Time Dependent Stress Fields Ahead of the Interface Cracks in Creep Regime

1996 ◽  
Vol 434 ◽  
Author(s):  
S. B. Biner
Keyword(s):  
Applied Load ◽  
Layered Materials ◽  
Time Dependent ◽  
Stress Fields ◽  
Mode I ◽  
Strain Condition ◽  
Transitional Layer ◽  
Interface Cracks ◽  
Stationary Interface ◽  
Creep Regime

AbstractIn this study the behavior of stationary interface cracks in layered materials at creep regime in plane-strain condition and pure opening dominated mode-I load state was studied numerically. The results indicate that the introduction of a transitional layer to the interface of the elastic-creeping bimaterials significantly elevates the stress values ahead of the interface cracks under identically applied load levels at creep regime.

Kinking of Transversal Interface Cracks Between Fiber and Matrix

2006 ◽  
Vol 74 (4) ◽  
pp. 703-716 ◽  
Author(s):  
Federico París ◽  
Elena Correa ◽  
Vladislav Mantič
Keyword(s):  
Boundary Element Method ◽  
Mixed Mode ◽  
Applied Load ◽  
Micromechanical Model ◽  
Circumferential Stress ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Interface Cracks ◽  
The Matrix

Under loads normal to the direction of the fibers, composites suffer failures that are known as matrix or interfiber failures, typically involving interface cracks between matrix and fibers, the coalescence of which originates macrocracks in the composite. The purpose of this paper is to develop a micromechanical model, using the boundary element method, to generate information aiming to explain and support the mechanism of appearance and propagation of the damage. To this end, a single fiber surrounded by the matrix and with a partial debonding is studied. It has been found that under uniaxial loading transversal to the fibers direction the most significant phenomena appear for semidebonding angles in the interval between 60deg and 70deg. After this interval the growth of the crack along the interface is stable (energy release rate (ERR) decreasing) in pure Mode II, whereas it is plausibly unstable in mixed mode (dominated by Mode I for semidebondings smaller than 30deg) until it reaches the interval. At this interval the direction of maximum circumferential stress at the neighborhood of the crack tip is approximately normal to the applied load. If a crack corresponding to a debonding in this interval leaves the interface and penetrates into the matrix then: (a) the growth through the matrix is unstable in pure Mode I; (b) the value of the ERR reaches a maximum (in comparison with other debonding angles); and (c) the ERR is greater than that released if the crack continued growing along the interface. All this suggests that it is in this interval of semidebondings (60-70deg) that conditions are most appropriate for an interface crack to kink. Experiments developed by the authors show an excellent agreement between the predictions generated in this paper and the evolution of the damage in an actual composite.

Stress Analysis in the Combination of Footplate and Caisson Foundation

2016 ◽  
Vol 845 ◽  
pp. 89-93
Author(s):  
Niken Silmi Surjandari ◽  
Yusep Muslih Purwana ◽  
Rensia Erlyana Majid
Keyword(s):  
Bearing Capacity ◽  
Stress Analysis ◽  
Plane Strain ◽  
Contact Pressure ◽  
Applied Load ◽  
Low Cost ◽  
Strain Condition ◽  
Conservative Approach ◽  
Depth Variation ◽  
Properties Of Soil

Currently, the combined footplate-caisson foundation has been used for some projects. This type of foundation is one of the chosen low cost foundations for the structure supporting medium load when the bearing capacity of conventional foundation is not sufficient. The inserted caisson underneath the footing enables to increase its performance; has a better bearing capacity and lower settlement. Unfortunately, the theoretical basic regarding this foundation is not available so that the design tends to use a conservative approach. For this reason, the study on footplate-caisson foundation is essential to obtain the information of its performances. In this study, the combined footplate-caisson was numerically modelled in plane-strain condition as a foundation resting on clay. The footplate was modelled in the depth variation of 0.75 m up to 1.5 m in fixed width of 1.5 m x 1.5 m; whereas the caisson was modelled in depth variation of 0.75 up to 4.5 m in fixed diameter of 1.0 m. The properties of soil and foundation are presented in the paper. The applied load on the model was varied from 60 kPa up to 1000 kPa. The result of the study indicates that the presence of caisson contributes to the decrease in contact pressure in footplate. The percentage of the contribution depends on the dimension of each element and the depth of caisson.

Dynamic cleavage in ductile materials

1986 ◽  
Vol 1 (1) ◽  
pp. 73-80 ◽  
Author(s):  
I.-H. Lin ◽  
R. M. Thomson
Keyword(s):  
Brittle Fracture ◽  
Mixed Mode ◽  
High Speed ◽  
Time Dependent ◽  
Mode I ◽  
Theoretical Treatment ◽  
Mixed Mode Loading ◽  
Dislocation Emission ◽  
Ductile Materials ◽  
Ductile Behavior

Ductile materials are found to sustain brittle fracture when the crack moves at high speed. This fact poses a paradox under current theories of dislocation emission, because even at high velocities, these theories predict ductile behavior. A theoretical treatment of time-dependent emission and cleavage is given which predicts a critical velocity above which cleavage can occur without emission. Estimates suggest that this velocity is in the neighborhood of the sound velocity. The paper also discusses the cleavage condition under mixed mode loading, and concludes that the cleavage condition involves solely the mode I loading, with possible sonic emission under such loadings

The Study of Dynamic Fracture Propagation Using a Special Finite Element Technique

1983 ◽  
Vol 105 (2) ◽  
pp. 232-236 ◽  
Author(s):  
K. W. Chan ◽  
F. T. C. Loo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fracture Propagation ◽  
Time Dependent ◽  
Mode I ◽  
Intensity Factors ◽  
Stationary Crack ◽  
Computational Costs ◽  
Propagating Crack ◽  
Element Technique

An efficient finite element method has been developed for the computation of time-dependent stress intensity factors for cracks of Mode I deformation infinite bodies. Quarter point elements are used near the crack tip to approximate the theoretical singularity. Problems considered herein are: the stationary crack subjected to transient loading conditions, and the rapidly propagating crack. The advantages inherent in this method with regard to accuracy and savings in computational costs are discussed.

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