scholarly journals A dislocation-based solution for stress introduced by arbitrary volume expansion in cylinders

2018 ◽  
Vol 24 (3) ◽  
pp. 598-615 ◽  
Author(s):  
Jici Wen ◽  
Yujie Wei
Keyword(s):  
Volume Expansion ◽  
Radial Direction ◽  
Failure Mechanisms ◽  
Stress Fields ◽  
Engineering Practice ◽  
Cylindrical Structure ◽  
Hydrostatic Tension ◽  
Current Configuration ◽  
The Core ◽  
Arbitrary Volume

A cylindrical structure undergoing volume expansion and contraction is common in engineering practice. For example, the charging (discharging) process of axisymmetrical batteries will give rise to volume expansion (shrinkage). The nitriding process of axles for better fatigue performance also introduces volume expansion. Here, by taking the equivalence of volume expansion (or shrinkage) as continuous insertion (or distraction) of infinitesimal dislocations, we supply a framework to solve the stress field of a cylinder with arbitrary insertion (distraction) profile of materials along the radial direction. Under the assumptions that the volume expansion profile along the axis of a cylinder is uniform and the deformation is small so that the current configuration is regarded as the original, we supply analytical solutions of stress fields to several typical volume expansion or shrinkage profiles. Our analysis shows that different volume variation gives rise to either high tensile stress in the surface or hydrostatic tension in the core, and supplies distinct failure mechanisms in cylindrical batteries.

scholarly journals Physical modelling of failure in composites

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150280 ◽  
Author(s):  
Ramesh Talreja
Keyword(s):  
Composite Materials ◽  
Failure Modes ◽  
Structural Integrity ◽  
Failure Mechanisms ◽  
Local Stress ◽  
Physical Modelling ◽  
Stress Fields ◽  
Systematic Analysis ◽  
Composite Failure ◽  
Failure Theories

Structural integrity of composite materials is governed by failure mechanisms that initiate at the scale of the microstructure. The local stress fields evolve with the progression of the failure mechanisms. Within the full span from initiation to criticality of the failure mechanisms, the governing length scales in a fibre-reinforced composite change from the fibre size to the characteristic fibre-architecture sizes, and eventually to a structural size, depending on the composite configuration and structural geometry as well as the imposed loading environment. Thus, a physical modelling of failure in composites must necessarily be of multi-scale nature, although not always with the same hierarchy for each failure mode. With this background, the paper examines the currently available main composite failure theories to assess their ability to capture the essential features of failure. A case is made for an alternative in the form of physical modelling and its skeleton is constructed based on physical observations and systematic analysis of the basic failure modes and associated stress fields and energy balances. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

Analytical Solutions of Stresses in Functionally Graded Circular Hollow Cylinder with Finite Length

2004 ◽  
Vol 261-263 ◽  
pp. 651-656 ◽  
Author(s):  
Z.S. Shao ◽  
L.F. Fan ◽  
Tie Jun Wang
Keyword(s):  
Young’S Modulus ◽  
Hollow Cylinder ◽  
Finite Length ◽  
Analytical Solutions ◽  
Radial Direction ◽  
Young's Modulus ◽  
Functionally Graded ◽  
Numerical Results ◽  
Stress Fields ◽  
Simply Supported

Analytical solutions of stress fields in functionally graded circular hollow cylinder with finite length subjected to axisymmetric pressure loadings on inner and outer surfaces are presented in this paper. The cylinder is simply supported at its two ends. Young's modulus of the material is assumed to vary continuously in radial direction of the cylinder. Moreover, numerical results of stresses in functionally graded circular hollow cylinder are appeared.

Experimental investigations on the sandwich composite beams and panels with elastomeric foam core

2017 ◽  
Vol 21 (3) ◽  
pp. 865-894 ◽  
Author(s):  
AR Nazari ◽  
H Hosseini-Toudeshky ◽  
MZ Kabir
Keyword(s):  
Carrying Capacity ◽  
Sandwich Structures ◽  
Failure Mechanisms ◽  
Composite Beams ◽  
Core Material ◽  
Foam Core ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying

In this paper, the load-carrying capacity and failure mechanisms of sandwich beams and panels with elastomeric foam core and composite laminate face sheets are investigated. For this purpose, the flexural behavior of laminated composite beams and panels (applied as face sheets) is firstly investigated under three-point bending and central concentrated loads, respectively. Then, the same examination is conducted for the sandwich beams and panels, in which the proposed elastomeric foam is utilized as the core material. It is shown that the failure mechanisms which are associated to the core in the sandwich structures with crushable foams are not considered in the examined sandwich structures. The collapse of the sandwich specimens, examined here, is observed due to the failure of the skins in some steps. By multi-step collapse of these specimens via separately failure of the top and bottom skins, a considerable amount of energy is absorbed between these steps. Due to non-brittle behavior of the core material under loading, a large compression resistance is observed after failure of the top skin which led to the recovery of the load-carrying capacity in the sandwich beams. A similar behavior for the sandwich panels led to the increase of the ultimate strength after appearance of the failure lines on the top skin. The general outcomes of this investigation promise a good influence for the application of elastomeric foam as core material for sandwich structures.

Displacement and Stress Fields in a Functionally Graded Fiber-Reinforced Rotating Disk With Nonuniform Thickness and Variable Angular Velocity

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Y. Zheng ◽  
H. Bahaloo ◽  
D. Mousanezhad ◽  
A. Vaziri ◽  
H. Nayeb-Hashemi
Keyword(s):  
Radial Direction ◽  
Volume Fraction ◽  
Rotating Disk ◽  
Outer Radius ◽  
Functionally Graded ◽  
Circumferential Direction ◽  
Stress Fields ◽  
Fiber Reinforced ◽  
Inner Radius ◽  
Nonuniform Thickness

Displacement and stress fields in a functionally graded (FG) fiber-reinforced rotating disk of nonuniform thickness subjected to angular deceleration are obtained. The disk has a central hole, which is assumed to be mounted on a rotating shaft. Unidirectional fibers are considered to be circumferentially distributed within the disk with a variable volume fraction along the radius. The governing equations for displacement and stress fields are derived and solved using finite difference method. The results show that for disks with fiber rich at the outer radius, the displacement field is lower in radial direction but higher in circumferential direction compared to the disk with the fiber rich at the inner radius. The circumferential stress value at the outer radius is substantially higher for disk with fiber rich at the outer radius compared to the disk with the fiber rich at the inner radius. It is also observed a considerable amount of compressive stress developed in the radial direction in a region close to the outer radius. These compressive stresses may prevent any crack growth in the circumferential direction of such disks. For disks with fiber rich at the inner radius, the presence of fibers results in minimal changes in the displacement and stress fields when compared to a homogenous disk made from the matrix material. In addition, we concluded that disk deceleration has no effect on the radial and hoop stresses. However, deceleration will affect the shear stress. Tsai–Wu failure criterion is evaluated for decelerating disks. For disks with fiber rich at the inner radius, the failure is initiated between inner and outer radii. However, for disks with fiber rich at the outer radius, the failure location depends on the fiber distribution.

Dynamic Response of Sandwich Shells of Revolution

1990 ◽  
Vol 112 (1) ◽  
pp. 98-104 ◽  
Author(s):  
A. V. Singh ◽  
S. Mirza ◽  
K. Gupgupoglu
Keyword(s):  
Radial Direction ◽  
Shell Theory ◽  
Flexural Rigidity ◽  
Elastic Analysis ◽  
Shells Of Revolution ◽  
Linear Elastic ◽  
The Core ◽  
Outer Periphery ◽  
Mass Matrices ◽  
Sandwich Shells

Development of an annular finite element, for the linear elastic analysis of sandwich shells, is reported here. The derivation of stiffness and mass matrices is based on improved shell theory which takes into account the effects of rotary inertia and transverse shear deformation. Flexural rigidity of the faces is included in the formulation. The core of the sandwich shell is assumed to be incompressible in the radial direction. Numerical examples of spherical sandwich shells with two types of boundary conditions—(i) fixed and (ii) pinned along the outer periphery—have been presented. The results are generated for displacements and frequencies.

Numerical Investigations of the Effect of Radial Power Distribution and Inlet Orifice on the Stability Behavior of Parallel Multichannel Type Natural Circulation Boiling Water Reactor

2018 ◽  
Vol 4 (3) ◽  
Author(s):  
Sapna Singh ◽  
Garima Singal ◽  
A. K. Nayak ◽  
Umasankari Kannan
Keyword(s):  
Low Power ◽  
Radial Direction ◽  
Natural Circulation ◽  
Boiling Water ◽  
Boiling Water Reactor ◽  
Type I ◽  
Type Ii ◽  
Water Reactor ◽  
The Core ◽  
The Stability

In a natural circulation boiling water reactor (BWR), the core power varies in both axial and radial directions inside the reactor core. The variation along the axial direction is more or less constant throughout the reactor; however, there exists variation of reactor power in the radial direction. The channels located at the periphery have low power compared to the center of the core and are equipped with orifices at their inlet. This creates nonuniformity in the radial direction in the core. This study has been performed in order to understand the effect of this radial variation of power on the stability characteristics of the reactor. Four channels of a pressure tube type natural circulation BWR have been considered. The reactor has been modeled using RELAP5/MOD3.2. Before using the model, it was first benchmarked with experimental measurements and then the characteristics of both low power and high power oscillations, respectively, known as type-I and type-II instability, have been investigated. It was observed that the type-I instability shows slight destabilizing effect of increase in power variation among different channels. However, in the case of type-II instability, it was found out that the oscillations get damped with an increase in power variation among the channels. A similar effect was found for the presence of orifices at the inlet in different channels. However, the increase in number of orificed channels showed stabilizing effect for both type-I and type-II instabilities.

Failures of sand tailings dams in a highly seismic country

2014 ◽  
Vol 51 (4) ◽  
pp. 449-464 ◽  
Author(s):  
Gabriel Villavicencio ◽  
Raúl Espinace ◽  
Juan Palma ◽  
Andy Fourie ◽  
Pamela Valenzuela
Keyword(s):  
Human Life ◽  
Failure Mechanisms ◽  
Geographical Area ◽  
Economic Losses ◽  
Environmental Damage ◽  
Engineering Practice ◽  
Tailings Dams ◽  
Key Characteristics ◽  
The World ◽  
Construction Operation

Chile is one of the main copper producers in the world. It is located in a geographical area where mega-earthquakes occur and this fact, together with the development of larger and higher sand tailings dams (with some facilities currently under development having final heights in excess of 250 m), requires that careful attention be paid to the safety and security of these facilities. In this paper, the main failure mechanisms of these sand tailings dams that have generated incidents of different magnitude involving loss of human life, significant environmental damage, and economic losses are described. Some key characteristics of reported incidents in Chile are presented, including failures resulting from the mega-earthquake that occurred on 27 February 2010 (Maule Region, Chile). Finally, the engineering practice and present Chilean regulatory framework, which have allowed progressive improvements in the construction, operation, and closure of such deposits, are described.

scholarly journals Mesoscopic Detection of the Influence of a Third Component on the Self-Assembly Structure of A2B Star Copolymer in Thin Films

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1636 ◽  
Author(s):  
Dan Mu ◽  
Jian-Quan Li ◽  
Xing-Shun Cong ◽  
Han Zhang
Keyword(s):  
Self Assembly ◽  
Molecular Design ◽  
Progressive Increase ◽  
Micellar Structure ◽  
Cylindrical Structure ◽  
Application Range ◽  
The Core ◽  
Assembly Structure ◽  
Rational Molecular Design ◽  
Reverse Micellar

The most common self-assembly structure for A2B copolymer is the micellar structure with B/A segments being the core/corona, which greatly limits its application range. Following the principle of structure deciding the properties, a reformation in the molecular structure of A2B copolymer is made by appending three segments of a third component C with the same length to the three arms, resulting (AC)2CB 3-miktoarm star terpolymer. A reverse micellar structure in self-assembly is expected by regulating the C length and the pairwise repulsive strength of C to A/B, aiming to enrich its application range. Keeping both A and B lengths unchanged, when the repulsion strength of C to A is much stronger than C to B, from the results of mesoscopic simulations we found, with a progressive increase in C length, (AC)2CB terpolymer undergoes a transition in self-assembled structures, from a cylindrical structure with B component as the core, then to a deformed lamellar structure, and finally to a cylindrical structure with A component as the core. This reverse micellar structure is formed with the assistance of appended C segments, whose length is longer than half of B length, enhancing the flexibility of three arms, and further facilitating the aggregation of A component into the core. These results prove that the addition of a third component is a rational molecular design, in conjunction with some relevant parameters, enables the manufacturing of the desired self-assembly structure while avoiding excessive changes in the involved factors.

The Core of Engineering Education Is to Cultivate the Students’ Engineering Practical Ability

2011 ◽  
Vol 317-319 ◽  
pp. 240-244
Author(s):  
Xian Wen Miao ◽  
Gen Fu Yuan
Keyword(s):  
Engineering Education ◽  
Engineering Practice ◽  
Education Philosophy ◽  
The Core ◽  
Advanced Experience ◽  
Foreign Countries ◽  
Teaching Position ◽  
Training Mode ◽  
Practice Teaching ◽  
Important Position

The higher engineering education of our country facing the challenge of Manufacturing Globalization, the urgent mission Is to cultivate the engineers who has international vision. Considering this, engineering universities reform of personnel training mode one after another, actively learn from the advanced experience of foreign countries, promoting practical teaching to the important position. Considering the objective of cultivation of our university which is to cultivate the high-quality applied talents, putting the CDIO engineering education philosophy as a guide, this article researches the problems such as practice teaching position and how to cultivate the Engineering consciousness, engineering practice and innovative ability of students in each teaching process of engineer training.

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