Selective mass scaling for distorted solid-shell elements in explicit dynamics: optimal scaling factor and stable time step estimate

2014 ◽  
Vol 101 (9) ◽  
pp. 700-731 ◽  
Author(s):  
G. Cocchetti ◽  
M. Pagani ◽  
U. Perego
Keyword(s):  
Optimal Scaling ◽  
Scaling Factor ◽  
Solid Shell ◽  
Time Step ◽  
Shell Elements ◽  
Mass Scaling ◽  
Explicit Dynamics

scholarly journals Application of P1-Nonconforming Element for Shell Structure of Incompressible Materiel

2011 ◽  
Vol 2-3 ◽  
pp. 1051-1056
Author(s):  
Lei Chen ◽  
Gang Won Jang ◽  
Tae Jin Chung ◽  
Tae Hyun Baek
Keyword(s):  
Topology Optimization ◽  
Shell Structure ◽  
Optimization Design ◽  
Incompressible Material ◽  
High Order ◽  
Solid Shell ◽  
Shell Elements ◽  
Volumetric Locking ◽  
Nonconforming Element ◽  
Nonconforming Elements

This research focused on solving volumetric locking problem of shell structure of incompressible material. Degenerated solid-shell elements are widely applied on curved structure. But, volumetric locking will take place when the structure is made of incompressible material, such as rubber. Due to Poisson’s locking free property of P1-nonconforming element, it is employed to solve volumetric locking problem of shell structure. Furthermore, the study on shell structure is extended to topology optimization design. To verify the volumetric locking free of P1-nonconforming element on shell structure of incompressible material, some structures are studied by different elements. Comparing with the utilization of high order elements to solve volumetric locking problems, P1-nonconforming elements can save calculation time and reduce the numerical cost.

scholarly journals In Vivo Biokinetics of 177Lu-OPS201 in Mice and Pigs as a Model for Predicting Human Dosimetry

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Seval Beykan ◽  
Melpomeni Fani ◽  
Svend Borup Jensen ◽  
Guillaume Nicolas ◽  
Damian Wild ◽  
...  
Keyword(s):  
Specific Activity ◽  
Somatostatin Receptor ◽  
Optimal Scaling ◽  
Relative Mass ◽  
Receptor Subtype ◽  
Data Sets ◽  
Mass Scaling ◽  
Time Scaling ◽  
Somatostatin Receptor Subtype 2

Introduction. 177Lu-OPS201 is a high-affinity somatostatin receptor subtype 2 antagonist for PRRT in patients with neuroendocrine tumors. The aim is to find the optimal scaling for dosimetry and to compare the biokinetics of 177Lu-OPS201 in animals and humans. Methods. Data on biokinetics of 177Lu-OPS201 were analyzed in athymic nude Foxn1nu mice (28 F, weight: 26 ± 1 g), Danish Landrace pigs (3 F-1 M, weight: 28 ± 2 kg), and patients (3 F-1 M, weight: 61 ± 17 kg) with administered activities of 0.19–0.27 MBq (mice), 97–113 MBq (pigs), and 850–1086 MBq (patients). After euthanizing mice (up to 168 h), the organ-specific activity contents (including blood) were measured. Multiple planar and SPECT/CT scans were performed until 250 h (pigs) and 72 h (patients) to quantify the uptake in the kidneys and liver. Blood samples were taken up to 23 h (patients) and 300 h (pigs). In pigs and patients, kidney protection was applied. Time-dependent uptake data sets were created for each species and organ/tissue. Biexponential fits were applied to compare the biokinetics in the kidneys, liver, and blood of each species. The time-integrated activity coefficients (TIACs) were calculated by using NUKFIT. To determine the optimal scaling, several methods (relative mass scaling, time scaling, combined mass and time scaling, and allometric scaling) were compared. Results. A fast blood clearance of the compound was observed in the first phase (<56 h) for all species. In comparison with patients, pigs showed higher liver retention. Based on the direct comparison of the TIACs, an underestimation in mice (liver and kidneys) and an overestimation in pigs’ kidneys compared to the patient data (kidney TIAC: mice = 1.4 h, pigs = 7.7 h, and patients = 5.8 h; liver TIAC: mice = 0.7 h, pigs = 4.1 h, and patients = 5.3 h) were observed. Most similar TIACs were obtained by applying time scaling (mice) and combined scaling (pigs) (kidney TIAC: mice = 3.9 h, pigs = 4.8 h, and patients = 5.8 h; liver TIAC: mice = 0.9 h, pigs = 4.7 h, and patients = 5.3 h). Conclusion. If the organ mass ratios between the species are high, the combined mass and time scaling method is optimal to minimize the interspecies differences. The analysis of the fit functions and the TIACs shows that pigs are better mimicking human biokinetics.

scholarly journals Single point incremental forming simulation with adaptive remeshing technique using solid-shell elements

2016 ◽  
Vol 33 (5) ◽  
pp. 1388-1421 ◽  
Author(s):  
José I.V. Sena ◽  
Cedric Lequesne ◽  
L Duchene ◽  
Anne-Marie Habraken ◽  
Robertt A.F. Valente ◽  
...  
Keyword(s):  
Finite Element ◽  
Incremental Forming ◽  
Single Point ◽  
Nonlinear Material ◽  
Single Point Incremental Forming ◽  
Solid Shell ◽  
Contact Conditions ◽  
Adaptive Remeshing ◽  
Content Type ◽  
Shell Elements

Purpose – Numerical simulation of the single point incremental forming (SPIF) processes can be very demanding and time consuming due to the constantly changing contact conditions between the tool and the sheet surface, as well as the nonlinear material behaviour combined with non-monotonic strain paths. The purpose of this paper is to propose an adaptive remeshing technique implemented in the in-house implicit finite element code LAGAMINE, to reduce the simulation time. This remeshing technique automatically refines only a portion of the sheet mesh in vicinity of the tool, therefore following the tool motion. As a result, refined meshes are avoided and consequently the total CPU time can be drastically reduced. Design/methodology/approach – SPIF is a dieless manufacturing process in which a sheet is deformed by using a tool with a spherical tip. This dieless feature makes the process appropriate for rapid-prototyping and allows for an innovative possibility to reduce overall costs for small batches, since the process can be performed in a rapid and economic way without expensive tooling. As a consequence, research interest related to SPIF process has been growing over the last years. Findings – In this work, the proposed automatic refinement technique is applied within a reduced enhanced solid-shell framework to further improve numerical efficiency. In this sense, the use of a hexahedral finite element allows the possibility to use general 3D constitutive laws. Additionally, a direct consideration of thickness variations, double-sided contact conditions and evaluation of all components of the stress field are available with solid-shell and not with shell elements. Additionally, validations by means of benchmarks are carried out, with comparisons against experimental results. Originality/value – It is worth noting that no previous work has been carried out using remeshing strategies combined with hexahedral elements in order to improve the computational efficiency resorting to an implicit scheme, which makes this work innovative. Finally, it has been shown that it is possible to perform accurate and efficient finite element simulations of SPIF process, resorting to implicit analysis and continuum elements. This is definitively a step-forward on the state-of-art in this field.

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