Hierarchical models for failure analysis of plates bent by distributed and localized transverse loadings     

Erasmo Carrera  Gaetano Giunta 《浙江大学学报(A卷英文版)》2008,9(5):600-613

The failure analysis of simply supported, isotropic, square plates is addressed. Attention focuses on minimum failure load amplitudes and failure locations, von Mises＇ equivalent stress along the plate thickness is also addressed. Several distributed and localized loading conditions are considered. Loads act on the top of the plate. Bi-sinusoidal and uniform loads are taken into account for distributed loadings, while stepwise constant centric and off-centric loadings are addressed in the case of localized loadings. Analysis is performed considering plates whose length-to-thickness ratio a/h can be as high as 100 （thin plates） and as low as 2 （very thick plates）. Results are obtained via several 2D plate models. Classical theories （CTs） and higher order models are applied. Those theories are based on polynomial approximation of the displacement field. Among the higher order theories （HOTs） HOTsa models account for the transverse shear deformations, while HOTs models account for both transverse shear and transverse normal deformations. LHOTs represent a local application of the higher order theories. A layerwise approach is thus assumed： by means of mathematical interfaces, the plate is considered to be made of several fictitious layers. The exact 3D solution is presented in order to determine the accuracy of the results obtained via the 2D models. In this way a hierarchy among the 2D theories is established. CTs provide highly accurate results for a/h greater than 10 in the case of distributed loadings and greater than 20 for localized loadings. Results obtained via HOTs are highly accurate in the case of very thick plates for bi-sinusoidal and centric loadings. In the case of uniform and off-centric loadings a high gradient is present in the neighborhood of the plate top. In those cases, LHOTs yield results that match the exact solution.  相似文献   

高速抓取并联机器人实验平台运动学建模与分析     

陈修龙  盛永超 《实验室研究与探索》2021,(1):101-106

提出了一种新型3-RRPaR高速抓取并联机器人结构,对3-RRPaR高速抓取并联机器人实验平台进行运动学建模和分析。介绍了3-RRPaR高速抓取并联机器人实验平台的结构特点,建立了实验平台的运动学正反解模型,并通过Matlab数值计算和ADAMS虚拟样机仿真验证了运动学分析的正确性。  相似文献   

“一带一路”背景下我国高职商务英语教学困境与纾解路径     

陈青凤 《孝感职业技术学院学报》2021,(1):49-52

“一带一路”倡议的实施要求高职商务英语教学更加突出复合型、应用型人才培养目标,而目前高职英语教学忽视了“一带一路”沿线国家本土化英语表达下的语言障碍,存在课程设置单一、教材内容滞后、师资力量薄弱等问题。为此,必须设置多样化培养课程,采用多元化教学模式与评价方式,推动产教融合,以培养“一带一路”建设所需的优质商务英语人才。  相似文献   

On design of continuous Lyapunov's feedback control     

Q. Wu  P. Sekhavat 《Journal of The Franklin Institute》2005,342(6):702-723

A common approach to Lyapunov's stability control is to design a controller such that a Lyapunov function can be derived for the control system to ensure stability. This procedure often leads to a discontinuous controller. When the controller is implemented, the discontinuous terms are replaced with continuous functions to avoid chattering of the control signal. Two associated problems have been overlooked during this procedure. One is that discontinuous control systems are non-smooth, which violates the fundamental assumptions of solution theories and the applicability of Lyapunov's stability theory is questionable. Another problem is that the replacement of discontinuous terms may weaken stability, which can be critical. In this paper, we discuss proper stability analysis of discontinuous control systems using the extended Lyapunov's second method based on Filippov's solution concept for non-smooth systems. We further propose to utilize the concept of Lyapunov exponents to quantitatively analyze the stability of continuous control systems obtained by replacing the discontinuous terms in the discontinuous controllers. An example involving the stabilization of a two-link non-fixed-base robotic manipulator is presented for demonstration. This research fills the gap in designing continuous Lyapunov's stability controllers regarding limited available Lyapunov functions.  相似文献   

面对跨国并购中国亟待解决的几个问题   总被引：1，自引：0，他引：1  

褚东风  黄汉江  褚东伟 《软科学》2001,15(6):42-45

90年代后期以来跨国并购出现高潮,并成为世界对外直接投资的主要形式。跨国并购高潮的出现是受利益驱动的,中国将不可避免地被卷入这种浪潮中。本文通过对跨国并购的国际趋势和理论以及跨国并购在中国的发展的分析,从经济政策、法律环境和经济手段等角度提出了几个中国亟待解决的问题。  相似文献   

B2C商务模式下信息不对称问题的解决方案   总被引：1，自引：0，他引：1  

邹婷婷  唐琼  杨芬 《现代情报》2006,26(8):65-68

基于B2C商务模式下商家和消费者的信息不对称现象。将多种因素引入商家与消费者交易的博彝模型，进行完全信息静态博彝分析，进而得出影响纯蚋什均衡和混合蚋什均衡的因素主要有：产品成本、商家的交易成本、消费者受骗的精神损失、消费者对商品的评估价值与商品价格之差。最后提出此种信息不对称的消减措施．从而提高B2C商务的市场效率。使商家和消费者的利益最大化。  相似文献   

积分方法在椭圆型方程解的存在性中的应用     

韩登利 《新乡师范高等专科学校学报》2007,21(2):16-17

结合ODE标准理论和积分方法,通过Lengendre变换,给出了一类拟线性椭圆型偏微分方程整体径向解存在(不存在)的一个充分必要条件。  相似文献   

Analytical Method Determining Resonant Response of Blade with Dry Friction Damper     

丁千  周翔 《天津大学学报(英文版)》2007,13(4):291-296

Service failures of turbine blades in many instancescan be attributedto highcyclefatigue caused bylarge reso-nance stress .As dryfrictioninterface may be the most im-portant source of energy dissipation,thefriction damperis atypical devicetoreduce vibrati…  相似文献   

略论我国司法解释的问题及对策   总被引：2，自引：0，他引：2  

李涛 《云南师范大学学报(哲学社会科学版)》2004,36(1):51-54

司法解释对于弥补法律规范本身存在的缺漏 ,保证法律的正确实施 ,具有重要的作用。目前我国法律实践中的司法解释还存在不少问题 ;对法律的实施产生了消极影响 ,只有采取针对性的措施解决这些问题 ,才能提高司法解释的质量 ,保证法律实施的准确和公正  相似文献   

实验室开放问题探析及应对策略   总被引：19，自引：13，他引：19  

张林 《实验室研究与探索》2006,25(10):1289-1292

从高校实验室开放实践看,实验室开放仍然存在许多问题,综合反映在实验技术队伍、运转维持费、开放效益三个方面,文章结合该校及部分高校实验室开放的实践和反映出的问题进行分析探讨,提出了相应的解决对策。  相似文献