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 paper, the mechanical properties of ultrananocrystalline diamond (UNCD) thin films were measured using microcantilever deflection and membrane deflection techniques.
Abstract: The mechanical properties of ultrananocrystalline diamond (UNCD) thin films were measured using microcantilever deflection and membrane deflection techniques. Bending tests on several free-standing UNCD cantilevers, 0.5 μm thick, 20 μm wide and 80 μm long, yielded elastic modulus values of 916–959 GPa. The tests showed good reproducibility by repeated testing on the same cantilever and by testing several cantilevers of different lengths. The largest source of error in the method was accurate measurement of film thickness. Elastic modulus measurements performed with the novel membrane deflection experiment (MDE), developed by Espinosa and co-workers, gave results similar to those from the microcantilever-based tests. Tests were performed on UNCD specimens grown by both micro and nano wafer-seeding techniques. The elastic modulus was measured to be between 930–970 GPa for the microseeding and between 945–963 GPa for the nanoseeding technique. The MDE test also provided the fracture strength, which for UNCD was found to vary from 0.89 to 2.42 GPa for the microseeded samples and from 3.95 to 5.03 for the nanoseeded samples. The narrowing of the elastic modulus variation and major increase in fracture strength is believed to result from a reduction in surface roughness, less stress concentration, when employing the nanoseeding technique. Although both methods yielded reliable values of elastic modulus, the MDE was found to be more versatile since it yielded additional information about the structure and material properties, such as strength and initial stress state.
77 citations
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TL;DR: In this paper, the composite behavior of the beams, the interaction of the plate, glue and concrete, and the influence of the glued plate on stiffness, cracking, plate slip, interface shear stress and ultimate strength of the reinforced concrete beams are discussed.
77 citations
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TL;DR: In this article, a two-variable refined plate theory was proposed to account for parabolic variation of transverse shear stress through the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factor.
77 citations
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TL;DR: In this article, the authors extended this technique to other porous materials, such as porous glass and cement paste, and analyzed the force required to sustain the deflection as a function of time.
Abstract: When a saturated porous material is deformed, pressure gradients are created in the liquid, and the liquid flows within the pores to equilibrate the pressure. This phenomenon can be exploited to measure permeability : a rod of saturated porous material is instantaneously bent by a fixed amount, and the force required to sustain the deflection is measured as a function of time. The force decreases as the liquid flows through the pore network, and the rate of decrease depends on the permeability. This technique has been applied successfully to determine the permeability of gels, as well as their viscoelastic properties; in this paper the method is extended to ceramic materials, such as porous glass and cement paste. The theory has been modified to take account of the compressibility of the solid and liquid phases (whereas, those factors are negligible for gels). Analyses are presented for constant deflection, constant rate of deflection, and sinusoidal oscillation, where the solid phase is either purely elastic or viscoelastic, and the beam is either cylindrical or square. Experimental tests on Vycor® glass and cement paste will be presented in companion papers.
77 citations
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TL;DR: In this paper, two minimization problems are presented that determine parameters for best practice single degree of freedom (SDOF) models, based on the blast response of structural members, using dynamic experimental data as obtained from pressure and laser deflection measurements.
76 citations