scholarly journals Finite element analysis to determine the role of porosity in dynamic localization and fragmentation: Application to porous microstructures obtained from additively manufactured materials

2021 ◽  
Author(s):  
Jose Rodriguez-Martinez ◽  
Mohammad Marvi-Mashhadi ◽  
Alvaro Vaz-Romero ◽  
Federico Sket
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Spatial Distribution ◽  
Void Volume ◽  
Void Size ◽  
Element Analysis ◽  
Finite Element Calculations ◽  
Porous Microstructure ◽  
Porous Microstructures

In this paper, we have performed a microstructurally-informed finite element analysis on the effect of porosity on the formation of multiple necks and fragments in ductile thin rings subjected to dynamic expansion. For that purpose, we have characterized by X-ray tomography the porous microstructure of 4 different additively manufactured materials (aluminium alloy AlSi10Mg, stainless steel 316L, titanium alloy Ti6Al4V and Inconel 718L) with initial void volume fractions ranging from 0.0007 % to 2 %, and pore sizes varying between 6 micrometers 110 micrometers. Three-dimensional analysis of the tomograms has revealed that the voids generally have nearly spherical shape and quite homogeneous spatial distribution in the bulk of the four materials tested. The pore size distributions quantified from the tomograms have been characterized using a Log-normal statistical function, which has been used in conjunction with a Force Biased Algorithm that replicates the experimentally observed random spatial distribution of the voids, to generate ring expansion finite element models in ABAQUS/Explicit which include actual porous microstructures representative of the materials tested. We have modeled the materials behavior using von Mises plasticity, and we have carried out finite element calculations for both elastic perfectly-plastic materials, and materials which show strain hardening, strain rate hardening and temperature softening effects. Moreover, we have assumed that fracture occurs when a critical value of effective plastic strain is reached. The finite element calculations have been performed for expansion velocities ranging from 50 m/s to 500 m/s. A key point of this investigation is that we have established individualized correlations between the main features of the porous microstructure (i.e. initial void volume fraction, average void size and maximum void size) and the number of necks and fragments formed in the calculations. In addition, we have brought out the effect of the porous microstrucure and inertia on the distributions of neck and fragment sizes. To the authors' knowledge, this is the first paper ever considering actual porous microstructures to investigate the role of material defects in multiple localization and dynamic fragmentation of ductile metallic materials.

scholarly journals New insights into the role of porous microstructure on adiabatic shear localization

2021 ◽  
Author(s):  
A. R. Vishnu ◽  
Mohammed Marvi-Mashhadi ◽  
Juan Carlos Nieto-Fuentes ◽  
Jose Rodriguez-Martinez
Keyword(s):  
Finite Element ◽  
Volume Fraction ◽  
Shear Bands ◽  
Shear Localization ◽  
Adiabatic Shear ◽  
Void Volume Fraction ◽  
Void Volume ◽  
Finite Element Calculations ◽  
Porous Microstructure

This paper provides new insights into the role of porous microstructure on adiabatic shear localization. For that purpose, we have performed 3D finite element calculations of electro-magnetically collapsing thick-walled cylinders. The geometry and dimensions of the cylindrical specimens are taken from the experiments of Lovinger et al. (2015), and the loading and boundary conditions from the 2D simulations performed by Lovinger et al. (2018). The mechanical behavior of the material is modeled as elastic-plastic, with yielding described by the von Mises criterion, an associated flow rule and isotropic hardening/softening, being the flow stress dependent on strain, strain rate and temperature. Moreover, plastic deformation is considered to be the only source of heat, and the analysis accounts for the thermal conductivity of the material. The distinctive feature of this work is that we have followed the methodology developed by Marvi-Mashhadi et al. (2021) to incorporate into the finite element calculations the actual porous microstructure of 4 different additively manufactured materials --aluminium alloy AlSi10Mg, stainless steel 316L, titanium alloy Ti6Al4V and Inconel 718-- for which the initial void volume fraction varies between 0.001% and 2%, and the pores size ranges from ≈ 6 µm to ≈ 110 µm. The numerical simulations have been performed using the Coupled Eulerian-Lagrangian approach available in ABAQUS/Explicit (2016) which allows to capture the shape evolution, coalescence and collapse of the voids at large strains. To the authors' knowledge, this paper contains the first finite element simulations with explicit representation of the material porosity which demonstrate that voids promote dynamic shear localization, acting as preferential sites for the nucleation of the shear bands, speeding up their development, and tailoring their direction of propagation. In addition, the numerical calculations bring out that for a given void volume fraction more shear bands are nucleated as the number of voids increases, while the shear bands are incepted earlier and develop faster as the size of the pores increases.

The role of greater tuberosity healing in reverse shoulder arthroplasty: a finite element analysis

2020 ◽  
Vol 29 (2) ◽  
pp. 347-354 ◽  
Author(s):  
Vani J. Sabesan ◽  
Diego J.L. Lima ◽  
Yang Yang ◽  
Matthew C. Stankard ◽  
Mauricio Drummond ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shoulder Arthroplasty ◽  
Reverse Shoulder Arthroplasty ◽  
Element Analysis ◽  
Greater Tuberosity

scholarly journals A Simulation Study to Calculate a Structure Conceived by Eugène Viollet-le-Duc in 1850 with Finite Element Analysis

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2576 ◽  
Author(s):  
Adela Rueda Márquez de la Plata ◽  
Pablo Alejandro Cruz Franco
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Simulation Study ◽  
Complex Materials ◽  
Calculation Methods ◽  
Element Analysis ◽  
Finite Element Calculations ◽  
Single Structure ◽  
Working Together ◽  
Subsequent Calculation

This study aims to investigate the application of finite element calculations to mixed structures of complex materials. As an example, we chose a vault designed by Eugène Viollet-le-Duc in 1850, at which time it was not possible to verify the complexities of the different materials working together in a single structure using these calculation methods. To carry out the simulation, the internal qualities of each material and its current equivalent are taken into account. Thus, the composition of each element is crucial for its integration into the whole structure and its modeling and subsequent calculation. With this research, we show that a finite element analysis can also be applied to structures that are yet to be built. Furthermore, we verify the technological, construction and materials knowledge that has led us here and demonstrate that what was once a utopian vision can now be realized using the structures and materials we have access to today.

scholarly journals New insights into the biomechanics of Legg-Calvé-Perthes’ disease

2018 ◽  
Vol 7 (2) ◽  
pp. 148-156 ◽  
Author(s):  
M. Pinheiro ◽  
C. A. Dobson ◽  
D. Perry ◽  
M. J. Fagan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Blood Supply ◽  
Vascular Occlusion ◽  
Perthes Disease ◽  
Element Analysis ◽  
Vascular Obstruction ◽  
Delayed Ossification ◽  
Skeletal Immaturity

Objectives Legg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition. Methods Finite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP. Results The results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression. Conclusion The findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease. Cite this article: M. Pinheiro, C. A. Dobson, D. Perry, M. J. Fagan. New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction. Bone Joint Res 2018;7:148–156. DOI: 10.1302/2046-3758.72.BJR-2017-0191.R1.

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