平面柔顺精密定位机构疲劳可靠性研究

发布时间：2018-03-22 21:24

本文选题：柔性铰链　切入点：精密定位机构　出处：《华南理工大学》2016年博士论文　论文类型：学位论文

【摘要】：柔顺精密定位平台在精密加工、半导体制造业和生物医学工程等领域得到广泛应用,构成平台主体的柔顺机构在重复运动过程中承受交变应力而易发生疲劳失效。传统平台往往基于静力强度和确定性方法设计,这可能导致机构提前疲劳失效或过量设计。本文主要对平面柔顺精密定位机构的疲劳可靠性进行研究,在此基础上优化设计了满足要求疲劳寿命和可靠性的机构。此外,建立了铰链的疲劳损伤刚度退化模型,并以此为基础研究了平面柔顺机构疲劳损伤特性分析方法,全文研究内容如下:(1)为了建立平面柔顺精密定位机构精确的分析模型,研究了柔顺机构建模分析的伪刚体封闭环方法和有限单元方法。推导了直圆型柔性铰链等典型单元的刚度矩阵,以平面三自由度柔顺精密定位机构为研究对象,采用有限单元方法求解了机构的雅克比矩阵、最大工作范围、驱动力、固有频率和各个铰链的最大静应力。分析结果与商业ANSYS软件的仿真结果进行对比,验证了本文方法的有效性。(2)综合考虑材料、尺寸参数和表面状况等对铰链疲劳极限的影响,基于材料静力强度估测了铰链的疲劳极限,给出了典型铰链的S-N曲线。以平面三自由度柔顺精密定位机构为研究对象,基于有限单元和序列二次规划方法对各个铰链的最大疲劳应力及其所在位置进行了分析。结合铰链S-N曲线,预测了铰链及机构在恒幅载荷下的疲劳寿命。采用雨流计数法进行循环计数,预测了机构在变幅载荷下的疲劳寿命。结果显示,基于静力强度理论设计的机构有时会提前疲劳失效。为此,以机构疲劳强度、最大驱动力及最低固有频率为约束条件,以机构的工作范围最大为目标函数,给出了一种新的基于疲劳强度理论的平面柔顺机构优化设计方法,有效解决了传统基于静力强度理论设计的机构会提前疲劳失效的问题。(3)将材料和尺寸参数等处理为随机变量,采用矩法和代数法分别计算机构中各个铰链疲劳应力及疲劳强度的方差,基于应力强度干涉理论,对铰链及机构的疲劳可靠性进行建模分析,结果显示基于静力强度设计的机构,疲劳可靠性有时不能满足要求。为此,以平面三自由度柔顺精密定位机构为研究对象,给出了一种基于疲劳可靠性理论平面柔顺机构优化设计方法,并分析了机构疲劳可靠性同各尺寸参数及方差的关系。最后通过Monte-Carlo仿真和实验验证了设计方法的有效性。(4)对直圆型柔性铰链进行疲劳试验,提出使用三个特征点和多段曲线对铰链刚度曲线进行建模的方法,并拟合了铰链特征寿命同疲劳应力的关系。通过改变铰链尺寸参数进行了疲劳试验,建立了铰链的疲劳应力集中系数同尺寸参数和特征寿命的关系。通过进行非零平均应力下铰链的疲劳试验,给出了其等效疲劳应力公式。在此基础上,研究了基于有限单元方法的平面柔顺机构疲劳损伤特性预测方法,以柔顺桥式放大机构为例,实验验证了方法的有效性。
[Abstract]:Compliant precision positioning platform in precision machining, widely used in semiconductor manufacturing and biomedical engineering field, compliant mechanism constituted the main part of the platform under repetitive motion in the process of alternating stress and prone to fatigue failure. The traditional platform often static strength and definite method based design, which may lead to early fatigue failure or excessive design. This paper makes the research on the fatigue reliability of planar compliant precision positioning mechanism, based on the optimization design to meet the requirements of fatigue life and reliability of the mechanism. In addition, the establishment of the fatigue damage of hinge stiffness degradation model, and based on the analysis method of fatigue damage characteristics of planar compliant mechanism, the research contents are as follows: (1) in order to establish the analysis model of planar compliant precision positioning mechanism accurately, study the pseudo rigid body sealing analysis of compliant mechanism modeling The closed loop method and finite element method. The stiffness matrix of right circular flexure hinge and other typical units are derived, with three degree of freedom planar compliant precision positioning mechanism as the research object, using the finite element method for solving the Jacobian matrix of the mechanism, the maximum working range, maximum driving force, natural frequency and static stress of each hinge. The simulation results were compared with the commercial ANSYS software results, verify the validity of this method. (2) considering the effect of material, size and surface condition of the hinge fatigue limit of material, static strength estimation of fatigue limit of hinge based on S-N curve is given. Taking the plane hinge three free precise positioning of compliant mechanism as the research object, the maximum fatigue finite element and the sequence of two quadratic programming method of each hinge based on stress and its position are analyzed. Combined with S-N curved hinge To predict the fatigue life of the hinge line, and in constant amplitude loadings. The rain flow counting method for cycle counting, prediction of fatigue life in institutions under variable amplitude loading. The results show that the static strength theory to design the mechanism based on sometimes early fatigue failure. Therefore, the mechanism of fatigue strength, maximum and minimum driving force the inherent frequency as constraints, the largest in the scope of work of the organization as the objective function, this paper presents a new optimization method based on planar compliant mechanism of fatigue strength theory, an effective solution to the traditional static strength design theory will advance the mechanism based on fatigue failure problems. (3) the material and size parameters are treated as random variables with the moment method and the algebra method. The computer is in the structure of each hinge fatigue variance force and fatigue strength, the stress strength interference theory based on fatigue reliability of hinge and mechanism Modeling and analysis results show that the static strength design of mechanism based on fatigue reliability, sometimes can not meet the requirements. Therefore, the planar three DOF compliant precision positioning mechanism as the research object, an optimization design method for fatigue reliability theory of planar compliant mechanism is proposed based on analysis of the relationship between the organization and the fatigue reliability with the dimension parameter and variance finally, the effectiveness of the design method is verified by Monte-Carlo simulation and experiments. (4) the fatigue test of straight circular flexure hinge, proposed method using three feature points and multi curve modeling of the hinge stiffness curve, and the relationship between the characteristics of life with hinge fitting fatigue stress by changing the hinge. The size parameters of the fatigue test, a hinge fatigue stress concentration factor with the size parameter and characteristic life relationship. Through the non zero mean stress The fatigue test of hinges is given, and the equivalent fatigue stress formula is given. Based on that, the prediction method of fatigue damage characteristics of planar compliant mechanism based on finite element method is studied. Taking the compliant bridge amplification mechanism as an example, the validity of the method is verified by experiments.

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH112

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