Stress concentration in frictional polymeric composites reinforced by oriented fibers

2020 ◽  
pp. 223-229
Author(s):  
V.V. Bardushkin ◽  
A.P. Sychev ◽  
А.А. Sychev
Keyword(s):  
Stress Concentration ◽  
Coordinate System ◽  
Polymer Composites ◽  
Glass Fibers ◽  
Arbitrary Point ◽  
Local Stress ◽  
Rectangular Coordinate System ◽  
Rank Tensor ◽  
External Stresses ◽  
Dispersed Inclusions

Multicomponent frictional polymer composites based on an epoxyphenol binder reinforced with E-glass fibers and dispersed inclusions of rubber, alumina, graphite, and barite are considered. It is believed that glass fibers are oriented along the X and Y axes of a rectangular coordinate system and have the same volume contents in these directions, which corresponds to the reinforcement of the material with fabric. Numerical calculations of the values of the components of the stress concentration operator (a fourth-rank tensor connecting the local stress values at an arbitrary point in an inhomogeneous medium with external stresses applied to the composite) were carried out for the considered frictional polymer composites, taking into account changes in the volume contents of their fillers.

Hemp Fiber Reinforced Composites: Morphological and Mechanical Properties

2011 ◽  
Vol 332-334 ◽  
pp. 121-125
Author(s):  
Xing Mei Guo ◽  
Yi Ping Qiu
Keyword(s):  
Polymer Composites ◽  
Unsaturated Polyester ◽  
Glass Fibers ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Hemp Fiber ◽  
Plant Fibers ◽  
Natural Plant ◽  
Reinforcing Fillers

The use of natural plant fibers as reinforcing fillers in fiber-polymer composites has drawn much interest in recent years. Natural plant fibers as reinforcing fillers have several advantages over inorganic fillers such as glass fibers; they are abundant, readily available, renewable, inexpensive, biodegradable, of low density, and of high specific strength. Hemp fibers are one of the most attractive natural plant fibers for fiber-reinforced composites because of their exceptional specific stiffness. In this review, we summarize recent progress in developments of the hemp fiber reinforced composites such as hemp fiber reinforced unsaturated polyester (UPE), hemp fiber reinforced polypropylene (PP), hemp fiber reinforced epoxy composites, and so on, illustrate with examples how they work, and discuss their intrinsic fundamentals and optimization designs. We are expecting the review to pave the way for developing fiber-polymer composites with higher strength.

An Optimization Design Platform for Fir-Tree Root and Groove for Steam Turbine

2018 ◽  
Author(s):  
Deqi Yu ◽  
Xiaojun Zhang ◽  
Jiandao Yang ◽  
Kai Cheng ◽  
Weilin Shu ◽  
...  
Keyword(s):  
Stress Concentration ◽  
Steam Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Optimization Design ◽  
Turbine Blades ◽  
Local Stress ◽  
Optimization Method ◽  
Steam Turbines ◽  
Geometry Configuration

Fir-tree root and groove profiles are widely used in gas turbine and steam turbine. Normally, the fir-tree root and groove are characterized with straight line, arc or even elliptic fillet and splines, then the parameters of these features were defined as design variables to perform root profile optimization. In ultra-long blades of CCPP and nuclear steam turbines and high-speed blades of industrial steam turbine blades, both the root and groove strength are the key challenges during the design process. Especially, in industrial steam turbines, the geometry of blade is very small but the operation velocity is very high and the blade suffers stress concentration severely. In this paper, two methods for geometry configuration and relevant optimization programs are described. The first one is feature-based using straight lines and arcs to configure the fir-tree root and groove geometry and genetic algorithm for optimization. This method is quite fit for wholly new root and groove design. And the second local optimization method is based on B-splines to configure the geometry where the local stress concentration occurs and the relevant optimization algorithm is used for optimization. Also, several cases are studied as comparison by using the optimization design platform. It can be used not only in steam turbines but also in gas turbines.

Axisymmetric Isothermal Forging

1989 ◽  
Author(s):  
Shiro Kobayashi ◽  
Soo-Ik Oh ◽  
Taylan Altan
Keyword(s):  
Finite Element ◽  
Coordinate System ◽  
Three Dimensions ◽  
Cold Forging ◽  
Axially Symmetric ◽  
Rectangular Coordinate System ◽  
Complex Deformation ◽  
Fem Method ◽  
Natural Coordinate System ◽  
Main Dimension

According to Spies, the majority of forgings can be classified into three main groups. The first group consists of compact shapes that have approximately the same dimensions in all three directions. The second group consists of disk shapes that have two of the three dimensions (length and width) approximately equal and larger than the height. The third group consists of the long shapes that have one main dimension significantly larger than the two others. All axially symmetric forgings belong to the second group, which includes approximately 30% of all commonly used forgings. A basic axisymmetric forging process is compression of cylinders. It is a relatively simple operation and thus it is often used as a property test and as a preforming operation in hot and cold forging. The apparent simplicity, however, turns into a complex deformation when friction is present at the die–workpiece interface. With the finite-element method, this complex deformation mode can be examined in detail. In this chapter, compression of cylinders and related forming operations are discussed. Since friction at the tool–workpiece interface is an important factor in the analysis of metal-forming processes, this aspect is also given particular consideration. Further, applications of the FEM method for complex-shaped dies are shown in the examples of forging and cabbaging. Finite-element discretization with a quadrilateral element is similar to that given in Chap. 8. The cylindrical coordinate system (r, ϑ, z) is used instead of the rectangular coordinate system. The element is a ring element with a quadrilateral cross-section, as shown in Fig. 9.1. The ξ and η of the natural coordinate system vary from −1 to 1 within each element.

A SIMPLIFIED TEXTURAL CLASSIFICATION DIAGRAM

1958 ◽  
Vol 38 (1) ◽  
pp. 54-55 ◽  
Author(s):  
J. A. Toogood
Keyword(s):  
Coordinate System ◽  
Rectangular Coordinate System

A textural diagram based on per cent clay and per cent sand is proposed. With a standard rectangular coordinate system it is easier to use than currently suggested triangles.

scholarly journals On the Moving Trajectory of a Ball in a Viscous Liquid between Two Concentric Rigid Spheres

2018 ◽  
Vol 23 (4) ◽  
pp. 77
Author(s):  
Sergey Gladkov ◽  
Sophie Bogdanova
Keyword(s):  
Differential Equations ◽  
Coordinate System ◽  
Viscous Liquid ◽  
Nonlinear Differential Equations ◽  
Reaction Force ◽  
Arbitrary Point ◽  
System Of Equations ◽  
Rigid Spheres ◽  
Dynamic Motion ◽  
Concentric Spheres

In the paper, the dynamic motion of a point ball with a mass of m , sliding in a viscous liquid between two concentric spheres under the influence of gravity and viscous and dry resistance, is investigated. In addition, it is considered that the ball starts its motion from some arbitrary point M 0 = M ( θ 0 , φ 0 ) . A system of nonlinear differential equations in a spheroidal coordinate system is obtained for the angular variables θ and φ to account for all the forces acting on the ball. The dependence of the reaction force on the angular variables is found, and the solution of the resulting system of equations is numerically analyzed. The projections of the trajectories on the plane x − y ,   y − z ,   x − z are found.

Determination of DC06+ZE Sheet Crack Cause

2016 ◽  
Vol 368 ◽  
pp. 121-125
Author(s):  
Pavel Kejzlar ◽  
Tomáš Pilvousek ◽  
Michal Tregler
Keyword(s):  
Stress Concentration ◽  
Tensile Stress ◽  
Deep Drawing ◽  
Crack Formation ◽  
Local Stress ◽  
Local Deformation ◽  
Local Stress Concentration ◽  
Bcc Lattice ◽  
Hard Particles

The present work deals with determination of the cause of crack occurring in a part of car body manufactured from deep-drawing sheet. UHR-SEM, EDS, EBSD and measurement of microhardness were used for evaluation of the structure, local deformation and crack formation mechanism. A material analysis discovered foreign particles in the material. These particles were identified as MgAl2O4 with BCC lattice. The occurrence of these hard particles led to local stress concentration, decrease in mechanical strength and sheet breach due to tensile stress during deformation.

scholarly journals Strain field evolution at the ductile-to-brittle transition: a case study on ice

Solid Earth ◽  
2017 ◽  
Vol 8 (5) ◽  
pp. 943-953 ◽  
Author(s):  
Thomas Chauve ◽  
Maurine Montagnat ◽  
Cedric Lachaud ◽  
David Georges ◽  
Pierre Vacher
Keyword(s):  
Stress Concentration ◽  
Dynamic Recrystallization ◽  
Strain Field ◽  
Crack Opening ◽  
Local Stress ◽  
Image Correlation ◽  
Brittle Transition ◽  
Field Evolution ◽  
Crack Tips ◽  
Ductile To Brittle Transition

Abstract. This paper presents, for the first time, the evolution of the local heterogeneous strain field around intra-granular cracking in polycrystalline ice, at the onset of tertiary creep. Owing to the high homologous temperature conditions and relatively low compressive stress applied, stress concentration at the crack tips is relaxed by plastic mechanisms associated with dynamic recrystallization. Strain field evolution followed by digital image correlation (DIC) directly shows the redistribution of strain during crack opening, but also the redistribution driven by crack tip plasticity mechanisms and recrystallization. Associated local changes in microstructure induce modifications of the local stress field evidenced by crack closure during deformation. At the ductile-to-brittle transition in ice, micro-cracking and dynamic recrystallization mechanisms can co-exist and interact, the later being efficient to relax stress concentration at the crack tips.

STUDY ON FATIGUE BEHAVIOR OF STRENGTHENED NON-LOAD-CARRYING CRUCIFORM WELDED JOINTS USING CARBON FIBER SHEETS

2012 ◽  
Vol 12 (01) ◽  
pp. 179-194 ◽  
Author(s):  
TAO CHEN ◽  
QIAN-QIAN YU ◽  
XIANG-LIN GU ◽  
XIAO-LING ZHAO
Keyword(s):  
Stress Concentration ◽  
Carbon Fiber ◽  
Welded Joints ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
Local Stress ◽  
Fatigue Loading ◽  
Cfrp Sheets ◽  
Load Carrying ◽  
Weld Toe

This paper reports an experimental study on the use of carbon fiber-reinforced polymer (CFRP) sheets to strengthen non-load-carrying cruciform welded joints subjected to fatigue loading. Failure modes and corresponding fatigue lives were recorded during tests. Scatter of test results was observed. Thereafter, a series of numerical analyses were performed to study the effects of weld toe radius, the number of CFRP layers and Young's modulus of reinforced materials on local stress concentration at a weld toe. It was found that fatigue life of such welded connections can be enhanced because of the reduction of stress concentration caused by CFRP strengthening. Parametric study indicates that the weld toe radius and the amount of CFRP are the key parameters influencing the stress concentration factors and stress ranges of the joint. Enhancement of modulus for adhesive and CFRP sheets can also be beneficial to the fatigue performance to some extent.

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