Deflection (engineering)

About: Deflection (engineering) is a research topic. Over the lifetime, 30862 publications have been published within this topic receiving 298849 citations.

Behavior of a simple concrete beam driven by shape memory alloy wires

Abstract: The behavior of a simple concrete beam driven by heated shape memory alloy (SMA) wires using electrical currents is studied in this paper. The test results indicate that recovery forces of the SMA wires can decrease the mid-span deflection of the simple concrete beam, decrease the absolute value of compressive strains and even compress the concrete in the tensile zone. Furthermore, the heated SMA wires can make cracks close and perform the task of emergency damage repair in civil structures. This study also attempts to conduct permanent damage repair using carbon fiber reinforced polymer (CFRP) plates after emergency damage repair using SMA wires. Moreover, the relationship between rate of change of resistance of the SMAs and mid-span deflection of the beam is obtained in this paper. It is devoted to damage detection for civil structures.

Size effect in micro-scale cantilever beam bending

Abstract: When the thickness of metallic cantilever beams reduces to the order of micron, a strong size effect of mechanical behavior has been found. In order to explain the size effect in a micro-cantilever beam, the couple-stress theory (Fleck and Hutchinson, J Mech Phys Solids 41:1825–1857, 1993) and the C-W strain gradient theory (Chen and Wang, Acta Mater 48:3997–4005, 2000) are used with the help of the Bernoulli–Euler beam model. The cantilever beam is considered as the linear elastic and rigid-plastic one, respectively. Analytical results of the cantilever beam deflection under strain gradient effects by applying these two kinds of theories are obtained, from which we find an explicit relationship between the intrinsic lengths introduced in the two kinds of theories. The theoretical results are further used to analyze the experimental observations, and predictions by both theories are further compared. The results in the present paper should be useful for the design of micro-cantilever beams in MEMS and NEMS.

Static and vibration analyses of thick, generally laminated deep curved beams with different boundary conditions

Abstract: A rigorous first order shear deformation theory is employed along with modified ABD parameters to analyze static and free vibration behavior of generally laminated deep curved beams. The deepness term (1 + z/R) is exactly integrated into ABD parameters formulation and equivalent modulus of elasticity is used instead of traditional stiffness terms to account for deepness and material coupling of the beam structures, respectively. Static as well as free vibration analyses were performed and the results for deflection, moment resultants, and natural frequencies were obtained. The exact solution for simply supported boundary condition as well as numerical solutions using GDQ for other boundary conditions are presented. Results are compared with those obtained using accurate three dimensional finite element simulations using commercial software. It has been shown that when considering more accurate stiffness parameter, FSDT can accurately predict static and free vibration behaviors of composite deep beams of any lamination and boundary condition.

Modelling of the mechanical behaviour of a differential capacitor acceleration sensor

Abstract: A mechanical model and its mathematical solution are presented, which have been developed in order to calculate the sensitivity and frequency behaviour of an acceleration sensor. The sensor is built up as an interdigitated differential capacitor and is driven in a 'high frequency' detection circuitry with an overall electromechanical closed-loop configuration. It is fabricated using surface micromachining techniques and consists of 2 μm thick polysilicon beams. Due to the processes during manufacturing technology, the material contains an inherent tensile stress, such that the mechanical behaviour is not only determined by the restoring bending moments of the suspension tethers. The calculated deflection of the sensor element amounts to only 0.6 nm g−1; its resonance frequency is about 21 kHz. The results will be discussed and compared with the results obtained by finite-element analysis.