Muhammad Arif Mahmood, Andrei C. Popescu, Mihai Oane, Carmen Ristoscu and Ion N. Mihailescu
This paper aims to develop efficient and simple models for thermal distribution, melt pool dimensions and controlled phase change in the laser additive manufacturing (AM) of bulk…
Abstract
Purpose
This paper aims to develop efficient and simple models for thermal distribution, melt pool dimensions and controlled phase change in the laser additive manufacturing (AM) of bulk and powder particles ceramic materials.
Design/methodology/approach
This paper proposes new analytical models for the AM of bulk and powder bed ceramic materials. A volumetric moving heat source, along with the complete melting of bulk and powder particle materials, is taken into account. Different values of laser absorption coefficient in solid and liquid states have been used to investigate the phase transformation. Furthermore, the pores and voids dimensions are also included in the modeling. Theoretical predictions have been compared with the experimental analyses and finite element simulations in laser to silicon nitride and laser to alumina interaction. The analysis focuses on the impact of laser power and scanning speed on the melt pool width and depth evolution into the bulk substrate and powder bed.
Findings
This study shows that the powder particles exhibit a higher thermal distribution value than the bulk substrate because of voids in the powder layer. The laser beam experiences multiple reflections in the presence of porosity/voids, thus increasing the surface absorption coefficient, which becomes relevant with the increment in the pore/void dimension. A direct relationship has been found between the laser power and melt pool dimensions, while the scanning speed displayed an inverse relationship for the melt pool width and length. Larger melt dimensions were inferred in the case of laser–powder particle interaction compared with laser–bulk substrate interaction. A close correlation was found between the analytical simulations, experimental investigations and numerical simulation results within the range of 4%–8%.
Originality/value
This paper fulfills an identified need to develop efficient and simplified models for ceramics laser AM by taking into account different laser absorption coefficients in solid and liquid form, voids and pores dimensions and controlled phase transformation to avoid vapors and plasma formation. The limitation of the finite element simulation model is that the solution is strongly dependent on the mesh quality and accuracy directly linked to the computation efficiency and time. A finer mesh requires a longer computing time than a coarse mesh. Finite element simulations require, however, specialized skills.
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Muhammad Arif Mahmood, Chioibasu Diana, Uzair Sajjad, Sabin Mihai, Ion Tiseanu and Andrei C. Popescu
Porosity is a commonly analyzed defect in the laser-based additive manufacturing processes owing to the enormous thermal gradient caused by repeated melting and solidification…
Abstract
Purpose
Porosity is a commonly analyzed defect in the laser-based additive manufacturing processes owing to the enormous thermal gradient caused by repeated melting and solidification. Currently, the porosity estimation is limited to powder bed fusion. The porosity estimation needs to be explored in the laser melting deposition (LMD) process, particularly analytical models that provide cost- and time-effective solutions compared to finite element analysis. For this purpose, this study aims to formulate two mathematical models for deposited layer dimensions and corresponding porosity in the LMD process.
Design/methodology/approach
In this study, analytical models have been proposed. Initially, deposited layer dimensions, including layer height, width and depth, were calculated based on the operating parameters. These outputs were introduced in the second model to estimate the part porosity. The models were validated with experimental data for Ti6Al4V depositions on Ti6Al4V substrate. A calibration curve (CC) was also developed for Ti6Al4V material and characterized using X-ray computed tomography. The models were also validated with the experimental results adopted from literature. The validated models were linked with the deep neural network (DNN) for its training and testing using a total of 6,703 computations with 1,500 iterations. Here, laser power, laser scanning speed and powder feeding rate were selected inputs, whereas porosity was set as an output.
Findings
The computations indicate that owing to the simultaneous inclusion of powder particulates, the powder elements use a substantial percentage of the laser beam energy for their melting, resulting in laser beam energy attenuation and reducing thermal value at the substrate. The primary operating parameters are directly correlated with the number of layers and total height in CC. Through X-ray computed tomography analyses, the number of layers showed a straightforward correlation with mean sphericity, while a converse relation was identified with the number, mean volume and mean diameter of pores. DNN and analytical models showed 2%–3% and 7%–9% mean absolute deviations, respectively, compared to the experimental results.
Originality/value
This research provides a unique solution for LMD porosity estimation by linking the developed analytical computational models with artificial neural networking. The presented framework predicts the porosity in the LMD-ed parts efficiently.
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Avant‐propos sous les auspices de l'Institut international de Coopération intellectuelle, paraissait en 1934 le t. I, consacré à l'Europe, du Guide international des Archives. Le…
Abstract
Avant‐propos sous les auspices de l'Institut international de Coopération intellectuelle, paraissait en 1934 le t. I, consacré à l'Europe, du Guide international des Archives. Le questionnaire envoyé à tous les États européens comportait sous les points 4 et 6 les questions suivantes: ‘Existe‐t‐il un guide général pour les diverses catégories d'Archives ou des guides particuliers pour l'une ou l'autre d'entre elles?’ et ‘Existe‐t‐il des catalogues imprimés, des publications tant officielles que privées, susceptibles de constituer un instrument complet de référence pour tout ou partie importante des fonds d'archives?’ Les réponses des divers pays à ces questions, malgré leur caractère très inégal, ont fait du Guide international un bon instrument d'information générale sur les Archives. Malheureusement les circonstances ont empêché la publication du volume consacré aux États non européens, tandis que le temps qui s'écoulait tendait à rendre périmés les renseignements fournis sur les Archives européennes.
Sarbjit Kaur, Niraj Bala and Charu Khosla
The biomaterials are natural or synthetic materials used to improve quality of life either by replacing tissue/organ or assisting their function in medical field. The purpose of…
Abstract
Purpose
The biomaterials are natural or synthetic materials used to improve quality of life either by replacing tissue/organ or assisting their function in medical field. The purpose of the study is to analyze the hydroxyapatite (HAP), HAP-TiO2 (25 percent) composite coatings deposited on 316 LSS by High Velocity Flame Spray (HVFS) technique.
Design/methodology/approach
The coatings exhibit almost uniform and dense microstructure with porosity (HAP = 0.153 and HAP-TiO2 composite = 0.138). Electrochemical corrosion testing was done on the uncoated and coated specimens in Ringer solution (SBF). As-sprayed coatings were characterized by XRD, SEM/EDS and cross-sectional X-ray mapping techniques before and after dipping in Ringer solution. Microhardness of composite coating (568.8 MPa) was found to be higher than HAP coating (353 MPa).
Findings
During investigations, it was observed that the corrosion resistance of steel was found to have increased after the deposition of HAP and HAP-TiO2 composite coatings. Thus, coatings serve as an effective diffusion barrier to prohibit the diffusion of ions from the SBF into the substrate. Composite coatings have been found to be more corrosion resistant as compared to HAP coating in the simulated body fluid.
Research limitations/implications
It has been concluded that corrosion resistance of HAP as well as composite coating is because of the desirable microstructural changes such as low porosity high microhardness and flat splat structures in coatings as compared to bare specimen.
Practical implications
This study is useful in the selection of biomedical implants.
Social implications
This study is useful in the field of biomaterials.
Originality/value
No reported literature on corrosion behavior of HAP+ 25%- TiO2 has been noted till now using flame spray technique. The main focus of the study is to investigate the HAP as well as composite coatings for biomedical applications.
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Zhen Li, Xianwei Liu, Yiwei Lian, Juan Xie, Xiaorui Gao and Tao Chang
This paper aims to report the conductivity measurement of ten different surfactant-free microemulsions (SFMEs)
Abstract
Purpose
This paper aims to report the conductivity measurement of ten different surfactant-free microemulsions (SFMEs)
Design/methodology/approach
The variations of electrical conductivity as a function of water volume fraction are examined at one constant alcohol (or DMF, ethyl lactate, γ-valerolactone)/water, alcohol (or DMF, ethyl lactate, γ-valerolactone)/oil volume ratios for each sample.
Findings
Most of the results are consistent with percolation character. The conductive mechanism of these SFMEs is discussed by the percolation model, and it is found that it might be described with the static percolation model below the percolation threshold.
Originality/value
Our report gives a systematic research on the percolation mechanism of as many species of SFMEs as possible by the theoretical models
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Mengjiao Wang, Yunxia Wang, Hao Liu and Fengyuan Yan
This paper aims to study the influence of load and environment medium on the fretting behavior of SAF 2507 SDSS.
Abstract
Purpose
This paper aims to study the influence of load and environment medium on the fretting behavior of SAF 2507 SDSS.
Design/methodology/approach
In this study, the effect of load on the fretting behavior of SAF 2507 SDSS in air and sea water were studied. The fretting wear tests under different loads were conducted with a ball-on-flat contact configuration. The friction coefficient, wear volume, surface morphology and oxidation component were determined.
Findings
With the increase of applied load, the friction coefficient decreases both in air and sea water. The fretting mechanism is gradually transformed from partial slip regime to slip regime in air while the fretting counterparts are all in the state of gross slip in sea water. In sea water, the friction coefficient is lower while the wear loss is higher compared with that in air.
Research limitations/implications
This research suggests that the fretting behavior of SAF 2507 SDSS is related to load and environment medium.
Practical implications
The results may help us to choose the appropriate load under different environments.
Originality/value
The main originality of the research is to reveal the fretting behavior of SAF 2507 SDSS under different loads in air and sea water, which would help us to realize fretting behavior of SAF 2507 SDSS is controlled by the combination of applied load and lubricating environment.
Peer review
The peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-08-2019-0335.
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Chenfei Zhao, Jun Wang and Lini Lu
In flexible electronics applications, organic inks are mostly used for inkjet printing. Three-dimensional (3 D) printing technology has the advantages of low cost, high speed and…
Abstract
Purpose
In flexible electronics applications, organic inks are mostly used for inkjet printing. Three-dimensional (3 D) printing technology has the advantages of low cost, high speed and good precision in modern electronic printing. The purpose of this study is to solve the high cost of traditional printing and the pollution emissions of organic ink. It is necessary to develop a water-based conductive ink that is easily degradable and can be 3 D printed. A nano-silver ink printed circuit pattern with high precision, high conductivity and good mechanical properties is a promising strategy.
Design/methodology/approach
The researched nano-silver conductive ink is mainly composed of silver nanoparticles and resin. The effect of adding methyl cellulose on the ink was also explored. A simple 3 D circuit pattern was printed on photographic paper. The line width, line length, line thickness and conductivity of the printed circuit were tested. The influence of sintering temperature and sintering time on pattern resistivity was studied. The relationship between circuit pattern bending performance and electrical conductivity is analyzed.
Findings
The experimental results show that the ink has the characteristics of low silver content and good environmental protection effect. The printing feasibility of 3 D printing circuit patterns on paper substrates was confirmed. The best printing temperature is 160°C–180°C, and the best sintering time is 30 min. The circuit pattern can be folded 120°, and the cycle is folded more than 60 times. The minimum resistivity of the circuit pattern is 6.07 µΩ·cm. Methyl cellulose can control the viscosity of the ink. The mechanical properties of the pattern have been improved. The printing method of 3 D printing can significantly reduce the sintering time and temperature of the conductive ink. These findings may provide innovation for the flexible electronics industry and pave the way for alternatives to cost-effective solutions.
Originality/value
In this study, direct ink writing technology was used to print circuit patterns on paper substrates. This process is simple and convenient and can control the thickness of the ink layer. The ink material is nonpolluting to the environment. Nano-silver ink has suitable viscosity and pH value. It can meet the requirements of pneumatic 3 D printers. The method has the characteristics of simple process, fast forming, low cost and high environmental friendliness.