Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104494
Ana Santana , Adriana Eres-Castellanos , Jonathan D. Poplawsky , David San-Martin , Jose Antonio Jimenez , Esteban Urones-Garrote , Amy J. Clarke , Carlos Capdevila , Francisca G. Caballero
The Laser Powder Bed Fusion process involves complex thermodynamic and heat transfer mechanisms which results in a complicated understanding of the material’s microstructure and phase transformation processes. In the case of additive manufacturing maraging steels, these present heterogeneous structures which mainly consist of Body-Centred Tetragonal (BCT) martensite and retained austenite (Face-Centred Cubic (FCC) phase structure), unlike conventionally processed material. Research has already been done on the competitive or collaborative nature of austenite growth/reversion and precipitation in these materials. However, for Laser Powder Bed Fusion maraging steels, studies have focused on either the effect of the heterogeneous structures on austenite reversion kinetics or the formation, evolution and behaviour of precipitation. Still, no comprehensive research exists that covers in detail the relation between solute heterogeneity from the meso- to the nanoscale and its influence on both phase distribution and ageing physical phenomena. To do so, multiscale chemical analyses and microstructural characterisation techniques were used to investigate a maraging steel M300 in different transformed conditions: as-built, aged at 480 and 540 °C. The results showed that competing mechanisms during printing caused segregation at the mesoscale, which remains in aged samples. Vaporisation led to Cr segregation, while melt convections caused Ni and Ti depletion at melt pool boundaries. Retained austenite location was found at melt pool boundaries and away from them on the as-built structure. Its preferential location remains unclear. Dissimilarities from conventional material were identified in nanosized clustering and precipitates on aged samples.
激光粉末床熔融工艺涉及复杂的热力学和热传导机制，导致对材料微观结构和相变过程的复杂理解。就增材制造马氏体时效钢而言，与传统加工材料不同，这些材料呈现出异质结构，主要包括体心四方（BCT）马氏体和残留奥氏体（面心立方（FCC）相结构）。关于这些材料中奥氏体生长/反转和析出的竞争或协作性质的研究已经完成。然而，对于激光粉末床熔融马氏体时效钢，研究主要集中在异质结构对奥氏体还原动力学的影响或沉淀的形成、演变和行为。不过，目前还没有全面的研究能详细涵盖从中观到纳米尺度的溶质异质性之间的关系及其对相分布和时效物理现象的影响。为此，我们使用多尺度化学分析和微结构表征技术研究了马氏体时效钢 M300 在不同转化条件下的情况：坯料、480 和 540 °C 时效。结果表明，印刷过程中的竞争机制导致了中尺度的偏析，这种偏析在老化样品中依然存在。汽化导致铬偏析，而熔体对流则造成熔池边界的镍和钛耗竭。在熔池边界和远离熔池边界的坯体结构上发现了残留奥氏体。其优先位置仍不清楚。与传统材料不同之处在于老化样品上的纳米级团聚和沉淀物。
{"title":"Solute and phase heterogeneous distribution at different scales and its effect on ageing physical phenomena in a laser powder bed fusion produced maraging steel","authors":"Ana Santana , Adriana Eres-Castellanos , Jonathan D. Poplawsky , David San-Martin , Jose Antonio Jimenez , Esteban Urones-Garrote , Amy J. Clarke , Carlos Capdevila , Francisca G. Caballero","doi":"10.1016/j.addma.2024.104494","DOIUrl":"10.1016/j.addma.2024.104494","url":null,"abstract":"<div><div>The Laser Powder Bed Fusion process involves complex thermodynamic and heat transfer mechanisms which results in a complicated understanding of the material’s microstructure and phase transformation processes. In the case of additive manufacturing maraging steels, these present heterogeneous structures which mainly consist of Body-Centred Tetragonal (BCT) martensite and retained austenite (Face-Centred Cubic (FCC) phase structure), unlike conventionally processed material. Research has already been done on the competitive or collaborative nature of austenite growth/reversion and precipitation in these materials. However, for Laser Powder Bed Fusion maraging steels, studies have focused on either the effect of the heterogeneous structures on austenite reversion kinetics or the formation, evolution and behaviour of precipitation. Still, no comprehensive research exists that covers in detail the relation between solute heterogeneity from the meso- to the nanoscale and its influence on both phase distribution and ageing physical phenomena. To do so, multiscale chemical analyses and microstructural characterisation techniques were used to investigate a maraging steel M300 in different transformed conditions: as-built, aged at 480 and 540 °C. The results showed that competing mechanisms during printing caused segregation at the mesoscale, which remains in aged samples. Vaporisation led to Cr segregation, while melt convections caused Ni and Ti depletion at melt pool boundaries. Retained austenite location was found at melt pool boundaries and away from them on the as-built structure. Its preferential location remains unclear. Dissimilarities from conventional material were identified in nanosized clustering and precipitates on aged samples.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104494"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104459
Baixi Chen, Xiaoping Qian
The inherent uncertainties, particularly material uncertainties, significantly impact the buildability of 3D concrete-printed curved walls, leading to substantial variations that complicate quality control. To address this, a data-driven stochastic analysis framework is proposed for reliability-oriented buildability evaluation. Material uncertainties are quantified using a maximum likelihood-based stochastic parameter estimation method and considered as the uncertainty sources. Subsequently, a data-driven model, namely sparse Gaussian process regression (SGPR) model, is trained and combined with Monte Carlo simulation to assess the stochastic behavior of curved wall buildability. The influences of print speed, layer height, and horizontal curvature on buildability are analyzed under varying reliability levels. Additionally, an empirical model is proposed for the rapid evaluation of maximum buildability at specified horizontal curvature and reliability levels, providing significant practical value for 3D concrete printing designers. The impact of other uncertainty sources including the model error on reliability-oriented buildability is also discussed. These sources exhibit negligible influence when their intensities are less than 30 % of that caused by material uncertainty. Furthermore, the feasibility of the data-driven reliability-oriented buildability analysis for more complex geometry is also demonstrated.
{"title":"Data-driven reliability-oriented buildability analysis of 3D concrete printed curved wall","authors":"Baixi Chen, Xiaoping Qian","doi":"10.1016/j.addma.2024.104459","DOIUrl":"10.1016/j.addma.2024.104459","url":null,"abstract":"<div><div>The inherent uncertainties, particularly material uncertainties, significantly impact the buildability of 3D concrete-printed curved walls, leading to substantial variations that complicate quality control. To address this, a data-driven stochastic analysis framework is proposed for reliability-oriented buildability evaluation. Material uncertainties are quantified using a maximum likelihood-based stochastic parameter estimation method and considered as the uncertainty sources. Subsequently, a data-driven model, namely sparse Gaussian process regression (SGPR) model, is trained and combined with Monte Carlo simulation to assess the stochastic behavior of curved wall buildability. The influences of print speed, layer height, and horizontal curvature on buildability are analyzed under varying reliability levels. Additionally, an empirical model is proposed for the rapid evaluation of maximum buildability at specified horizontal curvature and reliability levels, providing significant practical value for 3D concrete printing designers. The impact of other uncertainty sources including the model error on reliability-oriented buildability is also discussed. These sources exhibit negligible influence when their intensities are less than 30 % of that caused by material uncertainty. Furthermore, the feasibility of the data-driven reliability-oriented buildability analysis for more complex geometry is also demonstrated.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104459"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104474
Sung Jin Park, Seunghyun Back, Bongchul Kang
We present a sustainable and efficient additive manufacturing method of silicon-based heterogeneous combinatorial functional surfaces designed to actively manipulate liquid droplet motion dynamics to address advanced rheological engineering challenges and applications. This additive manufacturing enables the instantaneous formation and control of hierarchical multiscale structures with tunable wettability through instantaneous plasmonic thermophysical sintering between laser and Si particles, eliminating the need for additional masks and subsequent processing steps. Furthermore, this fabrication approach can selectively implement heterogeneous combinatorial functional surfaces in a single domain by reversibly switching extreme wettability modes (e.g., from superhydrophobic to superhydrophilic) upon laser irradiation. Continuous superhydrophilic channels in a superhydrophobic background created by selective laser re-irradiation provide sufficient local attraction to manipulate droplet motion along the channel due to van der Waals forces and Laplace pressure fields generated by the difference in wettability. Active manipulation of droplet dynamic motion, such as trajectory tracking and antigravity self-propulsion, can be realized by simply designing a laser scanning path that determines the geometry of the local channel. The manipulation platform for liquid motion dynamics can be applied to active microfluidic channels with no cavity, without the need for an external power source. This advancement has important implications for broad fluid and rheological engineering applications.
{"title":"Additive manufacturing of heterogeneous combinatorial functional surface by plasmonic hierarchical sintering of silicon particles for active manipulation of rheological liquid motion","authors":"Sung Jin Park, Seunghyun Back, Bongchul Kang","doi":"10.1016/j.addma.2024.104474","DOIUrl":"10.1016/j.addma.2024.104474","url":null,"abstract":"<div><div>We present a sustainable and efficient additive manufacturing method of silicon-based heterogeneous combinatorial functional surfaces designed to actively manipulate liquid droplet motion dynamics to address advanced rheological engineering challenges and applications. This additive manufacturing enables the instantaneous formation and control of hierarchical multiscale structures with tunable wettability through instantaneous plasmonic thermophysical sintering between laser and Si particles, eliminating the need for additional masks and subsequent processing steps. Furthermore, this fabrication approach can selectively implement heterogeneous combinatorial functional surfaces in a single domain by reversibly switching extreme wettability modes (e.g., from superhydrophobic to superhydrophilic) upon laser irradiation. Continuous superhydrophilic channels in a superhydrophobic background created by selective laser re-irradiation provide sufficient local attraction to manipulate droplet motion along the channel due to van der Waals forces and Laplace pressure fields generated by the difference in wettability. Active manipulation of droplet dynamic motion, such as trajectory tracking and antigravity self-propulsion, can be realized by simply designing a laser scanning path that determines the geometry of the local channel. The manipulation platform for liquid motion dynamics can be applied to active microfluidic channels with no cavity, without the need for an external power source. This advancement has important implications for broad fluid and rheological engineering applications.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104474"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104430
Rafael Quelho de Macedo , Rafael Thiago Luiz Ferreira , Andrew Gleadall , Ian Ashcroft
The mechanical properties of parts built with material extrusion additive manufacturing are highly dependent on the material distribution within parts’ microstructure. This varies with the choice of process parameters. Therefore, when designing a functional printed part, one must tailor the printing parameters in order to obtain the desired properties, such as minimal voids. The present work proposes an optimisation method that designs printing parameters to minimise manufacturing time while keeping the void volume fraction at very low values (hence improving mechanical properties), keeping dimensions within tight tolerances and guaranteeing structural integrity. The new optimisation method utilises the authors’ previously developed software VOLCO-X, which is capable of efficiently predicting material distribution from filament extrusion within printed parts, including print track dimensions and microstructure geometry, without the need for any experimental calibration. In order to validate the proposed optimisation scheme, optimised printed parts using the scheme and parts using printing parameters determined by a commercial slicing software were manufactured and compared for different printing speeds and deposition strategies. At printing speed of 16 mm/s, it was possible to decrease the manufacturing time by more than 20% and structural mass by more than 5% in comparison to the commercial slicer printed part, whilst maintaining similar mechanical properties. At printing speed of 96 mm/s, due to the high printing speed, the commercial printed part presented gap faults between deposited strands, while the optimised part had structural integrity. At this printing speed, the optimised printed part presented significant improvements in terms of mechanical properties. The proposed optimisation methodology, in conjunction with VOLCO-X, is a powerful tool that can be used to improve manufacturing by filament extrusion. This innovative tool allows the identification of printing parameters without experiments and trial-and-error approaches, thus saving time and expense.
{"title":"Optimisation of microstructures from filament extrusion additive manufacturing based on numerical simulation with VOLCO-X","authors":"Rafael Quelho de Macedo , Rafael Thiago Luiz Ferreira , Andrew Gleadall , Ian Ashcroft","doi":"10.1016/j.addma.2024.104430","DOIUrl":"10.1016/j.addma.2024.104430","url":null,"abstract":"<div><div>The mechanical properties of parts built with material extrusion additive manufacturing are highly dependent on the material distribution within parts’ microstructure. This varies with the choice of process parameters. Therefore, when designing a functional printed part, one must tailor the printing parameters in order to obtain the desired properties, such as minimal voids. The present work proposes an optimisation method that designs printing parameters to minimise manufacturing time while keeping the void volume fraction at very low values (hence improving mechanical properties), keeping dimensions within tight tolerances and guaranteeing structural integrity. The new optimisation method utilises the authors’ previously developed software VOLCO-X, which is capable of efficiently predicting material distribution from filament extrusion within printed parts, including print track dimensions and microstructure geometry, without the need for any experimental calibration. In order to validate the proposed optimisation scheme, optimised printed parts using the scheme and parts using printing parameters determined by a commercial slicing software were manufactured and compared for different printing speeds and deposition strategies. At printing speed of 16 mm/s, it was possible to decrease the manufacturing time by more than 20% and structural mass by more than 5% in comparison to the commercial slicer printed part, whilst maintaining similar mechanical properties. At printing speed of 96 mm/s, due to the high printing speed, the commercial printed part presented gap faults between deposited strands, while the optimised part had structural integrity. At this printing speed, the optimised printed part presented significant improvements in terms of mechanical properties. The proposed optimisation methodology, in conjunction with VOLCO-X, is a powerful tool that can be used to improve manufacturing by filament extrusion. This innovative tool allows the identification of printing parameters without experiments and trial-and-error approaches, thus saving time and expense.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104430"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104439
Oluwatobi H. Aremu , Faisal S. Alneif , Mohammad Salah , Hasan Abualrahi , Abdulaziz M. Alotaibi , Awad B.S. Alquaity , Usman Ali
The adverse effects of spatter particles are well known in laser powder-bed fusion (LPBF) additive manufacturing. To prevent the deposition of spatter particles, an inert gas flow is commonly used to transport these spatters away from the build plate. However, the inert gas flow does not remove all spatters due to varying spatter sizes and ejection angles. Therefore, it is essential to understand and predict spatter trajectories to achieve superior LPBF parts. The present study focuses on numerical modelling of spatter trajectories in Renishaw AM250 using an Eulerian-Lagrangian discrete phase model. The argon velocity profile and spatter trajectories with and against the flow are computed for various materials, sizes and ejection angles. The simulation results are validated with experimental results and show a presence of uneven flow due to inlet geometry along with varying flow profiles across the build height due to inlet location. Spatter analysis shows three methods which result in spatter deposition. Spatter particles either fall directly on the build plate, are transported by the airflow or are re-directed in the recirculation zone. The findings presented in this work indicate the importance of build chamber design along with material-based parameter optimization that results in maximum spatter removal.
{"title":"Spatter transport in a laser powder-bed fusion build chamber","authors":"Oluwatobi H. Aremu , Faisal S. Alneif , Mohammad Salah , Hasan Abualrahi , Abdulaziz M. Alotaibi , Awad B.S. Alquaity , Usman Ali","doi":"10.1016/j.addma.2024.104439","DOIUrl":"10.1016/j.addma.2024.104439","url":null,"abstract":"<div><div>The adverse effects of spatter particles are well known in laser powder-bed fusion (LPBF) additive manufacturing. To prevent the deposition of spatter particles, an inert gas flow is commonly used to transport these spatters away from the build plate. However, the inert gas flow does not remove all spatters due to varying spatter sizes and ejection angles. Therefore, it is essential to understand and predict spatter trajectories to achieve superior LPBF parts. The present study focuses on numerical modelling of spatter trajectories in Renishaw AM250 using an Eulerian-Lagrangian discrete phase model. The argon velocity profile and spatter trajectories with and against the flow are computed for various materials, sizes and ejection angles. The simulation results are validated with experimental results and show a presence of uneven flow due to inlet geometry along with varying flow profiles across the build height due to inlet location. Spatter analysis shows three methods which result in spatter deposition. Spatter particles either fall directly on the build plate, are transported by the airflow or are re-directed in the recirculation zone. The findings presented in this work indicate the importance of build chamber design along with material-based parameter optimization that results in maximum spatter removal.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104439"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104450
Ritam Pal , Brandon Kemerling , Daniel Ryan , Sudhakar Bollapragada , Amrita Basak
Additive manufacturing, especially laser powder bed fusion (L-PBF), is extensively used for fabricating metal parts with intricate geometries. However, parts produced via L-PBF suffer from varied surface roughness, which affects the fatigue properties. Accurate prediction of fatigue properties as a function of surface roughness is a critical requirement for qualifying L-PBF parts. In this work, an analytical methodology was put forth to predict the fatigue life of L-PBF components having heterogeneous surface roughness. Thirty-six Hastelloy X specimens were printed using L-PBF followed by industry-standard heat treatment procedures. Half of these specimens had as-printed gauge sections and the other half were printed as cylinders from which fatigue specimens were extracted via machining. Specimens were printed in a vertical orientation and an orientation of 30° from the vertical axis. The surface roughness of the specimens was measured using computed tomography and parameters such as the maximum valley depth were used to build an extreme value distribution. Fatigue testing was conducted at an isothermal condition of 500 °F. It was observed that the rough specimens failed much earlier than the machined specimens due to the deep valleys present on the surfaces of the former ones. The valleys behaved as notches leading to high strain localization. Based on this observation, an analytical functional relationship was formulated that treated surface valleys as notches and correlated the strain localization around these notches with fatigue life, using the Coffin-Manson-Basquin and Ramberg-Osgood equations. The functional relationship was generated with the average of the extreme value distribution. The mean life curve from the functional relationship showed a maximum difference of 2 % from the experimental mean fatigue life observations for vertically built rough specimens and 10 % for 30⁰-built rough specimens. In conclusion, the proposed analytical model successfully predicted the fatigue life of L-PBF specimens at an elevated temperature undergoing different strain loadings.
{"title":"Fatigue life prediction of rough Hastelloy X specimens fabricated using laser powder bed fusion","authors":"Ritam Pal , Brandon Kemerling , Daniel Ryan , Sudhakar Bollapragada , Amrita Basak","doi":"10.1016/j.addma.2024.104450","DOIUrl":"10.1016/j.addma.2024.104450","url":null,"abstract":"<div><div>Additive manufacturing, especially laser powder bed fusion (L-PBF), is extensively used for fabricating metal parts with intricate geometries. However, parts produced via L-PBF suffer from varied surface roughness, which affects the fatigue properties. Accurate prediction of fatigue properties as a function of surface roughness is a critical requirement for qualifying L-PBF parts. In this work, an analytical methodology was put forth to predict the fatigue life of L-PBF components having heterogeneous surface roughness. Thirty-six Hastelloy X specimens were printed using L-PBF followed by industry-standard heat treatment procedures. Half of these specimens had as-printed gauge sections and the other half were printed as cylinders from which fatigue specimens were extracted via machining. Specimens were printed in a vertical orientation and an orientation of 30° from the vertical axis. The surface roughness of the specimens was measured using computed tomography and parameters such as the maximum valley depth were used to build an extreme value distribution. Fatigue testing was conducted at an isothermal condition of 500 °F. It was observed that the rough specimens failed much earlier than the machined specimens due to the deep valleys present on the surfaces of the former ones. The valleys behaved as notches leading to high strain localization. Based on this observation, an analytical functional relationship was formulated that treated surface valleys as notches and correlated the strain localization around these notches with fatigue life, using the Coffin-Manson-Basquin and Ramberg-Osgood equations. The functional relationship was generated with the average of the extreme value distribution. The mean life curve from the functional relationship showed a maximum difference of 2 % from the experimental mean fatigue life observations for vertically built rough specimens and 10 % for 30⁰-built rough specimens. In conclusion, the proposed analytical model successfully predicted the fatigue life of L-PBF specimens at an elevated temperature undergoing different strain loadings.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104450"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104472
Aqila Che Ab Rahman, Bum-Joo Lee, Sooman Lim
Advancements in vat photopolymerization printing technology have enabled the fabrication of components with varying mechanical properties within a single print job. Using a digital light projector to cure photopolymer resins layer by layer, it allows the fabrication of parts with both flexibility and rigidity, in different regions. It simplifies the manufacturing process by eliminating the need for multiple steps. Specifically, for applications such as microneedles, printing onto a stretchable substrate is crucial compared to a rigid substrate, as it conforms better to the contours of the skin, ensuring more effective and comfortable drug delivery. However, a notable limitation of vat photopolymerization printing is the current lack of biocompatible materials, which restricts its application for microneedle fabrication. The challenge lies in developing materials that meet biocompatibility standards, while also being compatible with the printing technique and capable to achieve precise microscale structures. Therefore, we have developed an ultraviolet (UV)-curable polymethyl methacrylate (PMMA) suitable for the vat photopolymerization printing and the microneedles were designed to have a hollow side structure, enhancing drug loading efficiency. Comprehensive testing has been conducted, including durability test, drug loading efficiency, and skin penetration capability.
{"title":"Optimizing polymethyl methacrylate (PMMA)-based stretchable microneedle arrays by vat photopolymerization for efficient drug loading","authors":"Aqila Che Ab Rahman, Bum-Joo Lee, Sooman Lim","doi":"10.1016/j.addma.2024.104472","DOIUrl":"10.1016/j.addma.2024.104472","url":null,"abstract":"<div><div>Advancements in vat photopolymerization printing technology have enabled the fabrication of components with varying mechanical properties within a single print job. Using a digital light projector to cure photopolymer resins layer by layer, it allows the fabrication of parts with both flexibility and rigidity, in different regions. It simplifies the manufacturing process by eliminating the need for multiple steps. Specifically, for applications such as microneedles, printing onto a stretchable substrate is crucial compared to a rigid substrate, as it conforms better to the contours of the skin, ensuring more effective and comfortable drug delivery. However, a notable limitation of vat photopolymerization printing is the current lack of biocompatible materials, which restricts its application for microneedle fabrication. The challenge lies in developing materials that meet biocompatibility standards, while also being compatible with the printing technique and capable to achieve precise microscale structures. Therefore, we have developed an ultraviolet (UV)-curable polymethyl methacrylate (PMMA) suitable for the vat photopolymerization printing and the microneedles were designed to have a hollow side structure, enhancing drug loading efficiency. Comprehensive testing has been conducted, including durability test, drug loading efficiency, and skin penetration capability.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104472"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104489
Ya-Chu Hsu, Dingchang Zhang, David C. Dunand
Equiatomic CoCuFeNi high-entropy alloy microlattices are created by 3D-extrusion printing of an ink containing a blend of binary oxides (Co3O4+CuO+Fe2O3+NiO) and graphite (C) powders. After printing, the green parts are subjected to a series of heat treatments under Ar leading to (i) carbon reduction of the oxides to form metallic particles, (ii) interdiffusion of these metallic particles to create an alloy, and (iii) sintering to remove porosity. The phase evolution in individual extruded filaments (similar to struts in the microlattices) is observed by in-situ X-ray diffraction, showing that intermediate suboxide phases (Cu2O, CoO, Fe3O4, CuFeO2, and FeO) form as the original oxides are reduced by carbon, before the final metallic alloy is formed. At 830 °C, the extruded filaments comprise a face-centered cubic CoCuNi(+Fe) alloy with unreduced FeO inclusions. After reduction and sintering at 1100 °C, homogeneous, densified, equiatomic CoCuFeNi microlattices are achieved, containing small amounts of a Cu-rich phase. At room temperature, the compressive strength of these CoCuFeNi microlattices increases as the strut diameter decreases from ∼260 to ∼130 µm, as expected from an observed drop in strut porosity resulting from more complete sintering. This is consistent with the easier escape of CO+CO2 gas created during carbothermic oxide reduction from the thinner struts undergoing reduction and sintering.
{"title":"Carbon reduction of 3D-ink-extruded oxide powders for synthesis of equiatomic CoCuFeNi microlattices","authors":"Ya-Chu Hsu, Dingchang Zhang, David C. Dunand","doi":"10.1016/j.addma.2024.104489","DOIUrl":"10.1016/j.addma.2024.104489","url":null,"abstract":"<div><div>Equiatomic CoCuFeNi high-entropy alloy microlattices are created by 3D-extrusion printing of an ink containing a blend of binary oxides (Co<sub>3</sub>O<sub>4</sub>+CuO+Fe<sub>2</sub>O<sub>3</sub>+NiO) and graphite (C) powders. After printing, the green parts are subjected to a series of heat treatments under Ar leading to (i) carbon reduction of the oxides to form metallic particles, (ii) interdiffusion of these metallic particles to create an alloy, and (iii) sintering to remove porosity. The phase evolution in individual extruded filaments (similar to struts in the microlattices) is observed by <em>in-situ</em> X-ray diffraction, showing that intermediate suboxide phases (Cu<sub>2</sub>O, CoO, Fe<sub>3</sub>O<sub>4</sub>, CuFeO<sub>2</sub>, and FeO) form as the original oxides are reduced by carbon, before the final metallic alloy is formed. At 830 °C, the extruded filaments comprise a face-centered cubic CoCuNi(+Fe) alloy with unreduced FeO inclusions. After reduction and sintering at 1100 °C, homogeneous, densified, equiatomic CoCuFeNi microlattices are achieved, containing small amounts of a Cu-rich phase. At room temperature, the compressive strength of these CoCuFeNi microlattices increases as the strut diameter decreases from ∼260 to ∼130 µm, as expected from an observed drop in strut porosity resulting from more complete sintering. This is consistent with the easier escape of CO+CO<sub>2</sub> gas created during carbothermic oxide reduction from the thinner struts undergoing reduction and sintering.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104489"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104486
Dac-Phuc Pham , Hong-Chuong Tran
Laser powder bed fusion (L-PBF) uses a controlled laser beam to melt specific regions of a metal powder bed in a layer-by-layer fashion to fabricate parts with an intricate geometry. However, due to the stochastic nature of the L-PBF process, many defects may occur during the build process, including distortion, porosity, and high surface roughness. A poor roughness of the upper surface is frequently associated with impaired mechanical properties and a lower corrosion resistance. Thus, laser polishing (LP) is commonly employed to smooth the surface of the component following the build process. The surface finish of the polished part is dependent not only on the initial morphology of the surface, but also the processing conditions employed in the polishing process (i.e., the laser power, scanning speed, and hatching space). The surface profile is also influenced by physical phenomena such as the surface tension force, recoil pressure, and Marangoni force. The present study thus proposes an integrated framework based on discrete element method (DEM) and computational fluid dynamics (CFD) simulations which takes account of all of these factors to predict the final surface morphology and roughness of L-PBF components following LP processing. The validity of the simulation model is confirmed by comparing the calculated mean surface roughness of the polished components (with the experimental values. It is found that the maximum error of the simulation results for different initial surface morphologies and LP processing conditions is less than 6.8 %.
{"title":"Multi-physics simulation for predicting surface roughness of laser powder bed fused parts after laser polishing","authors":"Dac-Phuc Pham , Hong-Chuong Tran","doi":"10.1016/j.addma.2024.104486","DOIUrl":"10.1016/j.addma.2024.104486","url":null,"abstract":"<div><div>Laser powder bed fusion (L-PBF) uses a controlled laser beam to melt specific regions of a metal powder bed in a layer-by-layer fashion to fabricate parts with an intricate geometry. However, due to the stochastic nature of the L-PBF process, many defects may occur during the build process, including distortion, porosity, and high surface roughness. A poor roughness of the upper surface is frequently associated with impaired mechanical properties and a lower corrosion resistance. Thus, laser polishing (LP) is commonly employed to smooth the surface of the component following the build process. The surface finish of the polished part is dependent not only on the initial morphology of the surface, but also the processing conditions employed in the polishing process (i.e., the laser power, scanning speed, and hatching space). The surface profile is also influenced by physical phenomena such as the surface tension force, recoil pressure, and Marangoni force. The present study thus proposes an integrated framework based on discrete element method (DEM) and computational fluid dynamics (CFD) simulations which takes account of all of these factors to predict the final surface morphology and roughness of L-PBF components following LP processing. The validity of the simulation model is confirmed by comparing the calculated mean surface roughness of the polished components (<span><math><mrow><msub><mrow><mi>S</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>)</mo><mspace></mspace></mrow></math></span>with the experimental values. It is found that the maximum error of the simulation results for different initial surface morphologies and LP processing conditions is less than 6.8 %.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104486"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-25DOI: 10.1016/j.addma.2024.104466
Clemens Maucher , Yeonse Kang , Stefan Bechler , Matthias Ruf , Holger Steeb , Hans-Christian Möhring , Fabian Hampp
Permeable, media transporting, components are an integral part in numerous technical applications. In gas turbines combustors, for example, gaseous oxidizer and fuel are transported separately into the burner, where they are injected and mixed, and subsequently combusted. The mixture homogeneity strongly affects the combustion performance and emissions formation and is, amongst other, determined by the spatial distribution of fuel injection ports. In this context, porous media provide the limiting case for a spatial distribution of media-injecting pores, yet is typically associated with a high pressure drop that yields a loss in efficiency. In this study, possibilities of achieving gas permeability in additively manufactured porous structures are investigated. The objective is to selectively functionalize the permeable layers for gaseous media supply with low pressure loss and, when needed, enable a targeted mixing of different gas streams. For this purpose, a laser-based powder bed fusion process (PBF-LB/M) was used in this study. It offers the opportunity to manufacture varying porosities inside complex monolithic metal parts. To produce the porous structures and to achieve gas permeability, the effect of scan rotation angle, hatch distance, build-up direction and length of the porous specimen is investigated. Due to the high temperatures present in combustion systems, the present work utilizes Inconel 718 material. The AM gas permeable specimen are experimentally characterized by means of surface topography, micro X-ray computed tomography (µXRCT) as well as flow and pressure loss test. The results show, that the AM process parameter provide effective control parameters to adjust the permeability. The strongest effect originates from the hatch distance for a given build-up direction. Depending on the scan rotation, the flow transitions from a turbulent pipe flow to a Darcy flow as present in conventional porous media. A structured alignment and connectivity of pores can be realized as evident in the µXRCT results, surface topography and the flow measurements. Residual powder, powder adhering to the pore walls and stochastic closure of pores or channels lead to deviations and need to be considered when designing respective parts. Nonetheless, the results further show that a directional dependence of the permeability and the build-up direction can be realized and controlled. Consequently, when considering the AM build-strategy in the design of components, this directed permeability can be functionalized in the generation of gas transporting and gas mixing layers separately by adjusting the AM processing parameter.
可渗透介质输送部件是众多技术应用中不可或缺的组成部分。例如，在燃气轮机的燃烧器中，气态氧化剂和燃料被分别输送到燃烧器中，在那里进行喷射和混合，然后进行燃烧。混合物的均匀性对燃烧性能和排放物的形成有很大影响，除其他外，还取决于燃料喷射口的空间分布。在这种情况下，多孔介质提供了介质喷射孔空间分布的极限情况，但通常与产生效率损失的高压力降有关。本研究探讨了在添加制造的多孔结构中实现气体渗透的可能性。其目的是有选择性地对透气层进行功能化处理，以便以较低的压力损失提供气体介质，并在需要时实现不同气流的定向混合。为此，本研究采用了激光粉末床熔融工艺（PBF-LB/M）。该工艺可在复杂的整体金属部件内制造不同的多孔结构。为了制造多孔结构并实现气体渗透性，研究了扫描旋转角度、舱口距离、堆积方向和多孔试样长度的影响。由于燃烧系统温度较高，本研究采用了铬镍铁合金 718 材料。通过表面形貌、微 X 射线计算机断层扫描 (µXRCT) 以及流量和压力损失测试，对 AM 气体渗透试样进行了实验表征。结果表明，AM 工艺参数提供了调整渗透性的有效控制参数。在给定的堆积方向上，最大的影响来自于舱口距离。根据扫描旋转的不同，流动会从湍流管流过渡到传统多孔介质中的达西流。从 µXRCT 结果、表面形貌和流动测量结果中可以明显看出，孔隙的结构排列和连通性得以实现。残留粉末、粘附在孔壁的粉末以及孔隙或通道的随机闭合会导致偏差，因此在设计相应部件时需要加以考虑。尽管如此，结果进一步表明，渗透率和堆积方向的定向依赖性是可以实现和控制的。因此，在设计部件时考虑 AM 构建策略时，可以通过调整 AM 加工参数，在生成气体输送层和气体混合层时将这种定向渗透性功能化。
{"title":"Towards bespoke gas permeability by functionally graded structures in laser-based powder bed fusion of metals","authors":"Clemens Maucher , Yeonse Kang , Stefan Bechler , Matthias Ruf , Holger Steeb , Hans-Christian Möhring , Fabian Hampp","doi":"10.1016/j.addma.2024.104466","DOIUrl":"10.1016/j.addma.2024.104466","url":null,"abstract":"<div><div>Permeable, media transporting, components are an integral part in numerous technical applications. In gas turbines combustors, for example, gaseous oxidizer and fuel are transported separately into the burner, where they are injected and mixed, and subsequently combusted. The mixture homogeneity strongly affects the combustion performance and emissions formation and is, amongst other, determined by the spatial distribution of fuel injection ports. In this context, porous media provide the limiting case for a spatial distribution of media-injecting pores, yet is typically associated with a high pressure drop that yields a loss in efficiency. In this study, possibilities of achieving gas permeability in additively manufactured porous structures are investigated. The objective is to selectively functionalize the permeable layers for gaseous media supply with low pressure loss and, when needed, enable a targeted mixing of different gas streams. For this purpose, a laser-based powder bed fusion process (PBF-LB/M) was used in this study. It offers the opportunity to manufacture varying porosities inside complex monolithic metal parts. To produce the porous structures and to achieve gas permeability, the effect of scan rotation angle, hatch distance, build-up direction and length of the porous specimen is investigated. Due to the high temperatures present in combustion systems, the present work utilizes Inconel 718 material. The AM gas permeable specimen are experimentally characterized by means of surface topography, micro X-ray computed tomography (µXRCT) as well as flow and pressure loss test. The results show, that the AM process parameter provide effective control parameters to adjust the permeability. The strongest effect originates from the hatch distance for a given build-up direction. Depending on the scan rotation, the flow transitions from a turbulent pipe flow to a Darcy flow as present in conventional porous media. A structured alignment and connectivity of pores can be realized as evident in the µXRCT results, surface topography and the flow measurements. Residual powder, powder adhering to the pore walls and stochastic closure of pores or channels lead to deviations and need to be considered when designing respective parts. Nonetheless, the results further show that a directional dependence of the permeability and the build-up direction can be realized and controlled. Consequently, when considering the AM build-strategy in the design of components, this directed permeability can be functionalized in the generation of gas transporting and gas mixing layers separately by adjusting the AM processing parameter.</div></div>","PeriodicalId":7172,"journal":{"name":"Additive manufacturing","volume":"94 ","pages":"Article 104466"},"PeriodicalIF":10.3,"publicationDate":"2024-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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