Gaojie Liu and Zhaoli Guo
The purpose of this paper is to investigate, numerically, the effects of the Prandtl number on the mixing process in two‐dimensional Rayleigh‐Taylor instability of incompressible…
Abstract
Purpose
The purpose of this paper is to investigate, numerically, the effects of the Prandtl number on the mixing process in two‐dimensional Rayleigh‐Taylor instability of incompressible and miscible fluids.
Design/methodology/approach
The simulations are carried out based on a double‐distribution‐function lattice Boltzmann method in which the Prandtl number can be adjusted.
Findings
The simulations reveal that the mixing‐zone grows inversely with increasing Prandtl number, but the processes of Rayleigh‐Taylor instability are nearly identical in terms of a dimensionless time as the Prandtl number ranges from 0.1 to 10. The symmetric property of the mixing‐zone is also studied, which is found to be closely dependent on the symmetry of the initial perturbations.
Originality/value
The results here show that the growth of the mixing‐zone is related to the Prandtl number, whereas most previous studies have been focused on the relationship between the growth of the mixing zone and time with a constant Prandtl number.
Details
Keywords
Hao Li, Shuai Zhang, Zhiran Yi, Jie Li, Aihua Sun, Jianjun Guo and Gaojie Xu
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…
Abstract
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.
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Keywords
Michele Ciotti, Giampaolo Campana and Mattia Mele
This paper aims to present a survey concerning the accuracy of thermoplastic polymeric parts fabricated by additive manufacturing (AM). Based on the scientific literature, the aim…
Abstract
Purpose
This paper aims to present a survey concerning the accuracy of thermoplastic polymeric parts fabricated by additive manufacturing (AM). Based on the scientific literature, the aim is to provide an updated map of trends and gaps in this relevant research field. Several technologies and investigation methods are examined, thus giving an overview and analysis of the growing body of research.
Design/methodology/approach
Permutations of keywords, which concern materials, technologies and the accuracy of thermoplastic polymeric parts fabricated by AM, are used for a systematic search in peer-review databases. The selected articles are screened and ranked to identify those that are more relevant. A bibliometric analysis is performed based on investigated materials and applied technologies of published papers. Finally, each paper is categorised and discussed by considering the implemented research methods.
Findings
The interest in the accuracy of additively manufactured thermoplastics is increasing. The principal sources of inaccuracies are those shrinkages occurring during part solidification. The analysis of the research methods shows a predominance of empirical approaches. Due to the experimental context, those achievements have consequently limited applicability. Analytical and numerical models, which generally require huge computational costs when applied to complex products, are also numerous and are investigated in detail. Several articles deal with artificial intelligence tools and are gaining more and more attention.
Originality/value
The cross-technology survey on the accuracy issue highlights the common critical aspects of thermoplastics transformed by AM. An updated map of the recent research literature is achieved. The analysis shows the advantages and limitations of different research methods in this field, providing an overview of research trends and gaps.