Plastic Limit Analysis of Perforated Material Under Finite Deformation

2005 ◽  
Author(s):  
Xinjian Duan ◽  
Arnaud Weck ◽  
David S. Wilkinson ◽  
Don R. Metzger
Keyword(s):  
Deformation Theory ◽  
Structural Model ◽  
Cell Model ◽  
Fracture Pattern ◽  
Plastic Strain Rate ◽  
Finite Element Models ◽  
Engineering Strain ◽  
Failure Path ◽  
Plastic Limit Analysis ◽  
Local Cell

In this paper, the fracture pattern of a perforated aluminum sheet is studied experimentally and numerically using finite element models on two different length scales: a full-scale structural and a local cell models based on the large deformation theory. Through appropriate application of boundary conditions, the more efficient local cell model is shown to produce almost the same results as the full structural model. It is also found that the failure path is significantly affected by the loading conditions (uniaxial vs. biaxial) and the hole distribution pattern. By plotting the instantaneous contour of plastic strain rate, the fracture path could clearly be distinguished by the time that the overall engineering strain had reached 3%.

Failure Modes of Perforated Material Under Finite Deformation

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Xinjian Duan ◽  
Arnaud Weck ◽  
David S. Wilkinson ◽  
Don R. Metzger
Keyword(s):  
Failure Modes ◽  
Structural Model ◽  
Cell Model ◽  
Local Deformation ◽  
Fracture Pattern ◽  
Plastic Strain Rate ◽  
Small Scale ◽  
Engineering Strain ◽  
Failure Path ◽  
Local Cell

Local deformation due to the interaction of small scale features such as voids or hard particles is expected to have a significant influence on the failure mode of a material. To this end, the fracture pattern of a perforated aluminum sheet is studied experimentally and numerically using finite element models on two different length scales: a full-scale structural model and a local cell model based on large deformation theory. Through the appropriate application of boundary conditions, the more efficient local cell model is shown to produce almost the same results as the full structural model. It is also found that the failure path is significantly affected by the loading conditions (uniaxial versus biaxial) and the hole distribution pattern. By plotting the instantaneous contours of the plastic strain rate, the fracture path can clearly be distinguished by the time that the overall engineering strain reaches approximately 3%. This model developed here has great potential to assess the integrity of high pressure components such as tubesheet.

The Collagen Fiber Kinematics in the Anteroinferior Glenohumeral Capsule Are Not Affine-Predicted

2011 ◽  
Author(s):  
Carrie A. Voycheck ◽  
Patrick J. McMahon ◽  
Richard E. Debski
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Glenohumeral Joint ◽  
Structural Models ◽  
Clinical Problem ◽  
Collagen Fibers ◽  
Material Behavior ◽  
Finite Element Models ◽  
Glenohumeral Ligament ◽  
Glenohumeral Capsule

Glenohumeral dislocation is a significant clinical problem and often results in injury to the anteroinferior (anterior band of the inferior glenohumeral ligament (AB-IGHL) and axillary pouch) glenohumeral capsule. [1] However, clinical exams to diagnose capsular injuries are not reliable [2] and poor patient outcome still exists following repair procedures. [3] Validated finite element models of the glenohumeral capsule may be able to improve diagnostic and repair techniques; however, improving the accuracy of these models requires adequate constitutive models to describe capsule behavior. The collagen fibers in the anteroinferior capsule are randomly oriented [4], thus the material behavior of the glenohumeral capsule has been described using isotropic models. [5,6] A structural model consisting of an isotropic matrix embedded with randomly aligned collagen fibers proved to better predict the complex capsule behavior than an isotropic phenomenological model [7] indicating that structural models may improve the accuracy of finite element models of the glenohumeral joint. Many structural models make the affine assumption (local fiber kinematics follow global tissue deformation) however an approach to account for non-affine fiber kinematics in structural models has been recently developed [8]. Evaluating the affine assumption for the capsule would aid in developing an adequate constitutive model. Therefore, the objective of this work was to assess the affine assumption of fiber kinematics in the anteroinferior glenohumeral capsule by comparing experimentally measured preferred fiber directions to the affine-predicted fiber directions.

Voronoi cells: An interesting and potentially useful cell model for interpreting the small-angle scattering of catalysts

1983 ◽  
Vol 16 (1) ◽  
pp. 83-88 ◽  
Author(s):  
H. Brumberger ◽  
J. Goodisman
Keyword(s):  
Small Angle ◽  
Heterogeneous Catalysts ◽  
Structural Model ◽  
Cell Model ◽  
Voronoi Cells ◽  
X Ray ◽  
Surface Areas ◽  
Angle Scattering ◽  
Metallic Catalyst ◽  
Polyhedral Cells

A structural model, based on Voronoi polyhedral cells partly filled with support and metallic catalyst, is proposed for interpreting the small-angle X-ray scattering of heterogeneous catalysts. The model's properties are described, and the model is applied to porous Al2O3 and Pt/porous Al2O3. Surface areas calculated from the X-ray data by means of the statistical geometry of Voronoi tesselations are found in good agreement with those determined by BET (Brunauer, Emmett & Teller) adsorption methods.

scholarly journals Homogenization of Ancient Masonry Buildings: A Case Study

2020 ◽  
Vol 10 (19) ◽  
pp. 6687
Author(s):  
Simona Di Nino ◽  
Daniele Zulli
Keyword(s):  
Structural Model ◽  
Pure Shear ◽  
Experimental Investigations ◽  
Finite Element Models ◽  
Masonry Building ◽  
Dynamic Mechanisms ◽  
Global Dynamic ◽  
Historical Masonry ◽  
Constitutive Parameters

With the aim of evaluating local and global dynamic mechanisms of a vast and historical masonry building, a homogeneous structural model is proposed here. It is realized with the assembly of othotropic plates and Timoshenko and pure shear beams as well. The identification of the constitutive parameters is carried out after realizing refined finite element models of building portions, and imposing energy or displacement equivalence with the corresponding homogeneous versions, depending on the complexity of the involved schemes. The outcomes are compared with those provided by experimental investigations, and help to give insight and interpretation on the dynamic behavior of the building.

Insights on Fractured Domains in Reservoirs Resulting from Modeling Complex Geology/Structures - Case Study of the Ratana Field in the Potwar Basin, Pakistan

2021 ◽  
Author(s):  
Jean-Christophe Wrobel-Daveau ◽  
Rodney Barracloughy ◽  
Sarah Laird ◽  
Nick Matthies ◽  
Bilal Saeed ◽  
...  
Keyword(s):  
Structural Model ◽  
Structural Complexity ◽  
High Amplitude ◽  
Fracture Pattern ◽  
Geophysical Modeling ◽  
Kinematic Evolution ◽  
Tight Carbonate ◽  
Exploration And Production ◽  
Incremental Strain ◽  
Interpretation Algorithm

Abstract Exploration success in fold-and-thrust belts, like the Potwar petroleum province, is impacted by seismic imaging challenges and structural complexity. Success partly relies on the ability to validate subsurface models and model a range of properties, such as reservoir permeability. This is particularly important in the case of tight carbonate reservoirs such as the Eocene Sakesar Formation, where the recovery of economic quantities of hydrocarbons is conditioned by the presence of fracture-enhanced permeability. This requires the application of geological and geophysical modeling techniques to address these challenges, to minimize uncertainty and drive exploration success. The interpretation and structural validation of the Ratana structure presented here allows the proposal of a consistent and robust structural model even in areas of higher uncertainty in the data, such as along faults. The dynamically updatable, watertight, complex 3D structural framework created for the top Sakesar reservoir was used in combination with an assisted fault interpretation algorithm to characterize the fault and fracture pattern. The results showed a higher density of high amplitude fractures on the flanks of the structure rather than along the hinge. These results are supported by the incremental strain modeling based on the kinematic evolution of the structure. Together, this helped to characterize potential fracture corridors in areas of the seismic volume that previously proved challenging for human driven interpretation. Our results allow us to reduce the uncertainty related to the geometrical characteristics of the reservoir and provide insights into potential exploration well targets to maximize chances of success, suggesting that permeability and hydrocarbon flow may be higher at the margins of the Ratana structure, and not at the crest, which was the focus of previous exploration and production efforts.

Applying Strip Theory Based Linear Seakeeping Loads to 3D Full Ship Finite Element Models

2013 ◽  
Author(s):  
Chengbi Zhao ◽  
Ming Ma ◽  
Owen Hughes
Keyword(s):  
Finite Element ◽  
Structural Model ◽  
Velocity Potential ◽  
Structural Models ◽  
Vertical Shear ◽  
Finite Element Models ◽  
3D Finite Element ◽  
Hull Girder ◽  
Strip Theory ◽  
Extreme Load

Panel based hydrodynamic analyses are well suited for transferring seakeeping loads to 3D FEM structural models. However, 3D panel based hydrodynamic analyses are computationally expensive. For monohull ships, methods based on strip theory have been successfully used in industry for many years. They are computationally efficient, and they provide good prediction for motions and hull girder loads. However, many strip theory methods provide only hull girder sectional forces and moments, such as vertical bending moment and vertical shear force, which are difficult to apply to 3D finite element structural models. For the few codes which do output panel pressure, transferring the pressure map from a hydrodynamic model to the corresponding 3D finite element model often results in an unbalanced structural model because of the pressure interpolation discrepancy. To obtain equilibrium of an imbalanced structural model, a common practice is to use the “inertia relief” approach to rebalance the model. However, this type of balancing causes a change in the hull girder load distribution, which in turn could cause inaccuracies in an extreme load analysis (ELA) and a spectral fatigue analysis (SFA). This paper presents a method of applying strip theory based linear seakeeping pressure loads to balance 3D finite element models without using inertia relief. The velocity potential of strip sections is first calculated based on hydrodynamic strip theories. The velocity potential of a finite element panel is obtained from the interpolation of the velocity potential of the strip sections. The potential derivative along x-direction is computed using the approach proposed by Salvesen, Tuck and Faltinsen. The hydrodynamic forces and moments are computed using direct panel pressure integration from the finite element structural panel. For forces and moments which cannot be directly converted from pressure, such as hydrostatic restoring force and diffraction force, element nodal forces are generated using Quadratic Programing. The equations of motions are then formulated based on the finite element wetted panels. The method results in a perfectly balanced structural model.

Structure-property relations of liquid crystalline polymers

1987 ◽  
Vol 45 ◽  
pp. 460-463
Author(s):  
Linda C. Sawyer
Keyword(s):  
Solid State ◽  
Liquid Crystalline ◽  
Structural Model ◽  
Crystalline Polymer ◽  
Liquid Crystalline Polymers ◽  
Mechanical Anisotropy ◽  
Structure Property ◽  
Preparation Methods ◽  
Crystalline Polymers ◽  
Extended Chain

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.

Deformation effects on transgranular carbide precipitation in 304 stainless steels

1992 ◽  
Vol 50 (1) ◽  
pp. 260-261
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D.J. Matlock ◽  
W.W. Fisher ◽  
P.M. Tarin ◽  
...  
Keyword(s):  
Stainless Steels ◽  
True Strain ◽  
Carbide Precipitation ◽  
Material Research ◽  
Chromium Depletion ◽  
Engineering Strain ◽  
Twin Fault ◽  
Heat Treated ◽  
Strain Induced Martensite ◽  
The Relationship

Plastic deformation is a key variable producing accelerated intergranular (IG) carbide precipitation and chromium-depletion (sensitization) development in stainless steels. Deformation above 20% also produces transgranular (TG) carbides and depletion in the material. Research on TG carbides in SS is, however, limited and has indicated that the precipitation is site-specific preferring twin-fault intersections in 316 SS versus deformation-induced martensite and martensite lath-boundaries in 304 SS. Evidences indicating the relation between martensite and carbides were, however, sketchy.The objective of this work was to fundamentally understand the relationship between TG carbides and strain-induced martensite in 304 SS. Since strain-induced martensite forms at twin-fault intersections in 304 SS and the crystallography of the transformation is well understood, we believed that it could be key in understanding mechanisms of carbides and sensitization in SS. A 0.051% C, 304 SS deformed to ∽33% engineering strain (40% true strain) and heat treated at 670°C/ 0.1-10h was used for the research. The study was carried out on a Hitachi H-8000 STEM at 200 kV.

The Hierarchic Order of Intermediate Filament Structure and Assembly

1985 ◽  
Vol 43 ◽  
pp. 722-725
Author(s):  
U. Aebi ◽  
E.C. Glavaris ◽  
R. Eichner
Keyword(s):  
Tissue Specificity ◽  
Structural Model ◽  
Eukaryotic Cells ◽  
Cdna Sequencing ◽  
Filament Structure ◽  
Keratin Filaments ◽  
Isoelectric Points ◽  
Immunological Crossreactivity

Five different classes of intermediate-sized filaments (IFs) have been identified in differentiated eukaryotic cells: vimentin in mesenchymal cells, desmin in muscle cells, neurofilaments in nerve cells, glial filaments in glial cells and keratin filaments in epithelial cells. Despite their tissue specificity, all IFs share several common attributes, including immunological crossreactivity, similar morphology (e.g. about 10 nm diameter - hence ‘10-nm filaments’) and the ability to reassemble in vitro from denatured subunits into filaments virtually indistinguishable from those observed in vivo. Further more, despite their proteinchemical heterogeneity (their MWs range from 40 kDa to 200 kDa and their isoelectric points from about 5 to 8), protein and cDNA sequencing of several IF polypeptides (for refs, see 1,2) have provided the framework for a common structural model of all IF subunits.

Video-microscopic measurement of cell-substratum traction forces generated by locomoting keratocytes

1993 ◽  
Vol 51 ◽  
pp. 188-189
Author(s):  
Tim Oliver ◽  
Michelle Leonard ◽  
Juliet Lee ◽  
Akira Ishihara ◽  
Ken Jacobson
Keyword(s):  
Silicone Rubber ◽  
Molecular Motors ◽  
Video Frame ◽  
Traction Forces ◽  
Cell Traction Forces ◽  
Latex Beads ◽  
Cell Traction ◽  
Local Cell ◽  
Microscopic Measurement ◽  
Kinetics Of

We are using video-enhanced light microscopy to investigate the pattern and magnitude of forces that fish keratocytes exert on flexible silicone rubber substrata. Our goal is a clearer understanding of the way molecular motors acting through the cytoskeleton co-ordinate their efforts into locomotion at cell velocities up to 1 μm/sec. Cell traction forces were previously observed as wrinkles(Fig.l) in strong silicone rubber films by Harris.(l) These forces are now measureable by two independant means.In the first of these assays, weakly crosslinked films are made, into which latex beads have been embedded.(Fig.2) These films report local cell-mediated traction forces as bead displacements in the plane of the film(Fig.3), which recover when the applied force is released. Calibrated flexible glass microneedles are then used to reproduce the translation of individual beads. We estimate the force required to distort these films to be 0.5 mdyne/μm of bead movement. Video-frame analysis of bead trajectories is providing data on the relative localisation, dissipation and kinetics of traction forces.

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