Intersection of Convex Cones as Stress Range for Plane Normal Elastic Bodies

2020 ◽  
pp. 87-101
Author(s):  
Massimiliano Lucchesi ◽  
Barbara Pintucchi ◽  
Nicola Zani
Keyword(s):  
Convex Cones ◽  
Stress Range ◽  
Plane Normal ◽  
Elastic Bodies ◽  
As Stress

Partial Contact of a Smooth Elastic Wavy Strip Pressed Between Two Flat Surfaces

2005 ◽  
Author(s):  
J. M. Block ◽  
L. M. Keer ◽  
R. Duddu
Keyword(s):  
Mixed Boundary ◽  
Contact Region ◽  
Fourier Series Expansion ◽  
Radius Of Curvature ◽  
Flat Surfaces ◽  
Various Boundary Conditions ◽  
Partial Contact ◽  
Elastic Bodies ◽  
As Stress ◽  
Lower Order Terms

The contact of a smooth elastic wavy strip pressed between two surfaces is solved by considering a curved beam in contact with a rigid half-space. In assuming so, the Michell Fourier series expansion for elastic bodies is shown to satisfy the resulting mixed boundary value problem. When the contact region is small compared to the radius of curvature of the beam, semi-analytical solutions are obtained by exploiting dual series equation techniques. The relation between the level of loading and the extent of contact, as well as stress on the surface and in the beam, are found. Various boundary conditions on the ends, which arise as lower order terms in the Michell solution, are considered. This semi-analytical solution may prove useful in analyzing the contact of a corrugated seal.

Creep Rupture of Multidirectional Polymer Composite Laminates — Influence of Time-Dependent Damage

2006 ◽  
Vol 128 (4) ◽  
pp. 611-617 ◽  
Author(s):  
A. Birur ◽  
A. Gupta ◽  
J. Raghavan
Keyword(s):  
Polymer Composite ◽  
Composite Laminates ◽  
Constant Load ◽  
Creep Rupture ◽  
Interlaminar Stresses ◽  
Fiber Fracture ◽  
Plane Normal ◽  
Matrix Cracks ◽  
Out Of Plane ◽  
As Stress

Evolution of various damage modes with time, in multidirectional laminates of a polymer composite (Hexcel F263-7/T300) subjected to a constant load, was experimentally studied and correlated to experimental creep rupture results to understand the influence of the former on the latter. Influence of various parameters, such as stress, temperature, thickness of inner plies, and outer-ply constraint, on damage evolution was evaluated. Observed damages include transverse (also referred in the literature as matrix cracks) cracking due to in-plane stresses, vertical cracking due to out-of-plane normal stress, delamination due to interlaminar stresses, splitting, and fiber fracture. The sequence of evolution of these damages varied with laminate stacking sequence, stress, and temperature. These damages significantly influenced one another and the creep rupture time.

Reconstruction of Objects from their Projections Using Orthogonal Functions

1973 ◽  
Vol 31 ◽  
pp. 268-269
Author(s):  
Elrnar Zeitler
Keyword(s):  
Unit Area ◽  
Three Dimensional ◽  
One Dimension ◽  
Spatial Density ◽  
Dimensional Representation ◽  
Orthogonal Functions ◽  
Object A ◽  
Plane Normal ◽  
Dimensional Object ◽  
Spatial Density Distribution

Considering any finite three-dimensional object, a “projection” is here defined as a two-dimensional representation of the object's mass per unit area on a plane normal to a given projection axis, here taken as they-axis. Since the object can be seen as being built from parallel, thin slices, the relation between object structure and its projection can be reduced by one dimension. It is assumed that an electron microscope equipped with a tilting stage records the projectionWhere the object has a spatial density distribution p(r,ϕ) within a limiting radius taken to be unity, and the stage is tilted by an angle 9 with respect to the x-axis of the recording plane.

Observation of secondary slip systems in tungsten bicrystals

1984 ◽  
Vol 42 ◽  
pp. 478-479
Author(s):  
J. R. Fekete ◽  
R. Gibala
Keyword(s):  
Stress Field ◽  
Grain Boundaries ◽  
Deformation Behavior ◽  
Stress Axis ◽  
Polycrystalline Materials ◽  
Slip Systems ◽  
Metallic Materials ◽  
Twist Boundary ◽  
Secondary Slip ◽  
Plane Normal

The deformation behavior of metallic materials is modified by the presence of grain boundaries. When polycrystalline materials are deformed, additional stresses over and above those externally imposed on the material are induced. These stresses result from the constraint of the grain boundaries on the deformation of incompatible grains. This incompatibility can be elastic or plastic in nature. One of the mechanisms by which these stresses can be relieved is the activation of secondary slip systems. Secondary slip systems have been shown to relieve elastic and plastic compatibility stresses. The deformation of tungsten bicrystals is interesting, due to the elastic isotropy of the material, which implies that the entire compatibility stress field will exist due to plastic incompatibility. The work described here shows TEM observations of the activation of secondary slip in tungsten bicrystals with a [110] twist boundary oriented with the plane normal parallel to the stress axis.

Defect structures of Nb1+αS2 sulfidation scales

1992 ◽  
Vol 50 (1) ◽  
pp. 38-39
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Stacking Faults ◽  
Rhombohedral Structure ◽  
Stacking Sequence ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plane Normal ◽  
Lower Case ◽  
Sulfur Layer ◽  
Two Phases

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.

FUTURE PERSPECTIVE OF PLANT BIOTECHNOLOGY: A REVIEW

2020 ◽  
Vol 1 (1) ◽  
pp. 36-41
Author(s):  
Gaurav Ranabhat ◽  
Ashmita Dhakal ◽  
Saurav Ranabhat ◽  
Ananta Dhakal ◽  
Rakshya Aryal
Keyword(s):  
Insect Pest ◽  
Ornamental Plants ◽  
Herbicide Tolerance ◽  
Plant Biotechnology ◽  
Future Perspective ◽  
New Development ◽  
Recent Developments ◽  
Modern Biotechnology ◽  
Stable Yield ◽  
As Stress

Modern biotechnology enables an organism to produce a totally new product which the organism does not or cannot produce normally through the incorporation of the technology of ‘Genetic engineering’. Biotechnology shows its technical merits and new development prospects in breeding of new plants varieties with high and stable yield, good quality, as well as stress tolerance and resistance. Some of the most prevailing problems faced in agricultural ecosystems could be solved with the introduction of transgenic crops incorporated with traits for insect pest resistance, herbicide tolerance and resistance to viral diseases. Plant biotechnology has gained importance in the recent past for increasing the quality and quantity of agricultural, horticultural, ornamental plants, and in manipulating the plants for improved agronomic performance. Recent developments in the genome sequencing will have far reaching implications for future agriculture. From this study, we can know that the developing world adopts these fast-changing technologies soon and harness their unprecedented potential for the future benefit of human being.

Damage accumulation near a hole under low cycle fatigue proceeding from measurements of local deformation response

2020 ◽  
Vol 86 (10) ◽  
pp. 46-55
Author(s):  
S. I. Eleonsky ◽  
Yu. G. Matvienko ◽  
V. S. Pisarev ◽  
A. V. Chernov
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Accumulation Process ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Deformation Response

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

The Frustration Regulation Journal: A Reflective Framework for Educators

Relay Journal ◽  
2019 ◽  
Author(s):  
Sam Morris
Keyword(s):  
Emotion Regulation ◽  
Process Model ◽  
Negative Impact ◽  
Language Education ◽  
Short Article ◽  
Language Classroom ◽  
As Stress ◽  
And Control ◽  
Important System ◽  
Behavioural Strategies

Teachers and advisors involved in the emotional business of language education feel frustrated from time to time, and if such emotions are not managed healthily, they may lead to negative outcomes such as stress and burnout. One important system for taking control of frustration is emotion regulation, the cognitive and behavioural strategies through which individuals manage their emotions. In this short article, I define frustration and discuss its negative impact on the language classroom. I then introduce a structured reflective journaling tool, built upon Gross’s Process model of emotion regulation (Gross, 2014, 2015) which may help teachers and advisors develop greater awareness and control over experiences of frustration.

Sign in / Sign up

Export Citation Format

Share Document