Uniaxial Loading Research Articles

Crystal plasticity based investigation of the effects of additive manufactured voids on the strain localization behaviour of Ti-6Al-4V

The presence of defects produced by additive manufactured (AM) processes in structural Ti alloys such as Ti-6Al-4V is known to have serious implications on the deformation and fatigue behaviour of engineering components. However, there is little understanding about the localised plastic deformation patterns that develop around AM defects, and the associated local conditions that could lead to the nucleation of micro-cracks under creep loading conditions. In this work, the effects of the morphology and volume fraction of AM defects and temperature on the strain localization behaviour around such defects in Ti-6Al-4V will be addressed. To that purpose, a novel rate-dependent crystal plasticity formulation is proposed to describe the mechanical behaviour of the alloy’s predominant α′(HCP)-phase. Representative volume elements (RVEs) of the AM produced microstructures are digitally reconstructed from EBSD orientation maps obtained on planes perpendicular and transversal to the microstructure’s AM growth direction. Calibration of the single crystal model for the α′-phase is carried out from macroscopic uniaxial tensile data from polycrystalline AM specimens at different strain rates and temperatures and published creep data.Furthermore, RVEs containing AM defects of different morphologies and volume fractions are relied upon to investigate the strain localization behaviour around the defects under uniaxial loading at ambient and high temperatures. It is found that the extent of the localised accumulated plastic strain around defects depends greatly on whether the voids surface are smooth or have sharp corners, with the latter being associated with more severe localisation patterns. Moreover, a numerical investigation into the crack initiation behaviour of AM Ti-6Al-4V under uniaxial creep loading at 450 ° C revealed that the development of the local conditions suitable for the nucleation of creep damage/micro-cracks is accelerated in the presence of typical AM defects, and the extent of that acceleration depends strongly on their morphology. An AM defect shape parameter is introduced to quantify the way their morphology affect the time for creep crack initiation/damage.

The deformation behavior and mechanism modeling of a corrosion-resistant Ni-Cr-Mo alloy with nanoscale precipitates at room and elevated temperatures

Ni-Cr-Mo alloys are widely-used materials in various critical applications owing to their excellent balance of strength and ductility. The precipitates play a significant role in the exceptional mechanical properties of these alloys, yet the precise microscopic mechanisms underpinning the enhanced properties are still open. Here, the atomistic simulation based on molecular dynamics (MD) was employed to investigate the deformation behavior and mechanism of the precipitation-strengthened single crystal Ni-Cr-Mo alloy under uniaxial loading at temperatures of 300K, 500K, 700K, and 900K. The results revealed high temperature-induced softening under both tension and compression. Furthermore, the tension-compression asymmetry in ultimate strength is influenced by the disparity in Schmid factor of leading Shockley partial dislocations. By monitoring the evolution of microscopic defects during deformation, the Shockley partial dislocation slip was identified as the primary deformation mechanism in the plastic regime at 300K, 500K, 700K, and 900K. Based on that, a flow stress representation model was proposed. Moreover, the investigation on the nanoscale Ni2(Cr, Mo) precipitates revealed the transition from the Orowan bypass mechanism to the shearing mechanism under uniaxial loading, accompanied by the formation of dislocation tangles. The dislocation tangles impeded dislocation slip, enhancing the mechanical properties of the alloy. The precipitate can significantly promote the formation of the lamellar dislocation structure under compression at 900K.

Tensile behaviour of a novel grouted sleeve splice for high-strength rebars

This study introduces a novel type of grouted sleeve fabricated from a standard low-alloy seamless steel pipe using cold-rolling techniques. The main goal is to achieve an effective connection between the high-strength steel (HSS) reinforcements in the joints of precast concrete structures. To investigate the structural performance of the developed splice under uniaxial tensile loading, 24 coupler specimens configured with 28 mm diameter HRB600 reinforcements were prepared. Two primary parameters, namely the embedded length of the spliced bar and number of inner concentric ribs rolled on the sleeve, were considered. By conducting direct pullout tests, the performance of the developed splices was thoroughly assessed based on the failure mode, bond stiffness, bond ductility, and strength. The test results demonstrated that increasing the bar embedded length and number of inner ribs enhances the initial bond stiffness and ductility of the splice. Increasing the quantity of inner ribs only in the inelastic region of the splice is effective for improving its tensile capacity. For grout splices with large-diameter HSS bars, an embedded length of 8db is recommended to guarantee bar fracture failure and satisfy the specification requirements. This length exceeds that of splices with normal-strength reinforcements. Finally, a formula was proposed to estimate the inelastic region length and tensile strength of the proposed splice.

Effect of amorphous layer parameters on tensile behavior of amorphous/crystalline CuZr/Cu composites

This study investigates the mechanical behavior and deformation property of CuZr/Cu amorphous/crystalline (AC) composites subjected to uniaxial tensile loading. The results reveal significant insights by varying amorphous shell thickness and amorphous alloy composition. Reducing the amorphous shell thickness from 20Å to 5Å increases the tensile strength of the composite from 2.715GPa to 4.668GPa due to the enhanced AC interface effect. The insertion of crystalline phases in the amorphous matrix induces nucleation zones for the shear bands and dislocations, affecting the plastic flow distribution. The shear strain and residual stress predominantly manifest in the amorphous shell. A thinner amorphous shell induces substantial shear strain in crystalline phases, promoting homogeneous deformation. The dislocations prompt plastic deformation in crystalline phases, altering atomic configurations. The AC interfaces initiate deformation nucleation, generating partial dislocations, stacking faults, and twinning in the tension. Besides, the total dislocation length rises with strain increase and thinner amorphous shell. Moreover, the increase of Cu content in the amorphous CuZr shell leads to increased tensile strength and elastic modulus. The higher Cu content increases the concentration of shear strain regions in the composites. The deformation mechanism is also switched from the dominant shear band to the homogenous deformation with increasing Cu content in the amorphous shell. Finally, the phase change shows that the FCC phase decreases and the amorphous phase gain is less as the percentage of Cu in the amorphous increases.

A rheological constitutive model to predict the anisotropic biaxial bending behavior of spiral strands subjected to variable axial force

Spiral strands exhibit dissipative bending behavior when subjected to external axial force. To the best of the authors’ knowledge, only the uniaxial bending behavior of spiral strands subjected to constant axial force has been studied in the literature so far. Thanks to a recently developed mixed stress–strain driven computational homogenization for spiral strands, this paper is the first to study the biaxial bending behavior of spiral strands subjected to variable tensile force. Based on the observed anisotropic behavior, a rheological constitutive model equivalent to multilayer spiral strands is proposed to predict their behavior under such loading. For an Nl-layer strand, the proposed model consists of several angularly distributed uniaxial spring systems, referred to as a multiaxial spring system, where each uniaxial spring system consists of a spring and Nl slider-springs. In a uniaxial spring system, the spring represents the slip contribution of all wires to the bending stiffness of the strand, while each slider-spring represents the stick contribution of each layer. A major advantage of the proposed scheme is its straightforward parameter identification, requiring only several monotonic uniaxial bendings under constant axial force. The proposed rheological model has been verified against the responses obtained from the mixed stress–strain driven computational homogenization through several numerical examples. These examples consist of complex uniaxial and biaxial load cases with variable tensile force. It has been shown that the proposed scheme not only predicts the response of the strand, but also provides helpful insight into the complex underlying mechanism of spiral strands. Furthermore, the low computational cost of the proposed models makes them perfect candidates for implementation as a constitutive law in a beam model. Using a single beam with the proposed constitutive law, spiral strand simulations can be performed in a few seconds on a laptop instead of a few hours or days on a supercomputer.

A FEM-based model for failure initiation in the microstructure of gray cast iron under uniaxial compression

PurposeThe purpose of this study was to validate the feasibility of the proposed microstructure-based model by comparing the simulation results with experimental data. The study also aimed to investigate the relationship between the orientation of graphite flakes and the failure behavior of the material under compressive loads as well as the effect of image size on the accuracy of stress–strain behavior predictions.Design/methodology/approachThis paper presents a microstructure-based model that utilizes the finite element method (FEM) combined with representative volume elements (RVE) to simulate the hardening and failure behavior of ferrite-pearlite matrix gray cast iron under uniaxial loading conditions. The material was first analyzed using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) to identify the different phases and their characteristics. High-resolution SEM images of the undeformed material microstructure were then converted into finite element meshes using OOF2 software. The Johnson–Cook (J–C) model, along with a damage model, was employed in Abaqus FEA software to estimate the elastic and elastoplastic behavior under assumed plane stress conditions.FindingsThe findings indicate that crack initiation and propagation in gray cast iron begin at the interface between graphite particles and the pearlitic matrix, with microcrack networks extending into the metal matrix, eventually coalescing to cause material failure. The ferritic phase within the material contributes some ductility, thereby delaying crack initiation.Originality/valueThis study introduces a novel approach by integrating microstructural analysis with FEM and RVE techniques to accurately model the hardening and failure behavior of gray cast iron under uniaxial loading. The incorporation of high-resolution SEM images into finite element meshes, combined with the J–C model and damage assessment in Abaqus, provides a comprehensive method for predicting material performance. This approach enhances the understanding of the microstructural influences on crack initiation and propagation, offering valuable insights for improving the design and durability of gray cast iron components.

Study on temperature evolution law of coal containing gas under uniaxial loading process with different loading rates

AbstractIn order to investigate the evolution law of coal temperature during the gestation process of coal and gas outburst, laboratory experiments and numerical simulation approaches were employed. Infrared thermal radiation experiments on the surface of outburst coal during uniaxial loading and failure of coal were conducted. A coal and gas thermal‐hydromechanical coupling model considering the endothermic effect of desorption was established. Numerical simulation of uniaxial loading of gas‐containing coal was implemented to study the influences of deformation energy, frictional heat, and adsorption/desorption endothermic effects on coal temperature. The results indicate that the temperature of coal samples during the uniaxial loading and failure process generally exhibits a stepwise temperature increase. In the initial stage, the elastic thermal effect leads to a slow and fluctuating rise in the temperature of coal samples. During the yield and plastic deformation stages, frictional heat causes a rapid increase in the temperature of coal samples. With the increase of the loading rate, the increment of the temperature of coal samples gradually decreases and reaches the peak when the loading stress is 70% of the peak stress. According to the numerical calculation results, with the increase of the loading rate, the temperature reduction caused by gas desorption relatively decreases. By comparing the experimental results and numerical simulation results, it is found that the temperature reduction caused by desorption is greater than the temperature increments caused by deformation energy and frictional heat. The desorption endothermic effect and frictional heat effect are the dominant factors controlling the temperature variation of coal during the gestation process of outburst. The research achievements have significant theoretical significance and practical value for revealing the temperature evolution mechanism during the gestation process of coal and gas outburst, predicting coal and gas outburst, and protecting the atmospheric environment.

Mechanical Behaviour of 7075-T6 Aluminium Alloy: Integrating Digital Image Correlation and Finite Element Analysis for Uniaxial and Biaxial Load Scenarios

The objective of this study is to investigate the mechanical properties of 7075-T6 Aluminium (Al) alloy under both uniaxial and biaxial loads. The study will be conducted using a combination of experimental and numerical methods. The experimental method used is the digital image correlation (DIC) technique, which was utilized to capture the deformation and strain fields of the material specimen under tensile test. A tensile machine was employed to apply uniaxial and biaxial loads on the sample. The strain and deformation distribution of the results was generated on the DIC and correlated software. The numerical method involved the use of a commercial finite element software to create a finite element model and simulate the mechanical behaviour of the material under the same loading conditions. The results obtained from the experimental and numerical methods were compared to validate the accuracy of the numerical model. The outcomes demonstrated that under uniaxial loading, localized necking and fracture were observed, while biaxial loading resulted in shear deformation and fracture. This research contributes to the development of more accurate models for predicting the mechanical behaviour of the model samples under different loading conditions.

Numerical analysis of failure mechanics of concrete under true dynamic triaxial loading using a four-phase meso-model

In the present paper, the failure mechanics of concrete under true triaxial dynamic loading is investigated. A four-phase concrete meso-model is developed. The meso-model consists of aggregate, mortar, interfacial transition zone (ITZ) and macropores. A finite element (FE) model of a split Hopkinson pressure bar is also created to apply true triaxial dynamic loading. The development of cracks in concrete is presented for the uniaxial, biaxial and triaxial loading cases. The presence of local discontinuity is modelled, and its effect on the failure of concrete is extensively investigated and discussed. In the last, the effect of aggregate distribution is also analysed. It is found that the internal structure of concrete changes the stress distribution from true triaxial to compression or extension triaxial, which is the prime cause of internal cracking.

Damage mechanisms of Ti60 under different uniaxial/multiaxial thermo-mechanical loading modes

The fatigue experiments for titanium alloy Ti60 under different uniaxial/multiaxial thermo-mechanical loading modes found that the combined action of high temperature and tensile stress can cause the debonding of the second phase strengthening particles between grain boundary, reducing the ability to resist deformation of Ti60, which leads to a decrease in the fatigue life of the material. In addition, mean tensile stress increases the ability of cracks to break through intergranular barriers and the non-proportional additional hardening caused by multiaxial loading exacerbates the formation of microcracks. Both will increase the fatigue damage of the material. The fatigue damage mechanism identified in this investigation can reasonably explain the fatigue life law under multiaxial loading at high temperature, uniaxial and multiaxial thermo-mechanical fatigue loadings.

Investigation of Fatigue Mechanics and Crack Evolution Characteristics of Jointed Specimens Under Cyclic Uniaxial Compression

ABSTRACTNonpersistent joints are prevalent in engineering rock masses and are sensitive to cyclic loads induced by geological movements and engineering disturbances. Therefore, studying the fatigue mechanisms of rock masses with nonpersistent joints under cyclic compressive loads is crucial for ensuring the rational design and long‐term stability of rock engineering structures. Based on laboratory experiments, this study employed the discrete element method to create specimens with different nonpersistent joints, and uniaxial compressive cyclic loading tests were conducted on these specimens with different maximum cyclic stress levels. The results show that the joint inclination significantly affects the characteristics of jointed rock, such as deformation modulus, irreversible strain, energy evolution, and crack characteristics. Increasing the maximum stress in the stress path results in a rapid release of hysteretic energy in the jointed regions of the rock, which leads to an exponential decrease in fatigue life while an increase in initial irreversible strain, final irreversible strain, and hysteretic energy density. Additionally, the shear fracture zones on both sides of the model expand, and the propagation and merging of cracks between joints become more extensive and complex. The results are significant for studying rock fatigue instability and structure engineering design.

Determination of the REV size for heterogeneous rocks with different grain sizes: Deep learning and numerical approaches

Accurate determination of the representative elementary volume (REV) size plays a pivotal role in analysing the mechanical properties and failure processes of heterogeneous rocks in complex engineering environments. In this study, a novel microstructure modelling strategy (NMMS) for determining the REV size is proposed by combining deep learning and an improved phase-field method (PFM). Micro- and macroscale experiments are systematically conducted to determine the real microstructural characteristics and mechanical properties of heterogeneous rocks with different grain sizes. On the basis of this experimental evidence, geometric models of different sizes were reconstructed through deep learning to avoid the limitations of human-based methods, and an improved PFM was used for numerical calculations. These models were then employed to perform numerical tests under uniaxial loading conditions, and the coefficient of variation was introduced to determine the REV size of heterogeneous rocks with different grain sizes. The research findings indicate that the final REV size is the maximum value of the REVs defined by the evaluation properties within an acceptable coefficient of variation. At a criterion of 5% for the coefficient of variation, the REV sizes are 60 mm×60 mm, 70 mm×70 mm, and 90 mm×90 mm for fine-medium-grained (FMG), medium-grained (MG), and coarse-grained (CG) rocks, respectively. Furthermore, the REV determined by the NMMS was applied to investigate the effects of microstructure on macromechanical properties and damage evolution under triaxial loading conditions. The numerical results show that the NMMS can accurately predict the macromechanical properties and microcracking patterns of heterogeneous rocks, especially the intracrystalline cracks in feldspar, the interfacial cracks in gravel, and the “voids” of cracks in biotite. This research can provide some basic references for the optimal choice of the REV size of heterogeneous rocks.

A Multi-Scale Model for Predicting Physically Short Crack and Long Crack Behavior in Metals.

The fatigue behavior of metal specimens is influenced by defects, material properties, and loading. This study aims to establish a multi-scale fatigue crack growth model that describes physically short crack (PSC) and long crack (LC) behavior. The model allows the calculation of crack growth rates for uniaxial loading at different stress ratios based on the material properties and specimen geometry. Furthermore, the model integrates the Gaussian distribution theory to consider material heterogeneity and the experimental measurement errors that cause fatigue scatter. The crack growth rate and fatigue life of metal specimens with different notch geometry were predicted. The curves generated by the multi-scale model were mainly consistent with the test data from the published literature at the PSC and LC stages.

Crack evolution and fractal characteristics of fractured red sandstone based on acoustic emission parameters

Rock is a widely used engineering material, and accurate understanding of its internal microcrack evolution process during loading can provide a theoretical basis for preventing instability and failure in rock engineering. The rock pressure test system and acoustic emission equipment were used to carry out uniaxial loading and acoustic emission monitoring tests on fractured red sandstone. Based on the RA and AF values of acoustic emission and the fractal theory, the internal crack patterns and evolution rules of red sandstone with different crack angles were explored. The results show that the compressive strength of red sandstone varies with the crack Angle in the shape of “U”, and there is an obvious stress drop after the elastic stage of 30° and 45° crack red sandstone, which has a good correspondence with the acoustic emission ringing count rate. During the loading process, the damage mainly caused by tension cracks first appears inside the rock, and then the tension cracks increase steadily and the shear cracks gradually increase, indicating that the rock enters the stage of fracture instability development. With the development of shear cracks, the peak strength is finally reached and the instability failure occurs. During the loading process of 30° fracture red sandstone, the corresponding stress drop phenomenon of “shear crack group” appears. According to the D/S statistical analysis of different crack samples based on acoustic emission ringing count, the fractal dimension presents a decreasing-rising-decreasing trend with the increase of crack inclination, which corresponds to the change of the complexity of crack development in rock.

In-situ experimental characterization and numerical investigation of the crack initiation of SMC composite under uniaxial tension

This paper explored the crack initiation of sheet molding compound (SMC) composite under uniaxial tensile loads by integrating in-situ experimental characterization and subsequent numerical analysis. Firstly, a synchrotron micro-X-ray computed tomography was utilized to character the morphology and evolution of the microstructure and fracture features of the SMC sample with different loading conditions. Meanwhile, the digital volume correlation technology was employed to determine the internal three-dimensional deformation. Then, a numerical analysis was conducted to describe the relationships among the microstructure, deformation distribution, and position of the crack initiation. Finally, a predictive model was developed based on the internal microstructure and the deformation distribution and then utilized to predict the location and sequence of crack initiation. The good agreement between the predicted results with the experimental ones reveals the feasibility of the proposed model in exploring the fracture behaviors of carbon fiber reinforced polymer composites with complex internal microstructure.

Data-Efficient Dimensionality Reduction and Surrogate Modeling of High-Dimensional Stress Fields

Abstract Tensor datatypes representing field variables like stress, displacement, velocity, etc., have increasingly become a common occurrence in data-driven modeling and analysis of simulations. Numerous methods [such as convolutional neural networks (CNNs)] exist to address the meta-modeling of field data from simulations. As the complexity of the simulation increases, so does the cost of acquisition, leading to limited data scenarios. Modeling of tensor datatypes under limited data scenarios remains a hindrance for engineering applications. In this article, we introduce a direct image-to-image modeling framework of convolutional autoencoders enhanced by information bottleneck loss function to tackle the tensor data types with limited data. The information bottleneck method penalizes the nuisance information in the latent space while maximizing relevant information making it robust for limited data scenarios. The entire neural network framework is further combined with robust hyperparameter optimization. We perform numerical studies to compare the predictive performance of the proposed method with a dimensionality reduction-based surrogate modeling framework on a representative linear elastic ellipsoidal void problem with uniaxial loading. The data structure focuses on the low-data regime (fewer than 100 data points) and includes the parameterized geometry of the ellipsoidal void as the input and the predicted stress field as the output. The results of the numerical studies show that the information bottleneck approach yields improved overall accuracy and more precise prediction of the extremes of the stress field. Additionally, an in-depth analysis is carried out to elucidate the information compression behavior of the proposed framework.

Transcriptome-Optimized Hydrogel Design of a Stem Cell Niche for Enhanced Tendon Regeneration.

Bioactive hydrogels have emerged as promising artificial niches for enhancing stem cell-mediated tendon repair. However, a substantial knowledge gap remains regarding the optimal combination of niche features for targeted cellular responses, which often leads to lengthy development cycles and uncontrolled healing outcomes. To address this critical gap, an innovative, data-driven materiomics strategy is developed. This approach is based on in-house RNA-seq data that integrates bioinformatics and mathematical modeling, which is a significant departure from traditional trial-and-error methods. It aims to provide both mechanistic insights and quantitative assessments and predictions of the tenogenic effects of adipose-derived stem cells induced by systematically modulated features of a tendon-mimetic hydrogel (TenoGel). The knowledge generated has enabled a rational approach for TenoGel design, addressing key considerations, such as tendon extracellular matrix concentration, uniaxial tensile loading, and in vitro pre-conditioning duration. Remarkably, our optimized TenoGel demonstrated robust tenogenesis in vitro and facilitated tendon regeneration while preventing undesired ectopic ossification in a rat tendon injury model. These findings shed light on the importance of tailoring hydrogel features for efficient tendon repair. They also highlight the tremendous potential of the innovative materiomics strategy as a powerful predictive and assessment tool in biomaterial development for regenerative medicine.

Design of the testing procedure for investigation of Eryx conicus dermal armour characteristics

The aim of this work is to develop an experimental method suitable for the mechanical testing of highly non-standard biological samples such as snake skin with osteoderms. The objective of the method is to determine, whether the osteoderms provide a protective function for the animal in its natural environment. For this purpose, a simulation of rodents biting the skin based on uni-axial compressive loading using a synthetic tooth as a penetrator was developed with an emphasis on integration with X-ray scanners to facilitate in-situ testing. To identify and characterise the structure of snake skin and to prove the protective function of osteoderms, all samples were subjected to high resolution X-ray computed tomography. The results of the experiments are presented in the form of stress-strain curves and a map of the tangent modulus.

Stress fracture of bone under physiological multiaxial cyclic loading: Activity-based predictive models

While it is known that excessive accumulation of fatigue damage from daily activities contributes to fracture, a model of bone failure under physiologically relevant multiaxial cyclic loading needs to be developed in order to develop effective management strategies for stress or fatigue fractures. The role of strain-induced damage from repetitive loading is a strong candidate for such a model, as cycles of mechanical loading leading to failure can be measured directly. However, this approach has been limited by the restrictions of uniaxial loading models, which often overestimates the fatigue life of bone and suggests that bone will only break well beyond the realistic limits of exercise. To address this gap and develop a physiologically relevant model, our study leverages the power of four commonly used engineering failure criteria as a model for multiaxial loading using a cohort of human tibiae from cadaveric donors (age range 21–85 years old). Four failure criteria (Von Mises, Tsai-Wu, Findley critical plane, and maximum shear strain) were found to be effective in vitro models of tibial fracture when age groups of donors were combined (r2 > 0.84) and stratified (younger: 21–52-years-old versus older: 57–85-years-old) (r2 > 0.83) (p < 0.001). Each failure criterion displayed distinctly lower fatigue curves for the older age group. The maximum shear strain model was used to determine the efficacy of this approach to predict fatigue fractures in humans using published in vivo data from human volunteers. Consistent with in vivo observations in general population, the model demonstrated failure at 5000 to 200,000 loading cycles depending on activities such as jumping, sprinting, and walking, with a 3-fold reduction of fatigue life in older donors. These findings dramatically improve estimates of fatigue life under repetitive loading and demonstrate how age-related changes in bone significantly increase its propensity for fatigue-induced fractures.

Impact Tendency Characteristics of Borehole Coal Samples under Real-Time and Uniaxial Loading Conditions: Insights from Physical Experiments

Real-time drilling depressurization technology is widely used in the prevention and control of dynamic disasters, such as deep-seated rock burst. However, current coal- and rock-loading tests under drilling conditions seldom account for real-time issues associated with drilling, thus failing to fully reflect the actual stress state of the surrounding rock during the implementation of drilling depressurization technology. Therefore, this study designed and implemented a uniaxial loading scheme for coal samples incorporating real-time-drilling characteristics. The results indicate a significant reduction in the uniaxial compressive strength (RC), elastic energy index (WET), and impact energy index (KE) of the samples post-drilling. These parameters show a clear decreasing trend with increasing axial stress during real-time drilling. The weakening effect of impact tendency following real-time drilling depressurization is significant, and the depressurization effect is pronounced. The RC, WET, and KE of each real-time-drilled sample exhibit a notable decrease with increasing drilling stress, with the reduction rate significantly diminishing after the drilling stress reaches 20% of the peak strength.