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Static Loading (static + loading)
Selected AbstractsNonlinear SEM numerical analyses of dry dense sand specimens under rapid and dynamic loadingINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2007C. di Prisco Abstract The paper mainly concerns the mechanical response of 2D dry dense sand specimens under shock loading. The problem is numerically analysed by means of a SEM dynamic code, within which an already conceived non-local viscoplastic constitutive model characterized by a non-associated flow rule and by an anisotropic strain hardening has been implemented. In particular the strain localization and time dependency of the material mechanical response are taken into consideration. Both rapid/static loading and dynamic histories are numerically simulated. In the first case, the time dependency of the material mechanical response can be captured by neglecting inertial effects, while in the second one the two factors are superimposed and the propagation of the stress waves within the specimen is discussed. The interest of these analyses derives from the fact that the diffusion phenomenon takes place within a specimen already localized. Copyright © 2006 John Wiley & Sons, Ltd. [source] Health Monitoring of Rehabilitated Concrete Bridges Using Distributed Optical Fiber SensingCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2006Wei Zhang As newly developed techniques, distributed optical fiber sensing (DOFS) have gradually played a prominent role in structural health monitoring for the last decade. This article focuses on the employment of two types of DOFS, namely fiber Bragg grating (FBG) and Brillouin optical time domain reflectometry (BOTDR), into an integrated HMS for rehabilitated RC girder bridges by means of a series of static and dynamic loading tests to a simply supported RC T-beam strengthened by externally post-tensioned aramid fiber reinforced polymer (AFRP) tendons. Before the loading tests, a calibration test for FBG and another one for BOTDR were implemented to, respectively, obtain good linearity for both of them. Monitoring data were collected in real time during the process of external strengthening, static loading, and dynamic loading, respectively, all of which well identified the relevant structural state. The beam was finally vibrated for 2 million cycles and then loaded monotonously to failure. Based on the bending strength of externally prestressed members, ultimate values for the test specimen were numerically computed via a newly developed simplified model, which satisfactorily predicted the ultimate structural state of the beam. And then the alert values were adopted to compare with the monitoring results for safety alarm. The investigation results show a great deal of applicability for the integrated SHM by using both DOFS in rehabilitated concrete bridges strengthened by external prestressing. [source] Flow Behavior of Sandwich Structures for Cooling Thermally Highly Loaded Steam Turbine Components,ADVANCED ENGINEERING MATERIALS, Issue 5 2009Paul Beiss To increase steam temperature and pressure in the steam turbine, a new cooling structure (see picture) was developed comprising a woven wire mesh interlayer between two plane sheets. Cooling steam is fed into the interlayer, where it can flow without severe losses. To characterize the mechanical high temperature behavior of the structure, the flow behavior under static loading was investigated and simulated by the finite element method (FEM). [source] Semi-analytical elastostatic analysis of unbounded two-dimensional domainsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 11 2002Andrew J. Deeks Abstract Unbounded plane stress and plane strain domains subjected to static loading undergo infinite displacements, even when the zero displacement boundary condition at infinity is enforced. However, the stress and strain fields are well behaved, and are of practical interest. This causes significant difficulty when analysis is attempted using displacement-based numerical methods, such as the finite-element method. To circumvent this difficulty problems of this nature are often changed subtly before analysis to limit the displacements to finite values. Such a process is unsatisfactory, as it distorts the solution in some way, and may lead to a stiffness matrix that is nearly singular. In this paper, the semi-analytical scaled boundary finite-element method is extended to permit the analysis of such problems without requiring any modification of the problem itself. This is possible because the governing differential equations are solved analytically in the radial direction. The displacement solutions so obtained include an infinite component, but relative motion between any two points in the unbounded domain can be computed accurately. No small arbitrary constants are introduced, no arbitrary truncation of the domain is performed, and no ill-conditioned matrices are inverted. Copyright © 2002 John Wiley & Sons, Ltd. [source] Numerical simulation of fatigue-driven delamination using interface elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2005Paul Robinson Abstract This paper presents a computational technique for the prediction of fatigue-driven delamination growth in composite materials. The interface element, which has been extensively applied to predict delamination growth due to static loading, has been modified to incorporate the effects of cyclic loading. Using a damage mechanics formulation, the constitutive law for the interface element has been extended by incorporating a modified version of a continuum fatigue damage model. The paper presents details of the fatigue degradation strategy and examples of the predicted fatigue delamination growth in mode I, mode II and mixed mode I/II are presented to demonstrate that the numerical model mimics the Paris law behaviour usually observed in experimental testing. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effect of simulated resin-bonded fixed partial denture clinical conditions on resin cement mechanical propertiesJOURNAL OF ORAL REHABILITATION, Issue 8 2003M. P. Walker summary The purpose of this study was to determine changes in flexural properties of resin cement under simulated resin-bonded fixed partial denture (RBFPD) clinical conditions using aqueous ageing and cyclic loading. Panavia F flexural modulus and strength were measured by static loading to failure after 48-h and 60-day aqueous ageing at 37 °C with and without simulated cyclic occlusal loading. Panavia F sorption and solubility were also measured. Scanning electron microscopy (SEM) was used to characterize the morphology of the fractured surfaces. A two-factor anova (P , 0·05) indicated that cyclic loading produced a significant increase in the flexural modulus with no significant effect on the flexural strength. Conversely, aqueous ageing time produced a significant decrease in flexural strength with no effect on the flexural modulus. The SEM fracture analysis indicated that resin matrix fracture occurred in static-aqueous specimens; while in the aqueous-cycled specimens, resin matrix fracture occurred in addition to an increasing proportion of filler/resin interface fracture. Collectively, these outcomes suggest that initial degradation under simulated resin cement clinical function may be related to breakdown of the filler/resin interface bond, which could contribute to in vivo RBFPD resin cement cohesive failure. [source] Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouthJOURNAL OF ORAL REHABILITATION, Issue 2 2001J. R. Strub Survival rate and fracture strength of incisors restored with different post and core systems after exposure in the artificial mouth. The survival rate and fracture resistance of 40 decapitated endodontically treated maxillary central incisors using four different post and core systems covered with all-ceramic copings was evaluated after exposure in the artificial mouth. Ten samples of the following post and core systems were investigated: high precious metal post (Permador®) and core (Olympia®) (A), zirconia post (Cerapost®) with a pre-fabricated bonded ceramic core (Ceracap®) (B), resin-ceramic post (experimental) with a pre-fabricated bonded ceramic core (Ceracap®) (C) and a zirconia post (Cerapost®) with a custom made ceramic core (Cosmo Ingots®) (D). The all-ceramic copings (Procera®) were cemented using Panavia TC®. The survival rates after 1 200 000 cycles in the artificial mouth are as follows: 90% (A), 80% (B), 60% (C) and 100% (D). The results of the means and standard deviations (s.d.) of the fracture resistance during static loading are: 1270 ± 312·5 (A), 1494·5 ± 333·5 (B), 1146·7 ± 182·6 (C) and 463·3 ± 46·2 (D). There are statistically significant differences between all groups with the exception of A and B, and A and C (Wilcoxon test). None of the zirconia posts with custom made ceramic cores covered with all-ceramic copings fractured during dynamic loading in the artificial mouth. The mean fracture strength during static loading was less favourable than that of groups A, B and C but above the clinical necessary level. [source] Effects of component properties and orientation on corrugated container endurancePACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2010Roman E. Popil Abstract Experiments are performed to determine the impact of several physical properties on the creep behavior of three different sets of corrugated containers subjected to static loading and a cyclic humidity environment ranging from 50% to 80% relative humidity in a 24,h period. One sample set had basis weights of the fluted medium varied from 68 to 205,g/m2 while keeping the basis weight of the linerboard facings at 205,g/m2. This varied the out-of-plane shear rigidity of the single wall board by a factor of three. Another set of corrugated samples investigated effects of lateral or linear corrugating by rotation of either linerboards, fluted medium or both. This equalizes hygroexpansivity and affects lifetime. A third series of boxes had barrier coatings applied to their surfaces to determine the effect on lifetime. Creep and lifetime are determined to be inversely related and a multiple regression model for lifetime was sought based on the data set. Homogenization of the corrugated board properties through either increased medium basis weight or component rotation (lateral or linear corrugating) and application of barrier coating will in general, increase the endurance of edge loaded corrugated board in cyclic humidity. Copyright © 2010 John Wiley & Sons, Ltd. [source] A design database for moulded pulp packaging structurePACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2004X. Ma Abstract In this study, a structural factor approach is developed to allow a modular design method be used for the packaging design of thin-walled structures. Numerical simulations of the structural units are carried out to evaluate the influence of the structural factors under static loading, by using the commercial finite element code ABAQUS/Explicit. Empirical relations between the load-bearing capacity of structural units and structural factors are established based on numerical simulations. A database is then constructed that has the ability to provide valuable information for the loading performances of different structural units. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mehraxiales mechanisches Ermüdungsmodell von Ultra-Hochfestem Beton: Experimentelle und analytische UntersuchungenBETON- UND STAHLBETONBAU, Issue 6 2007Jürgen Grünberg Prof. Dr.-Ing. Die besonderen Eigenschaften von ultra-hochfestem Beton (UHPC) gegenüber normalfestem Beton erfordern für numerische Analysen die Entwicklung eines mehraxialen mechanischen Modells. Im Dreiphasenmodell werden sowohl sprödes als auch duktiles Baustoffverhalten durch charakteristische Verläufe der Hauptmeridiane, insbesondere des Druckmeridians der Bruchumhüllenden beschrieben. Die anisotrope Ermüdungsschädigung wird im Hauptspannungsraum durch unterschiedliche Schädigungsraten für den Zug- bzw. Druckmeridian berücksichtigt. In umfangreichen experimentellen Untersuchungen werden zur Kalibrierung des Dreiphasenmodells für UHPC die Modellparameter für die Beschreibung der Hauptmeridianverläufe bestimmt. In dynamischen Untersuchungen werden die Parameter für die anisotrope Schädigung bestimmt. Multiaxial Mechanical Model of Ultra-High-Performance Concrete The special and outstanding characteristics of ultra-high-performance concrete (UHPC) require the development of a multiaxial mechanical model for numerical investigations. With the three phases model it is possible to describe the behaviour of concrete from extremely brittle to more ductile using the characteristic development of the principal meridians, in particular the compressive meridian of the fracture surface. Furthermore, the anisotropic damage due to fatigue is considered in the principal-stressarea by different grades of damage in relation to the tensile and the compressive meridian. In experimental investigations, the necessary parameters are determined to calibrate the three phases model for UHPC by specifying the principal meridians for static loading. In further dynamic investigations the parameters for an anisotropic damage model are determined for fatigue loading. [source] | ||||||||||