Effects of normal stress on the off-axis mechanical behavior of a plain-woven C/C composite

2003 ◽  
Vol 12 (2-3) ◽  
pp. 123-137
Author(s):  
Takuya Aoki ◽  
Toshio Ogasawara ◽  
Takashi Ishikawa
Keyword(s):  
Mechanical Behavior ◽  
Normal Stress

The influence of loading path on fault reactivation: a laboratory perspective

2020 ◽  
Author(s):  
Carolina Giorgetti ◽  
Marie Violay
Keyword(s):  
Shear Stress ◽  
Stress Field ◽  
Mechanical Behavior ◽  
Normal Stress ◽  
Principal Stress ◽  
Maximum Principal Stress ◽  
Fault Reactivation ◽  
Loading Path ◽  
Normal Faults ◽  
Loading Paths

<p>Despite natural faults are variably oriented to the Earth's surface and to the local stress field, the mechanics of fault reactivation and slip under variable loading paths (sensu Sibson, 1993) is still poorly understood. Nonetheless, different loading paths commonly occur in natural faults, from load-strengthening when the increase in shear stress is coupled with an increase in normal stress (e.g., reverse faults in absence of the fluid pressure increase) to load-weakening when the increase in shear stress is coupled with a decrease in normal stress (e.g., normal faults). According to the Mohr-Coulomb theory, the reactivation of pre-existing faults is only influenced by the fault orientation to the stress field, the fault friction, and the principal stresses magnitude. Therefore, the stress path the fault experienced is often neglected when evaluating the potential for reactivation. Yet, in natural faults characterized by thick, incohesive fault zone and highly fractured damage zone, the loading path could not be ruled out. Here we propose a laboratory approach aimed at reproducing the typical tectonic loading paths for reverse and normal faults. We performed triaxial saw-cut experiments, simulating the reactivation of well-oriented (i.e., 30° to the maximum principal stress) and misoriented (i.e., 50° to the maximum principal stress), normal and reverse gouge-bearing faults under dry and water-saturated conditions. We find that load-strengthening versus load-weakening path results in clearly different hydro-mechanical behavior. Particularly, prior to reactivation, reverse faults undergo <em>compaction</em> even at differential stresses well below the value required for reactivation. Contrarily, normal faults experience <em>dilation</em>, most of which occurs only near the differential stress values required for reactivation. Moreover, when reactivating at comparable normal stress, normal faults (load-weakening path) are more prone to slip seismically than reverse fault (load-strengthening path). Indeed, the higher mean stress that normal fault experienced before reactivation compacts more efficiently the gouge layer, thus increasing the fault stiffness and favoring seismic slip. This contrasting fault zone compaction and dilation prior to reactivation may occur in different natural tectonic settings, affecting the fault hydro-mechanical behavior. Thus, to take into account the loading path the fault experienced is fundamental in evaluating both natural and induced fault reactivation and the related seismic risk assessment.</p>

scholarly journals Anchor Stress and Deformation of the Bolted Joint under Shearing

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Hang Lin ◽  
Youyan Zhu ◽  
Jianyu Yang ◽  
Zhijie Wen
Keyword(s):  
Rock Mass ◽  
Mechanical Behavior ◽  
Normal Stress ◽  
Shear Test ◽  
Bolted Joint ◽  
Yield Displacement ◽  
Supporting Effect ◽  
Stress And Deformation ◽  
Safety And Stability ◽  
Better Than

Bolts are widely used in rock mass engineering, wherein the bolt support improves the safety and stability of the rock mass. To reveal the mechanical behavior of the bolt and failure mechanism of the bolted joint in the shearing process, a direct shear test was conducted by changing the state of grouting, number of bolt, and inclination angle of the bolt. The change in the axial force of the anchor in the shearing process was evaluated by conducting a strain gauge test, and the mechanical behavior of the bolt under the external force was studied. The results showed that under the same normal stress, the yield displacement of the bolt decreased and the stiffness of the joint gradually increased with increased number of bolts. At the same number of bolts, their yield displacement increased with increased normal stress. Analysis further revealed that grouting on the joint improved the force condition of the bolt, increased the yield displacement of the bolt, and coordinated the deformation of the grouting body and bolt, thereby improving the shear strength of the joint. Lastly, when the anchor angles differed, the axial pulling resistance of the anchor changed, and the yield displacement of the anchor with 45° inclination was <90°. The yield displacement of the bolt showed that the supporting effect of the bolt with a 45° inclination was better than that of the bolt with a 90° inclination.

scholarly journals Investigation of the Shear Mechanical Behavior of Sandstone with Unloading Normal Stress after Freezing–Thawing Cycles

Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 339
Author(s):  
Shuailong Lian ◽  
Jiashen Li ◽  
Fei Gan ◽  
Jing Bi ◽  
Chaolin Wang ◽  
...  
Keyword(s):  
Fracture Surface ◽  
Mechanical Behavior ◽  
Normal Stress ◽  
Direct Shear Test ◽  
Shear Test ◽  
Shear Displacement ◽  
Normal Displacement ◽  
Direct Shear ◽  
Thawing Cycle ◽  
Unloading Rate

Freezing–thawing action has a great impact on the physical and mechanical deterioration processes of rock materials in cold areas where environmental changes are very complicated. The direct shear test under unloading normal stress was adopted to investigate the shear mechanical behavior of sandstone samples after a freezing–thawing cycle in this paper. The failure shear displacement (Dsf), the failure normal displacement (Dnf), the shear displacement of unloading (Dsu), and the normal displacement of unloading (Dnu) were analyzed to describe the evolution of shear and normal deformation during the test. The results indicated that the shear displacement increased as the freezing–thawing cycle duration increased in a direct shear test under unloading normal stress. The unloading rate and the number of freezing–thawing cycles affected the failure pattern of the rock sample significantly in both the direct shear test under unloading normal stress and the direct shear test. The three-dimensional inclination angle, the distortion coefficient, and the roughness correlation coefficient of the fracture surface are dependent on the number of freezing–thawing cycles and the unloading rate. The surface average gradient mode of the fracture surface decreased as the freezing–thawing cycle times and unloading rate rose.

Analysis of Bending Strength of the Rectangular Hole Honeycomb Beam

2013 ◽  
Vol 405-408 ◽  
pp. 993-996
Author(s):  
Su Juan Dai ◽  
Bao Chen Zhu ◽  
Qing Chen
Keyword(s):  
Mechanical Behavior ◽  
Normal Stress ◽  
Calculation Method ◽  
Bending Strength ◽  
Calculation Formula ◽  
Rectangular Hole ◽  
Stress Calculation ◽  
Behavior Based

This paper introduces the characteristics and practicability of the honeycomb beam and analyses the mechanical behavior. Based on the vierendeel truss theory, the normal stress calculation method of the rectangular hole honeycomb beam is discussed, and the calculation formula is deduced. Finally using the derived formula, the paper calculates the normal stress of the rectangular hole honeycomb beams with different parameters, and analyses the influence of the opening rate and the hole spacing on the strength of honeycomb beam by comparing the same section of solid web beam, thus, provides reference for design of steel honeycomb beam.

scholarly journals Apparatus development for contact mechanics of energy pile-soil interface

2020 ◽  
Vol 205 ◽  
pp. 05009
Author(s):  
Dan Zhang ◽  
Yulong Gao ◽  
Guangya Wang ◽  
Guanzhong Wu
Keyword(s):  
Mechanical Behavior ◽  
Normal Stress ◽  
Contact Mechanics ◽  
Earth Pressure ◽  
Hoop Strain ◽  
Energy Pile ◽  
Heating And Cooling ◽  
Fiber Technology ◽  
Pile Model ◽  
Soil Interface

An Energy Pile-Soil Interface Characteristic Apparatus (EPSICA) was developed to investigate the contact mechanics of the pile-soil interface. In the center of the apparatus, there is an energy pile model, around which different soil can be filled to simulate pile in different subsoil. The soil can be saturated. By applying loads on the top of the soil, the different depths were simulated. The temperature of energy piles was controlled by the cycling fluid with a water bath. The Pt100 sensors were installed in the pile and soil to measure the temperature changes. The miniature earth pressure cells were installed on the pile surface to measure the normal stress of the pile-soil interface. The FBG quasi-distributed optical fiber technology was used to measure the hoop strain to evaluate the circumferential deformation of the pile model. Taking the sand foundation as an example, the mechanical behavior of pile-soil contact behavior during the heating and cooling cycle was studied based on the temperature of pile and soil, normal stress of pile-soil interface and hoop strain of pile. The developed apparatus provides a new method for the study of thermos-mechanical behavior of energy pile.

Application of TEM to Deformation, Wear, and Fracture of Ceramics

1974 ◽  
Vol 32 ◽  
pp. 472-473
Author(s):  
B. J. Hockey
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Brittle Materials ◽  
High Temperature Strength ◽  
Wide Range ◽  
Corrosive Environments ◽  
Further Development

Ceramics, such as Al2O3 and SiC have numerous current and potential uses in applications where high temperature strength, hardness, and wear resistance are required often in corrosive environments. These materials are, however, highly anisotropic and brittle, so that their mechanical behavior is often unpredictable. The further development of these materials will require a better understanding of the basic mechanisms controlling deformation, wear, and fracture.The purpose of this talk is to describe applications of TEM to the study of the deformation, wear, and fracture of Al2O3. Similar studies are currently being conducted on SiC and the techniques involved should be applicable to a wide range of hard, brittle materials.

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