Large plastic strains in surface grains

2001 ◽  
Vol 11 (PR5) ◽  
pp. Pr5-309-Pr5-315
Author(s):  
M. Sauzay
Keyword(s):  
Plastic Strains

A new method of complex structure analysis by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 628-629
Author(s):  
V.V. Rybin ◽  
E.V. Voronina
Keyword(s):  
Complex Structure ◽  
Reciprocal Lattice ◽  
Stacking Faults ◽  
Plastic Strains ◽  
Base Position ◽  
Structural Regularity ◽  
Orientation Matrix ◽  
Computerized Processing ◽  
Fully Automatic ◽  
Diffraction Patterns

Recently, it has become essential to develop a helpful method of the complete crystallographic identification of fine fragmented crystals. This was maainly due to the investigation into structural regularity of large plastic strains. The method should be practicable for determining crystallographic orientation (CO) of elastically stressed micro areas of the order of several micron fractions in size and filled with λ>1010 cm-2 density dislocations or stacking faults. The method must provide the misorientation vectors of the adjacent fragments when the angle ω changes from 0 to 180° with the accuracy of 0,3°. The problem is that the actual electron diffraction patterns obtained from fine fragmented crystals are the superpositions of reflections from various fragments, though more than one or two reflections from a fragment are hardly possible. Finally, the method should afford fully automatic computerized processing of the experimental results.The proposed method meets all the above requirements. It implies the construction for a certain base position of the crystal the orientation matrix (0M) A, which gives a single intercorrelation between the coordinates of the unity vector in the reference coordinate system (RCS) and those of the same vector in the crystal reciprocal lattice base : .

scholarly journals Modeling of Personalized Anatomy Using Plastic Strains

2021 ◽  
Vol 40 (2) ◽  
pp. 1-21
Author(s):  
Bohan Wang ◽  
George Matcuk ◽  
Jernej Barbič
Keyword(s):  
Magnetic Resonance Imaging ◽  
Computed Tomography ◽  
Magnetic Resonance ◽  
Large Strain ◽  
Human Anatomy ◽  
Shape Deformation ◽  
Human Hand ◽  
Plastic Strains ◽  
Resonance Imaging ◽  
Deformation Method

We present a method for modeling solid objects undergoing large spatially varying and/or anisotropic strains, and use it to reconstruct human anatomy from medical images. Our novel shape deformation method uses plastic strains and the finite element method to successfully model shapes undergoing large and/or anisotropic strains, specified by sparse point constraints on the boundary of the object. We extensively compare our method to standard second-order shape deformation methods, variational methods, and surface-based methods, and demonstrate that our method avoids the spikiness, wiggliness, and other artifacts of previous methods. We demonstrate how to perform such shape deformation both for attached and un-attached (“free flying”) objects, using a novel method to solve linear systems with singular matrices with a known nullspace. Although our method is applicable to general large-strain shape deformation modeling, we use it to create personalized 3D triangle and volumetric meshes of human organs, based on magnetic resonance imaging or computed tomography scans. Given a medically accurate anatomy template of a generic individual, we optimize the geometry of the organ to match the magnetic resonance imaging or computed tomography scan of a specific individual. Our examples include human hand muscles, a liver, a hip bone, and a gluteus medius muscle (“hip abductor”).

Experimental and Three-Dimensional Finite Element Study of Scratch Test of Polymers at Large Deformations

2004 ◽  
Vol 126 (2) ◽  
pp. 372-379 ◽  
Author(s):  
J. L. Bucaille ◽  
E. Felder ◽  
G. Hochstetter
Keyword(s):  
Strain Hardening ◽  
Penetration Depth ◽  
Large Deformations ◽  
Numerical Study ◽  
Scratch Test ◽  
Scratch Resistance ◽  
Plastic Strains ◽  
Thermosetting Polymer ◽  
Scratch Tests ◽  
Hardening Coefficient

An experimental and numerical study of the scratch test on polymers near their surface is presented. The elastoplastic response of three polymers is compared during scratch tests at large deformations: polycarbonate, a thermosetting polymer and a sol-gel hard coating composed of a hybrid matrix (thermosetting polymer-mineral) reinforced with oxide nanoparticles. The experiments were performed using a nanoindenter with a conical diamond tip having an included angle of 30 deg and a spherical radius of 600 nm. The observations obtained revealed that thermosetting polymers have a larger elastic recovery and a higher hardness than polycarbonate. The origin of this difference in scratch resistance was investigated with numerical modelling of the scratch test in three dimensions. Starting from results obtained by Bucaille (J. Mat. Sci., 37, pp. 3999–4011, 2002) using an inverse analysis of the indentation test, the mechanical behavior of polymers is modeled with Young’s modulus for the elastic part and with the G’sell-Jonas’ law with an exponential strain hardening for the viscoplastic part. The strain hardening coefficient is the main characteristic parameter differentiating the three studied polymers. Its value is equal to 0.5, 4.5, and 35, for polycarbonate, the thermosetting polymer and the reinforced thermosetting polymer, respectively. Firstly, simulations reveals that plastic strains are higher in scratch tests than in indentation tests, and that the magnitude of the plastic strains decreases as the strain hardening increases. For scratching on polycarbonate and for a penetration depth of 0.5 μm of the indenter mentioned above, the representative strain is equal to 124%. Secondly, in agreement with experimental results, numerical modeling shows that an increase in the strain hardening coefficient reduces the penetration depth of the indenter into the material and decreases the depth of the residual groove, which means an improvement in the scratch resistance.

MEASUREMENT OF TRANSIENT THERMAL PLASTIC STRAINS

Strain ◽  
1968 ◽  
Vol 4 (4) ◽  
pp. 14-20 ◽  
Author(s):  
R. DECHAENE ◽  
J. COCK ◽  
M. CALUWE
Keyword(s):  
Plastic Strains ◽  
Transient Thermal

Elastic and Plastic Strains Misfits During the Reverse Martensitic Transformation

2022 ◽  
Author(s):  
Federico Guillermo Bonifacich ◽  
Osvaldo Agustín Lambri ◽  
Ricardo Raúl Mocellini ◽  
Fernando Daniel Lambri ◽  
José Ignacio Pérez-Landazábal ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Plastic Strains ◽  
Reverse Martensitic Transformation

Development of Distortion Modeling Methods for Large Welded Structures

2010 ◽  
Author(s):  
Y. P. Yang ◽  
H. Castner ◽  
N. Kapustka
Keyword(s):  
Thermal Analysis ◽  
Plastic Strain ◽  
Computation Time ◽  
Thermomechanical Analysis ◽  
Global Model ◽  
Temperature History ◽  
Plastic Strains ◽  
Local Models ◽  
Welded Structures ◽  
Modeling Methods

Two distortion modeling methods, mapping plastic strain and lump-pass modeling, were developed and validated for predicting distortion on large welded structures to reduce the computation time. The mapping plastic-strain method requires two kinds of models, local models and a global model. The local models are analyzed to predict plastic strains and the global model is analyzed by mapping the plastic strains to predict distortions. The lump-pass modeling method includes two kinds of analyses: a thermal analysis and a thermomechanical analysis. The thermal analysis is conducted to predict temperature history. The thermomechanical analysis is performed to predict distortion by inputting the predicted temperature history.

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