【作者】 张凯；

【导师】 李刚；

【作者基本信息】 大连理工大学 ， 工程力学， 2012， 博士

【摘要】 大载荷、大惯量、多自由度的重载操作机具有较强的多维度力位操控能力,与大型的液压机协调作业,可以大大提高制造能力、制造精度、生产效率和材料利用率,降低能耗。如何保证在极端条件下,重载操作机的操作性能、构件之间的力承载能力、界面特性以及操作机关键构件的刚度特性是重载操作装备设计所面临的关键问题。本文结合国家重点基础研究发展计划(973计划,2006CB705403)课题“非连续工况下重载装备的界面行为与力学特性”,开展了重载操作机关键构件的相关研究。将不确定性分析和优化思想应用于重载操作装备,重点研究了基于降维法可靠性算法以及相关变量的可靠性算法,深入讨论了重载操作机关键构件的力学性能、可靠性分析和结构优化设计,为重载操作装备的设计提供相关的理论、方法与技术支持。本文的主要内容如下：1.提出归一化的基于矩的积分方法(NMBQR)。针对单变量维数缩减法(降维法)中的MBQR方法存在的数值不稳定问题,提出了改进降维法中NMBQR方法。当求解问题中输入参数的均值很大或者变异系数很小的时候,NMBQR方法通过矩阵系数归一化可以有效地改善线性方程组求解过程中由于系数矩阵奇异导致的数值不稳定问题。2.通过将改进的降维法与计算响应概率密度函数(PDF)的最大熵方法进行联合,提出了改进降维法的可靠性算法。并通过各种算例验证了改进降维法求解结构可靠度的优点在于不需要求解响应函数的导数以及不需要迭代求解最可失效概率点(MPP点)等,在进行结构可靠性分析的时候具有较高的计算效率。3.提出了基于改进降维法的相关变量可靠性算法。通过Nataf变换和Winterstein近似可以对任意分布的相关变量进行标准正态化,并采用Cholesky分解进行变量的独立化,最后采用改进降维法求解结构的可靠度。与仅在MPP点进行等概率变换的基于JC法的相关变量可靠性方法相比,Nataf变换方法是在设计空间的全域内进行等概率变换。本文采用二维Gauss-Hermite积分来进行求解Nataf变换前后的相关系数；通过求解多项式方程可以得到Winterstein近似变换后相关系数的解析解,具有较高的计算效率。4.进行了基于替代模型的操作机侧壁结构的可靠性分析。考虑操作机侧壁结构中不确定性参数,如肋板的厚度、侧板的厚度以及载荷等信息,通过经典的替代模型方法得到这些参数与结构响应的显式函数关系。考虑输入载荷之间具有较强的相关关系,利用本文提出的基于改进降维法的相关变量可靠性算法计算操作机侧壁结构的可靠度。5.对重载操作机侧壁结构进行了拓扑与尺寸优化设计,提出了一种新型的重载操作机侧壁框架结构,降低了材料用量而且提高了结构的力学性能。针对操作机侧壁框架的初始设计不能充分地利用材料以及有效地提供侧壁框架侧向刚度的问题,本文进行了基于最大化结构刚度的拓扑优化设计。其主导思想是通过拓扑优化确定材料的分布区域,用于指导侧壁肋板的分布,并根据拓扑优化的结果建立新的侧壁框架有限元模型,然后采用了基于替代模型的尺寸优化设计来获得最优的设计尺寸。优化结果显示,在减少材料用量的情况下,仍然能够保持结构的强度和刚度不降低甚至有所提高。更多还原

【Abstract】 The heavy duty forging manipulator, with the heavy load, large inertia and multi-degree-of freedom, has the capacity of multi-dimensional control of forces and positions, which could greatly improve the capacity and precision of manufacture, production efficiency, material utilization and reduce the energy consumption working together with the heavy duty hydraulic. The key issues for the heavy duty forging manipulator design focus on how to guarantee the operating performance of the forging manipulator, the capacities of strength and stiffness of the components, the interface characteristics between the key components under the extreme conditions. With the support of the973Program "the mechanical properties and interface characteristics of the heavy load manipulator under discontinuous load cases"(No.2006CB705403),this paper introduces the uncertainty analysis and optimization thoughts into the heavy duty equipment concentrates on the reliability algorithm based on the Univariate Dimension Reduction Method(UDRM,DRM) and the correlated random variable for the reliability algorithm, and discusses the key issues, such as the mechanical properties of the key component of the forging manipulator, reliability analysis and the structural optimization design.Related studies of this paper are listed as follows:1. The Normalized Moment Based Quadrature Rule (NMBQR) is proposed. The numerical instability of the Moment Based Quadrature Rule (MBQR) in the DRM could occur in the condition of the great mean value or the small coefficient of variation of the input parameters. The NMBQR could effectively improve the numerical instability of singular coefficient matrix by normalizing the parameters when solving the linear equations.2. The reliability algorithm based on the Improved Dimension Reduction Method is proposed by combining the Improved DRM and Maximum Entropy Method (MEM) which is used to calculate the probability density function (PDF) of the response. The results of the numerical examples show that the reliability algorithm based on the Improved DRM has the great advantages, such as no need of the derivative of the response function and the iterative procedure for the Most Probable failure Point (MPP), resulting in high computational efficiency.3. The Improved DRM based reliability algorithm for the correlated random variables is proposed. The Nataf transformations and Winterstein approximations could normalize the correlated random variables with arbitrary distributions. The independent random variables could be obtained by the Cholesky factorization and the reliability can be calculated by the improve DRM. Compared to JC method for the correlated variables, the Nataf transformations give the equivalent probability transformations on all domain of the design space. As for the correlation coefficient in the Nataf transformations, the two-dimensional Gauss-Hermite quadrature is carried out instead of the empirical formula. The correlation coefficient is obtained by the polynomial equation for the Winterstein approximations, which has the closed-form solution with high computational efficiency.4. The reliability analysis for the wall frame of the forging manipulator based on the surrogate model is carried out. The uncertainty factors include the thickness of the ribs, the thickness of the side wall and the load. The explicit function of the structural response with respect to the input parameters can be achieved by the Design of Experiment (DOE) and Response Surface Method (RSM).The reliability of the wall frame of the forging manipulator is calculated by the proposed method considering the strong correlated relationship between the loads.5. The structural optimization for the wall frame of the forging manipulator is performed and a new type of wall frame structure of the forging manipulator is proposed. The mechanical properties of the new type wall frame structure are improved with the less material consumption. Due to the lack of the effective utilization of the materials and the less contribution to the side stiffness of the original design of the wall frame, the topology optimization for the maximum structural stiffness is given. The results of the topology optimization is introduced to the distribution of the ribs of the wall frame and the new finite element model (FEM) is built. Then the optimal designs are obtained by the sizing optimization based on the surrogate model, which show that the stiffness and strength are improved with the reduction of the materials.更多还原