject to ex situ management to ensure recovery of wild populations.’ Comparable calls are included in Global Amphibian Assessment documents. Cali Zoological Foundation, Colombia, and Zoo Zürich, Switzerland, are committed to contribute to amphibian conservation by running an ex situ conservation centre and conservation research and education programmes. This project may serve as a model for further amphibian conservation activities in neotropical countries.
Color Evolution of Aqueous Solutions Obtained by Thermal Processing of Carrot (Daucus carota L.) Roots: Influence of Light
Authors: This H. , Cazor A. , Trinh D.
Published: April 2008

ABSTRACT:  The color of aqueous solutions obtained by heating carrot (Daucus carota L.) roots in water (“stocks”) is different when the thermal treatment is applied with or without exposure to light. CIE L*, a*, and b* scale values of stocks processed for different times were recorded and 4 patterns were initially observed. To explain the 1st part of this evolution (patterns 1 and 2), pectin extraction and β‐elimination in stocks were studied. Light dependence was investigated to explain patterns 3 and 4. A model with 2 compounds is proposed to explain all the color variations.
Indicators of iron status in elite soccer players during the sports season
Authors: OSTOJIC S. M. , AHMETOVIC Z.
Published: April 2008

The main aim of the study was to investigate the changes of hematologic status in elite soccer players throughout a competitive season. Study was conducted with 35 male professional soccer players and the measurements were collected at the start of the conditioning period, at the start of the season, in the mid‐season and at the end of the season. Blood was drawn from an antecubital vein for a complete blood count, serum iron, and transferrin and ferritin levels. We found significantly higher hematocrit at preseason assessment as compared with other sampling periods (P < 0.05). No other differences were found between any of the hematologic variables during the study. The lowest hemoglobin level, mean corpuscular volume (MCV), serum iron, ferritin and transferrin encountered in the study were Hb of 11.2 g/dl, MCV of 77.9 fl, serum iron of 34 μg/dl, ferritin of 15.1 μg/l, transferrin of 224 μg/dl in a 20‐year‐old soccer player at the start of the season. The variability of the iron status indicators in elite soccer players seems to be stable and poorly related to training phase during sports season.
The Wayward Girl Revisited: Understanding the Gendered Nature of Juvenile Justice and Delinquency
Authors: Pasko Lisa
Published: April 2008

Traditional explanations of delinquency have mostly focused on male offending. While men were the primary subjects of criminological research as well as the central focus of the justice system, gender was rarely explicitly examined, and consequently, girls often went unnoticed. Today, however, female juvenile offenders’ visibility both in research and in the system has changed. This essay reviews feminist theorizing of girls’ delinquency, with a concentrated focus on the ‘pathways’ perspective; the scope of girls’ lawbreaking; and their historical and contemporary experiences inside and outside the juvenile justice system. This essay concludes with an examination of two promising girl‐specific juvenile justice initiatives.
The Gendered Face of Terrorism
Authors: Ferber Abby L. , Kimmel Michael S.
Published: April 2008

What does sociology have to contribute to our understanding of terrorism? As scholars of gender and the Far Right, we believe that we have much to offer the current debates. In this article, we focus both on contemporary cases of terrorism, the attacks of September 11 and the Oklahoma City bombing, and terrorist movements as gendered: as enactments of masculinity. In particular, we focus on the contemporary white supremacist movement, the most dangerous domestic terrorist threat faced by the USA. We suggest that the ideology and organization of many terrorist groups are saturated with gendered meanings, both as the analytic prism through which they view their situation, and also as a means of political mobilization.
Social Movements in Organizations
Authors: Arthur Mikaila Mariel Lemonik
Published: April 2008

This article reviews the literature on social movements within organizations such as colleges and universities, corporations, religious orders, and governmental agencies. It brings together work from disparate fields to advance an understanding of how movements happen within organizations to introduce students and scholars to the promise of such research.
An ex‐post analysis of the German Upper Rhine: data gathering and numerical modelling of morphological changes in the 19th century
Authors: Spinewine B. , Zech Y.
Published: April 2008

To ensure sustainability, long‐term effectiveness and limited maintenance, river flood management practices should take into consideration the potential morphological adaptations resulting from the imposed changes to a river system. To illustrate the ability of numerical models to provide a valuable tool for flood management planners, an ex‐post analysis of the Rhine during the 19th century is carried out. The Upper German Rhine has been reshaped deeply by large engineering works over this century. The initially braided reach Basel–Maxau was constricted into a single channel, while the reach Maxau–Mainz was significantly shortened by meander shortcuts. Both types of works resulted in intense erosion upstream and spread deposition downstream, with most of the changes occurring during high‐flow periods. As ancient data are generally difficult to obtain, the paper shows how fragmentary ancient data may be complemented with more recent data adequately interpreted for reconstructing a realistic set of initial conditions. The study is an attempt at reproducing qualitatively the behaviour of the Upper Rhine with a dataset collected only from publicly available sources.
Importation of Dogs into the United States: Risks from Rabies and Other Zoonotic Diseases
Authors: McQuiston J. H. , Wilson T. , Harris S. , Bacon R. M. , Shapiro S. , Trevino I , Sinclair J. , Galland G. , Marano N.
Published: April 2008

The importation of dogs into the United States poses a risk for the introduction of rabies and other zoonotic diseases. Federal regulations (42 CFR 71.51) currently require proof of valid rabies vaccination for imported dogs, but allow the importation of some unvaccinated dogs, including dogs less than 3 months of age, provided certain requirements for confinement are met until the dog is vaccinated. Although there are no accurate surveillance data on the number of dogs imported each year, it is estimated based on extrapolated data that over 287 000 dogs were imported into the United States during 2006. Of these, approximately 25% were either too young to be vaccinated or lacked proof of valid rabies vaccination. Import trends suggest that an increasing number of unvaccinated puppies are being imported into the United States, many through commercial resale or rescue operations. Since 2004, foreign canine rabies virus variants have been documented in at least two imported puppies. Federal regulations are currently being reviewed by the Centers for Disease Control and Prevention to determine if they can be updated to address current import trends and disease risks, such as requiring a health screen and valid rabies vaccinations for all dogs prior to entry.
Nonlocal Modeling and Simulation of Ductile Damage and Failure in Metal Matrix Composites
Authors: Reusch Frederick , Hortig Christian , Svendsen Bob
Published: April 2008

The purpose of the current work is the application of a recent nonlocal extension (Reusch, F., Svendsen, B., and Klingbeil, D., 2003, “Local and Non-Local Gurson-Based Ductile Damage and Failure Modelling at Large Deformation,” Eur. J. Mech. A∕Solids, 22, pp. 779–792; “A Non-Local Extension of Gurson-Based Ductile Damage Modeling,” Comput. Mater. Sci., 26, pp. 219–229) of the Gurson–Needleman–Tvergaard (GTN) model (Needleman, A., and Tvergaard, V., 1984, “An Analysis of Ductile Rupture in Notched Bars,” J. Mech Phys. Solids, 32, pp. 461–490) to the simulation of ductile damage and failure processes in metal matrix composites at the microstructural level. The extended model is based on the treatment of void coalescence as a nonlocal process. In particular, we compare the predictions of the local with GTN model with those of the nonlocal extension for ductile crack initiation in ideal and real Al–SiC metal matrix microstructures. As shown by the current results for metal matrix composites and as expected, the simulation results based on the local GTN model for both the structural response and predicted crack path at the microstructural level in metal matrix composites are strongly mesh-dependent. On the other hand, those based on the current nonlocal void-coalescence modeling approach are mesh-independent. This correlates with the fact that, in contrast to the local approach, the predictions of the nonlocal approach for the crack propagation path in the real Al–SiC metal matrix composite microstructure considered here agree well with the experimentally determined path.
Effects of Manufacturing-Induced Voids on Local Failure in Polymer-Based Composites
Authors: Chowdhury K. A. , Talreja R. , Benzerga A. A.
Published: April 2008

This paper presents results of a computational study focused on examining the role of manufacturing-induced voids in the initiation and growth of damage at the microstructural level in polymer matrix composites loaded in tension normal to fibers. The polymer deformation is described by an improved macromolecular constitutive model accounting for strain-rate-, pressure-, and temperature-sensitive yielding, isotropic hardening before peak yield, intrinsic postyield softening, and rapid anisotropic hardening at large strains. A new craze model that accounts for craze initiation, growth, and breakdown mechanisms is employed. An energy-based criterion is used for cavitation induced cracking that can lead to fiber/matrix debonding. The role of voids is clarified by conducting a comparative study of unit cells with and without voids. The effects of strain rate and temperature are investigated by a parametric study. The overall composite stress-strain response is also depicted to indicate manifestation of microlevel failure on macroscopic behavior.
Quantitative Stress Analysis of Recrystallized OFHC Cu Subject to Deformation In Situ
Authors: Bernier Joel V. , Miller Matthew P. , Park Jun-Sang , Lienert Ulrich
Published: April 2008

Quantitative strain analysis (QSA) provides a means for assessing the orientation-dependent micromechanical stress states in bulk polycrystalline materials. When combined with quantitative texture analysis, it facilitates tracking the evolution of micromechanical states associated with selected texture components for specimens deformed in situ. To demonstrate this ability, a sheet specimen of rolled and recrystallized oxygen-free high conductivity Cu was subject to tensile deformation at APS 1-ID-C. Strain pole figures (SPFs) were measured at a series of applied loads, both below and above the onset of macroscopic yielding. From these data, a lattice strain distribution function (LSDF) was calculated for each applied load. Due to the tensorial nature of the LSDF, the full orientation-dependent stress tensor fields can be calculated unambiguously from the single-crystal elastic moduli. The orientation distribution function (ODF) is used to calculate volume-weighted average stress states over tubular volumes centered on the ⟨100⟩∥[100], ⟨311⟩∥[100], and ⟨111⟩∥[100] fibers—accounting for ≈50% of the total volume—are shown as functions of the applied load along [100]. Corresponding weighted standard deviations are calculated as well. Different multiaxial stress states are observed to develop in the crystal subpopulations despite the uniaxial nature of the applied stress. The evolution of the orientation-dependent elastic strain energy density is also examined. The effects of applying stress bound constraints on the SPF inversion are discussed, as are extensions of QSA to examine defect nucleation and propagation.
Multiproperty Microstructure and Property Design of Magnetic Materials
Authors: Li Dongsheng , Rollett Anthony D. , Vialle Greg , Garmestani Hamid
Published: April 2008

Microstructure sensitive design was used in this study to design a textured soft magnet material to meet a range of magnetic properties. The evolution of microstructure and magnetic properties during mechanical processing was simulated and presented in a spectral representation for microstructure (texture hull) and magnetic property (property hull). The set of properties for a single path (or multiple processing paths) is represented in the property hull with a direct link to the range of desired microstructures. A methodology is proposed to achieve microstructures satisfying the requirement of multiple properties.
Advances in Virtual Metal Forming Including the Ductile Damage Occurrence: Application to 3D Sheet Metal Deep Drawing
Authors: Saanouni K. , Badreddine H. , Ajmal M.
Published: April 2008

An advanced numerical methodology to simulate virtually any sheet or bulk metal forming including various kinds of initial and induced anisotropies fully coupled to the isotropic ductile damage is presented. First, the fully coupled anisotropic constitutive equations in the framework of continuum damage mechanics under large plastic deformation are presented. Special care is paid to the strong coupling between the main mechanical fields such as elastoplasticity, mixed nonlinear isotropic and kinematic hardenings, ductile isotropic damage, and contact with friction in the framework of nonassociative and non-normal formulation. The associated numerical aspects concerning both the local integration of the coupled constitutive equations as well as the (global) equilibrium integration schemes are presented. The local integration is outlined, thanks to the Newton iterative scheme applied to a reduced system of ordinary differential equations. For the global resolution of the equilibrium problem, the classical dynamic explicit (DE) scheme with an adaptive time step control is used. This fully coupled procedure is implemented into the general purpose finite element code for metal forming simulation, namely, ABAQUS/EXPLICIT. This gives a powerful numerical tool for virtual optimization of metal forming processes before their physical realization. This optimization with respect to the ductile damage occurrence can be made either to avoid the damage occurrence to have a nondamaged part as in forging, stamping, deep drawing, etc., or to favor the damage initiation and growth for some metal cutting processes as in blanking, guillotining, or machining by chip formation. Two 3D examples concerning the sheet metal forming are given in order to show the capability of the proposed methodology to predict the damage initiation and growth during metal forming processes.
Asymmetric Indentation of a Finite Elastically Supported Beam
Authors: Peck J. A. , Schonberg W. P.
Published: April 2008

This paper presents the results of an investigation into the behavior of an elastic beam that is loaded by a frictionless cylindrical indenter. Results are obtained using a solution which incorporates both local contact behavior as well as global beam behavior. The solution is obtained by superposing an elastic layer solution derived through the use of integral transforms and the cylindrical bending solution for a flat plate. The problem reduces to two coupled Fredholm integral equations of the second kind which are solved numerically. Local contact stresses and load-deflection relations are examined in detail for various geometric and contact parameters. The results are compared to Hertz theory contact stresses and beam theory deflection predictions.
Crack Propagation in a Nonlinearly Viscoelastic Solid With Relevance to Adhesive Bond Failure
Authors: Knauss W. G. , Losi G. U.
Published: April 2008

The problem of crack propagation through a material possessing nonlinearly viscoelastic material response is considered, including the influence of stress-induced free-volume changes on the rheology, as well as the formation of voids as material failure is approached. This particular material response is confined to a thin layer along the crack propagation axis, while the bulk of the material behaves in a linearly viscoelastic manner, thus simulating the situation arising in the growth of a crazeled crack, or the failure of a bonded joint with a thin adhesive layer strained uniformly across its thickness. The nonlinear material behavior thus governs simultaneously the stress and strain distribution at the crack tip as well as the crack speed solely in dependence on the applied load (stress intensity factor). Only quasi-static motion is considered, the velocities being understood to be “reduced” by temperature according to a time-temperature superposition principle. Comparisons with a model based on linearly viscoelastic considerations and rate-insensitive properties of the damaged material are presented.
Cyclic Viscoplastic Constitutive Equations, Part II: Stored Energy—Comparison Between Models and Experiments
Authors: Chaboche J.-L.
Published: April 2008

The cyclic constitutive equations developed at ONERA have been incorporated into a general thermodynamic framework (Part I). In the present part, systematic comparisons are given between the model predictions and experimental data for both the mechanical response and the energy stored in the material. The models are specified in their rate—independent-form and closed-form solutions are obtained for tension-compression monotonic and cyclic conditions. By superposing one or two nonlinear kinematic rules and one isotropic hardening equation, the available experimental data are fairly well reproduced. In particular it is possible to describe the low values of stored energy, the decrease of the ratio of stored energy to total plastic work as a function of strain, and the partial release of stored energy at every half cycle of a cyclic loading.
Rayleigh-Type Wave Propagation on a Micropolar Cylindrical Surface
Authors: Mrithyumjaya Rao K. , Reddy M. Pratap
Published: April 2008

A detailed study of a Rayleigh wave propagating on the surface of a micropolar elastic circular cylinder in an azimuthal direction is considered. At the cutoff frequency if the particle displacement is purely azimuthal and equivoluminal, then only this type of wave exists. A number of deviations from the results of the classical theory are observed. For example, the phase velocity corresponding to the same branch is given to be single valued, whereas it seems to be multivalued at some intervals. Due to the micropolar effect there exists an extra wave whose frequency spectrum is also obtained. The dependence of the microrotation and couple stress amplitudes on depth are evaluated. The frequency of the Rayleigh wave increases due to the micropolar effect.
Influence of Porosity on Plane Strain Tensile Crack-Tip Stress Fields in Elastic-Plastic Materials: Part II
Authors: Miao Y. , Drugan W. J.
Published: April 2008

This paper continues the investigation of Drugan and Miao (1992). There we studied analytically the influence of a uniform porosity distribution on the stress field near a plane strain tensile crack tip in ductile (elastic-ideally plastic) material, assuming that material very near the tip is at yield at all angles about the tip. Our solutions exhibited completely continuous stress fields for porosity f ≤ 0.02979, but for higher porosities they involved radial surfaces of radial normal stress jumps. Here we investigate whether, for this higher range of porosity, relaxing our assumption of yield at all angles about the tip will facilitate solutions exhibiting fully continuous stress fields. The answer to this is shown to be yes, with a single near-tip sector assembly providing such solutions for this entire higher porosity range. On either side of the crack symmetry plane, this solution configuration consists of a leading plastic sector possessing radial stress characteristics (“generalized centered fan ”), followed by a plastic sector of constant Cartesian components of stress, followed finally by a sector of purely elastic material adjacent to the crack flank. The angular extents of these sectors vary substantially with porosity level. In regions of purely elastic response, we have accounted for the influence of porosity on the overall, or effective, elastic moduli. Among the interesting features of these new solutions are a significantly enlarged generalized centered fan sector as compared to that of the fully plastic Part I solutions for the same f values, and for f values just slightly above the 0.02979 level, a narrow elastic sector exists in which stresses vary so rapidly with angle that they appear to be nearly discontinuous. This rapid variation spreads out as the elastic sector enlarges with increasing f, and, in contrast to the fully plastic solutions, the radial normal component of stress becomes negative near the crack flank.
Interactions Among General Systems of Cracks and Anticracks: An Integral Equation Approach
Authors: Hu K. X. , Chandra A.
Published: April 2008

Cracks and rigid line inclusions, or anticracks, are commonly observed in many engineering materials, such as ceramics, intermetallics, etc. Interactions among these cracks and anticracks can significantly affect the load-carrying capacities and other mechanical properties of these materials. Accordingly, modeling of the interactions among general systems of cracks and anticracks subject to general loading conditions is the main thrust of this paper. An integral equation approach based on the fundamental solutions due to point loads and point dislocations in an elastic body is utilized for this purpose. A Gauss-Chebychev quadrature is used to reduce the integral equations to a system of linear equations consisting of the distributions of Burger’s dislocation vectors and forces on the cracks and the anticracks, respectively. The proposed solution procedure also allows direct determination of the rigid-body rotations for the anticracks. For a collinear crack-anticrack system, the results obtained from the present analysis are verified against those obtained from a Green’s function approach. Numerical results are also presented for sample systems of cracks and anticracks, and salient features of amplification and shielding of stress singularities are investigated.
The Mechanism of Nip-Induced Tension in Wound Rolls
Authors: Good J. K. , Wu Z.
Published: April 2008

Models which can be used to calculate the internal stresses within wound rolls of web material have all been confirmed to the center winding technique to date. The mechanism by which a nip roller can increase the wound in tension in the outer layer of the wound roll is presented. Results of this work have been used to establish new winding models which can accurately predict the internal stresses within a center wound roll with an impinged nip.
Instability of Loaded Fractal Trees
Authors: Go´mez J. B. , Pacheco A. F. , Segui´-Santonja A. J.
Published: April 2008

We analyze the failure strength of loaded structures of the fractal-tree type, from a probabilistic perspective. The consideration of the intrinsic fragilities of the basic elements at each level of the tree makes the tree differ from being equivalent to a mere hierarchically organized bundle of fibers. A simple criterion for having a linear proportionality between the size of the tree and the inverse of the threshold strength for failure is found.
Analytic Solutions for a Spinning Rigid Body Subject to Time-Varying Body-Fixed Torques, Part II: Time-Varying Axial Torque
Authors: Tsiotras P. , Longuski J. M.
Published: April 2008

In this paper we extend the methodology developed in Part I in order to accommodate the case of an axial time-varying torque (in addition to the two transverse timevarying torques) acting on a rotating rigid body. The analytic solutions thus derived describe the general attitude motion of a near-symmetric rigid body subject to timevarying torques about all three body-fixed axes.
Free Vibration Analysis of Rectangular Plates with Nonuniform Lateral Elastic Edge Support
Authors: Gorman D. J.
Published: April 2008

The method of superposition is utilized to obtain a solution for the free vibration of thin rectangular plates resting on non-uniform lateral elastic edge supports. The stiffness of the elastic supports may have any desired distribution along the edges, including discontinuities and local concentrations. Convergence is found to be rapid. Graphical results are plotted for square plates in order to verify that proper frequency limits are approached as the edge stiffness approach limits of zero and infinity. Results are tabulated for square and nonsquare plates in order that other researchers will have data against which they can compare their results.
Dynamic Response of a Spinning Timoshenko Beam With General Boundary Conditions and Subjected to a Moving Load
Authors: Zu J. W.-Z. , Han R. P. S.
Published: April 2008

The dynamic response of a spinning Timoshenko beam with general boundary conditions and subjected to a moving load is solved analytically for the first time. Solution of the problem is achieved by formulating the spinning Timoshenko beams as a non-self-adjoint system. To compute the system dynamic response using the modal analysis technique, it is necessary to determine the eigenquantities of both the original and adjoint systems. In order to fix the adjoint eigenvectors relative to the eigenvectors of the original system, the biorthonormality conditions are invoked. Responses for the four classical boundary conditions which do not involve rigidbody motions are illustrated. To ensure the validity of the method, these results are compared with those from Euler-Bernoulli and Rayieigh beam theories. Numerical simulations are performed to study the influence of the four boundary conditions on selected system parameters.
Criteria of Dynamic Crack Initiation
Authors: Watanabe Masaaki
Published: April 2008

A criteria of dynamic crack initiation is proposed as Klcdyn=Klcσcdyn.σctq.s.tαS/2 for t≤tq.s., where Klcdyn. is the dynamic critical stress intensity factor for initiation and Klc, the static fracture toughness. σc and σcdyn. are critical stresses for a growth of microcracks generated at the tip of a crack, in quasi-static and dynamic loading conditions, respectively. tq.s. is the characteristic time of quasi-static growth of a crack and t is a loading time. αs is a positive number. This criteria is compared with various different experiments and found to be in qualitative agreement with them.
The End Problem of Incompressible Elastic Cylinders
Authors: Ling Yun , Engel P. A. , Geer J. A.
Published: April 2008

The end problem of incompressible elastic cylinders is formulated and is solved by an eigenfunction expansion method. Various methods for the determination of the unknown coefficients of the expansion are studied and a variational approach which minimizes the total potential energy is suggested. A transformation is introduced for a better calculation of the stiffness of a cylinder. The Benthem and Minderhoud (1972) expansion is used to describe the interfacial stress distributions. The difficulties of using this expansion for thin cylinders are overcome by utilizing the Cesaro sum (Powell and Shah, 1972). Numerical results for the compression of bonded rubber cylinders are presented and discussed.
Analysis of a Kinked Interfacial Crack Under Out-of-Plane Shear
Authors: Choi S. R. , Lee K. S. , Earmme Y. Y.
Published: April 2008

A kinked interfacial crack under out-of-plane shear is analyzed where a straight interfacial crack is kinked into material 1 out of the interface. Employing the Wiener- Hopf technique, the solution is obtained in a closed form. Discontinuity in the stress intensity factor as the kink angle to approaches zero is found, while the energy release rate is shown to be continuous at ω = 0. The limit case of the kinked length b approaching zero is also investigated. The result shows that the stress field has 1/r singularity and the energy release rate at b = 0+ is enhanced at some ω if the crack kinks into the more compliant material.
A Progressive Damage Modeling Based on the Continuum Damage Mechanics and its Finite Element Analysis
Authors: Kim Seung Jo , Kim Wie Dae
Published: April 2008

A continuum damage modeling based on the theory of materials of type N is proposed and its nonlinear finite element approximation and numerical simulation are carried out. To solve the finite elastoplasticity problems, the reasonable kinematical strain measure for large deformed solids are introduced and constitutive relations based on the theory of materials of type N are derived. These highly nonlinear equations are reduced to the incremental weak formulation and approximated by the theory of nonlinear finite element method. To verify the theory and the computer code, the computational simulation of the uniaxial elongation is carried out and the results are compared with the actual experiment. Two example problems, bending problem and billet forming problem, are simulated, and the deformed shapes and the progressive results of the damage variable are presented.
Mechanical and Thermal Wrinkling of Polymer Membranes
Authors: Chiu H. C. , Benson R. C. , Fiscella M. D. , Burns S. J.
Published: April 2008

A finite element method by Roddeman was modified in order to study wrinkling of polymer membranes due to mechanical loads and thermal shrinkage. Thermal shrinkage was incorporated as a prestrain and the elastic modulus was allowed to be dependent on temperature. The following wrinkling cases were studied: (1) a circular membrane with a heated spot at the center and a uniform radial displacement at the outer edge, (2) a rectangular membrane with wrinkles emanating from an imperfection in the boundary, and (3) a rectangular membrane with wrinkles emanating from a heated spot at the center.
A Second-Law Analysis of Thermoelastic Damping
Authors: Kinra V. K. , Milligan K. B.
Published: April 2008

In accordance with the Thomson effect (Thomson, 1853), when a thermoelastic solid is subjected to a tensile stress, it cools. Similarly, when a homogeneous material is subjected to an inhomogeneous stress field or when an heterogeneous material is subjected to any stress field (homogeneous or inhomogeneous), different parts of the material undergo different temperature changes. As a result irreversible heat conduction occurs and entropy is produced. In this paper we take the second law of thermodynamics as our starting point and develop a general theory for calculating the thermoelastic damping from the entropy produced.
Characteristics of Modal Coupling in Nonclassically Damped Systems Under Harmonic Excitation
Authors: Park I. W. , Kim J. S. , Ma F.
Published: April 2008

The normal coordinates of a nonclassically damped system are coupled by nonzero off-diagonal elements of the modal damping matrix. The purpose of this paper is to study the characteristics of modal coupling, which is amenable to a complex representation. An analytical formulation is developed to facilitate the evaluation of modal coupling. Contrary to widely accepted beliefs, it is shown that enhancing the diagonal dominance of the modal damping matrix or increasing the frequency separation of the natural modes need not diminish the effect of modal coupling. The effect of modal coupling may even increase. It is demonstrated that, within the practical range of engineering applications, neither diagonal dominance of the modal damping matrix nor frequency separation of the natural modes would be sufficient for neglecting modal coupling.
The Effect of Wire Rope Mechanics on the Mechanical Response of Cord Composite Laminates: An Energy Approach
Authors: Shield C. K. , Costello G. A.
Published: April 2008

The behavior of one-ply and two-ply laminated cord-rubber composite plates in uniaxial tension is presented. The plate mechanical properties are presented as functions of cord angle for various cord-modulus to matrix-modulus ratios. The model developed takes account of the extension-twisting coupling of the cord, as well as the exact location of the cord within the composite plate. An energy method formulation is used, and the model is solved using the Ritz method. The current results are compared to classical lamination theory results to show the limits of usefulness for classical lamination theory for this class of composite.
The Buckling of an Elastic Layer Bonded to an Elastic Substrate in Plane Strain
Authors: Shield T. W. , Kim K. S. , Shield R. T.
Published: April 2008

The solution for buckling of a stiff elastic layer bonded to an elastic half-space under a transverse compressive plane strain is presented. The results are compared to an approximate solution that models the layer using beam theory. This comparison shows that the beam theory model is adequate until the buckling strain exceeds three percent, which occurs for modulus ratios less than 100. In these cases the beam theory predicts a larger buckling strain than the exact solution. In all cases the wavelength of the buckled shape is accurately predicted by the beam model. A buckling experiment is described and a discussion of buckling-induced delamination is given.
A Novel Boundary Element Method for Linear Elasticity With No Numerical Integration for Two-Dimensional and Line Integrals for Three-Dimensional Problems
Authors: Nagarajan A. , Lutz E. , Mukherjee S.
Published: April 2008

This paper presents a novel application of the boundary element method to solve problems in linear elasticity. The new method is called the Boundary Contour Method. This approach requires no numerical integration at all for two-dimensional problems and numerical evaluation of line integrals only for three-dimensional problems; even for curved line or surface boundary elements of arbitrary shape! Numerical results are presented for some two-dimensional problems.
Isotropy of Strain Energy Functions Which Depend Only on a Finite Number of Directional Strain Measures
Authors: Elata D. , Rubin M. B.
Published: April 2008

Motivated by studies of low-density materials and fiber-dominated composites, we consider an elastic material whose strain energy function depends only on a finite number of directional strain measures, which correspond to the strains of material fibers in specific material directions. It is shown that an arbitrary set of six distinct direction vectors can be used to define six symmetric base tensors which span the space of all symmetric second-order tensors. Using these base tensors and their reciprocal tensors we develop a representation for the strain tensor in terms of six directional strain measures. The functional form of the strain energy of a general anisotropic nonlinear elastic material may then be expressed in terms of these directional strain measures. Next, we consider general nonlinear isotropic response by developing explicit functional forms for three independent strain invariants in terms of these directional strain measures. Finally, with reference to previous work, we discuss isotropy of specific functional forms of directional strain measures associated with up to 15 directions in space.
Reflection of Waves at the Free Edge of a Laminated Circular Cylinder
Authors: Rattanawangcharoen N. , Shah A. H. , Datta S. K.
Published: April 2008

A wave function expansion method is employed to solve the reflection problem of time-harmonic elastic waves incident upon the free edge of a semi-infinite laminated circular cylinder. Wave functions are obtained using a propagator matrix approach for laminated isotropic cylinders and by a Rayleigh-Ritz type approximation for laminated composite cylinders. The least-square technique as well as the variational method are employed to evaluate the complex amplitudes and the energy flux associated with the reflected waves. To validate the solutions and present algorithm, results are compared with analytical solutions whenever available. Examples include free-end reflection of waves in an isotropic solid rod, a two-layered isotropic cylinder, and a four-ply [ + 15/ −15/ +15/ −15] graphite/epoxy cylinder. Numerical experimentation shows that the least-square method provides poor results for the laminated anisotropic cylinder compared to those obtained through the variational technique.
An Exact Stiffness Method for Elastodynamics of a Layered Orthotropic Half-Plane
Authors: Wang Y. , Rajapakse R. K. N. D.
Published: April 2008

A method is presented in this paper to compute displacements and stresses of a multilayered orthotropic elastic half-plane under time-harmonic excitations. The half-plane region under consideration consists of a number of layers with different thicknesses and material properties. Exact layer stiffness matrices describing the relationship between Fourier transforms of displacements and tractions at the upper and bottom surface of each layer are established explicitly by using the analytical general solutions for displacements and stresses of a homogeneous orthotropic elastic medium. The global stiff ness matrix which is also symmetric and banded is assembled by considering the traction continuity conditions at the interface between adjacent layers of the multilayered half-plane. The numerical solution of the global stiffness equation results in the solutions for Fourier transform of displacements at layer interfaces. Thereafter displacements and stresses of the multilayered plane can be obtained by the numerical integration of Fourier integrals. Only negative exponential terms of Fourier transform parameter are found to appear in the elements of layer stiffness matrices. This ensures the numerical stability in the solution of the global stiffness equation. In addition, the size of the final equation system is nearly onehalf of that corresponding to the conventional matrix approach for layered media based on the determination of layer arbitrary coefficients. The present method provides accurate solutions for both displacements and stresses over a wide range of frequencies and layer thicknesses. Selected numerical results are presented to portray the influence of layering, material orthotropy, and frequency of excitation on the response of five layered systems. Time-domain solutions are also presented to demonstrate the features of transient surface displacements due to a surface loading pulse applied to layered orthotropic half-planes.
Two-Dimensional Grained Composites of Extreme Rigidity
Authors: Vigdergauz S.
Published: April 2008

A thin elastic plate with nonidentical periodical inclusions is considered as an adequate model to optimize mechanical characteristics of a two-phase composite, given the mean stresses and phase volume fraction. Geometrical forms of these inclusions minimizing the total stress energy are obtained explicitly through the analytical solution of a specific boundary value problem so their parametrical equations are expressed in terms of elliptic functions. Such approach is used also to find the effective moduli of the composite. Finally, the similar finite-step procedure is suggested to construct multiphase optimal structure with macroisotropy.
Motion and Force Prediction of a Pushed Object by Maximum Dissipation Method
Authors: Sakurai Hiroshi
Published: April 2008

When an object on a horizontal surface is pushed hard enough to overcome the friction between the object and the surface, the object moves. It was proved by interpreting Kuhn-Tucker’s optimality condition that when a pusher moves an object, the motion and the friction force of the pushed object corresponding to the pusher motion are those that maximize the power dissipated to friction under Coulomb’s friction law. This is different from the principles of maximum and minimum dissipation postulated in the past in that it involves the pusher motion too whereas the principles do not. It allows us to treat the prediction of the motion and the friction force of a pushed object as an optimization problem. Since this optimization can be performed with linear programming within any desired accuracy, it offers us a simple, robust, and fast method to predict the motion and the friction force of a pushed object. The method was verified with an experiment of pushing a wooden block. It was applied to the estimation of the necessary clamping force infixturing for machining.
Maximal Lyapunov Exponent and Almost-Sure Stability for Coupled Two-Degree-of-Freedom Stochastic Systems
Authors: Sri Namachchivaya N. , Van Roessel H. J. , Talwar S.
Published: April 2008

In this paper, a perturbation approach is used to calculate the asymptotic growth rate of stochastically coupled two-degree-of-freedom systems. The noise is assumed to be white and of small intensity in order to calculate the explicit asymptotic formulas for the maximum Lyapunov exponent, The Lyapunov exponents and rotation number for each degree-of-freedom are obtained in the Appendix. The almost-sure stability or instability of the four-dimensional stochastic system depends on the sign of the maximum Lyapunov exponent. The results presented here match those presented by the first author and others using the method of stochastic averaging, where approximate Itoˆ equations in amplitudes and phase are obtained in the sense of weak convergence.
Simulation of Cone Bore Growth in Bearings With a Three-Ring Model
Authors: Neu R. W. , Sehitoglu Huseyin
Published: April 2008

Cone bore growth in case-carburized bearings was modeled by incorporating the mechanisms of thermal-induced phase transformation and low temperature creep in an approximate model of the cone. The inner case, core, and outer case regions of the bearing cone are modeled by three concentric rings. Using a mechanics of materials approach with the aid of some simplifying assumptions (i.e., radial stresses remain zero throughout the ring thickness and net circumferential strain is the same for all three rings), the influence of temperature, interference fit stresses, initial case carburizing stresses, and stress relaxation on the change in bore diameter and circumferential stress during service could be determined. The model indicated that both thermal-induced transformation and low temperature creep may play a role in bore growth during service. As temperature was increased from 70° C to 200°C, the susceptibility to bore growth became greater. Also, an increase in the interference fit increased the initial cone bore growth rate. In addition, the effect of the recondition treatment on the bore diameter and residual stresses was studied. The bore diameter generally decreased during the recondition treatment, and this was attributed to the relaxation of residual stresses by low temperature creep.