Finite element modeling of the surface roughness of 5052 Al alloy subjected to a surface severe plastic deformation process

The surface of 5052 Al alloy plates is severely plastically deformed via multiple impacts by high-velocity tungsten carbide/cobalt (WC/Co) balls in a surface nanocrystallization and hardening (SNH) process. The surface roughness of 5052 Al alloy plates as a function of the impacting ball size and processing time has been evaluated via non-contact 3D profilometry. A three-dimensional finite element (FE) model has been developed to simulate the formation of peaks and valleys during the SNH process. The peak-to-valley distance predicted from the FEM matches the maximum PV value measured experimentally quite well, indicating that surface roughening of 5052 Al alloy plates during the SNH process using WC/Co balls is mainly dictated by the indentation process of the impacting balls. The implications of this surface roughening mechanism in the final surface roughness, processing time, related microstructure change, and property alteration are discussed.     

碾压强化有限元建模及分析研究

碾压是强化金属表层的一种重要且很有发展潜力的强化方法,工件表层经碾压变形强化后会表层留有应力,能提高表层硬度和强度,同时还能改善工件表面粗糙度.对装备构件进行碾压模拟,模拟结果显示工件表层经碾压后产生较高应力且内部状态无明显变化,强化效果明显.接着改变下压量进行模拟,发现在一定范围内,随下压量增大,碾压强化效果愈好.     

外螺纹冷滚压精密成形工艺研究进展

螺纹冷滚压成形技术是一种少无切削加工工艺,具有生产效率高、成形零件机械性能增加、零件表面质量好等优点,在航空、航天、车辆等工业中高性能、高强度螺纹类零件生产中广泛应用。分别从有限元建模仿真、表面硬化、工艺参数等方面评述了目前螺纹冷滚压成形工艺研究的国内外研究现状、存在的问题和发展趋势,指出了该工艺应用发展方向及需要解决的关键技术问题:局部加载多道次耦合下螺纹冷滚压成形高效建模仿真与优化技术;系统的螺纹冷滚压成形工艺理论;螺纹冷滚压成形过程运动特征研究及成形过程精确控制;大直径重载丝杠的精确滚压成形核心技术及新工艺。     

Finite element modeling of friction stir welding—thermal and thermomechanical analysis

Friction stir welding (FSW) is a relatively new welding process that may have significant advantages compared to the fusion processes as follow: joining of conventionally non-fusion weldable alloys, reduced distortion and improved mechanical properties of weldable alloys joints due to the pure solid-state joining of metals. In this paper, a three-dimensional model based on finite element analysis is used to study the thermal history and thermomechanical process in the butt-welding of aluminum alloy 6061-T6. The model incorporates the mechanical reaction of the tool and thermomechanical process of the welded material. The heat source incorporated in the model involves the friction between the material and the probe and the shoulder. In order to provide a quantitative framework for understanding the dynamics of the FSW thermomechanical process, the thermal history and the evolution of longitudinal, lateral, and through-thickness stress in the friction stirred weld are simulated numerically. The X-ray diffraction (XRD) technique is used to measure the residual stress of the welded plate, and the measured results are used to validate the efficiency of the proposed model. The relationship between the calculated residual stresses of the weld and the process parameters such as tool traverse speed is presented. It is anticipated that the model can be extended to optimize the FSW process in order to minimize the residual stress of the weld.     

Finite element modeling of erosive wear

Material damage caused by the attack of particles entrained in a fluid system impacting a surface at high speed is called ‘Erosion’. Erosion is a phenomenon that takes place in several engineering applications. It also can be used in several manufacturing process such as abrasive waterjet machining. Erosion is a complex process dependent on particle speed, size, angle of attack as well as the behavior of the eroded material. Extensive experimental results have been reported in the literature on the erosion of different materials. Simulating the erosion process through finite element enables the prediction of erosion behavior of materials under different conditions, which will substitute the need of experimentation, and will enable the identification of constants required for existing analytical models.In this paper, an elasto-plastic finite element (FE) model is presented to simulate the erosion process in 3D configuration. The FE model takes into account numerical and material damping, thermal elastic–plastic material behavior and the effect of multiple particle impacts as well as material removal. The workpiece material modeled was Ti–6Al–4V. The effects of strain hardening, strain rate and temperature were considered in the non-linear material model. Comparison against results reported in literature and erosion models by Finnie, Bitter and Hashish are made. It is shown that the predicted results are in agreement with published results obtained experimentally and from analytical erosion models.     

无缝钢管轧制变形过程有限元模拟

利用Pro/E三维CAD设计软件建模,导入ANSYS/LS_DYNA显式动力学有限元软件对无缝钢管轧制过程进行有限元数值模拟,分析无缝钢管截面的变形特点及轧制力和应力应变的变化规律。研究表明显式动力学有限元作为连轧无缝钢管轧制过程的分析方法是行之有效的,对生产实践有指导意义。     

Thermo-mechanical modeling of orthogonal machining process by finite element analysis

A plane strain finite element method is used with a new material constitutive equation for 1020 steel to simulate orthogonal machining with continuous chip formation. Deformation of the workpiece material is treated as elastic–viscoplastic with isotropic strain hardening, and the numerical solution accounts for coupling between plastic deformation and the temperature field, including treatment of temperature-dependent material properties. To avoid numerical errors associated with large deformation of elements, automatic remeshing is used, with at least 15 rezonings required to achieve a satisfactory solution. Effects of the uncertainty in the constitutive model on the distributions of strain, stress and temperature around the shear zone are presented, and the model is validated by comparing average values of the predicted stress, strain, strain rate and temperature at the shear zone with experimental results. Parametric effects associated with cutting speed and initial work temperature are considered in the simulations.     

Finite element modelling of the scattering of ultrasonic waves by isolated flaws

A two-dimensional finite element model with absorbing boundary conditions has been developed to investigate the scattering of ultrasonic waves in infinite isotropic solids. The model is capable of showing a complex mode-conversion, when a short duration sinusoidal pulse interacts with a flaw. The emphasis is on narrow crack-like defects, cylindrical and spherical holes of size equal to the wavelength of the incident wave. The results, which are presented in the form of snapshots and scattering cross-sections, assist in understanding wave–flaw interaction, especially mode-conversion of the incident field and optimizing the ultrasonic NDT.     

钢管三辊连轧成型过程的有限元分析

本文采用弹塑性、大变形和接触非线性有限元法,应用MARC软件对Y型三辊两道冷轧钢管的成型过程进行了分析,得到了钢管在成型过程中横截面的变形图和应力应变的分布规律.根据数值计算结果绘制了钢管冷轧成型过程中的轴向应力、环向和径向应力分布曲线,根据应力分布规律分析了对成品钢管直径和壁厚精度的影响因素.研究成果可以作为冷轧钢管成型工艺参数和成型辊设计的参考.     

螺纹钢切分轧制有限元分析

用三维大变形热力耦合有限元法模拟了螺纹钢二切分轧件的变形情况 (K6～K3) ,分析了切分轧制轧件断面上存在的不均匀变形及其分布 ,同时分析了各道次的宽展 ,指出螺纹钢切分轧制宽展控制的重要性。调整来料的尺寸可在一定程度上控制K6、K5孔轧件的宽展 ,获得形状规整的弧边方轧件 ;K4、K3孔不易充满 ,其孔型的设计应有利于轧件的宽展。     

不同空心率铅锭轧制过程的有限元模拟

应用有限元法对不同空心率铅锭方坯的轧制过程进行了模拟计算,得出了不同空心率对铅锭的变形及应力的影响,计算结果与试验结果相符。由于铅在室温下的变形状态与高温时钢的变形状态有很多相似之处,本文的研究结果对研究钢的带液芯轧制有一定的指导意义。     

基于流面条元法的热带钢连轧仿真分析

根据流面条元法 ,对 145 0mm六机架热带钢连轧进行了数值仿真。得到了各道次单位轧制压力、前后张应力和出口横向位移的分布。仿真结果表明 ,轧后带钢侧面呈鼓形 ,与实际情况一致。各道次的后张应力和前张应力有类似的分布规律。各道次总轧制压力的计算值和实测值很接近。仿真实例表明 ,流面条元法是一种模拟板带轧制三维变形的实用的工程数值方法。它具有计算量较少 ,适用范围较宽的特点。仿真结果对热带钢连轧工艺规程的制定具有指导意义。     

二辊平整机数值建模及平整机理分析

运用ABAQUS有限元软件,采用二维、三维弹塑性有限元法相结合方式,对二辊平整机加工过程进行模拟。完成了对极薄板的不同摩擦系数、不同弯辊力等因子条件下的有限元模拟,得出各因子对带钢平整变形的相关影响;由受力分析得出了接触区内纵向变形区的分布特点及形成原因;得到了剥落等失效形式以及边缘降产生的依据,并进行了与实验结果的对比。为板形分析与控制提供了新的方法和依据。     

环件辗扩过程仿真中的自适应单元重划分

在环件辗扩过程动力显式有限元分析中发现,大变形造成单元的畸变.研究了单元自适应重划分算法.在分析工件单元变形的度量基础上,提出了基于空间域离散误差的单元重划分触发准则.基于传统的栅格法思想,针对环件辗扩的特殊性建立了标准栅格,通过边界拟合和节点平滑完成了重划单元的生成.通过平滑物理量、新单元节点在旧单元中包含测试以及新旧单元间物理量的映射完成了物理量的继承和传递.最后,通过算例验证了单元自适应重划分算法的有效性.     

Finite element and dimensional analysis algorithm for the prediction of mechanical properties of bulk materials and thin films

In this work, the applicability of a new algorithm for the estimation of mechanical properties from instrumented indentation data was studied for thin films. The applicability was analyzed with the aid of both three-dimensional finite element simulations and experimental indentation tests. The numerical approach allowed studying the effect of the substrate on the estimation of mechanical properties of the film, which was conducted based on the ratio h_max/l between maximum indentation depth and film thickness. For the experimental analysis, indentation tests were conducted on AISI H13 tool steel specimens, plasma nitrated and coated with TiN thin films. Results have indicated that, for the conditions analyzed in this work, the elastic deformation of the substrate limited the extraction of mechanical properties of the film/substrate system. This limitation occurred even at low h_max/l ratios and especially for the estimation of the values of yield strength and strain hardening exponent. At indentation depths lower than 4% of the film thickness, the proposed algorithm estimated the mechanical properties of the film with accuracy. Particularly for hardness, precise values were estimated at h_max/l lower than 0.1, i.e. 10% of film thickness.     

铝箔轧制中辊端压靠的有限元分析

将铝箔轧机辊系及轧件统一考虑建立了有限元分析模型,分别计算了模型在冷辊(开始轧制)和热辊(稳定轧制)状态下,铝箔轧机辊缝内轧制压力的轴向分布规律;判断了辊端压靠的发生;说明了压靠对铝箔板形的影响。     

环件轧制过程的显式有限元模拟分析

用于金属成形模拟的有限元方程的求解方法 ,主要有隐式和显式积分两种方法。对于复杂的三维变形分析 ,如环件轧制 ,隐式方法需要很长的运行时间。而利用显式方法 ,可以达到很好的效果。本文利用Abaqus /Ex plicit通用有限元程序对径向环轧进行了模拟。     

带钢热连轧过程轧制力三维有限元模拟

在现代计算机控制的带钢生产中,轧制力的设定极其重要.根据宝钢轧制力模型和现场实测数据,结合热连轧过程中带钢三维变形和热力耦合的特点,应用DEFORM-3D软件建立了带钢热连轧前两个道次的有限元模型,模拟了热连轧过程中两个道次的轧制力变化,并与宝钢模型计算值和实测值进行了对比.结果表明,有限元法计算的轧制力与现场实测数据接近,两者误差在5.0%以内,同时有限元法的计算精度高于宝钢轧制力模型,特别是在第一道次,轧制力计算精度高出4.0%,该模拟为现场轧制工艺参数的调整优化提供了重要的参考价值.     

带张力轧制铝管的有限元分析

采用大型非线性有限元软件ANSYS/LS - DYNA对三辊单机架轧管机轧制过程进行有限元模拟.分析了带张力轧制铝管时前张力、后张力对轧制力、芯棒轴向摩擦力以及金属延伸率的影响,为连轧机孔型设计及轧辊速度调整提供了理论依据.     

T型管接头挤压胀形过程的有限元分析

根据T形管挤压胀形双重非线性的变形特点,建立了动力分析有限元方程。开发了在HP715／50工作站上运行的程序软件SFMP。对T形管挤压胀形过程及主要因素的影响进行模拟分析,总结归纳了分析结果。