Triaxial Stress State Research Articles

Axial strain accumulation projection model for sand in cyclic loading

Strain accumulation analysis is important to understand the deformation mechanism of soil structure subjected to cyclic loading. An empirical model is a superior choice for the description of strain accumulation. However, the ambiguity and sensitivity for the physical meaning of the parameters in the empirical model hindered the understanding of the strain accumulation mechanism. Compared with conventional empirical models by directly fitting experimental data, this study proposed a new approach to formulate an empirical model of strain accumulation using the intrinsic relationship between the reloading process in cyclic loading and the monotonic loading process. All axial strain accumulation increments of silica powder during cyclic loading with constant cyclic stress amplitude were projected onto the corresponding monotonic loading stress-strain curve, and the evolution of strain accumulation was described by the projection modulus, which was regarded as an intrinsic parameter of the projection stress-strain curve. An empirical formulation for describing the connection between projection modulus and stress levels was proposed. In addition, the prediction model of total axial strain in cyclic loading was presented by combining the accurate representation of elastic and plastic moduli during primary loading. Finally, discussions on the intrinsic relation mentioned above were enhanced by presenting more experimental evidence. This paper provided novel insight into the mechanism of strain accumulation in cyclic triaxial conditions by linking strain accumulation with a unified stress-strain relation. However, limited by the triaxial stress conditions in this study, it is recommended to extend this projection method to other cyclic load tests.

Research on the “three shells” cooperative support technology of large-section chambers in deep mines

The “three shells” cooperative support technology was proposed herein according to both the large deformation of the rock surrounding large-section chambers in deep mines and the precarious stability of the support structures therein. The development range of the plastic zone in the surrounding rock was controlled by a stress shell to reduce the difficulty of controlling the surrounding rock. Additionally, the residual strength of the rock mass in the plastic zone and the self-bearing capacity of the surrounding rock were improved by a reinforced load-bearing shell. Furthermore, a passive load-bearing shell could restore the triaxial stress state of the surrounding rock on the free surface, reduce the influence of the external environment on the surrounding rock, and reinforce the surrounding rock with the strength of the shell. Reasonable layouts of large-section chambers were determined by analyzing the control effect of the stress shell on the surrounding rock under three kinds of in situ stress fields. The orthogonal test method was applied to reveal the influences of different support parameters in the reinforced load-bearing shell and passive load-bearing shell on the surrounding rock stability. The surrounding rock control effect of the “three shells” collaborative support technology was analyzed through numerical simulation and field monitoring. The results show that the maximum displacement between the roof and floor of the coal preparation chamber in the Xinjulong coal mine was approximately 48 mm, and the maximum displacement between its two sides was approximately 65 mm, indicating that the technology proposed herein could meet the long-term control requirements of the surrounding rock stability for large-section chambers in deep mines.

A Novel Multi-Axial Pressure Sensor Probe for Measuring Triaxial Stress States Inside Soft Materials.

This paper presents the concept, design, construction, and validation of a novel probe based on the hexadic disposition of six pressure sensors suitable for measuring triaxial stress states inside bulky soft materials. The measurement of triaxial stress states inside bulk materials such as brain tissue surrogates is a challenging task needed to investigate internal organs’ stress states and validate FE models. The purpose of the work was the development and validation of a 17 × 17 × 17 mm probe containing six pressure sensors. To do so, six piezoresistive pressure sensors of 6 mm diameter were arranged into an hexad at three cartesian axes and bisecting angles, based on the analytical solution of the stress tensor. The resulting probe was embedded in a soft silicone rubber of known characteristics, calibrated under cyclic compression and shear in three orientations, and statically validated with combined loads. A calibration matrix was computed, and validation tests allowed us to estimate Von Mises stress under combined stress with an error below 6%. Hence, the proposed probe design and method can give indications about the complex stress state developing internally to soft materials under triaxial high-strain fields, opening applications in the analysis of biological models or physical surrogates involving parenchyma organs.

Impact-induced twinning in a magnesium alloy under different stress conditions

We investigate deformation twinning in a highly textured magnesium alloy plate of Mg-3.1%Al-0.9%Zn-0.4%Mn under edge-on impact with in situ, synchrotron-based, ultrafast X-ray diffraction measurements, and corresponding stress states are simulated with the finite element method. Deformation twinning and its anisotropy under the triaxial stress condition are explained by a statistical analysis of resolved shear stress. The critical resolved shear stress criterion is applicable under complicated stress conditions induced by high strain rate impact loading. Three typical simple stress conditions are further explored as verification and application cases: uniaxial-stress, uniaxial-strain, and plane-stress. Extension twinning in the magnesium alloy is prone to occur for impact loading applied perpendicular to the crystallographic c-axis, regardless of the exact stress conditions.

Hydromechanical behaviors of andesite under different stress states during fluid injection

Water reinjection into the formation is an indispensable operation in many energy engineering practices. This operation involves a complex hydromechanical (HM) coupling process and sometimes even causes unpredictable disasters, such as induced seismicity. It is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during injection. However, due to the limitations of current testing techniques, it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions, such as in triaxial extension stress states. To this end, a numerical study of HM changes in rocks during injection under different stress states is conducted. In this model, the saturated rock is first loaded to the target stress state under drainage conditions, and then the stress state is maintained and water is injected from the top to simulate the formation injection operation. Particular attention is given to the difference in HM changes under triaxial compression and extension stresses. This includes the differences in the pore pressure propagation, mean effective stress, volumetric strain, and stress-induced permeability. The numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks, but the degree of influence is different under the two triaxial stress states. The HM changes caused by the triaxial compression stress states are generally greater than those of extension, but the differences decrease with increasing differential stress, indicating that the increase in the differential stress will weaken the impact of the stress state on the HM response. In addition, the shear failure potential of fracture planes with various inclination angles is analyzed and summarized under different stress states. It is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of injection-induced seismicity. • A numerical model of the hydromechanical coupling process during injection is established and verified based on laboratory testing data. • The effects of three stress states on the hydromechanical behavior and the shear failure potential of rocks are studied, the differences in hydromechanical changes under triaxial compression and extension stress states are studied.

Finite-Element Limit Analysis for Solid Modeling of Reinforced Concrete

AbstractComplex triaxial stress states are present in many reinforced concrete structures. These structures are often analyzed using simple hand calculations based on methods designed for plane str...

Effect of thermal shock on laboratory hydraulic fracturing in Laizhou granite: An experimental study

This paper aims to investigate the effect of thermal shock on hydraulic fracturing in hot dry rock (HDR). To simulate the thermal shock effect caused during the injection of cold water, several natural granite specimens were slowly heated to various target temperatures and then rapidly cooled down by flowing water. Laboratory hydraulic fracturing experiments were performed on granite specimens under triaxial stress condition and room temperature. After that, computed tomography (CT) scanning technique, scanning electron microscope (SEM) observation, and surface profile scanning (SPS) tests were combined to analyze the influence of thermal shock on fracture morphology from micro-scale to macro-scale. Moreover, the characteristics of injection pressure curve were discussed. Experimental results show that a single main hydraulic fracture with large aperture is created and approximately propagates along the direction perpendicular to the minimum principal stress before 300 °C. When the thermal treatment temperature is higher than 300 °C, multiple hydraulic fractures with branches tend to be created due to the existence of thermally-induced damage zone near the well hole. Experimental results of SPS tests indicate that the maximum height difference of the hydraulic fracture surface increases with increasing thermal treatment temperature. The tortuosity of hydraulic fracture significantly increases when the thermal treatment temperature is higher than 300 °C. Additionally, the analysis of injection pressure response shows that apparent non-linear pressurization, and decrease in pressurization rate and breakdown pressure are observed after 300 °C.

Soil element assessment of cyclic-load-induced settlement considering combination of vertical, horizontal, and shear stresses in cohesive soil

Grounds subjected to cyclic loading, either continuous or fragmentary, widely exist in natural deposits and at reclaimed sites, e.g., induced by traffic loads, earthquakes, and wave-induced loading environments. Assessing the ground deformation under cyclic loading conditions is necessary for proper design and maintenance planning for traffic services. Accordingly, a testing program, in which vertical, horizontal, and shear stresses are automatically controlled, were newly developed in this study to reproduce the actual cyclic traffic load conditions using a hollow-cylindrical torsional shear apparatus.Estimations based on the results obtained from cyclic triaxial stress conditions were seen to underestimate the ground settlement compared to actual stresses, with combined vertical, horizontal, and shear stresses. Two kinds of vertical strain arose after a certain number of cycles: incremental collapse, in which unstable deformation (failure) is caused, and plastic creep, in which deformation continues to accumulate with the dampened rate (per cycle). The number of cycles of combined vertical, horizontal, and shear stresses necessary to reach a certain vertical strain increased linearly on a logarithmic scale when the magnitude of loading decreased. Moreover, the relationship between vertical strain and excess pore water pressure presented the same trend independent of the magnitude of loading. Practical uses of the obtained results were proposed and discussed.

Effect of the Triaxial State of Stress in the Hydraulic Fracturing Processes of Granite: Part 1—Visual Observations and Interpretation

A set of hydraulic fracturing tests were conducted in prismatic granite specimens to investigate the influence of the triaxial state of stress on the cracking processes. The tests considered three states of stress, in which the horizontal and out-of-plane loads were 2 MPa, while the vertical loads were either 1 MPa, 2 MPa, or 4 MPa. A hydraulic pressure inside pre-fabricated flaws was increased at a constant injection rate until hydraulic fractures initiated and propagated. In order to materialize this state of stress, a test setup was developed to independently apply and control three orthogonal stresses in the prismatic granite specimens while simultaneously applying a hydraulic pressure inside pre-fabricated flaws. More importantly, the setup also allowed one to observe the damage processes visually and through acoustic emission monitoring. This paper (the first of two) looks into the visual (macroscopic) observations, whereas the companion paper focuses on the acoustic emission monitoring. In particular, the present paper looks into the white patching (micro-damage) development, crack initiation, propagation and coalescence, and relates these with fracture initiation and breakdown pressures. From the tests, it was observed that the initiation of visible cracks is, generally, preceded by white patching and occurs at or near the pre-fabricated flaws. The visual analysis showed that the induced fractures were primarily intragranular when the triaxial stresses were same in the three orthogonal directions and intergranular otherwise. Additionally, micro-fracture initiation pressures were obtained based on white patch initiation pressures (visually) and using a graphical method which relates the changes in pressurization rate to fracture initiation. It was observed that the graphical method identifies when the initial damage occurred significantly earlier than the visual method, which indicates that important micro-damage processes may occur without macroscopic evidence. Most importantly, the coalescence patterns and the ratio between the breakdown pressure and the vertical stress are stress-state dependent. In fact, for lower vertical loads (VL = 1 MPa), the ratio between the breakdown pressure and vertical load is approximately 10 and for higher vertical loads (VL = 4 MPa) approaches 1.0, which is in agreement with data observed in the field.

Time Dependent Mechanical Crack Closure as a Potential Rapid Source of Post‐Seismic Wave Speed Recovery: Insights From Experiments in Carrara Marble

AbstractSeismological observations indicate strong variations in wave velocities around faults both co‐seismically during earthquakes, and post‐seismically. Recovery is commonly associated with a reduction in crack damage. Here, we explore the recovery associated with time‐dependent mechanical closure of cracks. We report results from laboratory experiments conducted on dry cores of Carrara marble at room temperature. We deformed cylindrical samples in the semi‐brittle regime to induce crack damage before subjecting them to hydrostatic and triaxial stress conditions for extended periods of time while recording dilatancy and wave speeds repeatedly. We report wave speed increases of up to 40% of the damage‐induced wave speed drop in samples subject to hydrostatic loading. Moreover, we report the occurrence of significant wave speed increases contemporaneously with time‐dependent creep in triaxially loaded samples. Wave speed recovery during creep is only observed below a threshold creep strain rate, a result we interpret as a transition from brittle to plastic creep with decreasing strain rate. We interpret the wave speed increase in terms of reduced crack density and increased contact area within the crack array, and show that around 40% of the total crack surface has to be closed to justify the observed wave speed recoveries. We propose that mechanical crack closure is driven by the viscous relaxation of the bulk rock under the influence of locked‐in stresses at low confining pressure, and of the external stresses at higher confining pressure. Our study shows that mechanical crack closure is a significant source of time‐dependent wave speed recovery.

Application of Spectral Method for Vibration-Induced High-Cycle Fatigue Evaluation of an High-Pressure Turbine Blade

Abstract A method of fluid–structure interaction coupling is implemented for a forced-response, vibration-induced fatigue life estimation of a high-pressure turbine blade. Two simulations approaches; a two-way (fully coupled) and one-way (uncoupled) methods are implemented to investigate the influence of fluid–solid coupling on a turbine blade structural response. The fatigue analysis is performed using the frequency domain spectral moments estimated from the response power spectral density (PSD) of the two simulation cases. The method is demonstrated in relation to the time-domain method of the rainflow cycle counting method with mean stress correction. Correspondingly, the mean stress and multi-axiality effects are also accounted for in the frequency domain spectral approach. In this case, a multiplication coefficient is derived based on the Morrow equation, while the case of multi-axiality is based on a criterion which reduces the triaxial stress state to an equivalent uniaxial stress using the critical plane assumption. The analyses show that while the vibration-induced stress histories of both simulation approaches are stationary, they violate the assumption of normality of the frequency domain approaches. The stress history profile of both processes can be described as platykurtic with the distributions having less mass near its mean and in the tail region, as compared to a Gaussian distribution with an equal standard deviation. The fully coupled method is right leaning with positive skewness while the uncoupled approach is left leaning with negative skewness. The directional orientation of the principal axes was also analyzed based on the Euler angle estimation. Although noticeable differences were found in the peak distribution of the normal stresses for both methods, the predicted Euler angle orientations were consistent in both cases, depicting a similar orientation of the critical plane during a crack initiation and propagation process. Finally, the fatigue life estimation was shown to be conservative in the fully coupled solution approach.

Experimental study on the flexural behavior of cold-formed U-shaped steel-encased confined prestressed RC beam

This paper discusses the flexural behavior of a cold-formed U-shaped steel-encased confined prestressed RC beam (CUSCPC). In this system, the U-shaped thin-walled steel girder provides the restraining stress to the partially confined concrete beams, participates the deformation of the composite beam under servicing loads and serves as a permanent formwork for the prestressed concrete (PC) beam during construction. Shear studs are welded on the inside of the closed end of U-shaped steel girder to provide a full shear connection between the concrete and thin-walled steel plate. Same number of CUSCPC specimen but with no shear studs were made for comparison purposes. Two additional parameters were also considered: ratio of tension reinforcement and ratio of P/S strands. The test results show that all specimens have excellent ductility and display a flexural failure pattern. The brittle behavior disappears due to the triaxial stress state of the partially confined concrete beam encased with the U-shaped thin-walled steel girder. It is also found that the load-bearing capacity of the CUSCPC beams with shear studs is increased by 5–10%, compared with the conventional PC members and the CUSCPC beams with no shear studs.

True triaxial mechanical properties of unsaturated loess in foundation pit engineering

Loess is a typical structural unsaturated soil. Because the matric suction of unsaturated loess changes with water migration, the properties of unsaturated soil clearly change. Therefore, the matric suction is considered the main factor affecting the properties of unsaturated loess. Generally, soils are subjected to three principal stresses in practical engineering. To investigate the properties of unsaturated natural loess under complex stress states, a suction-controlled true triaxial apparatus with a rigid-flexible boundary was applied to test unsaturated loess under true triaxial loading. Four sets of suction-controlled tests, including isotropic consolidation followed by monotonic shearing, were carried out, and the matric suction was controlled in the true triaxial tests. The compression yield characteristics of loess were investigated under different matric suctions. The influence of the matric suction and intermediate principal stress parameter were analysed based on the test results. Consolidated drained tests of loess with constant matric suctions were performed under a constant net mean stress and deviatoric stress with different intermediate principal stress parameters. Stress-strain curves and failure envelopes of loess were also presented. The stress-strain-strength properties of unsaturated loess are related to the matric suction and intermediate principal stress parameter under true triaxial stress conditions. The earth pressure of the Q3 loess stratum of the loess foundation pit was analysed based on a strength criterion of unsaturated loess with matric suction.

A Large-Scale True Triaxial Seepage Apparatus for Evaluating Impact under High Stress State and High Hydraulic Heads

Seepage phenomenon can be characterized as a hydromechanical coupled issue that threatens the performance of hydraulic facilities as well as infrastructures. In this study, a large-scale true triaxial seepage apparatus was developed to investigate the hydraulic parameters of coarse-grained cohesionless soil under complex stress states and various water heads. A specimen with a maximal size of 1,050 by 550 by 550 mm was provided, and a 3-D loading system was equipped. The loading capacity in all 3 directions reaches 9 MPa, and the water supply system can produce a water head equivalent to 300 m. A detailed description of each component of the true triaxial seepage apparatus is presented. A series of tests were carried out using coarse-grained cohesionless soil naturally sampled from BaTang Dam in Sichuan Province, China. The experimental arrangement encompassed the repeatability tests and various horizontal seepage tests under different triaxial stress states. Test results show that the hydraulic conductivity of the test soil exhibits a negative power relationship with the hydraulic gradient. The newly developed apparatus is verified to be a useful tool to investigate the hydraulic features of coarse-grained cohesionless soil under triaxial stress conditions.

Laboratory-Scale Investigation of the Slippage of a Natural Fracture Resulting from an Approaching Hydraulic Fracture

The interaction between a natural fracture (NF) and a hydraulic fracture (HF) has been studied extensively, both experimentally and numerically, to better understand the potential for crossing and arrest of a hydraulic fracture intersecting a natural fracture. However, the actual mechanical interaction between a hydraulic and a natural fracture or a bedding plane has not been studied, particularly under triaxial stress and injection conditions. Analysis of field microseismic data recorded during hydraulic fracturing shows that the bedding plane could slip due to the approaching hydraulic fracture. In this paper, we present the results of some lab-scale experimental work, demonstrating HF/NF interaction with an emphasis on the slippage of a discontinuity surface. Injection pressure, stress applied, and the sample deformation are monitored during the tests. Acoustic Emission (AE) technology is employed to record the AE signals generated during fracture initiation, propagation, and during the sliding of the joint. In addition, strain gauges are used to measure the slippage on the natural fracture. The tests are carried out on 101.6 mm diameter cylindrical samples of PMMA, shale, and granite. The calculated displacement based on the recorded strain clearly shows a jump at the breakdown point, which is accompanied by increased AE activity and stress drop. Analysis of the data clearly shows the occurrence of slippage on the joint in response to an approaching hydraulic fracture. Expectedly, the degree of shear slip varies with natural fracture dip and friction angle.

Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour.

The mechanical properties and fracture behaviour of concretes under different triaxial stress states were investigated based on a 3D mesoscale model. The quasistatic triaxial loadings, namely, compression–compression–compression (C–C–C), compression–tension–tension (C–T–T) and compression–compression–tension (C–C–T), were simulated using an implicit solver. The mesoscopic modelling with good robustness gave reliable and detailed damage evolution processes under different triaxial stress states. The lateral tensile stress significantly influenced the multiaxial mechanical behaviour of the concretes, accelerating the concrete failure. With low lateral pressures or tensile stress, axial cleavage was the main failure mode of the specimens. Furthermore, the concretes presented shear failures under medium lateral pressures. The concretes experienced a transition from brittle fracture to plastic failure under high lateral pressures. The Ottosen parameters were modified by the gradient descent method and then the failure criterion of the concretes in the principal stress space was given. The failure criterion could describe the strength characteristics of concrete materials well by being fitted with experimental data under different triaxial stress states.

Plasticity and Deformation Mechanisms of Ultrafine-Grained Ti in Necking Region Revealed by Digital Image Correlation Technique.

The conventional engineering stress-strain curve could not accurately describe the true stress-strain and local deformability of the necking part of tensile specimens, as it calculates the strain by using the whole gauge length, assuming the tensile specimen was deformed uniformly. In this study, we employed 3D optical measuring digital image correlation (DIC) to systematically measure the full strain field and local strain during the whole tensile process, and calculate the real-time strain and actual flow stress in the necking region of ultrafine-grained (UFG) Ti. The post-necking elongation and strain hardening exponent of the UFG Ti necking part were then measured as 36% and 0.101, slightly smaller than those of the coarse grained Ti (52% and 0.167), suggesting the high plastic deformability in the necking part of the UFG Ti. Finite elemental modeling (FEM) indicates that when necking occurs, strain is concentrated in the necking region. The stress state of the necking part was transformed from uniaxial in the uniform elongation stage to a triaxial stress state. A scanning electron microscopic (SEM) study revealed the shear and ductile fracture, as well as numerous micro shear bands in the UFG Ti, which are controlled by cooperative grain boundary sliding. Our work revealed the large plastic deformability of UFG metals in the necking region under a complex stress state.

Acoustic Emission Source Location Monitoring of Laboratory-Scale Hydraulic Fracturing of Coal Under True Triaxial Stress

Crack monitoring is an important issue in coal and rock hydraulic fracturing (HF). In this study, we conducted experimental coal HF acoustic emission (AE) monitoring tests under true triaxial stress by using a self-developed experiment system. The results showed that the AE signal statistical parameters had a good positive correlation with the water pressure curve. Based on the STA/LTA, improved AIC and simplex algorithm, we developed a new method for AE event automatic identification and source location for coal HF. By using this new method, we were able to detect and locate more accurately the AE events induced by HF. Hydraulic crack propagation and temporal-spatial AE event distribution were located with high accuracy. According to the AE event temporal-spatial distribution of AE events, coal hydraulic crack propagation was not uniform. In the middle and late HF stages, especially when hydraulic cracks approach the coal sample boundary, the hydraulic crack propagation speed was accelerated significantly. The important factors that affected hydraulic crack initiation, propagation, steering, and acceleration included the triaxial stress state, original joints and cracks, and local stress disturbance caused by hydraulic cracks. These results offer a reference for designing optimized, safe and effective HF programs, which are important in preventing coal/rock dynamic disasters and ensuring safe and efficient mining.

Development of a poly-axial platen for testing true-triaxial behavior of rocks

Mining at greater depths can lead to stress-induced failure, especially in areas of high horizontal in situ stress. The induced stresses around the opening are known to be in a poly-axial stress state where, σ1 ≠ σ2 ≠ σ3 with special case of σ3 = 0 and σ1, σ2 ≠ 0 at its boundary, where σ1, σ2, σ3 are major, intermediate, minor principal stress, respectively. The conventional triaxial testing does not represent the actual in situ strength of the rock in regions of high horizontal stress, as it ignores the influence of intermediate principal stress (σ2). The typical poly-axial testing (biaxial and true-triaxial tests) of intact rock mostly requires sophisticated and expensive loading systems. This study investigated the mechanical behavior of intact rock under a poly-axial stress state using a simple and cost-effective design. The apparatus consists of a biaxial frame and a confining device. The biaxial frame has two platens that apply equal stress in both directions (σ1 = σ2) on a 50.8 mm cubical specimen when placed inside the uniaxial loading device. The confining device performed separate biaxial tests under constant intermediate principal stress (σ2 = constant) and true-triaxial tests when used along with the biaxial frame. This study then compared the failure modes and peak strength of Berea sandstone specimens with other biaxial–triaxial devices to validate the design of the poly-axial apparatus. We also performed uniaxial tests on both standard cylindrical samples and prismatic specimens of different slenderness ratios. These tests provided a complete understanding of the failure mode transition from standard uniaxial compressive tests to triaxial stress conditions on cubical specimens. Additionally, this study determined best-fitted strength envelopes for biaxial and triaxial stress state. Based on regression analysis, we found a quadratic polynomial to be a good fit to biaxial strength envelope. For the true-triaxial strength envelope, we found the three-dimensional (3D) failure criterion to be a good fit with R2 of 0.964.

The formation of intragranular stress concentration in plastic deformed Ni-base superalloy: Governing factors and process

Abstract For Ni-base superalloy, the creep property is still vital. Polycrystalline Ni-base superalloy samples with different creep strain are investigated by electron backscatter diffraction along with phase field simulation to analyze the formation of intragranular stress concentration (ISC) with respect to the governing factors and process. The results show that ISCs are more likely to form at vicinity of grain boundaries (GBs) because of the multiple-slips near GBs which are activated by the mediated stress at GBs. The frequency of ISCs near the GBs decreases first at low strain and then increases with increasing strain because of the formation and destroy of stress concentrations in grain interior. The ISCs are more likely to form at vicinity of the GBs with misorientation of 45°–55°, independent of the strain. In addition, the GBs parallel or perpendicular to the loading direction will not emit dislocations to activate multiple-slips near GBs when the strain is small because of their triaxial stress state. As the strain increases, these GBs begin to emit dislocations because of the change of stress state or the formation of ‘weak points’. The GBs perpendicular to the applied stress own the highest probability when the strain is 9.38%. Our results provide unique and critical data to support future optimization of alloy properties and the development of new alloys.