Solution of the Static Deflection Mode Shape Function of the Cantilever Beam under Transverse Flow Based on the Boundary Shooting Method

According to the characteristics of the reactor internal structure of nuclear power plants, the vibration of the secondary core support pillar in water can be modeled as the vibration of the cantilever beam structure under the action of transverse flow, and its first beam mode is highly likely to be activated. It is thus necessary to dedicate a separate study on the first-order beam mode. In this work, we study the secondary core support pillar in nuclear reactor AP1000 under the action of transverse flow and focus on the derivation of its static cantilever deflection mode shape function in order to lay a foundation for the calculation of hydrodynamic added mass and frequency for the nuclear reactor internal components and their structural integrity evaluation. First, we proposed a set of nonlinear differential equations for the analysis of the single cantilever beam. Second, to solve the nonlinear differential equations, we used a boundary shooting framework in combination with the Runge–Kutta method. The results of the numerical simulation agree with the analytical solution to a very high degree, which demonstrates the effectiveness of the simulation method. Finally, we solved the static deflection mode shape function of the secondary core support pillar under the normal operating conditions. The nonlinear differential model and simulation method proposed in this paper can be used to solve the static cantilever deflection mode shape function of the equipment support tube.

Friction and Mechanical Properties of AFM-Scan-Induced Ripples in Polymer Films

When compliant samples such as polymer films are scanned with an atomic force microscope (AFM) in contact mode, a periodic ripple pattern can be induced on the sample. In the present paper, friction and mechanical properties of such ripple structures on films of polystyrene (PS) and poly-n-(butyl methacrylate) (PnBMA) are investigated. Force volume measurements allow a quantitative analysis of the elastic moduli with nanometer resolution, showing a contrast in mechanical response between bundles and troughs. Additionally, analysis of the lateral cantilever deflection when scanning on pre-machined ripples shows a clear correlation between friction and the sample topography. Those results support the theory of crack propagation and the formation of voids as a mechanism responsible for the formation of ripples. This paper also shows the limits of the presented measuring methods for soft, compliant, and small structures. Special care must be taken to ensure that the analysis is not affected by artefacts.

Investigation of a metrological atomic force microscope system with a combined cantilever position, bending and torsion detection system

This article presents a new metrological atomic force microscope (MAFM) head with a new beam alignment and a combined one-beam detection of the cantilever deflection. An interferometric measurement system is used for the determination of the position of the cantilever, while a quadrant photodiode measures the bending and torsion of the cantilever. To improve the signal quality and reduce disturbing interferences, the optical design was revised in comparison to the systems of others (Dorozhovets et al., 2006; Balzer et al., 2011; Hausotte et al., 2012). The integration of the MAFM head in a nanomeasuring machine (NMM-1) offers the possibility of large-scale measurements over a range of 25mm×25mm×5 mm with sub-nanometre resolution. A large number of measurements have been performed by this MAFM head in combination with the NMM-1. This paper presents examples of the measurements for the determination of step height and pitch and areal measurement.

The molecular mechanism of load adaptation by branched actin networks

Branched actin networks are self-assembling molecular motors that move biological membranes and drive many important cellular processes. Load forces slow the growth and increase the density of these networks, but the molecular mechanisms governing this force response are not well understood. Here we use single-molecule imaging and AFM cantilever deflection to measure how applied forces affect each step in branched actin network assembly. Unexpectedly, force slows the rate of filament nucleation by promoting the interaction of nucleation promoting factors with actin filament ends, limiting branch formation. This inhibition is countered by an even larger force-induced drop in the rate of filament capping, resulting in a shift in the balance between nucleation and capping that increases network density. Remarkably, the force dependence of capping is identical to that of filament elongation because they require the same size gap to appear between the filament and load for insertion. These results provide direct evidence that Brownian Ratchets generate force and govern the load adaptation of branched actin networks.

Cantilever-Based Sensor Utilizing a Diffractive Optical Element with High Sensitivity to Relative Humidity

High-sensitivity and simple, low-cost readout are desirable features for sensors independent of the application area. Micro-cantilever sensors use the deflection induced by the analyte presence to achieve high-sensitivity but possess complex electronic readouts. Current holographic sensors probe the analyte presence by measuring changes in their optical properties, have a simpler low-cost readout, but their sensitivity can be further improved. Here, the two working principles were combined to obtain a new hybrid sensor with enhanced sensitivity. The diffractive element, a holographically patterned thin photopolymer layer, was placed on a polymer (polydimethylsiloxane) layer forming a bi-layer macro-cantilever. The different responses of the layers to analyte presence lead to cantilever deflection. The sensitivity and detection limits were evaluated by measuring the variation in cantilever deflection and diffraction efficiency with relative humidity. It was observed that the sensitivity is tunable by controlling the spatial frequency of the photopolymer gratings and the cantilever thickness. The sensor deflection was also visible to the naked eye, making it a simple, user-friendly device. The hybrid sensor diffraction efficiency response to the target analyte had an increased sensitivity (10-fold when compared with the cantilever or holographic modes operating independently), requiring a minimum upturn in the readout complexity.

Analysis on the Influence Factors of Construction Linear Control of Continuous Rigid Structure Bridge

In order to study the influence of prestress on cantilever deflection and construction linear control of continuous rigid frame bridge in construction stage, this paper introduces the significance of continuous rigid frame bridge’s linear control, the calculation principle and deflection influence analysis of vertical formwork elevation in cantilever construction. According to a specific continuous rigid frame bridge, this paper use the finite element software to simulate and calculate the deflection of prestress to the cantilever construction of continuous rigid frame bridge. The influence of friction coefficient between prestressed steel bundle and bellows and prestress loss on cantilever deflection and construction line control of continuous rigid frame bridge is also analyzed, furtherly brings out the solution to deal with the problems due to the change of prestress.

Theoretical study on thermal response of bimaterial microcantilevers of different coating materials

Bilayer microcantilever is a versatile tool in thermal and bio-sensing that responses relying on the mismatch between the two constituting materials. The cantilever response, such as the deflection and resonance frequency shift, could be involved when the cantilever is in contact with an arbitrary heat source in the ambient environment. In this study, the thermally induced deflection will be theoretically examined assuming a heat source locating at various positions on the cantilever. The combined contributions of the heat absorption, thermal conductivity, and material rigidity on thermal deflection will be revealed. Selecting an optimal spot position leads to 1.5 times enhancement of the cantilever deflection in comparison to the thermal excitation at the cantilever end in conventional experiments, which implies a significant increase in thermal sensitivity. Furthermore, response of cantilevers of different coating materials of Au, Al, Cu, or Ni have been examined and shown a dominant sensitivity of Al- and Ni- over Cu- and Au-coated cantilevers. These results could help to explain recently experimental result and to figure out an optimal thermal excitation of microcantilevers in sensing.

Static and Dynamic Analysis of Carbon Nano Tube Cantilever for Nano Electro Mechanical Systems Based Applications

The cantilever is the most basic form of the MEMS and NEMS-based applications. It may include actuators and sensors in multiple domains for the detection of deflections due to change in mass and charge from atomic to sub-atomic levels. The main constraints in the real-time environment for sensing applications are good sensitivity and selectivity along with good response time and wide dynamic range. CNTs (Carbon Nano Tubes) possess excellent electrical characteristics with good mechanical strength like elasticity, flexibility, tensile strength and good thermal conductivity. These properties make use of CNTs in NEMS that gives rise to good sensing platforms. In this paper we propose, design and analysis of CNT based Cantilever structure using FEM to determine the change in deflection due to varying load under static analysis. Similarly from dynamic analysis change in resonance frequency for change in thickness of Cantilever is performed. From the experimental results using COMSOL simulation, it is observed that the CNT based Cantilever deflection sensitivity is 9.85 x 10-8 m under maximum stress of 6.71 x 10-9 N/m2. From the dynamic analysis, resonant frequency occurs at 1.8 x 107 Hz for 10 nm thickness and for 50 nm is 7.5 x 107 Hz respectively.