Cyclic Stress Research Articles

Mechanical Properties of Latex-Modified Cement Stone under Uniaxial and Triaxial Cyclic Loading.

During the cyclic injection and extraction process in underground storage wellbores, the cement sheath undergoes loading and unloading stress cycles. In this study, we investigated the mechanical properties of latex-modified cement stone (LMCS), widely used in oil and gas wells, through uniaxial and triaxial cyclic loading and unloading tests. The aim of the study was to determine the effect of various loading conditions on the compressive strength and stress-strain behavior of LMCS. The results show that the stress-strain curve of LMCS exhibits a hysteresis loop phenomenon, with the loop intervals decreasing throughout the entire cyclic loading and unloading process. As the number of cycles increases, the cumulative plastic strain of the LMCS increases approximately linearly. Under uniaxial cyclic loading and unloading conditions, the elastic modulus tends to stabilize. However, under triaxial conditions, the elastic modulus increases continuously as the number of cycles increases. This result provides data for engineering predictions. Furthermore, a comparison of the uniaxial and triaxial cyclic loading and unloading of LMCS shows that its cumulative plastic strain develops rapidly under uniaxial conditions, while the elastic modulus is larger under triaxial conditions. These findings provide a valuable reference for constructing underground storage wellbores.

Precursors of rock failure under cyclic loading and unloading: From the perspective of energy and acoustics

The precursor characteristics of rock failure under cyclic loading and unloading are crucial to the prevention of underground engineering disasters. Taking sandstone as an example, this work conducted rock failure experiments under uniaxial cyclic loading and unloading combined with active wave velocity and passive acoustic emission (AE). The damage evolution process of rock was analyzed from the perspectives of energy, AE, and wave velocity. The results show that as the cyclic load stress level increases, the rigidity of the rock continuously increases, the proportion of elastic energy may reach a peak, and there will be an extreme time difference between the wave velocity and stress. The occurrence of the peak point of elastic energy proportion is a sufficient and unnecessary condition for the precursor characteristics of rock failure. The appearance of numerous AE events with high amplitude and high count is an effective precursor characteristic of rock failure. The stress continues to increase while wave velocity decreases is a key precursor characteristic of rock failure. There is a clear linear relationship between wave velocity drop and dissipated energy, it implies that both the which can quantitatively evaluate the rock damage under cyclic loading and unloading. The variation of wave velocity exhibits obvious anisotropic characteristics. This paper is not only a beneficial supplement to the theoretical system of rock failure precursors, but also provides new ideas and methods for rock stability monitoring and failure disaster early warning in underground engineering.

Antimicrobial adhesive self-healing hydrogels for efficient dental biofilm removal from periodontal tissue

ObjectivesOral biofilms, including pathogens such as Porphyromonas gingivalis, are involved in the initiation and progression of various periodontal diseases. However, the treatment of these diseases is hindered by the limited efficacy of many antimicrobial materials in removing biofilms under the harsh conditions of the oral cavity. Our objective is to develop a gel-type antimicrobial agent with optimal physicochemical properties, strong tissue adhesion, prolonged antimicrobial activity, and biocompatibility to serve as an adjunctive treatment for periodontal diseases. MethodsPhenylboronic acid-conjugated alginate (Alg–PBA) was synthesized using a carbodiimide coupling agent. Alg–PBA was then combined with tannic acid (TA) to create an Alg–PBA/TA hydrogel. The composition of the hydrogel was optimized to enhance its mechanical strength and tissue adhesiveness. Additionally, the hydrogel’s self-healing ability, erosion and release profile, biocompatibility, and antimicrobial activity against P. gingivalis were thoroughly characterized. ResultsThe Alg–PBA/TA hydrogels, with a final concentration of 5 wt% TA, exhibited both mechanical properties comparable to conventional Minocycline gel and strong tissue adhesiveness. In contrast, the Minocycline gel demonstrated negligible tissue adhesion. The Alg–PBA/TA hydrogel also retained its rheological properties under repeated 5 kPa stress owing to its self-healing capability, whereas the Minocycline gel showed irreversible changes in rheology after just one stress cycle. Additionally, Alg–PBA/TA hydrogels displayed a sustained erosion and TA release profile with minimal impact on the surrounding pH. Additionally, the hydrogels exhibited potent antimicrobial activity against P. gingivalis, effectively eliminating its biofilm without compromising the viability of MG-63 cells. SignificanceThe Alg–PBA/TA hydrogel demonstrates an optimal combination of mechanical strength, self-healing ability, tissue adhesiveness, excellent biocompatibility, and sustained antimicrobial activity against P. gingivalis. These attributes make it superior to conventional Minocycline gel. Thus, the Alg–PBA/TA hydrogel is a promising antiseptic candidate for adjunctive treatment of various periodontal diseases.

Flubendiamide provokes oxidative stress, inflammation, miRNAs alteration, and cell cycle deregulation in human prostate epithelial cells: The attenuation impact of synthesized nano-selenium using Trichodermaaureoviride

Flubendiamide (FBD) is a novel diamide insecticide extensively used with potential human health hazards. This research aimed to examine the effects of FBD on PrEC prostate epithelial cells, including Oxidative stress, pro-inflammatory responses, modifications in the expression of oncogenic and suppressor miRNAs and their target proteins, disruption of the cell cycle, and apoptosis. Additionally, the research investigated the potential alleviative effect of T-SeNPs, which are selenium nanoparticles biosynthesized by Trichoderma aureoviride, against the toxicity induced by FBD. Selenium nanoparticles were herein synthesized by Trichoderma aureoviride. The major capping metabolites in synthesized T-SeNPs were Isochiapin B and Quercetin 7,3′,4′-trimethyl ether. T-SeNPs showed a spherical shape and an average size between 57 and 96.6 nm. FBD exposure (12 μM) for 14 days induced oxidative stress and inflammatory responses via overexpression of NF-κB family members. It also distinctly caused upregulation of miR-221, miR-222, and E2F2, escorted by downregulation of miR-17, miR-20a, and P27kip1. FBD encouraged PrEC cells to halt at the G1/S checkpoint. Apoptotic cells were drastically increased in FBD-treated sets. Treatment of T-SeNPs simultaneously with FBD revealed its antioxidant, anti-inflammatory, and antitumor activities in counteracting FBD-induced toxicity. Our findings shed light on the potential FBD toxicity that may account for the neoplastic transformation of epithelial cells in the prostate and the mitigating activity of eco-friendly synthesized T-SeNPs.

Mechanical evaluation of human cadaveric lumbar soft tissues suggests possible physiological stress shielding within musculoskeletal soft tissues by the thoracolumbar fascia.

This study investigates the potential for stress shielding within musculoskeletal soft tissues through analysis of stress distributions between lumbar fascial and muscle tissues via mechanical testing. Using a custom apparatus, 51 posterior thoracolumbar fascia (TLF) samples and 18 erector spinae (ES) cadaveric samples underwent tensile testing involving three loading-unloading cycles, followed by loading to 6% strain, to mechanically characterize samples. Parallel tensile testing using 20 pairs of two TLF samples, and seven pairs of TLF and ES samples was then conducted for stress distribution analysis between tissues. P<0.05 was deemed significant. The TLF and ES exhibited an average elastic modulus of 150.9MPa and 0.6MPa, respectively. At 6% strain, parallel testing of the TLF pairs yielded an average tensile stress of 8.4MPa and 1.7MPa (p<0.001) exhibited by the stiffer and less stiff TLF samples, respectively. Similarly, TLF-ES parallel testing resulted in average tensile stresses of 7.1MPa and 0.07MPa of the TLF and ES (p<0.002). Results suggest elevated loading towards stiffer TLF samples relative to less stiff TLF and ES samples. In soft tissues affected by LBP, skewed stress distributions may result in the TLF withstanding the majority of stress, yielding cyclical stress shielding that may contribute to and/or promote LBP. This novel study demonstrates a potential load allocation bias towards the TLF, laying the foundation for stress shielding within lumbar musculoskeletal soft tissues affected by degenerative musculoskeletal conditions.

Tidally modulated seismic velocity changes observed using submarine dark fiber and the virtual-source method

Natural cyclical stress perturbations, including wet and solid earth tides, coupled with repeatable seismic monitoring approaches, provide a tool for understanding the elastic properties of rocks at depth. Ocean tides, in particular, perturb the overburden and pore pressure, affecting hydraulic and elastic rock properties. The recent emergence of distributed acoustic sensing (DAS) and seismology using existing dark telecom fiber offers an unprecedented opportunity to instrument the seas and oceans with seismic monitoring networks of large aperture, fine spatial resolution, and broadband sensitivity. We use a submarine dark-fiber array to methodologically assess whether the changes in seafloor seismic velocities are modulated by ocean tidal loading. Considering oceanic ambient noise (AN) in the frequency range between 1 and 5 Hz, we find it possible to retrieve reliable surface-wave estimates using relatively short time windows (approximately 60 min). Next, using the power of linear arrays to capture AN energy from the stationary-phase zones and AN processing techniques commonly used in DAS applications for subsurface monitoring in urban settings, we introduce a methodological approach to turn each segment of dark fiber into a short-offset monitoring array (2 km), providing redundant, hourly, surface-wave estimates. Using four days of AN data recorded by the Monterey Accelerated Research System (MARS) 20 km section offshore cable, we generate the virtual-source gathers for 10 segments spanning the whole MARS cable. We then use virtual-source data from one segment to estimate the hourly velocity changes that are then quantitatively compared with the tidal data. The results suggest that changes in seafloor seismic velocities are likely modulated by tidal height, even in regions without large tidal excursions. This advance demonstrates a new application of submarine telecom fibers for monitoring the seismic stress response of near-seafloor sediments.

Flexible and robust polypyrrole/cross-linked collagen sponge with collagen aggregates as building blocks for piezoresistive sensing

The polypyrrole/cross-linked collagen sponge (PPy/CCS) was synthesized through in-situ polymerization of PPy nanoparticles onto the collagen skeleton composed of mesoscopic collagen aggregates (CAs) as building blocks, which was employed as a sensing material. The structure and morphology of PPy/CCS were characterized using scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermal analysis (TA). The conductivity and mechanical properties of PPy/CCS can be regulated by adjusting the polymerization conditions. The PPy/CCS treated with glycerin aqueous solution exhibits exceptional recovery performance under 10,000 compression stress cycles, with a short response time of 420 ms and recovery time of 400 ms, along with high sensitivity of 1.13 kPa−1 within a control pressure range of 0–43 kPa. The assembled PPy/CCS-based sensors enable monitoring of human movement behavior and achieving multi-touch control, thereby demonstrating significant potential in flexible wearable devices and human–machine interaction.

Research on energy consumption evaluation and energy-saving design of cranes in service based on structure-mechanism coupling

Aiming at the problem that the life cycle energy consumption index of hoisting machinery is difficult to be objectively quantified, a crane energy consumption evaluation calculation method based on the working cycle of the service period is proposed, the typical service working mode of the crane is analyzed, and the working cycle process of the mechanism is clarified. On this basis, the stress cycle characteristics of the crane structure during the service period are determined based on the coupling relationship between the mechanism and the structure, which lays the foundation for accurately evaluating the life index of the crane. According to the relationship between the load rate and effective power of each mechanism during the service period of the crane, the calculation method for the evaluation and calculation of the structure energy consumption during the service period of the crane is studied. Finally, the crane is designed based on the concept of absolute service safety, and an optimal design model of the main girder structure of the crane with the goal of the lowest energy consumption in service is established. Using the research method of this paper to study a certain type of bridge crane, the energy consumption of the hoisting machinery during its service period is not only related to the accumulation of the operating characteristics of the mechanism but also related to the characteristic parameters such as the structure self-weight. The comprehensive evaluation of energy consumption provides an effective quantitative method and a reliable green design theory for crane design.

Corrosion susceptibility of mooring chain steel under cyclic stress

Corrosion susceptibility of mooring chain steel under cyclic stress

Apoptosis-Cell Cycle-Autophagy Molecular Mechanisms Network in Heterogeneous Aggressive Phenotype Prostate Hyperplasia Primary Cell Cultures Have a Prognostic Role.

Our study highlights the apoptosis, cell cycle, DNA ploidy, and autophagy molecular mechanisms network to identify prostate pathogenesis and its prognostic role. Caspase 3/7 expressions, cell cycle, adhesion glycoproteins, autophagy, nuclear shrinkage, and oxidative stress by flow-cytometry analysis are used to study the BPH microenvironment's heterogeneity. A high late apoptosis expression by caspases 3/7 activity represents an unfavorable prognostic biomarker, a dependent predictor factor for cell adhesion, growth inhibition by arrest in the G2/M phase, and oxidative stress processes network. The heterogeneous aggressive phenotype prostate adenoma primary cell cultures present a high S-phase category (>12%), with an increased risk of death or recurrence due to aneuploid status presence, representing an unfavorable prognostic biomarker, a dependent predictor factor for caspase 3/7 activity (late apoptosis and necrosis), and cell growth inhibition (G2/M arrest)-linked mechanisms. Increased integrin levels in heterogenous BPH cultures suggest epithelial-mesenchymal transition (EMT) that maintains an aggressive phenotype by escaping cell apoptosis, leading to the cell proliferation necessary in prostate cancer (PCa) development. As predictor biomarkers, the biological mechanisms network involved in apoptosis, the cell cycle, and autophagy help to establish patient prognostic survival or target cancer therapy development.

Low-Cycle Fatigue Damage Mechanism and Life Prediction of High-Strength Compacted Graphite Cast Iron at Different Temperatures.

Tensile and low-cycle fatigue tests of high-strength compacted graphite cast iron (CGI, RuT450) were carried out at 25 °C, 400 °C, and 500 °C, respectively. The results show that with the increase in temperature, the tensile strength decreases slowly and then decreases rapidly. The fatigue life decreases, and the life reduction increases at high temperature and high strain amplitude. The oxide layer appears around the graphite and cracks at high temperature, and the dependence of crack propagation on ferrite gradually decreases. With the increase in strain amplitude, the initial cyclic stress of compacted graphite cast iron increases at three temperatures, and the cyclic hardening phenomenon is obvious. The fatigue life prediction method based on the energy method and damage mechanism for compacted graphite cast iron is summarized and proposed after comparing and analyzing a large amount of fatigue data.

Rotating bending fatigue behavior of high-pressure diecast AlSi10MgMn alloy based on T5 heat treatment parameters

Abstract The study investigates fatigue failure, a common phenomenon in machine elements subjected to cyclic stresses. The analysis emphasizes that the actual stress experienced by materials often falls below their tensile and yield strengths due to repetitive variable stresses, leading to fatigue damage. Fatigue life is measured by the number of cycles endured before failure. This paper focuses on the aluminum alloy of AlSi10MgMn, extensively used in manufacturing due to its strength, low density, and corrosion resistance. Experimental procedures encompassed tensile testing, microstructural examination, SEM analysis, and fatigue testing. Tensile tests provided initial stress values for fatigue testing. Microstructure analyses verified that heat-treated samples exhibited precipitates. SEM analysis disclosed microstructural characteristics, while fracture surface examinations demonstrated higher fatigue resistance in heat-treated specimens. Hardness measurements were conducted, with heat-treated samples showing higher values. Theoretical calculations based on stress and cycle numbers were compared to experimental fatigue results. The derived equations aligned well with the tests. Ultimately, the study underlines the importance of heat treatment on material behavior and fatigue resistance, shedding light on alloy performance and durability enhancement.

Comparison of fatigue characteristics and failure analysis of Ni-based superalloy subjected to thermomechanical fatigue under different phase conditions

In this research, the thermomechanical fatigue (TMF) characteristics of a second-generation Ni-based single-crystal superalloy were investigated. The combined effects of temperature cycling and mechanical stress were examined using a strain-controlled approach under different TMF testing conditions. The results indicated that cyclic softening occurred during the early stages during in-phase (IP) loading. In contrast, out-of-phase (OP) tests exhibited cyclic hardening, as evidenced by an increase in the stress range, which intensified at higher mechanical strain amplitudes. This resulted in a shorter fatigue life compared to the IP TMF case. The crack distribution patterns and damage mechanisms on the cross-sectional and fracture surfaces of the failed specimens were analyzed. In the OP TMF tests, oxidation-assisted cracking was identified as the primary damage mechanism. The dominance of oxide layers was a key distinguishing feature. Additionally, twinning-related deformation and topologically close-packed (TCP) phase particles were observed in specimens subjected to a higher mechanical strain of 0.6%, where they ran parallel to the main crack, contributing to a reduction in lifetime. Conversely, the IP TMF cases were mainly dominated by creep damage mechanisms, with some signs of oxidation penetration observed during testing. The application of the Ostergren model to the fatigue life prediction of a Ni-based single-crystal superalloy under both conditions was evaluated. As this model was insufficient, a modified Ostergren model was proposed by incorporating the maximum and amplitude stresses in the power law forms.

Study of the Bias Driven Threshold Voltage Drift of 1.2 kV SiC MOSFETs in Power Cycling and High Temperature Gate Bias Tests

Threshold voltage instability remains a challenging aspect for metal-oxide semiconductor-field-effect-transistors (MOSFETs) made from silicon carbide (SiC). SiC MOSFETs from two manufacturers, with planar and trench gate structure respectively, have been tested under different test procedures, including power cycling and high temperature gate bias tests. The standard power cycling test setup has been modified to enable an in situ threshold voltage read-out procedure with the hysteresis method. The recorded threshold voltage drift has been compared with results from high temperature gate bias tests applying a simple power law fit, with the intention to predict the drift in power cycling tests. For the group with trench MOSFETs comparable results between power cycling and gate stress tests have been achieved.

The influence of cyclic creep on the long-term oxidation behavior of a directionally-solidified nickel-based superalloy

This work investigates the effect of cyclic creep on the long-term oxidation of a directionally-solidified nickel-based superalloy DZ445 up to 1800 h. The stress application of cyclic creep refines the oxides, increases the oxidation weight gain, reduces the oxidation rate exponent, and decreases the activation energy. It enhances the content of Al2O3 and TiO2 in the outermost layer and in the sub-outer layer of CrTaO4 in the film. It delays the formation of the continuous innermost layer of Al2O3 and the sub-inner layer that is rich in Al2O3. The change of phase content and type in the oxidation layers could be ascribed to the diffusion kinetic effect of cyclic creep stress in the superalloy.

Phase-field modeling of crack growth under coupled creep-fatigue

Crack growth under coupled creep-fatigue strongly influences service life of metallic components operating at high temperatures. However, there lack numerical models that enable direct simulations of crack growth and plasticity development under coupled creep-fatigue. In this study, a unified phase-field model is developed for simulating crack growth under fatigue, creep, and coupled creep-fatigue. This model is able to reproduce the Paris laws for both brittle and ductile materials in pure fatigue mode, which shows that the degradation rate due to cyclic stress in ductile materials is generally larger than that in brittle materials. Fatigue simulations with different yield strengths demonstrate that plasticity facilitates crack growth in typical ductile materials. High-throughput simulations are performed under coupled creep-fatigue conditions, with varying hold-stress levels and hold-time. By analyzing crack growth rate under different hold-time, a creep-fatigue interaction term is obtained. Simulation results demonstrate that the creep-fatigue interaction is caused by smaller stress gradient and enhanced degradation rate ahead of the crack tips under coupled creep-fatigue, compared to the situation of pure fatigue. This work reveals the origin of different Paris-law exponents in brittle and ductile materials and demonstrates how the interplay between creep and fatigue affects crack growth.

Physical model investigation of a hybrid GRS integral bridge abutment under cyclic thermal stresses

GRS integral bridge abutments develop large lateral earth pressure on the facing during seasonal/diurnal thermal expansion/contraction, causing significant surface settlements. To mitigate these issues, researchers prefer the use of different kinds of facing to withstand lateral pressure in conjunction with reinforcing of backfill to reduce surface settlement. The present research investigates the performance of a hybrid integral abutment under lateral movement of the facing due to cyclic thermal expansion/contraction of the bridge deck through scaled down 1 g physical model tests. Using the optimized facing and reinforcement configuration, an integral abutment model was proposed and analyzed under varying rate of loading and different loading offsets for three displacement modes till 100 cycles of excitation. The assessment included the development of lateral pressure on facing, surface settlement, magnitude and location of peak reinforcement forces, followed by evaluating long-term performance in terms of permanent strains, stiffness degradation, and strain energy dissipation. The observations revealed that the proposed model having strong connection between the reinforcement and facing along with inclusion of secondary reinforcements along the entire height of abutment in the bearing zone exhibits rapid dissipation of accumulated strain energy, leading to a 48 % reduction in surface settlement under cyclic thermal stresses.

Study on fatigue properties with composite waveform and variable amplitude of TC21 titanium alloy pulsed laser-arc hybrid welded joints

TC21 titanium alloy is widely used in the manufacturing of key components such as aerospace industry, its welded structure in actual service is often subjected to the cyclic loading with composite waveform and variable amplitude and leads to fatigue failure. Therefore, in this work, the composite waveform and variable amplitude fatigue properties of TC21 titanium alloy pulsed laser-arc hybrid welded joints were investigated in this paper, and the micro-deformation mechanism and crack initiation mechanism of welded joints under different initial maximum cyclic stresses were revealed. The results indicated that the micro-deformation mechanism was the competition between twinning and dislocation slip in the α′ phase at low stress. When the initial maximum cyclic stress increased, the generation and slip of dislocation dominated, and the main distribution of dislocations gradually transitioned from the α′ phase to the β phase. This caused the phase transition in the β phase to the α phase, which increased the energy at the α/β phase interface and reduced the resistance of fatigue microcrack initiation accordingly, thus promoting fatigue failure. In addition, pores were the main factor of fatigue failure for welded joints. Therefore, in this work, the influence of defect size, location and shape on the fatigue life of welded joints was considered to develop a fatigue life prediction model based on the control parameter Z-parameter and equivalent stress amplitude. The predicted composite waveform and variable amplitude fatigue life of TC21 titanium alloy welded joints was within the triple error band.

Surface integrity and fatigue performance of Ti6Al4V alloy peened by sinking bead abrasive jet

Exploring a green, low-cost peening process to improve the surface integrity of titanium alloys, increasing fatigue life, and breaking through the limitations in large-scale applications is an urgent need at present. The study presents a novel peening method using sinking beads as the shot, combined with the low dust pollution and water film cushioning advantages of waterjet peening. The impact of the process on the surface integrity of titanium alloys is meticulously discussed to elucidate the microstructural evolution. Constant stress fatigue tests are performed to evaluate the effectiveness of the proposed method. It was found that the jet pressure and feed rate determined the energy density and the number of peening for sinking bead abrasives, which were the key factors affecting the surface material properties of the peening specimen. By optimizing the process parameters, the maximum surface residual compressive stress can reach 875.5 MPa, the microhardness can attain 481.7 HV, and the surface roughness can be reduced to 1.594 μm. The surface of the peened specimen is covered with impact craters, exhibiting a plastic deformation layer with evident grain refinement and lattice distortion. The ductility of the peened specimen decreased, with axial deformation reducing from 0.278 mm to 0.260 mm under constant cyclic stress. Due to the increase in microhardness and the introduction of residual compressive stresses, the fatigue cycles of the specimen were increased from 20692 to 33615, improving the fatigue life by 62.45%.

Study on the Evolution of Mechanical Properties and Acoustic Emission of Medium-Permeability Sandstone under Multi-Level Cyclic Loading Stress Paths

Study on the Evolution of Mechanical Properties and Acoustic Emission of Medium-Permeability Sandstone under Multi-Level Cyclic Loading Stress Paths