Mechanism of the Transition From In-Plane Buckling to Helical Buckling for a Stiff Nanowire on an Elastomeric Substrate

2016 ◽  
Vol 83 (4) ◽  
Author(s):  
Youlong Chen ◽  
Yong Zhu ◽  
Xi Chen ◽  
Yilun Liu

In this work, the compressive buckling of a nanowire partially bonded to an elastomeric substrate is studied via finite-element method (FEM) simulations and experiments. The buckling profile of the nanowire can be divided into three regimes, i.e., the in-plane buckling, the disordered buckling in the out-of-plane direction, and the helical buckling, depending on the constraint density between the nanowire and the substrate. The selection of the buckling mode depends on the ratio d/h, where d is the distance between adjacent constraint points and h is the helical buckling spacing of a perfectly bonded nanowire. For d/h > 0.5, buckling is in-plane with wavelength λ = 2d. For 0.27 < d/h < 0.5, buckling is disordered with irregular out-of-plane displacement. While, for d/h < 0.27, buckling is helical and the buckling spacing gradually approaches to the theoretical value of a perfectly bonded nanowire. Generally, the in-plane buckling induces smaller strain in the nanowire, but consumes the largest space. Whereas the helical mode induces moderate strain in the nanowire, but takes the smallest space. The study may shed useful insights on the design and optimization of high-performance stretchable electronics and three-dimensional complex nanostructures.

Author(s):  
Lei Huang ◽  
Andy Y F Leung

The influence of soil variability on three-dimensional (3D) probabilistic slope stability analysis has been previously investigated for soils that display isotropic spatial variability features or anisotropic horizontal fabric patterns. However, due to various soil deposition processes, weathering, filling or tectonic movements, the assumptions of isotropy or horizontal layering may not always be realistic. This study presents 3D analyses of slopes with spatially variable soils associated with rotated transverse anisotropy features. The results show that for cross-dip slopes where the strike direction of soil strata is perpendicular to the out-of-plane direction of the slope, the reliability depends on various factors including strata rotation angle and autocorrelation distances, and differs significantly from slopes with horizontally deposited soil fabric. The influence of strata orientation is also pronounced for dip slopes and reverse dip slopes, and these are presented in terms of reliability indices of the slopes and statistics of the length of sliding mass, and elaborated by considering the failure mechanism under different scenarios. Through these analyses, this paper discusses the key features of slope reliability considering rotated transverse anisotropy in soil properties, and their major differences from situations involving horizontal soil layers or two-dimensional probabilistic assessments.


2019 ◽  
Vol 86 (3) ◽  
Author(s):  
Yin Huang ◽  
Zhuangzhuang Mu ◽  
Peng Feng ◽  
Jianghong Yuan

Inorganic stretchable electronics based on the island-bridge layout have attracted great attention in recent years due to their excellent electrical performance under the extreme condition of large deformations. During the mechanics design of interconnects in such devices, the major task is not only to maximize the elastic stretchability of device but also to smoothen the whole deformation process of interconnects. In this work, a novel design strategy is proposed for free-standing fractal serpentine interconnects to improve their elastic performance comprehensively without reducing the areal coverage of functional/active components of device. By modifying the classical design slightly, the new strategy can achieve a larger elastic stretchability, a smaller maximum out-of-plane displacement, and most strikingly, a smoother post-buckling deformation. This study will provide helpful guidance to the mechanics design of stretchable electronics with free-standing interconnects.


2012 ◽  
Vol 229-231 ◽  
pp. 1939-1943 ◽  
Author(s):  
Abid Ali ◽  
R.A. Azim ◽  
U.S. Khan ◽  
A.A. Syed ◽  
U. Izhar

This work presents the design and optimization of out of plane electrothermal MEMS actuators. The proposed concept is capable of generating large out of plane displacement at low driving power and a low actuation temperature. The performance of this actuator is evaluated and simulated in ANSYS. The out of plane displacement of 291µm at a temperature increase of 135°C from ambient has been achieved with the applied power of 2.7mW(0.7V). Moreover, a thermal time constant of 5.6ms and a frequency of 85Hz is accomplished for this actuator.


2011 ◽  
Vol 228-229 ◽  
pp. 526-531
Author(s):  
Cai Xia You ◽  
Guang De Zhang

This paper describes the basic concept of the new technique for the modeling of the structural-acoustic coupling between the pressure field in an acoustic cavity with arbitrary shape and the out-of-plane displacement of a flat plate with arbitrary shape. It is illustrated through a three-dimensional validation example that the new prediction technique yields a high accuracy. The effect of the cavity depth and the coupling interface area on the strength of mutual coupling interaction are discussed in detail.


Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1900
Author(s):  
Christian Marschik ◽  
Wolfgang Roland ◽  
Marius Dörner ◽  
Sarah Schaufler ◽  
Volker Schöppner ◽  
...  

Due to progress in the development of screw designs over recent decades, numerous high-performance screws have become commercially available in single-screw extrusion. While some of these advanced designs have been studied intensively, others have received comparatively less attention. We developed and validated a semi-numerical network-theory-based modeling approach to predicting flows of shear-thinning polymer melts in wave-dispersion screws. In the first part (Part A), we systematically reduced the complexity of the flow analysis by omitting the influence of the screw rotation on the conveying behavior of the wave zone. In this part (Part B), we extended the original theory by considering the drag flow imposed by the screw. Two- and three-dimensional melt-conveying models were combined to predict locally the conveying characteristics of the wave channels in a discretized flow network. Extensive experiments were performed on a laboratory single-screw extruder, using various barrel designs and wave-dispersion screws. The predictions of our semi-numerical modeling approach for the axial pressure profile along the wave-dispersion zone accurately reproduce the experimental data. Removing the need for time-consuming numerical simulations, this modeling approach enables fast analyses of the conveying behavior of wave-dispersion zones, thereby offering a useful tool for design and optimization studies and process troubleshooting.


2019 ◽  
Vol 688 ◽  
pp. 137435 ◽  
Author(s):  
Dong-Bin Moon ◽  
Jaedeuk Lee ◽  
Eun Roh ◽  
Nae-Eung Lee

Author(s):  
Niranjan Desai ◽  
Joel Poling ◽  
Gregor Fischer ◽  
Christos Georgakis

This investigation determined the effect of specimen out-of-plane movement on the accuracy of strain measurement made applying two-dimensional (2D) and three-dimensional (3D) measurement approaches using the representative, state-of-the-art digital image correlation (DIC)-based tool ARAMIS. DIC techniques can be used in structural health monitoring (SHM) by measuring structural strains and correlating them to structural damage. This study was motivated by initially undetected damage at low strains in connections of a real-world bridge, whose detection would have prevented its propagation, resulting in lower repair costs. This study builds upon an initial investigation that concluded that out-of-plane specimen movement results in noise in DIC-based strain measurements. The effect of specimen out-of-plane displacement on the accuracy of strain measurements using the 2D and 3D measurement techniques was determined over a range of strain values and specimen out-of-plane displacements. Based upon the results of this study, the 2D system could measure strains as camera focus was being lost, and the effect of the loss of focus became apparent at 1.0 mm beam out-of-plane displacement while measuring strain of the order of magnitude of approximately 0.12%. The corresponding results for the 3D system demonstrate that the beam out-of-plane displacement begins to affect the accuracy of the strain measurements at approximately 0.025% strain for all magnitudes of out-of-plane displacement, and the 3D ARAMIS system can make accurate strain measurements at up to 2.5 mm amplitude at this strain. Finally, based upon the magnitudes of strain and out-of-plane displacement amplitudes that typically occur in real steel bridges, it is advisable to use the 3D system for SHM of stiff structures instead of the 2D system.


Author(s):  
Yi-Chung Tung ◽  
Jeong-Gil Kim ◽  
Katsuo Kurabayashi

This paper investigates a novel silicon/polymer hybrid MEMS actuator and reports on its design optimization. The actuator, incorporating a three-dimensional poly(dimethylsiloxane) (PDMS) flexural microstructure, is designed to generate multi-axis displacement of motion. This work develops a four-bar linkage model for parametric design of the actuator and validates it using finite element analysis (FEA). The optimization of the device geometry is performed using Genetic Algorithm (GA) such that the resulting out-of-plane displacement can achieve a maximum value under several design constrains due to fabrication and operation limitations. The out-of-plane displacement of the optimized actuator structure is calculated to be as large as 60 μm at 50 V input actuation voltage. Due to its unique mechanical and optical material properties, the PDMS microstructure allows the proposed device to achieve actuation performances suitable for a wide variety of micro-optics applications, including micro optical scanners, dynamic-focus micro lens holders, and mechanically flexible optical gratings.


2008 ◽  
Author(s):  
Yihong Yang ◽  
Roe-Hoan Yoon ◽  
Demetri P. Telionis ◽  
Asa Weber ◽  
Don Foreman

The flow in stirred tanks is very complicated because it passes around the rotating impeller blades, interacts with the stationary baffles or stator blades leading to high-intensity turbulence, and then goes through loops and returns to the impeller region. A penetrating understanding of the flow in stirred tanks is necessary for the tank design and optimization, because it could have a significant impact to the overall design characteristics, which will affect directly the production, the quality of the product and the maintenance costs. Despite the recent advances in computational fluid dynamics (CFD), testing still plays a vital role in the development of high-performance stirred tanks. This paper describes measurements and results obtained by traversing a five-hole probe in a 6-m3 stirred tank. The three-dimensional flow field was obtained. The separation region was also detected. The majority of the measurements were conducted in the 6-m3 tank, but unique to this investigation are measurements we have conducted with Pitot tubes in an 160-m3 geometrically-similar full-scale tank. We also have earlier results obtained by Particle Image Velocimetry (PIV) in another geometrically-similar but much smaller tank, namely a 0.1m3 tank. This provides the unique opportunity to explore how such flows scale with size and speed, extending to Reynolds numbers that approach ten million. Some numerical results were also conducted, using the commercial code FLUENT, and the results are presented together with the experimental data.


Author(s):  
Lee D. Peachey ◽  
Lou Fodor ◽  
John C. Haselgrove ◽  
Stanley M. Dunn ◽  
Junqing Huang

Stereo pairs of electron microscope images provide valuable visual impressions of the three-dimensional nature of specimens, including biological objects. Beyond this one seeks quantitatively accurate models and measurements of the three dimensional positions and sizes of structures in the specimen. In our laboratory, we have sought to combine high resolution video cameras with high performance computer graphics systems to improve both the ease of building 3D reconstructions and the accuracy of 3D measurements, by using multiple tilt images of the same specimen tilted over a wider range of angles than can be viewed stereoscopically. Ultimately we also wish to automate the reconstruction and measurement process, and have initiated work in that direction.Figure 1 is a stereo pair of 400 kV images from a 1 micrometer thick transverse section of frog skeletal muscle stained with the Golgi stain. This stain selectively increases the density of the transverse tubular network in these muscle cells, and it is this network that we reconstruct in this example.


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