Flow Stress Behavior of 3104 Aluminum Alloy

According to different deformation conditions required in working process for manufacturing of 3104 aluminum alloy, the authors design the simulation experiments of hot rolling process at different deformation temperature and strain rates, analyze the relationships of deformation resistance, flow stress and strain rate, deformation temperature when alloy deformation. Based on experimental data analysis, it was concluded that the dominant factors affecting flow stress were the strain rate and deformation temperature, and the two parameters were also important for deforming process control.     

Dissipative Energy Based Description for Hardening and Its Application to Non-proportional Cyclic Plasticity

The heterogeneous nature of metallic materials result in residual microstress fields during plastic deformation.The energy stored in the residual microstress fields affects the subsequent plastic deformation. Based on this concept, a nonclassical constitutive model is developed. On the other hand, it is found that there exists difference of dissipative plastic energy between different plastic strain paths. A dissipative plastic energy based hardening parameter is proposed and introduced into the hardening function, which isthen embedded in the non-classical constitutive model. The stress responses of 304 stainless steel subjected to biaxial non-proportional loading are analyzed and the results coincide well with the experimental results.     

Mechanical model and computational analysis of pipeline plastic failure under radial load

When large damage, such as rupture and leakage, occurs in buried pipeline, a steel pipeline extrusion throttle device is applied to crush the pipeline and block the oil flow quickly in a short time. An extrusion model under uniformly distributed radial load is established based on the theory of plastic deformation and the principle of virtual work. The pipeline plastic deformation is analyzed and computed and the pipeline extruding load is obtained. The extrusion of X60 steel tube of 325 mm diameter and 6 mm thickness loaded by indenter of 18 mm width is examined. The load-deformation curve of pipeline extrusion is obtained. The results of the comparison between experimental data and theoretical data show that the model is in good agreement with the experiment. This model can be used to calculate the extruding load of pipelines of different sizes and provide the theoretical and practical reference for urgent repair of pipeline leakage.     

Mechanical properties and numerical simulation of unloading of brittle rocks under high geostress

The investigations on the deformation mechanisms, estimation of stability and technique of disasters controlled of brittle rocks excavated under high geostress are difficult points for rock mechanics and engineering geology. The evolutionary rule of mechanical parameters and deformation failure of brittle rocks are discussed based on unloading under high geostress, and the obvious characteristics of strain strength for brittle rocks under high geostress is found. It is presented that the brittle rock yielded follows Griffith rule of strain strength at peak. The elasto brittle plastic numerical calculation method is established considering the dynamical variation of mechanical parameters in course of unloading yield, and it is validated by practical engineering.     

Study on strain localization and progressive failureof surrounding rock under high pressure environment

This paper uses the Mohr-Coulomb criterion with tension cut-off strain-softening model and the large-strain calculation method to study the localized deformation and progressive failure.It investigates the process of stain localization appearing,growing and sample failure,and uses the physical and numerical simulation to explore the relationship between strain localization and progressive failure of surrounding rock.The results show that the soften character of rock sample is caused by stain localization.The breach point of progressive failure is founded based on the distribution law of plastic zones and soften strips.The key causes of the tunnel convergence deformation after opening are the plastic extrusion and the elastic deformation of rock yield units caused by stress release.     

Numerical analysis on the evolutionary features of deformation and failure modes of slopes

The failure of slope is a gradual accumulation process. Under the effect of many interior and exterior factors, some parts in the slope reach yield with the increase of stress, and sliding surface forms gradually till complete transfixion. With continuous increase of the plastic strain, overall failure happens on the slope. Traditional analysis method cannot display the mechanic conditions and the whole process of deformation, transfixion of sliding surfaces and failure. Meanwhile, FEM strength reduction can quantitatively show the deformation features and the process of occurrence and development of sliding surface. Based on the previous researches, the paper classifies slopes according to the features of rock and soil and the slope structure. Through analyzing the graphs of deformation and the nephograms of plastic strain under different reduction factors or safety factors, the researchers can directly find the deformation tendency of slopes and the whole process of the extension, transfixion and failure of sliding surface with the reduction of safety factor. So, the failure mechanism of slope can be found intuitively, which can provide effective basis for the prevention and governance of slopes.     

Numerical Analysis of Drained undrained Triaxial Tests for Overconsolidated Clays

In the framework of critical state soil mechanics, a simplified hardening law is proposed to describe the change between subloading surface and the normal consolidation surface with plastic deformation based on subloading surface concept proposed by Hashiguchi. The characteristics of overconsolidated clays, such as stress strain relationship, strain hardening and softening and stress dilatancy are simulated, and the results are in accordance with the data from triaxial drained compression test. Numerical model is also used to predict the stress strain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests.     

滴灌条件下富士苹果树茎流速率变化规律研究

摘 要：旨在了解矮砧密植富士苹果树体内茎流速率变化规律,为其制定合理的旱作节水灌溉制度提供理论基础。利用热扩散式探针法实时采集树体茎流速率数据,结合自动气象站监测所得各气象因子数据,设计不同灌水下限滴灌试验,进行气象因子等对茎流速率影响的试验研究。富士苹果树在4月份茎流速率最低平均值为2.07 mL/(cm2?h)],到了6—7月份最大,平均值为9.56 mL/(cm2?h)];生育期内茎流速率有明显昼夜变化规律,在晴天时变化规律呈单峰曲线,阴天时变化较平缓,多云天气时呈多峰曲线变化趋势。茎流速率变化规律与太阳辐射强度、大气温度和土壤温度变化均呈极显著正相关,相关系数分别为：0.9746、0.9389、0.9119;与大气湿度为显著负相关性;相关系数为-0.7526;茎流速率与土壤水分相关性不显著,但是降低土壤含水量会造成树体茎流速率的降低。富士苹果树干茎流速率与各气象因子间相关性由高到低排序为：太阳辐射强度＞大气温度＞土壤温度＞大气湿度＞土壤水分。以茎流速率为因变量,各个气象因子为自变量,经逐步回归线性分析得出茎流速率与太阳辐射强度和大气温度之间的回归方程：Y=-8.81+0.013X1+0.52X2。太阳辐射强度是影响树体茎流速率即蒸腾耗水的直接因素。     

Deformation Analysis of Thermo Elastic Plastic on ReinforcedConcrete Structure Subjected to Fire

To investigate the mechanical behavior of reinforced concrete structure subjected to fire, the incremental thermo elastic plastic creep constitutive equations of steel and concrete in consideration of temperature and creep deformation were obtained based on different yield rules and the elastic plastic theories. The nonlinear analysis for reinforced concrete simply supported slab was carried out with consideration the variation of the mechanical properties of steel and concrete with temperature. The effectiveness and applicability of the constitutive equations were verified with the test results from relevant literature. The nonlinear analysis was employed for one bay one storey reinforced concrete frame under fire and the variation of displacement at partial nodes was analysed. It was found that the reinforced concrete structure at a high temperature would have a significant deformation. And the displacement change curves of beam column joints of reinforced concrete frame were not monotonous trend and there were inflexion points. The vertical displacement values of beam column joints were less than those at midspan of cross beam.     

A Stress Path Damage Constitutive Model for Sang

A hypothesis that the skeleton deformation of sand is only the deformation of the interfaces of grains, and the deformation characteristics including nonlinearity, plastic deformation and shear dilation are controlled by the sliding of interfaces of grains within skeleton, is presented.The contact between grains is classified as perfect contact and sliding contact in this paper.In the elastic deformation phase, the contact between grains is regarded as perfect contact.With the increase of shear stress, there are gradual conversions from perfect contacts to sliding contacts which are viewed of damages in this paper.Based on Mohr Coulomb law, a calculation method for the damage ratio is given according to the relative distance of the stress point to the initial damage line and failure line.On this basis, a damage constitutive model is proposed.The model properties can be conveniently obtained through conventional triaxial compression test and constant stress ratio consolidation test.Test results indicate that the model is capable of predicting deformation behavior for various conditions, including varying consolidation conditions and stress paths.     

Elasto-plastic analysis on surrounding rock of roadways based on seepage, strain softening and dilatancy

According to seepage body force, strain softening and rupture expansion of rock mass, elastic-plastic mechanics theory, distribution laws of stress and displacement of surrounding rock in seepage field are derived, and relationships between different zonation range of the surrounding rocks, pore water pressure, strain softening and rupture expansion are established. The results show that the pore water pressure and rupture expansion rock mass have a more obvious impact on the surrounding rock rupture area than the plastic zone. Both the plastic zone and the rupture area are larger when the seepage field is considered. The impact of strain softening on both the plastic zone and the rupture zone of surrounding rock is very significant, and both seepage and strain softening rupture expansion affect deformation of surrounding rock of roadways obviously. It provides certain reference values for the roadway support engineering in seepage field.     

3D FEM Analysis of Subgrade Soil Movement and Deformation Caused by Extra Shallow Underground Pipe Jacking

Pavement structures will be damaged by subgrade soil movement around the pipes introduced by extra shallow underground pipe jacking. Soil layer deformation with shallow deposits on pipes during extra shallow underground pipe jacking is analyzed using 3D FEM. The effects on pavement deformation created by the friction between shield and soil, injection slurry, jacking forces and the vehicle loads are studied with a practical project. The analytical results show that the ground surface deformation is an uplift first followed by settling with the lower part of the cover moving faster than the upper layers. It is demonstrated by comparing computational results of FEM simulation and the observed data from the in situ test that these FEM models can be applied to real world engineering. Subgrade soil settling on extra shallow underground pipe jacking in a cross section will be stable when the shield has passed through a section with a length twice the diameter of the pipe. Horizontal surface subsidence along the lateral distribution is similar to a normal distribution curve, with the primary affected areas on both sides of the axis approximately 1.5 times the diameter of the pipe.     

Numerical Simulation of Eelastoplastic Multi-scales Model for Casting Magnesium Alloy

To realize the transforms of stress and strain and obtain the multi-scale constitutive equation across micro/meso/macro scales.strain-stress curves for magnesium alloy(AM60) and magnesium matrix are carried out with the machine MTS.By means of mixture law,mechanical property of particle is obtained.Based on the character of magnesium alloy structure,the finite element model of unit-cell included complex micro-structures is carried out.Via finite element numerical simulation of magnesium alloy unit-cell,the methodology overcome the limitation of present analytical method.Finally the multi-scale constitutive equation has been used for the analysis of the tensile stress vs. strain curve for magnesium alloy.Results show satisfactory agreement between the stress vs strain curve by the present methodology and the experimental data for AM60.     

Energy-absorbing Properties and Crushing Flow Stress Equation of Lightweight Foamed Concrete

Lightweight foamed concrete is a new arresting material for arresting overrun aircraft. To reveal its compression properties and mechanism of deformation and destruction, a study on lightweight foamed concrete with different density, 0.21 and 0.31 g/cm 3 respectively, has been carried out. Experiment system include CSS4410 electronic universal testing machine and Dynatup9250 drop-hammer testing machine and VHS8800 high strain rate system. Then, extrusion strength under different indenter area is predicted with a theoretical model, and a crushing flow stress constitutive equation is proposed. The results show that it is characterized by the movement of crushing driving interface during the process of deformation, crush to compaction of the material, and the deformation is notably in local. The compression strength is relevant to density and impact velocity. Moreover, theoretical model can predict the extrusion strength under different indenter area exactly, and the crushing flow stress equation can describe mechanic properties of compression well.     

Work-hardening Mechanism of Non-magnetic High Manganese ZG25Mn18Cr4 Castings

The important character of non-magnetic high manganese ZG25 Mn18Cr4 alloy is rapid work-hardening under external stress. With X-ray diffraction and TEM analysis, it is proved that the microstructures of both undeformed and deformed matrixes are austenite and carbide with some striation structure in the matrixes, the amount of stripes in the deformed matrix is obviously more than that in the undeformed matrix. Electronic diffraction analysis confirmed that the stripes in coarse austenite grains are high density lamination fault sheets. A great deal of lamination fault sheets produced by plastic deformation divides up austenite matrix, shortens the free distance of dislocation movement and results in the rapid work-hardening of ZG25Mn18Cr4 alloy.     

The Micro/Macro Mechanic Analysis of PD3 Pearlitic Steel with Layered Microstructures

A micro/macroscopic analysis of PD3 pearlitic steel with layered microstructure is carried on.Based on the compatibilit conditions of stress and strain at the interface between two layers as well as the mixed law of composites,constitutive equations of an effective homogeneous inclusion are obtained.combining these equations with the K B W self consistent model,the micro macroscopic transition has been estabilished.It turns out that the analysis is capable of determining the overall responses of materials as well as local stress evolution in microstructure under monotonic and cyclic loading.It is found that stress in the thin cementite layer is very high.This is caused by intersification of the local plastic flow of the soft ferrite layer in which more loading is transferred cycle by cycle to the hard phase.Furthermore,a strength dimension law that the strength is inversely proportional to the square root of the layer thickness is developed to explain the high strength of the cementite layer.     

Analysis on Reinforced Concrete Flexural Members Using Deformation Condensation Method

Traditional nonlinear analysis of RC structures usually adopts nonlinear FEM based on continuum mechanics, and it is hard to reflect macroscopic deformation characteristic, such as local rotation in crack sections and plastic hinge of failure stage. From the perspective of physical model, a new deformation condensation method is developed. The analysis of RC flexural members in the 1-D elastic problem involve three stages based on the concept of deformation condensation. RC flexural members were divided into several elements according to average crack spacing to get numerical model consistent with the physical model with higher computational efficiency tests of RC flexural members reinforced with high strength rebars conducted by Institute of Prestressed Structures in Tongji University, were simulated and the simulation results agreed well with the experimental data indicating that this novel method is applicable.     

Experimental Study on the Frictional Performance of Water Lubricated Plastic Alloy Bearings

It''s difficult to form hydrodynamic lubrication because of the low viscosity of water, but it is founded by experiment that there is low co-friction on water lubricated plastic alloy bearings working. The main factors that affect co friction are revs, loaded and clearance. Significance and effect of every factor that affect co friction is analyzed by variance analysis and orthogonal experiment. goaphs of every factor that affect co friction are list. From the goaphs, it is founded that there is elastic hydrodynamic because of elastic deformation in the plastic alloy.     

Friction and Wear Characteristics of Plastic Alloy Bearings under Different Lubricating Condition

Ultra High Molecular Weight Polyethylene (UHMW-PE) is a kind of high anti-wear engineering plastic with many excellent physical and mechanical performances. It has been widely applied in the field of mechanism such as bearing and pump. Effect of load, speed, time on friction and wear properties of Ultra High Molecular Weight Polyethylene(UHMW-PE)plastic alloy bearings under different Lubricating Condition are studied by using MPV-200 model friction and wear testing machine. The test results show that water lubrication reduces the friction coefficient of bearings but increases the wear rate as compared with dry friction. At the same time, wear mechanisms are analyzed systemically. It provides a theoretic basic for practical application of plastic alloy bearings     

结构消(耗)能元件芯材SN490B本构关系数值模拟

采用消(耗)能元件的结构在遭受地震作用时,元件芯材首先屈服进入塑性阶段,利用其滞回变形消耗地震输入能量,保护主体结构,元件芯材本构关系的数值模拟是对采用消(耗)能元件结构进行抗震分析与设计的基础。为更真实地模拟结构消(耗)能元件芯材在单调和循环荷载下的本构响应,更准确地对采用消(耗)能元件结构进行结构弹塑性地震响应分析,对常用作消(耗)能元件芯材的日本高延性钢材SN490B的单调、循环加载本构及循环骨架曲线进行了数值模拟,包括：采用Esmaeily-Xiao二次流塑性模型模拟材料在单调荷载作用下弹性段、屈服段、强化段和二次流塑段4个阶段;采用混合强化模型模拟材料循环荷载作用下的本构响应,运用大型通用有限元软件ABAQUS结合数值模拟参数对16种不同循环加载制度下的循环加载试验进行模拟,并与试验结果进行对比;采用Ramberg-Osgood模型、无量纲化的Ramberg-Osgood模型及两段式模型模拟循环骨架曲线。研究结果表明：所采用数学模型可以较好地模拟SN490B钢材单调、循环加载本构响应及循环骨架曲线,数值模拟与试验结果拟合较好。