Compressive deformation of semi-solid SiC_p/ZA27 composites

1　INTRODUCTIONTheapplicationofcastingSiCp/ZA2 7compositesisgreatlylimitedduetotheinhomogeneousdistribu tionofSiCpandtheporosityexistedinthematrix[1] .However,semi solidformingtechnology (SSF )e mergedintherecentyearscannotonlydecreaseore liminatetheporosityandenhancethecompactnessofthematrix ,butalsoimprovetheuniformdistributionofthereinforcementthroughtheredistributionofthereinforcementfromitsuniquecharacteristicsofmouldfilling[2 ] .Inaddition ,SSFisanearnet shapeform ingtechnology …     

几何造型的自由畸变方法

几何造型是计算机图形学的重要研究内容，ＣＡＤ／ＣＡＭ的核心技术，现行的许多造型系统仅限于造型二次曲面及旋转曲面，没有自由曲面造型能力，本文研究的自由畸变为法，很容易扩展这些系统的自由曲面造型功能，该方法已成功地用于扩展ＭＯＶＩＥ．ＢＹＵ系统的自由曲面造型功能。     

方盒形带凸缘件的板料形状优化设计

本文用大变形刚塑性有限元模拟正方形板料在方冲头拉延下的凸缘变形过程，并以所获得的工件形状与金属流动方向为依据，对初始板料形状进行修正。对修正后的坯料形状进行二次模拟，获得了与给定凸缘形状基本吻合的拉延件形状。文中对不同凸缘圆角对极料优化形状的影响作了计算，讨论了在保证边界轮廓位置不变的条件下网格划分的方法。     

Application of Galerkin Method to Dynamical Behavior of Viscoelastic Timoshenko Beam with Finite Deformation

The motion equations governing the dynamical behavior of a viscoelasticTimoshenko beam with finite deformation are derived and simplified byGalerkin method. The viscoelastic material is assumed to obey thethree-dimensional fractional derivative constitutive relation. Thedynamical behaviors of the simplified systems with order 1 and order 2are numerically computed and compared by using the computational methodpresented by the authors. The dynamical behaviors of the systems areuniform qualitatively, but there is a little deviation quantitatively.And the truncated system with order 1 is safer than the one of order 2.It is also shown that the lower order system is reasonable. Theinfluences of the load parameter and the fractional derivative parameter(material parameter) on the deflection of the beam are consideredrespectively. The numerical methods in nonlinear dynamics, such as phasediagram, and Poincaré section, are applied to reveal dynamical behaviorsof the nonlinear viscoelastic Timoshenko beam. There are plenty ofdynamical behaviors, such as periodicity, bifurcation, quasi-periodicityand chaos in the dynamical system.     

6063铝合金型材挤压"堵模"的成因及其对策

从6063铝合金铸锭、挤压工艺条件、模具、金属的不均匀变形等方面分析型材挤压时发生“堵模”现象的原因；提出了其防止措施。     

小浪底水库调水调沙运用对大坝变形的影响分析

自2002年以来,小浪底水库汛前利用预泄汛限水位以上水量、腾空防洪库容的有利时机,连续5年进行集中调水调沙,获得了巨大的减淤效益.但在调水调沙期间,由于大流量下泄,水库水位下降较快,大坝变形明显增大,表现为水平位移向上游变化、垂直位移加速沉降变化的特点.监测分析结果表明,调水调沙运用不影响大坝安全稳定运行.     

管线钢管夏比冲击试验注意事项

结合管线钢管标准规范,分别从取样、试样加工、试验设备及试验过程等方面分析了管线钢管夏比冲击试验中可能出现的问题,并针对试验温度控制和操作过程提出了几点建议.     

薄板坯表面变形实验分析

对连铸薄板坯的坯壳表面变形的物理模拟实验方法进行了分析,提出一种"铜裹铅双金属"新实验方案,并对坯壳表面弯曲变形进行了分析.     

Ultrasonic measurement of the inter-electrode gap in electrochemical machining

During the process of electrochemical machining the dependency of the inter-electrode gap with time and process parameters can be used to determine process characteristics and to define the shape of the workpiece surface relative to the tool surface. Defining process variables to map out the required gap-time function requires the use of time-consuming iterative trials. In-line monitoring of the gap would enable process control and tool to workpiece transfer characteristics to be achieved (for ideal conditions) without the requirement to generate such parameter maps. This work explores the use of ultrasound applied as a passive, non-intrusive, in-line gap measurement system for ECM. The accuracy of this technique was confirmed through correspondence between the generated gap-time and current time data and theoretical models applicable to ideal conditions. Gap measurements are also used to demonstrate and quantify the degree of departure from ideal behaviour for an In718/chloride system as the electrolyte flow rate is reduced from 16 to 4 l min⁻¹. The monitoring of the gap size has also been shown to be effective when determining shape convergence under ideal conditions, for the example case of a 2D sinusoidal profile.