Critical Depth Research Articles

Transient resonance of sloshing liquid with time-varying mass

This study examines the sloshing of liquid with time-varying mass in a tank. A set of innovative experiments is carried out involving a shaking table supporting a water tank equipped with a drain pipe. Physical evidence of transient resonance is observed for the first time. Transient resonance occurs under specific excitation conditions when the instantaneous average water level (AWL) approaches a critical depth. During transient resonance, the oscillatory amplitude of the free-surface elevation increases sharply and then decreases in an envelope pattern. A bifurcation of the frequency band is first found in the Morlet-wavelet time–frequency spectrum, coinciding with the appearance of the maximum oscillatory amplitude. How the excitation conditions, drainage rate, and initial water depth affect transient resonance is recognized. Two mathematical models—one based on linear modal theory and the other based on nonlinear asymptotic theory and the Bateman–Luke variational principle—are derived to replicate the physical observations, by which application scopes of both models have been greatly broadened. The linear solution fails to predict the key feature of transient resonance, namely, the asymmetric envelopes of the oscillatory component about the AWL. By contrast, the nonlinear asymptotic solution captures this asymmetric feature accurately, and predicts both the steady and maximum oscillatory amplitudes well. The nonlinear solution is decomposed into terms of order 1/3, 2/3, and 1 using an asymptotic series for component analyses. A special nonlinear jump behavior is observed. The effects of draining and filling on transient resonance are compared.

Dynamic failure assessment analysis of 15MnTi steel supporting structure with a circumferential surface crack under impact loads

Supporting structures, whose strength have great influence on the safe operation of the whole equipment, are widely used in various ship equipment. In this paper, dynamic failure assessment analysis is carried out to discuss the structural integrity of the cracked supporting structure under impact loads. Considering the dynamic response characteristics of structures, the dynamic fracture toughness determined by the loading rate of dynamic J-integrals is used to calculate the failure assessment point (FAP). Due to the widespread uncertainties in practical engineering, such as crack size and mechanical properties of materials, the failure assessment results will also have uncertainty. To analyze the structural integrity affected by uncertain variables, the polygonal convex set (PCS) model is introduced to the failure assessment diagram (FAD) to propose a non-probabilistic failure assessment method. The FAP is extended to a failure assessment region, and structural integrity can be analyzed by the non-probabilistic reliability degree. Compared with the traditional interval model, the non-probabilistic reliability degree calculated by PCS model is closer to the probabilistic reliability degree, which avoids premature judgement of structural failure. For the 15MnTi supporting structure with a circumferential semi-elliptical surface crack under impact loads, the critical depth obtained by non-probabilistic methods decrease by 10% compared with deterministic results, and the failure mechanism is summarized as plastic collapse resulting from the excessive net section stress. In the absence of statistical data on crack size or mechanical properties, the non-probabilistic failure assessment method can be used as an effective alternative to the probabilistic method.

Indenting a thick gel with a solid spherical inclusion

A spherical inclusion is embedded in a soft gel block. A vertical force is applied on the gel surface by means of a spherical indenter. The loading axis is not aligned with the inclusion but placed at a horizontal offset displacement from the inclusion. The measurement of indentation force and inclusion trajectory are compared to the computational results from two-dimensional (2D) Finite Element Analysis (FEA) simulations. A discernible instability emerges when the indentation reaches a critical depth, in accordance with the Southwell instability theory. The three-dimensional (3D) trajectory shows distinct features that were previously not captured by the 2D FEA simulations.

Uniform descriptions of pseudospin symmetries in bound and resonant states

As a continuation of our previous work on the conservation and breaking of the pseudospin symmetry (PSS) in resonant states [Phys. Lett. B 847, 138320 (2023)], in this work, the PSS in nuclear single-particle bound and resonant states are investigated uniformly within a relativistic framework by exploring the poles of the Green's function in spherical Woods-Saxon potentials. As the potential depths increase from zero to finite depths, the PS partners evolve from resonant states to bound states. In this progress, the PSS is broken gradually with energy, width, and density splittings. Specially, the energy and width splittings for the resonant and bound states are directly determined by the ratio of the pseudo spin-orbit potentials between the PS partners. Obvious threshold effect is observed for the energy splitting at a critical potential depth, with which one PS partner has become a quasi-bound state inside the centrifugal barrier while the other one is still a high-energy resonant state outside the centrifugal barrier. The differences in the density distributions of the lower component between the PS partners are manifested in the phase shift for the resonant states and amplitudes for bound states.

Micromechanical effects of substrate hardness on graphene nano-cutting quality

In the nanocutting process of graphene, the mechanism on the atomic scale of the effect of substrate hardness on the edge quality of graphene nanoribbons has not been thoroughly investigated. In this paper, we construct a diamond probe (radius of 5 Å) to cut graphene (190 Å × 113 Å) models with different substrates (silicon/sapphire/silicon carbide), molecular dynamics simulations were used to study the effect of substrate hardness and cutting depth on the atomic structure of graphene nanoribbon edges by observing the atomic morphology, the number of C-C bonds, the radial distribution function and friction. The results show that during the nanoindentation stage, when graphene is in the critical damage state, the substrate with high hardness has high deformation strength, the substrate deformation is small, and graphene undergoes deformation is also small, but the force Fz on the probe, the critical graphene stress σz and the equivalent stress are all large, and the number of C atoms with CN=3 is large; At the nano-cutting stage, the breakage of C-C bonds and the generation of edge defects are caused by local stress concentration, and the graphene stress σxx along the x-direction has a clear directionality. With the same cutting depth (critical damage depth of silicon substrate), silicon substrate hardness is small, the graphene nanoribbon obtained has less number of circular defects generated at the edge, less total number of defective atoms, more number of CN=3 atoms, large peak of radial distribution function of graphene after cutting, and graphene integrity is better. The hardness of the silicon carbide substrate is large, and the number of C-C bond breaks in graphene during the cutting process is high. Each substrate is cut at its own critical damage depth, and the substrate hardness has no significant effect on the number of C-C bond breaks, the number of circular defects, the total number of defective atoms, and the number of CN=3 atoms in graphene. When the silicon substrate was used, the stable force of the probe is small, the edge structure of graphene has little impact, the edge effect obtained is good. The cutting depth and substrate hardness have little effect on the graphene temperature during the nano-cutting process. In this paper, the atomic structure of graphene edges after cutting is analysed and investigated on the atomic scale, and the above results are combined to provide theoretical guidance for obtaining efficient and high-quality and low-damage graphene nanoribbon cutting.

Non-rigid scene reconstruction of deformable soft tissue with monocular endoscopy in minimally invasive surgery.

The utilization of image-guided surgery has demonstrated its ability to improve the precision and safety of minimally invasive surgery (MIS). Non-rigid scene reconstruction is a challenge in image-guided system duo to uniform texture, smoke, and instrument occlusion, etc. METHODS: In this paper, we introduced an algorithm for 3D reconstruction aimed at non-rigid surgery scenes. The proposed method comprises two main components: firstly, the front-end process involves the initial reconstruction of 3D information for deformable soft tissues using embedded deformation graph (EDG) on the basis of dual quaternions, enabling the reconstruction without the need for prior knowledge of the target. Secondly, the EDG is integrated with isometric nonrigid structure from motion (Iso-NRSFM) to facilitate centralized optimization of the observed map points and camera motion across different time instances in deformable scenes. For the quantitative evaluation of the proposed method, we conducted comparative experiments with both synthetic datasets and publicly available datasets against the state-of-the-art 3D reconstruction method, DefSLAM. The test results show that our proposed method achieved a maximum reduction of 1.6mm in average reconstruction error compared to method DefSLAM across all datasets. Additionally, qualitative experiments were performed on video scene datasets involving surgical instrument occlusions. Our method proved to outperform DefSLAM on both synthetic datasets and public datasets through experiments, demonstrating its robustness and accuracy in the reconstruction of soft tissues in dynamic surgical scenes. This success highlights the potential clinical application of our method in delivering surgeons with critical shape and depth information for MIS.

Critical depths of the vertical transition zone between modern infiltration water and fossil groundwater in China

Older groundwater is generally more susceptible to overdraft and also more difficult to recover once contaminated. To understand the prevalence and vulnerability of fossil groundwater infiltrated before Holocene, a global assessment has been conducted recently, but the analysis results for China have been limited by the collection of data. In this study, we combined the groundwater isotope data from the literature databases of CNKI (China national knowledge infrastructure) and SCIE (Science citation expanded) and established the groundwater age dataset of China by virtue of the water samples from 1441 wells. By reconstructing the historical precipitation 3H records of China and using the late-Quaternary atmospheric 14C, the fractions of the modern groundwater that infiltrated after the year 1953 and the fossil groundwater that infiltrated before 12,000 years in the groundwater samples have been calculated based on the straight-forward mixing models. Then we evaluated the extent and depths of the modern and fossil groundwater in the major 16 groundwater-supply areas of China. The results show that the exploitation of deep groundwater mainly occurs in northern China, such as in the Ordos Basin, the North China Plain, and the Hexi corridor, etc. The average critical depth of the vertical transition zone between modern infiltration water and fossil groundwater in China is about 300 m, beneath which more than half of the water samples are dominated by fossil groundwater. Meanwhile, at depth greater than 420 m, the groundwater can rarely be recharged by the modern precipitation. Besides, in China, modern and fossil groundwater, respectively, share 15–45 % and 20–85 % of the total groundwater storage in the uppermost 1000 m of the crust.

Stability of boulders on cobble streambeds

The placement of boulders in streams enhances aquatic habitat by increasing the heterogeneity of flow conditions. Practical design must ensure the stability of individual boulders, requiring calculation of their incipient movement conditions. The stability of a boulder on a cobble bed is shown experimentally to depend on its size, the bed material size, the degree of embedment of the boulder, the slope of the bed and the flow velocity and depth. An equation is derived through a pivoting analysis for predicting the relationship between the critical ambient depth-averaged velocity and the critical flow depth; this, together with a resistance equation, can be used to predict the flow conditions for boulder stability. The equation is used to develop a simpler form for unsubmerged spherical boulders and cobbles. The stability equation is tested against the experimental data, using an experimentally determined drag coefficient relationship.

Finite element simulation and experimental investigation of in-situ laser-assisted diamond turning of monocrystalline silicon

While the effectiveness of in-situ laser-assisted diamond turning (In-LAT) for promoting the ductile machinability of monocrystalline silicon has been demonstrated, the underlying cutting mechanisms remain inadequately understood. In this study, we investigate the fundamental mechanisms involved in the In-LAT of monocrystalline silicon by finite element (FE) simulations and experiments. Specifically, a FE model of In-LAT of monocrystalline silicon is developed, which incorporates a Drucker–Prager constitutive model to address the brittle fracture of the material, as well as temperature-dependent materials properties to address the thermal softening effect. Furthermore, experiments of In-LAT of monocrystalline silicon are conducted with the self-developed In-LAT device, including tapering cutting and end face cutting. Simulation results demonstrate that In-LAT significantly increases the critical depth of cut for the brittle-to-ductile transition of monocrystalline silicon in tapering cutting mode by 72.2% compared to conventional cutting, accompanied with significantly reduced cutting forces, continuous chip profile and reduced surface brittle damage. The promotion of ductile machinability of monocrystalline silicon under In-LAT is attributed to the reduction and dispersion of stress in the cutting zone, which is in contrast to the significant stress concentration at the rake face and cutting edge in conventional cutting. And simulation results also provide an optimal temperature field of 900 K for the In-LAT of monocrystalline silicon, above which the excessive plastic flow accompanied by thermal accumulation results into deteriorated surface roughness. These findings provide valuable insights for understanding the cutting mechanisms of In-LAT and the parameter optimization for In-LAT application.

Experimental investigation on local scour downstream of stepped chutes with a flip bucket

Stepped chutes and flip buckets are the most prevalent energy dissipators in emergency spillways at dams. Given the impact that scour depth has on the stability and safety of these structures, the effects of stepped and smooth chutes on the local scour process downstream of a flip bucket for various hydraulic and geometric conditions were experimentally investigated in the present study. Experiments were conducted for 1:1 and 1:2 chute slopes (V: H), bucket exit angles of 15° and 30°, and a ratio of critical flow depth to step height (yc/h) between 0.53 and 0.97. The comparison of results revealed that installing steps over the chute profile reduced the maximum scour depth downstream in range of 15–51 percent, compared to smooth chute. By changing chute slope from 1:1 to 1:2, the maximum scour depth was reduced by an average of 16 and 25 percent for smooth and stepped chutes, respectively.

The Removal of As(III) Using a Natural Laterite Fixed-Bed Column Intercalated with Activated Carbon: Solving the Clogging Problem to Achieve Better Performance

Natural laterite fixed-bed columns intercalated with two types of layers (inert materials, such as fine sand and gravel, and adsorbent materials, such as activated carbon prepared from Balanites aegyptiaca (BA-AC)) were used for As(III) removal from an aqueous solution. Investigations were carried out to solve the problem of column clogging, which appears during the percolation of water through a natural laterite fixed-bed column. Experimental tests were conducted to evaluate the hydraulic conductivities of several fixed-bed column configurations and the effects of various parameters, such as the grain size, bed height, and initial As(III) concentration. The permeability data show that, among the different types of fixed-bed columns investigated, the one filled with repeating layers of laterite and activated carbon is more suitable for As(III) adsorption, in terms of performance and cost, than the others (i.e., non-intercalated laterite; non-intercalated activated carbon, repeating layers of laterite and fine sand; and repeating layers of laterite and gravel). A study was carried out to determine the most efficient column using breakthrough curves. The breakthrough increased from 15 to 85 h with an increase in the bed height from 20 to 40 cm and decreased from 247 to 32 h with an increase in the initial As(III) concentration from 0.5 to 2 mg/L. The Bohart–Adams model results show that increasing the bed height induced a decrease in the kAB and N0 values. The critical bed depths determined using the bed depth service time (BDST) model for As(III) removal were 15.23 and 7.98 cm for 1 and 20% breakthroughs, respectively. The results show that the new low-cost adsorptive porous system based on laterite layers with alternating BA-AC layers can be used for the treatment of arsenic-contaminated water.

Different scenarios in sloshing flows near the critical filling depth

In the present paper, the sloshing flow in a cuboid tank forced to oscillate horizontally is investigated with both experimental and numerical approaches. The filling depth chosen is $h/L=0.35$ (with h the water depth and L the tank height), which is close to the critical depth. According to Tadjbakhsh & Keller (J. Fluid Mech., vol. 8, issue 3, 1960, pp. 442–451), as the depth passes through this critical value the response of the resonant sloshing dynamics changes from ‘hard spring’ to ‘soft spring’. The experimental tank has a thickness of $0.1L$ , reducing three-dimensional effects. High-resolution digital camera and capacitance wave probes are used for time recording of the surface elevation. By varying the oscillation period and the amplitude of the motion imposed on the tank, different scenarios are identified in terms of free-surface evolution. Periodic and quasi-periodic regimes are found in most of the frequencies analysed but, among these, sub-harmonic regimes are also identified. Chaotic energetic regimes are found with motions of greater amplitude. Typical tools of dynamical systems, such as Fourier spectra and phase maps, are used for the regime identification, while the Hilbert–Huang transform is used for further insight into doubling-frequency and tripling-period bifurcations. For the numerical investigation, an advanced and well-established smoothed particle hydrodynamics method is used to aid the understanding of the physical phenomena involved and to extend the range of frequencies investigated experimentally.

When disability and homoparenting meet: the adoption of children with disability by same sex couples.

The present theoretical essay is based on six reports concerning same-sex couples and gay and lesbian people in order to interconnect homoparenting and the adoption of children with disabilities, through the lenses of human and social sciences in public health. The reports were interpreted in light of studies on same-sex adoption and the adoption of children with disabilities. Feminist approaches related to care and disability were also included in the interpretative perspective, operating as expressive webs of grammars of ableism. It was found that media approaches endorse the right to family formation and the adoption of children with disabilities by homoparental families, but with little critical depth on the category of disability and without highlighting support for the adoption of all adoptee profiles. Moreover, the intersections between homophobia and ableism increase discriminatory and oppressive logics, with the union of social groups considered to be "undesirable" representing a strategy of governmentality that reveals the complexity of grammars of ableism, applied to the sexual and reproductive rights of LGBTQIA+ adopters and to the fundamental rights of children and adolescents with disabilities who are available for adoption.

Influence of diamond abrasives on material removal of single crystal SiC in mechanical dicing

Mechanical dicing is a critical step in producing electronic chips and devices. Single crystal silicon carbide (SiC) is a vital wafer material in modern electronic chips because of its exceptional physical properties, such as wide bandgap and high breakdown voltage. However, the high hardness of SiC makes it extremely challenging to achieve the dicing quality required for the reliable functioning of electronic chips. The removal characteristics of single crystal SiC in mechanical dicing process remains largely unclear. This work aims to systematically investigate the influences of diamond abrasives in ultrathin blades on the dicing force, chipping size, surface roughness, and material removal of single crystal SiC in mechanical dicing. Experimental results indicate the diamond abrasives considerably affect the chipping formation and the material removal of SiC workpieces by changing the undeformed chip thickness. Theoretical analysis based on the classic brittle-ductile transition model reveals that single crystal SiC can be removed in a ductile-like mode using relatively large abrasive size and low concentration, as long as the undeformed chip thickness is sufficiently smaller than the calculated critical depth of cutting. In addition, the mounting method of single crystal SiC workpieces and the wear characteristics of diamond blades play a crucial role in the removal behaviours and, therefore, the dicing quality. An example was given to demonstrate the feasibility of simultaneously improving the dicing quality and the removal rate via appropriately increasing concentration and reducing sizes of abrasives in ultrathin blades. Ultimately, the findings in this research provide a guideline for further optimization of the dicing tools and parameters for other hard-and-brittle solids.

Roadway rock burst prediction based on catastrophe theory

In order to quantitatively calculate the critical depth and critical load of mines affected by rock burst, and to achieve effective prevention and control of rock burst in coal mines, this paper proposes a mechanical model for predicting the occurrence of rock burst in coal mine roadways based on catastrophe theory. Additionally, a theoretical calculation formula for initiating rock burst is derived. The first step was to establish a mechanical analysis model, which directly correlated with the in-situ stress, physical and mechanical characteristics of the coal-rock mass, and engineering structural parameters. Following this, a mechanical instability criterion was derived for the key load-bearing circle within the surrounding rock of the roadway. In the final step, the critical depth and load for rock burst initiation were verified for 25 distinct coal mines in China that were prone to rock burst hazards. The research results demonstrate that the discrepancy between the theoretically calculated critical depth and the actual measured statistical values was less than 35%. In addition, the difference between the theoretically determined critical depth and the value calculated by Pan Yishan was less than 32%. Notably, the ratio of the theoretically calculated critical load to the uniaxial compressive strength of the coal-rock mass ranged from 0.38 to 1.93. This aligns with empirical data on rock burst occurrences, as set out in the engineering classification standards for rock masses. These research outcomes substantiated the practical utility of the proposed theory, thereby laying a robust theoretical groundwork for the quantitative control of rock burst.

Calculation model for critical depth of kinked dents on pipelines with internal pressure

Kinked dent is caused by the external force on the oil and gas pipeline, and its curvature is small, which seriously affects the operation safety of the pipeline. This paper focuses on the study of the critical depth of kinked dent for steel pipelines with internal pressure, to propose the safety evaluation criterion for pipelines with kinked dents. First, a full-scale hydraulic bursting test of a steel pipeline with kinked dents is designed, and the pressure-bearing capacity and the strain response law of the kinked dent in the test process are obtained. The results show that the pipeline does not fail at the kinked dent, and the kinked dent almost completely rebounds and has a certain pressure-bearing capacity. Then, a finite element simulation model of the pipeline with kinked dents is established, and the accuracy of the model is verified by comparing with the test. After that, the pressure-bearing failure mode and failure criterion of the pipeline with kinked dents are determined, the sensitive parameters affecting the failure are analyzed, and the effects of the parameters such as the depth and angle of the kinked dent, the diameter thickness ratio and yield ratio of the pipeline on the pressure-bearing capacity are obtained. Finally, based on many numerical simulation results, a calculation model for the critical depth is proposed as a safety evaluation criterion for the pressure-bearing failure of pipelines with kinked dents.

A theoretical and experimental investigation on the surface formation mechanism in elliptical vibration cutting of single crystal magnesium fluoride

Manufacturing precise microstructures on magnesium fluoride surface remains challenging due to its brittleness and anisotropy. This study investigates the surface formation mechanism in ductile machining of single crystal magnesium fluoride and explores the feasibility of fabricating sophisticated microstructures on magnesium fluoride surfaces by applying elliptical vibration cutting technology. We conducted a systematic study on the ductile-brittle transition behavior, material removal mechanism, and fabrication performance of microstructures through theoretical analysis and cutting experiments. A theoretical model that takes into account the elliptical trajectory's orientation angle has been established to determine the evolution of instantaneous uncut chip thickness and the characteristic nominal depth of cut in one cycle during elliptical vibration cutting. By comprehensively examining the influence of the elliptical trajectory, determined by vibration amplitudes, orientation angle, and nominal cutting speed, on the dynamic behaviour of the ductile-brittle transition, we verified the proposed theoretical model with convincing experimental results. Larger critical depth of cut for ductile-brittle transition and smaller cutting forces achieved by EVC contribute to the improved ductile machinability of MgF2. With optimal vibration parameters, the critical depth of cut increases by 56 times compared to ordinary cutting. Theoretical findings regarding plastic deformation parameters and cleavage fracture parameters align well with experimental observations, providing a more comprehensive understanding of the anisotropy influence on damage evolution during the surface formation in elliptical vibration cutting of magnesium fluoride. Furthermore, leveraging our fundamental understanding of material removal and surface formation mechanisms, we successfully generated bi-sinusoidal arrays on magnesium fluoride surfaces with exceptional accuracy (machining error < 1.5%) and high efficiency (machining time < 121.5 min) by applying elliptical vibration cutting.

Influence of planetary rotation on metal-silicate mixing and equilibration in a magma ocean

At a late stage of its accretion, the Earth experienced high-energy planetary impacts. Following each collision, the metal core of the impactor sank into molten silicate magma oceans. The efficiency of chemical equilibration between these silicates and the metal core controlled the composition of the Earth interior and left a signature on geochemical and isotopic data. These data constrain the timing, pressure and temperature of Earth formation, but their interpretation strongly depends on the efficiency of metal-silicate mixing and equilibration. We investigate the role of planetary rotation on the dynamics of the sinking metal and on its chemical equilibration using laboratory experiments of particle clouds settling in a rotating fluid. Our clouds initially sink as spherical turbulent thermals, but after a critical depth, rotation becomes important and they transition to a vortical columnar flow aligned with the rotation axis. Applied to Earth formation, our results predict that rotation strongly affects the fall of metal in the magma ocean for impactors smaller than 459 km in radius on a proto-Earth that rotates twice faster than today. On a proto-Earth spinning 5 times faster than today, rotation is important for any impactor smaller than the Earth itself. In contrast with a thermal that grows in all directions, the vortical column grows vertically but keeps a constant horizontal extent. The slower dilution in vortical columns reduces chemical equilibration compared to previous estimates that neglect planetary rotation. We find that rotation significantly affects the degree of equilibration for highly siderophile elements with partition coefficients larger than 103. In this case, for a planet spinning twice faster than today, the degree of equilibration decreases by up to a factor 2 compared to previous estimates that neglect the effect of rotation. Finally, the ultimate fate of iron drops is to be detrained from the vortical column as an iron rain, reconciling the traditional iron rain scenario with the model of turbulent thermal.

Atomistic simulation of nanoindentation behavior of amorphous/crystalline dual-phase high entropy alloys

High-entropy alloys (HEAs) are a new type of multi-principal metal materials that exhibit excellent mechanical properties. However, the strength–ductility balance in the HEAs remains a challenge that needs to be addressed. The amorphous/crystalline (A/C) structure is a new design strategy to achieve high strength and excellent ductility of the HEAs. Here, the influences of amorphous layer spacing, indenter velocity, and indenter radius on the mechanical properties and microstructure evolution of the A/C dual-phase CoCrFeMnNi HEAs under nanoindentation were investigated by molecular dynamics (MD) simulation. The results indicate that the plastic deformation mechanism of the monocrystalline HEAs is mainly dominated by the nucleation and slip of dislocations, while the plastic deformation mechanism of the dual-phase HEAs is mainly dominated by the interaction between dislocations and amorphous phases. The results show that the average indentation force of the dual-phase HEAs increases with the increase of the amorphous layer spacing. The amorphous layer in the HEAs can hinder the expansion of dislocations, limiting them to the crystalline matrix between the two amorphous layers. The results also indicate that Young's modulus of the HEAs increases with the increase of the indentation velocity and indentation radius. However, the hardness of HEAs is positively correlated with the indenter velocity, and negatively correlated with the indenter radius. It should be noted that the critical indentation depth and critical indentation force for the plastic deformation of the dual-phase HEAs decrease with the increase of indenter velocity, which is opposite to that of the single-phase crystalline HEAs.

Study on the Vertical Stability of Drilling Wellbore under Optimized Constraints

With the development of coal resource extraction and wellbore construction proceeding towards deeper depths, the stability of drilling wellbore structures has become increasingly severe, even posing a barrier to the use of drilling method technology in deep wellbore construction. To address this issue, this study raised an optimized constraints method involving pre-throwing cement slurry to the bottom before wellbore decent, altering bottom constraints. Firstly, the critical depth and instability criterion of this optimized method was derived by catastrophe theory. Subsequently, the role of single-factor and multi-factor sensitivity analyses on critical depth was discussed. The engineering effects of optimized constraint methods were contrasted and examined in several drilling projects. Finally, the characteristic values of real engineering were computed using numerical techniques and ABAQUS2020 software, and the efficacy of optimization approaches was examined and validated. The results revealed that the critical depth increased by 41.39 ± 5%. The influence factors described in order of the degree were the counterweight water height, the elastic modulus, the thickness of the wellbore, and the self-weight of the wellbore, sequentially. The conclusion on structural stability between the numerical calculation solution and theoretical calculation solution was completely the same. The optimized constraints method can effectively improve the stability of the wellbore structure.