scholarly journals Experimental Characterization and Finite Element Modeling of the Effects of 3D Bioplotting Process Parameters on Structural and Tensile Properties of Polycaprolactone (PCL) Scaffolds

2020 ◽  
Vol 10 (15) ◽  
pp. 5289
Author(s):  
Lokesh Karthik Narayanan ◽  
Rohan A. Shirwaiker
Keyword(s):  
Finite Element ◽  
Tensile Properties ◽  
Element Model ◽  
Extrusion Pressure ◽  
Fibroblast Cells ◽  
Experimental Characterization ◽  
Efficient Design ◽  
Strand Spacing ◽  
Nih 3T3 ◽  
Process Structure

In this study we characterized the process–structure interactions in melt extrusion-based 3D bioplotting of polycaprolactone (PCL) and developed predictive models to enable the efficient design and processing of scaffolds for tissue engineering applications. First, the effects of pneumatic extrusion pressure (0.3, 0.4, 0.5, 0.6 N/mm2), nozzle speed (0.1, 0.4, 1.0, 1.4 mm/s), strand lay orientation (0°, 45°, 90°, 135°), and strand length (10, 20, 30 mm) on the strand width were investigated and a regression model was developed to map strand width to the two significant parameters (extrusion pressure and nozzle speed; p < 0.05). Then, proliferation of NIH/3T3 fibroblast cells in scaffolds with two different stand widths fabricated with different combinations of the two significant parameters was assessed over 7 days, which showed that the strand width had a significant effect on proliferation (p < 0.05). The effect of strand lay orientation (0° and 90°) on tensile properties of non-porous PCL specimens was determined and was found to be significantly higher for specimens with 0° lay orientation (p < 0.05). Finally, these data were used to develop and experimentally validate a finite element model for a porous PCL specimen with 1:1 ratio of inter-strand spacing to strand width.

Viscoelastic Finite-Element Modelling of Cell Deformation in an Optical Stretcher

2007 ◽  
Author(s):  
Soo Kng Teo ◽  
Kim Parker ◽  
K.-H. Chiam
Keyword(s):  
Finite Element ◽  
Cellular Response ◽  
Element Model ◽  
Cell Deformation ◽  
Normal Fibroblast ◽  
Transformed Cells ◽  
Fibroblast Cells ◽  
Normal Cells ◽  
Optical Stretcher ◽  
Maximal Stress

In this paper, we discuss the results arising from using a finite-element model [1] of cell deformation to study the optical stretching [2,3] of normal and malignantly transformed fibroblast cells. The key feature of our model is the use of a constitutive viscoelastic fluid element [4] whose parameters are both spatially and temporally varying so as to mimic the experimentally-observed spatiotemporal heterogeneity of cellular material properties. First, we show that normal fibroblast cells can undergo active cellular response by increasing their cellular viscosity when optically stretched for loading times of between 0.2s and 2.5s. Second, we show that, under similar optical conditions, cells of a smaller radius will experience more stretching compared to cells of a larger radius. This may explain why malignantly transformed cells experience higher strains than normal cells. Third, we compute the extent of the propagation of stress in the cytoplasm, and show that, for malignantly transformed cells, the maximal stress does propagate into the nuclear region whereas for normal cells, the maximal stress does not. We discuss how this may impact the transduction of cancer signalling pathways.

scholarly journals Hot Tearing in Steels During Solidification: Experimental Characterization and Thermomechanical Modeling

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Cerri Olivier ◽  
Chastel Yvan ◽  
Bellet Michel
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Element Model ◽  
Hot Tearing ◽  
Experimental Characterization ◽  
High Fraction ◽  
Thermomechanical Modeling ◽  
Major Defect ◽  
Do So ◽  
Cast Products

Hot tearing is a major defect in castings or semifinished cast products. It corresponds to the opening of cracks in the mushy zone and, more precisely, in the areas with high fraction of solid (typically 0.9 and beyond) when the material is subjected to deformations leading to local tensile stress. Various kinds of criteria have been developed to highlight a risk of formation of hot tears. The aim of this study is to evaluate their capability to predict the occurrence of hot tears correctly. In order to do so, two kinds of tests have been analyzed with the use of a thermomechanical finite element model.

Experimental Characterization and Modelling Validation of Shape Memory Alloy Negator Springs

2013 ◽  
Author(s):  
Andrea Spaggiari ◽  
Eugenio Dragoni ◽  
Ausonio Tuissi
Keyword(s):  
Finite Element ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Analytical Model ◽  
Element Model ◽  
Design Tool ◽  
Experimental Characterization ◽  
Finite Element Software ◽  
Spiral Spring ◽  
Force Displacement

This paper is aimed at the experimental characterization and modelling validation of shape memory alloy (SMA) negator springs. A Negator spring is a spiral spring made of strip of metal wound on the flat with an inherent curvature such that, in repose, each coil wraps tightly on its inner neighbour. The main feature of a Negator springs is the nearly-constant force displacement behaviour in the unwinding of the strip. Moreover the stroke is very long, theoretically infinite as it depends only on the length of the initial strip. A Negator spring made in SMA is built and experimentally tested to demonstrate the feasibility of this actuator. The shape memory Negator spring behaviour is predicted both with an analytical model and with a a finite element software. In both cases the material is modelled as elastic in austenitic range while an exponential continuum law is used to describe the martensitic behaviour. The experimental results confirms the applicability of this kind of geometry to the shape memory alloy actuators and the analytical model is confirmed to be a powerful design tool to dimension and predict the spring behaviour both in martensitic and austenitic range, as well as the finite element model developed.

scholarly journals Effective Elastic Properties of 3D Carbon-Carbon Composites at High Temperature

1996 ◽  
Vol 5 (2) ◽  
pp. 096369359600500
Author(s):  
X.D. He ◽  
J.C. Han ◽  
S.Y. Du
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Elastic Modulus ◽  
High Temperature ◽  
Finite Element Model ◽  
Tensile Properties ◽  
Elastic Properties ◽  
Element Model ◽  
Carbon Composites ◽  
Fiber Spacing

This paper describes a mini-finite element model for evaluation of high temperature elastic modulus of 3D C/C composite and the variation of tensile properties with substrate parameters such as xy-woven layers, fiber boundles and fiber spacing was analyzed. The results predicted suit the experimental data well.

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Finite Element Simulation of Tire-Rim Interface

1989 ◽  
Vol 17 (4) ◽  
pp. 305-325 ◽  
Author(s):  
N. T. Tseng ◽  
R. G. Pelle ◽  
J. P. Chang
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Finite Element Simulation ◽  
Contact Pressure ◽  
Element Model ◽  
Experimental Measurements ◽  
Inflation Pressure ◽  
Interference Fit ◽  
Element Simulation ◽  
Rubber Composite

Abstract A finite element model was developed to simulate the tire-rim interface. Elastomers were modeled by nonlinear incompressible elements, whereas plies were simulated by cord-rubber composite elements. Gap elements were used to simulate the opening between tire and rim at zero inflation pressure. This opening closed when the inflation pressure was increased gradually. The predicted distribution of contact pressure at the tire-rim interface agreed very well with the available experimental measurements. Several variations of the tire-rim interference fit were analyzed.

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