Predicting Crack-Formation Life

1979 ◽  
Vol 21 (4) ◽  
pp. 263-273 ◽  
Author(s):  
T. V. Duggan ◽  
M. T. Lowcock ◽  
B. C. Staples
Keyword(s):  
Strain Gradient ◽  
Crack Formation ◽  
Experimental Studies ◽  
Strain Gradients ◽  
Local Material ◽  
Strain Gradient Effects ◽  
Predicted Values ◽  
The Relationship ◽  
Gradient Effects

This paper discusses the parameters likely to influence the crack-formation life of components. In particular, the relationship between the fatigue life of plain and notched specimens is considered, and a mathematical model for predicting the crack-formation life of components is proposed. This allows for the effects of mean stresses and strains and is dependent upon the determination of local material behaviour. The approach is original in that it makes allowances for the influence of the degree of plasticity around a notch, represented in terms of the strain gradient. The Neuber method is evoked, suitably modified to allow for strain gradient effects, and strain gradients are estimated by differentiating Neuber's rule in the immediate vicinity of the notch. Experimental studies have been conducted to determine strain distributions, strain gradients and cyclic lives, and the results compared with predicted values; correlation is good.

Lattice Rotation Patterns and Strain Gradient Effects in Face-Centered-Cubic Single Crystals Under Spherical Indentation

2015 ◽  
Vol 82 (6) ◽  
Author(s):  
Y. F. Gao ◽  
B. C. Larson ◽  
J. H. Lee ◽  
L. Nicola ◽  
J. Z. Tischler ◽  
...  
Keyword(s):  
Single Crystals ◽  
Crystal Plasticity ◽  
Strain Gradient ◽  
Lattice Rotation ◽  
Spherical Indentation ◽  
Strain Gradients ◽  
Discrete Dislocation ◽  
Rotation Field ◽  
Strain Gradient Effects ◽  
Gradient Effects

Strain gradient effects are commonly modeled as the origin of the size dependence of material strength, such as the dependence of indentation hardness on contact depth and spherical indenter radius. However, studies on the microstructural comparisons of experiments and theories are limited. First, we have extended a strain gradient Mises-plasticity model to its crystal plasticity version and implemented a finite element method to simulate the load–displacement response and the lattice rotation field of Cu single crystals under spherical indentation. The strain gradient simulations demonstrate that the forming of distinct sectors of positive and negative angles in the lattice rotation field is governed primarily by the slip geometry and crystallographic orientations, depending only weakly on strain gradient effects, although hardness depends strongly on strain gradients. Second, the lattice rotation simulations are compared quantitatively with micron resolution, three-dimensional X-ray microscopy (3DXM) measurements of the lattice rotation fields under 100 mN force, 100 μm radius spherical indentations in 〈111〉, 〈110〉, and 〈001〉 oriented Cu single crystals. Third, noting the limitation of continuum strain gradient crystal plasticity models, two-dimensional discrete dislocation simulation results suggest that the hardness in the nanocontact regime is governed synergistically by a combination of strain gradients and source-limited plasticity. However, the lattice rotation field in the discrete dislocation simulations is found to be insensitive to these two factors but to depend critically on dislocation obstacle densities and strengths.

Strain-Gradient Effects in Microlayers

1966 ◽  
Vol 92 (5) ◽  
pp. 67-86
Author(s):  
F.D. Day ◽  
Yechiel Weitsman
Keyword(s):  
Strain Gradient ◽  
Strain Gradient Effects ◽  
Gradient Effects

scholarly journals The appliance of prefabricated soil-cement slabs processed with a hydrophobizing material for the road construction

2018 ◽  
Vol 196 ◽  
pp. 04026
Author(s):  
Sergey Sannikov ◽  
Sergey Kuyukov ◽  
Alexey Zamyatin ◽  
Alexandr Zhigailov
Keyword(s):  
Crack Formation ◽  
Experimental Studies ◽  
Road Construction ◽  
Full Scale ◽  
Complex Method ◽  
The Road ◽  
Soil Cement ◽  
Cement Mixture ◽  
Scale Experiment

The paper presents a complex method for increasing water resistance and reducing crack formation by using a prefabricated foundation of soil-cement slabs with surface processing with a hydrophobizing material on basis of organosilicon compounds. Theoretical, laboratory and full-scale experimental studies were made. Theoretical studies are based on the substantiation of the geometric parameters of the slab in order to exclude the probability of its destruction under its own weight during building and installation works. The result of the first stage of laboratory studies is the determination of the optimum composition of soil-cement mixture in order to achieve a grade of strength M20. At the second stage, the effectiveness of the influence of hydrophobizing materials "Tiprom U" and "Penetron-Admix" on water absorption and compressive strength of soil-cement was determined. The final stage of the research was a full-scale experiment. In the factory environment, soil-cement slabs were manufactured in metal forms. Based on the results of the research, conclusions about the effectiveness of this complex method were made. The use of soil-cement slabs allows reducing crack formation, as well as to work all year round due to manufacturing and surface treatment of slabs in the factory conditions.

Strain gradient effects on cyclic plasticity

2010 ◽  
Vol 58 (4) ◽  
pp. 542-557 ◽  
Author(s):  
Christian F. Niordson ◽  
Brian Nyvang Legarth
Keyword(s):  
Strain Gradient ◽  
Cyclic Plasticity ◽  
Strain Gradient Effects ◽  
Gradient Effects
Sign in / Sign up

Export Citation Format

Share Document