Bilinear Cohesive Zone Model Research Articles

Study on damage of CRTS II slab tracks in coated-uncoated transition zones subjected to temperature and train loads

The CRTS II ballastless track is sensitive to temperature due to its longitudinal continuity. The application of reflective insulation coating can efficiently lower the temperature of the track slab, thereby decelerating track deterioration. Given the considerable length of high-speed railway lines, the application of reflective insulation coatings leads to numerous transitions between coated and uncoated sections. This study investigates the influence of reflective insulation coatings on the structural damage of coated-uncoated transition zones in railways. To this end, a CRTS II slab track model involving the bilinear cohesive zone model and the concrete plastic damage model is established. The model examines the combined impact of high temperature and train loading, aiming to investigate the damage patterns within the coated-uncoated transition zone of the track. The results indicate: (1) During high temperature loading, the center of the track slab layer is predisposed to warping compared to the sides. (2) If the cohesion parameter falls below 0.04 MPa, augmenting the cohesion model parameter effectively alleviates track slab arching. (3) In instances where the track slab lacks complete coverage of reflective insulation coatings, train loading may shift the location of the maximum vertical displacement and interface failure mode.

Behavior prediction of reinforced concrete beams shear strengthened with CFRP

This work presents the computational modeling of reinforced concrete beams, strengthened to shear with carbon fiber-reinforced polymers (CFRP), using the finite element method (FEM) and the customized ANSYS software, version 19.2. It is important to emphasize that contact elements and bilinear cohesive zone models provided by ANSYS were used to model the concrete-reinforcement interface. These models were used to identify the modes of premature failure caused by the debonding of the reinforcement, which causes poor use of the CFRP's resistance properties. The structural elements used in this analysis were twelve simply supported reinforced concrete beams, without and with shear reinforcement using CFRP, which were experimentally tested by Khalifa (1999). From the analysis of the results, it was observed that the developed numerical models were able to accurately predict the behavior of the simulated beams, both in terms of load-displacement, as well as the load and rupture mode of the beams.

Energy-based criteria for identification of impact-induced interfacial damage of longitudinally connected slab ballastless track structure

Interfacial damage as a potential threat affects the stability of the longitudinally connected slab ballastless track structure (LCSBTS). In most related research, the interfacial damage of LCSBTS is identified in terms of stiffness degradation, which makes it difficult to explore the role of energy in the development of the interfacial damage. As an alternative, a set of energy-based criteria rooted in a bilinear cohesive zone model was proposed, together with a new damage indicator that evaluates the loss of interfacial fracture energy. The proposed criteria were utilized in the simulation of the interfacial damage of LCSBTS subjected to wheel impact. Results show that, the energy-based damage indicator describes the growth of the interfacial damage at a slower speed than the stiffness-based damage indicator, better coordinating with the variation of the interfacial fracture energy. Under wheel impact, interfacial damages are most likely to occur out of a peanut-shaped region surrounding the impact point where shear stress surpasses tension stress. However, by considering a coupling action of the positive temperature gradient, severe interfacial damages appear around the center of the track slab where tension stress surpasses shear stress and interfacial damages caused by shear stress are located near the longitudinal edges of the track slab.

Dynamic propagation of tensile and shear fractures induced by impact load in rock based on the dual bilinear cohesive zone model

PurposeThe purpose of this study is to simulate the tensile and shear types of fractures using the mixed fracture criteria considering the energy evolution based on the dual bilinear cohesive zone model and investigate the dynamic propagation of tensile and shear fractures induced by an impact load in rock. The propagation of tension and shear at different scales induced by the impact load is also an important aspect of this study.Design/methodology/approachIn this study, based on the well-developed dual bilinear cohesive zone model and combined finite element-discrete element method, the dynamic propagation of tensile and shear fractures induced by the impact load in rock is investigated. Some key technologies, such as the governing partial differential equations, fracture criteria, numerical discretisation and detection and separation, are introduced to form the global algorithm and procedure. By comparing with the tensile and shear fractures induced by the impact load in rock disc in typical experiments, the effectiveness and reliability of the proposed method are well verified.FindingsThe dynamic propagation of tensile and shear fractures in the laboratory- and engineering-scale rock disc and rock strata are derived. The influence of mesh sensitivity, impact load velocities and load positions are investigated. The larger load velocities may induce larger fracture width and entire failure. When the impact load is applied near the left support constraint boundary, concentrated shear fractures appear around the loading region, as well as induced shear fracture band, which may induce local instability. The proposed method shows good applicability in studying the propagation of tensile and shear fractures under impact loads.Originality/valueThe proposed method can identify fracture propagation via the stress and energy evolution of rock masses under the impact load, which has potential to be extended into the investigation of the mixed fractures and disturbance of in-situ stresses during dynamic strata mining in deep energy development.

Error analysis for determining transverse tensile delamination strength of REBCO coated conductors by anvil test: numerical simulation demonstrations

RE–Ba–Cu–O (REBCO, where RE = Y, Gd, Sm, and other rare earth elements) coated conductor (CC) tapes exhibit considerable potential for application within the domains of high-energy physics and high-field science. Nevertheless, weak interfacial properties pose a significant obstacle, impeding the progress and practical implementation in high-field scenarios. The anvil tension method has been extensively employed for the assessment of transverse delamination strength of REBCO CC tapes. However, the outcomes derived from anvil tension exhibit severe dispersion, thereby impeding its efficacy in evaluating material performance. The underlying cause of this phenomenon remains unidentified. In this study, error analysis of anvil measurement method in determining the transverse tensile delamination strength (TTDS) of REBCO CC tapes was conducted based on finite element (FE) numerical simulations. A two-dimensional multilayer elastic-plastic delamination FE model with main layers of REBCO CC tapes, solder connecting layers and anvil materials were developed based on the bilinear cohesive zone model. The effects of anvil test conditions and the structural configuration of the conductor itself on the test results were discussed. Simulation results show that localized premature cracking of the interface due to stress concentration and plastic yielding of the CC tape around the loading boundary is the root reason for the discrepancy between the anvil test results and the true interfacial strength. Therefore, anvil test conditions (including top anvil dimensions, soldering conditions, loading eccentricity angle, and anvil material properties) as well as the structural configuration of the conductor itself (including edge initial crack length, edge encapsulation width, and stabilizer thickness) have a significant impact on anvil test-based TTDS results.

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.

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.

Measurement of the interfacial energy release rate (ERR) and cohesive law parameters of polyvinyl butyral laminated glass using a novel beam-type test specimen

The polyvinyl butyral (PVB) laminated glass (LG) structures are widely used in architectural and automotive sectors. Determination of the interfacial fracture energy (i.e. G) between the PVB layer and glass is one of the most vital procedures for ensuring the structural safety and fracture resistance of these kinds of components. The present study investigates the adhesion characteristics between glass and PVB interface in a LG composite structure. A new simple test fixture is introduced to measure the mixed-mode fracture energy from pure mode I (i.e. GI) to pure mode II (i.e. GII). By making use of the concept of Equivalent material Concept (EMC), linear elastic fracture mechanics (LEFM) formulations together with finite element (FE) analysis can be used to compute the compliance parameter of the system and pure modes I/II fracture energies. Besides, the interaction of cohesive forces between the PVB layer and glass are simulated by using a FE method based on a bi-linear cohesive zone model (CZM) technique. In this regard, the cohesive law parameters are computed for mode I and mode II in an iterative process. Then, the obtained pure mode cohesive law parameters are utilized to predict the mixed-mode load–displacement diagrams. The obtained results demonstrate the satisfactory accuracy of the cohesive law parameters and fracture energies in predicting the mixed-mode loading results across four different loading rates (i.e. LR = 2, 5, 10, and 15 mm/min).

Interaction between eye movements and adhesion of extraocular muscles

The contact and pull-off tests and finite element simulations were used to study the extraocular muscle-sclera adhesion and its variation with eye movement in this research. The effect of the adhesion on the eye movements was also determined using equilibrium equations of eye motion. The contact and pull-off tests were performed using quasi-static and non-quasi-static unloading velocities. Finite element models were developed to simulate these tests in cases with high unloading velocity which could not be achieved experimentally. These velocities range from the eye's fixation to saccade movement. The tests confirmed that the pull-off force is related to the unloading velocity. As the unloading velocity increases, the pull-off force increases, with an insignificant increase at the high ocular saccade velocities. The adhesion moment between the extraocular muscles and the sclera exhibited the same trend, increasing with higher eye movement velocities and higher separation angles between the two interfaces. The adhesion moment ratio to the total moment was calculated by the traditional model and the active pulley model of eye movements to assess the effect of adhesion behavior on eye movements. At the high ocular saccade velocities (about 461 deg/s), the adhesion moment was found to be 0.53% and 0.50% of the total moment based on the traditional and active pulley models, respectively. The results suggest that the adhesion behavior between the extraocular muscles and the sclera has a negligible effect on eye movements. At the same time, this adhesion behavior can be ignored in eye modeling, which simplifies the model reasonably well. Statement of Significance1. Adhesion behavior between the extraocular muscles and the sclera at different indenter unloading velocities determined by contact and pull-off tests. 2. A finite element model was developed to simulate the adhesive contact between the extraocular muscles and the sclera at different indenter unloading velocities. The bilinear cohesive zone model was used for adhesive interactions. 3. The elastic modulus and viscoelastic parameters of the extraocular muscle along the thickness direction were obtained by using compressive stress-relaxation tests. 4. The influence of the adhesion moment between the extraocular muscles and the sclera on eye movement was obtained according to the equation of oculomotor balance. The adhesion moment between the extraocular muscles and the sclera was found to increase with increased eye movement velocity and increased separation angle between the two interfaces.

Deep neural network aided cohesive zone parameter identifications through die shear test in electronic packaging

AbstractThe die shear test is a feasible and conventional method to characterize the shear strength of die‐attaching layer materials in electronic packaging. A new method for determining cohesive zone model (CZM) parameters using deep neural networks (DNN) and die shear tests is proposed, different from classical fracture framework or lap shear test‐based methods. With the sintered nano‐silver die shear test, the results show that the bilinear CZM inversion results agree well with the experimental results. It is found that the DNN model has high accuracy in predicting and identifying the maximum shear traction strength τmax, separation displacement of the interface δf, and the interface stiffness k1 of CZM parameters for sintered nano‐silver adhesive layer through die shear test load versus displacement curves. The presented DNN‐aided inverse identifying method through the die shear test in this paper could provide an alternative and convenient method for extracting CZM parameters of various kinds of adhesive materials in electronic packaging.

Mode I fracture toughness with fiber bridging of unidirectional composite laminates under cryogenic temperature

Carbon fiber reinforced polymer (CFRP) composites have widely been used in the aerospace field owing to their excellent mechanical properties. However, composite structures often fail under complex space environmental conditions. In particular, the fiber bridging and cryogenic temperature may greatly change the fracture toughness of CFRP composites. Herein, the effects of cryogenic temperature and fiber bridging on the fracture toughness of unidirectional composite laminates were experimentally examined by double cantilever beam (DCB) testing at different temperatures (room temperature, −50 °C, −70 °C, −100 °C, −150 °C, and −180 °C). Different calculation methods of fracture toughness were used and the results were compared. A method without measuring the delamination length at low temperatures was used and the results were consistent with other methods. The average difference in fracture toughness values was less than 5 %. The fiber-bridging microstructures of composites under cryogenic temperatures were examined by confocal microscopy along with the geometric morphology and parameters of surface roughness. The results suggested changes in the matrix failure mechanism at −50 °C, resulting in maximum fracture toughness, which is 26.45 % higher than that at room temperature. A semi-analytic approach was then proposed to express the bridge stress, and a bilinear cohesive zone model was established to simulate the delamination of composite laminates at low temperatures. Overall, the numerical data agreed well with the experimental results (peak force maximum error of 17 %), suggesting the usefulness of the proposed method for the prediction of interlamination properties and structural damage design of composite structures at cryogenic temperature.

Numerical modelling of the mode I fracture behavior in composite laminates with significant R-curve effect

Significant R-curve effect is very common in the mode I fracture of composite laminates. Accurate simulation of fracture with R-curve effect is important for damage tolerance design of composite structures. However, traditional numerical methods usually do not consider the R-curve effect. In this work, four methods, including three phenomenological methods and cohesive zone model with multi-linear constitutive relation are presented. The three phenomenological methods are based on bilinear cohesive zone model, virtual crack closure technique and extended finite element method respectively with the consideration of R-curve. It is interesting to know which method is more suitable for modelling delamination growth with significant R-curve effect. To achieve this goal, double cantilever beam specimen is modeled and delamination growth is simulated using above four methods. Comparisons between the numerical results and the experimental results of laminates with different material types and stack sequences are made for these methods. Finally, the accuracy, computational efficiency and parameter acquisition of these methods are discussed with the goal of finding a suitable method for delamination modelling in laminated composites. It is shown that the cohesive zone model with multi-linear constitutive relation shows good accuracy in all studied cases.

Experimental study and simulation of the interface shear deformation behavior in AISI304/Q235 clad plate with thin cladding layer

The mechanical properties and interface damage characteristics of hot-rolled bonded stainless steel/carbon steel (SS/CS) clad plate with thin cladding were investigated. The focus is on mechanical property-microstructure relationships in shear deformation. In detail, the mechanical response of the cladding components and clad plate were characterized. Then a hybrid numerical–experimental identification procedure for the cohesive zone model (CZM) in the simulation of heterogeneous SS/CS interface using finite element (FE) method was developed. A mixed-mode bilinear CZM, considering the anisotropy of the thin cladding was coupled FE model, showing a high accuracy for predicting the shear deformation behavior. The results showed obvious differences in the microstructure and mechanical properties of the SS and CS layers and the formation of an inhomogeneous interfacial layer. Additionally, the bond strength and delamination position of SS/CS clad plate are highly dependent on the interfacial oxide distribution and elemental diffusion behavior. Interestingly, the thin cladding is subjected to bending moments in shear deformation, resulting in delamination of the interface that is not completely dominated by one shear mode. And these abrupt interfacial failures could be clarified via stress-strain state and local damage analysis of the well-reproduced FE model of cladding material.

Inverse identification of cohesive zone parameters for sintered nano-silver joints based on dynamic convolution neural network

The inverse identification of cohesive zone parameters is an important topic in the field of fracture mechanics. In this paper, three data-driven models, including multilayer perceptron (MLP), convolutional neural network (CNN), and dynamic convolutional neural network (DCNN), were presented to predict the cohesive zone parameters of sintered nano-silver end notched flexure (ENF) joints. Based on the construction of experimental and numerical datasets of load versus displacement curves, bilinear cohesive zone model (CZM) parameters of sintered silver joints are adopted as the prediction target. The investigation shows that MLP, CNN, and DCNN are all valid for predicting CZM parameters through load versus displacement curves with reasonable accuracy. However, DCNN has better prediction accuracy and performance than those of CNN and MLP models based on loss analysis, statistical indicator comparison, and K-fold cross-validation. DCNN can be adopted as the suitable surrogate model for CZM parameters inverse identification with high prediction accuracy. Otherwise, DCNN is also not sensitive to the load versus displacement curves data length. However, the computation efficiency of DCNN during the training process is not as high as that of MLP. Those three methods presented in this paper are very hopeful to be adopted for other inverse identifications of CZM parameters for various kinds of adhesive joints.

Correlation between microstructural evolution and mechanical properties of CMDB propellant during uniaxial tension

AbstractNumerical simulation of the deformation and damage evolution process of composite modified double base (CMDB) propellant based on the microstructure is of great significance for improving its macro‐mechanical properties. The macro‐mechanical properties and damage evolution of CMDB propellant were studied experimentally and numerically in current work. To establish the correlation between microstructural evolution and the macro‐mechanical response of the propellant, a three‐dimensional microstructure model of the CMDB propellant was constructed utilizing the molecular dynamics particle filling approach. At the interface between RDX particles and the nitrocellulose‐nitroglycerine (NC‐NG) matrix, the conventional cohesive element was replaced by cohesive contact, and the parameters of the cohesive zone model (CZM) at the interface between the particles and the matrix were obtained by parameter inversion based on the Hooke‐Jeeves parameter optimization algorithm. The processes of damage initiation, propagation, convergence, and failure at the cohesive interface were simulated using the bilinear cohesive zone model (BCZM). The results revealed that the fracture strength of NC‐NG propellant with added RDX particles was significantly increased and the fracture elongation was reduced. The three‐dimensional microstructure model can accurately describe the microstructure of CMDB, and dewetting at the interface is the primary cause of propellant degradation when subjected to an external load, which compromises the mechanical properties of the propellant.

Theoretical analysis and numerical simulation of axial tensile behavior of pipe joints based on bi-linear cohesive bond-slip model

PurposeDue to its inexpensive production costs, low stress concentration and maintenance-friendliness, the adhesive bonded pipe joint is frequently utilized for pipe connection. However, further theoretical analysis is needed to understand the debonding failure mechanism of such bonded pipe joints under axial tension.Design/methodology/approachIn this study, based on the bi-linear cohesive zone model, the integrated closed-form solutions were derived by considering the axial stiffness ratio and failure stage to determine the relative interfacial slip, interfacial shear stress and relationship of tension–displacement in the bonded pipe joint.FindingsAdditionally, solutions for the critical bonded length and the ultimate load capacity were put forth. Besides, the numerical study was conducted to verify the theoretical solutions regarding the load–displacement relationship. The interfacial shear stress distribution at different failure stages was presented to understand the interfacial shear stress transmission and debonding process. The effect of bonded length on the ultimate load and ductility of pipe joints was also discussed.Originality/valueThe findings in this study can give a reference for the design of bonded pipe joints in their actual engineering applications.

Finite Element Simulation and Sensitivity Analysis of the Cohesive Parameters for Delamination Modeling in Power Electronics Packages.

Delamination is a critical failure mode in power electronics packages that can significantly impact their reliability and performance, due to the large amounts of electrical power managed by the most recent devices which induce remarkable thermomechanical loads. The finite element (FE) simulation of this phenomenon is very challenging for the identification of the appropriate modeling tools and their subsequent calibration. In this study, we present an advanced FE modeling approach for delamination, together with fundamental guidelines to calibrate it. Considering a reference power electronics package subjected to thermomechanical loads, FE simulations with a global-local approach are proposed, also including the implementation of a bi-linear cohesive zone model (CZM) to simulate the complex interfacial behavior between the different layers of the package. A parametric study and sensitivity analysis is presented, exploring the effects of individual CZM variables on the delamination behavior, identifying the most crucial ones and accurately describing their underlying functioning. Then, this work gives valuable insights and guidelines related to advanced and aware FE simulations of delamination in power electronics packages, useful for the design and optimization of these devices to mitigate their vulnerability to thermomechanical loads.

Effects of debonding repairment on interfacial damage and thermal deformation of CRTS II slab ballastless track

The effects of debonding repairment on the interfacial damage and thermal deformation of CRTS II slab ballastless track are further assessed in this work. An improved mixed-mode bilinear cohesive zone model was adopted in an attempt to obtain a more accurate prediction of the interfacial damage. A finite element model of CRTS II slab ballastless track was built with the debonding repairment considered, based on which the interfacial damage and structural deformation of CRTS II slab ballastless track were simulated under the field-measured temperature gradient loads. The results show that the debonding repairment restores the capacity of CRTS II slab ballastless track to resist the thermal deformation, but that capacity will gradually decrease with the accumulation of interfacial damage. The re-debonding in the upper interlayer of CRTS II slab ballastless track, which may happen after a one-year cyclic temperature gradient load, will result in the emergence of an opposite-sided debonding in the lower interlayer. In addition, implementing the debonding repairment with the rebars-implanting has significant impact on reducing the re-debonding height.

Numerical analysis on axial crushing damage of aluminum/CFRP hybrid thin-walled tubes

Metal/CFRP hybrid structures have been increasingly applied in the automotive industry due to their favorable weight-saving and crashworthiness. In this article, a nonlinear finite element (FE) model is established to study the axial crushing behavior of aluminum/CFRP thin-walled tube structures. A progressive damage constitutive model is employed to capture the intra-laminar response of composites; Johnson-Cook model is used to describe the crushing process of aluminum layers and a bilinear cohesive zone model is applied for modeling the inter-layer delamination during the collapse process. A user material subroutine VUMAT involving these damage models is coded and executed to attain the numerical solution based on ABAQUS/Explicit solver. The axial crushing processes of thin-walled tubes with different configurations are simulated, and the corresponding damage characteristics are analyzed thoroughly. The influence of aluminum layer arrangement and cross-sectional shape on the crashworthiness and energy absorption of thin-walled tubes is discussed, which provides a design basis for the application of energy absorption elements.