ANALYSIS OF SYMMETRIC LAMINATED RECTANGULAR PLATES IN PLANE STRESS

Symmetric laminated plates used usually are anisotropic plates. Based on the fundamental equation for anisotropic rectangular plates in plane stress problem, a general analytical solution is established accurately by method of stress function. Therefore the general formula of stress and displacement in plane is given. The integral constants in general formula can be determined by boundary conditions. This general solution is composed of solutions made by trigonometric function and hyperbolic function, which can satisfy the problem of arbitrary boundary conditions along four edges, and the algebraic polynomial solutions which can satisfy the problem of boundary conditions at four corners. Consequently this general solution can be used to solve the plane stress problem with arbitrary boundary conditions. For example, a symmetric laminated square plate acted with uniform normal load, tangential load and nonuniform normal load on four edges is calculated and analyzed.     

CAD／CAM技术在模具中的应用

本文介绍了模具行为中应用ＣＡＤ／ＣＡＭ技术的特点、优越性以及典型模具ＣＡＤ／ＣＡＭ软件系统的功能结构，以期推广模具ＣＡＤ／ＣＡＭ技术在我院民品的应用。     

区域集群下板材订单配置模型及算法研究

针对集群企业板材资源滞留、无法共享、加工旺季材料短缺等问题,依据区域板材特性和区域企业集群地理相关优势,建立以减少需求方板材订单采购费用最小化为目标的板材订单分配模型,采用以粒子群、免疫算法相结合的混合调度算法。计算过程中,将订单分配对应企业编号作为免疫系统的抗体基因,通过比较适应度函数解与订单预算成本的关系,将抗体群区分为支配解与非支配解,提高算法对抗原的免疫能力和最优解的选择概率。最后以板材订单分配实例进行试验仿真,分别采用PSO算法与IA-PSO算法进行试验对比,对平台上6家订单发布企业寻找合适地理位置相近和价格相对低廉的供应商。试验结果表明,IA-PSO算法能够有效地解决区域集群内板材订单的匹配问题,并且在寻找价格更低和位置更合适的供应商上更有优势。     

具有碳纤维材料环的超高压模具

介绍了一种使用钢环和碳纤维复合材料环共同预紧方式的两面顶超高压模具,该结构在全钢环两面顶模具的基础上,使用一层碳纤维复合材料环代替最外层钢环,得到了一种具有碳纤维复合材料环的超高压模具。这种设计避免了大直径钢环难以制造加工的问题,形成一种以钢环与复合材料环共同对压缸预紧的新型预紧方式。数值分析表明:该模具结构设计具有可行性,可以在一定程度上减小压缸的周向应力、最大剪切应力和等效应力。此外,对碳纤维复合材料环进行了失效判别。     

基于透光性能分析的微藻光生物反应器构筑板材选型

利用配备人工光源的光生物反应器(AL-PBR)培养微藻是实现微藻快速增殖,进而满足相关产业需求的重要手段。为指导AL-PBR的构筑材质选型,完善了现有方法,比选了7种市售透明板材。考虑到微藻在不同入射光波段的光生态学,应综合分析板材在光合有效辐射波段(400~700nm)、红光波段(630~700nm)、蓝光波段(430~480nm)和中波紫外线波段(UV-B,280~320nm)的透光性能。前三波段的平均透射率越高越好,UV-B波段反之。测定结果表明:如果AL-PBR以太阳光作为外部光源,现阶段宜采用进口聚碳酸酯板和普通玻璃板作为构筑材质,且前者更佳;如果以单色LEDs灯或荧光灯作为外部光源,宜选用聚甲基丙烯酸甲酯板。     

Belt型两面顶模具温度场和应力场有限元分析及钢带缠绕数值模拟初探

在人造金刚石合成工艺中,两面顶模具合成腔体内的压力和温度起着至关重要的作用.根据对叶蜡石力学和热学行为的研究,基于MSC·Mare非线性有限元软件,建立了压缸温度场和应立场的有限元模型,模型中考虑了热导率等物理参数随温度的变化规律.采用FORTRAN语言开发了适用于温度和压力边界条件加载的相应程序,获得了合成状态下压缸的温度场和应力场分布情况.由温度梯度引起的热应力数值较小,对压缸所产生的影响程度较小.压缸内壁径向应力达到5GPa,接近硬质合金极限抗压强度.轴向应力最大值1GPa,出现在压缸外壁中心处.同时还建立了钢带缠绕模具其动态缠绕过程的简化模型,采用一种修正的库仑摩擦边界条件,模拟了钢带的缠绕过程,获得了钢带缠绕层间的应力、应变分布情况.     

板材冲压翻边的解析理论模型

基于全量塑性理论及膜应变假设,给出两种新的冲压板材内曲拉伸／外曲收缩翻边坯料尺寸预示解析数学模型。引入板材冲压成形性分析软件KMAS系统中,对铁路客车牵引架实际冲压件的翻边成形坯料尺寸进行了预示,并与其它解析模型的预示结果以及实验及实测数据进行了对比。讨论了板材的面内各向异性对翻边高度的影响。     

ELECTRICALLY FORCED THICKNESS-SHEAR VIBRATIONS OF QUARTZ PLATE WITH NONLINEAR COUPLING TO EXTENSION

We study electrically forced nonlinear thickness-shear vibrations of a quartz plate resonator with relatively large amplitude. It is shown that thickness-shear is nonlinearly coupled to extension due to the well-known Poynting effect in nonlinear elasticity. This coupling is relatively strong when the resonant frequency of the extensional mode is about twice the resonant frequency of the thickness-shear mode. This happens when the plate length/thickness ratio assumes certain values. With this nonlinear coupling, the thickness-shear motion is no longer sinusoidal. Coupling to extension also affects energy trapping which is related to device mounting. When damping is 0.01, nonlinear coupling causes a frequency shift of the order of 10^-6 which is not insignificant,and an amplitude change of the order of 10^-8. The effects are expected to be stronger under real damping of 10^-5 or larger. To avoid nonlinear coupling to extension, certain values of the aspect ratio of the plate should be avoided.     

PARALLEL FINITE ELEMENT ANALYSIS OF HIGH FREQUENCY VIBRATIONS OF QUARTZ CRYSTAL RESONATORS ON LINUX CLUSTER

Quartz crystal resonators are typical piezoelectric acoustic wave devices for frequency control applications with mechanical vibration frequency at the radio-frequency （RF） range. Precise analyses of the vibration and deformation are generally required in the resonator design and improvement process. The considerations include the presence of electrodes, mountings, bias fields such as temperature, initial stresses, and acceleration. Naturally, the finite element method is the only effective tool for such a coupled problem with multi-physics nature. The main challenge is the extremely large size of resulted linear equations. For this reason, we have been employing the Mindlin plate equations to reduce the computational difficulty. In addition, we have to utilize the parallel computing techniques on Linux clusters, which are widely available for academic and industrial applications nowadays, to improve the computing efficiency. The general principle of our research is to use open source software components and public domain technology to reduce cost for developers and users on a Linux cluster. We start with a mesh generator specifically for quartz crystal resonators of rectangular and circular types, and the Mindlin plate equations are implemented for the finite element analysis. Computing techniques like parallel processing, sparse matrix handling, and the latest eigenvalue extraction package are integrated into the program. It is clear from our computation that the combination of these algorithms and methods on a cluster can meet the memory requirement and reduce computing time significantly.     

中等精度塑料光学透镜的批量生产技术

提高批量生产中塑料光学透镜的质量及稳定性，需采取综合的技术和管理措施。如提高模具的精度，特别是型芯、型腔的精度；在模具上采用特种浇注系统、控温系统；选择合适的设备；采用合理的工艺及参数；加强生产时的在线质量监控等等。通过二种较典型的塑料光学透镜的生产，证明只要措施得当，就能大批量、稳定地生产出较高合格率的产品。