scholarly journals The coupled criterion for description of fatigue fracture. Material embrittlement in pre-fracture zone

2018 ◽  
Vol 165 ◽  
pp. 13008 ◽  
Author(s):  
Vladimir M. Kornev
Keyword(s):  
Cyclic Loading ◽  
Fracture Zone ◽  
Average Rate ◽  
Crack Tip ◽  
Loading Conditions ◽  
Dugdale Model ◽  
Zone Width ◽  
Loading Mode ◽  
Tip Extension ◽  
Specific Implementation

Step-wise extension of a crack in quasi-brittle materials under low-cycle loading conditions is considered. Both steady and unsteady loadings in pulsating loading mode are studied. It is proposed to use quasi-brittle fracture diagrams for bodies under cyclic loading conditions. When diagrams are plotted, both necessary and sufficient fracture criteria by Neuber-Novozhilov are used. A specific implementation is made on the base of the Leonov-Panasyuk-Dugdale model for the mode I cracks when the pre-fracture zone width coincides with the plasticity zone width near the crack tip. The condition of a step-wise crack tip extension has been derived. A crack extends only in the embrittled material of the pre-fracture zone. The number of cycles between jumps of the crack tip is calculated by the Coffin equation, when damage accumulation in material in the pre-fracture zone is taken into account. Critical fracture parameters under low-cyclic loading conditions have been obtained in a closed form. Estimates of the average rate of crack tip advance for a loading cycle at step-wise crack extension and S − N curves have been obtained.

Crack Tip Damage Mechanism under Monotonic and Cyclic Loading Conditions

2009 ◽  
Vol 417-418 ◽  
pp. 105-108
Author(s):  
Himadri Roy ◽  
S. Sivaprasad ◽  
S. Tarafder ◽  
Kalyan Kumar Ray
Keyword(s):  
Stainless Steel ◽  
Cyclic Loading ◽  
Fracture Resistance ◽  
Compressive Load ◽  
Crack Tip ◽  
Damage Mechanism ◽  
J Integral ◽  
Loading Conditions ◽  
R Ratio ◽  
304Ln Stainless Steel

Fracture resistance of AISI 304LN stainless steel has been examined by monotonic and cyclic J-integral tests, the latter being carried out using periodic unloading as per pre-determined R-ratio. The cyclic fracture resistance is found to be almost 1/5th of its corresponding monotonic value. The deterioration of fracture resistance under cyclic loading has been attributed to crack tip resharpening due to smearing and smashing of voids owing to rubbing of adjacent crack surfaces in the compressive load cycles.

The Effect of T-Stress on Crack-Tip Plastic Zones Under Cyclic Mixed-Mode Loading Conditions

2013 ◽  
Author(s):  
Qays Nazarali ◽  
Xin Wang
Keyword(s):  
Stress Intensity ◽  
Cyclic Loading ◽  
Stress Field ◽  
Plastic Zone ◽  
Mixed Mode ◽  
Crack Tip ◽  
Mode I ◽  
Loading Conditions ◽  
T Stress ◽  
Plastic Zones

In this paper, the influence of T-stress on crack-tip plastic zones under mixed-mode I and II loading conditions under cyclic loading is examined. The crack-tip stress field is defined in terms of the ranges of mixed-mode stress intensity factors and the T-stress using William’s series expansion. The crack-tip stress field is incorporated into the Von Mises yield criteria to develop an expression that determines the cyclic crack-tip plastic zone. Using the resultant expression, the cyclic plastic zone is obtained for various combinations of mode II to mode I stress intensity factor ratios and levels of T-stress. For the purpose of demonstrating the significance of the T-stress, this paper further analyses the plastic zone size for center cracked plate (CCP) specimen subjected to bi-axial mixed-mode cyclic loading.

CTOD Application to Elastic-Plastic Fracture Mechanics Using Cyclic Ramberg-Osgood Law and HRR Solution

2012 ◽  
Author(s):  
Piotr Bednarz ◽  
Ilya Fedorov ◽  
Jaroslaw Szwedowicz
Keyword(s):  
Cyclic Loading ◽  
Fracture Mechanics ◽  
Crack Closure ◽  
Crack Tip ◽  
Compact Tension ◽  
Loading Conditions ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Tip Opening ◽  
Closure Effect

Very often in the open literature the crack propagation simulation is based on the linear elastic fracture mechanics. This article describes a novel application of the cyclic crack tip opening displacement (ΔCTOD) method for evaluation of the cyclic nonlinear energy release rate under large plasticity and cyclic loading conditions. In order to consider the cyclic loading in the Hutchinson-Rice-Rosengren (HRR) solution, the monotonic plastic deformation of the material behaviour needs to be replaced by its cyclic counterpart. During cyclic loading conditions, a reverse plasticity occurs and leads to a crack closure effect via blunting of the crack tip. As a result, crack flanks are in contact during compression. This effect is determined from the effective difference between the maximum and minimum crack deformation. Then, the cyclic crack tip opening displacement is evaluated by applying the Shih rule. The proposed extension of the HRR solution in application to cyclic loading conditions via stress and strain transformation as well as accounting for the crack closure effect is validated in a good agreement with Dowling and Begley Compact Tension (CT) experiment. Potential crack closure due to crack surface roughness is neglected in current modeling. The proposed methodology extends the existing HRR solution for the reliable lifetime prediction.

scholarly journals In situ monitoring of dislocation, twinning, and detwinning modes in an extruded magnesium alloy under cyclic loading conditions

2021 ◽  
Vol 806 ◽  
pp. 140860
Author(s):  
Di Xie ◽  
Zongyang Lyu ◽  
Yuan Li ◽  
Peter K. Liaw ◽  
Huck Beng Chew ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Cyclic Loading ◽  
In Situ Monitoring ◽  
Loading Conditions

Fatigue Crack Growth Tests on Glass Fibre Reinforced Polymer Matrix Composite

2005 ◽  
Vol 473-474 ◽  
pp. 189-194
Author(s):  
Zilia Csomós ◽  
János Lukács
Keyword(s):  
Cyclic Loading ◽  
Crack Opening Displacement ◽  
Matrix Composite ◽  
Glass Fibre ◽  
Crack Opening ◽  
Loading Conditions ◽  
Opening Displacement ◽  
Interfacial Cracks ◽  
Glass Fibre Reinforced ◽  
Number Of Cycles

E-glass fibre reinforced polyester matrix composite was investigated, which was made by pullwinding process. Round three point bending (RTPB) specimens were tested under quasi-static and mode I cyclic loading conditions. Load vs. displacement (F-f), load vs. crack opening displacement (F-v) and crack opening displacement range vs. number of cycles (ΔCOD-N) curves were registered and analysed. Interfacial cracks were caused the final longitudinal fracture of the specimens under quasi-static and cyclic loading conditions.

Electrical Resistance and Acoustic Emission During Fatigue Testing of Pristine and High Velocity Impact SiC/SiC Composites at Room and Elevated Temperature

2016 ◽  
Author(s):  
Zipeng Han ◽  
Gregory N. Morscher ◽  
Emmanuel Maillet ◽  
Manigandan Kannan ◽  
Sung R. Choi ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Acoustic Emission ◽  
Cyclic Loading ◽  
Electrical Resistance ◽  
Fatigue Testing ◽  
Early Stage ◽  
Loading Conditions ◽  
Initial Attempt ◽  
Matrix Cracks ◽  
Sic Composites

Electrical resistance (ER) is a relatively new approach for real-time monitoring and evaluating damage in SiC/SiC composites for a variety of loading conditions. In this study, ER of woven silicon carbide fiber-reinforced silicon carbide composite systems in their pristine and impacted state were measured under cyclic loading conditions at room and high temperature (1200C). In addition, modal acoustic emission (AE) was also monitored, which can reveal the occasion of matrix cracks and fiber. ER measurement and AE technique are shown in this study to be useful methods to monitor damage and indicate the failure under cyclic loading. Based on the slope of the ER evolution, an initial attempt has been made to develop a method allowing a critical damage phase to be identified. While the physical meaning of the critical point is not yet clear, it has the potential to allow the failure to be indicated at its early stage.

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