Pub Date : 2024-12-09DOI: 10.1177/10567895241305324
Alper Gunoz, Memduh Kara
The use of carbon and kevlar fiber-reinforced composite materials continues to grow in high-tech applications such as aerospace engineering. One of the most desired properties in composite structures is a strong interfacial bond between the matrix and the fiber. Nano-material reinforcement is one of the most preferred methods for strengthening the fiber-matrix interfacial bond. In the present research, polyamide 6.6 (PA 6.6) nanofiber and multi-walled carbon nanotubes (MWCNTs) reinforced kevlar fabric (KF), carbon fabric (CF) and epoxy matrix nanocomposite plates were produced by functional grading of these two fabrics. PA 6.6 nanofibers, obtained by electrospinning, were placed between the layers, and 12-layer nanocomposite plates were fabricated using a vacuum-assisted hand lay-up method. In producing MWCNTs reinforced nanocomposite plates, 0.3 wt.% of MWCNTs were added into the epoxy matrix. A comprehensive set of 16 distinct composite plates was manufactured, encompassing unreinforced plates, plates reinforced with MWCNTs, plates reinforced with PA 6.6, and plates reinforced with a combination of PA 6.6 and MWCNTs (PA 6.6-MWCNTs). The impact strengths of the produced composite plates were investigated at energy levels of 20, 40 and 60 J. The effects of reinforcing the composite structure with MWCNTs, PA 6.6, and PA 6.6-MWCNTs, as well as functionally grading KF/CF on impact strength, were investigated in detail. The damages that occurred in the material as a result of the low-velocity impact tests were interpreted by examining the high-resolution camera and optical microscope images. Thus, the nanofiber and nanoparticle reinforcement to composite structure and hybridization effect were evaluated together. With the reinforcement of PA 6.6, MWCNTs and PA 6.6-MWCNTs, the impact strength of the nanocomposite samples increased significantly compared to the unreinforced samples. Moreover, the amount of damage caused by the low-velocity impact test in reinforced samples was significantly reduced.
{"title":"Damage behavior of functionally graded kevlar/carbon epoxy nanocomposites reinforced with polyamide 6.6 nanofiber and MWCNTs subjected to low-velocity impact","authors":"Alper Gunoz, Memduh Kara","doi":"10.1177/10567895241305324","DOIUrl":"https://doi.org/10.1177/10567895241305324","url":null,"abstract":"The use of carbon and kevlar fiber-reinforced composite materials continues to grow in high-tech applications such as aerospace engineering. One of the most desired properties in composite structures is a strong interfacial bond between the matrix and the fiber. Nano-material reinforcement is one of the most preferred methods for strengthening the fiber-matrix interfacial bond. In the present research, polyamide 6.6 (PA 6.6) nanofiber and multi-walled carbon nanotubes (MWCNTs) reinforced kevlar fabric (KF), carbon fabric (CF) and epoxy matrix nanocomposite plates were produced by functional grading of these two fabrics. PA 6.6 nanofibers, obtained by electrospinning, were placed between the layers, and 12-layer nanocomposite plates were fabricated using a vacuum-assisted hand lay-up method. In producing MWCNTs reinforced nanocomposite plates, 0.3 wt.% of MWCNTs were added into the epoxy matrix. A comprehensive set of 16 distinct composite plates was manufactured, encompassing unreinforced plates, plates reinforced with MWCNTs, plates reinforced with PA 6.6, and plates reinforced with a combination of PA 6.6 and MWCNTs (PA 6.6-MWCNTs). The impact strengths of the produced composite plates were investigated at energy levels of 20, 40 and 60 J. The effects of reinforcing the composite structure with MWCNTs, PA 6.6, and PA 6.6-MWCNTs, as well as functionally grading KF/CF on impact strength, were investigated in detail. The damages that occurred in the material as a result of the low-velocity impact tests were interpreted by examining the high-resolution camera and optical microscope images. Thus, the nanofiber and nanoparticle reinforcement to composite structure and hybridization effect were evaluated together. With the reinforcement of PA 6.6, MWCNTs and PA 6.6-MWCNTs, the impact strength of the nanocomposite samples increased significantly compared to the unreinforced samples. Moreover, the amount of damage caused by the low-velocity impact test in reinforced samples was significantly reduced.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"70 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142797125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-09DOI: 10.1177/10567895241305596
Yi Luo, Chao Ye, Pengpeng Ni, Zhixing Zeng, Yixian Liu
Many historical earthen buildings are damaged due to fire exposure in the past. It is important to understand the strength degradation of rammed earth after elevated temperature for guiding the strategy of building protection or rehabilitation. A total of 24 unconfined compression tests are conducted on lime-stabilized rammed earth specimens after elevated temperature up to 700°C. A quasi-linear reduction in strength and stiffness is found for rammed earth with the increase of temperature. At high temperature, the ductility of rammed earth is enhanced, e.g., strain at peak strength of 2.5% and 1.5% at 700°C and 20°C, respectively. Microstructural analyses demonstrate that with the increase of temperature, the specimen becomes more porous with reduced calcium carbonate precipitation, explaining the strength reduction. A new thermal damage model is proposed to describe the behavior of rammed earth after elevated temperature, in which the closure of pores is captured to show unrecoverable deformation, and the skeleton part is simulated using a thermal damage variable in a statistical manner to present the damage evolution (strain softening). By comparing with the measured stress-strain curves, one can confirm that the proposed method can provide effective prediction for the response of rammed earth after elevated temperature.
{"title":"Statistical damage model with strain softening for lime-stabilized rammed earth after elevated temperature","authors":"Yi Luo, Chao Ye, Pengpeng Ni, Zhixing Zeng, Yixian Liu","doi":"10.1177/10567895241305596","DOIUrl":"https://doi.org/10.1177/10567895241305596","url":null,"abstract":"Many historical earthen buildings are damaged due to fire exposure in the past. It is important to understand the strength degradation of rammed earth after elevated temperature for guiding the strategy of building protection or rehabilitation. A total of 24 unconfined compression tests are conducted on lime-stabilized rammed earth specimens after elevated temperature up to 700°C. A quasi-linear reduction in strength and stiffness is found for rammed earth with the increase of temperature. At high temperature, the ductility of rammed earth is enhanced, e.g., strain at peak strength of 2.5% and 1.5% at 700°C and 20°C, respectively. Microstructural analyses demonstrate that with the increase of temperature, the specimen becomes more porous with reduced calcium carbonate precipitation, explaining the strength reduction. A new thermal damage model is proposed to describe the behavior of rammed earth after elevated temperature, in which the closure of pores is captured to show unrecoverable deformation, and the skeleton part is simulated using a thermal damage variable in a statistical manner to present the damage evolution (strain softening). By comparing with the measured stress-strain curves, one can confirm that the proposed method can provide effective prediction for the response of rammed earth after elevated temperature.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"83 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142797126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pre-stressed anchor bolts serve as an effective means to reinforce fractured rock masses. The long-term efficacy of their anchoring function significantly impacts the safety throughout the entire lifecycle of rock engineering projects. Over time, fractured rock masses undergo creep deformation, which interacts synergistically with the time-dependent changes in the pre-stress of anchor bolts. In this work, we conduct uniaxial tensile tests and tensile creep tests on fractured rock specimens anchored by pre-stressed bolts, analyzing the coordinated deformation between the pre-stressed anchor bolts and the fractured specimens. Firstly, conventional uniaxial tensile tests were conducted on the pre-stressed anchorage specimen. The study found that the tensile strength of the anchored specimens was significantly higher than that of the unanchored specimens. Additionally, the ability of the specimens to withstand tensile stresses and deformation improved as pre-stress increased. Secondly, uniaxial tensile creep tests were conducted on the prestressed anchored specimens. The results indicate that, as the stress level increases, the creep strain continues to increase. The application of prestress can effectively limit the tensile deformation of the specimen and delay its damage time. The greater the pre-stress, the smaller the instantaneous strain and creep strain rate during the graded loading test. Finally, based on the synergistic deformation of pre-stressed anchor bolts and the creeping rock mass, we establish a constitutive model reflecting the creep properties of fractured rock mass and derive a theoretical viscoelastic creep formula for anchored rock mass under uniaxial tension. Comparing the creep model with the test results shows that this model is highly applicable and accurate in verifying the tensile creep deformation of prestressed anchorage specimens.
{"title":"Investigation into the time-dependent mechanical behavior of pre-stressed anchor bolts and fractured rock specimens under synchronized tensile loads","authors":"Wendong Yang, Chuntian Liu, Yiwe Li, Bingqi Wang, Xiang Zhang","doi":"10.1177/10567895241303164","DOIUrl":"https://doi.org/10.1177/10567895241303164","url":null,"abstract":"Pre-stressed anchor bolts serve as an effective means to reinforce fractured rock masses. The long-term efficacy of their anchoring function significantly impacts the safety throughout the entire lifecycle of rock engineering projects. Over time, fractured rock masses undergo creep deformation, which interacts synergistically with the time-dependent changes in the pre-stress of anchor bolts. In this work, we conduct uniaxial tensile tests and tensile creep tests on fractured rock specimens anchored by pre-stressed bolts, analyzing the coordinated deformation between the pre-stressed anchor bolts and the fractured specimens. Firstly, conventional uniaxial tensile tests were conducted on the pre-stressed anchorage specimen. The study found that the tensile strength of the anchored specimens was significantly higher than that of the unanchored specimens. Additionally, the ability of the specimens to withstand tensile stresses and deformation improved as pre-stress increased. Secondly, uniaxial tensile creep tests were conducted on the prestressed anchored specimens. The results indicate that, as the stress level increases, the creep strain continues to increase. The application of prestress can effectively limit the tensile deformation of the specimen and delay its damage time. The greater the pre-stress, the smaller the instantaneous strain and creep strain rate during the graded loading test. Finally, based on the synergistic deformation of pre-stressed anchor bolts and the creeping rock mass, we establish a constitutive model reflecting the creep properties of fractured rock mass and derive a theoretical viscoelastic creep formula for anchored rock mass under uniaxial tension. Comparing the creep model with the test results shows that this model is highly applicable and accurate in verifying the tensile creep deformation of prestressed anchorage specimens.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"77 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142776461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-23DOI: 10.1177/10567895241292761
Ali Akbar Jahanitabar, Vahid Lotfi
This paper presents a new constitutive model based on the combination of plasticity and anisotropic damage mechanics to predict the nonlinear response of plain concrete. The aim is to overcome the deficiencies of the previous anisotropic damage-plasticity models in simulating concrete failure under multiaxial loadings. To effectively combine plasticity and damage, a decoupled algorithm and consequently a strain equivalence hypothesis are employed. A stress-based yield criterion and a non-associative flow rule are used in the plasticity formulation. The stress tensor is decomposed into positive and negative parts to consider the unilateral effect of concrete damage. Consequently, two sets of damage criteria and two anisotropic damage tensors are defined, which leads to automatically accounting for the stiffness recovery in transition from tensile to compressive stress. The viscous model of Duvaut–Lions is employed to improve mesh dependency. Moreover, the formulation is regularized to capture large crack opening and closing when the material has experienced large amounts of strain. The numerical implementation of the proposed model is described in detail. A special in-house finite element program incorporating the proposed approach is developed. The efficiency of the model is verified by comparing numerical results and experimental data for different benchmark problems such as monotonic and cyclic uniaxial tests, monotonic biaxial test, and mixed-mode multidimensional structural tests.
{"title":"Formulation and verification of an anisotropic damage plasticity constitutive model for plain concrete","authors":"Ali Akbar Jahanitabar, Vahid Lotfi","doi":"10.1177/10567895241292761","DOIUrl":"https://doi.org/10.1177/10567895241292761","url":null,"abstract":"This paper presents a new constitutive model based on the combination of plasticity and anisotropic damage mechanics to predict the nonlinear response of plain concrete. The aim is to overcome the deficiencies of the previous anisotropic damage-plasticity models in simulating concrete failure under multiaxial loadings. To effectively combine plasticity and damage, a decoupled algorithm and consequently a strain equivalence hypothesis are employed. A stress-based yield criterion and a non-associative flow rule are used in the plasticity formulation. The stress tensor is decomposed into positive and negative parts to consider the unilateral effect of concrete damage. Consequently, two sets of damage criteria and two anisotropic damage tensors are defined, which leads to automatically accounting for the stiffness recovery in transition from tensile to compressive stress. The viscous model of Duvaut–Lions is employed to improve mesh dependency. Moreover, the formulation is regularized to capture large crack opening and closing when the material has experienced large amounts of strain. The numerical implementation of the proposed model is described in detail. A special in-house finite element program incorporating the proposed approach is developed. The efficiency of the model is verified by comparing numerical results and experimental data for different benchmark problems such as monotonic and cyclic uniaxial tests, monotonic biaxial test, and mixed-mode multidimensional structural tests.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"18 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142694128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1177/10567895241302520
Zhanming Shi, Jiangteng Li, PG Ranjith, Mengxiang Wang, Hang Lin, Dongya Han, Kaihui Li
To reveal the mechanical properties and energy laws of high-temperature rock mass engineering under fatigue disturbance, this paper conducted a multi-scale study on thermally damaged granite. First, the macroscopic mechanical properties of the samples were studied. Secondly, the law of energy evolution was summarized based on thermodynamic theory. Then, a rockburst index was introduced, and NMR and SEM technologies were used to conduct a multi-scale discussion on the mechanism of influence on temperature. Finally, an improved nonlinear continuous damage model (INCDM) was established, and a hardening index and damage growth rate of low-cycle fatigue were defined. The result shows that temperature first strengthens and then weakens the fatigue mechanical properties of the sample, with a threshold temperature of 225°C. Temperatures below the threshold cause uneven expansion of mineral particles to squeeze natural pores, reduce the porosity of the sample, and thus increase the fatigue life and strength of the sample. Temperatures above the threshold cause dehydration and phase change of the minerals such as quartz, feldspar, and mica, forming transgranular/intergranular cracks, parallel cleavage and stratification, thus reducing the fatigue strength of the sample. In addition, the total energy, elastic energy and dissipated energy density of the sample all show a step-like increasing trend with the normalized cycle index. Energy storage satisfies a linear law. Affected by accelerated energy release, energy dissipation changes from linear to nonlinear law. As the temperature increases, the rockburst tendency first increases and then decreases. The fatigue failure changes from sudden instability to progressive instability mode. The fatigue-thermal damage of the sample satisfies a power law, and increases as a compound power function with the normalized cycle index.
{"title":"Multi-scale study on the fatigue mechanical properties and energy laws of thermal-damage granite under fatigue loading","authors":"Zhanming Shi, Jiangteng Li, PG Ranjith, Mengxiang Wang, Hang Lin, Dongya Han, Kaihui Li","doi":"10.1177/10567895241302520","DOIUrl":"https://doi.org/10.1177/10567895241302520","url":null,"abstract":"To reveal the mechanical properties and energy laws of high-temperature rock mass engineering under fatigue disturbance, this paper conducted a multi-scale study on thermally damaged granite. First, the macroscopic mechanical properties of the samples were studied. Secondly, the law of energy evolution was summarized based on thermodynamic theory. Then, a rockburst index was introduced, and NMR and SEM technologies were used to conduct a multi-scale discussion on the mechanism of influence on temperature. Finally, an improved nonlinear continuous damage model (INCDM) was established, and a hardening index and damage growth rate of low-cycle fatigue were defined. The result shows that temperature first strengthens and then weakens the fatigue mechanical properties of the sample, with a threshold temperature of 225°C. Temperatures below the threshold cause uneven expansion of mineral particles to squeeze natural pores, reduce the porosity of the sample, and thus increase the fatigue life and strength of the sample. Temperatures above the threshold cause dehydration and phase change of the minerals such as quartz, feldspar, and mica, forming transgranular/intergranular cracks, parallel cleavage and stratification, thus reducing the fatigue strength of the sample. In addition, the total energy, elastic energy and dissipated energy density of the sample all show a step-like increasing trend with the normalized cycle index. Energy storage satisfies a linear law. Affected by accelerated energy release, energy dissipation changes from linear to nonlinear law. As the temperature increases, the rockburst tendency first increases and then decreases. The fatigue failure changes from sudden instability to progressive instability mode. The fatigue-thermal damage of the sample satisfies a power law, and increases as a compound power function with the normalized cycle index.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"6 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142690733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1177/10567895241292746
Yuhao Gong, Jinxing Liu, Naigang Liang
A method is proposed to analyze the effective moduli of periodically defective beam lattices by using the Lattice Green’s Functions (LGF). The LGF of beam lattices is built to calculate the displacement caused by external nodal forces. We describe the stress redistribution due to defects by applying extra nodal forces. Then, analyzing a defective unit cell is equivalently transformed to that on its perfect counterpart by representing the influence of defects by an equivalent force field based on the superposition principle. Based on the obtained displacement field of the defective unit cell, the elastic moduli of defective lattices can be calibrated based on the equivalence of strain energy, which indicates that the strain energy of the structural energetic expression is equal to its continuum counterpart. By comparing it with finite element simulations, the prediction ability of the proposed method has been demonstrated. Systematic parametric analyses are then carried out to illustrate the effects of element types, defect types, the defect number density, and the slenderness ratio on the effective moduli of defective lattices.
{"title":"On effective moduli of defective beam lattices via the lattice green’s functions","authors":"Yuhao Gong, Jinxing Liu, Naigang Liang","doi":"10.1177/10567895241292746","DOIUrl":"https://doi.org/10.1177/10567895241292746","url":null,"abstract":"A method is proposed to analyze the effective moduli of periodically defective beam lattices by using the Lattice Green’s Functions (LGF). The LGF of beam lattices is built to calculate the displacement caused by external nodal forces. We describe the stress redistribution due to defects by applying extra nodal forces. Then, analyzing a defective unit cell is equivalently transformed to that on its perfect counterpart by representing the influence of defects by an equivalent force field based on the superposition principle. Based on the obtained displacement field of the defective unit cell, the elastic moduli of defective lattices can be calibrated based on the equivalence of strain energy, which indicates that the strain energy of the structural energetic expression is equal to its continuum counterpart. By comparing it with finite element simulations, the prediction ability of the proposed method has been demonstrated. Systematic parametric analyses are then carried out to illustrate the effects of element types, defect types, the defect number density, and the slenderness ratio on the effective moduli of defective lattices.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"1 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142690732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-21DOI: 10.1177/10567895241292747
Peng Yue, Changyu Zhou, Junfu Zhang, Xiao Zhang, Xinfa Du, Pengxiang Liu
Fatigue life estimation of aero-engine turbine components under combined high and low cycle fatigue (CCF) is of significance for guaranteeing the structural reliability during operation. According to the investigations on damage evolution process, a nonlinear damage accumulation method is proposed for life prediction under CCF loadings, and the interaction effect between high cycle fatigue (HCF) and low cycle fatigue (LCF) is considered by integrating the interaction factor and stress ratio of CCF. Furthermore, experimental results of alloys and turbine blades are utilized to validate the proposed method and conduct a comparative analysis among Miner’s rule and other two typical nonlinear cumulative damage methods under combined loading conditions. Comparative results demonstrate that the developed model holds better prediction robustness and accuracy than those of others.
{"title":"A comparative study on combined high and low cycle fatigue life prediction model considering loading interaction","authors":"Peng Yue, Changyu Zhou, Junfu Zhang, Xiao Zhang, Xinfa Du, Pengxiang Liu","doi":"10.1177/10567895241292747","DOIUrl":"https://doi.org/10.1177/10567895241292747","url":null,"abstract":"Fatigue life estimation of aero-engine turbine components under combined high and low cycle fatigue (CCF) is of significance for guaranteeing the structural reliability during operation. According to the investigations on damage evolution process, a nonlinear damage accumulation method is proposed for life prediction under CCF loadings, and the interaction effect between high cycle fatigue (HCF) and low cycle fatigue (LCF) is considered by integrating the interaction factor and stress ratio of CCF. Furthermore, experimental results of alloys and turbine blades are utilized to validate the proposed method and conduct a comparative analysis among Miner’s rule and other two typical nonlinear cumulative damage methods under combined loading conditions. Comparative results demonstrate that the developed model holds better prediction robustness and accuracy than those of others.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"19 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-14DOI: 10.1177/10567895241297313
Alberto Carpinteri, Federico Accornero
The load-displacement softening response of quasi-brittle solids exhibits an unstable structural behavior, which is characterised by a negative slope in the post-peak regime. In severely brittle situations, the post-peak behaviour can show a virtual positive slope, the fracture propagation occurring unexpectedly with a catastrophic loss in the load-carrying capacity. In this case, if the displacement controls the loading process, the curve exhibits a discontinuity and the representative point drops to the lower branch with a negative slope. On the other hand, in order to obtain a stable crack growth, a decrease both in load and in displacement is required. In the last forty years, in-depth study of the so-called snap-back instability was conducted in relation to crack propagation phenomena in quasi-brittle materials. In the present work, the structural response of two brittle-matrix specimens is analysed: the first contains a distribution of collinear micro-cracks, whereas the second presents multiple parallel reinforcing fibres embedded in the matrix. In both cases, it is shown that the structural response presents a discrete number of snap-back instabilities with related peaks and valleys, the crack propagation occurring alternately within the matrix and through the heterogeneities. Thus, the strong analogy between weakened and strengthened zones consists in a multiple snap-back mechanical response, where descending branches of propagating cracks alternate with ascending (linear) branches of arrested cracks.
{"title":"Micro-damage instability mechanisms in composite materials: Cracking coalescence versus fibre ductility and slippage","authors":"Alberto Carpinteri, Federico Accornero","doi":"10.1177/10567895241297313","DOIUrl":"https://doi.org/10.1177/10567895241297313","url":null,"abstract":"The load-displacement softening response of quasi-brittle solids exhibits an unstable structural behavior, which is characterised by a negative slope in the post-peak regime. In severely brittle situations, the post-peak behaviour can show a virtual positive slope, the fracture propagation occurring unexpectedly with a catastrophic loss in the load-carrying capacity. In this case, if the displacement controls the loading process, the curve exhibits a discontinuity and the representative point drops to the lower branch with a negative slope. On the other hand, in order to obtain a stable crack growth, a decrease both in load and in displacement is required. In the last forty years, in-depth study of the so-called snap-back instability was conducted in relation to crack propagation phenomena in quasi-brittle materials. In the present work, the structural response of two brittle-matrix specimens is analysed: the first contains a distribution of collinear micro-cracks, whereas the second presents multiple parallel reinforcing fibres embedded in the matrix. In both cases, it is shown that the structural response presents a discrete number of snap-back instabilities with related peaks and valleys, the crack propagation occurring alternately within the matrix and through the heterogeneities. Thus, the strong analogy between weakened and strengthened zones consists in a multiple snap-back mechanical response, where descending branches of propagating cracks alternate with ascending (linear) branches of arrested cracks.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"9 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-11DOI: 10.1177/10567895241297392
Nan Hou, Qiang Guo, Fahmi Zaïri, Huixia Xu, Ning Ding
This paper presents a finite element analysis of steady-state crack propagation in viscoelastic soft solids exhibiting Mullins softening. A cohesive-zone model is employed to simulate the localized processes at the tip of a Mode I crack in materials governed by viscoelastic behavior and damage-induced Mullins effects. The study numerically evaluates the intrinsic dissipation characteristics of typical rubber-like materials, focusing on the influence of key factors such as Mullins damage, relaxation modulus, and relaxation time. The impact of these factors on material toughening is examined, with particular emphasis on their role in crack propagation. The results reveal that crack propagation velocity is highly sensitive to the interplay between energy dissipation mechanisms. Specifically, Mullins damage parameters are shown to increase fracture toughness by raising the local energy release rate threshold at the crack tip. Additionally, the relaxation modulus enhances viscous dissipation, further elevating this threshold and subsequently reducing crack propagation velocity. Interestingly, an inverse relationship between relaxation time and crack propagation velocity is observed. The study provides a detailed analysis of the dissipation mechanisms at the crack tip, offering valuable insights for improving material toughness.
本文对粘弹性软固体中呈现 Mullins 软化的稳态裂纹扩展进行了有限元分析。采用内聚区模型模拟了受粘弹性行为和破坏诱导的 Mullins 效应支配的材料中模式 I 裂纹顶端的局部过程。研究以数值方式评估了典型橡胶类材料的内在耗散特性，重点关注穆林斯损伤、松弛模量和松弛时间等关键因素的影响。研究了这些因素对材料增韧的影响，特别强调了它们在裂纹扩展中的作用。结果表明，裂纹扩展速度对能量耗散机制之间的相互作用非常敏感。具体来说，Mullins 损伤参数可通过提高裂纹尖端的局部能量释放率阈值来增加断裂韧性。此外，松弛模量会增强粘性耗散，进一步提高阈值，从而降低裂纹扩展速度。有趣的是，弛豫时间与裂纹扩展速度之间存在反比关系。该研究详细分析了裂纹尖端的耗散机制，为提高材料韧性提供了宝贵的见解。
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Pub Date : 2024-11-08DOI: 10.1177/10567895241292745
Chuangxiang Shi, Songxuan Zhang, Xiaoliang Zhang, Shaofan Li
Concrete is prone to damage under explosive loads, which can cause a large number of casualties and property losses. The concrete fragmentation process during explosion is transient and dynamic, and the experimental measurement of such events is difficult and risky to conduct, and the intermediate explosion process is difficult to observe in the experimental tests. Therefore, the numerical simulation is an ideal method to model and simulate the explosion process of concrete. Different from the traditional finite element method, Peridynamics (PD) method uses the spatial integral equation to replace the traditional local differential equation to solve the fragmentation problem with massive and complex discontinuous patterns. In this study, a peridynamics (PD) model is developed to simulate the failure process of reinforced concrete (RC) structures under radial blasting. Concrete PD models with different cavity sizes and reinforcement conditions were established and calibrated with the experimental data. We find that the crack growth and damage pattern obtained in the peridynamics simulation is consistent with the experiment test results, which verifies the feasibility of peridynamics method as a modeling tool for modeling concrete damage under explosive load and for evaluating anti-explosion performance of RC concrete structures.
{"title":"Peridynamics simulations of the damage of reinforced concrete structures under radial blasting","authors":"Chuangxiang Shi, Songxuan Zhang, Xiaoliang Zhang, Shaofan Li","doi":"10.1177/10567895241292745","DOIUrl":"https://doi.org/10.1177/10567895241292745","url":null,"abstract":"Concrete is prone to damage under explosive loads, which can cause a large number of casualties and property losses. The concrete fragmentation process during explosion is transient and dynamic, and the experimental measurement of such events is difficult and risky to conduct, and the intermediate explosion process is difficult to observe in the experimental tests. Therefore, the numerical simulation is an ideal method to model and simulate the explosion process of concrete. Different from the traditional finite element method, Peridynamics (PD) method uses the spatial integral equation to replace the traditional local differential equation to solve the fragmentation problem with massive and complex discontinuous patterns. In this study, a peridynamics (PD) model is developed to simulate the failure process of reinforced concrete (RC) structures under radial blasting. Concrete PD models with different cavity sizes and reinforcement conditions were established and calibrated with the experimental data. We find that the crack growth and damage pattern obtained in the peridynamics simulation is consistent with the experiment test results, which verifies the feasibility of peridynamics method as a modeling tool for modeling concrete damage under explosive load and for evaluating anti-explosion performance of RC concrete structures.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"1 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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