消失模铸造金属液流动前沿气隙中气体压力的研究

利用基础理论计算出消失模铸造正常浇注时金属液流动前沿气隙中压力P膜随直浇道的面积S直与液态金属在其内部的流速ν直的乘积、浇注温度T膜、模型的密度ρ模、涂层厚度H的增大而增大;随真空度P真、铸件的水平周长S、透气性K的增加而减小,并通过生产实践加以验证.     

消失模铸造充型过程中的气膜压力及其厚度的数值模拟

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中的气膜压力和气膜厚度的影响.结果表明,液态金属充型的驱动力并非重力而是消失模的退让速度,而这一速度是由气膜压力和气膜厚度的相互自动变化来调节,使充型达到稳态.结合理论计算,得到底注式浇注时充型可达到稳态,且气膜厚度和气膜压力随浇注温度、模样密度、涂料层厚度的增大而增大,随负压度和涂层透气性的增大而减小.     

消失模负压铸造液态金属流动前沿气隙的厚度研究

利用基础理论计算出消失模铸造正常浇注时金属液流动前沿气隙的厚度δ与静压头h、砂箱的真空度P真、模样水平截面积的周长S、涂层的透气性K、直浇道面积S直与其内的液态金属流速v直的积及模型的密度ρ模、涂层的厚度H、液态金属的浇注温度T金的关系,并根据理论分析预言消失模铸造将要走向取消真空、减薄或取消涂层的方向.     

消失模铸造充型速度和流动前沿温度的数值模拟研究

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中金属液前沿的流动速度和温度的影响规律.结果表明,液态金属充型速度随浇注温度、负压度和涂层透气性的增大而增大,随模样密度和涂层厚度的增大而减小;金属液流动前沿温度随模样密度和涂层厚度的增大而下降,而随负压度的增大而提高.     

镁合金消失模铸造液模气隙尺寸的数值模拟

消失模铸造中充型的平稳性非常重要,充型越均匀铸件质量越好。使用SOLA-VOF计算方法模拟了镁合金在消失模铸造中的充型过程,计算了金属液和泡沫模样之间的气隙距离。结果表明液模气隙在充型过程中逐渐减小并趋向恒定值。。     

不同浇注方式对消失模铸造充型的影响

运用ProCAST软件研究了铝合金铸件的消失模铸造充型过程,考察了不同浇注方式对铸件消失模铸造过程的影响。研究表明,底注式浇注系统的充型相对平稳,是一种比较好的消失模铸造浇注系统方案。浇注系统、浇注速度和界面气隙压力对消失模铸造的充型有很大影响。     

干砂消失模铸造铁液流动前沿气隙的研究

对消失模铸造铸铁件流动前沿的气隙进行了研究，探讨了气隙与坍塌缺陷的相互关系，试验结果表明，铸铁件流动前沿不仅存在明显的气隙，而且采用聚苯乙烯模样材料，负压下浇注时，其气隙压力低于1个大气压。     

消失模铸造中泡沫热解气体逸出的数值分析

消失模铸造中受泡沫模样热解气化的影响,使得消失模铸造成形过程比普通砂型铸造复杂得多.基于ProCAST的计算流体动力学求解内核,研究了球墨铸铁QT250消失模铸造时泡沫遇高温金属液发生热解,在金属液与泡沫间产生气隙,气隙气体从型砂中选出的速度、压力大小及其分布的相关规律,以及对铸件成形质量的影响.为实际生产提供有益参考.     

真空消失模铸造铸铁件铸型坍塌缺陷成因的研究

对真空消失模铸造铸铁件铸型坍塌缺陷的形成机理进行了系统研究 ,结果表明 :铸型坍塌缺陷的形成是由于铁水充型时 ,其流动前沿气隙内外真空度的急剧下降 ,同时内外受力失去平衡 ,造成干砂向气隙内流动而引起的。提出了铸型坍塌缺陷的力学关系式 ,通过变速箱体的实验室和现场浇注试验 ,证明了上述坍塌缺陷形成机理和力学关系式的正确性。     

消失模铸造钢铁基表面复合材料的研究现状

与其他制备表面复合材料相比,由于消失模铸造钢铁基表面复合材料成本低、操作简便、依据铸件的工况要求即可实现整体复合亦可实现局部复合,因此,近年来发展很快.本文介绍了消失模铸造钢基、铁基表面复合材料研究现状,复合材料的组织组成及性能特点,归纳了消失模铸造钢铁基表面复合材料的应用现状,指出粘结剂的选择、铸件厚度和合金涂层厚度之比及浇注温度控制是消失模法制备表面复合材料的技术关键,并对消失模法制备表面复合材料的发展前景进行了展望.     

中厚板头尾厚度补偿技术的应用

分析了中厚板轧制过程中头尾部厚度超差的原因。结合文丰中厚板厂实际生产的特点,采用了一种新型头部厚度补偿方法,使钢板头尾部厚度超差由0.45 mm减少到0.2 mm,并提高了产品的成材率,为企业创造了可观的经济效益。     

Changes in the tensile strength and fracture mode with thickness of electrodeposited copper foil

The tensile strength and fracture mode changed with thickness of copper foil obtained from an acid copper sulfate bath under a same electrodeposition condition. The tensile strength decreased with increasing foil thickness due to an increase in average grain size of the foil. The tensile fracture mode changed from fractures normal to tensile axis to inclined fractures with increasing film thickness. The phenomena have been discussed based on a hardness distribution along the thickness and the local necking and fracture strains.     

铝管锥形模机械扩径变形区壁厚分布规律

研究了管材锥形模机械扩径变形区应力分布的特点,根据应力-应变关系,分析了变形区壁厚可能存在的分布规律,通过求解变形区应力分布,根据全量理论和体积不变原则,提出了变形区壁厚分布的解析式,基于该公式,分析了扩径系数和摩擦系数对壁厚分布的影响,结果表明,扩径系数较小时,摩擦系数对壁厚分布影响较小,变形区壁厚均减薄;当扩径系数较大时,变形区存在壁厚分界面,分界面之前(靠近模具前端)壁厚增厚,分界面之后壁厚减薄,并且摩擦系数越大,分界面半径越大。进一步数值模拟证明,该壁厚分布公式正确。     

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  运用电子背散射衍射(EBSD)和X射线衍射(XRD) 技术对硅钢热轧板的织构在板厚方向的分布进行了研究,并分析了两种织构测量方法的特点。EBSD技术能直观给出板厚方向的微观织构,XRD能得到钢板的宏观统计织构信息,结合两种技术的分析,能更直观更精确的研究不同织构在板厚方向的分布。     

Plasma distribution in the slender bore excited by coaxial rf electrode

A metal coaxial radio-frequency (rf) electrode has been utilized to produce plasma and deposit the coating onto the inner wall of the tubes. The inner electrode acts both as a plasma source and as a sputtering target to achieve plasma-based IBAD. The non-uniformity of thickness of deposited films and plasma density in the bore has been investigated for tubes with different lengths and inner diameters. The experimental results demonstrate that plasma density is higher at two ends of the tube and lower in the middle section of the tube. The uniformity of plasma density may increase with the inner diameter of tubes increasing, but will decrease with the length of tubes increasing. Copper films have been deposited using this technique and the variation of film thickness agrees with the distribution of plasma density along the bore axis. It is also observed that the uniformity of plasma density is higher than that of film thickness due to diffusion behavior of plasmas.     

Thickness of grain-boundary liquid phase and its effect on the mechanism of superplastic deformation

For a series of matrix aluminum alloys, an estimation of the thickness of the grain-boundary liquid phase under the optimum conditions of the manifestation of high-temperature superplasticity has been performed. It has been established that the contribution of grain-boundary sliding to the total deformation under these conditions is determining. It has been shown that the greater values of the thickness of the grain-boundary liquid phase correspond to greater values of the parameter m of the strain-rate sensitivity of the flow stress. The obtained dependences of the thickness of the grain-boundary liquid phase on m indicate that with increasing amount of the liquid phase the grain-boundary sliding progressively acquires features of viscous flow.     

6063-H112铝合金板材加工裂纹产生的原因

厚度25 mm的6063-H112铝合金板材,用户在加工过程中发现个别加工件存在裂纹.根据用户提供的试样,从裂纹的外观形貌、断口的显微组织特征和扫描电镜特征等几个方面进行了系统地分析,并结合生产工艺的特点,判断出厚度为25 mm的6063-H112铝合金板材裂纹是由于铸锭侧表面的偏析瘤压入所致.对其形成机制和预防措施进行了阐述.     

基于随机可靠度的300MN模锻水压机主工作缸壁厚的设计

300MN模锻水压机是国防和基础建设的关键设备，主工作缸是水压机的重要部件之一。本文根据概率法设计了主工作缸的壁厚，所设计的主工作缸壁厚只有传统设计壁厚的35％，有效的减轻了主工作缸重量。主工作缸壁厚的偏差变化对其可靠度有一定的影响，在生产制造中很有必要对壁厚的偏差进行控制。本文为主工作缸的设计提供了参考依据。     

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 金属板材的成形极限是板材成形领域中的重要性能指标和工艺参数。目前,国内外均已开展以厚度减薄率作为成形极限判据的成形极限试验模拟研究,其厚度减薄率的测试过程较为复杂,不适合实验室大批量检验工作。提出了2种金属板材拉伸厚度减薄率的测试方法,一种为人工测试断后试样断口附近厚度分布,得到厚度减薄率变化曲线;另一种方法是通过公式推导,将厚度减薄率与试样纵向应变联系起来,通过测试纵向应变,得到集中性失稳前的厚度减薄率变化规律。     

Numerical studies on the stress distribution in weldbonded joints with different adhesives

The Effect of elastic modulus and thickness of the adhesives on the stress distribution in weldbonded joints hasbeen studied with three-dimensional elastoplastic finite element method (FEM). Stress distribution curves have beenobtained at the edges of the spot welds and the lap zones in weldbonded joints, which werem made with adhesives ofdifferent elastic modulus or different thickness. Results show that there exists larger stress concentration at the edge of thespot Welds, though the shear stresses in the adhesive layers are smaller for weldbonded joints with low elastic modulus orthick adhesive layers. the stress concentration decreases and the shear stresses in adhesive layers increase with the increaseof the elastic modulus or the decrease of the adhesive thickness. It is concluded that the thiner adhesive layers with higherelastic modulius are preferable in weldbonded joints to cut down the stress concentration.