嵌地半圆形刚平台双自由度传感系统地动响应

利用波函数展开法和振动理论讨论了半空间界面半圆形刚性平台上双自由度振动系统的反平面响应问题。利用弹性波动理论写出半空间介质内的总位移波场,应用振动理论列出双自由度振动系统满足的二阶常系数微分方程组,通过半圆形刚性平台与介质界面之间的位移和应力连续条件求出散射波函数中未知系数,最后确定出振子和半圆形刚性平台分别相对于入射波振幅的位移振幅比以及刚性平台边界处介质内的环向应力集中系数的变化规律,并通过数值算例给出了计算结果,说明了分析结论的正确性。     

半空间界面弹性柱支撑体对反平面SH波的动态响应

利用波函数展开法和格林(Green)函数法讨论半空间水平界面上弹性柱支撑体对入射反平面SH(shearinghorizontal)波的散射效应。首先解一个双曲偏微分方程定解问题,确定出不含界面弹性柱支撑体的完整半空间内的自由位移场及其对应的格林函数解;其次,利用叠加原理得到含界面弹性柱支撑体时半空间内的总位移场,并通过牛顿定律列出弹性柱支撑体的动态响应方程;最后借助于问题的位移边界条件和力边界条件写出未知力满足的定解积分方程,并给出其解析解。通过一个算例的数值解说明方法的可行性。     

直角平面内圆形刚性动夹杂对边界出平面点源载荷的动态响应

采用复变函数法和多极坐标移动技术研究二维直角平面区域内可动圆形刚性夹杂在边界出平面点源载荷作用下的动态响应问题.首先构造出直角平面区域内不含有夹杂时满足直角边界应力条件的格林(Green)函数解;其次求解波动方程边值问题,建立直角平面区域内含有夹杂时满足直边界应力自由条件的散射波解,利用叠加原理写出问题的总波场.借助于夹杂边界处的位移条件和夹杂运动的动力学条件,确定夹杂运动的位移幅度和散射波解中的未知系数.给出的算例结果表明本文方法的有效实用性.     

双材料界面裂纹动态扩展的数值模拟

基于扩展有限元方法(XFEM),研究了双材料中界面裂纹和亚界面裂纹的动态扩展问题.建立了双材料板界面裂纹和亚界面裂纹的动态增长分析模型,该模型使用集中质量矩阵代替传统的一致质量矩阵以提高效率,并利用Newmark法进行时间积分.将该模型与在有限元软件中建立的二维弹性模型计算获得的动力响应和能量值进行比较.通过数值算例,研究了应变率和材料特性对圆形和直线双材料中界面和亚界面裂纹扩展的影响.     

利用状态空间法实现对系统的控制

现代控制理论中的状态空间法对线性与非线性问题均适用．通过状态空间理论建立系统的状态方程及其解法。实现对系统的控制。利用实际算例，表明状态空间法是分析系统动态响应的一种有效方法。     

谐波位移激励下螺旋形弹簧的拉扭耦合动力响应

建立了一种普遍的解析理论 ,利用简正模态法研究确定性位移激励下拉扭耦合螺旋形弹簧的动力响应。假定位移激励是谐波变化的 ,得到了各种谐波位移激励下封闭形式的解。提出并讨论了动力拉伸位移和扭转位移的数值结果     

基于关键时间点的能量等效静态载荷法及结构动态响应优化

基于位移的等效静态载荷法是目前解决动态约束处理困难、计算收敛性差的结构动态响应优化问题的有效途径,针对位移等效静态载荷法的优化结果不准确、工程实用性差等不足,提出一种基于能量等效的动态载荷静态转化方法。该方法通过结构在动、静态载荷作用下能量变化关系推导,分析能量等效的基本原理,在载荷等效转化时刻识别基础上,进一步构建了基于能量等效理论的动态载荷等效静态转化的优化模型,最后应用全局优化算法求解找到了等效静态载荷,并以文献经典算例——124杆桁架结构为例验证方法的有效性和准确性;将理论研究成果应用于发动机活塞的动态优化设计中,验证了方法的工程实用性,同时为基于等效静态载荷法的结构动态响应优化设计提供了一种新的思想。     

剪切载荷作用下胶接材料界面动应力强度因子的研究

主要研究剪切载荷作用下,胶接材料中弹性和粘弹性界面间Griffith裂纹尖端动态应力强度因子的时间响应.采用积分变换方法,得到Laplace域内弹性和粘弹性材料的应力和位移的含未知系数的表达式;引入位错密度函数,并通过边界条件和界面连接条件,导出反映裂纹尖端奇异性的奇异积分方程组,采用Gauss积分,并运用Gauss-Jacobi求积公式化奇异积分方程组为代数方程组,利用配点法进行求解;最后经过Laplace逆变换,求得动态应力强度因子的时间响应.得到Ⅱ型动应力强度因子随着粘弹性材料的剪切松弛参量的增加而增大,膨胀松弛参量的增加而减小;随着弹性材料的剪切模量和泊松比的增加而增大.     

升船机多钢丝绳受力液压均衡特性研究

在提升钢丝绳和船厢之间设立液压油缸,可起到均衡钢丝绳受力的作用。而升船机液压均衡子系统为一阶反馈系统,与机械提升等二阶结构子系统在建模方式上存在巨大差异,无法求其动态响应。为此,利用卷扬系统与液压系统在界面耦合处力和位移协调关系,提出一种动态耦合的分析方法,建立机械卷扬-液压均衡系统数学模型;根据合并后的机械卷扬-液压均衡系统数学模型,提出利用界面凝聚的动态子系统方法,建立包括机械卷扬-液压均衡、承船厢和塔柱等子系统在内的升船机综合动力学方程。最后,利用整体动态仿真结果对液压均衡油缸的拉力均衡特性进行动态分析。     

半空间边界半圆形凹陷对SH波散射的模糊响应

利用波函数展开法考虑半空间边界半圆形凹陷对SH(shearing horizontal)波的(模糊)散射问题,得到边界半圆形凹陷处环向动应力集中系数和位移放大系数与波数之间的非线性关系式,考虑到波数的模糊性,为避免区间算法的不可逆性以及非线性方程求解的困难,特将模糊量隶属函数分段处理,使隶属度与模糊量一一对应,从而将原来的模糊问题转化为分段处理的确定性问题.给出的算例具体讨论凹陷边界处环向动应力集中系数和位移放大比率由于波数的模糊性而带来的模糊变化分布情况.     

具有不连续表面细长轴的表面精糙度与磨削振痕间关系的探讨

本文从被加工表面磨削条痕的间接研究出发,提出周向振痕和轴向振痕的概念,解决了生产中振痕测量问题。运用统计学手段,采用大样本对影响磨削振痕的几个主要工艺参数进行相关分析,解出回归方程。阐明表面粗糙度与磨削振痕间的关联可用一条双曲线解释。对于磨削振痕的旋向,指出有直纹、左旋和右旋。同时发现外圆交叉网纹状振痕,其再现率仅为12.5%。通过正交试验,指明在外圆、内圆和无心磨削中有效地控制磨削振痕的工艺方法。     

基于特征的复杂曲面反求建模技术研究

几何建模技术是先进制造技术的基础,反求工程是建立产品几何模型的重要手段,复杂曲面几何模型的重建是反求工程研究的重点内容。系统研究了基于实物的复杂曲面几何形状反求建模技术。提出了一种基于特征的复杂曲面几何建模方法,它包括四个主要步骤：首先,对数字化数据进行必要的处理,并建立数字化点之间的拓扑关系;然后,利用这些拓扑关系,提取曲面的几何特征,并依据这些特征对复杂曲面进行分块处理;接着,对每块进行基于特征的曲面构造和数据压缩;最后,将各块拼接形成整体光滑的曲面。     

基于实物的复杂曲面零件反求工程中未知区域测量数据补充及曲面重构技术

针对基于实物的复杂零件反求工程中含有部分形状未知区域（如裁减曲面中的被裁减部分、测量盲区等）的复杂曲面反求CAD建模问题,提出了三种测量数据补充方法:①局部区域实物填充法。②补充设计数据补充法。③基于逼近曲面或三角曲面的测量数据自动补充法。研究了基于三角曲面模型初始表达的复杂曲面分区NURBS曲面重构方法。最后,给出了结合上述方法和反求工程软件RE-SOFT所解决的摩托车塑料件反求CAD建模实例。实践表明,综合运用所提出的数据补充和曲面重构方法,能够大大缩短实物样件的反求CAD建模时间,提高复杂曲面产品的设计效率。     

MACHINING OF CORTICAL BONE: SURFACE TEXTURE,SURFACE INTEGRITY AND CUTTING FORCES

Cutting, drilling and reaming of human bone are conducted in total joint replacement procedures and the placement of dental implants. In the current study orthogonal machining of cortical bone was performed and the cutting and thrust forces, as well as the machined surface quality, were evaluated over a range of osteon orientations and cutting conditions. Results showed that cutting perpendicular to the osteons resulted in the highest machining forces, largest surface roughness and extensive sub-surface damage for some parametric conditions. The average surface roughness of the machined bone ranged from 1 μm to over 70 μm, was largest for positive rake angle tools and increased with the depth of cut. There was no correlation between the cutting forces and machined surface quality. While negative rake angle tools resulted in the largest cutting forces, they provided the lowest surface roughness and highest apparent surface quality. Overall, the results show that orthogonal cutting of bone can result in near-surface damage that reduces the degree of contact between bone and implanted devices and is potentially detrimental to the post-surgical recovery rate.     

MACHINING OF CORTICAL BONE: SURFACE TEXTURE, SURFACE INTEGRITY AND CUTTING FORCES

Cutting, drilling and reaming of human bone are conducted in total joint replacement procedures and the placement of dental implants. In the current study orthogonal machining of cortical bone was performed and the cutting and thrust forces, as well as the machined surface quality, were evaluated over a range of osteon orientations and cutting conditions. Results showed that cutting perpendicular to the osteons resulted in the highest machining forces, largest surface roughness and extensive sub-surface damage for some parametric conditions. The average surface roughness of the machined bone ranged from 1 μm to over 70 μm, was largest for positive rake angle tools and increased with the depth of cut. There was no correlation between the cutting forces and machined surface quality. While negative rake angle tools resulted in the largest cutting forces, they provided the lowest surface roughness and highest apparent surface quality. Overall, the results show that orthogonal cutting of bone can result in near-surface damage that reduces the degree of contact between bone and implanted devices and is potentially detrimental to the post-surgical recovery rate.     

TIG焊熔池表面张力的测定及表面活性剂的影响

利用熔池振荡及熔池谐振信号的检测,以熔池自身固有振荡频率与熔池尺寸的内在关系测定熔池金属表面 张力,研究了薄板ＳＵＳ３０４不锈钢ＴＩＧ焊不同熔地尺寸的表面张力变化以及活性剂对熔池表面张力的影响。试验研 究方法为焊接熔池表面张力测定中的最初应用。     

广义断裂性能曲面

分别利用多参数的福尔曼（Ｆｏｒｍａｎ）和沃克尔（Ｗａｌｋｅｒ）裂纹扩展模型,将应力强度　因子变程ΔＫ和应力强度因子均值Ｋｍ作为二元变量,建立了空间Ｋｍ－ｄａ／ｄＮ－ΔＫ曲面。考虑应力幅值和均值的共同作用,建立了沃　克尔型裂纹扩展　寿命　的σａ－σｍ－Ｎ＊曲面。作为表征材料断裂可靠性性能的重要指标,　讨论了断裂性能曲面的测定与拟合方法,并给出了具体应用实例。     

PERIODIC DEFORMATION OF PARAMETRIC SURFACE

Deformation is a powerful tool for geometric modeling and design. Such a tool can be used to create a new shape from existing shape without restarting whole design process. A new mathematical model for producing controllable periodic deformations is proposed. By introducing cosine extension functions construct a shape operator matrix and then use the matrix to transform the position vector of some points on the object surface so as to create the deformation effects. Because the cosine extension (Unctions have a number of variable parameters with different properties, the method has corresponding interactive control means. The user can manipulate those parameters to get desirable periodic deformation effects. Experimental results show that the method is feasible and applicable to engineering and research fields such as sheet metal forming by stamping and CAD.     

A MINIATURE SURFACE PLASMON RESONANCE BIOANALYTICAL SYSTEM FOR FIELD DETECTION OF MICROCYSTIN-LR IN SURFACE WATER

A miniature surface plasmon resonance (SPR)–based immunoassay system for analyzing microcystin-LR (MC-LR) in surface water has been developed. A Spreeta biosensor was adopted in the SPR flow injection analysis (FIA) system. An optional biofilm immobilization method was exploited using covalent-coupling between a bioconjugate of microcystin-LR and bovine serum albumin [(MC-LR)-BSA] and the golden surface. An acceptable relative standard deviation of repeatability, 1.29% (n = 20), was achieved. An analysis of the calibration curve showed that this method has a detection limit of 0.55 ng/mL, a half-maximal inhibitory concentration (IC₅₀) of 5.6 ng/mL, and a quantitative range of 1.56–25.00 ng/mL. The recovery from water samples containing varying concentrations of MC-LR ranged from 90% to 112%. After samples of tap water and pool water were assayed, it was concluded that tap water did not contain a measurable amount of the analyte, whereas pool water contained 2.39 ng/mL. Compared to other methods of analysis, SPR immunoassay has the advantage of being label-free, rapid, and cost-effective and can easily detect levels of MC-LR within the World Health Organization (WHO) drinking water guidelines. The SPR FIA system with reusable biosensor is compact and convenient for instant in situ determination of MC-LR levels in environmental water.     

ISSUES IN MODELING MACHINED SURFACE TEXTURES

This paper discusses the issues involved in modeling surface textures generated during machining and presents the potential of scale-sensitive fractal analysis in addressing these issues. Modeling surface texture creation supports the design machining processes for producing product surface textures with desired properties. The current understanding of how surface textures behave is largely incomplete. In order to understand how surface textures influence surface behavior, it is necessary to a) develop surface texture characterization methods with enough sophistication to capture the essence of the information inherent in the surface texture, and b) convey it so that the discovery of functionality, or behavior, of the texture is enabled. For a model of texture formation to be useful, the parameters that it calculates must be the same as the parameters that explain the texture behavior.