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Dynamic Loads (dynamic + load)
Terms modified by Dynamic Loads Selected AbstractsA NEW TEST APPARATUS AND METHOD FOR FRICTION FORCE MEASUREMENT IN JOURNAL BEARINGS UNDER DYNAMIC LOADING: Part IEXPERIMENTAL TECHNIQUES, Issue 5 2005A. Biyiklio No abstract is available for this article. [source] Vibration of a space arc subject to a critical dynamic loadINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2005Lazarus Teneketzis Tenek Abstract The present study concerns the dynamic behaviour of a space arc subject to a midarc vertical buckling load dynamically applied. The arc is discretized with a set of three-dimensional beam finite elements and the non-linear dynamic equation (large displacements) is solved by means of an unconditionally stable time-dependent scheme over time. The vertical excitation gives rise to a very fast and erratic horizontal wave as the structure begins to vibrate in all directions. This horizontal wave has chaotic characteristics as its attractor indicates. Time,displacement curves are obtained for all components of the midarc point. Although the time algorithm was executed here for 2000 time steps, simulation over longer periods of time can reveal the vibration characteristics and even simulate structural failure under the imposed dynamic buckling load for the space arc structure. Copyright © 2004 John Wiley & Sons, Ltd. [source] Echtzeit-Röntgenuntersuchungen an duktilen stabförmigen Holzverbindungen bei dynamischer BeanspruchungBAUTECHNIK, Issue 10 2008Jörg Wehsener Dipl.-Ing. Der Beitrag beschreibt die Möglichkeiten von Röntgenuntersuchungen an stabförmigen Holzverbindungsmitteln im beanspruchten Bauteil. Trotz verschiedenartiger Untersuchungsmethoden ist die Bestimmung des tatsächlichen Verhaltens von metallischen Verbindungsmitteln im Holz während der Belastung nicht ausreichend gelöst. Mit Hilfe verschiedener mathematischer Ansätze und der Einbeziehung von Materialkennwerten ist die Modellierung von Holzverbindungen möglich. Die Nutzung von Röntgenstrahlen unter Echtzeitwiedergabe ermöglicht es, das Verformungsverhalten von metallischen Verbindungsmitteln während der Lasteinleitung zu beobachten. Ziel der Versuche war die Bestimmung des Verformungsverhaltens einer Stabdübelverbindung in Echtzeit unter quasistatischer und dynamischer Belastung. Mit der Echtzeit-radio-graphischen Messung wurden Versuche am Einzelstabdübel und einer Dübelgruppe durchgeführt. Die beim Versuch genutzte Anlage besteht aus einer mobilen Röntgenröhre und einem Detektor, sowie der dazugehörigen digitalen Bildverarbeitung. Bei maximaler Geschwindigkeit von 30 Bildern in der Sekunde wird eine Grenzwertauflösung von 1,97 lp/mm erreicht. Die Pixelteilung ist mit 127 ,m2 durch das Empfängermodul vorgegeben [10]. In Abhängigkeit der gewählten Parameter konnte die Verschiebung um einen Bildpunkt (0,21 mm) verifiziert werden. Eine Überprüfung der gemessenen Verformungen der Stabdübel erfolgte mit Hilfe von direkt aufgebrachten Dehnmessstreifen. Real time radioscopy investigations on ductile dowel-type fastener under dynamic load. This article discusses an application of real-time radioscopy in the investigation of dynamically loaded connections. Real-time radioscopy is especially suitable for connections of wood structures due to differences in density that are required for a radiographic image. With a real-time system, one can observe deformations of fasteners inside the investigated specimen. Theoretically, deformations can be quantified using image-processing techniques. The evaluation of deformations is, however, relatively complex due to the dimensionality of the problem where a 3-dimenional object is collapsed into its 2-D projection. A radiographic system capable of 30Hz frame acquisition frequency was used to study monotonically and cyclically loaded spliced and beam-to-column connections and an image-processing technique was used to estimate strains and study failure modes of the fasteners. [source] Non-linear behavior of mass concrete in three-dimensional problems using a smeared crack approachEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2005H. Mirzabozorg Abstract A smeared crack approach has been proposed to model the static and dynamic behavior of mass concrete in three-dimensional space. The proposed model simulates the tensile fracture on the mass concrete and contains pre-softening behavior, softening initiation, fracture energy conservation and strain rate effects under dynamic loads. The validity of the proposed model has been checked using the available experimental results under static and dynamic loads. The direct and indirect displacement control algorithms have been employed under incremental increasing static loads. It was found that the proposed model gives excellent results and crack profiles when compared with the available data under static loads. The Koyna Dam in India has been used to verify the dynamic behavior of the proposed model. It was found that the resulting crack profiles were in good agreement with the available experimental results. Finally, the Morrow Point Dam was analyzed, including the dam,reservoir interaction effects, to consider its non-linear seismic behavior. It was found that the resulting crack profiles were in good agreement with the contour of maximum principal stresses and no numerical instability occurred during the analysis. Copyright © 2004 John Wiley & Sons, Ltd. [source] Nanoscopic fatigue and stress corrosion crack growth behaviour in a high-strength stainless steel visualized in situ by atomic force microscopyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2005K. MINOSHIMA ABSTRACT In situ atomic force microscope (AFM) imaging of the fatigue and stress corrosion (SC) crack in a high-strength stainless steel was performed, under both static and dynamic loading. The AFM systems used were (1) a newly developed AFM-based system for analysing the nanoscopic topographies of environmentally induced damage under dynamic loads in a controlled environment and (2) an AFM system having a large sample stage together with a static in-plane loading device. By using these systems, in situ serial clear AFM images of an environmentally induced crack under loading could be obtained in a controlled environment, such as in dry air for the fatigue and in an aqueous solution for the stress corrosion cracking (SCC). The intergranular static SC crack at the free corrosion had a sharp crack tip when it grew straight along a grain boundary. The in situ AFM observations showed that the fatigue crack grew in a steady manner on the order of sub-micrometre. The same result was obtained for the static SC crack under the free corrosion, growing straight along a grain boundary. In these cases, the crack tip opening displacement (CTOD) remained constant. However, as the static SC crack was approaching a triple grain junction, the growth rate became smaller, the CTOD value increased and the hollow ahead of the crack tip became larger. After the crack passed through the triple grain junction, it grew faster with a lower CTOD value; the changes in the CTOD value agreed with those of the crack growth rate. At the cathodic potential, the static SC crack grew in a zigzag path and in an unsteady manner, showing crack growth acceleration and retardation. This unsteady crack growth was considered to be due to the changes in the local hydrogen content near the crack tip. The changes in the CTOD value also agreed with those of the crack growth rate. The CTOD value in the corrosive environment was influenced by the microstructure of the material and the local hydrogen content, showing a larger scatter band, whereas the CTOD value of the fatigue crack in dry air was determined by the applied stress intensity factor, with a smaller scatter band. In addition, the CTOD value in the corrosive environment under both static and dynamic loading was smaller than that of the fatigue crack; the environmentally induced crack had a sharper crack tip than the fatigue crack in dry air. [source] Considerations of the discontinuous deformation analysis on wave propagation problemsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2009Jiong Gu Abstract In rock engineering, the damage criteria of the rock mass under dynamic loads are generally governed by the threshold values of wave amplitudes, such as the peak particle velocity and the peak particle acceleration. Therefore, the prediction of wave attenuation across fractured rock mass is important on assessing the stability and damage of rock mass under dynamic loads. This paper aims to investigate the applications of the discontinuous deformation analysis (DDA) for modeling wave propagation problems in rock mass. Parametric studies are carried out to obtain an insight into the influencing factors on the accuracy of wave propagations, in terms of the block size, the boundary condition and the incident wave frequency. The reflected and transmitted waves from the interface between two materials are also numerically simulated. To study the tensile failure induced by the reflected wave, the spalling phenomena are modeled under various loading frequencies. The numerical results show that the DDA is capable of modeling the wave propagation in jointed rock mass with a good accuracy. Copyright © 2009 John Wiley & Sons, Ltd. [source] Vertical dynamic response of pile in a radially heterogeneous soil layerINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2009D. Y. Yang Abstract An analysis of a pile vertical response considering soil inhomogeneity in the radial direction under dynamic loads is presented. The solution technique is based on a three-dimensional axisymmetric model, which includes the consideration of the vertical displacement of the soil. The soil domain is subdivided into a number of annular vertical zones, and the continuity of the displacements and stresses are imposed at both the interface of pile,soil and the interfaces of adjacent soil zones to establish the dynamic equilibrium equations of the pile,soil interaction. Then, the equations of each soil zone and of the pile are solved one by one to obtain the analytical and semi-analytical dynamic responses at the top of the pile in the frequency domain and time domain. Parametric studies have been performed to examine the influence of soil parameters' variations in the radial direction caused by the construction effect on the dynamic responses of pile. The results of the studies have been summarized and presented in figures to illustrate the influences of the soil parameters as they change radially. The effect of the radius of the disturbed soil zone caused by construction is also studied in this paper. Copyright © 2008 John Wiley & Sons, Ltd. [source] Analysis of thick functionally graded plates by local integral equation methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2007J. Sladek Abstract Analysis of functionally graded plates under static and dynamic loads is presented by the meshless local Petrov,Galerkin (MLPG) method. Plate bending problem is described by Reissner,Mindlin theory. Both isotropic and orthotropic material properties are considered in the analysis. A weak formulation for the set of governing equations in the Reissner,Mindlin theory with a unit test function is transformed into local integral equations considered on local subdomains in the mean surface of the plate. Nodal points are randomly spread on this surface and each node is surrounded by a circular subdomain, rendering integrals which can be simply evaluated. The meshless approximation based on the moving least-squares (MLS) method is employed in the numerical implementation. Numerical results for simply supported and clamped plates are presented. Copyright © 2006 John Wiley & Sons, Ltd. [source] Elastic properties of nanowiresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2010Claus-Christian Röhlig Abstract The elastic properties of metallic and semiconducting nanowires were analyzed by different techniques employing static and dynamic loads. The reliability of the methods is verified by analyzing well defined microstructures and a good agreement for the values of the Young's modulus determined by the different methods was achieved. For the investigated materials systems (Au, W, Si, InN), basically no differences in the Young's moduli were observed between microstructures, bulk material, and nanowires with radii of 20,300,nm. Microstructure, morphological undulation, defects, and contaminations, however, can drastically change the apparent Young's moduli of nanowires. Examples are given, where an apparent increasing or decreasing of the Young's modulus with decreasing diameter is caused by such effects. The same effects have also influence on the fracture strength in nanowires. While perfect Au nanowires exhibit fracture strengths exceeding the bulk values up to two orders of magnitude, any anomaly causes earlier failure. In addition, failure mechanisms are observed to be dependent on the microstructure. While single crystalline Au nanowires have shown a pure elastic deformation upon load, polycrystalline nanowires show a remarkable plastic deformation before breaking. [source] Effects of dynamic loads acting on carrying cable in operating ropewayPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008Marta Knawa The model of a carrying rope under in,service loads is developed to analyze dynamic response of the cable during ropeway operation including: start conditions while carriers leave the station, steady ride, an emergency stop of a system. The pendulum model of a moving passenger carrier is formulated to define loads acting on the cable. Equations of motion of the cable loaded by moving pendulums are derived by applying Ritz approximate method and Lagrangian description of motion. Some numerical results are presented to illustrate applicability of proposed method in an investigation of carrying cable vibrations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||