Stress Characteristics Research Articles

Study on the Stress Evolution and Strengthening Support Timing of the Retracement Channel under the Super-Thick Nappe

The superposition effect of the advanced support pressure of the working face in the final mining stage and the lateral support stress of the roadway is a key factor affecting the stability of the retracement channel. To study the stress evolution of the retracement channel under the super-thick nappe and the timing of strengthening support, this paper takes the mining of the 360808 working face in Xinji No. 1 Mine as the engineering background, analyzes the occurrence conditions of the working face and the measured rock pressure law, and constructs a roof structure model of the retreat area. The UDEC discrete element numerical simulation software was used to analyze the evolution characteristics of concentrated stress and the failure law of surrounding rock around the retracement channel under gradual excavation conditions. Based on the relationship between the position of the main roof fracture and the stability of the surrounding rock of the retracement channel, the instability mechanism of the surrounding rock of the retracement channel was revealed. A mechanical model of the surrounding rock of the retracement channel under the condition of a gradient coal pillar was established, and the energy criterion K for the instability of the surrounding rock was obtained. The method of adding anchor cables to strengthen the support of the surrounding rock of the retracement channel was proposed. The results indicate that the accumulation of energy in the surrounding rock of the retracement channel is greater than the internal consumption of energy, which is the direct reason for the instability of the surrounding rock of the retracement channel. The time to strengthen the support of the roof is when the working face is 15 m away from the retracement channel. According to the analysis of on-site monitoring results, the roof convergence and the two-sides convergence before and after strengthening the support were reduced by 90 mm and 140 mm, respectively. Under the strengthening of support, the slope of the retracement channel in the 360808 working face is slight, without roof fall, and the surrounding rock of the channel is effectively controlled, which is of great significance for ensuring the safe application of the retracement channel. It has reference value for the safety production of surrounding mines and is conducive to promoting the sustainable development of local resource-based society and economy.

Hot Deformation Behavior and Processing Maps of 26CrMo7S Steel Used in Oil Exploration.

The hot deformation behavior and flow stress characteristics of experimental 26CrMo7S steel were analyzed using a thermal simulator under a range of conditions, including a strain rate range of 0.01~10 s-1, a temperature range of 850~1250 °C, and a maximum deformation amount of 70%. The Arrhenius constitutive model was built for the corresponding conditions, and the model's accuracy was verified through error analysis. Additionally, hot processing maps were constructed to analyze the processing zone of the steel under different hot deformation conditions. Finally, the microstructure of the processing zones was observed and verified using the electron backscattered diffraction (EBSD). The results indicate that the interaction of work hardening and dynamic softening influences the hot deformation behavior of 26CrMo7S steel. The Arrhenius constitutive equation with a value of the correlation coefficient (r = 0.99523) accurately predicts the flow behavior of 26CrMo7S steel under different strains. The optimal processing zone obtained with the hot processing maps is within a deformation range of 1010~1190 °C and a strain rate range of 0.01~10-1.5 s-1, and the obtained microstructure is in good agreement with the analysis results.

Numerical simulation of mechanical characteristics and tension-torsion coupling effect of tension-type anchor cable

PurposeThe purpose of this paper is to simulate the tension process of tension-type anchor cable and to explore the mechanical characteristics and tension-torsion coupling effect of anchor cable subjected to tension.Design/methodology/approachABAQUS numerical software is applied to construct the numerical models of tension-type anchor cables with different diameters. Through explicit contact, the characteristics of contact between grouting body-anchor cable and grouting body-rock mass are determined. Confining pressure is applied to the model through surface pressure, and drawing force is applied to the model by displacement loading so as to simulate the tension process of the anchor cable.FindingsThe results show that the stress is transmitted in both axial and radial directions in the anchorage section and distributed in a cone. The shear stress in the grouting body is unevenly distributed, and its peak value increases with the rise in confining pressure and anchor cable diameter. The stress characteristics of torque and axial force are basically consistent and evenly distributed in the free section; they gradually decrease in the anchorage section. Due to the tension-torsion coupling effect, the internal stress characteristics of the anchor cable structure vary. On average, the anchorage performance of each anchor cable model is improved by 6.19%.Originality/valueThe proposed method of numerical modelling is effective in addressing the interface contact between the anchor cable and the grouting body and in solving the problem with convergence of calculation. Compared with the indoor test, this method is more suited to collecting the internal mechanical data of the anchor body.

Comparative Analysis of Mechanical Properties of Three Typical Bolts under the Influence of Bed Separation

In order to compare the mechanical characteristics and supporting performance of the lengthened anchored pre-stressed bolt, the full-length anchored bolt and the full-length anchored pre-stressed bolt under the bed separation conditions, theoretical and numerical analysis models of the three typical bolts were established, respectively. The influences of preload, bed separation values, bed separation numbers and bed separation positions on the mechanical properties of the three typical bolts were studied by numerical simulation method, and the mechanical properties of the three typical bolts were compared and analysed, and the sensitivity analysis of the crack opening of the three typical bolts was carried out. Results indicate that the initial preload can exert obvious restraint on the surrounding rock, in which the preload transmission range of the full-length anchored pre-stressed bolt is larger, and the restraint effect on the surrounding rock is better. Under the different bed separation conditions, the stress characteristics of the three typical bolt bodies at the bed separation basically follow the same law except for the free section of the lengthened anchored pre-stressed bolt. Under the action of the bed separation, the initial bonding section of the full-length anchored pre-stressed bolt and the free section of the lengthened anchored bolt have a certain influence on the distribution of the axial force and shear stress at the anchorage interface. The sensitivity of the two kinds of full-length anchored bolts is higher than that of the lengthened anchored pre-stressed bolt under the left bed separation condition. There is little difference in sensitivity between three typical bolts under the middle and right bed separation conditions. The research results can provide theoretical guidance for the selection of bolts in roadway support.

Investigation of casing stress distribution and parameter optimization during the transient impact process of multi-hole perforation operations

Perforation operation is critical in bridging completion and production enhancement operations. At the same time, the perforation parameters also affect the structural integrity of the casing. Still, there are fewer studies on the stress distribution of the casing under the blast transient impact loading of multi-hole perforation. To address this, considering the engineering application of helical perforation in unconventional oil and gas reservoirs, a three-dimensional numerical model of perforating charge-casing-cement sheath-formation is established, and the Holmquist-Johnson-Cook (HJC) rock dynamics material model, as well as the fluid–solid coupling and Arbitrary Lagrange-Euler (ALE) algorithms. On this basis, the variation rule and distribution characteristics of the effective stress in the double-perforation holes stress superposition area under different perforation density, phase angle, and geostress conditions are analyzed with the casing strength safety threshold as the optimization judgment condition of perforation parameters. The research results show that the numerical simulation result has good consistency in the results of engineering practice, perforation aperture diameter error is 3.04%, and jet head velocity error is 6.85%. The variation rule of perforation density and phase angle has a significant effect on the effective stress distribution in the stress superposition area around the hole: with the decreasing perforation density or increasing phase angle, the casing stress superposition area in the middle part of the neighboring perforation holes is gradually narrowed down, and when the perforation density is more than 9 P/m and 51°, the casing stress in the stress superposition area between the perforated holes is lower than the safety threshold value. With the increasing ground stress, the stress in the middle of the neighboring perforated holes increases continuously, showing a quadratic function change trend. The perforation density should be appropriately reduced, and the phase angle should be increased when the geostress is high to ensure the integrity of the casing structure after the perforation operation. The research results can provide a practical reference for conducting perforation engineering operations and optimizing perforation parameters.

Numerical analysis on mechanical and fatigue behaviors of aviation electrical connector considering structural effect

AbstractThis work is motivated by the fact that the reliability of electrical connectors influenced by their mechanical behavior and fatigue life directly affects the working performance of the whole equipment system. In this paper, theoretical analyses of insertion force, maximum stress, and fatigue life in an aviation electrical connector are presented and the corresponding mathematical models are firstly derived. Then, to numerically investigate its mechanical behavior and fatigue life, a simplified 3D FE model is developed by using ABAQUS and FE‐SAFE software and verified by experiments and theoretical analysis. Finally, the distribution and evolution characteristics of contact forces, stress and fatigue life considering the influences of reed thickness and slot width are quantitatively analyzed in details. The results indicate that the insertion force first increases and then stabilizes at the level of 0.16 N as the pin head is fully inserted into the jack, which shows an opposite to the evolution of extraction force. Moreover, the maximum value of stress and the minimum value of fatigue life are all located at the root of the jack reed. Besides, unlike the small effect of slot width, the Fimax and σmax values obviously increase and the Nf value decreases with the increment of reed thickness.

Comprehensive evaluation on conjugate heat transfer and thermal stress performance of film cooling

Film cooling is a commonly used cooling technology in gas turbines, which could reduce heat load by spreading cooling air. However, it faces the problem of stress concentration in structures with holes. The present work focuses on conjugate heat transfer and thermal stress characteristics for a flat film cooling plate through an experimentally validated numerical approach. It discusses the effect of three geometry factors: inclination angle, compound angle, and ellipticity. An engine case simulation and a laboratory case simulation are compared to validate the analogy principle of conjugate heat transfer and thermal stress analysis derived from theoretical analysis. According to the analogy principle, the laboratory flat plate film cooling cases are set to conduct numerical studies. The maximum Mises stress of the film hole is equal to the product of the reference stress and the stress concentration factor. The reference Mises stress is proportional to the overall cooling effectiveness. The stress concentration factor is mainly related to the geometry of the film hole. Reducing the inclination angle of the film hole from 90° to 30° increases the overall cooling effectiveness and drastically increases the stress concentration factor from 2.7 to 5.5. Based on a cylinder hole with a 30° inclination angle, increasing the compound angle enhances the overall cooling effectiveness and slightly increases the stress concentration factor. Based on a cylinder hole with a 30° inclination angle, increasing the ellipticity increases the overall cooling effectiveness and reduces the stress concentration factor. With the increase of ellipticity from 0 to 4, the stress concentration factor decreases from 5.5 to 2. Elliptical film holes are ideal for future low-stress, high-cooling-efficiency turbine blades to extend the life of cooling vanes.

Evaluation on Displacement and Stress Characteristics according to Structural Shape in Panel Bridges

Evaluation on Displacement and Stress Characteristics according to Structural Shape in Panel Bridges

Mechanical response and field measurement analysis of custom-shaped steel sleeves during urban shield tunnel construction

Urban shield tunnel construction is typically affected by limited construction space and the inability to begin from the main line. Conventional lateral initiation solutions result in construction delays and incurs additional construction costs. Hence, based on the Beijing Metro Line 27 project, a novel custom-shaped steel sleeve for lateral initiation is proposed. Numerical simulations are conducted to analyse the stress and deformation characteristics of the steel sleeve during shield initiation. The simulation results, which are validated based on on-site measurements, show that the maximum tensile stress of the shaped steel sleeve structure increases with the shield thrust, and that the average maximum stress occurred at the waist position at the long side of the barrel. However, the stress at the base reduced significantly and a stress concentration occurred at the connection between the sleeve and tunnel portal. The deformation of the sleeve is characterised by a larger long side and a smaller short side owing to the constraint of the tunnel portal. The axial force on the connection bolts below the waist of the sleeve is the highest, whereas the axial force near the tunnel portal is lower. The waist position and the lower section of the sleeve structure are areas where the stress and deformation are weak during the shield initiation of the steel sleeve. Results of engineering test shows that using a shaped steel sleeve for lateral initiation is safe and feasible. However, the waist and bolt connections of the shaped steel sleeve must be scrutinised when used in engineering practice, and standardised construction operations and strengthened monitoring should be implemented.

Biomechanical Finite Element Analysis of Percutaneous Endoscopic Lumbar Discectomy via a Transforaminal Approach

Based on the previously established 3-dimensional model, this study uses the finite element analytical method to observe the effects of superior articular process resection and intervertebral discectomy on the stress of the surgical segment under different motion states. A validated L3-S1 finite element model was modified for simulation. And on the basis of the normal lumbar spine model, the superior articular process and discs of different parts of L4-L5 were simulated for resection. The resection models were divided into 6 groups, and the stress characteristics of articular process and discs of the lumbar spine under different postoperative motion conditions were examined under the same loading conditions. Simultaneous resection of the tip and base of the superior articular process increased the stress on the facet joint under various motion states compared with separate resections. In addition, the fewer herniated discs that are removed, the smaller the increase in facet joint stress. excision of the tip of the superior articular process caused a smaller stress increase in the facet joint than excision of the base under the forward bending and right-lateral flexion, and the opposite results were found under left-lateral flexion, posterior extension, and rotation. Resection of the tip of the superior articular process increases disc stress more than resection of the base of the superior articular process. Select resection of the superior articular process base as much as possible to expose the target of the disc. And minimize annulus damage and disc removal.

Study of the OLR Anomalies before the 2023 Turkey M7.8 Earthquake

Using the model of the additive tectonic stress from celestial tide-generating force, we studied the relationship between the seismogenic structure and celestial tide-generating stress in the M7.8 Turkey earthquake on 6 February 2023. We analyzed the daily continuous variation characteristics of OLR before and after the Turkey earthquake and discussed the correlation characteristics of tidal stress, OLR, and the earthquake. The results showed that the observed OLR anomaly according to the tidal stress variation cycle “C” (1–15 February) presented a phase change in time, which was synchronized with a continuous trough-to-peak change in the additional tectonic main pressure stress. The spatial distribution of OLR anomalies was mainly concentrated in the southwest section of the East Anatolian Fault Zone, which indicates that seismic tectonic movements were the main causes of OLR anomaly variation during this earthquake. An OLR anomaly change was related to this M7.8 “Swarm Type” of earthquake in Turkey. Impending earthquake OLR anomalies represent that the stress of the seismogenic structure in the seismogenic region has entered a critical state, which can provide stress monitoring and a seismogenic region indication for earthquakes induced by tidal force. The change cycle of the celestial tide-generating force provides a time indication for the identification of seismic thermal anomalies, and it indicates that the combination of the additional tectonic stress of the tidal force and the change of OLR anomaly has value for the research on the short-impending earthquake precursor.

Research on the Overall and Local Mechanical Behaviors of Steel Box Girder Cable-Stayed Bridge via Incremental Launching Construction

In this paper, a large-span cable-stayed bridge with double pylons and double cable planes is employed to study the overall and local mechanical behaviors. The steel box girder bridge is constructed by incremental launching with the maximum span of 50 m. Through the overall stress analysis, the most unfavorable stress position of the structure in the incremental launching construction is identified; the refined local stress analysis is carried out for the girder section at this position, and the local stress characteristics of the structure are studied. The mechanical performance and the applicability of incremental launching are determined by comparing four kinds of elastic cushion. This paper aims at improving the safety of incremental launching construction of steel box girder bridge, and can provide reference for similar projects.

Analysis of longitudinal stress and deformation characteristics of shield tunnel under faulting dislocation

Fault dislocation seriously threatens the structural security of cross-fault tunnels during operation. Regarding the mechanical response of the tunnel across faults, the tunnel was equated as the Timoshenko beam on the Vlasov foundation in the present study, and the mechanical analytical model of the cross-fault tunnel was established and solved by the finite difference method. Published cases were utilized to validate the reasonableness of the analytical model. The influence law of critical parameters of the model on the response of the tunnel was investigated by parameter sensitivity analysis. Finally, the mechanical properties of the tunnel under the non-homogeneous foundation conditions were discussed. The calculation results of the proposed analytical model were similar to the existing model test monitoring data, and the trend was the same, demonstrating the correctness of the analytical model. The tunnel-fault distance, foundation reaction coefficient, foundation shear stiffness, and effective factor of bending stiffness changed the maximum tunnel bending moment, while the fault inclination changed the position where the maximum bending moment occurred. For the non-homogeneous foundation, the difference of adjacent foundation parameters significantly affected the response law of tunnel longitudinal internal forces, and the maximum tunnel bending moment presented a particular nonlinearity with the change of foundation parameters.

Numerical Simulation Study on Application of T-Shaped Composite Pile Support System in Super-Large Foundation Pit Support Engineering

To reduce the impact of the one-time excavation of deep and large foundation pits on nearby subway tunnels, the excavation should be performed separately; thus, a T-shaped pile support system was studied. First, several foundation pit support structures were compared and selected, and a pile support system was proposed. In terms of space, a T-shaped support structure was formed to reduce the spatial requirements of the foundation pit. Through finite element software, a 1:1 restoration of the foundation pit using a T-shaped pile support system was carried out. The stress characteristics and support effect of the support structure were studied under two working conditions of symmetric and asymmetric excavation. The study found that there was a central effect on the foundation pit using a T-shaped pile support system, that is, the support piles farther away from the center of the T-shaped structure gradually increased the maximum pile bending moment and displacement owing to the constraints of vertical piles and the influence of the pit angle effect, respectively. In the case of symmetrical excavation, the T-shaped structure was simplified into a triangular structure, and the stress form of this type of structure could be reduced to a cantilever double-row pile structure, which met the requirements of pit excavation. The application of a T-shaped pile support structure can provide new design ideas for foundation pit engineering near regional subway lines.

Mechanical properties analysis of asphalt nanostructures based on atomic force microscope and discrete element method

In order to further reveal the mechanical properties of asphalt nanostructures, the formation and evolution of "bee structure" were analyzed by means of discrete element method (DEM) combined with atomic force microscope (AFM). Firstly, asphalt AFM images, including virgin asphalt and aged asphalt, were obtained by AFM, and the "bee structure" characteristics were preliminarily analyzed. Secondly, the micro models of asphalt AFM images were established by using DEM, and the mechanical parameters provided by known correlation experiments were assigned to asphalt nanostructures. Finally, the mechanical simulation and analysis of the asphalt nanostructure models based on DEM were carried out to obtain the stress characteristics of "bee structures" under different stress states (tensile stress, compressive stress and shearing stress). It is found that the location of newly formed "bee structures" during asphalt aging is not random, which is related to the stress concentration of asphalt nanostructures. When the asphalt nanostructures were subjected to external forces, the "bee structure" has stronger resistance to external forces, but its overall mechanical properties depend on the "non-bee structure". The spatial characteristics of "bee structure" can be explained by the non-uniform stress at the same location of asphalt nanostructures. The research results provide a theoretical basis for the crack resistance of asphalt nanostructures, and have certain significance for the research and development of asphalt nanostructures.

Evaluation of the effects of exogenous cortisol manipulation and the glucocorticoid antagonist, RU486, on the exploratory tendency of bluegill sunfish (Lepomis macrochirus)

In teleost fishes, activation of the hypothalamic-pituitary-interrenal axis leads to an elevation of circulating cortisol levels as a primary stress response. While acute elevation of cortisol is generally beneficial, long-term elevation, a common characteristic of chronic stress, may lead to detrimental effects on health and physiological performance in fishes. Some stress-mediated behavioural shifts, such as variation along the shy-boldness axis in fish, may influence individual fitness. The present study evaluated the role of cortisol and its mechanisms of action in the exploratory behaviour of the bluegill sunfish (Lepomis macrochirus). Fish were implanted with cocoa butter alone (sham treatment), or cocoa butter containing cortisol, or cortisol and the glucocorticoid receptor antagonist, RU486. A control (untreated) group was also used. Animals were held for 48 h following treatment and then were subjected to a Z-maze trial to characterize the exploratory behaviour. Cortisol treatment had no measurable effect on the exploratory behaviour of bluegill sunfish. Despite presenting a higher probability of refuge emergence, fish treated with cortisol combined with RU486 behaved similarly to cortisol-treated and control groups. While these results suggest that cortisol may not be involved in the mechanisms controlling boldness, the influence of cortisol elevation across longer time periods plus validation in different contexts will be necessary to confirm this conclusion.

Chemical and functional properties of nutrient-dense beverages developed from underutilised crops

Beverages are typically seen as wholesome snacks that can be included in a daily diet. Despite being part of the regular diet, the majority of these beverages are low in nutrients and high in calories. Worldwide, a variety of industrial processes, raw ingredients and microorganisms are used to manufacture fermented food. Many indigenous or traditional fermented foods and beverages are still prepared today as a form of domestic art. They are created in small businesses, communities and homes. Among the fermented foods that are important to people's diets worldwide are beverages that might have a non-dairy origin. In this study, Moringa oleifera Leaf Powder (MoLP) was used to fortify two beverages, including Amasi (Bambara groundnut) and Mageu (sorghum), at 0% (control), 1% and 5%. After fortifying the fermented and unfermented variations, the beverages' biochemical, chemical and functional properties were analysed. The effects of MoLP (1% and 5%) on the stress, viscosity and torque characteristics of Amasi were significant (p ?0.05). For all of the samples, Amasi and Mageu's values for protein, ash and moisture increased significantly (p ?0.05) due to the inclusion of MoLP. These findings indicate that MoLP-fortified beverages can act as a source of nutrients to address micronutrient deficiencies in children and adults.

Mindfulness influences the psycho-social dimension of chronic pain: A randomized controlled clinical trial in Indian context.

In India, the awareness about the psycho-social dimension of chronic pain is minimal among physicians and patients. The research with community-based group therapies (like mindfulness) to address the psycho-social aspects in chronic pain patients remains limited. The aim of this randomized controlled trial was to see the effects of mindfulness on pain intensity, pain catastrophizing, chronic pain acceptance, perceived stress, well-being, and mindfulness characteristics. In this two-site, parallel group, clinical trial, 170 patients attending pain outdoors of two government hospitals in West Bengal, India, were randomized to attend five weekly in-person mindfulness sessions (cases) or usual care sessions (controls) within the hospital premises. Pre-program and post-program data were collected and analyzed using statistical methods like repeated measures analysis of variance. In participants of the mindfulness group, significant changes post session were noted in pain intensity [F(1,326) = 15.0122; P = 0.0001291], pain acceptance [F(1,326) = 4.5311; P = 0.03403], and perceived stress score [F(1,326) = 13.2788; P = 0.0003122] compared to pre-session. The changes in pain catastrophizing, World Health Organization well-being and Freiburg mindfulness inventory scores were non-specific. Mindfulness had a positive influence on pain intensity, pain acceptance, and perceived stress of Indian chronic pain patients. The effects on pain catastrophizing, mindfulness characteristics, and well-being (non-specific) were also encouraging. Further studies will be required to substantiate these results.

Stressed-deformed state of the system «main pipeline – soil» in the karst sections (on the example of the section of the main gas pipeline «Power of Siberia», «Chayanda – Lensk»)

Currently, modern gas pipeline systems are increasingly demanding in terms of reliability, durability, industrial and environmental safety. Gas pipeline routes are located in poorly established regions where there are no long-term observations of hazardous natural processes. Currently, karst is the most latently occurring and difficult to predict hazardous engineering and geological process. In case of karst process along the pipeline route, additional load may be applied. In this regard, the analysis of the stress-strain state of the trunk gas pipeline-soil system is the most important task for determining the quantitative characteristics of stresses that can cause the development of emergency. The article considers the section currently built, the main gas pipeline "Power of Siberia," "Chayanda - Lensk." Carbonate formations of Cambrian age are widespread within the considered territory, there are manifestations of surface and underground forms of karst. In this regard, it is possible to activate the process during the operation stage, while during the design these geotechnical features may not have caused concerns. In this work, stress-strain analysis was carried out in case of joint deformation of the pipeline and soil under the influence of a possible load - karst dip. Proposals on the use of the obtained results at the operation stage are given.

Factors influencing age at onset of colorectal polyps and benefit-finding after polypectomy.

Screening, followed by colonoscopic polypectomy, has been widely performed in China. However, factors influencing age at onset of colorectal polyps and benefit-finding after polypectomy have been insufficiently studied or ignored. A total of 152 patients with colorectal polyps first detected in First Affiliated Hospital of Huzhou University from July to September 2022 were enrolled in this study. We selected 11 factors associated with the risk of colorectal polyps, including gender, body mass index, occupational stress, education level, income satisfaction, smoking, alcohol consumption, exercise frequency, diet, family history and polyp characteristics. Benefit-finding after polypectomy was obtained by follow-up for 142 of these patients. Multivariate linear regression analysis showed that being overweight (i.e., body mass index ≥25 kg/m2), higher education level, lower exercise frequency, and refrigerated food preference were associated with early-onset colorectal polyps. Patients with a preference for pickled food and age ≥50 years at first colorectal polyp detection had lower benefit findings after colonoscopic polypectomy. Colorectal polyps may develop earlier in people who are overweight, well-educated, exercise less, and prefer refrigerated food. In addition, patients who prefer pickled food and age at onset ≥50 years have lower benefit-finding requiring more attention in future colonoscopy follow-ups.