Abrasive waterjet machining simulation by SPH method

Abrasive waterjet machining (AWJM) is a non-conventional process. The mechanism of material removing in AWJM for ductile materials and existing erosion models are reviewed in this paper. To overcome the difficulties of fluid–solid interaction and extra-large deformation problem using finite element method (FEM), the SPH-coupled FEM modeling for abrasive waterjet machining simulation is presented, in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by FE. The two parts interact through contact algorithm. The creativity of this model is multi-materials SPH particles, which contain abrasive and water and mix together uniformly. To build the model, a randomized algorithm is proposed. The material model for the abrasive is first presented. Utilizing this model, abrasive waterjet penetrating the target materials with high velocity is simulated and the mechanism of erosion is depicted. The relationship between the depth of penetration and jet parameters, including water pressure and traverse speed, etc., are analyzed based on the simulation. The results agree with the experimental data well. It will be a benefit to understand the abrasive waterjet cutting mechanism and optimize the operating parameters.     

金属材料的喷丸强化及其应用

介绍了传统喷丸强化的原理、工艺、作用、研究现状及发展趋势,概述了包括预应力喷丸、热喷丸、超声喷丸及高压水喷丸等新技术,并介绍了计算机仿真技术在喷丸强化中的应用.     

基于SPH法的土壤切削刀具三维数值模拟及优化

为优化刀具结构,减小土壤切削的功耗,采用大型动力学软件LS—DYNA中的光滑粒子流体动力学（SPH）求解器,结合MAT147材料模型就松土刀具对土壤的切割过程进行了三维动态仿真。建立了反旋凿切的数值模拟模型;并结合正交试验法对松土铲耕作条件进行了仿真。仿真结果表明：利用SPH方法对土壤材料进行大应变、高应变率的变形计算是有效的;定性地得到了耕宽与耕深的关系,且结合相关理论将可以更全面合理地对松土铲刀具结构进行优化。     

Multiphysics simulation on electromagnetic peening of predrilled holes

The areas around predrilled holes are highly stressed regions where cracks can easily form, which decreases the resistance of metal components to fatigue and causes serious problems in industry, such as aerospace, automobile, and ship building. In this paper, a novel method utilizing the effects of a strong pulsed electromagnetic field is introduced to effectively produce residual compressive stress into the surface of a predrilled hole. Basic principles of electromagnetic peening (EMP) are investigated using a multiphysics simulation approach. Simulations of EMP process on the surface of a work piece with predrilled blind hole are carried out by COMSOL Multiphysics 3.4. The distributions of stress and strain are presented and discussed, which demonstrate the feasibility of EMP on inducing compressive residual stress into the interior surface around a hole. In addition, the distribution of residual stress varies with various hole depth and work piece thickness is investigated. Finally, the influence of process parameters is also studied. The results of this work will help design process of strengthening 3D surfaces in metal components in manufacturing industry.     

喷丸与激光喷丸强化高强度钢对比试验

为了考察和对比喷丸(SP)和激光喷丸(LSP)2种表面强化技术对金属零件的强化效果,以30CrMnSiNi2A钢为试样,进行喷丸和激光喷丸强化处理试验。试验结果显示,2种强化试样的残余压应力和硬度都有较大的提高。分别测定了喷丸强化和激光喷丸强化试样在同一应力水平下的疲劳寿命,并运用扫描电镜分析了两者的疲劳断口。试验结果表明,激光喷丸强化试样中值疲劳寿命是喷丸强化试样的1.11~2.75倍,激光喷丸强化比喷丸强化在提高金属零件表面性能方面的效果更佳。     

基于SPH方法的磨削机理仿真研究

采用光滑粒子流体动力学(SPH)法对单颗粒磨粒磨削过程进行了数值仿真.从工件材料的应力分布和变形情况以及切屑的形成情况对不同磨削深度和磨粒负前角下的仿真结果进行了分析.结果显示:基于SPH法的磨削仿真可以很好地解释磨削过程中工件材料的弹塑性变形行为和切屑的形成情况;在磨削过程中存在着一个刚好产生切屑的临界磨削深度;仿真中不同磨削深度下比磨削能的变化与磨削过程中的尺寸效应现象一致;随着磨粒负前角的增大,挤压作用增强而切削作用减弱,磨粒的挤压作用对工件表面质量具有重要影响.     

Incompressible SPH simulation and experimental validation of Buoy-Wave interaction

Understanding the motions of offshore structures, which are continuously affected by waves, is important. Thus, experimental approaches have traditionally been favored. However, computational methods are currently preferred because they reflect dynamic behavior more efficiently than experiments. The incompressible smoothed particle hydrodynamics was used in this study to model the waves and interactions with a buoy. Validation data for wave-structure interactions were obtained by using a wave tank. An incident sinusoidal wave was generated by a piston-type wave-maker, while a non-moored cylindrical buoy moved freely horizontally and vertically. Vertical motions must be predicted because the vertical motions of offshore structures considerably affect system performance. An IWD-IMU V1 sensor was used to measure buoy motion, and the vertical acceleration was compared with simulation data. The wave-structure interaction method considers the buoyancy force by the reference to the mass difference between a solid and a hollow buoy. Wave periods of 1.42, 1.58, 2.0, and 2.24 s were used. Buoy vertical acceleration was in increasingly good agreement with the experimental results as the wave period increased. This finding confirms that the proposed method predicts vertical buoy motion.     

无网格法中SPH方法和有限元方法的对比分析

无网格法是近期发展起来的一种数值计算方法,根据形函数构造可分为多种样式.在此主要介绍了较常用的一种方法:光滑粒子法(SPH)并对这种方法的原理和计算过程与有限元方法进行对比.从而阐述SPH方法的特点,后边又用这两种方法对一个简单例子进行求解.     

基于SPH法的板结土壤深耕技术研究

为解决板结土壤的耕作问题,提出了用于小型作业机的反旋凿切和正旋旋耕相结合的耕作机具。利用光滑粒子流体动力学(SPH)方法对正旋旋耕土壤过程进行了三维数值模拟,从而得出不同参数下旋耕刀具的受力情况,结合反旋凿切的仿真数据,进行刀具的匹配并设计相应的相位角,使反旋凿切刀和正旋旋耕刀相互抵消各自的作用力,降低能耗,提高工作效率,从而开发出适合在板结土壤上进行耕作的小型作业机。本研究方案所得数据和分析过程对于小型作业机的开发设计具有重要意义。     

基于 SPH／FEM 方法的机器人脚在土壤中的沉陷特性研究

基于SPH／FEM方法,将数值模拟方法与贝克经验公式进行了比较;建立了机器人脚与土壤的相互作用模型,进行了机器人脚在土壤中的沉陷研究。结果表明,当机器人脚底部圆弧曲率半径R为16cm时,机器人脚的几何形状更为理想。     

基于Adomian分解方法的暂态稳定并行仿真研究

针对目前大规模电力系统难以实现快速实时仿真的问题,提出了一种基于Adomian分解方法的暂态稳定仿真并行算法。首先,在考虑节点权重的同时,采用METIS将大系统拆分成若干子系统,然后采用波形松弛方法对系统进行并行求解。为加速各子系统的迭代过程,所有状态变量经过隐式梯形积分格式差分化后,采用基于Adomian分解的迭代算法配合非诚实牛顿算法进行了求解;为了进一步提高波形松弛法的整体收敛性,同时还使用了窗口方法、预处理方法与波形预测方法;最后,采用2 383节点和12685节点两个算例进行了测试,发电机采用复杂模型,同时考虑励磁调速系统,并通过共享内存的并行环境加以实现。测试研究结果表明,上述算法可以取得较为理想的收敛速度和并行加速比,同时实现了上万节点的超实时仿真。     

SPH方法在冲击破坏中的爆炸现象分析

由于SPH方法已被广泛应用到工程模拟的各个方面,虽然已有很大成功,但是还有很多的方面不成熟,其中之一就是爆炸现象,笔者对这种现象产生的原因进行了分析。     

Effects of simulation parameters on residual stresses for laser shock peening finite element analysis

By using finite element analysis, we proposed an applicable finite element method of laser shock peening (LSP) and discussed various parameters, such as solution time, stability limit, dynamic yield stress, peak pressure, pressure pulse duration, laser spot size, and multiple LSP. The effects of parameters related to the finite element simulation of the LSP process on the residual stresses of 35CD4 30HRC steel alloy are discussed. Parametric sensitivity analyses were performed to establish the optimum processing variables of the LSP process. In addition, we evaluated the effects of initial residual stress, such as welding-induced residual stress field.     

SPH method applied to high speed cutting modelling

The purpose of this study is to introduce a new approach of high speed cutting numerical modelling. A Lagrangian smoothed particle hydrodynamics (SPH)-based model is carried out using the Ls-Dyna software. SPH is a meshless method, thus large material distortions that occur in the cutting problem are easily managed and SPH contact control permits a “natural” workpiece/chip separation. The developed approach is compared to machining dedicated code results and experimental data. The SPH cutting model has proved is ability to account for continuous to shear localized chip formation and also correctly estimates the cutting forces, as illustrated in some orthogonal cutting examples. Thus, comparable results to machining dedicated codes are obtained without introducing any adjusting numerical parameters (friction coefficient, fracture control parameter).     

基于仿真评价方法的适应性合作换线策略

在多品种、小批量的生产方式下,换线操作频繁发生,合作换线常常作为一种组织驱动因素用于改善系统性能.当前对于合作换线策略的研究均基于固定规则,导致策略对系统性能的优化程度有限,且缺乏对于不同生产环境的适应能力.为解决这一问题,提出一种基于仿真评价方法的适应性合作换线策略.首先,介绍了合作换线的操作过程和4种基于规则的换线策略,提出了适应性策略的思路和特点.其次,给出了适应性策略的编码方式,使用模拟退火算法进行策略迭代,并借助于生产过程仿真实现对当前策略的评价.再次,为实现对合作换线策略的仿真,提出了基于agent的生产过程仿真模型.最后,将提出的适应性合作换线策略应用于某生产单元.实验结果表明,相比基于规则的策略,适应性策略在各种生产环境下均具有显著优势.     

基于CAD曲面测量方法研究及仿真

曲面可以具体的分为规则的曲面与自由的曲面其依据就是对于标准的数学模型是否可以进行适用.若是依据特征对曲面进行分类,又可以对CAD模型进行已知和未知的曲面划分.对曲面进行测量是为了给予曲面在进行精度检验以及反求的时候提供保证.利用三坐标测量机进行测量能够保证高精度、目的明确以及灵活的方法,可以使得在测量大部分加工过程中的参数对于误差的表现包括形状以及位置都满足要求.因此,被广泛应用于曲面的测量.本论文对基于CAD的已知曲面和未知曲面的测量分别进行了研究分析.     

基于ANSYS/LS-DYNA的受控喷丸工艺过程仿真

将喷丸过程简化为丸粒撞击工件的模型,丸粒看作刚性体,运用ANSYS/LS-DYNA软件进行了数值模拟,分析了覆盖率对残余压应力分布的影响,得出在不完整喷丸覆盖率下工件表面会产生残余拉应力.在单个丸粒模型中,将丸粒的材料改为塑性硬化材料,分析丸粒的速度对残余压应力分布的影响,得出丸粒的材料参数一定时,存在最优喷丸速度,丸速过高会导致丸粒的变形能增加,而使工件表层的最大压应力值和应力层深度下降.     

A Contact algorithm in the low velocity impact simulation with SPH

The formulation of Smoothed Particle Hydrodynamics (SPH) and a shortcoming of traditional SPH in contact simulation are presented. A contact algorithm is proposed to treat contact phenomenon between two objects. We describe the boundary of the objects with non-mass artificial particles and set vectors normal to the contact surface. Contact criterion using non-mass particles is established in this study. In order to verify the contact algorithm, an algorithm is implemented in to an in-house program; elastic wave propagation is an analysed under low velocity axial impact of two rods. The results show that the contact algorithm eliminates the undesirable phenomena at the contact surface; numerical result with the contact algorithm is compared with theoretical one.     

基于ADAMS的装载机工作装置动力学仿真方法研究

文中针对装载机工作装置进行动应力测试需要较高的时间与人力成本,以国产额定载重9t装载机为研究对象。提出一种应用虚拟样机技术快速获得装载机工作装置应力特性的方法。在ADAMS中建立了工作装置虚拟样机模型,对工作装置在不同工况下利用Step函数进行多刚体动力学仿真分析,得到的铰点载荷与实测载荷进行对比,验证仿真方法的合理性。利用Ansys生成动臂、摇臂以及连杆的柔性体文件,采用模态叠加法建立工作装置刚柔耦合动力学模型,导入不同工况下实测液压缸位移与铰点载荷,进行了工作装置动力学仿真分析,与Step函数仿真结果对比,结果表明：对于刚体动力学仿真分析,利用Step函数模拟铲装作业可以较好地反映铰点处的峰值载荷。对于刚柔耦合动力学仿真分析,基于实测载荷的最大应力与基于Step函数模拟的最大应力相对误差不超过26%,研究为装载机工作装置的强度分析与结构优化提供参考依据。     

基于状态空间平均法的伺服控制系统设计与仿真

以状态空间平均法建立了光电经纬仪伺服控制系统PWM控制电动机的双极性模型,并以全桥主电路为实现对象,控制系统采用输出角速度和位置信号为反馈信号,前馈控制和PID控制相结合的控制算法;理论分析和仿真结果说明对斜坡输入和阶跃干扰的稳态误差为零.