scholarly journals A Novel Approach to Predict the Process-Induced Mechanical Behavior of Additively Manufactured Materials

2021 ◽  
Author(s):  
Andreas Kergaßner ◽  
Johannes A. Koepf ◽  
Matthias Markl ◽  
Carolin Körner ◽  
Julia Mergheim ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Yield Criterion ◽  
Grain Structure ◽  
The Finite Element Method ◽  
Present Contribution ◽  
Plastic Properties ◽  
Novel Approach ◽  
Grain Structures ◽  
Selective Electron Beam Melting ◽  
Yield Loci

AbstractThe grain structure and texture of additively manufactured materials depend strongly on the local temperature gradients during the solidification of the material. These grain structures and textures influence the mechanical behavior, ranging from isotropy to transversal and orthotropic symmetry. In the present contribution, a cellular automaton is used to model the grain growth during selective electron beam melting. The resulting grain structures and textures serve as input for a mesoscopic mechanical model. The mechanical behavior on the mesoscale is modeled by means of gradient-enhanced crystal plasticity, applying the finite element method. Computational homogenization is applied to determine the resulting macroscopic elastic and plastic properties of the additively manufactured metals. A general orthotropic yield criterion is identified by means of the initial yield loci computed with mesoscopic simulations of representative volume elements. The numerical results are partly validated with experimental data.

Effect of Wall Thickness Transitions on Texture and Grain Structure in Additive Layer Manufacture (ALM) of Ti-6Al-4V

2012 ◽  
Vol 706-709 ◽  
pp. 205-210 ◽  
Author(s):  
Alphons A. Antonysamy ◽  
Philip B. Prangnell ◽  
Jonathan Meyer
Keyword(s):  
Electron Beam Melting ◽  
Random Distribution ◽  
Skin Effect ◽  
Grain Structure ◽  
Thin Walls ◽  
Β Phase ◽  
Transformation Texture ◽  
Grain Structures ◽  
Selective Electron Beam Melting ◽  
Layer Manufacture

In titanium alloys it is known that in bulk sections the solidification conditions in ALM commonly lead to undesirable, coarse, columnar β grain structures. Here, we have investigated the effect of build geometry on the grain structure and associated texture in Ti-6Al-4V ALM components produced by Selective Electron Beam Melting (SEBM). Through reconstruction of the primary β-phase, it has been confirmed that in thick sections large columnar β grains grow with a strong <001>βfibre texture, although there is a significant skin effect. In contrast, in thin walls nucleation off the surrounding powder and growth inwards dominates. Local heterogeneities are also observed within section transitions. It is shown that the weaker α transformation texture arises from a random distribution across the possible habit variants.

A Contribution to the Simulation of Molded Micro Components and Systems With Regard to the Grain Structure

2008 ◽  
Author(s):  
Albert Albers ◽  
Hans-Georg Enkler ◽  
Pablo Leslabay
Keyword(s):  
Stress Distribution ◽  
Grain Structure ◽  
The Finite Element Method ◽  
Component Level ◽  
Grain Structures ◽  
Micro Parts ◽  
Transfer Behavior ◽  
Manufacturing Techniques ◽  
The Individual ◽  
Multi Body

Experimental work for characterizing materials’ properties as well as components’ and systems’ behaviors have to be supplemented by numerical analyses when regarding micro components and systems. In order to accomplish a complete possibilities’ overview for micro machines these analyses should cover both component and system issues. On a component level, established macroscopic approaches are extended by methods that allow the consideration of components’ grain structures influence, including possible superficial and internal defects. Because of technological restrictions, especially when applying miniaturized conventional manufacturing techniques, shape and material deviations cannot be scaled down in the same dimensions like micro parts. Thus, high tolerances accepted for the individual components and their effects on the expected transfer behavior of the whole system are taken primarily into account. This paper presents approaches for the simulation of micro components and systems using the Finite Element Method and Multi Body Simulation. Methods to overcome the above mentioned issues will be shown, as well as the effects of grain structure on the stress distribution in the individual components. Some effects over the system’s behavior of this inhomogeneous stress distribution are also discussed.

scholarly journals Finite Pure Plane Strain Bending of Inhomogeneous Anisotropic Sheets

Symmetry ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 145
Author(s):  
Sergei Alexandrov ◽  
Elena Lyamina ◽  
Yeong-Maw Hwang
Keyword(s):  
Plane Strain ◽  
Yield Criterion ◽  
Large Strains ◽  
Rigid Plastic ◽  
Plastic Properties ◽  
Elastic Plastic ◽  
Starting Point ◽  
The Difference ◽  
Inside Radius ◽  
Elastic Unloading

The present paper concerns the general solution for finite plane strain pure bending of incompressible, orthotropic sheets. In contrast to available solutions, the new solution is valid for inhomogeneous distributions of plastic properties. The solution is semi-analytic. A numerical treatment is only necessary for solving transcendent equations and evaluating ordinary integrals. The solution’s starting point is a transformation between Eulerian and Lagrangian coordinates that is valid for a wide class of constitutive equations. The symmetric distribution relative to the center line of the sheet is separately treated where it is advantageous. It is shown that this type of symmetry simplifies the solution. Hill’s quadratic yield criterion is adopted. Both elastic/plastic and rigid/plastic solutions are derived. Elastic unloading is also considered, and it is shown that reverse plastic yielding occurs at a relatively large inside radius. An illustrative example uses real experimental data. The distribution of plastic properties is symmetric in this example. It is shown that the difference between the elastic/plastic and rigid/plastic solutions is negligible, except at the very beginning of the process. However, the rigid/plastic solution is much simpler and, therefore, can be recommended for practical use at large strains, including calculating the residual stresses.

scholarly journals The effect of the outlet angle β2 on the thermomechanical behavior of a centrifugal compressor blade

2020 ◽  
Vol 29 (1) ◽  
pp. 1-8
Author(s):  
Ahmed Allali ◽  
Sadia Belbachir ◽  
Ahmed Alami ◽  
Belhadj Boucham ◽  
Abdelkader Lousdad
Keyword(s):  
Mechanical Behavior ◽  
Centrifugal Compressor ◽  
Three Dimensional ◽  
Complex Form ◽  
Compressor Blade ◽  
Stress Fields ◽  
The Finite Element Method ◽  
Mechanical Fatigue ◽  
Outlet Angle ◽  
The Impact

AbstractThe objective of this work lies in the three-dimensional study of the thermo mechanical behavior of a blade of a centrifugal compressor. Numerical modeling is performed on the computational code "ABAQUS" based on the finite element method. The aim is to study the impact of the change of types of blades, which are defined as a function of wheel output angle β2, on the stress fields and displacements coupled with the variation of the temperature.This coupling defines in a realistic way the thermo mechanical behavior of the blade where one can note the important concentrations of stresses and displacements in the different zones of its complex form as well as the effects at the edges. It will then be possible to prevent damage and cracks in the blades of the centrifugal compressor leading to its failure which can be caused by the thermal or mechanical fatigue of the material with which the wheel is manufactured.

DESIGN AND ANALYSIS OF NEW STENT PATTERNS FOR ENHANCED PERFORMANCE

2020 ◽  
Vol 20 (06) ◽  
pp. 2050039
Author(s):  
NISANTHKUMAR PANNEERSELVAM ◽  
SREEKUMAR MUTHUSWAMY
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Blood Flow ◽  
Coronary Artery ◽  
Mechanical Behavior ◽  
Internal Diameter ◽  
Cell Design ◽  
The Finite Element Method ◽  
Stent Expansion ◽  
Stenting Procedure

Deploying a stent to restore blood flow in the coronary artery is very complicated, as its internal diameter is smaller than 3[Formula: see text]mm. It has already been proven that mechanical stresses induced on stent and artery during deployment make the placement of stent very difficult, besides the development of complications due to artery damage. Various stent designs have already been developed, especially in the metallic category. Still, there are possibilities for developing new stent designs and patterns to overcome the complexities of the existing models. Also, the technology of metallic stents can be carried forward towards the development of bioresorbable polymeric stents. In this work, three new stent cell designs (curvature, diamond, and oval) have been proposed to obtain better performance and life. The finite element method is utilized to explore the mechanical behavior of stent expansion and determine the biomechanical stresses imposed on the stent and artery during the stenting procedure. The results obtained have been compared with the available literature and found that the curvature cell design develops lower stresses and, hence, be suitable for better performance and life.

A Visco-hyperelastic Model for the Thermo-mechanical Behavior of Polymer Fibers

2010 ◽  
Vol 20 (7) ◽  
pp. 1002-1020 ◽  
Author(s):  
G.P. Potirniche ◽  
A. Pascu ◽  
N. Shoemaker ◽  
P.T. Wang ◽  
M.F. Horstemeyer ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Penetration Resistance ◽  
Polymer Chains ◽  
Polymer Fibers ◽  
Deformation Characteristics ◽  
Uniaxial Deformation ◽  
The Finite Element Method ◽  
Dynamic Event ◽  
Hyperelastic Model ◽  
Strain Rate Hardening

A visco-hyperelastic model for the thermo-mechanical behavior of polymer yarns is presented. The model assumes that the stress in a yarn during uniaxial deformation results from the superposition of strain rate hardening effects and the softening caused by filament damage. The filament damage accounts for the fracture of polymer chains and the failure of inter-chain bonds. The constitutive model was implemented in the finite element method as a 1D rope element, and was applied to the study of nylon 6.6 and Kevlar ® 29 behavior. Numerical simulations of fabrics subjected to ballistic impact were performed, and the model is shown to predict the fabric penetration resistance and the deformation characteristics during the dynamic event.

Biomechanical Behavior of All-Ceramic Crowns with Variable Thicknesses of Zirconia Frameworks

2016 ◽  
Vol 835 ◽  
pp. 97-102
Author(s):  
Liliana Porojan ◽  
Florin Topală ◽  
Sorin Porojan
Keyword(s):  
Mechanical Behavior ◽  
Equivalent Stress ◽  
The Finite Element Method ◽  
Static Loads ◽  
Biomechanical Behavior ◽  
All Ceramic ◽  
Ceramic Crowns ◽  
Von Mises Equivalent Stress ◽  
Von Mises ◽  
Posterior Restorations

Zirconia is an extremely successful material for prosthetic restorations, offering attractive mechanical and optical properties. It offers several advantages for posterior restorations because it can withstand physiological posterior forces. The aim of the study was to achieve the influence of zirconia framework thickness on the mechanical behavior of all-ceramic crowns using numerical simulation. For the study a premolar was chosen in order to simulate the mechanical behavior in the components of all-ceramic crowns and teeth structures regarding to the zirconia framework thickness. Maximal Von Mises equivalent stress values were recorded in teeth and restorations. Due to the registered maximal stress values it can be concluded that it is indicated to achieve frameworks of at least 0.5 mm thickness in the premolar area. Regarding stress distribution concentration were observed in the veneer around the contact areas with the antagonists, in the framework under the functional cusp and in the oral part overall and in dentin around and under the marginal line, also oral. The biomechanical behavior of all ceramic crowns under static loads can be investigated by the finite element method.

Identification of Post-Necking Hardening Behaviour of Sheet Metal: a Practical Application to Clinch Forming

2011 ◽  
Vol 473 ◽  
pp. 251-258 ◽  
Author(s):  
Sam Coppieters ◽  
Pascal Lava ◽  
Hugo Sol ◽  
Paul van Houtte ◽  
Dimitri Debruyne
Keyword(s):  
Sheet Metal ◽  
Uniform Elongation ◽  
The Finite Element Method ◽  
Practical Application ◽  
Plastic Properties ◽  
Sheet Metal Parts ◽  
Forming Load ◽  
Alternative Material ◽  
Local Plastic Deformation ◽  
Material Tests

Clinching is a mechanical joining technique which involves severe local plastic deformation of two or more sheet metal parts resulting in a permanent mechanical interlock or joint. The required forming load and energy can be determined with the aid of the finite element method. However, a good knowledge of the elasto-plastic properties is of utmost importance to perform a sufficiently accurate simulation. This paper presents two alternative material tests to identify the hardening behaviour of sheet metal beyond the point of maximum uniform elongation. In addition, the material tests were applied to DC05 and the identified material behaviour is evaluated through the prediction of the forming load during clinching.

scholarly journals Microstructural Transitions during Powder Metallurgical Processing of Solute Stabilized Nanostructured Tungsten Alloys

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 159
Author(s):  
Nicholas Olynik ◽  
Bin Cheng ◽  
David J. Sprouster ◽  
Chad M. Parish ◽  
Jason R. Trelewicz
Keyword(s):  
Extreme Environments ◽  
High Energy ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Grain Boundary Engineering ◽  
Carbon Impurities ◽  
Grain Structures ◽  
Metallurgical Processing ◽  
Size Population

Exploiting grain boundary engineering in the design of alloys for extreme environments provides a promising pathway for enhancing performance relative to coarse-grained counterparts. Due to its attractive properties as a plasma facing material for fusion devices, tungsten presents an opportunity to exploit this approach in addressing the significant materials challenges imposed by the fusion environment. Here, we employ a ternary alloy design approach for stabilizing W against recrystallization and grain growth while simultaneously enhancing its manufacturability through powder metallurgical processing. Mechanical alloying and grain refinement in W-10 at.% Ti-(10,20) at.% Cr alloys are accomplished through high-energy ball milling with transitions in the microstructure mapped as a function of milling time. We demonstrate the multi-modal nature of the resulting nanocrystalline grain structure and its stability up to 1300 °C with the coarser grain size population correlated to transitions in crystallographic texture that result from the preferred slip systems in BCC W. Field-assisted sintering is employed to consolidate the alloy powders into bulk samples, which, due to the deliberately designed compositional features, are shown to retain ultrafine grain structures despite the presence of minor carbides formed during sintering due to carbon impurities in the ball-milled powders.

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