基于界面相互作用的黏附接触数学模型研究进展

黏附接触现象在各个领域都有着很重要的作用和影响。若要分析物体间的黏附接触行为,则建立相应的数学模型是有效的方法之一。现有文献中的数学模型种类繁多,对于不同受力情况下的黏附现象所适用的理论也不尽相同。针对常见的黏附现象,按照其不同的受力形式分为弹性体接触、粗糙表面黏附及基材表面剥离等几大类,分别对以上几类接触行为采用的理论模型及其应用进行了归纳分析整理。综合叙述了基于计算机模拟技术的现代仿真模型的基本原理、应用和发展,重点介绍了适用于一般物体之间黏附行为分析的通用模型,以期为黏附接触领域的研究和建模提供指导和参考。对于弹性体接触的情况,重点介绍了经典力学接触理论的基本公式和适用类型,包括Hertz接触理论、JKR模型和DMT模型等,并依据Tabor数讨论了JKR模型与DMT模型的差异。对于粗糙表面的黏附接触,重点介绍了Greenwood和Williamson(GW模型)所提出的多凸起模型的基本理论和局限性。对于材料的表面剥离情况,重点介绍了剥离力学中应用最广泛的Kendall剥离模型的基本理论。对于现代仿真技术手段,重点介绍了分子动力学模型(MD模型)和有限元模型(FEM)的基本思想和优缺点。之后分别对以上各类模型的拓展完善、应用领域及研究进展进行了归纳总结,最后对黏附接触领域数学模型的发展方向进行了展望。     

基于灵敏度分析方法的渐开线直齿圆柱齿轮的疲劳强度研究

论文依据齿轮疲劳强度计算的数学模型,采用Latin超立方采样作为输入,对输出采用五点插值数值微分法进行计算,获得了齿轮各结构参数对疲劳强度的灵敏度,找出了齿轮各结构参数对疲劳强度的影响规律及敏感程度。该研究成果为齿轮的参数优化提供了重要的理论依据,同时也有助于其它机械传动装置的灵敏度研究。     

射流管电液伺服阀特性分析

针对基于经验和数学推导得出的射流管式电液伺服阀各部分数学关系,得到的动态特性不够精确的问题,分别对射流管电液伺服阀的衔铁反馈组件刚度、力矩马达的电磁力矩以及射流管接收器的流场,运用有限元分析工具得出了具有物理意义的数据,运用MATLAB拟合得到它们之间的数学关系。将上述拟合得到的数学关系用Simulink进行多物理场联合仿真,进而得到阀整体的输入输出关系、频率响应和阶跃响应规律,可以比较准确地反映阀实际的工作状态,仿真结果与实际工作过程相吻合,同时在有限元分析过程中考虑了材料和关键设计尺寸的影响,从而为射流管式电液伺服阀整体设计提供了新的思路。     

电液位置伺服系统的自适应抗饱和控制

针对电液位置伺服系统的不确定性与输入饱和问题,提出自适应抗饱和控制策略。建立阀控缸系统的数学模型;在基于反步法的设计框架下,将输入饱和导致的跟踪误差加入到李亚普诺夫函数当中,并根据该李亚普诺夫函数设计控制器。通过使李亚普诺夫函数渐近稳定,使得系统跟踪误差收敛于零。针对系统模型中的不确定参数,通过自适应算法对其进行迭代更新,以保证控制器的有效性。以跟踪误差最小为目标函数,采用粒子群搜索算法优化控制器的4个参数。结果表明：加入抗饱和时的控制信号比未考虑输入饱和时的控制信号的幅值明显减小,消除了输入饱和现象;在参数不确定和输入饱和情况下液压缸活塞的最大跟踪误差仅为5.8×10-6mm,相对无抗饱和算法时的跟踪误差有了大幅减小。     

A model for work of solid–liquid adhesion in multicomponent melts

The thermodynamic work of solid–liquid adhesion in multicomponent melts is important in many fields. Quantitative calculation of the work of solid–liquid adhesion has not, however, been well developed. A model for quantitative calculation of the work of solid–liquid adhesion in a multicomponent melt has been proposed based on the expansion of the Maclaurin infinite series in the neighborhood of each pure component of the binary alloy. The parameters used in this model are assessed through the statistical thermodynamic model of surface and interface tensions, which is based on the monolayer approximation for metal–vapor and metal–solid interfaces and Bragg–Williams statistics. According to the present model, the work of adhesion–concentration dependency over the whole concentration range for binary alloy can be theoretically determined from only the physical parameters of the pure components. The model has been successfully applied to calculate the work of adhesion for various solid–liquid systems.     

A study of the effect of the deformation parameters on recrystallization behavior in the rod rolling process

Rod rolling is a process in which the deformation of the workpiece between the work rolls is quite different from the rod drawing process, but the area strains (natural logarithm of area reduction ratio) multiplied by a constant have been used in the calculation of the pass-by-pass evolution of austenite grain size in rod (or bar) rolling without any verification. Considering that the deformation parameters (strain and strain rate) at a given pass play a crucial role in determining recrystallization behavior, the calculation method for the deformation parameters associated with rod rolling should be examined. In this study, a series of numerical simulations has been carried out using an area strain model [5] and an analytic model [6] which calculate the pass-by-pass strain in the rod rolling process, focusing on the effect of the calculation method for the pass-by-pass strain on the recrystallization behavior and evolution of AGS (austenite grain size) during a given pass. These have been investigated for a six-pass rolling sequence (oval-round or round-oval) designed for this study by incorporating the recrystallization and AGS evolution model being widely used in hot rolling. It was found that the recrystallization behavior and evolution of AGS during a given pass were significantly influenced by the calculation methods for deformation parameters. The area strain model lacks mathematical grounds to be used as input to the equations for recrystallization and AGS evolution.     

Sensitivity analysis of submerged arc welding process parameters

Selection of process parameters has great influence on the quality of a welded connection. Mathematical modelling can be utilized in the optimization and control procedure of parameters. Rather than the well-known effects of main process parameters, this study focuses on the sensitivity analysis of parameters and fine tuning requirements of the parameters for optimum weld bead geometry. Changeable process parameters such as welding current, welding voltage and welding speed are used as design variables. The objective function is formed using width, height and penetration of the weld bead. Experimental part of the study is based on three level factorial design of three process parameters. In order to investigate the effects of input (process) parameters on output parameters, which determine the weld bead geometry, a mathematical model is constructed by using multiple curvilinear regression analysis. After carrying out a sensitivity analysis using developed empirical equations, relative effects of input parameters on output parameters are obtained. Effects of all three design parameters on the bead width and bead height show that even small changes in these parameters play an important role in the quality of welding operation. The results also reveal that the penetration is almost non-sensitive to the variations in voltage and speed.     

脉冲逆变焊接电源建模与仿真

构建了包含输入、输出整流滤波和逆变、降压等电路的物理模型,通过非线性接口模型,研究了主回路和数字控制系统的整体建模与仿真.建立了动态焊接过程的系统数学模型,利用Matlab对焊接电源系统进行了仿真研究,然后定量分析了扰动作用下各物理量变化规律和系统动态响应过程,有效预测了脉冲MIG焊接电源的工作过程,指出了焊接电流和电弧电压控制的意义,为进一步研究指明了方向.     

基于神经网络的注射工艺分析模拟

在一般注射模CAE环境下 ,对某塑件输入一组工艺参数可得出相应的分析结果 ,但如何在不同工艺参数中确定一组值 ,使得工艺条件实现最优化 ,则需建立输入(工艺参数)与输出(分析结果)的对应关系 ,而通过人工神经网络则能反映输入转化成输出的数学表达式。通过对塑件工艺分析的人工神经网络模拟 ,建立了可供工艺优化计算的数学模型。     

基于蚁群遗传算法的舵机系统辨识

舵机作为船用重要部件,是保证船舶航行和操控的关键。目前液压舵机在大型船舶上被广泛使用,大型液压舵机在应用是面临着参数非线性,负载变化等问题,因此,在设计过程中需要对其进行系统参数辨识,以精准设计其控制器。为实现高效设计控制器,应用蚁群算法对其进行系统参数辨识,首先根据数学模型推导舵机的动态方程,然后对一组信号的输出和系统响应进行辨识,根据辨识的结果对控制模型进行修正。为大型液压舵机的设计和系统参数辨识奠定了理论基础。     

航空压气机叶片增材修复最优热输入分析

建立了压气机叶片MPAW增材修复传热模型，首先通过分析合金的热物性，计算出叶片MPAW增材修复的热输入范围，得到了不同热输入下熔池的温度分布. 之后创建了增材高度与送丝速度的数学模型，求解出不同送丝速度下的增材高度，并通过对焊缝截面温度分布的数值分析，进一步缩小热输入范围，得到试验参数. 最后通过数值分析及试验对比，揭示了合金修复区组织形貌与热输入率的演化规律，得到了最优的热输入和匹配的焊接参数.结果表明，试验结果与理论模型吻合度较好，验证了理论方法的有效性. 对于1 mm厚度的超薄压气机叶片的增材修复，采用研究得到的焊接参数，可达到最优热输入率，实现较好的增材形貌和增材修复效果.     

气压式熔融沉积系统丝宽与轮廓补偿研究

介绍了气压式熔融沉积系统的工作原理及工艺特点,提出了挤出丝的截面形状模型,建立了成型过程的数学物理方程,推出了理论丝宽的表达式,测量了AJS系统成型过程中不同温度和压力条件下材料的挤出速率,通过理论计算与实际测量结果的比较,确定了丝宽截面模型。最终根据得到的不同工艺条件下的丝宽值确定了扫描间距和轮廓补偿半径等工艺参数。     

自动埋弧焊接过程的电弧控制方程与热学分析

埋弧焊系统由恒流特性逆变焊接电源、送丝机、行走小车和控制器组成.控制器的输入是电弧电压Uarc和设置电压Uset,控制器的输出是PWM方式调节DC电源,驱动并调节送丝速度.用一阶微分方程建立了埋弧焊接过程中焊丝送进速度与焊接电弧之间的数学模型,模型描述了埋弧焊接过程中焊丝一边在电弧中燃烧,一边由送丝机不断送到燃弧区的平衡关系.通过电源、熔池、焊丝的热平衡分析,得到焊接系统的焊丝选取方法,该方法是焊丝直径与焊接电流的平方根成正比,文中还给出了焊丝直径与焊接电流的定量选取公式.     

Method for the Optimization of Kinematic and Dynamic Properties of Parallel Kinematic Machines

The following paper introduces an approach, which allows the consideration of the kinematic as well as the dynamic properties of parallel kinematic machines. Based on the results of a preceding kinematic optimization, a FEM-model with arbitrary input parameters is designed. The full kinematic functionality of struts and joints used is ensured. By coupling the FEM-model to the GNU Octave numerical program system, a variety of movements including machining forces can be simulated. A Broyden-Fletcher-Goldfarb-Shanno optimization algorithm, using GNU Octave, was written and coupled to the FEM-system. Now, this algorithm is able to influence the model's arbitrary input parameters during the optimization process. Thus, the model is optimized automatically for a certain machining process and/or dynamic behavior. This procedure is demonstrated using the example of a delta robot structure originally designed by Raymond Clavel [7].     

基于ADAMS与AMESim的油气悬架密封圈阻尼作用影响分析

油气悬架在工程自卸车中应用普遍,密封圈作为重要组成单元,摩擦作用产生阻尼对油气悬架性能具有重要影响。针对油气悬架密封圈阻尼作用的影响进行分析,建立单气室油气悬架的数学模型。基于ADAMS搭建二自由度的1/4自卸车的悬架模型,基于AMESim搭建油气悬架数学模型,二者联立搭建油气悬架整个工作系统的分析模型,采用正弦性周期激励作为系统输入,对密封圈阻尼作用影响进行分析。搭建油气悬架试验台,对系统特性进行分析,根据试验结果对分析模型进行修正并对模型的准确性进行验证。结果可知:考虑密封圈阻尼作用影响时,当簧载质量发生变化时,修正后模型使得车身加速度和车轮相对动载荷的最大值都明显降低,整车性能改善明显;对比分析可知修正后模型的准确性与可靠性;为此类自卸车悬架系统设计研究提供参考。     

电液比例溢流阀加载系统参数模型辨识与实验研究

利用电液比例压力-流量控制实验台搭建了一套电液比例溢流阀加载系统。根据系统遵循的物理定律与规律,采用机制建模法建立了系统的传递函数参数模型,并对系统进行动态测试。采集试验数据并进行分析处理,确定系统数学模型的阶次。利用ARMAX模型与传递函数模型对系统分别进行参数模型辨识,并分析了残差的相关性。最后通过对得出的辨识模型进行对比分析,结果表明:系统数学模型是准确可靠的,从而使输入电信号可以对输出扭矩进行准确地控制。     

多环槽式磁流变阻尼器阻尼力计算及实验结果分析

根据节流和剪切混合模型及工作原理设计加工了双出杆多环槽式磁流变阻尼器,结合实验建立了计算磁流变阻尼器的阻尼力的数学模型,并拟合出以电流为参数的速度与阻尼力的实验公式,该公式具有参数少、拟合精度高的特点.     

Effects of Process Parameters on Mechanical Adhesion of Thermal Oxide Scales on Hot-Rolled Low Carbon Steels

The present work investigated the effects of process parameters in a hot-rolling line, finishing and coiling temperatures, on mechanical adhesion of scale on low carbon steel substrate using a tensile test. Modification of our previous model to quantify mechanical adhesion energy was proposed for a system consisting of a cracked scale on a metallic substrate by introducing a distribution function of stress in scale. When a linear distribution was assumed, the quantified mechanical adhesion energy lay in the range of 40–890 J m^?2. Higher finishing temperature had a prominent role on increasing final scale thickness and weakening scale adhesion. For scale with similar thickness, the mechanical adhesion energy was lowered for the sample subjected to higher temperature gradient between finishing and coiling temperatures. This was considered to be from the increased water vapour in atmosphere due to the higher amount of water used to cool down the steel strip. The mechanical adhesion test was further conducted to attest this assumption. It was found that humidified atmosphere during oxidation weakened the scale adhesion to low carbon steel substrate measured at room temperature.     

Optimization of steel casting feeding system based on BP neural network and genetic algorithm

The trial-and-error method is widely used for the current optimization of the steel casting feeding system, which is highly random, subjective and thus ineff icient. In the present work, both the theoretical and the experimental research on the modeling and optimization methods of the process are studied. An approximate alternative model is established based on the Back Propagation(BP) neural network and experimental design. The process parameters of the feeding system are taken as the input, the volumes of shrinkage cavities and porosities calculated by simulation are simultaneously taken as the output. Thus, a mathematical model is established by the BP neural network to combine the input variables with the output response. Then, this model is optimized by the nonlinear optimization function of the genetic algorithm. Finally, a feeding system optimization of a steel traveling wheel is conducted. No shrinkage cavities and porosities are induced through the optimization. Compared to the initial design scheme, the process yield is increased by 4.1% and the volume of the riser is decreased by 5.48×10~6 mm3.     

基于MATLAB的沟槽型节流缓冲装置仿真与分析

针对沟槽型节流缓冲装置缓冲过程进行理论分析,建立了缓冲过程的数学模型,并通过MATLAB软件对其缓冲过程进行仿真,分析了沟槽节流缓冲装置各个参数对缓冲效果的影响。仿真结果表明:所建立仿真模型能够反映液压缸的缓冲过程,为沟槽型缓冲装置的设计提供一定的理论依据。