基于Kriging代理模型的注塑件残余应力优化分析

以注塑成型制品中脱模后的最大Mises-Hencky残余应力为目标函数,运用基于Kriging代理模型及EI加点准则的序列优化方法,对聚碳酸酯材料制品进行了工艺参数(包括熔体温度、模具温度、注射速率、保压压力及保压时间)优化。算例结果表明,所提出方法可以有效地降低注塑件内的最大Mises-Hencky残余应力。在此基础上对充填阶段进行深入分析,用贝塞尔曲线控制方式代替常规的常速率充填控制方式,进一步降低了制件内的残余应力。     

铬微凝胶体系交替注入参数优化

通过室内物理模拟实验,研究了注入方式对采收率的影响。研究表明,从注聚开始到调剖剂注入结束,含水率明显下降,在聚驱阶段采收率提高幅度较大,为7.27个百分点;总的提高幅度为16.36%,最终采收率为65.71%,与前置调剖实验相比,两者的水驱采收率分别为49.35%和50.68%两者相差不大,但是总提高幅度比前置调剖要低0.9个百分点,最终采收率相差2.23个百分点。说明前置调剖更有利于提高采收率。从综合成本及经济效益因素来考虑,最佳注入方式选用前置调剖段塞0.05 PV。最佳候凝时间为7~10 d。     

汽车后挡风玻璃热弯成形及回弹过程研究

基于粘弹性材料的有限元理论,应用有限元模拟方法研究了具有深弯复杂曲面特征的汽车后挡风玻璃的热弯成形工艺及回弹问题。使用广义Maxwell模型来描述玻璃在高温下的粘弹性质。利用有限元分析软件,合理简化模型,对采用压模成形工艺的汽车后挡风玻璃的热弯成形和回弹进行了有限元仿真。研究了汽车后挡风玻璃在经过压制、落模、回弹阶段的应力分布和变形情况。针对玻璃的回弹问题,分析了主要工艺参数对玻璃回弹的影响情况及应力与回弹的关系,为提高玻璃型面质量和模具设计精度提供参考。     

并联混合动力系统参数匹配优化研究

混合动力汽车动力系统参数匹配对整车动力性和燃油经济性有显著影响。为了得到合理的动力系统参数匹配方案,采用车辆传统理论和经验公式对混合动力系统进行了初步匹配,然后基于正交试验理论设计了4因素正交试验对选取的部件参数进行优化,得到了一组最优参数组合方案。利用先进的汽车仿真软件AVL-Cruise的组件变量(Component Variation)功能,设计了9组DOE Plan仿真试验,对优化方案进行了验证和对比。结果表明:正交试验方法理论思路合理,实际可行,能得到准确度较高的动力系统参数寻优结果。     

基于支持向量机数控机床切削能耗预测方法研究

数控机床在制造业中耗能比例大,研究其耗能至关重要。在数控机床切削过程中,切削参数的不同直接影响数控机床切削能耗大小。基于此分析切削过程中切削速度、进给量和切削深度等切削参数对数控机床切削能耗的影响,搭建基于支持向量机数控机床能耗与切削参数的模型。实例对比验证了基于支持向量机数控机床能耗预测方法的可行性,简化了传统经验公式繁琐的计算过程,相对于BP神经网络法比较精确,为数控机床节能问题、能耗定额等实际问题提供了基础理论依据。     

基于切削力与振动特性钛合金铣削工艺参数研究

针对钛合金材料的难加工性,基于正交试验,研究了工艺参数对切削力、切削振动等影响规律,提出了综合考虑切削力、切削振动的工艺参数优化方法。研究结果表明,轴向切深、径向切深和进给速度对切削力影响显著,其中轴向切深、径向切深对X方向(垂直加工表面)切削力影响非常显著;切削速度对切削振动影响显著,频谱分析表明试验条件下未发生切削颤振。考虑各工艺参数对切削力、切削振动的显著程度,建立了以切削力、切削振动为约束条件,最大金属切除率为优化目标的工艺参数优化模型,进而获得了不同约束条件下的工艺参数优化组合。     

The role of the experimental data base used to identify material parameters in predicting the cyclic plastic response of an austenitic steel

The first objective of this paper investigates the influence of the previous strain history on ratcheting. New tests were performed where different strain-controlled histories have been applied prior to ratcheting tests. It is demonstrated that under the same conditions, one can observe ratcheting, plastic shakedown or elasticity according to the prior strain-controlled history. The second objective points out the correlation between the experimental data base devoted to the identification of the material parameters and the quality of the predictions in cyclic plasticity. The results suggest that the choice of the tests should be closely linked to the capabilities of the model. In particular, the presence of non proportional strain-controlled tests in the data base may be not a good choice if the model itself is not able to represent explicitly such a character. All tests considered here were performed on 304L SS at room temperature.     

基于轻质多孔结构的机床工作台性能研究

将轻质多孔结构应用到DVG850高速加工中心的工作台结构中,设计出的多孔结构工作台比原工作台的总质量减少了16.894 kg；通过对工作台的静、动态分析得出:多孔结构工作台的最大变形量比原结构减小了20.54％,前6阶固有频率比原结构平均提高86.97 Hz,最大提高22.17％,并给出了主要设计参数(正方形单体壁厚δ、边长L)对工作台的最大静变形和总质量的影响曲线,为其进一步的设计与研究提供了理论参考.     

Assessing Parameter Identifiability of Activated Sludge Model Number 1

The main difficulties reported in the identification of biokinetic models describing the activated sludge process are related to poor convergence or nonconvergence of the identification algorithms and nonuniqueness of the parameter estimates (i.e., different values for the parameters produce approximately the same response from the model). In the present paper, we assessed the identifiability of the Activated Sludge Model Number 1 parameters for a simulated full-scale WWTP calibrating situation, using both noise-free and noise-corrupted simulated data, and analyzed the efficiency of different optimization methods in the identification process. We began by comparing the performance, in terms of the rate of convergence, for different identification algorithms based on three distinct optimization methods. Finally, a procedure based on the information content of the Fisher and covariance matrices was applied in order to define the set of best identifiable parameters in different calibration situations.     

Lateral Weir Flow Model using a Curve Fitting Analysis

A numerical approach is considered for flow over side weirs as a substantial part of distribution channels in irrigation systems and treatment units. The model is based on the energy principle and a curve-fitting technique. For this purpose, the side weir was divided into elementary strips to develop generalized equations for discharge and surface profile. The change in water surface elevation towards the weir crest and the inclination of the deflected flow over the weir were also taken into account. Dimensionless parameters were used and the normalized equations solved to obtain the hydraulic parameters of side weirs. The results were plotted to determine general relationships based on the curve-fitting technique. A practical application of the derived equations to obtain hydraulic parameters of side weirs is performed using literature data.