Preliminary DEM Analysis on Micro-Mechanical Behavior of the Composite Cemented Granules Under Complex Stress Conditions

2016 ◽  
pp. 525-534 ◽  
Author(s):  
M. J. Jiang ◽  
Wei Liu ◽  
B. L. Xi ◽  
S. L. Jin
Keyword(s):  
Mechanical Behavior ◽  
Complex Stress ◽  
Stress Conditions ◽  
Dem Analysis

Failure behavior of multi-state system considering functional and physical isolation effects

2021 ◽  
pp. 1748006X2110418
Author(s):  
Ying Chen ◽  
Ze Wang ◽  
Yanfang Wang ◽  
Rui Kang
Keyword(s):  
Transition Probabilities ◽  
Functional Dependence ◽  
Great Difficulty ◽  
Complex Stress ◽  
State System ◽  
Stress Conditions ◽  
State Transitions ◽  
Failure Behavior ◽  
Physical Isolation ◽  
Isolation Effects

The multi-state system (MSS) is a system that may exhibit multiple states or performance levels. Most existing studies assumed that the transition probabilities from states to states are known. However, in practical engineering, the complex stress conditions lead to great difficulty of collecting the statistical data of state transitions. In this paper, based on physics-of-failure theory, we consider different levels of damages caused by failure mechanisms (FMs) are the main reasons to components’ multiple states. Besides, the physical isolation (PI) effect on degradations of FMs is also studied, which is neglected in the existing studies about the MSS with functional dependence groups. Decision-diagram based methods are used for modeling the failure behavior of the MSS. An automatic collision avoidance system is analyzed for illustrating the proposed modeling and analyzing methods. The results show that comparing to the results without the consideration of PI effect, the probabilities of different states with PI effect of multi-state components and system may decrease or increase, which depends on the actual PI effects to the stress conditions.

Effects of Grain Shape on Mechanical Behavior of Granular Materials Using DEM Analysis

2021 ◽  
Author(s):  
Byeong-Su Kim ◽  
Tatsuo Sakakibara ◽  
Seong-Wan Park ◽  
Shoji Kato
Keyword(s):  
Mechanical Behavior ◽  
Granular Materials ◽  
Grain Shape ◽  
Dem Analysis

scholarly journals INVESTIGATION OF MULTI-CYCLE FATIGUE OF EQUIPMENT AND MACHINERY ELEMENTS UNDER COMPLEX STRESS CONDITIONS AND NON- STATIONARY LOADING

2020 ◽  
Vol 3 (77) ◽  
pp. 11-17
Author(s):  
S. J. JASEN ◽  
◽  
D. K. JAKIYEV ◽  
S. S. ZHUNISBEKOV ◽  
◽  
...  
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Cyclic Stress ◽  
Complex Stress ◽  
Stress Conditions ◽  
Energy Concentration ◽  
Structural Elements ◽  
Cycle Fatigue ◽  
Stationary Loading ◽  
Comparison Of The Results

A computational and experimental method for estimating the fatigue life of structural elements of machines operating under complex cyclic stress conditions and non-stationary loading is considered. Comparison of the results of the calculations and experimental data indicated the effectiveness of the kinetic equation of multi-cycle fatigue damage based on the energy concentration of fatigue failure.

Improving fracture initiation and potential impact on fracture coverage by implementing optimal well-planning and drilling methods for typical stress conditions in the Cooper Basin, central Australia

2015 ◽  
Vol 55 (2) ◽  
pp. 403 ◽  
Author(s):  
Raymond Johnson ◽  
Hani Abul Khair ◽  
Rob Jeffrey ◽  
Jeremy Meyer ◽  
Carly Stark ◽  
...  
Keyword(s):  
Numerical Models ◽  
Model Development ◽  
High Stress ◽  
Fracture Initiation ◽  
Horizontal Stress ◽  
Complex Stress ◽  
Stress Conditions ◽  
Natural Fractures ◽  
Fracture Conductivity ◽  
Cooper Basin

Drilling conditions involving high mean and deviatory stresses, and natural fractures in the Cooper Basin present challenges in drilling and introduce wellbore rugosities, leaving a damaged wellbore subject to a stress cage effect. Fracture initiations have been problematic in vertical Cooper Basin wells, exhibiting high initiation and treating pressure frac treatments, and with high stress conditions posing greater risks in non-vertical completions. While far-field fracture complexity should be simplified, the near wellbore complexity results in reduced fracture conductivity. The authors believe that present drilling practices and wellbore azimuths may be contributing to sub-optimal hydraulic fracture initiations and complexities. Present analytical modelling methodologies can derive initiation pressures for circular wellbores, but require more complex numerical models to include flaws and ellipticity to represent natural fractures and wellbore rugosities. This study compares initiation pressures and presents graphical results, comparing circular and elliptical wellbore cases with flaws. This extended abstract outlines the criteria used in these models and remarks on areas needing further research and model development. The authors also propose improved drilling techniques to achieve more stable, smoother wellbores, potentially reducing some rugosity and drilling induced fractures. By using data from recent research and other cases with complex stress environments, it is proposed that initiation pressures might be reduced by inclining wells for hydraulic fracturing treatments in a favourable alignment in the maximum horizontal stress direction (σH-Max), and implementing completion techniques that aid better fracture initiation.

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