A Fully-Compliant, In-Plane Rotary, Bistable Micromechanism

2005 ◽  
Author(s):  
Rajesh Luharuka ◽  
Peter J. Hesketh
Keyword(s):  
Aspect Ratio ◽  
Element Model ◽  
Relative Advantage ◽  
Test Results ◽  
Positive Photoresist ◽  
Out Of Plane ◽  
Symmetric Geometry ◽  
Optical Shutter ◽  
Bistable Mechanism ◽  
The Individual

A fully compliant bistable micromechanism (hereafter identified as an in-plane rotary bistable micromechanism or IPRBM) is designed to accomplish in-plane rotary motion with two stable positions. The micromechanism consists of four individually bistable mechanisms arranged in a cyclically symmetric geometry about a central proof mass. This class of bistable mechanism can be used in gate valve, optical shutter, and other switching applications. Two classes of IPRBMs are investigated in this paper. The bistable micromechanism size is less than 1 mm and fabricated by electroplating a soft magnetic material — Permalloy (80% Ni, 20% Fe) in a positive photoresist mold. Minimum feature size in the IPRBM, which corresponds to the width of flexible linkages, is 4 μm. The fabricated IPRBMs have been tested for their force-deflection response using an image based force sensing method. The test results were then compared with the simulated results obtained from a finite element model of the IPRBM. The IPRBM are shown to reversibly undergo 10 to 20 degrees of in-plane rotation and required a maximum torque of 1 to 2 μNm depending on the design. The experimental results showed good overall agreement with the design. A comparison within and between the two classes of IPRBM have been completed for three different design cases between which the tether width and aspect ratio was varied. The study showed a relative advantage of slender tethers with high aspect ratio in minimizing out-of-plane deflection. Also, the radial separation of the individual bistable mechanisms is important.

Investigation of Discrete Out-of-Plane Waviness in Composite Wind Turbine Blades Using Ultrasonic Nondestructive Evaluation

2011 ◽  
Author(s):  
Sunil Kishore Chakrapani ◽  
Vinay Dayal ◽  
Daniel Barnard ◽  
David Hsu
Keyword(s):  
Aspect Ratio ◽  
Nondestructive Evaluation ◽  
Wind Turbine ◽  
High Frequency ◽  
Turbine Blades ◽  
Element Model ◽  
Wind Turbine Blades ◽  
Out Of Plane ◽  
Process Detection ◽  
Air Coupled Ultrasonics

With the need for larger and more efficient wind turbine blades, thicker composite sections are manufactured and waviness becomes difficult to control. Thus, there is a need for more effective and field implementable NDE. In this paper we propose a method of detection and quantification of waviness in composite wind turbine blades using ultrasonics. By employing air coupled ultrasonics to facilitate faster and easier scans, we formulated a two step process. Detection was performed with single sided air coupled ultrasonics, and characterization was performed with the help of high frequency contact probes. Severity of the wave was defined with the help of aspect ratio, and several samples with different aspect ratio waves were made. A finite element model for wave propagation in wavy composites was developed, and compared with the experimental results.

Out-of-Plane Bending (OPB) Test of Large Diameter Mooring Chains

2020 ◽  
Author(s):  
P. Barros ◽  
E. Carlberg ◽  
I. S. Høgsæt ◽  
M. R. Karimi ◽  
J. Braun ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Large Diameter ◽  
Element Model ◽  
Maximum Diameter ◽  
Test Results ◽  
Test Setup ◽  
Out Of Plane ◽  
Plane Bending ◽  
A Chain

Abstract Chevron Corporation and Bluewater Energy Services (BES) performed a chain out-of-plane bending (OPB) test, called OPB MAX hereafter, at DNV GL’s laboratory in Høvik-Norway. The test was performed to study the OPB phenomenon for a chain diameter which was larger than the maximum diameter tested by the OPB JIP. The goal was to understand chain OPB physics for such a large diameter, measure interlink stiffness and maximum sliding moments and validate BES’ in-house finite element model. The current study is a collaboration between all involved parties and the results will be presented in three papers. The first paper summarizes the test setup and instrumentation. The second paper describes the test results, compares them with the OPB JIP estimations and tries to describe the chain OPB physics. The third and the last paper presents the FEA results performed by BES’ in-house finite element model. This paper is the first of the three and focuses on the test setup and instrumentation. The testing machine has been developed by DNV GL and is capable of applying tensions up to 350 t and interlink rotations in the range of ±3 degrees. Two 7-link chain specimens of R4 and R4s grades, both with the nominal diameter of 168 mm were tested at five tension levels from 150, to 350 t. Testing was performed in both wet and dry conditions. Twenty strain gauges were used to measure 3 OPB and 2 IPB moments at 5 mid-link positions. Twelve strain gauge rosettes were used on 3 links to evaluate SCF’s on the OPB hotspots. Seven inclinometers were used to monitor link rotations. DNV GL utilized a digital image processing tool to capture relative movements of chain links and developed a specific data processing tool to calculate the interlink stiffness, perform statistical analysis and provide several levels of data evaluation and comparison between the tests. The paper will provide a description of the test matrix and test objectives are given with the background of the previously performed OPB tests. Next a detailed description of the test rig is presented including the utilized instrumentation. Finally, an explanation of the implemented real-time test monitoring and the performed post-processing on the readings, in line with the test objectives is mentioned. The initial test results are briefly provided at the end.

Laminated Photoresist Sacrificial Layer Process for 3-D Movable Suspension Microstructures in LIGA-Based Surface Micromachining

2010 ◽  
Vol 97-101 ◽  
pp. 2538-2541 ◽  
Author(s):  
Yi Bo Wu ◽  
Gui Fu Ding ◽  
Cong Chun Zhang ◽  
Hong Wang
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Sacrificial Layer ◽  
Low Cost ◽  
Three Dimensional ◽  
Mems Devices ◽  
Metal Structures ◽  
Positive Photoresist ◽  
Out Of Plane ◽  
Freely Moving

The fabrication process of three-dimensional (3D) high-aspect-ratio MEMS devices entirely made of electroplated metals with suspending multilayered microstructures is reported. The technology used is a LIGA-liked micromachining process, called the laminated positive photoresist sacrificial layer process (LPSLP). The LPSLP allows in UV-lithography not only for thick resist mould for electroplating of cascaded metal structures but also for the sacrificial layer for supporting mechanically the suspensions. So far the LPSLP procedure has incorporated with more than five sacrificial layers, which allows for the creation of overhanging structures and freely moving parts like out-of-plane cantilever stacks. A description of the underlying fabrication principle and processing details is discussed in this paper. Thus the proposed procedures open a low-cost route for fabricating micro-components such as cantilevers, bridges, movable electrodes, and freestanding parts.

scholarly journals Numerical Investigation on the Influence of In-Plane Damage on the Out-of-Plane Behavior of Masonry Infill Walls

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Xiaomin Wang ◽  
Weitong Zhao ◽  
Jingchang Kong ◽  
Tiejun Zhao
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
Finite Element Model ◽  
Slenderness Ratio ◽  
Element Model ◽  
Infill Wall ◽  
Infill Walls ◽  
Masonry Infill ◽  
Masonry Infill Walls ◽  
Out Of Plane

This study presents a finite element model to investigate the bidirectional seismic behavior of masonry infill walls. The test data are utilized to verify the numerical model. The comparison between the analytical and the experimental results indicates that the finite element model can successfully predict the failure mode, stiffness, and strength of the masonry infill wall. Based on the model, the effects of aspect ratio (height to length), slenderness ratio (height to thickness), and masonry strength on the out-of-plane (OOP) response of infill wall with in-plane (IP) damage are explored. Considering the aspect ratio, slenderness ratio, and masonry strength of infill wall, the OOP behavior of infill wall with and without IP damage is studied. Finally the reduction of the stiffness and strength in the OOP direction, due to the IP damage, is discussed.

Analysis of the critical stresses in high-voltage composite winding insulations under thermal loads

2019 ◽  
Vol 54 (15) ◽  
pp. 2073-2084
Author(s):  
Harish Kalyan Ram Pothukuchi ◽  
Peter Fuchs ◽  
Clara Schuecker
Keyword(s):  
Thermal Stresses ◽  
Interfacial Shear Stress ◽  
Element Model ◽  
Critical Range ◽  
Out Of Plane ◽  
Alternating Temperature ◽  
Critical Components ◽  
The Individual ◽  
Temperature Loads ◽  
Winding Insulation

Stator bars are the critical components in generators with respect to their lifespan. The winding insulation may be susceptible to damage under excessive alternating temperature loads incurred by a high number of start–stop cycles and heavy overloads. The differences in thermal expansion between the different components in the multi-layered winding insulation lead to thermal stresses. This work deals with the thermo-mechanical characterisation of the individual constituents of the winding insulation and the finite element model of a stator bar, based on the material data obtained from the tests that enable the identification of the thermal stresses leading to delamination over thermal cycles. The out-of-plane and the interfacial shear stress are found to be in the critical range with respect to the relatively low cohesive strength of the included individual mica layers.

Out-of-Plane Bending (OPB) Test of Large Diameter Mooring Chains: Test Results

2021 ◽  
Author(s):  
M. R. Karimi ◽  
P. Barros ◽  
E. Carlberg ◽  
P. Vargas
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Large Diameter ◽  
Element Model ◽  
Maximum Diameter ◽  
Test Results ◽  
Out Of Plane ◽  
Dry Conditions ◽  
Plane Bending ◽  
A Chain

Abstract Chevron Corporation and Bluewater Energy Services performed a chain out-of-plane bending (OPB) test campaign, called OPB MAX hereafter, at DNV’s laboratory in Høvik-Norway. The test was performed to study the OPB phenomenon for a chain diameter which was larger than the maximum diameter tested by the OPB JIP [12]. The goal was to understand chain OPB physics for such a large diameter, measure interlink stiffness and maximum sliding moments and validate Bluewater’s in-house finite element model. The current study is a collaboration between all involved parties and the results are presented in three papers. The first paper, Barros et al. [1], summarized the test setup, initial observations and the assumptions used in the post-processing. The current paper describes some of the test results, compares them with the OPB JIP estimations and describes the observed chain OPB physics. The third and the last paper will present the FEA results done by Bluewater’s in-house finite element model. Two seven-link chain specimens of R4 and R4S grades, both with the nominal diameter of 168 mm were tested. Five tension levels of 150, 200, 250, 300 and 350 t were used throughout the tests. Chain sliding was performed in both wet and dry conditions. Twenty strain gauges were attached to five links of each specimen except for the two end-links to measure three OPB and two IPB moments at mid-link. Twelve strain gauge rosettes were used on three links to evaluate SCF on the OPB hotspots. Seven inclinometers were used to monitor link rotations. DNV’s ARAMIS image processing tool was utilized to capture chain movements. A handheld temperature sensor gun monitored the interlink area’s temperature. Interlink stiffness was measured at both ends of each specimen and four intermediate links. Several sensitivity studies were conducted to investigate the effect of loading speed, initial interlink angle and acquisition frequency. The interlink stiffness values that were initially found based on tests at small interlink angles (±0.2 °) were quite consistent and repeatable. Further tests that were performed at large interlink angles (±2.5 °) showed that interlink moment vs. angle hysteresis changes over time and is not unique. This was attributed to deformations observed at the interlink areas that had happened during the tests. The mentioned deformations directly influenced the hysteresis and the associated interlink stiffness values. The nature of deformations and stiffness variations was different during dry and wet tests at large angles. Furthermore, the interlink stiffness values measured on the R4S specimen were quite close to R4 results.

scholarly journals Children’s Astronomy. Development of the Shape of the Earth Concept in Polish Children between 5 and 10 Years of Age

2021 ◽  
Vol 11 (2) ◽  
pp. 75
Author(s):  
Jan Amos Jelinek
Keyword(s):  
Mental Model ◽  
Cultural Influences ◽  
Test Results ◽  
The Earth ◽  
Spherical Earth ◽  
The Individual ◽  
High Level ◽  
Cognitive Problems ◽  
Teaching Situations ◽  
Model Approach

The Earth’s shape concept develops as consecutive cognitive problems (e.g., the location of people and trees on the spherical Earth) are gradually resolved. Establishing the order of problem solving may be important for the organisation of teaching situations. This study attempted to determine the sequence of problems to be resolved based on tasks included in the EARTH2 test. The study covered a group of 444 children between 5 and 10 years of age. It captured the order in which children solve cognitive problems on the way to constructing a science-like concept. The test results were compared with previous studies. The importance of cultural influences connected to significant differences (24%) in test results was emphasised. Attention was drawn to the problem of the consistency of the mental model approach highlighted in the literature. The analysis of the individual sets of answers provided a high level of consistency of indications referring to the same model (36%), emphasising the importance of the concept of mental models.

scholarly journals Experimental and Numerical Investigation on the Steel Reinforced Grout (SRG) Composite-to-Concrete Bond

2020 ◽  
Vol 4 (4) ◽  
pp. 182
Author(s):  
Luciano Ombres ◽  
Salvatore Verre
Keyword(s):  
Bond Length ◽  
Failure Modes ◽  
Peak Load ◽  
Element Model ◽  
Test Results ◽  
Shear Tests ◽  
Bond Slip ◽  
Bond Behavior ◽  
Direct Shear Tests ◽  
Inorganic Matrix

In the paper, the bond between a composite strengthening system consisting of steel textiles embedded into an inorganic matrix (steel reinforced grout, SRG) and the concrete substrate, is investigated. An experimental investigation was carried out on medium density SRG specimens; direct shear tests were conducted on 20 specimens to analyze the effect of the bond length, and the age of the composite strip on the SRG-to-concrete bond behavior. In particular, the tests were conducted considering five bond length (100, 200, 250, 330, and 450 mm), and the composite strip’s age 14th, 21st, and 28th day after the bonding. Test results in the form of peak load, failure modes and, bond-slip diagrams were presented and discussed. A finite element model developed through commercial software to replicate the behavior of SRG strips, is also proposed. The effectiveness of the proposed numerical model was validated by the comparison between its predictions and experimental results.

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