Combining FEM and MD to simulate C60/PA-12 nanocomposites

2019 ◽  
Vol 10 (3) ◽  
pp. 380-392
Author(s):  
Georgios I. Giannopoulos ◽  
Stelios K. Georgantzinos ◽  
Androniki Tsiamaki ◽  
Nicolaos Anifantis
Keyword(s):  
Mechanical Behaviour ◽  
Numerical Scheme ◽  
Mechanical Performance ◽  
Numerical Technique ◽  
Computational Cost ◽  
Md Simulations ◽  
Unit Cell ◽  
Content Type ◽  
Polyamide 12 ◽  
Solid Element

Purpose The purpose of this paper is the computation of the elastic mechanical behaviour of the fullerene C60 reinforced polyamide-12 (PA-12) via a two-stage numerical technique which combines the molecular dynamics (MD) method and the finite element method (FEM). Design/methodology/approach At the first stage, the proposed numerical scheme utilizes MD to characterize the pure PA-12 as well as a very small cubic unit cell containing a C60 molecule, centrally positioned and surrounded by PA-12 molecular chains. At the second stage, a classical continuum mechanics (CM) analysis based on the FEM is adopted to approximate the elastic mechanical performance of the nanocomposite with significantly lower C60 mass concentrations. According to the computed elastic properties arisen by the MD simulations, an equivalent solid element with the same size as the unit cell is developed. Then, a CM micromechanical representative volume element (RVE) of the C60 reinforced PA-12 is modelled via FEM. The matrix phase of the RVE is discretized by using solid finite elements which represent the PA-12 mechanical behaviour predicted by MD, while the C60 neighbouring location is meshed with the equivalent solid element. Findings Several multiscale simulations are performed to study the effect of the nanofiller mass fraction on the mechanical properties of the C60 reinforced PA-12 composite. Comparisons with other corresponding experimental results are attempted, where possible, to test the performance of the proposed method. Originality/value The proposed numerical scheme allows accurate representation of atomistic interfacial effects between C60 and PA-12 and simultaneously offers a significantly lower computational cost compared with the MD-only method.

Bonding quality and fracture analysis of polyamide 12 parts fabricated by fused deposition modeling

2017 ◽  
Vol 23 (6) ◽  
pp. 973-982 ◽  
Author(s):  
Hao Li ◽  
Shuai Zhang ◽  
Zhiran Yi ◽  
Jie Li ◽  
Aihua Sun ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Rheological Properties ◽  
Fused Deposition Modeling ◽  
Mechanical Performance ◽  
Melt Viscosity ◽  
Bonding Quality ◽  
Content Type ◽  
Polyamide 12 ◽  
Fused Deposition ◽  
Deposition Modeling

Purpose This work aims to evaluate the influence of rheological properties of building materials on the bonding quality and ultimate tensile strength in the fused deposition modeling (FDM) process, through the investigation of parts printed by semi-crystalline and amorphous resins. Little information is currently available about the influence of the crystalline nature on FDM-printed part quality. Design/methodology/approach Semi-crystalline polyamide 12 and amorphous acrylonitrile butadiene styrene (ABS) were used to assess the influence of rheological properties on bonding quality and the tensile strength, by varying three important process parameters: materials, liquefier temperature and raster orientation. A fractography of both tensile and freeze-fractured samples was also investigated. Findings The rheological properties, mainly the melt viscosity, were found to have a significant influence on the bonding quality of fused filaments. Better bonding quality and higher tensile strength of FDM parts printed with semi-crystalline PA12, as compared with amorphous ABS, are suggested to be a result of higher initial sintering rates owing to the lower melt viscosity of PA12 at low shear rates. Near-full dense PA12 parts were obtained by FDM. Originality/value This project provides a variety of data and insight regarding the effect of materials properties on the mechanical performance of FDM-printed parts. The results showed that FDM technique allows the production of PA12 parts with adequate mechanical performance, overcoming the greatest limitation of a dependence on amorphous thermoplastics as a feedstock for the production of prototypes.

scholarly journals Mechanical behaviour and interface evaluation of hybrid MIM/PBF stainless steel components

2020 ◽  
Vol 26 (10) ◽  
pp. 1809-1825
Author(s):  
Aldi Mehmeti ◽  
Pavel Penchev ◽  
Donal Lynch ◽  
Denis Vincent ◽  
Nathalie Maillol ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behaviour ◽  
Production Efficiency ◽  
Mechanical Performance ◽  
Cost Effective ◽  
Content Type ◽  
Powder Bed ◽  
Technical Requirements ◽  
Small Series ◽  
American Society

Purpose The paper reports an investigation into the mechanical behaviour of hybrid components produced by combining the capabilities of metal injection moulding (MIM) with the laser-based powder bed fusion (PBF) process to produce small series of hybrid components. The research investigates systematically the mechanical properties and the performance of the MIM/PBF interfaces in such hybrid components. Design/methodology/approach The MIM process is employed to fabricate relatively lower cost preforms in higher quantities, whereas the PBF technology is deployed to build on them sections that can be personalised, customised or functionalised to meet specific technical requirements. Findings The results are discussed, and conclusions are made about the mechanical performance of such hybrid components produced in batches and also about the production efficiency of the investigated hybrid manufacturing (HM) route. The obtained results show that the proposed HM route can produce hybrid MIM/PBF components with consistent mechanical properties and interface performance which comply with the American Society for Testing and Materials (ASTM) standards. Originality/value The manufacturing of hybrid components, especially by combining the capabilities of additive manufacturing processes with cost-effective complementary technologies, is designed to be exploited by industry because they can offer flexibility and cost advantages in producing small series of customisable products. The findings of this research will contribute to further develop the state of the art in regards to the manufacturing and optimisation of hybrid components.

scholarly journals Porosity in multi-axis material extrusion of short-fibre composites

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Nathaniel Kaill ◽  
Robert Campbell ◽  
Patrick Pradel
Keyword(s):  
Mechanical Behaviour ◽  
Design Methodology ◽  
Mechanical Performance ◽  
Low Cost ◽  
Short Fibre ◽  
Internal Stresses ◽  
Content Type ◽  
Material Extrusion ◽  
Fibre Composites ◽  
The Relationship

Purpose This study aims to investigate the relationship between part porosity and mechanical properties of short-fibre reinforced polylactic acid printed via multi-axis material extrusion (MAMEX) to establish guidelines for optimal process configurations. Design/methodology/approach Material properties graphs provide the basis for studying the relationship between porosity and mechanical behaviour. Using the correlations found in this study, the way to improve printing strategies and filament properties can be deducted directly from an analysis of the print path and the final influence on mechanical performance. Findings Some commercial brands of short-fibre reinforced filament present inherent porosity that weakens the mechanical behaviour of MAMEX components. Originality/value Low-cost MAMEX allows the production of components that do not present anisotropic behaviour and are mechanically optimised through the alignment of the filaments along with internal stresses. This paper also addresses the effects of multi-axis deposition strategies on the resulting porosity and proposes improvements to reduce residual porosity, thus increasing the mechanical performance in the future.

Uncertain dynamic responses of imprecisely defined arbitrary order fractionally damped beam subject to various loads

2018 ◽  
Vol 35 (2) ◽  
pp. 818-842 ◽  
Author(s):  
Diptiranjan Behera ◽  
Hong-Zhong Huang ◽  
Smita Tapaswini
Keyword(s):  
Differential Equations ◽  
Fuzzy Numbers ◽  
Numerical Technique ◽  
Computational Cost ◽  
Accurate Solution ◽  
Interval Uncertainty ◽  
Dynamic Responses ◽  
Beam Equation ◽  
Parametric Form ◽  
Content Type

PurposeRecently, fractional differential equations have been used to model various physical and engineering problems. One may need a reliable and efficient numerical technique for the solution of these types of differential equations, as sometimes it is not easy to get the analytical solution. However, in general, in the existing investigations, involved parameters and variables are defined exactly, whereas in actual practice it may contain uncertainty because of error in observations, maintenance induced error, etc. Therefore, the purpose of this paper is to find the dynamic response of fractionally damped beam approximately under fuzzy and interval uncertainty.Design/methodology/approachHere, a semi analytical approach, variational iteration method (VIM), has been considered for the solution. A newly developed form of fuzzy numbers known as double parametric form has been applied to model the uncertainty involved in the system parameters and variables.FindingsVIM has been successfully implemented along with double parametric form of fuzzy number to find the uncertain dynamic responses of the fractionally damped beam. The advantage of this approach is that the solution can be written in power series or compact form. Also, this method converges rapidly to have the accurate solution. The uncertain responses subject to impulse and step loads have also been computed and the behaviours of the responses are analysed. Applying the double parametric form, it reduces the computational cost without separating the fuzzy equation into coupled differential equations as done in traditional approaches.Originality/valueUncertain dynamic responses of fuzzy fractionally damped beam using the newly developed double parametric form of fuzzy numbers subject to unit step and impulse loads have been obtained. Gaussian fuzzy numbers are used to model the uncertainties. In the methodology using the alpha cut form, corresponding beam equation is first converted to an interval-based fuzzy equation. Next, it has been transformed to crisp form by applying double parametric form of fuzzy numbers. Finally, VIM has been applied to solve the same for the general fuzzy responses. Various numerical examples have been taken in to consideration.

Supportless printing of lattice structures by metal fused filament fabrication (MF3) of Ti-6Al-4V: design and analysis

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammad Qasim Shaikh ◽  
Serena Graziosi ◽  
Sundar Vedanarayan Atre
Keyword(s):  
Relative Density ◽  
Mechanical Performance ◽  
Unit Cell ◽  
Lattice Structures ◽  
Fused Filament Fabrication ◽  
Cross Sectional ◽  
Content Type ◽  
Aspect Ratios ◽  
Lattice Geometry ◽  
Starting Point

Purpose This paper aims to investigate the feasibility of supportless printing of lattice structures by metal fused filament fabrication (MF3) of Ti-6Al-4V. Additionally, an empirical method was presented for the estimation of extrudate deflection in unsupported regions of lattice cells for different geometric configurations. Design/methodology/approach Metal-polymer feedstock with a solids-loading of 59 Vol.% compounded and extruded into a filament was used for three-dimensional printing of lattice structures. A unit cell was used as a starting point, which was then extended to multi-stacked lattice structures. Feasible MF3 processing conditions were identified to fabricate defect-free lattice structures. The effects of lattice geometry parameters on part deflection and relative density were investigated at the unit cell level. Computational simulations were used to predict the part quality and results were verified by experimental printing. Finally, using the identified processing and geometry parameters, multi-stacked lattice structures were successfully printed and sintered. Findings Lattice geometry required considerable changes in MF3 printing parameters as compared to printing bulk parts. Lattice cell dimensions showed a considerable effect on dimensional variations and relative density due to varying aspect ratios. The experimental printing of lattice showed large deflection/sagging in unsupported regions due to gravity, whereas simulation was unable to estimate such deflection. Hence, an analytical model was presented to estimate extrudate deflections and verified with experimental results. Lack of diffusion between beads was observed in the bottom facing surface of unsupported geometry of sintered unit cells as an effect of extrudate sagging in the green part stage. This study proves that MF3 can fabricate fully dense Ti-6Al-4V lattice structures that appear to be a promising candidate for applications where mechanical performance, light-weighting and design customization are required. Originality/value Supportless printing of lattice structures having tiny cross-sectional areas and unsupported geometries is highly challenging for an extrusion-based additive manufacturing (AM) process. This study investigated the AM of Ti-6Al-4V supportless lattice structures using the MF3 process for the first time.

Application of generalized Fourier heat conduction law on MHD viscoinelastic fluid flow over stretching surface

2019 ◽  
Vol 30 (6) ◽  
pp. 3481-3496 ◽  
Author(s):  
Arif Hussain ◽  
Muhammad Yousaf Malik ◽  
Mair Khan ◽  
Taimoor Salahuddin
Keyword(s):  
Heat Flux ◽  
Fluid Flow ◽  
Friction Factor ◽  
Numerical Technique ◽  
Wall Heat Flux ◽  
Constitutive Law ◽  
Wall Friction ◽  
Theoretical Physics ◽  
Stretching Surface ◽  
Content Type

Purpose The purpose of current flow configuration is to spotlights the thermophysical aspects of magnetohydrodynamics (MHD) viscoinelastic fluid flow over a stretching surface. Design/methodology/approach The fluid momentum problem is mathematically formulated by using the Prandtl–Eyring constitutive law. Also, the non-Fourier heat flux model is considered to disclose the heat transfer characteristics. The governing problem contains the nonlinear partial differential equations with appropriate boundary conditions. To facilitate the computation process, the governing problem is transmuted into dimensionless form via appropriate group of scaling transforms. The numerical technique shooting method is used to solve dimensionless boundary value problem. Findings The expressions for dimensionless velocity and temperature are found and investigated under different parametric conditions. The important features of fluid flow near the wall, i.e. wall friction factor and wall heat flux, are deliberated by altering the pertinent parameters. The impacts of governing parameters are highlighted in graphical as well as tabular manner against focused physical quantities (velocity, temperature, wall friction factor and wall heat flux). A comparison is presented to justify the computed results, it can be noticed that present results have quite resemblance with previous literature which led to confidence on the present computations. Originality/value The computed results are quite useful for researchers working in theoretical physics. Additionally, computed results are very useful in industry and daily-use processes.

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

scholarly journals Real-Time Path Planning Based on Harmonic Functions under a Proper Generalized Decomposition-Based Framework

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 3943
Author(s):  
Nicolas Montés ◽  
Francisco Chinesta ◽  
Marta C. Mora ◽  
Antonio Falcó ◽  
Lucia Hilario ◽  
...  
Keyword(s):  
Path Planning ◽  
Real Time ◽  
Harmonic Functions ◽  
Autonomous Navigation ◽  
Numerical Technique ◽  
Computational Cost ◽  
Main Idea ◽  
Main Property ◽  
Proper Generalized Decomposition ◽  
Computational Vademecum

This paper presents a real-time global path planning method for mobile robots using harmonic functions, such as the Poisson equation, based on the Proper Generalized Decomposition (PGD) of these functions. The main property of the proposed technique is that the computational cost is negligible in real-time, even if the robot is disturbed or the goal is changed. The main idea of the method is the off-line generation, for a given environment, of the whole set of paths from any start and goal configurations of a mobile robot, namely the computational vademecum, derived from a harmonic potential field in order to use it on-line for decision-making purposes. Up until now, the resolution of the Laplace or Poisson equations has been based on traditional numerical techniques unfeasible for real-time calculation. This drawback has prevented the extensive use of harmonic functions in autonomous navigation, despite their powerful properties. The numerical technique that reverses this situation is the Proper Generalized Decomposition. To demonstrate and validate the properties of the PGD-vademecum in a potential-guided path planning framework, both real and simulated implementations have been developed. Simulated scenarios, such as an L-Shaped corridor and a benchmark bug trap, are used, and a real navigation of a LEGO®MINDSTORMS robot running in static environments with variable start and goal configurations is shown. This device has been selected due to its computational and memory-restricted capabilities, and it is a good example of how its properties could help the development of social robots.

A new weighted fraction Monte Carlo method for particle coagulation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiao Jiang ◽  
Tat Leung Chan
Keyword(s):  
Monte Carlo ◽  
Design Methodology ◽  
Computational Cost ◽  
Particle Coagulation ◽  
Content Type ◽  
Aerosol Dynamics ◽  
Stochastic Error ◽  
Adjustable Weight ◽  
Initial Distributions ◽  
Coagulation Kernel

Purpose The purpose of this study is to investigate the aerosol dynamics of the particle coagulation process using a newly developed weighted fraction Monte Carlo (WFMC) method. Design/methodology/approach The weighted numerical particles are adopted in a similar manner to the multi-Monte Carlo (MMC) method, with the addition of a new fraction function (α). Probabilistic removal is also introduced to maintain a constant number scheme. Findings Three typical cases with constant kernel, free-molecular coagulation kernel and different initial distributions for particle coagulation are simulated and validated. The results show an excellent agreement between the Monte Carlo (MC) method and the corresponding analytical solutions or sectional method results. Further numerical results show that the critical stochastic error in the newly proposed WFMC method is significantly reduced when compared with the traditional MMC method for higher-order moments with only a slight increase in computational cost. The particle size distribution is also found to extend for the larger size regime with the WFMC method, which is traditionally insufficient in the classical direct simulation MC and MMC methods. The effects of different fraction functions on the weight function are also investigated. Originality Value Stochastic error is inevitable in MC simulations of aerosol dynamics. To minimize this critical stochastic error, many algorithms, such as MMC method, have been proposed. However, the weight of the numerical particles is not adjustable. This newly developed algorithm with an adjustable weight of the numerical particles can provide improved stochastic error reduction.

An adaptive wavelet collocation method for the optimal heat source problem

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mahmood Khaksar-e Oshagh ◽  
Mostafa Abbaszadeh ◽  
Esmail Babolian ◽  
Hossein Pourbashash
Keyword(s):  
Heat Source ◽  
Numerical Technique ◽  
State Function ◽  
Adaptive Wavelet ◽  
Content Type ◽  
Optimal Heat ◽  
Wavelet Collocation Method ◽  
Collocation Approach ◽  
Interpolating Wavelets ◽  
Accurate Numerical Solution

Purpose This paper aims to propose a new adaptive numerical method to find more accurate numerical solution for the heat source optimal control problem (OCP). Design/methodology/approach The main aim of this paper is to present an adaptive collocation approach based on the interpolating wavelets to solve an OCP for finding optimal heat source, in a two-dimensional domain. This problem arises when the domain is heated by microwaves or by electromagnetic induction. Findings This paper shows that combination of interpolating wavelet basis and finite difference method makes an accurate structure to design adaptive algorithm for such problems which usually have non-smooth solution. Originality/value The proposed numerical technique is flexible for different OCP governed by a partial differential equation with box constraint over the control or the state function.

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