The strength and failure characteristics of most natural rock mass are influenced by discontinues such as fissures, joints, and weak surfaces. In the present study, the strength and failure behavior of ubiquitous- joi...The strength and failure characteristics of most natural rock mass are influenced by discontinues such as fissures, joints, and weak surfaces. In the present study, the strength and failure behavior of ubiquitous- joint rock-l!ke specimens under uniaxial loading have been investigated by DIC （digital image correlation） and discrete element numerical method （PFC2D）. The results are obtained. Firstly, the UCSJ of spec- imens with γ= 15° or 30° shows similar tendency while α goes from 0° to 75°. With γ= 45° or 60°, the UCSJ of specimens increases when α goes from 0° to 30° and decreases after α goes beyond 30°. With γ=75°, the peak UCSJ value is reached when α=0°. The UCSJ value shows an increasing trend when α goes from 60° to 75°. Secondly, the ubiquitous-joint specimens present different failure modes for various levels of α and γ（β-α）. Based on the experimental results, the failure mode of ubiquitous-joint specimens can be classified into three categories： stepped path failure, failure through parallel plane, and failure through cross plane.展开更多
Tungsten inert gas （TIG） welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG...Tungsten inert gas （TIG） welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG joints represents an important issue in their manufacturing and strength evaluation. Experimental and numerical simulation methods were used to investigate the effects of weld toe shape and weld toe position on the tensile behavior and mechanical properties of these joints. The simulation results indicated that the relative difference in elongation could be as large as 96.9% caused by the difference in weld toe shape. The joints with weld toes located in the weld metal or in the partially melted zone （PMZ） exhibited larger elongation than joints with weld toes located at the juncture of the weld metal and the PMZ.展开更多
This work is dedicated to the experimental study of the shear properties of three-dimensional reinforced composites taking into account their structural features,in Iosipescu tests.Shear strains have been determined u...This work is dedicated to the experimental study of the shear properties of three-dimensional reinforced composites taking into account their structural features,in Iosipescu tests.Shear strains have been determined using Vic-3D non-contact three-dimensional digital optical system.The evolution of inhomogeneous strain fields on the surface of composite specimens of the structure under study has been analyzed.The variants of strain averaging in the specimen working area have been analyzed using Vic-3D tools.AMSY-6 acoustic emission system has been used to assess the structural integrity of composite materials under loading.展开更多
A novel separation identification strategy for the neural fuzzy Wiener–Hammerstein system using hybrid signals is developed in this study.The Wiener–Hammerstein system is described by a model consisting of two linea...A novel separation identification strategy for the neural fuzzy Wiener–Hammerstein system using hybrid signals is developed in this study.The Wiener–Hammerstein system is described by a model consisting of two linear dynamic elements with a nonlinear static element in between.The static nonlinear element is modeled by a neural fuzzy network(NFN)and the two linear dynamic elements are modeled by an autoregressive exogenous(ARX)model and an autoregressive(AR)model,separately.When the system input is Gaussian signals,the correlation technique is used to decouple the identification of the two linear dynamic elements from the nonlinear element.First,based on the input and output of Gaussian signals,the correlation analysis technique is used to identify the input linear element and output linear element,which addresses the problem that the intermediate variable information cannot be measured in the identified Wiener–Hammerstein system.Then,a zero-pole match method is adopted to separate the parameters of the two linear elements.Furthermore,the recursive least-squares technique is used to identify the nonlinear element based on the input and output of random signals,which avoids the impact of output noise.The feasibility of the presented identification technique is demonstrated by an illustrative simulation example and a practical nonlinear process.Simulation results show that the proposed strategy can obtain higher identification precision than existing identification algorithms.展开更多
基金funding from Project (Nos.51474249 and 51404179) supported by National Natural Science Foundation of ChinaProject Supported by Innovation Driven Plan of Central South University of China (No.2016CX019)Project (No. SKLGDUEK1405) funded by the Open Projects of State Key Laboratory for Geo-mechanics and Deep Underground Engineering of China University of Mining and Technology,in China
文摘The strength and failure characteristics of most natural rock mass are influenced by discontinues such as fissures, joints, and weak surfaces. In the present study, the strength and failure behavior of ubiquitous- joint rock-l!ke specimens under uniaxial loading have been investigated by DIC （digital image correlation） and discrete element numerical method （PFC2D）. The results are obtained. Firstly, the UCSJ of spec- imens with γ= 15° or 30° shows similar tendency while α goes from 0° to 75°. With γ= 45° or 60°, the UCSJ of specimens increases when α goes from 0° to 30° and decreases after α goes beyond 30°. With γ=75°, the peak UCSJ value is reached when α=0°. The UCSJ value shows an increasing trend when α goes from 60° to 75°. Secondly, the ubiquitous-joint specimens present different failure modes for various levels of α and γ（β-α）. Based on the experimental results, the failure mode of ubiquitous-joint specimens can be classified into three categories： stepped path failure, failure through parallel plane, and failure through cross plane.
文摘Tungsten inert gas （TIG） welded joints for 2219-T87 aluminum alloy are often used in the fuel tanks of large launch vehicles. Because of the massive loads these vehicles carry, dealing with weld reinforcement on TIG joints represents an important issue in their manufacturing and strength evaluation. Experimental and numerical simulation methods were used to investigate the effects of weld toe shape and weld toe position on the tensile behavior and mechanical properties of these joints. The simulation results indicated that the relative difference in elongation could be as large as 96.9% caused by the difference in weld toe shape. The joints with weld toes located in the weld metal or in the partially melted zone （PMZ） exhibited larger elongation than joints with weld toes located at the juncture of the weld metal and the PMZ.
基金the Russian Foundation for Basic Research within the Projects(Grants 19-31-90148 and 18-01-00763)The experimental studies of shear material properties were conducted within the State Assignment of the Ministry of Education and Science of the Russian Federation(9.7529.2017/9.10).
文摘This work is dedicated to the experimental study of the shear properties of three-dimensional reinforced composites taking into account their structural features,in Iosipescu tests.Shear strains have been determined using Vic-3D non-contact three-dimensional digital optical system.The evolution of inhomogeneous strain fields on the surface of composite specimens of the structure under study has been analyzed.The variants of strain averaging in the specimen working area have been analyzed using Vic-3D tools.AMSY-6 acoustic emission system has been used to assess the structural integrity of composite materials under loading.
基金Project supported by the National Natural Science Foundation of China(No.62003151)the Changzhou Science and Technology Bureau(Nos.CJ20220065 and CM20223015)+1 种基金the Qinglan Project of Jiangsu Province,China(No.2022[29])the Zhongwu Youth Innovative Talents Support Program of Jiangsu University of Technology,China(No.202102003)。
文摘A novel separation identification strategy for the neural fuzzy Wiener–Hammerstein system using hybrid signals is developed in this study.The Wiener–Hammerstein system is described by a model consisting of two linear dynamic elements with a nonlinear static element in between.The static nonlinear element is modeled by a neural fuzzy network(NFN)and the two linear dynamic elements are modeled by an autoregressive exogenous(ARX)model and an autoregressive(AR)model,separately.When the system input is Gaussian signals,the correlation technique is used to decouple the identification of the two linear dynamic elements from the nonlinear element.First,based on the input and output of Gaussian signals,the correlation analysis technique is used to identify the input linear element and output linear element,which addresses the problem that the intermediate variable information cannot be measured in the identified Wiener–Hammerstein system.Then,a zero-pole match method is adopted to separate the parameters of the two linear elements.Furthermore,the recursive least-squares technique is used to identify the nonlinear element based on the input and output of random signals,which avoids the impact of output noise.The feasibility of the presented identification technique is demonstrated by an illustrative simulation example and a practical nonlinear process.Simulation results show that the proposed strategy can obtain higher identification precision than existing identification algorithms.
