期刊文献+
共找到14篇文章
< 1 >
每页显示 20 50 100
Retrieval of the effective constitutive parameters from metamaterial absorbers
1
作者 Shaomei Shi Xiaojing Qiao +1 位作者 Shuo Liu Weinan Liu 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第11期590-596,共7页
The equivalent medium theory of metamaterials provides a way to obtain their effective constitutive parameters.However,because of its non-reciprocity,the complexity of the electromagnetic coupling,and a metallic botto... The equivalent medium theory of metamaterials provides a way to obtain their effective constitutive parameters.However,because of its non-reciprocity,the complexity of the electromagnetic coupling,and a metallic bottom layer,it has been challenging to retrieve them from a metamaterial absorber.In this paper,we propose a method without any approximation to obtain them,in which the non-reciprocity and the strong electromagnetic coupling are included.Compared with the three methods such as symmetric metamaterial method,asymmetric metamaterial method and metasurface method,our method can reveal the metamaterial absorber’s electrical and magnetic resonance and show its electromagnetic coupling coefficients.To deal with a metamaterial absorber with a metallic bottom layer,four corners of the metallic bottom layer in the unit cell are removed,making it possible to retrieve the electromagnetic parameters.Surprisingly,these results show that the metamaterial absorber with a metallic bottom layer in our example operates in a negative refraction state at the half absorption frequencies,which helps further understand the absorbing mechanism of these metamaterial absorbers. 展开更多
关键词 effective constitutive parameters metamaterial absorber negative refraction
下载PDF
Identification of constitutive model parameters for nickel aluminum bronze in machining 被引量:2
2
作者 付中涛 杨文玉 +2 位作者 曾思琪 郭步鹏 胡树兵 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2016年第4期1105-1111,共7页
The material of nickel aluminum bronze (NAB) presents superior properties such as high strength, excellent wear resistance and stress corrosion resistance and is extensively used for marine propellers. In order to est... The material of nickel aluminum bronze (NAB) presents superior properties such as high strength, excellent wear resistance and stress corrosion resistance and is extensively used for marine propellers. In order to establish the constitutive relation of NAB under high strain rate condition, a new methodology was proposed to accurately identify the constitutive parameters of Johnson?Cook model in machining, combining SHPB tests, predictive cutting force model and orthogonal cutting experiment. Firstly, SHPB tests were carried out to obtain the true stress?strain curves at various temperatures and strain rates. Then, an objective function of the predictive and experimental flow stresses was set up, which put the identified parameters of SHPB tests as the initial value, and utilized the PSO algorithm to identify the constitutive parameters of NAB in machining. Finally, the identified parameters were verified to be sufficiently accurate by comparing the values of cutting forces calculated from the predictive model and FEM simulation. 展开更多
关键词 nickel aluminum bronze constitutive parameter Johnson-Cook model identification method
下载PDF
Inverse identification of constitutive parameters of Ti_2AlNb intermetallic alloys based on cooperative particle swarm optimization 被引量:5
3
作者 Linjiang HE Honghua SU +1 位作者 Jiuhua XU Liang ZHANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2018年第8期1774-1785,共12页
Ti_2AlNb intermetallic alloy is a relatively newly developed high-temperature-resistant structural material, which is expected to replace nickel-based super alloys for thermally and mechanically stressed components in... Ti_2AlNb intermetallic alloy is a relatively newly developed high-temperature-resistant structural material, which is expected to replace nickel-based super alloys for thermally and mechanically stressed components in aeronautic and automotive engines due to its excellent mechanical properties and high strength retention at elevated temperature. The aim of this work is to present a fast and reliable methodology of inverse identification of constitutive model parameters directly from cutting experiments. FE-machining simulations implemented with a modified Johnson-Cook(TANH) constitutive model are performed to establish the robust link between observables and constitutive parameters. A series of orthogonal cutting experiments with varied cutting parameters is carried out to allow an exact comparison to the 2 D FE-simulations. A cooperative particle swarm optimization algorithm is developed and implemented into the Matlab programs to identify the enormous constitutive parameters. Results show that the simulation observables(i.e., cutting forces, chip morphologies, cutting temperature) implemented with the identified optimal material constants have high consistency with those obtained from experiments,which illustrates that the FE-machining models using the identified parameters obtained from the proposed methodology could be predicted in a close agreement to the experiments. Considering the wide range of the applied unknown parameters number, the proposed inverse methodology of identifying constitutive equations shows excellent prospect, and it can be used for other newly developed metal materials. 展开更多
关键词 constitutive parameters Cooperative particle swarmoptimization Finite element modelling Inverse identification Ti2A1Nb intermetallic alloys
原文传递
An inverse strategy to determine constitutive parameters of tubular materials for hydroforming processes
4
作者 Bin ZHANG Benny ENDELT +3 位作者 Lihui LANG Yang ZHAO Shu YAN Karl Brian NIELSEN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2022年第6期379-390,共12页
This paper is to determine the flow stress curve of 5049-O aluminium alloy by a tube hydraulic bulging test with fixed end-conditions. During this test, several tubular specimens are bulged under different internal pr... This paper is to determine the flow stress curve of 5049-O aluminium alloy by a tube hydraulic bulging test with fixed end-conditions. During this test, several tubular specimens are bulged under different internal pressures before their bursting, and the corresponding bulging height and wall thickness at the pole are measured. An inverse strategy is developed to determine the constitutive parameters of tubular materials based on experimental data, which combines the finite element method with gradient-based optimization techniques. In this scheme, the objective function is formulated with the sum of least squares of the error between numerical and experimental data, and finite difference approximation is used to calculate the gradient. The tubular material behavior is assumed to meet the von Mises yield criterion and Hollomon exponential hardening law. Then, constitutive parameters identification is performed by minimization of the objective function. In order to validate the performance of this framework, identified parameters are compared with those obtained by two types of theoretical models, and tensile tests are performed on specimens cut from the same tubes. The comparison shows that this inverse framework is robust and can achieve a more accurate parameter identification by eliminating mechanical and geometrical assumptions in classical theoretical analysis. 展开更多
关键词 Aluminum alloy constitutive parameter Hydraulic bulging test Inverse modelling Tubular material
原文传递
CONSTITUTIVE EQUATION OF A NEW AVIATION LUBRICATING OIL 被引量:6
5
作者 DENG Sier TENG Hongfei +2 位作者 WANG Yanshuang LI Yunfeng YANG Boyuan 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2007年第5期28-31,共4页
The traction of a new aviation lubricating oil was measured on a self-made test rig. The calculating formulae of the rheological parameters of the oil such as Erying stress, limiting shear stress and shear elastic mod... The traction of a new aviation lubricating oil was measured on a self-made test rig. The calculating formulae of the rheological parameters of the oil such as Erying stress, limiting shear stress and shear elastic modulus were obtained under the condition of the high shear strain rate in elastohydrodynamic lubrication(EHL). The constitutive equation of this oil was determined and verified by test. The results of experiments show that the behavior of the new aviation lubricating oil behaves as visco-elastic fluid and the theoretical value agrees fairly well with the measured data, which implies that the constitutive equation of this oil is correct and feasible. 展开更多
关键词 Lubricating oil constitutive equation Rheological parameters Traction
下载PDF
Disturbed state concept as unified constitutive modeling approach 被引量:4
6
作者 Chandrakant S.Desai 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2016年第3期277-293,共17页
A unified constitutive modeling approach is highly desirable to characterize a wide range of engineeringmaterials subjected simultaneously to the effect of a number of factors such as elastic, plastic and creepdeforma... A unified constitutive modeling approach is highly desirable to characterize a wide range of engineeringmaterials subjected simultaneously to the effect of a number of factors such as elastic, plastic and creepdeformations, stress path, volume change, microcracking leading to fracture, failure and softening,stiffening, and mechanical and environmental forces. There are hardly available such unified models. Thedisturbed state concept (DSC) is considered to be a unified approach and is able to provide materialcharacterization for almost all of the above factors. This paper presents a description of the DSC, andstatements for determination of parameters based on triaxial, multiaxial and interface tests. Statementsof DSC and validation at the specimen level and at the boundary value problem levels are also presented.An extensive list of publications by the author and others is provided at the end. The DSC is considered tobe a unique and versatile procedure for modeling behaviors of engineering materials and interfaces. 2016 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. This is an open access article under the CC BY-NC-ND license 展开更多
关键词 Disturbed state concept (DSC)constitutive model parameters Soils Interfaces Validations
下载PDF
Statistical condition assessment of existing structures using virtual work error estimator
7
作者 蔡晶 吴智深 《Journal of Southeast University(English Edition)》 EI CAS 2007年第4期577-582,共6页
A statistical damage detection and condition assessment scheme for existing structures is developed. First a virtual work error estimator is defined to express the discrepancy between a real structure and its analytic... A statistical damage detection and condition assessment scheme for existing structures is developed. First a virtual work error estimator is defined to express the discrepancy between a real structure and its analytical model, with which a system identification algorithm is derived by using the improved Newton method. In order to investigate its properties in the face of measurement errors, the Monte Carlo method is introduced to simulate the measured data. Based on the identified results, their statistical distributions can be assumed, the status of an existing structure can be statistically evaluated by hypothesis tests. A 5-story, two-bay steel frame is used to carry out numerical simulation studies in detail, and the proposed scheme is proved to be effective. 展开更多
关键词 virtual work constitutive parameter parameter estimation hypothesis test
下载PDF
Effect of Alternation of Aging and Seawater Erosion on Properties of Rubber Material Used in Lead Rubber Bearing
8
作者 Yanmin Li Guifeng Zhao +1 位作者 Yuhong Ma Rong Liu 《Journal of Renewable Materials》 SCIE EI 2022年第6期1641-1658,共18页
An artificially accelerated alternation of aging and seawater erosion test of rubber materials used in lead rubber bearing(LRB)was performed,mainly to study the time-varying laws of rubber materials mechanical propert... An artificially accelerated alternation of aging and seawater erosion test of rubber materials used in lead rubber bearing(LRB)was performed,mainly to study the time-varying laws of rubber materials mechanical properties.Time-varying laws of the Mooney–Rivlin and Neo-Hookean constitutive parameters of rubber materials under the alternation of aging and seawater erosion were also analyzed.Results indicate that the rubber material mechanical properties were significantly affected by alternation of aging and seawater erosion.Hardness and elongation stress increased exponentially with test time.And 120 days after the test,the hardness increased by 14%,the maximum percentage increase in stress of 124.76%occurred at 100%constant elongation and the minimum percentage increase in stress of 68.32%occurred at 300%constant elongation;Tensile strength and elongation at break decreased by 44.96%and 53.09%.Besides,constitutive parameters of Mooney–Rivlin and Neo-Hookean all changed greatly with test duration.Finally,time-varying laws of constitutive parameters were verified by comparing the simulated and experimental results of the lead rubber bearing’s stiffness.Research results are of great significance to the seismic performance research and life-cycle performance analysis of offshore traffic engineering such as cross-sea bridges and bridges in the marine environment. 展开更多
关键词 Alternation of aging and seawater erosion lead rubber bearing rubber material properties constitutive parameters time-varying law
下载PDF
An Anisotropic Geomechanical Model for Jointed Rock Masses at Taishan Nuclear Power Station, Southern China 被引量:1
9
作者 ZHENG Wentang CHENG Xiaojiu WANG Huaan 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2013年第3期858-870,共13页
An anisotropic geomechanical model for jointed rock mass is presented. Simultaneously with deriving the orthotropic anisotropy elastic parameters along the positive axis, the equivalent compliance matrix for the defle... An anisotropic geomechanical model for jointed rock mass is presented. Simultaneously with deriving the orthotropic anisotropy elastic parameters along the positive axis, the equivalent compliance matrix for the deflection axis orthotropic anisotropy was derived through a three- dimensional coordinate transformation. In addition, Singh's analysis of the stress concentration effects of intermittent joints was adopted, based on two groups of intermittent joints and a set of cross- cutting joints in the jointed rock mass. The stress concentration effects caused by intermittent joints and the coupling effect of cross-cutting joints along the deflection-axis are also considered. The proposed anisotropic mechanics parameters method is applied to determine the deformation parameters of jointed granite at the Taishan Nuclear Power Station. Combined with the deterministic mechanical parameters of rock blocks and joints, the deformation parameters and their variability in jointed rock masses are estimated quantitatively. The computed results show that jointed granite at the Taishan Nuclear Power Station exhibits typical anisotropic mechanical characteristics; the elastic moduli in the two horizontal directions were similar, but the elastic modulus in the vertical direction was much greater. Jointed rock elastic moduli in the two horizontal and vertical directions were respectively about 24% and 37% of the core of rock, showing weakly orthotropic anisotropy; the ratio of elastic moduli in the vertical and horizontal directions was 1.53, clearly indicating the transversely isotropic rock mass mechanical characteristics. The method can be popularized to solve other rock mechanics problems in nuclear power engineering. 展开更多
关键词 Nuclear Power Station jointed rock masses anisotropic characteristics constitutive model mechanical parameters
下载PDF
Nonsingularity in two-dimensional cylindrical invisible cloaks
10
作者 王新华 屈绍波 +8 位作者 夏颂 王斌科 徐卓 马华 王甲富 顾超 吴翔 鲁磊 周航 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第6期293-296,共4页
The method of designing electromagnetic invisible cloaks is usually based on the form-invariance of Maxwell's equations in coordinate transformation. The exterior boundary of a cylindrical invisible cloak is unchange... The method of designing electromagnetic invisible cloaks is usually based on the form-invariance of Maxwell's equations in coordinate transformation. The exterior boundary of a cylindrical invisible cloak is unchanged and the interior boundary is extended from that of a point to that of a cylindrical region in coordination transformation. This transformation process makes perfect cloaks, but it causes singularity in the constitutive material parameters of cloaks. This singularity makes the cloaks impossible to realize in practice. In order to remove this singularity, this paper sets a small cylindrical region replacing a point in the space transformation. The cylindrical region is so small that it does not affect the invisibility effects, but it can remove the singularity for material parameters. Full wave simulations based on the finite element method were used to verify the designed cloaks. 展开更多
关键词 invisible cloak arbitrary shapes SINGULARITY constitutive material parameters
下载PDF
Multi-window invisible cloaks
11
作者 王新华 屈绍波 +8 位作者 夏颂 王斌科 徐卓 马华 王甲富 顾超 吴翔 鲁磊 周航 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第6期289-292,共4页
This paper reports that a general method of designing invisible cloaks is using variant constitutive material parameters to realize the space transformation. A hollow region can be hidden after this transformation. It... This paper reports that a general method of designing invisible cloaks is using variant constitutive material parameters to realize the space transformation. A hollow region can be hidden after this transformation. It was recently shown (Ma H, Qu S B, Xu Z and Wang J F 2009 Appl. Phys. Lett. 94 103501) that when the original point moves to the boundary of a cloak, the cloak can be designed to be open. Based on this theory, we propose multi-window invisible cloaks which can conceal a group of objects. Full wave simulations for invisible cloaks with regular and irregular shapes verified this method. 展开更多
关键词 invisible cloaks transformation optics constitutive material parameters
下载PDF
Identification of Mechanical Properties of Thin-Film Elastoplastic Materials by Machine Learning 被引量:2
12
作者 Xu Long Changheng Lu +1 位作者 Ziyi Shen Yutai Su 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2023年第1期13-21,共9页
Nanoindentation can effectively evaluate the mechanical properties of materials in the form of bulk and coating.However,the relationship between the indentation response and the stress–strain curve of thin-film elast... Nanoindentation can effectively evaluate the mechanical properties of materials in the form of bulk and coating.However,the relationship between the indentation response and the stress–strain curve of thin-film elastoplastic materials is complex and thus difficult to be elucidated using traditional physics-based,empirical or statistical models.In this study,the convolutional neural network(CNN),as a practical machine learning method,is adopted and trained to rapidly obtain the mechanical properties of thin-film elastoplastic materials using nanoindentation.The proposed method is targeted for efficiently predicting mechanical properties of thin-film materials from the applied load–penetration depth curve.Combined with the power-law model to describe the elastoplastic characteristics,a dataset comprising 228 nanoindentation cases with wide ranges of material properties is numerically simulated by ABAQUS and the corresponding results are adopted for the CNN training and validating.By addressing the important elastoplastic properties characterized by elastic modulus,yield strength,and hardening exponent,the impacts of CNN’s architecture and training epochs on the predicting performance are investigated in detail.By varying the number of convolutional layers,the influence of mechanical parameters of thin-film materials on the CNN prediction accuracy is discussed.The results show that compared with the traditional reverse algorithm,CNN can greatly reduce the computational complexity and computation time and has better prediction accuracy for the constitutive parameters of thin-film elastoplastic materials. 展开更多
关键词 Machine learning NANOINDENTATION Thin-film material Elastoplasticity constitutive parameters
原文传递
Characterization of material mechanical properties using strain correlation method combined with virtual fields method 被引量:1
13
作者 Yangyang Li Jiaqiang Li +2 位作者 Qiyuan Duan Huimin Xie Sheng Liu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2021年第3期456-471,I0002,共17页
The isotropic and anisotropic behaviors are considered as the important formats of the constitutive behaviors,and can also be called the global properties.To improve the identification ability of virtual fields method... The isotropic and anisotropic behaviors are considered as the important formats of the constitutive behaviors,and can also be called the global properties.To improve the identification ability of virtual fields method(VFM)when the global properties are unknown,this paper proposes the strain correlation method(SCM)to determine the global properties before the parameter identification using the VFM.Firstly,the basic principle of SCM is described in detail.Then,the feasibility and accuracy of SCM are verified through the numerical experiments based on the three-point bending configuration and the real experiment of polymethyl methacrylate(PMMA).The influence of the additive Gaussian white noise,local errors in the strain fields,and missing data at the specimen edges on the characterization results are evaluated.The results show that the SCM has good noise immunity and lower accuracy requirements for the strain fields.As an application,the mechanical properties of Ti-6A1-4V alloys fabricated by selective laser melting(SLM)are characterized by the SCM.The results show that the alloys are isotropic,and the isotropic VFM is utilized to determine the mechanical parameters.By using the SCM,the accuracy of identification results can be improved for the isotropic or bidirectional reinforced orthotropic materials when using VFM. 展开更多
关键词 Global properties constitutive parameter identification Strain correlation method Virtual fields method
原文传递
Hot Deformation Behavior of a Novel Ni-Cr-Mo-B Ultra-heavy Plate Steel by Hot Compression Test 被引量:2
14
作者 Zhi-yu GAO Tao PAN +2 位作者 Zhuo WANG Guo-quan LIU Hang SU 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2015年第9期818-826,共9页
Hot deformation behavior of a novel Ni-Cr-Mo-B heavy plate steel was studied by hot compression tests,which were conducted on a Gleeble-3800thermo-mechanical simulator corresponding to the temperature range of850-1 15... Hot deformation behavior of a novel Ni-Cr-Mo-B heavy plate steel was studied by hot compression tests,which were conducted on a Gleeble-3800thermo-mechanical simulator corresponding to the temperature range of850-1 150℃ with the strain rates of 0.01-10s-1 and the true strain of 0.8.The results suggest that the majority of flow curves exhibit a typical dynamic recrystallization(DRX)behavior with an apparent single peak stress followed by agradual fall towards a steady-state stress.Important characteristic parameters of flow behavior as critical stress/strain for initiation of DRX and peak and steady-state stress/strain were derived from curves of strain hardening rate versus stress and stress versus strain,respectively.Material constants of the investigated steel were determined based on Arrhenius-type constitutive equation,and then the peak stress was predicted by the equation with the hot deformation activation energy of 379 139J/mol,and the predicted values agree well with the experimental values.Furthermore,the effect of Zener-Hollomon parameter on the characteristic points of flow curves was studied using the power law relation,and the ratio of critical stress and strain to peak stress and strain were found to be 0.91and0.46,respectively. 展开更多
关键词 Ni-Cr-Mo-B heavy plate steel hot deformation constitutive equation activation energy characteristic parameter
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部