拉坯速度对连铸大方坯凝固的影响

结合现场研究,利用显式有限差分法计算出不同工艺条件下的铸坯凝固情况;进行了拉坯速度对出结晶器坯壳厚度、铸坯表面温度、铸坯凝固终点位置和铸坯质量影响的模拟分析研究.模拟结果表明,拉速对铸坯表面温度和凝固终点的影响较大,随拉速的增大,表面温度升高,出结晶器坯壳厚度减薄,铸坯液相穴拉长.     

重轨钢大方坯轻压下位置的预报

采用有限元方法,对某钢厂新建的重轨钢大方坯在不同的位速和过热度条件下的凝固过程温度场分布情况、坯壳生长规律和凝固分率进行了预测性的模拟研究,从而为该钢厂新建的重轨钢大方坯连铸机的结晶器和二冷区的冷却制度的制定和轻压下区间的选取提供理论依据和技术指导.     

核壳型阳离子丙烯酸酯乳液的合成

采用核壳乳液聚合法,制得可用于木器底漆的核壳型阳离子丙烯酸酯乳液。考察了反应型乳化剂DADMAC、种子引发剂AIBA、功能单体GMA用量及乳化剂配比、软硬单体配比对乳液性能的影响。研究表明,反应型乳化剂DADMAC质量分数为单体总量的0.45%,种子引发剂质量分数为引发剂总量的0.4%,乳化剂配比m(核)∶m(壳)=1∶1,功能单体GMA质量分数为1.2%,软硬单体配比为m(MMA)∶m(St)∶m(BA)=18∶13∶10时可制得性能较佳的核壳型阳离子丙烯酸酯乳液。     

Simulation of thermomechanical behavior during continuous casting process based on MiLE method

A new method called mixed Lagrangian and Eulerian method(MiLE method) was used to simulate the thermomechanical behavior during continuous casting process of steel YF45MnV.The simulation results are basically in agreement with the measured data.The delaying period at the beginning of solidification is about 0.1 in square root of solidification time which is agreement with the data in literatures,and shell thickness increases in linear relation to square root of solidification time.The bloom surface temperature decreases gradually as the casting proceeds.The effective stress in the corner is much larger than that in the mid-face.The corner area is the dangerous zone of cracking.The effects of mold flux break temperature on the air gap and hot tearing indicator were also modeled.The model predicts that the bloom surface temperature increases with the increase of the mold flux break temperature,but the heat flux decreases with the increase of the mold flux break temperature.The hot tearing indicator is much smaller when the mold flux break temperature is higher.     

碳纤维和尼龙纤维对TiAl合金型壳退让性的影响

为了改善TiAl合金精密铸造用氧化锆陶瓷型壳的退让性,利用电子万能试验机和扫描电子显微镜对添加不同含量碳纤维和尼龙纤维后的型壳退让性进行了测试.结果表明,添加少量碳纤维可以提高型壳湿强度并降低型壳室温和高温干强度,但当所添加碳纤维的质量分数达到10%后,会同时提高型壳的三种强度.当尼龙纤维的质量分数处于10%以内时,型壳三种强度均会降低.当碳纤维的质量分数达到5%时,型壳的湿强度和室温干强度可分别提高51. 9%和20. 7%,高温干强度降低8. 5%,同时改善了型壳的退让性并降低了铸件的裂纹倾向.     

Vibration of functionally graded sandwich doubly curved shells using improved shear deformation theory

Nonlinear forced vibrations and natural frequency of sandwich functionally graded material doubly curved shallow shell with a rectangular base are investigated. The sandwich functionally graded material (FGM) doubly curved shell is subjected to a harmonic point load at centre. The sandwich doubly curved shell with homogeneous face sheets and FGM face sheets is considered respectively when the natural frequencies are studied. Reddy’s third order shear deformation theory is expanded in which stretching effects in thickness are considered by introducing the secant function. Hamilton’s principle and von-Karman type nonlinear geometric equation are applied to obtain partial differential equation of the FGM sandwich doubly curved shell. Comparative studies with other shear deformation theories are carried out to validate the present formulation. Navier method is used to discuss the natural vibration frequencies of the FGM sandwich doubly curved shell. Numerical simulation is applied to demonstrate the nonlinear dynamic responses of the FGM sandwich doubly curved shell. Multiple periods, quasi-period and chaos are detected for the dynamic system for different core thickness.     

氢氧化钠预处理工艺对花生壳酶解制备还原糖的影响

针对花生壳直接酶解制备还原糖得率低的问题,提出了氢氧化钠(NaOH)预处理再进行酶解的方法.该方法通过对NaOH浓度、预处理温度、预处理时间进行单因素试验,然后在单因素试验的基础上确定正交试验工艺参数范围,以酶解后还原糖得率为指标,得出NaOH预处理花生壳的优化工艺条件.结果表明:在试验范围内固液比1∶10,预处理工艺条件为NaOH质数分数2％,温度70 ℃,预处理时间6h,纤维素酶水解后还原糖得率达到了72.5％,较未处理前提高了53.9％.     

利用钛有机骨架材料制备微米级TiO2色谱填料

以钛有机骨架材料（MIL?125(Ti)）作为核和壳材料,通过外延生长法合成了粒径更大、更均匀的核壳材料,即MIL?125(Ti)包覆MIL?125(Ti) (MOFs@MOFs),再通过煅烧可得到微米级TiO₂色谱填料。考察了核加入质量、壳溶液稀释倍数、反应时间、包覆层数等对包覆效果的影响,得到最佳的制备条件为核加入质量30 mg,不稀释壳溶液,反应24 h,包覆1层。结果表明,利用钛有机骨架材料制备得到的TiO₂色谱填料为锐钛矿型,比表面积76.0 m²/g,粒径可以达到7 μm左右,厚度为2.5 μm左右,不仅保留了其优良的性能,还具备粒径大、可调控多孔结构等特点。此外,该方法操作简便,无需苛刻的合成条件,可操作性强。     

Deformation response of roof in solid backfilling coal mining based on viscoelastic properties of waste gangue

Solid backfill mining(SBM) is a form of green mining, the core of which is to control and minimize the deformation and movement of strata above longwall coal mines. Establishing a mechanical model that can reliably describe roof deformation by considering the viscoelastic properties of waste gangue is important as it assists in improving mine designs and reducing the environmental impact on the surface.In this paper, the time-dependent deformation characteristics of gangue under different stress levels were obtained by using lateral confinement compression, that reliably represents the compaction of goaf.The viscoelastic foundation model for gangue mechanical response is different from the traditionally used elastic foundation model, as it considers the time factor and viscoelasticity. A mechanical model using a thin plate on a fractional viscoelastic foundation was established, and the roof deflection, bending moment, time-dependent, viscous and other characteristics of SBM were included and analyzed.Compared with the existing elastic foundation model, the proposed fractional order viscoelastic foundation model has higher accuracy with laboratory data. The plate deflection increases by 50.9% and the bending moment increases by 37.9% after 100 days, which the elastic model would not have been able to predict.     

甲醇水溶液结构和扩散性质的分子动力学模拟

采用分子动力学模拟方法研究了不同浓度甲醇水溶液的热力学、微观结构和动力学性质。模拟发现随着甲醇浓度的增加，溶液的超额混合焓呈先降低后增加的趋势，在XM（摩尔分数）为0．36时出现最小值，与实验结果相当吻合；甲醇分子配位圈内水分子的配位数NMw随甲醇浓度的增加而减小，水分子配位圈内水分子的配位数Nww也随甲醇浓度的增加而减小；溶质的加入使水分子间的间隙变小，配位数Nαβ与组成XM呈线性关系。     

考虑液体晃动和罐底提离储液罐的研究

一直以来没有一个简便、有效的模型来模拟壳-液的多种移动边界、几何大变形和流体液面大幅晃动、粘性等多种非线性因素耦合作用的三维的地震反应分析问题.运用大型有限元程序ANSYS中的单元建立考虑液体晃动和罐底提离的储液罐模型,分析了地震作用下无锚固储液罐的动力响应.通过与经典的C lough试验结果进行比较,验证了所建模型的可靠性.模型在数值分析结果中成功的再现了液面的大幅晃动的现象和无锚固储液罐的罐底提离现象.     

Effects of electric pulse on microstructure of Al-Si alloy in liquid and solid states

In order to investigate the change in liquid microstructure of Al-Si alloy treated by electric pulse (EP), X-ray diffraction tests with liquid A1-Si alloy and ZL109 alloy treated or not by EP were carried out. The results show that the number of Al-Si atomic clusters decreases and that of Al-Al and Si-Si atomic clusters increases for the treated samples. The tests with ZL109 alloy indicate that a large amount of primary crystal Si appears in the solidified microstructure after treated by EP. It is found that EP can change the microstructure of liquid metal by affecting the probability of electrons appearing in different atoms (Al and Si) in the liquid metal.The combining force of different atoms decreases relatively, and that of the same atoms increases, which is the main reason of re-ducing the atomic cluster with different atoms (Al-Si) and increasing the atomic cluster with the same atoms (Al-Al, Si-Si). The in-creasing of the atomic cluster with the same atom cluster resulted in the increasing of Si activity and the higher point of eutectics in the phase diagram. It makes a lot of primary silicon appeared in ZL109 alloy.     

Effect of milling process on the core-shell structures and dielectric properties of fine-grained BaTiO3-based X7R ceramic materials

Fine-grained BaTiO3-based X7R ceramic materials were prepared and the effects of milling process on the core-shell structures and dielectric properties were investigated using scanning electron microscope, transmission electron microscope, and energy dispersive spectroscopy (EDS). As the milling time extends, the dielectric constant of the ceramics increases, whereas the temperature coefficient of capacitance at 125°C drops quickly. The changes in dielectric properties are considered relevant to the micro-s...     

连续三相喷射环流反应器的实验和数值模拟

利用Pavlov管和电导探针分别测量含小颗粒（Stokes数小于1.0）的连续气液固三相喷射环流反应器内轴向液速和气体体积分数分布. 提出大气泡-小气泡-浆态相三相流体力学模型,以模拟三相喷射环流反应器的流体力学行为,对大气泡相和小气泡相分别考虑尾涡加速和气泡阻碍效应并修正其曳力. 对于上升区和下降区,流场模拟结果均与实验结果较吻合. 利用模型预测不同固体体积分数下的气体体积分数与轴向液速分布,结果表明,在考虑的固体体积分数范围内,气体体积分数随固体体积分数增加而下降,液体循环速度随固体体积分数增加而略有上升,其原因主要是反应器内平均气泡直径随固体体积分数增加而增大,进而导致气泡浮升速度加大并增强周围流体的加速运动.     

微冲头的微观粘附力及预接触变形分析

有关微观物体的粘附力与变形分析在微机械和表面物理中越来越重要.文章以表面形状由幂函数描述的轴对称微冲头与半空间体为研究对象,分析作用于微冲头上的分子间作用力和液桥张力,分析了在微观力作用下的微冲头接触前的弹性变形.最后以液桥张力作用力下微冲头的特例--微球为对象,分析了液桥体积对微冲头顶端竖向变形的影响.分析结果表明,小间距时,作用于微冲头顶端的液桥力随间距的增大而减小,并随液桥体积的增大而增大.在较大间距时,液桥力与液桥体积之间的关系却出现了一种波动现象,而在小间距时,微冲头的变形随液桥体积的增加而减小,同时随液桥体积变化而先增后减的波动,大间距时这种波动现象愈加明显.微冲头的粘附接触特性中出现的这种波动现象也说明了微观尺寸效应的存在.     

Zn-22Al泡沫夹芯复合板的三点弯曲性能

以Zn-22Al(ZA22)基泡沫材料为芯材,LY12铝板为面板制备了泡沫夹芯复合板。研究了泡沫夹芯复合板的三点弯曲行为,观察了复合板的破坏模式,分析了复合板弯曲性能的影响因素,运用层合梁刚度优化理论探讨了其机理。研究结果表明,ZA22泡沫夹芯复合板的三点弯曲载荷-位移曲线可按线性段、非线性段和失稳段表示其特征;其弯曲极限载荷随孔隙率的增大而减小,并且泡沫夹芯复合板表现出明显的层合效果。三点弯曲载荷作用下,泡沫夹芯复合板的主要失效模式为芯材的剪切破坏。     

热挤压碳素钢减压器壳体流动成形分析及模具设计

本文用金属塑性变形滑移线理论,分析了碳素钢氧气(乙炔)减压器壳体热挤压成形情况,找出金属流动的规律,在此基础上合理地制定出该件的生产工艺,设计出热挤压复合模及反挤压模具。     

聚苯乙烯包覆石蜡相变微胶囊的制备及性能分析

采用悬浮聚合法制备以聚苯乙烯为壁材,58#石蜡为芯材的相变微胶囊。考察了乳化时间、交联剂二乙烯基苯（DVB）的配比、聚合时间以及芯壁比对微胶囊性能的影响,采用傅立叶红外光谱仪、场发射扫描电镜、差示扫描量热仪、热重分析等手段对微胶囊的化学结构、表观形貌、储热性能以及热稳定性等进行了表征。结果表明,乳化时间对微胶囊的热性能影响不大;单体St与交联剂DVB的质量比为6∶1制备的微胶囊的形貌较佳,缩皱和碎屑明显减少;聚合时间为3 h制备的微胶囊形貌较好、大小相对均一、相变潜热和芯材石蜡质量分数相对较高;而随着芯壁比的增大,芯材石蜡质量分数相继增大,其中芯壁比为3∶1制备的微胶囊相变潜热增大到125.2 J/g,芯材石蜡质量分数高达80.9%,且热稳定性好。     

激光辐照金属圆柱壳体热应力分析

研究了激光辐照金属圆柱壳体的热力效应,运用有限元法计算了金属圆柱壳体三维热传导模型的温升与热应力分布,计算中考虑了材料的热学和力学性质的非线性,讨论了几个特定时刻的圆柱壳体内外表面的热应力和热变形。结果表明,光斑边缘附近区域的等效应力最大并随加载时间增加向外移动,圆柱壳体的热变形在光斑区由内表面向外凸出。     

包钢大方坯连铸机结晶器凝固传热的数值模拟

根据包钢的现场条件,建立了大方坯连铸机结晶器内二维非稳态凝固传热数学模型,采用有限差分法对数学模型求解,得出结晶器中铸坯的温度分布规律和凝固坯壳生成规律,同时研究了拉坯速度对坯壳生成厚度的影响。