Cyclic Model Research Articles

Identifiability of the parameters contained in a cyclic cohesive zone model for CFRP-to-steel bonded joints

The application of externally bonded CFRP reinforcements has shown its effectiveness in reducing crack growth and extending fatigue life of steel elements subjected to cyclic loadings. Failure usually occurs due to cohesive debonding within the adhesive interface and therefore the interfacial behavior is crucial in guaranteeing the effectiveness of the bonded system. The adoption of cohesive zone models represents a valid approach for the description of interfaces between two adherends (i.e. CFRP and steel substrate), providing a useful tool for the analytical and numerical investigation of CFRP-to-steel bonded systems. An important issue generally associated with the use of a cohesive model is the correct calibration of its parameters, necessary to guarantee a reliable use of the model. Therefore, this work proposes a robust inverse analysis procedure to investigate the identifiability of the parameters governing the fatigue behavior of an exponential cyclic cohesive zone model. Single-lap direct shear tests are considered for the numerical investigation of the interfacial bond behavior. The input data chosen for the inverse algorithm are the axial strain measurements in a discrete number of points along the bonded interface and the values of relative displacement between the two adherends measured at peak and valley of each cycle at the specimen loaded end (i.e. the global slip). Virtual data perturbed by different levels of noise are used and a meta-model reduction technique is adopted to reduce the computational cost of the forward operator and to solve the inverse problem in a stochastic context through a Monte Carlo like procedure.

On Some Mathematical Connections between the Cyclic Universe, Inflationary Universe, p-Adic Inflation, p-Adic Cosmology and Various Sectors of Number Theory

On Some Mathematical Connections between the Cyclic Universe, Inflationary Universe, p-Adic Inflation, p-Adic Cosmology and Various Sectors of Number Theory

MCD-LightGBM System for Intelligent Analyzing Heterogeneous Clinical Drug Therapeutic Effects.

Causal effect estimation of individual heterogeneity is a core issue in the field of causal inference, and its application in medicine poses an active and challenging problem. In high-risk decision-making domain such as healthcare, inappropriate treatments can have serious negative impacts on patients. Recently, machine learning-based methods have been proposed to improve the accuracy of causal effect estimation results. However, many of these methods concentrate on estimating causal effects of continuous outcome variables under binary intervention conditions, and give less consideration to multivariate intervention conditions or discrete outcome variables, thus limiting their scope of application. To tackle this issue, we combine the double machine learning framework with Light Gradient Boosting Machine (LightGBM) and propose a double LightGBM model. This model can estimate binary causal effects more accurately and in less time. Two cyclic structures were added to the model. Data correction method was introduced and improved to transform discrete outcome variables into continuous outcome variables. Multivariate Cyclic Double LightGBM model (MCD-LightGBM) was proposed to intelligently estimate multivariate treatment effects. A visual human-computer interaction system for heterogeneous causal effect estimation was designed, which can be applied to different types of data. This paper reports that the system improved the Logarithm of the Minimum Angle of Resolution (LogMAR) of visual acuity change after Vascular Endothelial Growth Factor (anti-VEGF) treatment in patients with diabetic macular degeneration. The improvement was observed in two clinical problems, from 0.05 to 0.33, and the readmission rate of diabetic patients after cure was reduced from 48.4% to 10.5%. The results above demonstrate the potential of the proposed system in predicting heterogeneous clinical drug treatment effects.

Residual Stress and Distortion Prediction for Laser Directed Energy Deposition Based on Cyclic Heat Transfer Model

Residual Stress and Distortion Prediction for Laser Directed Energy Deposition Based on Cyclic Heat Transfer Model

Discovering cyclic causal models in psycho-logical research

Statistical network models have become popular tools for analyzing multivariate psychological data. In empirical practice, network parameters are often interpreted as reflecting causal relationships – an approach that can be characterized as a form of causal discovery. Recent research has shown that undirected network models are likely to perform poorly as causal discovery tools in the context of discovering acyclic causal structures, a task for which many alternative methods are available. However, acyclic causal models are likely unsuitable for many psychological phenomena, such as psychopathologies, which are often characterized by cycles or feedback loop relationships between symptoms. A number of cyclic causal discovery methods have been developed, largely in the computer science literature, but they are not as well studied or widely applied in empirical practice. In this paper, we provide an accessible introduction to the basics of cyclic causal discovery for empirical researchers. We examine three different cyclic causal discovery methods and investigate their performance in typical psychological research contexts by means of a simulation study. We also demonstrate the practical applicability of these methods using an empirical example and conclude the paper with a discussion of how the insights we gain from cyclic causal discovery relate to statistical network analysis.

Anisotropy and cyclic loading characteristics of a stiff Bolders Bank glacial till at Cowden

Glacial tills are widespread across the world, common in northern Europe and found under the North and Baltic Seas. Their geological and geotechnical characterisation is important to the geotechnical design of a wide range of onshore and offshore structures. This paper reports outcomes from coordinated monotonic small-strain stress probing, cyclic and larger strain triaxial and hollow cylinder apparatus (HCA) testing on a natural low-to-medium plasticity, apparent highly over consolidated, stiff glacial clay till. Monotonic HCA and triaxial experiments investigated the till’s stiffness and shear strength anisotropy from its limited linear elastic range up to ultimate failure, showing that stiffnesses are higher in the horizontal direction than in the vertical and that higher undrained shear strengths develop under “passive” horizontal loading than “active” vertical loading. The cyclic triaxial tests revealed the impact of cycling on effective stress paths and strain development, and cyclic stiffness degradation. Stable, metastable and unstable patterns of behaviour are identified, along with different cyclic failure modes, which are related to the till’s static yielding behaviour. The experiment results provide the basis for developing, testing and calibrating monotonic and cyclic constitutive models and establishing simplified design procedures for piles installed in comparable tills to support offshore energy and other structures.

МЕТОДОЛОГІЧНІ АСПЕКТИ ФОРМУВАННЯ ЦІНОВОЇ ПОЛІТИКИ НА ПІДПРИЄМСТВІ

The article studies and systematizes the theoretical and methodological aspects of price policy management in the modern market environment, emphasizing its importance for maintaining competitiveness, profitability, and overall financial stability. It examines various definitions of "pricing policy" and proposes its interpretation as a set of managerial actions aimed at optimizing prices to meet both strategic and tactical business objectives. The study defines the methodology of pricing policy as a system of interconnected rules, principles, and procedures, that account for internal and external factors, ensuring price flexibility, adaptability, and overall effectiveness in a dynamic market environment. This research aims to enhance the existing approaches to pricing policy by introducing a cyclical methodology that allows for continuous analysis, fine-tuning, and adjustment of pricing strategies over time. The proposed model integrates key stages such as comprehensive market analysis, decision-making processes, pricing implementation, and consistent post-implementation monitoring. The study employs an analytical method, reviewing a wide range of existing literature on pricing strategies, market dynamics, and price management to identify current gaps and propose concrete improvements. The results highlight the growing importance of a flexible, adaptive pricing strategy that not only reacts to market changes but anticipates shifts, ensuring sustained competitive advantage and long-term financial stability. It has been firmly established that enterprises today require a more dynamic pricing approach, which involves regular and strategic price adjustments based on evolving competitive conditions, consumer behaviors, and fluctuating market demands. The theoretical contribution of the article lies in the refinement and further development of pricing policy management, while the practical implications provide enterprises with actionable tools and frameworks for implementing adaptive pricing strategies in real-world scenarios. The originality of the research is evident in the development of a cyclical model that enhances the responsiveness of businesses to market fluctuations and varying consumer needs. Future research may explore the application of this model in specific industries or test its efficacy across different market environments.

Fatigue crack propagation of AA2024 alloy under texture control using crystal plasticity coupled with accelerated cyclic cohesive zone model

The texture for AA2024 alloy is a predominant factor in the control of Fatigue Crack Propagation (FCP) behavior, and this texture feature can be well simulated using Crystal Plasticity (CP) methodology. Besides, Cyclic Cohesive Zone Model (CCZM) possesses the higher reliability than Cohesive Zone Model (CZM) in simulating FCP behavior because of its consideration of damage evolution law. In this work, CP is first integrated with CCZM to predict FCP behavior of AA2024 alloy under texture control. To decrease time-consuming, an acceleration strategy is also tactfully implemented into this coupled CP-CCZM under XFEM framework, as an attempt to faster and accurately predict the texture influence on FCP behavior. FCP and Electron Back Scattered Diffraction (EBSD) experiments are also carried out to provide a reference for checking the reliability and accuracy of this model. It is found that this coupled methodology shows a strong capability and robustness in simulating FCP behavior under texture control. This coupled methodology is then utilized to simulate three typical FCP features induced by sole strong Goss, Cube and Brass textures, and the corresponding FCP behaviors are comparatively analyzed in details.

Validating cyclic plasticity material model for three materials subjected to asynchronous axial-torsion conditions

In the present work, a cyclic plasticity model based on Ohno-Wang kinematic hardening rule and Tanaka non-proportionality parameter, is proposed to simulate the cyclic stress strain response of three materials. The proposed model has been validated with respect to reported test results on two grades of steel (SA 333 Gr. 6 and E355) and one grade of austenitic stainless steel (X5CrNi18-10) under asynchronous axial-torsion loading conditions with a wide range of frequency ratios. The proposed model resulted in a comparable assessment of axial and shear stress–strain response with respect to the test loops for all three materials.

Experimental study and constitutive modelling of wire arc additively manufactured steel under cyclic loading

Wire arc additive manufacturing (WAAM) is an efficient and cost-effective method of metal 3D printing that is well suited to structural engineering applications. Fundamental test data on the mechanical properties of WAAM materials, especially under cyclic loading, are however lacking. To address this, an experimental study into the cyclic behaviour of WAAM steel plates has been undertaken and is reported herein. Following geometric and quasi-static mechanical characterisation, a total of 40 as-built and machined coupons were tested under different cyclic loading protocols. Key results from the tests, including the full hysteresis curves, are presented and discussed. A cyclic constitutive model allowing for a yield plateau and the degradation of elastic modulus is proposed and validated against the test data. It is shown that the examined WAAM steel exhibited cyclic hardening behaviour dependent on the strain amplitude and strain history. The elastic modulus of the WAAM material was found to decrease in the first few cycles and then remain stable with increasing accumulated plastic strain. Good energy dissipation performance was also observed, indicating the potential of WAAM steels for seismic applications.

Numerical implementation of a modified cohesive zone model for HCF behavior of adhesively bonded composite laminates under mixed mode loading

In this paper, the cohesive zone model for high-cycle fatigue (HCF) behavior of adhesively bonded composite laminates subjected to mixed mode loading is implemented in Abaqus/Standard 6.14. The cyclic cohesive zone model takes into account mode-dependent penalty stiffness and fracture process zone size in adhesively bonded orthotropic composite laminates. Unlike earlier cyclic cohesive-based models, the developed UEL/UMAT is made available to the readers and end users for their specific needs. The model is validated extensively against the available experimental results in both load as well as displacement control. The model exhibited superior accuracy, positioning it as a valuable research tool. Furthermore, a novel parametric study was conducted to investigate the impact of fracture toughness and strength on HCF behavior. Finally, numerical simulation on a single fiber composite system is performed to explore micro-scale debonding using the developed model.

A multiscale interfacial cyclic debonding model for fibre-reinforced composites using micromechanics and molecular dynamics

In this study, a novel multiscale model based on the finite-volume direct averaging micromechanics (FVDAM) theory and molecular dynamics (MD) was developed to predict the interfacial cyclic debonding behaviour of composites. At the microscale, a solid interface with accumulated damage was incorporated using FVDAM, which enabled the simulation of both localised and homogenised interfacial damage responses under cyclic loading; a significant reduction in strength was observed after 10 loading cycles, implying the interfacial damage accumulation. At the atomic-scale, an interface model was built and subjected to cyclic loadings using MD simulation; the stress peak after 5 cycles was approximately half of the initial value, which provides damage parameters for upper-scale calculations and reveals the fundamental mechanism of interfacial cyclic debonding. The experimental data of unidirectional SCS-6/Ti-15-3 composites under cyclic loading were adopted to verify the proposed model. Furthermore, the influence of thermal residual stress and fibre orientation was investigated, which offers valuable insights for composite design and manufacturing.

Orange Ware production and exchange in formative central Mexico as an index of regionalization of pottery styles

Ceramics present archaeologists with a medium to explore the range and intensity of interactions across space and over time. Style associations between regions indicate, at a minimum, communication, trade, or possibly migration coupled with an open disposition with respect to social identity formation. Conversely, style boundaries may develop for a variety of reasons, including but not limited to geographically restricted levels of interaction and more insular attitudes towards outgroups. Gordon Willey (1991) drew these alternatives into a cyclical model, shifting between broad style horizons and regionalized traditions. Early Mesoamerican style horizons as expressed through ceramics developed along broad networks of open cultural exchanges during the Early and Middle Formative periods. By the Late Formative, however, Mesoamerica fragmented into distinctive regionalized ceramic traditions. We provide a small-scale view of this process at the end of the Middle Formative using compositional sourcing to identify a divergence in the ceramic traditions of two neighboring regions: the Basin of Mexico and Morelos. During this timeframe, groups across lowland Mesoamerica developed an Orange Ware tradition that extended into Morelos. As revealed through neutron activation analysis (NAA) and petrography, the majority of orange/yellow Lacquer Ware found in the Basin of Mexico was imported from Morelos during the late Middle Formative, but Basin potters never adopted Orange Wares into their own style repertoires. The Morelos Orange Ware tradition is the first ceramic style in a long history of interaction between the two regions that was not matched by parallel developments in both regions, thus serving as a reference to an inflection point in the cycling between horizontal integration and regional differentiation that Willey hypothesized. This process continued into the Late Formative when Basin groups realigned with groups to the northwest through the adoption of Chupícuaro ceramic traits.

Effect of martensitic transformation on ratchetting in medium-manganese steel: Experiment and homogenized constitutive model

Transformation-induced plasticity (TRIP) behavior and related cyclic plasticity model of medium-manganese steel subjected to uniaxial cyclic loading were studied. Cyclic loading tests were conducted at different mean stresses and stress amplitudes. The results show that medium-manganese steel exhibits two different ratchetting evolution characteristics. Moreover, microscopic characterizations reveal that martensitic transformation occurs in medium-manganese steel during asymmetrical cyclic stressing, and the higher the applied stress amplitude, the greater the ratchetting strain and the more likely the martensitic transformation will occur. The interaction between TRIP and ratchetting leads to accelerated accumulation of plastic strain. Based on the existing meso-mechanics cyclic elastoplastic constitutive model, a kinetic equation for the strain-induced martensitic transformation and a modified nonlinear kinematic hardening equation are introduced. Subsequently, the two-leveled homogenization method was used to construct a homogenized cyclic plasticity model containing a three-phase microstructure of austenite, martensite, and ferrite. By comparing the predicted results with the experimental results, the proposed model can reasonably describe the evolutionary features of each phase and the effect of the phase transformation on the ratchetting of medium-manganese steel. Finally, ratchetting is further predicted and discussed for different austenite contents and phase transformation rates using the proposed model.

KATI ATIK ARITIMINA KISA BİR BAKIŞ VE TÜRKİYE'DEKİ GÜNCEL UYGULAMALAR

High rates of energy and goods consumption, combined with increasing population growth and high living standards, lead to the ever-increasing production of solid waste. The amount of solid waste generated today has reached a level that poses serious threats to the environment and the sustainable management of the country's economies. Although action plans are being prepared and implemented by countries, unions and institutions for the environmentally friendly and sustainable management of solid waste, it is seen that the threat still exists for the near future. Within the scope of solid waste, management of household waste is undoubtedly one of the most important issues today. The MSW EU average for 2021 reached 530 million tons. Similarly, a total of 104.8 million tons of waste was generated in Turkey in 2020, 32.3 million tons of which were domestic waste. Although, today, the most common method of solid waste control globally is storage in open or controlled landfills, it is seen that Thermal conversion, MTB or Liquefaction applications, which enable energy production especially within the cyclical economy and production model, are increasingly increasing.
 The aim of this compilation study, in which global and country-based statistics are briefly presented, is to raise awareness of the increasing threat.

Constitutive modelling and damage prediction of AlSi10Mg alloy manufactured by SLM technology with emphasis on ratcheting in LCF regime

The present work has been aimed at developing an improved cyclic plasticity model in the framework of Ohno-Wang kinematic hardening formulation and evaluating the performance of the model with reference to the critical experimental investigation. LCF test specimens of the AlSi10Mg aluminium alloy have been fabricated through selective laser melting technology. The material shows strain-range dependent variation of modulus of elasticity under symmetric strain-controlled loading. The modulus of elasticity decreases with increasing strain amplitude. Stress–strain responses have been critically examined under multistep uniaxial ratcheting in the LCF regime with incremental mean stress and stress amplitude. Damage calculation considering ratcheting and LCF mechanisms as independent gives unconservative predictions. The linear damage accumulation rule taking the largest contribution of both is bringing much more accurate estimates. The proposed model incorporates effects of mean stress and stress amplitude under uniaxial multistep ratcheting in the LCF regime. All fatigue tests in the LCF regime have been simulated using the proposed improved model. Evolution of strain-range dependent elastic modulus has been incorporated in the formulation of the improved model through the memory history dependent parameter. The ratcheting parameter is newly formulated in this present work to account for the effects of accumulated mean plastic strain on the opening of stress strain hysteresis loops that results in a better prediction of the behaviour of cyclic plastic deformation. The proposed model has been validated by comparing simulated results with experimental observations and reference published simulation results.

Biotechnological Basis of the Pulp and Paper Industry Circular Economic System

To ensure development sustainability, the linear economic approach is being transformed into a cyclical model. For the pulp and paper industry (PPI), which occupies a significant place in the Russian economy, the shift of circular principles to the field of bioeconomics is becoming more important. This requires the development of basic biotechnological approaches implemented in closed cycles (biorefining). The aim of this study was to develop the biotechnological foundations of the circular economic system of the pulp and paper industry. To achieve the goal, the factors for the implementation of the circular mechanism in the pulp and paper industry were established. The composition of pulp and paper waste was systematized, taking into account the places of their occurrence; the directions and forms of the biorefining of pulp and paper secondary renewable resources were determined; and the principal possibility of obtaining bioethanol, based on the whole complex of sugars from cellulose production wastes, is shown. A wide range of general scientific methods was involved (analysis, synthesis, classification, modeling, etc.). Statistical methods were used to process experimental results in the field of pulp and paper waste bioconversion. The biotechnologies involved included methods of destruction, detoxification, and conversion of useful resources into secondary raw materials and final products. From the standpoint of the environmental approach, there are serious efficiency imbalances in the pulp and paper industry, which justify the implementation of circular mechanisms for organizing economic systems. The overall efficiency is ensured by the use of renewable resources and obtaining environmental effects. Algorithms and parameters of green biotechnological regulations for pulp and paper industry waste recycling provide the possibility of microbiological production of a complex of products: biocomposites, bioplastics, medical products, fertilizers, feed additives, vitamin supplements, and bioenergy resources. A strategy for the efficient biochemical processing of pulp and paper waste into green ethanol was determined. The possibility of increasing the efficiency of alcoholic fermentation using various biocatalysts was experimentally confirmed. The technological features of this method, associated with the need for microaerobic fermentation modes, were determined.

Multisolitons-like patterns in a one-dimensional MARCKS protein cyclic model

In this paper, we study the nonlinear dynamics of the MARCKS protein between cytosol and cytoplasmic membrane through the modulational instability phenomenon. The reaction–diffusion generic model used here is firstly transformed into a cubic complex Ginzburg–Landau equation. Then, modulational instability (MI) is carried out in order to derive the MI criteria. We find the domains of some parameter space where nonlinear patterns are expected in the model. The analytical results on the MI growth rate predict that phosphorylation and binding rates affect MARCKS dynamics in opposite way: while the phosphorylation rate tends to support highly localized structures of MARCKS, the binding rate in turn tends to slow down such features. On the other hand, self-diffusion process always amplifies the MI phenomenon. These predictions are confirmed by numerical simulations. As a result, the cyclic transport of MARCKS protein from membrane to cytosol may be done by means of multisolitons-like patterns.

A novel defect-related cyclic damage model driven by strain energy density for LPBF titanium alloy

The unavoidable defects in additive manufacturing (AM) material have an impact on the deformation behavior and fatigue lifetime. In this study, a series of experiments on Laser powder bed fusion (LPBF) Ti-6Al-4 V under symmetrical tension–compression cyclic loading were conducted, and the corresponding damage mechanism was then investigated. It is revealed that due to the nucleation, growth, and coalescence of micro-voids, LPBF Ti-6Al-4 V exhibits accelerated softening behavior after reaching cyclic stability. Based on the physical mechanism, a cyclic damage model with a critical initiation criterion was developed using fracture mechanics principles, in which plastic strain energy as the driving parameter is introduced to describe the defect evolution, and the void’s closure effect during the tension–compression cycle is considered. Experimental validation has demonstrated that the damage model can accurately predict the cyclic stress–strain curves for LPBF Ti-6Al-4 V vertical and horizontal specimens, with errors in predicting crack initiation and growth lifetime falling within the ± 1.6 and ± 2.5 scatter bands.

DEM filtration modelling for granular materials: Comparative analysis of dry and wet approaches

AbstractA detailed study comparing two – dry and wet – numerical approaches to model filtration processes at stake in actual granular filters is presented using the discrete element method (DEM). In the first approach, the migration of fines is provided by gravitational forces, while in the second, hydrodynamic forces induce their movement. Numerical filtration tests were performed on granular filters involving materials with different gradings and porosities. The study demonstrated that the wet filtration approach generates higher tortuosity due to the possibility for fines to deviate from direct paths towards more open sideways. It leads to a lower coefficient of retention for the filter than if it were characterised using a dry filtration approach. However, the intensity of this feature greatly depends on the grading and the porosity of the granular filter. Finally, an enhanced dry filtration model designated as the “equivalent cyclic wet filtration model” is presented, which better mimics the results obtained through the preferable wet filtration model compared to the original dry filtration model. This new model constitutes a valuable alternative tool for studies of filtration properties in granular materials.