Deformation Fracture Research Articles

High Complication Rate After Percutaneous Screw Fixation for Valgus-Impacted Femoral Neck Fractures Without Sagittal Malalignment.

To evaluate the rate of reoperation in patients without sagittal plane malalignment who underwent percutaneous screw fixation of a valgus-impacted femoral neck fracture. Retrospective case series. Two Level 1 academic trauma centers. Two hundred seven patients >50 years of age with valgus-impacted femoral neck fractures treated with at least 3 large-diameter (>6.5 mm) cancellous screws from 2013 to 2019. Patients were excluded if there was a sagittal plane fracture deformity. The primary outcome was reoperation. Secondary outcomes considered "major complications" included: avascular necrosis, varus collapse or implant cutout, nonunion, deep infection, and hematoma requiring reoperation. Surgical fixation strategies (screw configuration, aim) and implant type (partial vs. fully threaded cancellous screws) were secondarily compared. Average patient age was 77 years, and median clinical follow-up was 658 days. Thirty-one patients (15%) required reoperation, and the major complication rate was 17.3% (36 complications in 33 patients). Logistic regression analysis demonstrated a higher risk of reoperation with constructs consisting of all partially threaded screws (17.0%) compared with the use of at least 1 fully threaded screw (7.5%) when an inverted triangle configuration was used (odds ratio, 2.50; 95% CI, 0.81-7.77). This study demonstrated a relatively high rate of reoperation and major complications in patients with valgus-impacted femoral neck fractures without sagittal malalignment treated with in situ percutaneous screw fixation. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Geomechanical modeling of ultradeep fault‐controlled carbonate reservoirs and its application, a case of the Fuman Oilfield in Tarim Basin

AbstractTo improve the development efficiency of ultradeep fault‐controlled carbonate reservoirs, the deformation and connectivity mechanism of fractures was revealed through large‐scale rock mechanical experiments. The in situ stress field and fracture activity distribution law of fault‐control carbonate reservoirs were clarified through geomechanical modeling. It is revealed that the fracture activity in different directions and the connectivity of the fracture and cavity in different parts are significantly different, the development effect of different well trajectories is analyzed, and the integrated working method of geological engineering is proposed to scientifically guide the well trajectory design and water injection scheme optimization. The results show that: (1) Large‐scale fractures and high‐angle fracture systems in the deformation of strike–slip faults are the key factors affecting reservoir quality. High‐pressure water injection can activate preexisting fractures, and it can extend on the basis of preexisting fractures, and even generate new fractures, which promote the interconnection of fault‐controlled fracture‐cave bodies in the vertical and horizontal directions. (2) During the process of high‐pressure water injection, the coupling change between mechanics and flow occurs inside the fracture body, the seepage environment is improved, and the oil and gas recovery factor is improved through cyclic lifting. (3) According to the shape and occurrence of the fault body and the dynamic shear deformation connectivity of the fault surface, the best well point and well trajectory of the directional well can be optimized, and the water injection scheme can be optimized. (4) The single‐well production increased by 1.45 × 104 t through high‐pressure water injection, the cumulative oil increase of the same fracture‐cavity body increased by 4.63 × 104 t. This method is highly efficient for ultradeep fault‐controlled oil reservoirs. The development provides a good theoretical basis and technical support, and plays a leading and exemplary role.

Study on surface quality of CNTs/2009Al composites in grinding process with a volume fraction ratio of 3%

Composite materials made of aluminum-based carbon nanotubes (CNTs/Al) are often employed in industries like aerospace and national defense that place a high priority on material processing accuracy at the material’s surface. The most popular machining technique for enhancing the surface quality of materials is grinding. This paper built a prediction model for the surface roughness of CNTs/2009Al composites and identified the process of micro-grinding. Using the ABAQUS software, a non-uniform finite element simulation model of the single abrasive grain grinding process of CNTs/2009AL composites was created. An electroplated diamond grinding rod with a diameter of 2 mm was used in the micro-grinding experiment on the CNTs/2009Al composite, and the impact of the grinding parameters on the quality of the machined surface was examined. According to the findings, the feed speed has the least impact on the material’s surface roughness, whereas the spindle speed and grinding depth both have a significant impact. The measurement of the minimal roughness is 0.117 m. A shallower grinding depth, a lower feed rate, and a correspondingly higher spindle speed should be used in order to provide a superior surface quality. According to the prediction model of micro-grinding surface roughness and laser confocal microscope scanning, the primary phenomena of CNTs in the grinding process include pull-out, fracture, and elastic deformation.

Embedded discrete fracture network method for numerical estimation of long-term performance of CO2-EGS under THM coupled framework

In enhanced geothermal system (EGS), the artificial fracture networks created by hydraulic fracturing provide highly conductive channel for heat extraction. Very complicated thermo-hydro-mechanical (THM) coupled processes will be involved during cold CO2 injection into the hot fractured reservoir. In this work, a new THM coupled approach is proposed for simulating the long-term performance of CO2-EGS based on embedded discrete fracture networks (DFNs). Due to significant temperature difference between the injection fluid and surrounding, the heat flow in fractures is governed by local thermal non-equilibrium theory. The THM coupling process is achieved by coupling the mechanical simulator FLAC3D and hydraulic-thermal simulator TOUGH2MP. The feasibility of proposed approach is verified and validated through comparing it with analytical solution and other method. The CO2 injection into a reservoir with stochastically generated DFNs is simulated for a period of 20 years, to study the flow behavior, fracture deformation, and thermal performance. The channeling flow is observed by streamlines of fluid and heat flow. The thermal stress due to temperature drop will enhance the fracture width, further decreasing the injection pressure, which shows the significance of incorporating the THM coupling effect in such high temperature reservoirs. This approach also enriches the tools for CO2-EGS simulation.

Enhancing acetabular reaming accuracy: optimal techniques and a novel reamer design

IntroductionSuccessful press-fit implantation relies on an accurately reamed bone cavity. Inaccurate reaming can lead to a suboptimal press-fit risking fracture and cup deformation or excessive micromotion and loosening. Several factors may impact reaming accuracy including the reamer design, the surgeon’s technique and the bone quality. The aim of this study is to investigate the accuracy of reaming techniques and the accuracy of a novel reamer design.MethodsEighty composite bone models, half high density and half low density, were reamed with either a conventional or an additively manufactured reamer with a novel design employing either a straight or ‘whirlwind’ reaming technique. Reamed cavities were scanned using a 3D laser scanner and the median difference between achieved and expected diameters compared.ResultsThe novel reamer design was more accurate than the unused conventional reamer, using both whirlwind (0.1 mm (IQR 0–0.2) vs. 0.3 mm (IQR 0.3–0.4); p < 0.001) and straight techniques (0.3 mm (IQR 0.1–1.0) vs. 1.2 mm (IQR 1–1.6); p = 0.001). Whirlwind reaming was more accurate than straight reaming using both conventional (0.3 mm (IQR 0.3–0.4) vs. 1.2 mm (IQR 1–1.6); p < 0.0001) and single use reamers (0.1 mm (IQR 0–0.2) vs. 0.3 mm (IQR 0.1–1.0); p = 0.007). Reaming errors were higher in low-density bone compared to high-density bone, for both reamer types and reaming techniques tested (0.6 mm (IQR 0.3–1.5) vs. 0.3 mm (IQR 0.1–0.8); p = 0.005).ConclusionWe present a novel reamer design that demonstrates superior accuracy to conventional reamers in achieving the desired reaming diameter. Improved reaming accuracy was also demonstrated using both devices and in both bone models, using a ‘whirlwind’ technique. We recommend the use of this novel reamer design employing a ‘whirlwind’ technique to optimize reaming accuracy. Particular attention should be paid toward patients with lower bone quality which may be more susceptible to higher inaccuracies.

Constructing a rigid-flexible grid structure for simultaneously strengthening and toughening bamboo flour/plastic composites through the introduction of continuous carbon fabric meshes via multi-layer co-extrusion

The defects of low strength, brittle fracture, and creep deformation of traditional wood–plastic composites (WPCs) significantly limit their applications as high-value-added products. This study aimed to develop advanced WPCs with high strength, toughness, and creep resistance via a structural design. A continuous rigid-flexible grid structure, sandwiched by carbon fabric mesh prepreg (CFMP) and casting film (MSF) with high toughness, was introduced into bamboo flour/high-density polyethylene composites (BPCs) via a multi-layer co-extrusion technology. The sandwiched grid structure was in-situ cured in the near-surface layers of BPCs to form a multi-layer composite (BPC-CFMP-F) during co-extrusion. The tensile strength, flexible strength, and impact strength of BPC-CFMP-F were 68.4 MPa, 89.0 MPa, and 22.5 kJ m−2, which are 138.3%, 96.4%, and 87.6% higher than those of BPCs, respectively, and the thermal expansion and 1000-hr creep strain of BPC-CFMP-F decreased by 45.8% and 61.7%, respectively. The simultaneous strengthening and toughening of BPCs were attributable to the rigid-flexible grid structure and the strong interfacial bonding between CFMP and BPCs and the surface- and core-layer BPCs through the grid of CFMP. Owing to these unique features, BPC-CFMP-F is a promising advanced composite with high strength, toughness, excellent creep resistance, and thermal stability for high value-added applications.

Study on the effect of fracture morphology on fracture deformation based on the thermal-hydraulic-chemical-deformation coupling model

The chemical reaction in the reservoir causes fracture deformation during the heat extraction of enhanced geothermal systems (EGS), affecting thermal performance. The reaction rate is sensitive to temperature, concentration, and reaction-specific surface area. While previous research mainly focuses on the influence of temperature and concentration on fracture deformation, conversely, the effect of fracture morphology(aperture and tortuosity) is ignored. In this study, the deformation characteristics of rough and flat fractures are compared, and the influences of aperture and tortuosity on fracture deformation are analyzed. According to the influence law, the fracture deformation relationship equation between the aperture deformation rate with tortuosity and aperture is fitted. Results show that the deformation of rough fracture is significantly higher than that of flat fracture, and the variations of fracture aperture increase with the aperture and tortuosity. Furthermore, the influence of tortuosity (the variation of aperture increased by 47.97% when the tortuosity increased from 1 to 1.5) is greater than the aperture (that increased by 4.8% when the aperture increased from 0.2 to 1). The rate of aperture change is a logarithmic function of tortuosity and a power function of the aperture. These results provide significant references for the study of EGS, subsurface karst et al.

Numerical Treatment of State‐Dependent Permeability in Multiphysics Problems

AbstractConstitutive laws relating fluid potentials and fluxes in a nonlinear manner are common in several porous media applications, including biological and reactive flows, poromechanics, and fracture deformation. Compared to the standard, linear Darcy's law, such enhanced flux relations increase both the degree of nonlinearity, and, in the case of multiphysics simulations, coupling strength between processes. While incorporating the nonlinearities into simulation models is thus paramount for computational efficiency, correct linearization, as is needed for incorporation in Newton's method, is challenging from a practical perspective. The standard approach is therefore to ignore nonlinearities in the permeability during linearization. For finite volume methods, which are popular in porous media applications, complete linearization is feasible only for the simplest flux discretization, namely the two‐point flux approximation. We introduce an approximated linearization scheme for finite volume methods that is exact for the two‐point scheme and can be applied to more advanced and accurate discretizations, exemplified herein by a multi‐point flux stencil. We test the new method for both nonlinear porous media flow and several multiphysics simulations. Our results show that the new linearization consistently outperforms the standard approach. Moreover our scheme achieves asymptotic second order convergence of the Newton iterations, in contrast to the linear convergence obtained with the standard approach.

Experimental Investigations of Fracture Deformation, Flow, and Transport Using a Pressure‐Controlled Hele‐Shaw Cell and Digital Fabrication

AbstractIn this paper we present a novel pressure‐controlled Hele‐Shaw cell to investigate different physical processes in rough fractures using 3D‐printed rock analogs. Our system can measure high‐resolution fracture aperture and tracer concentration maps under relevant field stress conditions. Using a series of hydraulic and visual measurements, combined with numerical simulations, we investigate the evolving fracture geometry characteristics, pressure‐dependent hydraulic transmissivity, flow channeling, and the nature of mass transport as a function of normal stress. Our experimental results show that as the fracture closes and deforms under increasing normal loading: (a) the contact areas grow in number and size; (b) the flow paths become more focused and tortuous; and (c) the transport dynamics of conservative tracers evolve toward a higher dispersive regime. Moreover, under the applied experimental conditions, we observed excellent agreement between the simulated‐ and the experimentally measured‐hydraulic behavior.

Carpal Joint Malalignment With Distal Radius Malunion and Factors in Correction After Distal Radius Osteotomy

There is a paucity of data regarding recommendations on when to correct for distal radius malunions and if the initial severity of the radiographic outcomes is correlated with the ability to correct to baseline. We evaluated the effects of distal radius corrective osteotomy on preoperative carpal joint malalignment resulting from distal radius malunions, correlated injury severity and osteotomy timing to radiographic outcomes, and developed a straightforward classification system for predicting radiocarpal and midcarpal maladaptive patterns. A retrospective review included 26 patients (27 wrists) who reported initial closed treatment for a distal radius fracture and who subsequently underwent a corrective osteotomy for malunion. Data included patient demographics, range of motion, preoperative fracture deformity, fracture deformity correction, and preoperative and postoperative radiographic measurements of the radiocarpal and midcarpal alignment patterns. Of 27 dorsally angulated malunions, 16 were classified as type 1 midcarpal adaptation and 11 as type 2 radiocarpal adaptation. The midcarpal group showed significant improvements in distal radius and carpal alignment parameters after surgery, except for the ulnar variance. The radiocarpal group showed significant improvements in distal radius and carpal alignment parameters, except for the radiolunate angle, radioscaphoid angle, and capitolunate angle. The radiocarpal group exhibited an overall decrease in range of motion compared with that of the midcarpal group. Severity of the fracture and time taken from injury to corrective osteotomy correlated with the ability to correct carpal radiographic parameters in dorsally angulated malunions of the distal radius, especially beyond 40 weeks. The severity of the initial fracture and time taken from injury to corrective osteotomy correlate with the ability to correct radiographic parameters in dorsally angulated malunions of the distal radius. Early correction of distal radius malunions is recommended, especially in radiocarpal malalignment patterns. A useful analysis for predicting midcarpal and radiocarpal adaptation patterns is the direct measurement of the distal articular surface of the radius to the lunate, termed the relative-radiolunate angle. Therapeutic IV.

Visual simulation of crack and bend generation in deteriorated films coated on metal objects: Combination of static fracture and position-based deformation

Visual simulation of crack and bend generation in deteriorated films coated on metal objects: Combination of static fracture and position-based deformation

Impact of stress-driven crack growth on the emergence of anomalous transport in critically connected natural fracture networks

We study the role of in-situ stresses in fluid flow and mass transport through a two-dimensional fractured rock. The fracture network is based on a real outcrop with a connectivity state around the percolation threshold. We simulate stress-dependent fracture propagation and deformation using a geomechanics model based on the hybrid finite-discrete element method. The hydrodynamic transport through the deformed rock mass is then modeled based on particle tracking simulations. By exploring various scenarios of different stress ratios and orientations, we systematically analyzed how the superimposed multiple geomechanical processes (i.e., compression-induced closure, shear-induced dilation, and stress-induced propagation) control the aperture patterns, flow fields, and transport behaviors of the fracture network. Our results show that an increased stress ratio tends to promote fracture shear dilation and thus enhance flow channelization, resulting in an anomalously early arrival of solute transport. Furthermore, the increased differential stress attempts to drive the growth of wing cracks that bridge pre-existing fractures and form new flow pathways. We observe a qualitative transformation of the flow structure from a disconnected to a connected regime accompanied by a significant alteration of its overall transport properties. This phenomenon is attributed to the superimposed effect of stress-driven crack propagation and shear-induced fracture dilation. By quantitative parameter analyses of global flow and transport properties, we further found that the breakthrough time median of particles is well correlated with the equivalent permeability of the fractured rock when the effect of new cracks is removed. However, this correlation is greatly reduced when fracture propagation is considered; instead, the breakthrough time shows a good correlation with mean tortuosity. Our findings have important implications for the strategy design of geothermal production and waste disposal in critically connected fractured geological media under various stress conditions.

An XFEM-based hydro-mechanical model to consider the non-Darcy flow in complex fracture networks

Geotechnical instability and failure are closely related to the hydro-mechanical coupled behavior of fractured rocks, and the existing studies often regard the fracture seepage as linear Darcy flow. Due to the neglect of non-Darcy effect caused by rough rock wall and high flow velocity, the estimated rock deformation and seepage flow can lead to incorrect assessment of geotechnical risks. Hence, this study proposed an efficient and robust hydro-mechanical (HM) coupled model to consider non-Darcy flow in complex fracture networks. The fractured rock mass's mechanical response, including the fracture surface's frictional contact, was calculated using the XFEM solver, and the widely used Forchheimer's law was adopted to describe the non-Darcy flow along the fractures. The fracture segments cut by mechanical element edges are considered one-dimensional flow elements, and the Newton-Raphson iteration method is adopted to solve the Forchheimer equation directly. To consider the influence of fracture deformation on the conductivity of fractures, the Barton-Bandis model was adopted to determine the hydraulic aperture of the fractures when the fracture was closed. Subsequently, a staggering Newton-Raphson method can be developed to decouple the fracture deformation and fluid flow process. Experimental results were adopted to validate the accuracy of the numerical model, and several numerical cases were used to illustrate the efficiency and robustness of the proposed model. The effects of inlet pressure, confining stress, and non-Darcy effect on the HM-coupled behavior of fractured rock were investigated. Numerical results suggested that the distribution of fluid pressure and failure process of rock mass based on Darcy assumption could be dramatically changed after considering the nonlinear seepage behavior.

Investigation of dynamic response of drilling parameters and deformation characteristics of coal around borehole during multi-stage reaming in tectonic coal

Tectonic coal refers to the coal with varying degrees of brittle fracture or ductile deformation under the action of one or multi-period tectonic stresses, showing the characteristics of low mechanical strength, weak cohesion and large deformation. Therefore, drilling in tectonic coal is easy to cause the aperture shrinkage or closure due to the poor anti-deformation capability. Enlarging the initial borehole can effectively increase the borehole diameter and reduce the risk of pipe jamming and burying without changing the borehole structure. In order to investigate the dynamic evolution characteristics of drilling parameters in the process of drilling and reaming in tectonic coal, a self-designed drilling experimental system that can monitor drilling parameters in real time was used in this study. Additionally, the acoustic emission (AE) response and borehole wall strain were observed to study the coal-breaking and the deformation characteristics of coal around borehole. The results demonstrate that the drilling rate and drilling torque increase sequentially in the initial drilling, primary reaming and secondary reaming stages. The magnitude of drilling rate is affected by both drilling thrust and rotational speed, whereas drilling torque is mainly affected by drilling thrust. The intensity of AE phenomena increases gradually at different stages of the borehole formation, which means that the drilling efficiency is improved and more strain energy is accumulated in the coal around the borehole during reaming. The borehole wall strain effectively reflects the convergence deformation of borehole wall, that is, the larger the borehole diameter, the greater the deformation of the borehole wall. The deformation of borehole is mainly affected by the redistribution of stress in the coal body, rather than the drilling parameters.

Numerical study of the long-term performance of EGS based on discrete fracture network with consideration of fracture deformation

During heat extraction in fractured reservoir, the perturbation of pressure, stress, temperature could alter the fracture aperture, which feeds back to the long-term performance of EGS. In this work, a 3D THM coupled model was developed for the long-term performance based on the discrete fracture network. The apparent improvement of this model is both shear dilatancy and normal closure/opening are considered in a complete constitutive relationship under the THM coupled framework TOUGH2M-FLAC3D. The feasibility is verified and validated through comparing with analytical solution and previous numerical work. In application of the new approach in a fractured reservoir, it is found that the phenomenon of channel flow will concentrate the heat mining in partial fractures, and the fracture enhancement further reinforce the channel flow. The pressure effect on fracture transfers faster than the thermal effect. In the sensitivity analysis, the zero-stress aperture has a positive impact on heat extraction. Higher thermal expansion coefficient promotes the heat extraction as well. While, the dilation angle in this work has a neglectable impact on heat extraction performance. The thermal effect accounts for the most fracture variation under high thermal expansion coefficient. Therefore, the thermal effect should be considered especially in high temperature geothermal reservoir.

Mechanical properties of mudstone caprock and influencing factors: implications for evaluation of caprock integrity

Mudstone is the most common cap rock in petroliferous basins. The mechanical properties of mudstone in different areas and buried depths are obviously different, which directly affects the brittleness and ductileness of caprock and its deformation characteristic. This research carried out X ray diffraction (XRD) rock mineral composition analysis, microscopic observation of mineral structural characteristics and rock mechanics triaxial compression tests under different conditions on six groups of mudstone samples from three basins. On this basis, establish numerical model to simulate the fracture deformation of mudstone under geological conditions, and to clarify the influence of different factors on the rock mechanics of mudstone. Compare and analyze the fracture characteristics and stress-strain curves of mudstone samples after the test show that, the confining pressure is the most direct factor affecting the mechanical properties and deformation mechanism of mudstone in the range of oil and gas enrichment depth. Although the formation temperature has a certain influence on the rock deformation, the effect is very limited, and it is difficult to have an essential influence on the rock deformation without the action of confining pressure. The mineral composition of mudstone is also one of the main factors affecting the mechanical deformation of rock. The comparison between the content of main minerals and the mechanical parameters of rock shows that the mechanical properties of rock and the transformation of brittleness and ductileness of mudstone have the most obvious correlation with clay minerals. Numerical simulations show that, pore fluid pressure is an important factor that cannot be ignored in overpressured caprocks. Higher pore fluid pressure can significantly inhibit the transition process of rock brittleness and ductileness, and at the same time affect the fracture mode of mudstone, which is of great significance for the evaluation of caprock integrity.

South Anze Structure and Its Control on Coalbed Methane Aggregation in the Qinshui Basin and the Mechanism of Syncline Gas Enrichment in the Qinshui Basin

The phenomenon of coalbed-methane synclinal accumulation in the Qinshui Basin has been widely reported, but it has mainly been observed in the core block of the Qinshui Syncline. The questions arise: does this phenomenon exist in the wing of the Qinshui Syncline and, if so, what is the mechanism behind it? Further study is required to answer these questions. This paper focuses on the South Anze No. 3 coal seam in the Qinshui Basin as an example. It conducts a systematic sorting of coalbed-methane geological characteristics and an analysis of the effects of structural assemblage characteristics, genetic mechanisms, and structural control on coalbed-methane accumulation. Additionally, it examines the basin structure and evolution during the critical period of the Qinshui Basin, as well as the gas geological characteristics of adjacent areas, in order to discuss the gas-rich mechanism of the syncline in the Qinshui Basin. Key insights obtained from the study include the following: (i) The whole South Anze is a nosing structure that plunges from west to east and superposes secondary folds and faults in different directions. Four deformation zones can be identified based on the characteristics of structural assemblage, including NEN-oriented compressive structures, ENE-trend shear fractures, EW-trend compressive fractures, and EW-trend compressive folds. The formation of structural assemblage in the study area is attributed to the compression in the Indosinian and Yanshanian, and the fault inversion in the Himalayan period. (ii) The ENE-trend shear fracture deformation area located in the nosing uplift is a low CBM (coalbed methane) content area due to gas diffusion during the Himalayan extension. The syncline in the combination of NEN-trend and EW-trend “ejective folds” in the west and south of the study area is a high-value area of coalbed-methane content. It is further verified that the law of syncline gas accumulation in the Qinshui Basin is also applicable to the wing of the Qinshui Syncline. (iii) Since the formation of the Qinshui Syncline, the main coal seam has been in an extensional environment below the neutral plane, resulting in the main dissipation of coalbed methane. During its geological history, surface water penetrated the aquifer above the main coal seam through two channels: the extensional area above the neutral plane of the adjacent anticline and the shear fracture. A hydrostatic pressure seal is formed in the Qinshui Syncline and the secondary syncline is superimposed upon it, which is the cause of gas enrichment in the syncline of the Qinshui Basin. (iv) Weak deformation in the syncline basin is the focus of global coalbed-methane exploration and development. The mechanism proposed in this paper can provide ideas and references for further understanding of coalbed-methane enrichment in this type of basin.

Seismic resistance of buckling restrained steel slit panels with X-Shaped restrainers

Steel slit panels (SSPs) serving as lateral load-resisting systems are steel plates (SPs) with rows of vertical slits forming a series of flexural links. The main deficiencies of SSPs subjected to shear forces are fair seismic performance characteristics due to either out-of-plane deformation of long links or fracture of relatively short links. To alleviate this problem, novel buckling restrained SSPs with X-shaped restrainers (referred to as XSSPs) are proposed in the current study. The restrainers are placed on both sides of SSPs to restrain only out-of-plane buckling of links. Refined finite element models of these systems are established and verified by the experiments. The explicit analysis is conducted on these models to evaluate the effects of different patterns of X-shaped restrainers on the seismic performance of these systems. Other parameters considered in this work, include the width-to-thickness ratio of the links, the length-to-width ratio of the links, the number of rows of links, and the width of edge stiffeners. It is found from the results that the hysteresis responses of XSSPs are rather stable with a large energy dissipation capacity. The pinching enhancement is particularly high in cases with a lower length-to-width ratio of the links. Applyin more restrainers in XSSPs models with a lower width-to-thickness ratio and a higher length-to-width ratio of the links improved the strength and the initial stiffness significantly. The strength and stiffness increases due to using diagonal X-shaped restrainers can reach up to 400% and 900%, respectively. The XSSPs have exhibited superior energy dissipation increases more than two times compared with the corresponding SSPs and SPs.

Mathematical modeling of the acetabulum fracture (type 62-B1.3 by AO/ASIF) deformities and hip endoprosthetics in combination with osteosynthesis

Secondary degenerative disabling changes in the hip joint often develop in the long term after surgical treatment of hip fractures. A well-founded differential approach to the selection of endoprosthesis components and additional means of stabilizing bone fragments is necessary. Objective. To investigate changes in relative deformation values in a hip joint model with a acetabulum fractures 62–B1.3 type by AO/ASIF classification under the conditions of its endoprosthesis using various osteosynthesis options. Methods. A basic finite-element model of the pelvic girdle of a person with a fracture of the bottom of the cruciate ligament type 62-B1.3 (АО/ASIF) was developed, on which 7 variants of endoprosthesis of the left hip joint were modeled: without fracture (1); without osteosynthesis of fragments (2); fixation of a fragment of the acetabulum back wall with two screws (3), two screws and a bone plate (4), two screws and a bone plate with a Jumbo cup implantation (5); 5 case, long screw in the front column (6); option 5, long screws in the front and rear columns (7). Results. When using a large-sized Jumbo cup, the relative deformations of the bone regenerate in the center of the bottom of the KZ were reduced to 1.0 %, regardless of the osteosynthesis option. Around the free fragment of the short circuit, the largest relative deformations (3.0 %) were found in version 5 of the model. The use of long rods in the columns led to decrease in the relative deformations of the bone regenerate around the free fragment of the KZ to 2.0 %. Conclusions. Mathematical models proved that an increase in the number of osteosynthesis tools under the conditions of the total hip endoprosthesis replacement, 62-B1.3 (АО/ASIF) type KZ fracture leads to a decrease in the relative deformations of the bone regenerate along the entire fracture line. The use of a large-sized Jumbo cup makes it possible to reduce the level of relative deformations of the bone regenerate in the cent­ral part of the KZ.

Fracture Evolution Characteristics and Deformation Laws of Overlying Strata during the Initial Period of Longwall Mining: Case Study

Coal mining causes overlying rocks to collapse and be destroyed. Overburdened crevasses provide a channel for gas discharge, which is a serious safety hazard. To study the evolution characteristics and migration pattern of overburdened fissures during the initial mining period, the 24207 working face of the Shaquan mine was used as a research object. Through similar physical simulation tests, a mechanical model of the mining structure during the initial mining period was constructed to explore the factors influencing the movement pattern of the overburden strata during the initial mining period. The research results show that the evolution of mining-induced fractures in the overburdened strata in the initial mining period mainly experience the slow and rapid rising stages of the fracture dimension, while the stable mining period is in the stable development stage of the fracture dimension. The research results will help supplement and improve the theory of gas disaster prevention and comprehensive resource utilization in the initial mining stage under the mining conditions of high gas and low permeability coal seam group, achieve the goal of “coal and gas co-mining”, and ensure the safe and efficient production of mines.