Pub Date : 2018-02-28DOI: 10.24247/IJMPERDFEB20185
Pankaj Kumar, J. Harivignesh
The need for super-plasticity and high strength leads to the development of Severe Plastic Deformation (SPD) techniques. The strength of the material is directly dependent upon the grain size of the material. During the simulation of ECAP process, the initial die designed with sharp corner angle reveals metal flash. Metal flash may fail the tip of the billet. To avoid and control the metal flash, the intersecting channels are redesigned with radius of 3mm and reveals smooth flow. ECAP die 900 and 1200 for square billets are made in H11 Steel channels, that are cut into 58×9.2×8.2mm for 900 machined in EDM process, similarly 1200 die with 52×9.2×8.2mm are made, including the Punch are made in same material of 155×9.2×8.2mm, respectively. Aluminum Automobile scrap were selected and melted in the open-hearth furnace, made round rods and square billets as per the die dimensions. Molybdenum di-sulphate, is used as a lubricant. Tensile Test was carried out for the Annelid specimen. Brinell hardness was checked and SEM test was carried out, for finding out the reason for the failure.
{"title":"Grain Refinement Through Design Modification of ECAP Dies","authors":"Pankaj Kumar, J. Harivignesh","doi":"10.24247/IJMPERDFEB20185","DOIUrl":"https://doi.org/10.24247/IJMPERDFEB20185","url":null,"abstract":"The need for super-plasticity and high strength leads to the development of Severe Plastic Deformation (SPD) techniques. The strength of the material is directly dependent upon the grain size of the material. During the simulation of ECAP process, the initial die designed with sharp corner angle reveals metal flash. Metal flash may fail the tip of the billet. To avoid and control the metal flash, the intersecting channels are redesigned with radius of 3mm and reveals smooth flow. ECAP die 900 and 1200 for square billets are made in H11 Steel channels, that are cut into 58×9.2×8.2mm for 900 machined in EDM process, similarly 1200 die with 52×9.2×8.2mm are made, including the Punch are made in same material of 155×9.2×8.2mm, respectively. Aluminum Automobile scrap were selected and melted in the open-hearth furnace, made round rods and square billets as per the die dimensions. Molybdenum di-sulphate, is used as a lubricant. Tensile Test was carried out for the Annelid specimen. Brinell hardness was checked and SEM test was carried out, for finding out the reason for the failure.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126701128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A computational study is conducted to investigate the aerodynamic performance of a newly designed corrugated airfoil of dragonfly at range of low Reynolds number 15000-38000. This study represents the transient nature of corrugated airfoils at low Reynolds number where flow is assumed to be laminar, unsteady, incompressible and two dimensional. This research comprises of the investigation of the aerodynamic performance of various corrugation configurations at different corrugated angle (i.e., 4°, 8°, 12°) with varying pitch length and peak height along the span wise and chordwise directions. The 12° corrugated angle is incorporated in the new modified design with varying pitch length, corrugated angle and peak height to achieve the higher lift to drag ratio. The simulation is carried out using Ansys CFD as a simulation tool and ICEM CFD as a modeling tool for 2-D corrugated airfoil. The design features of corrugated airfoil used in this research is not used in earlier studies. The simulation includes a sharp interface cartesian grid-based meshing and k-e model for turbulence model. The computational results show that the newly designed corrugated aero foil generates more lift and less drag compared to flat plate and NACA 0015 aero foil and also helps in preventing large scale flow separation.
{"title":"Computational Analysis of Bio-Inspired Corrugated Airfoil with Varying Corrugation Angle","authors":"Md. Akhtar Khan, C. Padhy, M. Nandish, K. Rita","doi":"10.2139/ssrn.3124809","DOIUrl":"https://doi.org/10.2139/ssrn.3124809","url":null,"abstract":"A computational study is conducted to investigate the aerodynamic performance of a newly designed corrugated airfoil of dragonfly at range of low Reynolds number 15000-38000. This study represents the transient nature of corrugated airfoils at low Reynolds number where flow is assumed to be laminar, unsteady, incompressible and two dimensional. This research comprises of the investigation of the aerodynamic performance of various corrugation configurations at different corrugated angle (i.e., 4°, 8°, 12°) with varying pitch length and peak height along the span wise and chordwise directions. The 12° corrugated angle is incorporated in the new modified design with varying pitch length, corrugated angle and peak height to achieve the higher lift to drag ratio. The simulation is carried out using Ansys CFD as a simulation tool and ICEM CFD as a modeling tool for 2-D corrugated airfoil. The design features of corrugated airfoil used in this research is not used in earlier studies. The simulation includes a sharp interface cartesian grid-based meshing and k-e model for turbulence model. The computational results show that the newly designed corrugated aero foil generates more lift and less drag compared to flat plate and NACA 0015 aero foil and also helps in preventing large scale flow separation.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124778338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Friction Stir Welding (FSW) is a solid-state welding process which produces welds due to the compressive force contact of work pieces which are either rotating or moving relative to each other. The heat required to join different specimens is generated by heating due to friction at the interface. Application of Friction Stir Welding in aerospace industries is very broad. Rolls-Royce now uses friction welding processes for its modern Trent aero engines that drive the Airbus A380 and the Boeing 787. In this paper, Friction Stir Welding of various dissimilar metals is reviewed. The microstructure, hardness, and flow characteristics are also reviewed.
{"title":"Friction Stir Welding of Dissimilar Metal: A Review","authors":"Akshansh Mishra","doi":"10.2139/ssrn.3104223","DOIUrl":"https://doi.org/10.2139/ssrn.3104223","url":null,"abstract":"Friction Stir Welding (FSW) is a solid-state welding process which produces welds due to the compressive force contact of work pieces which are either rotating or moving relative to each other. The heat required to join different specimens is generated by heating due to friction at the interface. Application of Friction Stir Welding in aerospace industries is very broad. Rolls-Royce now uses friction welding processes for its modern Trent aero engines that drive the Airbus A380 and the Boeing 787. In this paper, Friction Stir Welding of various dissimilar metals is reviewed. The microstructure, hardness, and flow characteristics are also reviewed.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128361330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Chaturvedi, V. R. Ikkurthi, S. Chaturvedi, A. Patil
Metal foams are one among the current active research topics the world over. They are increasingly being recognised as of utmost importance as far as low specific weight coupled with higher energy absorption requirement is concerned. They offer viable solutions to engineering problems involving protective structures which could be subject to impact loads during their service life. In recent times, fresh details regarding their behaviour under dynamic loading conditions have been reported by many researchers. In this overview article, an attempt has been made to keep the reader abreast with the latest happenings as regards the impact/High strain rate behavioural characterisation of metal foams while at the same time familiarise him with some of the underlying concepts relevant to this emerging subject.
{"title":"An Overview on Mechanical Characterisation of Metal Foams by Impact and Higher Strain Rate Loadings","authors":"A. Chaturvedi, V. R. Ikkurthi, S. Chaturvedi, A. Patil","doi":"10.2139/ssrn.3101620","DOIUrl":"https://doi.org/10.2139/ssrn.3101620","url":null,"abstract":"Metal foams are one among the current active research topics the world over. They are increasingly being recognised as of utmost importance as far as low specific weight coupled with higher energy absorption requirement is concerned. They offer viable solutions to engineering problems involving protective structures which could be subject to impact loads during their service life. In recent times, fresh details regarding their behaviour under dynamic loading conditions have been reported by many researchers. In this overview article, an attempt has been made to keep the reader abreast with the latest happenings as regards the impact/High strain rate behavioural characterisation of metal foams while at the same time familiarise him with some of the underlying concepts relevant to this emerging subject.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128485092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This Letter reports an anomalous discontinuous variation in spall strength associated with shock-induced microstructure. It is known that elastic deformation, dislocation and stacking fault, and shock FCC-BCC phase transition will appear in turn with the increase of shock intensity. Our molecular dynamics simulations of single-crystal aluminum reveal that the damage evolution during release process may show an evident dependence on the shock-induced microstructure. The nanovoids nucleate homogeneously in the region of elastic deformation or phase transition, resulting in higher spall strength. However, the nanovoids nucleate heterogeneously in the region of dislocation and stacking fault, which leads to a sudden decrease in spall strength. This anomalous change is accompanied by a higher temperature rise, and we find that both homogeneous and heterogeneous nucleation satisfy the same spall strength-spall temperature relationship.
{"title":"Spalling Characteristics Associated with Shock-Induced Microstructure Based on Molecular Dynamics Simulation of Single-Crystal Aluminum","authors":"Dongdong Jiang, Bao Wu, Pei Wang, J. Shao, A. He","doi":"10.2139/ssrn.3855731","DOIUrl":"https://doi.org/10.2139/ssrn.3855731","url":null,"abstract":"This Letter reports an anomalous discontinuous variation in spall strength associated with shock-induced microstructure. It is known that elastic deformation, dislocation and stacking fault, and shock FCC-BCC phase transition will appear in turn with the increase of shock intensity. Our molecular dynamics simulations of single-crystal aluminum reveal that the damage evolution during release process may show an evident dependence on the shock-induced microstructure. The nanovoids nucleate homogeneously in the region of elastic deformation or phase transition, resulting in higher spall strength. However, the nanovoids nucleate heterogeneously in the region of dislocation and stacking fault, which leads to a sudden decrease in spall strength. This anomalous change is accompanied by a higher temperature rise, and we find that both homogeneous and heterogeneous nucleation satisfy the same spall strength-spall temperature relationship.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133040946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a comparative study between the structural, electronic, elastic, and thermal conductivity of cement compounds (C3S, C2S, C3A, and C4AF) using first-principles calculations. The calculated structural properties are in good agreement with the experimental data. The electronic properties of cement compounds are mainly contributed from the O 2s and Ca 3d orbitals due to the strong ionic character. Herein, C3S and C2S are insulators, with respective band gap energy of 3.34 and 5.217 eV. Moreover, the cement compounds contribute to the strength increment by investigating the independent elastic constants, Debye temperature, and Grüneisen parameter. In the comparison, the highest thermal conductivity of C4AF compound was up to 2.423 W m−1K−1, which is ~11 times higher than that of C2S (0.218 W m−1K−1).
我们采用第一性原理计算对水泥化合物(C3S、C2S、C3A和C4AF)的结构、电子、弹性和导热性进行了比较研究。计算的结构性能与实验数据吻合较好。由于强离子特性，水泥化合物的电子性质主要来自于o2s和Ca三维轨道。其中，C3S和C2S为绝缘子，带隙能量分别为3.34和5.217 eV。此外，通过研究独立弹性常数、德拜温度和颗粒 neisen参数，水泥化合物对强度增加有贡献。对比发现，C4AF化合物的最高导热系数为2.423 W m−1K−1，是C2S (0.218 W m−1K−1)的11倍。
{"title":"Chemical Bonding, Electronic Properties, Mechanical Strength, and Thermal Conductivity of Cement Compounds by First-Principles Study","authors":"Saravana Karthikeyan Sks, Shameen Banu Ib","doi":"10.2139/ssrn.3854493","DOIUrl":"https://doi.org/10.2139/ssrn.3854493","url":null,"abstract":"We present a comparative study between the structural, electronic, elastic, and thermal conductivity of cement compounds (C3S, C2S, C3A, and C4AF) using first-principles calculations. The calculated structural properties are in good agreement with the experimental data. The electronic properties of cement compounds are mainly contributed from the O 2s and Ca 3d orbitals due to the strong ionic character. Herein, C3S and C2S are insulators, with respective band gap energy of 3.34 and 5.217 eV. Moreover, the cement compounds contribute to the strength increment by investigating the independent elastic constants, Debye temperature, and Grüneisen parameter. In the comparison, the highest thermal conductivity of C4AF compound was up to 2.423 W m<sup>−1</sup>K<sup>−1</sup>, which is ~11 times higher than that of C2S (0.218 W m<sup>−1</sup>K<sup>−1</sup>).","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122447378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on our analysis, the grain size effect in the most widely used models such as the Kocks-Mecking-Estrin (KME) model cannot account for the transitional work hardening behaviors of nano-crystalline or ultrafine-crystalline metals processed by severe plastic deformation (SPD). Alternatively, from the perspective of material's initial state, this study provides a consistent interpretation of their work hardening behaviors in terms of the microstructural features and the mechanical properties.
{"title":"Transition of Working Hardening Behaviors of Severe Plastic Deformation Processed Metals","authors":"Peng Wang, Tenghao Yin, S. Qu","doi":"10.2139/ssrn.3435685","DOIUrl":"https://doi.org/10.2139/ssrn.3435685","url":null,"abstract":"Based on our analysis, the grain size effect in the most widely used models such as the Kocks-Mecking-Estrin (KME) model cannot account for the transitional work hardening behaviors of nano-crystalline or ultrafine-crystalline metals processed by severe plastic deformation (SPD). Alternatively, from the perspective of material's initial state, this study provides a consistent interpretation of their work hardening behaviors in terms of the microstructural features and the mechanical properties.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117306420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zeyi Guan, Chase S. Linsley, S. Pan, Gongcheng Yao, Benjamin M. Wu, D. Levi, Xiaochun Li
Zinc (Zn) and Zn-based alloys have been extensively studied as innovative materials for bioresorbable stents (BRS) in the last decade due to their favorable biodegradability and biocompatibility. However, most Zn alloys lack the necessary combination of adequate strength, ductility and corrosion rate needed for such clinical applications. Additionally, due to the low melting temperature of Zn, Zn-based alloys are also thermally unstable and undergo microstructural changes over time at ambient and physiological temperatures, which negatively impacts the mechanical properties during storage, implantation, and service. In this study, tungsten carbide (WC) nanoparticles were successfully incorporated into Zn alloyed with 0.5 wt.% magnesium (Mg). The resulting Zn-0.5Mg-WC nanocomposite’s microstructure, mechanical properties, in vitro corrosion rate and aging behavior were evaluated. SEM and TEM microstructural analysis showed that Mg2Zn11 precipitates with a granular morphology formed at the Zn/WC nanoparticle interface. This microstructure resulted in a combination of enhanced strength and ductility, and the Zn-0.5Mg-WC nanocomposite was able to survive at least 10 million cycles of tensile loading. Due to the granular precipitate morphology, the loss of ductility caused by aging was not observed over a 90-day study. Furthermore, the Zn-0.5Mg-WC nanocomposite had an in vitro corrosion rate comparable to pure Zn, which is ideal for BRS applications. Stent prototypes were fabricated using this composition and were successfully deployed during bench testing without fracture. This study shows that the Zn-0.5Mg-WC nanocomposite is a promising material for BRS applications.
{"title":"Study on Anti-Aging Zn-Mg-WC Nanocomposites for Bioresorbable Cardiovascular Stents: Microstructure, Mechanical Properties, Fatigue, and in vitro Corrosion","authors":"Zeyi Guan, Chase S. Linsley, S. Pan, Gongcheng Yao, Benjamin M. Wu, D. Levi, Xiaochun Li","doi":"10.2139/ssrn.3873674","DOIUrl":"https://doi.org/10.2139/ssrn.3873674","url":null,"abstract":"Zinc (Zn) and Zn-based alloys have been extensively studied as innovative materials for bioresorbable stents (BRS) in the last decade due to their favorable biodegradability and biocompatibility. However, most Zn alloys lack the necessary combination of adequate strength, ductility and corrosion rate needed for such clinical applications. Additionally, due to the low melting temperature of Zn, Zn-based alloys are also thermally unstable and undergo microstructural changes over time at ambient and physiological temperatures, which negatively impacts the mechanical properties during storage, implantation, and service. In this study, tungsten carbide (WC) nanoparticles were successfully incorporated into Zn alloyed with 0.5 wt.% magnesium (Mg). The resulting Zn-0.5Mg-WC nanocomposite’s microstructure, mechanical properties, in vitro corrosion rate and aging behavior were evaluated. SEM and TEM microstructural analysis showed that Mg2Zn11 precipitates with a granular morphology formed at the Zn/WC nanoparticle interface. This microstructure resulted in a combination of enhanced strength and ductility, and the Zn-0.5Mg-WC nanocomposite was able to survive at least 10 million cycles of tensile loading. Due to the granular precipitate morphology, the loss of ductility caused by aging was not observed over a 90-day study. Furthermore, the Zn-0.5Mg-WC nanocomposite had an in vitro corrosion rate comparable to pure Zn, which is ideal for BRS applications. Stent prototypes were fabricated using this composition and were successfully deployed during bench testing without fracture. This study shows that the Zn-0.5Mg-WC nanocomposite is a promising material for BRS applications.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127209473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Biofabrication by 3D-printing is a promising method in tissue engineering which permits the processing of a wide range of hydrogels for restoration, replacement, and regeneration of tissues and organs. Among hydrogels, collagen is the most widely used one for 3D-printing, due to its hydrophilic structure with natural binding sites, resulting in high cell viability and proliferation rates. In this paper, we reviewed bioprinting and crosslinking of cell-laden collagen based bioinks and their shape integrities and cell viabilities in the final constructs. This paper is concerned with the role of the rheology on the bioprinting of collagens. The occurrences' of flow, gelling and crosslinking during 3D-printing are examined under two sequential stages: 1) micro-extrusion, 2) layer stacking. The main objective of this paper is to discuss the impact of rheology of collagen hydrogels on those two stages of bioprinting. In these areas, it is generally considered that characterizations by dynamic linear deformation measurements are sufficient. However, we reviewed the rheological properties of collagen solutions under dynamic linear deformations and steady-state shear flow conditions. While the dynamic measurements are more useful to characterize structures of collagen gels and their changes by crosslinking, the steady shear flow measurements are used to investigate the filament micro-extrusion and layer-stacking. For the first time to understand those stages of the collagen 3D-bio printing process, we brought the role of other non-Newtonian material functions, such as first normal stress difference and extensional viscosity in addition to shear viscosity. Extensional viscosity and the viscoelasticity manifested through normal-stress differences are significant in needle extrusion flow. We also suggested caution to use dynamic viscosity vs. oscillation frequency data in the place of steady shear viscosity vs. shear rate measurement. Finally, we discuss the role of flow conditions and crosslinking on cell viability. Those discussions are focused on collagens, nevertheless they are valid on the 3D-printing of other hydrogels.
{"title":"Addressing Rheological Issues at the Micro-Extrusion and Layer-Stacking Stages of Collagen Bioprinting","authors":"Xiaoyi Lan, A. Adesida, Y. Boluk","doi":"10.2139/ssrn.3455072","DOIUrl":"https://doi.org/10.2139/ssrn.3455072","url":null,"abstract":"Biofabrication by 3D-printing is a promising method in tissue engineering which permits the processing of a wide range of hydrogels for restoration, replacement, and regeneration of tissues and organs. Among hydrogels, collagen is the most widely used one for 3D-printing, due to its hydrophilic structure with natural binding sites, resulting in high cell viability and proliferation rates. In this paper, we reviewed bioprinting and crosslinking of cell-laden collagen based bioinks and their shape integrities and cell viabilities in the final constructs. This paper is concerned with the role of the rheology on the bioprinting of collagens. The occurrences' of flow, gelling and crosslinking during 3D-printing are examined under two sequential stages: 1) micro-extrusion, 2) layer stacking. The main objective of this paper is to discuss the impact of rheology of collagen hydrogels on those two stages of bioprinting. In these areas, it is generally considered that characterizations by dynamic linear deformation measurements are sufficient. However, we reviewed the rheological properties of collagen solutions under dynamic linear deformations and steady-state shear flow conditions. While the dynamic measurements are more useful to characterize structures of collagen gels and their changes by crosslinking, the steady shear flow measurements are used to investigate the filament micro-extrusion and layer-stacking. For the first time to understand those stages of the collagen 3D-bio printing process, we brought the role of other non-Newtonian material functions, such as first normal stress difference and extensional viscosity in addition to shear viscosity. Extensional viscosity and the viscoelasticity manifested through normal-stress differences are significant in needle extrusion flow. We also suggested caution to use dynamic viscosity vs. oscillation frequency data in the place of steady shear viscosity vs. shear rate measurement. Finally, we discuss the role of flow conditions and crosslinking on cell viability. Those discussions are focused on collagens, nevertheless they are valid on the 3D-printing of other hydrogels.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116236747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In tissue engineering (TE) strategies, cell processes are regulated by mechanical stimuli. Although TE scaffolds have been developed to replicate tissue-level mechanical properties, it is experimentally prohibitive to measure and prescribe the cellular micromechanical environment (CME) generated within these constructs. Accordingly, this study aimed to fill this lack of understanding by modelling the CME in TE scaffolds using the finite element method. A repeating unit of composite fiber scaffold for annulus fibrosus repair with a fibrin hydrogel matrix was prescribed a series of loading, material, and architectural parameters. The CME was predicted and the corresponding cell phenotypes were predicted based on previously hypothesized criteria. Scaffold multi-axial loading was demonstrated as the most pertinent parameter contributing to the CME criteria being satisfied. Specifically, radial-direction compression with biaxial tension lead to a prediction of regeneration for 66.5% of the cell volumes. Additionally, the architectural scale had a moderate influence on the CME with minimal change in the tissue-level properties of the scaffold. All other scaffold materials and architectures considered had secondary influences on the predicted regeneration by modifying the scaffold loading. By predicting the regeneration potential of different scaffold designs, the developed high-fidelity computational tool described in this study enables for a more comprehensive understanding of the relationship between tissue-level and cell-level mechanics for a broad range of tissue engineering applications.
{"title":"Effects of Scaffold Architecture, Materials, and Loading on Cellular Micromechanical Environment in Tissue Engineering Strategies","authors":"Mitchell I Page, P. Linde, C. Puttlitz","doi":"10.2139/ssrn.3694094","DOIUrl":"https://doi.org/10.2139/ssrn.3694094","url":null,"abstract":"In tissue engineering (TE) strategies, cell processes are regulated by mechanical stimuli. Although TE scaffolds have been developed to replicate tissue-level mechanical properties, it is experimentally prohibitive to measure and prescribe the cellular micromechanical environment (CME) generated within these constructs. Accordingly, this study aimed to fill this lack of understanding by modelling the CME in TE scaffolds using the finite element method. A repeating unit of composite fiber scaffold for annulus fibrosus repair with a fibrin hydrogel matrix was prescribed a series of loading, material, and architectural parameters. The CME was predicted and the corresponding cell phenotypes were predicted based on previously hypothesized criteria. Scaffold multi-axial loading was demonstrated as the most pertinent parameter contributing to the CME criteria being satisfied. Specifically, radial-direction compression with biaxial tension lead to a prediction of regeneration for 66.5% of the cell volumes. Additionally, the architectural scale had a moderate influence on the CME with minimal change in the tissue-level properties of the scaffold. All other scaffold materials and architectures considered had secondary influences on the predicted regeneration by modifying the scaffold loading. By predicting the regeneration potential of different scaffold designs, the developed high-fidelity computational tool described in this study enables for a more comprehensive understanding of the relationship between tissue-level and cell-level mechanics for a broad range of tissue engineering applications.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125206313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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