scholarly journals Assumption of Constraining Force to Explain Distortion in Laser Additive Manufacturing

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2327 ◽  
Author(s):  
Deqiao Xie ◽  
Jianfeng Zhao ◽  
Huixin Liang ◽  
Zongjun Tian ◽  
Lida Shen ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Contributory Factor ◽  
Sectional Area ◽  
Laser Additive Manufacturing ◽  
Element Analysis ◽  
Cross Sectional ◽  
Fea Model ◽  
Metal Additive ◽  
Distortion Mechanism

Distortion is a common but unrevealed problem in metal additive manufacturing, due to the rapid melting in metallurgy and the intricate thermal-mechanical processes involved. We explain the distortion mechanism and major influencing factors by assumption of constraining force, which is assumed between the added layer and substrate. The constraining force was set to act on the substrate in a static structural finite element analysis (FEA) model. The results were compared with those of a thermal-mechanical FEA model and experiments. The constraining force and the associated static structural FEA showed trends in distortion and stress distribution similar to those shown by thermal-mechanical FEA and experiments. It can be concluded that the constraining force acting on the substrate is a major contributory factor towards the distortion mechanism. The constraining force seems to be primarily related to the material properties, temperature, and cross-sectional area of the added layer.

scholarly journals A Novel Approach to Design Lesion-Specific Stents for Minimum Recoil

2016 ◽  
Vol 11 (1) ◽  
Author(s):  
Muhammad Farhan Khan ◽  
David Brackett ◽  
Ian Ashcroft ◽  
Christopher Tuck ◽  
Ricky Wildman
Keyword(s):  
Finite Element Analysis ◽  
Topology Optimization ◽  
Material Properties ◽  
Sectional Area ◽  
Element Analysis ◽  
Cross Sectional ◽  
Design Concepts ◽  
Novel Approach ◽  
Stenosed Artery ◽  
Stenotic Arteries

Stent geometries are obtained by topology optimization for minimized compliance under different stenosis levels and plaque material types. Three levels of stenosis by cross-sectional area, i.e., 30%, 40%, and 50% and three different plaque material properties, i.e., calcified, cellular, and hypocellular, were studied. The raw optimization results were converted to clear design concepts and their performance was evaluated by implanting them in their respective stenosed artery types using finite element analysis. The results were compared with a generic stent in similar arteries, which showed that the new designs showed less recoil. This work provides a concept that stents could be tailored to specific lesions in order to minimize recoil and maintain a patent lumen in stenotic arteries.

scholarly journals Measurement and calibration of the nucleus position and its cross-sectional area ratio to increase the accuracy of finite element analysis

2020 ◽  
Author(s):  
Jingchi Li ◽  
Zhipeng Xi ◽  
Xiaoyu Zhang ◽  
Shenglu Sun ◽  
Lin Xie ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Imaging Data ◽  
Element Analysis ◽  
Cross Sectional ◽  
Fea Model ◽  
Nucleus Position

Abstract Background: As a widely used biomechanical research method, finite element analysis (FEA) is an important tool for investigating the pathogenesis of disc degenerative diseases and optimizing spine surgical methods. However, the definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard, thus affecting the accuracy (ACC) of the FEA. Hence, this study aimed to determine a precise definition of the relative nucleus position and its cross-sectional area ratio to increase the ACC of the following FEA studies. Methods: The lumbar relative nucleus position and its cross-sectional area ratio were measured from magnetic resonance imaging data and then calibrated and validated via FEA. Imaging data from patients without disc degeneration were used. The L4-L5 nucleus and disc cross-sectional areas and the distances between the edges of the annulus and nucleus were measured; the ratios between these values were calculated as P1 and P2, respectively. The FEA model was constructed using these measured values, and the relative nucleus position was calibrated by estimating the differences in the range of motion (ROM) between the model, wherein the ligaments, facet joints and nucleus were suppressed, and that of an in vitro study. Then, the ACC was re-estimated in the model with all non-bony structures by comparing the ROM, the intradiscal pressure (IDP), the facet contact force (FCF) and the disc compression (DC) under different sizes and directions of moments magnitudes to validate the measured and calibrated indicators. Results: The interobserver homogeneity was acceptable, and the measured P1 and P2 values were 1.22 and 38%, respectively. Furthermore, an ACC of up to 99% was attained for the model under flexion–extension conditions when the calibrated P1 value (1.62) was used, with a model validation of greater than 90% attained under al most all of the loading conditions considering the different indicators and moment magnitude s. Conclusion: The measured and calibrated relative nucleus position and its cross-sectional area ratio increase the ACC of the FEA model and can therefore be used in subsequent studies.

scholarly journals Measurement and calibration of the nucleus position and its cross-sectional area ratio to increase the accuracy of finite element analysis

2019 ◽  
Author(s):  
Jingchi Li ◽  
Zhipeng Xi ◽  
Xiaoyu Zhang ◽  
Shenglu Sun ◽  
Lin Xie ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Imaging Data ◽  
Element Analysis ◽  
Cross Sectional ◽  
Fea Model ◽  
Nucleus Position

Abstract Background: As a widely used biomechanical research method, finite element analysis (FEA) is a significant tool for investigating the pathogenesis of disc degenerative diseases and optimizing of spine surgical methods. However, the definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard, thus affecting the accuracy (ACC) of the FEA. Hence, this study aimed to determine a precise definition of the relative nucleus position and its cross-sectional area ratio to increase ACC of following FEA studies. Methods: The lumbar relative nucleus position and its cross-sectional area ratio were measured from magnetic resonance imaging data, and then calibrated and validated via FEA. Imaging data from patients without disc degeneration were recruited. The L4-L5 nucleus and disc cross-sectional areas and the distances between the edges of the annulus and nucleus were measured; the ratios between these values were calculated as P1 and P2, respectively. The FEA model was constructed using these measured values, and the relative nucleus position was calibrated by estimating the differences in the range of motions (ROMs) between the model, wherein the ligaments, facet joints and nucleus were supressed, and an in vitro study. Then, ACC were re-estimated in the model with all non-bony structures to validate the measured and calibrated indicators. Results: The interobserver homogeneity is acceptable, and the measured P1 and P2 values are 1.22 and 38%, respectively. Furthermore, an ACC of up to 99% was attained for the model under flexion–extension conditions when the calibrated P1 value (1.62) was used, with a model validation of greater than 90% attained under all loading conditions. Conclusion: The measured and calibrated relative nucleus position and its cross-sectional area ratio increase the ACC of the FEA model, and can therefore be used in subsequent studies.

scholarly journals Measurement and calibration of the nucleus position and its cross-sectional area ratio to increase the accuracy of finite element analysis

2020 ◽  
Author(s):  
Jingchi Li ◽  
Zhipeng Xi ◽  
Xiaoyu Zhang ◽  
Ke Zhang ◽  
Shenglu Sun ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Imaging Data ◽  
Element Analysis ◽  
Cross Sectional ◽  
Fea Model ◽  
Nucleus Position

Abstract Backgrounds: As a widely used biomechanical research method, finite element analysis (FEA) is an important tool for investigating the pathogenesis of disc degenerative diseases and optimizing spine surgical methods. However, the definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard, thus affecting the accuracy (ACC) of the FEA.Objectives: This study aimed to determine a precise definition of the relative nucleus position and its cross-sectional area ratio to increase the ACC of the following FEA studies.Methods: The lumbar relative nucleus position and its cross-sectional area ratio were measured from magnetic resonance imaging data and then calibrated and validated via FEA. Imaging data from patients without disc degeneration were used. The L4-L5 nucleus and disc cross-sectional areas and the distances between the edges of the annulus and nucleus were measured; the ratios between these values were calculated as P1 and P2, respectively. The FEA model was constructed using these measured values, and the relative nucleus position was calibrated by estimating the differences in the range of motion (ROM) between the model, wherein the ligaments, facet joints and nucleus were suppressed, and that of an in vitro study. Then, the ACC was re-estimated in the model with all non-bony structures by comparing the ROM, the intradiscal pressure (IDP), the facet contact force (FCF) and the disc compression (DC) under different sizes and directions of moments magnitudes to validate the measured and calibrated indicators.Results: The interobserver homogeneity was acceptable, and the measured P1 and P2 values were 1.22 and 38%, respectively. Furthermore, an ACC of up to 99% was attained for the model under flexion–extension conditions when the calibrated P1 value (1.62) was used, with a model validation of greater than 90% attained under almost all of the loading conditions considering the different indicators and moment magnitudes.Conclusions: The measured and calibrated relative nucleus position and its cross-sectional area ratio increase the ACC of the FEA model and can therefore be used in subsequent studies.

Computational Modeling and Energy Absorption Behavior of Thin-Walled Tubes with the Kresling Origami Pattern

2021 ◽  
Vol 62 (2) ◽  
pp. 71-81
Author(s):  
Jiaqiang Li ◽  
Yao Chen ◽  
Xiaodong Feng ◽  
Jian Feng ◽  
Pooya Sareh
Keyword(s):  
Energy Absorption ◽  
Material Properties ◽  
Rotation Angle ◽  
Programming Model ◽  
Mixed Integer ◽  
Element Analysis ◽  
Cross Sectional ◽  
Thin Walled Tube ◽  
Absorption Performance ◽  
Thin Walled

Origami structures have been widely used in various engineering fields due to their desirable properties such as geometric transformability and high specific energy absorption. Based on the Kresling origami pattern, this study proposes a type of thin-walled origami tube the structural configuration of which is found by a mixed-integer linear programming model. Using finite element analysis, a reasonable configuration of a thin-walled tube with the Kresling pattern is firstly analyzed. Then, the influences of different material properties, the rotation angle of the upper and lower sections of the tube unit, and cross-sectional shapes on the energy absorption behavior of the thin-walled tubes under axial compression are evaluated. The results show that the symmetric thin-walled tube with the Kresling pattern is a reasonable choice for energy absorption purposes. Compared with thin-walled prismatic tubes, the thin-walled tube with the Kresling pattern substantially reduces the initial peak force and the average crushing force, without significantly reducing its energy absorption capacity; moreover, it enters the plastic energy dissipation stage ahead of time, giving it a superior energy absorption performance. Besides, the material properties, rotation angle, and cross-sectional shape have considerable influences on its energy absorption performance. The results provide a basis for the application of the Kresling origami pattern in the design of thin-walled energy-absorbingstructures.

Effect of Time Spacing and Hatch Spacing on Thermal Material Properties and Melt Pool Geometry in Additive Manufacturing of S316L

2019 ◽  
Author(s):  
Elham Mirkoohi ◽  
Daniel E. Sievers ◽  
Steven Y. Liang
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Material Properties ◽  
Metal Additive Manufacturing ◽  
Melt Pool ◽  
Experimental Values ◽  
Melt Pool Size ◽  
Transfer Mechanisms ◽  
Hatch Spacing ◽  
Metal Additive

Abstract A physics-based analytical solution is proposed in order to investigate the effect of hatch spacing and time spacing (which is the time delay between two consecutive irradiations) on thermal material properties and melt pool geometry in metal additive manufacturing processes. A three-dimensional moving point heat source approach is used in order to predict the thermal behavior of the material in additive manufacturing process. The thermal material properties are considered to be temperature dependent since the existence of the steep temperature gradient has a substantial influence on the magnitude of the thermal conductivity and specific heat, and as a result, it has an influence on the heat transfer mechanisms. Moreover, the melting/solidification phase change is considered using the modified heat capacity since it has an influence on melt pool geometry. The proposed analytical model also considers the multi-layer aspect of metal additive manufacturing since the thermal interaction of the successive layers has an influence on heat transfer mechanisms. Temperature modeling in metal additive manufacturing is one of the most important predictions since the presence of the temperature gradient inside the build part affect the melt pool size and geometry, thermal stress, residual stress, and part distortion. In this paper, the effect of time spacing and hatch spacing on thermal material properties and melt pool geometry is investigated. Both factors are found statistically significant with regard to their influence on thermal material properties and melt pool geometry. The predicted melt pool size is compared to experimental values from independent reports. Good agreement is achieved between the proposed physics-based analytical model and experimental values.

scholarly journals Numerical Study on the Temperature-Dependent Viscosity Effect on the Strand Shape in Extrusion-Based Additive Manufacturing

2020 ◽  
Vol 4 (2) ◽  
pp. 46 ◽  
Author(s):  
Behrouz Behdani ◽  
Matthew Senter ◽  
Leah Mason ◽  
Ming Leu ◽  
Joontaek Park
Keyword(s):  
Experimental Data ◽  
Additive Manufacturing ◽  
Polylactic Acid ◽  
Extrusion Process ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Cross Sectional ◽  
Dependent Viscosity

A numerical model that incorporates temperature-dependent non-Newtonian viscosity was developed to simulate the extrusion process in extrusion-based additive manufacturing. Agreement with the experimental data was achieved by simulating a polylactic acid melt flow as a non-isothermal power law fluid using experimentally fitted parameters for polylactic acid. The model was used to investigate the temperature effect on the flow behavior, the cross-sectional area, and the uniformity of the extruded strand. OpenFOAM, an open source simulation tool based on the finite volume method, was used to perform the simulations. A computational module for solving the equations of non-isothermal multiphase flows was also developed to simulate the extrusion process under a small gap condition where the gap between the nozzle and the substrate surface is smaller than the nozzle diameter. Comparison of the strand shapes obtained from our model with isothermal Newtonian simulation, and experimental data confirms that our model improves the agreement with the experimental data. The result shows that the cross-sectional area of the extruded strand is sensitive to the temperature-dependent viscosity, especially in the small gap condition which has recently increased in popularity. Our numerical investigation was able to show nozzle temperature effects on the strand shape and surface topography which previously had been investigated and observed empirically only.

scholarly journals Disc measurement and nucleus calibration in a smoothened lumbar model increases the accuracy and efficiency of in-silico study

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Jingchi Li ◽  
Chen Xu ◽  
Xiaoyu Zhang ◽  
Zhipeng Xi ◽  
Shenglu Sun ◽  
...  
Keyword(s):  
In Silico ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Computational Time ◽  
Sectional Area ◽  
Imaging Data ◽  
Cross Sectional ◽  
Fea Model ◽  
In Silico Study ◽  
Nucleus Position

Abstract Backgrounds Finite element analysis (FEA) is an important tool during the spinal biomechanical study. Irregular surfaces in FEA models directly reconstructed based on imaging data may increase the computational burden and decrease the computational credibility. Definitions of the relative nucleus position and its cross-sectional area ratio do not conform to a uniform standard in FEA. Methods To increase the accuracy and efficiency of FEA, nucleus position and cross-sectional area ratio were measured from imaging data. A FEA model with smoothened surfaces was constructed using measured values. Nucleus position was calibrated by estimating the differences in the range of motion (RoM) between the FEA model and that of an in-vitro study. Then, the differences were re-estimated by comparing the RoM, the intradiscal pressure, the facet contact force, and the disc compression to validate the measured and calibrated indicators. The computational time in different models was also recorded to evaluate the efficiency. Results Computational results indicated that 99% of accuracy was attained when measured and calibrated indicators were set in the FEA model, with a model validation of greater than 90% attained under almost all of the loading conditions. Computational time decreased by around 70% in the fitted model with smoothened surfaces compared with that of the reconstructed model. Conclusions The computational accuracy and efficiency of in-silico study can be improved in the lumbar FEA model constructed using smoothened surfaces with measured and calibrated relative nucleus position and its cross-sectional area ratio.

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