Compressive mechanical properties and pore-fissure characteristics of coal rock specimens from three stably developed coal seams M 1 , M 8 and M 12 in the Xinjiang Yili Basin were investigated in detail by a series of tests. The results show that the compressive mechanical properties of coal rocks in the Yili Basin are significantly affected by the confining pressure. The peak axial stress increases and the peak modulus of elasticity decreases as the confining pressure increases. The peak axial strain increases and then remains constant, while the peak circumferential strain and peak volumetric strain increase and then decrease. The confining pressure has almost no effect on Poisson’s ratio of the coal rock specimens. In addition, electron microscopy tests show that the microscopic fraction of the coal rock specimens is predominantly vitrinite, accounting for 83.1%-89.2%, while the percentage of the inertinite group is relatively small, at 10.3%-16.1%. The throat radius of the coal rock is mainly concentrated around 1-2 µ m, while the pore radius of the coal rock is between 150-200 µ m. The coal rock has an overall fine throat and low permeability, and the coal rock in the Yili Basin of Xinjiang is a typical low-permeability coal rock.
{"title":"Study of triaxial compression mechanical properties and pore-fracture characteristics of coal rocks in the Yili Basin, Xinjiang","authors":"Cheng Shen, Ling Yue, Yang Liu","doi":"10.15632/jtam-pl/159670","DOIUrl":"https://doi.org/10.15632/jtam-pl/159670","url":null,"abstract":"Compressive mechanical properties and pore-fissure characteristics of coal rock specimens from three stably developed coal seams M 1 , M 8 and M 12 in the Xinjiang Yili Basin were investigated in detail by a series of tests. The results show that the compressive mechanical properties of coal rocks in the Yili Basin are significantly affected by the confining pressure. The peak axial stress increases and the peak modulus of elasticity decreases as the confining pressure increases. The peak axial strain increases and then remains constant, while the peak circumferential strain and peak volumetric strain increase and then decrease. The confining pressure has almost no effect on Poisson’s ratio of the coal rock specimens. In addition, electron microscopy tests show that the microscopic fraction of the coal rock specimens is predominantly vitrinite, accounting for 83.1%-89.2%, while the percentage of the inertinite group is relatively small, at 10.3%-16.1%. The throat radius of the coal rock is mainly concentrated around 1-2 µ m, while the pore radius of the coal rock is between 150-200 µ m. The coal rock has an overall fine throat and low permeability, and the coal rock in the Yili Basin of Xinjiang is a typical low-permeability coal rock.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"31 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74343089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Considering vibration of centrifugal air-conditioning chillers at working conditions of 300Hz and 386Hz, a vibration reduction method for centrifugal air-conditioning chillers based on particle damping is proposed. Firstly, the vibration transfer path of the chillers is determined based on dynamic characteristics analysis of the chillers. Secondly, the vibration sensitive area of the compressor is determined by finite element analysis. Then the energy dissipation is calculated by the discrete element method (DEM) to determine the optimal installation scheme of the damper. Finally, the vibration reduction effect of the chillers after arranging the damper is verified by experiments.
{"title":"Research on optimal design of vibration reduction of centrifugal air conditioning chiller based on particle damping","authors":"Wangqiang Xiao, Jinsong Shi, Hui Chen, Hua Liu","doi":"10.15632/jtam-pl/158842","DOIUrl":"https://doi.org/10.15632/jtam-pl/158842","url":null,"abstract":"Considering vibration of centrifugal air-conditioning chillers at working conditions of 300Hz and 386Hz, a vibration reduction method for centrifugal air-conditioning chillers based on particle damping is proposed. Firstly, the vibration transfer path of the chillers is determined based on dynamic characteristics analysis of the chillers. Secondly, the vibration sensitive area of the compressor is determined by finite element analysis. Then the energy dissipation is calculated by the discrete element method (DEM) to determine the optimal installation scheme of the damper. Finally, the vibration reduction effect of the chillers after arranging the damper is verified by experiments.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"119 3 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80018217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the process of reliability modeling and design of a wind power gearbox, the influence of failure correlation of system components and random dynamic loads can not be ignored. In this paper, taking the output power of each shaft of the gearbox as the starting point, distribution parameters of stress and strength for critical failed components (gear and bearing) of the gearbox are solved. After normalization of these parameters, and when there is a linear correlation between the loads of each component, finally, the time-varying reliability related to failure correlation is calculated based on a full probability differential method by using the stress strength interference theory at the system level, and the results are verified by the Monte-Carlo simulation method. It is found that the failure correlation caused by the external dynamic loads between components can significantly reduce reliability of the gearbox system. The stronger the correlation, the lower the reliability of the gearbox system. Meanwhile, the time-varying reliability conforms to characteristics of the “failure bathtub curve” of typical mechanical products. This paper can lay a foundation for the time-varying reliability optimization design and structural robustness design of the wind power gearbox.
{"title":"Research on time-varying reliability of wind power gearbox with failure correlation","authors":"Mingliang Zheng","doi":"10.15632/jtam-pl/158008","DOIUrl":"https://doi.org/10.15632/jtam-pl/158008","url":null,"abstract":"In the process of reliability modeling and design of a wind power gearbox, the influence of failure correlation of system components and random dynamic loads can not be ignored. In this paper, taking the output power of each shaft of the gearbox as the starting point, distribution parameters of stress and strength for critical failed components (gear and bearing) of the gearbox are solved. After normalization of these parameters, and when there is a linear correlation between the loads of each component, finally, the time-varying reliability related to failure correlation is calculated based on a full probability differential method by using the stress strength interference theory at the system level, and the results are verified by the Monte-Carlo simulation method. It is found that the failure correlation caused by the external dynamic loads between components can significantly reduce reliability of the gearbox system. The stronger the correlation, the lower the reliability of the gearbox system. Meanwhile, the time-varying reliability conforms to characteristics of the “failure bathtub curve” of typical mechanical products. This paper can lay a foundation for the time-varying reliability optimization design and structural robustness design of the wind power gearbox.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"13 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83693593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shuang-quan Guo, Delin Xu, Kaiguang Shang, Shuo Yang, Di Wang, Geng Li, B. Zheng, Yong Jiao
The progressive collapse of a space grid structure which has a large number of members and a large span is the focus of current research. Before the progressive collapse of the structure, there is a problem of instability of the members. In this paper, dynamic nonlinear analysis of a super-long span latticed steel arch structure is carried out to study its progressive collapse process using a Kinematic Hardening Plasticity constitutive model compiled by Vumat material subprogram in Abaqus, which takes into account instability of the members. Differences in the dynamic response process of the structure at the collapse moment and the failure sequence of the members using the member stability model and the material failure constitutive model are compared. Compared with the material failure constitutive model, when the member stability constitutive model is used, the proportion of compressive buckling members in the structural failure is higher, and the bearing capacity of the structure is lower when the initial failure occurs. The structure suffers from localized member compressive failure rather than material yielding, which leads to the progressive collapse of the structure.
{"title":"Analysis of progressive collapse of a super-long span latticed steel arch structure","authors":"Shuang-quan Guo, Delin Xu, Kaiguang Shang, Shuo Yang, Di Wang, Geng Li, B. Zheng, Yong Jiao","doi":"10.15632/jtam-pl/157311","DOIUrl":"https://doi.org/10.15632/jtam-pl/157311","url":null,"abstract":"The progressive collapse of a space grid structure which has a large number of members and a large span is the focus of current research. Before the progressive collapse of the structure, there is a problem of instability of the members. In this paper, dynamic nonlinear analysis of a super-long span latticed steel arch structure is carried out to study its progressive collapse process using a Kinematic Hardening Plasticity constitutive model compiled by Vumat material subprogram in Abaqus, which takes into account instability of the members. Differences in the dynamic response process of the structure at the collapse moment and the failure sequence of the members using the member stability model and the material failure constitutive model are compared. Compared with the material failure constitutive model, when the member stability constitutive model is used, the proportion of compressive buckling members in the structural failure is higher, and the bearing capacity of the structure is lower when the initial failure occurs. The structure suffers from localized member compressive failure rather than material yielding, which leads to the progressive collapse of the structure.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"115 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80581773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A theoretical method for analyzing the initial yield of a typical bending-dominant periodic lattice (BDPL) is established. Based on the principle of strain energy equivalence, the macroscopic effective stiffnesses of lattices are calculated. An empirical formula is employed to consider the contributions of both the axial force and bending moment. The initial yield surface of BDPL can be figured out by comparing the effective stress of each strut to the yield strength of the matrix material. The method is applicable to various BDPLs, which we believe is a helpful extension to the method for lattices comprising axial-tension bars in the literature.
{"title":"On the yield surface of a typical bending-dominant periodic lattice metamaterial","authors":"Yongjun Wang, Jinxing Liu","doi":"10.15632/jtam-pl/158574","DOIUrl":"https://doi.org/10.15632/jtam-pl/158574","url":null,"abstract":"A theoretical method for analyzing the initial yield of a typical bending-dominant periodic lattice (BDPL) is established. Based on the principle of strain energy equivalence, the macroscopic effective stiffnesses of lattices are calculated. An empirical formula is employed to consider the contributions of both the axial force and bending moment. The initial yield surface of BDPL can be figured out by comparing the effective stress of each strut to the yield strength of the matrix material. The method is applicable to various BDPLs, which we believe is a helpful extension to the method for lattices comprising axial-tension bars in the literature.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"24 Sup9 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84425825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To explore the mechanical response of anchored rock mass with an interaction of fatigue and creep, this paper selects the fatigue amplitude and fatigue frequency as influencing factors to carry out a fatigue-creep experiment of the anchored rock mass. Based on fractional order theory and binary perturbation theory, a new fractional order creep model is constructed. The results show that compared with the Burgers model, the newly proposed creep model can better describe the whole process of creep deformation of the anchored jointed rock mass under fatigue loading.
{"title":"Research on creep-fatigue model of anchored jointed rock mass","authors":"Yang Song, B. Fan, Yongqi Li, Heping Wang","doi":"10.15632/jtam-pl/157510","DOIUrl":"https://doi.org/10.15632/jtam-pl/157510","url":null,"abstract":"To explore the mechanical response of anchored rock mass with an interaction of fatigue and creep, this paper selects the fatigue amplitude and fatigue frequency as influencing factors to carry out a fatigue-creep experiment of the anchored rock mass. Based on fractional order theory and binary perturbation theory, a new fractional order creep model is constructed. The results show that compared with the Burgers model, the newly proposed creep model can better describe the whole process of creep deformation of the anchored jointed rock mass under fatigue loading.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"113 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80582778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A novel analytical model to predict fracture resistance of a quasi-brittle material, like wood, is presented. The model is based on a scaling parameter introduced into the non-local fracture theory to take into account the specimen size effect on the development of the damage zone. An expression for length of the critical process zone, which can be used in damage tolerant design of wooden structures is derived from this theory. The model is validated with mixed-mode bending tests. A numerical analysis using cohesive elements is performed to understand the role of specimen size in the development of the damage zone. The analytical predictions of the fracture resistance and the critical process zone length for wood are compared with numerical results and experimental data available in the literature.
{"title":"Predictions of fracture resistance of spruce wood under mixed mode loading using non-local fracture theory and numerical modelling","authors":"M. Romanowicz","doi":"10.15632/jtam-pl/158823","DOIUrl":"https://doi.org/10.15632/jtam-pl/158823","url":null,"abstract":"A novel analytical model to predict fracture resistance of a quasi-brittle material, like wood, is presented. The model is based on a scaling parameter introduced into the non-local fracture theory to take into account the specimen size effect on the development of the damage zone. An expression for length of the critical process zone, which can be used in damage tolerant design of wooden structures is derived from this theory. The model is validated with mixed-mode bending tests. A numerical analysis using cohesive elements is performed to understand the role of specimen size in the development of the damage zone. The analytical predictions of the fracture resistance and the critical process zone length for wood are compared with numerical results and experimental data available in the literature.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"1 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88622685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article presents an analysis of vibration evolution of a ball bearing without the cage. A vibration model in which time-varying displacement, time-varying stiffness, contact force and collision force are comprehensively considered, is proposed. On this basis, the law of motion of the bearing is studied. It is shown that a variable-diameter raceway affects the radius of curvature, which effects the dispersion of rolling elements. The damaged variable-diameter raceway leads to discrete failure, contact force and collision force of rolling elements, which are main reasons that cause vibration mutation. The bearing motion changes from quasi-periodic to chaotic motion.
{"title":"Research on vibration evolution of a ball bearing without the cage under local variable-diameter raceway damage","authors":"Enwen Zhou, Yanling Zhao, Huanqing Zhang","doi":"10.15632/jtam-pl/157462","DOIUrl":"https://doi.org/10.15632/jtam-pl/157462","url":null,"abstract":"This article presents an analysis of vibration evolution of a ball bearing without the cage. A vibration model in which time-varying displacement, time-varying stiffness, contact force and collision force are comprehensively considered, is proposed. On this basis, the law of motion of the bearing is studied. It is shown that a variable-diameter raceway affects the radius of curvature, which effects the dispersion of rolling elements. The damaged variable-diameter raceway leads to discrete failure, contact force and collision force of rolling elements, which are main reasons that cause vibration mutation. The bearing motion changes from quasi-periodic to chaotic motion.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"112 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80800739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Analytical study on the cutting force and residual stress in whirlwind milling of a large screw","authors":"Qin Guo, Yulin Wang, Bin Zhou","doi":"10.15632/jtam-pl/157479","DOIUrl":"https://doi.org/10.15632/jtam-pl/157479","url":null,"abstract":"","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"26 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82246304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Structural components are often operated under combined stress conditions (primary and secondary stresses), but the stress levels generated by residual stress (or secondary stress) is hardly ever evaluated. Hence, stress intensity factors at the crack tips of a compact tension (CT) specimen under a pre-compressed load condition are analyzed using the finite element method. Then, the average residual stress intensity factor is calculated and analyzed. As the crack length a 0 /W increases, the average residual stresses σ ave /σ 0 grows under the same pre-compression load. σ ave /σ 0 increases rapidly at a low range of the pre-compression load but tends to a constant in a high range of the load. The distribution of the average residual stress intensity factors K ave and σ ave /σ 0 of the CT specimen with same crack length under different pre-compression loads have the same tendency. Additionally, the distribution of K ave and K FEM under different pre-compression loads are also similar. Nevertheless, K ave estimated by the average residual stress is too conservative and not accurate, and the method is complex, which depends on the analysis of simulation. Therefore, a simple method for calculating Mode I stress intensity factor K for this model is presented. A group of examples is presented to verify the accuracy of the method.
{"title":"Study on the stress intensity factor of a compact specimen under the pre-compressed load condition","authors":"Dongquan Wu, Zixiang Liu, Dinghe Li, Zhiqiang Zhang, Jianguo Chen","doi":"10.15632/jtam-pl/157556","DOIUrl":"https://doi.org/10.15632/jtam-pl/157556","url":null,"abstract":"Structural components are often operated under combined stress conditions (primary and secondary stresses), but the stress levels generated by residual stress (or secondary stress) is hardly ever evaluated. Hence, stress intensity factors at the crack tips of a compact tension (CT) specimen under a pre-compressed load condition are analyzed using the finite element method. Then, the average residual stress intensity factor is calculated and analyzed. As the crack length a 0 /W increases, the average residual stresses σ ave /σ 0 grows under the same pre-compression load. σ ave /σ 0 increases rapidly at a low range of the pre-compression load but tends to a constant in a high range of the load. The distribution of the average residual stress intensity factors K ave and σ ave /σ 0 of the CT specimen with same crack length under different pre-compression loads have the same tendency. Additionally, the distribution of K ave and K FEM under different pre-compression loads are also similar. Nevertheless, K ave estimated by the average residual stress is too conservative and not accurate, and the method is complex, which depends on the analysis of simulation. Therefore, a simple method for calculating Mode I stress intensity factor K for this model is presented. A group of examples is presented to verify the accuracy of the method.","PeriodicalId":49980,"journal":{"name":"Journal of Theoretical and Applied Mechanics","volume":"29 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74655668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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