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1.
The existing numerical simulations of hydrodynamic characteristics of abrasive waterjet in a cutting head were mainly based on Eulerian grid or arbitrary Lagrange–Eulerian grid method to establish computational fluid dynamics models. However, using these two methods, the abrasive and water were premixed and given an identical initial velocity, which were different from the mixing and acceleration processes of abrasive in the cutting head. This paper presents a more suitable numerical model that the abrasive particle enters into the mixing chamber in a low velocity and is accelerated in the focus tube by a high-speed waterjet from the orifice. In order to model this mixing-and-acceleration process of abrasive and high-speed waterjet, the smooth particle hydrodynamics (SPH) coupled finite element method (FEM) is adopted, in which SPH particles are used to model the high-speed waterjet to adapt its extremely large deformation and FEM is applied to model the discrete abrasive particle, cutting head, and workpiece. As a result, evolution of abrasive and waterjet velocities along focus tube is analyzed; trajectory of single abrasive particle in focus tube is sighted; the relationships between abrasive particle velocities and different water pressures are described; the rule of outlet velocities of abrasive particle vs. dimensionless ratio of diameter is conducted; depth of penetration caused by single abrasive particle impact is obtained. The current model is validated by the existing theoretical and experimental data.  相似文献   

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市场状况 据美国《磨料磨具产品与市场》报告预测,到2004年,整个磨料磨具产品的需求总量将达到58亿美元,年均增长4%。航天和电子产品市场的增长将带动制造业对磨料磨具的需求,保守的估计也将会达到年均增长3.8%。其中,磨料将占有最大的销售份额,之后是粘结磨具。随着产品的进步,使用寿命不断增长,需求量将受  相似文献   

4.
Shot peening is a complex surface-treating process which is usually employed to improve the fatigue strength of metallic part or members. In dealing with shot peening simulation, existing literatures apply finite element method (FEM) to establish only a single shot or several shots models, thus the effect of a mass of shots impacting repeatedly and the interaction among adjacent shots are ignored. To overcome these defects of FEM models, smoothed particle hydrodynamics (SPH) coupled FEM modeling is presented, in which the shots are modeled by SPH particles and the target material is modeled by finite elements. Contact algorithm is used to simulate the interaction between shots and target. Utilizing this model, material model for shots is established, the relationships between compressive residual stress and peening frequencies, coverage, and velocities are analyzed. Steady compressive residual stress can be gotten by multiple peening; higher coverage can improve the compressive residual stress; faster velocities can induce greater and deeper maximum residual stress in target subsurface. The simulation results agree well with the existing experimental data. The study will not only provide a new powerful tool for the simulation of shot peening process, but also be benefit to optimize the operating parameters.  相似文献   

5.
根据车削加工的特点,研究了数控车床加工过程的三维仿真问题.提出了一种新的基于刀具轨迹斜率变化量的工件离散化和特征点筛选方法,与传统三维仿真方法相比,大大减少了工件建模所需的特征点数,提高了计算速度.文末通过算例证明了所提出方法的有效性.  相似文献   

6.
Abrasive waterjet (AWJ) machining is widely applied in the fields of civil and mechanical engineering. In this study, a general and theoretical analysis procedure was presented before computing application. It mainly focused on the kinetic energy model and wear rate model in machining process. Then, the multi-objective cuckoo algorithm was employed for optimization design of AWJ cutting head model, making sure to maximize the output energy and minimize the nozzle erosion rate while keeping the other factors constant. To demonstrate the effectiveness of the above strategy, a practical AWJ machining system was selected for investigation purpose. The proposed model was compared with experimental data for investigating the difference between the initial design and the optimized model. The results showed that the multi-objective cuckoo algorithm has great ability in prediction of outlet power and wear rate. Meanwhile, the optimized parameters were also superior to the original design, compared with experimental test data. The developed model can be used as a systematic approach for prediction in an advanced manufacturing process.  相似文献   

7.
The operation of a single abrasive grain in internal grinding by a composite abrasive wheel is considered. In particular, the transition from deformation to microcutting is analyzed on the basis of the Kragel’skii criterion.  相似文献   

8.
The effects of a water-mixture film adhering to solid materials on the impact contact are examined by employing exact solutions for an inhomogeneous contact problem and the Hertz impact theory. The elastic modulus of the water on a surface is assumed to be zero and the modulus of the water-mixture between a water surface and a target material varies from zero to the modulus of the target material. Non-elastic deformation is considered based on an energy balance. A new expression of closed form for impact force is obtained. The film effect on the impact force is very significant for low impact energy and becomes stable and less influential once impact energy increases to a certain value. Experimental results for quasi-static force are in agreement with the theoretical analysis in which two unknown parameters are ascertained by experiments. The minimum effective velocity of garnet abrasives achieved in this work for waterjet machining is consistent with previous results.  相似文献   

9.
基于VERICUT的五轴联动数控加工仿真   总被引:9,自引:0,他引:9  
以五轴联动的车铣复合机床为原型,介绍使用VER ICUT数控仿真软件构建数控仿真平台的过程,并介绍了构建完成后进行仿真操作、验证仿真平台及数据仿真所实现的功能。最后介绍了针对西门子840D数控系统实现五轴联动数控仿真的关键因素。  相似文献   

10.
D. Arola  M. Ramulu 《Wear》1997,210(1-2):50-58
An experimental study was conducted to determine the influence of material properties on the surface integrity and texture that results from abrasive waterjet (AWJ) machining of metals. A microstructure analysis, microhardness measurements, and profilometry were used in determining the depth of plastic deformation and surface texture that result from material removal. Models now available for dry abrasive erosion were adopted and found useful in understanding the influence of material properties on the hydrodynamic erosion process. It was found that the depth of subsurface plastic deformation is inversely proportional to a metals strength coefficient and extends the greatest depth near jet entry in the initial damage region (IDR). Furthermore, surface skewness in AWJ machining of metals increases with ductility and the corresponding critical strain for lip formation.  相似文献   

11.
The topic of this paper is the application of abrasive flow machining (AFM) to gear tool inserts polishing. Polished surface on plastic gear teeth improves surface geometry stability, and it increases the lifespan, which was proved on the gear testing rig. Experiments have shown that it is an efficient alternative to the hand polishing procedure. Besides significant cost and processing time savings, AFM generates constant surface quality. The achieved roughness is homogeneous on the entire machined surface; it is reduced from R a?=?0.68 μm to R a?=?0.08 μm in 120 s. At the same time, the tooth geometry profile is not damaged. The first time, surface polishing should be done at request because of individually manufactured tool inserts. Processing parameters depend on the type of the abrasive machine, the polishing paste and part geometry. Computer-aided abrasive flow analyses and practical experiments assist in setting optimum AFM process parameters. The paper presents a working set of parameters and a detailed report on machined surface measurement data. On the base of better understanding of AFM process, the surface roughness prediction model and thickness of removed material model was setup. It has high accuracy and reliability for specific applications. The use of plastic gears for various applications is widespread; the presented process improvement is an important innovation for injection molding tools manufacturers.  相似文献   

12.
The utilization of abrasive waterjet (AWJ) cutting/drilling, and in particular its application into hard-to-cut materials, is growing. However, the mechanics of AWJ cutting is complex; the material removal process is not fully understood and, consequently, it has not been accurately modeled. In the current study, work was undertaken to mesh in a first stage the waterflow into the waterjet nozzle in order to use the finite element (FE) method to simulate the pure waterjet flow. The main objective is to investigate and analyze in detail the workpiece material behavior under waterjet impingement; a non-linear FE model (using LS-DYNA 3D code) has been developed, which simulates the erosion of the target material caused by the high-pressure waterjet flow. A combination of Eulerian–Langrangian elements is used for the waterjet and the target material, respectively, in order to handle their interaction. Damaged zones can be localized on impinged materials. Elements’ failure is handled by introducing a threshold strain after which Langrangian elements are removed. The results obtained from this numerical simulation (velocity profile, stress, erosion stages) show a good agreement with the results from previous experimental work that is available in bibliography. The next step of the research will be focused on the simulation of the whole procedure using various abrasives.  相似文献   

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Journal of Mechanical Science and Technology - The 3-2-1 constraint principle has been widely applied as the boundary conditions for the finite element method (FEM) to simulate machining...  相似文献   

15.
This paper details the studies on the use of single mesh size garnet abrasives in abrasive waterjet machining for cutting aluminum. The influence of three different single mesh size abrasives, pressure, traverse rate, and abrasive flow rate; on depth of cut, top kerf width, bottom kerf width, kerf taper, and surface roughness are investigated. Experiments designed using standard L9 orthogonal array and the analysis of variance helped in the determination of highly significant, significant and weakly significant cutting parameters. Single mesh size abrasives are found to yield decreased surface roughness than multi mesh size abrasives. Based on these studies, response equations are developed to predict the target parameters. Using single mesh abrasives, a practitioner not only can cut faster but also achieve reduced surface roughness.  相似文献   

16.
Journal of Mechanical Science and Technology - This study discusses the development of an Adaptive neuro–fuzzy inference system (ANFIS) model for determining the surface roughness (Ra) during...  相似文献   

17.
Fluid bearings have features of high speed and high rotation accuracy, and therefore, they are used in spindle motors of hard disk drives, cooling fans of central processing units, and other devices. Further, these bearings have microherringbone grooves on the shaft or sleeve inner surface that help generate dynamic pressure in the lubricant fluid around the shaft. Although the depth of the groove is constant, dynamic pressure can be increased by decreasing the depth from both ends to the central corner of each groove on a micron scale. This study aims to verify the effect of sloped herringbone grooves using computational fluid dynamics (CFD) analysis and to develop a new microfabrication method for manufacturing microsloped herringbone grooves on the shaft surface using abrasive jet machining. The generated dynamic pressure is analyzed using CFD; the results indicated that the sloped herringbone grooves result in an increase in the dynamic pressure at the groove tips and cause a decrease in the fluctuations in dynamic pressure in the circumferential direction.  相似文献   

18.
核电稳压封头尺寸大,质量大,难以加工,生产效率低.目前,国内对提高核电稳压封头加工效率的研究很少.本研究首先以最高生产效率为目标建立铣削参数数学模型,通过遗传算法对数控加工参数优化,利用优化的参数对封头进行加工仿真.研究结果表明:适当的参数优化在保证加工要求的情况下,能够缩短加工时间,提高加工效率.  相似文献   

19.
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.  相似文献   

20.
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.  相似文献   

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