scholarly journals Design and Analysis of a Novel Flexure-Based Dynamically Tunable Nanopositioner

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 212
Author(s):  
Zeying Li ◽  
Pengbo Liu ◽  
Peng Yan
Keyword(s):  
Magnetic Field ◽  
High Performance ◽  
Dynamic Models ◽  
Elastic Beam ◽  
Beam Theory ◽  
Variable Stiffness ◽  
Sustained Load ◽  
Element Analysis ◽  
Dynamic Tuning ◽  
Trade Offs

Various tools, such as biomedical manipulators, optical aligners, and ultraprecision manufacturing tools, implement nanopositioners that must be dynamically tunable to satisfy the requirements of different working conditions. In this paper, we present the design and analysis of a flexure-based nanopositioner with dynamically tunable characteristics for the implementation of a high-performance servomechanism. The nanopositioner is composed of four flexure beams that are positioned in parallel and symmetric configurations sandwiched between magnetorheological elastomers (MREs). The properties of MREs impart dynamicity to the nanopositioner, allowing the workspace, stiffness, and damping characteristics in particular to be tuned under the action of an external magnetic field. By utilizing elastic beam theory and electromagnetic field coupling analysis, kinetostatic and dynamic models of the proposed nanopositioner were established to predict the variable stiffness property and dynamically tunable characteristics. The models were validated by performing a finite element analysis. Herein, it is shown that the proposed nanopositioner model can actively adjust the trade-offs between the working range, speed, and sustained load capability by changing the magnetic field. The proposed dynamic tuning method offers new insight into the design of flexure-based nanopositioners for real applications.

Comparison of ASME B31.1 Sustained Load Stresses to Corresponding Tresca Stresses

2012 ◽  
Author(s):  
Marvin J. Cohn
Keyword(s):  
Circumferential Stress ◽  
Elastic Beam ◽  
Beam Theory ◽  
High Energy ◽  
Parent Material ◽  
Sustained Load ◽  
Piping System ◽  
Longitudinal Stress ◽  
Analytical Methodology ◽  
Sustained Loads

Conventional United States designs of high energy piping (HEP) systems use the American Society of Mechanical Engineers (ASME) B31.1 Power Piping Code. The analytical methodology in this code is based on linear elastic beam theory. The ASME B31.1-2010 Power Piping Code (Code) [1] recommends Equation 15 to calculate the piping stress due to sustained loads. Many practitioners believe that the sustained load stress (SL) results using Equation 15 are not significantly less than using a Tresca methodology for the same set of forces and moments. This paper provides a comparison of the ASME B31.1 SL stresses to the corresponding Tresca stresses in parent material, based on empirical HEP system stress analyses. The results of three piping system evaluations are considered, including examples of longitudinal stress lower than the circumferential stress and examples where the longitudinal stress is greater than the circumferential stress. This study considers the elastic primary stresses on the outside surface of the pipe, prior to any creep redistribution. At locations where the longitudinal stress is greater than the circumferential stress, the SL stress is nearly the same as the elastic Tresca stress. At locations where the longitudinal stress is considerably less than the circumferential stress, the SL stress is considerably less than the elastic Tresca stress. This conclusion is due to the fact that the SL stress is primarily governed by longitudinal loading. The paper also considers inelastic primary stresses, after complete creep redistribution. For piping materials operating in the creep regime, the axial and circumferential pressure stresses are eventually redistributed and are maximum at the outer surface of the pipe. After several years of operation, the Code SL stresses and elastic Tresca stresses are significantly less than the inelastic Tresca stresses. Consequently, the use of SL stresses and elastic Tresca stresses for estimating component inelastic primary stresses would be nonconservative.

scholarly journals Displacement amplification ratio modeling of bridge-type nano-positioners with input displacement loss

2019 ◽  
Vol 10 (1) ◽  
pp. 299-307
Author(s):  
Jinyin Li ◽  
Peng Yan ◽  
Jianming Li
Keyword(s):  
Experimental Testing ◽  
Elastic Beam ◽  
Beam Theory ◽  
Element Analysis ◽  
Compliance Matrix ◽  
Amplification Ratio ◽  
Practical Applications ◽  
Analysis And Design ◽  
Proposed Model ◽  
Bridge Type

Abstract. This paper presents an improved modeling method for bridge-type mechanism by taking the input displacement loss into consideration, and establishes an amplification ratio model of bridge-type mechanism according to compliance matrix method and elastic beam theory. Moreover, the amplification ratio of the designed bridge-type nano-positioner is obtained by taking the guiding mechanism as the external load of bridge-type mechanism. Comparing with existing methods, the proposed model is more accurate, which is further verified by finite element analysis(FEA) and experimental test. The consistency of the results obtained from theoretical model, FEA and experimental testing indicates that the proposed model can accurately predict the amplification characteristics of nano-positioners, which helps the analysis and design of bridge-type nano-positioners in practical applications.

Characteristic analysis of a micro-/nanopositioning stage with coupling errors by the gravity

2019 ◽  
Vol 233 (16) ◽  
pp. 5860-5873
Author(s):  
Chao Lin ◽  
Pingyang Li ◽  
Zhonglei Shen ◽  
Jiang Yu
Keyword(s):  
Theoretical Model ◽  
Virtual Work ◽  
Elastic Beam ◽  
Beam Theory ◽  
Experimental Results ◽  
Characteristic Analysis ◽  
Element Analysis ◽  
Positioning Stage ◽  
The Impact ◽  
Coupling Deformation

The piezo-actuated micro-/nanopositioning stages are often used in the current precision engineering applications, and the coupling deformation under the gravity of the stage is critical to error analysis. Considering the torsional deformation and bending deformation of the flexure hinges, the coupling error’s analytical model of the positioning stage along the Z-axis is derived by using the virtual work principle and the elastic beam theory. The performance of the proposed theoretical model is analyzed and verified by the comparison between two common materials, and the quantities of the piezoelectric actuators are also analyzed with the impact on the coupling deformation of the stage along the Z-axis. Through the comparison and analysis of theoretical results, simulation results and experimental results, the maximum error between finite element analysis and experimental results is 11.43%, with the rest fluctuates within 10%, which proves the correctness of the theoretical model. It is concluded that gravity generated by the workload and the stage does have an influence on the coupling deformation along the Z-axis of the micro-/nanopositioning stage. It cannot be ignored in the analysis and consideration of the positioning stage.

scholarly journals Design and Modelling of a Cable-Driven Parallel-Series Hybrid Variable Stiffness Joint Mechanism for Robotics

2017 ◽  
Vol 8 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Cihat Bora Yigit ◽  
Pinar Boyraz
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Kinematic Model ◽  
Variable Stiffness ◽  
Research Field ◽  
Universal Joint ◽  
Element Analysis ◽  
Translational Movement ◽  
Profile Characteristics ◽  
Parallel Series

Abstract. The robotics, particularly the humanoid research field, needs new mechanisms to meet the criteria enforced by compliance, workspace requirements, motion profile characteristics and variable stiffness using lightweight but robust designs. The mechanism proposed herein is a solution to this problem by a parallel-series hybrid mechanism. The parallel term comes from two cable-driven plates supported by a compression spring in between. Furthermore, there is a two-part concentric shaft, passing through both plates connected by a universal joint. Because of the kinematic constraints of the universal joint, the mechanism can be considered as a serial chain. The mechanism has 4 degrees of freedom (DOF) which are pitch, roll, yaw motions and translational movement in z axis for stiffness adjustment. The kinematic model is obtained to define the workspace. The helical spring is analysed by using Castigliano's Theorem and the behaviour of bending and compression characteristics are presented which are validated by using finite element analysis (FEA). Hence, the dynamic model of the mechanism is derived depending on the spring reaction forces and moments. The motion experiments are performed to validate both kinematic and dynamic models. As a result, the proposed mechanism has a potential use in robotics especially in humanoid robot joints, considering the requirements of this robotic field.

Performance Evaluation on Jointed Pipes Used Underground for Fire Protection at a Nuclear Power Plant as a Response to the Effects of the 2007 Niigata-Ken Chuetsu-Oki Earthquake

2009 ◽  
Author(s):  
Yusuke Sato ◽  
Yukihiro Toyoda ◽  
Shinichi Matsuura ◽  
Michiya Sakai
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Nuclear Power ◽  
Welded Joint ◽  
Limit State ◽  
Elastic Beam ◽  
Beam Theory ◽  
Bending Moment ◽  
Ground Displacement ◽  
Element Analysis

This study discusses the strength of jointed pipes used underground for fire protection at a nuclear power plant and their capacity to accommodate ground displacement. For this purpose, bending tests, a finite element analysis and an elastic beam theory analysis were conducted. The bending tests were conducted for four types of joints previously subjected to actual use, including welded, flange, screw and coupling types. The welded and flange joints demonstrated significantly higher load capacity; five times that of the coupled joint. The bending test results for the flange, screw and coupling joints were applied to identify the bending moment and rotation angle at the moment the internal pressure reached the level of the atmospheric pressure due to leakage. The limit state of the welded joint was not obtained in the experiment but was estimated by nonlinear finite element analysis. The bending moment and rotation angle of the welded joint were identified at the moment the welded joint reached the limit state. Finally, the test results and finite element analysis were applied to estimate the capacity of each joint to accommodate ground displacement. The elastic beam theory was used by modeling the pipe as an elastic beam and idealizing the joint as an elastic rotational spring. Consequently, the ground displacement capacity of the welded joint exceeded that of the coupling and screw joints by more than 500 per cent.

Parallel Computing for Tire Simulations

2011 ◽  
Vol 39 (3) ◽  
pp. 193-209 ◽  
Author(s):  
H. Surendranath ◽  
M. Dunbar
Keyword(s):  
High Performance ◽  
Effective Means ◽  
Cost Effective ◽  
Turnaround Time ◽  
Careful Consideration ◽  
Rolling Contact ◽  
Element Analysis ◽  
Parallel Solvers ◽  
Design Changes ◽  
Highly Nonlinear

Abstract Over the last few decades, finite element analysis has become an integral part of the overall tire design process. Engineers need to perform a number of different simulations to evaluate new designs and study the effect of proposed design changes. However, tires pose formidable simulation challenges due to the presence of highly nonlinear rubber compounds, embedded reinforcements, complex tread geometries, rolling contact, and large deformations. Accurate simulation requires careful consideration of these factors, resulting in the extensive turnaround time, often times prolonging the design cycle. Therefore, it is extremely critical to explore means to reduce the turnaround time while producing reliable results. Compute clusters have recently become a cost effective means to perform high performance computing (HPC). Distributed memory parallel solvers designed to take advantage of compute clusters have become increasingly popular. In this paper, we examine the use of HPC for various tire simulations and demonstrate how it can significantly reduce simulation turnaround time. Abaqus/Standard is used for routine tire simulations like footprint and steady state rolling. Abaqus/Explicit is used for transient rolling and hydroplaning simulations. The run times and scaling data corresponding to models of various sizes and complexity are presented.

High-Performance Image Filters via Sparse Approximations

2020 ◽  
Vol 3 (2) ◽  
pp. 1-19
Author(s):  
Kersten Schuster ◽  
Philip Trettner ◽  
Leif Kobbelt
Keyword(s):  
High Performance ◽  
Hardware Acceleration ◽  
Optimization Method ◽  
Translation Invariant ◽  
Approximation Quality ◽  
Trade Offs ◽  
Sparse Approximations ◽  
Image Filters ◽  
Good Trade ◽  
And Performance

We present a numerical optimization method to find highly efficient (sparse) approximations for convolutional image filters. Using a modified parallel tempering approach, we solve a constrained optimization that maximizes approximation quality while strictly staying within a user-prescribed performance budget. The results are multi-pass filters where each pass computes a weighted sum of bilinearly interpolated sparse image samples, exploiting hardware acceleration on the GPU. We systematically decompose the target filter into a series of sparse convolutions, trying to find good trade-offs between approximation quality and performance. Since our sparse filters are linear and translation-invariant, they do not exhibit the aliasing and temporal coherence issues that often appear in filters working on image pyramids. We show several applications, ranging from simple Gaussian or box blurs to the emulation of sophisticated Bokeh effects with user-provided masks. Our filters achieve high performance as well as high quality, often providing significant speed-up at acceptable quality even for separable filters. The optimized filters can be baked into shaders and used as a drop-in replacement for filtering tasks in image processing or rendering pipelines.

Accelerated testing of super lightweight UHPC waffle deck under heavy vehicle simulator

2021 ◽  
Vol 16 (2-3) ◽  
pp. 61-74
Author(s):  
Sahar Ghasemi ◽  
Amir Mirmiran ◽  
Yulin Xiao ◽  
Kevin Mackie
Keyword(s):  
High Performance ◽  
Failure Modes ◽  
High Performance Concrete ◽  
High Strength ◽  
Heavy Vehicle ◽  
Wheel Load ◽  
Element Analysis ◽  
Vehicle Simulator ◽  
Pavement Testing ◽  
Heavy Vehicle Simulator

A super lightweight deck can enhance load rating and functionality of a bridge, especially those identified as structurally deficient. This study was aimed to develop and experimentally validate a novel bridge deck as an ultra-lightweight low-profile waffle slab of ultra-high-performance concrete (UHPC) with either carbon fiber reinforced polymer (CFRP) or high strength steel (HSS) reinforcement. The proposed system lends itself to accelerated bridge construction, rapid deck replacement in bridges with load restrictions, and bridge widening applications without the need to replace girders. Performance and failure modes of the proposed deck were initially assessed through extensive lab experiments and finite element analysis, which together confirmed that the proposed deck panel meets the AASHTO LRFD requirements. The proposed deck system is not susceptible to punching shear of its thin slab and fails in a rather ductile manner. To evaluate its long-term performance, the system was further tested under the dynamic impact of wheel load at the Accelerated Pavement Testing (APT) facility of the Florida Department of Transportation using a Heavy Vehicle Simulator (HVS).

scholarly journals Effect of magnetic field on nanofluid free convection in Conical Partially Annular Space

2020 ◽  
Vol 330 ◽  
pp. 01005
Author(s):  
Abderrahmane AISSA ◽  
Mohamed Amine MEDEBBER ◽  
Khaled Al-Farhany ◽  
Mohammed SAHNOUN ◽  
Ali Khaleel Kareem ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Boussinesq Approximation ◽  
Simulation Software ◽  
Comsol Multiphysics ◽  
Governing Equations ◽  
Element Analysis ◽  
Vertical Side ◽  
Side Walls

Natural convection of a magneto hydrodynamic nanofluid in a porous cavity in the presence of a magnetic field is investigated. The two vertical side walls are held isothermally at temperatures Th and Tc, while the horizontal walls of the outer cone are adiabatic. The governing equations obtained with the Boussinesq approximation are solved using Comsol Multiphysics finite element analysis and simulation software. Impact of Rayleigh number (Ra), Hartmann number (Ha) and nanofluid volume fraction (ϕ) are depicted. Results indicated that temperature gradient increases considerably with enhance of Ra and ϕ but it reduces with increases of Ha.

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