scholarly journals Suggestion of a new criterion of dynamic fracture initiation

1995 ◽  
Vol 71 (4) ◽  
pp. R77-R78 ◽  
Author(s):  
Ya-Pu Zhao
Keyword(s):  
Dynamic Fracture ◽  
Fracture Initiation ◽  
New Criterion

Dynamic Fracture of a Beam or Plate in Plane Bending

1976 ◽  
Vol 43 (1) ◽  
pp. 112-116 ◽  
Author(s):  
L. B. Freund ◽  
G. Herrmann
Keyword(s):  
Crack Length ◽  
Dynamic Fracture ◽  
Crack Tip ◽  
Bending Moment ◽  
Fracture Initiation ◽  
Fracture Plane ◽  
Multiple Reflections ◽  
Pure Bending ◽  
Strain Fracture ◽  
Beam Thickness

The dynamic fracture response of a long beam of brittle elastic material subjected to pure bending is studied. If the magnitude of the applied bending moment is increased to a critical value, a crack will propagate from the tensile side of the beam across a cross section. An analysis is presented by means of which the crack length and bending moment at the fracturing section are determined as functions of time after fracture initiation. The main assumption on which the analysis rests is that, due to multiple reflections of stress waves across the thickness of the beam, the stress distribution on the prospective fracture plane ahead of the crack may be adequately approximated by the static distribution appropriate for the instantaneous crack length and net section bending moment. The results of numerical calculations are shown in graphs of crack length, crack tip speed, and fracturing section bending moment versus time. It is found that the crack tip accelerates very quickly to a speed near the characteristic terminal speed for the material, travels at this speed through most of the beam thickness, and then rapidly decelerates in the final stage of the process. The results also apply for plane strain fracture of a plate in pure bending provided that the value of the elastic modulus is appropriately modified.

Dynamic fracture initiation behavior of an HY-100 steel

1993 ◽  
Vol 24 (4) ◽  
Author(s):  
Sunghak Lee ◽  
Je Won Rhyu ◽  
Kyung-Mox Cho ◽  
Jacques Duffy
Keyword(s):  
Dynamic Fracture ◽  
Fracture Initiation

An Experimental Evaluation of the Effects of Filtercake in Wellbore Strengthening: Filtercake Rupture Resistance and Fracture Sealing Time

2019 ◽  
Vol 142 (4) ◽  
Author(s):  
Mingzheng Yang ◽  
Yuanhang Chen
Keyword(s):  
Drilling Fluid ◽  
Experimental Tests ◽  
Fracture Initiation ◽  
Vital Role ◽  
Fracture Sealing ◽  
Initiation Stage ◽  
Induced Fractures ◽  
Wellbore Strengthening ◽  
New Criterion

Abstract Recent research studies have indicated that filtercakes play a role in preventing fracture initiation, blocking pre-existing narrow fractures, and isolating drilling-induced fractures at the initiation stage. The ability of the filtercakes to effectively strengthen the wellbore expectedly depends on its capability in maintaining its integrity and providing the barrier to isolate pressure and fluid transmission between the wellbore and fractures. In this research, a modified permeability apparatus was used to evaluate the quality of drilling fluid filtercakes. A new criterion defined as filtercake rupture resistance is proposed to characterize the filtercake quality regarding its ability to sustain pressure over an open fracture. Experimental tests were conducted to investigate how filtercake thickness and filtercake yield strength affect the rupture resistance. The mechanism of filtercake in sealing the narrow fractures is explored, and it was observed that solid's plugging/bridging plays the vital role in this mechanism. A thicker and stronger filtercake also contributes to a faster establishment of complete fracture seal. The results of this research can be utilized as a reference that guides the optimization of drilling fluid for continuously strengthening the wellbore.

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