|
|
Study of crack growing through an interface of two different materials based on analysis of crack profile in the vicinity of crack tip
Bareš, Pavel
Paper describes a numerical study of a crack penetrating the interface between two different elastic materials. The stability conditions of a crack terminating at the interface are formulated. The method introduces herein for these purposes is based on the assumption that the crack will start to propagate through the interface into the second material M2 when the shape of the crack face in the immediate vicinity of the crack tip will correspond to that in the same sample but made of purely homogeneous material M2. The numerical calculations are performed on the sample with surface protective layer under the small scale yielding conditions. The resulting critical stresses are compared with those obtained by other approaches. All results are in qualitative agreement. This method should be applicable in cases of larger crack-tip plastic deformations as well, where so far known methods are not able. All numerical calculations are performed by finite element method (system ANSYS).
|
|
|
Redistribuce napětí a její vliv na precipitaci v mikrostruktuře
Holec, David ; Dlouhý, Antonín
The present study considers two mechanisms that can contribute to the local redistribution of stresses in the microstructure of engineering alloys. The first model takes into account the anisotropy of thermal expansion coefficients and predicts a stress state generated close to a boundary between two differently oriented grains after a temperature change. The second model addresses a stress distribution in a polycrystalline aggregate characterized by anisotropic elastic constants and subjected to the isothermal aging under the assistance of external stress. The influence of local stress states on the selective precipitation of the Ni4Ti3 crystallographic variants in the microstructure of the NiTi shape memory alloy is demonstrated.
|
|
|
A possible approach for assessment of general singular stress concentrators on the basis of linear elastic fracture mechanics
Náhlík, Luboš
This paper studies a stress distribution around a general singular stress concentrator tip on the basis of linear elastic fracture mechanics. A procedure for development of stability criteria of general singular stress concentrators is shown. Three different methods for determination of an essential critical stress for crack propagation from the stress concentrator tip are introduced. Each of used method is useful for different mechanism of crack propagation. The described procedures are based on three dissimilar physical basis: on the energetic ground – the generalized strain energy density factor is mentioned, on the failure stress of material grain ahead of concentrator tip and on the size of plastic zone in front of concentrator tip. The numerical results can contribute to better understanding of general stress concentrators behaviour and can be used for design of engineering structures with mentioned type of stress concentrator
|
|
|
Kritérium stability bi-materiálového vrubu se dvěma singularitami
Klusák, Jan
Interfaces with a step change of material properties occur often in technical constructions. In combination with a sharp notch it usually leads to singular stress distribution in a vicinity of such a wedge. The existence of two singularities seems to be the main problem within study of this stress concentrator. The other problem is that each singularity does not correspond to particular mode of loading. The presented contribution studies stress distribution in a bi-material wedge vicinity and shows a method of solution of the problems in case of existence of multiple stress singularity
|
|
| |
guest ::
