scholarly journals Effect of plastic deformation on the evolution of wear and local stress fields in fretting

2016 ◽  
Vol 82 ◽  
pp. 1-8 ◽  
Author(s):  
Zupan Hu ◽  
Wei Lu ◽  
M.D. Thouless ◽  
J.R. Barber
Keyword(s):  
Plastic Deformation ◽  
Local Stress ◽  
Stress Fields

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’.

scholarly journals Local stress fields in solids estimated by acoustical emission method

2021 ◽  
Vol 2103 (1) ◽  
pp. 012064
Author(s):  
V L Hilarov ◽  
E E Damaskinskaya
Keyword(s):  
Time Series ◽  
Acoustic Emission ◽  
Stress Field ◽  
Estimation Method ◽  
Local Stress ◽  
Stress Fields ◽  
Emission Method ◽  
Macroscopic Fracture ◽  
Stress Estimation ◽  
Kinetic Concept

Abstract Based on the Zhurkov’s kinetic concept of solids’ fracture a local internal stress estimation method is introduced. Stress field is computed from the time series of acoustic emission intervals between successive signals. For the case of two structurally different materials the time evolution of these stresses is examined. It is shown that temporal changes of these stresses’ accumulation law may serve as a precursor of incoming macroscopic fracture.

Comparison between Pile-Up Singularities and Stress Fields Induced by Thin Slip Bands. Application to the Prediction of Grain Boundary Microcrack Nucleation

2013 ◽  
Vol 592-593 ◽  
pp. 61-66
Author(s):  
Maxime Sauzay ◽  
Mohamed Ould Moussa
Keyword(s):  
Slip Band ◽  
Tensile Deformation ◽  
Finite Thickness ◽  
Local Stress ◽  
Stress Fields ◽  
Stress Concentrations ◽  
Griffith Criterion ◽  
Slip Bands ◽  
Pile Up ◽  
Microcrack Initiation

Slip localization is widely observed in metallic polycrystals after tensile deformation, cyclic deformation or pre-irradiation followed by tensile deformation. Such strong deformation localized in thin slip bands induces local stress concentrations in the quasi-elastic matrix around, at the intersections between slip bands (SBs) and grain boundaries (GBs) where microcrack initiation is often observed. Since the work of Stroh, such stress fields have been mostly modeled using the dislocation pile-up theory which leads to stress singularities similar to the LEFM ones. The Griffith criterion has then been widely applied, leading usually to strong underestimations of the macroscopic stress to GB crack initiation. In fact, slip band thickness is finite: 20nm-1000nm depending on material, temperature and loading conditions. Then, many slip planes are plastically activated through the thickness, and not only one single atomic plane. To evaluate more realistic stress fields, numerous crystalline finite element (FE) computations have been carried out using microstructure inputs (slip band aspect ratio, crystal and GB orientation...). A strong influence of slip band thickness close to the slip band corner has been highlighted, which is not accounted for by the pile-up theory. But far away, the thickness has a negligible effect and the predicted stress fields are close to the one predicted by the pile-up theory. Closed-form expressions are deduced from the numerous FE computation results allowing a straightforward prediction of GB stress fields. Slip band plasticity parameters, such as length and thickness, as well as crystal orientation, GB plane and remote stress are taken into account. The dependence with respect to the various parameters can be understood in the framework of matching expansions usually applied to cracks with V notches of finite thickness. As the exponent of the GB stress close-field is only about one-half of the pile-up or LEFM crack one, the Griffith criterion may not be used for GB microcrack prediction in case of finite thickness. That is why finite crack fracture mechanics is used together with both energy and stress criteria. Taking into account SB finite thickness, t>0, leads to predicted remote stresses to GB microcrack initiation three to six times lower than the ones predicted using the to pile-up theory, in agreement with experimental data.

Disordered Nanoparticle Packings under Local Stress Exhibit Avalanche-Like, Environmentally Dependent Plastic Deformation

Nano Letters ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 5418-5425 ◽  
Author(s):  
Joel A. Lefever ◽  
Jason P. Mulderrig ◽  
Jyo Lyn Hor ◽  
Daeyeon Lee ◽  
Robert W. Carpick
Keyword(s):  
Plastic Deformation ◽  
Local Stress

Short Intergranular Cracks in Elasto-Plastic Polycrystalline Aggregate

2002 ◽  
Author(s):  
Leon Cizelj ◽  
Heinz Riesch-Oppermann
Keyword(s):  
Grain Size ◽  
Stress Corrosion ◽  
Steam Generator ◽  
Local Stress ◽  
Stress Fields ◽  
Computational Algorithms ◽  
Polycrystalline Aggregate ◽  
Intergranular Stress Corrosion ◽  
Crack Tips ◽  
Steam Generator Tubes

Computational algorithms aiming at modeling and visualization of the initiation and growth of intergranular stress corrosion cracks (e.g., in the steam generator tubes) on the grain-size scale have already been proposed. Main focus of the paper addresses the influence of randomly oriented anisotropic elasto-plastic grains on the microscopic stress fields at crack tips. The limited number of calculations indicate that the incompatibility strains, which develop along the boundaries of randomly oriented grains, influence the local stress fields (J-integrals) at crack tips significantly.

The Interphase in Unidirectional Fiber-Reinforced Epoxies: Effect on Local Stress Fields

1994 ◽  
Vol 16 (1) ◽  
pp. 21 ◽  
Author(s):  
WS Johnson ◽  
JE Masters ◽  
TK O'Brien ◽  
K Jayaraman ◽  
Z Gao ◽  
...  
Keyword(s):  
Local Stress ◽  
Stress Fields ◽  
Fiber Reinforced ◽  
Unidirectional Fiber

scholarly journals On the Role of Local Grain Interactions on Twin Nucleation and Texture Evolution in Hexagonal Materials

2011 ◽  
Vol 702-703 ◽  
pp. 265-268 ◽  
Author(s):  
Anand K. Kanjarla ◽  
Irene J. Beyerlein ◽  
Ricardo A. Lebensohn ◽  
Carlos Tomé
Keyword(s):  
Grain Boundaries ◽  
Texture Evolution ◽  
Probability Model ◽  
Local Stress ◽  
Stress Fields ◽  
Full Field ◽  
Twin Nucleation ◽  
Deformation Twins ◽  
Hexagonal Materials

Texture evolution in plastically deformed HCP metals is strongly influenced by the nucleation and growth of deformation twins and twin variant selection. Statistically based EBSD analyses of deformed microstructures in HCP metals indicate that the nucleation of deformation twins depends on, among other factors, the local stress fields arising from neighboring grain interactions at grain boundaries [1]. Inspired by these findings a probability model for twin nucleation was developed [2,3], based on the activation of defect sources statistically occurring in grain boundaries. This nucleation model was implemented in a Visco-Plastic Self-Consistent (VPSC) code. Because the latter is based on an Effective Medium assumption and the inclusion formalism, it only provides average stress values in the grains, and the nature of local stress fields at grain boundaries had to be considered in a heuristic manner. In order to have better insight on the effect of local textures on twin nucleation, in this work we employ a viscoplastic full field Fast Fourier Transform (FFT) method as a numerical tool for conducting virtual experiments to study the role of crystal orientation and local neighbor grain interactions on stress localization close to the interfaces and, consequently, on twin nucleation in hexagonal materials, such as Zr and Mg.

The Influence of Aging on Critical Transformation Stress Levels and Martensite Start Temperatures in NiTi: Part I—Aged Microstructure and Micro-Mechanical Modeling

1999 ◽  
Vol 121 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Ken Gall ◽  
Huseyin Sehitoglu ◽  
Yuriy I. Chumlyakov ◽  
Irina V. Kireeva ◽  
Hans J. Maier
Keyword(s):  
Aging Treatment ◽  
Local Stress ◽  
Stress Fields ◽  
Shear Stresses ◽  
Subsequent Paper ◽  
Surrounding Matrix ◽  
Stress Levels ◽  
The Matrix ◽  
Peak Aging ◽  
Transformation Stress

Transmission electron microscopy is used to determine the microstructures of a Ti-50.8 at% Ni alloy given different aging treatments. Two different peak-aging treatments are shown to result in disk shaped semi-coherent Ti3Ni4 precipitates with a diameter ranging from 50 nm to 200 nm depending on the aging temperature. In the peak-aged materials, strong strain fields are clearly visible on TEM micrographs. An Eshelby based model is used to predict the local stress fields due to the differences in the lattice parameters of the precipitates and surrounding matrix. The position dependent local stress fields are then resolved onto the 24 different martensite correspondence variant pairs (CVP’s). It is further demonstrated that due to the unique orientation relationship that exists between the precipitate variants and the martensite CVP’s, the local resolved shear stresses are extremely large on some CVP’s and negligible on others. When the Ni rich NiTi is over-aged, it is found that the precipitates coarsen to approximately 1000nm, they become in-coherent, and the local stress fields disappear. It is also determined that after over-aging the average composition of the matrix drops from 50.8 at% Ni to approximately 50.4 at% Ni. In a subsequent paper (part II) the results here are used to explain the dependence of the critical transformation stress levels and martensite start temperatures on the aging treatment.

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