Topic
Deflection (engineering)
About: Deflection (engineering) is a research topic. Over the lifetime, 30862 publications have been published within this topic receiving 298849 citations.
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TL;DR: In this article, the identification of a single crack in a beam based on the knowledge of the damage-induced variations in the static deflection of the beam is discussed and sufficient conditions on static measurements which allow for the unique identification of the crack are presented and discussed.
86 citations
TL;DR: In this article, the static and dynamic behavior of carbon nanotube-reinforced composite plates resting on the Pasternak elastic foundation including shear layer and Winkler springs is investigated.
86 citations
TL;DR: In this article, the authors investigated the damage character of reinforced concrete beams under close-in blast loading through experiments and showed that the spallation area increases with the decrease of the scaled distance.
86 citations
TL;DR: In this paper, the authors provide an in-depth synthesis of knowledge acquired over the last several decades pertaining to the analysis and design of doweled slab-on-grade pavement systems.
Abstract: This paper provides an in‐depth synthesis of knowledge acquired over the last several decades pertaining to the analysis and design of doweled slab‐on‐grade pavement systems. This task is accomplished on the basis of rigorous, theoretically sound engineering principles, and relies extensively on the application of dimensional analysis for the interpretation of finite element data pertaining to the behavior of doweled joints. A design procedure is derived that allows, for the first time, the determination of the dowel diameter and spacing required to achieve a desired level of load transfer, or a threshold value of dowel‐concrete bearing stress. The proposed approach eliminates the need for any a priori assumptions with respect to the distribution of dowel shear forces. An efficient and general method for the backcalculation of the modulus of dowel reaction, K, from deflection data is also suggested. These research findings constitute a mechanistic structural model for JPCP and contribute significantly tow...
86 citations
TL;DR: The high speed cantilever piezovalve may find broad applicability in experiments where short and strong gas pulses are needed with only modest pumping, the effective use of (expensive) samples, or the production of cold atomic and molecular beams.
Abstract: In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4× 10 22 particles/ (s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5× 10-6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever valve makes it possible to design very compact single chamber molecular beam machines with high quality cold and intense supersonic beams. The high speed cantilever piezovalve may find broad applicability in experiments where short and strong gas pulses are needed with only modest pumping, the effective use of (expensive) samples, or the production of cold atomic and molecular beams. © 2009 American Institute of Physics.
86 citations