聚丙烯/硬石膏复合材料的非等温结晶动力学

采用DSC研究了聚丙烯(PP)及聚丙烯/硬石膏复合材料的非等温结晶动力学,对所得数据用修正Avrami方程的Jeziorny法和Mo法进行处理。结果表明:硬石膏的加入提高了PP的结晶温度Tp和结晶速率,降低了结晶活化能ΔE,使实际降温速率下PP更易结晶。同样的含量下,经铝酸酯偶联剂改性硬石膏使PP结晶速率加快,但ΔE有小幅上升。研究表明,硬石膏有异相成核作用,填加20%时异相成核多于填加10%时,铝酸酯偶联剂的改性对该作用无明显影响。     

不同温度环境下Al–7Zn–2.5Mg–2.0Cu–0.1Zr–0.2Sc合金的力学行为研究

目的 研究不同时效时间对Al–7Zn–2.5Mg–2.0Cu–0.1Zr–0.2Sc合金强度的影响,以及室温和-40℃这2种温度环境对该合金疲劳行为的影响。方法 在不同时效时间下对Al–7Zn–2.5Mg–2.0Cu–0.1Zr–0.2Sc合金进行热处理,并采用透射电镜观察其显微结构以解释不同时效时间下强度变化的原因。在不同外加总应变幅的条件下,对T6态该合金进行低周疲劳实验,对比研究Al–7Zn–2.5Mg–2.0Cu–0.1Zr–0.2Sc合金在不同温度环境下的低周疲劳行为。结果 随着时效时间的延长,不同温度环境下Al–7Zn–2.5Mg–2.0Cu–0.1Zr–0.2Sc合金的屈服强度和抗拉强度都先升高后降低,-40℃环境下的屈服强度和抗拉强度均高于室温环境下的。在低应变幅时,合金的循环应力响应行为特征总体呈稳定趋势,在高应变幅时,合金的循环应力响应行为先表现为循环稳定特征,后表现为循环硬化特征。同一应变幅下,-40℃环境下合金的循环应力幅值高于室温环境下的,而合金的低周疲劳寿命则随着温度的降低而下降。此外,在室温和-40℃低周疲劳加载条件下,疲劳变形机制为平面滑移机制。当应变幅...     

高硅铝合金缸套材料腐蚀加工技术研究

采用三维视频显微金相技术对高硅铝合金缸套材料的组织构成、颗粒尺寸以及碱腐蚀深度进行测试与评价;用激光共聚焦显微镜技术对碱腐蚀界面颗粒凹凸以及表面纹理进行观察与描述;用往复式摩擦磨损实验机对碱腐蚀试样进行摩擦学性能评价。结果表明:高硅铝合金组织中主要由硅颗粒及第二相硬质点颗粒构成,平均硅颗粒尺寸为4.00μm,平均第二相颗粒尺寸为3.05μm;随腐蚀时间、深度的增加,腐蚀界面区域增大,表面凸凹及纹理更加清晰,当碱的质量分数为5%,溶液温度为40℃,腐蚀时间为30~40 s,摩擦学性能最优越。     

氢氧化铝生产过程中结晶助剂有效成分的测定

研究了拜尔法生产氢氧化铝过程中,用溶剂浮选-气相色谱法测定结晶助剂有效成分硬脂酸钠的方法。选择环己酮为浮选溶剂,样品经酸化,溶剂浮选30 min进行富集,再经CH3OH/BF3甲酯化,以毛细管色谱柱分离,邻苯二甲酸二乙酯为内标,氢火焰离子化检测器检测。硬脂酸与内标的质量比在0.1~10范围内有良好的线性关系,检出限为0.1 mg/L。方法重复性较好,硬脂酸钠的回收率为96.6%~97.8%,在现场试用取得良好效果。     

Process design for multi-stage stretch forming of aluminium alloy aircraft skin

A process design approach for multi-stage stretch forming was proposed by combining the strain distribution method and finite element method (FEM) to determine the minimum stage number and deformation amount of each stage. The strain distribution method was used to calculate the deformation amount of each stage and evaluate the formability through a safety criterion. FE simulation was taken as an analysis tool to reveal the deformation behaviour, to predict the strain contour and to determine the process parameters at each stage. To evaluate the effect of heat treatment after pre-strain on occurrence of deformation defects during the subsequent deformation, a multi-stage uniaxial tension test for 2B06 aluminium alloy sheet was carried out. A case study demonstrates that the approach has high reliability and good practicability.     

Analysis of semi-solid response under rapid compression tests using multi-scale modelling and experiments

Simulating semi-solid metal forming requires modelling semi-solid behaviour. However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material. In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented. This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity. Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression. This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid. A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data. More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured. The effect of solid fraction on mechanical response is in qualitative agreement with experiments.     

铝圆筒持久强度试验

鉴于用户对铝圆筒持久性能测定的高可靠性要求,却因无法制取满足国标要求的持久强度试验的试样而无法对其进行测试,因此专门设计并制造了一套铝圆筒持久强度试验台(专利号01101063.O),对成品铝圆筒进行持久强度测试.结果表明:外推得到95%置信度下铝圆筒在40℃服役10 a(年)的持久强度σ1040=(399±18)MPa.铝圆筒的持久性能可以满足用户要求.     

准分布式光纤Bragg光栅传感器在微生物燃料电池温度场测量中的应用

微生物燃料电池(MFC)在近些年得到了迅猛了发展,尤其是MFC具有产电且同时处理废水的效果,引起了世界各国科学家的高度关注。如何提高MFC产电效率的问题一直是MFC的研究重点,其中温度是影响微生物活性的一个重要因素,进而影响MFC的产电效率。为了能够更好地了解温度场与MFC的产电效率的关系,本文采用准分布式光纤Bragg光栅(FBG)阵列,对MFC阳极室内温度场分布进行实时测量。实验表明:该方法能够测量MFC运行阶段阳极室内温度场分布,反应前后温度差3-4℃,该方法为研究MFC内温度与产电效率的关系提供一种新的手段。     

基于Dynaform的印涂铝盖拉深压边力控制技术

起皱和拉裂是印涂铝盖在冲压拉深过程中的两大主要缺陷,合适的压边力对防止起皱和拉裂具有十分重要的作用。实际中,通常采用理论计算和模具调试的方法来获得合适的压边力数值,但理论计算方法计算复杂、可操作性差,而模具调试繁琐且费时费工。针对这一问题,以非线性有限元分析软件Dynaform为平台,对印涂铝盖冲压拉深工艺过程和压边力进行数值模拟和理论分析,确定了压边力的合理范围,并根据压边力范围试冲产品以确定最佳压边力。结果表明,1716印涂铝盖首次拉深的压边力数值的合理范围为7~8.8 k N,最理想的压边力数值在8.8 k N附近。该方法减少了压边力调试的盲目性,缩短了模具调试时间,减少了模具调试难度,最终达到降低产品制造成本的目的。     

Study on spinel-based inert anode for aluminium electrolysis

1 IntroductionSince the Hall-Heroult process was applied in aluminium production,an inert anode was al ways thetarget that the aluminiumindustry is seeking for in the newtechnology field. The greenhouse gases CO2and the fluoride CFnemittedfromthe present carbon anodes ,give a huge pressure onthe environment .Theapplication of inert anodes will help us go through this trouble :a cell with inert anodes emits oxygen in-stead of CO2and other nocuous gases ;the newtype of cell with inert anodes …