An anisotropic constitutive model of geomaterials based on true triaxial testing and its application

Journal of Central South University - Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus. The loads were applied from the major principal and minor...     

Seepage-stress coupling constitutive model of anisotropic soft rock

To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship, a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argillaceous siltstone and brown mudstone) were performed by using an MTS-815.02 tri-axial rock mechanics test system, with which the stress—strain curves according to the seepage variation were obtained. Based on the experimental results and by employing Hooke’s law, the formulation of the coefficient of strain-dependent permeability was presented and introduced to establish a coupling model. In addition, the mathematical expression and the incremental formulation for coupling model were advanced, in which five parameters that can be respectively determined by using the experimental results were included. The calculated results show that the proposed coupling model is capable of simulating the stress—strain relationship with considering the seepage-stress coupling in the nonlinear elastic stage of two kinds of soft rock. Foundation item: Projects(50378069, 50639090) supported by the National Natural Science Foundation of China; Project(50639090) supported by the Joint Fund of Yalong River Hydropower Development, China     

桥梁结构损伤识别理论的研究进展

从三个方面：（1）基于模型修正理论的结构损伤识别;（2）损伤指数法;（3）人工神经网络法等,对近年来国内外基于振动分析和结构动力学参数的结构损伤识别理论进行了比较系统地总结和评述,介绍了结构损伤识别领域研究的现状,给出了基于动力学参数和振动分析的结构损伤识别的模式,并分析了存在的困难以及需要进一步研究的问题．     

Vibrational shear flow of anisotropic viscoelastic fluid with small amplitudes

Using the constitutive equation of co-rotational derivative type for anisotropic viscoelastic fluid-liquid crystalline(LC),polymer liquids was developed.Two relaxation times are introduced in the equation:λn represents relaxation of the normal-symmetric stress components;λs represents relaxation of the shear-unsymmetric stress components.A vibrational rotating flow in gap between cylinders with small amplitudes is studied for the anisotropic viscoelastic fluid-liquid crystalline polymer.The time-dependent constitutive equation are linearized with respect to parameter of small amplitude.For the normal-symmetric part of stress tensor analytical expression of the shear stress is obtained by the constitutive equation.The complex viscosity,complex shear modulus,dynamic and imaginary viscosities,storage modulus and loss modulus are obtained for the normal-symmetric stress case which are defined by the common shear rate.For the shear-unsymmetric stress part,two shear stresses are obtained thus two complex viscosities and two complex shear modulus(i.e.first and second one) are given by the constitutive equation which are defined by rotating shear rate introduced by author.The dynamic and imaginary viscosities,storage modulus and loss modulus are given for each complex viscosities and complex shear modulus.Using the constituive equation the rotating flow with small amplitudes in gap between two coaxial cylinders is studied.     

FRP筋与混凝土粘结性能研究进展及本构模型改进

近年来,FRP（纤维增强聚合物）筋代替钢筋在混凝土结构中得到越来越广泛的应用。与钢筋相比,FRP筋具有各向异性、非均质、表面形式不同等特性,这导致FRP筋与混凝土之间的粘结机制不同于钢筋与混凝土。为全面了解FRP筋与混凝土之间的粘结性能,收集数据建立由342个拉拔试验试件组成的数据库,分析粘结性能与各因素之间的关系,对没有达成一致结论的观点进行补充和讨论,分析高温、冻融循环、电解质溶液对FRP筋与混凝土粘结性能的影响;校核常用的粘结-滑移本构模型的计算精度,基于建立的试验数据库,提出新的精度更高的粘结-滑移本构上升段表达式。     

Hot deformation behavior and constitutive relationship of Q420qE steel

Isothermal compression tests at temperatures from 1 273 to 1 423 K and strain rates from 0.1 to 10 s-1 were carried out to investigate the flow behaviors of Q420qE steel.Stress-strain data collected from the tests were employed to establish the constitutive equation,in which the influence of strain was incorporated by considering the effect of strain on material constants Q,n,α,and ln A.The results show that the flow stress curves are dependent on the strain,strain rate and deformation temperature.They disp...     

一种修正的莫尔-库仑本构模型及其应用

莫尔-库仑本构模型是理想弹塑性的，只考虑了强度随围压的变化，但没有考虑弹性模量随围压和应力水平的变化情况，这不符合地质材料的实际特性，借助于邓肯-张非线性弹性模型对切线模量的处理方法，对M-C模型中的弹性模量进行了修正。修正以后，弹性阶段的应力-应变曲线将表现为双曲线。为了将该修正模型写进FLAC^3D程序，特编制了前处理程序，并用来对刚性桩的横向承载力进行了数值分析。因为该模型没有对卸载模量重新定义，所以该模型较适合于持续加载的情况。     

一种修正的莫尔-库仑本构模型及其应用

莫尔-库仑本构模型是理想弹塑性的,只考虑了强度随围压的变化,但没有考虑弹性模量随围压和应力水平的变化情况,这不符合地质材料的实际特性.借助于邓肯-张非线性弹性模型对切线模量的处理方法,对M C模型中的弹性模量进行了修正.修正以后,弹性阶段的应力-应变曲线将表现为双曲线.为了将该修正模型写进FLAC3D程序,特编制了前处理程序,并用来对刚性桩的横向承载力进行了数值分析.因为该模型没有对卸载模量重新定义,所以该模型较适合于持续加载的情况.     

Rheological constitutive model of rock mass based on viscoplastic theory

With many major projects under construction,more and more attention is paid to rheological mechanical properties of rock mass,and extensive researches are carried out for rheological constitutive modeling of rock mass.Based on viscoplastic theory,a new rheological constitutive model is proposed.The rationality and validity of proposed model are verified through the creep test data.The results show that the rheological constitutive model based on viscoplastic theory is able to simulate the typical creep curves of rock mass and the identified parameters are reasonable.Therefore,the rheological constitutive model could be used to describe the rheological mechanical behaviour of rock mass.     

不同条件下硫化橡胶的动态黏弹性能分析

为了研究橡胶材料滞后生热以及生热对其力学性能的影响,在分析橡胶材料生热机理的基础上,对挤压接触对滚的一对钢-橡胶辊在转动过程中的生热进行研究,分析了随时间变化胶料温度升高的规律,以及橡胶的硬度和厚度参数对其生热的影响.通过实验数据,分析了温度升高对橡胶力学性能,包括硬度、损耗因子等的影响.结果表明：初始硬度大的橡胶温升大,橡胶层厚度越小温升越大,且温度升高会导致橡胶硬度减小、损耗因子先增大后减小.

     

热力学优化理论的研究进展

介绍近年来在不可逆热机理论、回热式燃气轮机循环分析、类热机装置分析和广义热力学优化理论研究中的一些进展，并简要阐述其发展方向。     

热力学优化理论的研究进展

介绍近年来在不可逆热机理论、回热式燃气轮机循环分析、类热机装置分析和广义热力学优化理论研究中的一些进展,并简要阐述其发展方向.     

Viscoelastoplastic constitutive model for creep deformation behavior of asphalt sand

A uniaxial viscoelastoplastic model that can describe whole creep behaviors of asphalt sand at different temperatures was presented.The model was composed of three submodels in series,which describe elastoplastic,viscoelastic and viscoplastic characteristics respectively.The constitutive equation was established for uniaxial loading condition,and the creep representation was also obtained.The constitutive parameters were determined by uniaxial compression tests under controlled-stress of 0.1 MPa with five different test temperatures of 20,40,45,50 and 60 ℃.Expressions of the model parameters in terms of temperatures were also given.The model gave prediction at various temperatures consistent with the experimental results,and can reflect the total deformation characterization of asphalt sands.     

臭蜣螂鞘翅的一维本构方程及黏弹性模型的建立

采用纳米压痕技术通过单一压痕研究了臭蜣螂鞘翅的各向异性特性。对臭蜣螂鞘翅进行了黏弹性分析,得到了臭蜣螂鞘翅表皮材料的一维本构方程,并建立了臭蜣螂鞘翅表皮的黏弹性模型的微分方程。该模型可望用于设计具有优异力学性能的仿生复合材料或涂层。     

Flow stress behavior and constitutive modeling of 20MnNiMo low carbon alloy

The hot deformation behavior of 20 Mn Ni Mo low carbon alloy was investigated by isothermal compression tests over wide ranges of temperature(1223-1523 K) and strain rate(0.01-10 s~(-1)). According to the experimental true stress-true strain data, the constitutive relationships were comparatively studied based on the Arrhenius-type model, Johnson-Cook(JC) model and artificial neural network(ANN), respectively. Furthermore, the predictability of the developed models was evaluated by calculating the correlation coefficient(R) and mean absolute relative error(AARE). The results indicate that the flow stress behavior of 20 Mn NiM o low carbon alloy is significantly influenced by the strain rate and deformation temperature. Compared with the Arrhenius-type model and Johnson-Cook(JC) model, the ANN model is more efficient and has much higher accuracy in describing the flow stress behavior during hot compressing deformation for 20 Mn Ni Mo low carbon alloy.     

船用907A钢的动态力学性能和本构关系

为了得到船用907A钢的动态力学性能及本构关系,运用静态试验机及分离式Hopkinson压杆加载装置,在应变率为0.000 33~2 680 s-1范围内得到了准静态拉伸及动态压缩条件下的应力应变曲线,对比了Cowper-Symonds模型和Johnson-Cook模型,并基于CS模型对应变硬化效应进行了修正。结果表明,船用907A钢具有明显的应变率强化效应和非线性应变硬化效应;CS模型比JC模型更能准确描述其应变率强化效应。     

Influence of SBS modifiers on viscoelastic mechanical behavior of modified asphalt

In order to verify the influence of different block proportions S/B on the effect of SBS modified asphalt,the dynamic mechanical performance test and static loading test were performed on the samples composed of different kinds of SBS with base asphalt. It is found that different S/B values fix on different modified effects and different viscoelastic mechanical behaviors,due to biphasic separate fabric of polybutadiene and polystyrene in SBS. In low-speed running pavement,the modified asphalt with lower S/B value shows better pavement performance,while in high-speed running pavement,the modified asphalt with higher S/B value shows better pavement performance. As far as SBS modified asphalt itself is concerned,mixing proportion impacts on resisting displacement and block proportion S/B ratio impacts on strain recovery capacity. In the case that the conditions are the same,SBS modified asphalt with different S/B values can be used for different travelling speed pavement construction demands to get an intelligent use.     

非饱和双重孔隙介质的势函数本构方程及应用

为了分析复杂岩土工程多场多相耦合效应,需要建立非饱和双重孔隙介质的一般本构理论框架.把双重孔隙介质视为两个单重孔隙介质的嵌套叠加,利用各组分应变与孔隙变形之间的内在联系,从经典混合物理论出发推导了非饱和双重孔隙介质的能量守恒方程.通过功共轭对之间的力学性质建立了小应变条件下非饱和双重孔隙介质的一般势函数本构方程.作为一...     

Corrosion and irradiation behavior of Fe-based amorphous coating in lead-bismuth eutectic liquids

Lead-bismuth eutectics (LBE) have considerable potential as a candidate material for accelerator-driven sub-critical systems (ADS). However, LBE corrosion and irradiation damage are two urgent challenges remaining to be solved for impellers of primary pumps. In this study, we have explored the possibility of using Fe-based amorphous coatings to overcome LBE corrosion and concurrently to sustain irradiation damage. Specifically, the Fe₅₄Cr₁₈Mo₂Zr₈B₁₈ amorphous coating was prepared by high-velocity oxygen-fuel (HVOF) spraying on 316L steel and exposed to saturated oxygen static LBE for 500 h at 400°C. The coating with high thermal stability (T_g=615°C and T_x=660°C) effectively prevented the substrate steel from being corroded by LBE owing to its unique long-range disordered atomic packing. The coating also exhibited strong irradiation resistance when being subjected to 45 dpa (displacement per atom) Au ion irradiation at room temperature, with no sign of crystallization even at the maximum implantation depth of 300 nm. Consequently, the hardness of the coatings before and after irradiation increased slightly. The current findings shed new insights into understanding corrosion mechanism and irradiation behavior of amorphous solids in LBE and expand the application range of amorphous materials.