bluuebunny/crossref_metadata_2025 huggingface dataset:
An Examination of Transtheoretical Predictors of Condom Use in Late‐Adolescent Heterosexual Men1
Authors: Noar Seth M. , Morokoff Patricia J. , Redding Colleen A.
Published: March 2008

The purpose of the current study was to examine Transtheoretical Model (TTM) predictors of condom use in heterosexual men and to test the applicability of additional predictors of condom use (condom attitudes and interpersonal processes). Participants were 168 sexually active undergraduate men. Multiple regression analyses indicated that pros, condom self‐efficacy, condom attitudes, and processes of change were significant predictors of condom use. Several variables added unique variance above and beyond others, and a final model accounted for 55% of the variance in condom use. Results underscore the importance of TTM variables and interpersonal processes such as partner support in heterosexual men. Suggestions for how these variables might be incorporated into interventions aimed at increasing condom use are discussed.
The Impact of Ethnicity and Response Bias on the Self‐Report of Negative Affect1
Authors: Bardwell Wayne A. , Dimsdale Joel E.
Published: March 2008

Psychosocial self‐report measures are increasingly used in primary health care settings. This experiment examined the impact of response bias on self‐report of psychosocial information in 74 Blacks and 52 Whites. Participants completed the Center for Epidemiological Studies‐Depression (CES‐D), Cook‐Medley Hostility/Stress (CM), Buss‐Durkee Hostility (BD), and Marlowe‐Crowne Social Desirability (MCSDS) scales. Blacks reported greater negative affect than Whites on 2 of 15 scores, and their MCSDS scores were 30% higher. After using MCSDS scores as a covariate, Blacks showed significantly greater negative affect on 10 of 15 scores. Socioeconomic status did not explain the results. Response bias may affect self‐report of negative affect more in Blacks than Whites. Self‐report instruments may underestimate mood symptoms experienced by Blacks
The Perceived Efficacy and Risks of Complementary and Alternative Medicine and Conventional Medicine: A Vignette Study1
Authors: Furnham Adrian , Lovett Joanna
Published: March 2008

Participants (N= 148), including CAM users and general practitioner (GP) patients who had never used CAM treatments, read a series of 6 vignettes describing 3 medical conditions being treated using orthodox and CAM methods. As expected, results indicated that both CAM users and GP patients were more likely to agree that their own treatments were effective and were associated with fewer generic risks. Contrary to expectation, both CAM and GP patients were more likely to agree that orthodox treatments were associated with more actual risks than were CAM treatments, and all orthodox treatments for each medical condition were perceived as having more side effects than CAM treatments.
Stress, Active Coping, and Academic Performance Among Persisting and Nonpersisting College Students
Authors: Shields Nancy
Published: March 2008

This article compares the stress, active coping, and academic performance of college students who persisted through an academic year with the same measures among a group of students who left after the fall semester. The hypothesis that stress is related to active coping efforts among persisters, but not among nonpersisters, was strongly supported. However, the hypothesis that stress is related to higher grade point averages (GPAs) among persisters and lower GPAs among nonpersisters was not strongly supported. Stress had a negative effect on GPA among persisters, but there was some evidence of a positive indirect effect through active coping efforts. Finally, a logistic regression analysis found that active coping, thinking it was important to get to know other students, gender, enrollment in more credit hours, GPA, and not being employed lead to greater retention. Active coping was strongly related to retention, and men were more likely to persist. The study provides support for the idea that social support is an active form of coping and that behavioral measures of active coping may be beneficial in studying the relationship between stress and coping.
Variation in Galium palustre s. lat. in the Baltic land‐uplift area
Authors: Apelgren Karin , Lernstål Rolf
Published: March 2008

Morphological variation, chromosome numbers, reproductive system and ecology were studied in Galium palustre s. lat. in some areas in the Baltic land‐uplift area. Two cytotypes were found; diploids with 2n = 24 and octoploids with 2n = 96. Each cytotype comprises a large amount of habitat‐correlated variation. Despite this, it is fairly easy to destinguish morphologically between the two cytotypes. It is therefore suitable to treat the diploid cytotype as one species, Galium palustre s. str., and the octoploid cytotype as another species, Galium elongatum. Both species grow in wet places, such as ditches, lake‐shores and wet woodland. There are practically no differences in habitat ecology between them, but a slight tendency can be discerned for octoploids to grow in localities which never dry out, while diploids can grow in drier localities. Only G. palustre s. str. grows on fairly exposed sea‐shores. A morphologically distinct from can also be distinguished, including diploids from sea‐shores and coastal areas below 5 m. a. s. 1. This ecotype is described as Galium palustre var. balticum var. nov. It is characterised by smooth or nearly smooth stems and short, narrow leaves. It has always a very rich flowering and fruit set, which may be regarded as an adaptation to coastal conditions.
SEM‐studies and general comments on pollen in tribe Mutisieae (Compositae) sensu Cabrera
Authors: Hansen Hans V.
Published: March 2008

Data based on SEM‐studies of about 70 genera in tribe Mutisieae (Compositae) sensu Cabrera plus a few other relevant genera are presented with a discussion of some pollen‐morphologic characters (exomorphology and TEM‐patterns). The phyloge‐netically important aspects are shown to relate to the shape of the pollen grains, the presence or absence of polar elevations, and to the TEM‐patterns. The circumscription of tribe Mutisieae s.str. (i.e. excl. subtribe Barnadesiinae) is briefly considered, although palynological data are of little help for this purpose.
A new species of Miliusa (Annonaceae) from Andaman Islands, India
Authors: Goel Anil K. , Sharma S. C.
Published: March 2008

A new species Miliusa jainii (Annonaceae) from South Andamans, India, is described and illustrated.
Notes on the genus Erythrochlamys (Lamiaceae)
Authors: Ryding Olof
Published: March 2008

A new species of the genus Erythrochlamys is described: E. frulicosa from Somalia and Ethiopia. An interesting variation in E, leucosphaera is also discussed.
A new species of Lamproderma (Myxomycetes) found in Java
Authors: Gilert Elisabeth , Neuendorf Magnus
Published: March 2008

A new species, Lamproderma retkulospomm, is described from Java. It is characterized by small sporangia, peridium with smooth, elevated patches, capillitium with numerous swellings, and completely banded‐reticulate spores.
Physiological properties of human diaphragm muscle fibres and the effect of chronic obstructive pulmonary disease
Authors: Stubbings Alison K. , Moore Alastair J. , Dusmet Michael , Goldstraw Peter , West Timothy G. , Polkey Michael I. , Ferenczi Michael A.
Published: March 2008

The contractile and actomyosin ATPase properties of single fibres were examined in human diaphragm muscle obtained from patients with and without chronic obstructive pulmonary disease (COPD). Costal diaphragm biopsies were taken from five patients without evidence of COPD and from 11 age‐matched individuals with varying degrees of the disease. Our aim was to establish whether changes in contractile properties of COPD diaphragm could be fully explained by the previously documented shift towards a greater proportion of type I myosin heavy chain isoform in COPD. The relative proportion of type I diaphragm fibres from non‐COPD and COPD patients was measured by gel electrophoresis, and was negatively correlated with FEV1 over the full range of values investigated. There was also significant atrophy of the type I fibre population in COPD diaphragms. Isometric tension was similar among the fibre types and between the COPD and non‐COPD patients. The intrinsic energetic properties of diaphragm fibres were examined by monitoring the time‐resolved actomyosin ATPase activity in COPD and non‐COPD fibres that produced similar isometric forces. The isometric ATPase rate in COPD fibres was reduced to 50% of the rate in non‐COPD fibres; hence, the cost of isometric contraction in type I and type IIA COPD fibres was reduced to between one‐third and one‐half of the tension cost calculated for non‐COPD fibres. The rate of force development in type I COPD fibres was reduced to 50% of the rate seen in non‐COPD type‐I fibres. No difference in the rate of ATP consumption between COPD and non‐COPD fibres was evident during isovelocity shortening. These data extend previous findings showing that aspects of breathing mechanics during progressive COPD are associated with remodelling of the diaphragm fibre‐type distribution; on top of the increase in type I fibres there are fibre‐specific reductions in force development rate (type I fibres) and ATPase rate that are consistent with the impairment of cross‐bridge cycling kinetics.
Development of Elemental Technologies for Advanced Humid Air Turbine System
Authors: Kuroki Hidetoshi , Hatamiya Shigeo , Shibata Takanori , Koganezawa Tomomi , Kizuka Nobuaki , Marushima Shinya
Published: April 2008

The advanced humid air turbine (AHAT) system improves the thermal efficiency of gas turbine power generation by using a humidifier, a water atomization cooling (WAC) system, and a heat recovery system, thus eliminating the need for an extremely high firing temperature and pressure ratio. The following elemental technologies have been developed to realize the AHAT system: (1) a broad working range and high-efficiency compressor that utilizes the WAC system to reduce compression work, (2) turbine blade cooling techniques that can withstand high heat flux due to high-humidity working gas, and (3) a combustor that achieves both low NOx emissions and a stable flame condition with high-humidity air. A gas turbine equipped with a two-stage radial compressor (with a pressure ratio of 8), two-stage axial turbine, and a reverse-flow type of single-can combustor has been developed based on the elemental technologies described above. A pilot plant that consists of a gas turbine generator, recuperator, humidification tower, water recovery system, WAC system, economizer, and other components is planned to be constructed, with testing slated to begin in October 2006 to validate the performance and reliability of the AHAT system. The expected performance is as follows: thermal efficiency of 43% (LHV), output of 3.6MW, and NOx emissions of less than 10ppm at 15% O2. This paper introduces the elemental technologies and the pilot plant to be built for the AHAT system.
Brazing and Wide Gap Repair of X-40 Using Ni-Base Alloys
Authors: Schoonbaert Stephen , Huang Xiao , Yandt Scott , Au Peter
Published: April 2008

Co-base superalloys are commonly used for vanes and parts of the combustion chamber in gas turbine engines. The Co-base superalloys are primarily solid solution strengthened and have good resistance to hot corrosion, creep, and thermal fatigue. In particular, Co-base alloy X-40 was used to fabricate the first stage NGV airfoils of T56 series engines; inspections after service have revealed that X-40 airfoils suffered from severe thermal fatigue damages. In this study, a new braze repair scheme is proposed; in which Ni-base alloys are used to repair the X-40 substrate in both narrow and wide gap configurations. Metallographic examination, X-ray mapping, and energy dispersive spectroscopy semiquantitative compositional analyses were carried out to study the microstructures in the braze joint in the as-brazed condition and after thermal exposure at 950°C. The results obtained so far suggest the formation of Cr-rich borides, eutectic phases, and various carbides in the joint. No TCP phases were found in the brazed joint and base metals adjacent to the joint. The high carbon content in the alloy X-40 may have played an important role in preventing the formation of TCP phases during brazing and subsequent thermal exposure.
Effects of Interleaves on Fracture of Laminated Composites: Part I—Analysis
Authors: Kaw A. K. , Goree J. G.
Published: April 2008

The influence of placing interleaves between fiber-reinforced plies in multilayered composite laminates is investigated. The geometry of the composite is idealized as a two-dimensional, isotropic, linearly elastic media consisting of a damaged layer bonded between two half-planes and separated by thin interleaves of low extensional and shear moduli. The damage in the layer is taken in the form of a symmetric crack perpendicular to the interface. The case of an H-shaped crack in the form of a broken layer with delamination along the interface is also analyzed. Fourier integral transform techniques are used to develop the solutions in terms of singular integral equations.
Dynamics and Stability of a Flexible Cylinder in a Narrow Coaxial Cylindrical Duct Subjected to Annular Flow
Authors: Paidoussis M. P. , Mateescu D. , Sim W.-G.
Published: April 2008

This paper considers analytically the dynamics of a flexible cylinder in a narrow coaxial cylindrical duct, subjected to annular flow. In the present analysis, in contrast to existing theory, the viscous forces are not derived by an adaptation of Taylor’s unconfined-flow relationships, but by a systematic, albeit approximate, solution of the Navier-Stokes equations, which accounts for the unsteady viscous effects much more fully than heretofore; it is found that, for very narrow annuli, the contribution of these unsteady viscous forces to the overall unsteady forces on the cylinder can be much larger than that of the steady skin friction and pressure-drop effects alone. The present analysis also differs from existing theory in that the in-viscid forces are not derived via the slender-body approximation, and hence the analysis is also applicable to bodies of relatively small length-to-radius ratio. The dynamics and stability of typical systems with fixed ends is investigated, concentrating mainly on viscous effects and comparing the results with those of previous work. It is found that, as the annular gap becomes narrower, the system loses stability by divergence at smaller flow velocities, provided the gap size is such that inviscid fluid effects are dominant. For very narrow annuli, however, where viscous forces predominate, this trend is reversed, and further narrowing of the annular gap has a stabilizing effect on the system; furthermore, in some cases the system loses stability by flutter rather than divergence.
Elastoplastic Finite Element Analysis of Three-Dimensional, Pure Rolling Contact at the Shakedown Limit
Authors: Kulkarni S. M. , Hahn G. T. , Rubin C. A. , Bhargava V.
Published: April 2008

This paper describes a three-dimensional elastoplastic finite element model of repeated, frictionless rolling contact. The model treats a sphere rolling on an elastic-perfectly plastic and an elastic-linear-kinematic-hardening plastic, semi-infinite half space. The calculations are for a relative peak pressure (po/k) = 4.68 (the theoretical shakedown limit for perfect plasticity). Three-dimensional rolling contact is simulated by repeatedly translating a hemispherical (Hertzian) pressure distribution across an elastoplastic semi-infinite half space. The semi-infinite half space is represented by a finite mesh with elastic boundaries. The calculations describe the distortion of the rim, the residual stress-strain distributions, stress-strain histories, and the cyclic plastic strain ranges in the vicinity of the contact.
Creep of a Hollow Sphere
Authors: Sakaki T. , Kuroki T. , Sugimoto K.
Published: April 2008

Using internal stress arising from a spherically symmetric, finite plastic strain, creep of a hollow sphere subjected to inner and outer pressures, and also thermal stress, is discussed. If computer-aided numerical calculation method is used, creep is easily followed up to a finite plastic strain range including initial transient creep, whatever type of creep law is employed. If assumed in a steady state, creep rate, stress, small plastic strain leading to a stress state in steady creep, and another small plastic strain relaxing thermal stress are analytically obtained. Numerical method is also applicable to creep relaxation. Further, the origin of residual stress after unloading is clarified.
Rayleigh and Love Waves in Cladded Anistropic Medium
Authors: Bouden M. , Datta S. K.
Published: April 2008

Guided waves in coated anisotropic medium are of interest in electronics. Also, in recent years, cladded fiber-reinforced composites are being developed for use as aerospace structures. This paper deals with guided wave propagation in a cladded or coated anisotropic medium. The cladding (coating) is assumed to be a thin isotropic layer, which is bonded to a transversely isotropic substrate with the axis of symmetry parallel to the layer. It is shown that the anisotropy of the substrate affects the dispersion behavior in a manner that is substantially different than in the case of isotropic substrate.
An Analysis of Shear Localization During Bending of a Polycrystalline Sheet
Authors: Becker R.
Published: April 2008

The development of shear localization in a polycrystalline sheet subject to pure bending is analyzed numerically using a slip-based constitutive model. The material response at each finite element integration point is determined by averaging the stiffness matrices from differently oriented FCC crystals. The effects of texture evolution, hardening, and strain-rate sensitivity are incorporated. The model predicts localized plastic deformation at both the tensile and the compressive surfaces of the sheet during bending. Comparison of the numerical results with a section of the bent sheet indicates that strain localization is predicted at the appropriate strain levels and orientations.
Interfacial Slippage of a Unidirectional Fiber Composite Under Longitudinal Shearing
Authors: Teng Hong , Agah-Tehrani A.
Published: April 2008

Interfacial slippage of a unidirectional fiber composite under longitudinal shearing is analyzed. The finite concentration of fibers has been taken into account by utilizing the composite cylinder model in the formulation of the problem. The resulting mixed boundary value problem leads to a system of dual series equations, which is then reduced to a Fredholm integral equation of the first kind with a logarithmic singularity. The extent of slip region, which depends on the level of applied load along with the distribution of shear tractions at the fiber-matrix interface, is determined by solving the integral equation numerically.
Influence of Porosity on Plane Strain Tensile Crack-Tip Stress Fields in Elastic-Plastic Materials: Part I
Authors: Drugan W. J. , Miao Y.
Published: April 2008

We perform an analytical first study of the influence of a uniform porosity distribution, for the entire range of porosity level, on the stress field near a plane strain tensile crack tip in ductile material. Such uniform porosity distributions (approximately) arise in incompletely sintered or previously deformed (e.g., during processing) ductile metals and alloys. The elastic-plastic Gurson-Tvergaard constitutive formulation is employed. This model has a sound micromechanical basis, and has been shown to agree well with detailed numerical finite element solutions of, and with experiments on, voided materials. To facilitate closed-form analytical results to the extent possible, we treat nonhardening material with constant, uniform porosity. We show that the assumption of singular plastic strain in the limit as the crack tip is approached renders the governing equations statically determinate with two permissible types of near-tip angular sector: one with constant Cartesian components of stress (“constant stress”); and one with radial stress characteristics (“generalized centered fan”). The former admits an exact asymptotic closed-form stress field representation, and although we prove the latter does not, we derive a highly accurate closed-form approximate representation. We show that complete near-tip solutions can be constructed from these two sector types for the entire range of porosity. These solutions are comprised of three asymptotic sector configurations: (i) “generalized Prandtlfield”for low porosities (0 ≤ f ≤ .02979), similar to the plane strain Prandtl field of fully dense materials, with a fully continuous stress field but sector extents that vary with porosity; (ii) “plane-stress-like field” for intermediate porosities (.02979 < f < .12029), resembling the plane stress solution for fully dense materials, with a ray of radial normal stress discontinuity but sector extents that vary with porosity; (iii) two constant stress sectors for the remaining high porosity range, with a ray of radial normal stress discontinuity and fixed sector extents. Among several interesting features, the solutions show that increasing porosity causes significant modification of the angular variation of stress components, particularly for a range of angles ahead of the crack tip, while also causing a drastic reduction in maximum hydrostatic stress level.
Unilateral Contract of a Springboard and a Fulcrum
Authors: Kuipers M. , van de Ven A. A. F.
Published: April 2008

A springboard, as commonly used in diving, is considered. It is hinged at the rear end and rests free on a rubber fulcrum at the middle of the board. If an excentric load is applied to its front end, then due to torsion it is possible that the board is lifted away from the fulcrum along a certain distance. This problem is investigated for a static load. Although a linear small displacement theory is applied, the problem is nonlinear due to the unknown length of noncontact.
Stability of the Vertical Autorotation of a Single-Winged Samara
Authors: Seter D. , Rosen A.
Published: April 2008

A numerical model to investigate the stability of the vertical autorotation of a singlewinged samara is presented. This model is obtained after the method of small perturbations about an equilibrium state is applied on the nonlinear equations of motion of the samara. The aerodynamic stability derivatives of the wing are obtained by numerical differentiation. The model is used in order to study the influence of different parameters on the stability. Since the stability is highly dependent on the basic equilibrium state, the influence of the different parameters on the basic state is also presented and discussed. The theoretical model is validated by comparing its results with qualitative experimental results.
Further Aspects of the Elastic Field for Two Circular Inclusions in Antiplane Elastostatics
Authors: Honein E. , Honein T. , Herrmann G.
Published: April 2008

The heterogenization technique, recently developed by the authors, is applied to the problem, in antiplane elastostatics, of two circular inclusions of arbitrary radii and of different shear moduli, and perfectly bonded to a matrix, of infinite extent, subjected to arbitrary loading. The solution is formulated in a manner which leads to some exact results. Universal formulae are derived for the stress field at the point of contact between two elastic inclusions. It is also discovered that the difference in the displacement field, at the limit points of the Apollonius family of circles to which the boundaries of the inclusions belong, is the same for the heterogeneous problem as for the corresponding homogeneous one. This discovery leads to a universal formula for the average stress between two circular holes or rigid inclusions. Moreover, the asymptotic behavior of the stress field at the closest points of two circular holes or rigid inclusions approaching each other is also studied and given by universal formulae, i.e., formulae which are independent of the loading being considered.
Sliding Inclusions and Inhomogeneities With Frictional Interfaces
Authors: Furuhashi R. , Huang Jin H. , Mura T.
Published: April 2008

Elastic fields due to a sliding inclusion and inhomogeneity with the frictional interface are investigated. The exact solution in closed form is presented for three cases: (i) a spherical inclusion which undergoes constant eigenstrains, (ii) a nondegenerate ellipsoidal inclusion with uniform shear eigenstrains and (iii) a nondegenerate ellipsoidal inhomogeneity subjected to an applied shear stress at infinity. Moreover, the existence of solution for a sliding inclusion and inhomogeneity with frictional interface is also demonstrated.
The Distribution of Simultaneous Fiber Failures in Fiber Bundles
Authors: Hemmer Per C. , Hansen Alex
Published: April 2008

A bundle of many parallel fibers, with stochastically distributed thresholds for individual fibers, is loaded until complete failure. Equal load sharing is assumed. During the breakdown process, bursts of several fibers breaking simultaneously at a given load occur. We determine the expected number of such bursts before complete failure, as well as the frequency of bursts in which Δ fibers break simultaneously. This distribution follows asymptotically a universal power-law Δ−5/2, for any statistical distribution of the individual fiber strengths.
An Evaluation of Convex Modeling for Multimode Dynamic Buckling
Authors: Lindberg Herbert E.
Published: April 2008

Convex and probabilistic model solutions are obtained for multimode dynamic buckling of cylindrical shells with uncertain imperfections under symmetric radial impulsive loads. It is found that the maximum possible buckling deformations for any imperfection within uniform bounds ± δˆ can be made comparable to the buckling deformations from the probabilistic models at a reliability of about 99.5 percent. Numerical evaluation and interpretation of the convex model is much simpler than for the probabilistic models, and the convex model solution provides means for quality control of each and every shell by simply recording δˆ from appropriately filtered imperfection measurements. The power and simplicity of convex modeling for multimode buckling shows promise for more complex problems than require finite element modal analysis.
Analytical Solutions for Nonlinear Strain-Gradient Softening and Localization
Authors: Schreyer H. L.
Published: April 2008

Strain softening, no matter how small, is usually accompanied by localization of the softening deformation field. Inside the zone of localization, a decrease in stress is accompanied by an increase in strain; outside the zone the strain decreases. One way to describe this phenomenon is to use a nonlocal theory of plasticity in which the yield stress depends on an invariant of the gradient of plastic strain. In this paper analytical solutions to two problems are obtained for the case where the functional dependence on the invariant is quadratic. The solutions are interpreted and correlations are made between predictions of load softening and the size of the localization zone based on material parameters and experimental data. Consistency with thermodynamical restrictions is shown.
Anisotropic Distortional Yield Model
Authors: Voyiadjis George Z. , Foroozesh Mehrdad
Published: April 2008

A yield surface model is proposed in this work which may be adapted to both small strain and large strain offset definitions of yielding. The proposed anisotropic distortional yield model is capable of translation, uniform expansion or contraction, as well as distortion of the subsequent yield surface. Two versions of the proposed model are introduced through variations in fourth-order anisotropy tensor M of the yield surface. Experimental observations by Phillips and co-workers (1973, 1974, 1977, 1979, 1985), Helling et al. (1986), and Stout et al. (1985) are taken into consideration in the development of the proposed model. The corresponding fourth-order elastoplastic stiffness matrix is formulated and specific examples are given.
Constraints on Moving Strong Discontinuity Surfaces in Dynamic Plane-Stress or Plane-Strain Deformations of Stable Elastic-Ideally Plastic Materials
Authors: Shen Yinong , Drugan W. J.
Published: April 2008

For dynamic deformations of compressible elastic-ideally plastic materials in the practically important cases of plane stress and plane strain, we investigate the possible existence of propagating surfaces of strong discontinuity (across which components of stress, strain, or material velocity jump) within a small-displacement-gradient formulation. For each case, an explicit proof of the impossibility of such a propagating surface (except at an elastic wave speed) is achieved for isotropic materials satisfying a Huber-Mises yield condition and associated flow rule, and we show that our method of proof can be generalized to a large class of anisotropic materials. Nevertheless, we demonstrate that moving surfaces of strong discontinuity cannot be ruled out for all stable (i.e., satisfying the maximum plastic work inequality) materials, as in the case of a material whose yield surface contains a linear portion. A clear knowledge of the conditions under which dynamically propagating strong discontinuity surfaces can and cannot exist is crucial to the attainment of correct and complete solutions to such practical elastic-plastic problems as dynamic crack propagation, impact and rapidly moving load problems, high-speed forming, cutting, and other manufacturing processes.
A Dislocation Green’s Function for the Analysis of Multiple Coplanar Cracks or Cracks With Nonuniform Crack Fronts
Authors: Hanson M. T.
Published: April 2008

This analysis considers the interaction between a penny-shaped crack or a circular external crack and a mode I “opening” point dislocation. The dislocation is taken to lie on the plane of the crack. Symmetry considerations allow the reduction to a mixed boundary value problem for a half space which is solved by well-known methods from potential theory. Closed-form expressions are obtained for the crack opening displacement, stress on the symmetry plane, and the mode I stress intensity factor around the internal or external crack. The use of the present solution for the accurate numerical treatment of cracks with large amplitude variations in the crack front curvature as well as cases of multiple coplanar cracks is outlined.
An Arbitrary Tangential Load Underneath a Smooth Circular Punch
Authors: Fabrikant V. I.
Published: April 2008

The problem of a smooth circular punch penetrating a transversely isotropic elastic half space and interacting with an arbitrarily located tangential concentrated load is considered. For the first time, a closed-form exact solution is obtained for the stress distribution under the punch as well as for the linear and angular displacements of the punch. The solution is based on the results previously obtained by the author and combined with the reciprocal theorem. A numerical example is presented as an illustration.
The Meniscus Instability in Non-Newtonian Negative Squeeze Films
Authors: Koguchi Hideo , Yada Toshio
Published: April 2008

This paper treats an instability at the free surface of non-Newtonian (power-law) fluid films between two tilted plates in a negative squeeze motion. The meniscus instability in a fluid with the power-law constitutive equation was analyzed on the basis of the linear stability theory. In the analysis, a capillary number for the power-law fluid was newly defined and the relationship between the capillary number and the criterion for the instability of meniscus was theoretically deduced. In the experiment, a water solution of polyacrylamide (separan) whose viscosity obeys a power-law of the strain rate was used as a sample fluid, the meniscus instability in the fluid was examined by using a VTR and the wavelength of disturbances was measured. The theoretical criterion for the instability was in good agreement with experiments and the capillary number could rearrange well the experimental results for the disturbances.
Flexural Waves in a Periodic Beam
Authors: Lee Sen Yung , Ke Huei Yaw , Kao Ming Jang
Published: April 2008

The flexural wave propagation in the periodic beam can be interpreted as the superposition of two pairs of waves propagating in opposite directions. One of them forms an attenuated standing wave. The dispersion spectrum of the other pair of waves shows the band structure, consisting of stopping and passing bands. For the symmetry structure, the dispersion equation at the end points of Brillouin zone is uncoupled into two equations. Each of them corresponds to a standing wave which is either symmetric or antisymmetric about the midplane of the layers.
The Hertzian Cone Crack
Authors: Yingzhi Li , Hills D. A.
Published: April 2008

Stress intensity factors are determined for cracks in the form of a frustum of a cone, and loaded by a Hertzian contact pressure distribution using a global-local finite element solution. These will be helpful in interpreting blunt indentation tests quantitatively, and it is shown that for most crack geometries occurring in practice, the mode II component is about a tenth of the mode I contribution.
Equations of Elastic Deformation of Laminated Composite Shallow Shells
Authors: Leissa A. W. , Qatu M. S.
Published: April 2008

Shallow shells of laminated composite materials are being increasingly used in structural applications. A complete and consistent theory is needed to deal with elastic deformation problems (i.e., static deflections and stresses, free and forced vibrations). The present work develops equations of motion, which may be solved either exactly or by an approximate method (e.g., Galerkin, finite differences) and energy functionals which may be used with the Ritz or finite element methods to obtain approximate solutions. The equations are developed in terms of arbitrarily-oriented (i.e., nonprincipal) shell coordinates, including twist as well as radii of curvature. The equations account for arbitrary layer thicknesses, fiber orientations, and stacking sequences. Shear deformation and rotary inertia effects are neglected.
Accurate Analytical-Type Solutions for the Free Vibration of Simply-Supported Parallelogram Plates
Authors: Gorman D. J.
Published: April 2008

A comprehensive study of the free vibration of simply-supported parallelogram plates is conducted. Solutions are obtained by utilizing the superposition method and by taking advantage of symmetry inherent in the problem. Toward this end a new alternating Le´vy-type solution is introduced. Verification tests are conducted by comparing computed eigenvalues with those of rhombic plates in the special case where all plate edges are of equal length. Eigenvalues are stored for eight vibration modes and for a wide range of plate geometry.
Calculations of Strains and Internal Displacement Fields Using Computerized Tomography
Authors: Gu R. J. , Hovanesian J. D. , Hung Y. Y.
Published: April 2008

A novel treatment of computerized tomography is developed to calculate strains and displacements at internal nodes from known boundary displacements. The formulation is blended with finite element numerical scheme. Numerical simulations are performed to verify accuracy of this new technique using several plane problems whose solutions exist in closed form. Excellent agreement shows the potential of developing the tomographic technique into a hybrid numerical-experimental method for solving mechanics problems.
Growth Instability During Nonuniform Directional Solidification of a Pure Metal Plate
Authors: Hector Louis G. , Aksel Bulent , Fridy Joseph
Published: April 2008

The singly periodic beam theory of freezing front growth instability in pure metal castings due to Richmond et al., (1990) is extended here to the more general case of a doubly periodic plate. The casting is cooled with a doubly periodic heat flux which oscillates along two orthogonal axes of the mold/casting interface. The cooling profile induces nonuniform growth of the freezing front and hence a strain distribution in the casting that leads to contraction of the metal at specific locations along the mold interface. Metal contraction is studied through calculation of the interface pressure. Growth instability occurs when the pressure falls to zero beneath a thickness minimum, thereby signalling the nucleation of an air gap, and simultaneously increases beneath a thickness maximum thereby enhancing the initial nonuniformity of the freezing front. The significant differences between the beam and plate theories for a given pure metal are found in the more extreme stress levels which accumulate within the plate, the magnitude of the admissible uniform cooling term and hence predicted times to air gap nucleation, and casting thickness at air gap nucleation as well as interface pressures beneath thickness maxima. The doubly periodic plate theory permits larger uniform cooling and hence earlier air gap nucleation beneath thickness minima than does the singly periodic beam theory with more severe interface pressures beneath thickness maxima.
Elasto-Plastic Finite Element Analysis of Three-Dimensional Pure Rolling Contact Above the Shakedown Limit
Authors: Kulkarni S. M. , Hahn G. T. , Rubin C. A. , Bhargava V.
Published: April 2008

This paper describes calculations for repeated, frictionless, three-dimensional rolling contact, for a relative peak pressure (po/k) of 6.0 (above the shakedown limit) for a circular contact patch. This analysis was carried out for two material responses, elastic-perfectly plastic (EPP) and elastic-linear-kinematic-hardening plastic (ELKP), using the elasto-plastic finite element model developed earlier. The ELKP material parameters are those appropriate for hardened bearing steel. Frictionless three-dimensional rolling contact is simulated by repeatedly translating a Hertzian pressure distribution across the surface of an elasto-plastic half space. The half space is represented by a finite mesh with elastic boundaries. The paper describes the complex stress state existing in the half space and the attending plasticity, as the load translates. The calculations present the distortion of the rim, the residual stress-strain distributions, stress-strain histories, and the cyclic plastic strain increments in the vicinity of the contact. Compared with the analyses at the shakedown limit, higher residual stresses and strains are observed.
Antiplane Shear Interface Cracks in Anisotropic Bimaterials
Authors: Wu Kuang-Chong , Chiu Yu-Tsung
Published: April 2008

An analysis of antiplane shear interface cracks in a finite anisotropic composite body is presented. The analysis is done by a new complex-variable integral equation formulation based on the solutions of a dislocation and body force in an infinite composite body. Numerical results of the stress intensity factors are presented for the composite bodies with finite rectangular cross-sections under uniform shear. The composite bodies are formed by bonding an orthotropic material to an isotropic material. The numerical results show that there exists a lower bound for the stress intensity factor for a fixed crack-length-to-height ratio and that the lower bound is attained in the case of isotropic bimaterial.
Analysis of Embedded and Surface Elliptical Flaws in Transversely Isotropic Bodies by the Finite Element Alternating Method
Authors: Rajiyah H. , Atluri S. N.
Published: April 2008

The general analytical solution to the problem of a flat elliptical crack embedded in an infinite, transversely isotropic solid, oriented perpendicular to the axis of elastic symmetry, is derived along the lines of Vijayakumar and Atluri’s solution procedure for the isotropic case. The prior work of Kassir and Sih on this problem is limited to some constant and linear variations of normal and shear tractions on the crack face. The generalized solution is employed in the Schwarz-Neumann alternating method in conjunction with the finite element method. Such a method of analysis is shown to be an efficient way to evaluate the stress intensity factors along the flaw border.
On Damping of the Normal Component of Fluctuations in the Wall Region of Turbulent Flow
Authors: Kozlowski Wlodzimierz
Published: April 2008

Effective model representation of the normal component of ordered motions in the wall region of a turbulent flow is proposed. Analysis of this model enables us to express the value given by the Van Driest damping function at a point with coordinate y (distance to the wall) as a relationship between intensities of the normal component of pulsations which are defined at points 2y, y, and y/2. The novel formula has no empirical coefficients and can successfully replace the Van Driest function in computations. It appears to take account of the damping effect which results locally from distinct classes of ordered motions directed wallwards or outwards within the wall region of a turbulent flow.
An Alternative Approach to the Symmetrical Top and Slender Member Analysis
Authors: Madsen Nels
Published: April 2008

This Note considers the problem of a symmetrical top under the action of gravity, or analogously the problem of a long, slender, initially straight linearly elastic, circular cross-section member loaded only at its ends. A nonbody fixed coordinate system is used. The standard results are obtained without any explicit reference to a space-fixed coordinate system.
An Expression of Elastic-Plastic Constitutive Law Incorporating Vertex Formation and Kinematic Hardening
Authors: Goya Moriaki , Ito Koichi
Published: April 2008

A phenomenological corner theory was proposed for elastic-plastic materials by the authors in the previous paper (Goya and Ito, 1980). The theory was developed by introducing two transition parameters, μ (α) and β (α), which, respectively, denote the normalized magnitude and direction angle of plastic strain increments, and both monotonously vary with the direction angle of stress increments. The purpose of this report is to incorporate the Bauschinger effect into the above theory. This is achieved by the introduction of Ziegler’s kinematic hardening rule. To demonstrate the validity and applicability of a newly developed theory, we analyze the bilinear strain-path problem using the developed equation, in which, after some linear loading, the path is abruptly changed to various directions. In the calculation, specific functions, such as μ (α) = Cos (.5πα/αmax) and β (α) = (αmax- .5π) α/αmax, are chosen for the transition parameters. As has been demonstrated by numerous experimental research on this problem, the results in this report also show a distinctive decrease of the effective stress just after the change of path direction. Discussions are also made on the uniqueness of the inversion of the constitutive equation, and sufficient conditions for such uniqueness are revealed in terms of μ(α), β(α) and some work-hardening coefficients.
Dynamic Damage in Certain Monolithic Ceramic Materials
Authors: Giannakopoulos A. E.
Published: April 2008

In the present work, the propagation of elasto-damage longitudinal stress waves in thin rods is investigated. The material behavior is characteristic to that of certain monolithic ceramics. The damage constitutive relation that characterizes this type of materials gives rise to certain dynamic behavior which is somewhat different from dynamic plastic behavior. Plastic and damage dynamic response are compared through an example.
Viscoplastic Deformation Analysis and Extrusion Die Design by FEM
Authors: Aravamadhu Balaji P. , Sundararajan T. , Lal G. K.
Published: April 2008

A viscoplastic model for extrusion is discussed which simultaneously predicts the deformation field, optimal die geometry, and plastic boundaries. The die geometry and plastic boundaries are expressed in terms of chosen trial functions that satisfy certain geometrical and physical constraints. The variational power integral is minimized in the trial plastic domain using FEM technique to determine the deformation field and shape coefficients for the die contour and plastic boundaries. The proposed method is implemented for the optimal design of an axisymmetric streamlined die. The predicted values are in reasonable agreement with the experimental observations and are in conformity with the results published earlier.
Analytical Solutions for the Plane-Strain Bifurcation of Compressible Solids
Authors: Bardet J. P.
Published: April 2008

Analytical solutions are presented for the diffuse and localized bifurcations of compressible solids subjected to plane-strain loadings. The solutions generalize the works for incompressible solids of Biot (1965) and Hill and Hutchinson (1975). They are verified by comparing them to results previously established for incompressible solids and elastoplastic Mohr-Coulomb materials.
Effect of Pleural Membrane on the Propagation of Rayleigh-Type Surface Waves in Inflated Lungs
Authors: Man Chi-Sing , Jahed Mehran , Lai-Fook Stephen J. , Bhagat Pramode K.
Published: April 2008

We model the lung parenchyma as an elastic half-space and the pleura as a taut elastic membrane in smooth or in welded contact with the half-space. In each instance we deduce that the presence of a sufficiently high surface tension T in the pleural membrane will lead to the existence of a cutoff frequency f0 for the Rayleigh-type surface waves, and we derive an equation which gives T in terms of f0 and parameters that characterize the layered medium. We performed experiments on four inflated horse lungs at transpulmonary pressures of 5, 10, and 15 cmH2O. A comparison of the experimental results and the theoretical predictions provides an empirical test to the validity of the modeling.
A Note on Rotor Instability Caused by Liquid Motions
Authors: Holm-Christensen O. , Tra¨ger K.
Published: April 2008

The stability conditions of a hollow rotor partially filled with a Newtonian liquid are investigated. The rotor is considered here to be a rigid body, supported by springs and dampers, and exposed to an external dynamic force in the shape of actions of the encountered liquid. The system has two degrees-of-freedom, defined by deflection in two mutually orthogonal fixed directions perpendicular to the rotor axis. The fluid motions are described by Navier-Stokes equations and comparison is made between the inviscid and viscous case in connection with their predictions of the stability conditions. Experiments are performed with two different rigidity ratios and results are found to be in agreement with theoretical data.
Analytical Estimation for Static Deformation of Wire Ropes With Fibrous Core
Authors: Kumar K. , Cochran J. E.
Published: April 2008

This papers develops closed-form solutions for the extension of twisted wire ropes with fibrous cores which are subjected to axial forces as well as axial moments. The analytical results are compared with the corresponding numerical results obtained by Costello and Phillips. A close agreement between the two establishes validity of the analytical solutions. Finally, an expression for the effective rigidity modulus of wire ropes with fibrous core is obtained in terms of the helix angle and the number of helical wires in the rope for each of the two end conditions.
Density Effects in Two-Dimensional Bins
Authors: Kruyt N. P.
Published: April 2008

Various theories exist for predicting the pressure on the walls of bins filled with granular material. These theories, such as Janssen’s (1895) theory, usually neglect the effect of the compressibility of the granular material, which is relevant for many materials. Here this effect is studied numerically, and the results are compared with a new approximate theory. This comparison shows that the agreement is excellent.
On Kinematical Assumptions of Refined Theories of Plates: A Survey
Authors: Jemielita G.
Published: April 2008

The paper presents a survey of the kinematical hypotheses and the governing equations of the refined theories of plates. By carrying out a comparative analysis of various, apparently different, kinematical hypotheses proposed by various authors, it is shown that the kinematical hypothesis by Vlasov (1957) is a pattern for all of them.