浅谈东川水库低弹模塑性混凝土大坝防渗墙施工技术要点

平和县东川水库于1967年9月建成,投入运行时间较长,工程存在诸多不安全因素,危及到水库的正常运行,需对水库进行除险加固。除险加固方案中坝体加固采用冲击钻造低弹模塑性混凝土防渗墙防渗。文章就东川水库低弹模塑性混凝土大坝防渗墙的施工技术要点进行总结,对其他类似工程具有参考意义和工程应用价值。

低弹模塑性砼的研究及工程应用

1 前言在土石坝及堤防工程中,基础与地基的联接及防渗大多是刚性砼结构,如砼防渗墙,龄墙等。一般结构尺寸往往较大,强度和刚度相对周围土体而言较大,结构设计时,为防止土体施于墙预应力过大和地基基础不均匀沉陷造成墙体断裂破坏,因而材料用量和造价较高,大江大河的堤坝基础与地基用塑性砼'软'结合。这不仅改善了墙体与地基及周围土体的变形适应性问题,同时也达到了防渗加固的目的。低弹塑性砼较之常态砼在材料方面表现为水泥用量少,在性能上表现为抗压强度低,切线弹模小,极限变形量较大,凝结时间较长,防渗性能好等特点。据有关文献介绍,低弹塑性砼墙体与周围冲积层地基土体的相对变形或沉降只有几个 mm 之差,既与地基基础的变形基本接近,从而使结构在地基及基础中的稳定性增强。

制造模塑性、不透气性和耐热性良好的聚酯

这种聚酯的酸组分中含有摩尔分数不小于4％的间苯二甲酸(Ⅰ)，二元醇组分主要为EG或1，4-丁二醇。所用Ⅰ中含有质量分数为(1～10)×10^-6(按碱金属计)的碱金属化合物。例如：将Ⅰ(含NaOH以Na计算为1．5×10^-6)和EG在磷酸三乙酯的存在下进行酯化，再在Sb2O3存在下与BHET-TPA-EG的低聚物进行缩聚，得到嵌段共聚物，其中Ⅰ的摩尔分数为79．2％(按总酸计算)。将含有10kg共聚物和40kg PET的塑坯进行吹塑制成瓶子，在模子中无沉积物。

洋后水库大坝防渗加固工程薄壁抓斗低弹模塑性混凝土防渗墙施工工艺

该文结合建瓯市洋后水库大坝防渗加固工程实践,介绍薄壁抓斗低弹模塑性混凝土防渗墙施工工艺,包括工作平台设置、混凝土导墙施工及槽段划分、造孔控制、泥浆制备、墙体材料及混凝土浇筑、墙段连接、施工质量控制等,可供类似工程参考。

一次性发泡塑料餐具替代品市场前景分析

200亿只一次性塑料发泡餐具，重10万吨，体积200万立方米。这是中国一年的使用量。但今年4月23日，国家经贸委一纸公文，禁止使用。

手机外壳注塑模具设计

本文分析了手机外壳的结构及工艺特点,对塑件的可模塑性进行了相关分析,利用Moldflow软件,进行产品最佳浇口位置、填充时间的参考,避免潜在成型问题,如短射(欠充填)及气穴,评估不同设计参数变更对产品成型的影响,以进行必要的设计变更及优化。

手机外壳注塑模具设计

本文分析了手机外壳的结构及工艺特点，对塑件的可模塑性进行了相关分析，利用Moldflow软件，进行产品最佳浇口位置、填充时M的参考，避免潜在成型问题，如短射（欠充填）及气穴，评估不同设计参数变更对产品成型的影响，以进行必要的设计变更及优化。

Influence of technical parameters on strength and ductility of AlSi9Cu3 alloys in squeeze casting

An orthogonal test was conducted to investigate the influence of technical parameters of squeeze casting on the strength and ductility of AISigCu3 alloys. The experimental results showed that when the forming pressure was higher than 65 MPa, the strength （ab） of A1Si9Cu3 alloys decreased with the forming pressure and pouring temperature increasing, whereas ab increased with the increase of filling velocity and mould preheating temperature. The ductility （6） by alloy was improved by increasing the forming pressure and filling velocity, but decreased with pouring temperature increasing. When the mould preheating temperature increased, the ductility increased first, and then decreased. Under the optimized parameters of pouring temperature 730 ℃, forming pressure 75 MPa, filling velocity 0.50 m/s, and mould preheating temperature 220 ℃, the tensile strength, elongation, and hardness of A1Si9Cu3 alloys obtained in squeeze casting were improved by 16.7%, 9.1%, and 10.1%, respectively, as compared with those of sand castings.

Deformation behavior and constitutive model for dual-phase Mg-Li alloy at elevated temperatures

In order to study the deformation behavior and evaluate the workability of the dual-phase Mg-9Li-3Al-2Sr alloy, isothermal hot compression tests were conducted using the Gleeble-3500 thermal-mechanical simulator, in ranges of elevated temperatures （423-573 K） and strain rates （0.001-1 s^-1）. Plastic instability is evident during the deformation which is in the form of serrated flow; serrated yielding is attributed to the locking of mobile dislocations by the Mg and Li atoms which diffuse during the deformation. The relationships between flow stress, strain rate and deformation temperature were analyzed and the deformation activation energy and some basic material factors at different strains were calculated using the Arrhenius equation. The effects of temperature and strain rate on deformation behavior were represented using the Zener–Hollomon parameter in an exponent-type equation. To verify the validity of the constitutive model, the predicted values and experimental flow curves under different deformation conditions were compared, the correlation coefficient （0.9970） and average absolute relative error （AARE=4.41%） were calculated. The results indicate that the constitutive model can be used to accurately predict the flow behavior of dual-phase Mg-9Li-3Al-2Sr alloy during high temperature deformation.

Deformation mechanisms of Mg-3Al-1Zn alloy by polycrystal plasticity modeling

A polycrystal plasticity model was developed to analyze the room-temperature deformation behaviors of Mg-3A1-1Zn alloy（AZ31）.The uniaxial tension and compression tests at room temperature were conducted using cast and extruded AZ31 rods with different textures and combined with the proposed model to reveal the deformation mechanisms.It is shown that,different flow curves of two specimens under tension and compression tests can be simulated by this model.The flow curves of AZ31 extrusions exhibit different shapes for tension and compression due to different activities of tensile twinning and pyramidalc＋a slip.The metallographic and TEM observations showed the equal twinning activities at the initial stage in tension and compression tests and the occurrence of pyramidalc＋a slip in compression of as-cast Mg-3A1-1Zn alloy with increasing the strain,which is consistent with the simulated results by the proposed model.

Advance and trend of friction study in plastic forming

Friction is a critical issue in plastic forming which influences forming force, metal flow, forming quality and service life of die. Since friction is a highly nonlinear physical phenomenon which is interactively affected by so many factors, great efforts have been made to study the friction mechanism and controlling. The research progress of friction issues in plastic forming was summarized and discussed from four aspects： testing, characterizing, modeling and optimization/controlling. Considering urgent demands for green, efficient and precise forming of high-performance, lightweight and complex components in high-tech industries such as aerospace and automotive, the trends and challenges of friction study in plastic forming were proposed.

Elasto-plastic constitutive model of aluminum alloy foam subjected to impact loading

A multi-parameter nonlinear elasto-plastic constitutive model which can fully capture the three typical features of stress-strain response, linearity, plasticity-like stress plateau and densification phases was developed. The functional expression of each parameter was determined using uniaxial compression tests for aluminum alloy foams. The parameters of the model can be systematically varied to describe the effect of relative density which may be responsible for the changes in yield stress and hardening-like or softening-like behavior at various strain rates. A comparison between model predictions and experimental results of the aluminum alloy foams was provided to validate the model. It was proved to be useful in the selection of the optimal-density and energy absorption foam for a specific application at impact events.

Plastic forming simulations of cold isostatic pressing of selective laser sintered components

A combined method of selective laser sintering （SLS） and cold isostatic pressing （CIP） was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components. K

Transition of plasticity and fracture mode of Zr-Al-Ni-Cu bulk metallic glasses with network structures

Effect of network structure on plasticity and fracture mode of Zr？Al？Ni？Cu bulk metallic glasses （BMGs） was investigated. The microstructures of transversal and longitudinal sections were exposed by chemical etching and observed by scanning electron microscopy （SEM）. The mechanical properties were examined by room-temperature uniaxial compression test. The results show that both plasticity and fracture mode are significantly affected by the network structure and the alteration occurs when the size of the network structure reaches up to a critical value. When the cell size （dc） of the network structure is ~3μm, Zr-based BMGs characterize in plasticity that decreases with increasingdc. The fracture mode gradually transforms from single 45° shear fracture to double 45° shear fracture and then cleavage fracture with increasingdc. In addition, the mechanisms of the transition of the plasticity and the fracture mode for these Zr-based BMGs are also discussed.

Construction and solution of strain model along thickness of aluminum alloy plate under plastic deformation

A thickness strain model of aluminium alloy plate under plastic deformation,based on thin plate assumption was proposed.It is found that when ratio of stress fractions is constant during in-plane loading,ratios of strain components under various loading conditions are linearly related and these points of ratios form a η-η line.Under these simple loadings,strains in thickness direction can be easily calculated by the η-η line equation without integral and differential work.When the plate is under more complicated loading conditions,the thickness can be computed by the proposed optimization and piecewise calculation model.Validation computations indicate that the relative error of the results of the presented model is less than 0.75% compared with the proven theories and FE simulation.Therefore,the developed model can be applied to engineering calculation,e.g.pre-stretching analysis of aerospace aluminium thick plate,with acceptable accuracy.

Electroplastic effect in AZ31B magnesium alloy sheet through uniaxial tensile tests

The electroplastic effect in AZ31B magnesium alloy sheet was investigated through uniaxial tensile tests. In order to show the athermal effect of the electrical pulses, two types of uniaxial tensile tests at the same testing temperature were carried out： uniaxial tension in environmental cabinet and uniaxial tension with electrical pulses. In addition, the distribution of temperature field in the cross-section area during uniaxial tension with electrical pulses was simulated. The results show that the distribution of temperature field along the cross-section area is homogeneous. By comparing the true stress？true strain curves of AZ31B alloy under uniaxial tensile tests, the athermal effect with electrical pulses was confirmed. The microstructure evolution after the uniaxial tension was studied by optical microscopy. The results indicate that the electrical pulses induced dynamic recrystallization plays an important role in the decrease of flow stress. Finally, a flow stress model of AZ31B sheet taking the influence of electroplastic effect into account was proposed and validated. The results demonstrate that the calculated data fit the experimental data well.