Local Effects and Defect Criticality in Homogeneous and Laminated Structures

1989 ◽  
Vol 111 (2) ◽  
pp. 136-150 ◽  
Author(s):  
J. T. Pindera
Keyword(s):  
Three Dimensional ◽  
Experimental Methods ◽  
Theoretical Framework ◽  
Stress Fields ◽  
Local Effects ◽  
Crack Tips ◽  
Plates And Shells ◽  
Stress States ◽  
Laminated Structures

The paper presents a theoretical framework of a more comprehensive methodology of analysis of behavior of homogeneous and composite materials and structures. The behavior of bolted flanged connections is taken as an illustrative example. Particular attention is given to the local effects. The term “local effects” denotes the actual, pronounced local three-dimensional stress states which exist in particular regions of the actual, weakly three-dimensional, stress fields occurring in plates and shells. Presented examples show that the local effects can be one of the major causes of failures of homogeneous or composite laminated structures. Within the chosen theoretical framework, an outline of new analytical/experimental methods is presented, called isodyne methods. It is demonstrated that the isodyne methods allow the determination of the normal and shear components of the stress states in plates and beams, including the three-dimensional stress states at the crack tips, tips of local disbounds or defects, or in the lamination planes.

The Determination of Macrostresses (Type-I Stresses) and Microstresses (Type-Ii Stresses) by Neutron Diffraction

1994 ◽  
Vol 376 ◽  
Author(s):  
T.M. Holden
Keyword(s):  
Neutron Diffraction ◽  
Experimental Methods ◽  
Stress Fields ◽  
Type I ◽  
Type Ii ◽  
Sources Of Error ◽  
Precision And Accuracy

ABSTRACTNeutron diffraction has been used as tool for measuring stress fields (type-I stresses) and intergranular or microstresses (type-II stresses) for a decade. The experimental methods for measuring the two types of stresses are outlined. Emphasis is placed on maximizing the precision and accuracy of the measurements. Some serious sources of error in measurements near surfaces and some subtle wavelength effects are considered.

Eigenstresses in Anisotropic Films

1991 ◽  
Vol 239 ◽  
Author(s):  
Ferdinando Auricchio ◽  
Mauro Ferrari
Keyword(s):  
Stress Field ◽  
Experimental Determination ◽  
Three Dimensional ◽  
Closed Form Solution ◽  
Form Solution ◽  
Ceramic Film ◽  
Stress States ◽  
Resultant Stress ◽  
Structural Theories

ABSTRACTA closed-form solution for a macroscopically homogeneous, fully anisotropie layer subject to non-uniform through-thickness eigenstrain is presented, and employed in determining the three-dimensional deformation and stress states of a thermally loaded ceramic film with microstructure-induced macroscopic anisotropy. The resultant stress field is compared with those that could be deduced by experimental determination of the curvature and the classical structural theories.

Dynamic Characteristics of Elastic Bonding in Composite Laminates: A Free Vibration Study

2003 ◽  
Vol 70 (6) ◽  
pp. 860-870 ◽  
Author(s):  
K. M. Liew ◽  
J. Z. Zhang ◽  
T. Y. Ng ◽  
J. N. Reddy
Keyword(s):  
Free Vibration ◽  
Composite Laminates ◽  
Present Model ◽  
Three Dimensional ◽  
Theory Of Elasticity ◽  
Bonding Layer ◽  
Dimensional Theory ◽  
Perfect Bonding ◽  
Stress States ◽  
Laminated Structures

In conventional analyses of composite laminates, the assumption of perfect bonding of adjoining layers is well accepted, although this is an oversimplification of the reality. It is possible that the bond strength may be less than that of the laminae. Thus, the study of weak bonding is an interesting focus area. In this study, an elastic bonding model based on three-dimensional theory of elasticity in a layerwise framework is used to study composite laminates. The differential quadrature (DQ) discretization is used to analyze the layerwise model. The present model enables the simulation of actual bonding stress states in laminated structures. The interfacial characteristics of transverse stress continuity as well as the kinematic continuity conditions are satisfied through the inclusion of the elastic bonding layer. The present model is employed to investigate the free vibration of thick rectangular cross-ply laminates of different boundary conditions and lamination schemes.

scholarly journals Application of J2 Integral Method in Calculating Complicated Stress Intensity Factors on Three-dimensional Components

2021 ◽  
Vol 293 ◽  
pp. 02012
Author(s):  
Long. Li ◽  
Yousheng. Deng ◽  
Liqing Meng ◽  
Lingtao Li ◽  
Yunfang Zheng
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Integral Method ◽  
Three Dimensional ◽  
Crack Tip ◽  
Stress Fields ◽  
Experimental Result ◽  
Intensity Factors ◽  
Corner Crack ◽  
Crack Tips

In this paper, a technique to determine complicated stress intensity factors on three-dimensional components, which based on the conservation law and the elementary mechanics is proposed, it only needs the geometric relationship between multiple singular stress fields from the crack section, and obtaind the relationship between the stress at different crack tips. In the expression of the stress intensity factor K, K is proportional to the stress σ at the crack tip, and we can get the supplementary equation of between different stress fields K according to the ratio of the stress at the crack tip, then use the J-integral method to calculate the stress intensity factors of different stress fields. In order to verify the feasibility of this method, a cracked R-fluted shells model was constructed. Under the action of the bending moment, the corner crack propagation is simulated through the reserved corner crack, and two crack tips with different stress fields are generated during the simulation. The experimental result indicates that the proposed method is effective for cracked R-fluted shells. It is also shown that the method has universal applicability for solving complex stress intensity factors on three-dimensional components.

Intragranular three-dimensional stress tensor fields in plastically deformed polycrystals

Science ◽  
2019 ◽  
Vol 366 (6472) ◽  
pp. 1492-1496 ◽  
Author(s):  
Yujiro Hayashi ◽  
Daigo Setoyama ◽  
Yoshiharu Hirose ◽  
Tomoyuki Yoshida ◽  
Hidehiko Kimura
Keyword(s):  
Stress Tensor ◽  
Multiscale Modeling ◽  
Uniform Elongation ◽  
Three Dimensional ◽  
High Energy ◽  
Stress Fields ◽  
Polycrystalline Materials ◽  
Tensor Fields ◽  
Deformation And Failure ◽  
Stress States

The failure of polycrystalline materials used in infrastructure and transportation can be catastrophic. Multiscale modeling, which requires multiscale measurements of internal stress fields, is the key to predicting the deformation and failure of alloys. We determined the three-dimensional intragranular stress tensor fields in plastically deformed bulk steel using a high-energy x-ray microbeam. We observed intragranular local stresses that deviated greatly from the grain-averaged stresses and exceeded the macroscopic tensile strength. Even under deformation smaller than the uniform elongation, the intragranular stress fields were in highly triaxial stress states, which cannot be determined from the grain-averaged stresses. The ability to determine intragranular stress tensor fields can facilitate the understanding and prediction of the deformation and failure of materials through multiscale modeling.

Research Advances in the Dynamic Stability Behavior of Plates and Shells: 1987–2005—Part I: Conservative Systems

2007 ◽  
Vol 60 (2) ◽  
pp. 65-75 ◽  
Author(s):  
S. K. Sahu ◽  
P. K. Datta
Keyword(s):  
Dynamic Stability ◽  
Parametric Excitation ◽  
Dynamic Instability ◽  
Three Dimensional ◽  
Plate And Shell ◽  
Plates And Shells ◽  
Instability Regions ◽  
Nonconservative Loading ◽  
Stability Of Structures

This paper reviews most of the recent research done in the field of dynamic stability/dynamic instability/parametric excitation/parametric resonance characteristics of structures with special attention to parametric excitation of plate and shell structures. The solution of dynamic stability problems involves derivation of the equation of motion, discretization, and determination of dynamic instability regions of the structures. The purpose of this study is to review most of the recent research on dynamic stability in terms of the geometry (plates, cylindrical, spherical, and conical shells), type of loading (uniaxial uniform, patch, point loading …), boundary conditions (SSSS, SCSC, CCCC …), method of analysis (exact, finite strip, finite difference, finite element, differential quadrature, and experimental …), method of determination of dynamic instability regions (Lyapunovian, perturbation, and Floquet’s methods), order of theory being applied (thin, thick, three-dimensional, nonlinear …), shell theory used (Sanders’, Love’s and Donnell’s), materials of structures (homogeneous, bimodulus, composite, FGM …), and the various complicating effects such as geometrical discontinuity, elastic support, added mass, fluid structure interactions, nonconservative loading and twisting, etc. The important effects on dynamic stability of structures under periodic loading have been identified and influences of various important parameters are discussed. A review of the subject for nonconservative systems in detail will be presented in Part 2. This review paper cites 156 references.

scholarly journals Revealing 3D magnetization of thin films with soft X-ray tomography: magnetic singularities and topological charges

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Hierro-Rodriguez ◽  
C. Quirós ◽  
A. Sorrentino ◽  
L. M. Alvarez-Prado ◽  
J. I. Martín ◽  
...  
Keyword(s):  
Thin Film ◽  
Topological Charge ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Experimental Methods ◽  
Transmission Microscopy ◽  
X Ray ◽  
Magnetic Dichroism ◽  
Topological Charges

AbstractThe knowledge of how magnetization looks inside a ferromagnet is often hindered by the limitations of the available experimental methods which are sensitive only to the surface regions or limited in spatial resolution. Here we report a vector tomographic reconstruction based on soft X-ray transmission microscopy and magnetic dichroism data, which has allowed visualizing the three-dimensional magnetization in a ferromagnetic thin film heterostructure. Different non-trivial topological textures have been resolved and the determination of their topological charge has allowed us to identify a Bloch point and a meron-like texture. Our method relies only on experimental data and might be of wide application and interest in 3D nanomagnetism.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

Sign in / Sign up

Export Citation Format

Share Document