数控切削中粗车循环参数确定初探     

马红英 《石家庄职业技术学院学报》2008,20(6):40-42

介绍了G71循环加工指令的格式、各参数的含义及其确定方法,并给出了编程实例,以提高编程质量和加工效率．  相似文献   

带右删失数据的非线性随机效应模型参数估计     

费绍金  宗序平  卞金萍 《洛阳师范学院学报》2008,27(5)

本文讨论了带右删失数据的非线性随机效应模型的参数估计,给出Gauss-Newton迭代法和改进后的Gauss-Newton迭代法,根据参数估计和算法给出数值模拟,验证了参数估计和算法的可行性.  相似文献   

微波场中温度分布的二维数值模拟     

李勇  房丽敏 《南阳师范学院学报》2008,7(6):24-26

时域有限差分法是解决电磁场问题的一种有效方法．根据电磁模型和热模型,通过α因子将热模型的时间步长降到和电磁模型时间步长同一数量级,将它们结合给出了微波加热模型．模拟了从四周加载波源来加热材料．并且给出了模拟的结果．  相似文献   

逆流降膜除湿器除湿过程的数值研究     

孙健  施明恒 《东南大学学报》2007,23(2):272-277

建立了模拟逆流降膜除湿过程传热传质的数学模型,给出了传热传质的控制方程和适当的边界条件和气液界面条件.采用氯化钙作为除湿剂,运用控制容积法对降膜除湿溶液与被处理空气之间的除湿过程进行了分析和计算.获得了相应的除湿溶液与被处理空气的速度场、温度分布和出口参数.计算结果表明:沿着除湿器高度方向溶液和空气的温度、溶液的浓度、空气的湿度在入口区域变化较快而在出口区域变化较慢.可分别通过增加竖壁的高度、溶液的入口浓度和溶液的流速来改善除湿过程;同样,也可通过降低空气的流速或空气入口湿度达到改善除湿过程的目的.研究结果有利于改进除湿器的性能,为太阳能液体除湿、空调系统的优化设计和运行调节提供了理论依据.  相似文献   

Numerical Simulation of Dynamic Response of an Existing Subway Station Subjected to Internal Blast Loading     

HU Qiuyun  YU Haitao  YUAN Yong 《天津大学学报(英文版)》2008,14(1)

In order to design and retrofit a subway station to resist an internal blast,the distribution of blast loading and its effects on structures should be investigated firstly.In this paper,the behavior of a typical subway station subjected to different internal blast Ioadings was analyzed.It briefly introduced the geometric characteristics and material constitutive model of an existing two-layer and three-span frame subway station.Then three cases of different explosive charges were considered to analyze the dynamic responses of the structure.Finally,the maximum principal stress,displacement and velocity of the columns in the three cases were obtained and discussed.It concluded that the responses of the columns are sensitive to the charge of explosive and the distance from the detonation.It's also found that the stairs between the two layers have significant effects on the distribution of the maximum principal stress of the columns in the upper layer.The explicit dynamic nonlinear finite element software-ANSYS/LS-DYNA was used in this study.  相似文献   

Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load   总被引：4，自引：0，他引：4  

ZHANG Xiuhua    DUAN Zhongdong  ZHANG Chunwei 《天津大学学报(英文版)》2008,(Z1)

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA. The multi-material Eulerian and Lagrangian coupling algorithm was adopted. A flu-id-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground, multiple ALE element for simulating air and TNT explosive material. Numerical simulations of the blast pressure wave propagation, struc-tural dynamic responses and deformation, and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed. The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure. The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation. The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic defor-mation subjected to intensive blast waves, and columns lost carrying capacity, subsequently lead-ing to the collapse of the whole structure. The approach coupling influence between struc-tural deformation and fluid load well simulated the progressive collapse process of structures, and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.  相似文献   

Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load     

ZHANG Xiuhua  DUAN Zhongdong  ZHANG Chunwei 《天津大学学报(英文版)》2008,14(1)

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA.The multi-material Eulerian and Lagrangian coupling algorithm was adopted.A fluid-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground,multiple ALE element for simulating air and TNT explosive material.Numerical simulations of the blast pressure wave propagation,structural dynamic responses and deformation,and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed.The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure.The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation.The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic deformation subjected to intensive blast waves,and columns lost carrying capacity,subsequently leading to the collapse of the whole structure.The approach coupling influence between structural deformation and fluid load well simulated the progressive collapse process of structures,and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.  相似文献   

Modelling impact of dredging and dumping in ebb-flood channel systems     

A. Hibma  Z. B. Wang  M. J. F. Stive  H. J. de Vriend 《天津大学学报(英文版)》2008,14(4):271-281

For a channel-shoal system in a funnel-shaped basin the impact of dredging and dumping is investigated using a complex process-based model. First, the residual flow and sediment transport circulations are analysed for the channel-shoal pattern, which has emerged after a long-term model simulation. Results are compared to the Western Scheldt estuary, which forms the inspiration for this study. Subsequently, different dredge and dump scenarios are modelled, according to a conceptual model, in which ebb-and flood-channels and enclosed shoals form morphodynamic units (cells) with their own sediment circulation. Model results show that dumping sediment in a channel further reduces the channel depth and induces erosion in the opposite channel, which enhances tilting of the cross-section of the cell and eventually can lead to the degeneration of a multiple channel system into a single channel. The impact of different dredging and dumping cases agrees with results from a stability analysis. This means that this type of model applied to a realistic geometry can potentially be used for better prediction of the impact of human interventions.  相似文献   

Numerical investigation of penetration performance of non-ideal segmented-rod projectiles     

ALY S Y  LI Q M 《天津大学学报(英文版)》2008,14(6):391-395

The design of a segmented-rod projectile is often simplified into an ideal one in theoretical analysis for the convenience of modeling of its performance. But the actual performance of non-ideal segmented-rod projectiles over the impact velocity range in practical applications was rarely explored. AUTODYN numerical code is used to investigate the influence of the component design upon the penetration performance of non-ideal segmented-rod projectiles over a wide range of impact velocities, which can be used to guide the optimal design of weaponry segmented-rod projectiles.  相似文献   

Compressive Strength of Hydrostatic-Stress-Sensitive Materials at High Strain-Rates     

LI Q M  LU Y B 《天津大学学报(英文版)》2008,14(5):324-328

Many engineering materials demonstrate dynamic enhancement of their compressive strength with the increase of strain-rate, which have been included in material models to improve the reliability of numerical simulations of the material and structural responses under impact and blast loads. The strain-rate effects on the dynamic compressive strength of a range of engineering materials which behave in hydrostatic-stress-sensitive manner were investigated. It is concluded that the dynamic enhancement of the compressive strength of a hydrostatic-stress-sensitive material may include inertia-induced lateral confinement effects, which, as a non-strain-rate factor, may greatly enhance the compressive strength of these materials. Some empirical formulae based on the dynamic stress-strain measurements over-predict the strain-rate effects on the compressive strength of these hydrostatic-stress-sensitive materials, and thus may over-estimate the structural resistance to impact and blast loads, leading to non-conservative design of protective structures.  相似文献