scholarly journals Simplified Kinematics of Continuum Robot Equilibrium Modulation via Moment Coupling Effects and Model Calibration

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Long Wang ◽  
Giuseppe Del Giudice ◽  
Nabil Simaan
Keyword(s):  
Experimental Data ◽  
Turning Point ◽  
Coupling Effects ◽  
Micro Scale ◽  
Modeling Approach ◽  
Macro Scale ◽  
Continuum Robot ◽  
Micro Motion ◽  
Scale Motion ◽  
Calibration Parameters

Recently, a new concept for continuum robots capable of producing macro-scale and micro-scale motion has been presented. These robots achieve their multi-scale motion capabilities by coupling direct actuation of push-pull backbones for macro-motion with indirect actuation whereby the equilibrium pose is altered to achieve micro-scale motion. This paper presents a first attempt at explaining the micro-motion capabilities of these robots from a modeling perspective. This paper presents the macro- and micro-motion kinematics of a single-segment continuum robot by using statics coupling effects among its subsegments. Experimental observations of the micro-scale motion demonstrate a turning point behavior which could not be explained well using the current modeling methods. We present a simplistic modeling approach that introduces two calibration parameters to calibrate the moment coupling effects among the subsegments of the robot. It is shown that these two parameters can reproduce the turning point behavior at the micro-scale. The instantaneous macro- and micro-scale kinematics Jacobians and the calibration parameters identification Jacobian are derived. The modeling approach is verified against experimental data showing that our simplistic modeling approach can capture the experimental motion data with the RMS position error of 5.82 μm if one wishes to fit the entire motion profile with the turning point. If one chooses to exclude motions past the turning point, our model can fit the experimental data with an accuracy of 4.76 μm.

Towards Identification of Lower Scale Composite Material Properties From Higher Scale Experimental Data via Inverse Analysis of Coupled Multiscale Models

2015 ◽  
Author(s):  
Foteini Komninelli ◽  
Athanasios Iliopoulos ◽  
John G. Michopoulos
Keyword(s):  
Experimental Data ◽  
Composite Material ◽  
Material Properties ◽  
Synthetic Data ◽  
Theoretical Development ◽  
Micro Scale ◽  
Macro Scale ◽  
Periodic Microstructures ◽  
Fiber Matrix ◽  
Optimization Methodology

In the present paper we demonstrate the application of a multiscale inverse methodology for identifying material properties of the constituents of a selected composite material with long fibers embedded in a polymer matrix by utilizing macro-scale experimental data. Taking advantage of a computational homogenization technique for periodic microstructures, the proposed optimization methodology allows, for the determination of a considerable number of the elastic properties of the composite material at the micro-scale of the constituents and their interface zone. Our approach describes the theoretical development and numerical implementation of a multi-scale modeling chain of the composite, extending from the periodic microstructure represented by a suitable unit cell and subjected to appropriate periodic boundary conditions at the micro scale, to the composite lamina at the meso-scale, to the laminated, multi-axially loaded material at the macro-scale. By applying the proposed methodology, we have been able to accurately calculate several fiber, matrix properties by utilizing properly generated synthetic data of the macro-scale behavior of the composite laminate. Furthermore, in an effort to explore the potential of our method for identifying quantities that manifest only after manufacturing including damage quantities at the micro-scale, we have initiated an effort to explore the capability of determining fiber-matrix interfacial properties and have demonstrated initial success.

scholarly journals A Multi-Scale Modeling Approach for Simulating Crack Sensing in Polymer Fibrous Composites Using Electrically Conductive Carbon Nanotube Networks. Part II: Meso- and Macro-Scale Analyses

2018 ◽  
Author(s):  
Konstantinos Tserpes ◽  
Christos Kora
Keyword(s):  
Carbon Nanotube ◽  
Fibrous Composites ◽  
Electrically Conductive ◽  
Micro Scale ◽  
Multi Scale ◽  
Modeling Approach ◽  
Scale Modeling ◽  
Macro Scale ◽  
Multi Scale Modeling ◽  
Meso Scale

This is the second of a two-paper series describing a multi-scale modeling approach developed to simulate crack sensing in polymer fibrous composites by exploiting interruption of electrically conductive carbon nanotube (CNT) networks. The approach is based on the finite element (FE) method. FE models at three different scales, namely the micro-scale, the meso-scale and the macro-scale, have been developed using the ANSYS PDL environment. In the present paper, the meso- and macro-scale analyses are described. In the meso-scale, a two-dimensional model of the CNT/polymer matrix reinforced by carbon fibers is used to develop a crack sensing methodology from a parametric study which relates the crack position and length with the reduction of current flow. In the meso-model, the effective electrical conductivity of the CNT/polymer computed from the micro-scale is used as input. In the macro-scale, the final implementation of the crack sensing methodology is performed on a CNT/polymer/carbon fiber composite volume using as input the electrical response of the cracked CNT/polymer derived at the micro-scale and the crack sensing methodology. Analyses have been performed for cracks of two different lengths. In both cases, the numerical model predicts with good accuracy both the length and position of the crack. These results highlight the prospect of conductive CNT networks to be used as a localized structural health monitoring technique.

scholarly journals A Multi-Scale Modeling Approach for Simulating Crack Sensing in Polymer Fibrous Composites Using Electrically Conductive Carbon Nanotube Networks. Part II: Meso- and Macro-Scale Analyses

Aerospace ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 106 ◽  
Author(s):  
Konstantinos Tserpes ◽  
Christos Kora
Keyword(s):  
Carbon Nanotube ◽  
Fibrous Composites ◽  
Electrically Conductive ◽  
Micro Scale ◽  
Multi Scale ◽  
Modeling Approach ◽  
Scale Modeling ◽  
Macro Scale ◽  
Multi Scale Modeling ◽  
Meso Scale

This is the second of a two-paper series describing a multi-scale modeling approach developed to simulate crack sensing in polymer fibrous composites by exploiting interruption of electrically conductive carbon nanotube (CNT) networks. The approach is based on the finite element (FE) method. Numerical models at three different scales, namely the micro-scale, the meso-scale and the macro-scale, have been developed using the ANSYS APDL environment. In the present paper, the meso- and macro-scale analyses are described. In the meso-scale, a two-dimensional model of the CNT/polymer matrix reinforced by carbon fibers is used to develop a crack sensing methodology from a parametric study which relates the crack position and length with the reduction of current flow. In the meso-model, the effective electrical conductivity of the CNT/polymer computed from the micro-scale is used as input. In the macro-scale, the final implementation of the crack sensing methodology is performed on a CNT/polymer/carbon fiber composite volume using as input the electrical response of the cracked CNT/polymer derived at the micro-scale and the crack sensing methodology. Analyses have been performed for cracks of two different lengths. In both cases, the numerical model predicts with good accuracy both the length and position of the crack. These results highlight the prospect of conductive CNT networks to be used as a localized structural health monitoring technique.

Micro-Scale Friction Model for Elastomers Considering Temperature Dependent Criterion for Wave Length Limit and Contribution of Adhesive Friction

2014 ◽  
Author(s):  
Erfan Afrasiabi ◽  
Francesco Braghin ◽  
Massimiliano Maggioni ◽  
Edoardo Sabbioni
Keyword(s):  
Experimental Data ◽  
Working Conditions ◽  
Wave Length ◽  
Friction Model ◽  
Temperature Dependent ◽  
Friction Law ◽  
Micro Scale ◽  
Friction Laws ◽  
Macro Scale ◽  
Friction Models

Existing friction laws for rubber like materials are tuned on available experimental data. Once their parameters are identified, a sensitivity analysis is carried out in order to check their extrapolation and prediction capabilities. It is seen that, although several fiction laws at micro scale are available in the literature, neither one is able to correctly predict the friction law at macro scale for all the tire working conditions. In the present paper a thorough review of the most advanced local friction models, i.e. Persson and Kluppel models, is carried out. Persson’s model is then integrated with a limiting criterion and an adhesive contribution is added to improve the prediction of the friction law at macro scale.

scholarly journals 2D-wavelet based micro and macro texture analysis for asphalt pavement under snow or ice condition

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Feng Li ◽  
Gulnigar Ablat ◽  
Siqi Zhou ◽  
Yixin Liu ◽  
Yufeng Bi ◽  
...  
Keyword(s):  
Wavelet Transform ◽  
Asphalt Pavement ◽  
Asphalt Mixture ◽  
Micro Scale ◽  
Braking System ◽  
Macro Scale ◽  
Texture Characteristics ◽  
The Mean ◽  
Resistance Performance

AbstractIn ice and snow weather, the surface texture characteristics of asphalt pavement change, which will significantly affect the skid resistance performance of asphalt pavement. In this study, five asphalt mixture types of AC-5, AC-13, AC-16, SMA-13, SMA-16 were prepared under three conditions of the original state, ice and snow. In this paper, a 2D-wavelet transform approach is proposed to characterize the micro and macro texture of pavement. The Normalized Energy (NE) is proposed to describe the pavement texture quantitatively. Compared with the mean texture depth (MTD), NE has the advantages of full coverage, full automation and wide analytical scale. The results show that snow increases the micro-scale texture because of its fluffiness, while the formation of the ice sheets on the surface reduces the micro-scale texture. The filling effect of snow and ice reduces the macro-scale texture of the pavement surface. In a follow-up study, the 2D-wavelet transform approach can be applied to improve the intelligent driving braking system, which can provide pavement texture information for the safe braking strategy of driverless vehicles.

Spatial-Pattern-Induced Evolution of a Self-Replicating Loop Network

2006 ◽  
Vol 12 (4) ◽  
pp. 461-485 ◽  
Author(s):  
Keisuke Suzuki ◽  
Takashi Ikegami
Keyword(s):  
Pattern Formation ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Spiral Structure ◽  
Scale Interactions ◽  
Micro Scale ◽  
Macro Scale ◽  
Loop Network ◽  
Spatial Pattern Formation

We study a system of self-replicating loops in which interaction rules between individuals allow competition that leads to the formation of a hypercycle-like network. The main feature of the model is the multiple layers of interaction between loops, which lead to both global spatial patterns and local replication. The network of loops manifests itself as a spiral structure from which new kinds of self-replicating loops emerge at the boundaries between different species. In these regions, larger and more complex self-replicating loops live for longer periods of time, managing to self-replicate in spite of their slower replication. Of particular interest is how micro-scale interactions between replicators lead to macro-scale spatial pattern formation, and how these macro-scale patterns in turn perturb the micro-scale replication dynamics.

scholarly journals Experimental study of the effects of wire EDM on the characteristics of ferritic steel, at a micro-scale on the contour cut surface

2018 ◽  
Vol 115 (4) ◽  
pp. 413
Author(s):  
Nida Naveed
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Surface Characteristics ◽  
Surface Damage ◽  
Cutting Process ◽  
Contour Method ◽  
X Ray Diffraction ◽  
Micro Scale ◽  
Macro Scale ◽  
Cut Surface

This study, on a micro-scale, of the WEDM cut surfaces of specimens to which the contour method of residual stress measurement is being applied provides detailed information about the effects of the cutting process on the surface quality. This is defined by a combination of several parameters: variation in surface contour profile, sub-surface damage and surface texture. Measurements were taken at the start, the middle and at the end of the cut. This study shows that during WEDM cutting, a thin layer, extending to a depth of a few micrometres below the surface of the cut, is transformed. This layer is known as the recast layer. Using controlled-depth etching and X-ray diffraction, it is shown that this induces an additional tensile residual stress, parallel to the plane of the cut surface. The WEDM cut surface and sub-surface characteristics are also shown to vary along the length of the cut. Moreover, these micro-scale changes were compared with macro-scale residual stress results and provides an indication of the point at which the changes occurred by cutting process can be significantly relative to the macro-scale residual stress in a specimen.

scholarly journals On the Two-Scale Modelling of Elastohydrodynamic Lubrication in Tilted-Pad Bearings

Lubricants ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 78 ◽  
Author(s):  
Gregory de Boer ◽  
Andreas Almqvist
Keyword(s):  
Surface Topography ◽  
Load Capacity ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Multiscale Methods ◽  
Operating Conditions ◽  
Real Surface ◽  
Micro Scale ◽  
Macro Scale ◽  
Heterogeneous Multiscale

A two-scale method for modelling the Elastohydrodynamic Lubrication (EHL) of tilted-pad bearings is derived and a range of solutions are presented. The method is developed from previous publications and is based on the Heterogeneous Multiscale Methods (HMM). It facilitates, by means of homogenization, incorporating the effects of surface topography in the analysis of tilted-pad bearings. New to this article is the investigation of three-dimensional bearings, including the effects of both ideal and real surface topographies, micro-cavitation, and the metamodeling procedure used in coupling the problem scales. Solutions for smooth bearing surfaces, and under pure hydrodynamic operating conditions, obtained with the present two-scale EHL model, demonstrate equivalence to those obtained from well-established homogenization methods. Solutions obtained for elastohydrodynamic operating conditions, show a dependency of the solution to the pad thickness and load capacity of the bearing. More precisely, the response for the real surface topography was found to be stiffer in comparison to the ideal. Micro-scale results demonstrate periodicity of the flow and surface topography and this is consistent with the requirements of the HMM. The means of selecting micro-scale simulations based on intermediate macro-scale solutions, in the metamodeling approach, was developed for larger dimensionality and subsequent calibration. An analysis of the present metamodeling approach indicates improved performance in comparison to previous studies.

A SIZE EFFECT STUDY ON THE SPLITTING CRACK INITIATION AND PROPAGATION IN OFF-AXIS LAYERS OF COMPOSITE LAMINATES

2021 ◽  
Author(s):  
YAO QIAO ◽  
QIWEI ZHANG ◽  
TROY NAKAGAWA ◽  
MARCO SALVIATO
Keyword(s):  
Crack Initiation ◽  
Size Effect ◽  
Fiber Reinforced Polymers ◽  
Structural Behavior ◽  
Crack Initiation And Propagation ◽  
Damage Mechanisms ◽  
Micro Scale ◽  
Morphological Studies ◽  
Initiation And Propagation ◽  
Macro Scale

This work proposes an investigation on size effects in micro-scale splitting crack initiation and propagation and their consequences on the macro-scale structural behavior carbon-fiber reinforced polymers under transverse tension. Towards this goal, size effect tests were experimentally conducted on both notch-free [90]n composites and specimens with different notch types under three-point bending. The mechanical tests were followed by morphological studies to identify the micro-scale damage mechanisms and their evolution. The results clearly show that splitting crack initiation in the transverse direction of composites not only happens at the fiber/matrix interface but also in the matrix. Moreover, the subsequent development of these damage mechanisms can depend on the structure size. This interesting phenomenon inherently leads to size-dependent structural behavior which can be described through Baznt’s Size Effect Laws. This study on the splitting crack initiation and propagation can provide unprecedented information for the calibration and validation of micromechanical models for the damage behavior of fiber composites at the microscale.

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