Cross-Scale Characteristics of Damage Evolution in Granite under High-Confining Pressure Cyclic Loading

2022 ◽  
Vol 22 (2) ◽  
Author(s):  
Dongjie Yang ◽  
Jianhua Hu ◽  
Tan Zhou ◽  
Xiaotian Ding
Keyword(s):  
Cyclic Loading ◽  
Damage Evolution ◽  
Confining Pressure ◽  
High Confining Pressure ◽  
Scale Characteristics

scholarly journals Mechanical Behavior and Damage Evolution for Granite Subjected to Cyclic Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Zhiliang Wang ◽  
Jikang Yao ◽  
Nuocheng Tian ◽  
Jingbin Zheng ◽  
Peng Gao
Keyword(s):  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Damage Evolution ◽  
Confining Pressure ◽  
Test System ◽  
Triaxial Tests ◽  
Dissipated Energy ◽  
Granite Sample ◽  
Cycle Number ◽  
Four Levels

This paper focuses on the mechanical behavior and damage evolution of Huashan granite subjected to cyclic loading. Four levels of confining pressure (0, 15, 25, and 35 MPa) were applied during cyclic axial loading by using a Rock Test System (MTS815) along with an acoustic emission (AE) monitoring device. Experimental results indicate that the number of AE activities is higher under cyclic triaxial loading compared to that under cyclic uniaxial loading. The measured stress-strain curves of both uniaxial and triaxial tests under cyclic loading are concave-up, but the degree of concavity is mild for the latter. As the cycle number rises, elastic modulus of the granite sample under different confining pressures increases. The slope of the peak strength versus confining pressure plot for the cyclic loading is larger than that for the monotonic loading. Besides, it is found that the dissipated energy increases with the increase of cyclic stress, but it hardly increases in proportion with the confining pressure. The damage parameters defined in terms of the plastic strain can be extended for the whole cyclic loading process, and they agree well with the energy-based damage parameters.

scholarly journals Fatigue Characteristics of Limestone under Triaxial Compression with Cyclic Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Yongjie Yang ◽  
Huiqiang Duan ◽  
Luyi Xing ◽  
Shan Ning ◽  
Jiakun Lv
Keyword(s):  
Cyclic Loading ◽  
Damage Evolution ◽  
Triaxial Compression ◽  
Peak Stress ◽  
Confining Pressure ◽  
Primary Phase ◽  
Fatigue Properties ◽  
Dissipated Energy ◽  
Loading Frequency ◽  
Compression Tests

This paper presents an experimental investigation of the fatigue properties of limestone subjected to triaxial compression with axial cyclic loading. Tests were conducted on intact limestone samples with a loading frequency of 0.5 Hz and a confining pressure of 10 MPa. The test results show the following five points. (1) Under triaxial conditions, the axial and circumferential deformations at the failure point induced by cyclic loading are slightly larger than the corresponding deformations at the peak stress achieved by conventional compression tests. (2) The first level cyclic loading process has a strong influence on rock deformation in the primary phase during subsequent level cyclic loading. A smaller difference in stress amplitude between the two loading stress levels leads to less deformation during the latter. (3) Circumferential and volumetric changes are more sensitive to fatigue failure in terms of deformation and strain rate than axial changes. (4) The three phases of dissipated energy evolution are consistent with a sample’s deformation such that the energy dissipation characteristics reflect the fatigue damage evolution process. (5) A new damage formula is proposed that can concisely describe a rock’s zero-cycle damage and damage evolution.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

Damage evolution and recrystallization enhancement of frozen loess

2017 ◽  
Vol 27 (8) ◽  
pp. 1131-1155 ◽  
Author(s):  
Zhiwei Zhou ◽  
Wei Ma ◽  
Shujuan Zhang ◽  
Cong Cai ◽  
Yanhu Mu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Damage Evolution ◽  
Deformation Process ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Recrystallization Process ◽  
Frozen Soils ◽  
Time Deformation ◽  
Pressure Melting

A series of multistage triaxial compression, creep, and stress relaxation tests were conducted on frozen loess at the temperature of −6℃ in order to study the damage evolution and recrystallization enhancement of mechanical properties during deformation process. The effect of strain rate, confining pressure, and hydrostatic stress history in the degradation laws of mechanical properties is investigated further. The strain rate has a significant influence on the stress–strain curve which dominates the evolution trend of mechanical properties. The mechanical behaviors (strength, stiffness, and viscosity) of frozen loess all exhibit evident response for the consolidation and pressure melting phenomenon caused by the confining pressure. The multistage loading tests under different hydrostatic stresses are capable of differentiating the development characteristics of mechanical properties during axial loading and hydrostatic compression process, respectively. The testing results indicated that the recrystallization of the ice particle in the frozen soils is an important microscopic factor for enhancement behaviors of mechanical parameters during the deformation process. This strengthening degree of mechanical properties is determined by temperature, duration time, deformation degree, and stress state during the recrystallization process. The phase transformation led by pressure melting and ice recrystallization is a nonnegligible changing pattern of frozen soils microstructure, which has apparent role in the damage evolution of mechanical properties.

Damage Evolution On Mechanical Parts Under Cyclic Loading

2007 ◽  
Author(s):  
P. Lestriez ◽  
F. Bogard ◽  
J. L. Shan ◽  
Y. Q. Guo
Keyword(s):  
Cyclic Loading ◽  
Damage Evolution ◽  
Mechanical Parts
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