Cohesive Stress Research Articles

Interfacial cohesive zone model based on atomic potential energy for CFRP

Carbon-fiber-reinforced polymer (CFRP) composites are utilized extensively in aero-engine casings, due to the superior specific mechanical properties and well-developed manufacturing techniques. The interface plays a key role in the macromechanical properties of CFRP. In this paper, an interfacial cohesive zone model (ICZM) of CFRP based on atomic potential energy is proposed, which can accurately characterize the interfacial mechanical behavior of CFRP. Then ICZM is applied to the unit cell model to predict the transverse mechanical behavior and damage evolution of CFRP, and verified by experimental results. The simulation results of the transverse modulus, strength, and ultimate strain for ICZM are 9.62 GPa, 66.87 MPa, and 0.78, respectively. The simulation errors of the transverse modulus, strength, and ultimate strain are all less than 3%, and the simulated damage evolution aligns with the experimental result, validating the precision of ICZM. The research shows that: for the infinite carbon atom layer and epoxy, the shear cohesive stress is zero; for the finite carbon atom layer and epoxy, the shear cohesive stress is much smaller than the tensile cohesive stress; the carbon fiber radius has little effect on cohesive energy; the simulated stress–strain curve for ICZM aligns with experiments, which means that ICZM can reflect the nonlinearity of CFRP. The research result can provide a calculating tool for the structural design of the aero-engine casing.

Discharge Flow of a Cohesive Granular Media from a Silo.

Cohesion can dramatically affect the flow of granular media. In this Letter, thanks to a cohesion-controlled granular material, we propose to investigate experimentally the effect of the cohesion on the discharge from a silo. We use two geometries, a cylindrical silo and a thin rectangular silo, with an adjustable bottom to control the size of the orifice. Similarly to cohesionless granular material, the mass flow rate is mostly controlled by the diameter of the outlet D, however, we observe that the cohesion tends to decrease the flow rate. We show that this effect is controlled by a cohesive length, based on the cohesive yield stress and gravity acceleration, which acts as an effective particle size. This cohesive length is also found to control the onset of flow.

Characteristics of Nurse Managers' Conflict Management Competency. A Systematic Review.

To identify and describe the characteristics that constitute a nurse manager's conflict management competency. This study is a systematic review conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The review protocol was registered in PROSPERO (CRD42024542605). A systematic search was conducted in Web of Science, Scopus and PubMed databases, covering literature published from 1 January 2014 to 1 April 2024. This review included 14 studies selected from an initial pool of 86 records. From the included articles, 71 characteristics associated with nurse manager conflict management competency were identified and categorised into seven distinct characteristics: Collaborative resolution (19.72%), collaborative support (18.31%), balanced compromise (14.08%), conflict avoidance (14.08%), supportive accommodation (14.08%), assertive dominance (12.68%) and leadership and resilience in conflict management (7.04%). The most frequent conflicts were interpersonal conflicts (22.22%), resource allocation issues (20.00%) and conflicts between personal values and organisational goals (17.78%). This review highlights the importance of developing characteristics, such as collaborative resolution, collaborative support and balanced compromise, for effective conflict management by nurse managers. Addressing interpersonal conflicts and aligning personal values with organisational goals is essential for maintaining team cohesion and reducing stress. Ethical leadership and emotional intelligence are crucial for managing conflicts and improving the work environment. Forward-looking healthcare organisations should prioritise the development of conflict management competencies to create healthy and efficient work environments capable of facing disruptive changes, such as those brought about by artificial intelligence. The characterisation of conflict management competency allows the creation of simulated scenarios that are free of associated risks. Additionally, the findings facilitate a comprehensive analysis of how conflict management competency influences leadership competency and ethical principles in nursing teams. This is particularly relevant in the context of profound and disruptive change. No patient or public involvement.

Influence of ambient temperature and humidity on the evolution of the tension softening behavior in concrete

The tension softening relationship is a crucial input parameter for modeling the crack propagation in concrete. To examine the influence of curing conditions on this parameter, fracture tests were performed on specimens kept at different temperatures and humidity levels across various ages. A best-fit maturity method for identifying optimal maturity model parameters was proposed and validated using test data. The results indicated that the area beneath the first branch of the softening curve increases, whereas the area under the tail decreases with ongoing hydration and higher humidity. The tensile strength ft and centroid coordinate σcg (vertical coordinate of softening curve area center) increase with rising temperatures up to 14 days, after which the trend reverses, with higher later-age ft and σcg observed in specimens exposed to elevated temperatures. Under high temperatures, the critical crack width wc (ultimate width at zero cohesive stress) and centroid coordinate wcg decrease. At the early stage, humidity has minimal effect on concrete softening properties. However, as the hydration progresses, the impact of decreasing humidity becomes more significant. At 60 days, ft, σcg, and wc are reduced by 23.3 %, 22.8 %, and 19.6 %, respectively, as humidity drops from 98 % to 30 %. The developed best-fit maturity method can predict various concrete properties with a maximum relative error within 7 %. The optimal activation energy Ea and moisture diffusion coefficient γ vary across temperature and humidity ranges, making it unfeasible to use a single set (Ea, γ) to predict properties under varying curing conditions.

Numerical Optimization of Drucker-Prager-Cap Model Parameters in Powder Compaction Employing Particle Swarm Algorithms

A growing number of scholars are drawn to using numerical approaches powered by computer simulations as a potential solution to industrial problems. Replicating the compaction process in powder metallurgy with accuracy is one such issue. The Drucker-Prager-Cap model requires parameter calibration as the most used method for simulating powder compaction. This paper addresses this issue and presents a new technique for doing so. Utilizing Abaqus software 2020, the compaction process was simulated for the benchmark powder, which is the alloy Ag57.6-Cu22.4-Sn10-In10. The difference between simulation results and experimental data was reduced by applying the Particle Swarm Optimization technique in Python. The suggested approach may accurately forecast the Drucker-Prager-Cap model parameters, as demonstrated by comparing the optimized parameters utilizing the research’s method with their experimental values. The findings revealed how well the suggested approach in this study calibrated the DPC model, yielding three parameters—Young’s modulus, material cohesion, and hydrostatic pressure yield stress—with respective RMSEs of 1.95, 0.12, and 324.64 concerning their experimental values.

Rock failure mechanisms based on rheological dynamics

This paper investigates the mechanisms of rock failure related to axial splitting and shear failure due to hoop stresses in cylindrical specimens. The hoop stresses are caused by normal viscous stress. The rheological dynamics theory (RDT) is used, with the mechanical parameters being determined by P- and S-wave velocities. The angle of internal friction is determined by the ratio of Young's modulus and the dynamic modulus, while dynamic viscosity defines cohesion and normal viscous stress. The effect of frequency on cohesion is considered. The initial stress state is defined by the minimum cohesion at the elastic limit when axial splitting can occur. However, as radial cracks grow, the stress state becomes oblique and moves towards the shear plane. The maximum and nonlinear cohesions are defined by the rock parameters under compressive strength when the radial crack depth reaches a critical value. The efficacy and precision of RDT are validated through the presentation of ultrasonic measurements on sandstone and rock specimens sourced from the literature. The results presented in dimensionless diagrams can be utilized in microcrack zones in the absence of lateral pressure in rock masses that have undergone disintegration due to excavation.

Triaxial drained behaviour of disposable face mask fibre reinforced sand

ABSTRACT The widespread usage of disposable face masks (DFM) during the COVID-19 pandemic has exacerbated waste management challenges, prompting an investigation into their potential reuse as a soil reinforcement material. Previous researchers have investigated the effect of mask fibres on pavement subbases and the environmental problems caused by these fibres. This study examines the mechanical properties of sandy soil enhanced with shredded and layered DFM under triaxial testing conditions, focusing on key parameters like shear resistance, elastic modulus, stress-strain characteristics, axial resistance, failure envelope, and brittleness index. Results show that adding DFM significantly improves soil cohesion, friction angle, shear strength, and peak deviatoric stress, especially at higher fibre contents and relative densities. However, increased DFM fibre content was associated with reduced elastic modulus, which stabilised in specimens with layered DFM, suggesting complex interactions between DFM content and soil mechanics. Concerns include potential void formation leading to asymmetric settlement and environmental issues on non-biodegradable fibre integration in soil. These findings highlight the need for meticulous mixture preparation, large-scale studies, and environmental assessments to evaluate the impact of using DFM in soil reinforcement, particularly for road construction and slope stabilisation. This research provides crucial insights into the potential of DFM for soil reinforcement.

Bolstering group cohesion & reducing stress through implementation of Stress First Aid

This quality improvement project sought to help health care workers (HCWs) identify and mitigate work-related stress using Stress First Aid. SFA training was offered to all psychiatric unit employees. Surveys assessing perceived stress, self-efficacy, and program outcomes were administered at four timepoints. Perceived stress significantly decline in the first post (p = .026) and was sustained. Self-efficacy showed no change across the four timepoints (p = .198). Group cohesion showed significant improvement from pre- to 3 months post (p = .002). Stress First Aid (SFA) is an evidence-based intervention that positively assists in the identification of stress and group cohesion.

Study on the mechanism of freeze-thaw cycles on the shear strength of geogrid-sand interface

The geogrid-soil interface characteristic is a critical factor influencing the behavior of reinforced soil structures. In seasonal frozen regions, the shear strength of the geogrid-soil interface fluctuates periodically with temperature, necessitating consideration of freeze-thaw cycle effects during engineering design. In this study, a series of large-scale direct shear tests were conducted to investigate the geogrid-sand interface behavior under different freeze-thaw cycles. The mechanism of the evolution and variation of the geogrid-sand interaction was discussed based on test results and the associated mesoscopic analysis. The results indicate that freezing enhances the shear strength of the geogrid-sand interface, whereas freeze-thaw cycles reduce the geogrid-sand interface shear stress. The cohesion and friction angle of the geogrid-sand interface decreased as the number of freeze-thaw cycles increased, but tended to stabilize after several freeze-thaw cycles. The influence of freeze-thaw cycles on the tensile strength and elongation of the geogrid was insignificant. Internal changes in sand during freeze-thaw cycles were considered as the key issue that led to the deterioration of the geogrid-sand interface. Furthermore, considering the interface cohesion and normal stress, the influence of freeze-thaw cycles on the interaction coefficient k between geogrid and soil was analyzed, which is referable for the design and application of reinforced soil engineering in cold regions under similar conditions.

Determining the Cohesive Length of Rock Materials by Roughness Analysis

In this research, the cohesive length of various rock types is measured using quantitative fractography alongside a recently developed multifractal analysis. This length is then utilized to gauge material cohesive stress through the theory of critical distances. Furthermore, the fracture process zone length of different rings sourced from identical rocks is assessed as a function of ring dimensions and experimental measurements of fracture toughness, in accordance with the energy criterion of the finite fracture mechanics theory. Subsequently, employing the stress criterion within coupled finite fracture mechanics, the failure stress corresponding to the fracture process zone is determined for various rings. Ultimately, through interpolation, the critical stress corresponding to the cohesive length, quantified via quantitative fractography, is approximated. Remarkably, the cohesive stress values derived from both methodologies exhibit perfect alignment, indicating the successful determination of cohesive length for the analyzed rock materials. The study also delves into the significant implications of these findings, including the quantification of intrinsic tensile strength in quasi-brittle materials and the understanding of tensile strength variations under diverse stress concentrations and loading conditions.

The Mediating Role of Psychological Capital in the Relationship Between Family Sense of Coherence and Caregiver Stress Among Parents of Children With Autism Spectrum Disorder.

Caregiving for children with autism spectrum disorder (ASD) poses significant stress for parents, necessitating an exploration of mitigating factors. This study investigates the interplay between Family Sense of Coherence, Psychological Capital and caregiver stress in this context. A total of 205 caregivers of children with ASD participated in this cross-sectional study. Data were collected on Family Sense of coherence, Psychological Capital (encompassing hope, resilience, optimism and self-efficacy) and caregiver stress. Structural equation modelling was employed to test the mediation effect of psychological capital between family sense of coherence and caregiver stress. The results indicated a strong positive correlation between family sense of coherence and all subdomains of psychological capital, with coefficients ranging from 0.541 to 0.610. Conversely, psychological capital demonstrated significant negative correlations with various domains of the Kingstone Caregiver Stress Scale, including caregiving, family issues and financial issues (coefficients from -0.443 to -0.427). Furthermore, family sense of coherence showed a direct negative effect on stress (β = -0.384, p < 0.001). Notably, the study revealed a significant mediating role of psychological capital in the relationship between family sense of coherence and caregiver stress, with an indirect effect of family sense of coherence on stress through psychological capital (β = -0.127). The findings underscore the crucial role of family sense of coherence and psychological capital in enhancing psychological resources and mitigating stress among caregivers of children with ASD. These results suggest that interventions aimed at strengthening family coherence and building psychological capital could be effective strategies in alleviating stress among caregivers of children with ASD. Healthcare professionals should consider incorporating family coherence approaches and psychological capital techniques in their support programs for these caregivers.

Inter-hemispheric somatosensory coherence and parental stress in hypersensitivity at 8 months old: An electroencephalography study

ObjectiveInfant hypersensitivity affects daily challenges and parental stress. Although the crucial role of tactile sensation in infants' brain function has been highlighted, hypersensitive infants and their families lack support. Electroencephalography may be useful for understanding hypersensitivity traits. We investigated the relationship between infant perceptual hypersensitivity and parental stress, somatosensory-evoked potential (SEP), and magnitude-squared coherence (MSC) in the general population. MethodsInfants aged 8 months (n = 63) were evaluated for hypersensitivity and parental stress using a questionnaire and for cortical activity using electroencephalography. Vibration stimuli were applied to the infant’s left foot. SEP components that peaked around 150 ms (N2) and at 200 ms (P2) after stimulus onset were evaluated by amplitude and latency at the midline electrode (Cz) and MSC between the midline electrodes (C3–C4). ResultsParental stress was associated with infant hypersensitivity. The latency of Cz was delayed, and C3–C4 delta MSC was high in infants with hypersensitivity. ConclusionsIncreasing inter-hemispheric MSC synchrony in the stimulated condition in infants with hypersensitivity suggested atypical somatosensory cortical function. SignificanceThese findings contribute to identifying, understanding the mechanisms of, and developing effective coping strategies for early-stage hypersensitivity.

Sense of coherence and Covid-19 related stress: A three-wave longitudinal study.

Sense of coherence (SOC) is the fundamental concept of the salutogenic approach to health promotion. The main aim of the current longitudinal study is to consider whether SOC has had a positive effect in reducing people's levels of stress during the prolonged time of the pandemic or rather stress has posed a threat to SOC. A large sample of Italian adults completed an online questionnaire at three different moments of the Covid-19 pandemic (from March 2020 to May 2021). To test the reciprocal associations between SOC and stress we estimated a cross-lagged panel model. Results questioned the stability of SOC, which changed across the different moments of the pandemic, and its causal role with respect to stress since, after controlling for gender and age, it emerged a significant effect only from stress to SOC. The implications of these results and the further expansions of the study are discussed.

Energy evolution of gravitational-granular flows

The catastrophe of natural disasters such as landslides, is a prevalent phenomenon in natural terrain conditions in high mountainous areas; however, the mobility of such landslides has not yet well understood due to the discrete nature of material and the coming to play of water. In this paper, we numerically study the mobility of an unsaturated gravitational-granular flow, occurring on a slope-break system that contains two regions: inclined-upstream and horizontal-downstream areas, by using three-dimensional discrete element simulations. A sliding volume composed of spherical grains collapses on the first region, then plunges and deposits on the second one. The upstream-plunging length and the cohesive stress exerted on grains affect differently on the energy evolution not only in the whole process but also in different regions and directions depending on the inclination angle. These findings provide a deep understanding of the mechanism and mobility of landslides, leading to good predictions about the potential impacts of the catastrophic landslides on buildings and human lives.

INTERFACE SHEAR STRENGTH DEGRADATION IN PROGRESSIVE LANDSLIDE OF WEATHERED CLAY SHALE OVERBURDEN ON UNDISTURBED CLAY SHALE

In accomplishing Sustainable Development Goals (SDGs), the construction of roads played a substantial role in achieving economic equity. However, landslides due to problematic soil would hinder its construction process. Thus, it is essential to understand the mechanism of slope movement to reduce landslide problems. A landslide that happened during the construction of the Semarang-Bawen toll road was analyzed in this research. The landslide was known to fail between the interface of the tuff breccia overburden and the problematic clay shale soil. This research proposed the direct shear test to determine the interface shearing behavior. Before the test, the overburden was differentiated as various sand and weathered clay shale ratios. After the overburden soils were compacted, a multistage interface direct shear test was conducted with three different loadings. Water was added to the overburden layer to model the infiltration at the interface by increasing the water content. From the test, results such as the interface cohesion, friction angle, and average stress ratio were obtained. Overall, the interface shear strength decreased as the water content increased. The decreasing value was due to the wetting at the interface. Thus, it would moisten the interface and disrupt the structure of both the top and bottom layers of the sample. In conclusion, the interface direct shear test was able to describe the shear behavior at the clay shale interface. It also indicated that water had a considerable role in triggering interface landslides for two different soil layers.

Interpenetrated and Bridged Nanocylinders from Self-Assembled Star Block Copolymers.

The design of functional polymeric materials with tunable response requires a synergetic use of macromolecular architecture and interactions. Here, we combine experiments with computer simulations to demonstrate how physical properties of gels can be tailored at the molecular level, using star block copolymers with alternating block sequences as a paradigm. Telechelic star polymers containing attractive outer blocks self-assemble into soft patchy nanoparticles, whereas their mirror-image inverted architecture with inner attractive blocks yields micelles. In concentrated solutions, bridged and interpenetrated hexagonally packed nanocylinders are formed, respectively, with distinct structural and rheological properties. The phase diagrams exhibit a peculiar re-entrance where the hexagonal phase melts upon both heating and cooling because of solvent-block and block-block interactions. The bridged nanostructure is characterized by similar deformability, extended structural coherence, enhanced elasticity, and yield stress compared to micelles or typical colloidal gels, which make them promising and versatile materials for diverse applications.

Collapse dynamics and deposition morphology of low-viscocohesive granular columns on a rough horizontal surface.

Using the three-dimensional discrete element method, we numerically investigate the collapse dynamics and deposition morphology of low-viscocohesive granular columns on a rough-horizontal plane by systematically varying a broad range of values of the initial column aspect ratio, cohesive stress, and liquid viscosity. The results show that the kinetic energy, half runout time, and runout distance increase with increasing the initial column aspect ratio but decrease with increasing the cohesive and viscous effects of the binding liquid, while the toe angle and deposit height decrease with increasing the aspect ratio and increase with increasing cohesive stress and liquid viscosity. Remarkably, by defining a dimensionless scaling number that incorporates the Bond number and initial column aspect ratio, this allows us to nicely describe the kinetic energy, half runout time, deposition height, runout distance, and toe angle. These unified descriptions may provide insights into the physical properties of the collapse dynamics and deposition morphology of low-viscocohesive granular columns, leading to good explanations of the complex properties of natural disaster events.

Risk Assessment Method for Analyzing Borehole Instability Considering Formation Heterogeneity

In the study of borehole instability, the majority of input parameters often rely on the average values that are treated as fixed values. However, in practical engineering scenarios, these input parameters are often accompanied by a high degree of uncertainty. To address this limitation, this paper establishes a borehole stability model considering the uncertainty of input parameters, adopts the Monte Carlo method to calculate the borehole stability reliability at different drilling fluid densities, evaluates the sensitivity of borehole instability to a single parameter, and studies the safe drilling fluid density window at different borehole stability reliability values under multi-parameter uncertainties. The results show that the uncertainty of rock cohesion has a great influence on the fracture pressure of the vertical and horizontal wells. The minimum horizontal stress has the greatest influence on the fracture pressure of the vertical and horizontal wells, followed by pore pressure. In the analysis of borehole stability, the accuracy of cohesion and minimum horizontal stress parameters should be improved. In scenarios involving multiple parameter uncertainties, while the overall trend of the analysis results remains consistent with the conventional borehole stability outcomes, there is a noteworthy narrowing of the safe drilling fluid density window. This suggests that relying on conventional borehole stability analysis methods for designing the safe drilling fluid density window can considerably increase the risks of borehole instability. Uncertainty assessment is crucial to determine the uncertainties associated with the minimum required mud pressure, thereby ensuring more informed decision-making during drilling operations. To meet practical application demands, structure and boundary condition uncertainties should be implemented for a more comprehensive assessment of borehole stability.

Direct cohesive law measurement under mixed-mode loading using semi-circular bend (SCB) specimens

The present paper suggests a new method to obtain pure mode and mixed mode traction-separation laws of adhesives using semi-circular bend (SCB) specimen by employing the digital image correlation (DIC) technique. This specimen was recently proposed by the same authors for fracture energy assessment of adhesives. This test method doesn't require any special apparatus or loading jig for mixed mode fracture tests ranging from pure mode I to pure mode II. Lower cost and higher precision than conventional methods are the most advantages of using SCB fracture tests. The primary drawback of this test method lies in its data reduction process. To address this limitation, this paper introduces a direct approach for measuring fracture energy and cohesive law parameters of the adhesive. In this method, substrate strains at the interface are used to calculate the cohesive stress applied to the adhesive layer at each desired section. Shear and normal separation values are obtained directly from DIC displacement results. The proposed method was applied to the SCB specimen subjected to pure modes I and II and for mixed-mode I/II cohesive laws. Four different SCB specimens were manufactured and tested to cover different mode mixities between pure mode I and pure mode II. The experimentally obtained cohesive laws were evaluated using finite element analysis (FEA). Good agreement between the experimental and numerical results were observed.

Water–rock two-phase flow model for water inrush and instability of fault rocks during mine tunnelling

Water inrush hazard is one of the major threats in mining tunnel construction. Rock particle migration in the seepage process is the main cause of water inrush pathway and rock instability. In this paper, a radial water–rock mixture flow model is established to study the evolution laws of water inrush and rock instability. The reliability of the proposed model is verified by the experimental data from a previous study. Through the mixture flow model, temporal-spatial evolution laws of different hydraulic and mechanical properties are analysed. And the proposed model’s applicability and limitations are discussed by comparing it with the existing water inrush model. The result shows that this model has high accuracy both in temporal evolution and spatial distribution. The accuracy of the model is related to the fluctuation caused by particle migration and the deviation of the set value. During the seepage, the porosity, permeability, volume discharge rate and volume concentration of the fluidized particle increase rapidly due to the particle migration, and this phenomenon is significant near the fluid outlet. As the seepage progresses, the volume concentration at the outlet decreases rapidly after reaching the peak, which leads to a decrease in the growth rate of permeability and porosity, and finally a stable seepage state can be maintained. In addition, the pore pressure is not fixed during radial particle migration and decreases with particle migration. Under the effect of particle migration, the downward radial displacement and decrease in effective radial stress are observed. In addition, both cohesion and shear stress of the rock material decreased, and the rock instability eventually occurred at the outlet.