Influence of microstructure morphology on multi-scale modeling of low-alloyed TRIP-steels

2018 ◽  
Vol 35 (2) ◽  
pp. 499-528 ◽  
Author(s):  
Stefan Prüger ◽  
Ashutosh Gandhi ◽  
Daniel Balzani
Keyword(s):  
Volume Fraction ◽  
Measurement Techniques ◽  
Content Type ◽  
Systematic Assessment ◽  
Microstructural Parameters ◽  
Multi Scale ◽  
Scale Modeling ◽  
Macro Scale ◽  
Microstructure Morphology ◽  
The Impact

Purpose The purpose of this study is to quantify the impact of the variation of microstructural features on macroscopic and microscopic fields. The application of multi-scale methods in the context of constitutive modeling of microheterogeneous materials requires the choice of a representative volume element (RVE) of the considered microstructure, which may be based on some idealized assumptions and/or on experimental observations. In any case, a realistic microstructure within the RVE is either computationally too expensive or not fully accessible by experimental measurement techniques, which introduces some uncertainty regarding the microstructural features. Design/methodology/approach In this paper, a systematical variation of microstructural parameters controlling the morphology of an RVE with an idealized microstructure is conducted and the impact on macroscopic quantities of interest as well as microstructural fields and their statistics is investigated. The study is carried out under macroscopically homogeneous deformation states using the direct micro-macro scale transition approach. Findings The variation of microstructural parameters, such as inclusion volume fraction, aspect ratio and orientation of the inclusion with respect to the overall loading, influences the macroscopic behavior, especially the micromechanical fields significantly. Originality/value The systematic assessment of the impact of microstructural parameters on both macroscopic quantities and statistics of the micromechanical fields allows for a quantitative comparison of different microstructure morphologies and a reliable identification of microstructural parameters that promote failure initialization in microheterogeneous materials.

scholarly journals Energy Dissipation During Prey Capture Process in Spider Orb Webs

2020 ◽  
Vol 87 (9) ◽  
Author(s):  
Yanhui Jiang ◽  
Hamid Nayeb-Hashemi
Keyword(s):  
Energy Dissipation ◽  
Significant Role ◽  
Prey Capture ◽  
Aerodynamic Drag ◽  
Material Damping ◽  
Capture Process ◽  
Spider Dragline Silk ◽  
Multi Scale ◽  
Scale Modeling ◽  
Macro Scale

Abstract Capture of a prey by spider orb webs is a dynamic process with energy dissipation. The dynamic response of spider orb webs under prey impact requires a multi-scale modeling by considering the material microstructures and the assembly of spider silks in the macro-scale. To better understand the prey capture process, this paper addresses a multi-scale approach to uncover the underlying energy dissipation mechanisms. Simulation results show that the microstructures of spider dragline silk play a significant role on energy absorption during prey capture. The alteration of the microstructures, material internal friction, and plastic deformation lead to energy dissipation, which is called material damping. In addition to the material damping in the micro-scale modeling, the energy dissipation due to drag force on the prey is also taken into consideration in the macro-scale modeling. The results indicate that aerodynamic drag, i.e., aero-damping, plays a significant role when the prey size is larger than a critical size.

From welfare to wealth creation

2018 ◽  
Vol 31 (2) ◽  
pp. 265-286 ◽  
Author(s):  
Divya Verma Gakhar ◽  
Abhijit Phukon
Keyword(s):  
Citation Analysis ◽  
Business Strategy ◽  
Public Management ◽  
Empirical Studies ◽  
Measurement Techniques ◽  
Negative Effects ◽  
Statistical Tools ◽  
Content Type ◽  
Positive Effects ◽  
The Impact

Purpose The purpose of this paper is to review several influential empirical studies that examine the performance of state-owned enterprises (SOEs). The paper undertakes a citation analysis of journals, authors and titles in the area of privatization and firm performance in general, and assesses the impact of privatization on the performance of SOEs in particular. Design/methodology/approach The methodology is based on a systematic and structured review of over 100 papers published in economics, public management, business strategy and related social sciences. The systematic review is based on citation analysis of journals, authors and titles. The journal and author citation counts were tabulated by leveraging the databases of SCImago Journal Rankings and Google Scholar and filtered it to find out the most highly cited journals and authors. The structured review is based on the framing opinion with respect to major findings, variables selected, measurement techniques and statistical tools applied by different researchers. The impact is measured through coding a value “P” in case of positive effects, “N” in case of negative effects and “NT” in case the study found both positive and negative effects. Findings The citation analysis reveals that American Economic Review, Journal of Financial Economics, Review of Financial Studies and Journal of Finance as the top-cited journals, and Megginson and Netter (3,468), Megginson et al. (1,737), Djankov and Murrell (1,356), Boardman and Vining (1,320), Balsam et al. (1,094) and DeWenter and Malatesta (1,018) as the top-cited authors in this particular research field. While majority research studies have revealed a significant improvement in the performance of SOEs in the post-privatization period, few studies have reserved their impact as neutral or even negative in some respects. Originality/value Given that economic transitions, corporate governance, and performance of SOEs have attracted a great attention from public management and business strategy scholars in recent years, this paper aims to summarize a large number of empirical studies that examine the performance of SOEs. The paper would be useful to future researchers especially the beginners and early career researchers in terms of its current trends, selection of variables, measurement techniques and statistical tools applied.

New Approach of Multi Scale Modeling Based on the Hygro-Cosserat Theory for Self Desiccation Deformation of Cement Mortars at Early Age

2010 ◽  
Vol 123-125 ◽  
pp. 563-566 ◽  
Author(s):  
J. Jeong ◽  
P. Mounanga ◽  
Hamidreza Ramezani ◽  
Marwen Bouasker ◽  
D. Bassir
Keyword(s):  
Autogenous Shrinkage ◽  
Early Age ◽  
Cosserat Theory ◽  
Sem Images ◽  
Element Analysis ◽  
New Approach ◽  
Multi Scale ◽  
Scale Modeling ◽  
Cement Mortars ◽  
Macro Scale

In the present paper, we concentrate on the heterogeneous cement mortars and we treat them as Cosserat-based media. The autogenous shrinkage phenomenon at early age (from 1 up to 3 days after mixing) has been analyzed by means of Cosserat theory. The characteristic length scale parameter Lc in this theory helps us to change the size specimen from macro-scale to micro-scale using the theoretical size effect aspects. This methodology is also capable of treating cracks initiation and their appearance in the cementitious matrix surrounding the sand-inclusions, which should occurred inside of the Representative Volume Elementary (RVE) of mortar subjected to self-desiccation shrinkage during hydration at early age. By taking advantage of the Nonlinear Finite Element Analysis (NFEA), the numerical experiments have been performed. The numerical outcomes are well agreed with the experimental observations coming from Scanning Electronic Microscopy (SEM) images. It concludes that the inclusions create not only a hygro stress concentration around the grains but also the number of inclusions should influence the network in cementitous matrix.

Degradation Modeling Research of Biodegradable Tissue Engineering Scaffold

2013 ◽  
Vol 873 ◽  
pp. 642-651
Author(s):  
Tao Hong Zhang ◽  
Shou Gang Xu ◽  
De Zheng Zhang ◽  
Aziguli Wulamu
Keyword(s):  
Tissue Engineering ◽  
Initial Step ◽  
Tissue Engineering Scaffold ◽  
Multi Scale ◽  
Modeling Methods ◽  
Degradation Modeling ◽  
Scale Modeling ◽  
Single Scale ◽  
Macro Scale ◽  
Scale Models

Although the degradation modeling of tissue engineering scaffold is in its initial step, it can direct the design, optimization of scaffold and help the application in medical case of illness. This paper analyzes the modeling methods and gives the speciality of every model which is put forward by researchers in China and abroad about the degradation of tissue engineering scaffold. These models are divided into micro scale, macro scale and two scale models based on the modeling scales. The recent research is belonging to single scale modeling. Some researchers abroad probed to two scale modeling. The future model is prospected in multi scale coupling macro, micro, and meta-macro model.

Integrating an Analytical Uncertainty Quantification Approach to Multi-Scale Modeling of Nanocomposites

2019 ◽  
pp. 1-22
Author(s):  
Pinar Acar
Keyword(s):  
Uncertainty Quantification ◽  
Uncertainty Propagation ◽  
Epoxy Nanocomposites ◽  
Linear Solution ◽  
Analytical Uncertainty ◽  
Multi Scale ◽  
Scale Modeling ◽  
Macro Scale ◽  
Multi Scale Modeling ◽  
Scale Properties

Abstract The present study addresses the integration of an analytical uncertainty quantification approach to multi-scale modeling of single-walled carbon nanotube (SWNT)-epoxy nanocomposites. The main highlight is the investigation of the stochasticity of nanotube orientations, and its effects on the homogenized properties. Even though the properties of SWNT-epoxy nanocomposites are well-studied in the literature, the natural stochasticity that arises from the nanotube orientations has not been observed. To understand the effects of the variability in SWNT orientations to material properties of interest, an analytical uncertainty quantification algorithm is utilized. The analytical scheme computes the propagation of the orientational uncertainty to the volume-averaged properties with a linear solution and uses the transformation of random variables principle to obtain the variations in non-linear properties. The results indicate that the uncertainty propagation affects the macro-scale properties, including stiffness, thermal expansion, thermal conductivity, and natural frequencies.

scholarly journals Numerical study of heat transfer in 90° bend tube by AI2O3 nano fluids using fluid injection

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hadi Mahdizadeh ◽  
Nor Mariah Adam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volume Fraction ◽  
Fluid Injection ◽  
Content Type ◽  
Nano Fluid ◽  
The Impact

Purpose This paper aims to investigate increasing heat transfer in bend tube 90° by fluid injection using nano fluid flow that was performed by expending varying Reynolds number. This paper studies the increased heat transfer in the bent tube that used some parameters to examine the effects of volume fraction, nanoparticle diameter, fluid injection, Reynolds number on heat transfer and flow in a bend pipe. Design/methodology/approach Designing curved tubes increases the thermal conductivity amount between fluid and wall. It is used the finite volume method and simple algorithms to solve the conservation equations of mass, momentum and energy. The results showed that the nanoparticles used in bent tube transfusion increase the heat transfer performance by increasing the volume fraction; it has a direct impact on enhancing the heat transfer coefficient. Findings Heat transfer coefficient enhanced 1.5% when volume fraction increased from 2 % to 6%, the. It is due to the impact of nanoparticles on the thermal conductivity of the fluid. The fluid is injected into the boundary layer flow due to jamming that enhances heat transfer. Curved lines used create a centrifugal force due to the bending and lack of development that increase the heat transfer. Originality/value This study has investigated the effect of injection of water into a 90° bend before and after the bend. Specific objectives are to analyze effect of injection on heat transfer of bend tube and pressure drop, evaluate best performance of mixing injection and bend in different positions and analyze effect of nano fluid volume fraction on injection.

Multi-scale finite element modeling of 3D printed structures subjected to mechanical loads

2018 ◽  
Vol 24 (1) ◽  
pp. 177-187 ◽  
Author(s):  
Dalia Calneryte ◽  
Rimantas Barauskas ◽  
Daiva Milasiene ◽  
Rytis Maskeliunas ◽  
Audrius Neciunas ◽  
...  
Keyword(s):  
Finite Element ◽  
Composite Structures ◽  
Computational Models ◽  
Three Dimensional ◽  
Structural Response ◽  
Content Type ◽  
Multi Scale ◽  
Macro Scale ◽  
Internal Constitution ◽  
3D Printed

Purpose The purpose of this paper is to investigate the influence of geometrical microstructure of items obtained by applying a three-dimensional (3D) printing technology on their mechanical strength. Design/methodology/approach Three-dimensional printed items (3DPI) are composite structures of complex internal constitution. The buildup of the finite element (FE) computational models of 3DPI is based on a multi-scale approach. At the micro-scale, the FE models of representative volume elements corresponding to different additive layer heights and different thicknesses of extruded fibers are investigated to obtain the equivalent non-linear nominal stress–strain curves. The obtained results are used for the creation of macro-scale FE models, which enable to simulate the overall structural response of 3D printed samples subjected to tensile and bending loads. Findings The validation of the models was performed by comparing the computed results against the experimental ones, where satisfactory agreement has been demonstrated within a marked range of thicknesses of additive layers. Certain inadequacies between computed against experimental results were observed in cases of thinnest and thickest additive layers. The principle explanation of the reasons of inadequacies takes into account the poorer quality of mutual adhesion in case of very thin extruded fibers and too-early solidification effect. Originality/value Flexural and tensile experiments are simulated by FE models that are created with consideration to microstructure of 3D printed samples.

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