Changes In Stress Distribution Research Articles

How does turbulence intensity affect the fatigue life of composite airfoils based on existing CFD and experimental data?

This research investigates the effect of airflow turbulence intensity on the fatigue life of composite airfoil structures in aerospace engineering. Using advanced Computational Fluid Dynamics (CFD) simulations, this study provides a comprehensive analysis of how varying levels of turbulence intensity—ranging from mild (5%) to severe (30%)—impact the mechanical degradation and fatigue performance of carbon-fiber-reinforced polymers (CFRPs) used in airfoil designs. The research quantifies the relationship between turbulence levels and changes in stress distribution, highlighting critical points of fatigue crack initiation and subsequent propagation. The study includes detailed comparisons of CFD results to experimental data to validate the predictive models and discusses how localized stress fluctuations under high-intensity turbulence accelerate the onset of fatigue failure. We present significant findings that demonstrate a non-linear relationship between turbulence intensity and the reduction in fatigue life, suggesting optimal design modifications for enhanced durability. Furthermore, this paper explores current challenges in merging CFD data with real-world fatigue testing and proposes advanced techniques such as adaptive mesh refinement and hybrid simulation models to improve predictive accuracy and computational efficiency in future research.

Stress Distribution Patterns of the Femorotibial Joint After Medial Closing-Wedge Distal Femoral Varus Osteotomy: An Evaluation Using Computed Tomography Osteoabsorptiometry

Background: Distal femoral varus osteotomy (DFVO) is an established surgical procedure for addressing valgus malalignment across various knee conditions. However, the effect of DFVO on stress distribution within the femorotibial joint has not been explored through in vivo studies. Purpose: To (1) explore the distribution pattern of subchondral bone density across the proximal tibia in nonarthritic knees without arthritis and in those of patients with valgus knees, (2) assess changes in the pattern of bone density distribution in patients with valgus knees before and after medial closing-wedge (MCW) DFVO, and (3) determine the correlation between leg alignment and changes in bone density distribution. Study Design: Cohort study; Level of evidence, 3. Methods: The authors retrospectively analyzed clinical and radiographic data from 14 patients (14 knees; mean age, 44 years; 3 men, 11 women) treated with MCW-DFVO for lateral compartment osteoarthritis (OA) due to valgus malalignment, alongside a control group of 18 patients (18 knees; mean age, 21 years; 4 men, 14 women) without OA. The distribution patterns of subchondral bone density distribution on the femorotibial articular surface of the tibia were examined both preoperatively and >1 year postoperatively using computed tomography osteoabsorptiometry. Quantitative analyses were conducted on the locations and percentages of the high-density areas (HDAs) on the articular surface. The mean time between surgery and the postoperative radiograph and computed tomography absorptiometry imaging was 13.6 months (range, 11-19 months). The mean length of clinical follow-up was 28.7 months (range, 14-62 months) after surgery. Results: The mean proportion of HDA in the lateral compartment relative to the total HDA (lateral ratio) was significantly greater in the preoperative OA group (58.8%) compared with the control group (41.1%) (P < .001). After MCW-DFVO, the mean lateral ratio in the OA group notably declined to 45.3% (P < .001). The lateral ratio exhibited a significant correlation with the hip-knee-ankle angle in both the control (r = 0.630; P = .011) and OA (r = 0.537; P = .047) groups. Moreover, the alteration in the lateral ratio after MCW-DFVO showed a significant relationship with changes in the hip-knee-ankle angle (r = 0.742; P = .002) and the mechanical lateral distal femoral angle (r = −0.752; P = .002). Within the lateral compartment, HDAs in the 3 lateral regions of the 4 lateral subregions diminished after MCW-DFVO, whereas in the medial compartment, HDAs in the 3 lateral subregions saw an increase. Conclusion: The mean lateral ratio was significantly greater in the preoperative OA group compared with the control group. MCW-DFVO resulted in a redistribution of HDA from the lateral to the medial compartment of the proximal tibial articular surface. The extent of alignment correction after MCW-DFVO was closely linked to the shifts in HDA distribution, reflecting changes in stress distribution.

The strength of an adhesive contact in the presence of interfacial defects

Adhesive contacts which possess a dominant stress concentration, such as at the contact edge in spherical junctions or at the detachment front in a peeling film, are well studied. More complex adhesive junction geometries, such as mushroom-shaped fibrils in bioinspired micropatterned dry adhesives, have exhibited a complex dependence of adhesive strength on the presence of interfacial defects within the contact. This has led to the emergence of statistical variation of the local behavior among micropatterned sub-contacts. In order to examine the interplay between geometry and interfacial defect character in control of the adhesive strength, the model system of a stiff cylindrical probe on an elastic layer is examined. Both experiments (glass on PDMS) and cohesive zone finite element simulations are performed, with analytical asymptotic limits also considered. The thickness of the elastic layer is varied to alter the interfacial stress distribution, with thinner layers having a reduced edge stress concentration at the expense of increased stress at the contact center. The size and position of manufactured interfacial defects is varied. It is observed that for the thickest substrates the edge stress concentration is dominant, with detachment propagating from this region regardless of the presence of an interfacial defect within the contact. Only very large center defects, with radius greater than half of that of the contact influence the adhesive strength. This transition is in agreement with analytical asymptotic limits. As the substrate is made thinner and the stress distribution changes, a strong decay in adhesive strength with increasing center defect radius emerges. For the thinnest substrate the flaw-insensitive upper bound is approached, suggesting that this decay is dominated by a reduction in the contact area. For penny-shaped defects at increasing radial positions, the adhesive strength for the thinnest substrates becomes non-monotonic. This confirms an intricate interplay between the geometry-controlled interfacial stress distribution and the size and position of interfacial defects in adhesive contacts, which will lead to statistical variation in strength when defects form due to surface roughness, fabrication imperfections, or contaminant particles.

Multiscale study of interfacial properties of carbon fiber reinforced polyphthalazine ether sulfone ketone resin matrix composites

In view of the limitations of traditional research tools on interfacial failure mechanisms in fiber/PPESK composites, this work proposes a multiscale research tool to carry out an in-depth study of the interfacial behavior between fibers and matrix. Based on microdroplet debonding tests, at the mesoscopic scale, the influence of residual thermal stress on the interface damage mode is explored through finite element (FEM) simulations. The evolution mechanism of composite material interfaces in spatial and temporal dimensions is examined based on changes in interfacial stress distribution, energy dissipation, and damage morphology during the debonding process, which can be summarized as follows: accompanied by elastic-plastic deformation and friction effects, the progressive process from localized to complete failure presents a dominant Type II damage mode at the interface. To further explore the interface failure mechanism at the molecular level, an interface model of CF/PPESK composite materials was established using molecular dynamics (MD) method. By monitoring the atom movement trend, the "fiber-matrix displacement synergistic effect" in the interfacial shear damage process was revealed, thereby establishing a multiscale mapping relationship of composite material interface. Based on this, the combination of FEM and MD was utilized to investigate the interface damage process of composite materials under different service conditions and to reasonably predict the initiation and expansion of microcracks. This study provides a pioneering perspective on interface damage research in composite materials with a "top-down" multiscale approach.

Направления обеспечения качества гипсоизвестковых вяжущих при реставрации

Purpose: to consider issues related to the standard definition of the strength characteristics of an air binder and a cement binder. To show a technological solution to the problem of regulating the strength of an air binder stone by stabilizing care during setting and hardening. Methods: during the research, GOST 23789- 2018 “Gypsum binders. Test methods”. Results: a distinctive feature of restoration plaster solutions is that structure formation and strength gain occur only in an air-dry environment. As a result, the availability of approved and applied standards for the manufacture and use of restoration plaster solutions does not fully guarantee the creation of a reliable and safe environment for the life of an architectural heritage monument. It has been established that the mechanical characteristics (compressive and bending strength limits), as well as elastic parameters should be the same or lower in historical and restoration solutions in order to avoid changes in stress distribution. Practical significance: developed taking into account the comprehensive care of hardening stone, gypsum-lime binders can have a wide range of applications. They can be used as mortars for the preservation of architectural heritage and in the reconstruction of modern buildings, self-supporting partitions, fire protection elements or drywall (in places where a higher mechanical load is expected).

Experimental study on the stability of noncohesive landslide dams based on seepage effect

Landslide dams composed of unconsolidated, noncohesive soil are easily affected by seepage. As seepage develops, the dam's characteristics change dynamically, indirectly affecting its stability. However, previous studies on dam failure have mostly assumed that the dam characteristics remain constant before failure, often overlooking these changes and their effects on stability. In this study, 48 sets of flume experiments were conducted to quantify the impact of seepage under varying upstream inflow rates, dam heights, downstream slope angles, and particle size distributions. During the storage phase, the rise rate of the water level is closely linked to the seepage's diversion capacity. The diversion rate of inflow reached as high as 0.747 in this study, but decreased to 0.230 as inflow increased. Furthermore, changes in the internal stress distribution within the dam, driven by seepage, contributed to dam settlement and the sliding of the downstream slope. Notably, dam settlement exhibited both non-uniform spatial distribution and temporal stage development. The maximum settlement ratio between the point in the upstream breach and the point in the downstream breach reached as high as 2.79. Regarding the soil changes within the dam, after the seepage channel became connected, the primary soil loss involved silt particles ranging from 10 to 20 μm in size. This result reflects the increasing non-uniformity within the dam caused by seepage. Finally, Considering the changes in dam characteristics under the influence of seepage, in this study, a logistic regression model was established to assess dam stability. Overall, this study enhances the understanding of how seepage affects dam stability by examining various dam properties and presenting a model for stability assessment.

Effect of weld-line position on springback behavior in advanced high-strength steel tailor-welded blanks on hat-shaped bending application

In this study, both experiments and finite-element analysis are performed to elucidate the effect of weld-line position on the springback behavior of advanced high-strength steel tailor-welded blanks (AHSS-TWBs). AHSS-TWBs are fabricated from grade 590Y high-strength steel and 980Y advanced high-strength steel, each with a thickness of 1.2 mm. Gas tungsten arc welding is performed to obtain autogenous butt-weld joints. Three distinct weld-line position patterns are systematically analyzed to investigate the springback phenomenon via hat-shaped draw bending. Experiments on the AHSS-TWBs show that the weld-line position affects springback. The stress distribution changes with the weld-line position, thereby initiating variations in both the components of the bending moment and the corresponding springback angle. Depending on the weld-line position, different springback behaviors and bending moments are resulted on the components.

Dynamic Evolution Law of Production Stress Field in Fractured Tight Sandstone Horizontal Wells Considering Stress Sensitivity of Multiple Media

Inter-well frac-hit has become an important challenge in the development of unconventional oil and gas resources such as fractured tight sandstone. Due to the presence of hydraulic fracturing fractures, secondary induced fractures, natural fractures, and other seepage media in real formations, the acquisition of stress fields requires the coupling effect of seepage and stress. In this process, there is also stress sensitivity, which leads to unclear dynamic evolution laws of stress fields and increases the difficulty of the staged multi-cluster fracturing of horizontal wells. The use of a multi-stage stress-sensitive horizontal well production stress field prediction model is an effective means of analyzing the influence of natural fracture parameters, main fracture parameters, and multi-stage stress sensitivity coefficients on the stress field. This article considers multi-stage stress sensitivity and, based on fractured sandstone reservoir parameters, establishes a numerical model for the dynamic evolution of the production stress field in horizontal wells with matrix self-supporting fracture-supported fracture–seepage–stress coupling. The influence of various factors on the production stress field is analyzed. The results show that under constant pressure production, for low-permeability reservoirs, multi-stage stress sensitivity has a relatively low impact on reservoir stress, and the amplitude of principal stress change in the entire fracture length direction is only within the range of 0.27%, with no significant change in stress distribution; The parameters of the main fracture have a significant impact on the stress field, with a variation amplitude of within 2.85%. The ability of stress to diffuse from the fracture tip to the surrounding areas is stronger, and the stress concentration area spreads from an elliptical distribution to a semi-circular distribution. The random natural fracture parameters have a significant impact on pore pressure. As the density and angle of the fractures increase, the pore pressure changes within the range of 3.32%, and the diffusion area of pore pressure significantly increases, making it easy to communicate with the reservoir on both sides of the fractures.

Wear-resistant enhanced composite coatings on TC4: Combining halide-activated pack cementation and plasma electrolytic oxidation

Enhancing the wear resistance is crucial to broadening titanium alloy application potential. In this study, we discovered that preparing a boron-infiltrated prefabricated coating using halide-activated pack cementation (HAPC) before plasma electrolytic oxidation (PEO) can significantly improve the wear resistance of TC4. The composite coatings (HAPC/PEO) produced through this method exhibit effective boron (B) penetration, with the main phase being H3BO3. We investigated the properties of HAPC/PEO and compared the wear resistance to a single PEO coating. Our results show that the hardness and modulus of elasticity of HAPC/PEO are enhanced, while its resistance to plastic deformation is increased and the coating is not easily damaged during friction. HAPC/PEO shows a 55 % decrease in the coefficient of friction and a 47 % reduction in wear rate compared to PEO coating, indicating superior wear resistance. We analyzed the stress distribution and displacement changes during friction between the PEO coating and HAPC/PEO using ABAQUS. The influence of the main phases' structure on the two coatings' wear resistance is also discussed, and the significant role of the laminated structure of H3BO3 in enhancing the wear resistance of HAPC/PEO was discovered.

A global springback compensation method for manufacturing metallic seal ring with complex cross-section and submillimeter precision

The fabrication of complex thin-walled components with irregular cross-sectional geometries often necessitates multi-pass forming processes. The springback phenomena at the microscale level contribute significantly difficulty to the precise control of geometrical accuracy for such components. To achieve submillimeter precision control of micro features in metal seal rings, this research proposed a global springback compensation method to facilitate the attainment of the optimized surfaces of dies. Through the analysis of changes in cross-sectional shape, stress distribution and bending moment in the multiple stages, several partition points were set up to divide the cross-section into four zones. For a partitional control of the manufactured surface, the compensation magnitudes for each segment are determined by iteratively refining the compensation factors using the secant method. The iteration of compensation factors is based on the deviation of dimensions measured by finite element simulation, which greatly saves experimental costs. The experimental results indicate that the predictive dimensional alterations by the global compensation agree with the experimental ones exhibiting a maximum error of less than 3 %. Furthermore, the springback behavior during the unloading and trimming stages coupling caused a dimensional error of 14.9 % for the wave width and 8.3 % for the peak width. Following the application of coupled compensation through two iterations, a distinct decrease in the relative average errors of springback values for both part width and peak width, achieving reductions to 2.4 % and 0.6 %, respectively. Compared to the traditional single springback compensation technique, the global compensation strategy effectively mitigates the out-of-tolerance issues induced by the trimming process.

Applications of Finite Element Analysis in Endodontics: A Systematic Review and Meta-Analysis

ABSTRACT Background: Endodontics increasingly uses finite element analysis (FEA) to evaluate stress distribution, fracture resistance, and temperature changes in treated teeth. FEA’s endodontic uses, benefits, and drawbacks are examined in this systematic review and meta-analysis. Methods: A PubMed systematic search found relevant studies published up to January 2022. Original endodontic research articles utilizing FEA to quantify stress distribution, fracture resistance, or temperature changes in treated teeth were eligible. The systematic review comprised 30 publications, 15 of which were meta-analyzed. Data were extracted using a standard form, and the “Newcastle-Ottawa Scale (NOS)” for observational studies and the Cochrane risk of bias tool for randomized controlled trials assessed quality. Random-effects models calculated pooled effect sizes and 95% confidence intervals in RevMan 5.4 meta-analysis. Results: Meta-analysis shows FEA-guided endodontic treatment improves stress distribution (P &lt; 0.001) and fracture resistance (P &lt; 0.05) compared to conventional treatments. The temperature did not vary significantly (P = 0.12). Stress distribution had an effect size of 0.75 (95% CI: 0.65–0.85), fracture resistance 0.42 (95%: 0.12–0.72), and temperature variations -0.18. Conclusion: In conclusion, FEA is a valuable technique in endodontics for stress distribution study and fracture resistance testing. FEA models’ accuracy, dependability, and clinical applicability were questioned, underlining the need for more research and development to maximize their endodontics clinical use.

Paradoxical Change in Subchondral Bone Density in the Medial Compartment of the Proximal Tibial Articular Surface After High Tibial Osteotomy: A Detailed Subchondral Bone Density Analysis.

High tibial osteotomy (HTO) aims to realign the varus knee to alleviate stress in the medial compartment. However, detailed information on the impact of HTO on stress distribution across the tibiofemoral joint surface still needs to be completely elucidated. The present study aimed to analyze the subchondral bone density distribution to validate the alignment threshold causing paradoxical changes. We hypothesized that there would be a paradoxical stress change in the medial compartment beyond a specific threshold for lower limb realignment after HTO. Case series; Level of evidence, 4. A retrospective clinical study of 32 knees from 30 patients who underwent medial opening-wedge HTO between 2015 and 2019 was conducted at Hokkaido University Hospital. The subchondral bone density across the tibiofemoral joint was analyzed using computed tomography-osteoabsorptiometry before and after HTO. The high-density area (HDA) within the medial and lateral compartments and their subregions, which were quartered in the coronal plane, was specifically examined. The hip-knee-ankle angle, medial proximal tibial angle (MPTA), joint line obliquity (JLO), and joint line convergence angle significantly changed after HTO (P < .01). The HDA of the medial compartment to the total HDA ratio decreased from 83% to 77%. Paradoxically, the HDA in the most central subregion of the medial compartment increased from 24% to 30%. There were significant differences between MPTA and JLO in patients with and without paradoxical changes in the HDA. MPTA and JLO cutoff values causing paradoxical changes in the HDA were 94° and 4°, respectively. There was a paradoxical stress increase in the M4 region at the medial compartment associated with the MPTA and JLO beyond specific thresholds. Therefore, surgical planning should be cautiously performed to prevent overcorrection, which can lead to adverse stress distribution changes.

How effective is proximal fibular osteotomy in redistributing joint pressures? Insights from an HTO comparative in-silico study

BackgroundKnee osteoarthritis (KOA) represents a widespread degenerative condition among adults that significantly affects quality of life. This study aims to elucidate the biomechanical implications of proximal fibular osteotomy (PFO), a proposed cost-effective and straightforward intervention for KOA, comparing its effects against traditional high tibial osteotomy (HTO) through in-silico analysis.MethodsUsing medical imaging and finite element analysis (FEA), this research quantitatively evaluates the biomechanical outcomes of a simulated PFO procedure in patients with severe medial compartment genu-varum, who have undergone surgical correction with HTO. The study focused on evaluating changes in knee joint contact pressures, stress distribution, and anatomical positioning of the center of pressure (CoP). Three models are generated for each of the five patients investigated in this study, a preoperative original condition model, an in-silico PFO based on the same original condition data, and a reversed-engineered HTO in-silico model.ResultsThe novel contribution of this investigation is the quantitative analysis of the impact of PFO on the biomechanics of the knee joint. The results provide mechanical evidence that PFO can effectively redistribute and homogenize joint stresses, while also repositioning the CoP towards the center of the knee, similar to what is observed post HTO. The findings propose PFO as a potentially viable and simpler alternative to conventional surgical methods for managing severe KOA, specifically in patients with medial compartment genu-varum.ConclusionThis research also marks the first application of FEA that may support one of the underlying biomechanical theories of PFO, providing a foundation for future clinical and in-silico studies.

Fatigue life analysis of scraper conveyor chain ring under different chain speeds and loads

This study aims to explore how different chain speeds and loads impact the fatigue life of the scraper conveyor chain ring. To achieve this, the study validates the reliability of a coupled simulation involving multi-body dynamics and the discrete element method. It also acquires time-varying tension load spectra under various operational conditions. The research evaluates the effects of distinct chain speeds and loads on parameters such as chain tension, vibration acceleration in the Y and Z-directions of the chain ring. Furthermore, finite element simulation is employed to examine stress distribution changes and fatigue life trends within the three-chain ring structure. The findings demonstrate that Y and Z-direction vibration accelerations of the chain ring correlate positively with the load. Additionally, the vibration acceleration in the Y-direction correlates positively with the chain speed. Across different chain speeds and loads, the maximum equivalent stress in the chain ring exhibits dynamic variations mirroring the load spectrum. Within the elastic deformation range of the chain ring, the highest stress within the transition region correlates linearly with chain tension. Load has a greater effect on the fatigue life of chain rings than chain speed. The fatigue life within the transition region of the chain ring decreases exponentially with increasing load at a constant chain speed. Conversely, at a constant load, chain ring life correlates positively with chain speed. Specifically, the fatigue life of the chain ring in LS 22 amounts to 32.64 days. When both chain speed and load are adjusted by 25%, the chain ring's lifespan reduces by 51.66% during simultaneous increments and increases by 39.26% with concurrent reductions in speed and load.

The effect of the pitch of the boards in the transverse layer on the deformability and stress distribution in a threelayer CLT panel rigidly clamped on both sides

CLT panels are made by gluing several layers of boards crosswise, which provides them with high load-bearing capacity and bending resistance. In addition to the number of layers in the panel, the deformability and bearing capacity are influenced by the geometric parameters of the plate, the way the layers are attached to each other, the way the structure is supported, etc. Due to the fact that the material has recently been used in construction, many issues remain poorly understood, and therefore there is an opportunity and need to optimize some aspects both in the CLT panels themselves and in the way they interact with other building structures.In this article, the influence of the pitch of boards in the transverse layer on the deformability and stress distribution in a three-layer CLT panel rigidly pinched on both sides was studied. Numerical studies of the finite element method (FEM) were carried out using the computing complex SCAD+. The computational model of the plate in this study is a composite orthotropic plate with rigid connections between the layers. The result of the study is numerical data reflecting the dependence of the distribution of normal stresses OX and OY and the transverse deformation of the plate on the pitch of the lamellae (boards) in the bottom layer. Projections of the computational model with normal stress isofields on the stretched and compressed plate layer are also obtained. This makes it possible to identify general patterns of stress distribution and deformation changes with variations in geometric parameters for this type of support for their use in the design of building structures using CLT panels as well as in the optimization of the structure in order to increase the cost efficiency of resources.

SIMULATION OF THE STRESSED-DEFORMED STATE OF THE ELASTIC DISCTOR RACK WITH A STIFFNESS REGULATOR

The paper involves the physical-mathematical modeling of the stress-strain state of an elastic stand of a developed disc harrow equipped with a stiffness regulator. The use of disc tools with individual attachment to elastic stands contributes to improving the quality and reducing the energy consumption of soil processing. This is due to the formation of oscillatory motion of the discs caused by the uneven resistance of the soil in the direction of the unit's movement. The goal of theoretical research is three-dimensional modeling of the stress-strain state of the elastic stand of the disc harrow with a stiffness regulator and substantiation of the range of its rational design parameters. To evaluate the interaction process between elastic working elements and the soil, a harmonic analysis was performed to determine the peak response of the system in a steady state to harmonic loads. In each step of the solution, all applied loads and base excitations have the same frequency, and the values are determined by the corresponding frequency curves. Using the SOLIDWORKS Simulation software package, the relevant physical-mathematical apparatus was compiled. On the basis of this approach, already at the stage of designing disk working bodies on elastic risers, it is possible to conclude about the possibility of them performing specific technological tasks, when by changing the parameters of the risers and conducting repeated studies, it is possible to obtain the corresponding dependencies in the form of regression equations. The results of numerical modeling provide visualization of the change in stress distribution over time in the stand. The dynamics of the change in maximum stress, located on the bend of the stand (R2) and the stiffness regulator (R1), were determined as the stress changes according to the law of damped oscillation with a specified natural frequency. In order to ensure the best working conditions of the elastic riser, it is necessary to ensure the greatest deformation of the riser at the place of attachment of the disc ΔL1 and, at the same time, the smallest value of the deformation of the tool frame ΔL2, by solving the trade-off problem in the Wolfram Cloud software package by maximizing the multiplicative function, the rational geometric dimensions of the diskator riser and constructive parameters of its placement in space.

Finite element analysis of biomechanical effects of percutaneous cement discoplasty in scoliosis

ObjectiveTo investigate the effect of bone cement on the vertebral body and biomechanical properties in percutaneous cement discoplasty (PCD) for degenerative lumbar disc disease.MethodsThree-dimensional reconstruction of L2 ~ L3 vertebral bodies was performed in a healthy volunteer, and the corresponding finite element model of the spine was established. Biomechanical analysis was performed on the changes in stress distribution in different groups of models by applying quantitative loads.ResultsModels with percutaneous discoplasty (PCD) showed improved stability under various stress conditions, and intervertebral foraminal heights were superior to models without discoplasty.ConclusionCement discoplasty can improve the stability of the vertebral body to a certain extent and restore a certain height of the intervertebral foramen, which has a good development prospect and potential.

Assessing stability of mine workings driven in stratified rock mass

Purpose.The research purpose is to assess the stability of mine workings driven in a stratified rock mass by studying the influence of the stratified rock bedding angle on the rock mass stress-strain state (SSS). Methods. The research uses both experimental and numerical methods. Experimental studies are carried out using rock samples with different angles of rock layer occurrence, while numerical modeling is performed using the RS2 (Geotechnical Finite Element Analysis) software based on the generalized Hoek-Brown failure criterion. The studies are carried out on models covering the border area of the mine workings driven in the mass with the angles of rock occurrence from 0 to 75°. Findings. Experimental and numerical studies have shown that when the rock layer inclination angle changes, significant changes occur in the stress concentration zones around the mine workings. An increased rock layer inclination angle is accompanied by a change in stress distribution, which is important for assessing the stability of mine workings. A particularly strong influence is observed at the angles of rock occurrence 30° and above. Originality. The research novelty is in revealing the patterns in the stress distribution in the stratified rock masses depen-ding on the rock layer inclination angle. Research results provide new data on the rock interaction mechanisms in difficult geological conditions. Practical implications. The results obtained can be used in the planning and operation of mine workings in difficult geological conditions. By taking into account the changes in stress zones caused by the rock layer inclination angle, it is possible to improve the safety and efficiency of mining operations.

The Effect of Carbide Concentration at Grain Boundaries on Thermal Stresses in Castings for Heat Treatment Furnace Tooling

Austenitic Fe-Ni-Cr alloys are commonly used for the production of castings intended for high-temperature applications. One area where Fe-Ni-Cr castings are widely used is the equipment for heat treatment furnaces. Despite the good heat resistance properties of the materials used for the castings, they tend to develop cracks and deformations over time due to cyclic temperature changes experienced under high temperature operating conditions. In the case of carburizing furnace equipment, thermal stresses induced by the temperature gradient in each operating cycle on rapidly cooled elements have a significant influence on the progressive fatigue changes. In the carburized subsurface zone, also the different thermal expansion of the matrix and non-metallic precipitates plays a significant role in stress distribution. This article presents the results of analyses of thermal stresses in the surface and subsurface layer of carburized alloy during cooling, taking into account the simultaneous effect of both mentioned stress sources. The basis for the stress analyzes were the temperature distribution in the cross-section of the cooled element as a function cooling time, determined numerically using FEM. These distributions were taken as the thermal load of the element. The study presents the results of analyses on the influence of carbide concentration increase on stress distribution changes caused by the temperature gradient. The simultaneous consideration of both thermal stress sources, i.e. temperature gradient and different thermal expansions of phases, allowed for obtaining qualitatively closer results than analyzing the stress sources independently

Three-dimensional finite element analysis on stress distribution after different palatoplasty and levator veli palatini muscle reconstruction.

To establish a three-dimensional finite element model of the upper palate, pharyngeal cavity, and levator veli palatini muscle in patients with unilateral complete cleft palate, simulate two surgical procedures that the two-flap method and Furlow reverse double Z method, observe the stress distribution of the upper palate soft tissue and changes in pharyngeal cavity area after different surgical methods, and verify the accuracy of the model by reconstructing and measuring the levator veli palatini muscle. Mimics, Geomagic, Ansys, and Hypermesh were applied to establish three-dimensional finite element models of the pharyngeal cavity, upper palate, and levator veli palatini muscle in patients with unilateral complete cleft palate. The parameters including length, angle, and cross-sectional area of the levator veli palatini muscle etc. were measured in Mimics, and two surgical procedures that two-flap method and Furlow reverse double Z method were simulated in Ansys, and the area of pharyngeal cavity was measured by hypermesh. A three-dimensional finite element model of the upper palate, pharyngeal cavity, and bilateral levator veli palatini muscle was established in patients with unilateral complete cleft palate ; The concept of horizontal projection characteristics of the palatal dome was applied to the finite element simulation of cleft palate surgery, vividly simulating the displacement and elastic stretching of the two flap method and Furlow reverse double Z method during the surgical process; The areas with the highest stress in the two-flap method and Furlow reverse double Z method both occur in the hard soft palate junction area; In resting state, as measured, the two flap method can narrow the pharyngeal cavity area by 50.9%, while the Furlow reverse double Z method can narrow the pharyngeal cavity area by 65.4%; The measurement results of the levator veli palatini muscle showed no significant difference compared to previous studies, confirming the accuracy of the model. The finite element method was used to establish a model to simulate the surgical procedure, which is effective and reliable. The area with the highest postoperative stress for both methods is the hard soft palate junction area, and the stress of the Furlow reverse double Z method is lower than that of the two-flap method. The anatomical conditions of pharyngeal cavity of Furlow reverse double Z method are better than that of two-flap method in the resting state. This article uses three-dimensional finite element method to simulate the commonly used two-flap method and Furlow reverse double Z method in clinical cleft palate surgery, and analyzes the stress distribution characteristics and changes in pharyngeal cavity area of the two surgical methods, in order to provide a theoretical basis for the surgeon to choose the surgical method and reduce the occurrence of complications.