This paper aims to investigate the interlaminar shear properties and failure mechanisms of plain woven carbon fabric/polyetheretherketone (CF/PEEK) thermoplastic composites under high strain rate impact loads at different temperatures (25°C, 120°C, 295°C). A reliable hot air flow heating method with SHPB is creatively employed for short beam shear experiments. A multi-scale model was developed to predict the impact behavior of plain CF/PEEK composites. Both results show that the thermoplastic composites have strong strain rate and temperature dependence, and which are more sensitive to temperature effect. As the temperature increases, the thermoplastic composites are mainly affected by the softening effect of the matrix due to the glass transition temperature. The shear modulus and peak stress appear to decline at high temperatures, while the failure strain tends to increase. The damage mode changes from interlayer delamination cracking at the glassy state to shear fracture and fiber pullout at a highly elastic state. As the strain rate increases, the failure strain decreases, while the shear modulus and peak stress show the opposite trend. Fiber bundle breakage, debonding, matrix cracking, and significant interlayer delamination occur at high strain rates.
{"title":"Effects of high temperature and strain rate on the impact-induced inter-laminar shear behavior of plain woven CF/PEEK thermoplastic composites","authors":"Xu Zhang, Zhongxiang Pan, Jiajia Yu, Chengcai Yang, Zhenyu Wu","doi":"10.1177/10567895241274780","DOIUrl":"https://doi.org/10.1177/10567895241274780","url":null,"abstract":"This paper aims to investigate the interlaminar shear properties and failure mechanisms of plain woven carbon fabric/polyetheretherketone (CF/PEEK) thermoplastic composites under high strain rate impact loads at different temperatures (25°C, 120°C, 295°C). A reliable hot air flow heating method with SHPB is creatively employed for short beam shear experiments. A multi-scale model was developed to predict the impact behavior of plain CF/PEEK composites. Both results show that the thermoplastic composites have strong strain rate and temperature dependence, and which are more sensitive to temperature effect. As the temperature increases, the thermoplastic composites are mainly affected by the softening effect of the matrix due to the glass transition temperature. The shear modulus and peak stress appear to decline at high temperatures, while the failure strain tends to increase. The damage mode changes from interlayer delamination cracking at the glassy state to shear fracture and fiber pullout at a highly elastic state. As the strain rate increases, the failure strain decreases, while the shear modulus and peak stress show the opposite trend. Fiber bundle breakage, debonding, matrix cracking, and significant interlayer delamination occur at high strain rates.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"8 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142166370","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 : 2024-09-10DOI: 10.1177/10567895241277948
Pingkuang Luo, Diyuan Li, Jinyin Ma, Junjie Zhao, Abdul Jabbar
The deformation and failure of a rock is closely related to the strain energy consumption during the load process of rock. To investigate the effect of water on energy evolution and damage characteristics of dolomite samples from a deep mine, the uniaxial compression tests were carried out on dry and water-saturated dolomite samples at different burial depths (900 m–1200 m). The effects of water on the evolution characteristics of elastic and dissipative energy ratios ( Ue/ U and Ud/ U) during rock deformation and failure was analyzed. Based on the variation rate of damage factor ( Df), a new brittleness index is proposed, which can effectively characterize the brittleness characteristics of water-bearing dolomite. The results show that the uniaxial compressive strength and elastic modulus of the water-saturated dolomite are significantly reduced compared to dry sample. The energy and damage evolution process of dolomite can be divided into four stages: initial damage stage, stable damage stage, pre-peak accelerated damage stage and post-damage stage. The variation rate of damage factor of the rock samples in the stable damage stage and the pre-peak accelerated damage stage appeared to increase significantly after water saturation treatment. Compared with water-saturated samples, more pronounced energy hardening characteristics and brittleness characteristics were observed in dry samples. In addition, the possible impact on the stability of deep rock engineering after the deterioration of rock mechanical properties and energy storage properties caused by water was analyzed. Groundwater can somewhat reduce rock burst proneness. However, it also has the potential to lead to greater rock engineering destabilization and failure hazards.
岩石的变形和破坏与岩石受载过程中的应变能消耗密切相关。为了研究水对深部矿山白云岩样品能量演化和破坏特征的影响，对不同埋深（900 米-1200 米）的干燥和水饱和白云岩样品进行了单轴压缩试验。分析了岩石变形和破坏过程中水对弹性能和耗散能比（Ue/ U 和 Ud/U）演变特征的影响。根据损伤因子（Df）的变化率，提出了一种新的脆性指数，该指数可有效表征含水白云岩的脆性特征。结果表明，与干燥样品相比，饱水白云岩的单轴抗压强度和弹性模量明显降低。白云岩的能量和损伤演化过程可分为四个阶段：初始损伤阶段、稳定损伤阶段、峰前加速损伤阶段和损伤后阶段。经饱和水处理后，岩石样品在稳定破坏阶段和峰值前加速破坏阶段的破坏因子变化率明显增加。与水饱和样品相比，干燥样品的能量硬化特征和脆性特征更为明显。此外，还分析了水导致岩石力学性能和储能性能恶化后对深层岩石工程稳定性可能产生的影响。地下水可以在一定程度上降低岩石的易爆裂性。但是，地下水也有可能导致岩石工程失稳和破坏的危险。
{"title":"Experimental study on energy and damage evolution of dry and water-saturated dolomite from a deep mine","authors":"Pingkuang Luo, Diyuan Li, Jinyin Ma, Junjie Zhao, Abdul Jabbar","doi":"10.1177/10567895241277948","DOIUrl":"https://doi.org/10.1177/10567895241277948","url":null,"abstract":"The deformation and failure of a rock is closely related to the strain energy consumption during the load process of rock. To investigate the effect of water on energy evolution and damage characteristics of dolomite samples from a deep mine, the uniaxial compression tests were carried out on dry and water-saturated dolomite samples at different burial depths (900 m–1200 m). The effects of water on the evolution characteristics of elastic and dissipative energy ratios ( U<jats:sub>e</jats:sub>/ U and U<jats:sub>d</jats:sub>/ U) during rock deformation and failure was analyzed. Based on the variation rate of damage factor ( D<jats:sub>f</jats:sub>), a new brittleness index is proposed, which can effectively characterize the brittleness characteristics of water-bearing dolomite. The results show that the uniaxial compressive strength and elastic modulus of the water-saturated dolomite are significantly reduced compared to dry sample. The energy and damage evolution process of dolomite can be divided into four stages: initial damage stage, stable damage stage, pre-peak accelerated damage stage and post-damage stage. The variation rate of damage factor of the rock samples in the stable damage stage and the pre-peak accelerated damage stage appeared to increase significantly after water saturation treatment. Compared with water-saturated samples, more pronounced energy hardening characteristics and brittleness characteristics were observed in dry samples. In addition, the possible impact on the stability of deep rock engineering after the deterioration of rock mechanical properties and energy storage properties caused by water was analyzed. Groundwater can somewhat reduce rock burst proneness. However, it also has the potential to lead to greater rock engineering destabilization and failure hazards.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"41 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142166405","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 : 2024-09-07DOI: 10.1177/10567895241280369
Shen Yan, Dajiang Geng, Ning Dai, Minjian Long, Zhicheng Bai
This study proposes an improved dual shear unified strength model by introducing the plastic internal variable which reflects the collective effects of strain softening, intermediate principal stress and unequal strength under tension and compression. The improved model is then simplified into simple forms for typical stress states, including uniaxial tension and compression, plane stress pure shear and tri-axial stress states. The smooth method and conjugate gradient method are utilized to facilitate its numerical implementation, avoiding numerical singularity and non-convergence in the solution process. The physical meanings of the parameters are further clarified and their values for self-compacting concrete are determined from the results of triaxial compression tests through a combination of direct determination, equation solution and back propagation (BP) neural network optimization. Validated against the test results, the improved model gives a more accurate prediction than the traditional dual shear unified strength model and Mohr-Coulomb model, in terms of both the overall trend and representative values. Validation results show that the improved model is applicable to materials for which the compressive strength is greater than the tensile strength and the tensile strength is greater than the shear strength.
{"title":"An improved dual shear unified strength model (IDSUSM) considering strain softening effect","authors":"Shen Yan, Dajiang Geng, Ning Dai, Minjian Long, Zhicheng Bai","doi":"10.1177/10567895241280369","DOIUrl":"https://doi.org/10.1177/10567895241280369","url":null,"abstract":"This study proposes an improved dual shear unified strength model by introducing the plastic internal variable which reflects the collective effects of strain softening, intermediate principal stress and unequal strength under tension and compression. The improved model is then simplified into simple forms for typical stress states, including uniaxial tension and compression, plane stress pure shear and tri-axial stress states. The smooth method and conjugate gradient method are utilized to facilitate its numerical implementation, avoiding numerical singularity and non-convergence in the solution process. The physical meanings of the parameters are further clarified and their values for self-compacting concrete are determined from the results of triaxial compression tests through a combination of direct determination, equation solution and back propagation (BP) neural network optimization. Validated against the test results, the improved model gives a more accurate prediction than the traditional dual shear unified strength model and Mohr-Coulomb model, in terms of both the overall trend and representative values. Validation results show that the improved model is applicable to materials for which the compressive strength is greater than the tensile strength and the tensile strength is greater than the shear strength.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"72 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142152407","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 : 2024-09-07DOI: 10.1177/10567895241275373
P Christie, MA Siddiq, RM McMeeking, ME Kartal
Metastable β titanium alloys are widely applied in many industries. These alloys can have plastic deformation via dislocation slip, twinning, stress-induced martensite (SIM), or a combination of these. These alloys fail in a ductile manner via a process of void nucleation, growth, and coalescence. Inherent defects, such as voids, are commonly attributed to poor mechanical properties. In this study, aspects of plastic anisotropy in damage accumulation are investigated for metastable crystals that deform by combined slip and SIM. The focus of this study is to understand the evolution of damage due to inherent voids in metastable Ti-10V-2Fe-3Al single crystals. This investigation is conducted using crystal plasticity-based 3D finite element (FE) calculations. A unit-cell FE model involving a spherical void is deformed under constant stress triaxiality and lode parameter. We investigated four triaxiality values at differing lode parameters in three crystal orientations. The void growth was found to be heavily dependent on crystal orientation at low triaxialities. At higher triaxialities, SIM is found to inhibit the void growth via accommodation of the required deformation in the surrounding material. Orientations aligned favourable with SIM undergo significantly less void growth. The accommodation of deformation in the surrounding matrix was found to help preserve the integrity of the void, preventing the localisation of deformation around the void. At lower lode parameter and at higher stress triaxiality this impedes the exponential growth of the void. While, at higher lode parameter with low triaxiality SIM was found to delay the collapse of the void into a crack like morphology. This study not only deepens our understanding of the mechanical behaviour of metastable β titanium alloys, but also unveils the complex interplay between inherent defects, stress-induced martensite, and slip-based plasticity within their crystalline structure, offering fresh perspectives on enhancing material performance.
{"title":"Interaction of defects, martensitic transformation and slip in metastable body centred cubic crystals of Ti-10V-2Fe-3Al: A study via crystal plasticity finite element methods (CPFEM)","authors":"P Christie, MA Siddiq, RM McMeeking, ME Kartal","doi":"10.1177/10567895241275373","DOIUrl":"https://doi.org/10.1177/10567895241275373","url":null,"abstract":"Metastable β titanium alloys are widely applied in many industries. These alloys can have plastic deformation via dislocation slip, twinning, stress-induced martensite (SIM), or a combination of these. These alloys fail in a ductile manner via a process of void nucleation, growth, and coalescence. Inherent defects, such as voids, are commonly attributed to poor mechanical properties. In this study, aspects of plastic anisotropy in damage accumulation are investigated for metastable crystals that deform by combined slip and SIM. The focus of this study is to understand the evolution of damage due to inherent voids in metastable Ti-10V-2Fe-3Al single crystals. This investigation is conducted using crystal plasticity-based 3D finite element (FE) calculations. A unit-cell FE model involving a spherical void is deformed under constant stress triaxiality and lode parameter. We investigated four triaxiality values at differing lode parameters in three crystal orientations. The void growth was found to be heavily dependent on crystal orientation at low triaxialities. At higher triaxialities, SIM is found to inhibit the void growth via accommodation of the required deformation in the surrounding material. Orientations aligned favourable with SIM undergo significantly less void growth. The accommodation of deformation in the surrounding matrix was found to help preserve the integrity of the void, preventing the localisation of deformation around the void. At lower lode parameter and at higher stress triaxiality this impedes the exponential growth of the void. While, at higher lode parameter with low triaxiality SIM was found to delay the collapse of the void into a crack like morphology. This study not only deepens our understanding of the mechanical behaviour of metastable β titanium alloys, but also unveils the complex interplay between inherent defects, stress-induced martensite, and slip-based plasticity within their crystalline structure, offering fresh perspectives on enhancing material performance.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"21 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142152406","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 : 2024-09-06DOI: 10.1177/10567895241276444
M Dastjerdi, F Haji Aboutalebi, MS Sadeghi Nezhad
Damage measurement of materials is a crucial challenge for researchers and engineers in manufacturing industries. In this study, based on the image processing technique, a developed approach for determining the Lemaitre’s ductile damage parameter by the direct measurement method is proposed. For this purpose, first, the micrographs pictures are provided by a scanning electron microscope to attain the damage evolution behavior of St37 steel. Then, prediction results of the suggested method and the Lemaitre’s direct approach as well as the microhardness technique and also a lately published numerical method in damage propagation, crack initiation, and ductile fracture of a few tensile samples are compared with the corresponding experimental tests. The comparison reveals the higher efficiency and accuracy of the current approach. Therefore, it is concluded that the new presented method is a reliable approach to achieve the Lemaitre’s ductile damage parameter and predict the damage evolution behavior of ductile materials.
{"title":"An enhanced direct method for ductile damage measurement","authors":"M Dastjerdi, F Haji Aboutalebi, MS Sadeghi Nezhad","doi":"10.1177/10567895241276444","DOIUrl":"https://doi.org/10.1177/10567895241276444","url":null,"abstract":"Damage measurement of materials is a crucial challenge for researchers and engineers in manufacturing industries. In this study, based on the image processing technique, a developed approach for determining the Lemaitre’s ductile damage parameter by the direct measurement method is proposed. For this purpose, first, the micrographs pictures are provided by a scanning electron microscope to attain the damage evolution behavior of St37 steel. Then, prediction results of the suggested method and the Lemaitre’s direct approach as well as the microhardness technique and also a lately published numerical method in damage propagation, crack initiation, and ductile fracture of a few tensile samples are compared with the corresponding experimental tests. The comparison reveals the higher efficiency and accuracy of the current approach. Therefore, it is concluded that the new presented method is a reliable approach to achieve the Lemaitre’s ductile damage parameter and predict the damage evolution behavior of ductile materials.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"9 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142144331","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}
Investigating the brittleness characteristics and damage evolution of deep rock masses under hydromechanical coupling has important significance. The variations in mechanical properties and brittleness characteristics of sandstone under different confining pressures and pore pressures were studied. Based on the stress threshold evolution and energy conversion analysis of the full stress-strain behavior characteristics of the rock, the new brittleness evaluation indexes were proposed, which effectively described the rock brittle failure mode and verified the reliability and applicability of the brittleness index. Additionally, from the perspective of rock pore micro-elements and the growth of matrix particle defects, the strain statistical damage theory was introduced to establish a rock statistical damage evolution model capable of accounting for the influence of pore pressure, thereby effectively capturing the nonlinear soft hardening of porous rocks under hydraulic coupling conditions. The correlation between rock brittleness and rock soft and hardening characteristics was reasonably expressed by constructing a new brittleness evaluation index, discovered from the relationship between rock damage parameters and brittleness characteristics. Eventually, based on the proposed nonlinear expression and statistical damage evolution model, the development trend of sandstone lateral strain is predicted well. The theoretical validation has good consistency with the experimental data and illustrates the rationality of the model.
{"title":"Brittleness evaluation and damage evolution of sandstone under hydromechanical coupling","authors":"Kuan Zhang, Wei Wang, Yajun Cao, Shifan Liu, Xuelei Duan","doi":"10.1177/10567895241277224","DOIUrl":"https://doi.org/10.1177/10567895241277224","url":null,"abstract":"Investigating the brittleness characteristics and damage evolution of deep rock masses under hydromechanical coupling has important significance. The variations in mechanical properties and brittleness characteristics of sandstone under different confining pressures and pore pressures were studied. Based on the stress threshold evolution and energy conversion analysis of the full stress-strain behavior characteristics of the rock, the new brittleness evaluation indexes were proposed, which effectively described the rock brittle failure mode and verified the reliability and applicability of the brittleness index. Additionally, from the perspective of rock pore micro-elements and the growth of matrix particle defects, the strain statistical damage theory was introduced to establish a rock statistical damage evolution model capable of accounting for the influence of pore pressure, thereby effectively capturing the nonlinear soft hardening of porous rocks under hydraulic coupling conditions. The correlation between rock brittleness and rock soft and hardening characteristics was reasonably expressed by constructing a new brittleness evaluation index, discovered from the relationship between rock damage parameters and brittleness characteristics. Eventually, based on the proposed nonlinear expression and statistical damage evolution model, the development trend of sandstone lateral strain is predicted well. The theoretical validation has good consistency with the experimental data and illustrates the rationality of the model.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"381 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142138194","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}
The mechanical behavior under static and fatigue loading induced by mechanical forces is examined in this article through the utilization of a non-destructive methodology. However, it is worth noting that the dynamics of elastic waves become notably more intricate when dealing with composite materials. In order to provide a comprehensive description of the green flax/epoxy system, a crucial component of this study involves the computation of guided wave dispersion curves within the test samples. By evaluating the longitudinal and shear modulus under varying stress conditions, the propagation of high-frequency ultrasonic waves, which serves as a dynamic mechanical deformation, can be leveraged to facilitate the comparison of both mechanical and ultrasonic data. The significant changes occurring during the aging process are closely associated with variations in velocity throughout the loading period. The wavelet transformation of all acquired ultrasonic echoes yields the experimental transfer function, thereby enhancing our understanding of the subject matter.
{"title":"Behavior monitoring of flax fiber reinforced composites by guided waves","authors":"Driss Hana, Beyaoui Moez, Kesentini Zeineb, El Mahi Abderrahim, Bentahar Mourad, Haddar Mohamed, Deba Datta Mandal","doi":"10.1177/10567895241275365","DOIUrl":"https://doi.org/10.1177/10567895241275365","url":null,"abstract":"The mechanical behavior under static and fatigue loading induced by mechanical forces is examined in this article through the utilization of a non-destructive methodology. However, it is worth noting that the dynamics of elastic waves become notably more intricate when dealing with composite materials. In order to provide a comprehensive description of the green flax/epoxy system, a crucial component of this study involves the computation of guided wave dispersion curves within the test samples. By evaluating the longitudinal and shear modulus under varying stress conditions, the propagation of high-frequency ultrasonic waves, which serves as a dynamic mechanical deformation, can be leveraged to facilitate the comparison of both mechanical and ultrasonic data. The significant changes occurring during the aging process are closely associated with variations in velocity throughout the loading period. The wavelet transformation of all acquired ultrasonic echoes yields the experimental transfer function, thereby enhancing our understanding of the subject matter.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"7 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142101002","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}
The vast changes in temperature are what produce thermal fatigue damage to concrete. In this study, concrete specimens in three different categories—C20, C40, and C60—are tested for thermal fatigue at temperatures ranging from 10°C to 80°C in an atmosphere with constant relative humidity. Utilizing ultrasonic nondestructive testing, the elastic modulus of concrete is determined. After thermal cycling, the mass reduction and appearance of samples are also recorded. The results demonstrate that the degrading effects of thermal fatigue clearly influence concrete. As the thermal cycle lengthens, the elastic modulus of concrete rapidly decreases, and C60 concrete experiences a greater reduction in elastic modulus than C20 concrete. With thermal cycles, the damage factor increases and the ultrasonic wave velocity steadily decreases, suggesting a propagation of the concrete’s interior microcracks. Additionally, the micromechanical thermal fatigue model is developed based on the experimental results. The ability to simulate and describe the physical behavior of concrete under thermal fatigue stress on the microscale is validated by the proposed micromechanical damage model.
{"title":"Experimental investigations and micromechanical thermal fatigue models of concrete","authors":"Haiyou Peng, Qiang Xie, Chong Wang, Shuai Zhou, J Woody Ju","doi":"10.1177/10567895241278666","DOIUrl":"https://doi.org/10.1177/10567895241278666","url":null,"abstract":"The vast changes in temperature are what produce thermal fatigue damage to concrete. In this study, concrete specimens in three different categories—C20, C40, and C60—are tested for thermal fatigue at temperatures ranging from 10°C to 80°C in an atmosphere with constant relative humidity. Utilizing ultrasonic nondestructive testing, the elastic modulus of concrete is determined. After thermal cycling, the mass reduction and appearance of samples are also recorded. The results demonstrate that the degrading effects of thermal fatigue clearly influence concrete. As the thermal cycle lengthens, the elastic modulus of concrete rapidly decreases, and C60 concrete experiences a greater reduction in elastic modulus than C20 concrete. With thermal cycles, the damage factor increases and the ultrasonic wave velocity steadily decreases, suggesting a propagation of the concrete’s interior microcracks. Additionally, the micromechanical thermal fatigue model is developed based on the experimental results. The ability to simulate and describe the physical behavior of concrete under thermal fatigue stress on the microscale is validated by the proposed micromechanical damage model.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"146 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142101001","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 : 2024-08-22DOI: 10.1177/10567895241277217
Cheng Hongming, Yang Xiaobin, Lu Jie, Dong Chuanlong, Lan Yongqing
The nonlinearity of the constitutive relation for rocks becomes more prominent with a more complex physical-mechanical environment and mechanical behavior. The accurate establishment of the constitutive relation affects the determination of rock deformation and damage state from physical features. In this study, a novel statistical damage constitutive model for rocks is proposed based on quantified energy conversion. The novelty of the model is that the nature of rock damage before and after damage stress is considered. In the constitutive model, the evolution characteristics of energy conversion show a five-stage evolution with a ‘spoon’ form and correspond to the rock deformation and damage process, which can be fitted with the modified GaussAmp function; the damage variable is deduced by the Weibull distribution with energy conversion as the distribution variable, which presents a monotonic decrease caused by initial defects before the σcd and shows a ‘S’ shape caused by nascent cracks after the σcd. Furthermore, triaxial test data of three types of rocks under different confining pressures were used to verify the proposed model, and the results were in good agreement with the test data in most cases. The characteristics of the crack closure stage, peak stress, residual strength, and stress drop process are controlled by the model parameters, which can be determined using experimental data. As these parameters definitely have a physical meaning and a relation to the confining pressure, the proposed model has the potential to be used in rock engineering.
{"title":"Statistical damage constitutive model based on energy conversion for rocks","authors":"Cheng Hongming, Yang Xiaobin, Lu Jie, Dong Chuanlong, Lan Yongqing","doi":"10.1177/10567895241277217","DOIUrl":"https://doi.org/10.1177/10567895241277217","url":null,"abstract":"The nonlinearity of the constitutive relation for rocks becomes more prominent with a more complex physical-mechanical environment and mechanical behavior. The accurate establishment of the constitutive relation affects the determination of rock deformation and damage state from physical features. In this study, a novel statistical damage constitutive model for rocks is proposed based on quantified energy conversion. The novelty of the model is that the nature of rock damage before and after damage stress is considered. In the constitutive model, the evolution characteristics of energy conversion show a five-stage evolution with a ‘spoon’ form and correspond to the rock deformation and damage process, which can be fitted with the modified GaussAmp function; the damage variable is deduced by the Weibull distribution with energy conversion as the distribution variable, which presents a monotonic decrease caused by initial defects before the σ<jats:sub>cd</jats:sub> and shows a ‘S’ shape caused by nascent cracks after the σ<jats:sub>cd</jats:sub>. Furthermore, triaxial test data of three types of rocks under different confining pressures were used to verify the proposed model, and the results were in good agreement with the test data in most cases. The characteristics of the crack closure stage, peak stress, residual strength, and stress drop process are controlled by the model parameters, which can be determined using experimental data. As these parameters definitely have a physical meaning and a relation to the confining pressure, the proposed model has the potential to be used in rock engineering.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"145 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142042493","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 : 2024-08-22DOI: 10.1177/10567895241275380
Xunjian Hu, Dongdong Ma, Ni Xie, Qizhi Zhu, Haibo Hu, Xiaonan Gong
Enhancing our understanding of the damage evolution in pre-heated rock is essential for safer design practices. Accordingly, a mechanical damage variable that accurately depicts the initial damage recovery process was proposed. Subsequently, a damage constitutive model is developed based on the generalized equivalent strain principle, enabling the identification of the initial nonlinear characteristics exhibited in the stress-strain curve. By integrating the above constitutive model with a statistical damage model that considers the residual strength based on the Weibull distribution, a comprehensive piecewise damage constitutive model specifically designed for pre-heated rocks was derived. The model consists of eight parameters, which can be directly determined through experimental results or readily obtained by fitting of the stress-strain data. A comparison of experimental data from multiple pre-heated rock types subjected to uniaxial compression is performed to validate the proposed model, revealing a strong agreement between the theoretical and experimental results. The comparison results demonstrate that the proposed model effectively captures the nonlinearity of the stress-strain curve throughout various stages, including the initial compaction, linear elastic, and strain-hardening stages before reaching the peak stress, as well as the subsequent strain-softening and residual stages. Furthermore, the proposed damage constitutive model elucidates the influence of temperature on crucial factors such as the elastic modulus, peak stress, residual strength, and stress-strain curve of pre-heated rocks, thereby enhancing its applicability in the design of deep underground rock projects.
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