Zone Model Research Articles

Simulation Modeling of the Process of Danger Zone Formation in Case of Fire at an Industrial Facility

Proactive prevention and fighting fire at industrial facilities, often located in urbanized clusters, should include the use of modern methods for modeling danger zones that appear during the spread of the harmful combustion products of various chemicals. Simulation modeling is a method that allows predicting the parameters of a danger zone, taking into account a number of technological, landscape, and natural-climatic factors that have a certain variability. The purpose of this research is to develop a mathematical simulation model of the formation process of a danger zone during an emergency at an industrial facility, including an explosion of a container with chemicals and fire, with the spread of an aerosol and smoke cloud near residential areas. The subject of this study was the development of a simulation model of a danger zone of combustion gases and its graphical interpretation as a starting point for timely decision making on evacuation by an official. The mathematical model of the process of danger zone formation during an explosion and fire at an industrial facility presented in this article is based on the creation of a GSL library from data on the mass of explosion and combustion products, verification using the Wald test, and the use of algorithms for calculating the starting and ending points of the danger zone for various factor values’ variables, constructing ellipses of the boundaries of the distribution of pollution spots. The developed model makes it possible to calculate the linear dimensions and area of the danger zone under optimistic and pessimistic scenarios, constructing a graphical diagram of the zones of toxic doses from the source of explosion and combustion. The results obtained from the modeling can serve as the basis for making quick decisions about evacuating residents from nearby areas.

On the adhesion of sinusoidal surfaces

In this work, we study the adhesive loading and unloading of a one-dimensional sinusoidal surface and use design of experiments to provide for response surface maps for the work of adhesion and the interaction length, which depend only on Johnson’s α parameter and the Maugis parameter μ. As showcased by some example, these can be used to replace the fine scale roughness by a cohesive zone model. Besides that, we provide ranges of α and μ in which the most common analytical solutions present accurate results. Finally, we characterize the presence of instabilities in the loading and unloading profiles.

Environmental and energetic impact of refrigeration systems using CO2 (R744): A Cuban case study

Despite the extensive use of CO2 in food retail refrigeration units, it has never been implemented, tested or simulated in Cuba. This work aims to evaluate by simulation a Booster and Parallel compression system in twelve Cuban cities using two different semi-empirical approaches to model the compressors and the gas cooler/condenser. The compressors are modeled with a semi-empirical model and the gas cooler/condenser is modeled with a lumped model based on the ε-NTU method, discretizing the gas cooler in a one-zone model and the condenser into a three zones model. According to the results, the Booster and Parallel average consumptions are 640 MWh and 540 MWh, respectively. Both systems are less efficient than the conventional R404A refrigeration system. The lower capital costs of transcritical systems make them cost-effective solutions compared to the conventional system. Moreover, the Parallel system is an economically feasible alternative compared to the Booster one. The payback period of the Booster system is 10 to 12 years by considering the environmental and operating costs savings respect the Direct eXpansion System, while for the Parallel system the payback period is between 8 and 8.5 years. Both transcritical systems are excellent environmental alternatives to the R404A conventional system.

The Use of Bilinear Cohesive Zone Model to Study the Fracture of Mode I in Adhesive Joints

Adhesively bonded joints can be numericallysimulated using the Cohesive Zone Model (CZM) concepts.CZM are widely used for the strength prediction of adhesivejoints. The critical strain energy release rate and criticalinterface strength are the parameters which must be knownwhen cohesive elements in ABAQUS software are used. Theformulation of the cohesive finite elements is based on theCZM approach with the bilinear traction-separation law. Inthis work, the parameters of two industrial adhesivesHuntsman Araldite 2015 and resin LY3505/XB3405 forbonding of epoxy composites are identified. DoubleCantilever Beam (DCB) test data was used for theidentification. Finally, cohesive parameters are identifiedcomparing numerically simulated load-displacement curveswith experimental data retrieved from literature.Parametric study is performed to evaluate the variation ofinput parameters like initial stiffness, element size, peakstress and energy release rate ‘G’. From the numericalevaluation, it was noted that CZM simulation relies largelyon element size and peak cohesive strength.

Determination traction-separation parameters and its sensitivity analysis of bilinear cohesive zone model through experimental and numerical peeling analysis of electrodes

The optimization of traction-separation parameters within the cohesive zone model (CZM) is crucial for accurately simulating electrode peeling failure in lithium-ion batteries. This study performed 180° peeling tests on NCM electrodes and used Abaqus software alongside the sim-flow optimization tool for simulation analysis, aiming to accurately replicate the failure behavior at the lithium-ion battery electrode interface. Experimental results were used to determine the fracture energy of the electrode interface, while numerical simulations analyzed the peeling performance of the electrode. By fitting the force-displacement curves from both simulation and experiment, the traction-separation parameters within the bilinear CZM were optimized. Additionally, the study analyzed the effects of traction-separation parameters, as well as the modulus and thickness of the current collector, on peeling behavior. The results showed that a significant increase in the interface stiffness and strength increased the steady-state peeling force. Among these, the fracture energy had the most significant influence on the steady-state peeling force. Furthermore, while the modulus and thickness of the current collector affected the maximum peeling force, their effect on the steady-state peeling force was negligible. These findings enhance the accuracy of simulating the failure behavior of the electrode interface.

Cracking behavior of segmented-casting joint in steel-UHPC composite bridge deck system: Experiment and numerical simulation

The cracking of the pre-/post-casting UHPC joint in the steel-UHPC composite bridge deck system can lead to continuous tensile damage in the UHPC layer, reducing its ability to stiffen the steel deck. This study aims to clarify the cracking mechanism of the segmented-casting UHPC joint, and to provide design recommendations for cracking control. Axial tension tests on full-scale composite deck specimens were conducted, in which the influence of with and without joint, and varying reinforcement ratios on cracking response were identified. Moreover, the nonlinear numerical model for the composite deck, where the UHPC-UHPC interface was simulated in three methods, i.e. unbonded case, cohesive zone model (CZM), and perfectly bonded case, was developed and validated to simulate the crack initiation and propagation of the UHPC layer. Based on the validated numerical model incorporating CZM, improving the bond strength of CZM is more effective in controlling crack opening at the interface than increasing the failure displacement. Finally, optimized reinforcement arrangement and joint shape recommendations were provided to enhance construction convenience, minimize stress concentration, and limit crack opening.

Macro-meso cracking inversion modelling of three-point bending concrete beam with random aggregates using cohesive zone model

An accurate description of concrete crack propagation is essential to practical engineering. In this paper, the cohesive zone model (CZM) is used to investigate the macroscopic mechanical properties and the microscopic crack damage behavior of concrete beams in the three-point bending test. Five key factors controlling the cracking of cohesive elements, namely mode I fracture energy, mode II fracture energy, shear strength, tensile strength, and elastic modulus (stiffness), are subjected to parametric examinations. Based on macro-mechanical properties and micro-cracking, the test results and parametric models of specimens are inversely analyzed. The applicable parameter range of control factors in the three-point bending simulation is obtained. Considering the quantitative aggregate information of specimens with different mix proportions, three computation models with different aggregate areas are established. The quantitative results of crack propagation are derived by applying the parameter range. Finally, the accuracy of the parameter range is validated based on the simulated and experimental mechanical properties and quantitative results of cracks.

Investigation of the bedding effect on coal rock under Brazilian splitting tests

This contribution focuses on understanding the bedding effect of coal rocks under the Brazilian splitting test. First, multiple Brazilian splitting tests were performed on coal rocks with various bedding angles to systematically investigate the influence of stratification. Subsequently, numerical models with stratified structures were constructed, and a continuous–discontinuous numerical analysis method based on the cohesive zone model (CZM) was employed to conduct the corresponding numerical investigations. Results indicate that the load–displacement curves of coal rock specimens with different bedding angles can be classified into four stages: initial compaction stage, elastic deformation stage, crack rapid coalescence stage, and final destruction stage. With increase in the bedding angle, the failure patterns of coal rock specimens can be categorized into three groups: 1) stretching damage along bedding planes; 2) mixed tension and shear failure along the bedding planes and the coal matrix; and 3) stretching failure passing through the coal matrix. Furthermore, the tensile strength and cumulative acoustic emission (AE) energy–displacement relations are significantly influenced by the bedding angle. The numerical model can effectively predict the mechanical responses and fracture behavior of coal rock specimens, providing empirical parameters for the simulation of similar rock engineering.

Focus zone model and depth determination based on amplitudes of pP phases

Analysis of difficulties connected with determination of crust tectonics seismic events is defined by rupture process. Detailed analysis showed that a set of first arrivals associated with an event contains arrivals generated on different depths. This indicates the existence of several instrumentally defined cofocuses in the focus zone. Consequently, the location algorithm should pick up several more significant by amplitude of fist arrivals. Then, seismic event depth will define that one rising maximal seismic signal. Investigation shoes – first arrivals may be projected into one point on seismic record even if they are generated at different depths. Thus, one impulse of first arrival may correspond to several depths. Hence appears the principal difficulties to determine depth solely using P phases. Solution of the problem is automated determination of time arrivals of depth phases pP. The last should be generated at a certain depth. The event depth is chosen by maximum value depth phase amplitude. Algorithm uses all records during the calculation process at the same time. Moreover it was revealed that local second events after first arrival have been registered. Second events may have time delays restricted by seconds. Second event impulse amplitude may be more than impulse amplitude of really first arrival at given depth. On the whole, a group of local first arrivals are in the frame of the period of base event impulse.

An extended multi-linear cohesive zone model for mixed-mode I/II delamination growth simulation in composite laminates with R-curve effects

An extended multi-linear cohesive zone model for mixed-mode I/II delamination growth simulation in composite laminates with R-curve effects

Numerical investigation on the crack resistance curve of thermally treated quartz‐diorite rock under mixed mode I + II loading

AbstractTo investigate the effects of thermal treatment and loading conditions on the crack initiation and propagation characteristics of quartz‐diorite, mixed mode I + II fracture tests were conducted by using three‐point bending (TPB) specimens. The numerical model, established on ABAQUS, couples the initial fracture toughness criterion and cohesive zone model to predict the crack initiation and propagation. The effects of thermal treatment and loading conditions on the crack propagation process, crack resistance curve, fracture path, and some fracture parameters at peak load have been analyzed and discussed. The results demonstrate that the thermal treatment has an obvious influence on the crack resistance curve of the specimen. The crack of the specimen will be dominated by the mode I fracture component with crack extension. The numerical results also show that the temperature and loading condition affect the crack length and fracture toughness at peak load.

Distributed model predictive control of fan coil system

To address the issues of large overshoot, long system stabilization time, and slow response associated with traditional PID-based and centralized model predictive control (MPC) of fan coil systems, this study proposes a distributed model predictive control (DMPC) method suitable for multi-zone building temperature regulation. Specifically, based on the thermal dynamic model of different zones, and aiming to constrain indoor temperature within set limits and minimize water system pressure drop and fan coil speed, a distributed MPC architecture for fan coil systems is developed. To solve the distributed optimization problem, the Nash equilibrium is introduced to find the global balance point within the distributed structure, and the Beetle Antennae Search-Particle Swarm Optimization (BAS-PSO) hybrid algorithm is used for online optimization of local MPCs. Experimental results show that compared to traditional PID control, the distributed MPC achieves coordinated multi-zone indoor temperature regulation with better dynamic performance, with the average absolute temperature error in each zone below 5 % and an energy savings rate of 16.23 %. Through semi-physical simulation, it is demonstrated that the proposed distributed MPC method has better applicability when the number of fan coils exceeds 10, compared to centralized MPC.

Investigation of damage and crack characteristics of epoxy modified recycled asphalt mixtures based on a three-dimensional meso-heterogeneous model

Epoxy asphalt has excellent fatigue resistance, making it a valuable addition to recycled asphalt mixtures. However, the lack of sufficient understanding of the cracking mechanism in epoxy-modified recycled asphalt mixtures (EMRAM) hinders its widespread application. The purpose of this paper was to investigate the damage and crack characteristics of EMRAM based on a three-dimensional meso-heterogeneous model. The coarse aggregates were first randomly generated using the secondary Delaunay algorithm. Meanwhile, the fracture parameters of each component material and asphalt-aggregate interface in EMRAM were tested through three-point bending tests and direct shear tests, respectively. Cohesive zone model elements were then inserted at the aggregates, asphalt mastic, and interfaces between different materials to establish a three-dimensional meso-heterogeneous model of EMRAM. Finally, based on the established model, the damage degree of each composition material in EMRAM was quantitatively analyzed to identify the vulnerable aspects of EMRAM during the crack propagation stage. Optimization strategies were proposed accordingly. The results demonstrated that the model established in this study can accurately represent the meso-heterogeneous of EMRAM and effectively simulate its cracking behavior. EMRAM was more susceptible to developing internal damage within the aggregates, followed by relatively noticeable damage at the interface and the internal regions epoxy-modified fine aggregate mastic. The cracking resistance of EMRAM showed a trend of initially increasing and then decreasing with an increase in the volume fraction of coarse aggregates with a size above 4.75 mm. The optimal range for the volume fraction of coarse aggregates in EMRAM was within 35–44 %. The fracture energy of EMRAM was improved by more than 30 % after gradation optimization compared to EMRAM with gradation at the median value of AC20. Within the designed service life, EMRAM durable pavement can save at least 30 % more in economic costs compared to ordinary asphalt concrete pavement.

Study of temperature-dependent interface with viscoelastic behavior through shear testing and modeling

In this work, the effect of temperature on interfaces with viscoelastic behavior was investigated using experimental and theoretical means. In particular, rubber/woven fabrics with thickness of 0.5 mm were subjected to self-designed shear tests at temperatures ranging from 263.15 to 383.15 K. Derived interface cyclic regeneration was observed through shear tests. Subsequently, a bi-linear cohesive zone model (CZM) was used to describe the shear test data. A novel image processing algorithm was developed to analyze the damaged morphology of the rubber/weave interface. It was found that hairniness amount decreased by 68.4 % when the temperature increased from 263.15 to 383.15 K. In addition, by combining the bi-linear CZM with the Kohlrausch–William–Watts law, Wiliams-Landel-Ferry equation and BK criterion, a 3D temperature-dependent constitutive model (KBW) was developed. The model successfully simulated the viscoelasticity of interfaces at different temperatures with margin of error less than 9 %. Thus, this study provides a strategy for elucidating the temperature dependence of interfaces with viscoelastic behavior.

A unified discontinuous Galerkin formulation for interfacial multiphysics modeling of thermo-chemically driven fracture

Many engineering and natural materials exhibit coupled thermo-chemo-mechanical phenomena, which can result in embrittlement and fracture. These fractures, in turn, can alter the subsequent thermal, chemical, and mechanical response. We present a theoretical formulation and computational framework for the analysis of thermo-chemically fractured solids, with emphasis on the post-fracture thermal and chemical interfacial behavior. The theoretical model is based on the thermodynamically-consistent formulation of Loeffel and Anand (IJP, 2011). The computational method extends the scalable discontinuous Galerkin/Cohesive Zone Model (DG/CZM) of Radovitzky et al. (CMAME, 2011) to thermo-chemo-mechanics, which facilitates coupled, large-scale simulations of materials and structures containing failed interfaces. In the proposed framework, all balance laws are enforced weakly via the DG formalism, resulting in a unified formulation for multiphysics problems in solids. This naturally enables the incorporation of general interface models, e.g. to account for effects such as the aeolotropic reduction in thermochemical transport due to the presence of fractures, or the acceleration of chemical reactions along crack flanks. The approach is verified against two analytical solutions of boundary value problems drawn from thermo-poro-elasticity and thermally-driven delamination. A scalable, three-dimensional simulation of thermochemically-driven concrete cracking illustrates the complete capabilities of the interfacial multiphysics modeling framework.

The effect of fiber bridging on mode I fatigue delamination propagation—part I: Testing

AbstractThe purpose of this investigation is to assess the effect of fiber bridging on fatigue delamination propagation. Fiber bridging occurs when testing beam type laminates specimens consisting of unidirectional plies. Unidirectional double cantilever beam specimens composed of the carbon fiber reinforced polymer prepreg AS4/8552 were tested by means of fatigue cycling. A Paris relation was determined based on these tests. Fiber bridging in beam specimens composed of unidirectional plies causes the apparent fatigue delamination curves to exhibit slower growth predicting overly conservative results. In Part I of this study, the effect of fiber bridging was eliminated experimentally from the results. In Part II of this study, a cohesive zone model is developed and used to carry out finite element analyses to simulate the experiments, as well as to eliminate the influence of fiber bridging.

Computational analysis of the failure mechanisms of a laminated composite in double-edge notch compression configuration

This manuscript presents a combined experimental–computational investigation of the compression failure response of laminated composites in double-edge notch compression (DENC) configuration. Analysis of in-situ and post-test DENC experiment results indicates the presence of multiple failure mechanisms, including ply splitting, delamination, and compression kink bands. In order to characterize the onset, growth, and interplay of the critical and subcritical damage mechanisms, a multiscale progressive damage analysis approach is implemented. A nonlocal multiscale damage model explicitly tracks the intraply failure mechanisms that lead to the formation and propagation of kink bands in the specimen. A cohesive zone model is used to track initiation and progression of ply splitting in the specimen. The splitting model was implemented using implicit finite element simulations and deployed with a pre-crack insertion technique to reduce simulation time while preserving prediction accuracy. Model parameters are calibrated based on available calibration data and measurements. The effects of split location and growth characteristics on model predictions are studied. The computational model along with a suite of experiments were employed to study the formation, growth and interactions of damage mechanisms in the composite specimens subjected to compression loading. The onset of matrix damage is not clear from the experimental images but the model predicts early onset around the onset time of splits which greatly reduce the stress concentration at the notches. Analysis of acoustic emission energy experimental data indicate that observable compression failure mechanisms are not causing nonlinearity consistently exhibited in the experiment responses. Simulation results demonstrate the capability of the multiscale modeling approach to predict critical kink bands and sub-critical matrix cracking and splitting in the DENC specimens while reducing computational cost compared to a direct numerical simulation of fibers and matrix.

A lifelong meta-learning approach for learning deep grey-box representative thermal dynamics models for residential buildings

Thermal dynamics models of residential buildings are crucial for managing energy use and maintaining desirable indoor environment quality, in the context of decarbonizing the electric grid. Despite recent developments in data-driven models, the implementation with a massive number of buildings in the real world remains infeasible because the computation is expensive and the thermostat data of buildings can be online and sparse. A representative model for aggregated study and acceleration of personalizing models is needed for many downstream tasks. In addition, most existing data-driven models lack physical interpretability questioning the representativeness of any aggregated model. In this paper, we present an online framework for learning meta-models of thermal dynamics across various residential buildings. The meta-models are physically explainable according to the building types and can accelerate fine-tuning personalized models for any building saving data and computation. Experiments suggest that our method performs well with a real-world online dataset that produces representative models of different climate zones and effective initialization for training individual models.

Stress Analysis Mapping for Mechanically Fastened Composite Bolted Lap Joints Using Cohesive Zone Model

Stress Analysis Mapping for Mechanically Fastened Composite Bolted Lap Joints Using Cohesive Zone Model

A New Numerical Simulation Method for Multi-stage in-Fracture Temporary Plugging and Diverting Fracturing: Based on the Modified Cohesive Zone Model

A New Numerical Simulation Method for Multi-stage in-Fracture Temporary Plugging and Diverting Fracturing: Based on the Modified Cohesive Zone Model