Begell House Inc.
Composites: Mechanics, Computations, Applications: An International Journal
CMCA
2152-2057
8
4
2017
CALCULATION OF THERMAL STRESSES IN A SUBSTRATE−COATING SYSTEM
267-286
10.1615/CompMechComputApplIntJ.v8.i4.10
A. N.
Astapov
Moscow Aviation Institute (National Research University), 4 Volokolamskoe
Highway, Moscow, 125080, Russia
D. V.
Nushtaev
TESIS Limited Liability Company, Moscow, Russia
Lev N.
Rabinskiy
Department of Engineering Education, Moscow Aviation Institute (National
Research University), 4 Volokolamskoe Highway, Moscow, 125080,
Russian Federation
multilayer system
substrate
functional coating
stress–strain state
thermal stresses
residual stresses
finite element method
This publication is devoted to the creation and development of mathematical models and methods for estimating the level and regions of localization of thermal stresses arising in the substrate–coating system. The study of the strain–stress state (SSS) is carried out by successively increasing the
mathematical model used in order to increase the degree of conformity between the results obtained and the physics of the process under consideration.
The SSS, free from external forces and fastenings, was analytically investigated for a two-layer substrate–coating system under smooth thermal loading. A simply connected thermoelasticity problem was considered in the formulation of a plane-stress state. The SSS estimate was carried
out in the zero-moment approximation (without including the bending) under the assumption of a constant temperature over the wall thickness. The temperature dependences of thermal stresses in the wall layers were constructed. It was revealed that the current level of stress in the layers
depends, first of all, on the difference between the true coefficients of the temperature linear expansion
of the substrate and coating materials, as well as on the values of their elasticity moduli, Poisson's
coefficients, and thicknesses.
The numerical solution built on the basis of the finite element method (FEM) of the boundary-value problem of classical thermoelasticity, corresponding to the model underlying the analytical solution, led to identical results. The shortcomings and limitations introduced into the solution by the considered assumptions have been revealed.
A refined solution of the problem of determining the SSS in the substrate–coating system was proposed for thermal loading on the basis of the FEM, taking into account the arising flexural deformations. The solution was obtained for a semi-infinite plate in the formulation for generalized
plane deformation. of the account for bending led to a significant change in the level and nature of the distribution of thermal stresses along the wall thickness. It is shown that calculating SSS without explicitly taking into account the geometric shape of the substrate, even in the simplest case of a semi-infinite plate, leads to unacceptable errors. The basic requirements for finite-element models applied to the study of SSS in the substrate–coating system have been developed.
The SSS correction was carried out in the substrate–coating system on the basis of FEM by including the possibility of formation of irreversible plastic deformations in the coating layer at various temperatures. The associated flow law with the Mises yield criterion was used for the description of the elastic-plastic behavior of the coating material. It was shown that the appearance of inelastic deformations in the coating significantly affects the level of thermal stresses in the entire system.
The evaluation of the level and nature of the stress distribution makes it possible to scientifically approach the development of the coating architecture (the choice of the chemical and phase composition of the layers, their number and thickness), and to significantly reduce the number of experimental studies and tests, as well as the time and costs for their implementation.
3D FINITE ELEMENT ANALYSIS OF DEFICIENT HOLLOW STEEL BEAMS STRENGTHENED USING CFRP COMPOSITE UNDER TORSIONAL LOAD
287-297
10.1615/CompMechComputApplIntJ.v8.i4.20
Amir Hamzeh
Keykha
Department of Civil Engineering, Zahedan Branch, Islamic Azad University, Zahedan, Iran
hollow steel beams
strengthening
CFRP
finite element investigation
torsional loading
In recent years, strengthening of steel square hollow sections (SHS) using carbon fiber reinforced polymer (CFRP) has attracted the attention of many researchers. Most of the previous research in this field has been done on the behavior of steel members without deficiency in bending, shear, and compression strengthened using CFRP composite. Few studies have been conducted on steel torsional
beams strengthened using CFRP, and to the author's knowledge, no research on the behavior of CFRP strengthened deficient hollow steel beams under torsional load has been presented. The deficiency in steel beams may be created due to the errors caused by construction, fatigue cracking,
drilling after building for passing building installation, corrosion, earthquake damage, and so on. However, this study explored the effect of the use of adhesively bonded CFRP flexible sheets on the structural behavior of SHS steel torsional beams having initial deficiencies, using finite element investigation. To study the effects of the CFRP strengthening method on recovering the strength lost in the deficient beams, twelve hollow steel beams with different deficiencies that were strengthened using CFRP sheets, four nonstrengthened hollow steel beams with different deficiencies, and one nonstrengthened hollow steel beams without deficiency as a control column were analyzed. To
analyze the beams, three-dimensional (3D) modeling and nonlinear static analysis methods using ANSYS software were applied. The results indicated that application of CFRP sheets for strengthening of deficient torsional hollow steel beams could recover the strength lost due to deficiency,
significantly.
BENDING OF A THIN RECTANGULAR ISOTROPIC PLATE: A COSSERAT ELASTICITY ANALYSIS
299-314
10.1615/CompMechComputApplIntJ.v8.i4.30
Soumen
Shaw
Indian Institute of Engineering Science and Technology,Shibpur
Cosserat elasticity
bending of a plate
transverse loading
theory of deflection
The present paper deals with the mechanical behavior of a thin rectangular isotropic plate obeying the Cosserat theory of elasticity. Within the framework of infinitesimal theory of elasticity, the bending of the plate subjected to transverse loading is analyzed. The governing equations of motion are obtained based on the method of hypothesis. A semianalytical solution is presented for the governing equations using the approximation theory of Timoshenko. The solution is endorsed by comparing the numerical results with their counterparts reported in the literature for the classical Timoshenko plate theory and the Kirchhoff theory of plate deformation.
BALLISTIC IMPACT PERFORMANCE OF SMATed 304 STAINLESS STEEL AND HYBRIDIZED COMPOSITES
315-338
10.1615/CompMechComputApplIntJ.v8.i4.40
Yun
Wan
School of Civil Engineer and Architecture, East China Jiaotong University,
Changbei Open and Developing District, Nanchang, 330013, China
Gusheng
Tong
School of Civil Engineer and Architecture, East China Jiaotong University,
Changbei Open and Developing District, Nanchang, 330013, China
Shenshen
Chen
School of Civil Engineer and Architecture, East China Jiaotong University,
Changbei Open and Developing District, Nanchang, 330013, China
Xing
Wei
School of Civil Engineer and Architecture, East China Jiaotong University,
Changbei Open and Developing District, Nanchang, 330013, China
ballistic impact
SMAT
hybrid material
interface damage evolution
Due to the excellent mechanical performance, much research on nanocrystalline metals has been done in recent years. Surface mechanical attrition treatment (SMAT) is an excellent method for obtaining nanocrystalline and nanotwinned ultrafine crystalline steels from coarse-grained AISI 304 stainless steel. These both appear to be suitable candidates for ballistic protection due to their
outstanding mechanical properties. In this paper, the methodology of numerical simulation of the ballistic performance (limited by 600 m/s) of SMATed 304 stainless steel hybridized with a carbon fiber–epoxy composite layer is presented. Based on the Johnson–Cook flow stress model, the user's material subroutine VUMAT, and the surface-based cohesive behavior (SBCB), the simulation demonstrates not only the residual velocity and deformation, but also the damage evolution of steel layers, composite layers, and the delamination between composites and steel layers. The
mechanisms of the failure of the hybrid material due to ballistic impact are very well represented. The accuracy and efficiency of our numerical methodology permits it to be used for predicting the ballistic performance and designing the structure of other hybrid materials.
HIGH-FREQUENCY APPROXIMATION OF PLANE WAVE PROPAGATION IN AN ELASTIC MEDIUM WITH PERIODIC DISTRIBUTION OF CRACKS
339-354
10.1615/CompMechComputApplIntJ.v8.i4.50
Alexey V.
Talonov
University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas,
NV 89154, USA
Viktoria L.
Savatorova
Central Connecticut State University, 1615 Stanley Str., New Britain,
CT 06050, USA
Alexander N.
Vlasov
Institute of Applied Mechanics, Russian Academy of Sciences, 7 Leningradsky Ave., Moscow, 125040, Russia
fractured periodic medium
acoustic waves
high-frequency approximation
two-scale expansions for homogenization
Floquet–Bloch waves
In this work, we consider the propagation of plane waves in elastic media weakened by isolated open cracks with periodic distribution of their concentration. The problem under study is essentially multiscale. One can distinguish several space scales such as the characteristic size of a crack,
a period of crack distribution l, wavelength λ, and the characteristic size of the sample as a whole L. We are interested in the high-frequency approximation, by which we mean the case where the wavelength is small in comparison with the macroscopic size of the problem (λ << L). In this situation, the classical multiscale homogenization does not work. However, for the case where the wavelength exceeds the characteristic size of a crack, but is of the same order of magnitude as the period of distribution of cracks concentration (λ ~ l), it is possible to perform perturbations with respect to the small parameter ε = l/L << 1 and get displacements and frequencies of oscillations in cracked media in the form of two-scale asymptotic expansions.
Index, Volume 8, 2017
355-359
10.1615/CompMechComputApplIntJ.v8.i4.60