Dynamic Stress Response Research Articles

Dynamic stress response and fatigue characteristics of tight sandstone reservoirs with pulsating hydraulic fracturing

Dynamic stress response and fatigue characteristics of tight sandstone reservoirs with pulsating hydraulic fracturing

Dynamic stress response in reservoirs stimulated by fluctuating fluid pressure during pulsating hydraulic fracturing

Determining the most effective scheme for fracturing operations depends on accurate calculations of reservoir stress. Traditional fracturing theories usually focus on stable fluid injection modes, which employ static assumptions in modelling and analysis. However, pulsating hydraulic fracturing (PHF) introduces fluctuating fluid pressure to stimulate reservoirs, which requires considering dynamic factors and exploring the dynamic stress response within the reservoir. Furthermore, reservoirs are often classified as homogeneous continuous or porous media materials, but the boundaries between these classifications are sometimes apparent. This paper investigated the development of both an elastodynamics model and a poroelastodynamics model for calculating dynamic stress responses during PHF. The staggered grid finite difference method addressed these models, with the outer boundary employing the perfectly matched layer (PML) method to simulate an infinite reservoir. The numerical simulation results were extensively verified and compared with analytical solutions, and the differences between various models and their relevant conditions were thoroughly analyzed. Analyzing fluid pressure fluctuation parameters revealed noteworthy insights into reservoir stress response characteristics. Results indicate that as the Biot coefficient and permeability increase, the disparities between the elastodynamics and poroelastodynamics models become prominent. In practical terms, high Biot coefficient or high permeability reservoirs necessitate using the poroelastodynamics model for accurate reservoir stress analysis. As the frequency of fluid pressure fluctuation increases, the amplitude of response of reservoir circumferential stress also increases, while the response amplitude of radial stress and fluid pressure decreases. These findings offer valuable theoretical guidance for parameter design in engineering applications during PHF.

A Comparative Study on Two Doses of Esmolol 0.5mg/Kg and 1.5mg/Kg to Attenuate the Hemo Dynamic Stress Response during Laryngoscopy and Endo Tracheal Intubation

A Comparative Study on Two Doses of Esmolol 0.5mg/Kg and 1.5mg/Kg to Attenuate the Hemo Dynamic Stress Response during Laryngoscopy and Endo Tracheal Intubation

Dynamic soil arching effect in pile-supported embankment due to train passages at high speeds

Pile-supported embankment has been widely adopted for high-speed railways constructed over soft soils to reduce post-construction settlement. The role of soil arching effect in stress distribution inside pile-supported embankment under static weight load has been extensively studied, while the dynamic soil arching effect due to train moving loads has been paid little attention. In this paper, a sophisticated three-dimensional (3D) track-embankment-pile-subsoil finite element model (FEM) has been developed to analyze dynamic stress responses due to train passages at high speeds. The numerical model has been validated by experimental results on a full-scale pile-supported railway embankment model. The numerical analyses reveal that the dynamic soil stress distribution in the embankment near the track is almost consistent with the Boussinesq solution, but the presence of piles underneath the embankment leads to the redistribution of dynamic soil stresses inside the embankment due to the dynamic soil arching effect. The soil arch height under train load is 2 m (2.5 times of the clear space of piles), higher than the height 1.6 m (2 times of the clear space of piles) under embankment self-weight. Besides, the pile efficacy (ratio of load borne by the pile cap to the total applied load) caused by moving train load at 100 m/s is 0.6, which also is higher than the pile efficacy 0.57 caused by embankment weight. Train passage at high speeds significantly amplifies the dynamic stress intensity in the embankment but barely changes the pile efficacy.

Critical speed of ballasted railway tracks: Influence of ballast and subgrade degradation

Track substructure layers such as ballast and subgrade involve progressive degradation with time in relation to the loading history. Degradation of track components directly influences the dynamic track response including the displacements and stresses. Determining the influence of real-world substructure degradation problems such as particle breakage, ballast fouling and mud pumping on the critical speed of a given track is essential to design ballasted tracks for high-speed passenger and freight trains. In this paper, a coupled rheological-continuum model is developed to predict the track dynamic response for different train speeds and axle loads. In this novel approach, field dispersion curves obtained from MASW (Multichannel Analysis of Surface Waves) testing can be adopted along with the proposed analytical model to predict the critical speed of track as well as the corresponding dynamic stress state in the substructure layers. Analytical modelling shows that problems such as ballast fouling and mud pumping lead to reduction in the computed critical speed, while also amplifying the dynamic stress response at lower train speeds. The influence of substructure degradation is found to be more prominent for heavy-haul (freight) trains imparting higher axle loads, when compared to passenger trains. Practical insights highlighting the influence of track improvements such as placing a thicker ballast layer and the addition of a capping layer on the critical speed are presented in this study with the objective of rejuvenating future track design.

Dynamics of Berry Characteristics, Biochemical Composition, and Physiological Responses Across Ripening Stages: Investigating the Impact of Pollinizer Varieties on Physiological Femaleness in Bozcaada Çavuşu (Vitis vinifera L. cv)

AbstractUnderstanding the dynamic changes in grape characteristics during ripening is crucial for enhancing grape quality, which, in turn, influences overall viticulture practices. This study aimed to investigate the temporal and cultivar-specific variations in grape characteristics, focusing on BAs, phenolic compounds, antioxidant enzymes, and organic acids. Our results revealed that Bozcaada Çavuşu*Kuntra and Kuntra grapes exhibited the most significant growth in size, weight, and maturity index at the final developmental stage (EL-38), while Vasilâki showed a nuanced maturation pattern with significant increases in berry width but not weight. Across all varieties, the highest maturity index and Total Soluble Solids percentages were observed at EL-38. The investigation of BAs revealed a significant decrease in Put levels from 2.62 at EL-32 to 2.04 mg L−1 at EL-38, contrasting with an increasing trend in Agm concentrations from 0.25 at EL-29 to 0.37 mg L−1 at EL-38. Bozcaada Çavuşu*Kuntra stood out with the highest Cad concentration at 2.96 mg L−1. The analysis of phenolic compounds highlighted a distinct temporal pattern for gallic acid, increasing from 1.60 at EL-29 to 3.77 g L−1 at EL-32 and maintaining stability at 3.74 g L−1 at EL-38. Bozcaada Çavuşu*Vasilâki consistently exhibited higher concentrations of phenolic compounds, such as epicatechin (5.69 g L−1) and tyrosol (7.00 g L−1). Antioxidant enzymes like catalase and superoxide dismutase in grape cultivars showed significant temporal variations, indicating a dynamic oxidative stress response during berry ripening. Catalase activity decreased from 14.04 to 11.20 EU/gr berry between EL-29 and EL-38. The multifaceted regulation of superoxide dismutase by sampling time and cultivar highlighted the complexity of antioxidant dynamics in grapevine physiology. In conclusion, this comprehensive study sheds light on the intricate interplay of temporal and cultivar-specific factors influencing grape characteristics, providing valuable insights for optimizing viticulture practices and enhancing overall grape quality.

Dynamic stress analysis of cracked rectangular blade: Simulation and experiment

Blade crack is one of the main causes of aero-engine failure, resulting in catastrophic accidents. At present, most of the research on dynamic characteristics of cracked blades is conducted based on acceleration response and displacement response and rarely based on dynamic stress response. To simulate the evolving stress state of the cracked rectangular blade (CRB) during the crack propagation, a dynamic model of the CRB is established by shell elements considering the crack-induced breathing effect simulated by the pseudo-contact spring, and a new surface stress calculation method is proposed by linear interpolation based on stress at Gauss integral points within elements. Based on the intact blade, the proposed modeling method and stress calculation method are verified by the measured natural frequencies and dynamic stress in resonance, respectively. Finally, a comparative analysis of the dynamic stress at the crack tip and the root of the CRB is conducted between simulation and experiment at different stages of crack propagation. The results show that (1) the maximum error of the dynamic stress amplitude between simulation and experiment is less than 15% at the root and crack tip of the CRB. (2) The root stress first increases slowly and then remains roughly constant as the crack propagates, while the stress at the crack tip exhibits a linear increase.

Dynamic Stress Response in a Novel Prestressed Subgrade under Heavy-Haul Train Loading: A Numerical Analysis

To explore the dynamic transient characteristics induced by passing heavy-haul trains in newly-developed prestressed subgrade, two three-dimensional finite element models were constructed in the time domain using ABAQUS software. These models are categorized as train-track-prestressed subgrade and train-track-unreinforced subgrade. The numerical models also incorporated the vertical track irregularity commonly found in heavy-haul railways. The investigation aims to discern the dynamic stress response differences in both types of subgrades under three distinct train axle loads. Model validation occurred through comparisons with field tests gathered from various heavy-haul railways in China, as well as analogous numerical simulation cases. The findings indicate that track irregularity results in an asymmetric distribution of dynamic stress on the subgrade surface beneath both left and right rails, aligned transversely with the subgrade centerline. Additionally, this asymmetry is notably pronounced. The peak dynamic stress on the subgrade surface beneath the rails for both subgrades increases with escalating train axle loads. However, the prestressed reinforcement structure (PRS) effectively modulates this phenomenon, with the controlling advantage intensifying as train axle load increases. The average dynamic stress level in the prestressed subgrade is marginally lower than in the unreinforced subgrade within the roadbed layer beneath rails. Furthermore, train axle loads amplify the variation level of dynamic stress in the subgrade. However, the variable coefficient of dynamic stress in the prestressed subgrade is less than in the unreinforced subgrade, suggesting that PRS contributes positively to maintaining subgrade dynamic stability. In terms of the longitudinal distribution of peak dynamic stress, both subgrades exhibit normal distribution at varying depths within the roadbed layer. Lastly, the additional dynamic stress in prestressed steel bars also rises with increasing train axle loads. Nonetheless, it remains substantially lower than the static target pre-tensile stress. Moreover, the dynamic responses of prestressed steel bars in different rows attenuate as depth increases away from the subgrade surface. In summary, the study establishes that PRS significantly enhances the dynamic stability of railway subgrade.

Experiments on the Coal Measures Sandstone’s Dynamic Mechanical Parameter Characteristics under the Combined Action of Temperature and Dynamic Load

This paper conducts impact dynamics experiments on coal measures sandstone in a deep mine via the established dynamic load and temperature split Hopkinson pressure bar (SHPB) experimental system. Firstly, the experimental conditions for the impact dynamics of fine sandstone were determined, with temperatures of 18, 40, 60, 80, and 100 °C, an axial static load range of 1–9 MPa, and a preset bullet incidence velocity of 1.0–5.0 m/s. Secondly, based on the analysis of the basic parameters and physical composition, the dynamic stress and strain responses of fine sandstone under different experimental conditions were obtained, and the change mechanism of its dynamic mechanical process was theoretically analyzed. When the temperature rose from 18 °C to 100 °C, the dynamic peak stress of fine sandstone increased from 36.04 MPa to 73.41 MPa, with an increase of 103.7%. At a temperature of 40 °C, when the axial static load increased from 1 MPa to 9 MPa, the dynamic stress peak of fine sandstone increased from 57.25 MPa to 80.01 MPa, and the corresponding peak strain also showed an increasing trend. The experiment analyzed the variation characteristics of dynamic stress in fine sandstone under the combined action of different strain rates or bullet incidence velocities and different temperatures. In the strain rate range of 47.1 s−1 to 140.9 s−1, there was a significant strain rate effect on the dynamic peak stress and peak strain of fine sandstone, which increased with the increase of strain rate. The study found a polynomial relationship between the dynamic mechanical parameters of fine sandstone and the impact of experimental parameters, with a coefficient of determination greater than 0.9. A dynamic stress constitutive model for fine sandstone under one-dimensional stress state under dynamic load and temperature action was established, and the model validation and parameter determination of dynamic stress changes in fine sandstone under different temperature conditions were carried out. The research results provide a new experimental method for the static and dynamic mechanical analysis of coal and rock masses under complex geological conditions and can provide a basic reference for the prevention and control of dynamic disasters in deep mining processes.

Stochastic stress response and dynamic reliability evaluation for transmission towers with semi-rigid behaviors

As a kind of typical wind-sensitive structure, transmission towers have attracted fast-growing attention in the field of their wind-induced dynamic response. Nevertheless, their dynamic response considering effects of semi-rigid connected joints and semi-rigid-constrained stability behaviors has not been investigated. To this end, based on the experimental and numerical study, this paper proposes a fitting formula for the stability coefficient of steel tube members with semi-rigid behaviors in transmission towers to determine the dynamic stress response. Then, the stiffness, mass, and damping matrices of steel-tube transmission towers (STTTs) with semi-rigid behaviors are determined to construct their stochastic dynamic finite element model. Subsequently, the integral form of the generalized density evolution equation is solved via a family of Dirac's sequences to conduct the stochastic stress response analysis for STTTs considering effects of semi-rigid connected joints and semi-rigid-constrained stability behaviors, and their dynamic reliability is evaluated by further introducing the extreme-value distribution method. Finally, an engineering example of an existing STTT is given, and the results indicate that the semi-rigid connected joints and semi-rigid-constrained stability behaviors would significantly affect the stochastic stress response and dynamic reliability of STTTs. Accordingly, taking into account semi-rigid connected joints and semi-rigid-constrained stability behaviors may be more applicable for analysis and design of STTTs.

FEM-BEM modeling dynamic responses of saturated soil around a fluid-filled lined tunnel subjected to water hammer

Dynamic stress responses of saturated soil around a fluid-filled lined tunnel caused by a water hammer are investigated by a frequency-domain FEM-BEM coupled model. The fluid is modeled as an inviscid and compressible fluid, the lining is modeled by elastic medium and conceptualized as a hollow cylinder of finite length, and the saturated poroelastic medium is adopted to model the soil. Initially, governing equations of fluid and those of lining are solved by FEM in the frequency domain, while those of soil are solved by BEM in the same domain. In the following, fluid, lining, and soil are coupled based on the conditions of deformation compatibility and force balance on their interfaces. Water pressure (inside the tunnel), the distribution of lining displacement and dynamic stress responses of saturated soil generated by the water hammer are presented. It is concluded that the dynamic stresses and the pore pressure change periodically in saturated soil under a water hammer. Modeling soil as an elastic medium inaccurately evaluates the distribution of lining displacement. The soil permeability has a significant influence on the normal stresses of soil and pore pressure but has a slight effect on the shear stresses of soil.

Finite element analysis of a 108-year-old unreinforced brick masonry tower following the 2015 Nepal earthquakes

After a visual inspection following the 2015 Nepal earthquakes, a finite element analysis (FEA) was conducted on a 108-year-old unreinforced brick masonry tower. The focus of study was on the brick masonry clock tower standing at a height of 30.48 m on the Senate Hall (SH) building of Allahabad University in India. This tower, which spans five storeys and features a rectangular cross-sectional shape, exhibits substantial cracks and material degradation across its connections and binding points. The process involved creating geometric plans and a 3D finite-element model through visual inspection and implementing ANSYS Workbench. The study utilised the mechanical properties of the aged materials, sourced from various studies encompassing surveys of old monumental structures, codes, and historical records. The clock tower’s behaviour was assessed through static, modal, and site-specific simulated time history analyses. The static analysis results revealed a maximum deflection of 3.76 mm at the top and a maximum equivalent (von-Mises) stress of 1.81 MPa at the joint of the first-floor level. Modal frequencies for the first three modes were determined to understand the tower’s free vibration behaviour. The time history analyses presented the acceleration, velocity, and displacement response under a peak ground acceleration (PGA) of 1.29 m/s2 simulated for the site. The dynamic analysis highlighted stress responses in critical locations, exposing severe cracks and damages across various points.

Dynamic stress response analysis of inhomogeneous medium containing inhomogeneous inclusions under action of SH waves

Dynamic stress response analysis of inhomogeneous medium containing inhomogeneous inclusions under action of SH waves

Dynamic calcium-mediated stress response and recovery signatures in the fungal pathogen, Candida albicans.

Intracellular calcium signaling plays an important role in the resistance and adaptation to stresses encountered by fungal pathogens within the host. This study reports the optimization of the GCaMP fluorescent calcium reporter for live-cell imaging of dynamic calcium responses in single cells of the pathogen, Candida albicans, for the first time. Exposure to membrane, osmotic or oxidative stress generated both specific changes in single cell intracellular calcium spiking and longer calcium transients across the population. Repeated treatments showed that calcium dynamics become unaffected by some stresses but not others, consistent with known cell adaptation mechanisms. By expressing GCaMP in mutant strains and tracking the viability of individual cells over time, the relative contributions of key signaling pathways to calcium flux, stress adaptation, and cell death were demonstrated. This reporter, therefore, permits the study of calcium dynamics, homeostasis, and signaling in C. albicans at a previously unattainable level of detail.

Dynamic Stress Response Analysis of Circular Inclusions in Inhomogeneous Media With Trigonometric Variations in Modulus and Density Under Shear Horizontal Waves

Dynamic Stress Response Analysis of Circular Inclusions in Inhomogeneous Media With Trigonometric Variations in Modulus and Density Under Shear Horizontal Waves

Key elements of cellular senescence involve transcriptional repression of mitotic and DNA repair genes through the p53-p16/RB-E2F-DREAM complex.

Cellular senescence is a dynamic stress response process that contributes to aging. From initiation to maintenance, senescent cells continuously undergo complex molecular changes and develop an altered transcriptome. Understanding how the molecular architecture of these cells evolve to sustain their non-proliferative state will open new therapeutic avenues to alleviate or delay the consequences of aging. Seeking to understand these molecular changes, we studied the transcriptomic profiles of endothelial replication-induced senescence and senescence induced by the inflammatory cytokine, TNF-α. We previously reported gene expressional pattern, pathways, and the mechanisms associated with upregulated genes during TNF-α induced senescence. Here, we extend our work and find downregulated gene signatures of both replicative and TNF-α senescence were highly overlapped, involving the decreased expression of several genes associated with cell cycle regulation, DNA replication, recombination, repair, chromatin structure, cellular assembly, and organization. We identified multiple targets of p53/p16-RB-E2F-DREAM that are essential for proliferation, mitotic progression, resolving DNA damage, maintaining chromatin integrity, and DNA synthesis that were repressed in senescent cells. We show that repression of multiple target genes in the p53/p16-RB-E2F-DREAM pathway collectively contributes to the stability of the senescent arrest. Our findings show that the regulatory connection between DREAM and cellular senescence may play a potential role in the aging process.

Study on Failure Mechanism of Roadway Surrounding Rock and Hierarchical Continuous Support Technology in Unidirectional Fault Area

A fault is a common geological structure in coal mining. Large deformation or even instability and collapse often occur in roadways in fault areas, which restricts the safe and efficient production of mines. With the track roadway of the 5206 working face of Xin’an Coal Mine as the engineering background, this study aims to explore the failure mechanism of surrounding rock under the influence of fault structures. Field investigation and numerical simulation were used comprehensively to analyze the failure characteristics of the surrounding rock under the influence of a unidirectional fault structure. Based on the principle of thick-layer transboundary anchorage, the hierarchical continuous support technology of transboundary anchoring in the fault structure area was proposed. The results show that the stress near the fault area is relatively concentrated, and the rock mass strength is low, which may easily cause the deformation and failure of the surrounding rock under the dynamic stress response. Using the new technology to reconstruct the bearing structure of the broken surrounding rock mass, the deformation of the surrounding rock can be effectively restrained. According to the monitoring feedback, the roadway deformation in the roof and two sides is reduced by 68.5% and 35.4%, respectively; and the maximum evolutionary depth of the roof crack is reduced to 3.5 m from 7.5 m in the original support scheme. Moreover, this study also explored the necessity of wedge anchorage for corner anchor cables and the deformation characteristics of surrounding rock at different fault dip angles. These results provide an important reference for the maintenance and control of coal roadways under the influence of unidirectional fault structures.

Effect of debonding damage on transient dynamic response on stern ramp door of passenger ship 6311 GT

The sandwich, as an advanced material, increases innovation in the field of ship construction. One of the applications is on the ramp door structure. The characteristics of sandwich material which are light and strong, are the main reasons for the application of this material. However, sandwich material also has drawbacks, one of which is debonding damage, where the bond between the face and core is released. This damage can affect the structure’s stiffness, which impacts reducing the strength of the structure on the ramp door. The effect of debonding is identified by performing numerical tests using finite element software. This test aims to identify the ramp door’s dynamic response due to the debonding damage’s influence. This research uses finite element software with an explicit dynamics method to determine the dynamic response of stress and displacement due to loading on the ramp door. The results of testing with finite element software show that an increase in the ratio of debonding damage causes the amplitude of the dynamic response to increase when subjected to transient loading.

Performance analysis of cross-frequency Doppler-assisted carrier phase tracking

Using the Doppler frequency obtained from tracking a GNSS pilot signal to aid in tracking another signal modulated with higher rate navigation messages in a different frequency band can improve tacking robustness and lower the message demodulation threshold. Based on an analysis of received signal frequency coherence, a linearized mathematical model of the cross-frequency Doppler-assisted carrier phase tracking loop is built, a thermal noise jitter calculation equation for the assisted tracking loop is derived, and its dynamic stress response characteristics are examined. The loop design requirements for eliminating the influence of inter-frequency frequency bias are clarified, as are the cross-frequency assist signal selection criteria. Monte Carlo simulations and preliminary field tests validate the theoretical results using the B1C pilot signal-aided tracking B2b signal of the MEO satellite in the BeiDou satellite navigation system (BDS). Experimental results show that the carrier phase tracking threshold of the B2b signal can be reduced by about 4 dB.

Discrete-continuous coupling simulation and analysis for asphalt pavement dynamic stress responses under a moving wheel load

Asphalt pavement stress responses are analyzed with the layered elastic system under static loads in the most popularly-used design specifications. In reality, however, traffic loads are moving and the pavement layer materials are mainly aggregated. In order to reasonably consider vehicular loads and layer material features, this paper presents a discrete-continuous coupling model for analyzing asphalt pavement dynamic stress responses under moving loads. The numerical model is divided into an asphalt pavement structure and a moving wheel load. Specifically, the wheel load and the asphalt layer under its load were modelled with the discrete element method to simulate the actual vehicle loads and meso-scopic components of the asphalt mixture. In contrast, the remaining parts of the pavement structure were modelled with the finite difference method. The wheel load was set to move on the surface layer of asphalt pavement at a constant speed as the numerical simulation was conducted. The results were analyzed based on special points of dynamic stress curves. The results showed that: different from the static stress responses, in a typical asphalt pavement dynamic stress curve, there existed three stages of stress responses, namely the stress smoothing stage, stress surge stage, and stress dissipation stage, which had significant fluctuations at high levels and asymmetry. Besides, the loading velocity and mixture meso-structure significantly influenced on the dynamic stress responses of asphalt pavement. Especially the average peak stress calculated by the discrete-continuous coupling model, which considered the mixture meso-structure decreased by 10% compared to the finite-difference model.