平面磨削淬硬薄工件磨削力研究

平面磨削淬硬薄工件实验测定的磨削力曲线呈现凸形,磨削后的工件表面呈现凹形,分析了曲线变化原因,并对磨削力变化进行了预测。通过磨削热力耦合有限元分析了工件变形,并对变形量影响磨削力的变化进行了分析。结果表明:工件变形导致磨削用量增大,是引起磨削力变化的主要原因,而且工件装夹方式对变形有很大影响。磨削力的变化又改变了流入工件的磨削热流密度,从而影响磨削温度场,导致磨削淬硬层分布不均。根据磨削力、磨削温度和工件变形之间的相互影响关系,通过逐步迭代法预测出磨削力变化曲线,并与实验曲线进行了对比。     

气缸套变形与活塞环摩擦功关系的研究

为了降低发动机摩擦损失,提高机械效率,重点研究缸套变形对活塞环与气缸套摩擦副的影响。首先,对两种不同状态的缸套进行有限元分析,找出缸套变形规律;然后,根据这些规律计算出活塞环与缸套润滑表面的油膜压力和油膜厚度;最后,将计算结果与试验结果进行对比,验证了该方法的正确性。研究结果表明,缸套变形的椭圆度直接影响摩擦功和机油消耗率的大小。     

毛竹材弧形竹片干燥特性研究

对毛竹材弧形竹片的干燥特性进行了研究,结果表明:干燥温度越高,干缩率越大,弦向平均干缩率大于径向平均干缩率;弦向竹青侧干缩率高于竹黄侧干缩率;当含水率降至5%以下时,干缩率趋于稳定;随着干燥温度的升高,弧形竹片依次产生翘曲、皱缩及开裂等现象。     

Interaction Working Behavior About the Internal and External Wall of Foam in place Cavity Wall

In order to study the stability of foam in place cavity wall, the capacity of reinforced concrete strip ear and tie involving in cavity wall deformation, the broken shapes and mechanical performance of the cavity wall, the effective measures was seaked to improve deformation capacity and overall performance of the cavity wall.13 patches of cavity wall and 1 patch of solid wall were built and seismic tests of which were carried out.The lnfluence of some constructional measures on mechanical behavior and deformation properties of the wall and vertical pressure and insulation layer thickness on the relative displacement difference of the internal and external wall of foam in place cavity wall was analyzed.Finally, the capability of reinforced concrete strip ear and tie working interactively between the internal and external wall of foam in place cavity wall was analyzed.It is found that deformation capacity of the cavity wall is improved efficiently with constructional column and the high bonding strength, shearing strength and pressure strength of foam in place insulating mortar have certainly a positive influence on the bearing capacity of the wall.The reinforced concrete strip ears play the leading role in reinforcing connection of the internal and external wall of foam in place cavity wall and guaranteeing out plane stability of the external wall.When walls crack seriously, the ties can play an important role in supporting and drawing the wall and preventing wall collapse.Furthermore, the reinforced concrete strip ears and ties which are the main construction measures to coordinate the internal and external wall work together perform a great variety of tasks.Therefore, the reinforced concrete strip ears and ties should be designed rationally to guarantee playing their respective roles.     

Localization Band Angle Prediction With Three invariant Model

The prediction with RR’s two invariant Model are smaller than the data, while it can catch the trend of linear increase in band angle with increasing mean stress for fixed values of the least compressive stress and a decrease with increasing values of the least compressive stress.Based on the RR’s two invariant Model, with a Lode angle as the third invariant and the more complicated yield condition, true trixial compression test was carried out.And three invariant model was proposed in good agreement between real data and predictions.     

基于热固耦合的高温热水泵口环形变分析

为避免高温热水泵在运行过程中出现转子部件咬合现象,对TEG 200-400型高温热水泵的口环间隙进行分析.利用ANSYS Workbench软件,对TEG 200-400型高温热水泵在不同温度下的热固耦合进行有限元分析,得到泵盖冷却水腔有无冷却冲洗以及不同温度条件下的泵口环的形变量.结果表明:冷却腔的冲洗对叶轮口环的位置形变影响较大,高温热水泵的使用过程中,尽量降低泵盖与托架连接处的温度,有利于减小叶轮口环的变形;泵体口环和叶轮口环形变量随介质温度的升高而增大,依据运行介质的温度、泵的自身结构、材料特征等,对热变形进行合理预估并选择设计口环间隙,可避免泵启动及运行时泵体口环与叶轮口环之间的动静摩擦;在250℃设计温度条件下,叶轮口环与泵体口环的半径间隙取为0.6 mm的方案是合理的.研究结果为合理选择叶轮口环和泵体口环之间的间隙提供了一定的依据.     

发动机凸轮轴磨削变形补偿技术研究

针对发动机凸轮轴数控磨削时产生连续变化的弹性变形问题,分析了凸轮轴受到磨削力变形对凸轮轮廓精度的影响,对轴向和径向变形进行了解耦,推导了不同位置、不同相位下凸轮受力变形量求解方程.分析了数控凸轮轴磨床的插补原理,建立了含有变形量误差的、工件旋转轴和砂轮进给轴联动的磨削运动学方程,提出了X轴变形量与理论插补值进行几何叠加的指令修正误差补偿方法.对某发动机进排气凸轮轴磨削变形进行了建模与仿真,对数控凸轮轴磨床进行了补偿与加工试验,仿真与加工试验结果均表明磨削变形补偿可以将凸轮轴的轮廓精度提高5 μm.     

黄河上游大柳树-沙坡头河段河床变形数值模拟

对黄河宁夏境内具有连续弯道的大柳树一沙坡头河段的泥沙运移及河床变形等进行了平面二维数值模拟研究．建立了修正的平面二维RNGκ-ε紊流泥沙数学模型,其中水流模块采用修正的RNGκ-ε紊流模型,泥沙模块采用全沙模型,考虑了不同粒径组悬移质和推移质运移对河床变形的影响。数值模拟结果与实测结果比较吻合。表明该模型可以用于模拟具有连续弯道的多沙河流泥沙运移及河床演变过程;在4种典型工况下分别进行了数值模拟,研究了不同水沙条件对水沙运移及河床变形的影响;吸取了关于泥沙数学模型中水流模块和泥沙模块的耦合式算法和分离式算法的优点,建立了一种半耦合算法,其计算量比耦合式算法大大减小,计算精度上比分离式算法要高。     

Effect of high-pressure treatment on rheological,thermal and structural changes in Basmati rice flour slurry

Rheological, thermal and structural changes in high pressure (HP) treated Basmati rice flour dispersions were studied as function of pressure level (350–650 MPa), slurry concentration (with 1:5, 1:3 and 1:2 flour-to-water ratios) and holding time (7.5–15 min). Rice flour dispersions exhibited a gradual liquid–solid gel transformation as they gelatinized and/or denatured and behaved as viscoelastic fluid following HP treatment. Mechanical strength (G′) of pressurized gel increased with applied pressure and rice concentration. Differential scanning calorimeter (DSC) thermograms of rice slurry measured after pressure treatment indicated a reduction in peak enthalpy in proportion with the extent of gelatinization and/or denaturation of starch and proteins. Pressure-treated rice samples had a progressively lower gelatinization temperature. A 15 min pressure treatment at 550 MPa was found sufficient to complete gelatinization of protein free isolated rice starch while the slurry required 650 MPa. The presence of proteins might have been responsible for the slower starch gelatinization in the rice slurry during pressure treatment. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier-transform infrared (FTIR) spectroscopy results indicated some minor changes in protein subunits and secondary structure of rice protein. This study has provided complementary information on pressure-induced changes in physical (thermal stability, overall structure) and molecular level (secondary structure) of rice protein.     

Effect of heat on rheology of gluten fractions from flours with different bread-making quality

Flours from wheat varieties of differing bread-making quality were fractionated using a sequential salt precipitation technique. The gluten fractions in the different varieties varied in the proportion of HMW, LMW glutenins and gliadins. Their rheological behaviour was examined using constant strain (2%) small deformation oscillation tests over frequencies ranging from 0.005 to 10 Hz, before and after heating at 90 °C. The fractions containing a higher proportion of HMW glutenins were associated with a predominantly elastic character, whereas fractions containing mostly gliadins exhibited a viscous-like behaviour. The frequency dependent rheological behaviour of fractions containing HMW proteins was less susceptible to heat, and their elastic character was maintained after heating, whereas the rheology of intermediate fractions and fractions containing mostly gliadins was more susceptible to heating, indicating a rapid change from viscous to elastic behaviour after heating.