Multi-Scale Finite Element Modeling of Alumina Ceramics Undergoing Laser-Assisted Machining

2014 ◽  
Author(s):  
Xiangyang Dong ◽  
Yung C. Shin
Keyword(s):  
Finite Element ◽  
High Temperatures ◽  
Cutting Forces ◽  
Scale Model ◽  
Zone Model ◽  
Alumina Ceramics ◽  
Weight Percentage ◽  
Laser Assisted Machining ◽  
Multi Scale ◽  
Wide Range

Alumina ceramics, due to their excellent properties of high hardness, corrosion resistance and low thermal expansion coefficient, are important industrial materials with a wide range of applications, but these materials also present difficulty in machining with low material removal rates and high tool wear. This study is concerned with laser-assisted machining (LAM) of high weight percentage of alumina ceramics to improve the machinability by a single point cutting tool while reducing the cutting forces. A multi-scale model is developed for simulating the machining of alumina ceramics. In the polycrystalline form, the properties of alumina ceramics are strongly related to the glass interface existing in their microstructure, particularly at high temperatures. The interface is characterized by a cohesive zone model (CZM) with the traction-separation law while the alumina grains are modeled as continuum elements with isotropic properties separated by the interface. Bulk deformation and brittle failure are considered for the alumina grains. Molecular dynamics (MD) simulations are carried out to obtain the atomistic structures and parameterize traction-separation laws for the interfaces of different compositions of alumina ceramics at high temperatures. The generated parameterized traction-separation laws are then incorporated into a finite element model in Abaqus to simulate the intergranular cracks. For validation purposes, simulated results of the multi-scale approach are compared with the experimental measurements of the cutting forces. The model is successful in predicting cutting forces with respect to the different weight percentage and composition of alumina ceramics at high temperatures in LAM processes.

Multiscale Finite Element Modeling of Alumina Ceramics Undergoing Laser-Assisted Machining

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Xiangyang Dong ◽  
Yung C. Shin
Keyword(s):  
Finite Element ◽  
High Temperatures ◽  
Cutting Forces ◽  
Cohesive Zone Model ◽  
Multiscale Approach ◽  
Zone Model ◽  
Alumina Ceramics ◽  
Weight Percentage ◽  
Laser Assisted Machining ◽  
Wide Range

Alumina ceramics, due to their excellent properties of high hardness, corrosion resistance, and low thermal expansion coefficient, are important industrial materials with a wide range of applications, but these materials also present difficulty in machining with low material removal rates and high tool wear. This study is concerned with laser-assisted machining (LAM) of high weight percentage of alumina ceramics to improve the machinability by a single point cutting tool while reducing the cutting forces. A multiscale model is developed for simulating the machining of alumina ceramics. In the polycrystalline form, the properties of alumina ceramics are strongly related to the glass interface existing in their microstructure, particularly at high temperatures. The interface is characterized by a cohesive zone model (CZM) with the traction–separation law while the alumina grains are modeled as continuum elements with isotropic properties separated by the interface. Bulk deformation and brittle failure are considered for the alumina grains. Molecular dynamics (MD) simulations are carried out to obtain the atomistic structures and parameterize traction–separation laws for the interfaces of different compositions of alumina ceramics at high temperatures. The generated parameterized traction–separation laws are then incorporated into a finite element model in Abaqus to simulate the intergranular cracks. For validation purposes, simulated results of the multiscale approach are compared with the experimental measurements of the cutting forces. The model is successful in predicting cutting forces with respect to the different weight percentage and composition of alumina ceramics at high temperatures in LAM processes.

scholarly journals A multi-scale model reveals cellular and physiological mechanisms underlying hyperpolarisation-gated synaptic plasticity

2018 ◽  
Author(s):  
Yubin Xie ◽  
Marcel Kazmierczyk ◽  
Bruce P. Graham ◽  
Mayank B. Dutia ◽  
Melanie I. Stefan ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Nerve Stimulation ◽  
Vestibular Nerve ◽  
Biochemical Reaction ◽  
Medial Vestibular Nucleus ◽  
Scale Model ◽  
Reaction Systems ◽  
Multi Scale ◽  
Wide Range

AbstractNeurons in the medial vestibular nucleus (MVN) display hyperpolarisation-gated synaptic plasticity, where inhibition believed to come from cerebellar cortical Purkinje cells can induce long-term potentiation (LTP) or long-term depression (LTD) of vestibular nerve afferent synapses. This phenomenon is thought to underlie the plasticity of the vestibulo-ocular reflex (VOR). The molecular and cellular mechanisms involved are largely unknown. Here we present a novel multi-scale computational model, which captures both electrophysiological and biochemical signalling at vestibular nerve synapses on proximal dendrites of the MVN neuron. We show that AMPA receptor phosphorylation at the vestibular synapse depends in complex ways on dendritic calcium influx, which is in turn shaped by patterns of post-synaptic hyperpolarisation and vestibular nerve stimulation. Hyperpolarisation-gated synaptic plasticity critically depends on the activation of LVA calcium channels and on the interplay between CaMKII and PP2B in dendrites of the post-synaptic MVN cell. The extent and direction of synaptic plasticity depend on the strength and duration of hyperpolarisation, and on the relative timing of hyperpolarisation and vestibular nerve stimulation. The multi-scale model thus enables us to explore in detail the interactions between electrophysiological activation and post-synaptic biochemical reaction systems. More generally, this model has the potential to address a wide range of questions about neural signal integration, post-synaptic biochemical reaction systems and plasticity.

scholarly journals Theoretical predictions of dynamic necking formability of ductile metallic sheets with evolving plastic anisotropy and tension-compression asymmetry

2021 ◽  
Author(s):  
Murlidhar Anil Kumar ◽  
Komi Espoir N'souglo ◽  
navab hosseini ◽  
Nicolas Jacques ◽  
Jose Rodriguez-Martinez
Keyword(s):  
Finite Element ◽  
Stability Analysis ◽  
Plastic Anisotropy ◽  
Theoretical Models ◽  
Unit Cell ◽  
Forming Limit ◽  
Plastic Behavior ◽  
Zone Model ◽  
Wide Range ◽  
The Stability

In this paper, we have investigated necking formability of anisotropic and tension-compression asymmetric metallic sheets subjected to in-plane loading paths ranging from plane strain tension to equibiaxial tension. For that purpose, we have used three different approaches: a linear stability analysis, a nonlinear two-zone model and unit-cell finite element calculations. We have considered three materials –AZ31-Mg alloy, high purity α-titanium and OFHC copper– whose mechanical behavior is described with an elastic-plastic constitutive model with yielding defined by the CPB06 criterion [10] which includes specific features to account for the evolution of plastic orthotropy and strength differential effect with accumulated plastic deformation [37]. From a methodological standpoint, the main novelty of this paper with respect to the recent work of N’souglo et al. [32] –which investigated materials with yielding described by the orthotropic criterion of Hill [19]– is the extension of both stability analysis and nonlinear two-zone model to consider anisotropic and tension-compression asymmetric materials with distortional hardening. The results obtained with the stability analysis and the nonlinear two-zone model show reasonable qualitative and quantitative agreement with forming limit diagrams calculated with the finite element simulations, for the three materials considered, and for a wide range of loading rates varying from quasi-static loading up to 40000 s−1, which makes apparent the capacity of the theoretical models to capture the mechanisms which control necking formability of metallic materials with complex plastic behavior. Special mention deserves the nonlinear two-zone model, as it does not need prior calibration –unlike the stability analysis– and it yields accurate predictions that rarely deviate more than 10% from the results obtained with the unit-cell calculations

Simulating the Emptying of a Water Bottle With a Multi-Scale Two-Fluid Approach

2018 ◽  
Author(s):  
Samuel Mer ◽  
Olivier Praud ◽  
Jacques Magnaudet ◽  
Véronique Roig
Keyword(s):  
Bubble Formation ◽  
Computational Cost ◽  
Scale Model ◽  
Water Bottle ◽  
Local Flow ◽  
Spatial And Temporal Scales ◽  
Multi Scale ◽  
Wide Range ◽  
Bottle Neck ◽  
Liquid Flows

Multiple industrial processes involve gas-liquid flows characterized by a wide range of spatial and temporal scales. Simulating such flows remains a major challenge nowadays, as the computational cost associated with Direct Numerical Simulation still makes it unaffordable. For such configurations, an interesting alternative to DNS is the use of multi-scale approaches. In the latter, large enough bubbles are fully resolved and may deform over time, while smaller bubbles are modeled as a dispersed phase using subgrid scale models. The interfacial momentum transfer terms are then tailored to the local flow configuration. The closure models still involved in these approaches and the influence of the cut-off length separating the resolved and modeled bubbles definitely need to be validated against detailed experiments. In order to assess the validity of these models, we present a one-to-one comparison between experiments performed in a simple configuration, namely the emptying of a water bottle, and numerical simulations using the aforementioned approach. The results are found to reliably reproduce the genesis of the oscillation mechanism, which is governed by the bubble formation at the bottle neck. The multi-scale model also qualitatively reproduces the fragmentation process of large bubbles during their rise in the water column. However local experimental data are required to assess more quantitatively these results.

ADAPTIVE-SCALE DAMAGE DETECTION FOR FRAME STRUCTURES USING BEAM-TYPE WAVELET FINITE ELEMENT: EXPERIMENTAL VALIDATION

2013 ◽  
Vol 07 (03) ◽  
pp. 1350024 ◽  
Author(s):  
SONGYE ZHU ◽  
WEN-YU HE ◽  
WEI-XIN REN
Keyword(s):  
Finite Element ◽  
Damage Detection ◽  
Experimental Validation ◽  
Detection Method ◽  
Human Vision ◽  
Scale Model ◽  
Multi Scale ◽  
Wavelet Finite Element ◽  
Portal Frame ◽  
Beam Type

The superior human vision system provides ingenious insight into an ideal damage detection strategy in which structural modeling scales are not only spatially varying but also dynamically changed according to actual needs. This paper experimentally examines the efficacy of a multi-scale damage detection method based on wavelet finite element model (WFEM). The beam-type wavelet finite element in this study utilizes the second-generation cubic Hermite multi-wavelets as interpolation functions. The dynamic testing results of a one-bay steel portal frame with multiple damages are employed in the experimental validation. Through a multi-stage updating of the WFEM, the multiple damages in the steel portal frame are detected in a progressive manner: the suspected region is first identified using a low-scale structural model, and the more accurate location and severity of the damage can be identified using a multi-scale model with local refinement. As the multi-scale WFEM considerably facilitates the adaptive change of modeling scales, the proposed multi-scale damage detection method can efficiently locate and quantify damage with minimal computation effort and a limited number of updating parameters and sensors, compared with conventional finite element methods.

scholarly journals MULTI-SCALE MODEL ELABORATION FOR CREDITWORTHINESS DIAGNOSTICS OF EXPORT PRODUCTION ENTERPRISES OF THE AGRICULTURAL TRADE MARKET

2019 ◽  
Vol 6 ◽  
pp. 19-30
Author(s):  
Olena Sergienko ◽  
Olena Shapran ◽  
Oleksandr Bilotserkivskyi ◽  
Iryna Alieksieieva
Keyword(s):  
Evaluation System ◽  
Agricultural Trade ◽  
Economic Indicators ◽  
Scale Model ◽  
Decision Making Process ◽  
One Dimensional ◽  
Multi Scale ◽  
Wide Range ◽  
Trade Market

The methodology for the agrarian enterprises’ creditworthiness diagnostic has been developed and implemented, and has allowed to solve the following objectives: conducting of observations and evaluating of financially-economic indicators, classification of enterprises by the level of creditworthiness, distinction and identification enterprises according to the level of creditworthiness and assessing the differences between classes by creditworthiness, with taking into account the sizes of enterprises. Based on the use of the complex of multidimensional analytical methods, the differences are defined under either one-dimensional evaluation system (by creditworthiness and size) or a two-level assessment of the joint cross impact of factors on creditworthiness. The proposed four-step technology for diagnosing of the agrarian enterprises creditworthiness substantially expands the components of the creditworthiness level evaluation of enterprises and, as a consequence, improves the timeliness of decision-making process about identifying and locating of weaknesses and "bottlenecks". The coverage of a sufficient number of financial and economic indicators and the implementation of a wide range of methods and models enable to fully evaluate and analyze the existing state of creditworthiness with a view to improve and establish the effective functioning of the enterprise as a whole.

A Computational Model for Predicting Damage Evolution in Laminated Composite Plates

1999 ◽  
Vol 121 (4) ◽  
pp. 436-444 ◽  
Author(s):  
M. L. Phillips ◽  
C. Yoon ◽  
D. H. Allen
Keyword(s):  
Finite Element ◽  
Fiber Composite ◽  
Composite Plates ◽  
Laminated Plates ◽  
Matrix Cracking ◽  
Interface Fracture ◽  
Zone Model ◽  
Desktop Computer ◽  
Multi Scale ◽  
Element Algorithm

A model is developed herein for predicting the evolution of interface degradation, matrix cracking, and delamination at multiple sites in laminated continuous fiber composite plates subjected to monotonic and/or cyclic mechanical loading. Due to the complicated nature of the many cracks and their interactions, a multi-scale micro-meso-local-global methodology is deployed in order to model all damage modes. Interface degradation is first modeled analytically on the microscale, and the results are homogenized to produce a cohesive zone model that is capable of predicting interface fracture. Subsequently, matrix cracking in the plies is modeled analytically on the meso-scale, and this result is homogenized to produce ply level damage dependent constitutive equations. The evolution of delaminations is considered on the local scale, and this effect is modeled using a three dimensional finite element algorithm. Results of this analysis are homogenized to produce damage dependent laminate equations. Finally, global response of the damaged plate is modeled using a plate finite element algorithm. Evolution of all three modes of damage is predicted via interfacing all four scales into a single multi-scale algorithm that is computationally tenable for use on a desktop computer. Results obtained herein suggest that this model may be capable of accurately predicting complex damage patterns such as that observed at open holes in laminated plates.

A finite-element, multi-scale model of the Scheldt tributaries, river, estuary and ROFI

2010 ◽  
Vol 57 (9) ◽  
pp. 850-863 ◽  
Author(s):  
Benjamin de Brye ◽  
Anouk de Brauwere ◽  
Olivier Gourgue ◽  
Tuomas Kärnä ◽  
Jonathan Lambrechts ◽  
...  
Keyword(s):  
Finite Element ◽  
River Estuary ◽  
Scale Model ◽  
Multi Scale

Nonlinear Finite Element Analysis of Non-Structural Components Anchorage under Extreme Wind Loads

2019 ◽  
Author(s):  
Sálvio A. ALMEIDA Jr ◽  
Serhan Guner
Keyword(s):  
Finite Element ◽  
Elevated Temperatures ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Nonlinear Finite Element ◽  
Scale Model ◽  
Structural Components ◽  
Element Analysis ◽  
Multi Scale ◽  
Service Load

<p>Steel anchors are widely used to fasten structures and non-structural components (NSC) to rooftop concrete slabs, especially in high-rise buildings. However, several NSC anchorage failures have been observed in the last decades upon the incidence of hurricanes, resulting in loss of service in essential buildings, detachment of the component, and water intrusion, all of which significantly delayed the recovery of the affected communities. From the observed failures, three main mechanisms were identified: steel rupture, concrete breakout, and bond failure. In this study, a three-dimensional nonlinear finite element methodology using a concrete damaged plasticity approach is developed to predict the response of steel anchors installed into a concrete slab. The methodology is verified with experimental results for each failure mechanism and subsequently used to study the effect of service-load concrete cracking and elevated temperatures – common conditions at rooftop level – on the response of the anchors. In addition, a first-of-its-kind multi-scale model of an NSC and its anchorage is created using the proposed methodology to investigate its behavior under dynamic hurricane load application. The findings suggest that these conditions can compromise the performance of NSC or promote its failure.</p>

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