Academic literature on the topic 'Normal stress continuity'
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Journal articles on the topic "Normal stress continuity"
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Khattatov, Eldar, and Ivan Yotov. "Domain decomposition and multiscale mortar mixed finite element methods for linear elasticity with weak stress symmetry." ESAIM: Mathematical Modelling and Numerical Analysis 53, no. 6 (November 2019): 2081–108. http://dx.doi.org/10.1051/m2an/2019057.
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Two non-overlapping domain decomposition methods are presented for the mixed finite element formulation of linear elasticity with weakly enforced stress symmetry. The methods utilize either displacement or normal stress Lagrange multiplier to impose interface continuity of normal stress or displacement, respectively. By eliminating the interior subdomain variables, the global problem is reduced to an interface problem, which is then solved by an iterative procedure. The condition number of the resulting algebraic interface problem is analyzed for both methods. A multiscale mortar mixed finite element method for the problem of interest on non-matching multiblock grids is also studied. It uses a coarse scale mortar finite element space on the non-matching interfaces to approximate the trace of the displacement and impose weakly the continuity of normal stress. A priori error analysis is performed. It is shown that, with appropriate choice of the mortar space, optimal convergence on the fine scale is obtained for the stress, displacement, and rotation, as well as some superconvergence for the displacement. Computational results are presented in confirmation of the theory of all proposed methods.
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Blanco, Pablo J., Simone Deparis, and A. Cristiano I. Malossi. "On the continuity of mean total normal stress in geometrical multiscale cardiovascular problems." Journal of Computational Physics 251 (October 2013): 136–55. http://dx.doi.org/10.1016/j.jcp.2013.05.037.
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Yu, Kai Qin, Yin Fei Yang, Liang Li, Ning He, Bo Chen, and Xue Feng Zhang. "Residual Stresses Measurement Base on Three Reference Points Theory Using Contour Method." Materials Science Forum 800-801 (July 2014): 726–30. http://dx.doi.org/10.4028/www.scientific.net/msf.800-801.726.
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The objective of this work is to measure the residual stress normal to the cut plane which has a large size using contour method. Translations and rotations are applied to the second point cloud to assure the continuity of the contour. There is still the same work on the opposing cut plane, align and combine the two contour datasets, perform the interpolation and then integrate with a finite element modelling package to apply many thousands of different boundary conditions. The finite element result shows a good continuity indicating the success of transformation means applied on the point cloud. The result gets the stress distribution normal to the cut plane. Beam forming is simulated to study the residual stress distribution of the stretch-wrap bend forming, the residual stress from contour method and forming simulation present the same trend.
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Carrera, E. "A Reissner’s Mixed Variational Theorem Applied to Vibration Analysis of Multilayered Shell." Journal of Applied Mechanics 66, no. 1 (March 1, 1999): 69–78. http://dx.doi.org/10.1115/1.2789171.
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A comprehensive model of anisotropic multilayered double curved shells fulfilling a priori the interlaminar continuity requirements for the transverse shear and transverse normal stress as well as the static conditions on the bounding surfaces of the shell is developed in this paper. To this end, Reissner’s mixed variational theorem is employed to derive the equations governing the dynamic equilibrium and compatibility of each layer, while the interlaminar continuity conditions are used to drive the equations at the multilayered level. No assumptions have been made concerning the terms of type thickness to radii shell ratio h/R. Classical displacement formulations and related equivalent single layer equations have been derived for comparison purposes. Comparison of frequency predictions based upon the presented structural model with a number of results spread throughout the specialized literature and obtained via other models reveals that this advanced model provides results in excellent agreement with the ones based on three-dimensional elasticity theory, and better as compared to the ones violating the interlaminar stress continuity requirements and/or transverse normal stress and related effects.
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Abo-Dahab, S. M. "Propagation of p-, T-, and SV-waves at the interface between two solid–liquid media with magnetic field and initial stress in the context of two thermoelastic theories." Canadian Journal of Physics 93, no. 7 (July 2015): 807–23. http://dx.doi.org/10.1139/cjp-2014-0193.
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In this paper, we study the effects of magnetic field and initial stress on p-, T-, and SV-waves propagation. We investigated the problem of reflection and refraction of thermoelastic waves at a magnetized solid–liquid interface in the presence of initial stress. In the context of classical theory and Green–Lindsay theory of thermoelasticity, the problem has been solved. The boundary conditions applied at the interface are: (i) displacement continuity; (ii) vanishing tangential displacement; (iii) continuity of normal force per unit initial area; (iv) tangential force per unit initial area must vanish; and (v) continuity of temperature. The amplitudes ratios for the incident p-, T-, and SV-waves have been obtained. The reflection and transmittion coefficients from the incident waves are computed numerically, considering the initial stress and magnetic field effect and the results obtained have been presented graphically.
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Wang, X., and G. Shi. "A simple and accurate sandwich plate theory accounting for transverse normal strain and interfacial stress continuity." Composite Structures 107 (January 2014): 620–28. http://dx.doi.org/10.1016/j.compstruct.2013.08.033.
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Brown, L. M. "Indentation Size Effect and the Hall-Petch ‘Law’." Materials Science Forum 662 (November 2010): 13–26. http://dx.doi.org/10.4028/www.scientific.net/msf.662.13.
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The flow of material out from under regions in compression must occur by the operation of many slip systems, which together produce rotational flow. Such flow requires the accumulation of geometrically necessary dislocations, and leads to the indentation size effect: smaller indents produce higher hardness, a component of the hardness being inversely proportional to the square-root of the indenter size. A pattern of flow in polycrystals which satisfies both continuity of normal stress and continuity of matter at boundaries can be achieved by rotational flow, and it leads to a grain-size effect. Under most circumstances, the flow stress has a component which is inversely proportional to the square-root of the grain size, the Hall-Petch law. The flow is accompanied by the build-up of internal stress which can be relieved by intercrystalline cracking, thereby limiting the cohesive strength of polycrystals. The relationship between these ideas and traditional views is briefly explained, and an analysis is given of recent experimental results.
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Yin, W. L. "Free-Edge Effects in Anisotropic Laminates Under Extension, Bending and Twisting, Part I: A Stress-Function-Based Variational Approach." Journal of Applied Mechanics 61, no. 2 (June 1, 1994): 410–15. http://dx.doi.org/10.1115/1.2901459.
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A variational method involving Lekhnitskii’s stress functions is used to determine the interlaminar stresses in a multilayered strip of laminate subjected to arbitrary combinations of axial extension, bending, and twisting loads. The stress functions in each layer are approximated by polynomial functions of the thickness coordinate. The equilibrium equations, the traction-free boundary conditions, and the continuity conditions of the interlaminar stresses are exactly satisfied in the present analysis, while the compatibility equations and the continuity of the displacements across the interfaces are enforced in an averaged sense by applying the principle of complementary virtual work. This yields an eigenvalue problem for the interfacial values of the stress functions and their normal derivatives. Interlaminar stresses for all three distinct loading cases may be obtained, in a single solution process, by combining the eigenfunctions with appropriate particular solutions (peculiar to each loading case) so as to ensure satisfaction of the traction-free boundary condition at the free edge.
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Saad, E. I. "Axisymmetric motion of a spherical porous particle perpendicular to two parallel plates with slip surfaces." Canadian Journal of Physics 93, no. 7 (July 2015): 784–95. http://dx.doi.org/10.1139/cjp-2014-0549.
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A combined analytical–numerical approach to the problem of the low Reynolds number motion of a porous sphere normal to one of two infinite parallel plates at an arbitrary position between them in a viscous fluid is investigated. The clear fluid motion governed by the Stokes equation and the Darcy–Brinkman equation is used to model the flow inside the porous material. The motion in each of the homogeneous regions is coupled with the continuity of the velocity components, the continuity of the normal stress, and the tangential stress jump condition. The fluid is allowed to slip at the surface of the walls. A general solution for the field equations in the clear region is constructed from the superposition of the fundamental solutions in both cylindrical and spherical coordinate systems. The collocation solutions for the hydrodynamic interactions between the porous sphere and the walls are calculated with good convergence for various values of the slip coefficient of the walls, the separation between the porous sphere and the walls, the stress jump coefficient, and a coefficient that is proportional to the permeability. For the special cases of a solid sphere, our drag results show excellent agreement with the available solutions in the literature for all relative particle-to-wall spacing.
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Banks, J. W., and B. Sjögreen. "A Normal Mode Stability Analysis of Numerical Interface Conditions for Fluid/Structure Interaction." Communications in Computational Physics 10, no. 2 (August 2011): 279–304. http://dx.doi.org/10.4208/cicp.060210.300910a.
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AbstractIn multi physics computations where a compressible fluid is coupled with a linearly elastic solid, it is standard to enforce continuity of the normal velocities and of the normal stresses at the interface between the fluid and the solid. In a numerical scheme, there are many ways that velocity- and stress-continuity can be enforced in the discrete approximation. This paper performs a normal mode stability analysis of the linearized problem to investigate the stability of different numerical interface conditions for a model problem approximated by upwind type finite difference schemes. The analysis shows that depending on the ratio of densities between the solid and the fluid, some numerical interface conditions are stable up to the maximal CFL-limit, while other numerical interface conditions suffer from a severe reduction of the stable CFL-limit. The paper also presents a new interface condition, obtained as a simplified characteristic boundary condition, that is proved to not suffer from any reduction of the stable CFL-limit. Numerical experiments in one space dimension show that the new interface condition is stable also for computations with the non-linear Euler equations of compressible fluid flow coupled with a linearly elastic solid.
Books on the topic "Normal stress continuity"
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Escudier, Marcel. Basic equations of viscous-fluid flow. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0015.
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In this chapter it is shown that application of the momentum-conservation equation (Newton’s second law of motion) to an infinitesimal cube of fluid leads to Cauchy’s partial differential equations, which govern the flow of any fluid satisfying the continuum hypothesis. Any fluid flow must also satisfy the continuity equation, another partial differential equation, which is derived from the mass-conservation equation. It is shown that distortion of a flowing fluid can be split into elongational distortion and angular distortion or shear strain. For a Newtonian fluid, the normal and shear stresses in Cauchy’s equations are related to the elongational and shear-strain rates through Stokes’ constitutive equations. Substitution of these constitutive equations into Cauchy’s equations leads to the Navier-Stokes equations, which govern steady or unsteady flow of a fluid. A minor modification of the constitutive equations for a Newtonian fluid allows consideration of generalised Newtonian fluids, for which the viscosity depends upon the shear-strain rates. The boundary conditions for the tangential and normal velocity components are discussed briefly.
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Carter, Bryan D., William G. Kronenberger, and Eric L. Scott. Children's Health and Illness Recovery Program (CHIRP). Oxford University Press, 2020. http://dx.doi.org/10.1093/med-psych/9780190070472.001.0001.
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Being a teenager with a chronic illness can be challenging. The symptoms of an illness, particularly pain and fatigue, can interfere with just being a normal teen. The Children’s Health and Illness Recovery Program, or CHIRP, was developed to teach teens and their family strategies to help them live as normal a life as possible while coping with the effects of their chronic illness. The skills acquired in the CHIRP intervention are life skills almost every teen can use, and these skills can be especially valuable for those working to overcome the negative effects of chronic illness. The CHIRP Teen and Family Workbook provides evidence-based activities shown to improve coping skills, stress management, communication skills, and functioning in teens with chronic medical conditions. In addition, family-based activities included in CHIRP assist teens and parents in developing more effective ways to communicate about their illness and increase teen confidence and independence in both managing their illness and their lifestyle. These skills are important building blocks to help teens move toward recovery and improve functioning and quality of life as they approach young adulthood. The skills acquired in the program also serve as a guide and motivation for continuing the gains that teens and their families make in CHIRP.
Book chapters on the topic "Normal stress continuity"
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Montaudon-Tomas, Cynthia M., Ingrid N. Pinto-López, Alicia L. Yañez-Moneda, and Anna Amsler. "The Effects of Remote Work on Family Relationships." In Research Anthology on Business Continuity and Navigating Times of Crisis, 1252–74. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-6684-4503-7.ch062.
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This chapter analyses the effects of remote work on family relationships during confinement due to the COVID-19 pandemic. The study is centered on faculty and staff members from a private business school in Puebla, Mexico. The research was conducted almost five months after the university closed its doors and moved all its activities online, having participants time to adapt to the new normal. A scale was developed and validated, and later on, it was applied in a country where family values, cultures, and traditions are strong. The scale included five distinct areas of study: remote working conditions, time and task management, work performance, stress, and family relations. All the business school faculty and administrative staff were invited to participate in the study. Results show employees' perceptions about how working remotely positively or negatively affected their relationships at home and their productivity at work, leading to the design of best practices and useful guidelines that will minimize the adverse effects of remote work while enhancing the positive ones.
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"Suffering in Isolation." In Incivility Among Nursing Professionals in Clinical and Academic Environments, 76–88. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7341-8.ch004.
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Unhealthy workplace environments have unfortunately been associated with the profession of nursing. Staffing shortages and long hours worked with high acuity patient caseloads can cause nursing professionals to feel overwhelmed, stressed, and anxious. Cultures of incivility can be accepted within some workplace environments as being normal. Nurse leaders that knowingly ignore patterns of disruptive behaviors by the nursing staff contribute to unit-based (and departmental) dysfunction. Perpetrators feel comfortable in continuing bullying behaviors because they have no fear of retribution. In these environments, nurse leaders themselves may engage in bullying and incivility behaviors. Chapter 4 provides nurses with instructions on how to report uncivil conduct that is not resolving and seek action against the perpetrator when mediation is not an option.
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McGrattan, Cillian. "Responsibility, justice, and reconciliation in Northern Ireland." In Theories of International Relations and Northern Ireland. Manchester University Press, 2017. http://dx.doi.org/10.7228/manchester/9781784995287.003.0013.
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The final substantive chapter explores the difficulty and importance of achieving reconciliation after the Agreement. Groups in Northern Ireland need to focus more on taking responsibility for their role in continuing sectarian differences rather than looking for reconciliation from or with others. Previous research has stressed the need for reconciliation, social learning, and dialogue as key mechanisms that allow a transformation of former enemies. Memory studies have recently looked to constructivism and studies of international norms in analysing the resilience of collective memory and the politics of apology, while commemoration studies have increasingly explored questions of globalisation and the transfer of internationally recognized tropes in producing memorial cultures. The chapter maps the various initiatives and policy proposals that have been developed in Northern Ireland, which have increasingly looked not only to international examples, but also the importance of cultivating US involvement.
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Magee, Patrick, and Mark Tooley. "Principles and Standards of Anaesthetic Monitoring." In The Physics, Clinical Measurement and Equipment of Anaesthetic Practice for the FRCA. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199595150.003.0015.
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The World Federation of Societies of Anaesthesiology (WFSA) adopted standards relating to the safe practice of anaesthesia in 1992 and such standards had already been proposed by a number of countries in order to cut the morbidity due to anaesthesia itself. In the modern era it is easy to forget that historically anaesthesia and surgery did indeed have associated morbidity and mortality and there was very little assistance from technology to monitor patients. The evolution of these standards is based on two main requirements of monitoring. The first is to record anticipated deviations from normal values, which require accurate measurement to ensure patient safety. The second is to warn of unexpected, life-threatening events that, by definition, occur without warning, and could affect the fit, young patient as easily as the old and infirm. All international standards stress the importance of the continual presence of a fully trained and accredited anaesthetic person, and one Australian study demonstrated that many mishaps occur in the absence of such a person [Runciman 1988]. This applies to general and regional anaesthesia, sedation and recovery. Because perceptions of safety and standards vary throughout the world, despite the presence of an International Standards Organisation, debate about the minimum requirements for monitoring continue. Central to the maintenance of these standards is the quality of persons entering the specialty, the quality of training programmes, and the continuing education of specialists throughout a professional lifetime [Sykes 1992]. It is difficult to determine with certainty the effect that additional technological monitoring has on safety. One clear example is the inability of the trained human eye to detect cyanosis, this human failure occurring maximally at 81–85% oxygen saturation. Clearly, the pulse oximeter has improved the quality of cyanosis detection. Numerous studies all over the world have shown that mortality due to anaesthesia itself fell significantly between the 1950s and the 1980s, by which time extensive technological monitoring was being introduced, and training programmes had been very much improved. Utting [1987] reviewed 750 cases of death and cerebral damage reported to the British General Medical Council between 1970 and 1982 that were thought to be the result of errors in technique.
Conference papers on the topic "Normal stress continuity"
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Morinishi, Y., and E. Nakamura. "Wall Asymptotic Behavior of Subgrid Scale Stress for Large Eddy Simulation." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37076.
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The objective of this study is to specify the wall asymptotic behavior of the subgrid scale stress for the large eddy simulation (LES) of wall bounded turbulent flows. The grid scale (GS) and subgrid scale (SGS) turbulent statistics are extracted from the numerical data of direct numerical simulation (DNS) of the turbulent channel flow at the Reynolds number of 300, based on the friction velocity and channel half width, in order to achieve this objective. The basic equations of the DNS are the Navier-Stokes and continuity equations for incompressible flows. The GS and SGS statistics are computed corresponding to various LES filters, that is, two-dimensional (plane) and three-dimensional filters with different filter widths. The Gaussian filter is used in the periodic directions. The filtering function in the wall-normal direction is top-hat for the three-dimensional filter. Then, the components of the SGS stress are compared with the analytical results by the Taylor expansion. The results estimated by the Taylor expansion and the DNS data indicate different wall asymptotic behaviors of the SGS stress for the plane and three-dimensional filters. In particular, the wall asymptotic behavior of the Reynolds stress, which has been assumed in the SGS modeling, is not true of the SGS stress for the three-dimensional filter.
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Carrera, Erasmo, Alberto García de Miguel, Alfonso Pagani, and Enrico Zappino. "Reissner’s Mixed Variational Theorem for Layer-Wise Refined Beam Models Based on the Unified Formulation." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71612.
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The present paper proposes the application of the Reissners Mixed Variational Theorem (RMVT) for the accurate stress analysis of general multi-layered beam problems. Laminated materials usually differ from homogeneous materials in that they exhibit much higher transverse shear and transverse normal deformabilities. These characteristics, and others such as the Transverse Anisotropy (TA) and the Interlaminar Continuity of transverse stresses (IC), make Classical Laminated Theories (CLT) inappropriate for the analysis of multi-layered structures. The Carrera Unified Formulation (CUF) sets a framework in which classical-to-refined beam models can be generated by expanding the unknown variables over the cross-sectional domain by means of arbitrary functions. A LW expansion is adopted for both displacements and transverse stresses over the cross-section section domain. In this manner, the ZZ condition is automatically satisfied through the use of independent kinematics for each layer in a LW sense, with no need of introducing ad-hoc ZZ functions.
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Xue, Guanyang, Xuanhong Cheng, and Alparslan Oztekin. "Computational Study of Viscoelastic Flows in Microchannels." In ASME 2021 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fedsm2021-65699.
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Abstract Computational Fluid Dynamics (CFD) simulations have been performed in a 2D cross-section of the microchannel to characterize the viscoelastic flow field using OpenFOAM with customized stabilizing methods. The continuity and momentum equations coupled with the Giesekus constitutive model are solved. The computational domain consists of a straight main channel that is 100 μm in width and a 1:4 square-shaped cavity in the middle of the channel. The mesh convergence study is performed with both structured and unstructured cells. Flow and stress fields are compared with different cell densities. The numerical study is carried out on various Deborah numbers (De). The first normal stress difference is computed to examine the elastic lift force for future studies for nanoparticle separations. The vortex on the expansion side shrinks while the contraction side expands as De is increased. A banded zone of stronger N1 in the bulk region of the cavity, observed at higher De, could be favorable in particle separation applications. As the simulation process being validated, this study can help with future improvements to achieve higher flow rates.
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Sforza, Pasquale M. "Entrainment in Free Jets." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77051.
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The mass flow passing through a plane normal to the mainstream direction of a free jet is the sum of the mass flow of the jet and that of the fluid entrained from surrounding ambient into which it issues. Manipulation of the instantaneous Navier-Stokes equations and the continuity equation yields an integro-differential equation for the instantaneous mass flow in the flow field. This equation is reduced to a form that suggests that jet entrainment may be viewed as a one-dimensional unsteady diffusion process with an integral source term arising from the gradient of forces in the axial direction of flow which are dependent, in general, on z and t. The small difference in the integrals of the net axial inertial force acting on the fluid in the volume defined by the limits of integration is balanced by an axial force arising from the viscous normal stress that is associated with axial rate of mass entrainment. Furthermore, it suggests that the kinematic viscosity of the fluid is the appropriate diffusion parameter. This formulation is used to assess the nature of the entrainment process in steady three-dimensional jets and to propose means for managing that process.
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Xue, Guanyang, Justin Caspar, Jaber Asiri, Xuanhong Cheng, and Alparslan Oztekin. "Parametric Study of Viscoelastic Flow Simulations in Microfluidic Devices." In ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-95153.
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Abstract The open-source C++ toolbox OpenFOAM is used to perform the Computational Fluid Dynamics (CFD) simulations in two-dimensional microfluidic devices to characterize the viscoelastic flow. The Oldroyd-B constitutive equation is coupled with continuity and momentum equations. Multiple stabilization methods are applied to the numerical simulation to simulate High Weissenberg Number Problem (HWNP) in the microchannel. We applied the Log Conformation Reformulation (LCR) method to guarantee the positive definiteness of the stress tensor. The CUBISTA scheme and the improved Both Side Diffusion (iBSD) method are applied to predict the flow behavior at high elasticity regions without numerical oscillations. Various microstructures, including circles and flat plates, are placed in the center of the channel as the confinement. Our previous work demonstrated that the polyhedral mesh with hexahedral inflation layers effectively meshes complex microstructures in microchannels. A viscoelastic fluid is injected from the inlet at varying flow rates, corresponding to the local Weissenberg number up to 25. A parametric study is conducted on the first normal stress difference (N1) in specific regions with an accurate prediction of the viscoelastic flow field near the microstructures.
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Frostig, Y. "Bending of Curved Sandwich Panels With Transversely Flexible Cores: Closed-Form High-Order Theory." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-0734.
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Abstract The bending behavior of a curved sandwich panel with a transversely flexible core, i.e. “soft” in the out of plane direction, is derived. It is formulated using a rigorous systematic closed-form approach based on variational principles. The effects of the transversely flexible core are incorporated resulting in non-linear patterns, denoted also as high-order effects, for the inplane and the transverse deformations through the height of the core. The governing equations along with the associated boundary and continuity conditions for a general type of sandwich panels, i.e. unidentical skins, composite laminated or metallic and a “soft” core are derived. General type of boundary conditions, including spring conditions, as well as different conditions at the upper and the lower skins at the same section are implemented and the effects of “stiff edge inserts, denoted as global boundary conditions, along with the induced localized effects are considered. Localized effects at support regions with or without edge stiffeners, with movable and immovable supports, and in the vicinity of concentrated loads are studied. The effects are described in terms of the internal resultants and displacements of each skin, peeling (transversely normal) stresses and shear stresses at the skin-core interfaces, and stress and displacement fields in the core through its height. Numerical results of a typical curved panel used in a test set-up and comparisons with experimental data are presented. A comparison, that is in very good agreement, between the analytical results and the experimental ones is conducted. The effects of a global boundary conditions, such as a “stiff” edge beam, and similar local boundary conditions on the localized effects are presented and discussed. The stress concentration involved in case of a concentrated load especially in its near vicinity is described.
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Cho, Y. B., E. J. Plaskacz, R. C. Averill, and R. F. Kulak. "Explicit Dynamic Finite Element Analysis of Laminated Composite Automotive Structures Using a New Composite Plate Element." In ASME 1997 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/imece1997-1189.
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Abstract Composite materials are being considered for use in the front end structures of vehicles to help reduce overall vehicle mass and, thus, improve fuel efficiency. Acceptance of composite material in structural members will depend on their ability to do crash energy management. Numerical simulations can greatly aid in the design of these critical structures and reduce the number of crash tests. A new finite element, which is based on laminated plate theory with cubic zig-zag approximations, was developed to model the relevant mechanics that occur in composite materials during crash events. The element was cast in the internal force format for use with explicit integration solvers. In the plate theory, the in-plane displacement fields in a laminate are assumed to be piecewise cubic functions and vary in a zig-zag fashion through the thickness of the laminate. The zig-zag functions are obtained by satisfying the continuity of transverse shear stresses at layer interfaces. This in-plane displacement field assumption accounts for discrete layer effects without increasing the number of degrees of freedom as the number of layers is increased. The transverse normal strain predictions are improved by assuming a constant variation of transverse normal stress through the thickness in a laminate. The finite element is developed with the topology of an eight-noded brick. Each node has five engineering degrees of freedom, three translations and two rotations. Thus, this element can be conveniently implemented into general purpose finite element codes. Consistent and lumped mass matrices are derived. The developed element is implemented into Argonne National Laboratory’s in-house code, NEPTUNE, which utilizes explicit direct integration method. In NEPTUNE the internal force vector is calculated from the developed element at each time step. Numerical performance of the current element is investigated in this research.
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Benson, David B., Tom I. P. Shih, and David O. Davis. "CFD Simulations of an Axisymmetric Mixed-Compresssion Inlet With Bleed Through Discrete Holes." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45076.
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CFD simulations were performed to investigate boundary-layer control through bleed patches in an axisymmetric mixed-compression inlet in which the bleed patches are modeled by two global bleed boundary conditions (BCs). In one bleed BC, the locations of the bleed holes are discerned. In the other bleed BC, each row of bleed holes is modeled as a porous surface, where the number of bleed holes in each row is accounted for by adjusting the discharge coefficient to give the correct bleed rate. Results are presented for the predicted bleed rates, pressure on the cowl and centerbody surfaces, and the flow field. Comparisons were made with available experimental data. Also presented is a method based on one-dimensional isentropic and normal shock solutions to get the flow “started” in CFD simulations of critical flow in mixed-compression inlets. This computational study is based on the ensemble-averaged conservation equations of mass (continuity), momentum (compressible Navier-Stokes), and total energy closed by shear-stress transport (SST) turbulence model, where integration is to the wall. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids.
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Ngo, C. C., and F. C. Lai. "Natural Convection From a Buried Pipe With a Superimposed Fluid Layer." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41395.
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Heat transfer induced by buoyancy from a pipe buried in a semi-infinite porous medium with a superimposed fluid layer has been numerically examined in this study. Due to the complexity involved, finite difference method along with body-fitted coordinate systems has been employed. The Brinkman-extended Darcy equations are used to model flow in the porous medium while Navier-Stokes equations are used for the fluid layer. The conditions applied at the interface between the fluid and porous layers are the continuity of temperature, heat flux, normal and tangential velocity, shear stress and pressure. A parametric study has been performed to investigate the effects of Rayleigh number, Prandtl number, Darcy number, and fluid layer thickness on the flow patterns and heat transfer rates. The results show that heat transfer increases with the Rayleigh number, but the convective strength decreases with the Darcy number. The heat transfer rate is smaller when the superimposed fluid is air instead of water. For a porous layer with Da ≤ 0.0005 and an overlaying fluid layer thickness of L/ri ≥ 1, convection is initiated in the fluid layer and it may develop into multiple recirculating cells at a moderate Rayleigh number (i.e., Ra ≤ 104), and may further develop into a single cell at a higher Rayleigh number of 105.
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Yuceoglu, U., and O¨ Gu¨vendik. "Effects of Position (or Location) of Non-Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint) on Bending Vibrations of Composite Mindlin Plates or Panels." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39045.
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In the present study, the “Effects of Position (or Location) of Non-Centrally Bonded Symmetric Double Doubler Joint in Composite Mindlin Plates or Panels” are theoretically analyzed and are numerically solved in some detail. The “Plate Adherends” and the upper and lower “Doubler Plates” of the “Bonded Joint System” are considered as dissimilar, orthotropic “Mindlin Plates” joined through the dissimilar upper and lower very thin adhesive layers. The transverse and rotary moments of inertia are included in the analysis. The relatively very thin adhesive layers are assumed to be linearly elastic continua with transverse normal and shear stresses. The “damping effects” in the entire “Bonded Joint System” are neglected. The sets of the dynamic “Mindlin Plate” equations of the “Plate Adherends”, the “Double Doubler Plates” and the thin adhesive layers are combined together with the orthotropic stress resultant-displacement expressions in a “special form”. This system of equations, after some further manipulations, is eventually reduced to a set of the “Governing System of the First Order Ordinary Differential Equations” in terms of the “state vectors” of the problem. Hence, the final set of the aforementioned “Systems of Equations” together with the “Continuity Conditions” and the “Boundary Conditions” facilitate the present solution procedure. This is the “Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials). The present theoretical analysis and the present method of solution are applied to a typical “Non-Centrally Positioned (or Located) Symmetric Double Lap Joint (or Symmetric Double Doubler Joint) System”. The effects of the location (or position) of the “Bonded Joint System” and also of the relatively “Stiff (or “Hard”) and the relatively “Flexible” (or “Soft”) adhesive properties, on the natural frequencies and mode shapes are considered in some detail. The very interesting mode shapes with their dimensionless natural frequencies are presented for various sets of “Boundary Conditions”. From the numerical results obtained, some important conclusions are drawn for the “Bonded Joint System” studied here.
Reports on the topic "Normal stress continuity"
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Seginer, Ido, Louis D. Albright, and Robert W. Langhans. On-line Fault Detection and Diagnosis for Greenhouse Environmental Control. United States Department of Agriculture, February 2001. http://dx.doi.org/10.32747/2001.7575271.bard.
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Background Early detection and identification of faulty greenhouse operation is essential, if losses are to be minimized by taking immediate corrective actions. Automatic detection and identification would also free the greenhouse manager to tend to his other business. Original objectives The general objective was to develop a method, or methods, for the detection, identification and accommodation of faults in the greenhouse. More specific objectives were as follows: 1. Develop accurate systems models, which will enable the detection of small deviations from normal behavior (of sensors, control, structure and crop). 2. Using these models, develop algorithms for an early detection of deviations from the normal. 3. Develop identifying procedures for the most important faults. 4. Develop accommodation procedures while awaiting a repair. The Technion team focused on the shoot environment and the Cornell University team focused on the root environment. Achievements Models: Accurate models were developed for both shoot and root environment in the greenhouse, utilizing neural networks, sometimes combined with robust physical models (hybrid models). Suitable adaptation methods were also successfully developed. The accuracy was sufficient to allow detection of frequently occurring sensor and equipment faults from common measurements. A large data base, covering a wide range of weather conditions, is required for best results. This data base can be created from in-situ routine measurements. Detection and isolation: A robust detection and isolation (formerly referred to as 'identification') method has been developed, which is capable of separating the effect of faults from model inaccuracies and disturbance effects. Sensor and equipment faults: Good detection capabilities have been demonstrated for sensor and equipment failures in both the shoot and root environment. Water stress detection: An excitation method of the shoot environment has been developed, which successfully detected water stress, as soon as the transpiration rate dropped from its normal level. Due to unavailability of suitable monitoring equipment for the root environment, crop faults could not be detected from measurements in the root zone. Dust: The effect of screen clogging by dust has been quantified. Implications Sensor and equipment fault detection and isolation is at a stage where it could be introduced into well equipped and maintained commercial greenhouses on a trial basis. Detection of crop problems requires further work. Dr. Peleg was primarily responsible for developing and implementing the innovative data analysis tools. The cooperation was particularly enhanced by Dr. Peleg's three summer sabbaticals at the ARS, Northem Plains Agricultural Research Laboratory, in Sidney, Montana. Switching from multi-band to hyperspectral remote sensing technology during the last 2 years of the project was advantageous by expanding the scope of detected plant growth attributes e.g. Yield, Leaf Nitrate, Biomass and Sugar Content of sugar beets. However, it disrupted the continuity of the project which was originally planned on a 2 year crop rotation cycle of sugar beets and multiple crops (com and wheat), as commonly planted in eastern Montana. Consequently, at the end of the second year we submitted a continuation BARD proposal which was turned down for funding. This severely hampered our ability to validate our findings as originally planned in a 4-year crop rotation cycle. Thankfully, BARD consented to our request for a one year extension of the project without additional funding. This enabled us to develop most of the methodology for implementing and running the hyperspectral remote sensing system and develop the new analytical tools for solving the non-repeatability problem and analyzing the huge hyperspectral image cube datasets. However, without validation of these tools over a ful14-year crop rotation cycle this project shall remain essentially unfinished. Should the findings of this report prompt the BARD management to encourage us to resubmit our continuation research proposal, we shall be happy to do so.
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Financial Stability Report - Second Semester of 2021. Banco de la República, September 2022. http://dx.doi.org/10.32468/rept-estab-fin.sem2.eng-2021.
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Banco de la República’s main objective is to preserve the purchasing power of the currency in coordination with the general economic policy that is intended to stabilize output and employment at long-term sustainable levels. Properly meeting the goal assigned to the Bank by the 1991 Constitution critically depends on preserving financial stability. This is understood to be a general condition in which the financial system assesses and manages the financial risks in a way that facilitates the economy’s performance and efficient allocation of resources while, at the same time, it is able to, on its own, absorb, dissipate, and mitigate the shocks that may arise as a result of adverse events. This Financial Stability Report meets the goal of giving Banco de la República’s diagnosis of the financial system’s and its debtors’ recent performance as well as of the main risks and vulnerabilities that could affect the stability of the Colombian economy. In this way, participants in financial markets and the public are being informed, and public debate on trends and risks affecting the system is being encouraged. The results presented here also serve the monetary authority as a basis for making decisions that will enhance financial stability in the general context of its objectives. In recent months, several positive aspects of the financial system have preserved a remarkable degree of continuity and stability: the liquidity and capital adequacy of financial institutions have remained well above the regulatory minimums at both the individual and consolidated levels, the coverage of past-due loans by loan-loss provisions remains high, and the financial markets for public and private debt and stocks have continued to function normally. At the same time, a surge in all the types of loan portfolios, a sharp downturn in the non-performing loan portfolio, and a rise in the profitability of credit institutions can be seen for the first time since the beginning of the pandemic. In line with the general recovery of the economy, the main vulnerability to the stability of the Colombian financial system identified in the previous edition—uncertainty about changes in the non-performing loans portfolio—has receded and remains on a downward trend. In this edition, the main source of vulnerability identified for financial stability in the short term is the system’s exposure to sudden changes in international financial conditions; the results presented in this Report indicate that the system is sufficiently resilient to such scenarios. In compliance with its constitutional objectives and in coordination with the financial system’s security network, Banco de la República will continue to closely monitor the outlook for financial stability at this juncture and will make the decisions necessary to ensure the proper functioning of the economy, facilitate the flow of sufficient credit and liquidity resources, and further the smooth functioning of the payment system. Leonardo Villar Gomez Governor Box 1 -Decomposition of the Net Interest Margin in Colombia and Chile Wilmar Cabrera Daniela Rodríguez-Novoa Box 2 - Spatial Analysis of New Home Prices in Bogota, Medellín, and Cali Using a Geostatistical Approach María Fernanda Meneses Camilo Eduardo Sánchez Box 3 - Interest Rate Model for the SYSMO Stress Test Exercise Wilmar Cabrera Diego Cuesta Santiago Gamba Camilo Gómez Box 4 - The Transition from LIBOR and other International Benchmark Rates Daniela X. Gualtero Briceño Javier E. Pirateque Niño