Variation Law Of Stress Research Articles

Surface chemo-mechanics coupling of MnO2/Au layered composites under electrochemical environment

The intersection of surface mechanics and electrochemistry has gradually become a prominent topic in the realm of new energy research. To explore the influence of the electrochemical process on the stress of energy storage electrode composite, supercapacitor material manganese dioxide (MnO2) was selected as the coating and the MnO2/Au composites were prepared by the electrochemical deposition. The surface stress of MnO2/Au composites under different electrochemical modes and the stress variation law of MnO2 with varying thicknesses were determined. The addition of MnO2 could alter the stress response and the strain magnitude of the gold electrode with varied electrochemical potential. The reversible tensile strain within the Au surface during 0.3 ∼ 0.8 V charging was induced by the absorption of SO42−, while the compressive strain of the MnO2/Au composites was related to the extraction of Na+ ions resulting from the redox pseudocapacitance of MnO2. Notably, the produced stress exhibited a linear correlation with the capacitance. And the long-cycle tests revealed that as the specific capacitance of electrodes decreased, the induced tensile stress progressively diminished. This study emphasized the surface chemo-mechanics coupling of both the Au layer and MnO2/Au composites, which would provide a new approach to regulating surface strain in the solid–liquid interface.

Research on the Mechanical Properties and Structural Optimization of Pipe String Joint under Deep Well Fracturing Operation

In order to reduce the failure accidents caused by the insufficient strength of fracturing string joints, theoretical calculation and string design methods were adopted to conduct finite element calculations on commonly used long circular threads. The distribution laws of stress and contact pressure of long round threads were obtained, a non-standard special thread was designed, and a finite element model of the joint of the casing was established. Considering different make-up torques, tensile loads, and tensile torque loads within a certain range, the stress variation law of the special casing threaded joint under this design size was analyzed. Finally, the stress and contact pressure variation law on the threaded tooth was analyzed under different structures, working conditions, and wall thickness parameters. The thread strength and sealing function were compared under various parameters. The results showed that the smaller the wall thickness of the joints, the greater the contact pressure at the threaded tooth. Among them, the contact pressure of the external threaded tooth is too high, and is prone to the sticking phenomenon. The distribution of contact pressure in the middle section is relatively reasonable. Compared with the original structure, the new structure significantly reduces the contact pressure at the head and tail ends of the threaded connection, reducing the risk of sticking.

Analysis of Dynamic Wear Characteristics of Joint Contact Friction Pair of Excavators Working Device

The working device of an excavator in construction machinery is prone to damage and wear under ordinary working conditions. Based on a model of an excavator under typical working conditions, the dynamic load-bearing situation of the three main joint friction subsets of the working device is simulated by using the virtual prototype technology; the location of the functional device with high stress is identified based on finite element analysis, and the correctness of the simulation results is verified by designing strain gauges. Based on this, the dynamic contact stress variation law of the contact surface of the end-face friction subsets was explored, and the end-face wear depth was calculated by combining Archard wear theory and finite element wear simulation technology; the specimens were worn on the end-face wear tester, and the surface wear was observed under the scanning electron microscope to summarize the wear mechanism and analyze the element content changes of the worn surface. The results show that the three main joints of the working device produce large dynamic fluctuations and are prone to wear, and the destructive degree is more prominent; the wear process is accompanied by higher temperatures, fatigue wear, and abrasive wear on the wear surface, and the wear depth value of the right end face is significantly larger than that of the left end face. This method has a significant reference value for reliability analysis and optimization improvement when using construction machinery’s main joint friction pairs.

Mechanical properties of poplar (NL-3412) branches

ABSTRACT The mechanical properties of poplar (NL-3412) branches are the basis for designing and optimizing the working parameters of branch pruning and crushing machinery. In this study, the tensile, compression, bending and shear properties of poplar branches were investigated by utilizing a precision microcomputer-controlled electronic universal testing machine. The test results suggested that the elastic constitutive relationship of the stress–strain curves of poplar branches under longitudinal compression, transverse compression, and bending conformed to Hooke's law, and longitudinal tensile and shear exhibited plastic damage; the anti-failure strength, anti-failure elastic modulus, and external work of poplar branches under longitudinal compression were greater than those under transverse compression. The analysis results indicated that the correlation function between the anti-failure strength and the external force work of poplar branches is positively correlated, and the external force work required to destroy poplar branches can be estimated by the established regression mathematical model. The results of the study can provide important data support for the optimal design of poplar branch pruning and shredding machinery and related simulation experimental research. HIGHLIGHTS The basic parameters of mechanical properties of poplar branches were determined. The variation law of stress–strain curve of poplar branch mechanical test was proved. The mathematical model between the strength and external force work was established. Provide reference for the optimal design of branch pruning and crushing machinery. Provide data support for the simulation cutting test of poplar branch.

Experimental investigation on stress distribution and migration of the overburden during the mining process in deep coal seam mining

Coal mining has a significant impact on the movement of the overburden, leading to potential safety hazards in the working face. In this paper, a similarity simulation experiment was conducted to investigate the migration of overburden during the mining process of a specific working face in the Liuzhuang Coal Mine located in southern China. Sand and gravel were used to simulate the geological environment of each rock stratum. The deformation of the stratum was monitored using strain gauges, the fracture and displacement changes of the overburden stratum were recorded using cameras, and the characteristics of roof collapse was monitored using infrared thermal imager. The experimental model fully simulated the situation of the working face, and the actual working face size was obtained by enlarging the model by 100 times. The experiment found that during the initial stage of mining, there was no significant subsidence of the roof. In the course of the advancement of the working face, the primary roof intermittently fractured behind the working face, with subsequent propagation of upper cracks in an upward direction. The overburden rock layer above the goaf experienced continuous compaction, leading to the gradual closure of the separation layer. Simultaneously, new cracks constantly emerged in front of the working face, resulting in the progressive stabilization of the height of the crack zone. The stress measurements at each point exhibit a pattern of initial increased, followed by decrease, and ultimately stabilization. By considering the stress variation law of the overburden rock, the stress changes in key layers of the bedrock during mining could be categorized into four zones: the stress stable zone, stress increasing zone, stress reducing zone, and compaction stable zone. During the initial phase of coal seam mining, the presence of rock layers provided support, resulting in minimal subsidence of the overburden rock. However, as the mining operation progressed, the disturbance force and collapse of the overburden rock leaded to further downward subsidence. When the working face reached the stop line, the collapsed overburden rock gradually consolidates, resulting in a deceleration of energy release and the formation of a pressure relief zone. Consequently, the overburden rock above the working face underwent a slight additional subsidence, reaching its maximum level. A short cantilever rock beam structure was formed in the experiment. This study will provide valuable reference for future coal mining and serve as a vital theoretical basis for roof control in deep coal seam mining.

Study on seismic response characteristics and failure mechanism of giant-span flat cavern

In order to study the seismic response characteristics of the giant-span flat cavern (GSFC), a nonlinear finite element model of the GSFC was firstly established by ABAQUS software to investigate the seismic deformation characteristics and stress variation law of the GSFC in detail. Secondly, the bearing mechanism of the GSFC was systematically analyzed. Finally, the damage evolution law and failure mechanism of the GSFC were revealed. The results showed that the deformation, stress and damage of the GSFC under design and rare earthquakes were within safe and controllable limits. The interaction between the linings had a certain damping and peak-elimination effect. When the PGA was 0.2 g, the peak acceleration of the inside lining was reduced by 10% compared to the outside lining, the deformation response was reduced by 39%, and its seismic stress distribution was more uniform. In the bearing system of the GSFC, the surrounding rock was supported the lining so that its self-bearing capacity was fully utilized, while the lining was embedded by the surrounding rock, improving its integrity and stiffness. Under extreme earthquakes, the damage evolution processes of the surrounding rock and the lining were coupled with each other. The continuous plastic strain occurred mainly at the bottom and top of the surrounding rock. The outside lining was mostly destroyed, and the inside lining gradually degraded into a double-hinged arch structure supported by the side walls, so that the seismic performance of the surrounding rock-lining bearing system was lost. The degraded structure can maintain a relatively stable vertical self-equilibrium state and is not prone to extreme damage such as overall collapse. The research conclusions could provide a theoretical basis and scientific reference for accurate seismic prediction and safety evaluation of the GSFC.

Study on stress variation law of hard concretion coal under the action of pick based on DYNA

Modeling and simulation of pick cutting hard concretion coal process are taken as a key link to analyze the stress variation law. To this aim, the properties of hard concretion coal in the target mining area were tested. Related model with high-quality common grid was generated using the mapping method through Hypermesh. the coal breaking process was performed using LS-DYNA, and the stress variation law of coal and hard concretion was analyzed. The results showed that the closer the action position to the middle point of long axis of hard concretion, the greater stress peak would be generated, stripping of the pick occurred when it acted on the 2/5 and 1/2 positions of the long axis. Using similarity theory, the model of hard concretion coal was made and the pick cutting experiment was performed. Compared with simulation torque result, the correctness of modeling and simulation has been verified.

Determination of In Situ Stress by Inversion in a Superlong Tunnel Site Based on the Variation Law of Stress — A Case Study

The Sejila tunnel, part of the Sichuan-Tibet railway, is in a complex geostress environment because of its deep burial depths and tectonic movement. Based on the measured stress data combined with the structural history and features, the stress characteristics of the Sejila area are preliminarily identified. Then, a three-dimensional numerical model that can provide real topographic features is established, and a distribution law of stress boundary conditions is proposed according to compilations of much measured stress data. By means of support vector regression (SVR), the stress field of the whole Sejila region is determined and finds a reasonable accordance with the measured stress data. Results show that the vertical stress in deep buried stratum can be approximately regarded as one of the principal stresses, and it is reasonable to apply the lateral stress to the model boundary according to a linear function with burial depth. The in situ stress in the tunnel site exhibits that σH >σV >σh, and the σH direction deflects when it encounters faults or strata interfaces; the larger that the intersecting angle between fault strike and σH is, the smaller the deflection. Compared to the entrance, the rear of the tunnel is subjected to a high maximum principal stress with a high angle; moreover, most sections of the tunnel are estimated to suffer from severe rockbursts, except for a range of 5 km away from the tunnel entrance and 2.5 km away from the exit, according to the Russense criterion. This paper can provide the basis for the prediction and prevention of rockbursts in the Sejila tunnel.

According the data analyse to study of the Frost Resistance of Corrugated Metal Pipe Culverts in Permafrost Regions

In this paper, we mainly studied the stress variation law of corrugated pipe culvert in permafrost regions under the influence of external load and temperature field, and formulated the corresponding experimental arrangement and observation scheme, in order to reveal the mechanical characteristics and action mechanism of corrugated metal pipe culverts.At the same time, we studied the law of the upper limit variation of permafrost foundation under corrugated pipe culvert, established the finite element model of corrugated pipe culverts, and for which we conducted mechanical analysis, frost heave analysis, and solution(thawing) settlement analysis; measured the variation of earth pressure and temperature field around pipe wall during and after filling soil.

Structural Stability Monitoring of Model Test on Highway Tunnel with Lining Backside Voids Using Dynamic and Static Strain Testing Sensors.

Voids behind a lining may develop due to insufficient backfilling, poor workmanship, water erosion or gravity. They affect the interaction between the surrounding rock and lining and even cause instability of the lining structure. To ensure the safe operation of tunnels, it is very important to study the influence of voids behind the lining of the lining structure. In this paper, a laboratory model of a tunnel lining was established by taking the voids behind the lining of the Wushan Tunnel as an example. By changing the position and size of the voids, the corresponding stress variation law of the lining was obtained, and the influence of the voids behind the lining on the structural stability of the highway tunnel was analyzed. The experimental results showed that the voids behind the lining led to an increase in the stress near the voids, especially the voids at the vault. The circumferential stress and axial stress increased with increasing void depth and length, and the increase was greater with increasing void depth than increasing length; that is, the void depth had a greater effect on the lining stress. When the vault void depth was 30 mm, the axial tensile stress of the vault was 0.281 MPa, and the maximum increase was 178.2% compared with that without voids. The safety factors at different lining positions, from large to small, are: arch foot > spinner > arch top > arch waist. In the processes of lining operation and maintenance, special attention should be given to the treatment of voids behind the lining, especially deep voids.

Study on Design and Deformation Law of Pile-Anchor Support System in Deep Foundation Pit

In this study, a deep foundation pit project of Nanlishi Road in the Xicheng District of Beijing was taken as the engineering background. Based on the monitoring method of that project and referring to its design scheme principle, this study applied advanced monitoring technology methods such as anchor axial force and deep horizontal displacement monitoring. The mechanism of pile–soil interaction, the stress change and deformation law of the three-pile and two-anchor support systems of deep foundation pits, and the stability of deep foundation pit support in an anhydrous sandy pebble stratum, were studied in depth. Results show: The axial force of the anchor rod had great loss in the early stage of prestressed tension locking; with the deepening of foundation pit excavation, the lateral pressure of stratum increased gradually, and the prestress of the anchor increased until the end of excavation, where it tended to be stable; the maximum horizontal displacement of the pile was smaller than the design value, and the maximum horizontal displacement was not at the top of the pile; the axial force of the prestressed anchor varied with the formation pressure and surrounding load; the tension of the lower anchor had a certain influence on the axial force of the upper anchor. Except for the east side of the foundation pit, the anchors of the first layer were all stabilized at about 140 kN, and the anchors of the second layer were stabilized at about 150 kN. The third row of anchors on the north side was stable at around 170 kN. By analyzing the variation law of stress and deformation of the supporting structure of the foundation pit, the timeliness of the data during the construction process was improved, and a reference is provided for the informatization construction of related working conditions.

Analysis of Deep Foundation Pit Pile-Anchor Supporting System Based on FLAC3D

Relying on a deep foundation pit project in Beijing, using FLAC3D three-dimensional finite-difference software simulation combined with displacement monitoring data verification method, the deep foundation pit excavation and three-pile and two-anchor rod support system in anhydrous sand pebble stratum are systematically analyzed, and summed up the variation law of formation stress, internal force of soil nail, axial force of bolt, stress and displacement of pile in the process of excavation and support of deep foundation pit. The results show that during the excavation of the foundation pit, the maximum horizontal displacement of the sidewall is not at the top of the pile and the top of the slope but at a certain distance below the top of the pile. The axial force of the anchor rod is unevenly distributed along the length direction, the axial force of the free section is equal, the axial force of the anchoring section decreases in turn, and the prestress of the anchor rod spreads to the anchoring section after tensioning and locking. The soil-nailed wall is a passive force-bearing system, the force is small during the excavation and support process, and the axial force distribution along the length direction is large in the middle and small at the two ends. By analyzing the variation law of stress and deformation, the timeliness of the data in the construction process is improved, and an effective and reasonable case reference is provided for the informatization construction of simulated relevant working conditions.

Numerical study on triaxial compressive behavior of engineered cementitious composites confined by circular steel tubes

The mechanism of engineered cementitious composites (ECC) in triaxial compression is still unclear, and the existing method cannot accurately predict its compressive capacity due to the lower elastic modulus and the effect of fiber bridging. In this paper, the compressive behavior of ECC confined by circular steel tubes was studied by performing a series of nonlinear finite element (FE) analysis. The non-linear material properties of ECC and steel and composite actions were considered in developing the FE models. The accuracy of the models was verified by comparison with the test results, such as load–displacement histories, failure modes and ultimate strengths. The verified model was utilized to explore contact pressure, the contribution of ECC to compressive capacity, ductility, energy absorption, and the influence of important parameters. Additionally, the effective confining stress (fr) was modified by average contact pressure, and a constitutive model of ECC under triaxial compression was developed by stress–strain relationships. It is shown that the effect of boundary confinement effect coefficient on the post-peak period of load–displacement history is classified and discussed. Meanwhile, the results of Richart’s model achieve a good accuracy by modifying the effective confining stress. Finally, a constitutive model of ECC under triaxial compression is proposed, of which the prediction results can describe the variation law of stress–strain relationship.

The finite element modeling of the impacting process of hard particles on pump components

Abstract Shield pumps which transport a variety of complex media are widely used in chemical industry, mineral industry, and other fields. However, the hard particles in the media erode the flow passage in the shield pump, seriously affecting the service life of the pump. Therefore, it is important to study the erosion process in the flow passage to extend the service life of the pump. This erosion process in the shield pump can be investigated by experiments, but it is difficult for the current experimental method to copy the real industrial service environment of impellers. For example, the environment temperature and speed range are found difficult to be reached by the current experimental method. Comparatively, the simulation by finite element method can overcome the above deficiency. In this article, the ANASYS software is used to simulate the erosion process in shield pump flow passage due to hard particles. Specifically, the structural static analysis module is used to build the model of thermal barrier coating components and hard particle components. Then the variation law of stress, strain, and material deformation of the flow passage components under concentrated force is obtained. Second, the extended finite element method is used to study the crack propagation caused by the erosion process. A linear elastic–linear softening constitutive model is established to simulate the stress variation during the crack propagation and material removal under the continuous erosion from hard particles. The proposed law regarding stress variation and crack propagation in the erosion process in this study contributes to theoretical support for damage detection and service life extension of shield pumps.

Complex function solution for deformation and failure mechanism of inclined coal seam roadway

The stressed environment of the inclined coal seam roadway is complex and changeable, and the damage degree of surrounding rock increases, threatening the safe mining of coal mines. In order to take targeted support measures to control the stability of roadway surrounding rock, it is very important to study the stress and deformation characteristics of roadway surrounding rock in inclined coal seam. Therefore, this paper analyzes the deformation and failure law of inclined coal seam roadway according to the theory of complex variable function. It optimizes the solution process and accuracy of the mapping function coefficient and deduces the analytical solution of surrounding rock stress and deformation inclined coal seam roadway. The deformation and failure mechanism of surrounding rock in inclined coal seam roadway is revealed theoretically, and further use numerical simulation and physical simulation tests for supplementary analysis and verification. The results show that the stress and deformation of roadway surrounding rock in inclined coal seam show obvious asymmetric distribution characteristics. The stress and deformation of roadway surrounding rock on the right side are greater than on the left side. The two sides of the roadway, the right side of the roof and the roof angle of the right side, are the key positions of roadway stress concentration and deformation. According to the variation law of stress and deformation distribution of roadway surrounding rock, roadway cyclic deformation and failure theory is put forward. The numerical simulation and physical simulation tests show that the deformation and failure law of roadway is consistent with the theoretical analysis results, and there are differences in numerical values. The cyclic deformation and failure mechanism of roadway in inclined coal seam is verified, which can provide theoretical guidance for roadway support design.

Study on the Stress Variation Law of Inclined Surrounding Rock Roadway under the Influence of Mining

This study takes three roadways with similar burial depths in different strata in Xieqiao Mine of Huainan as its research object. This study involves the observation and analysis of borehole stress gauge data under the influence of mining pressure. The observation data show that: (1) under the influence of mining, the high-wall vertical stress increases as the distance from the roadway surface increases, and the peak point is at 6 m. The increment value of vertical stress at the low side has a maximum value at 8 m and a peak value at 14 m. The increase value of horizontal stress of the high side has two peaks, which are 4 m and 6 m, respectively. The increment of horizontal stress in low walls is also about 8 m. (2) The mining influence range of working face mining is about 150 m. Mining influence distance can be divided into three stages: 0–25 m, 25–60 m, and beyond 60 m. The increase of vertical and horizontal stress caused by mining increases sharply within 25 m from the working face. (3) The buried depth of the roadway has an influence on the range of mining influence and the increase of mining stress caused by working face mining. The more the buried depth of the roadway increases, the greater the range of mining influence and the increased value of mining stress. (4) After roadway excavation, the surface deformation of roadway surrounding rock reduces the increase of mining stress near the roadway surface. The mutual verification between the analysis results and theoretical calculation results is helpful to roadway support design and advanced support design of the working face.

Low-Cycle Fatigue Performance of the Sealing Plate Connection in Aluminum-Alloy Bolt-Sphere Joints

The low-cycle properties of aluminum-alloy bolt-sphere joints were investigated in this study through experimental research, finite element simulations, and theoretical analyses. To obtain the fatigue performance of the material, low-cycle fatigue tests of 6061-T6 aluminum alloy were first performed as the basis for component fatigue estimation. The low-cycle fatigue tests were then used to investigate the failure mode and fatigue life of the sealing plate connection specimens. The specimens failed at the junction of the sealing plate and the aluminum-alloy tube. The fatigue life is primarily determined by the precise size of the connection part. A finite-element model for a sealing plate connection was created to investigate stress and strain distribution. The results show a high-stress concentration at the bottom thread's root. The maximum stress variation law is consistent with the low-cycle fatigue life variation law. Finally, a prediction for low-cycle fatigue life was attempted using the finite element result and the material's fatigue performance based on the local strain approach. The prediction results were consistent with the test results.

Study on Stress Field Distribution during the Construction of a Group of Tunnels Using the Pile–Beam–Arch Method

To study stress field distributions during the construction of a group of tunnels using the pile–beam–arch method, the excavation for an underground station of Beijing subway line 7 was taken as an engineering problem, and a numerical structural model of a tunnel group was built with the aid of software. In this model, four stress-monitoring planes were set up to extract the data obtained from monitoring stress. The construction of the pilot tunnels was simulated according to six established construction schemes, and images were generated for the stress field distribution on each monitoring plane using different schemes. Finally, a verification of physical model tests was carried out. The results show that the effect of excavation on vertical stress in pilot tunnels has a range that is essentially equal to twice the width of the station. After the excavation of pilot tunnels, peaks appeared both at the tops of the pilot tunnels and between the bottoms of the tunnels; moreover, valleys appeared both at the bottoms of the pilot tunnels and between the tops of the tunnels. Pilot tunnels located at the top of the group were less affected during excavation than the tunnels located at the bottom of the group both in stress concentration factor and in the point of extreme stress. Finally, the model verified the numerical simulation results of the stress variation law.

Simplified hygromechanical coupling model and numerical simulation analysis of fibre reinforced composite deep-sea and underwater structures

The water absorption of composites will affect the safety and performance of the structure, resulting in the inability to give full play to its excellent lightweight and high-strength characteristics. This key issue is currently being experienced by composite deep-sea and underwater structures. The water absorption of composites is a complex problem involving the coupling of multiple scales. At present, the expressions of some water absorption theories are generally more complicated, which makes it impossible to apply the theories directly to the design and verification of deep-sea and underwater structures. This research assumes the uniformity of fibre distribution, with cylindrical-cube unit cells as the research object. A simplified hygromechanical coupling model of composites was proposed. Furthermore, by adding subroutines and considering the uneven distribution of the diffusion coefficients of each layer, the finite element method was used to simulate the whole process of water absorption of the composite laminate. Finally, it is compared with the experimental results to verify the effectiveness of the simplified model. Based on this comparison, the water absorption distribution, diffusion coefficient and interlayer stress variation law of composites in different time periods are obtained.

HOT COMPRESSION DEFORMATION BEHAVIOR AND CONSTITUTIVE ANALYSIS OF EXTRUDED MAGNESIUM-BISMUTH ALLOYS

The isothermal compression experiments of Mg-2Bi alloys were carried out under different temperature and strain rate by Gleeble 3500D thermal simulation test machine. The rheological stress variation law of the Mg-2Bi alloy was analysed under 200-350oC and 0.001-1.0 s-1. The results present that the peak stress enhances and the dynamic recrystallization grain size reduces with the decline of deformation temperature and the improvement of strain rate during isothermal compression of the Mg-2Bi alloy. In addition, the activation energy for alloy deformation is 130.03 kJ/mol. The softening mechanism of the Mg-2Bi alloy is mainly twin and dynamic recrystallization under a low temperature (200oC) condition. While at a higher temperature of 350oC, the softening mechanism changes to single dynamic recrystallization.