scholarly journals Plastic Deformation and Crystalline Texture in Equibiaxial Expansion

1979 ◽  
Vol 3 (3) ◽  
pp. 149-168 ◽  
Author(s):  
C. Gaspard ◽  
P. Messien ◽  
J. Mignon ◽  
T. Greday
Keyword(s):  
Plastic Deformation ◽  
Dimensional Analysis ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Deformation Model ◽  
Theoretical Treatment ◽  
Slip Systems ◽  
Factors Influencing ◽  
Experimental Behavior ◽  
Shear Planes

The classical three-dimensional analysis (O.D.F.) has been extended in such a manner as to obtain the representation of the texture, and, more precisely, the distribution of the slip systems <111> {hkℓ} in the planes where shear stresses induced in equibiaxial expansion are maximum.Quantification of the slip systems configuration allows the development of a deformation model which takes into account the factors influencing the degree of stretchability of the steels. From this model it is possible to define true hardening rates and equibiaxiality coefficients characterizing the ability of the steel to distribute the deformation in the macroscopic shear planes.In association with the resistance to thinning defined by the configuration of the slip systems, the theoretical treatment makes it possible to grade different steels according to their experimental behavior.

Evolution of Slip Through the Thickness of a Single-Crystal Nickel-Base Superalloy Notched Specimen

2006 ◽  
Author(s):  
Shadab Siddiqui ◽  
Nagaraj K. Arakere ◽  
Fereshteh Ebrahimi
Keyword(s):  
Stress Concentration ◽  
Single Crystal ◽  
Normal Stress ◽  
Elastic Anisotropy ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Specimen Thickness ◽  
Face Centered Cubic ◽  
Slip Systems ◽  
Base Superalloy

Deformation mechanisms and failure modes of FCC (face centered cubic) single crystal components subjected to triaxial states of static and fatigue stress are very complicated to predict, because plasticity precedes fracture in regions of stress concentration, and the evolution of plasticity on the surface and through the thickness is influenced by elastic and plastic anisotropy. The triaxial stress state at regions of stress concentration results in the activation of many slip systems that otherwise would not be activated during uniaxial testing. We recently presented [1] results from a numerical and experimental investigation of evolution of slip systems at the surface of notched FCC single crystal specimens, as a function of secondary crystallographic orientation. Results showed that the slip sector boundaries have complex curved shapes with several slip systems active simultaneously near the notch. We extend our work on slip at the surface to investigating the evolution of slip or plastic deformation through the thickness of the specimen. A single crystal double-edge-notched rectangular specimen of a Ni-base superalloy, under the tensile loading ([001] load orientation and [110] notch direction) is considered. A three dimensional (3-D) finite element model (FEM) including elastic anisotropy is used for the numerical investigation. Results indicate that the stress distribution and slip fields are a strong function of axial location through the thickness. Numerical results are verified by comparing them with experimentally observed slip fields. We demonstrate that inclusion of three dimensional analysis and elastic anisotropy is important for predicting evolution of slip at the surface and through the specimen thickness. The resolved shear stresses (RSS) on the dominant slip systems and the normal stress on the dominant planes are shown to vary significantly from the surface to the midplane of the specimen. Based on the consideration of RSS, normal stress and the number of activated slip systems at each thickness level, it is concluded that fatigue cracks most likely start in the midplane, for the orientation reported here.

Shear on the Flow Surface of Metallic Crystals

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Michel G. Darrieulat ◽  
Asdin Aoufi
Keyword(s):  
Three Dimensional ◽  
Shear Stresses ◽  
Slip Systems ◽  
Geometric Description ◽  
Cubic Metals ◽  
Maximum Value ◽  
Flow Surface ◽  
Kinematic Study ◽  
Principal Directions ◽  
Octahedral Slip

The present article addresses the following question: How is it that shears are so common in the plastic deformation of metallic alloys? An answer is sought in a geometric description of the shear flow when the deformation is produced by slip systems gliding according to the Schmid law. Such flows are represented schematically by what is called “simple shear” and a kinematic study is done of the way these shears can be produced by the joint activity of various slip systems. This implies specific conditions on the glide rates, which can be known analytically thanks to adequate parametrizations. All the possible shears have been calculated in the case of cubic metals deforming with identical critical resolved shear stresses (Bishop and Hill polyhedron). Three dimensional representations are given in the space of the Bunge angles associated with the principal directions of the shears. A special attention has been given to the number of slip systems involved. Most of the shears are not far from some combination of two or three systems. This is quantified by defining the misorientation ω between a shear taken at random and the set of shears produced by the glide on two or three octahedral slip systems. It is found that in most cases, ω<15 deg. The maximum value of ω (30.5 deg) is found for the orientations called Cube and U in rolled metals.

Crystal Plasticity Analysis of Thermal Deformation and Dislocation Accumulation in Gaas/Si Patterned Structure

1991 ◽  
Vol 226 ◽  
Author(s):  
Tetsuya Ohashi ◽  
Naoyuki Honda
Keyword(s):  
Thermal Deformation ◽  
Three Dimensional ◽  
Film Deposition ◽  
Shear Stresses ◽  
Slip Systems ◽  
Quantitative Expression ◽  
Plastic Slip ◽  
Dislocation Densities ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

AbstractPlastic slip deformation in patterned.GaAs films on Si substrate during cooling from film deposition temperature are numerically simulated under a continuum mechanics approximation. The plastic slip is assumed to take place on (111) <110> slip systems and activation condition of the slip systems is given by the Schmid's law. The critical resolved shear stresses for the activation of slip systems are expressed as a function of accumulated dislocation densities, which are evaluated by models for their movement and interaction. A three dimensional finite element computer program is developed, in which strain hardening behaviour is given a quantitative expression by the models for dislocations. Results of the simulation reveal process of plastic slip and dislocation accumulation in GaAs film. Residual stress evaluated by the simulation agreed well with results obtained by photo-luminescent experiments.

scholarly journals Three-Dimensional Analysis of Busulfan-Induced Spermatogenesis Disorder in Mice

2020 ◽  
Vol 8 ◽  
Author(s):  
Hiroki Nakata ◽  
Taito Nakano ◽  
Shoichi Iseki ◽  
Atsushi Mizokami
Keyword(s):  
3D Reconstruction ◽  
Dimensional Analysis ◽  
Intraperitoneal Injection ◽  
Three Dimensional ◽  
Stage I ◽  
Seminiferous Tubules ◽  
Factors Influencing ◽  
Branching Points ◽  
Normal Spermatogenesis ◽  
Single Testis

We examined if the distribution of impaired or normal spermatogenesis differs along the length of seminiferous tubules in disorders of spermatogenesis. For this purpose, three-dimensional (3D) reconstruction of seminiferous tubules was performed in mice with experimental spermatogenesis disorder induced by intraperitoneal injection of busulfan, and the areas of impaired and normal spermatogenesis were analyzed microscopically. The volume of the testis and length of seminiferous tubules decreased, and the proportion of tubule areas with impaired spermatogenesis increased depending on the dose of busulfan. With the highest dose of busulfan, although the proportion of impaired spermatogenesis was similar among individual seminiferous tubules, it was slightly but significantly higher in shorter tubules and in tubule areas near branching points. The tubule areas with impaired and normal spermatogenesis consisted of many segments of varying lengths. With increasing doses of busulfan, the markedly impaired segments increased in length without changing in number, whereas normal segments, although reduced in number and length, remained even with the highest dose of busulfan. Individual remaining normal segments consisted of several different stages, among which stage I and XII were found at higher frequencies, and stage VI at a lower frequency than expected in normal seminiferous tubules. We also examined if the distribution of impaired or normal spermatogenesis differs among different 3D positions in the testis without considering the course of seminiferous tubules. Although the proportions of impaired spermatogenesis with the minimum dose of busulfan and normal spermatogenesis with the highest dose of busulfan greatly varied by location within a single testis, there were no 3D positions with these specific proportions common to different testes, suggesting that the factors influencing the severity of busulfan-induced spermatogenesis disorder are not fixed in location among individual mice.

Investigation of Three-Dimensional Stress Fields and Slip Systems for fcc Single-Crystal Superalloy Notched Specimens

2005 ◽  
Vol 127 (3) ◽  
pp. 629-637 ◽  
Author(s):  
Nagaraj K. Arakere ◽  
Shadab Siddiqui ◽  
Shannon Magnan ◽  
Fereshteh Ebrahimi ◽  
Luis E. Forero
Keyword(s):  
Plastic Deformation ◽  
Plastic Zone ◽  
Single Crystal ◽  
Single Crystals ◽  
Crystallographic Orientation ◽  
Elastic Anisotropy ◽  
Three Dimensional ◽  
Stress Fields ◽  
Slip Systems ◽  
Zone Formation

Metals and their alloys, except for a few intermetallics, are inherently ductile, i.e., plastic deformation precedes fracture in these materials. Therefore, resistance to fracture is directly related to the development of the plastic zone at the crack tip. Recent studies indicate that the fracture toughness of single crystals depends on the crystallographic orientation of the notch as well as the loading direction. In general, the dependence of crack propagation resistance on crystallographic orientation arises from the anisotropy of (i) elastic constants, (ii) plastic deformation (or slip), and (iii) the weakest fracture planes (e.g., cleavage planes). Because of the triaxial stress state at the notch tips, many slip systems that otherwise would not be activated during uniaxial testing become operational. The plastic zone formation in single crystals has been tackled theoretically by Rice and his co-workers [Rice, J. R., 1987, Mech. Mater. 6, pp. 317–335; Rice, J. R., and Saeedvafa, M., 1987, J. Mech. Phys. Solids 36, pp. 189–214; Saeedvafa, M., and Rice, J. R., 1988; ibid., 37, pp. 673–691; Rice, J. R., Hawk, D. E., Asaro, R. J., 1990, Int. J. Fract. 42, pp. 301–321; Saeedvafa, M., and Rice, J. R., 1992, Modell. Simul. Mater. Sci. Eng. 1, pp. 53–71] and only limited experimental work has been conducted in this area. The study of the stresses and strains in the vicinity of a fcc single-crystal notch tip is of relatively recent origin. We present experimental and numerical investigation of three-dimensional (3D) stress fields and evolution of slip sector boundaries near notches in fcc single-crystal PWA1480 tension test specimens and demonstrate that a 3D linear elastic finite element model, which includes the effect of material anisotropy, is shown to predict active slip planes and sectors accurately. The slip sector boundaries are shown to have complex curved shapes with several slip systems active simultaneously near the notch. Results are presented for surface and mid-plane of the specimens. The results demonstrate that accounting for 3D elastic anisotropy is very important for accurate prediction of slip activation near fcc single-crystal notches loaded in tension. Results from the study will help establish guidelines for fatigue damage near single-crystal notches.

Texture and plastic anisotropy for thin sheets made of molybdenum alloy TsM-2A

2020 ◽  
pp. 20-25
Author(s):  
A. S. Kolyanova ◽  
◽  
V. N. Serebryany ◽  
Keyword(s):  
Experimental Data ◽  
Plastic Deformation ◽  
Plastic Anisotropy ◽  
Tensile Tests ◽  
Deformation Texture ◽  
Molybdenum Alloy ◽  
Shear Stresses ◽  
Slip Systems ◽  
Thin Sheets ◽  
Taylor Model

Using the Taylor model of plastic deformation, texture and parameters of plastic anisotropy of thin sheets made of the molybdenum alloy TsM-2A (Mo—Ti—Zr) molybdenum alloy have been investigated. The calculated values of the parameters of plastic anisotropy were compared with the experimental data obtained as a result of tensile tests. The best coincidence was achieved under the condition of the action of two slip systems (110) <111> and (211) <111> and the ratio of critical shear stresses τ211 / τ110 = 0.5.

Calculation of the Stress Interaction between Dislocation Pile-Ups in Neighbouring Misoriented Grains

2016 ◽  
Vol 879 ◽  
pp. 1731-1736 ◽  
Author(s):  
R. Schouwenaars ◽  
A. Ortiz ◽  
V. H. Jacobo
Keyword(s):  
Plastic Deformation ◽  
Grain Boundaries ◽  
External Stress ◽  
Dislocation Slip ◽  
Shear Stresses ◽  
Slip Systems ◽  
Dislocation Loops ◽  
Stress Concentrations ◽  
Pile Up ◽  
Schmid Factor

During the early stages of the plastic deformation of a polycrystal, dislocations can pile-up against grain boundaries. Experimental results on large-grained materials have provided excellent verification of this phenomenon. Such a pile-up may activate dislocation slip in the neighbouring grain. Whether this occurs depends on the misorientation between the grains and the resolved shear stresses in the affected grain. Several approximate criteria have been proposed to predict the occurrence of this mechanism. Here, the problem will be assessed directly by calculating the Peach-Köhler force produced by a single dislocation pile-up in one grain on all the possible slip systems in the neighbouring grain, in combination with the effect of the applied external stress as obtained through calculation of the Schmid factor. It will be seen that the problem is significantly more complex than what is generally assumed in basic explanations of the Hall-Petch effect: highly localised stress concentrations are generated for certain misorientations, which are capable of punching out small dislocation loops which may then propagate into the neighbouring grain.

In situ investigation of the primary recrystallization of alpha titanium in HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 634-635
Author(s):  
S. Naka ◽  
R. Penelle ◽  
R. Valle
Keyword(s):  
Dimensional Analysis ◽  
Texture Evolution ◽  
Cold Work ◽  
Three Dimensional ◽  
Primary Recrystallization ◽  
Thin Foils ◽  
In Situ Investigation ◽  
Grain Growth Model ◽  
Alpha Titanium

The in situ experimentation technique in HVEM seems to be particularly suitable to clarify the processes involved in recrystallization. The material under investigation was unidirectionally cold-rolled titanium of commercial purity. The problem was approached in two different ways. The three-dimensional analysis of textures was used to describe the texture evolution during the primary recrystallization. Observations of bulk-annealed specimens or thin foils annealed in the microscope were also made in order to provide information concerning the mechanisms involved in the formation of new grains. In contrast to the already published work on titanium, this investigation takes into consideration different values of the cold-work ratio, the temperature and the annealing time.Two different models are commonly used to explain the recrystallization textures i.e. the selective grain growth model (Beck) or the oriented nucleation model (Burgers). The three-dimensional analysis of both the rolling and recrystallization textures was performed to identify the mechanismsl involved in the recrystallization of titanium.

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