Microcracks in fatigued FCC polycrystals by interaction between persistent slip bands and grain boundaries

1987 ◽  
Vol 22 (1) ◽  
pp. 113-121 ◽  
Author(s):  
G. Dörr ◽  
C. Blochwitz
Keyword(s):  
Grain Boundaries ◽  
Slip Bands ◽  
Persistent Slip Bands

What types of grain boundaries can be passed through by persistent slip bands?

2003 ◽  
Vol 18 (5) ◽  
pp. 1031-1034 ◽  
Author(s):  
Z. F. Zhang ◽  
Z. G. Wang ◽  
J. Eckert
Keyword(s):  
Grain Boundaries ◽  
Large Angle ◽  
Fatigue Cracking ◽  
Stress Axis ◽  
Slip Systems ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
Different Types ◽  
The Difference ◽  
Intergranular Fatigue Cracking

Three typical interactions of persistent slip bands (PSBs) with different types of grain boundaries (GBs) were investigated and analyzed in fatigued copper crystals. The results show that PSBs cannot transfer through all types of large-angle GBs, regardless of their orientation with respect to the stress axis. Secondary slip was often observed near the GBs, leading to strain incompatibility. When the slip systems of the two adjacent crystals are coplanar, the transmission of a PSB across a GB strongly depends on the slip directions of the two adjacent crystals. It was found that only the low-angle GBs can be passed through by PSBs, and accordingly they are insensitive to intergranular fatigue cracking. For a special copper bicrystal with coplanar slip systems, the ladderlike dislocation arrangements within the adjacent PSBs become discontinuous and a dislocation-affected-zone appears near the GB due to the difference in the slip direction of the two adjacent crystals. Therefore, the necessary conditions for the transmission of a PSB across a GB are that the neighboring grains have a coplanar slip system and identical slip directions.

Ex and in situ investigations on the role of persistent slip bands and grain boundaries in fatigue crack initiation

2017 ◽  
Vol 32 (23) ◽  
pp. 4276-4286 ◽  
Author(s):  
Heinz Werner Höppel ◽  
Philip Goik ◽  
Christian Krechel ◽  
Mathias Göken
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Grain Boundaries ◽  
Fatigue Crack Initiation ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
Image Position

Abstract

The initial fatigue crack

1957 ◽  
Vol 242 (1229) ◽  
pp. 189-197 ◽  
Keyword(s):  
Fatigue Crack ◽  
Grain Boundaries ◽  
Low Temperatures ◽  
Room Temperature ◽  
Fatigue Cracks ◽  
Slip Bands ◽  
Persistent Slip Bands

A discussion is given of the formation of persistent slip bands during cyclic stressing and their development into fatigue cracks. In copper and in aluminium at low temperatures fatigue cracks appear to be formed in this way; at room temperature in aluminium they may form also along grain boundaries.

Experimental investigation of cyclic plasticity continuum damage evolution in an engineering component subjected to thermal loading

1993 ◽  
Vol 28 (4) ◽  
pp. 263-272 ◽  
Author(s):  
F P E Dunne ◽  
D B Puttergill ◽  
D R Hayhurst ◽  
Q J Mabbutt
Keyword(s):  
Grain Boundaries ◽  
Thermal Loading ◽  
Cyclic Plasticity ◽  
Test Facility ◽  
Thermal Shock Test ◽  
Continuum Damage ◽  
Loading Test ◽  
Cyclic Thermal Loading ◽  
Slip Bands ◽  
Persistent Slip Bands

A thermal shock test facility is designed and built to enable to enable a copper model slag tap component to be tested under cyclic thermal loading conditions. Infra-red line heaters and pumped cooling water are used to impose temperature loading cycles on to the specimen. Accurate focussing of the line heaters using a two degree of freedom adjustment mechanism, enables a heating area of width 3 mm to be applied to the specimen. Both the heating and the cooling processes are controlled by a proportional, integral, and derivative feedback micro-processor controller. Specimen temperature fields are obtained using thermocouples, and specimen displacements and strains are measured using linear voltage displacement transducers and strain gauges. A cyclic thermal loading test is carried out for approximately 7150 cycles on a model slag tap component. The variations of specimen strains and displacements are recorded and compared with results obtained from a finite element viscoplastic damage analysis. Good agreement between the predicted and experimental results is obtained. Microstructural examination of the specimen reveals the development of persistent slip bands and micro-cracking at grain boundaries. This occurs at the regions of the specimen undergoing cyclic plasticity due to the imposed cyclic thermal loading. The experimental observations of cyclic plasticity damage formation in copper undergoing cyclic thermal loading indicates the suitability of the Continuum Damage Mechanics (CDM) theory to model the evolution of cyclic plasticity damage. The damage is characterized by the development of fields of micro-cracked grain boundaries due to the formation and interaction of persistent slip bands within the grains.

Formation of Persistent Slip Band in Fatigued Copper Single Crystals

1982 ◽  
Vol 40 ◽  
pp. 470-471
Author(s):  
N. Y. Jin
Keyword(s):  
Volume Fraction ◽  
Fatigue Cracks ◽  
Wall Structure ◽  
Matrix Structure ◽  
Dislocation Dipole ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
The Matrix ◽  
Hard Shell ◽  
Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

Fatigue hardening and nucleation of persistent slip bands in copper

1982 ◽  
Vol 30 (3) ◽  
pp. 711-718 ◽  
Author(s):  
O.B Pedersen ◽  
A.T Winter
Keyword(s):  
Slip Bands ◽  
Persistent Slip Bands
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